With the rising rates, and associated costs, of total knee arthroplasty (TKA), enhanced clarity regarding patient appropriateness for TKA is warranted. Towards addressing this gap, we elucidated in qualitative research that surgeons and osteoarthritis (OA) patients considered TKA need, readiness/willingness, health status, and expectations of TKA most important in determining patient appropriateness for TKA. The current study evaluated the predictive validity of pre-TKA measures of these appropriateness domains for attainment of a good TKA outcome.

This prospective cohort study recruited knee OA patients aged 30+ years referred for TKA at two hip/knee surgery centers in Alberta, Canada. Those receiving primary, unilateral TKA completed questionnaires pre-TKA assessing TKA need (WOMAC-pain, ICOAP-pain, NRS-pain, KOOS-physical function, Perceived Arthritis Coping Efficacy, prior OA treatment), TKA readiness/willingness (Patient Acceptable Symptom State (PASS), willingness to undergo TKA), health status (PHQ-8, BMI, MSK and non-MSK comorbidities), TKA expectations (HSS KR Expectations survey items) and contextual factors (e.g., age, gender, employment status). One-year post-TKA, we assessed for a ‘good outcome’ (yes/no), defined as improved knee symptoms (OARSI-OMERACT responder criteria) AND overall satisfaction with TKA results. Multiple logistic regression, stepwise variable selection, and best possible subsets regression was used to identify the model with the smallest number of independent variables and greatest discriminant validity for our outcome. Receiver Operating Characteristic (ROC) curves were generated to compare the discriminative ability of each appropriateness domain based on the ‘area under the ROC curve’ (AUC). Multivariable robust Poisson regression was used to assess the relationship of the variables to achievement of a good outcome.

f 1,275 TKA recipients, 1,053 (82.6%) had complete data for analyses (mean age 66.9 years [SD 8.8]; 58.6% female). Mean WOMAC pain and KOOS-PS scores were 11.5/20 (SD 3.5) and 52.8/100 (SD 17.1), respectively. 78.1% (95% CI 75.4–80.5%) achieved a good outcome. Stepwise variable selection identified optimal discrimination was achieved with 13 variables. The three best 13-variable models included measures of TKA need (WOMAC pain, KOOS-PS), readiness/willingness (PASS, TKA willingness), health status (PHQ-8, troublesome hips, contralateral knee, low back), TKA expectations (the importance of improved psychological well-being, ability to go up stairs, kneel, and participate in recreational activities as TKA outcomes), and patient age. Model discrimination was fair for TKA need (AUC 0.68, 95% CI 0.63-0.72), TKA readiness/willingness (AUC 0.61, 95% CI 0.57-0.65), health status (AUC 0.59, 95% CI 0.54-0.63) and TKA expectations (AUC 0.58, 95% CI 0.54-0.62), but the model with all appropriateness variables had good discrimination (AUC 0.72, 95% CI 0.685-0.76). The likelihood of achieving a good outcome was significantly higher for those with greater knee pain, disability, unacceptable knee symptoms, definite willingness to undergo TKA, less depression who considered improved ability to perform recreational activities or climb stairs ‘very important’ TKA outcomes, and lower in those who considered it important that TKA improve psychological wellbeing or ability to kneel.

Beyond surgical need (OA symptoms) and health status, assessment of patients’ readiness and willingness to undergo, and their expectations for, TKA, should be incorporated into assessment of patient appropriateness for surgery.

In Canada, hip and knee replacements are each among the top three surgeries performed annually. In 2020, surgeries across the country were cancelled in response to the COVID-19 pandemic. We examined the impact on these joint replacement surgeries throughout the year.

Using the Discharge Abstract Database and National Ambulatory Care Reporting System, we developed a dataset of all 208,041 hip and knee replacements performed in Canada (except from Quebec) between January 1, 2019 to December 31, 2020. We compared patient and surgical characteristics (including sex, age, main diagnosis, and type of surgery (planned/urgent, primary/revision, inpatient/day surgery) in 2020 to 2019.

In 2020, hip and knee replacements volumes decreased by 18.8% compared to 2019. In April and May 2020, hip and knee replacements fell by 69.4% and 93.8%, respectively, compared to the same period in 2019. During those months, 66.5% of hip replacements were performed to treat hip fracture versus 20.2% in April and May 2019, and 64.5% of knee replacements were primaries versus 93.0% in April and May 2019. Patterns by patient age group and sex were similar compared to 2019. These patterns were similar across all provinces. By the summer, planned surgeries resumed across the country and volumes mostly returned to pre-pandemic monthly levels by the end of the year. We also found that there was an increase in the proportion of hip and knee replacements done as day surgery, with 4% in 2020 versus 1% in 2019, and patients undergoing day surgery replacement for osteoarthritis were older, with a median age of 64 for hip patients and 65 for knee patients, versus 63 for both joints the previous year.

As a result of the COVID-19 pandemic, there was a notable drop in 2020 of hip and knee replacements performed in Canada. With the demand for joint replacements continuing to grow, the resulting backlog will have an immediate, significant impact on wait lists and patient quality of life. The shift to a greater proportion of joint replacements performed as day surgeries may have an effect on patient outcomes as well shifts in access to care. It will be important to continue monitor patient outcomes following day surgery and the impact on patients for which day surgery was not an option.

Canada is second only to the United States worldwide in the number of opioid prescriptions per capita. Despite this, little is known about prescription patterns for patients undergoing total joint arthroplasty (TJA). The purpose of this study was to detail preoperative opioid use patterns and investigate the effect it has on perioperative quality outcomes in patients undergoing elective total hip and total knee arthroplasty surgery (THA and TKA).

The study cohort was constructed from hospital Discharge Abstract Data (DAD) and National Ambulatory Care Reporting System (NACRS) data, using Canadian Classification of Health Intervention codes to select all primary THA and TKA procedures from 2017-2020 in Nova Scotia. Opioid use was defined as any prescription filled at discharge as identified in the Nova Scotia Drug Information System (DIS). Emergency Department (ED) and Family Doctor (FD) visits for pain were ascertained from Physician Claims data. Multivariate logistic regression was used to test for associations controlling for confounders. Chi-squared statistics at 95% confidence level used to test for statistical significance.

In total, 14,819 TJA patients were analysed and 4306 patients (29.0%) had at least one opioid prescription in the year prior to surgery. Overall, there was no significant difference noted in preoperative opiate use between patients undergoing TKA vs THA (28.8% vs 29.4%). During the period 2017-2019 we observed a declining year-on-year trend in preoperative opiate use. Interestingly, this trend failed to continue into 2020, where preoperative opiate use was observed to increase by 15% and exceeded 2017 levels. Within the first 90 days of discharge, 22.9% of TKA and 20.9% of THA patients presented to the ED or their FD with pain related issues. Preoperative opiate use was found to be a statistically significant predictor for these presentations (TKA: odds ratio [OR], 1.45; 95% confidence interval [CI], 1.29 to 1.62; THA: OR, 1.46; 95% CI, 1.28 to 1.65).

Preoperative opioid consumption in TJA remains high, and is independently associated with a higher risk of 90 day return to the FD or ED. The widespread dissemination of opioid reduction strategies introduced during the middle of the last decade may have reduced preoperative opiate utilisation. Access barriers and practice changes due to the COVID-19 pandemic may now have annulled this effect.

The coronavirus pandemic has reduced the capability of Canadian hospitals to offer elective orthopaedic surgery requiring admission, despite ongoing and increasing demands for elective total hip and total knee arthroplasty surgery (THA and TKA). We sought to determine if the coronavirus pandemic resulted in more outpatient THA and TKA in Nova Scotia, and if so, what effect increased outpatient surgery had on 90 day post-operative readmission or Emergency Department/Family Doctor (FD) visits.

The study cohort was constructed from hospital Discharge Abstract Data (DAD), inpatient admissions, and National Ambulatory Care Reporting System (NACRS) data, day surgery observations, using Canadian Classification of Health Intervention codes to select all primary hip and knee procedures from 2005-2020 in Nova Scotia. Emergency Department and General Practitioner visits were identified from the Physician Billings data and re-admissions from the DAD and NACRS. Rates were calculated by dividing the number of cases with any visit within 90 days after discharge. Chi-squared statistics at 95% confidence level used to test for statistical significance. Knee and hip procedures were modelled separately.

There was a reduction in THA and TKA surgery in Nova Scotia during the coronavirus pandemic in 2020. Outpatient arthroplasty surgery in Nova Scotia in the years prior to 2020 were relatively stable. However, in 2020 there was a significant increase in the proportion and absolute number of outpatient THA and TKA. The proportion of THA increased from 1% in 2019 to 14% in 2020, while the proportion of TKA increased from 1% in 2019 to 11% in 2020. The absolute number of outpatient THA increased from 16 cases in 2019, to 163 cases in 2020. Outpatient TKA cases increased from 21 in 2019, to 173 in 2020. The increase in outpatient surgery resulted in an increase in 90 day presentations to ED following TKA but not THA which was not statistically significant. For outpatient THA and TKA, there was a decrease in 90 day readmissions, and a statistically significant decrease in FD presentations.

Outpatient THA and TKA increased significantly in 2020, likely due to the restrictions imposed during the coronavirus pandemic on elective Orthopaedic surgery requiring admission to hospital. The increase in outpatient surgery resulted in an increase in 90 day presentations to ED for TKA, and a decrease in 90 day readmissions and FD presentations for THA and TKA. Reducing the inpatient surgical burden may result in a post-operative burden on ED, but does not appear to have caused an increase in hospital readmission rates.

Purpose

The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery.

Purpose

Identifying knee osteoarthritis patient phenotypes is relevant to assessing treatment efficacy. Biomechanics have not been applied to phenotyping, yet features may be related to total knee arthroplasty (TKA) outcomes, an inherently mechanical surgery. This study aimed to identify biomechanical phenotypes among TKA candidates based on demographic and gait mechanic similarities, and compare objective gait improvements between phenotypes post-TKA.

Aims

A retrospective study was conducted to measure short-term in vivo linear and volumetric wear of polyethylene (PE) inserts in 101 total knee arthroplasty (TKA) patients using model-based radiostereometric analysis (MBRSA).

Hip abductor deficiency (HAD) associated with hip arthroplasty can be a chronic, painful condition that can lead to abnormalities in gait and instability of the hip. HAD is often confused with trochanteric bursitis and patients are often delayed in diagnosis after protracted courses of therapy and steroid injection. A high index of suspicion is subsequently warranted.

Risk factors for HAD include female gender, older age, and surgical approach. The Hardinge approach is most commonly associated with HAD because of failure of repair at the time of index surgery or subsequent late degenerative or traumatic rupture. Injury to the superior gluteal nerve at exposure can also result in HAD and is more commonly associated with anterolateral approaches. Multiple surgeries, chronic infection, and chronic inflammation from osteolysis or metal debris are also risk factors especially as they can result in bone stock deficiency and direct injury to muscle. Increased offset and/or leg length can also contribute to HAD, especially when both are present.

Physical exam demonstrates abductor weakness with walking and single leg stance. There is often a palpable defect over the greater trochanter and palpation in that area usually elicits significant focal pain. Note may be made of multiple incisions. Increased leg length may be seen.

Radiographs may demonstrate avulsion of the greater trochanter or significant osteolysis. Significant polyethylene wear or a metal-on-metal implant should be considered as risk factors, as well as the presence of increased offset and/or leg length. Ultrasound or MRI are helpful in confirming the diagnosis but false negatives and positive results are possible.

Treatment is difficult, especially since most patients have failed conservative management before diagnosis of HAD is made. Surgical options include allograft and mesh reconstruction as well as autologous muscle transfers. Modest to good results have been reported, but reproducibility is challenging. In the case of increased offset and leg length, revision of the components to reduce offset and leg length may be considered. In the case of significant instability, abductor repair may require constrained or multi-polar liners to augment the surgical repair.

HAD is a chronic problem that is difficult to diagnose and treat. Detailed informed consent appropriately setting patient expectations with a comprehensive surgical plan is required if surgery is to be considered. Be judicious when offering this surgery.

Conventional total knee arthroplasty aims to place the joint line perpendicular to the mechanical axis resulting in an overall neutral mechanical alignment. This objective is promulgated despite the fact healthy adult populations are on average in varus with few proximal tibias being neutral to the mechanical axis. The goal of a neutral mechanical axis is based largely on historical studies and the fact that it is easier to make a neutral tibial cut with conventional jigs and the eye. In order to balance the flexion and extension gaps to accommodate a neutral tibial cut, in most patients, asymmetrical distal and posterior femoral cuts are required. The resulting position of the femoral component could be considered to be “mal-rotated” with respect to the patient's soft tissue envelope. Soft tissue releases are often required to “balance” the knee. Planning and execution of the surgery are largely based off 2-dimensional radiographs which grossly oversimplifies the concept of alignment to the coronal plane, largely ignoring what happens to the knee in 3-dimensions through range of motion and 4-dimensions with respect to gait, stair climbing, etc. Subsequently, neutral mechanical for all engenders the “looks good, feels bad” phenomenon seen in many patients that may in part drive the higher dissatisfaction rates seen in knee arthroplasty globally compared to hip arthroplasty.

Additionally, because most tibias are in varus in the native state, placement of the tibial component in a neutral position results in a valgus orientated position during weight bearing post-operatively. Placing the tibial component in a varus, kinematic aligned position negates this deleterious condition and has been linked to improved outcomes in recent studies.

New imaging and surgical techniques allow for the identification of patient specific alignment targets and the ability to more precisely execute the surgical plan with respect to 3-dimensional placement of the components. Long-term outcomes studies as well as more recent studies on “kinematic” positioning suggest that deviation away from a neutral mechanical target is safe with respect to survivorship and provides better function with a more “natural” feeling knee.

Conventional total knee arthroplasty aims to place the joint line perpendicular to the mechanical axis resulting in an overall neutral mechanical alignment. This objective is promulgated despite the fact healthy adult populations are on average in varus with few proximal tibias being neutral to the mechanical axis. The goal of a neutral mechanical axis is based largely on historical studies and the fact that it is easier to make a neutral tibial cut with conventional jigs and the eye. In order to balance the flexion and extension gap to accommodate a neutral tibial cut, in most patients, asymmetrical distal and posterior femoral cuts are required. The resulting position of the femoral component could be considered to be “mal-rotated” with respect to the patient's soft tissue envelope. Soft tissue releases are often required to “balance” the knee. Planning and execution of the surgery are largely based off 2-dimensional radiographs which grossly oversimplifies the concept of alignment to the coronal plane, largely ignoring what happens to the knee in 3 dimensions through range of motion and 4 dimensions with respect to gait, stair climbing, etc. Subsequently, sticking with neutral mechanical for all engenders the “looks' good, feels bad” phenomenon seen in many patients that may in part drive the higher dissatisfaction rates seen in knee arthroplasty globally compared to hip arthroplasty.

New imaging and surgical techniques allow for the identification of patient specific alignment targets and the ability to more precisely execute the surgical plan with respect to 3-dimensional placement of the components. Long-term outcomes studies as well as more recent studies on “kinematic” positioning suggest that deviation away from a neutral mechanical target may in fact be safe with respect to survivorship and provide better function with a more “natural” feeling knee.

Background

Total Knee Replacement (TKR) is an effective treatment for knee arthritis. One long held principle of TKRs is positioning the components in alignment with the mechanical axis to restore the overall limb alignment to 180 ± 3 degrees. However, this view has been challenged recently. Given the high number of replacements performed, clarity on this integral aspect is necessary. Our objective was to investigate the association between malalignment and outcome (both PROMs and revision) following primary TKR.

Like all surgery, if you can see it, you can usually get the job done. This is especially true for extracting well-fixed components, as iatrogenic bone loss is a serious consideration regarding the reconstruction challenge. While reasons for revision are varied, several general principles are useful to consider during the pre and peri-operative course.

Pre-operatively, forewarned is forearmed. Certain factors pre-operatively can suggest the degree of operative difficulty regarding exposure. Revisions for stiffness obviously would suggest difficulty with exposure. Revisions in knees with patellar baja are almost always challenging as the patella is difficult to evert. When revising infected knees, an exuberant synovial response can result in beefy, friable synovium that has a volume effect with decreased tissue compliance. Further, the hyperemic friable tissue bleeds easily, even with tourniquet, and is difficult to anticoagulate.

Peri-operatively, the general principles to consider are as follows: 1) Don't rush exposure. Good exposure is the result of a series of deliberate and sequential steps that safely reduce tissue volume and improvement in tissue compliance. These steps include in almost all cases: a. Extend the incision as necessary, there is no call for minimally invasive revision knee surgery; b. Tenolysis of the patellar tendon; c. Clearing of the medial and lateral gutter; d. Clearing of the flexion space; e. Clearing of quadriceps adhesions.

2) Protect the extensor mechanism, above all else. Carefully monitor the insertion of the patellar tendon when beginning to flex the knee. If an avulsion begins, back off flexion and spend more time on clearing of scar tissue, as above. If still unsuccessful, then extensile exposure should be considered, such as a quadriceps snip. Be especially careful when osteolysis is present around the tibial tubercle.

3) The most difficult area to of the knee to expose in revision surgery is the posterior lateral corner, resulting in difficulty in exposing the posterior lateral femur and the posterior corner of the tibial component. Extensile exposures do not necessarily result in complete exposure of these regions. Redoubling efforts to remove scar tissue is often more successful. Bovie dissection of soft tissue on the proximal medial tibia can assist, with extension back to the semimembranosus insertion sometimes being necessary. While adequate exposure can result because of the increased ability to externally rotate the tibia, this exposure can also destabilise the medial side of the knee, sometimes resulting in the need to add constraint. The pros and cons need to be considered on a case-by-case basis.

4) Be judicious in the utilization of extensile exposures, and choose the exposure technique best suited for the situation. If the patellar tendon is normal, consider a simple quadriceps snip. If the knee is particularly stiff or the tibial tubercle or patellar tendon insertion is in jeopardy, then the snip can be extended into a V-Y turndown. If the patellar tendon is contracted resulting in patellar baja, then a tibial tubercle osteotomy (TTO) can be considered. Careful removal of tissue in scar tissue, as above, allows for relative external rotation of the tibia on the femur that translates the patella laterally, reducing the need for TTO. TTO can also be effective when approaching a cemented tibial stem.

Background

Total knee arthroplasty (TKA) is a routine, cost-effective treatment for end-stage arthritis. While the evidence for good-to-excellent patient-reported outcomes and objective clinical data is present, approximately 20% of patients continue to be dissatisfied with results of their surgery. Dissatisfaction is strongly correlated with unmet patient expectations, and these patients may experience a higher cost of care due to recurring office and emergency visits. Therefore, this survey asked a large group of United States (U.S) and international surgeons to prioritize areas of opportunity in primary TKA. Specifically, we compared surgeon responses regarding: 1) the top 5 areas needing improvement; which were stratified by: 2) surgeons' years of experience; and 3) surgical case volume.

Significant advances in perioperative pain management, such as multimodal periarticular injection, and subtler advances in surgical technique have resulted in improved postoperative experiences for patients with less pain, earlier rehabilitation, and shorter stays in hospital. Concurrently, and by applying the learnings from above, significant advances have been made in unicompartmental knee arthroplasty care pathways leading to safe programs for outpatient surgery. A natural extension of this process has been the exploration of outpatient total joint arthroplasty (TJA).

There are some papers written on the topic, but not many. The papers are generally report that outpatient TJA can be a safe and effective procedure, but the devil is in the detail. Firstly, most authors in this field carry a bias towards positive outcomes given they fact they are expert, academic, and innovative surgeons, often having controlling interest in the management of the complete perioperative pathway. Secondly, and largely as a result of the above, there is a major selection bias as to who receives outpatient TJA. In all cases, the patients are younger, fitter, and with less comorbidities. Patients reported in the published literature on outpatient TJA therefore do not represent the average patient that the average surgeon would operate on. Recall, TJA patients are becoming heavier and older patients (85+) are also receiving TJA at increasing rates.

It is useful to remember that TJA is a stressful event from a physiological perspective for the patient. Serious complications, including death, can and do occur. Further, some significant events, like cardiac ischemia occur around the second to third day postoperatively. These patients often require medical intervention for stabilization and need readmission when sent home before these events occur. This obviously is not a trivial issue given the penalties applied to hospitals in the US for early readmissions after TJA.

The fundamental questions at this early stage of outpatient TJA are 1) whether it is scalable to a larger audience, and 2) whether or not processes can be developed to make it a routine, standard of care. Given that the current literature is limited and written by expert surgeons on a highly select group of patients, and given that patients in general are getting older and less healthy, it is difficult to imagine a future of TJA as drive through surgery.

Hospital type is an indicator for structures and processes of care. The effect of hospital type on hip fracture in-hospital mortality is unknown. We determine whether hip fracture in-hospital mortality differs according to hospital type.

We retrieved records of hip fracture for 167,816 patients aged 65 years and older, who were admitted to a Canadian acute hospital between 2004 and 2012. For each hospital type we measured and compared the cumulative incidence of in-hospital death by in-patient day, accounting for discharge as a competing event.

The cumulative incidence of in-hospital death at in-patient day 30 was lowest for teaching hospital admissions (7.3%) and highest for small community hospital admissions (11.5%). The adjusted odds of in-hospital death were 12% (95% CI 1.06–1.19), 25% (95% CI 1.17–1.34), and 64% (95% CI 1.50–1.79) higher for large, medium, and small community hospital versus teaching hospital admissions. The adjusted odds of nonoperative death were 1.6 times (95% CI 1.42–1.86), and 3.4 times (95% CI 2.96–3.94) higher for medium and small community hospital versus teaching hospital admissions. The adjusted odds of postoperative death were 14% (95% CI 1.07–1.22) and 20% (95% CI 1.10–1.31) higher at large and medium community hospitals versus teaching hospitals. The adjusted odds of postoperative death were largest at small community hospitals but the confidence interval crossed 1 (OR = 1.25, 95% CI 0.92–1.70).

A higher proportion of hip fracture patients die at non-teaching compared to teaching hospitals accounting for length of stay. Higher mortality at small community hospitals may reflect disparities in access to resources and delay to treatment.

Articulation of the polyethylene (PE) insert between the metal femoral and tibial components in total knee replacements (TKR) results in wear of the insert which can necessitate revision surgery. Continuous PE advancements have improved wear resistance and durability increasing implant longevity. Keeping up with these material advancements, this study utilises model-based radiostereometric analysis (mbRSA) as a tool to measure in vivo short-term linear PE wear to thus predict long-term wear of the insert.

Radiographic data was collected from the QEII Health Sciences Centre in Halifax, NS. Data consisted of follow-up RSA examinations at post-operative, six-, 12-, and 24-month time periods for 72 patients who received a TKR. Implanted in all patients were Stryker Triathlon TKRs with a fixed, conventional PE bearing of either a cruciate retaining or posterior stabilised design. Computer-aided design (CAD) implant models were either provided by the manufacturer or obtained from 3D scanned retrieved implants. Tibial and femoral CAD models were used in mbRSA to capture pose data in the form of Cartesian coordinates at all follow-ups for each patient. Coordinate data was manually entered into a 3D modeling software (Geomagic Studio) to position the implant components in virtual space as presented in the RSA examinations. PE wear was measured over successive follow-ups as the linear change in joint space, defined as the shortest distance between the tibial baseplate and femoral component, independently for medial and lateral sides. A linear best-fit was applied to each patient's wear data; the slope of this line determined the annual wear rate per individual patient. Wear rates were averaged to provide a mean rate of in vivo wear for the Triathlon PE bearing.

Mean linear wear per annum across all 72 patients was 0.088mm/yr (SD: 0.271 mm/yr) for the medial condyle and 0.032 mm/yr (SD: 0.230 mm/yr) for the lateral condyle. Cumulative linear wear at the 2-year follow-up interval was 0.207mm (SD: 0.565mm) and 0.068mm (SD: 0.484mm) for the medial and lateral condyles, respectively.

Linear PE wear measurements using mbRSA and Geomagic Studio resulted in 0.056mm/yr additional wear on the medial condyle than the lateral condyle. Large standard deviations for yearly wear rates and cumulative measurements demonstrate this method does not yet exhibit the accuracy needed to provide short-term in vivo wear measurement. Inter-patient variability from RSA examinations is likely a source of error when dealing with such small units of measure. Further analysis on patient age and body mass index may eliminate some variability in the data to improve accuracy. Despite high standard deviations, the results from this research are in proximity to previously reported linear wear measurements 0.052mm/yr and 0.054mm/yr. Linear wear analysis will continue upon completion of >100 patients, in addition to volumetric PE wear over the entire articulating surface.

Over the past 15 years metal on metal hip resurfacing (MOMHR) has seen a spectacular resurgence in utilization followed by near abandonment of the procedure. A select group of surgeons still offer the procedure to a select group of patients suggesting that there are benefits of MOMHR over total hip arthroplasty (THA). This is problematic for the following reasons:

1)

MOMHR does not lead to increased survivorship. The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the England and Wales National Joint Registry, from countries with high rates of utilization of MOMHR, both report significantly worse survivorship with MOMHR compared to all types of conventional THA. Risk factors for revision of resurfacing were older patients, females, smaller femoral head size, patients with developmental dysplasia, and certain implant designs.

In conclusion, it is relatively straightforward to oppose and argue against the use of hip resurfacings as they have worse outcomes in all National Joint Registries, produce metal ions with significant clinical consequences, are more invasive, are difficult to revise with subsequent inferior outcomes when compared to a conventional primary THA, and do not provide better function. These adverse features come with a premium price when compared to a conventional THA.

The trabecular metal Monoblock TKR is comprised of a porous tantalum base plate with the polyethylene liner embedded directly in the porous metal. An alternative design, the trabecular metal Modular TKR, allows polyethylene liner insertion into the locking base plate after base plate implantation, but removes the low modulus of elasticity that was inherent in the Monoblock design. The purpose of this study was to compare the fixation of the Monoblock and Modular trabeucular metal base plates in a randomised controlled trial.

Fifty subjects (30 female) were randomly assigned to receive the uncemented trabecular metal Monoblock or uncemented trabecular metal Modular knee replacement. A standard procedure of tantalum marker insertion in the proximal tibial and polyethylene liner was followed with uniplanar radiostereometric analysis (RSA) examinations immediately post-operatively and at 6 week, 3 month, 6 month, and 12 month follow-ups. The study was approved by the Research Ethics Board and all subjects signed an Informed Consent Form.

Twenty-one subjects received Monoblock components and 20 received Modular components. An intra-operative decision to use cemented implants occurred in 5 cases and 4 subjects did not proceed to surgery after enrollment. The clinical precision of implant migration measured as maximum total point motion (MTPM) was 0.13 mm (upper limit of 95% confidence interval of double exams). Implant migration at 12 months was 0.88 ± 0.64 mm (mean and standard deviation; range 0.21 – 2.84 mm) for the Monoblock group and 1.60 ± 1.51 mm (mean and standard deviation; range 0.27 – 6.23 mm) for the Modular group. Group differences in 12 month migration approached clinical significance (p = 0.052, Mann Whitney U-test).

High early implant migration is associated with an increased risk for late aseptic loosening. Although not statistically significant, the mean migration for the Modular component group was nearly twice that of the Monoblock, which places it at the 1.6 mm threshold for “unacceptable” early migration (Pijls et al 2012). This finding is concerning in light of the recent recall of a similar trabecular metal modular knee replacement and adds validity to the use of RSA in the introduction of new or modified implant designs.

Reference: Pijls, B.G., et al., Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties. Acta Orthop, 2012. 83(6): p. 614–24.

Modular total hip arthroplasty (MTHA) stems were introduced in order to provide increased intra-operative flexibility for restoring hip biomechanics, improving stability and potentially reducing revision risk. However, the additional interface at the neck-body junction provides another location for corrosion or mechanical failure of the stem. To delineate the mid term revision risk of MTHA stems, we examined data from the Canadian Joint Replacement Registry (CJRR) at the Canadian Institute for Health Information (CIHI).

Kinectiv, Profemur and Rejuvenate modular stems were identified from CJRR records submitted between 2004 and 2014. Revision status was determined by examining the discharge abstract database (DAD) also housed by CIHI, which collects information on all revisions, regardless of whether the procedure was submitted to CJRR.

A total of 2446 modular stems were identified with a mean follow up of 4.2 years (range 0 to 10). Their usage peaked in 2012 (the first year of mandatory CJRR form submission for BC, ON and MB), and dropped rapidly thereafter. A total of 155 (6.3%) were revised. This consisted of 5/301 Kinectiv (1.7%), 141/2050 ProFemur (6.9%), and 9/96 Rejuvenate (9.4%) stems. As a group, this falls below the National Institute for Clinical Excellence (NICE) guidelines of 95% survival at 10 years.

While MTHA stems were introduced to improve outcomes and reduce revision risk, our findings of a 6.3% revision risk at a mean follow up of 4.2 years does not appear to support this.

Total knee arthroplasty (TKA) has been shown to improve knee joint function during gait post-operatively. However, there is considerable patient to patient variability, with most gait mechanics metrics not reaching asymptomatic levels. To understand how to target functional improvements with TKA, it is important to identify an optimal set of functional metrics that remain deficient post-TKA. The purpose of this study was to identify which combination of knee joint kinematics and kinetics during gait best discriminate pre-operative gait from postoperative gait, as well as post-operative from asymptomatic.

Seventy-three patients scheduled to receive a TKA for severe knee osteoarthritis underwent 3D gait analysis 1 week before and 1 year after surgery. Sixty asymptomatic individuals also underwent analysis. Eleven discrete gait parameters were extracted from the gait kinematic and kinetic waveforms, as previously defined (Astephen et al., J Orthop Res., 2008). Stepwise linear discriminant analyses were used to determine the sets of parameters that optimally separated pre-operative from post-operative gait, and post-operative from asymptomatic gait. Cross-validation was used to quantify group classification error.

Knee flexion angle range, knee adduction moment first peak, and gait velocity were included in the optimal discriminant function between the pre- and post-operative groups (P<0.05), with relatively equal standardised canonical coefficients (0.567, −0.501, 0.565 respectively), and a total classification rate of 74%. A number of metrics were included in the discriminant function to optimally separate post-operative and asymptomatic gait function, including the knee flexion angle range, peak stance knee flexion angle, minimum late stance knee extension moment, minimum mid-stance knee adduction moment, and peak knee internal rotation moment (P<0.05). The mid-stance knee adduction moment had the largest standardised canonical coefficients in the function, and 89.5% of cases were correctly classified.

Separation of pre and post-operative gait patterns included only three parameters, suggesting that current standard of care TKA significantly improves only walking velocity, knee flexion angle range, and the peak value of the knee adduction moment. A number of gait metrics, which were included in the discriminant function between post-operative and asymptomatic gait, could benefit from further improvement either through rehabilitation or design. With almost 90% classification, separation of post-operative gait function from asymptomatic levels is significant. The consolidation of knee joint function during gait into single, discrete discriminant scores allows for an efficient summary representation of patient-specific (or implant-specific) improvement in gait function from TKA surgery.

Introduction

Debate over appropriate alignment in total knee arthroplasty has become a topical subject as technology allows planned alignments that differ from a neutral mechanical axis. These surgical techniques employ patient-specific cutting blocks derived from 3D reconstructions of pre-operative imaging, commonly MRI or CT. The patient-specific OtisMed system uses a detailed MRI scan of the knee for 3D reconstruction to estimate the kinematic axis, dictating the cutting planes in the custom-fit cutting blocks machined for each patient [1, 2].

The purpose of this study was to evaluate the correlation between post-operative limb alignment and implant migration in subjects receiving shape match derived kinematic alignment.

Introduction

The dual mobility design concept for acetabular liners is intended to reduce the risk of dislocation and increase range of motion, but the wear pattern of this design is unclear and may have implications in implant fixation. Additionally, the solid back cups do not have the option for supplementary screw fixation, providing an additional smooth articulating surface for the liner to move against. The objective of this study was to assess cup fixation by measuring implant migration. A secondary objective was to evaluate the mobile bearing motion after rotating the hip.

Introduction

Surgical techniques for implant alignment in total knee arthroplasty (TKA) is a expanding field as manufacturers introduce patient-specific cutting blocks derived from 3D reconstructions of pre-operative imaging, commonly MRI or CT. The patient-specific OtisMed system uses a detailed MRI scan of the knee for 3D reconstruction to estimate the kinematic axis, dictating the cutting planes in the custom-fit cutting blocks machined for each patient. The resulting planned alignment can vary greatly from a neutral mechanical axis. The purpose of this study was to evaluate the early fixation of components in subjects randomized to receive shape match derived kinematic alignment or conventional alignment using computer navigation. A subset of subjects were evaluated with gait analysis.

The proximal modular neck in total hip arthroplasty is not a new concept, but there has been resurgence in interest with multiple companies offering proximal modularity.

The proposed advantages of proximal modularity are 1) reduced impingement and subsequent reduced risk of ceramic liners, 2) reduced risk of dislocation and 3) fine tuning of leg length and offset. All of these surgical goals can be accomplished with careful surgical planning and technique, without introducing the risks associated with new technologies. Further, according to the Australian Orthopaedic Association 2014 Joint Replacement Registry annual report, the dislocation rate for components with femoral neck modularity is actually higher than fixed necks. As such, there are no advantages to modular necks.

Modular necks introduce new problems and risks. Modular necks introduce an additional source of corrosion and fretting, and specific systems have been recalled over such concerns. There are numerous case reports of dissociation and fracture at the junction. Fracture appears to be a significant issue in some systems. Retroversion of the neck to reduce the chance of dislocation is not necessarily benign with respect to implant fixation and stability, with RSA and registry data suggesting caution in the application of retroverted necks. Modular necks are difficult to dissociate when in vivo, negating the long-term benefit of modular conversion. Finally, proximal neck modularity significantly increases the cost of the implant, without any documented improvement in long-term outcome.

Modular necks offer limited advantages with significant potential downside. On balance of the evidence, the routine use of modular necks in primary total hip arthroplasty is difficult to justify.

Preoperative planning is important – an ounce of prevention is worth a pound of cure. It is perhaps useful to consider the process of preoperative planning in three areas: 1) the patient, 2) the hip, and 3) the operative environment.

The Patient - The patient must first be an appropriate candidate for surgery. By this, they should have confirmed arthritis of the hip by radiograph and physical exam and should have failed conservative management. They should have pain and/or physical disability that impair their activities of daily living. They should be fit and willing to undergo surgery. Their expectations of surgical outcome should be reasonable and the anticipated net clinical benefit of the procedure should outweigh the risks.

There are several patient variables that should be optimised prior to surgery. Blood glucose control in diabetics should be tightly controlled prior to surgery as failure to do so results in an increased risk of infection. Anemia should be ascertained in the history and diagnosed with a CBC if suspected. Reasons for anemia should be addressed and hemoglobin should be optimised preoperatively. Nutrition is important to reduce the risk of infection. Be aware of paradoxical malnutrition in the obese. Understand if the patient has an allergy to penicillin and what specifically the reaction is. Patients with a history that is not characteristic of an IgE mediated response should be offered a cephalosporin. The patient's risk of bleeding or clot as well as their tolerance of specific anticoagulants should be understood and planned for regarding the postoperative anticoagulant. Assess the patient for risk of dislocation.

The Hip - Assessment of the hip is important. An AP of the pelvis and lateral of the hip should be obtained in all cases. Any pelvic obliquity should be assessed in relation to leg length discrepancy, and, if necessary, a 3-foot standing x-ray should be obtained. Leg length and offset should be assessed carefully. Beware of the patient with the operative hip presenting as the longer leg as it is difficult to shorten a hip via THA and the net effect of the intervention is most often lengthening. Patients with low offset should be planned for carefully so that low offset components are available. Patients with high offset need corresponding high offset implants in order to avoid leg lengthening. The acetabulum should be assessed for true center of rotation and orientation, as well as for dysplasia or deficiency. The femur should be assessed for shape, offset and neck angle, as well as for any proximal or distal mismatch. Be prepared to remove hardware that will be in the way.

Template all your cases. The most experienced surgeons still template for THA. Have a Plan A and a Plan B for every case

The Operative Environment - The surgeon is ultimately in control of the operative environment. Make sure that the implants anticipated and sizes are available. I personally put them in the room before the case. Ensure that qualified assistants and nurses are available. Know in advance and communicate when high BMI patients are involved. Display the radiographs and anticipated plan and make sure the team is aware of it. Ensure that antibiotics and tranexamic acid (if not contra-indicated) are administered at a timely fashion. Tell the staff in the time out that traffic flow is important and should be reduced to a minimum. Plan to close one of the doors during the case. Make sure protective covering is available and worn, such as protective eyewear and hair covers.

The initial success of modern total hip arthroplasty can in large part be attributed to the reliable fixation of the femoral component with the use of acrylic bone cement. Early success with cement led to a common pathway of development in North America and the European countries. Much of the early to mid-term research concentrated on refinement of variables related to the methodology and technique of cement fixation. Scandinavian registries were subsequently able to report on improved survivorship with better cementing technique. The net effect has been standardisation towards a small number of cemented implants with good long-term outcomes representing the majority of stems implanted in Sweden, for example.

In North America, during the mid-term development of THA in the late 1980's, the term “cement disease” was coined and the cemented THA saw a precipitous decline in use, now to the point where many American orthopaedic residents are completing training never having seen a cemented THA. Modern uncemented femoral components can now claim good long-term survivorship, perhaps now comparable to cemented fixation. However, this has come at a cost with respect to the premium expense applied to the implant itself as well as lineage of failed uncemented constructs. The last several years have seen a proliferation of uncemented implants, usually at a premium cost, with no demonstrated improvement in survivorship. Osteolysis has not been solved with uncemented implants and cement disease has largely been recognised as a misnomer.

Long-term outcomes of cemented femoral fixation have consistently demonstrated excellent survivorship, even in the younger age group. Cemented stems allow for variable positioning of the stem to allow for better soft tissue balancing, without the need for proximal modularity. Cemented stems are more forgiving and fail less often secondary to a reduced incidence of intra-operative complications, such as peri-prosthetic fracture. Cemented stems tend to be less expensive and also have the advantage of adding antimicrobial agents into the cement. This is important in emerging markets. The next iteration of orthopaedic innovation driven by the emerging markets may indeed be back to the future.

Key Points: The initial success of total hip arthroplasty was based on cemented femoral fixation. Long-term outcomes in the United States demonstrate good results for cemented femoral fixation. Despite this, cemented fixation is not frequently used in the United States. Results from multiple national joint replacement registries demonstrate superior long-term performance of cemented femoral fixation. European countries, perhaps because of the excellent results in the national registries, use cemented femoral fixation more often than not. Cemented femoral fixation is cost neutral if not less expensive and allows for the addition of antimicrobials. Cemented femoral fixation is perhaps easier to perform as the component can be potted in a range of positions as opposed to the position being dictated by the femoral anatomy.

Total knee replacement is one of the most successful procedures in orthopaedic surgery. Although originally limited to more elderly and less active individuals, the inclusion criteria for TKA have changed, with ever younger, more active and heavier patients receiving TKA. Currently, wear debris related osteolysis and associated prosthetic loosening are major modes of failure for TKA implants of all designs.

Initially, tibial components were cemented all-polyethylene monoblock constructs. Subsequent long-term follow up studies of these implants have demonstrated excellent durability in survivorship studies out to twenty years. Aseptic loosening of the tibial component was one of the main causes of failure in these implants. Polyethylene wear with osteolysis around well fixed implants was rarely (if ever) observed.

Cemented metal-backed nonmodular tibial components were subsequently introduced to allow for improved tibial load distribution and to protect osteoporotic bone. Long-term studies have established that many one-piece nonmodular tibial components have maintained excellent durability.

Eventually, modularity between the polyethylene tibial component and the metal-backed tray was introduced in the mid-80s mainly to facilitate screw fixation for cementless implants. These designs also provided intra-operative versatility by allowing interchange of various polyethylene thicknesses, and to also aid the addition of stems and wedges. Other advantages included the reduction of inventory, and the potential for isolated tibial polyethylene exchanges as a simpler revision procedure. However, since the late 1980's, the phenomena of polyethylene wear and osteolysis have been observed much more frequently when compared with earlier eras. The reasons for this increased prevalence of synovitis, progressive osteolysis, and severe polyethylene wear remain unclear, but it is likely associated with the widespread use of both cementless and cemented modular tibial designs. Backside wear between the metal tray and polyethylene has been implicated.

Recent RSA studies comparing fixation of all-polyethylene to modular components has shown that their RSA migration patterns are superior and fixation is in fact better with the all-polyethylene construct. Further, in a recent meta-analysis, all-polyethylene components were equivalent to metal-backed components regarding revision rates and clinical scores.

The promise of modular tibial components affording a simple liner exchange to revise a knee has not borne out in the literature. Several studies have revealed that the effectiveness of isolated tibial insert exchange in revision TKR is of limited value. Isolated tibial insert exchange led to a surprisingly high rate of early failure. Tibial insert exchange as an isolated method of total knee revision should therefore be undertaken with caution even in circumstances for which the modular insert was designed and believed to be of greatest value.

Because of the modularity, extra materials, and extra processing, modular tibial components are significantly more expensive than all-polyethylene components.

The proximal modular neck in total hip arthroplasty is not a new concept, but there has been a recent resurgence in interest with multiple companies offering proximal modularity. Proponents of neck modularity suggest that inherent advantages include improved soft tissue balancing and decreased risk of dislocation, particularly in cases with difficult anatomy. Favorable results have been reported in DDH and other cases with excessive femoral anteversion, for example. There are numerous theoretical and published negative aspects of proximal neck modularity that should be considered. Modular necks can be an additional source of corrosion and fretting, and specific systems have been recalled over such concerns. There are case reports of dissociation and fracture at the junction. Fracture appears to be a significant issue in some systems. Retroversion of the neck to reduce the chance of dislocation is not necessarily benign with respect to implant fixation and stability, with RSA data suggesting caution in the application of retroverted necks. Modular necks are difficult to dissociate when in-vivo, negating the long-term benefit of modular conversion. Finally, proximal neck modularity significantly increases the cost of the implant, without any documented improvement in long-term outcome.

Modular necks offer limited advantages with significant potential downside. On balance of the evidence, the routine use of modular necks in primary total hip arthroplasty is difficult to justify.

There has been a renewed interest in surface replacement arthroplasty over the last decade, with the hope and expectation that this procedure would provide an advantage over conventional total hip arthroplasty, especially in the young, active patient. More specifically, the promises of surface replacement arthroplasty have been: 1) preservation of bone stock so that future revisions would be easier, 2) potential to be minimally invasive in their approach, 3) better functional outcomes because of the stability associated with a larger femoral head with potential associated proprioceptive advantages, and 4) improved survivorship. Unfortunately, these promises have not been realised.

Surface replacement arthroplasty does maintain more initial bone stock on the femur, but also tends to remove more bone initially on the acetabular side. Long term, it is the loss of acetabular bone stock that is more problematic from a reconstructive perspective. Further, the “simple” revision afforded in surface replacement arthroplasty has led to reports of inferior clinical outcomes, especially with respect to subjective complaints of pain.

Surface replacement arthroplasty is more invasive than conventional total hip arthroplasty as the femoral head is maintained and the window to the acetabulum is subsequently partially blocked. This is exacerbated by the fact that many of these patients are young active males.

There is no compelling evidence that surface replacement arthroplasty offers improved functional outcomes over conventional total hip arthroplasty, particularly when considering gait and proprioception. Some studies have in fact shown inferior outcomes. The concept of the larger femoral head in surface replacement arthroplasty providing increased range of motion and subsequent better function is flawed as it is the head-to-neck ratio that appears to be a more important determinant of outcome in this sense. Total hip arthroplasty generally has a more favorable ratio.

Surface replacement arthroplasty has inferior survivorship to conventional total hip arthroplasty, even when accounting for the younger age of this patient cohort. This finding is consistent across multiple national joint replacement registries. The outcomes and survivorship are particularly poor in females, with many authors now advocating that the procedure be reserved for males.

Surface replacement arthroplasty has introduced several new problems and mechanisms of failures, most concerning of which is the formation of pseudotumors in some patients. It is unclear as to who is at risk for this significant complication, and the ability to diagnose and treat this disorder is difficult and still in evolution. Likely associated is the significant elevation of metal ions in the serum and urine of some surface replacement arthroplasty patients. Neck fractures and loss of bone stock around the femoral implant have also been noted as problematic for these devices. Some of these problems have led to specific surface replacement arthroplasty systems being recalled.

Finally, surface replacement arthroplasties are premium products with associated increased costs, which, frankly, are not justified.

The initial success of modern total hip arthroplasty can in large part be attributed to the reliable fixation of the femoral component with the use of acrylic bone cement. Early success with cement led to a common pathway of development in North America and the European countries. Much of the early- to mid-term research concentrated on refinement of variables related to the methodology and technique of cement fixation. Scandinavian registries were subsequently able to report on improved survivorship with better cementing technique. The net effect has been standardisation towards a small number of cemented implants with good long-term outcomes representing the majority of stems implanted in Sweden, for example.

In North America, during the mid-term development of THA in the late 1980's, the term “cement disease” was coined and the cemented THA saw a precipitous decline in use, now to the point where many American orthopaedic residents are completing training never having seen a cemented THA. Modern uncemented femoral components can now claim good long-term survivorship, perhaps now comparable to cemented fixation. However, this has come at a cost with respect to the premium expense applied to the implant itself as well as lineage of failed uncemented constructs. The last several years have seen a proliferation of uncemented implants, usually at a premium cost, with no demonstrated improvement in survivorship. Osteolysis has not been solved with uncemented implants and cement disease has largely been recognised as a misnomer.

Long-term outcomes of cemented femoral fixation have consistently demonstrated excellent survivorship, even in the younger age group. Cemented stems allow for variable positioning of the stem to allow for better soft tissue balancing, without the need for proximal modularity. Cemented stems are more forgiving and fail less often secondary to a reduced incidence of intraoperative complications, such as periprosthetic fracture. Cemented stems tend to be less expensive and also have the advantage of adding antimicrobial agents into the cement. This is important in emerging markets. The next iteration of orthopaedic innovation driven by the emerging markets may indeed be back to the future.

The proximal modular neck in total hip arthroplasty is not a new concept, but there has been a recent resurgence in interest with multiple companies offering proximal modularity. Proponents of neck modularity suggest that inherent advantages include improved soft tissue balancing and decreased risk of dislocation, particularly in cases with difficult anatomy. Favourable results have been reported in DDH and other cases with excessive femoral anteversion, for example. There are numerous theoretical and published negative aspects of proximal neck modularity that should be considered. Modular necks can be an additional source of corrosion and fretting, and specific systems have been recalled over such concerns. There are case reports of dissociation and fracture at the junction. Fracture appears to be a significant issue in some systems. Retroversion of the neck to reduce the chance of dislocation is not necessarily benign with respect to implant fixation and stability, with RSA data suggesting caution in the application of retroverted necks. Modular necks are difficult to dissociate when in vivo, negating the long-term benefit of modular conversion. Finally, proximal neck modularity significantly increases the cost of the implant, without any documented improvement in long-term outcome.

Modular necks offer limited advantages with significant potential downside. On balance of the evidence, the routine use of modular necks in primary total hip arthroplasty is difficult to justify.

Conventional total knee arthroplasty aims to place the joint line perpendicular to the mechanical axis, despite the fact that the normal knee is inclined approximately 3 degrees, resulting in a medial proximal tibial angle of 87 degrees. The goal of a neutral mechanical axis is based largely on historical biomedical studies and the fact that it is easier to make a neutral tibial cut with conventional jigs and the eye. In order to balance the flexion and extension gap to accommodate a neutral tibial cut, in most patients, asymmetrical distal and posterior femoral cuts are required. The resulting position of the femoral component could be considered to be “mal-rotated” with respect to the patient's soft tissue envelope. Soft tissue releases are often required.

The target of neutral mechanical axis, or “straight and narrow,” represents a compromise position with respect to the kinematics of the knee. Neutral mechanical alignment may not confer any befits with respect to survivorship but dissatisfaction rates are high globally, with approximately 20% of patients being dissatisfied after total knee arthroplasty in multiple studies.

Computer assisted surgery and shape matching allow for consideration of placing total knee components to match an individual's anatomy, as opposed to forcing the knee into an unnatural neutral mechanical alignment.

Multiple large studies, including from national registries, have demonstrated that satisfaction rates after total knee arthroplasty are limited to approximately 80%. That is, surprisingly, one in five patients are not satisfied. Furthermore, satisfaction rates have not improved over the last decade.

The strongest correlates to satisfaction are firstly the relief of pain and secondly the improvement in physical function. However, satisfaction may be disparate to other reported subjective outcomes. It is a nebulous outcome metric.

The largest risk for patient dissatisfaction is unmet expectations post total knee arthroplasty.

Keeping the above risks in mind, an effective strategy to improve satisfaction rates likely should concentrate on reducing pain both immediately post-operatively and long term, improving function of the knee, perhaps through a patient specific alignment approach, and most importantly, by understanding and counseling patients regarding expectations pre-operatively.

Introduction

Locking compression plate (LCP) fixation is an established method of treatment of distal third tibial fractures. No biomechanical data exists in the literature regarding their use. Additionally no data exists on the biomechanical advantage of locking screw fixation over non-locking screw fixation for these fractures. In this study the axial and torsional stiffness, axial load to failure and fatigue performance of a 3.5 mm LCP medial distal tibia Synthes plate was evaluated for the stabilisation of distal third tibial fractures. Additionally the performance of the plate in uni and bicortical locked mode as well as non-locked mode was evaluated.

Several factors have been identified that may affect outcome after total knee replacement (TKR). We performed a systematic review of studies that looked at the association of pre-operative factors and outcome after primary total knee replacement for osteoarthritis.

All study types that investigated TKR for osteoarthritis were considered except retrospective case-series. Studies that included patients undergoing revision TKR were excluded if they did not provide separate results for primary and revision knee replacement. Any patient factor that was measured in the pre-operative period was included.

The factors measured included age, sex, race, income, body mass index (BMI), medical or joint co-morbidity, level of education, disease specific scores and their subcategories and general health scores. Studies that recorded outcome measures were only included if evidence of validation for use after total knee replacement was available.

We identified 590 studies purporting to evaluate TKR for OA. Of these, 25 studies were retrieved for in-depth consideration and 10 were found to meet the inclusion criteria. Most of these were cohort studies that used some form of regression analysis.

The results showed that the strongest and most consistent correlations were between pre-operative pain scores, pre-operative function scores, co-morbidity and post-operative function scores. Age, gender and level of education were not significant predictors of outcome. However, even the best models could only predict 36% of the variance in outcome.

Understanding which factors influence outcome the most will be of great benefit to patients and those who plan and deliver healthcare.

Thromboprophylaxis remains a controversial issue and many disagree about the optimum method or even if it is required at all.

We present a new method of performing meta-analysis incorporating studies with both experimental and observational study designs. We have developed a model that compares study cohorts of several different methods of thromboprophylaxis with a simulated matched control group whose variance helps to adjust for bias. This allows meaningful comparisons between studies and treatments that have not been directly compared.

We performed a systematic review of the literature from 1981 to October 2004. Studies where more than one method of prophylaxis was used were excluded from analysis. For each individual method of prophylaxis, data was extracted, combined and converted to give estimates of the rates of symptomatic, proximal DVT, fatal PE and major bleeding events. We identified 1242 studies of which 203 met the inclusion criteria for further analysis. This represented the results of over fifty thousand studied patients. We expressed the results for the different prophylactic methods as odds ratios compared to no prophylaxis.

All methods showed a beneficial effect in reducing VTEs apart from stockings and aspirin which showed an increase in the number of PE events. These results are particularly interesting when viewed from the standpoint of an individual NHS hospital trust that performs around 500 hip and knee replacements per year. Over a 5 year period, the more effective methods of prophylaxis prevented between 15 and 40 symptomatic DVTs and up to 3 fatal PEs compared to no treatment. However, they cause between 8 and 40 more major bleeding events. We do not know the proportion of these major bleeding events that are fatal.

Introduction: Surgical fixation of intra-articular distal femoral fractures has been associated with nonunion & varus collapse. The soft tissuestripping associated with this fracture andthe surgical exposure have been factors associated with delayed union & infection. The limited soft tissue exposure has been lauded the as a solution to this fracture. However, it has occurred with the new fixation as well.(Locked Plate)

Aims: This study is an attempt to look at the fixation. Does the LISS system improve the results of this difficult fracture? Is there truly a difference in the outcome of this fracture utilizing the Locked plate system or is the percieved difference due to the surgical mini invasive approach.

Patients & Methods: One hunderd & forty patients were screened, only 53 were randomized and fixed in six academic centers over 5 years. All C3 fractures were excluded as they were felt not to be treatable by the DCS device, but they were treated appropiately. 35 females and 18 males were included in the study and randomized appropiatley.

Results: Fifty-three patients were randomized, 28 had the LISS implant and 25 had the DCS utilized. There were 3 nonunions in the LISS group plus two patients with early loss of reduction that required reoperation in the early post operative period. One patient developed arthrofibrosis requiring arthroscopic release and subsequently the implant failed necessitating refixation. In the DCS group, only one nonunion reported & required second surgery. This translated to a reoperation rate of 21% in the LISS group compared to 4% with DCS.

Conclusion: This prospective randomized multicentre trial showed a difference when comparing the LISS to the DCS in the supracondylar distal femur fractures.

Hip resurfacing arthroplasty has become a popular treatment option for younger active patients. The early published results from designing surgeons/centers have been favourable. We undertook a prospective multi-center trial to determine the outcome of hip resurfacing arthroplasty at independent centers. The clinical, radiographic and functional results were assessed.

A prospective IRB approved study was initiated in July 2003 to assess the outcome of hip resurfacing arthroplasty using a contemporary design implant. (Conserve Plus - Wright Medical Technology) Disease specific (Harris Hip Score/WOMAC) and global (Rand self assessment index) outcome measures were used. Radiographs were reviewed for component position and migration as well as any signs of lysis or loosening. Complications and re-operations were recorded.

A total of one hundred and eighty-eight patients have been enrolled in the study to date. One hundred and four patients have a minimum one year follow-up and forty-six patients have a minimum two year follow-up. Mean Harris Hip Scores (pre-op, one year, two years) were fifty-five, eighty-nine and ninety-one. Mean WOMAC pain scores were forty-seven, ninety and ninety. Mean WOMAC stiffness scores were forty, seventy-eight and eighty-two. Mean WOMAC function scores were forty-six, eighty-seven and eighty. RAND physical function mean scores were thirty-three, seventy-six and seventy-six and the RAND physical limitations mean scores were nineteen, sixty-seven and seventy-five. Radiographic analysis showed average cup abduction to be forty-six degrees (range twenty-six to sixty-three). Average femoral stem position was one hundred and thiry-eight degrees (range one hundred and eighteen to one hundred and fifty-seven). Nine patients have been revised to date (4.8%). Four for acetabular loosening, two for neck fracture, one for femoral loosening, one for impingement and one for persistent pain. There have been eight other patients requiring re-operation without revision. Medical complications occurred in fifteen patients.

Early results have demonstrated a good return of function in patients with hip resurfacing arthroplasty. A high early revision rate (4.8%) was seen in our study. Technical factors appear to be the main contributor to the high early complication rate. Hip resurfacing is associated with a steep learning curve. We continue to utilise hip resurfacing in select patients but recommend caution for those who are new to the technique.

The purpose of this study was to characterise the neuromuscular patterns associated with different severities of knee osteoarthritis (OA).

Forty-five patients with moderate OA, thirty-seven with severe OA and thirty-eight asymptomatic controls underwent a complete gait analysis with only the electromyographic (EMG) findings presented in this abstract. Severity levels were established through the Kellgren-Lawrence radiographic grading system, functional ability, and those classified with severe OA were tested within one-week of total knee replacement surgery. All OA patients had medial joint involvement. Subjects walked along a five-meter walkway a total of five times at a self- selected walking speed. Muscle activation patterns of the vastus medialis and lateralis, medial and lateral hamstring and medial and lateral gastrocnemius were recorded and normalised to maximum voluntary isometric contractions. All EMG waveforms were analyzed for group differences using PCA [1] followed by an ANOVA (group by muscle) for the PCA scores for each muscle group. These scores reflect both magnitude and shape changes.

The control group was significantly younger (53.3 ±9.5 yrs) and lighter (77.5 ±14.5 Kg) than the patient groups (Moderate =59.8 ±8.0 years and 94.2 ±19.2 Kg and Severe = 63.1 ±7.9 yrs and 95.8 ±14.6Kg). The severe OA group walked significantly slower (0.9 ±0.2 m/s) than the asymptomatic (1.3 ±0.1) m/s) and the moderate OA (1.2 ±0.2 m/s) groups. The PCA analysis of the EMG waveforms revealed statistically significant differences (P< 0.05) in patterns among the three groups and between muscles within the three muscle groups tested.

The neuromuscular differences found among groups during gait demonstrate that the role of the musculature surrounding the knee is altered slightly in those with moderate OA and altered drastically in those with end-stage OA compared to asymptomatic subjects, reflecting a progression. The differences are consistent with the severe group adopting a co-activation strategy of agonist and antagonists, more lateral activation and a reduction in plantar flexion during push off. These are consistent with strategies to increase dynamic stability and reduce medial joint loading. The moderate OA group illustrates a trend toward adopting this pattern but with only very subtle differences from asymptomatic subjects as has been previously reported. These neuromuscular alterations have implications with respect to muscle function and may assist in defining severity.

The purpose of this study was to assess the effect of total knee arthroplasty (TKA) on the gait symmetry of patients suffering from osteoarthritis. TKA is an effective method of relieving pain and restoring function but many established outcome measures are subjective and based on patient self-report. This study used clinical gait analysis with the Walkabout Portable Gait MonitorTM (WPGM) to describe pre and post-operative function in a more objective manner.

The WPGM is a tri-axial arrangement of accelerometers that a subject wears around the waist, approximating the position of the center of mass (COM). Twenty-one TKA patients underwent a standardised WPGM assessment (a walk at a self-selected speed along a 50m hospital corridor) and completed the WOMAC and SF-36 subjective questionnaires preoperatively and three years after surgery. Data was recorded at 200 Hz for approximately twenty to twenty-five seconds. Automated Fast Fourier transformations (FFT) of the displacement data in three axes yields data on the ‘repeating irregularities’ that result from musculoskeletal injury or compensatory mechanisms and provides three clinically significant ratios Surge (asymmetry in the gait cycle in the forward direction), Lurch (side to side displacements that becomes asymmetrical with unilateral pathology) and Functional Leg Length Difference (FLLD) (asymmetry in vertical displacement during the gait cycle).

Paired t-tests show that mean Surge (p< 0.006), FLLD (p< 0.0001) and Lurch (p< 0.008) were reduced following TKA for treatment of osteoarthritis. This is evidence that the asymmetry of gait was successfully reduced and subsequently overall gait was improved following surgical intervention. Patients’ WOMAC and SF-36 questionnaires showed significant improvements in patient pain, stiffness and physical function post-operatively (p’s< 0.01).

Advantages of using the WPGM in addition to standard patient self-report questionnaires include the ease of testing, quick analysis and ability to detect musculo-skeletal health changes that might otherwise be masked by extraneous variables. A small subset of patients did not realise significant improvement in gait parameters post-operatively. On closer inspection, these patients had near normal gait patterns pre-operatively. This suggests the WPGM has great potential for objectively prioritizing patients waiting for TKA and assessing post-operative outcome.

To compare strength and recruitment of periarticular knee muscles in subjects with severe osteoarthritis (OA) one week before and one year after a total knee replacement (TKR).

Twenty-eight subjects, mean age = 64.5 years, with severe knee OA performed maximum voluntary isometric contractions for six exercises designed to test knee flexor and extensor and plantarflexor muscle strength. Torque and surface electromyograms (EMG) from the lateral and medial gastrocnemius, lateral and medial hamstring, vastus lateralis and medialis and rectus femoris muscles were recorded. Exercises included knee extension and flexion at mid range (45°) and closed-pack (15°) positions and plantarflexion with knee extended. Subjects completed WOMAC questionnaires to assess function. Custom software written in Matlab version 7.0.4 was used to calculate muscle torque and process EMG data. Paired Student t-tests (alpha = 0.05) were used to detect significant differences between pre-test and post-test data. Statistical analyses were performed in Minitab.

Post-TKR torque increases ranged from 1.6% to 19.7%, but only knee extension with the subject’s knee at 45° showed a statistically significant (p< 0.05) increase (74.3 ± 29.5 Nm to 86.1 ± 28.5 Nm). EMG amplitudes increased for the quadriceps and hamstring muscles (p< 0.05) post TKR, but the relative contributions of each muscle did not change, excepting rectus femoris. Within each exercise, some subjects increased their torque, but almost as many decreased their post-TKR torque. WOMAC scores for pain, stiffness, and function improved significantly (p< 0.05) by one year after TKR.

TKR surgery is becoming more common as a treatment for OA, but few studies have examined muscle strength before and after, which impacts patient function and the lifespan of the implant. By one year post-TKR subjects reported significant decreases in pain and stiffness, and significant improvements in function. This is consistent with the literature. Half of the subjects decreased in muscle strength to levels lower than pre-surgery. The results provide evidence that post-TKR management must address muscular strength deficits in addition to subjective assessments of improved symptoms to measure success.

The purpose of this investigation was to determine the changes in frontal plane kinetics (loading) and neuromuscular responses pre and post unilateral total knee replacement surgery (TKR) during walking.

Thirty-four patients with severe knee osteoarthritis (within one week prior to TKR surgery) underwent a gait analysis. 3D kinematics, kinetics and electromyographic (EMG) recruitment patterns from seven lower limb muscles (vastus medialis and lateralis, medial and lateral hamstrings, medial and lateral gastrocnemius and rectus femoris) were recorded while walking at their self-selected walking speed. This was repeated one-year post-TKR surgery. EMG data were normalised to maximum voluntary isometric contractions and the knee adduction moment was normalised to body mass. All waveforms were normalised in time to 100% of the gait cycle. Principal component analysis was applied to the pre-and post-TKR waveforms. T-tests and ANOVA models tested pre-post TKR differences and differences between muscles.

At pre-TKR, the average age of the subjects was 66 ± 6.6 years and there were no statistically significant differences between pre and post TKR measures of mass (90Kg). The walking velocity significantly (p< 0.05) increased from the pre-TKR (.9 ±.23 m/s) to the post-TRK (1.07 ±.21 m/s). There were statistically significantly (p< 0.05) magnitude and shape differences between the pre-and-post-TKR waveforms for the knee adduction moment and the EMG waveforms. In general there were reduced adduction moments and EMG amplitudes for quadriceps and hamstrings post-TKR.

The results show improved function with the increased walking velocity, but more important are the differences with respect to joint loading and muscle function. The decreased knee adduction moment post-TKR reflects reduced loading on the medial compartment of the prosthesis. The alterations in the quadriceps and hamstrings illustrate that post-TKR the muscles no longer co-activate at high percentage of their maximum during the majority of the gait cycle as was shown in the pre-TKR waveforms. Finally the high lateral hamstring activity found pre-operatively was reduced resulting in a more balanced activation between the medial and lateral sites post operatively. These post-TKR changes have implications for improved joint loading, reduced risk of muscle fatigue and decreased metabolic costs associated with walking.

Tumour cells induce osteolysis by producing multiple cytokines that indirectly activate osteoclasts; this process is dependent upon surface expression of a protein known as “receptor activator of nuclear factor kB ligand (RANK-L)” on osteoblasts (OB), and subsequent osteoclast (OC) interaction via surface expressed RANK. Harnessing this RANK-RANK-L interaction has potential for reducing cancer osteolysis. The aim of this study is to prevent tumour-induced osteolysis by ablating osteoclast activation.

A monocyte cell line (RAW 264.7) was grown in vitro in the presence of RANK-L and recombinant mouse macrophage colony stimulating factor (rmM-CSF) to produce osteoclasts. Tumour-associated cytokines IL-1a, TNF-a, and IL-6, and the regulatory cytokine osteoprotegerin (OPG) were added to assess osteoclast cell number (cytospin analysis with TRAP staining) and function (resorption pit number on dentine slices). Short interfering sequence of RNA directed towards RANK receptor (RANK RNAi) was used to assess the effect of abrogating RANK-RANK-L signaling in this pathway.

Tumour-associated cytokines failed to significantly alter OC cell number or function in the model tested. When TNF-a, IL-1a, and IL-6 were added together, the effect on OC function was variable, without a clear trend towards OC activation. The addition of the cytokine OPG revealed a trend towards reducing OC function, but this did not reach statistical significance. RANK RNAi also revealed a trend towards reducing OC function in the presence and absence of tumour-associated cytokines.

Tumour associated cytokines failed to enhance OC function using the monocyte cell line RAW 264.7. Both OPG and RANK RNAi revealed a trend towards reducing OC function, although further testing is required to confirm this observation. Future direction with include analysis of fresh bone marrow-derived OC, which may be more appropriate for this model.

Perioperative delirium (POD) is not uncommon in orthopaedics. We prospectively followed one hundred and thirty-two arthroplasty patients and thirty hip fracture patients using POD as the outcome. Patient interviews, chart reviews and application of the Mini Mental Status Exam (MMSE) were used to identify risk factors for POD. Having two or more risk factors or low scores on the MMSE was predictive of POD. Development of POD significantly increased patient length of stay. It may be possible to identify “at risk” patients for POD and intervene preoperatively so as to improve outcomes.

The purpose of this study was to identify risk factors for delirium in arthroplasty and hip fracture patients among routinely collected data.

Risk factors for perioperative delirium (POD) in arthroplasty and hip fracture patients can be identified. In elderly hip fracture patients, cognitive impairment as measured by preoperative performance on the Mini Mental Status Exam (MMSE), appears to have a strong association with development of POD.

As delirium is associated with adverse outcomes, it may be possible to target interventions to reduce the incidence of POD in patients who are at greatest risk, and potentially improve outcomes.

The incidence of POD was lower in elective orthopaedic patients (13.6%) than in fracture patients (40%). Among elective arthroplasty patients, having two or more risk factors was associated with an eight-time increase in the incidence of delirium and increased length of stay (9.5 days versus six days). Length of stay was considerably higher in hip fracture patients with two or more risk factors (18.9 days vs. 9.9). A low score on the MMSE was the best predictor of developing POD in hip fracture patients.

We recorded age, sensory impairment, functional status, history of previous POD, and use of alcohol or benzodiazepines, in one hundred and thirty-two hip or knee arthroplasty patients, and thirty elderly patients awaiting surgery for hip fracture. All patients completed the MMSE preoperatively.

Delirium was documented prospectively by the Confusion Assessment Method.

POD has an adverse effect on outcomes and is not uncommon in orthopaedics. Risk factors have been identified that could be used for preoperative screening and intervention.

A retrospective chart review of three hundred and eighty-seven PFC© and PFC Sigma© total knee replacements performed by a single surgeon over a seven-year period was completed. During that time, there were fourteen revisions for polyethylene failure. Survival analysis indicates a failure rate of 8%. Previous reports in the literature of the survivorship of the original PFC design demonstrated a five percent failure rate over a ten-year period. Gamma sterilization in air of the PFC polyethylene and the locking mechanism of the articular surface have been implicated in premature wear and failure of this prosthesis.

The purpose of this study was to determine the revision rate due to polyethylene failure for a cohort of PFC© and PFC Sigma© total knee prostheses implanted by a single surgeon.

The early to mid-term revision rate (8%) of the PFC© and PFC Sigma© polyethylene component appears to be abnormally high. The early failure of this tibial articulating component may be related to faulty polyethylene inserts and/or failure of the locking mechanism. Attention to preparation of the polyethylene and locking mechanism of the tibial insert may need to be addressed.

Three hundred and eighty-seven total knees were performed in a cohort of three hundred and twenty-two patients (64% female; mean age = 70 ± 9 years; mean BMI = 31 ± 6). Mean follow-up was forty-one months (± 23). The revision rate at seven years was 8%. At time of revision most prostheses were solidly fixed with no overt signs of loosening of the tibial component. However, there was movement of the polyethylene in the tibial tray in both the mediolateral and AP direction with obvious surface and backside wear. Marked synovitis with evidence of osteolysis, particularly on the femoral side, was also noted. Bone graft was required in almost all cases.

A retrospective chart review was conducted for PFC© and PFC Sigma© total knee systems implanted by a single surgeon between 1995 and 2002. Collected data included patient demographics, age, gender, body mass index, and reason for surgery. The amount of synovitis and osteolysis was documented during revision surgery.

During the routine follow-up of this cohort, patients were identified with marked synovitis and increasing pain in the knee even though there was no gross mal-alignment of the tibial or femoral component.

Data from the wait list management system and hospital databases was used to develop a computer model simulating the resource requirements required during patient flow into, through, and out of orthopaedic surgery for TKR, THR and knee arthroscopy. Results from the simulation model suggested that inpatient beds, rather than operating room time was the constraining resource and an extra twenty-five beds and 30% more OR time would stabilize and subsequently reduce the wait time at the institution. In addition, simulations suggested that pooling surgeon wait lists reduced patient wait time. Simulation models are an effective resource allocation decision-making tool for orthopaedic surgery.

To develop and implement a wait list simulation model to analyze the existing system and guide resource allocation decision-making at the QEII Health Sciences Centre.

The simulation model suggests an immediate increase in inpatient surgical beds from sixty-six to ninety-one followed by a 30% increase in OR time in thirty months to stabilize and subsequently reduce patient wait times.

Simulations showed that pooling surgeon waiting lists reduced patient wait time, however, dividing orthopaedics resources among two facilities had little effect. Adding twenty-five beds reduced the wait time growth rate substantially, but not to zero, while adding fifty beds reduced the wait time growth rate to zero. Adding twenty-five beds and 30% more OR time had the same result as adding fifty beds.

Simulation models can be effective for guiding resource allocation decisions for orthopaedic surgery. Recommendations based on the wait list simulation model results were immediately adopted by the provincial Department of Health.

A simulation model of the orthopaedic surgery system at the institution was created using Arena simulation software. Empirical statistical distributions were developed based on Wait List Management System and administrative data to assign values to model variables: number of patient referrals seen per office session; proportion of patient referrals actually converting to a surgery booking; type of procedure required; admission status; time required for surgery; and length of stay. The model was tested, and validated. Several scenarios with adjusted levels of resources variables (OR time, number of surgeons, length of stay, inpatient bed availability) were simulated.

Purpose: To assess patients quality of life, pain, and functional limitations with with endstage ankle arthritis (EAA) and compared this to a similar cohort of patients with endstage hip arthritis (EHA).

Methods: Preoperative data (Short Form SF36) was collected prospectively from patients (n=130) with end stage ankle arthritis and compared to a similar cohort of patients (n=130) with end stage hip arthritis. Patients with ankle arthritis were registered in the Canadian Orthopedic Foot and Ankle Society (COFAS) multi-center study investigating the clinical outcome of ankle arthroplasty and fusion and patients with hip arthritis were randomly selected from the Halifax Joint Replacement Registry Database.

Results: All symptom and functional SF36 subscales for patients with EAA or EHA, were approximately two standard deviations below normal population scores. All differences between ankle and hip SF36 subscales scores were less than 4 points (40% of STD) in both direct and adjusted comparisons. A direct comparison of SF36 scores revealed that patients with EAA had significantly worse mental health according to the SF36 Mental Component Summary Score (MCS) (p= 0.0059), physical limitations with work and daily activities - role physical score (p= < 0.0001), and general health (p= 0.0004). Patients with EHA reported poorer physical function (p= 0.0007) although the Physical Component Summary Score (PCS) for the SF36 was not significant (p= 0.0510). Total Summary SF36, Physical Component Summary (PCS), bodily pain, vitality, role-emotional, social functioning, and mental health subscales were all not significantly different between cohorts (p> 0.05).

Conclusions: Patients with EAA have devastating losses of quality of life, which are comparable to patients with EHA. These findings suggest that increased resources should be directed towards alleviating the severe pain and disability associated with ankle arthritis.

The demand for knee arthroplasty (TKR) is increasing yet there are no established criteria for prioritizing patients. We investigated surgeon inter-observer reliability and factors that influenced their prioritization of patients by having three surgeons each independently consult on twelve randomly selected patients waiting for TKR. Surgeons had high reliability and were most influence by the patient’s pain and gait pattern when assigning priority. Surgeon assigned priority also correlated with common subjective outcome metrics. Formalized gait assessment may allow for more objective prioritization of patients waiting for TKR.

The purpose of this study was to investigate the inter-observer reliability of surgeons assessing the priority of patients waiting for elective total knee arthroplasty (TKR) surgery, and to assess the discriminative methodology surgeons employ when assessing patients.

Surgeon’s can reliably assign a priority to their patients waiting for TKR. Surgeons generally consider the patients pain and gait pattern when assigning priority.

Wait lists for elective TKR are increasing and the demand will continue to grow. Objective criteria for prioritizing patients would allow for rational delivery of limited surgical resources.

Surgeons have high inter-observer reliability when assigning patient priority (ICC = 0.86). Pain and gait pattern have a significant impact on the surgeon’s assessment of priority (p=0.25 and p< 0.001, respectively). The oxford twelve most closely correlated to the surgeon’s prioritization (r=0.80).

Twelve patients waiting for TKR were randomly selected from three surgeons wait lists. Each surgeon independently examined all twelve patients and recorded their assessment of the patient’s acuity (priority) on a visual analogue scale. The impact of various aspects of the patient’s presentation on the surgeon’s assessment, such as pain control, function, gait, joint contracture and radiographic appearance, were recorded. All patients completed the SF-36, Oxford twelve and WOMAC questionnaires. Linear regression and Intra-Class Correlation Coefficients were used to assess the data.

Through the complex patient-surgeon interaction during a standard consultation, surgeons are able to prioritize their patient’s with high reliability. Improved objective metrics for prioritizing patient’s may be possible by more formalized methods of gait assessment.

Purpose: The Advance Medial Pivot (MP) knee has higher congruency and postulated different kinematics than traditional posterior stabilized knee implants. This could lead to increased micromotion at the tibial component/bone interface potentially resulting in premature loosening. To investigate the stability of the MP knee we used maximum total point motion (MTPM) as determined with RSA to compare micromotion at the tibial component/bone interface between the Advance MP and PS knees.

Methods: A power calculation determined that a minimum sample size of 40 (20/group) was required. Sixty-six patients (48 females) with primary osteoarthritis of the knee were randomized to receive the Advance MP (n=36) or PS (n=30) knee. Three experienced knee surgeons followed a standardized surgical technique (PCL resection, patella resurfacing, RSA bead placement in polyethylene and tibia) and post-operative protocol (CPM as tolerated, no drains, WBAT). SF-36, WOMAC, PCS, KSCRS were administered to all patients pre-operatively and at 6, 12 and 24 months post-operatively and BMI was recorded. Within 4 days of surgery and at 6, 12 and 24 months post-operatively patients underwent bi-planar x-rays.

Results: Fifteen patients were lost to follow-up (2 infections, 1 death, 2 dropped out, 10 lost due to technical issues). There was no difference in MTPM between groups at 2 years. Physical function was better (p< 0.03) for the PS group at 6 months but there was no difference at 1 year.

Conclusions: There was no difference in MTPM between groups at 2 years post-op. The Advance PS knee appears to result in earlier post-operative improvements in physical function. The altered kinematics and increased congruency of the Advance MP knee does not seem to alter the forces at the tibial component/bone interface and therefore does not appear to be more prone to migration and premature aseptic loosening.

Funding : Other Education Grant

Funding Parties : Unrestricted grant from Wright Medical Inc.

Purpose: The Less Invasive Stabilization System (LISS), Dynamic Condylar Screw (DCS) and Condylar Buttress Plate (CBP) are three common fixation methods for supracondylar femur fractures. The DCS and CBP are compression plates while the LISS uses locking screws to transfer load from bone to plate without compression. We developed a study to determine if the theoretical biomechanical advantages of the LISS would be evident in laboratory testing.

Methods: Identical AO type C fractures were created in eighteen composite femurs and fixed with either LISS, CBP, or DCS (6 each). Roentgen Stereophotogrammetric Analysis (RSA) was used for analysis. Reference markers were implanted into each bone segment. Biplanar x-rays were taken to give a three-dimensional representation of the fracture. The femurs were loaded axially in an Instron 1350 and subjected to cyclic loading (50kg ± 25 for 50000 cycles). After loading, the bones were x-rayed to determine relative motion between fracture segments. To examine inducible displacement under static loading, the femurs were x-rayed in an unloaded and loaded (50 kg) condition. Again, RSA was used for analysis.

Results: RSA-CMS software was used to analyze relative motion between the bone segments. After cyclic loading, the condylar buttress plate showed significantly more permanent deformation between the medial condyle and shaft of the femur than the DCS or LISS. Under static load, the LISS showed greater displacement than the other devices between the medial condyle and shaft, and between the lateral condyle and shaft.

Conclusions: The LISS demonstrated less permanent deformation but greater inducible deformation between the medial femoral condyle and femoral shaft, compared to the DCS and CBP. The results were statistically significant. These results may have clinical implications regarding the choice of fixation devices for this difficult fracture pattern.

Funding : Other Education Grant

Funding Parties : Capital Health Research Grant