gms | German Medical Science

Introduction: The treatment of ulnar neuropathy with either simple decompression, medial epicondylectomy, or nerve transposition is still of major debate. Although a recent meta- analysis in a clinical setting showed that in-situ neurolysis of the ulnar nerve is a reasonable alternative to anterior transposition for the surgical transposition of the ulnar nerve compression until now there is no experimental proof evaluation of the afore mentioned techniques.

Purpose: In a new rabbit model (scarred ulnar nerve model) the influence of neurolysis, nerve transposition and epicondylectomy on the functional and morphologic integrity of the ulnar nerve was investigated.

Material and methods: 48 Female Chinchilla Bastard rabbits were used in the study (six controls). All operations were performed in deep anethesia, in 42 rabbits the left ulnar nerve was exposed and attached to the soft tissues between Struther´s arcade and the flexor carpi ulnaris muscle using epineural resorbable sutures (7-0 PDS) leading to reproducable scarring of the nerve in this area. In three operative groups either in- situ neurolysis, anterior transposition or medial epicondylectomy was performed. Using optical markers placed in equidistant reference points, nerve tension was recorded using mechanical distraction in 80° of flexion of the elbow. Measurement of nerve conduction velocity (NCV) was performed using a minituarized electric stimulator (Micromed). Cristal Fast Blue was applied after transection of the ulnar nerve in a silicon tube sutured to the nerve to perform retrograde tracing of the spinal ganglion perikarya and motoneurons by . 10 days after the retrograde labelling the rabbits were killed via transcardial perfusion and vibratome sections were used for neuronal counting using the fractionator method.

Results: Tensile properties were siginificangly altered after epicondylectomy and transposition with loss of normal tensile properties in the joint and non- joint region; the NCV was not significantly altered in the neurolysis group (60m/s ± 10), but significantly dropped in the transposition and epicondylectomy group (40 m/s ± 15). Nerve cell integrity and cell number was not altered in the neurolysis group (1350 ± 300)compared to non- operated control animals (1400 ± 250) and was reduced in the transposition and epicondylectomy group (1100 ± 250).

Conclusion: In-situ neurolysis of the scarred ulnar nerve in a new rabbit model is less invasive and does not affect the electrophysiologic, biomechanical and cellular properties as transposition or epicondylectomy.