Distal nerve transfer from the median nerve lumbrical fibers to the distal ulnar nerve motor branches in the palm: An anatomical cadaveric study

Ulnar Nerve Injury during Treatment of Fourth and Fifth Metacarpal Fractures: A Case Report and Anatomical Review

The deep branch of the ulnar nerve (DBUN) is a pure motor nerve. It passes through a hypothenar fibromuscular tunnel and courses radially on the interossei surface. The DBUN is not frequently considered during hand fracture surgery, despite the anatomical course of the nerve in close relation to the carpal and metacarpal bones, which makes it vulnerable to penetrating injury and being injured during hand surgery fixations. In this article, we describe a case of DBUN injury after percutaneous pinning of the fourth and fifth metacarpal bone fractures complicated by intrinsic muscle wasting of the hand that was treated with neuroma excision and sural nerve graft. We present the case of a 36-year-old man, who had a fracture of the base of the fourth and fifth metacarpal bones, which was treated with multiple K-wires. A few months later, the patient presented with weak abduction/adduction of the three ulnar fingers and prominent wasting in the intrinsic muscles of the hand. On hand exploration, a 2-cm neuroma was found along the course of the DBUN distal to the hypothenar fibromuscular tunnel, which was treated by neuroma excision and nerve grafting. Fractures of the fourth and fifth metacarpals and carpometacarpal dislocations are very common and are often treated surgically. To fix these fractures, awareness of the DBUN course in the hand and its proximity to the carpal and metacarpal bones is important. High caution should be taken during percutaneous pinning by inserting K-wires under radiological guidance, minimizing pining attempts and limiting pin tip protrusion to 1-2 mm.

Histological Compatibility in Distal Neurotizations: A Systematic Review

Considering the importance of defining the minimum number of axons between recipient and donor branches, that is, the definition of histological compatibility in distal neurotizations for the success of the procedure and the surgeon's freedom to choose individualized strategies for each patient, this systematic review was conducted to find out the most recent studies on the subject. The objective of this systematic review was to determine the importance of the number of axons and the relationship between axon counts in the donor and recipient nerves in the success of nerve transfer. A literature review was performed on five international databases: Web of Science, Scopus, Wiley (Cochrane Database), Embase, and PubMed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed (2020 version), a guide designed to guide the elaboration of systematic literature reviews. One hundred and fifty-seven studies were found, and 23 were selected based on the eligibility criteria. The articles presented were conclusive in determining the importance of the number of axons in the success of nerve transfer. Still, the relationship between the number of axons in the donor and recipient nerves seems more relevant in the success of transfers and is not always explored by the authors. The review of the articles has provided compelling evidence that the number of axons is a critical determinant of the success of nerve transfer procedures. However, the relationship between the number of axons in the donor nerve and that in the recipient nerve appears to be even more crucial for successful transfers, a factor that is not always adequately explored by authors in the existing literature. Level of evidence : Level IV, therapeutic study.

Lumbrical Muscles Neural Branching Patterns: A Cadaveric Study With Potential Clinical Implications

BACKGROUND

Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding metacarpophalangeal joints, in front of the deep transverse metacarpal ligament. The first and second lumbrical muscles are typically innervated by the median nerve, and third and fourth by the ulnar nerve. A plethora of lumbrical muscle variants has been described, ranging from muscles' absence to reduction in their number or presence of accessory slips. The current cadaveric study highlights typical and variable neural supply of lumbrical muscles.

MATERIALS

Eight (3 right and 5 left) fresh frozen cadaveric hands of 3 males and 5 females of unknown age were dissected. From the palmar wrist crease, the median and ulnar nerve followed distally to their terminal branches. The ulnar nerve deep branch was dissected and lumbrical muscle innervation patterns were noted.

RESULTS

The frequency of typical innervations of lumbrical muscles is confirmed. The second lumbrical nerve had a double composition from both the median and ulnar nerves, in 12.5% of the hands. The thickest branch (1.38 mm) originated from the ulnar nerve and supplied the third lumbrical muscle, and the thinnest one (0.67 mm) from the ulnar nerve and supplied the fourth lumbrical muscle. In 54.5%, lumbrical nerve bifurcation was identified.

CONCLUSION

The complex innervation pattern and the peculiar anatomy of branching to different thirds of the muscle bellies are pointed out. These findings are important in dealing with complex and deep injuries in the palmar region, including transmetacarpal amputations.

Innervation of the lumbrical and interosseous muscles in hand: analysis of distribution of nerve fascicles and quantification of their surface projections

We aimed to determine the surface locations of the nerve fascicles that innervate the lumbricals and interossei, re-examine the branching pattern of the deep branch of the ulnar nerve (dUN), and provide a clear description of their course. Eleven fresh-frozen adult cadaver hands were investigated. Nerve fascicles that innervate the lumbricals, interossei, and surface landmarks including the distal wrist crease and 2-5 proximal finger creases were marked by radio opaque fibers and subjected to X-ray. We analyzed the images and set a quadrant-linked hand surface. Subsequently, we measured the lengths of both axes and the coordinates of the branch locations in the quadrant. The surface locations of branches that innervated the lumbricals and interossei were clearly quantified. The branches of dUN exhibited a 4-group distribution pattern. Novel methods for quantitatively locating the surface anatomy of these branches and demonstration of a 4-group branching pattern of the dUN were established.