Upper Extremity Skeletal Muscle Mass Asymmetry Exacerbated by Shoulder Imbalance in Lenke1A Adolescent Idiopathic Scoliosis

Abstract

Limb muscle strength asymmetry affects many physical abilities. The present study (1) quantified limb muscle asymmetry in patients with adolescent idiopathic scoliosis (AIS); (2) compared AIS patients with major thoracolumbar/lumbar (TL/L) or major thoracic (MT) curves; (3) examined correlations between limb muscle asymmetry and radiographic parameters. Patients with AIS with major TL/L curves (Lenke type 5C) and MT curves (Lenke Type 1A) who underwent posterior spinal fusion at our university hospitals were included. Patients with left hand dominance were excluded. Body composition was measured using whole-body dual-energy X-ray absorptiometry and asymmetry of left and right side skeletal muscles were evaluated. Upper extremity skeletal muscles on the dominant side were significantly larger than those on the nondominant side in both Lenke1A and 5C groups. The asymmetry of upper extremity skeletal muscles was significantly greater in the Lenke1A group than in the Lenke5C group. Additionally, the size of the asymmetry did not correlate with the magnitude of the major curve and rotational deformation but did correlate with a right shoulder imbalance in the Lenke1A group. These results suggest that in AIS with a constructive thoracic curve, right shoulder imbalance is an independent risk factor for upper extremity skeletal muscle asymmetry.

Clinical Significance of Pose Estimation Methods Compared to Radiographic Parameters in Adolescent Idiopathic Scoliosis Patients

“…From the radiography, we can also assess shoulder balance and trunk imbalance, which have been considered characteristics of the deformity in idiopathic scoliosis. [2][3][4] Posture changes increase the risk of psychosocial complications (self-image, body image, mental health, and quality of life) 5,6 . However, patients with AIS may also be at increased risk for damage to health because of radiography, increasing the risks for developing leukemia or breast cancer, or a heritable defect higher than the baseline risk.…”