Journal of Spine & NeurosurgeryISSN: 2325-9701

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Short Communication, J Spine Neurosurg Vol: 5 Issue: 6

Ulnar Nerve Palsy with Dislocation of the Nerve around the Ulna Following a Fracture of the Distal Radius

de Ruiter GCW1* and den Hollander PHC2
1Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands
2Department of Orthopaedic Surgery, Medical Center Haaglanden, The Hague, The Netherlands
Corresponding author : Godard C W de Ruiter
Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands
Tel: 0031703302000
Fax: 0031703574356
E-mail: [email protected]
Received: March 10, 2016 Accepted: August 09, 2016 Published: August 17, 2016
Citation: de Ruiter GCW, den Hollander PHC (2016) Ulnar Nerve Palsy with Dislocation of the Nerve around the Ulna Following a Fracture of the Distal Radius. J Spine Neurosurg 5:6. doi: 10.4172/2325-9701.1000243

Abstract

Ulnar nerve injury is a rare complication following fracture of the distal radius. Dislocation of the nerve due to additional disruption of the distal radio-ulnar joint (DRUJ) occurs even less frequently with only a number of cases reported in the literature. In this article we present a unique case of dislocation of the ulnar nerve following distal radius fracture with dislocation of the ulnar nerve through the DRUJ and rotation around the ulna. Surgical repositioning of the ulnar nerve in this case resulted in nearly complete recovery of nerve function. In addition to its rareness, this case shows the importance of careful neurologic examination in distal radius fractures and the need for early explorative surgery or advanced imaging in cases with combined DRUJ dislocation and suspected ulnar nerve injury.

Keywords: Disruption distal radio-ulnar joint; Nerve injury

Keywords

Disruption distal radio-ulnar joint; Nerve injury

Introduction

Ulnar nerve injury is a rare complication following distal radius fracture (0.05%) [1]. Dislocation of the ulnar nerve occurs even less frequently, with only a number of cases reported in the literature [2- 4]. A rotation of the ulnar nerve around the ulna is unique. Apart from its rareness, several lessons can be learned from this case.

Case Report

A nineteen year-old man was involved in a car crash in June 2012. He remembered that during the collision he tried to prevent to be thrown out of the car by firmly pressing his hands against the steering wheel with his left arm and wrist extended. At the same time the airbag opened, which dislocated his left hand away from the steering wheel. He was brought to the Emergency Room of our hospital. At presentation he noted a tingling sensation in digit IV and V of his left hand. Motor function could not be reliably tested due to severe pain. X-ray demonstrated an extra-articular distal radius and ulnar styloid fracture with a complete dorsal dislocation of the wrist (Figure 1). The wrist was re-aligned with manual traction into a volar direction. The next day an external fixation device was placed, because internal fixation was not possible due to extensive swelling of the wrist. After three days he developed a recurrent dislocation of his distal radio-ulnar joint (DRUJ), which was corrected in the operating room by closed reduction and fixation with a K-wire that was left in place for 6 weeks. Motor and sensory function could still not be reliably tested due to the extensive swelling of the wrist. After 2 weeks a definitive fixation was performed by volar plating of the distal radius. Postoperative X-ray demonstrated a normal configuration of the DRUJ. At that time the swelling had decreased. He had started to use again his right hand and for the first time he noticed weakness and a decreased sensation of digit IV and V. He was referred to a neurologist, who initially advised to wait and see if spontaneous recovery would occur. At neurologic examination he had hypothenar atrophy with complete paralysis of his interossei and abductor digiti minimi (ADM) muscles. Electromyography (EMG) showed signs of denervation in the ADM. In time his ulnar nerve function did not recover and nine months after the injury his was referred to us. Explorative surgery was performed within a couple of weeks, during which the ulnar nerve was found in a rotated position around the ulna (Figure 2). The DRUJ was opened, the ulnar nerve was relocated and DRUJ was reconstructed and fixed with a K-wire for another 6 weeks. After this surgery his motor function slowly recovered to normal strength nine months after the surgery. Only sensation was still slightly decreased and he experienced synkinesis of all fingers when he was trying to spread them individually. Wrist flexion, extension and rotation were all normal.
Figure 1: Lateral and AP X-ray images demonstrating distal radius and ulnar styloid fracture with dorsal displacement of the wrist.
Figure 2: Intraoperative images showing (A) the dislocation of the ulnar nerve in the left forearm before release (black arrows pointing in direction proximal to distal, asterisks at distal ulna, and (B) after release (white arrow pointing at previous site of compression with a decreased calibre of the ulnar nerve).

Discussion

Ulnar nerve dislocation is a rare complication following distal radius fracture. Two cases of displacement of the ulnar nerve dorsal to the ulnar styloid have been reported [2,4] and one case with dorsal displacement through the distal radio-ulnar joint [3]. We present a unique case with rotation of the ulnar nerve around the ulna.
To understand the mechanism for dislocation in our case it is important to know that the ulnar nerve in the forearm is mobile, far more than for example the median nerve that is constrained inside the carpal tunnel [l,3,5]. This mobility may partly explain why the nerve is less frequently injured following minor trauma compared to the median nerve. In the other cases reported in the literature on ulnar nerve injury following distal radius fracture the nerve injury was also caused by high-energy trauma [3,4,6-8]. The dislocation with rotation around the ulna in our case however is extreme. It is of course speculative what could have caused the ulnar nerve to rotate around the ulna. Possibly the steering wheel and the air bag forced the wrist in a dorsal and radial direction causing a complete dislocated extra-articular distal radius fracture with dislocation in the DRUJ. With the hand and wrist now likely positioned more dorsal and radial to the forearm and shortened for more than 1 cm, the ulnar nerve was allowed to pass through the dislocated DRUJ. Upon reduction with axial traction, followed by volar translation, the ulnar nerve could then loop around the shaft of the ulna and remain dorsal as the radius came back into a reduced position at the DRUJ. Although this course of events is speculative, it confirms the mobility of the ulnar nerve at the wrist found in the anatomic study by Clarke and Spencer [3].
In addition to the fact that this case is rare, it also shows the importance of careful neurologic examination in distal radius fractures. Although ulnar nerve injury is not frequently observed following distal radius fracture [1], our case shows that if nerve injury occurs that it might be quite severe. This can also be concluded from the synkinesis that was observed in our case after full recovery of muscle strength had occurred. Synkinesis, the simultaneous contraction of different muscles, is a sign that the nerve injury was more severe than merely an axonotmesis injury. This phenomenon is for example also observed after facial nerve injury and is the result of simultaneous reinnervation of different muscles by axons originating from the same moto-neuron, which is caused by misdirection of some of the axonal branches during the regeneration process across the injury site [9]. In our case the nerve injury thus was so severe that it had resulted in partial disruption of the internal nerve basal lamina tubes (partial neurotmesis injury). It is again speculative if this severe injury was caused by traction, compression or a combination. In any event, the absence of recovery shows the importance of surgical exploration or advanced imaging (ultrasonography or MRI) to exclude entrapment of the nerve. Explorative surgery was also performed in the third case reported by Clarke et al. after eight weeks of conservative treatment (closed manipulation and application of a below-elbow plaster cast) [3]. During surgery they found the ulnar nerve displaced dorsally through the DRUJ, embedded in thick scar tissue. After volar mobilisation of the nerve the DRUJ was also repaired with a K-wire. Their case fully recovered in 3 months. In our case explorative surgery was performed in a relatively late phase due to doctor’s delay in referral. Fortunately, the nerve still recovered to nearly complete function nine months after the surgery. We recommend however to perform explorative surgery in the acute phase if ulnar nerve injury is suspected following a distal radius fracture with disruption of the DRUJ.

Statements

Informed consent was obtained from the patient described in this case report. The authors have no conflict of interest or disclosures. Funding was not obtained for this report.

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