Measurement of coronal pelvic parameters and compensation of pelvis and lower limbs in spinal deformity

English Keywords:Spinal deformity  Coronal balance  Pelvic parameter

English Abstract:

  【Abstract】 Objectives: To explore coronal pelvic parameters and investigate the compensation of pelvis and lower limbs in coronal spinal alignment. Methods: The X-ray images of 49 subjects with adolescent idiopathic scoliosis(AIS) and 46 subjects with degenerative lumbar scoliosis(DLS) were respectively reviewed, and all of them were with major thoracolumbar/lumbar curve. Three coronal pelvic parameters including sacral obliquity(SO), iliac obliquity(IO) and hip obliquity(HO) were measured twice at an interval of 1 month by two spinal surgeons separately in posterior-anterior X-ray. The reliability of the parameters was tested. Then coronal spinal parameters including coronal decompensation(CD), thoracolumbar/lumbar curve(TL/L), lumbosacral curve(LS) and pelvis-leg curve(PL) were measured. The correlation analysis was performed between SO, IO, HO and TL/L before operation. The differences of the 3 parameters at pre-operation, post-operation and follow-up were analysed. Results: In AIS group, for SO, IO and HO, the inter-observer reliability was 0.986, 0.979 and 0.989 respectively, and the intra-observer reliability was 0.988, 0.983 and 0.976 respectively. In DLS group, the inter-observer reliability of SO, IO and HO was 0.863, 0.979 and 0.996, and the intra-observer reliability of those was 0.920, 0.986 and 0.995. At pre-operation, the correlation between TL/L and SO, IO and HO in AIS group was 0.805, 0.735 and 0.324, respectively; the correlation between SO and IO and HO was 0.800 and 0.518(P<0.05). The correlation between TL/L and SO, IO and HO in DLS group was 0.649, 0.651 and 0.457; the correlation between SO and IO and HO was 0.529 and 0.359(P<0.05). In AIS group, SO was 4.5°±2.6° at pre-operation, 2.3°±2.1° after operation and 3.3°±2.3° at follow-up; IO was 2.0°±1.6°, 0.6°±1.8° and 1.4°±1.6° respectively; HO was 0.5°±1.5°, -0.9°±1.8° and -0.1°±1.6°. In DLS group, SO was 3.1°±3.4°, 1.1°±4.3° and 1.4°±3.2°; IO was 1.2°±2.0°, -0.2°±3.1° and 0.4°±2.1°; HO was 0.5°±1.9°, -0.9°±2.9° and -0.5°±2.0°. In post-operation, SO, IO and HO decreased in both groups(P<0.05). At the final follow-up, SO, IO and HO increased(P<0.05) comparing with that after operation in AIS group, while there was no significant differences(P>0.05) in DLS group. Conclusions: SO, IO and HO are reliable coronal pelvic parameters, and the 3 radiographic parameters could be used to evaluate the compensation of pelvis and lower limbs in spinal deformity. The pelvis and lower limbs act as spinal vertebrae or intervertebral discs in accordance with coronal spinal alignment. The region could be considered as a compensatory spinal curve named PL.