Neuromuscular effects of two types of fracture treatment

Immobilisation causes denervation-like changes in the motor endplates, decr eases the content of IGF-I, and increases the number of IGF-I receptors in the spinal cord. In the rat we investigated whether similar changes occur a fter a fracture of the midshaft of the femur which had been treated by intr amedullary fixation with adequate or undersized pins. A more pronounced reduction in muscle wet weight was seen after fixation by undersized pins as well as decreased ash density of the ipsilateral tibia which did not completely return to normal within the 12-week experimental p eriod. The nicotinic cholinergic receptors in the motor endplates of tibial is anterior were increased (p < 0.01) and there was a significant increase (p < 0.02) in IGF-I receptors in the lumbar spinal cord ipsilateral to the fracture after treatment by undersized nails. These changes may be associat ed with the impaired proprioception, co-ordination and motor activity which are sometimes seen after fractures.