Cobb, Tyson K.

The relative risk of nonunion in smokers versus nonsmokers after ankle arthrodesis was determined in a case control study. Twenty-two patients were matched to 22 controls by age, sex, surgeon, surgical technique, and preoperative diagnosis. Information on duration, amount, and past history of smoking was obtained for these 44 patients. Ten of the patients were actively smoking at the time of surgery compared with four of the controls. Six of the patients had no history of smoking and six had stopped smoking before surgery. Eleven of the controls had no history of cigarette smoking and 7 had stopped smoking before surgery. The relative risk of nonunion was increased 3.75 times for active smokers. When patients did not have any known risk factors for nonunion, the risk of nonunion for smokers was 16 times the risk of nonunion for nonsmokers

Carpal tunnel syndrome is one of the many so-called cumulative trauma disorders thought by some to be related to the performance of repetitive tasks in the work-place. The cause of this disorder is unknown. We have observed lumbrical muscle incursion into the carpal tunnel during finger flexion. This study was conducted to determine the amount of this incursion in normal wrists. Five cadaver upper limbs were analyzed radiographically with radiopaque markers on the flexor retinaculum and the lumbrical muscle origins in four finger positions: full extension, 50% flexion, 75% flexion, and 100% finger flexion. The lumbrical muscle origins were an average of 7.8 mm distal to the carpal tunnel in full finger extension. They moved an average of 14 mm into the carpal tunnel with 50% finger flexion, 25.5 mm with 75% flexion, and 30 mm with 100% flexion. Abnormal lumbrical muscles have been cited as a possible cause of carpal tunnel syndrome. These findings suggest that lumbrical muscle incursion during finger flexion is a normal occurrence and is a possible cause of work-related carpal tunnel syndrome.

Endoscopic carpal tunnel release has been shown in recent studies to result in a significant number of incomplete releases of the distal aspect of the flexor retinaculum. The significance of this complication is unknown. To address this question, we measured the amount of carpal arch widening after incomplete and complete release. The mean amount of change in carpal arch width in five cadaveric hands after partial release (all but the distal 4 mm) was 0.74 mm, which was statistically significant. The mean additional change after release of the remaining 4 mm of the flexor retinaculum was 0.12 mm, which was not significant. Incomplete release of the distal 4 mm of the distal aspect of the flexor retinaculum allows carpal arch widening that is no different from that of complete sectioning of the flexor retinaculum in the cadaver limb.

The boundaries of Guyon’s canal have recently been redefined by a series of anatomical dissections. These showed that the confines of this space do not extend from the pisiform to the hook of the hamate, as currently accepted. The fascial roof extends radial to the hook of the hamate, which allows the ulnar neurovascular bundle to course radial to the hamate hook. The position of the ulnar nerve and artery is of particular significance for endoscopic carpal tunnel release. Most endoscopic devices are designed to divide the flexor retinaculum just to the radial aspect of the hamate hook. Utilizing cross-sectional analysis of nine cadaver specimens, we found the ulnar artery to course radial to the hamate hook in five and palmar to it in four. Therefore, the ulnar artery may be at greater risk of injury during endoscopic procedures than previously recognized.

Abstract A modified approach to endoscopic carpal tunnel release has been developed and tested in 60 cadaveric specimens by three surgeons using the Agee endoscopic carpal tunnel release system. The modified approach, which includes specific localization of the hook of the hamate, flexor retinaculum, and the superficial palmar arch utilizing topographical landmarks, avoids entry into Guyon's canal and injury to the ulnar artery and nerve, median nerve, and common digital nerves. Use of the anatomic approach resulted in significantly superior results. There were fewer incomplete releases, and fewer surgical passes were required, for the inexperienced surgeons. When these anatomic considerations were not included, the learning curve was much steeper. For surgeons planning endoscopie surgical release of the transverse carpal ligament, the described topographical approach improves the technical competence with the procedure and reduces the number of complications and learning curve associated with new procedures. We recommend the use of topographical landmarks and other anatomic considerations during endoscopic carpal tunnel release.