Intraoperative Neurophysiological Monitoring in Total Hip Arthroplasty for Crowe Types 3 and 4 Hips.

Background: Crowe types 3 and 4 dysplastic hips usually need total hip arthroplasty (THA) with femoral shortening osteotomy (FSO) to facilitate reduction, equalize limb length, and decrease the traction stress in nerves. The frequency of peripheral nerve palsy after primary THA has been reported to range from 0.08% to 3.7%. Apart from direct trauma to the nerve, the excessive extension of the extremity is also reported as a common cause of nerve damage. The current study aimed to evaluate the outcomes of intraoperative neurophysiological monitoring (IONM) in THA for Crowe types 3 and 4 hips. Methods: The data of patients who underwent primary THA with IONM were retrospectively reviewed using our medical records. Patients with Crowe types 3 and 4 dysplastic hips were included in the study. Motor-evoked potentials and somatosensory-evoked potentials were assessed intraoperatively. Preoperative dislocation height and postoperative trochanter minor differences were measured using preoperative and postoperative radiographs. Results: Twenty-three hips of 19 patients (4 bilateral THAs) with a mean age of 45 years participated in the study. Ten hips (43%) were classified as Crowe type 4, whereas 13 hips (57%) were Crowe type 3. The mean preoperative dislocation height was 41.6 mm (range, 15-100 mm). Postoperatively, only 6 patients had a difference between trochanter minor levels with a mean of 8.5 mm (range, 3-17 mm). Three patients underwent a subtrochanteric FSO to achieve reduction. Postoperatively, no patient had any motor and sensory nerve dysfunction. Conclusions: According to the results acquired from this study, no nerve palsy was observed after THA for Crowe types 3 and 4 hips, and subtrochanteric FSO was not performed in all Crowe type 3 hips and 70% of Crowe type 4 hips with the aid of IONM.