Anastomose de Riché-Cannieu: estrutura, função e significância clínica

Abstract

Objective To define the anatomy pattern and the incidence of Riché-Cannieu anastomosis, that is, median and ulnar communication in the palmar aspect of the hand. Materials Methods A total of 80 anatomical dissections were performed on 60 hands of 30 cadavers from 1979 to 1982, and on 20 hands from 2012 to 2015. All of these procedures were performed at the Department of Anatomy of our institution. The incidence of Riché-Cannieu anastomosis and the innervation of the thenar muscles were studied. Results Riché-Cannieu anastomosis was identified in every dissected hand (100%). The extramuscular Riché-Cannieu anastomosis was recorded in 57 hands, and the intramuscular, in 19 hands. The association of extra- and intramuscular Riché-Cannieu anastomoses occurred in four hands. The ulnar component always originated from the deep branch. The anastomotic branch arising from the median nerve originated from the motor thenar branch (recurrent branch) of the median nerve in most of the observations. The median-ulnar double innervation only to the deep head of the flexor pollicis brevis was identified in 29 of 80 hands. The double innervation only of the superficial head of the flexor pollicis brevis was found in 13 hands. In 12 hands, the deep head of the flexor pollicis brevis was absent. The double innervation of the superficial and deep heads of the flexor pollicis brevis occurred in 14 hands. The oblique head of the adductor pollicis received double innervation in 12 hands. The deep head of the flexor pollicis brevis and the oblique head of adductor pollicis were doubly-innervated in nine hands. The transverse head of the adductor pollicis received double innervation in two hands. Double innervation of the deep head of the flexor pollicis brevis and the transverse head of the adductor pollicis were found in one hand. Conclusion According to the present study, Riché-Cannieu anastomosis should be considered a normal anatomical neural connection, not an anatomical variation. Knowledge of this anastomosis is essential because the presence of such neural communication may result in confusing clinical, surgical, and electromyographic findings in cases of median or ulnar damage or entrapment.

Comprehensive Summary of Anastomoses between the Median and Ulnar Nerves in the Forearm and Hand

“…Some studies have reported rates as great as 70 to 80%, which the authors emphasized could potentially be higher with finer techniques. 32,33 This belief is supported by the findings in another study by Caetano et al, 34 in which the presence of RCA was recorded in 100% of dissected fresh cadaver hands (n = 80), with the use of careful, high magnification (10-16 ×) technique. It may therefore be feasible to consider RCA as a normal anatomical neural connection.…”

“…It may therefore be feasible to consider RCA as a normal anatomical neural connection. 7,34 Further, race might factor into observed prevalence. 33,35 For example, in a study by Kimura et al 33 , African-Americans presented with RCA significantly less frequently than other racial groups, and no significant difference was found between Hispanics and Caucasians.…”

Anatomical Variants of the Upper Limb Nerves: Clinical and Preoperative Relevance

“…The innervation variations of these small muscles are of high clinical importance because in the case of a complete lesion of the MN or UN, some of these muscles may or may not be paralyzed, possibly leading to the erroneous conclusion of a partial rather than complete lesion. 28,31 Profound knowledge of these anastomoses is essential for accurate interpretation of clinical findings and to avoid the risk of iatrogenic injuries during surgical procedures. 32…”

Anastomosis Patterns between the Median and Ulnar Nerves in the Upper Limbs

“…Carpal tunnel syndrome, in particular, has been associated with exacerbated or decreased symptoms in the presence of these anastomoses. 52,54 It can generate an "ulnar-hand" phenomenon in some cases, in which the muscles in the tenar eminence only present innervation from the ulnar nerve, with no contribution from the median nerve. 55 In an electroneuromyographic study, 56 it caused difficulty in interpreting the results, especially in the evaluation of the lesions to the median nerve, the opponens pollicis muscle, amd the abductor pollicis brevis muscle.…”