The influence of congenital lumbosacral deformity on pelvic balance

English Keywords:Lumbosacral deformity  Hemivertebra  Pelvic balance  Pelvic obliquity  Pelvic rotation

English Abstract:

  【Abstract】 Objectives: To analyze the influence of lumbosacral deformity on pelvic balance by retrospectively reviewing the medical images of lumbosacral deformity patients. Methods: All lumbosacral deformity patients treated in our hospital between January 2007 and September 2018 were retrospectively reviewed. Those with only sagittal deformity, previous spinal surgery, discrepancy of leg length ≥2cm or hip disease were excluded. 26 patients were recruited with a mean age of 13.8±6.9, including 8 male patients and 18 female patients. These patients were divided into group A(only lumbosacral deformity, n=9), group B(lumbosacral deformity combined with vertebral deformity in other regions, n=12) and group C(complex deformity in lumbar and sacral region, n=5). Segmental Cobb angles were measured and compared in group A and B. Pelvic obliquity(PO) in coronal plane, sacral inclination angle(SIA) in sagittal plane and pelvic rotation(PR) in transverse plane were measured. The three-dimensional pelvic balance was analyzed and compared among three groups. PO>2°, SIA<30° or >45° and PR>1.2 were set as the criteria for pelvic imbalance in coronal, sagittal and transverse planes respectively. Results: The three groups had no statistically significant difference in age or gender. The mean segmental Cobb angles in group A and B were 24.0°±13.6° and 28.3°±14.4° respectively, with no statistically significant difference(P=0.497). Mean PO in three groups was 1.7°±2.3°, 4.9°±6.7° and 18.9°±12.7°, with PO in group C significantly greater than that in group A and B (group C vs group A: P=0.002, group C vs group B: P=0.009) and no statistically significant difference between group A and B(P=0.200). Mean SIA in three groups was 38.7°±6.8°, 36.1°±18.2° and 28.4°±9.3°, with no statistically significant difference between three groups(P=0.418). Mean PR in three groups were 1.09±0.05, 1.22±0.15 and 1.44±0.51, with PR in group B significantly greater than that in group A(P=0.002) and no statistically significant difference between group A and C(P=0.061) or between group B and C(P=0.191). The incidence of pelvic imbalance in three groups (group A, group B, group C) in coronal, sagittal and transverse planes was 33.3%, 77.8%, 100%; 11.1%, 58.3%, 40.0% and 0%, 41.7%, 60.0% respectively. No significant pelvic imbalance was identified in cases with only lumbosacral hemivertebrae. All patients with PR>1.15 and 93.3% patients with PR>1.10 had their pelvis rotated in consistence with the direction of main curves. Conclusions: The pelvis can maintain balance in patients with only lumbosacral hemivertebrae. The lumbosacral deformities combined with other vertebral deformities, especially complex lumbar and sacral deformities, are more likely to cause three-dimensional pelvic imbalance. The direction of pelvic rotation caused by lumbosacral deformity is consistent with the direction of main curve