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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_16 | Pages 13 - 13
17 Nov 2023
Armstrong R McKeever T McLelland C Hamilton D
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Abstract

Objective

There is no specific framework for the clinical management of sports related brachial plexus injuries. Necessarily, rehabilitation is based on injury presentation and clinical diagnostics but it is unclear what the underlying evidence base to inform rehabilitative management.

Methods

A systematic review of the literature was undertaken in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We applied the PEO criteria to inform our search strategy to find articles that reported the rehabilitative management of brachial plexus injuries sustained while playing contact sports. An electronic search of Medline, CINAHL, SPORTDiscus and Web of Science from inception to 3rd November 2022 was conducted. MESH terms and Boolean operators were employed. We applied an English language restriction but no other filters. Manual searches of Google Scholar and citation searching of included manuscripts were also completed. All study types were considered for inclusion provided they were published as peer-reviewed primary research articles and contained relevant information. Two investigators independently carried out the searches, screened by title, abstract and full text. Two researchers independently extracted the data from included articles. Data was cross-checked by a third researcher to ensure consistency. To assess internal validity and risk of bias, the Joanna Briggs Institute (JBI) critical appraisal tools were utilised.


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_16 | Pages 12 - 12
17 Nov 2023
Cowan G Hamilton D
Full Access

Abstract

Objective

Meta-analysis of clinical trials highlights that non-operative management of degenerative knee meniscal tears is as effective as surgical management. Surgical guidelines though support arthroscopic partial meniscectomy which remains common in NHS practice. Physiotherapists are playing an increasing role in triage of such patients though it is unclear how this influences clinical management and patient outcomes.

Methods

A 1-year cohort (July 2019–June 2020) of patients presenting with MRI confirmed degenerative meniscal tears to a regional orthopaedic referral centre (3× ESP physiotherapists) was identified. Initial clinical management was obtained from medical records alongside subsequent secondary care management and routinely collected outcome scores in the following 2-years. Management options included referral for surgery, conservative (steroid injection and rehabilitation), and no active treatment. Outcome scores collected at 1- and 2-years included the Forgotten Joint Score-12 (FJS-12) questionnaire and 0–10 numerical rating scales for worst and average pain. Treatment allocation is presented as absolute and proportional figures. Change in outcomes across the cohort was evaluated with repeated measures ANOVA, with Bonferroni correction for multiple testing, and post-hoc Tukey pair-wise comparisons. As treatment decision is discrete, no direct contrast is made between outcomes of differing interventions but additional explorative outcome change over time evaluated by group. Significance was accepted at p=0.05 and effect size as per Cohen's values.


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_8 | Pages 20 - 20
11 Apr 2023
Hamilton R Holt C Hamilton D Garcia A Graham C Jones R Shilabeer D Kuiper J Sparkes V Khot S Mason D
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Mechanical loading of joints with osteoarthritis (OA) results in pain-related functional impairment, altered joint mechanics and physiological nociceptor interactions leading to an experience of pain. However, the current tools to measure this are largely patient reported subjective impressions of a nociceptive impact. A direct measure of nociception may offer a more objective indicator. Specifically, movement-induced physiological responses to nociception may offer a useful way to monitor knee OA. In this study, we gathered preliminary data on healthy volunteers to analyse whether integrated biomechanical and physiological sensor datasets could display linked and quantifiable information to a nociceptive stimulus.

Following ethical approval, 15 healthy volunteers completed 5 movement and stationary activities in 2 conditions; a control setting and then repeated with an applied quantified thermal pain stimulus to their right knee. An inertial measurement unit (IMU) and an electromyography (EMG) lower body marker set were tested and integrated with ground reaction force (GRF) data collection. Galvanic skin response electrodes for skin temperature and conductivity and photoplethysmography (PPG) sensors were manually timestamped to the integrated system.

Pilot data showed EMG, GRF and IMU fluctuations within 0.5 seconds of each other in response to a thermal trigger. Preliminary analysis on the 15 participants tested has shown skin conductance, PPG, EMG, GRFs, joint angles and kinematics with varying increases and fluctuations during the thermal condition in comparison to the control condition.

Preliminary results suggest physiological and biomechanical data outputs can be linked and identified in response to a defined nociceptive stimulus. Study data is currently founded on healthy volunteers as a proof-of-concept. Further exploratory statistical and sensor readout pattern analysis, alongside early and late-stage OA patient data collection, can provide the information for potential development of wearable nociceptive sensors to measure disease progression and treatment effectiveness.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_16 | Pages 19 - 19
1 Dec 2021
Brzeszczynski F Brzeszczynska J Murray I Duckworth A Simpson H Hamilton D
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Abstract

Objectives

Sarcopenia is characterised by generalised progressive loss of physical performance, skeletal muscle mass and strength. This systematic review evaluated the effects of sarcopenia on postoperative functional recovery outcomes and mortality in patients undergoing orthopaedic surgery and secondarily assessed the methods used to diagnose and define sarcopenia in orthopaedic literature.

Methods

A systematic search was conducted in MEDLINE, EMBASE and Google Scholar databases according to the PRISMA guidelines. Studies involving sarcopenic patients who underwent defined orthopaedic surgery and recorded postoperative outcomes were included. The quality of the criteria by which a sarcopenia diagnosis was made was evaluated and publication quality was assessed using Newcastle-Ottawa Scale.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_16 | Pages 64 - 64
1 Dec 2021
Hamilton R Holt C Hamilton D Jones R Shillabeer D Kuiper JH Sparkes V Mason D
Full Access

Abstract

Objectives

Current tools to measure pain are broadly subjective impressions of the impact of the nociceptive impulse felt by the patient. A direct measure of nociception may offer a more objective indicator. Specifically, movement-induced physiological responses to nociception may offer a useful way to monitor knee OA. In this proof-of-concept study, we evaluated whether integrated biomechanical and physiological sensor datasets could display linked and quantifiable information to a nociceptive stimulus.

Method

Following ethical approval, we applied a quantified thermal pain stimulus to a volunteer during stationary standing in a gait lab setting. An inertial measurement unit (IMU) and an electromyography (EMG) lower body marker set were tested and integrated with ground reaction force (GRF) data collection. Galvanic skin response electrodes and skin thermal sensors were manually timestamp linked to the integrated system.


Bone & Joint Research
Vol. 9, Issue 4 | Pages 162 - 172
1 Apr 2020
Xie S Conlisk N Hamilton D Scott C Burnett R Pankaj P

Aims

Metaphyseal tritanium cones can be used to manage the tibial bone loss commonly encountered at revision total knee arthroplasty (rTKA). Tibial stems provide additional fixation and are generally used in combination with cones. The aim of this study was to examine the role of the stems in the overall stability of tibial implants when metaphyseal cones are used for rTKA.

Methods

This computational study investigates whether stems are required to augment metaphyseal cones at rTKA. Three cemented stem scenarios (no stem, 50 mm stem, and 100 mm stem) were investigated with 10 mm-deep uncontained posterior and medial tibial defects using four loading scenarios designed to mimic activities of daily living.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_2 | Pages 34 - 34
1 Jan 2019
Sehgal A Burnett R Howie C Simpson H Hamilton D
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Instability accounts for approximately 20% of revision total knee arthroplasty (TKA) operations, however, diagnostic tests remain relatively subjective. The aim of this examination was to evaluate the feasibility of using pressure mat analyses during functional tasks to identify abnormal biomechanics associated with TKA instability.

Five patients (M = 4; age = 69.80±7.05 years; weight = 79.73±20.12 kg) with suspected TKA instability were examined compared to 10 healthy controls (M = 4; age = 44.6±7.52 years; weight = 70.80±14.65). Peak pressure and time parameters were measured during normal gait and two-minute bilateral stance. Side-to-side pressure distribution was calculated over 10-second intervals during the second minute. Mann-Whitney tests compared loading parameters between groups and side-to-side differences in TKA patients (significance level = p<0.05).

Pressure distribution was expressed relative to bodyweight. Notable differences were seen during bilateral stance. Uneven side loading was greater – favouring the non-operated limb – in TKA patients during bilateral stance compared to controls. This was significantly different at 30s (p=0.0336) and 60s (p=0.0336). Gait analyses showed subtle pressure distribution differences in unstable TKA patients. Stance time was indifferent. TKA patients tended to exhibit longer heel contact time (0.76s vs. 0.64s and reduced weight acceptance (50.75% vs. 56.75%) on the operated limb compared to the non-operated limb. Side-to-side differences in peak toe-off forces were significantly more pronounced in TKA patients versus controls (9.25% +/− 1.5% vs. 1.67% +/−5.79%; p=0.0039).

Conclusion: This feasibility work demonstrates subtle differences in limb loading mechanics during simple clinical tests in unstable TKA patients that might be invisible to the naked eye. In the long-term, pressure analyses may be a useful diagnostic tool in identifying patients that would benefit from revision surgery for TKA instability.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_16 | Pages 6 - 6
1 Nov 2018
Hamilton D
Full Access

Physiotherapy is generally accepted as an important component in the care pathway surrounding total knee replacement. Therapy interventions can be delivered prior to surgery, as part of the inpatient stay, and post-operation through outpatient appointments. Though ‘physiotherapy’ is generally promoted there is considerable national and international variation in actual therapy provision. Specific rehabilitation protocols are strongly entrenched at individual physiotherapy departments however the wider efficacy of varying physiotherapeutic interventions is poorly established. This uncertainty as to effectiveness of physiotherapy makes it difficult for commissioning organisations, healthcare providers, and patients to make decisions as to what therapy is ‘needed’ and therefore the correct level and mechanism of funding for such services. This talk will explore the variation in physiotherapy service provision and evidence for different interventions surrounding total knee replacement.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_15 | Pages 88 - 88
1 Nov 2018
Griffin MTA Simpson A Hamilton D
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The first three months following Total Knee Arthroplasty (TKA) provide an early window into a patient's functional outcomes, with the change of function in this time yielding valuable insight.

20 patients due to undergo primary TKA were recruited to the study. Data were recorded at three time points; pre-assessment clinic (PAC) before the operation, 6-weeks-post-operation (6WKs), at 12-weeks-post-operation (12WKs). Functional activity levels were monitored during early post-operative recovery for changes in early functional outcome, and allowed a comparison of metrics at each time point. This included direct functional testing of power output, timed functional performance in clinic, patient reported outcome measures, and multiday activity monitoring devices. Maximal power output symmetry (Power) was similar at 6WKs vs PAC (p = 0.37). At 12WKs, it had increased (p < 0.05). Timed functional performance (Performance) remained similar across all three time points (p = 0.27). Patient reported activities of daily living (ADL) performance significantly increased at 6WKs vs PAC (p < 0.05). At 12WKs, it remained similar (p = 0.10). Patient daily step count significantly decreased at 6WKs vs PAC (p < 0.05). By 12WKs, this had increased to similar levels to PAC (p = 0.30). Within the functional outcome measures, strong post-operative correlations were observed between Power and Performance (r = 0.62), Power and ADL (r = 0.49), and Performance and ADL (r = 0.61). Despite reduced measured step count and similar functional performance, patients report improved ADL at 6WKs. When symmetrical power output and measured step count have improved at 12WKs, patients report similar ADL to that at 6WKs. Multiple measures are required to get a full picture, however this highlights the different aspects measured by different tools.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_14 | Pages 65 - 65
1 Nov 2018
Sehgal A Burnett R Howie C Simpson H Hamilton D
Full Access

Instability accounts for approximately 20% of all revision total knee arthroplasty (TKA), however diagnostic tests remain crude and subjective. The aim of this examination was to evaluate the feasibility of pressure mat (SB Mat, TekScan) analyses of functional tasks to differentiate instability in a clinical setting. Five patients (M = 4; age = 69.80±7.05 years; weight = 79.73±20.12 kg) with suspected TKA instability were examined compared to five healthy controls (M = 1; age = 46.80±7.85 years; weight = 71.54±16.17 kg). Peak pressure and time parameters were measured during normal gait and two-minute bilateral stance. Side-to-side pressure distribution was calculated over 10-second intervals during the second minute. Pressure distributions were expressed relative to bodyweight (%BW). T-tests compared loading parameters between groups (significance level = p<0.05). Analyses showed subtle differences in pressure distribution in unstable TKA patients versus healthy controls. Stance time during gait was indifferent. TKA patients tended to exhibit longer heel contact time (0.76 vs. 0.64 sec) and reduced weight acceptance (50.75% vs. 56.75%) on the operated versus non-operated limb. Side-to-side differences in toe-off forces were significantly more pronounced in TKA patients versus controls (9.25% vs. 3.75%; p=0.0088). Uneven loading was significantly greater – favouring the non-operated limb – in TKA patients during bilateral stance compared to controls (p<0.05). This feasibility work demonstrates subtle differences in limb loading and biomechanics during simple clinical tests in unstable TKA patients that might be undetectable to the naked eye. Pressure analyses may therefore be a useful diagnostic tool. These findings warrant further investigation.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_3 | Pages 13 - 13
1 Apr 2018
Giesinger J Loth F McDonald D Giesinger K Patton J Simpson H Howie C Hamilton D
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Aim

To investigate the validity of threshold values for the Oxford Hip and Knee Score (OHS and OKS) for treatment success 12 months after total knee or hip replacement.

Methods

Questionnaires were administered to patients undergoing total hip (THA) or knee (TKA) replacement before and 12 months after surgery alongside questions assessing key accepted aspects of treatment success (satisfaction, pain relief, functional improvement) to form a composite criterion of success and assessed using receiver operator characteristic (ROC) analysis. Thresholds providing maximum sensitivity and specificity for predicting treatment success were determined for the total sample and subgroups defined by pre-surgery scores.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_3 | Pages 2 - 2
1 Apr 2018
Hamilton D Loth F MacDonald D Giesinger K Patton J Simpson H Howie C Giesinger J
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Aim

To evaluate the association of BMI and improvement in patient-reported outcomes after TKA.

Methods

Knee replacement outcome data for procedures carried out over an eight month period was extracted from a regional arthroplasty register in the UK. Data was available before surgery and 12 months after. We analysed the impact of overweight on post-operative change in the Forgotten Joint Score − 12 (FJS-12) measuring joint awareness and the Oxford Knee Score (OKS) measuring pain and function using five BMI categories (A: <25, B: 25–29.9, C: 30–34.9, D: 35–39.9 and E: >40).


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_16 | Pages 43 - 43
1 Oct 2016
Hamilton D Giesinger K Giesinger J Loth F Simpson A Howie C
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Obese patients undergoing total knee arthroplasty (TKA) face increased risks of complications such as joint infection and early revision. However, the influence of obesity on measures of patient function following TKA is poorly defined.

Knee arthroplasty outcome data for procedures carried out over an eight month period was extracted from a regional database in the UK. We analysed the impact of weight categories (BMI<30, BMI=30–34.9, and BMI≥35) on the Forgotten Joint Score – 12 (FJS-12) and Oxford Knee Score (OKS). Data was available preoperatively and 12 months postoperatively. Physical and mental health was assessed with the SF-12 one year after surgery.

Data from 256 patients were available. 49.6% had a BMI<30, 27.4% had a BMI 30–34.9 and 23.1% had a BMI≥35. Mean FJS-12 results at 1-year were 48.7 points for patients with a BMI<30, 40.7 points for patients with a BMI=30–34.9 and 34.0 points for patients with a BMI≥35. Effect sizes for change from baseline to 12-month post-op were 3.0 (Cohen's d) in patients with BMI<30 and d=2.2 in patients with BMI≥35. Mean OKS results at 1 year were 36.9 (BMI<30), 33.7 (BMI=30–34.9) and 32.0 (BMI≥35) respectively. Effect sizes for change from baseline to 12-month was d=2.1 (BMI<30) and d=1.9 (BMI≥35). Differences between BMI groups with regard to post-operative change were statistically significant for the FJS-12 (p=0.038) but not for the OKS (p=0.229).

This study highlights that outcome scores may differ in their ability to capture the impact of obesity on patient function following TKA. The FJS-12 showed significant differences in outcome based on patient obesity category, whereas the OKS did not detect between group differences.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_16 | Pages 32 - 32
1 Oct 2016
Hamilton D Gaston P Simpson A
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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.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_16 | Pages 19 - 19
1 Oct 2016
Griffin M Annan J Hamilton D Simpson A
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3D imaging is commonly employed in the surgical planning and management of bony deformity. The advent of desktop 3D printing now allows rapid in-house production of specific anatomical models to facilitate surgical planning. The aim of this pilot study was to evaluate the feasibility of creating 3D printed models in a university hospital setting.

For requested cases of interest, CT DICOM images on the local NHS Picture Archive System were anonymised and transferred. Images were then segmented into 3D models of the bones, cleaned to remove artefacts, and orientated for printing with preservation of the regions of interest. The models were printed in polylactic acid (PLA), a biodegradable thermoplastic, on the CubeX Duo 3D printer.

PLA models were produced for 4 clinical cases; a complex forearm deformity as a result of malunited childhood fracture, a pelvic discontinuity with severe acetabular deficiency following explantation of an infected total hip replacement, a chronically dislocated radial head causing complex elbow deformity as a result of a severe skeletal dysplasia, and a preoperative model of a deficient proximal tibia as a result of a severe tibia fracture. The models materially influenced clinical decision making, surgical intervention planning and required equipment. In the case of forearm an articulating model was constructed allowing the site of impingement between radius and ulnar to be identified, an osteotomy was practiced on multiple models allowing elimination of the block to supination. This has not previously been described in literature. The acetabulum model allowed pre-contouring of a posterior column plate which was then sterilised and eliminated a time consuming intraoperative step.

While once specialist and expensive, in house 3D printing is now economically viable and a helpful tool in the management of complex patients.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_16 | Pages 40 - 40
1 Oct 2016
Hamilton D Simpson P Patton J Howie C Burnett R
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Patient function is poorly characterised following revision TKA. Modern semi-constrained implants are suggested to offer high levels of function, however, data is lacking to justify this claim.

52 consecutive aseptic revision TKA procedures performed at a single centre were prospectively evaluated; all were revision of a primary implant to a Triathlon total stabiliser prosthesis. Patients were assessed pre-operatively and at 6, 26, 52 and 104 weeks post-op. Outcome assessments were the Oxford Knee Score (OKS), range of motion, pain rating scale and timed functional assessment battery. Analysis was by repeated measures ANOVA with post-hoc Tukey HSD 95% simultaneous confidence intervals as pairwise comparison. Secondary analysis compared the results of this revision cohort to previously reported primary TKA data, performed by the same surgeons, with identical outcome assessments at equivalent time points.

Mean age was 73.23 (SD 10.41) years, 57% were male. Mean time since index surgery was 9.03 (SD 5.6) years. 3 patients were lost to follow-up. All outcome parameters improved significantly over time (p <0.001). Post-hoc analysis demonstrated that all outcomes changed between pre-op, 6 week and 26 weeks post-op assessments.

No difference was seen between primary and revision cohorts in OKS (p = 0.2) or pain scores (p=0.19). Range of motion and functional performance was different between groups over the 2 year period (p=0.03), however this was due to differing pre-operative scores, post-hoc analysis showed no difference between groups at any post-operative time point.

Patients undergoing aseptic revision TKA with semi-constrained implants made substantial improvements in OKS, pain scores, knee flexion, and timed functional performance, with the outcomes achieved comparable to those of primary TKA. High levels of function can be achieved following revision knee arthroplasty, which may be important considering the changing need for, and demographics of, revision surgery.


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 29 - 29
1 Jul 2014
Hamilton D Lane J Gaston P Patton J MacDonald D Simpson H Howie C
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Summary Statement

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.

Background

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.


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 30 - 30
1 Jul 2014
Hamilton D Clement N Patton J Burnett R Gaston P Howie C Simpson H
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Summary Statement

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.

Purpose

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.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_13 | Pages 8 - 8
1 Mar 2013
Hamilton D Gaston P Simpson A
Full Access

INTRODUCTION

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.

METHODS

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.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVI | Pages 67 - 67
1 Aug 2012
Hamilton D Gaston P Simpson A
Full Access

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.