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.

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.

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

In recent years articulating cement spacers have been used to treat infected knee arthroplasty. The aim has been to better maintain tissue planes and joint mobility thereby improving second stage re-implantation surgery. Two groups of patients treated for infected knee arthroplasty were reviewed. Twenty-six patients with articulating and forty patients with static antibiotic-impregnated methyl-methacrylate spacers were compared. The articulating spacers demonstrated easier surgical exposure at second stage and improved range of knee motion after re-implantation. There was no compromise in the rate of infection eradication with articulating spacers. Bone loss at revision was independent of spacer type.

To compare the results of patients treated with articulating versus static antibiotic-impregnated spacers for infected knee arthroplasty.

Articulating cement spacers facilitate re-implantation surgery by maintaining tissue planes and joint mobility without compromising joint stability or eradication rate of infection. Patients demonstrate better range of motion and less complications related to the extensor mechanism with the articulated spacer.

Antibiotic impregnated methyl-methacrylate spacers have become a mainstay in two-stage revision arthroplasty for sepsis. It is thought that articulating cement spacers facilitate prosthesis re-insertion by better maintaining tissue planes and joint mobility between stages.

In the articulating group fewer extensile exposure methods were required at second stage prosthesis reimplantation (19% vs 36 %). No tibial tuberosity osteotomies have been required since using the articulating spacer. The articulating group demonstrated a significantly improved range of flexion compared to the static group(106 vs 97 degrees- p=0.045) and had fewer patients with significant loss of extension or quadriceps lag. Eradication of infection was improved in the articulating group (92% vs 82%) but at shorter average follow-up. The need for augments and stabilized prostheses at revision surgery as a measure of bone loss was no different between the groups but was related to the number of prior surgical procedures.

Twenty-six patients treated with articulating spacers were compared to a matched consecutive group of forty patients treated with static spacers. Minimum follow-up was twelve months from second stage re-implantation (average twenty-two months articulating, forty months static)

Funding: No direct funding from any commercial source has been received for this study. The primary author’s fellowship position is partially funded by Smith and Nephew Richards Inc.

In recent years articulating cement spacers have been used to treat infected knee arthroplasty. The aim has been to better maintain tissue planes and joint mobility thereby improving second stage re-implantation surgery. Two groups of patients treated for infected knee arthroplasty were reviewed. Twenty-six patients with articulating and forty patients with static antibiotic-impregnated methyl-methacrylate spacers were compared. The articulating spacers demonstrated easier surgical exposure at second stage and improved range of knee motion after re-implantation. There was no compromise in the rate of infection eradication with articulating spacers. Bone loss at revision was independent of spacer type.

To compare the results of patients treated with articulating versus static antibiotic-impregnated spacers for infected knee arthroplasty.

Articulating cement spacers facilitate re-implantation surgery by maintaining tissue planes and joint mobility without compromising joint stability or eradication rate of infection. Patients demonstrate better range of motion and less complications related to the extensor mechanism with the articulated spacer.

Antibiotic impregnated methyl-methacrylate spacers have become a mainstay in two-stage revision arthroplasty for sepsis. It is thought that articulating cement spacers facilitate prosthesis re-insertion by better maintaining tissue planes and joint mobility between stages.

In the articulating group fewer extensile exposure methods were required at second stage prosthesis reimplantation (19% vs 36 %). No tibial tuberosity osteotomies have been required since using the articulating spacer. The articulating group demonstrated a significantly improved range of flexion compared to the static group(106 vs 97 degrees- p=0.045) and had fewer patients with significant loss of extension or quadriceps lag. Eradication of infection was improved in the articulating group (92% vs 82%) but at shorter average follow-up. The need for augments and stabilized prostheses at revision surgery as a measure of bone loss was no different between the groups but was related to the number of prior surgical procedures.

Twenty-six patients treated with articulating spacers were compared to a matched consecutive group of forty patients treated with static spacers. Minimum follow-up was twelve months from second stage re-implantation (average twenty-two months articulating, forty months static)

Funding: No direct funding from any commercial source has been received for this study. The primary author’s fellowship position is partially funded by Smith and Nephew Richards Inc.

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.

We identified five (2.3%) fractures of the stem in a series of 219 revision procedures using a cementless, cylindrical, extensively porous-coated, distally-fixed femoral stem. Factors relating to the patients, the implant and the operations were compared with those with intact stems. Finite-element analysis was performed on two of the fractured implants.

Factors associated with fracture of the stem were poor proximal bone support (type III–type IV; p = 0.001), a body mass index > 30; (p = 0.014), a smaller diameter of stem (< 13.5 mm; p = 0.007) and the use of an extended trochanteric osteotomy (ETO 4/5: p = 0.028). Finite-element analysis showed that the highest stresses on the stem occurred adjacent to the site of the fracture. The use of a strut graft wired over an extended trochanteric osteotomy in patients lacking proximal femoral cortical support decreased the stresses on the stem by 48%.

We recommend the use of a strut allograft in conjunction with an extended trochanteric osteotomy in patients with poor proximal femoral bone stock.

We carried out the Bernese periacetabular osteotomy for the treatment of 13 dysplastic hips in 11 skeletally mature patients with an underlying neurological diagnosis. Seven hips had flaccid paralysis and six were spastic. The mean age at the time of surgery was 23 years and the mean length of follow-up was 6.4 years. Preoperatively, 11 hips had pain and two had progressive subluxation.

Before operation the mean Tönnis angle was 33°, the mean centre-edge angle was −10°, and the mean extrusion index was 53%. Postoperatively, they were 8°, 25° and 15%, respectively. Pain was eliminated in 7 patients and reduced in four in those who had preoperative pain. One patient developed pain secondary to anterior impingement from excessive retroversion of the acetabulum. Four required a varus proximal femoral osteotomy at the time of the pelvic procedure and one a late varus proximal femoral osteotomy for progressive subluxation.

Before operation no patient had arthritis. At the most recent follow-up one had early arthritis of the hip (Tönnis grade I) and one had advanced arthritis (Tönnis grade III).

Our results suggest that the Bernese periacetabular osteotomy can be used successfully to treat neurogenic acetabular dysplasia in skeletally mature patients.