Background: Preoperative psychological distress has been reported to
be an important risk factor for poor outcome following lower-extremity
arthroplasty. We determined the independent impact of preoperative
psychological distress on three, twelve, and twenty-four-month WOMAC (Western
Ontario and McMaster Universities Osteoarthritis Index) pain and function
scores and on change scores over those time periods.
Methods: Data were obtained from an international group of 952
patients in thirteen centers participating in the Kinemax Outcomes Study.
Patients completed the WOMAC and Short Form-36 (SF-36) questionnaires. The
mental health (MH) scale of the SF-36 was used to quantify the impact of
psychological distress on WOMAC pain and function scores. We also dichotomized
patients into groups with and without psychological distress on the basis of
evidence-based cut-points. Repeated-measures models were used to derive mean
preoperative and three, twelve, and twenty-four-month WOMAC pain and function
scores and general linear models were used to derive change scores for
patients with and without psychological distress after adjustment for
covariates.
Results: Psychological distress, when examined on a continuous
scale, was found to predict pain and function at all time-points. WOMAC pain
scores for psychologically distressed patients were 3 to 5 points lower,
depending on the time-frame, than the scores for the non-distressed patients,
after adjustment for covariates. WOMAC function scores did not differ
significantly between the two groups following surgery. The changes in the
WOMAC pain and function scores for the psychologically distressed patients
were not significantly different from those for the non-distressed
patients.
Conclusions: Many patients with psychological distress demonstrate a
substantial decrease in that distress following surgery. Patients who are
distressed have slightly worse pain preoperatively and for up to two years
following knee arthroplasty as compared with patients with no psychological
distress. With the exception of preoperative scores, these differences are not
likely to be measurable at the individual patient level. WOMAC pain and
function change scores do not differ between patients with and without
distress after adjustment for covariates.
Level of Evidence: Prognostic Level I. See Instructions
to Authors for a complete description of levels of evidence.