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 purpose of this study was to determine the greater than 20 year survivorship of the PCA total hip arthroplasty (THA) in patients with severe hip osteoarthritis.

Method: A prospective follow-up of 315 consecutive patients treated with a PCA cementless THA in patients with hip osteoarthritis was performed. Patients had postoperative assessments and radiographs every two years. Overall THA, femoral stem and acetabular cup revisions and Kaplan-Meier survivorship was determined. Revision rates and survivorship was also investigated across gender.

Results: The mean age of our patients was 61 years old (range 20 to 86) with 47% female patients. 226 cases used a 26mm articulation and 89 cases a 32mm articulation. At 23 years follow-up, 188(60%) patients were alive with retained implants while 85(27%) were deceased with still implants that were functioning well. Forty-two cases (13%) were revised (30 sockets, 13 stems), five of which later deceased. The 20 year Kaplan Meier survivorship for the overall THA, stem component and acetabular cup were 86%, 97% and 90% respectively. Survivorship of the acetabular cup for 26mm and 32mm articulations was 92% and 85% respectively (p=0.016). Females had a worse THA survivorship than males, 82% and 91% respectively (p=0.036).

Conclusion: The PCA cementless THA has performed well beyond 20 years with 26 mm articulations doing better than 32 mm, and male gender associated with better outcomes. The authors postulate that polyethylene thickness is key to predicting failure.

Purpose: The purpose of this study was to investigate the mid to long term (minimum 10 years follow-up) survivorship of the AMK total knee arthroplasty (TKA), as well as determine the effect of implant fixation on outcome.

Method: Between 1988 and 2000, 1074 AMK primary total knee arthroplasties were preformed on 843 patients. All diagnosis included, the distribution was 90% osteoarthritis (971), 7% inflammatory arthritis (76) and 3% other diagnoses (27). Average time from surgery was 15 years (range 10–21 years). Average age at primary procedure was 68 years (range 22–99). Fifty-six percent were female (599) and 44% male (475). Preoperative alignment consisted of 56% varus (601) and 17% valgus (182). Ninety percent (968) had patella resurfacing performed, 62% (661) received cemented TKA fixation, on 32% hybrid fixation (cemented femoral component, cementless tibial tray) was performed and 6% (66) had cementless fixation. Two hundred thirty-seven cases were deceased before 20 years follow-up (22%).

Results: At 10 to 21 years follow-up, 129 revisions were performed (12%). The most common reasons for revision were polyethylene wear, particle induced osteolysis, instability and pain (43% of revisions). Implant fixation significantly influenced the rate of revision with cemented fixation having a 6.7% rate of revision (44/661), hybrid fixation a 14% revision rate (47/336) and cementless a 36.4% revision rate (24/66). Excluding infections (11 cases), overall Kaplan-Meier survivorship at five, 10 and 15 years was 96.4%, 91.9% and 85.8%, respectively. At 20 years the predicted Kaplan-Meier survivorship was estimated at 83.5% (no revisions beyond 17.5 years). Cemented fixation was associated with significantly better survivorship than hybrid and cementless fixation (p< 0.0001). At 5, 10 and 15 years cemented AMK TKA survivorship was 97.5%, 94.9% and 91.9% respectively (no revision performed beyond 13.5 years). For hybrid fixation the survival at 5, 10 and 15 years was 97.8%, 92.2% and 85.1% respectively. Cementless AMK THA had a Kaplan-Meier survivor-ship of 88.9%, 78.2% and 57.4% at 5, 10 and 15 years respectively.

Conclusion: Cemented fixation had superior outcomes compared to cementless and hybrid fixation with the most common reasons for revision being polyethylene wear and osteolysis. To our knowledge this the first medium to long term follow-up of the AMK TKA and it demonstrates that method of fixation had a major influence on revision rates and survivorship.

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 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.

Purpose: A randomised controlled trial comparing fixation of a Mallory-Head prosthesis for total hip arthroplasty (THA) with and without cement was performed with average 19 years (range 17–21 years) of continuous follow-up.

Method: Two hundred and fifty patients were randomised to undergo THA using either a Mallory-Head THA prosthesis designed to be inserted with cement or one designed for cementless insertion. Both patients and those involved in outcome assessment were blinded to the type of implantation. Patients were followed yearly after the first post-operative year for outcomes including mortality, revision arthroplasty, and health-related quality of life assessment scores.

Results: Primary THA was performed with cement in 124 patients and without cement in 126 patients. Mean age at the time of surgery was 64 years, and 48% were female. During the period of review, there were 78 (31%) deaths in the cohort, and 75 (30%) patients underwent revision surgery. Kaplan-Meier survivorship analysis revealed significantly increased revision rates in cemented compared with cementless THA using failure of either component (p=0.01) or femoral component (p< 0.001) as endpoints. Although acetabular failure accounted for most revisions overall, no significant difference between groups was noted (p=0.075). With the exception of cost to quality adjusted life years, all quality of life outcome measures improved post-operatively and, although reducing modestly through the period of review, demonstrated no difference between groups at final follow-up.

Conclusion: This study has demonstrated a concerning high revision rate with both cemented and cementless THA in patients with a mean age of 64 years at the time of surgery, which significantly affected cost effectiveness. With the implants studied, cementless femoral fixation was superior to cemented, with no cementless femoral component failures through the duration of this study. This study demonstrates the importance of post-market surveillance and evidence-based improvements in THA design (i.e., bearing couples and fixation).

Purpose: Accurate acetabular cup positioning is essential to successful total hip arthroplasty (THA). Intra-operative navigation of the acetabular component can optimize positioning, but often necessitates registration of the pelvis in the supine position. The majority of surgeons use the lateral position, however, which hides commonly employed registration landmarks. The purpose of this study was to identify novel anatomical landmarks for use in navigated THA from the lateral approach.

Method: We identified 156 patients that underwent pelvic CT scans for non-orthopaedic reasons from which 60 patients (mean age 62 years; 30 males, 30 females) were included in the study. CT scans were analyzed with sophisticated software (region grow, isosurface creation, and geometry overlay features). Saved coordinates from each scan were inputted into the program MATLAB (Mathworks, Natick, MA), v7.0, on a Macintosh-based workstation. A code was created to be able to calculate the normal vector for both planes and then calculate the angle formed between the normal vectors. The anterior plane (pubic tubercle (PT) and anterior superior iliac spine (ASIS)) was defined in addition to a series of lateral planes by retaining the ipsilateral PT and ASIS from the anterior plane, plus a variable third landmark. Angles obtained were those between the anterior and lateral planes. Angle conversions between the planes were analyzed using a paired t-test with a p-value of < 0.05 accepted as significant.

Results: The list of landmarks acquired included those used for supine registration (PT and ASIS) in addition to: posterior superior iliac spine (PSIS); posterior inferior iliac spine, (PIIS); ischial tuberosity (IT); tuber-culum of the iliac crest (TIC); and a line drawn along the outer lip of the iliac crest. The angle between the anterior plane and the novel lateral planes did not show a significant level of variance for two of the proposed lateral planes (P< 0.05).

Conclusion: An imageless navigation system in THA that can be accurately employed in the lateral position will benefit many surgeons. The invariance in angle calculations for the lateral planes calculated using the PSIS and the TIC suggest that they could be novel pelvic landmarks for lateral plane registration.

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: Unicompartmental knee arthroplasty remains a viable treatment modality for arthrosis confined to the medial compartment of the knee. Few studies have reported survivorship of this procedure into the second decade. The purpose of this study was to report our long-term experience with this procedure at a mean follow-up of fifteen years.

Method: Between 1989 and 2000, 113 medial unicompartmental knee arthroplasties in 84 patients were performed using the Miller-Galante prosthesis. The 84 patients had an average age of 68 years old at the time of surgery; 45 of which were male and 39 female. At a mean of fifteen-year follow-up, 22 patients (25 arthroplasties) had died, and the remaining 62 patients (88 arthroplasties) were reviewed and evaluated. No patient was lost to follow-up.

Results: The mean Knee Society knee and function scores had an improvement from 53 and 48 points pre-operatively to 77 and 90 points respectively at time of most recent evaluation. Twenty unicompartmental knee arthroplasties were revised, at an average of seven years (one to fourteen) following index procedure. The five, ten and fifteen-year rates of survival were 94%, 90%, and 86% respectively with revision to tricompartmental knee arthroplasty as the end point.

Conclusion: The Miller-Galante medial unicompartmental knee arthroplasty provided excellent pain relief and restoration of function in carefully selected patients and demonstrated durable implant survival at fifteen years. Progression of arthrosis is the primary mode of failure.

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.

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.

This study reports on the clinical and wear performance of a prospective randomised controlled trial comparing highly cross-linked (XLPE) to conventional polyethylene (PE) in total hip arthroplasty at five years minimum follow-up.

One hundred patients enrolled in a prospective randomised controlled trial received identical hybrid total hip arthroplasties with the exception of the polyethylene insert. Fifty patients received a PE liner (2.5 MRads; gamma-in-nitrogen sterilization) and fifty patients received a XLPE liner (10Mrads; gas-plasma sterilization). Clinical outcomes were determined using Harris Hip, WOMAC and SF-12 scores by an independent study nurse. Femoral head penetration rates were determined using a validated radiographic technique (Hip Analysis Suite 8.0.1.1) based on radiographs at six weeks, one year and yearly post-operatively. Linear regression analysis was performed for both the entire polyethylene groups and on each patient, where the slope represents the steady state head penetration rate (after bedding in) from one to five years follow-up.

None of the patients were lost to follow-up, however, nine patients were deceased before their five year follow-up. Two patients have been revised for loose stems. At average follow-up of 6.0 years (range 5.1–6.8 years), there were no differences in Harris Hip, WOMAC or SF-12 scores. XLPE had a significantly lower (p= 0.03) steady-state head penetration rate of 0.018 mm/year compared to 0.050 mm/year for XLPE (approximately 64% reduction). Analysis of individual patient’s head penetration rates demonstrated a similar significantly lower rate with XLPE (0.004 ± 0.067 mm/year) compared to PE (0.045 ± 0.083 mm/year). Interestingly, when examined by gender, the male PE group had a significantly higher head penetration rate (0.081 ± 0.084 mm/year) than both the male and female XLPE (−0.013 ± 0.104, 0.011 ± 0.074 mm/year, respectively).

At minimum five years follow-up, there were no clinical differences between groups. After bedding-in, there was a significant lower head penetration rate with XLPE compared to PE. Thus, mid-term follow-up appears to demonstrate a significant wear reduction (based on head penetration rates) afforded by first generation XLPE. Long-term follow-up is required to demonstrate the clinical benefit of this new material.

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

Background: Reduced implant survivorship due to aseptic loosening has prompted research into alternative bearing materials. Simulator testing is useful, but clinical studies are the gold standard to evaluate the wear characteristics of new bearing materials. Net compression molded polyethylene has clinically reported improved wear characteristics over traditionally used RAM extruded UHMWPE 1,4,17,22. Machining of the compression molded acetabular component however may be detrimental to its wear properties 29. We report a 23–29% increase in 2D and 3D linear and volumetric wear in a cohort of patients in which machined compression molded acetabular components were used.

Methods: Ninety-two patients matched for gender, body mass index, primary pathology, Charnley grade, and length of follow up underwent uncemented total hip replacement using an identical acetabular and femoral implant. Group 1 (52 patients) had a RAM extruded polyethylene liner (GUR 4150 HP) and Group 2 (40 patients) had a machined compression molded polyethylene liner (Montell H 1900). UHMWPE sterilisation regimes were identical. Antero-posterior and lateral radiographs were analysed for acetabular wear using the Martell technique at a minimum follow up of five years and a maximum mean follow up of 87.4 months for group 1 (SD=8.7) and 84.9 months for group 2 (SD 7.7).

Results: Both 2D and 3D linear and volumetric wear rates in patients with a RAM extruded polyethylene acetabular component were 23–29% less compared to patients that received a machined compression molded acetabular liner. There was a statistical difference in age between to the two groups (P=0.007). Looking at acetabular wear in patients over 55 years, machined compression poly was still 16–31 % worse then RAM extruded polyethylene although statistical difference could not be reached for 3D linear and volumetric wear. The incidence of acetabular osteolysis on review of radiographs at maximum follow up was similar in both groups (group 1 =16.3% versus group 2 =15%).

Conclusions: Despite favourable reports of improved wear characteristics of net compression molded UHMWPE, this study shows a 23– 29% increase in 2D and 3D linear and volumetric wear in machined compression molded acetabular components. It appears that machining of compression molded polyethylene bar stock, to obtain the final component, is detrimental to the wear properties of the acetabular liner.