Variables affecting axonal regeneration following end-to-side neurorrhaphy

The concept that end-to-side nerve coaptation can induce collateral sprouting was recently reintroduced by Viterbo. However, other authors have reported conflicting results with this technique of nerve repair The current paper studies some of the variables affecting axonal regeneration following end-to-side repair. The first part of the study compares the rate of axonal regeneration following end-to-side neurorrhaphy with nerve grafts using epineurial versus perineurial sutures. The rat sciatic nerve model was used and fresh autogenous nerve grafts were sutured to the side of intact sciatic nerves. A total of 20 rats were divided into 2 groups. In group A (n=10), suturing of the nerve graft was done to the epineurium. In group B (n=10), suturing was done to the perineurium. Histological and electron microscopic evaluation of the nerve grafts was done 50 days following the repair. In group A, none of the nerve grafts showed regenerating axons. In group B, 50% of grafts showed evidence of axonal regeneration. The difference between the two groups was statistically significant. Electron microscopy showed that the repair process following end-to-side neurorrhaphy was structurally similar to axonal regeneration following end-to-side neurorrhaphy. It was concluded that axonal regeneration following end-to-side nerve coaptation is mon likely to occur when the nerve graft is sutured to the parent nerve using perineurial rather than epineurial sutures. The second part of the study focused on investigating the feasibility of inducing collateral sprouting by silicone tubes sutured in an end-to-side fashion to the epineurium or perineurium of intact sciatic nerves. Following a 50-day recovery period, the site of silicone tube attachment was exposed and the tube carefully removed. The silicone tube contained soft tissue which was firmly attached to the side of the nerve and this was called the Attached Soft Tissue Segment (ASTS). Histological and electron microscopic examination showed no evidence of any nerve regeneration within the ASTS. The failure to demonstrate collateral sprouting within the ASTS may be explained by the absence of Schwann cells in the transplanted silicone tubes.