Relocation Nerve Grafting: A Technique for Management of Symptomatic Digital Neuromas

Abstract

Digital neuromas are a common problem following amputation, often severely impairing hand function. Surgical treatment of terminal digital nerve neuroma is challenging because of the lack of surrounding soft tissue in the hand. To help tackle this problem, we describe a novel technique, “relocation nerve grafting,” to relocate the nerve ends into the interosseous muscles at the midcarpal level.

Introduction

Following nerve injury, axons regenerate from the site of injury along the endoneurial tubes toward the distal target. 1 2 3 A neuroma may develop when the perineurium is injured and fascicular growth occurs outside the epineurium or if there is no distal nerve end available. 1 3 4 This results in disorganized regeneration, which may lead to a painful mass composed of axons and scar. 1 Terminal neuromas develop after amputation while neuromas-in-continuity can develop following nerve laceration, compression/crush injury, traction injury, or poorly performed neurorrhaphy. 1 3 5 6 Symptoms include pain in a defined anatomic nerve distribution, positive Tinel’s sign, cold intolerance, and numbness. 7 8

Whereas neuromas-in-continuity may be treated with excision and nerve repair or reconstruction (based on the availability of the distal nerve stump), terminal neuromas are treated by excision with consideration of multiple surgical techniques for the nerve stump. 5 9 10 11 12 Surgical techniques addressing this include relocation into the muscle or bone, nerve cap, centro-central neurorrhaphy, targeted muscle reinnervation (TMR), or regenerative peripheral nerve interface (RPNI). 9 12 13 14 15 16 17 18

In the setting of digital amputation, the development of a terminal neuroma is inevitable and requires surgery in 6.6% of cases. 19 Surgical treatment is challenging because of the limited soft tissue near the distal end of the nerve, in addition to the short terminal nerve length. We propose a technique to treat terminal digital nerve neuromas by relocation nerve grafting (RNG), a technique in which the terminal nerve stump is coapted to a nerve graft and directed proximally toward a deeper, less painful anatomic area.

Clinical Case

A 41-year-old man who sustained a traumatic multidigit amputation of his nondominant hand presented with pain over the index finger metacarpal stump. Six months prior, the patient underwent revision amputations of his thumb and middle finger at the proximal phalangeal level ( Fig. 1 ) and the index finger at the metacarpal neck. The patient had incapacitating pain and a positive Tinel’s sign overlying the remaining second metacarpal stump. Infiltration of bupivacaine at the Tinel’s sign reduced his Visual Analog Score pain from 9 to 2, and he was diagnosed with symptomatic neuroma. Surgical intervention with neuroma excision and RNG was planned.

Fig. 1.

Anteroposterior radiographs of the hand status post revision amputation.

Intraoperatively, neuromas of the radial and ulnar digital nerve stumps of the index finger were visualized ( Fig. 2 ). The neuromas were excised, and the digital nerves were dissected proximally. Proximal dissection of the ulnar digital nerve was limited by the common digital nerve bifurcation, resulting in insufficient length to translate the end proximally into the intrinsic musculature. The radial digital nerve was also dissected proximally. A 3 × 70-mm nerve allograft (Axogen, Inc., Alachua, Florida, United States) was divided into two 35-mm segments, and end-to-end microsurgical neurorrhaphies of the digital nerves to the allografts were performed ( Fig. 3 ). The distal end of each allograft was then tunneled dorsally into the interosseous muscles at the mid-metacarpal level, away from the palmar surface of the hand ( Fig. 4 ).

Fig. 2.

Intraoperative exposure of terminal neuroma of the radial and ulnar digital nerve of the index finger.

Fig. 3.

End-to-end microsurgical neurorrhaphies of the terminal radial and ulnar nerve with nerve allograft.

Fig. 4.

Tunneling of nerve allografts dorsally into the interossei muscles at the mid-metacarpal level.

At 6 months postoperatively, the patient had complete resolution of pain in his first webspace. He was able to return to work, although he had some discomfort of the middle finger stump.

There are technical considerations for RNG. Proximal dissection of the involved nerves is critical for tension-free relocation of the nerve graft. Additionally, the relocated graft end must be within an area of adequate muscle bulk. When using allograft, appropriate sizing to the correct nerve diameter is important. If using autograft, the risk of donor site morbidity (neuroma, infection) and risk-benefit analysis should be discussed with the patient.

Discussion

Several techniques have been described for the management of terminal neuromas and can be divided into active and passive interventions. 20 Passive techniques following neuroma excision include relocation of the distal end (muscle, bone, or vein), traction neurectomy, centro-central neurorrhaphy, and nerve capping. Active management strategies include hollow-tube, allograft, or autograft reconstruction, “end-to-side” neurorrhaphy, targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI). However, none of the aforementioned techniques are perfectly effective in preventing recurrence of symptoms, particularly in more distal injuries in the hand. 20

In the setting of digital ray amputations, RNG may be preferable to TMR and RPNI because of the limited soft tissue coverage in the hand. Relocation of the nerve end to a deeper anatomical location prevents both the frequency and magnitude of mechanical stimulation. Additionally, it may have the additional advantage of increasing the distance from the effects of cutaneous nerve growth factor (NGF), which may stimulate neuroma formation. 21

Ultimately, the mechanisms surrounding symptomatic neuroma formation remain unclear. Stump neuromas develop because of the location and the lack of a distal target. In the case of a stump neuroma within the hand or foot, NGF may play a role in stimulating neuroma development because of a relative high concentration near the skin. 21 RNG may be successful in addressing stump neuromas as it provides a distal target that stimulates nerve growth away from NGF.

The dissipation of axonal regeneration into a long decellularized nerve graft may reduce symptomatic neuroma formation. In addition, if the distal nerve allograft is placed into a tissue with low NGF expression, such as muscle, this may also decrease neuroma formation. 22

RNG is a novel technique providing durable resolution in symptoms that should be considered for surgical management of symptomatic terminal digital neuromas. Techniques such as TMR and RPNI have been shown to be effective for more proximal injuries; however, the scarcity of soft tissue in the hand may make RNG more suitable in preventing pain recurrence. RNG may be successful via multiple mechanisms: providing a neural architecture for growth cone progression, allowing for placement of the terminal nerve end (graft) into adequate soft tissue bulk, and dissipating axonal signaling.

Authors’ Contributions

Data assembly: B.B.F., E.W., J.L., K.R.E. Initial draft: B.B.F., E.W., J.L., K.R.E. Final approval of manuscript: B.B.F., E.W., J.L., K.R.E.

Funding Statement

Funding None.