Patient selection has always been considered an important criterion in determining the success or failure of a TKA. In the early days of TKA, orthopaedic surgeons and patients were both uncertain as to the long-term outcomes and most TKAs were performed in patients >65 years of age. Since that time, a number of peer-reviewed studies have provided Level III evidence indicating that TKA was a reliable procedure with 91% to 99% survivorship during the first decade and 85% to 97% during the second decade of follow-up. These encouraging TKA results have prompted a growth in TKA utilisation, particularly in younger patients and a move away from procedures such as osteotomy and UKA which have been associated with higher re-operation rates. As a result, over the past decade, the fastest growing TKA patient cohorts have been in the 45–54 (337% increase for females, 271% for males) and 55–64 (260% increase for females and 213% for males) year old patient groups!

The Swedish Knee Arthroplasty Register has followed Swedish TKA patients since 1975 and has provided useful insights with regards the use of knee arthroplasties in younger patients (i.e. an encouraging TKA revision risk reduction from 1976 to 2009, a higher revision rate for UKAs and higher revision rates for both TKAs and UKAs in younger patients). The Australian National Joint Replacement Registry has also found that age adversely affects knee arthroplasty revision rates, noting higher cumulative, ten-year revision rates for both UKA and TKA patients <55 years of age (UKA 25%, TKA 13%) and 55–64 years of age (UKA 17%, TKA 8%) and a 6X greater revision rate for TKA patients <55 compared to those >75 years of age! In addition, although mobile-bearing TKAs have often been promoted for use in younger patients, higher cumulative revision rates were noted for mobile-bearing TKAs (7%) as compared to fixed-bearing TKAs (5%) at 10 years.

In summary, although TKA outcomes have improved with time, the lack of long-term supporting data should prompt surgeons to be cautious in offering TKA to patients with 20 to 40 more years of life expectancy. New TKA bearing couple technologies (ie. cross-linked polyethylenes and improved femoral counterfaces) should be encouraged, but their introduction should not be based on laboratory tests alone, but also supported by safety and efficacy studies in patients and long-term post-market surveillance data.

Obesity is a growing worldwide health issue! In my home country, the percentage of obese Canadians grew from 13.8% in 1979 to 23.1% in 2004. Interestingly, TKA rates have grown substantially during this time frame and obesity seems to have been a major contributor. In a large study, we found that increasing obesity had an exponential effect on TKA rates (i.e. patients with a body mass index >40 having a 33X greater relative risk of receiving a TKA compared to a normal weight patients). This is an important issue, as obese TKA patients have been shown to have greater pre-operative disability, have longer waits for surgery, be associated with greater technical difficulties (i.e. wound healing, infection, ligamentous injury, deep vein thrombosis and medical issues) and have more peri-operative complications. As a result, some countries have advocated deferring TKAs in obese patients until they have lost a substantial amount of weight despite the fact that many studies have demonstrated that the required weight reduction is seldom achieved. In an effort to understand this issue, we have conducted several studies. In a multicentre study, we could find no link between patient obesity and the level of patient satisfaction following a primary TKA. In another mid-term study, we found that obese patients had equal implant survivorship, but did note that obese patients had lower pre-operative and post-operative health-related quality of life outcome scores. However, in this manuscript we advocated determining the ‘improvement or delta score’ (i.e. difference between the pre-operative and post-operative scores) and found that when this was done, obese TKA patients actually demonstrated more improvement than normal and overweight patients!

Based on our research, we would make the following recommendations: (1) the public should be educated on the effect of obesity on TKA rates, (2) weight management should be an important part of non-operative knee arthritis management and (3) TKA should ‘not’ be withheld from obese patients with end-stage knee arthritis.

Purpose

The pros and cons of general anesthesia versus spinal anesthesia in total hip arthroplasty has been a long debated topic. The purpose of this study was to compare the surgical times, blood loss and transfusion requirements between anesthetic types in patients undergoing primary total hip arthroplasty.

Introduction

The new Knee Society Score has been developed and validated, in part, to characterize better the expectations, components of satisfaction, and the physical activities of the younger, more diverse modern population of TKA patients. This study aims to reveal patients' activity levels' post-TKA and to determine how it contributes to their subjective evaluation of the surgery.

Wear of the polyethylene (PE) insert in total knee replacements can lead to wear-particle and fluid-pressure induced osteolysis. One major factor affecting the wear behaviour of the PE insert in-vivo is the surface characteristics of the articulating femoral components. Contemporary femoral components available in Canada are either made of cast Cobalt Chromium (CoCr) alloy or have an oxidized zirconium surface (Oxinium). The latter type of femoral components have shown to have increased abrasive wear resistance and increased surface wettability, thus leading to reduced PE wear in-vitro compared with conventional cast CoCr components. Although surface damage has been reported on femoral components in general, there have been no reports in the literature as to what extent the recommended operating techniques affect the surface tribology of either type of femoral component.

Twenty-two retrieved total knee replacements were identified with profound surface damage on the posterior aspect of the femoral condyles. The femoral components were of three different knee systems: five retrievals from the NexGen(r) total knee system (Zimmer Inc., Warsaw, IN), twelve retrievals from the Genesis II(r) total knee system (CoCr alloy or Oxinium; Smith & Nephew Inc., Memphis, TN), and five retrievals from the Duracon(r) total knee system (Stryker Inc., Mahwah, NJ). Reasons for revision were all non-wear-related and included aseptic loosening in two cases, painful flexion instability, and chronic infection. All retrieved femoral components showed evidence of surface damage on the condyles, at an average of 99° flexion (range, 43° – 135° flexion). Titanium (Ti) alloy transfer and abrasive surface damage were evident on all retrieved CoCr alloy femoral components that came in contact with Ti alloy tibial trays. Surface damage on the retrieved Oxinium femoral components was gouging, associated with the removal and cracking of the oxide and exposure of the zirconium alloy substrate material. CoCr alloy femoral components that had unintended contact with CoCr alloy tibial trays also showed evidence of gouging and abrasive wear.

All femoral components showed severe surface damage in the posterior aspect of the condyles. The femoral surface was heavily scratched and the oxidized zirconium coating surface appeared removed. The surface analysis suggested that the surface damage most likely occurred during the time of initial implantation. In particular, it appeared that the femoral condyles were resting on the posterior aspect of the tibial tray in flexion, thus scratching the femoral components. Such scratches could potentially lead to accelerated PE insert wear and reduced implant longevity, thus making expensive revisions surgery necessary. The authors strongly suggest a revision of the current operating techniques recommended by the implant manufacturer to prevent this type of surface damage from occurring.

Summary Sentence: Cementless solid tri-spiked titanium shells, with a polished inner surface and improved locking mechanism, demonstrated excellent fixation and survivorship at mid-term (minimum 5 years) follow-up.

Introduction: The tri-spiked Reflection cup (Smith & Nephew, Memphis) is a second-generation solid titanium shell with a polished inner surface, no screw holes and an improved locking mechanism. The purpose of this prospective study was to evaluate the minimum 5-year clinical & radiographic results and survivorship of this second-generation acetabular component.

Methods: Between 1997 and 2003, 659 primary THA were performed using the Reflection tri-spiked socket. None of the shells had adjuvant fixation with screws. The mean follow-up time was 7.0 years (5 to 11 yrs). The patients were followed prospectively using validated clinical outcome scores (WOMAC, SF-12, Harris Hip scores) and yearly radiographs.

Results: Twenty-seven patients had died before the minimum 5-year follow-up period. The mean Harris Hip and WOMAC scores were 89 and 79 respectively at last follow-up. Three sockets (0.6%) had been revised: two for infection, one for component malpositioning. No cup was revised for aseptic loosening. Six liners were exchanged: three for residual instability, 3 for wear associated with aseptic loosening of the stem. Radiographic review of remaining cups in-situ identified no cases of loosening and only a small number of cups (< 3%) with any osteolysis. The KM survivorship analysis with revision for any reason, was 97.5% and 97.4% at 5 and 10 years, while survivorship of the acetabular component was 99.8% at 5 and 10 years.

Conclusions: This second-generation cementless solid tri-spiked titanium shell, with a polished inner surface and improved locking mechanism, demonstrated excellent fixation and survivorship at mid-term follow-up.

Sixty four patients undergoing total hip replacement (THR) were randomized to receive a peri-articular intra-operative multi modal drug injection or to receive no injection. All patients received patient controlled analgesia (PCA) for 24 hours after surgery.

Patients receiving the peri-articular injection showed significantly less PCA consumption 6 hours postoperatively (P< 0.002). The 24 hour PCA requirement post surgery was also less (P< 0.009).

The VAS score for pain on activity in the post anaesthetic care unit (PACU) was significantly less for injected patients (P< 0.04). The VAS satisfaction score for injected patients in the PACU and 4 hours post-operatively showed no statistical difference.

Peri-articular intra-operative injection with multimodal drugs can significantly reduce post-operative patient controlled analgesia requirements and pain on activity in patients undergoing total hip replacement with no apparent increase in risk.

Background: Short-term cure rates of two stage revision for infection after TKR are approximately 90%. Little is known about the long-term reinfection-free survival or the mechanical durability of the reimplanted prostheses. The purpose of the study is to evaluate the mid to long term results of this technique with regards to persistence of infection, clinical and radiographic results. The hypothesis is that the success rate of the technique is maintained through long term follow-up, with a low rate of recurrent infection and mechanical implant failure.

Methods: from January 1990 to august 2002, 124 two stage revision TKR for infection were performed at Our Institution with mean follow-up of 9,8 years (5 to 17,5).

The clinical results were evaluated with SF12, WOMAC, and KSCRS performed preoperatively and postoperatively at 5 and 10 years. A radiographic analysis was performed using x-rays of the last available follow-up.

Results: the WOMAC and KSCRS significantly improved at the 5 years follow-up decreasing slightly at 10 years. The SF12 postoperative variation was not significant. The radiographic results showed possible loosening of the tibial or femoral components on 17% and 12% of patients respectively. There were 17 reoperations, 10 of which for persistent infection (85% of survival at 10 years).

Discusssion and conclusion: we are encouraged by the rate of eradication of infection at 10 or more years in these difficult cases. The long term clinical and radiographic results are satisfactory. The study supports the sustained use of this technique for infected total knee arthroplasties.

The purpose of the current study was to compare mid-term outcomes of posterior cruciate retaining(CR) versus posterior cruciate substituting (PS)procedures, using the Genesis II total knee arthroplasty (TKA) system(Smith and Nephew, Memphis TN). Ninety nine CR and 93 PS TKA’s were analysed in this prospective, randomised, clinical trial. Surgeries were performed at seven medical centres by participating surgeons. Clinical outcomes (Knee Society Score, Range of Motion, WOMAC, SF 12 : and radiographic findings), in addition to postoperative complications, were evaluated with a minimum follow-up of five years. Following data analysis, there were no Significant differences in patient demographics or pre-operative clinical measures between the two groups. At the latest follow-up interval, no Significant differences were found between the CR and PS groups with regard to functional assessment, patient satisfaction or post-operative complications. However the PS group did display statistically Significant improvements in range of motion when compared with the CR group. The results of this investigation would suggest that while comparable in regards to supporting good clinical outcomes, the PS Genesis II design does appear to support significantly improved post-operative range of motion when compared with the CR design

Aim: The purpose of this study was to report our experience mid to long-term results of hybrid cement fixation in revision total knee arthroplasty.

Methods: Patients who underwent revision total knee arthroplasty using a hybrid cement technique (press-fit diaphyseal fixation and cemented metaphyseal fixation) with a titanium fluted revision knee implant were reviewed. There were 127 patients. Mean age at surgery was 71 years (range 41–94 years). There were 56 males and 71 females. Mean follow-up was 5 years (range, 2–12 years). A Kaplan-Meier survivorship analysis using an end-point of revision surgery or radiographic loosening was employed to determine probability of survival at 5 and 10 years.

Results: 127 patients (135 knees), 31 patients (36 knees) died and 2 patients (2 knees) were lost to follow-up. Six patients (six knees) were revised at a mean of 3.5 years (range 1–8 yrs). Of the 6 revisions, two were for re-infection, two were for (MCL) instability, and two were for aseptic loosening. Mean Knee Society clinical and functional scores were 86 and 55 points, respectively. The mean range of motion was 108 degrees. End of stem pain was not reported in this group of patients. Kaplan-Meier survivorship analysis revealed a probability of survival free of revision for aseptic loosening of 98% at 12 years.

Discussion: The results of this study suggest that the use of a hybrid cement technique in revision knee arthroplasty can provide good mid to long-term results. Radiographic analysis has shown continued satisfactory appearances regardless of constraint, stem size and augments. Our experience has shown that the survivorship of a hybrid fixation technique for revision knee arthroplasty is comparable to reported long-term survivorship of cemented revision knee arthroplasty.

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.

There is an increasing trend towards performing a high tibial osteotomy (HTO) with a medial opening wedge technique. Amongst the potential advantages is easier conversion to a total knee replacement (TKR), although literature regarding this is scarce. We report our early clinical and radiological results, along with the technical issues encountered.

From our database, we identified thirty-one patients who had undergone thirty-two TKRs after medial opening wedge HTOs. Clinic and operative records were reviewed, and our database used for knee society scores. Those patients not seen in the last twelve months were reviewed in clinic. All pre- and postoperative radiographs were reviewed. The average age of the patients was fifty-seven years, and the average time from HTO to TKR was 4.5 years.

Difficulties with patella eversion were seen in 12.5%, and the knee balanced easily in 85% of cases. The tibia had minimal deformity in most cases, and all osteotomies were healed at the time of conversion. A stem was used in ten cases, and only if metalwork was removed at the time of conversion (which was done in twenty-three of the thirty-two). Minimum one year follow-up was available for twenty-six patients, with a mean follow-up time of twenty-eight months (range twelve to ninety-three months). The average Knee Society knee score was eighty-eight, function score seventy-five, and total score one hundred and sixty-two. Compared to non-matched group of 1149 primary TKRs (of older average age), the knee score was significantly lower, and there was a higher percentage of patients in the poor category. Poor results correlated strongly to the presence of chronic pain or workers compensation issues, and also to whether the knee had undergone revision HTO prior to TKR.

We conclude that the conversion of a medial opening wedge HTO to a TKR is relatively straightforward technically, and some aspects are easier than performing a TKR after a lateral closing wedge osteotomy (using historical controls). The clinical results appear inferior to that of a TKR performed without a prior osteotomy, although the results in our osteotomy group were skewed by a small group of chronic pain and workers compensation cases.

The purpose of this study was to analyse the twenty to twenty-five year outcomes of one hundred and ninetyfive cemented, matte finish, HD-2 THRs performed in one hundred and sixty-six patients with osteoarthritis of the hip by two surgeons.

The one hundred and ninety-five THRs (one hundred and sixty-six patients) were followed prospectively by clinical assessment using the Harris Hip Score (HHS) and radiographic analysis.

One hundred and forty-nine patients (90%) died with their implant still functioning or still had a successful implant at twenty to twenty-five years follow-up. Ten patients (6%) underwent a revision for aseptic loosening of the acetabular (n=2, 1.2%) or femoral (n=4, 2.4%) component, or both (n=4, 2.4%), that was related to wear-induced osteolysis. 7 (4.2%) patients (eight hips) were lost to follow-up. The mean HHS at the latest follow-up (twenty to twenty-five years) was 88±9. Radiographically, twenty-nine (85%) of the acetabular components were well fixed and four (12%) were probably or possibly loose. Two hips (6%) had probable or possible loosening of the femoral component. At twenty five years, the calculated cumulative survival rate (Kaplan-Meier method) revealed excellent results for revisions (83%±6, any cause) and aseptic loosening (86%±6, femoral component, 93%±3, acetabular component).

The surviving patients had a good mean follow-up and radiographic fixation, proving the exceptional long-term success of this implant.

The purpose of this study is to compare the long-term clinical results of two total knee replacement designs (the SAL-II mobile-bearing implant and the fixed-bearing Genesis I implant) to see if there are any advantages to the use of a mobile-bearing design in the long-term.

One hundred and ninety-two patients with an age range between twenty-five to ninety who were implanted with either an SAL-II (Group A) or GEN I (Group B) at London Health Sciences Center, University of Western Ontario, were included in the study. Patients with a diagnosis of inflammatory arthritis or with previous high tibial osteotomy were excluded from the study. Demographic data as well as functional outcome measures such as range of motion, knee alignment, specific measures of activities with daily tasks, and composite knee scores such as the Knee Society Clinical Score and Functional Score were collected from the patients’ medical charts and compared. Data was analyzed using SPSS V14.0 statistical software.

Group A included eighty-three mobile-bearing platform arthroplasties in seventy-seven patients. There were forty-one males and thirty-six females. The average age of the patients at the time of surgery was 67.7. Average follow up time was 10.56 years from the date of surgery. Eleven patients were excluded from the study, ten due to previous HTO surgery and one due to rheumatoid arthritis. At latest follow-up, ten patients required revision, and fifteen patients died. Group B included one hundred and thirty-one fixed-bearing knee arthroplasties in one hundred and fourteen patients. There were forty-one males and seventy-three females. The average age of the patients at the time of surgery was 65.8. Average follow up time was 9.58 years from the date of surgery. Twenty five patients were excluded from the study, twenty three patients due to previous HTO surgery and two patients due to rheumatoid arthritis. At latest follow-up, thirteen patients required revision, and twelve patients had died. Include Results and p-values at this stage. No statistically significant difference was found between the groups, either for the knee score (p=0.536), the function score (p=0.115), the range of movement (p=0.718) and number of revisions. Ten years survivorship for mobile bearing group was significantly lower than the fixed bearing group (p=0.005) although this equalised at fifteen years.

This study is the first long-term study that compares the results of the mobile-bearing and fixed bearing designs performed by the same surgeons in the same period of time. The results of this study show no difference in these two designs at a mean of ten years follow-up although fixed bearing design demonstrated better overall ten years survivorship. This difference can be related to the earlier mobile bearing revisions due to aseptic loosening and instability. Mobile bearing designs have yet to prove their theoretical advantage in clinical practice.

The purposes of this study were to determine the effect of severity, wait times and patient perspective on outcomes and to create an eivdence-based prioritization tool.

Patients who received a primary hip or knee replacement were followed forward from decision date for surgery to one-year follow-up (N = 4437) and outcomes assessed according to baseline severity. At decision date for surgery, patient baseline severity was captured using the WOMAC disability questionnaire. Twelve to eighteen months after surgery, a questionnaire (WOMAC, satisfaction) was sent to patients to compare pre- and post-operative data.

The chance of a good outcome from TJR surgery gets worse as wait times get longer. Baseline severity affects outcome more than wait times. Patients with a baseline WOMAC less then 30/100 should have surgery within three months (20% patients) If surgery cannot be done within three months, then three priority levels are recommended: Priority I – One month maximum: catastrophic hip or knee joint conditions – complications that are an immediate threat to independence. Priority II – three months maximum: extreme pain and disability because of hip or knee joint condition that will be a threat to role and independence within three months (baseline WOMAC less than or equal to 30/100). Priority III – six months maximum: severe pain or disability because of hip or knee joint condition, but role and independence not threatened (baseline WOMAC over 30/100).

The priority levels and wait time thresholds recommended in this study are the result of an analysis of pre-operative severity scores, the length of the wait and post-operative outcomes and are consistent with data from other sources.

This study reports the survivorship free of revision or radiographic loosening of one hundred and eight consecutive cemented Miller-Galante unicompartmental knee arthroplasties at a mean ten-year follow-up.

The purpose of this study was to report our experience with the Miller-Galante (MG) unicompartmental knee arthroplasty (UKA) at a mean ten-year follow-up in order to determine if this procedure can provide durable long-term clinical results.

One hundred and eight cemented MG-UKAs in eighty-two patients performed by two surgeons between 1988 and 1997 were reviewed. There were one hundred and six medial and two lateral MG-UKAs performed. Mean age at surgery was sixty-seven years (range, thirty-nine to eighty-seven). There were forty-four males and thirty-eight females. Mean follow-up was ten years (range, five to thirteen). A Kaplan-Meier survivorship analysis using an end-point of revision surgery or radiographic loosening was employed to determine probability of survival at five and ten years.

Of the eighty-two patients (one hundred and eight knees), nine patients (eleven knees) died and one patient (two knees) was lost to follow-up. Eleven patients (eleven knees) were revised at a mean of four years (range, one to nine), and one patient demonstrated radiographic loosening of the tibial component at seven years. Of the eleven revisions, only two required use of revision components. Mean pre-operative and final follow-up Knee Society clinical and functional scores were forty-seven and fifty-three, and ninety and seventy-nine points, respectively. Kaplan-Meier survivorship analysis revealed a probability of survival free of revision or radiographic loosening of 93% at five years and 88% at ten years.

The results of this study demonstrate that the MG-UKA can provide reliable pain relief and restoration of function in selected patients. Our experience has shown that the survivorship of the MG-UKA approaches that of tricompartmental knee arthroplasty, and suggests that UKA may offer the advantage of ease of revision.

The results of a randomized controlled clinical trial of ninety patients comparing resurfacing to non-resurfacing of the patella in total knee arthroplasty (TKA) are reported with a minimum of ten-years of follow-up. Using a cruciate retaining hybrid TKA, the outcome measures included Knee Society Clinical Rating scores, functional testing (stair climb and flexion extension torques), patient satisfaction, anterior knee pain, and a patellofemoral specific questionnaire. The results indicated no difference between the groups in all categories. Results at two and ten years postoperatively are compared. This study represents the longest follow-up to date comparing resurfacing to nonresurfacing of the patella.

Patellar resurfacing in TKA remains controversial.

Purpose: To evaluate the results of resurfacing/non-resurfacing of the patella in a randomized controlled clinical trial at a minimum of ten-years of follow-up.

One hundred knees (ninety patients) with osteoarthritis were enrolled in a prospective randomized controlled double-blinded trial using the same posterior cruciate retaining total knee replacement. Patients were randomized to resurfacing or nonresurfacing of the patella. Evaluations were performed preoperatively and yearly to a minimum ten years (range, 10.1–11.5 years) postoperatively. Disease specific (Knee Society Clinical Rating System), functional (stair climbing, knee flex-ion/extension torques, patellar examination) outcomes were measured. Patient satisfaction, anterior knee pain, and patellofemoral questionnaires were completed. Intraoperative grading of the articular cartilage was performed.

No patients were lost to follow-up; forty-six knees remained alive. Nine revisions (9/90-ten percent) were performed – 7/48 (fifteen percent) in the nonresurfaced and 2/42 (five percent) in the resurfaced group. Three knees in the nonresurfaced group were revised to a resurfaced patella for anterior knee pain. One resurfaced patella was complicated by AVN and fracture, requiring revision. No significant difference was found between the groups regarding revision rates, KSCR score, functional, satisfaction, anterior knee pain, patellofemoral, and radiographic outcomes. Intraoperative cartilage quality was not a predictor of outcome.

This study represents the longest follow up to date of a randomized controlled clinical trial to examine patellar resurfacing in TKA. The results showed no significant difference between the groups for all outcome measures at a minimum of ten-years.

The pathogenesis of osteolysis in failed total hip arthroplasty is not fully understood. The purpose of this study is to identify CD4+CD25+ Regulatory T cells in periprosthetic tissues in failed total hip replacements secondary to osteolysis. Intra-operative tissue samples and peripheral blood were collected from patients undergoing revision total hip arthroplasty surgery. Regulatory T cells were present in the tissues, and significantly increased in the peripheral blood in patients with failed total hips compared to normal controls. Further characterization of these regulatory T cells are warranted as they may play a role in osteolysis in loose total hip replacements.

Osteolysis remains the most common complication following total joint arthroplasty. To date, no authors have investigated the role of CD4+CD25+ regulatory T cells (T_REG) participating in the osteolytic pathogenesis. The purpose of this study is to quantitate the presence of T_REG cells in periprosthetic tissues in failed total hip replacements secondary to osteolysis.

Fifteen consecutive patients booked for revision total hip arthroplasty secondary to osteolysis were included. Tissue samples were collected: peripheral blood (PB), synovial fluid (SF), synovial tissue (ST), and interface tissue (IT) between the failed component and the bone defect. Total lymphocytes were isolated and analyzed using fluorescent-tagged antibody cell sorting (FACS) for the presence of T_REG cells. Frozen sections of ST and IT were analyzed with immunohistochemistry for T_REG cells.

T_REG cells were significantly upregulated (p< 0.01) in the PB (68%) of revision hip patients compared to normal controls PB (44%). In the synovial tissue (ST) and interface tissue (IT), 57% of the lymphocytes isolated were TREG cells. The presence of T_REG cells in the ST and IT were confirmed with immunohistochemistry.

T_REG cells are upregulated in the peripheral blood of patients with failed total hips secondary to osteolysis. The TREG cells are also present in the synovial tissue and interface tissue.

Evidence for involvement of regulatory T cells contribute to our understanding of this complex biologic response to artificial wear particles.

Functional studies of these T_REG cells are warranted as they are upregulated in patients with loose total hip replacements.

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL^® (mobile bearing) versus the AMK^® and Genesis II^® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).

The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL^®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK^®, Depuy and Genesis II^®, Smith and Nephew).

Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°).

No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Funding: London Health Sciences Centre Internal Research Fund

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL^® (mobile bearing) versus the AMK^® and Genesis II^® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).

The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL^®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK^®, Depuy and Genesis II^®, Smith and Nephew).

Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°).

No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Funding: London Health Sciences Centre Internal Research Fund