Purpose

To compare the incidence and nature of ‘neurophysiological events’ identified, post hoc, by a consultant neurophysiologist with those identified intra-operatively by clinical physiologists, before and after intervention(s).

Introduction: End-to-side nerve repair is an experimental technique for repairing peripheral nerves when severe injury renders the proximal nerve stump not available for end-to-end repair or for conventional nerve grafting techniques. This study uses a large animal model to compare two variations of end-to-side neurorrhaphy techniques with conventional clinically established methods of nerve repair to assess the feasibility of end-to-side suture as a technique for possible future clinical use.

Methods: 12 age and weight matched sheep underwent end-to-side neurorrhaphy of the distal stump of the transected median nerve to the lateral side of the adjacent intact ulnar nerve through an epineurial window. 12 sheep underwent the same procedure as above but with the proximal stump of the transected median nerve similarly attached 2cm proximal to the first neurorrhaphy site to create a double end-to-side model. 18 sheep underwent conventional methods of nerve repair. All the experiments were randomized and the author performed all the surgery. The nerve repairs were assessed electrophysiologically and histologically and the muscles supplied by the repaired nerves were assessed physiologically at one-year post repair. Normal median nerves and donor ulnar nerves were also tested in the same ways.

Results: There were no significant differences in the outcomes of nerve repair between different conventional techniques. Half the end-to-side repairs failed but the double end-to-side repair consistently supported nerve regeneration. Both end-to-side methods were inferior to conventional techniques of nerve repair in all measures of outcome except twitch and tetanic muscle tensions. The function of the donor ulnar nerves in terms of conduction velocity was compromised in the double end-to-side repair but not the end-to-side repair.

Discussion and Conclusions: End–to-side nerve repair did support nerve regeneration but it was all or nothing. It is likely that the double end-to-side neurorrhaphies regenerated more consistently than the single end-to-side neurorrhaphies due the conduit effect of the donor ulnar nerve bridge supporting axon growth. Donor ulnar nerve damage in the double end-to-side group suggests regeneration may have occurred from terminal sprouts rather than collateral sprouts.

Although end-to-side neurorrhaphy did support nerve regeneration with sometimes good return of muscle function, the use of this technique as a clinical tool at this time cannot be recommended.

An experimental model was established to investigate the possibility of repairing cervical nerve roots avulsed from the spinal cord, as occurs in traction injuries of the brachial plexus. In five sheep the C6 root was avulsed and the ventral root was reattached using freeze-thawed muscle as a short graft (0.5 cm). Recovery was assessed after one year by electrophysiology and histology. Stimulation of the root produced muscle contractions in four out of five sheep. Action potentials were recorded distal to the grafts in all five sheep. Histological examination showed regenerated fibres in the ventral roots in all cases. These fibres could be traced distally to the brachial plexus. Our study confirms that motor fibres can regenerate out of the spinal cord into the ventral roots and reinnervate muscles, and suggests that reimplantation of avulsed roots is a surgical option in selected cases of traction injury of the brachial plexus.

We used freeze-thawed muscle grafts to restore continuity to the affected nerve in 22 painful cutaneous neuromas. In 11 of the 15 neuromas in the upper limb, pain was partially or completely relieved; in six of these there was some recovery of distal sensation. Partial pain relief was achieved in only two of the seven neuromas in the lower limb. The difference is attributed to the longer grafts required in the lower limb.

An experimental model was established to investigate the possibility of repairing cervical nerve roots damaged above the dorsal root ganglion, as occurs in traction injuries of the brachial plexus. In four sheep the C6 root was divided and repaired within the dura using freeze-thawed muscle grafts. Recovery was assessed after eight months by electrophysiology and histology. Action potentials were recorded distal to the grafts in all four sheep, indicating regeneration of motor fibres. Histological examination showed regenerated fibres in the ventral roots below the grafts in all cases. These fibres could be traced distally to the brachial plexus. There was no evidence of recovery of dorsal roots.

Coaxial autografts of skeletal muscle which had been frozen then thawed were used to repair injured digital nerves in eight patients. Assessment from three to 11 months after operation showed recovery to MRC sensory category S3+ in all but one patient, an excellent level of recovery. We conclude that bespoke muscle grafts treated and used in this way may offer significant advantages over conventional nerve grafts or cable grafts especially where large peripheral nerves are involved.

Skeletal muscle grafts, when thawed after freezing, can be used to repair peripheral nerves. This method was used after transection of the median nerve in the upper arm in marmosets. Examination at 28 days showed total denervation of flexor carpi radialis; at 150 days electrophysiological evidence of recovery of nerve conduction across the graft and of muscle activation was seen. Sections at this time showed nerve fibres and new functional neuromuscular junctions in the muscle. It is concluded that effective reinnervation of target muscles is possible after peripheral nerve repair using skeletal muscle autografts.

An orientated substratum has been implicated in the development and regeneration of axons and synapses. We prepared a basement membrane matrix from autogenous striated muscle, used it to repair the sciatic nerve in rats, then investigated the results by histology and electrophysiology. When treated grafts were coaxially aligned with the nerve fascicles functional recovery appeared within 30 days, with good growth of axons into the distal nerve. Grafts with myotubes at right angles to the nerve fascicles supported nerve regeneration but at a slower rate. Grafts of coaxially aligned but untreated muscle allowed axon penetration only through naturally degenerated muscle fibres, with minimal axon penetration of the distal nerve. It is concluded that in the rat a treated graft with correctly orientated empty myotubes can facilitate and guide the regeneration of peripheral nerve after injury and so lead to recolonisation of the distal stump with functional recovery.