gms | German Medical Science

Objectives: Patients with stiff spinopelvic mobility (SPM) were previously identified, being more likely to show a combined sagittal index value of >243° in standing position, potentially being at greater risk for dislocation as reported in the literature. The present study aimed to 1) assess whether abnormal spinopelvic mobility is associated with worse, pre-operative, symptoms; and 2) identify whether SPM can be predicted from clinical and static anatomic parameters in patients with end stage hip osteoarthritis.

Methods: A cohort of 122 patients with end-stage hip OA was prospectively studied. Patient reported outcome measures (PROMs) and clinical data were assessed. Sagittal SPM was calculated as the change from standing to sitting position for the lumbar lordosis angle (ΔLL), sacral slope (ΔSS), pelvic tilt (ΔPT), pelvic-femoral angle (ΔPFA) and acetabular ante-inclination (ΔAI) on lateral view radiographs. PROMs were compared between patients with normal (10°≤ΔPT≤30°) or abnormal spinopelvic mobility (stiff: ΔPT< 10°; hypermobile ΔPT >30°). Predictors for spinopelvic mobility were identified using a regression and receiver operating characteristic (ROC) curve analysis. A power analysis indicated an adequate sample size.

Results and conclusion: There was no difference for the Oxford Hip Score and Oswestry Disability Index between patients with stiff, normal and hypermobile spinopelvic mobility (23±8 vs. 20±8 vs. 23±9, p=0.32 and 38±14 vs. 40±17 vs. 39±16, p=0.94, respectively). Maximum hip flexion (coefficient: -0.26; p=0.001), standing PT (coefficient: -0.33; p=0.002) and standing AI were identified as independent predictors for spinopelvic mobility (R²=0.42) (Table 1 [Tab. 1]).

The combined thresholds for a standing PT ≥13°and hip flexion greater/equal than ≥88°in the clinical examination had 90% sensitivity and 63% specificity of predicting spinopelvic stiffness and a sacral slope of ≥ 42°had 84% sensitivity and 67% specificity of predicting spinopelvic hypermobility (Figure 1 [Fig. 1], Table 2 [Tab. 2]).The present, prospective study provides a holistic assessment of patients with hip OA due to have THA. Patients with abnormal spinopelvic mobility, potentially being at greater risk for dislocation after THA, could not be screened with PROMs, but identified by combing the information on maximum hip flexion and radiographic measurements of pelvic tilt and sacral slope on standing lateral pelvic/lumbar spine radiographs. Therefore, in order to limit overuse of resources, we would advise surgeons to commence screening with a standing lateral radiograph of the spinopelvic complex only.