Degenerative changes of sagittal alignment in patients with Roussouly type 1

Abstract

STUDY DESIGN: A cross-sectional radiological study. OBJECTIVES: We aimed to examine the degenerative changes of sagittal alignment in patients with Roussouly type 1. Roussouly type 1 is unique in shape, characterized by short lumbar lordosis (LL) with the apex at L5 and thoracolumbar kyphosis (TLK). Because of the unique shape of sagittal alignment and the small pelvic incidence (PI) in Roussouly type 1, the degenerative changes of sagittal alignment may differ. METHODS: A total of 145 patients with Roussouly type 1 were recruited and distributed into three age groups; Group I (N = 40) were young patients (20-40 years of age), Group II (N = 47) were middle-aged patients (45-60 years of age), and Group III (N = 48) were elderly patients (>65 years of age). Sagittal parameters including sagittal vertical axis (SVA), PI, pelvic tilt (PT), L1S1 LL, L4S1 LL, thoracic kyphosis (TK), and TLK were measured using Surgimap((R)) software. The occurrence of lumbar retrolisthesis was also examined. RESULTS: The SVA, PI, PT, L1S1 LL, L4S1 LL, TK, and TLK in group I were - 25.9 degrees +/- 23.4 mm, 37.1 degrees +/- 5.3 degrees , 10.3 degrees +/- 5.5 degrees , 42.7 degrees +/- 8.8 degrees , 35.5 degrees +/- 6.9 degrees , 29.5 degrees +/- 23.5 degrees , and 9.7 degrees +/- 5.9 degrees , respectively. Among the Groups I, II, and III, there was a stepwise increase in the SVA, PT, TLK, and lumbar retrolisthesis (all P < 0.001). The PI, L4S1 LL, and TK were identical among the three groups. CONCLUSIONS: Degenerative changes of Roussouly type 1 include increase in the SVA, PT, TLK, and lumbar retrolisthesis, while the PI, L4S1 LL, and TK remain unchanged. LEVEL OF EVIDENCE: Level IV.