Aims

To compare the in vivo long-term fixation achieved by two acetabular components with different porous ingrowth surfaces using radiostereometric analysis (RSA).

HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques.

Remelted, single annealed and sequentially annealed retrieved HXLPE acetabular liners with in vivo times greater than 4.5 years were obtained from our implant retrieval laboratory. All retrieved liners underwent an identical sanitation and storage protocol. For mechanical testing, a total of 55 explants and 13 control liners were tested. Explant in vivo time ranged from 4.6 – 14 years and ex vivo time ranged from 0 – 11.6 years. Rim mechanical properties were tested by microindentation hardness testing using a Micromet II Vickers microhardness tester following ASTM standards. A subset of 16 explants with ex vivo time under one year along with five control liners were assessed for oxidation by FTIR, crystallinity by Raman spectroscopy, and evidence of microcracking by SEM.

No significant difference in in vivo or ex vivo was found between thermal stabilization groups in either set of explants studied. In the mechanically tested explants, there was no significant correlation between in vivo time and Vickers hardness in any thermal stabilization group. A significant correlation was found between ex vivo time and hardness in remelted liners (r=.520, p = .011), but not in either annealed cohort. ANCOVA with ex vivo time as a covariate found a significant difference in hardness between the thermal free radical stabilization groups (p 0.1) was found in retrieved remelted (25%), single annealed (100%) and sequentially annealed (75%) liner rims. Crystallinity was increased in the subsurface region relative to control liners for both annealed, but not remelted, liner rims. Hardness was increased in oxidized rims for both annealed cohorts but not in the remelted cohort. Microcracking was only found along the surface of one unoxidized remelted liner rim.

Mechanical properties were reduced at baseline and worsened after in vivo time for remelted HXLPE liner rims. Rim oxidation was detected in all groups. Oxidation was associated with increased crystallinity and hardness in annealed cohorts, but not remelted liners. Increased crystallinity and oxidation do not appear to be directly causing the worsened mechanical behavior of remelted HXLPE liner rims after extended in vivo time.

While Oxidized Zirconium (OxZr) femoral heads matched with highly cross-linked polyethylene (XLPE) have demonstrated the lowest rate of revision compared to other bearing couples in the Australian National Joint Registry, it has been postulated that these results may, in part, be due to the fact that a single company offers this bearing option with a limited combination of femoral and acetabular prostheses. The purpose of this study was to assess clinical and radiographic outcomes in a matched cohort of total hip replacements (THR) utilizing an identical cementless femoral stem and acetabular component with either an Oxidized Zirconium (OxZr) or Cobalt-Chrome (CoCr) femoral heads at a minimum of 10 years follow-up.

We reviewed our institutional database to identify all patients whom underwent a THR with a single cementless femoral stem, acetabular component, XLPE liner and OxZr femoral head with a minimum of 10 years of follow-up. These were then matched to patients who underwent a THR with identical prosthesis combinations with CoCr femoral head by gender, age and BMI. All patients were prospectively evaluated with WOMAC, SF-12 and Harris Hip Score (HHS) preoperatively and postoperatively at 6 weeks, 3 months, 1 and 2 years and every 2 years thereafter. Charts and radiographs were reviewed to determine the revision rates and survivorship (both all cause and aseptic) at 10 years for both cohorts. Paired analysis was performed to determine if differences exist in patient reported outcomes.

There were 208 OxZr THRs identified which were matched with 208 CoCr THRs. There was no difference in average age (OxZr, 54.58 years, CoCr, 54.75 years), gender (OxZr 47.6% female, CoCr 47.6% female), and average body max index (OxZr, 31.36 kg/m2, CoCr, 31.12 kg/m2) between the two cohorts. There were no significant differences preoperatively in any of the outcome scores between the two groups (WOMAC (p=0.449), SF-12 (p=0.379), HHS(p=0.3718)). Both the SF12 (p=0.446) and the WOMAC (p=0.278) were similar between the two groups, however the OxZr THR cohort had slightly better HHS compared to the CoCr THR cohort (92.6 vs. 89.7, p=0.039). With revision for any reason as the end point, there was no significant difference in 10 years survivorship between groups (OxZr 98.5%, CoCr 96.6%, p=0.08). Similarly, aseptic revisions demonstrated comparable survivorship rates at 10 year between the OxZr (99.5%) and CoCr groups (97.6%)(p=0.15).

Both THR cohorts demonstrated outstanding survivorship and improvement in patient reported outcomes. The only difference was a slightly better HHS score for the OxZr cohort which may represent selection bias, where OxZr implants were perhaps implanted in more active patients. Implant survivorship was excellent and not dissimilar for both the OxZr and CoCr groups at 10 years. Therefore, with respect to implant longevity at the end of the first decade, there appears to be no clear advantage of OxZr heads compared to CoCr heads when paired with XLPE for patients with similar demographics. Further follow-up into the second and third decade may be required to demonstrate if a difference does exist.

Introduction

Trunnion wear has been reported as a cause for failure of modern total hip replacement implants. While there are several reports on the prevalence of trunnion corrosion with specific stem designs, little is known about the prevalence of this problem across other femoral stem designs. The purpose of this study is to review three commonly used uncemented femoral stems and to correlate any established risk factors with rates of revision.

Introduction

HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques.

Aims

The purpose of the present study was to compare patient-specific instrumentation (PSI) and conventional surgical instrumentation (CSI) for total knee arthroplasty (TKA) in terms of early implant migration, alignment, surgical resources, patient outcomes, and costs.

Introduction

The infection rate after total joint arthroplasty (TJA) has been shown to be 1–2% in multiple series and registry data. Irrigation, debridement, and polyethylene exchange (IDPE) is a common first line treatment in many cases of acute prosthetic joint infection (PJI). The reinfection rate in open IDPE procedures is variable with studies showing reinfection rates of 10–70% depending on various patient and microbial factors. Our pilot study aimed to determine if the bacterial load in infected total joints was sufficiently reduced by IDPE to allow for the use of post-debridement cultures as an independent marker of procedural success.

Purpose

The success of total knee replacement (TKR) surgery can be attributed to improvements in TKR design, instrumentation, and surgical technique. Over a decade ago oxidized zirconium (OxZr) femoral components were introduced as an alternative bearing surface to cobalt-chromium (CoCr), based on strong in-vitro evidence, to improve the longevity of TKR implants. Early reports have demonstrated the clinical success of this material however no long-term comparative studies have demonstrated the superiority of OxZr implants compared to a more traditional CoCr implant. This study aims to compare long-term survivorship and outcomes in OxZr and CoCr femoral components in a single total knee design.

Introduction

The effectiveness of patient specific instrumentation (PSI) to perform total knee arthroplasty (TKA) remains controversial. Multiple studies have been published that reveal conflicting results on the effectiveness of PSI, but no study has analyzed the contact kinematics within knee joints replaced with the use of PSI. Since a departure from normal kinematics can lead to eccentric loading, premature wear, and component loosening, studying the kinematics in patients who have undergone TKA with PSI can provide valuable insight on the ability of PSI to improve functionality and increase longevity. The goal of the present study was to compare femoral and tibial component migration (predictive of long-term loosening and revision) and contact kinematics following TKA using conventional instruments (CI) and PSI based surgical techniques.

Introduction

The purpose of this study is to estimate the cost-effectiveness of performing total hip arthroplasty (THA) versus nonoperative management (NM) in non-obese (BMI 18.5–24.9), overweight (25–29.9), obese (30–34.9), severely-obese (35–39.9), morbidly-obese (40–49.9), and super-obese (50+) patients.

Aims

The aim of this study was to determine whether there is a difference in the rate of wear between acetabular components positioned within and outside the ‘safe zones’ of anteversion and inclination angle.

Aims

The aim of this study was to evaluate the long-term inducible displacement of cemented tibial components ten years after total knee arthroplasty (TKA).

Aims

The purpose of the present study was to examine the long-term fixation of a cemented fixed-bearing polished titanium tibial baseplate (Genesis ll).

INTRODUCTION

The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in both total hip arthroplasty (THA) and total knee arthroplasty (TKA). The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxinium femoral components have demonstrated clear improvements in wear characteristics in-vitro. The purpose of this prospective study was to evaluate the mid-term (minimum 5 year) clinical and radiographic results and survivorship of the Genesis II™ knee implant system using an Oxinium femoral component.

Introduction

Total knee arthroplasty (TKA) has proven clinical success with reported longterm survivorship of 92% in the elderly population. Concerns regarding increased loosening rates and potential need for multiple revision surgeries in patients younger than 60 years have traditionally discouraged TKA in younger patients. The purpose of this study was to review the longterm clinical and radiographic results of patients under the age of 45 yrs who underwent a total knee replacement.

Aims

The purpose of this study was to compare the long-term results of primary total hip arthroplasty (THA) in young patients using either a conventional (CPE) or a highly cross-linked (HXLPE) polyethylene liner in terms of functional outcome, incidence of osteolysis, radiological wear and rate of revision.

Introduction

The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in total hip arthroplasty (THA) and total knee arthroplasty (TKA). One of the most common causes of failure of THA is aseptic loosening secondary to polyethylene wear debris. The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxidized zirconium is a relatively new material that features an oxidized ceramic surface chemically bonded to a hard metallic substrate. This material possesses the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture While short-term results of oxidized zirconium in THA have been reported, there have been no reports on retrieved highly cross linked PE articulating with Oxinium headsObjectives:

The purpose of this study was to compare clinical outcomes of total knee arthroplasty (TKA) after manipulation under anaesthesia (MUA) for post-operative stiffness with a matched cohort of TKA patients who did not requre MUA.

In total 72 patients (mean age 59.8 years, 42 to 83) who underwent MUA following TKA were identified from our prospective database and compared with a matched cohort of patients who had undergone TKA without subsequent MUA. Patients were evaluated for range of movement (ROM) and clinical outcome scores (Western Ontario and McMaster Universities Arthritis Index, Short-Form Health Survey, and Knee Society Clinical Rating System) at a mean follow-up of 36.4 months (12 to 120). MUA took place at a mean of nine weeks (5 to 18) after TKA. In patients who required MUA, mean flexion deformity improved from 10° (0° to 25°) to 4.4° (0° to 15°) (p < 0.001), and mean range of flexion improved from 79.8° (65° to 95°) to 116° (80° to 130°) (p < 0.001). There were no statistically significant differences in ROM or functional outcome scores at three months, one year, or two years between those who required MUA and those who did not. There were no complications associated with manipulation.

At most recent follow-up, patients requiring MUA achieved equivalent ROM and clinical outcome scores when compared with a matched control group. While other studies have focused on ROM after manipulation, the current study adds to current literature by supplementing this with functional outcome scores.

Cite this article: Bone Joint J 2015;97-B:1640–4.

This was a randomised controlled trial studying the safety of a new short metaphyseal fixation (SMF) stem. We hypothesised that it would have similar early clinical results and micromovement to those of a standard-length tapered Synergy metaphyseal fixation stem. Using radiostereometric analysis (RSA) we compared the two stems in 43 patients. A short metaphyseal fixation stem was used in 22 patients and a Synergy stem in 21 patients. No difference was found in the clinical outcomes pre- or post-operatively between groups. RSA showed no significant differences two years post-operatively in mean micromovement between the two stems (except for varus/valgus tilt at p = 0.05) (subsidence 0.94 mm (sd 1.71) vs 0.32 mm (sd 0.45), p = 0.66; rotation 0.96° (sd 1.49) vs 1.41° (sd 2.95), p = 0.88; and total migration 1.09 mm (sd 1.74) vs 0.73 mm (sd 0.72), p = 0.51). A few stems (four SMF and three Synergy) had initial migration > 1.0 mm but stabilised by three to six months, with the exception of one SMF stem which required revision three years post-operatively. For most stems, total micromovement was very low at two years (subsidence < 0.5 mm, rotation < 1.0°, total migration < 0.5 mm), which was consistent with osseous ingrowth. The small sample makes it difficult to confirm the universal applicability of or elucidate the potential contraindications to the use of this particular new design of stem.

Cite this article: Bone Joint J 2015; 97-B:595–602.

Background:

Varus-valgus constrained (VVC) implants are used in cases of severe valgus deformity, attenuated medial collateral ligament and difficulty in balancing the medial and lateral gaps of the knee. The increased constraint has been postulated to lead to more stress at the bone-implant interface and early loosening. The objective of this study was to compare the wear characteristics of the polyethylene liner in VVC prosthesis with the posterior-stabilized (PS) prosthesis and identify the factors leading to more wear in the VVC tibial inserts.

Purpose

The objective of this study was to compare the wear characteristics and damage scores in highly crosslinked (XLPE) and conventional polyethylene (CPE) acetabular liners.

Introduction:

Alignment of the initial femoral guidewire is critical in avoiding technical errors that may increase the risk of failure of the femoral component. A novel alternative to conventional instrumentation for femoral guidewire insertion is a computed tomography (CT) based alignment guide. The aim of this study was to assess the accuracy of femoral component alignment using a CT-based, patient specific femoral alignment guide.

Background:

Polyethylene wear in total knee arthroplasty (TKA) is influenced by patient, surgeon and implant factors. The objective of this study is to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts.

Purpose

The mobile-bearing total knee arthroplasty was designed to increase the contact area with the polyethylene bearing, through the functional range of motion, and subsequently decrease the wear rate previously seen in fixed-bearing implants. In the literature there is no clear clinical advantage between the different designs in the short to mid-term follow-up.

The purpose of this study was to compare the results between a cruciate retaining mobile-bearing design (SAL II, Sulzer) and two cruciate retaining fixed-bearing designs (AMK, Depuy, and the Genesis II, Smith and Nephew).

Purpose: Efforts to decrease polyethylene wear have lead to advances in polyethylene and counter-face technology for total hip replacement. In particular, the use of highly cross-linked polyethylene (XLPE) and more recently, oxidized zirconium (Oxinium) heads, have demonstrated significant in-vitro improvements in THR wear. This study reports on the early clinical performance and wear (measured with RSA) of an randomized controlled trial (RCT) comparing Oxinium and CoCr heads on XLPE and conventional polyethylene (CPE).

Method: Forty patients were enrolled in a RCT and stratified to receive either an Oxinium (Ox) or CoCr head against either XLPE or CPE (ie 10 patients in each group). All patients had otherwise identical THRs and had tantalum beads inserted in the pelvis and polyethylene for wear analysis. There were no significant differences between groups with respect to patient demographics and the average age was 68 years (range 57–76) at index procedure. RSA wear analysis was performed immediately post-op, at six weeks, three and six months and then at one and two years. All patients are a minimum of four years post-op (average 4.6, range 4 – 5.8). Patients were followed prospectively using validated clinical outcome scores (WOMAC, SF-12, Harris Hip scores) and radiographs.

Results: All health-related outcomes were significantly improved from pre-operative with a mean Harris Hip score and WOMAC at last follow-up of 90.9 and 80.2, respectively. Total 3D femoral head penetration at two years for each group were the following: CoCrXLPE (0.068±0.029mm); OxXLPE (0.115±0.038mm); CoCrCPE (0.187±0.079mm); and OxCPE (0.242±0.088mm). Thus, OxCPE was significantly higher than OxXLPE and CoCrXLPE but not CoCrCPE (p=0.001, p> 0.0001 and p=0.094, respectively). In other words, head penetration was higher with CPE compared to XLPE but there was no significant difference between Ox and CoCr heads. Similarily, regardless of head type (ie combining similar poly types), there was a significant difference in 3D head penetration at two years between CPE and XLPE ( CPE 0.213±0.086; XLPE 0.093±0.041, p> 0.0001).

Conclusion: The early results of this RCT, using RSA as the wear analysis tool, indicate a significant improvement in wear with XLPE compared to CPE. However, it failed to show a clear advantage to the use of Oxinium over CoCr against either polyethylene. Longer follow-up is required to determine steady-state wear rates (after bedding-in) and allow comparison between bearing groups.

Purpose: The Genesis II total knee arthroplasty system was introduced in 1996 as the next evolution in TKR design characterized by “built-in” femoral external rotation and improved trochlear design to optimize patellar tracking and femoral/tibial kinematics, as well as a polished tibial base plate and ethylene-oxide sterilized polyethylene to minimize wear. The purpose of this prospective study was to evaluate the long-term (minimum 10 year) clinical and radiographic results and survivorship of this novel TKA implant system.

Method: Between 1996 and 1999, 478 Genesis II Primary TKRs were implanted and followed prospectively in 414 patients (mean follow-up 11.25±1.11 years). Diagnosis at index surgery included: 94% osteoarthritis, 5% inflammatory arthritis, 1% other diagnoses. Average age at index TKR was 68 years (range 38 to 93 years). There were 149 posterior cruciate retaining (31%) and 329 cruciate sacrificing (69%) knees implanted. Patella resurfacing was performed on 89% (432) of the cases. Sixty-seven deaths occurred prior to 10 years follow-up. Patients were followed prospectively using validated clinical outcome scores (WOMAC, SF-12, Knee Society scores) and radiographs. Kaplan-Meier survival analysis was performed.

Results: All health-related outcomes were significantly improved from preoperative with a mean Knee Society Score and WOMAC at last follow-up of 162 and 69, respectively. To date, 16 revision procedures have been performed. Revisions for infection included six two-stage revisions and two cases of irrigation & debridement with polyethylene exchange. In addition, there were three re-operations for stiffness and one for patellar instability. To date, there have been only two revisions for aseptic loosening and/or osteolysis. Excluding revisions for infection, the Kaplan-Meier survivorship analysis of the total knee system was 98.9±0.5% at five years and 98.2±0.6% at 10 years.

Conclusion: The Genesis II total knee arthroplasty system, characterized by “built-in” femoral external rotation, improved trochlear design, a polished tibial base plate and ethylene-oxide sterilized polyethylene, has demonstrated excellent clinical & radiographic results and long-term survivorship (98% at 10 years) at our institution.

Purpose: The range of motion after TKA depends on many patient, surgical technique, and implant factors. Recently, high-flexion designs have been introduced as a means of ensuring or gaining flexion after TKA. We therefore evaluated factors affecting postoperative flexion to determine whether implant design influences long-term flexion.

Method: We prospectively collected data on patients receiving a primary Genesis II total knee replacement with a minimum of 1-year followup (mean, 5.4 years; range, 1–13 years). We recorded pre – and postoperative outcome measures, patient demographics, and implant design (cruciate retaining [CR, n = 160], posterior stabilized [PS, n = 1177], high-flex posterior stabilized [HF-PS, n = 197]).

Results: Backward stepwise linear regression modeling revealed the following factors that significantly affected postoperative flexion: preoperative flexion, gender, body mass index, and implant design. Independent of gender, body mass index, and preoperative flexion, patients who received a HF-PS and PS design implant resulted in 8° and 5° more flexion, respectively, than those who received a CR implant. Based on analysis examining pre-operative flexion categories, patients with low flexion preoperatively (< 100°) were more likely to gain flexion, whereas those with high flexion preoperatively (> 120°) were most likely to maintain or lose flexion postoperatively. Controlling for implant design, patients with high flexion preoperatively (> 120°) were more likely to gain flexion with the HF-PS design implant (HF-PS = 32.0%; PS = 15.1%; CR = 4.5%).

Conclusion: In summary, our data demonstrate postoperative range of motion after TKA is related to several factors, confirming the important role of the patient’s preoperative range of motion. In addition, our review suggests knee design and, in particular, the use of a so called “high-flexion” PS polyethylene design may be advantageous in maintaining or improving flexion postoperatively, especially in those patients with good pre-operative range of motion.

Purpose: A ceramic head coupled to a metal liner is a proposed new alternate bearing in THA. The authors participated in an FDA approved multicentre prospective, randomized, blinded clinical trial comparing ceramic-on-metal (CoM) to metal-on-metal (MoM) in patients receiving a THA.

Method: 390 patients received the same acetabular component and metal insert. 194 patients received a delta ceramic head (CoM) and 196 received a metal head (MoM). Metal ions were evaluated in 72 patients (36-CoM, 36-MoM). Harris Hip scores, radiographs, and metal ion levels (cobalt, chromium and titanium in serum, erythrocytes and urine) were evaluated pre-operatively and at three, 12 and 24 months.

Results: No patients were lost to follow-up. There were no differences between groups’ baseline demographics and clinical scores. At two years there were no differences in Harris Hip scores, radiographs, adverse events or postoperative complications. Both groups had overall very low median metal ion profiles with no statistically significant differences. 24 month MoM vs CoM; Serum cobalt ( g/L), mean: 1.2(+/−0.5) vs 1.1(+/−0.3), median: 0.66(range: 0.2–5.6) vs 1.0 (range: 0.3–2.7); Serum chromium ( g/L), mean: 1.1(+/−0.5) vs 1.4(+/−0.4), median: 0.86(range: 0.3–6.9) vs 1.2(range: 0.3–4.9). Urine cobalt and urine chromium ( g/day) demonstrated similar trends to serum ion levels.

Conclusion: While CoM is a new bearing surface in North America and not currently FDA or HPB approved, it has been in clinical use globally since 2006. Results of this non-inferiority RCT demonstrated no clinical outcome, metal ion, radiographic or adverse event differences between CoM and MoM cohorts.

Purpose: Total knee arthroplasty (TKA) is a proven intervention in the management of end-stage knee arthritis. However, the demands of younger, more active patients may result in increased rates of wear and aseptic loosening. The purpose of this study was to assess the long-term outcome of a large cohort of young patients, and to assess if the outcomes of cemented implants differed from non-cemented implants.

Method: Between 1984 and 2003, 350 TKAs were performed in 283 patients who were under 55 years old. Patients were followed a minimum of 5 years. Mean age at time of surgery was 49.0±5.5 years; 64% of patients were female. Primary knee pathologies included degenerative and post-traumatic arthritis (271), inflammatory arthritis (62), and others (17). Multiple implant designs were used; 296 knees were cemented and 54 were non-cemented. The Knee Society Clinical Rating Score (KSCRS) at latest follow-up was calculated. The Kaplan-Meier survivorship was calculated using an endpoint of revision total knee arthroplasty.

Results: Mean follow-up was 8.7±3.4 years. Seventeen knees were revised at a mean of 7.1±4.4 years after the index procedure. Fifteen patients (twenty-five knees) died. Fifty-one patients (sixty-two knees) were lost to follow-up. Sixty patients (sixty-seven knees) had incomplete KSCRS forms. Average function and knee domains of the KSCRS were 70.0±26.7 and 87.3±16.2 respectively. The Kaplan-Meier survival at five, ten, and fifteen years was 0.965±0.011, 0.941±0.015, and 0.933±0.017. The rate of revision was 5.9%. There was no statistically significantly difference observed between the outcomes of cemented and non-cemented implants, male and female patients, or inflammatory versus non-inflammatory arthritis.

Conclusion: This study demonstrates that total knee replacement in younger patients can demonstrate excellent survival rates free of revision. There does not appear to be an obvious survival advantage of cementless designs, or difference in outcomes based on sex of the patient or primary diagnosis of inflammatory or non-inflammatory arthritis.

Purpose: Approximately, 10% of two-stage TKA revisions for deep sepsis become re-infected. The purpose of this study was to determine the success in terms of sepsis eradication and factors associated with failure of repeat two-stage revision TKA.

Method: Between 1991 and 2006, 129 two-stage revision TKRs for deep sepsis were performed. Ten cases which became re-infected were identified. These unfortunate patients, representing 8% of all the two-stage TKA revisions performed during this time period, are the focus of this study. Their progress and treatment interventions were followed for the purposes of this study.

Results: Ten patients were identified with a two-stage revision TKA which became re-infected. Mean patient age was 72 with 40 % being female. Following recurrent sepsis all patients went on to require more than one further two-stage revision (mean 3.67 further revision surgeries). Infection was only successfully eradicated in 28.7% of cases, the remaining require chronic suppressive therapy or have ongoing active infection. Two patients went on to have an arthrodesis (both remain on suppressive anti-biotics) and one patient had trans-femoral amputation. Staph Aureus and Coagulase neg Staph accounted for 80% of primary infective organisms with only one primary infection with methicillin resistant staph aureus (MRSA). Cultures at subsequent revisions were the same organism in 67% cases. Additional organism cultured included Pseudomonas and Propionibacterium. These patients had an increased incidence of multiple medical co-morbidities including Type-2 Diabetes Mellitus and Rheumatoid Arthritis.

Conclusion: Patients with recurrent sepsis after a two-stage revision for infection in TKR all required multiple further surgeries. Eradication of infection was only achieved in 28.7% cases. Risk factors for recurrent sepsis include Rheumatoid Arthritis and Type-2 Diabetes Mellitus.

Purpose: There is no consensus whether the posterior cruciate ligament (PCL)should be preserved (CR) or sacrificed (CS) during primary total knee replacement (TKR). The purpose of this study was to compare the greater than 10 year survivorship and health related outcomes of CR and CS TKRs using a single implant system.

Method: Between 1996 and 2000, 478 Genesis II Primary TKRs were inserted in 414 patients. Excluding those with a primary diagnosis other than osteoarthritis, body mass index greater then 40, history of prior patellectomy, fusion or osteotomy, 358 cases in 310 patients were included. 134 (37%) had a PCL preserving (CR) and 224 (63%) had a PCL sacrificing implant (CS). The two patient cohorts were compared for Kaplan-Meier survivorship, health-related outcomes (Knee Society scores, WOMAC, SF-12), range of motion (ROM) and radiographic loosening or wear.

Results: Mean follow-up was 11.87±1.04 years for CR and 10.96±0.87 years for CS (p=0.001). Four cases were revised for infection. No significant differences were noted between the CR and CS Genesis II cohorts at 10 year Kaplan-Meier survivorship excluding infections (CR 0.984±0.011, CS 0.986±0.008, p=0.30). Overall revisions were two for CR (1.5%, no infections) and seven for CS (1.7%, four for infection; 1.3% excluding infections). Revision rates were not significantly different between groups including or excluding infections (p=0.493 and p=1.00 respectively). CS had significantly greater postoperative ROM than CR (CS=114.20±13.60, CR=111.35±12.38, p=0.024). At 10 years, no differences were observed in satisfaction, health-related outcomes or radiographic wear/loosening. Crepitus was reported more frequently in CS design.

Conclusion: Most studies comparing PCL sacrificing (CS) versus retaining (CR) TKRs are short term. In this large, long term, single implant CR versus CS study, no differences were found in Kaplan-Meier survivorship, health-related outcomes or patient satisfaction. The CS design had more range of motion, but also a higher incidence of peripatellar crepitus than the CR design. We conclude that both CR and CS TKR designs can yield excellent long term clinical outcomes.

Purpose: High contact stresses and wear after total knee replacement (TKR) has been a problem. Mobile bearing TKRs have been advocated as a means to increase load bearing area, reduce contact stresses and minimize wear. The purpose of this study was to compare two, large, consecutive cohorts of TKR patients with greater than 10 years follow-up, one with a fixed bearing and one with a mobile bearing design.

Method: One hundred and three SAL II mobile bearing TKR’s were compared to a gender, age, BMI and time from surgery matched fixed bearing Genesis II cohort of equal size. All surgeries were performed between September 1993 and December 2000 (average follow-up, 11.64±1.64 years). Inclusion criteria included patients with osteoarthritis of the knee. Exclusion criteria included revision arthroplasty, inflammatory arthritis, a prior osteotomy or a prior patellectomy. The > 10 year Kaplan-Meier survivorship, health-related outcomes (Knee Society scores, WOMAC and SF-12), radiographs and retrieved implants for the fixed and mobile bearing TKR cohorts were compared.

Results: Fixed bearing TKRs demonstrated better 10 year Kaplan-Meier survivorships for any re-operation, 1.000±0.000 compared to 0.969±0.018 for mobile bearings (Genesis II and SAL I/II respectively). Revision rates were significantly different between groups with fixed bearing having no revisions and mobile four revisions (3.9%). No cases were revised for sepsis. Mobile bearing revisions were for pain (1), patellar maltracking (1), polyethylene wear (1) and aseptic loosening (1). At 10 years, health-related outcomes were similar between the two cohorts. Fixed bearing TKRs demonstrated more range of motion (111.42±12.76 vs 107.19±14.74 degrees) although not significant (p=0.052). Wear was more frequently noted in mobile bearing TKRs on > 10 year radiographs.

Conclusion: In this comparison of two contemporary TKRs, the fixed bearing TKR outperformed the mobile bearing TKR.

Purpose: The purpose of this prospective blinded randomized control trial was to compare the stem migration of two cemented stem designs using radiostereometric analysis (RSA). This was essentially a safety study in which our hypothesis was that the newer design (CPCS, Smith and Nephew Inc) would demonstrate similar micro-motion to the well-established Exeter (Stryker) design.

Method: Thirty patients were consented and enrolled into a blinded RCT in which 15 patients received a dedicated RSA CPCS stem and 15 patients received a RSA Exeter stem. Both stems are collarless tapered polished cemented stems, the only difference being a slight lateral to medial taper with the CPCS design. Outcome measures were compared (Hip Society Score, WOMAC, SF-12). RSA analysis was conducted immediately postoperatively, at 6 weeks, 3 months, 6 months, 1 year and 2 years.

Results: No difference was found in any of the outcome measures pre-operatively or postoperatively. At 2 years, stem subsidence for the CPCS stem was approximately half that seen for the Exeter stem (0.565±0.189mm and 0.981±0.209mm respectively, p< 0.0001). In contrast, posterior (internal) rotation of the CPCS was approximately twice that of the Exeter stem (1.496±1.215° and 0.716±0.818° respectively, p=0.221). Other migration patterns were no different between stems.

Conclusion: As expected with this stem design, both stems showed some axial and rotational migration within the cement mantle. The subtle differences in design may explain the differences in migration patterns. Our data suggests that the newer CPCS design should perform well over the long-term.

Purpose: The Synergy femoral component was introduced in late 1996 as a second generation titanium proximally porous-coated tapered stem with dual offsets (standard & high) to help better restore femoral offset at THR. The purpose of this prospective study was to evaluate the long-term (minimum 10 year) clinical and radiographic results and survivorship of this second-generation femoral component at our institution.

Method: From December 1996 to December 1999, 256 cementless Synergy femoral components were inserted and followed prospectively in 254 patients requiring THR. 185 were standard offset stems(72.3%) while 71 stems (27.7%) were high offset. The average follow-up was 11.2 years (range 10.0 to 12.9 years). Average age at index THR was 58.9 years (range 19 to 86 years). Two hundred eight stems had standard porous coating while 48 had additional HA coating. Fifty-two cases were either lost to follow-up or had died prior to 10 years follow-up. Patients were followed prospectively using validated clinical outcome scores (WOMAC, SF-12, Harris Hip scores) and radiographs. Kaplan-Meier survival analysis was performed.

Results: All health-related outcomes were significantly improved from pre-operative with a mean Harris Hip score and WOMAC at last follow-up of 91.6 and 81.8, respectively. From the initial 256 femoral stems inserted, only 5 stems have been revised. Two stems have been revised for infection. To date, only one stem has been revised due to subsidence at nine months following surgery likely, as a result of a calcar fracture occurring at the index THR. Two stems were revised for peri-prosthetic fracture as a result of patient falls at six months and 9.8 years post-op. Radiographic review of remaining stems in-situ identified no cases of loosening with all stems showing evidence of osseous integration. The Kaplan-Meier survivorship analysis of the femoral component, with revision for aseptic loosening, was 99.2%±0.008 at five, 10 and 12 years.

Conclusion: The Synergy femoral component, a second generation titanium proximally porous-coated tapered stem design with dual offsets, has demonstrated excellent clinical & radiographic results and long-term survivorship (99% at 10 years) at our institution.

Purpose: The growing trend of morbidly obese (BMI 40+) patients requiring a total joint replacement is becoming major concern in total knee Arthroplasty (TKA). The purpose of this study was to investigate the affects that BMI may have on implant longevity and clinical patient outcome using historical patient data.

Method: A consecutive cohort of 3083 TKA’s in 2048 patients since 1995 (minimum 2 years follow-up) were evaluated. Pre-operative scores, latest scores, and change in clinical outcome scores (KSCRS, SF12, WOMAC) were analyzed using ANOVA and Kaplan-Meier (K-M) survivorship was determined.

Results: K-M cumulative survival at 10 years by BMI group was 0.951±0.033 for Normal and Underweight (< 25, n=277), 0.944±0.024 for Overweight (25–29.9, n=915), 0.882±0.032 for Obese (30–39.9, n=1460) and 0.843±0.076 for Morbidly Obese (40+, n=352). Cumulative revision rates were 1.8% for Normal and Underweight, 1.9% for Overweight, 2.9% for Obese and 2.8% for Morbidly Obese. All pre-operative clinical scores were significantly different between the Morbidly Obese and all other BMI groups (p< 0.05), with the non-morbidly obese having higher scores in all cases. Significant difference was found in the change in WOMAC domain scores and the KSCRS knee score (p< 0.05) between the morbidly obese group and all other BMI groups, with the morbidly obese having the greatest improvement in all domains.

Conclusion: The morbidly obese patient cohort (BMI > 40) undergoing TKA demonstrated the most significant improvement in clinical outcome scores; however also had the lowest cumulative 10 year survivorship. This risk/benefit information is important in pre-operative discussions with this challenging, and increasingly prevalent, patient population.

Purpose: There are two broad-based categories of cementless femoral components performed during total hip arthroplasty: proximally coated versus fully porous coated. While both have enjoyed widespread clinical applications, there remains debate regarding differences in clinical outcome scores, relative incidence of thigh pain and the development of stress shielding. The purpose of this study was to investigate these variables in a multi-center prospective randomized blinded clinical trial.

Method: Between three centers 388 patients were enrolled in this clinical trial. 198 patients received a proximally coated tapered cementless femoral component (Synergy, Smith and Nephew, Memphis) and 190 patients received a fully porous coated cementless femoral component (Prodigy, Depuy, Warsaw). Patients were evaluated pre-operatively, at 3, 6, 12 months and annually thereafter, with multiple validated outcome measures including WOMAC, SF12, HSS, UCLA activity and thigh pain scores. A cohort of 72 patients underwent preoperative and postoperative DEXA scanning.

Results: 367 patients had a minimum of 2 years follow-up (average 6.4 years). There were no differences in age at surgery, BMI, or pre-operative clinical outcome scores (WOMAC, SF12, HSS, UCLA activity, thigh pain) between groups. There were no differences in any post-operative clinical outcome scores at any interval of follow-up. There were no differences in incidence of thigh pain between groups at any time. The only measurable difference between study groups was in bone mineral density evaluation. Bone density change in Gruen zone 7 was 23.7% with the Prodigy stem and 15.3% with the Synergy stem (p=0.011).

Conclusion: Both fully porous coated and proximally porous coated cementless stems performed well, with no clinical differences at a minimum of 2 years follow-up. Only bone mineral density evaluations could detect any differences between these femoral components designs.

We present a case of early retrieval of an Oxinium femoral head and corresponding polyethylene liner where there was significant surface damage to the head and polyethylene. The implants were retrieved at the time of revision surgery to correct leg-length discrepancy just 48 hours after the primary hip replacement. Appropriate analysis of the retrieved femoral head demonstrated loss of the Oxinium layer with exposure of the underlying substrate and transfer of titanium from the acetabular shell at the time of a reduction of the index total hip replacement. In addition, the level of damage to the polyethylene was extensive despite only 48 hours in situ.

The purpose of this report is to highlight the care that is required at the time of reduction, especially with these hard femoral counter-faces such as Oxinium. To our knowledge, the damage occurring at the time of reduction has not been previously reported following the retrieval of an otherwise well-functioning hip replacement.

We evaluated the outcome of primary total hip replacement (THR) in 3290 patients with the primary diagnosis of osteoarthritis at a minimum follow-up of two years. They were stratified into categories of body mass index (BMI) based on the World Health Organisation classification of obesity. Statistical analysis was carried out to determine if there was a difference in the post-operative Western Ontario and McMaster Universities osteoarthritis index, the Harris hip score and the Short-Form-12 outcome based on the BMI.

While the pre- and post-operative scores were lower for the group classified as morbidly obese, the overall change in outcome scores suggested an equal if not greater improvement compared with the non-morbidly obese patients. The overall survivorship and rate of complications were similar in the BMI groups although there was a slightly higher rate of revision for sepsis in the morbidly obese group.

Morbid obesity does not affect the post-operative outcome after THR, with the possible exception of a marginally increased rate of infection. Therefore withholding surgery based on the BMI is not justified.

This was a safety study where the hypothesis was that the newer-design CPCS femoral stem would demonstrate similar early clinical results and micromovement to the well-established Exeter stem. Both are collarless, tapered, polished cemented stems, the only difference being a slight lateral to medial taper with the CPCS stem. A total of 34 patients were enrolled in a single-blinded randomised controlled trial in which 17 patients received a dedicated radiostereometric CPCS stem and 17 a radiostereometric Exeter stem. No difference was found in any of the outcome measures pre-operatively or post-operatively between groups. At two years, the mean subsidence for the CPCS stem was nearly half that seen for the Exeter stem (0.77 mm (−0.943 to 1.77) and 1.25 mm (0.719 to 1.625), respectively; p = 0.032). In contrast, the mean internal rotation of the CPCS stem was approximately twice that of the Exeter (1.61° (−1.07° to 4.33°) and 0.59° (0.97° to 1.64°), respectively; p = 0.048). Other migration patterns were not significantly different between the stems. The subtle differences in designs may explain the different patterns of migration.

Comparable migration with the Exeter stem suggests that the CPCS design will perform well in the long term.

Purpose: The increasing trend of morbidly obese patients (BMI 40+) requiring joint replacement is becoming a growing concern in Total Hip Replacement (THR) surgery. The purpose of this study was to investigate the influence that BMI may have on implant longevity and clinical outcome using prospectively collected patient data.

Method: A consecutive cohort of 2864 THR’s in 2488 patients with osteoarthritis and a minimum 2 years follow-up were evaluated. Patients were divided into appropriate BMI categories; Normal and Underweight (BMI< 25, n=650), Overweight (BMI 25–29.9, n=1069), Obese (BMI 30–39.9, n=981), and Morbidly Obese (BMI 40+, n=164). Pre-operative, latest, and change in clinical outcome scores (HSS, SF12, WOMAC) were analyzed using ANOVA and Kaplan-Meier (K-M) survivorship was determined. Categorical variables such as gender and survival status were analyzed using chi-squared.

Results: Morbidly Obese patients requiring THR’s were significantly younger than all other BMI groups by 5.4±0.83 years (p< 0.0001). Gender was also significant to BMI grouping with more females being Morbidly Obese and Normal or Underweight (p< 0.0001). All pre-operative and latest HHS and WOMAC domain scores were lower for the Morbidly Obese, significantly in all preoperative score domains and latest HHS Function (p< 0.05). The change in clinical scores from pre-operative to latest was greatest in all domains for the Morbidly Obese group. K-M cumulative survival with implant revision as the endpoint at 10 years was not different between the BMI groups. Revision rates for infection for the Morbidly Obese, Obese, Overweight, and Normal were 1.3%, 0.65%, 0.3% and 0.69% respectively. Overall Revision rates for the Morbidly Obese, Obese, Overweight, and Normal were 6.7%, 5.4%, 6.9% and 5.7% respectively and were not found to be significant (p=0.496).

Conclusion: The Morbidly Obese cohort undergoing THR had significantly lower preoperative and lower postoperative clinical outcome scores than all other BMI groups but demonstrated the most significant improvement. No difference was found in the K-M survivorship although revisions and revisions for infection were not equal between the groups

Purpose: The results of medial unicompartmental knee replacement have been reported as excellent over the intermediate term with both fixed and mobile bearing designs. However not all publications report equal success, with different outcomes also reported between mobile and fixed bearing designs. The purpose of this study was to compare the outcomes of mobile and fixed bearing medial unicompartmental arthroplasties.

Method: We evaluated the results of 230 consecutive medial unicompartmental knee arthroplasties (UKA) designs performed between 1989 and 2006 at a single academic centre (London Health Sciences Centre). Eighty mobile bearing UKA (63 patients, mean follow up3.2 years) and 160 fixed bearing UKA (117 patients, mean follow up 6.2 years) were reviewed. The mean age of the patients at the time of surgery was 66 years. Forty nine patients died at a mean of 12.7 years after the index arthroplasty. Patients were evaluated clinically using the Knee Society, WOMAC and SF12 outcome scores and radiographically using the Knee Society rating system.

Results: In the fixed bearing group 21 knees underwent revision at a mean of 6.9 years after the index procedure. In the mobile bearing group 7 knees underwent revision at a mean of 2.6 years. The mean Knee Society knee and function scores for the patients who had not had a revision improved in both groups, with the fixed bearing group mean function and Knee Society Scores improving from 53 and 48 points preoperatively to 80 and 93 points at the time of the most recent evaluation. In the mobile bearing group the mean function and Knee Society Scores improved from 55 and 44 points preoperatively to 85 and 91 points at the time of the most recent evaluation. The five year cumulative survival rates were 96% (SE +/− 0.18) and 89% (SE +/− 0.46) for the fixed and mobile bearing designs respectively, with ten year cumulative survival rates of 85% (SE +/− 0.35) in the fixed bearing group using an endpoint of revision to tricompartmental knee arthroplasty.

Conclusion: Both bearing designs of medial unicompartmental knee arthroplasty provided excellent pain relief and restoration of function in carefully selected patients and demonstrated durable implant survival over the midterm. In this study the fixed bearing designs demonstrated improved survivorship over the mobile bearing designs at 5 years. This may be related to the learning curve of the different bearing systems.

Purpose: The purpose of this study is to compare the clinical results of a standard polyethylene tibial insert versus the high flex polyethylene tibial insert component designs of a posterior cruciate substituting total knee replacement.

Method: One-hundred patients were entered into a prospective, randomized clinical trial comparing standard polyethylene tibial inserts versus the high flex polyethylene tibial insert component designs of posterior cruciate substituting total knee replacement(Genesis II, Smith & Nephew, Memphis, TN). Patients were evaluated pre-operatively, at 3, 12 months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

Results: No patients were lost to follow-up. One patient died prior to the two year follow up. Ninety- nine patients were reviewed at an average follow-up of 2.7 years (range 2.3 – 3.1 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (Standard − 170, High Flex −171). There were no differences in knee flexion at 2 years (Standard− 125°, High Flex − 126°).

Conclusion: In this prospective randomized clinical trial, no differences could be seen between standard polyethylene and a “Hi- Flex” polyethylene design at a minimum of 2 years follow-up. In particular, no improvement in knee flexion was observed. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Purpose: The purpose of this study was to determine the clinical and radiographic outcomes at a minimum follow-up of ten years of patients who underwent a total knee arthroplasty with an inset patellar component. The incidence of anterior knee pain and the factors which may contribute to were also studied.

Method: Patients who had genesis I/II TKA with an inset patellar button with a minimum follow-up of 10 years were identified. 448 patients with 521 knees were identified. Patients were excluded if they were deceased, had incomplete data, were unable to be contacted or had a known or impending revision. Those who had revision were included in a Kaplan-Meier survivorship analysis. The included patients, deceased patients and those lost to follow-up were named group1, 2, and 3 respectively. Demographics and Knee society scores(KSS) were studies for all 3 groups. This was to identify any exclusion bias. Presence and severity of anterior knee pain as well as radiographic factors were collected for group 3. Logistic regression analysis was used to identify and variables that influenced the KSS and presence of anterior knee pain. Kaplan-Meier survivorship analysis was performed for patellar revision and tibial/femoral revision endpoints.

Results: 144 patients with 175 TKA were included in this study. They were on average 66 years old, 64% female, had a BMI of 30 and had a diagnosis of OA 92% of the time. Their average f/u was 11.3 years. Groups 2 and 3 had similar demographics but of course a much shorter f/u. Group 1 had a pre-op KSS of 84 a post-op KSS of 151 and a KS change score of 67. Groups 2 and 3 had similar pre-op, post-op and KSS change scores. We found anterior knee pain occurred in 5% of patients with an average severity of 5/10. Linear regression analysis did not identify any variables including radiographic parameters that had an independent influence on KSS or anterior knee pain. Kaplan-Meier survivorship with patellar revision for any reason as an endpoint was 96% at 10 years and 94% at 17 years. 20 patella were known to have had a revision or were undergoing a revision.

Conclusion: We conclude that use of an inset patellar component can give excellent durable results over time with a low rate of anterior knee pain and complications

Purpose: Gender specific total knee replacement design has been a recently debated controversial topic. The purpose of this study was to investigate the survivor-ship and clinical outcomes of a large primary total knee arthroplasty cohort, specifically assessing any differences between gender groups.

Method: A consecutive cohort of 3817 patients with osteoarthritis, having undergone 5289 primary total knee replacements (3100-female, 2179-male) with a minimum of 2 years follow-up were evaluated. All surgeries were performed at the same institution by one of four surgeons. Pre-operative scores, latest scores, and change in clinical outcome scores (KSCRS, SF12, WOMAC) were compared and tested for significance using the students t-test. Kaplan Meier (K-M) survivor-ship was determined and tested for significance and categorical variables were compared using chi-squared.

Results: Men were significantly taller and heavier than women, while women had significantly higher BMI’s (p< 0.0001). While men had higher raw scores preoperatively, women demonstrated statistically greater improvement (p< 0.019) in all WOMAC domains including pain (29.87 vs. 27.30), joint stiffness (26.78 vs. 24.26), function (27.21 vs. 23.09) and total scores (28.34 vs. 25.09) There were no gender differences in improvements of the SF12 scores. Men demonstrated statistically greater improvement (p< 0.0001) in Knee Society function (22.10 vs. 18.63) and total scores (70.01 vs. 65.42), but not the Knee Society knee score (47.83 vs. 46.64, p=0.084). K-M cumulative survivorship at 10 years was 87.4±.01 for females and 82.9±.014 for males. K-M survivorship distribution was found to be significantly different between gender groups (p< 0.013, Mantel-Cox, Breslow, Tarone-Ware). Revision rates were 10.2% for males and 8.3% for females which was found to be significant by crosstabs with chi-squared (p=0.006).

Conclusion: In this cohort of patients undergoing total knee replacements, women demonstrated statistically greater implant survivorship, statistically greater improvement in WOMAC scores and less improvement in KSCR scores, leading one to question the hypothesis of an inferior clinical outcome in total knee arthroplasty that is gender based.

The purpose of this study was to assess the influence of patient factors on six to eleven year TKR outcomes.

Three hundred and sixty-five consecutive patients (436 Genesis II TKR’s) were prospectively analyzed according to gender, diagnosis, body mass index, pre-operative deformity, pre-operative range of motion and implant type.

The Kaplan-Meier survivorship for the TKR patients was 98% ±.8% at nine years. Large and significant improvement in pre-operative health related quality of life (HRQL) outcomes (KSCR, WOMAC and SF-12) were noted Female patients demonstrated significantly worse pre-operative and post-operative KSCR, WOMAC and SF-12 scores but similar change scores and decreased post-operative range of motion compared to their male counterparts. Patients with rheumatoid arthritis had significantly inferior pre-operative and post-operative HRQL indices, but similar change scores. Rheumatoid patients achieved greater post-operative range of motion than patients with osteoarthritis. Patients with a body mass index > 30 had significantly less pre-operative and one year range of motion, but beyond two years follow-up health-related quality of life indices and range of motion were similar to other BMI categories. Pre-operative deformity did not affect patient outcome. Pre-operative range of motion had a significant effect on post-operative range of motion. Comparable outcomes were achieved with both posterior cruciate ligament preserving and sacrificing total knee replacements; however, the posterior cruciate ligament sacrificing implants had significantly greater postoperative range of motion.

With a contemporary total knee replacement with 98% Kaplan-Meier survivorship at nine years, male gender, a diagnosis of osteoarthritis and a good pre-operative range of motion were indicators of improved post-operative outcomes. Change scores of health-related outcomes are a better indicator of efficacy than simply noting pre- and post-operative scores.

We performed a prospective, randomised, blinded clinical trial comparing metal versus polyethylene bearing surfaces in patients receiving a THA.

Forty-one patients were randomised to receive a metal (twenty-three) or a polyethylene (eighteen) insert with identical femoral and acetabular components. The metal bearing was a 28mm low carbon on high carbon couple. Patients were evaluated pre-operatively, at three, six, twelve months and annually thereafter, including an evaluation of erythrocyte and urine cobalt, chromium, and titanium, outcome measures (WOMAC, SF-12, Harris Hip Score) and radiographs.

No patients were lost to follow-up. At an average 7.2 (range 6.1 – 7.8) years follow-up there were no differences in any outcome measures or radiographic findings. Patients receiving metal liners had significantly elevated metal ion measurements. At most recent follow-up, compared to the polyethylene control group, patients receiving a metal on metal bearing had erythrocyte cobalt levels were eleven times elevated (median 1.4 μg/L (metal) vs 0.12 μg/L (poly), p< .001). Urine cobalt levels were thirty-nine times elevated (median 11.4 μg/L/day (metal) vs 0.29 μg/day (poly), p< .001) and urine chromium levels were twenty-eight times elevated (median 4.75 μg/day (metal) vs 0.17 μg/day (poly), p< .001). Additionally the metal ion levels reached an early steady state level and did not decrease over time. (Erythrocyte Co (μg/L): 1.29 (6 mos), 1.20 (1 yr), 1.0 (2 yr), 1.10 (3 yr), 1.35 (4 yr), 1.40 (5 yr)).

Both cobalt and chromium ion measurements were significantly elevated in the blood and urine of the patients randomised to receive the metal on metal THA at all time intervals. Contrary to previous reports, in 34% of patients with a metal liner, metal ion (erythrocyte cobalt) elevation was still increasing at latest follow-up, and in the overall metal on metal patient cohort, metal ion median levels were not decreasing over time. As in polyethylene wear data, metal ion results are not necessarily generalizable, but are bearing design specific.

In patients with previous patellectomy the optimal constrained implant is not well understood. Previous outcome studies have shown contradictory results. There interpretation is limited by small number of patients, included primary and revision implants or involved a heterogeneous group of different constraint implants.

We performed retrospective match controlled analysis of a posterior stabilised primary total knee arthroplasty in forty-two patients who had previous patellectomy. There were nineteen male and twenty-three female patients. The average age of patients at the time of surgery was fifty-nine years (range from forty-one to seventy-four years). The average time from patellectomy to total knee arthroplasty was seventeen years (range from one to thirty-four years). The average duration of follow-up was 5.3 years with minimum two years follow up (range from two to sixteen years). The control group was matched by age, sex, prosthesis type and surgeon. We used the student-t test to compare the outcome measurement.

Preoperatively, the patellectomy and control groups were not significantly different in terms of Knee Society clinical and functional scores or range of motion. Postoperatively clinical component of the knee society score had a significant difference (p< 0.05) however the functional part of the knee society score didn’t (p> 0.05). In patellectomy group the postoperative clinical and functional score were equal to seventy and fifty-eight respectively. The average clinical component of knee society score in the patellectomy group was twelve points (SE=4.8) lower compare to the knee with intact patella. The patellectomy group also had higher extension lag and poorer extension (higher flexion contracture) at the most recent follow up (p< 0.05).

This study demonstrated the outcome of the largest series of primary total knee arthroplasty with posterior stabilised implant in patient with previous patellectomy. The outcome of surgery was significantly improved but not as good as the knee with intact patella especially the function of the extensor mechanism.

The purpose of this study was to evaluate the impact of dalteparin use on transfusion rates and blood loss in patients undergoing primary total joint arthroplasty at our center.

We prospectively studied the transfusion patterns of 1642 patients who underwent primary total hip or knee arthroplasty between January 2004 and December 2005 by five arthroplasty surgeons. The influence of daltaperin use, release of tourniquet in total knee arthroplasty, and the turnover of house staff were analyzed using SPSS V14.0 statistical software.

We identified seven hundred and three total hip and nine hundred and thirty-nine knee arthroplasty patients. The mean haemoglobin drop was statistically significant between 2004 and 2005 (p< 0.001). This was seen in both hip (p=0.014) and knee (p< 0.001) patients. Subgroup analysis of total knee arthroplasty revealed a significant difference in haemoglobin drop between surgeons who released the tourniquet prior to closure compared to release at the end of the case (p=0.005). In addition, there were significant monthly differences that corresponded with the turnover of house staff (p=0.039). Overall, no statistically significant increase in allogeneic transfusion rates was observed between years, months, and individual surgeons.

The use of dalteparin was found to be associated with a significantly increased haemoglobin drop in primary total joint replacement when compared to warfarin. However, the use of dalteparin was not associated with an increase in allogeneic transfusions at our center. The results also suggest that there may be an advantage to releasing the tourniquet and achieving hemostasis prior to closure in knee arthroplasty. Finally, the results emphasise the importance of educating new house staff on methods to reduce intra-operative blood loss and transfusion rates.

Background: Post-operative analgesia using parenteral opioids or epidural analgesia can be associated with troublesome side effects.

Locally administered pre-emptive analgesia is effective, reduces central hyper sensitisation and avoids systemic drug related side-effects and may be of benefit in total knee replacement.

Materials and Methods: 64 patients undergoing total knee replacement were randomised to receive a periarticular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing.

All patients received patient controlled analgesia (PCA) for 24 hours post surgery, followed by standard analgesia. Visual Analogue Scale (VAS) pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at 6 week follow up. PCA consumption and overall analgesic requirement were measured.

Results: PCA use at 6,12 and over 24 hours post surgery was significantly less in patients receiving the injection (P< 0.01, P=0.016, P< 0.01). Patient satisfaction in PACU and 4 hrs post operation was greater (P=0.016, P=0.013). VAS for pain during activity in PACU and at 4 hrs were significantly less (P= 0.04, P=0.007) in the injected group. The average ROM at 6 weeks was no different. Overall hospital stay and the incidence of wound complications was not different between the two groups.

Conclusion: Peri-articular intra-operative multimodal analgesia significantly reduces post-operative PCA requirement. Patient satisfaction was greater in the injection group.

Femoral stem fracture occurred in five (2%) of 283 revision hip arthroplasties when extensively coated, distal fixation femoral implants were used. Common features were complex revisions, high body mass index, poor proximal support, smaller stems (< 13.5 mm) and use of an extended trochanteric osteotomy. Use of strut allografts can reduce femoral stem stresses.

The purpose of this study was to analyze the surgical factors associated with fracture of cementless distal fixation revision femoral stems and supplement this analysis with a finite element analysis.

Data from our institutional joint replacement database identified five (2%) fractured femoral stems (three Solution, two Echelon) in a cohort of two hundred and eighty-three cementless distal fixation femoral stems (one hundred and eighty-two Solution, one hundred and one Echelon) followed over two years. Patient, surgical and implant factors were compared between the fractured and not fractured stems. Finite element analysis was performed on two fractured stem cases to better understand the fracture mechanism.

Common clinical features of the five fractured stems were complex revisions, high patient body mass index, poor proximal bone support, smaller stems (< 13.5 mm) and use of an extended trochanteric osteotomy (ETO) (3/5). Fatigue failure was the mode failure in all cases.

Finite element analysis confirmed that the location of highest stem stress was near the location of the stem fracture and that use of a strut graft over an extended trochanteric osteotomy in patients lacking proximal femoral cortical support decreased the stem stresses by 48%.

Use of cementless distal fixation revision femoral stems is accompanied by a 2% risk of stem fracture in the face of proximal femoral support of the stem and/or use of a stem with a diameter less than 13.5 mm. When an extended trochanteric osteotomy is used, the stem fracture rate increased to 4%. Use of a strut allograft in conjunction with the ETO can reduce stem stresses by 48% and the risk of stem fracture.

Funding: Research support from J& J DePuy and Smith & Nephew