Abstract
During revision hip surgery, damage to the sciatic nerve is due most commonly to excessive tension. While the nerve is strong in tension and is able to tolerate this remarkably, it is sensitive to lateral compression against angled structures and it is likely that tension causes injury by such pressure.
In a personal series of 441 revision hip procedures, sciatic nerve injury occurred in 9 recognised cases:
2 were complete with no useful recovery
2 were severe with some incomplete recovery
3 were predominantly lateral popliteal with incomplete recovery
2 were transient and clinically fully recovered.
In only two of these were the cause and the time of injury identifiable. In these cases, pain was not a serious feature but in eight separate medico-legal cases, burning pain of variable distribution has been the most serious complaint. Medical negligence has been successfully sustained on the grounds of res ipsa locitur. Regrettably, patients must be given informed consent with yet another potential hazard being listed.
We have found that in normal individuals the range of straight leg raising varies between 30 and 90 degrees. Towards the limit of this range the nerve is tight and a crude cadaveric test indicated a tension force of 40 newtons! In an athlete this may be extreme and yet the nerve does not complain. Excluding direct compression (e.g. by a retractor) and thermal injury, we suggest that the tension developed during unguarded straight leg raising while the patient is still anaesthetised is a serious risk factor. After even conservative lengthening, the tension rises alarmingly during such action. It is possible that pre-existing lumbar degenerative disk disease can contribute to the hazard and be source of pain.
These abstracts were prepared by Mr Peter Kay. Correspondence should be addressed to him at The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
