The bent spine syndrome: myopathy + biomechanics = symptoms

Abstract

Background context The bent spine syndrome, which mimics spinal stenosis, is thought to be a focal paraspinal myopathy, but because paraspinal fatigue with ambulation is not a feature of more severe myopathies, the cause of symptoms is not clear. Purpose To evaluate electromyographic and biomechanical aspects of the bent spine syndrome. Study design/setting University spine clinic. Methods A patient with severe disability from the bent spine syndrome was compared with a fortuitously discovered asymptomatic research subject with the syndrome, in terms of physical examination, magnetic resonance imaging, and electrodiagnostic testing. Results Both subjects had fatty paraspinal replacement on magnetic resonance imaging and electromyography. More detailed electromyography of the patient showed abnormalities medially and caudally, but changes including apparent myopathic motor units up to the high thoracic region. The research subject had no hip flexion contracture, whereas the patient had severe contracture. Correction of contracture increased ambulation from 20 to 300 meters. Conclusions Bent spine syndrome is likely a paraspinal myopathy, but symptoms do not occur unless there is also a hip flexion contracture.