Investigating the diagnostic accuracy of physical examination in digital nerve injury: a study within a trial

Digital nerve injuries are the most common peripheral nerve injuries, usually diagnosed through physical examination and confirmed by surgical exploration. Exploration, while important for informing management, carries risk and associated healthcare costs. The diagnostic accuracy of physical examination in identifying complete nerve lacerations requiring repair remains uncertain. This study within a trial (SWAT) aimed to determine the positive predictive value (PPV) of specialist physical examination in identifying complete digital nerve lacerations requiring repair.

This prospective SWAT was embedded within the NEON (Digital Nerve, Suture or Not) randomized controlled trial (ISRCTN16211574). Adult patients presenting with suspected complete digital nerve injury in flexor zone 2 across nine UK NHS hospitals (September 2020 to March 2024) were included. Physical examination was performed by hand surgery specialists, with surgical exploration as the reference standard. The primary outcome was the positive predictive value (PPV) of physical examination for complete laceration requiring repair.

Of 593 referred patients, 242 underwent surgical exploration. Complete laceration was confirmed in 137 (true positives), while 105 had partial or no visible lacerations (false positives), yielding a PPV of 57%.

Specialist physical examination was unable to reliably predict complete digital nerve injury, resulting in a high false positive rate, with 43% of explored patients not requiring repair. Despite this limitation, surgical exploration remains pivotal, as no alternative bedside test currently provides sufficient accuracy. These findings highlight the urgent need for improved point-of-care diagnostic modalities to support surgical decision making and informed patient consent.

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