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Abstract
Objectives Osteoarthritis (OA) structural status is imperfectly classified using radiographic assessment. Statistical shape modelling (SSM), a form of machine-learning, provides precise quantification of a characteristic 3D OA bone shape. We aimed to determine the benefits of this novel measure of OA status for assessing risks of clinically important outcomes.
Methods The study used 4796 individuals from the Osteoarthritis Initiative cohort. SSM-derived femur bone shape (B-score) was measured from all 9433 baseline knee MRIs. We examined the relationship between B-score, radiographic Kellgren-Lawrence grade (KLG) and current and future pain and function as well as total knee replacement (TKR) up to 8 years.
Results B-score repeatability supported 40 discrete grades. KLG and B-score were both associated with risk of current and future pain, functional limitation and TKR; logistic regression curves were similar. However, each KLG included a wide range of B-scores. For example, for KLG3, risk of pain was 34.4 (95% CI 31.7 to 37.0)%, but B-scores within KLG3 knees ranged from 0 to 6; for B-score 0, risk was 17.0 (16.1 to 17.9)% while for B-score 6, it was 52.1 (48.8 to 55.4)%. For TKR, KLG3 risk was 15.3 (13.3 to 17.3)%; while B-score 0 had negligible risk, B-score 6 risk was 35.6 (31.8 to 39.6)%. Age, sex and body mass index had negligible effects on association between B-score and symptoms.
Conclusions B-score provides reader-independent quantification using a single time-point, providing unambiguous OA status with defined clinical risks across the whole range of disease including pre-radiographic OA. B-score heralds a step-change in OA stratification for interventions and improved personalised assessment, analogous to the T-score in osteoporosis.
- osteoarthritis
- magnetic resonance imaging
- knee osteoarthritis
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Footnotes
Handling editor Josef S Smolen
Contributors PGC, NB, MAB, KK, OA and AB wrote the first draft of the manuscript. All statistical analyses were conducted by MAB, KK, OA and BD. All authors revised and approved the final manuscript for submission.
Funding The OAI is a public-private partnership comprising five contracts (N01-AR-2-2258; N01-AR-2-2259; N01-AR-2-2260; N01-AR-2-2261; N01-AR-2-2262) funded by the National Institutes of Health, a branch of the Department of Health and Human Services, and conducted by the OAI Study Investigators. Private funding partners include Merck Research Laboratories; Novartis Pharmaceuticals Corporation, GlaxoSmithKline and Pfizer, Inc. Private sector funding for the OAI is managed by the Foundation for the National Institutes of Health. This manuscript was prepared using an OAI public use dataset and does not necessarily reflect the opinions or views of the OAI investigators, the NIH, or the private funding partners. Support for this study was provided by: Flexion Therapeutics; Imorphics; Versus Arthritis (grant 20800); Versus Arthritis Experimental Osteoarthritis Treatment Centre (ref 20083); the EPSRC (Programme Grant EP/P001076/1); and the National Institute for Health Research (NIHR) through the Leeds Biomedical Research Centre. This article presents independent research funded in part by the NIHR.
Disclaimer The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.
Competing interests MAB and AB are employees of Imorphics, a wholly owned subsidiary of Stryker Corporation. KK is a consultant for Flexion Therapeutics Inc. OA and BD have no conflicts of interest to disclose. NB is an employee of Flexion Therapeutics. PGC has done consultancies or speakers bureaus for AbbVie, Bristol Myers Squibb, Eli Lilly, EMD Serono, Flexion Therapeutics, Galapagos, GlaxoSmithKline, Novartis, Pfizer, Roche, Samumed and Stryker.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on reasonable request. All source data are available from the osteoarthritis initiative (OAI), https://data-archive.nimh.nih.gov/oai/. The datasets generated and/or analysed within this publication are available from the corresponding author on reasonable request.
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