Peripheral nerve damage, usually caused by trauma or the surgical removal of tumours, can result in severe disability. As nerve cell regeneration is inefficacious, any sensory or motor deficits resulting from such damage is therefore likely to persist.

However, the human amniotic membrane (HAM), a by-product of birth which has biological characteristics that make it an ideal natural scaffold, can make a decisive contribution to repairing peripheral nerves by promoting and modulating axonal regeneration. Easy to harvest and store in tissue banks, the main clinical application of HAM is the repair of peripheral nerve damage characterised by tissue loss, i.e., a wide break in the nerve, a condition that traditionally prevents proper axonal regeneration.

HAM can be used in place of nerve grafts, which are plagued by limited availability, the inevitable sensory deficits inflicted on the donor area, and poor functionality, especially in motor or mixed nerves and axonal breaks over 3 cm long.

SURGICAL TECHNIQUE: AMNIOTIC MEBRANE TUBULE AND SKELETAL MUSCLE GRAFTS

During the operation, the two broken ends of the damaged nerves are surgically exposed so that the length of the gap can be assessed. A suitably large section of skeletal muscle is then taken from the damaged area via an incision parallel to the direction of the muscle fibres. The excised muscle segment is then cut into several small sections, compatible with the gap in the nerve, and either fresh or dehydrated/lyophilised (freeze-dried) human amniotic membrane (HAM) is applied.

Fresh HAM can only be used in scheduled operations, as it needs to be requested from the tissue bank at least two days in advance, but dehydrated/lyophilised HAM is on hand in the operating theatre, and can therefore also be used in emergency surgery. In this case, the required amount of HAM is re-hydrated by immersing it in physiological solution (saline), and, once ready for use, it can be rolled into a tube around the muscle fragments and stitched together so that the pieces of muscle are equidistant. The stitching is performed using an optical magnifying glass, together with sutures and tools suitable for microsurgery. Sutures are generally not required along the length of the HAM tubule, which sticks together firmly by itself, but it is essential to fix the tubule to each broken end of the damaged nerve; two stitches on the posterior (back) wall and two on the anterior (front) wall are generally sufficient.