Clin Orthop Surg.  2017 Mar;9(1):57-62. 10.4055/cios.2017.9.1.57.

Association between Sacral Slanting and Adjacent Structures in Patients with Adolescent Idiopathic Scoliosis

• Cho JH
• Lee CS
• Joo YS
• Park J
• Hwang CJ
• Lee DH

• KMID: 2412304
• DOI: http://doi.org/10.4055/cios.2017.9.1.57

Abstract

BACKGROUND
Sacral slanting is a frequent unique phenomenon in patients with adolescent idiopathic scoliosis (AIS) and may be important for selecting the distal fusion level. However, the reason of the phenomenon remains unknown. The purpose of this study was to determine the association between sacral slanting and adjacent structures in patients with AIS.
METHODS
A total of 303 AIS patients who underwent both whole spine standing anteroposterior (AP) and whole leg standing AP radiography were included. The degree of sacral slanting, pelvic obliquity, lumbar curve angles (L1-L4), and L4 tilt were assessed on whole spine standing AP radiographs. Whole leg standing AP radiographs were used to assess the degree of leg length discrepancy (LLD). Demographic data and radiological parameters were analyzed descriptively. Pearson correlation analysis and partial correlation analysis of the parameters were performed. A p-value of less than 0.05 was considered statistically significant.
RESULTS
The proportion of patients with ≥ 5° of sacral slanting among those with < 3° of pelvic obliquity was 8.9% (27/303). Thirty-two patients (10.6%, 32/303) showed more than 10 mm of LLD. Sacral slanting was positively correlated with pelvic obliquity and lumbar curve (r = 0.445 and r = 0.325, respectively). Pelvic obliquity was also correlated with LLD and L4 tilt (r = 0.123 and r = 0.311, respectively). However, partial correlation analysis showed that LLD was not directly correlated with sacral slanting (r = −0.034).
CONCLUSIONS
Sacral slanting can be thought to be a compensatory mechanism for large lumbar curves, which is accompanied by pelvic obliquity. In contrast, a congenitally slanted upper sacrum may contribute to scoliosis in some cases. LLD was not directly correlated with sacral slanting.

Keyword

Scoliosis; Adolescent; Sacrum; Pelvis; Leg length inequality

MeSH Terms

Adolescent
Biomechanical Phenomena
Child
Female
Humans
Leg Length Inequality/etiology
Lumbar Vertebrae/*diagnostic imaging
Lumbosacral Region/*diagnostic imaging
Male
Pelvic Bones/*diagnostic imaging
Radiography
Sacrum/*diagnostic imaging
Scoliosis/complications/*diagnostic imaging

Figure

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  Fig. 1 Measurements of radiological parameters. a: degree of sacral slanting, b: degree of pelvic obliquity, c: degree of L4 tilt, d: degree of lumbar curve.

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  Fig. 2 Distribution of curve types based on Lenke classification.

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  Fig. 3 Distribution of leg length discrepancy.

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  Fig. 4 Illustration of the relationship between sacral slanting and other radiological parameters. Plausible cause and effect relationships are indicated with white arrows. LLD: leg length discrepancy.

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