This is a closed cohort analysis, secondarily analyzing existing prospectively collected data of 1198 patients, who participated in three multicenter randomized controlled trials evaluating different rehabilitation measures. Data from 362 of those patients suggested ergometer cycling enhanced rehabilitation after THA, but not after TKA [17
For these trials, eligible patients were identified by the admitting physicians and were approached to participate in the trial. Participating centers were two university hospitals, two rural, and one municipal hospital, all located in Germany. Patients providing written informed consent were enrolled in the trial. Information regarding the study was given to participants on the day of admission to the hospital. These patients were enrolled from January 1, 2003, to April 30, 2006. After exclusion of the patients who had a THA, and of 99 patients who were unwilling to participate or who had one of the following exclusion criteria: (1) history of septic arthritis; (2) hip or knee fracture; (3) intraoperative complications; (4) revision arthroplasty; (5) rheumatoid arthritis; (6) lower extremity amputations; (7) malignancy; and (8) inability to complete the questionnaires because of cognitive or language difficulties, 494 patients were left. Followups were performed after 3, 6, 12, and 24 months. Of the 494 patients, 443 (90%) completed the postal questionnaire at 3 months. The followup rate decreased to 88% at 6 months, 81% at 12 months, and 76% at 24 months. There was no association between patients who did not respond to the followup questionnaire and patient baseline characteristics. The study protocol was approved by the local ethics committee. A data and safety monitoring board monitored the study.
Of the 494 patients, 353 (71%) were women and 141 (29%) were men. At the time of surgery, their average age was 70.0 years. The mean body mass index (BMI) was similar in males and females as were the number of comorbidities, and additional limitations resulting from other joints of the lower or upper extremities, or the result of low back pain (Table ).
All patients received a standard total or UKA (Table ). As the cohort includes patients who had a UKA, we have provided an analysis for the whole cohort and one for TKA only.
All patients participated in a standard postsurgery program of daily supervised physiotherapy during hospitalization, consisting of ROM activities, exercises for improvement of muscle tension, venous return, balance, coordination and gait, and instruction in activities of daily living, including transfers, walking, and negotiation of stairs and uneven surfaces. Patients were mobilized starting postoperative Day 1, initially using a walker and later using crutches. Continuous passive motion machines were used on a daily basis after removal of suction drains. All patients were given analgesics and mechanical and medical thrombosis prophylaxis according to a standard scheme.
The primary outcome was self-reported physical function 3, 6, 12, and 24 months postoperatively. We chose 3 and 6 months as the appropriate study intervals because the most improvement in postoperative physical health occurs during these times [9
]. We added 12-month and 24-month study intervals to standardize our research with that of others who have analyzed health-related quality of life after TKA [9
]. This was measured using the WOMAC osteoarthritis index [3
] using a validated translated version [22
]. Secondary outcomes consisted of leg-specific stiffness and pain measured with the WOMAC and the physical component summary (PCS) and mental component summary (MCS) of the 36-item SF-36 [5
]. For the WOMAC, responses were recorded on a visual analog scale with terminal descriptors. Scores were added for each category and standardized to a score of 0 to 100 with higher scores indicating more pain, more stiffness, or more dysfunction. All patients were asked to answer the questionnaire at the time of hospital admission. During the hospital stay, the study nurse visited the patients to ensure the questionnaire was filled in completely. The questionnaire included, among others, the list of comorbidities adapted from the “current health assessment” section of the Hip and Knee—Baseline Questionnaire of the musculoskeletal outcomes data evaluation and management system developed by the AAOS [13
]. After 3, 6, 12, and 24 months, participants were mailed a questionnaire in a prepaid return envelope. Nonresponding participants were reminded by mail up to three times at intervals of 2 weeks. Participants still not responding were contacted by telephone to determine their reason for not responding. Data were entered in a database at the coordinating center.
At the time of surgery, the women were a mean of 3 years older compared with the men (Table ), and they reported lower physical function, more pain, and more stiffness as measured by the WOMAC. In addition, women scored lower on the MCS of the SF-36 and the Knee Society function score (Table ).
Absolute baseline and followup scores of the outcome scores were evaluated. Because the baseline scores were not comparable between genders, we calculated improvement (change) scores for the outcomes. Continuous data initially were tested for normal distribution with the Kolmogorov-Smirnov test. Apart from age, BMI, and the improvement (change) scores, these data were not normally distributed. Therefore, we used the nonparametric Mann-Whitney U test to determine differences between genders in the absolute WOMAC and SF-36 scores. To adjust for potential confounding variables, multivariable regression models were developed in which the improvement of the primary outcome (WOMAC physical function) served as the dependent variable and the dichotomous variable for gender served as an independent variable, along with BMI, age, and number of comorbidities as confounding variables. The type III sum-of-squares option was used to calculate the adjusted effect of gender on the improvement of WOMAC physical function for each of the four followup periods. All p values are two-tailed; no corrections were made for multiple comparisons. Effect sizes [1
] as the standardized differences between two groups were calculated as described by Cohen [7
]. We used SPSS (SPSS Inc, Chicago, IL, USA) for data analysis.