HISTOLOGY AND ULTRASTRUCTURE OF ARTERIES, VEINS, AND PERIPHERAL-NERVES DURING LIMB LENGTHENING

The effects of lengthening of the metacarpal bone on peripheral nerves and blood vessels were studied in 8 calves. Specimens for light and e lectron microscopy were obtained from the palmar neurovascular bundle at 1 cm (8% of the initial length), 2.5 cm (20% of the initial length) , and 4 cm (33% of the initial length) of metacarpal lengthening. In 2 calves, specimens were studied 2 months after the end of the lengthen ing procedure. At 8% of lengthening, myelinated fibers of the palmar n erve showed moderate degenerative changes in the myelin sheath. This b ecame severe at 20% and 33% of lengthening, and affected the axoplasm as well. At 20% of lengthening the palmar vein started to show fibrous metaplasia of the smooth muscle tissue of the tunica media. This beca me much thinner than normal. The palmar artery showed moderate alterat ions of the inner part of the tunica media and the intima. The palmar nerve and blood vessels recovered their normal structure almost comple tely 2 months after the end of the lengthening procedure. The morpholo gic alterations of peripheral nerves and vessels may constitute the pa thophysiologic basis of the nervous and circulatory disturbance observ ed in clinical practice.