Phillips, J.B.; Tillett, R.L.; Georgeu, G.A.; Bunting, S.C.J.; Afoke, A.; Hall, S.M. and Brown, R.A.
Investigation of mechanical interactions between intraneural elements of the rat sciatic nerve after repair.
In: Peripheral Nerve Society 2003, 26-30 July 2003, Banff, Canada.
The development of tissue engineered conduits for the surgical repair of peripheral nerves has raised important questions with regard to the mechanical aspects of neuroanatomy. Restoration of the ability of a repaired nerve to accommodate the movements required during limb movement is an important consideration in the design of repair strategies. A model has been developed for
use alongside existing experimental assays of nerve function to explore the restoration of mechanical features in the regenerating rat sciatic nerve. This is based on the presence of a distinct core and sheath with an interface at the level of the innermost perineurial cell layer. The core and sheath can be separated
experimentally using tensile testing equipment which allows quantification of the force required. This force has been shown to be consistent in control nerves from
unoperated animals, providing a reference for the subsequent investigation of the interaction between these neural regions after repair. In this investigation, the left sciatic nerves in 18 Wistar rats were transected and immediately repaired using epineurial sutures. Animals were sacrificed 2, 4, 8 and 12 weeks post-repair and
the nerves underwent mechanical testing to measure the force required for separation of the core and sheath. Controls were unoperated contralateral sciatic
nerves from animals in the experimental group. The ability to separate the endoneurial core from the nerve sheath depends on the maximal force required
being less than the break-strength of either region. 4 weeks after primary repair, separation of core and sheath was possible and required a greater force than
controls. At the other time points the endoneurial core failed before separation from the sheath could take place, suggesting that the strength of the interface
was greater than the strength of the endoneurial core. These data provide an insight into the mechanical changes that occur following primary repair in the rat
sciatic nerve. Knowledge of such changes provides an additional means by which to compare alternative approaches to nerve regeneration in this animal
model with a view to developing implantable devices which restore mechanical integrity along with conductional functionality.
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