Inferior long-term Results of a Prospective Randomized Controlled Trial initially demonstrating enhanced Sensory Nerve Recovery using a Chitosan Nerve Tube.

INTRODUCTION: Traumatic peripheral nerve injuries can result in significant functional impairments and long-term sequelae. This study evaluated the long-term outcomes of a chitosan tube implantation protecting the epineural coaptation after peripheral nerve injuries using two different tube versions (V 1.0 and V 2.0 with different wall thickness and resorption characteristics) compared to a control group. The study focused on pain levels, sensory function, and overall functional outcomes.

METHODS: Patients who received tube implantation around direct coaptation sites of digital nerves were prospectively randomized and compared to control patients without additional tube protection. Pain levels, sensory function, grip force, and functional scores were assessed at different time points, ranging from three months to five years after the procedure. Furthermore, biodegradation of the tubes was measured via high-resolution MR-neurography (MRN) and categorized.

RESULTS: Long-term evaluation revealed that patients with V 1.0 had higher pain levels compared to the control group after five years. They also reported more symptoms of numbness and hypersensitivity. V 2.0 patients exhibited higher pain levels at three months, which did not persist at six months. However, they showed compromised sensory function, with higher values of two-point discrimination compared to V 1.0 and the control group. No differences were found in grip force or functional scores between the groups. MRI displayed remnants of implants even in long-term follow-up.

DISCUSSION: The findings suggest potential limitations due to pain increase and impaired sensory function associated with tube implantation in the long term. However, in the short term, the material seemed to have a protective effect (as published previously). The resorption process was not completed at the end of the observation period of five years. This might explain the prolonged scarring and inferior long-term results. Future research should focus on improving tube materials and design to minimize adverse effects and enhance functional outcomes in patients with peripheral nerve injuries.