The aim of the present study was a comparative investigation of the functional improvement reported by patients suffering from primary osteoarthritis of the knee or hip undergoing total joint replacement and assessed at 3 months.
In a prospective, controlled clinical trial, 56 patients with primary osteoarthritis of the hip and 59 patients with primary osteoarthritis of the knee undergoing total joint replacement were assessed at two measuring times (day of admission = t1 and 3-month follow-up = t2) using the XSMFA-D (Extra Short Musculoskeletal Function Assessment Questionnaire--German version), WOMAC (Western Ontario and McMasters Universities) arthrosis index and FFb-H OA (Function Assessment Questionnaire Hannover Osteoarthritis). The statistical analysis included effect sizes as standardised response mean, t-test and covariance analysis.
Both groups of patients demonstrated significant improvements of the musculoskeletal functions measured. The effect sizes between baseline scores and 3-month follow-up scores range from 0.4 to 2.0 and can be considered as large effects. The covariance analysis showed significant differences between patients with osteoarthritis of the hip and knee for almost every score examined. Patients with hip replacement showed large improvements. A significant influence of the presurgery baseline score on the 3-month score was found consistently. Further analysis showed that patients with medium or strong degrees of disability according to the Function index of the XSMFA-D showed the strongest effects of change at 3 months. However, their scores at t2 were less than the scores of the less disabled patients at t1.
We conclude that patients with hip replacement show more improvement 3 months after the surgery than patients with knee replacement. Furthermore, it was seen that patients who were more disabled before surgery achieved more improvement than the less-disabled patients. However, they did not achieve the level of the less disabled patients. Thus, the recommendation that total joint replacement should be performed as late as possible should be reviewed.