Patients with Scheuermann’s Kyphosis have a Lower Pelvic Incidence but Higher Lumbar Lordosis than Young Asymptomatic Volunteers: A HARMS and MEANS Study
Complex Adult and Pediatric Spine Fellow Columbia University Irving Medical Center Columbia New York Presbyterian Och Spine Hospital
Introduction: Scheuermann’s Kyphosis (SK) is characterized by rigid hyperkyphosis of the thoracic or thoracolumbar spine in adolescents or young adults. This study will examine the baseline radiographic parameters of SK patients in comparison with a normative cohort to investigate the inherent differences in the structural anatomy of SK prior to surgical intervention.
Methods: The HARMS Study Group SK database consisted of 97 patients with preoperative visits between 2006 and 2011; we included only patients with available pelvic parameters [n=53]. This SK cohort was compared with a prospectively enrolled multi-ethnic alignment normative study (MEANS) cohort consisting of 467 asymptomatic volunteers; we included only age < 40 years to promote meaningful comparison with the young HARMS cohort [n=254]. Existing HARMS preoperative and MEANS baseline radiographic imaging and parameters were obtained; supplemental fields were measured. Unpaired two-tailed t-tests and chi-squared tests were utilized.
Results: As expected, baseline thoracic kyphosis (TK, T1-T12) measurements were significantly higher in SK than in MEANS [74.1 ± 12.4 vs 41.9 ± 10.2; p< 0.00001]. Cervical sagittal angle (CSA, C2-C7) [-18.1 vs 2.3; p< 0.00001] and T1 slope (T1S) [37.7 vs 21.5; p< 0.00001] were significantly greater in SK than MEANS. All SK lumbar measures, including lumbar lordosis (LL, L1-S1) [-69.6 vs -57.3; p< 0.00001], proximal LL (pLL, L1-L4) [-25.5 vs -20.1; p=0.00008], and distal LL (dLL, L4-S1) [-44.1 vs -37.3; p< 0.00001], were significantly higher than MEANS. In contrast, SK pelvic parameters were significantly lower than MEANS in terms of pelvic incidence (PI) [40.2 vs 50.6; p< 0.00001], pelvic tilt (PT) [6.7 vs 10.8; p=0.00007], and sacral slope (SS) [33.4 vs 39.7; p< 0.00001].
Conclusion : As anticipated, baseline TK in SK was significantly higher than the norm. Despite the high TK, PI and PT were found to be significantly lower in SK than in asymptomatic volunteers, suggesting fundamental differences in pelvic anatomy. When compared with the MEANS cohort, SK was also found to have significantly greater CSA and T1S as well as higher LL, pLL, and dLL, reflecting considerable cervical and lumbar compensation, respectively. The global sagittal alignment in SK patients is inherently different at baseline than that of a young asymptomatic population.