Axial traction with use of a fracture-style table with a perineal post has been utilized for many years in orthopaedic surgery for various procedures and has been associated with a relatively low complication rate. Traction has been applied in both the lateral and the supine position, and with a well-padded or minimally padded post. In general, the traction is applied grossly by the pull of the surgeon on the leg and then refined by adjusting the crank on the table. Factors that could contribute to complications associated with traction-table use are patient characteristics (nerve anatomy and body habitus), patient orientation, type of post, force of traction (initial or cumulative), and traction time.
The rates of complications reported during hip arthroscopy range from 0% to 27%1-5. In the majority of the papers reporting nerve injuries during hip arthroscopy, the range has been 2% to 10%, with the sciatic nerve and the pudendal nerve being the most commonly involved. Historically, authors have suggested limiting traction time to less than two hours in order to minimize the nerve injury rate2. This line of thinking implies that the mechanism of injury is a time-dependent ischemic event similar to the use of a tourniquet. In the tourniquet literature, the recommendation is to limit tourniquet time to less than two hours6. However, if the injury is actually occurring because the traction force is causing an axial nerve traction injury, as suggested in the study by Telleria et al., then ischemia and time are not the culprits.
This study is a prospective case series of hip arthroscopy cases done with the patient in the lateral decubitus position with monitoring of transcranial motor (tcMEP) and/or somatosensory (SSEP) evoked potentials in the posterior tibial and common peroneal nerves to measure sciatic nerve changes during traction. The authors found that 58% (thirty-five) of the patients had intraoperative nerve dysfunction and 7% (four) had a clinical nerve injury. Significant increases in the odds of a nerve event were correlated only with maximum traction weight and not traction time. The mean traction weight was 38.1 kg in the group with nerve dysfunction and 32.9 kg in the group without nerve dysfunction. The odds of a nerve event increased 4% with every 0.45-kg increase in the traction amount.
I know of no other study in the literature in which the authors looked objectively at nerve injury during hip arthroscopy. Nerve injury is one of the commonly reported complications of hip arthroscopy; therefore, Telleria et al. aptly caution hip arthroscopists to be mindful of the traction force applied, and perhaps this force should be monitored with a tensiometer as previous authors have suggested2.
However, there are limitations to the study, which the authors point out. The study included only patients who were operated on in the lateral position and, as the authors note, sciatic nerve injury has been almost exclusively reported during hip arthroscopy done with the patient in the lateral position. Hip arthroscopy done with the patient supine has been associated with pudendal nerve injury instead of sciatic nerve injury. In addition, Telleria et al. reported no information on the end result of the four patients with clinical sciatic nerve injury. With hip arthroscopy in the supine position, the majority of pudendal nerve injuries resolve between two and twelve weeks after injury.
In a study of 1054 hip arthroscopy procedures done with the patient in the lateral position, Clarke et al. reported only three cases of sciatic nerve injury, all of which were transient1. In a series of 530 hip arthroscopy procedures (519 done with the patient in the lateral position), Sampson reported ten peroneal, four pudendal, and four sciatic nerve injuries2. All of the neurapraxias resolved, and the author concluded that “too much force for too long causes neuropraxias [sic] from stretching of the nerves or compression injuries.”
The current study suggests that Sampson’s report is half correct, and that the duration of traction is not significant. However, it seems logical that excessively long traction time would cause compression-type injuries and/or ischemic “tourniquet like6” events to the nerves in the perineum. This would place the pudendal nerve, but not necessarily the sciatic nerve, at risk.
One possible conclusion is that, since lateral-position hip arthroscopy seems to be more highly correlated with sciatic nerve injury, total traction weight should be carefully monitored when patients are in the lateral position. Caution should be exercised when trying to apply the findings of the current study to hip arthroscopy with the patient in the supine position since sciatic nerve injury is much less common in that position. In addition, hip arthroscopy with the patient in the supine position is associated with a higher incidence of pudendal nerve injury, which is more likely to be a compression-type injury. Therefore, careful monitoring of total traction time is likely important in this setting, an issue that is not addressed in the current study.