ab21501

Are adolescent idiopathic scoliosis and ankylosing spondylitis counter-opposing conditions ? A hypothesis on bio-mechanical contributions predisposing to these spinal disorders

A.T. Masi¹, J.L. Dorsch², J. Cholewicki³

¹Department of Medicine, ²Library of the Health Sciences, University of Illinois College of Medicine at Peoria (UICOMP), Peoria, Illinois; ³Biomechanics Research Laboratory, Department of Orthopaedics & Rehabilitation, Yale University School of Medicine, New Haven, Connecticut, USA.

ABSTRACT
Human spinal biomechanics are profoundly complex and not well understood, especially in terms of the dynamic spine function. Translation of biomechanics to disease is difficult, particularly since cause must be separated from effect. Primary dynamics predisposing to the onset of chronic spinal disorders, e.g., adolescent idiopathic scoliosis (AIS) or ankylosing spondylitis (AS), must clearly be differentiated from secondary alterations.
This commentary addresses primary biomechanics that may predispose to these idiopathic diseases. A novel hypothesis is proposed, based upon inferences regarding their contrasting muscular dynamics. The hypothesis postulates opposing inherent muscle tonicity in AIS versus AS. Converse degrees of spinal stability may predispose to the respective curvature deformities of AIS and the enthesopathy lesions of AS. One condition is suspected to counter-oppose the other, within a polymorphic spectrum of spinal stability.

Key words
Adolescent idiopathic scoliosis, ankylosing spondylitis, co-occurrence, counter-oppose, biomechanics, muscle properties, muscle tone, spinal stability, spinal stiffness.

This study was supported in part by the Department of Medicine, UICOMP, and
by a gift from the MTM Foundation.
Dr. Cholewicki is supported by a research grant from the National Institute of
Arthritis and Musculoskeletal and Skin Disease (5R01 AR 46844).
Please address correspondence and reprint requests to: Dr. Alfonse T. Masi, MD, DR.P.H., Department of Medicine, University of Illinois College of Medicine at Peoria (UICOMP), One Illini Drive, Box 1649, Peoria, Illinois 61656, USA.