The Effects of Hypertonic Dextrose Injection on Connective Tissue and Nerve Conduction Through the Rabbit Carpal Tunnel

Yoshii Y, Zhao C, Schmelzer JD, Low PA, An K-N, Amadio PC. The effects of hypertonic dextrose injection on connective tissue and nerve conduction through the rabbit carpal tunnel. Objective: To investigate the effects of hypertonic dextrose injection on the subsynovial connective tissue (SSCT) in a rabbit model. We hypothesized that dextrose injection would induce proliferation of the SSCT, hinder median nerve conduction, and alter SSCT mechanical properties, similar to what is observed in patients with carpal tunnel syndrome (CTS). Design: Randomized, controlled prospective study. Setting: Not applicable. Participants: New Zealand white rabbits (N=28) weighing 4.0 to 4.5kg. Intervention: One forepaw was randomly injected with 0.1mL 10% dextrose solution. The contralateral paw was injected with a similar amount of 0.9% saline solution as a control. Animals were killed at 12 weeks after injection. Main Outcome Measures: Animals were evaluated by electrophysiology (EP), mechanical testing, and histology. EP was evaluated by distal motor latency and amplitude. Shear force was evaluated when the middle digit flexor digitorum superficialis tendon was pulled out from the carpal tunnel. The ultimate tensile load and the energy absorption were also measured. Tissue for histology was evaluated qualitatively. Results: EP demonstrated significant prolongation of distal motor latency. The energy absorption and stiffness were also significantly increased in the dextrose group. Histologically, the dextrose group showed thickening of the collagen bundles and vascular proliferation within the SSCT compared with the saline group. Conclusions: These results are consistent with the findings in patients with CTS and suggest that hypertonic dextrose injection has the potential to create a novel animal model in which to study the evolution of CTS.