PAPER 177: THE RELATIONSHIP OF TRACTION FORCES, TRACTION TIME AND NERVE CONDUCTION ABNORMALITIES DURING HIP ARTHROSCOPY

Abstract

Purpose: The purpose of this study is to investigate the relationships of traction force, traction time, and hip distraction to the development of nerve conduction abnormalities during hip arthroscopy.

Method: Thirteen patients with hip pathology underwent hip arthroscopy. Traction forces applied to the operative leg were measured using a load-cell force transducer. Distraction of the hip joint was assessed using fluoroscopy. Nerve conduction studies of the tibial nerve was performed measuring the latency of the Hoffmann reflex (Hlat reflex). Measurements of the traction force, distraction of the hip, and nerve conduction studies were performed at routine intervals during the procedure, and compared to pre- and post-op values.

Results: Nerve Conduction Studies- The mean baseline Hlat reflex was 30.4+/−2.2 milliseconds for all patients. Three patients lost the Hlat reflex immediately (t=0), and an additional three patients lost the Hlat reflex during the procedure (t=30, t=30, t=60). The remaining seven patients all had delayed conduction of the Hlat reflex over time. At one-hour post-op, the Hlat reflex was documented in all patients (mean 31.9+/−2.9 ms) and remained significantly different from baseline (p< 0.01). Clinically, one patient in the lost Hlat reflex group had an associated neuropraxia post-operatively. Traction Forces- The mean initial traction force at time of application for all patients was 97+/−28 lbs. The mean initial traction force of the lost Hlat reflex group and retained Hlat reflex group was 104+/−32.6 lbs and 91+/−24.1 lbs, respectively (p=0.44). Hip Distraction- The mean initial hip distraction at time of application of traction for all patients was 8.8+/−2 mm. The mean initial distraction of the lost Hlat reflex group and retained Hlat reflex group was 9.6+/−1.4 mm and 8+/−2.2 mm, respectively (p=0.15).

Conclusion: Traction during hip arthroscopy is associated with significant nerve conduction abnormalities in the immediate post-operative period. Six of thirteen patients had complete loss of the Hlat reflex of the tibial nerve, one of these patients exhibiting clinical neuropraxia. Although length of time in traction may be a factor for the development of nerve conduction abnormalities, a more significant factor may be the change in length over time of the surrounding peripheral nerves.