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Appropriate matching of proximal and distal fibers is a major objective when suturing a lacerated nerve. Recent studies suggest that neurotropic factors may influence motor/sensory specificity and affect the functional outcome. This was studied in animal models by direct coaptation of cut nerve ends inside a 5-mm collagen tube with and without appropriate sensory/motor alignment, as well as in models where the cut nerve ends were placed in a 10-mm collagen tube with a 5-mm gap, with and without appropriate sensory/motor alignment. The radial nerve of 49 New Zealand white rabbits was chosen because it has distinct motor and sensory divisions. The animals were killed at 24 weeks and electrophysiologic, histologic, and muscle contraction studies were performed. Axon counts and diameters were measured from the distal motor and sensory stumps. Nerve conduction velocity, dry muscle weight, and motor axon counts were not statistically different between the groups. The malaligned group without a gap had better regeneration in sensory nerves than other groups. The muscle contraction force of the malaligned group without a gap was significantly less than the other groups. The malaligned group with a 5-mm gap had the same muscle contraction force as the aligned group without a gap. In this study, a short nerve gap lessened the misdirection of motor fibers after nerve-end coaptation.

METHODS An elliptically shaped skin flap is designed on the lateral aspect of hypothenar over ADM muscle avoiding dorsal hairy skin area. ADM myocutaneous island flap is elevated based on the neurovascular branches of the ulnar artery and nerve. An incision along the line connecting radial aspect of MP joint and pisiformis is made over hypoplastic thenar area. The ligamentous insertion of the ADM is detached and the flap is set in the defect created in the thenar area and the detached ligament is weaved into the ligamentous tissue around the radial base of the proximal phalanx of the thumb with an appropriate tension. Three weeks after surgery, the thumb is mobilized. We started this procedure based on our original idea in March 1996 for the Blauth type II hypoplastic thumb. This procedure was applied to 18 hands in 16 cases (8 male and 8 female) by 2010. This series included 7 Blauth type II, 6 type III, 3 type IV (after reconstructive procedures) and 5 type V (after pollicization). The age at operation ranged from 1 year 1 month to 8 years 3 month with an average of 4 years 11 months. The postoperative time was 1 years and 6 months to 14 years 11 months with an averaged of 7 years and 6 months. All of the patients had thumb hypoplasia of different degree on the other side.

The hypothesis that improved axonal regeneration occurs through nerve grafts when scarred tissue is removed and distal coaptation completed during a delayed, secondary operation was tested in a rabbit model. The ulnar nerve was used as a donor nerve graft to a final three-centimeter deficit of the contralateral median nerve. This was done either in one stage or in two stages, with resection of scar and coaptation at the distal site done ten weeks later. Evaluation included nerve conduction velocity, compound action potential area, muscle contraction force, muscle weight, and axon counts. Two-stage nerve grafts at 24 weeks were significantly inferior to one-stage grafts only in compound action potential area. Both nerve grafts showed significant improvement in function from twenty-four to sixty-two weeks as measured by nerve conduction velocity; two-staged grafts in addition showed a significant increase in compound action potential area and twitch contraction force. The data are inconclusive regarding the absolute superiority of two-stage versus one-stage grafting. Different timing for the second stage may be required.

Previous studies have established the superiority of a vascularized nerve graft (VNG) over a nonvascularized nerve graft in a scarred recipient bed. This study compared the functional results of VNGs with nonvascularized nerve grafts (conventional nerve graft [CNG]) in a normal recipient bed. Forty rabbits were divided into two groups of 20 each. In one group a median nerve VNG was created in one forelimb. In the other group a CNG was created. Postoperative evaluation was performed at 10 and 24 weeks. Nerve conduction velocity, compound action potential area, axon diameter, and muscle weight did not demonstrate statistically significant differences. Axon counts and muscle strength did show a superior value for VNGs at 24 weeks.