Ulnar Neuroma-in-Continuity Following Distal Radius Fracture: A Rare Complication Requiring Reconstruction with Nerve Allograft and Dynamic Tendon Transfer

Abstract

Ulnar nerve injury following distal radius fracture is uncommon and typically presents as transient neuropraxia. We report a case of traumatic ulnar nerve neuroma-in-continuity following open distal radius fracture in a 57-year-old man with associated scapholunate dissociation. Two months after surgical fixation, he developed intrinsic muscle wasting over the left hand and persistent sensory deficits in the ring and little fingers. Nerve conduction study and EMG suggested axonotmesis of the ulnar nerve. Magnetic resonance imaging demonstrated fusiform thickening of ulnar nerve consistent with neuroma-in-continuity. Patient underwent excision of neuroma-in-continuity with nerve allograft reconstruction and dynamic tendon transfer using flexor digitorum superficialis tendon of the middle finger. At 9 months, the patient demonstrated resolution of claw deformity and satisfactory functional recovery. Persistent neurological deficits after distal radius fractures should prompt early investigation and consideration for structural nerve injury.

Distal radius fracture represents one of the most common wrist injuries encountered in clinical practice. Neurological complications are well-recognized sequelae of these fractures, most frequently involving the median nerve. Acute median nerve compression has been documented in approximately 2% to 7% of distal radius fractures.¹ In contrast, ulnar nerve injury following distal radius fracture is less common with rates closer to 1%.² The available literature on ulnar neuropathy is largely confined to isolated case reports and small case series.3, 4, 5 Ulnar neuropathy can manifest in different patterns, ranging from complete motor and sensory injury to pure sensory neuropathy of the dorsal cutaneous branch of the ulnar nerve.⁶

Few reports describe symptomatic ulnar neuroma formation after distal radius fracture. We report a case of traumatic ulnar neuroma-in-continuity following an open distal radius fracture with scapholunate dissociation, treated with neuroma excision, nerve allografting, and dynamic claw deformity correction.

Case Report

A 57-year-old gentleman presented with an open left distal radius fracture with scapholunate dissociation after sustaining a fall on outstretched hand. He sustained a 1 cm wound that was located over the ulnar head. The patient reported generalized numbness over all digits and the palm of his left hand at the initial presentation.

The patient underwent emergency surgery on the same day. The ulnar nerve and artery were noted to be in continuity intraoperatively. Open reduction and internal fixation of left distal radius fracture with volar locking plate and Kirschner wire 1.2 mm (0.047 in) pinning of the scapholunate joint were performed. The wire was removed 2 months later.

Two months after the index surgery, he reported persistent numbness over the left ring and little fingers. There was also shooting pain to the left ring and little fingers with a pain score of 8 out of 10. Examination revealed ulnar clawing of the ring and little fingers. Thumb adduction, finger abduction and adduction in the left hand were weaker when compared to the right. Froment sign was positive. Sensory examination revealed hypoaesthesia of the ulnar half of the left ring finger and anesthesia of the left little finger. The dorsal cutaneous branch of the ulnar nerve was not involved. Tinel sign was positive at 3 cm proximal to the distal volar wrist crease. The patient was able to extend the interphalangeal joints of the left ring and little fingers when the metacarpophalangeal joints were flexed on performing Bouvier test.

Nerve conduction study and EMG suggested axonotmesis of the ulnar nerve at the level of the wrist. Magnetic resonance imaging (MRI) of the left wrist demonstrated focal, fusiform thickening of the ulnar nerve at the level of distal radioulnar joint, consistent with neuroma formation (Fig. 1A, B). The MRI also visualized complete tear of the dorsal fibers of the scapholunate ligament, as well as complete tear of the foveal attachment and sprain of the ulnar styloid attachment of the triangular fibrocartilage complex.

Figure 1.

Axial and sagittal views of MRI, arrows demonstrating focal, fusiform thickening of the ulnar nerve at the level of the distal radioulnar joint.

Three months after the index surgery, the patient’s symptoms persisted and ulnar claw worsened (Fig. 2). He underwent surgical reconstruction consisting of the following: (1) left arthroscopic dorsal scapholunate capsuloligamentous repair; (2) Guyon canal exploration and carpal tunnel release; (3) ulnar nerve neurolysis, excision of neuroma-in-continuity and repair with nerve allograft; and (4) left ring finger and little finger ulnar claw correction with middle finger flexor digitorum superficialis transfer.

Figure 2.

Ulnar claw of left hand.

The ulnar nerve was found encased in dense scar tissue at the level of the distal radioulnar joint, appearing swollen proximal to the scar tissue and atrophic distally (Fig. 3A). Intrafascicular neurolysis was attempted and revealed perineural tears with disrupted fascicles involving the whole nerve (Fig. 3B). The disrupted fascicles were encased within a thick layer of scar tissue that was difficult to separate; hence, both scar tissue and disrupted fascicle ends were resected (Fig. 3C, D). The nerve gap of 3 cm was bridged by processed nerve allograft (Fig. 3E–F), followed by application of a nerve wrap and reinforcement with fibrin glue.

Figure 3.

A Microscopic image of the ulnar nerve encased in dense scar tissue at the level of the distal forearm. The green arrow indicates the proximal end, and white arrow indicates the distal end. B Neurolysis performed. C Resection of unhealthy portion of ulnar neuroma-in-continuity. D Resection of neuroma-in-continuity until healthy fascicular morphology. E Nerve gap of 3 cm after resection, arrows pointing to the stumps of the nerve ends. F Nerve gap bridged by processed nerve allograft.

Dynamic claw correction was performed with two slips of the middle finger flexor digitorum superficialis passed volar to the deep transverse metacarpal ligament, through the lumbrical canal of the ring and little finger and weaved into the extensor hood of the ring and little fingers (Fig. 4A, B).^7,8

Figure 4.

A Dynamic claw correction demonstrating isolation of the ring finger flexor digitorum superficialis into two slips, with the radial slip directed to the ring finger and the ulnar slip to the little finger. B Dynamic claw correction demonstrating transfer of the flexor digitorum superficialis slips to the extensor tendon

Histopathology confirmed neuroma-in-continuity. At 9 months after surgery, there was complete resolution of the ulnar claw (Fig. 5A, B). Wrist and digital range of motion were satisfactory, with the ring and little fingers demonstrating metacarpophalangeal joint flexion up to 90° and full interphalangeal joint extension. Two-point discrimination was 10 mm in the ulnar aspect of the ring finger and >15 mm in the little finger, consistent with ongoing nerve regeneration. Pain score was 3 out of 10. The patient expressed satisfaction with the overall outcome, with marked improvement in pain and resolution of claw deformity and Tinel sign after surgery.

Figure 5.

Postoperative clinical photographs showing resolution of ulnar claw deformity.

Verbal and written informed consent was obtained from the patient for their anonymized information to be published in this article.

Discussion

Ulnar nerve injury following distal radius fracture has been reported less frequently than median neuropathy. In the literature review by Soong et al⁵ from 1922 to 2004, only 30 reported cases were identified over more than eight decades. More contemporary case series suggest that ulnar neuropathy may be under-recognized. Soong et al identified five cases of ulnar nerve injury over a 2-year period at a level 1 trauma center. More recently, Magtoto et al⁴ reported four cases over a 2-year period and conducted a comprehensive literature review spanning 1991 to 2023, identifying 28 patients with ulnar neuropathy associated with distal radius fractures. These reports show that ulnar neuropathy after distal radius fracture is uncommon but recognized. The literature consists mainly of small case series and case reports. The majority of cases were transient neuropraxia with gradual spontaneous recovery.⁴

This case describes a symptomatic ulnar neuroma-in-continuity requiring surgical reconstruction following distal radius fracture. Although there was one patient in the series reported by Magtoto et al who developed a probable neuroma, he declined surgery because of minimal symptoms, and the neuroma was not histologically proven. Our patient presented with persistent symptoms that required definitive surgical management including nerve reconstruction and tendon transfer for secondary deformity. Despite initial exploration, the nerve injury was not identified because of an intact epineurium, underscoring the importance of continued neurovascular monitoring. Persistent or progressive ulnar deficits after distal radius fractures warrant early investigation.

Several mechanisms have been proposed to explain the ulnar neuropathy following distal radius fractures, including traction or contusion neuropraxia because of fracture displacement, direct entrapment within the fracture site, and compression secondary to edema or hematoma.³ High-energy trauma and displaced fracture patterns appear to be commonly associated with ulnar nerve injury.^4,5 In our patient, the open distal radius fracture with associated scapholunate dissociation likely resulted in traction injury to the ulnar nerve, which resulted in axonotmesis and the formation of a neuroma-in-continuity, presenting with secondary claw deformity.

Early identification of suspected ulnar nerve injury requires detailed clinical assessment. Electrophysiological studies, including nerve conduction study and EMG, are valuable for confirming the diagnosis, localizing the lesion and assessing severity.⁴ Imaging modalities, particularly ultrasonography and MRI, can provide additional anatomical information. Ultrasonography offers dynamic evaluation of nerve continuity, displacement, or entrapment, whereas MRI may be useful in complex cases to assess surrounding soft tissue and structural integrity. The MRI finding of a fusiform thickening of the ulnar nerve in our patient supported the diagnosis of neuroma-in-continuity and guided surgical management.

Management strategies for ulnar nerve injury following distal radius fracture remain controversial, particularly in terms of the timing of surgical exploration. There are currently no standardized guidelines for the management of ulnar nerve injury following distal radius fracture. Most reported cases demonstrate gradual spontaneous recovery, regardless of whether surgical intervention was performed. Recommendations range from early decompression within 24–36 hours in cases of suspected acute compression to delayed intervention after several months of observation.^9,10 In the absence of clear evidence of transection or entrapment, a period of observation is commonly advocated. The initial intraoperative finding of nerve in-continuity masked the disrupted fascicles within the ulnar nerve and the injury was not recognized immediately. Close monitoring with early investigation is warranted and useful to consider exploration if symptoms persist or worsen.

In our patient, the 3 cm nerve gap was bridged with nerve allograft. The allograft provided a scaffold for nerve regeneration and avoided donor site morbidity. Dynamic claw correction was performed in the same setting as intrinsic muscle recovery was uncertain. The tendon transfer restored metacarpophalangeal joint flexion and interphalangeal joint extension, enabling earlier rehabilitation. At 9 months after surgery, the claw deformity resolved with good functional improvement.

Consent Statement

Verbal and written informed consent was obtained from the patient for their anonymized information to be published in this article.

Conflicts of Interest

No benefits in any form have been received or will be received related directly to this article.