Significance of incomplete release of the distal portion of the flexor retinaculum. Implications for endoscopic carpal tunnel surgery.

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.