Sagittal spinopelvic alignment in adolescents associated with Scheuermann's kyphosis: a comparison with normal population

Spinopelvic alignment is increasingly considered as a main factor in the energy-efficient posture of the individual in normal and pathological status. However, the spinopelvic characteristics in Scheuermann's kyphosis (SK) are poorly defined in the literature. The purpose of this study was to determine whether differences of the spinopelvic parameters exist between adolescents with SK and age-matched normal controls. In this study, 55 patients with SK and 60 healthy age-matched adolescents were recruited consecutively. Sagittal spinal and pelvic parameters were measured from the standing lateral radiograph, including global kyphosis, thoracic kyphosis (TK), cervical lordosis (CL), lumbar lordosis (LL), pelvic incidence (PI), sacrum slope (SS), pelvic tilt (PT) and sagittal vertical axis (SVA). According to the location of the kyphosis, patients were subdivided into Scheuermann's thoracic kyphosis (STK) group and Scheuermann's thoracolumbar kyphosis (STLK) group. The radiographic comparison and correlation analysis were further performed. SK patients had significantly lower PI and PT than normal controls (32.0A degrees vs. 45.0A degrees, P < 0.001 for PI; 0.2A degrees vs. 11.9A degrees, P < 0.001 for PT). The rate of a negative PT was 41.8 % (22/55) in SK patients, which was remarkably higher than in normal controls (10.0 %, 6/60). The CL, TK and LL were significantly increased in STK group when compared with STLK and control groups. A significant correlation was noticed between TK and CL and also between TK and LL in STK group. Both TK and LL were decreased in STLK patients, and a significant correlation was found between them (r = -0.687, P < 0.001). A significantly strong correlation was also observed between LL and SS in STLK patients (r = -0.641; P < 0.001). Adolescents with SK have a significantly lower PI when compared with age-matched normal controls. Patients with different curve patterns (STK vs. STLK) could have distinct compensatory mechanisms to maintain the sagittal balance.