Bent spine syndrome: computed tomographic study and isokinetic evaluation

Primary acquired lumbar kyphosis of the adult, or bent spine syndrome, is probably secondary to late-onset muscle dystrophy preferentially involving the paravertebral muscles. In order to better define the extent of this myopathy, we compared spinal computerized tomography scans and muscle force, power, and fatigability, assessed by isokinetic tests, of the spinal erector and pelvic and shoulder girdle muscles in 23 patients with primary acquired lumbar kyphosis (20 women and 3 men, mean age 72.8 years) and 15 matched control subjects. Patients had decreased spinal and shoulder muscle density. Force, power, and work done were reduced in their paravertebral muscles, whereas in the scapular and gluteus medius muscles only work done after a series of 20 rapid movements showed a decrease. Primary acquired lumbar kyphosis in the adult may be considered as a late-onset girdle myopathy with subclinical involvement of the muscles of the pelvic and shoulder girdles.