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· DOS Abstracts
Minimal Important Change determined with a novel
method focusing on patients’ perspectives of important
change for the Oxford Knee Score and the Forgotten Joint
Score after knee replacement
Lina Holm Ingelsrud, Ewa Roos, Kirill Gromov, Henrik Husted, Berend Terluin, Anders
Troelsen
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre;
Department of Sports Science and Clinical Biomechanics, University of Southern
Denmark; Department of Orthopaedic Surgery, Copenhagen University Hospital
Hvidovre; Department of Orthopaedic Surgery, Copenhagen University Hospital
Hvidovre; Department of General Practice and Elderly Care Medicine, VU Univer-
sity Medical Center, Amsterdam; Department of Orthopaedic Surgery, Copenhagen
University Hospital Hvidovre
Background:
Interpreting changes in Oxford Knee Score (OKS) and Forgotten Joint
Score (FJS) after undergoing knee replacement is challenged by lack of method-
ologically rigorous methods to derive on Minimal Important Change (MIC) values.
Purpose / Aim of Study:
To determine MIC values for the OKS and FJS in patients
undergoing primary knee replacement in Denmark.
Materials and Methods:
Patients undergoing knee replacement between January
2015 and May 2016 were selected from one hospital’s arthroplasty database. OKS
and FJS were completed preoperatively and at 1 year postoperatively, accompanied
by a 7-point anchor question ranging from “better, an important improvement”
to “worse, an important worsening”. MIC improvement values were defined with
the predictive modelling approach based on logistic regression, with patients’ deci-
sions on important improvement as dependent variable and change in OKS/FJS as
independent variable. Furthermore, the MIC was adjusted for the high proportion
of improved patients.
Findings / Results:
We identified 341 patients with 1-year follow-up data, with
a mean age of 67.4 years (63% female). Complete data for OKS, FJS and anchor
questions were found for 307/341 patients (90%), and 85% (n=261) of these
patients were importantly improved. The Spearman’s correlation between the an-
chor and the change score was 0.59 for OKS, and 0.61 for FJS. Adjusted predictive
MIC values (95% CI) for improvement were 6.6 (4.6; 9.2) for OKS and 13.0 (8.4;
19.4) for FJS.
Conclusions:
The MIC value of 6.6 for OKS and 13.0 for FJS, determined with
novel MIC methodology, corresponds to minimal improvements that the average
patient finds important. These values may aid in evaluating the clinical relevance of
improvement after knee replacement surgery.
No conflicts of interest reported
4.