Sagittal-spinopelvic alignment improves in patients with bilateral highly dislocated hip (Crowe type IV) after subtrochanteric shortening total hip arthroplasty: A retrospective radiographic study.

In patients with bilateral highly dislocated hips (HDHs), total hip arthroplasty with subtrochanteric shortening osteotomy (S-THA) is a viable option for achieving adequate reconstruction with restoration of the anatomical hip center. This procedure has the potential to improve sagittal spinopelvic alignment (SSPA). However, reports are scarce owing to the rarity of this disease. The objective of this study is to investigate pre- and post-operative SSPA in patients with HDHs who had undergone S-THA. This retrospective radiographic study included 55 patients (54 females and 1 male; average age, 63.1 ± 6.9 years) who underwent S-THA. Lateral spine radiographs in the standing position were obtained pre- and post-operatively. The SSPA included lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI), and intervertebral disc (ID) angle of L1/2-L5/S. The SSPA pre- and post-S-THA was compared using a paired t test. Pearson correlation coefficient was used to assess the relationships between parameters. The mean pre- and post-operative LL and SS values were 62° and 49° (LL) and 50° and 39° (SS), respectively (P < .001). The ID angle was significantly reduced post-operatively at all levels (P < .001). The correlation coefficients between preoperative LL and SS and postoperative LL and PI were 0.81 and 0.38, respectively (P < .01). The preoperative SSPA of Crowe type IV HDHs revealed excessive pelvic anteversion and lumbar hyperlordosis, with a high correlation between LL and SS, suggesting that these alterations were compensatory changes to maintain body balance. Furthermore, in patients with HDHs and residual spinal flexibility, restoring the original pelvic morphology with S-THA may contribute to improved SSPA.