Paul Michelin1,2,3, Grégoire Leleup4, Mourad Ould-Slimane5, Marie Caroline Merlet5, Benjamin Dubourg4, Fabrice Duparc6,7,5. 1. Department of Radiology, University Hospital of Rouen, Hopital Charles Nicolle, 76031, Rouen Cedex 1, France. paul.michelin@chu-rouen.fr. 2. Laboratory of Anatomy, Faculty of Medicine, University of Rouen, Rouen, France. paul.michelin@chu-rouen.fr. 3. CETAPS Laboratory, EA3832, Faculty of Sport Sciences, University of Rouen, Rouen, France. paul.michelin@chu-rouen.fr. 4. Department of Radiology, University Hospital of Rouen, Hopital Charles Nicolle, 76031, Rouen Cedex 1, France. 5. Department of Orthopaedic Surgery and Traumatology, University Hospital of Rouen, Rouen, France. 6. Laboratory of Anatomy, Faculty of Medicine, University of Rouen, Rouen, France. 7. CETAPS Laboratory, EA3832, Faculty of Sport Sciences, University of Rouen, Rouen, France.
Abstract
BACKGROUND: Chronic ulnar nerve entrapment worsened by elbow flexion is the most common injury, but rare painful conditions may also be related to ulnar nerve instability. The posterior bundle of the medial collateral ligament (pMCL) and the retinaculum, respectively form a soft floor and a ceiling for the cubital tunnel. The aim of our study was to dynamically assess these soft structures of the cubital tunnel focusing on those involved in the biomechanics of the ulnar nerve. METHODS: Forty healthy volunteers had a bilateral ultrasonography of the cubital tunnel. Elbows were scanned in full extension, 45° and 90°, and maximal passive flexion. Morphological changes of the nerve and related structures were dynamically assessed on transverse views. RESULTS: Both the pMCL and the retinaculum tightened with flexion. During elbow flexion, the tightening of the pMCL superficially moved the ulnar nerve remote from the osseous floor of the retroepicondylar groove. A retinaculum was visible in all 69 tunnels with stable nerves (86.3%), tightened in flexion, but absent in 11 tunnels with unstable nerves (13.7%). The retinaculum was fibrous in 60 elbows and muscular in nine, the nine muscular variants did not significantly influence the biomechanics of stable nerves. Stable nerves flattened in late flexion between the tightened pMCL and retinaculum, whereas unstable nerves transiently flattened when translating against the anterior osseous edge of the groove. CONCLUSION: The retinaculum and the pMCL are key structures in the biomechanics of the ulnar nerve in the cubital tunnel of the elbow.
BACKGROUND:Chronic ulnar nerve entrapment worsened by elbow flexion is the most common injury, but rare painful conditions may also be related to ulnar nerve instability. The posterior bundle of the medial collateral ligament (pMCL) and the retinaculum, respectively form a soft floor and a ceiling for the cubital tunnel. The aim of our study was to dynamically assess these soft structures of the cubital tunnel focusing on those involved in the biomechanics of the ulnar nerve. METHODS: Forty healthy volunteers had a bilateral ultrasonography of the cubital tunnel. Elbows were scanned in full extension, 45° and 90°, and maximal passive flexion. Morphological changes of the nerve and related structures were dynamically assessed on transverse views. RESULTS: Both the pMCL and the retinaculum tightened with flexion. During elbow flexion, the tightening of the pMCL superficially moved the ulnar nerve remote from the osseous floor of the retroepicondylar groove. A retinaculum was visible in all 69 tunnels with stable nerves (86.3%), tightened in flexion, but absent in 11 tunnels with unstable nerves (13.7%). The retinaculum was fibrous in 60 elbows and muscular in nine, the nine muscular variants did not significantly influence the biomechanics of stable nerves. Stable nerves flattened in late flexion between the tightened pMCL and retinaculum, whereas unstable nerves transiently flattened when translating against the anterior osseous edge of the groove. CONCLUSION: The retinaculum and the pMCL are key structures in the biomechanics of the ulnar nerve in the cubital tunnel of the elbow.
Authors: Kamal Mezian; Jakub Jačisko; Radek Kaiser; Stanislav Machač; Petra Steyerová; Karolína Sobotová; Yvona Angerová; Ondřej Naňka Journal: Front Neurol Date: 2021-05-14 Impact factor: 4.003