Iatrogenic nerve injury

Patients with iatrogenic injuries represent almost 25% of the patients with peripheral nerve injuries. The sciatic nerve is most commonly affected. This may be reflect to the nerve’s deep location and its limited visibility during surgical procedures in this region. Lesions are more often observed in dogs than in cats. Anatomic differences (greater size, more fatty tissue in dogs) and the variety of pelvic surgical procedures performed in dogs may explain this finding. No breed predilection is observed but medium to large breed dogs are more frequently affected which may reflect a more difficult surgical approach but being overweight was not a consistent risk factor. The sciatic is an important nerve for locomotion and weight-bearing and functional deficit is debilitating. Even with physiotherapy, only some animals will be able to compensate for sciatic nerve damage by flipping the paw and walking on the plantar surface after many months. Injury to less essential nerves, eg, median nerve injury occurring during elbow arthrotomy results in slight lameness that can be confused with the original orthopedic condition. Consequently, such lesions may remain undiagnosed and thus the incidence of iatrogenic peripheral nerve injury may be substantially underestimated.

Inability to adequately visualize the nerve during pelvic surgical procedures is probably the most common cause of iatrogenic sciatic nerve injury and may explain why the site of injury is located proximal to the great trochanter in most patients and why pelvic orthopedic surgery is the primary cause of injury. Excessive manipulation or elongation of the nerve during acetabular- or ilial fracture fragment manipulation will lead to neurapraxia (transient physiologic conduction block of nerve transmission that will typically resolve in 3 - 6 weeks). To prevent this complication the nerve should be cautiously exposed before fracture reduction to allow greater mobility of the nerve during manipulation. If the sciatic nerve is not carefully elevated from the ilium during exposure of the fracture fragments, the nerve may also become entrapped either in the fracture gap itself or within the jaws of the reduction forceps, leading to an irreversible crushing injury. Nerve regeneration, even if only axonotmesis is present, is impaired by endoneurial fibrous tissue, leading to poor functional results. [...]