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Variation in the origin of the first motor branch of the ulnar nerve to the flexor carpi ulnaris muscle
Author(s) -
Dugan Sonja Hedblom,
Lundgren Mary,
Inouye Sandra,
Molen Jonathan Vander,
Freemyer-Brown Anna
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.01901
Subject(s) - epicondyle , flexor carpi ulnaris , extensor carpi ulnaris , ulnar nerve , medicine , cubital tunnel , anatomy , cadaveric spasm , cadaver , ulna , humerus , median nerve , ulnar neuropathy , elbow , forearm , cubital tunnel syndrome
/Purpose Surgical decompression of the ulnar nerve in the treatment of cubital tunnel syndrome is performed in close proximity to the first motor branch of the ulnar nerve to flexor carpi ulnaris (FCU). Understanding the variability of this branch is important for improving surgical interventions. The purpose of this study was to determine the location and anatomical variation of the first motor branch to flexor carpi ulnaris. Methods Embalmed cadavers were dissected to expose the ulnar nerve as it courses past the medial epicondyle of the humerus. Digital calipers were used to measure the distance between the point of origin of the first motor branch of the ulnar nerve to FCU and the most prominent aspect of the medial epicondyle. The length of the ulna was also measured and correlated with data from ulnar nerve measurements. Statistical significance was defined as a p‐value < 0.05. Outcomes Data was obtained from 113 cadaveric elbows. The location of the branch point was most consistently found (88.5% of specimens) distal to the medial epicondyle (average 19.42 mm, standard deviation 4.39, 95% confidence interval 18.54 – 20.29). In 11.5% of elbows, however, the branch point occurred proximal to the medial epicondyle (average 16.02 mm, standard deviation 4.53, 95% confidence interval 13.28 – 18.76 mm). The average distance was 18.42 mm distal to the medial epicondyle in females and 20.45 mm in males, with a statistically significant difference between genders (p‐value = 0.02). The correlation between the branch point of the first motor branch of the ulnar nerve to FCU and ulna body size was also explored. Conclusion This study has demonstrated that the first motor branch of the ulnar nerve is most consistently located 18.54 to 20.29 mm distal to the medial epicondyle. Males had a significantly greater distance from the origin of the first motor branch of the ulnar nerve to FCU from the medial epicondyle compared to females. No statistically significant correlation was found related to laterality. Additionally, the prevalence of the anatomical variant in which branching of the first motor nerve from the ulnar nerve occurs proximal to the medial epicondyle was estimated. Prior to this study, the prevalence of this variant had not been reported. Support or Funding Information The authors would like to thank Midwestern University for the use of the specimens in this study.