The dorsal cutaneous branch of the ulnar nerve. An anatomic clarification with six case reports

Causes of Dorsal Cutaneous Branch of the Ulnar Nerve Neuropathy Among Patients Undergoing Electrodiagnostic Studies: A Series of 14 Patients

BACKGROUND

Isolated neuropathy of the dorsal cutaneous branch of the ulnar nerve (DCBUN) is rare and most cases are secondary to trauma, often iatrogenic. The topography of sensory abnormalities and abnormal electrodiagnostic (EDX) findings are crucial in confirming DCBUN neuropathy.  Materials and methods: This is a retrospective study of patients with isolated involvement of the DCBUN from among patients referred for EDX studies for upper extremity symptoms. All patients underwent a focused neurological examination followed by EDX studies. Ultrasound (US) studies were performed in two patients.  Results: Of the 14 patients with DCBUN neuropathy, decreased pinprick sensation in the distribution of the DCBUN was noted in 11 (78%) patients. DCBUN sensory nerve action potential (SNAP) was not recordable in 13 (92%) patients. In one patient who had a recordable SNAP, the latency was prolonged, and the amplitude was decreased. Four (28%) patients had incidental EDX abnormalities suggestive of entrapment of the median nerve at the carpal tunnel. The most common cause of DCBUN neuropathy was trauma in 13 (92%) patients, of which eight were iatrogenic. No specific etiology was detected in one patient (7%). Of the two patients who underwent US studies, one had increased cross-sectional area (CSA) at the wrist with prominent fascicles and hyperechoic scar tissue, while the CSA was normal in the other patient.

CONCLUSIONS

Although rare, DCBUN neuropathy can be readily confirmed by typical clinical features and EDX findings. Surgeons should be aware of the anatomy and clinical features of DCBUN neuropathy and avoid injuring the nerve during surgical procedures at the wrist and forearm.

Retrograde Fixation of the Ulna in Pediatric Forearm Fractures Treated With Elastic Stable Intramedullary Nailing

Introduction

This study analyzes the outcomes of retrograde fixation of the ulna in pediatric forearm fractures treated with elastic stable intramedullary nailing (ESIN).

Materials and Methods

A retrospective analysis was conducted by reviewing patient records of forearm fractures treated with ESIN by retrograde fixation. The study included 30 children (26 boys and 4 girls). The mean age at the time of injury was 11.7 years (range: 6.6 to 14.3 years). The technique is described. All patients were followed up until hardware removal.

Results

The mean time for fracture healing was 5.3 weeks (range: 4 to 8.8 weeks). The mean time for nail removal was 6.6 months (range: 5 to 10 months). There were five cases with rotation deficits, one of which was a re-fracture.

Conclusions

When antegrade nailing is performed, the ulna is sometimes complicated by non-union as well as entry point irritation. We did not encounter such complications. Retrograde fixation of the ulna in pediatric forearm fractures treated with ESIN is a safe and effective alternative to common fixation (antegrade ulnar fixation) and offers technical advantages.

Superficial radial nerve-lateral antebrachial cutaneous nerve anatomic variation

INTRODUCTION

This study focuses on an anatomic variation in which the lateral antebrachial cutaneous nerve (LACN) innervates the radial border of the dorsum of the hand and thumb in addition to, or replacing, the superficial radial nerve (RSN). Here, we propose a technique of nerve conduction that identifies this variation.

METHODS

We studied nerve conduction in 200 upper limbs of two series of 50 volunteers. We sought evidence of the aforementioned variation on the dorsum of the hand and in the thumb.

RESULTS

We found eight occurrences of this variation on the dorsum of the hand and 11 variants on the thumb within the two respective series of 100 upper limbs studied.

DISCUSSION

The RSN-LACN anatomic variation can be studied using nerve conduction. The knowledge of this variation is particularly important for the evaluation of proximal radial nerve injury.

Anatomical study of the dorsal cutaneous branch of the ulnar nerve using ultrasound

OBJECTIVES

To determine whether ultrasound allows precise assessment of the course and relations of the dorsal cutaneous branch of the ulnar nerve (DCBUN).

METHODS

This work, initially undertaken in cadavers, was followed by high-resolution ultrasound study in 20 healthy adult volunteers (40 nerves) by two musculoskeletal radiologists in consensus. Location and course of the DCBUN and its relations to adjacent anatomical structures were analysed.

RESULTS

The DCBUN was consistently identified along its entire course by ultrasound. Mean cross-sectional area of the nerve was 1.6 mm(2) (range 1.1-2.2). The level at which the DCBUN branches from the ulnar nerve was located a mean of 57 mm (range 40-80) proximal to the ulnar styloid process and 11 mm (range 7-15) radial to the medial border of the ulna. The DCBUN then crossed the medial border of the ulna a mean of 14 mm (range 6-25) proximal to the ulnar styloid process.

CONCLUSION

The DCBUN is clearly depicted by ultrasound. Precise mapping of its anatomical course could have significant clinical applications, such as preventing injury during surgery of the ulnar side of the wrist or helping in the diagnosis of chronic pain of the ulnar side of the hand.

KEY POINTS

• The dorsal cutaneous branch of the ulnar nerve (DCBUN) is often injured. • The DCBUN originates from the ulnar nerve in the distal third of the forearm. • It can be clearly depicted by ultrasound. • The level at which the DCBUN crosses the ulna is variable. • Precise mapping of its anatomical course could have significant clinical applications.

Surgical approaches to the distal radius

INTRODUCTION

Fractures of the distal radius are among the most common fractures seen. They encompass a myriad of presentations and fracture patterns that often benefit from various open reduction and internal fixation techniques-including volar plating, dorsal plating, radial plating, intramedullary nailing, and fragment-specific fixation. In order to obtain optimal reduction of these fractures, surgeons require a thorough understanding of the anatomy and various surgical exposures.

ANATOMY

The distal radius is surrounded by a soft tissue envelope rich in vascularity and cutaneous innervation. The osseous surface consists of two articular surfaces and three cortical sides covered almost entirely by soft tissue.

SURGICAL APPROACHES

Approaches to the distal radius can be broadly divided into volar, radial, and dorsal. Visualization of the articular surface can be accomplished best arthroscopically. Arthroscopy can be performed alone or in conjunction with other open approaches to the distal radius.

SUMMARY

This article will review the pertinent anatomy and various surgical approaches in order to facilitate the surgeon's ability to safely expose a distal radius fracture.