Physical outcome following total knee arthroplasty is variable. Satellite cells are undifferentiated myogenic precursors considered to be muscle stem cells. We hypothesised that; the recovery of muscle strength and physical function following knee arthroplasty would be influenced by the underlying number of muscle satellite cells. 16 patients provided a distal quadriceps muscle biopsy at time of surgery. Satellite cells were identified with a primary mouse antibody for Pax7 – a cytoplasmic protein marker, and the myonuclei with DAPI. Positive cells were identified on the basis of immunofluorescent staining in association with nuclear material, and confirmed by position under the basal lamina. Patient function was assessed using a validated physical assessment protocol, the Aggregated Locomotor Function (ALF) score, muscle strength assessed using the leg extensor power-rig, and clinical outcome assessed with the Oxford Knee Score (OKS) pre-operatively and at 1 year post operatively. Muscle satellite cell content varied amongst the patient group (Positive Staining Index 3.1 to 11.4). Satellite cell content at time of surgery correlated with change in outcomes between pre-operative and 1 year assessments in all assessed parameters (ALF, r = 0.31; muscle power, r = 49; OKS, r = 0.33). Regression analysis employing a forward stepwise selection technique employed satellite cell volume in models of pre-operative to 1 year change for all outcome parameters. Physical function (satellite cell content, patient age and pre-operative ALF score) adjusted R2 = 0.92; Muscle power (pre-operative power and satellite cell content) adjusted R2 = 0.38; Clinical outcome (pre-operative OKS and satellite cell content) adjusted R2 = 0.28. Muscle satellite cell content influences recovery of muscle power and physical function following total knee arthroplasty. Importantly it is also associated with change in clinical scores; suggesting it to be a biomarker for patient outcomes.
Service industry metrics (the net promoter score) are being introduced as a measure of UK healthcare satisfaction. Lower limb arthroplasty, as a ‘service’, scores comparably with the most successful commercial organisations. Satisfaction with care is important to both the patient and the payer. The Net Promoter Score, widely used in the service industry, has been recently introduced to the UK National Health Service as an overarching metric of patient satisfaction and to monitor performance. This questionnaire asks ‘customers’ if they would recommend a service or products to others. Scores range from −100 (everyone is a detractor) to +100 (everyone is a promoter). In industry, a positive score is well regarded, with those over 50 regarded as excellent. Our aims were to assess net promoter scores for joint arthroplasty, to compare these scores with direct measures of patient satisfaction, and to evaluate which factors contributed to net promoter response.Summary Statement
Background
Using current analysis/methodology, new implant technology is unlikely to demonstrate a large enough change in patient function to impact on the cost-effectiveness of the procedure. Cost effectiveness is an increasingly important metric in today's healthcare environment, and decisions surrounding which arthroplasty prosthesis to implant are not exempt from such health economic concerns. Quality adjusted life years (QALYs) are the typical assessment tool for this type of evaluation. Using this methodology, joint arthroplasty has been shown to be cost effective, however studies directly comparing the QALY achieved by differing prostheses are lacking.Summary Statement
Purpose
This study investigates the relationship between direct measurement of outcome and patient report of that outcome via the OKS. The stability of this relationship over time following surgery is also assessed. 183 TKA patients were assessed pre-operatively and at 6, 26 and 52 weeks post-op. Oxford Knee Score was obtained along with measures of pain intensity, knee flexion, lower limb power and timed functional assessment. Correlation of performance variables with the OKS was assessed, and regression analysis performed on those that formed significant associations. Significance was accepted at p = 0.05.INTRODUCTION
METHODS
End-stage osteoarthritis is characterised by pain and reduced physical function, for which total knee arthroplasty (TKA) is recognised to be a highly effective treatment. Most implants are multi radius in design, though modern kinematic theory suggests a single flexion/extension axis is located in the femur. A recently launched TKA implant (Triathlon, Stryker US), is based on this theory, adopting a single radius of curvature femoral component. It is hypothesised that this design allows better function, and specifically, that it results in enhanced efficiency of the quadriceps group through a longer patello-femoral moment arm. Change in power output was compared between single and multi radius implants as part of a larger ongoing randomised controlled trial to benchmark the new implant. Power output was assessed using a Leg Extensor Power Rig, well validated for use with this population, pre-operatively and at 6, 26 and 52 weeks post-operatively in 101 Triathlon and 82 Kinemax implants. All patients were diagnosed with osteoarthritis, and drawn from a single centre. Output was reported as maximal wattage (W) generated in a single leg extension, and expressed as a proportion of the contralateral limb power output to act as an internal control. The results are shown in the table below. Two-way repeated measures ANOVA demonstrated a significant effect of TKA on the quadriceps power output, F = 249.09, p = <0.001 and also a significant interaction of the implant group on the output F = 11.33, p = 0.001. Independent samples t-tests of between group differences at the four assessment periods highlighted greater improvement in the single radius TKA group at all post-operative assessments (p <0.03), see table. The theoretical enhanced quadriceps efficiency conferred by single radius design was found in this study. Power output was significantly greater at all post-operative assessments in the single radius compared to the multi radius group. This difference was particularly relevant at early 6 week and 1 year assessment. Lower limb power output is known to link positively to functional ability. The results support the hypothesis that TKAs with a single radius design have enhanced recovery and better function.
Recovery of muscle strength following Total Knee Replacement (TKR) is variable, and can affect the resultant function of the patient. Satellite cells are undifferentiated myogenic precursors considered to be muscle stem cells that lie quiescently around the muscle fibre. These cells repair damaged fibres and have the potential to generate new muscle fibres. Therefore, theoretically, they could be associated with the variation in muscle recovery following surgery. We hypothesised that the recovery of muscle strength following knee replacement in a given patient would be influenced by the underlying number of satellite cells in that patient. 20 patients undergoing TKR were recruited from the waiting list of a single consultant. A muscle biopsy was taken at the time of surgery from the distal quadriceps. This was fixed in paraffin wax, and sections obtained. Satellite cells were identified with a primary mouse antibody for Pax7 - a cytoplasmic protein marker - and an immunofluorescent goat anti-mouse secondary. Slides were counterstained with DAPI to stain the myonuclei. The positive staining index (PSI) was calculated (number of satellite cells/total number of myonuclei x 100). Recovery of muscle (quadriceps) strength was assessed using the leg extensor power-rig (LegRig) pre-operatively, at 6 and 26 weeks post-operatively. Statistical analysis was performed using the Minitab version 15 software, the level of significance was set as p = 0.05.Introduction
Methods
The aim of this randomised, controlled
