Richard Burnett

Total knee replacement in patients with concomitant back pain results in a worse functional outcome and a lower rate of satisfaction

This study assessed the effect of concomitant back pain on the Oxford knee score (OKS), Short-Form (SF)-12 and patient satisfaction after total knee replacement (TKR). It involved a prospectively compiled database of demographics and outcome scores for 2392 patients undergoing primary TKR, of whom 829 patients (35%) reported back pain. Compared with those patients without back pain, those with back pain were more likely to be female (odds ratio (OR) 1.5 (95% confidence interval (CI) 1.3 to 1.8)), have a greater level of comorbidity, a worse pre-operative OKS (2.3 points (95% CI 1.7 to 3.0)) and worse SF-12 physical (2.0 points (95% CI 1.4 to 2.6)) and mental (3.3 points (95% CI 2.3 to 4.3)) components. One year post-operatively, those with back pain had significantly worse outcome scores than those without with a mean difference in the OKS of 5 points (95% CI 3.8 to 5.4), in the SF-12 physical component of 6 points (95% CI 5.4 to 7.1) and in the mental component of 4 points (95% CI 3.1 to 4.9). Patients with back pain were less likely to be satisfied (OR 0.62, 95% CI 0.5 to 0.78). After adjusting for confounding variables, concomitant back pain was an independent predictor of a worse post-operative OKS, and of dissatisfaction. Clinicians should be aware that patients suffering concomitant back pain pre-operatively are at an increased risk of being dissatisfied post-operatively.

The Influence of Obesity on Patient Reported Outcomes following Total Knee Replacement

This study retrospectively analysed the effects of obesity as described by Body Mass Index (BMI) on patient reported outcomes following total knee replacement. Participants (105 females and 66 males) who had undergone surgery under the care of a single surgeon were included in the review and were grouped according to their preoperative BMI into nonobese (BMI < 30 kg/m2), (n = 73) obese (BMI ≥ 30 kg/m2) (n = 98). Oxford Knee Score (OKS) and Short Form 12 scores (SF12) were taken preoperatively and 6 and 12 months after surgery to analyse differences between groups in the absolute scores as well as changes from before to after surgery. Preoperatively, the obese group had a significantly poorer OKS compared to non obese (44.7 versus 41.2, P = 0.003). There were no statistically significant group effects on follow-up or change scores of the OKS and SF12. Correlations coefficients between BMI and follow-up and change scores were low (r < 0.201). There were no significant differences in the number of complications and revisions (local wound infection, 6.7% non obese, 11% obese, postoperative systemic complication, 8% non obese, 12% obese, revision, 4% nonobese, 3% obese). In conclusion, our findings indicate similar degrees of benefits from the surgery irrespective of patient BMI.

Primary total knee replacement in patients with mental disability improves their mental health and knee function: A prospective study

We assessed the effect of mental disability on the outcome of total knee replacement (TKR) and investigated whether mental health improves post-operatively. Outcome data were prospectively recorded over a three-year period for 962 patients undergoing primary TKR for osteoarthritis. Pre-operative and one year Short-Form (SF)-12 scores and Oxford knee scores (OKS) were obtained. The mental component of the SF-12 was stratified into four groups according to level of mental disability (none ≥ 50, mild 40 to 49, moderate 30 to 39, severe < 30). Patients with any degree of mental disability had a significantly greater subjective physical disability according to the SF-12 (p = 0.06) and OKS (p < 0.001). The improvement in the disease-specific score (OKS) was not affected by a patients mental health (p = 0.33). In contrast, patients with mental disability had less of an improvement in their global physical health (SF-12) (p < 0.001). However, patients with any degree of mental disability had a significant improvement in their mental health post-operatively (p < 0.001). Despite a similar improvement in their disease-specific scores and improvement in their mental health, patients with mental disability were significantly more likely to be dissatisfied with their TKR at one year (p = 0.001). Patients with poor mental health do benefit from improvements in their mental health and knee function after TKR, but also have a higher rate of dissatisfaction.

Dealing with the predicted increase in demand for revision total knee arthroplasty: challenges, risks and opportunities

Worldwide rates of primary and revision total knee arthroplasty (TKA) are rising due to increased longevity of the population and the burden of osteoarthritis. Revision TKA is a technically demanding procedure generating outcomes which are reported to be inferior to those of primary knee arthroplasty, and with a higher risk of complication. Overall, the rate of revision after primary arthroplasty is low, but the number of patients currently living with a TKA suggests a large potential revision healthcare burden. Many patients are now outliving their prosthesis, and consideration must be given to how we are to provide the necessary capacity to meet the rising demand for revision surgery and how to maximise patient outcomes. The purpose of this review was to examine the epidemiology of, and risk factors for, revision knee arthroplasty, and to discuss factors that may enhance patient outcomes.

Lengthening the moment arm of the patella confers enhanced extensor mechanism power following total knee arthroplasty

We investigated whether a postulated biomechanical advantage conferred to the extensor mechanism by a change in knee implant design was detectable in patients by direct physical testing. 212 TKA patients were enrolled in a double blind randomized controlled trial to receive either a traditional implant or one which incorporated new design features. Extensor mechanism power output and physical performance on a battery of timed functional activities was assessed pre‐operatively and then at 6, 26, and 52 weeks post‐operatively. Significantly enhanced power output was observed in both groups post‐arthroplasty; however, the new design implant group demonstrated a greater change in power output than the traditional implant group. Posthoc testing of between group differences highlighted greater improvement at all post‐operative assessments. At 52 weeks, patients receiving the implant with the postulated biomechanical advantage achieved 116% of the power output of their contralateral limb, whereas patients with the traditional design achieved 90%. No between group difference was detected in the patients time to complete functional tasks. Thus, patients receiving a knee implant of a modern design (theoretically able to confer a mechanical advantage to the extensor mechanism) were found to generate significantly greater extensor power than those receiving a traditional implant without the postulated mechanical advantage.

Regional Differences Between Perisynovial and Infrapatellar Adipose Tissue Depots and Their Response to Class II and Class III Obesity in Patients With Osteoarthritis

Obesity is associated with an increased risk of developing osteoarthritis (OA), which is postulated to be secondary to adipose tissue–dependent inflammation. Periarticular adipose tissue depots are present in synovial joints, but the association of this tissue with OA has not been extensively explored. The aim of this study was to investigate differences in local adipose tissue depots in knees with OA and characterize the changes related to class II and class III obesity in patients with end‐stage knee OA.

Regional Differences Between Perisynovial and Infrapatellar Adipose Tissue Depots and Their Response to Class II and III Obesity in Patients with OA

Obesity is associated with an increased risk of developing osteoarthritis (OA), which is postulated to be secondary to adipose tissue–dependent inflammation. Periarticular adipose tissue depots are present in synovial joints, but the association of this tissue with OA has not been extensively explored. The aim of this study was to investigate differences in local adipose tissue depots in knees with OA and characterize the changes related to class II and class III obesity in patients with end‐stage knee OA.

A technique of predicting radiographic joint line and posterior femoral condylar offset of the knee

Purpose. To describe a reliable method of predicting native joint line and posterior condylar offset (PCO) using true lateral digital radiographs of the distal femur. Methods. PCO was measured relative to a line drawn parallel to the posterior cortex of the distal femur and the joint line was measured from the posterior condylar flare to the articular surface. A ratio was then calculated for these measurements relative to the width of the femur at the level of the flare. Two independent observers measured PCO and joint line ratio for 105 radiographs of the different knees and one repeated these measurements after one week. Results. There was a significant correlation between the width of the femoral diaphysis at the level of the posterior condylar flare with joint line (P = 0.008) and PCO (P = 0.003). Joint line and PCO could be predicted within 4 mm and 2 mm, respectively, using the identified ratio between the width of the femoral diaphysis at the level of the posterior condylar flare with measured joint line and PCO. The inter- (P < 0.001) and intra- (P < 0.001) observer reliability for these ratios were high. Conclusion. These ratios could be used to predict the native joint line and PCO.

Posterior condylar offset is an independent predictor of functional outcome after revision total knee arthroplasty

Objectives Preservation of posterior condylar offset (PCO) has been shown to correlate with improved functional results after primary total knee arthroplasty (TKA). Whether this is also the case for revision TKA, remains unknown. The aim of this study was to assess the independent effect of PCO on early functional outcome after revision TKA. Methods A total of 107 consecutive aseptic revision TKAs were performed by a single surgeon during an eight-year period. The mean age was 69.4 years (39 to 85) and there were 59 female patients and 48 male patients. The Oxford Knee Score (OKS) and Short-form (SF)-12 score were assessed pre-operatively and one year post-operatively. Patient satisfaction was also assessed at one year. Joint line and PCO were assessed radiographically at one year. Results There was a significant improvement in the OKS (10.6 points, 95% confidence interval (CI) 8.8 to 12.3) and the SF-12 physical component score (5.9, 95% CI 4.1 to 7.8). PCO directly correlated with change in OKS (p < 0.001). Linear regression analysis confirmed the independent effect of PCO on the OKS (p < 0.001) and the SF-12 physical score (p = 0.02). The overall rate of satisfaction was 85% and on logistic regression analysis improvement in the OKS (p = 0.002) was a significant predictor of patient satisfaction, which is related to PCO; although this was not independently associated with satisfaction. Conclusion Preservation of PCO should be a major consideration when undertaking revision TKA. The option of increasing PCO to balance the flexion gap while maintaining the joint line should be assessed intra-operatively. Cite this article: N. D. Clement, D. J. MacDonald, D. F. Hamilton, R. Burnett. Posterior condylar offset is an independent predictor of functional outcome after revision total knee arthroplasty. Bone Joint Res 2017;6:172–178. DOI: 10.1302/2046-3758.63.BJR-2015-0021.R1.

Reply to the letter to editor by Macchi et al

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