Impaired Preoperative Spinopelvic Function Does Not Compromise the Patient-Reported Outcome at 2-Years After Total Hip Arthroplasty

Background Impaired spinopelvic function contributes to instability after total hip arthroplasty (THA). It remains unclear whether preoperative spinopelvic function affects patient-reported-outcomes (PROs) in patients undergoing THA. We hypothesized that preoperative pathological spinopelvic function is associated with worse postoperative PROs at 2-years-follow-up (2Y-FU) after THA. Methods A follow-up study of a prospective cohort undergoing primary THA was performed. PROs at 2Y-FU included Hip-Disability-and-Osteoarthritis-Outcome-Score (HOOS), Harris-Hip-Score (HHS), and Subjective-Hip-Value (SHV). Pelvic mobility (∆Pelvic Tilt=PT standing -PT sitting ) was defined as a key parameter. Pelvic mobility was classified as stiff(∆PT<10°), normal(∆PT≥10°-30°) and hypermobile(∆PT>30°). PROs were compared between groups stratified according to pelvic mobility. The relationship between spinopelvic function, cup position and PROs at 2Y-FU was analyzed. Results A total of 144 patients (N = 79 females; mean 68.9years; mean body mass index 26.9kg/m 2 , follow-up rate 73.1% (144/197)) were followed-up (mean 29.1months). HOOS-subdomains, HHS and SHV did not differ between the groups stratified for preoperative pelvic mobility at 2Y-FU. Higher pelvic mobility and lower standing and sitting lumbar lordosis were associated with better HOOS and HHS. No dislocation was reported in our cohort. Conclusions This study demonstrated that impaired preoperative pelvic mobility does not adversely affect PROs in patients undergoing elective THA at 2Y-FU. It can be concluded that primary THA patients without risk factors (eg, spinal fusion, neurological disease) do not face limited outcomes, regardless of their preoperative pelvic mobility. Nevertheless, spinopelvic function and functional cup position appear to be associated with PROs, and the underlying mechanisms require further investigation.