Macroscopic study of the medio-ulnar anastomoses of the hand

The connections between the branches of the median and ulnar nerves innervating the palm of the hand were studied anatomically and under the microscope. There are two median-ulnar anastomoses in the hand: the first is deep and motor. The second is superficial, known as Berrettini's anastomosis. These variations in anastomoses help to explain atypical patterns in the affected areas and should be well understood so as not to confuse them with signs of recovery. The objectives of our study are: - To assess the prevalence of anastomoses. - To study the topography and morphometry of the Berrettini anastomosis in relation to the flexor retinaculum. To describe the shape, volume and direction of this anastomosis. - To study the topography and morphometry of the Riche-Cannieu anastomosis, which may explain the clinical atypicalities observed following lesions of the ulnar or median nerves. This paper explains the variable innervation of the flexor pollicis brevis and the variable impact on thumb opposition and the Froment's sign of lesions to the ulnar and median nerves, respectively.