Low pelvic incidence with low lordosis and distal apex of lumbar lordosis associated with higher rates of abnormal spinopelvic mobility in patients undergoing THA

AimsThe risk factors for abnormal spinopelvic mobility (SPM), defined as an anterior rotation of the spinopelvic tilt ( increment SPT) & GE; 20 & DEG; in a flexed-seated position, have been described. The implication of pelvic incidence (PI) is unclear, and the concept of lumbar lordosis (LL) based on anatomical limits may be erroneous. The distribution of LL, including a unusual shape in patients with a high lordosis, a low pelvic incidence, and an anteverted pelvis seems more relevant. MethodsThe clinical data of 311 consecutive patients who underwent total hip arthroplasty was retrospectively analyzed. We analyzed the different types of lumbar shapes that can present in patients to identify their potential associations with abnormal pelvic mobility, and we analyzed the potential risk factors associated with a increment SPT & GE; 20 & DEG; in the overall population.Results increment SPT & GE; 20 & DEG; rates were 28.3%, 11.8%, and 14.3% for patients whose spine shape was low PI/ low lordosis (group 1), low PI anteverted (group 2), and high PI/high lordosis (group 3), respectively (p = 0.034). There was no association between increment SPT & GE; 20 & DEG; and PI & LE; 41 & DEG; (odds ratio (OR) 2.01 (95% confidence interval (CI)0.88 to 4.62), p = 0.136). In the multivariate analysis, the following independent predictors of increment SPT & GE; 20 & DEG; were identified: SPT & LE;-10 & DEG; (OR 3.49 (95% CI 1.59 to 7.66), p = 0.002), IP- LL & GE; 20 (OR 4.38 (95% CI 1.16 to 16.48), p = 0.029), and group 1 (OR 2.47 (95% CI 1.19; to 5.09), p = 0.0148).ConclusionIf the PI value alone is not indicative of SPM, patients with a low PI, low lordosis and a lumbar apex at L4 -L5 or below will have higher rates of abnormal SPM than patients with a low PI anteverted and high lordosis.