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.