The minimal clinically important difference in the Oxford knee score and Short Form 12 score after total knee arthroplasty
- 1.4k Downloads
The aim of this study was to identify the minimal clinically important difference (MCID) in the Oxford knee score (OKS) and Short Form (SF-) 12 score after total knee arthroplasty (TKA).
Prospective pre-operative and 1 year post-operative OKS and SF-12 scores for 505 patients undergoing a primary TKA for osteoarthritis were collected during a one-year period. Patient satisfaction with their (1) patient relief and (2) functional outcome was used as the anchor questions. Their response to each question was recorded using a 5-point Likert scale: excellent, very well, well, fair, and poor. Simple linear regression was used to calculate the MCID for improvement in the OKS and physical component of the SF-12 score according to the level of patient satisfaction with their pain relief and function.
The OKS improved by 15.5 (95 % CI 14.7–16.4) points and the SF-12 physical component score improved by 10.1 (95 % CI 9.1–11.2) points for the study cohort. The level of patient satisfaction with their pain relief and function correlated with the improvement in the OKS (r = 0.56; p < 0.001, and r = 0.56; p < 0.001) and the physical component of the SF-12 score (r = 0.51; p < 0.001, and r = 0.60; p < 0.001), respectively. The MCID for the OKS was 5.0 (95 % CI 4.4–5.5) and 4.3 (95 % CI 3.8–4.8) points and for the physical component of the SF-12, it was 4.5 (95 % CI 3.9–5.2) and 4.8 (95 % CI 4.2–5.4) points for pain relief and function, respectively.
The MCID identified for the OKS and SF-12 physical component score after TKA is the best available estimate and can be used to power studies and ensure that a statistical difference is also recognised by a patient.
Level of evidence
Retrospective diagnostic study, Level III.
KeywordsMinimal clinical important difference Total knee arthroplasty Outcome Oxford knee score Short Form 12
Conflict of interest
The authors declare no conflict of interest with the content of this study.
- 1.Andrew G, Beard D, Nolan J, Murray DW, Tuson K (2006) Which approach for total hip replacement? Hip Int 16:118–119Google Scholar
- 4.Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW (1988) Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 15:1833–1840PubMedGoogle Scholar
- 14.Department for health (2010) Equity and excellence: liberating the NHS http://www.dh.gov.uk/en/Publlicationsandstatistics/Publications/PubicationsPolicyAndGuidance/DH_117353
- 16.General Register Office for Scotland (2008) http://www.gro-scotland.gov.uk/files2/stats/gros-mid-2008-population-estimates-scotland-population-estimates-by-sex-age-and-administrative-area/j1075008.htm
- 23.Parker SL, Mendenhall SK, Shau DN, Adogwa O, Anderson WN, Devin CJ, McGirt MJ (2012) Minimum clinically important difference in pain, disability, and quality of life after neural decompression and fusion for same-level recurrent lumbar stenosis: understanding clinical versus statistical significance. J Neurosurg Spine 16:471–478CrossRefPubMedGoogle Scholar