Assessment of Sensitivity and Specificity of Common Sensory Tests in Diagnosing Digital Nerve Lacerations

Digital nerve lacerations are common. Current methods employed to differentiate intact and transected digital nerves lack diagnostic accuracy. This may result in patients with intact nerves undergoing unnecessary surgery. The objective of the study was to determine the best diagnostic method for detecting true sensory nerve transections and to delineate the sensitivities and specificities of common sensory tests.

Patients aged 18-65 years with suspected complete digital nerve lacerations were recruited. Sensory testing including static two-point discrimination (s2PD), Semmes-Weinstein Monofilaments, and Quantitative Sensory Testing were used prior to surgical exposure to evaluate different categories of sensory nerve fibers. Likelihood ratios, sensitivity, and specificity of each test were compared to direct visualization intraoperatively. Receiver operating characteristic (ROC) curves were used to determine the area under the curve (AUC) for each test.

Of the 60 patients recruited, 41 (68%) had complete digital nerve transections while 19 (32%) had intact nerves. Heat pain threshold testing showed the greatest AUC at 0.812 ± 0.067 with a sensitivity of 90% and specificity of 65% at a cutoff of 22.1 just noticeable difference (JND). However, combining s2PD (7 mm, 100% sensitivity, 32% specificity) and warm detection threshold (WDT) (25 JND, 100% sensitivity, 37% specificity) in a two-step algorithm achieved 100% sensitivity and increased the specificity to 58%.

Implementing a two-step diagnostic algorithm combining s2PD and WDT can effectively diagnose complete digital nerve laceration with high sensitivity and improved specificity. These findings underscore the utility of both tests in accurately identifying complete digital nerve lacerations.