Standard therapy for nerve injuries of the hand without a gap is a direct tension free microsurgical repair. Often, a nerve tube is used in addition to a direct nerve suture to protect the nerve from scar formation and guide the regenerating axons to the distal stump, but there is still a lack of data for this approach. The basic design of these nerve tubes is similar but they are made of different resorbable biomaterials. Chitosan, a derivative of chitin, is biocompatible and is similar to natural glycosaminoglycans. In vivo studies showed positive effects on the survival and orientation of Schwann cells as well as the survival and differentiation of neuronal cells and prevention of painful neuromas. Therefore it is the ideal material for a nerve tube. In this study we want to test a Chitosan based nerve tube (already certified German medical product with European label (CE-label)) - as an additional treatment for digital nerve injuries without a gap.

This study will enroll participants with traumatic sensory nerve lesions from 3 Centres: Trauma Center Ludwigshafen (Ludwigshafen, Germany), Trauma Center Frankfurt am Main (Frankfurt am Main, Germany) and Trauma Center Bochum (Bochum, Germany). After being informed about the study and its potential risks, patients with traumatic sensory nerve lesions will be consecutively screened for eligibility. The study will be conducted in four successive periods. All enrolled participants will be randomized locally by alternating local lists in the Double-Blind Period. After enrolment, the assigned subject number will be used on all Case Report Forms. The kind of intervention is blinded for the participant and for the investigator of the follow-up that was not involved in surgery. Enrolled participants will be randomized in a 1:1 ratio to primary microsurgical repair with the additional use of a nerve tube, or direct tension free microsurgical repair alone.

Data will be collected in Case Report Forms (CRFs) according to European DIN standard (International Standards Organization (EN ISO) 14155) and Good Clinical Practice recommendations. CRFs will be transmitted electronically to the executive study centre in Ludwigshafen and will be checked there for integrity, quality and consistency. The executive study centre will also ensure standardisation of the registry process, operative procedure and follow-up in all participating centers by periodic monitoring. Furthermore written instructions and a course of instruction will be provided to each Investigator. Data will be collected and analyzed in the executive study centre. There will be also CRFs for reporting drop-outs and for reporting adverse events.

The static 2-point-discrimination (2PD) after 6 months will bet the primary outcome parameter. Assumptions for the gold standard treatment can be made from literature. The mean of 2-PD after 6 months is approximately 8 mm with a standard deviation of 3 mm. A decrease of 2 mm in the 2-PD would be clinically relevant and is assumed for the experimental intervention. Using a 2-sided t-test with a level of 0.05 and a power of 80%, will require 37 patients per group in order to show superiority. The primary endpoint is tested in the per-protocol set (PPS) via an analysis of covariance with centre as factor and distance between lesion and finger pulp as covariate. Secondary objectives will be described without confirmatory analysis. In order to compensate a loss of follow-up or data 50 patients per group will be randomized.