Pre-operative pressure pain thresholds do not meaningfully explain satisfaction or improvement in pain after knee replacement: a cohort study.

OBJECTIVES: Pain sensitization could be a risk factor for poor outcomes after knee replacement surgery (KR) for knee osteoarthritis (KOA). We aimed to evaluate the association between pre-operative central and peripheral pain sensitization measured using a digital pressure algometer and KR outcomes. METHODS: Consecutive patients with severe KOA listed for KR were recruited. Sociodemographic and symptoms data were collected prior to surgery. Pre-operative pressure pain thresholds (PPTs) were measured using a digital pressure algometer at the index knee and forearm. Patient satisfaction at 6 and 12 months after KR was assessed using a 4-point Likert scale, and dichotomized to satisfied and dissatisfied to KR. Western Ontario and McMaster Universities Index (WOMAC) Pain and function was assessed. The associations between pre-operative PPTs with KR outcomes at 6 and 12 months were evaluated. RESULTS: Of the 243 patients recruited, response rate at 6 and 12 months were 95.5% and 96.7%. The dissatisfaction rates were 8.2% and 5.1% at 6 and 12 months. There was no statistically significant association between pre-operative index knee or forearm PPTs and patient satisfaction. PPTs measured at the knee, but not the forearm, were weakly associated with change in the WOMAC pain score at 12 months, after adjustment for confounding factors. CONCLUSION: Pre-operative central sensitization, measured by handheld digital algometry, was not statistically significantly associated with satisfaction or change in pain after KR. Pre-operative peripheral sensitization was associated with change in pain symptoms after KR; however, this association was weak and unlikely to be a meaningful predictor of KR outcome in clinical practice.

Systematic review of management of chronic pain after surgery.

BACKGROUND: Pain present for at least 3 months after a surgical procedure is considered chronic postsurgical pain (CPSP) and affects 10-50 per cent of patients. Interventions for CPSP may focus on the underlying condition that indicated surgery, the aetiology of new-onset pain or be multifactorial in recognition of the diverse causes of this pain. The aim of this systematic review was to identify RCTs of interventions for the management of CPSP, and synthesize data across treatment type to estimate their effectiveness and safety. METHODS: MEDLINE, Embase, PsycINFO, CINAHL and the Cochrane Library were searched from inception to March 2016. Trials of pain interventions received by patients at 3 months or more after surgery were included. Risk of bias was assessed using the Cochrane risk-of-bias tool. RESULTS: Some 66 trials with data from 3149 participants were included. Most trials included patients with chronic pain after spinal surgery (25 trials) or phantom limb pain (21 trials). Interventions were predominantly pharmacological, including antiepileptics, capsaicin, epidural steroid injections, local anaesthetic, neurotoxins, N-methyl-d-aspartate receptor antagonists and opioids. Other interventions included acupuncture, exercise, postamputation limb liner, spinal cord stimulation, further surgery, laser therapy, magnetic stimulation, mindfulness-based stress reduction, mirror therapy and sensory discrimination training. Opportunities for meta-analysis were limited by heterogeneity. For all interventions, there was insufficient evidence to draw conclusions on effectiveness. CONCLUSION: There is a need for more evidence about interventions for CPSP. High-quality trials of multimodal interventions matched to pain characteristics are needed to provide robust evidence to guide management of CPSP.

Persistent pain after knee replacement: do factors associated with pain vary with degree of patient dissatisfaction?

OBJECTIVE: Up to 20% of patients experience long-term pain and dissatisfaction following knee replacement. The aim of this study was to investigate factors associated with persistent pain following knee replacement and their implications for patient satisfaction. DESIGN: A case-controlled analysis compared patients with established persistent pain with patients who were pain-free. 2:1 frequency matching for age, gender, time from surgery and prosthesis was performed. 1310 patients were approached and 100 patients with persistent pain and 200 matched pain-free controls were included. Variables assessed included mechanical, biological, psychosocial and generalised factors. RESULTS: The study found that the degree of dissatisfaction experienced by the patient with persistent pain following knee replacement affected the factors associated with pain. In the most dissatisfied patients, pain was associated with instability in the coronal plane (OR 19.8, 95% CI 3.8-104.0), stiffness (OR 6.4, 95% CI 2.3-18.4) and negative social support (OR 3.3, 95% CI 1.1-10.0). In patients who were less dissatisfied, pain was associated with patellofemoral problems (OR 10.3, 95% CI 3.6-29.6), elevated BMI (OR 2.8, 95% CI 1.4-5.7) and reduced local pain thresholds (OR 4.4, 95% CI 2.0-9.6). Depression (OR 13.6, 95% CI 1.9-96.6) and presence of proximal tibial tenderness (OR 23.5 95% CI 7.8-70.7) were strongly associated with pain regardless of level of satisfaction. CONCLUSIONS: Patients with persistent pain after knee replacement are dissatisfied. This study identifies factors associated with the worst pain outcomes, which lead to the greatest levels of dissatisfaction. Particular efforts with a holistic multidisciplinary approach should be focused towards these "red flag" factors in order to minimise persistent pain after knee replacement.

The association between pre-operative pain sensitisation and chronic pain after knee replacement: an exploratory study.

OBJECTIVE: Chronic pain after total knee replacement (TKR) is a prevalent condition, affecting about 20% of patients. The aim of this study was to explore the relationship between pre-operative pain thresholds and chronic pain after TKR. DESIGN: Patients listed for a TKR because of osteoarthritis participated in a Quantitative Sensory Testing (QST) session prior to surgery. Pressure pain thresholds (PPTs) and hot pain thresholds were assessed at the osteoarthritic knee and the forearm. Patients were followed-up at 1-year after TKR, and the severity of pain in the replaced knee was assessed using the WOMAC Pain score. Pre-operative median QST thresholds were compared to thresholds from a normative database collected from 50 people with no knee pain. The relationship between pre-operative pain thresholds and pain severity post TKR were tested using correlations. RESULTS: Fifty-one patients participated in a pre-operative QST session and completed a 1-year WOMAC Pain score. Pre-operatively, patients demonstrated evidence of localised (knee) and widespread (forearm) pain sensitisation in response to pressure stimuli compared to healthy participants. Pre-operative PPTs at the forearm were found to be significantly correlated with 1-year WOMAC Pain scores (r = 0.37, P = 0.008). CONCLUSIONS: This study provides preliminary evidence that pre-operative widespread pain sensitisation, measured using pressure algometry, may be associated with chronic pain after TKR. Further research is needed to explore the predictive value of an assessment of pre-operative widespread pain sensitisation in identifying who is likely to develop chronic pain after TKR.

The effectiveness of non-pharmacological sleep interventions for improving inpatient sleep in hospital: A systematic review and meta-analysis.

BACKGROUND: Sleep disturbance is common in hospital. The hospital environment can have a negative impact on sleep quality, through factors such as noise, light, temperature, and nursing care disruptions. Poor sleep can lead to delays in recovery, wound healing, and increase risk of post-operative infection. METHODS: We conducted a systematic review evaluating the effectiveness of non-pharmacological sleep interventions for improving inpatient sleep. The primary outcome was sleep quality, the secondary outcome was length of hospital stay, the harm outcome was adverse events. MEDLINE, Embase, CINAHL, PsycINFO and the Cochrane Library were searched from inception to 17th February 2022. Meta-analysis was conducted using a fixed effects model, with narrative synthesis for studies with no useable data. Risk of bias was assessed with the Cochrane tool. RESULTS: 76 studies identified with 5375 people randomised comparing 85 interventions. Interventions focused on physical sleep aids (n = 26), relaxation (n = 25), manual therapy (n = 12), music (n = 9), psychological therapy (n = 5), light therapy (n = 3), sleep protocols (n = 2), milk and honey (n = 1), exercise (n = 1), and nursing care (n = 1). In meta-analysis, medium to large improvements in sleep quality were noted for sleep aids, relaxation, music, and manual therapies. Results were generally consistent in studies at lower risk of bias. Length of hospital stay and adverse events were reported for some studies, with benefit in some trials but this was not consistent across all interventions. CONCLUSIONS: Physical sleep aids, relaxation, manual therapy and music interventions have a strong evidence base for improving inpatient sleep quality. Research is needed to evaluate how to optimise interventions into routine care.

The assessment of persistent pain after joint replacement.

This study used 'think aloud' to explore issues around using a standardised questionnaire to assess persistent pain after joint replacement. Twenty participants with moderate-extreme persistent pain in their replaced hip or knee completed the Chronic Pain Grade (CPG) while 'thinking aloud'. The interviews were audio-recorded, transcribed and analysed using thematic analysis. Completion of the CPG by patients was influenced by four issues: challenges with the question wording or response options on the CPG items; the fluctuating nature of pain and functional limitations; the need to account for co-morbidities and pain elsewhere; and adjustment to pain. These issues reflect those that have arisen previously in patients with musculoskeletal pain, and need to be considered when assessing persistent joint pain, both before and after joint replacement.

Quantitative sensory testing in painful osteoarthritis: a systematic review and meta-analysis.

OBJECTIVE: To systematically review the use of quantitative sensory testing (QST) in pain characterisation (phenotyping) in osteoarthritis (OA). METHODS: Six bibliographic databases (Medline, Embase, Amed, Cinahl, PubMed, Web of Science) were searched to identify studies published before May 2011. Data were extracted based on the primary site of OA, QST modalities, outcome measures and test sites. Standardised mean difference (SMD) and 95% confidence intervals (CIs) were calculated if possible. Publication bias was determined using funnel plot and Egger's test. Heterogeneity was examined using Cochran Q test and I2 statistic. Random effects model was used to pool the results. RESULTS: Of 41 studies (2281 participants) included, 23 were case control studies, 15 case only studies, two randomised controlled trials, and one uncontrolled trial. The majority of studies examined pressure pain with smaller numbers using electrical and/or thermal stimuli. QST was more often applied to the affected joint than distal and remote sites. Of 20 studies comparing people with OA and healthy controls, seven provided sufficient information for meta-analysis. Compared with controls, people with OA had lower pressure pain thresholds (PPTs) both at the affected joint (SMD = -1.24, 95% CI -1.54, -0.93) and at remote sites (SMD = -0.88, 95% CI -1.11, -0.65). CONCLUSION: QST of PPTs demonstrated good ability to differentiate between people with OA and healthy controls. Lower PPTs in people with OA in affected sites may suggest peripheral, and in remote sites central, sensitisation. PPT measurement merits further evaluation as a tool for phenotyping OA pain.

Test-retest reliability of Quantitative Sensory Testing in knee osteoarthritis and healthy participants.

Quantitative Sensory Testing (QST), which assesses somatosensory function by recording participant's responses to external stimuli of controlled intensity, is a useful tool to provide insight into the complex pathophysiology of osteoarthritis (OA) pain. However, QST is not commonly used in rheumatology because the test-retest reliability properties of QST in OA patients have not yet been established. This brief report presents the finding of a study which assessed the test-retest reliability of light touch thresholds, pressure pain thresholds, thermal sensation thresholds and thermal pain thresholds in 50 knee OA patients and 50 healthy participants. Pressure pain thresholds were found to be the least variable measurement, as median thresholds did not differ significantly over the 1 week period and the results were highly correlated. This provides support for the inclusion of pressure algometry in studies assessing pain perception abnormalities in OA.

Value, transparency, and inclusion: A values-based study of patient involvement in musculoskeletal research.

BACKGROUND: Patient and public involvement work (PPI) is essential to good research practice. Existing research indicates that PPI offers benefits to research design, conduct, communication, and implementation of findings. Understanding how PPI works and its value helps to provide information about best practice and highlight areas for further development. This study used a values-based approach to reporting PPI at a Research Unit focused on musculoskeletal conditions within a UK medical school. METHODS: The study was conducted between October 2019 and January 2020 using Gradinger's value system framework as a theoretical basis. The framework comprises three value systems each containing five clusters. All PPI members and researchers who had attended PPI groups were invited to participate. Participants completed a structured questionnaire based on the value system framework; PPI members also provided further information through telephone interviews. Data were deductively analysed using a framework approach with data mapped onto value systems. RESULTS: Twelve PPI members and 17 researchers took part. Views about PPI activity mapped onto all three value systems. PPI members felt empowered to provide their views, and that their opinions were valued by researchers. It was important to PPI members that they were able to 'give back' and to do something positive with their experiences. Researchers would have liked the groups to be more representative of the wider population, patients highlighted that groups could include more younger members. Researchers recognised the value of PPI, and the study highlighted areas where researchers members might benefit from further awareness. CONCLUSIONS: Three areas for development were identified: (i) facilitating researcher engagement in training about the value and importance of PPI in research; (ii) support for researchers to reflect on the role that PPI plays in transparency of healthcare research; (iii) work to further explore and address aspects of diversity and inclusion in PPI.

Clinical outcomes and fusion success associated with the use of BoneSave in spinal surgery.

BACKGROUND: Achieving spinal fusion is the guiding principle behind surgical treatment for a range of spinal pathologies, often requiring a substantial amount of bone-graft. Iliac crest autograft represents the gold standard although associated morbidities and limited graft material have led to the development of alternatives. BoneSave (Stryker, UK), a porous tricalcium phosphate-hydroxyapatite ceramic, is one such alternative, employed in spinal fusion over the past few years. Very little research exists into the clinical outcomes associated with its use. METHODS: Clinical data was collected retrospectively from the case notes of 45 patients who underwent posterolateral inter-transverse spinal fusion involving the application of BoneSave between June 2003 and January 2005. Latest follow-up information was collected via a postal questionnaire (average follow-up of 46 months). Validated outcome instruments employed included the Short Form 36 and Oswestry Disability Index. In addition visual analogue scales for pain, patient global impression of change, work status, persisting symptoms and patient satisfaction data were collected. Radiological evaluation of fusion was carried out from the most recent spinal radiographs available for each patient. RESULTS: Qualitative post-operative data was available in 96%, with a questionnaire response rate of 68.4%. Radiographical evaluation was possible in 67%. Significant post-operative improvements were seen across all outcome measures in the large majority of cases. Successful fusion was achieved in 56.7% of cases. CONCLUSIONS: The clinical outcomes associated with the use of BoneSave in spinal fusion are comparable to those available in the literature for more conventional techniques. The fusion rate was not significantly lower.

Prevalence and functional impact of patient-perceived leg length discrepancy after hip replacement.

The aim of this postal survey was to determine the prevalence and impact of patient-perceived leg length discrepancy (LLD) at 5-8 years after primary total hip replacement (THR). A postal audit survey was undertaken of all consecutive patients who had a primary unilateral THR at one elective orthopaedic centre between April 1993 and April 1996. The questionnaire included the Oxford hip score (OHS) and questions about LLD. Questionnaires were received from 1,114 patients. In total, 329 THR patients (30%) reported an LLD, although radiographic analysis revealed that only 36% of these patients had anatomical LLD. Patients with a perceived LLD had a significantly poorer OHS (p < 0.001) and reported more limping than those patients without a perceived LLD. This study found that a third of patients perceived an LLD after THR and that perceived LLD was associated with a significantly poorer midterm functional outcome.

Optimising recruitment into trials using an internal pilot.

BACKGROUND: Recruitment to trials can be difficult. Despite careful planning and research that outlines ways to improve recruitment, many trials do not achieve their target on time and require extensions of funding or time. METHODS: We describe a trial in which an internal pilot with embedded qualitative research was used to improve recruitment processes and inform recruitment projections for the main trial. At the end of the pilot, it was clear that the sample size would not be met on time. Three steps were taken to optimise recruitment: (1) adjustments were made to the recruitment process using information from the qualitative work done in the pilot and advice from a patient and public involvement group, (2) additional recruiting sites were included based on site feasibility assessments and (3) a projection equation was used to estimate recruitment at each site and overall trial recruitment. RESULTS: Qualitative work during the pilot phase allowed us to develop strategies to optimise recruitment during the main trial, which were incorporated into patient information packs, the standard operating procedures and training sessions with recruiters. From our experience of feasibility assessments, we developed a checklist of recommended considerations for feasibility assessments. For recruitment projections, we developed a four-stage projection equation that estimates the number of participants recruited using a conversion rate of the number randomised divided by the number screened. CONCLUSIONS: This work provides recommendations for feasibility assessments and an easy-to-use projection tool, which can be applied to other trials to help ensure they reach the required sample size. TRIAL REGISTRATION: ISRCTN, ISRCTN92545361 . Registered on 6 September 2016.

Is social support associated with patient-reported outcomes after joint replacement? A systematic review and meta-analysis.

BACKGROUND: Identifying prognostic factors for outcomes after joint replacement could improve the provision of stratified care. This systematic review evaluated whether social support is a prognostic factor for better patient-reported outcomes after total hip replacement (THR) and total knee replacement (TKR). METHODS: MEDLINE, Embase and PsycINFO were searched from inception to April 2019. Cohort studies evaluating the association between social support and patient-reported outcomes at three months or longer after THR or TKR were included. Data were extracted from study reports. Study quality was assessed using the QUIPS tool. Data were synthesized using meta-analysis and narrative synthesis. The review was registered on PROSPERO (CRD42016041485). FINDINGS: Searches identified 5,810 articles and 56 studies with data from 119,165 patients were included. In meta-analysis, the presence of social support had a beneficial effect on long-term post-operative WOMAC (mean difference 2.88; 95% CIs 1.30; 4.46) and Oxford Knee Score (0.29; 0.12, 0.45). Social support measured using a validated questionnaire was found to be associated with WOMAC pain (0.04; 0.00, 0.08) but not WOMAC function (-0.01; -0.12, 0.11). The presence of social support had a positive association with some SF-36 subscales but not others. For all outcomes, results of narrative synthesis were inconsistent. INTERPRETATION: There is evidence that social support is a prognostic factor for some outcomes after joint replacement. Development and evaluation of complex interventions to improve social support and social integration is warranted. FUNDING: This study was supported by the NIHR Biomedical Research Centre at University Hospitals Bristol NHS Foundation Trust and the University of Bristol.

Ninety-day mortality after elective total hip replacement: 1549 patients using aspirin as a thromboprophylactic agent.

Thromboprophylaxis after elective orthopaedic surgery remains controversial. Recent guidelines from the National Institute for Clinical Excellence (NICE) have suggested that low molecular weight heparin should be given to all patients undergoing total hip replacement. The British Orthopaedic Association is currently debating this guideline with NICE, as it is not clear whether published evidence supports this view. We present the early mortality in our unit after total hip replacement using aspirin as chemical thromboprophylaxis. The 30-day and 90-day mortality after primary total hip arthroplasty was zero. We compare this with that reported previously from our unit without using chemical thromboprophylaxis. With the introduction of routine aspirin thromboprophylaxis, deaths from cardiovascular causes have dropped from 0.75% to zero. These results demonstrate that there is a strong argument for the routine administration of aspirin after elective total hip replacement.

Total knee replacement: is it really an effective procedure for all?

Total knee replacement (TKR) is considered an effective intervention for the treatment of chronic knee pain and disability. Yet there is increasing evidence, based on research using patient-based outcome measures, that a significant proportion of patients experience chronic knee pain, functional disability, a poor quality of life and dissatisfaction after TKR. Although some poor outcomes after TKR are due to surgical technique and implant factors, much of the pain and disability after surgery is medically unexplained. A range of possible patient factors could contribute to a poor outcome after TKR. Socio-demographic factors that have been found to correlate with a poor outcome after TKR include female gender, older age and low socio-economical status. Medical factors that are highly predictive of pain and disability after TKR are a greater number of co-morbidities and a worse pre-operative status. A range of psychological factors could be predictive of a poor outcome after surgery including depression, low self-efficacy, poor pain coping strategies, somatization, low social support and patient expectations. It is also proposed that a biological explanation for continuing pain after TKR could involve central sensitisation, a dysfunction of pain modulation by the central nervous system. To improve patient selection for TKR, future research needs to focus on developing a pre-operative screening protocol to identify those patients at risk of medically unexplained pain and disability after TKR.

The effect of numbness on outcome from total knee replacement.

INTRODUCTION Some patients report continuing pain and functional limitations after total knee replacement (TKR). While numbness around the TKR scar is common, the impact of numbness is less clear. One particular activity that could be influenced by numbness is kneeling. The aim of this study was to explore the impact of numbness around TKR scars on health related quality of life and kneeling ability. METHODS Fifty-six patients were recruited one year after primary TKR. Sensation around the knee was assessed through patient self-reporting, monofilament testing and vibration, and patients' distress was measured on a visual analogue scale. Patient reported outcome measures (PROMs) including the Western Ontario and McMaster Universities (WOMAC®) index, the Knee injury and Osteoarthritis Outcome Score (KOOS), the painDETECT® (Pfizer, Berlin, Germany) questionnaire and the EQ-5D™ (EuroQol, Rotterdam, Netherlands) questionnaire were used. Participants were also asked about kneeling ability. RESULTS While 68% of patients reported numbness around their TKR scar, there was no statistically significant correlation between numbness and distress at numbness (self-report: 0.23, p=0.08; monofilament: 0.15, p=0.27). Furthermore, numbness did not correlate significantly with joint specific PROMs (WOMAC®: 0.21, p=0.13; KOOS: 0.18, p=0.19). However, difficulty with kneeling did correlate with both self-reported numbness (0.36, p=0.020) and worse PROM scores (WOMAC® pain subscale: 0.62, p<0.001; KOOS: 0.64, p<0.001). CONCLUSIONS Numbness after knee replacement is common but is not associated with worse patient reported outcomes.

Central sensitization as a determinant of patients' benefit from total hip and knee replacement.

BACKGROUND: Discrepancies exist between osteoarthritic joint changes and pain severity before and after total hip (THR) and knee (TKR) replacement. This study investigated whether the interaction between pre-operative widespread hyperalgesia and severity of radiographic osteoarthritis (OA) was associated with pain severity before and after joint replacement. METHODS: Data were analysed from 232 patients receiving THR and 241 receiving TKR. Pain was assessed pre-operatively and at 12 months post-operatively using the WOMAC Pain Scale. Widespread hyperalgesia was assessed through forearm pressure pain thresholds (PPTs). Radiographic OA was evaluated using the Kellgren and Lawrence scheme. Statistical analysis was conducted using multilevel models, and adjusted for confounding variables. RESULTS: Pre-operative: In knee patients, there was weak evidence that the effect of PPTs on pain severity was greater in patients with more severe OA (Grade 3 OA: ß = 0.96 vs. Grade 4: ß = 4.03), indicating that in these patients higher PPTs (less widespread hyperalgesia) was associated with less severe pain. In hip patients, the effect of PPTs on pain did not differ with radiographic OA (Grade 3 OA: ß = 3.95 vs. Grade 4: ß = 3.67). Post-operative: There was weak evidence that knee patients with less severe OA who had greater widespread hyperalgesia benefitted less from surgery (Grade 3 OA: ß = 2.28; 95% CI -1.69 to 6.25). Conversely, there was weak evidence that hip patients with more severe OA who had greater widespread hyperalgesia benefitted more from surgery (Grade 4 OA: ß = -2.92; 95% CI -6.58 to 0.74). CONCLUSIONS: Widespread sensitization may be a determinant of how much patients benefit from joint replacement, but the effect varies by joint and severity of structural joint changes. SIGNIFICANCE: Pre-operative widespread hyperalgesia and radiographic osteoarthritis (OA) severity may influence how much patients benefit from joint replacement. Patients undergoing knee replacement with less severe OA and greater widespread hyperalgesia benefitted less from surgery than patients with less hyperalgesia. Patients undergoing hip replacement with more severe OA and greater widespread hyperalgesia benefitted more than patients with less hyperalgesia.

Selecting, assessing and interpreting measures of function for patients with severe hip pathology: The need for caution.

INTRODUCTION: It is not always possible to use a combination of patient-reported outcome measures (PROMs), performance tests and clinician-administrated measures to assess physical function prior to hip surgery. We hypothesised that there would be low correlations between these three types of measure and that they would be associated with different patients' characteristics. MATERIALS AND METHODS: We conducted a cross-sectional analysis of the preoperative information of 125 participants listed for hip replacement. The WOMAC-function subscale, Harris Hip Score (HHS) and walk, step and balance tests were assessed by questionnaire or during a clinic visit. Participant's socio-demographics and medical characteristics were also collected. Correlations between functional measures were investigated with correlation coefficients. Regression models were used to test the association between the patient's characteristics and each of the three types of functional measures. RESULTS: None of the correlations between the PROM, clinician-administrated measure and performance tests were very high (<0.90). Associations between patient's characteristics and functional scores varied by type of measure. Psychological status was associated with the PROM (P-value<0.0001) but not with the other measures. Age was associated with the performance test measures (P-value ranging from ≤0.01 to <0.0001) but not with the PROM. The clinician-administered measure was not associated with age or psychological status. DISCUSSION: Substantial discrepancies exist when assessing hip function using a PROM, functional test or a clinician-administered test. Moreover, these assessment methods are influenced differently by patient's characteristics. Clinicians should supplement their pre-surgery assessment of function with patient-reported measure to include the patient's perspective. LEVEL OF EVIDENCE: III, observational cross-sectional study.

Assessment of physical function following total hip arthroplasty: Inertial sensor based gait analysis is supplementary to patient-reported outcome measures.

BACKGROUND: Functional outcome assessment after total hip arthroplasty often involves subjective patient-reported outcome measures whereas analysis of gait is more objective. The study's aims were to compare subjective and objective functional outcomes after total hip arthroplasty between patients with low and high self-reported levels of pre-operative physical function. METHODS: Patients undergoing total hip arthroplasty (n=36; m/f=18/18; mean age=63.9; SD=9.8 years; BMI=26.3; SD=3.5) were divided into a low and high function subgroup, and prospective measures of WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) function score and gait were compared at baseline and 3 and 12 months post-operatively. FINDINGS: WOMAC function scores significantly improved in both low and high function subgroups at 3 months post-operatively whereas gait parameters only improved in patients with a low pre-operative function. Between 3 and 12 months post-operatively, WOMAC function scores had not significantly further improved whereas several gait parameters significantly improved in the low function group. WOMAC function scores and gait parameters were only moderately correlated (Spearman's r=0.33-0.51). INTERPRETATION: In a cohort of patients undergoing total hip arthroplasty, pre-operative differences in mean WOMAC function scores and gait parameters between low and high function subgroups disappeared by 3 months post-operatively. Gait parameters only improved significantly during the first 3 post-operative months in patients with a low pre-operative function, highlighting the importance of investigating relative changes rather than the absolute changes and the need to consider patients with high and low functions separately.