J Orthopaed Traumatol (2008) 9:155–158 Table 2 WOMAC results where up to 5.3% of all answers are missing, contradictory or multiple [12]. Patients in the THA literature generally have primary osteoarthritis [11, 13, 14]. Osteoarthritis secondary to CHD usually represents only 2–3% of all diagnoses [11, 14]. With respect to the SF-36 survey, our results were equivalent or better than studies where primary OA was the principal diagnosis (with higher patient mean ages) (Fig. 1). Published role-physical preoperative values range from 19.5 to 27.05, and post-operative values from 52.41 to 66.6, while these values ranged from 18.55 to 84.52 in our patient cohort [11, 13, 14]. We noticed the same tendency for the bodily pain scale, with preoperative values ranging from 27.1 to 32.90 and post-operative values from 58.79 to 72.8 in the literature, versus a range of 23.26–83.39 in our study [11, 13, 14]. General health and vitality pre-operative values in our study were mainly lower than in the literature, and post-operative values were higher [11, 13, 14]. Role- emotional values were higher both pre- and post-opera- tively in our study [11, 13]. A lower mean age, with a resultant lower comorbidity disease burden, may explain why our patient cohort achieved higher ﬁnal post-operative clinical SF-36 results than primary OA patients from the literature [19]. Patients in our cohort had lower pre-operative mental health scores than the published literature: younger patients may be less able to cope with functional limitations than their older peers. Post-operative scores were similar (79.4 vs. 79.4). This reasoning may equally apply to social functioning as well. Interestingly, our patient cohort displayed better post- operative results on the SF-36 than healthy controls aged 45–54 years, except for the role-physical scale (Fig. 2). This could have been due to a recall bias: recently reha- bilitated patients may have tended to overvalue their current physical condition when making a pre-operative comparison (when the clinical and psychological effects of their condition were presumably at their worst). Comparison of our patients with the literature using the WOMAC was complicated by the diverse methods used to report results (raw score, percentage, visual analog scale) [8, 15–18]. We generally observed a greater score decrease (meaning improvement in QoL) among our cohort (Fig. 3). This was probably due to the relatively lower mean patient Scale Pain Stiffness Function Global Pre-operative mean value (SD) 14.06 (5.05) 4.26 (2.62) 42.68 (12.83) 61 (17.35) Post-operative mean value (SD) 0.84 (1.83) 0.52 (0.99) 5.39 (5.70) 6.74 (7.41) P value Effect size 0.000 0.000 0.000 0.000 2.62 1.43 2.91 3.13 157 % Relative increase 1,573.80 719.23 691.84 805.04 Fig. 1 SF-36 pre and post-operative results in CHD and primary hip OA [11, 13, 14] Fig. 2 SF-36 pre- and post-operative results in CHD and healthy populations in the 45–54-year-old age group [4, 5] age (51 vs. 65–68 years), and to clinical differences between CHD and primary OA [11, 13]. Considering that CHD essentially affects young women, social functioning and mental health evaluation is critical: it has been observed that females aged \65 years who are affected by chronic disease suffer more frequently from psychological disorders than men [14]. Our results indicate that both the SF-36 and WOMAC are valid and complementary evaluation instruments. The WOMAC assesses physical outcomes, while the SF-36 is 123