Trunk rotation and hip joint range of rotation in adolescent girls with idiopathic scoliosis: does the "dinner plate" turn asymmetrically ?

Abstract

Background: In patients with structural idiopathic scoliosis the body asymmetries involve the pelvis and the lower limbs; they are included in many theories debating the pathogenesis of idiopathic scoliosis.

Methods: Hip joint range of motion was studied in 158 adolescent girls, aged 10-18 years (mean 14.2 +/- 2.0) with structural idiopathic scoliosis of 20-83 degrees of Cobb angle (mean 43.0 degrees +/- 14.5 degrees ) and compared to 57 controls, sex and age matched. Hip range of rotation was examined in prone position, the pelvis level controlled with an inclinometer; hip adduction was tested in five different positions.

Results: In girls with structural scoliosis the symmetry of hip rotation was less frequent (p = 0.0047), the difference between left and right hip range of internal rotation was significantly higher (p = 0.0013), and the static rotational offset of the pelvis, calculated from the mid-points of rotation, revealed significantly greater (p = 0.0092) than in healthy controls. The detected asymmetries comprised no limitation of hip range of motion, but a transposition of the sector of motion, mainly towards internal rotation in one hip and external rotation in the opposite hip. The data failed to demonstrate the curve type, the Cobb angle, the angle of trunk rotation or the curve progression factor to be related to the hip joint asymmetrical range of motion.

Conclusion: Numerous asymmetries around the hip were detected, most of them were expressed equally in scoliotics and in controls. Pathogenic implications concern producing a "torsional offset" of muscles patterns of activation around the spine in adolescent girls with structural idiopathic scoliosis during gait.

Figure 1

According to the Nottingham concept, in between the rotation inducing system and the rotation defending system, the mobile thoraco-lumbar vertebrae are susceptible to repeated rotation and tilt.

Figure 2

Asymmetrical pelvis, including both the position and the shape, is a common finding in children with idiopathic scoliosis (A). Apparent symmetry of hip internal rotation may be due to a non level pelvis (B). Scoliometer is a simple tool to enhance the precision of measures (C).

Figure 3

Technique of the measurement of the hip joint range of rotation. Patient in prone position, hips in neutral position, knees in 90° flexion. In spontaneous position there is an obliquity of the pelvis, masking asymmetry of rotation, and detected with the scoliometer placed over the posterior superior iliac spines (A). Asymmetry of the range of internal rotation: left hip = 25°, right hip = 55° (B). Asymmetry of the range of external rotation: left hip = 30° (C), right hip = 5° (D). The sum of rotation range is 55° for the left and 60° for the right hip. Transposition of the sector of rotation towards internal rotation may be diagnosed within the right hip, instead of claiming the limitation of hip motion. The mid-point of rotation is 2.5° for the left and 25° for the right hip. Therefore there is a static rotational offset of the pelvis of 22.5°, directed to the right side.

Figure 4

Range of hip adduction is precisely assessed in prone position, "at the end of the table", controlling the pelvis with one hand and the lower limb with the other hand.