Abstract
To develop and validate a clinical prediction model of patient-reported pain and function after undergoing total knee replacement (TKR). We used data of 1,649 patients from the Knee Arthroplasty Trial who received primary TKR across 34 centres in the UK. The external validation included 595 patients from Southampton University Hospital, and Nuffield Orthopaedic Centre (Oxford). The outcome was the Oxford Knee Score (OKS) 12-month after TKR. Pre-operative predictors including patient characteristics and clinical factors were considered. Bootstrap backward linear regression analysis was used. Low pre-operative OKS, living in poor areas, high body mass index, and patient-reported anxiety or depression were associated with worse outcome. The clinical factors associated with worse outcome were worse pre-operative physical status, presence of other conditions affecting mobility and previous knee arthroscopy. Presence of fixed flexion deformity and an absent or damaged pre-operative anterior cruciate ligament (compared with intact) were associated with better outcome. Discrimination and calibration statistics were satisfactory. External validation predicted 21.1% of the variance of outcome. This is the first clinical prediction model for predicting self-reported pain and function 12 months after TKR to be externally validated. It will help to inform to patients regarding expectations of the outcome after knee replacement surgery.
Highlights
Total knee replacement (TKR) surgery is a common procedure with 86,438 performed in 2014 in England, Wales, Northern Ireland and the Isle of Man[1]; and 7,169 primary knee arthroplasties performed in 2013 in Scotland[2]
We have developed and externally validated a new prediction model for patient-reported pain and function after total knee replacement (TKR) by using patient characteristics and clinical variables that are easy to measure
Presence of a fixed flexion deformity, and an absent or damaged pre-operative anterior cruciate ligament (ACL) were all significantly associated with better outcome
Summary
Total knee replacement (TKR) surgery is a common procedure with 86,438 performed in 2014 in England, Wales, Northern Ireland and the Isle of Man[1]; and 7,169 primary knee arthroplasties performed in 2013 in Scotland[2]. Pain and functional status after knee surgery depends on a wide range of factors, such as age[8,9], gender[10,11], socioeconomic status[12,13], social support[14], mental health[14,15], pain and function before the surgery[16], number of comorbidities[17], and implant and hospital type[18] These studies provide information on different risk factors, they have been unable to explain much of the variability in outcome following surgery. As an example application of clinical prediction model, we developed and externally validated a simple prediction model for improvement in pain and function 12 months after TKR using data from the Knee Arthroplasty Trial (KAT)[20,21] (development dataset) and the Clinical Outcomes in Arthroplasty study (COASt) (validation dataset)
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