Sagittal spino-pelvic alignment in rapidly destructive coxarthrosis

Tadatsugu Morimoto, Masaru Kitajima, Masatsugu Tsukamoto, Tomohito Yoshihara, Motoki Sonohata, Masaaki Mawatari

To investigate the sagittal spino-pelvic alignment (SSPA) in patients with rapidly destructive coxarthrosis (RDC). SSPA was investigated in 44 patients with RDC and 70 patients with hip osteoarthritis (HOA). The study included only female patients over the age of 70 years because epidemiological reports indicate that RDC most commonly occurs in this group of patients. The SSPA parameters that were analyzed included lumbar lordosis (LL), lumbar range of motion (ΔLL), sacral slope (SS), pelvic incidence (PI), and pelvic tilt (PT). The pelvic inclination angle (PIA) in the supine position and the change in the PIA from the supine to the standing position (ΔPIA) were measured using anteroposterior pelvic radiographs. The values of these parameters were compared between the two groups. The levels of the SRS-Schwab classification modifiers were used to investigate the degree of sagittal malalignment. The RDC group showed significant lower LL, ΔLL and SS values, and significantly higher PT and ΔPIA values than the HOA group (P < 0.01). With regard to the sagittal modifiers in the SRS-Schwab classifications of the patients, the PI-LL and PT levels of the RDC group were significantly worse than those in the HOA group (P < 0.01). The present study suggests that the static factors of a reduction in the lumbar lordotic angle and greater posterior pelvic tilt, the dynamic factors of small ΔLL values and large ΔPIA values and the complex interaction of these two types of factors, may play important roles in the development of RDC.