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In 2002, a patient underwent revision total hip arthroplasty for polyethylene wear. The acetabular cup was well fixed, and it was decided to cement a new polyethylene liner into the existing cup. In 2006, the patient presented with inability to weight bear and easy subluxation of the hip. Revision surgery was performed, and all components were examined postoperatively. Investigation with microcomputed tomography revealed that the liner had plastically deformed at the superior pole resulting in the hip instability. The reasons for this are suspected to be related to the abducted nature of the original cup and an uneven cement mantle. This report suggests that cementation of polyethylene liners into metal cups has limitations and is not appropriate in all circumstances.

Erratum to ‘‘Co-activation differences in lower limb muscles between asymptomatic controls and those with varying degrees of knee osteoarthritis during walking” [Clin. Biomech. 24 (2009) 407–414] Cheryl L. Hubley-Kozey *, Nicholas A. Hill , Derek J. Rutherford , Michael J. Dunbar , William D. Stanish b,c a School of Physiotherapy, Dalhousie University, 5869 University Avenue, Halifax, NS, Canada B3H 3J5 b School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada Department of Surgery, Dalhousie University, Halifax, NS, Canada

Long stemmed implants are frequently utilized during revision total knee arthroplasties (TKA) to reduce load at the proximal tibial bone implant interface. Yet, the surgeon performing the revision TKA is faced with many decisions including the mode of fixation and stem configurations. There is a growing interest among surgeons to better quantify the effects of stem parameters. Past finite element [Au, 2005], in-vitro [Stern, 1997], and clinical [Fehring, 2003] studies have quantified individual parameters, but no consensus has been reached. These past studies quantified their results based on one parameter at a time analysis. Yet factorial analysis allows us to not only investigate the effect of individual parameters, but also how these parameters interact with each other. Therefore the goal of this study was to perform a three factor factorial analysis to investigate which parameters have the largest effect on maximum micromotion, and if there are any interactions among these parameters.

Question: In patients having total hip replacement, is celecoxib as effective as ibuprofen in preventing heterotopic ossification 3 months after surgery? Design: Randomized (allocation concealed), blinded (outcome assessors), controlled trial with 3-month follow-up. Setting: A university hospital in Geneva, Switzerland. Patients: 250 patients (mean age, 70 y; 54% women) with severe osteoarthritis of the hip who were scheduled for total hip replacement. Exclusion criteria were moderate to severe renal impairment, a history of gastrointestinal ulcers, and immediate-type hypersensitivity to nonsteroidal anti-inflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors. 240 patients (96%) were available for follow-up. Intervention: Patients were allocated to receive celecoxib, 200 mg twice daily (n = 123), or ibuprofen, 400 mg 3 times daily (n = 127) for 10 days after surgery. All patients had total hip replacement by a direct lateral approach, with an uncemented acetabular component and a cemented femoral stem, and received prophylaxis for deep venous thrombosis with low-molecular-weight heparin for 5 days after surgery and oral anticoagulation for the next 6 weeks. Main outcome measures: Presence ofheterotopic ossification on an anteroposterior radiograph of the pelvis at 3 months. Heterotopic ossification was assessed according to the Brooker classification (class I = islands of bone within soft tissue around the hip; class II = bone spurs from the pelvis or proximal aspect of the femur, leaving ≥1 cm between opposing bone surfaces; class III = bone spurs from the pelvis or proximal aspect of the femur, leaving

The Swedish Knee Arthroplasty Registry (SKAR) has recorded knee arthroplasties prospectively in Sweden since 1975. The only outcome measure available to date has been revision status. While questionnaires on health outcome may function as more comprehensive endpoints, it is unclear which are the most appropriate. We tested various outcome questionnaires in order to determine which is the best for patients who have had knee arthroplasty as applied in a cross-sectional, discriminative, postal survey. Four general health questionnaires (NHP, SF-12, SF-36 and SIP) and three disease/site-specific questionnaires (Lequesne, Oxford-12, and WOMAC) were tested on 3600 patients randomly selected from the SKAR. Differences were found between questionnaires in response rate, time required for completion, the need for assistance, the efficiency of completion, the validity of the content and the reliability. The mean overall ranks for each questionnaire were generated. The SF-12 ranked the best for the general health, and the Oxford-12 for the disease/site-specific questionnaires. These two questionnaires could therefore be recommended as the most appropriate for use with a large knee arthroplasty database in a cross-sectional population.

SummaryObjectiveObesity is a highly cited risk factor for knee osteoarthritis (OA), but its role in knee OA pathogenesis and progression is not as clear. Excess weight may contribute to an increased mechanical burden and altered dynamic movement and loading patterns at the knee. The objective of this study was to examine the interacting role of moderate knee OA disease presence and obesity on knee joint mechanics during gait.MethodsGait analysis was performed on 104 asymptomatic and 140 individuals with moderate knee OA. Each subject group was divided into three body mass categories based on body mass index (BMI): healthy weight (BMI30). Three-dimensional knee joint angles and net external knee joint moments were calculated and waveform principal component analysis (PCA) was applied to extract major patterns of variability from each. PC scores for major patterns were compared between groups using a two-factor ANOVA.ResultsSignificant BMI main effects were found in the pattern of the knee adduction moment, the knee flexion moment, and the knee rotation moment during gait. Two interaction effects between moderate OA disease presence and BMI were also found that described different changes in the knee flexion moment and the knee flexion angle with increased BMI with and without knee OA.ConclusionOur results suggest that increased BMI is associated with different changes in biomechanical patterns of the knee joint during gait depending on the presence of moderate knee OA.

Summary Objective Little is known about the relationships among pain, function, psychological variables like perceived helplessness and emotional health, and patient satisfaction in people with revision knee replacement surgery. We hypothesized that pain and function would have a direct association with satisfaction as well as an indirect association through patient perceptions of helplessness and emotional health. Design This longitudinal study included 145 participants undergoing revision knee replacement surgery. Demographic data and expectation of benefit from surgery were recorded prior to surgery. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Arthritis Helplessness Scale (AHS) and the Mental Component Scale (MCS) of the SF-36 (emotional health) were collected prior to and 2 years post-surgery. Satisfaction was recorded 2 years post-surgery. Regression analyses were conducted to test for mediation effects of helplessness and MCS. Results Participants were on average 69 years old and 54% were women. Participants were satisfied with the results of the surgery (mean ± standard deviation (SD) = 70.42 ± 31.46). Less pain and functional disability were associated with increased patient satisfaction and, the effect of pain or function was also mediated through helplessness whereby more pain and disability were associated with perceptions of helplessness and helplessness was associated with lower satisfaction. MCS did not mediate the relationship of pain and function with satisfaction. Conclusion Helplessness plays an important role in understanding patient satisfaction. Interventions aimed at improving patient outcome should target not only pain and function but also should address strategies to support people in managing following knee revision surgery to maximize satisfaction with outcome.

Background While some studies have identified patient readiness as a key component in their decision whether to have total joint replacement surgery (TJR), none have examined how patients determine their readiness for surgery. The study purpose was to explore the concept of patient readiness and describe the factors patients consider when assessing their readiness for TJR. Methods Nine focus groups (4 pre-surgery, 5 post-surgery) were held in four Canadian cities. Participants had been either referred to or seen by an orthopaedic surgeon for TJR or had undergone TJR. The method of analysis was qualitative thematic analysis. Results There were 65 participants, 66% female and 34% male, 80% urban, with an average age of 65 years (SD 10). Readiness reflected both the surgeon’s advice that the patient was clinically ready for surgery and the patient’s feeling that they were both mentally and physically ready for surgery. Mental readiness was described as an internal state or feeling of being ready or prepared while physical readiness was described as being physically fit and in good shape for surgery. Factors associated with readiness included: 1) pain: its severity, the ability to cope with it, and how it affected their quality of life; 2) mental preparation; 3) physical preparation; 4) the optimal timing of surgery, including age, anticipated rate of deterioration, prosthesis lifespan and the length of the waiting list. Conclusions Patient readiness should be assessed prior to TJR. By assessing patient readiness, health professionals can elucidate and deal with concerns and fears, understand and calibrate expectations, assess coping strategies, and use this information to help determine optimal timing, both before and after the surgical consultation.