MOTOR NERVE REGENERATION ACROSS A CONDUIT GEDGE D. ROSSON, M.D., 1,2 * ERIC H. WILLIAMS, M.D., 1,2 and A. LEE DELLON, M.D., Ph.D. 2,3 A 3-cm gap in the ulnar nerve at the elbow in a subhuman primate was the first model of nerve regeneration across a polyglycolic, bioab- sorbable conduit. When a prospective trial was begun in humans, the first clinically available bioabsorbable conduit, the Neurotube TM , was utilized to reconstruct sensory nerves, but motor nerve injuries were not included. Thus, we sought to evaluate our patients with short-gap motor nerve injuries repaired with bioabsorbable conduits. We performed a retrospective chart review of all patients with bioabsorbable nerve conduit repair of short-gap motor nerve injuries over a 7-year period—six patients were identified. All patients had some return of motor function. Our case series, along with the nonhuman primate studies and other human reports, demonstrates that motor nerves will regenerate through bioabsorbable conduits and will reinnervate appropriate motor-target end-organs if they can reach them within an appropriate time frame for persistence of the motor-endplates. V VC 2008 Wiley-Liss, Inc. Microsurgery 29:107–114, 2009. A 3-cm gap in the ulnar nerve at the elbow was the first experimental model used to evaluate nerve regeneration across a polyglycolic, bioabsorbable conduit in a subhu- man primate. 1 In that model, at 1 year after nerve recon- struction, there was electromyographic evidence of intrin- sic muscle recovery in five of the six monkeys. However, when this type of reconstruction was begun in humans, the first conduits were utilized only to reconstruct sensory nerve defects, as these were the nerves that were most commonly injured. 2–5 When a prospective trial was begun in humans, the first clinically available bioabsorbable conduit, the Neurotube TM , was utilized to reconstruct sen- sory nerve defects. Motor nerves were not studied in that trial. 6 Basic science evidence, in the sciatic nerve model in the rat, has suggested that regeneration may proceed differently in motor nerves than in sensory nerves: given a choice, motor neurons seem to prefer regeneration across a motor nerve instead of a sensory nerve substra- tum, 7–9 and use of motor nerve architectural units instead of sensory nerve architectural units results in better re- covery when reconstructing a motor nerve defect. 10–12 These observations raise the question of how motor nerve recovery is affected clinically when a ‘‘pure’’ motor nerve or a mixed nerve is reconstructed with a nerve conduit in the absence of architectural substrata across the defect. To provide insight into this question, it is appropriate to review the results of motor nerve reconstruction with bio- absorbable conduits in the subhuman and human primate. We sought to evaluate the results of our patients with short-gap motor nerve injuries repaired with bioabsorb- able nerve conduits and compare them with others reported in the literature. METHODS We performed a retrospective chart review of all patients at the Dellon Institute for Peripheral Nerve Sur- gery in Baltimore, Maryland with bioabsorbable polygly- colic acid nerve conduit (Neurotube TM , Synovis Micro Companies Alliance, Birmingham, AL) repair of short- gap motor nerve injuries. Six patients were identified and no patients are excluded from analysis. During the period from January 1999 through December 2006, 80 patients underwent various nerve grafting procedures, of which six were bioabsorbable nerve conduit repair of short-gap motor nerves, whereas the remainder were autologous nerve grafts of gaps greater than 3 cm or sensory nerve injuries. These patients were identified via review of bill- ing records. The patients’ mean age was 47 years (range 9–61), one patient was a woman, five patients were men, and mean follow-up time was 39 months (range 4–66). This is a small sample size of six selected patients based on this treatment modality. Detailed description of the entubulation technique for the operation is published pre- viously. 2,6 Because of the nature of a retrospective chart review, much of the analysis is descriptive. Our patient results will be internally quantitatively analyzed and also qualitatively compared with other case reports and case series in the literature. Primary efficacy measures are clinical motor strength and electrodiagnostic testing. All testing is two-sided at the 0.05 alpha level. A chi-square statistic is used when the characteristic or outcome is cat- egorical, and a Student’s t-test is used when the variable ‘Devices used in the study described in this article were provided by Syno- vis Microsystems. Dr. Dellon is entitled to a share of royalty received on sales of products described in this article. The terms of this arrangement are being managed by the Johns Hopkins University in accordance with its conflict of interest policies.’ 1 Division of Plastic and Reconstructive Surgery, Johns Hopkins University, Baltimore, MD 2 Dellon Institute for Peripheral Nerve Surgery, Baltimore, MD 3 Division of Plastic Surgery and Department of Neurosurgery, Johns Hopkins University, Baltimore, MD *Correspondence to: Gedge D. Rosson, M.D., Division of Plastic and Recon- structive Surgery, Johns Hopkins University School of Medicine, Suite 8161, 601 North Caroline Street, Baltimore, Maryland 21287. E-mail: gedge@jhmi.edu Received 27 March 2008; Accepted 22 August 2008 Published online 22 October 2008 in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/micr.20580 V VC 2008 Wiley-Liss, Inc.