Pelvic incidence and hip disorders.

Background and purpose - The role of pelvic incidence in hip disorders is unclear. Therefore, we undertook a literature review to evaluate the evidence on that role. Methods - A search was carried out on MEDLINE, SCOPUS, CENTRAL, and CINAHL databases. Quantitative analysis was based on comparison with a reference population of asymptomatic subjects. Results - The search resulted in 326 records: 15 studies were analyzed qualitatively and 13 quantitatively. The estimates of pelvic incidence varied more than 10 degrees from 47 (SD 3.7) to 59 (SD 14). 2 studies concluded that higher pelvic incidence might contribute to the development of coxarthrosis while 1 study reported the opposite findings. In 2 studies, lower pelvic incidence was associated with a mixed type of femoroacetabular impingement. We formed a reference population from asymptomatic groups used or cited in the selected studies. The reference comprised 777 persons with pooled average pelvic incidence of 53 (SD 10) degrees. The estimate showed a relatively narrow 95% CI of 52 to 54 degrees. The 95% CIs of only 4 studies did not overlap the CIs of reference: 2 studies on coxarthrosis, 1 on mixed femoroacetabular impingement, and 1 on ankylosing spondylitis Interpretation - We found no strong evidence that pelvic incidence plays any substantial role in hip disorders. Lower pelvic incidence may be associated with the mixed type of femoroacetabular impingement and hip problems amongst patients with ankylosing spondylitis. The evidence on association between pelvic incidence and coxarthrosis remained inconclusive.