Patterns of coronal and sagittal deformities in adolescent idiopathic scoliosis

Abstract

Background: Thoracic scoliosis has been shown to be associated with hypokyphosis in adolescent idiopathic scoliosis (AIS). However, the relationship of sagittal spino-pelvic parameters with different coronal curve patterns and their influence on patient-perceived quality of life is unknown. This study aims to determine the association between coronal and sagittal malalignment in patients with AIS and to determine their effects on SRS-22r scores.

Methods: A cross-sectional study was conducted on 1054 consecutive patients with AIS. The coronal Cobb angle, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), PI-LL mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) were measured on standing radiographs. The coronal Cobb angle (mild: 10-20°; moderate: > 20-40°; severe: > 40°) and PI (low: < 35°; average: 35-50°; high: > 50°) were divided into 3 sub-groups for comparison. Relationship between coronal curve magnitudes and sagittal parameters was studied as was their association with SRS-22r scores.

Results: Low PI had smaller SS (30.1 ± 8.3° vs 44.8 ± 7.7°; p < 0.001), PT (- 0.3 ± 8.1° vs 14.4 ± 7.5°; p < 0.001), and LL (42.0 ± 13.2° vs 55.1 ± 10.6°; p < 0.001), negative PI-LL mismatch (- 12.1 ± 13.1° vs 4.1 ± 10.5°; p < 0.001) as compared to large PI. There were no significant relationships with PI and TK (p = 0.905) or curve magnitude (p = 0.431). No differences in sagittal parameters were observed for mild, moderate or severe coronal Cobb angles. SRS-22r scores only correlated with coronal Cobb angle and larger Cobb angles were negatively correlated with the function, appearance and pain domains.

Conclusions: The sagittal profile for AIS is associated with the pelvic parameters especially PI but not with the coronal curve pattern. All patients have a similar TK regardless of coronal curve type. However, it appears that the coronal deformity is a greater influence on quality of life outcomes especially those > 40°.

Keywords: Adolescent idiopathic scoliosis; Lumbar lordosis; Pelvic incidence; Pelvic tilt; Sacral slope; Thoracic kyphosis.

Fig. 1

Flowchart of included patients for analysis

Fig. 2

Examples of two patients with similar lumbar coronal deformity but markedly different sagittal alignment. For the first patient with (a) lumbar curve of 24.2° at T12-L4, (b) sagittal parameters included lumbar lordosis of 50.8°, reciprocal thoracic kyphosis of 39.4°, pelvic incidence of 60.2°, pelvic tilt of 25.6°, sacral slope of 34.6°, Pelvic incidence – lumbar lordosis of 9.4°. Despite a similar (c) coronal curve magnitude (23.6° at T12-L4), there was a (d) greater mismatch between pelvic and spinal parameters (− 14.2°) with hypokyphotic thoracic spine (15.4°). Other sagittal parameters included pelvic incidence of 32.9°, pelvic tilt of − 2.8°, sacral slope of 35.7°, and lumbar lordosis of 47.0°

Fig. 3

Examples of two patients with similar thoracic coronal deformity but markedly different sagittal alignment. For the first patient with (a) thoracic curve of 19.5° at T5-T10, (b) sagittal parameters included thoracic kyphosis of 41.9°, lumbar lordosis of 66.2°, pelvic incidence of 42.3°, pelvic tilt of 14.6°, sacral slope of 37.5°, Pelvic incidence – lumbar lordosis of − 14.1°. Despite a similar (c) coronal curve magnitude (19.2° at T5-T10), there was a (d) greater negative mismatch between pelvic and spinal parameters (− 26.1°) with less thoracic kyphosis (30.2°). Other sagittal parameters included pelvic incidence of 42.9°, pelvic tilt of − 4.1°, sacral slope of 49.3°, and lumbar lordosis of 71.4°