Surgical (with external fixation device; series I) and conservative (series II) treatment of experimental unilateral transverse fracture of the body and ramus of ischium was carried out in 35 mongrel dogs. Roentgenometry, pathological, and histological studies showed sciatic nerve injury in both series, a complication of the fracture emerging at the moment of primary lesion. Further damage to the nerve due to its compression in an anatomical narrowings with fibrous degenerative tissues and bone fragments under conditions of conservative therapy, tunnel neuropathy, was paralleled by more pronounced destructive changes persisting for one year after the experiment.