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The Impact of Early Active Motion Protocol on Digital Nerve Repairs in a Cadaver Model
Jordan E Nus, BS
1, Timothy J Trobridge, BS
1, Anita Sayar, BS
1, Margaret Szymanski, BS
2, Khusboo Desai, MD
1; Erin L Weber, MD, PhD
2(1)Indiana University School of Medicine, Indianapolis, IN, (2)Indiana University, Indianapolis, IN
IntroductionIn finger injuries, it is common for both flexor tendons and digital nerves to be lacerated. However, postoperative rehabilitation protocols for these injuries differ significantly. Flexor tendon repairs benefit from early active mobilization while traditional digital nerve repair protocols recommend immobilization for three weeks to prevent disruption of the repair. This presents a clinical challenge when both structures are injured concurrently. In this cadaver study, we investigated the impact of an early active motion protocol on digital nerve repairs.
Materials and MethodsThree cadaveric hands, amputated mid-forearm, were used to evaluate digital nerve repair integrity during progressive digit mobilization. FDP tendons were lacerated and repaired and skin closed to mimic operative scenarios. Digital nerve repairs were performed with two 8-0 nylon sutures at three levels: middle phalanx (n=8), PIP joint (n=8), and proximal phalanx (n=7), with 3 mm nerve excision followed by 1 cm excision. Hands were placed in a dorsal blocking splint with MPs at 50° flexion. To simulate an early active motion protocol, each digit underwent passive DIP and PIP flexion (200 repetitions each), passive full-fist flexion (200 repetitions), and active flexion to 25%, 50%, and 75% of a composite fist (180 repetitions each). Active flexion and extension were simulated by pulling suture attached to the respective tendons. The splint was then removed for 100 cycles each of full passive and active flexion-extension. Nerve repairs were inspected every 50-60 repetitions for evidence of gapping, thinning, or rupture.
ResultsFor 3 mm nerve excisions, no complete ruptures occurred. Minor gapping of 1-2 mm was observed in three repairs (13%) following 50 repetitions of full passive flexion/extension. In contrast, 1 cm nerve excisions demonstrated higher rates of disruption. Nerve thinning, gapping (0.5-2 mm), and rupture occurred across all hands during both passive and active motion, particularly during early repetitions of passive DIP/PIP movement and full active flexion-extension. A total of 10 ruptures (42%) were observed, with seven occurring before splint removal. The middle and ring fingers ruptured most often.
ConclusionsDigital nerve repairs under minimal tension (3 mm excision) withstand an early active motion protocol without disruption. 1 cm excisions are significantly more vulnerable to rupture during early cycles of digit motion. Additional studies with larger sample sizes are needed to validate these findings. Future work will apply this same motion protocol to nerve graft repairs.
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