Nerve autografts have long been considered the “gold standard” of treatment in peripheral nerve injuries spanning >3 cm in length due to their efficacy in promoting regeneration and the return of function.  But autograft use is not without difficulties.  The critical drawback is that once a nerve is cut, there will be no more input to any structure distal to that lesion.  This simple fact limits the pool of donor nerves that the surgeon can draw from as there is little “collateral innervation” to the various structures in the human body.  To make matters more complicated, the donor nerve also needs to have a matching diameter as well as the same number of fascicles to the injured nerve.  If any of these criteria are mismatched, the repair may fail or have suboptimal function.  This creates need for a better alternative, and one that has been promoted strongly by surgeons is the conduit.

A conduit is defined as natural or artificial channel through which something is conveyed.  In the context of peripheral nerve repair, researchers and physicians alike hope that something will be a regenerating nerve.  Conduits are currently in use for peripheral nerve lacerations spanning <3 cm and seem to have an equal effect as autografts used in the same degree of damage.  However, currently they are not as effective as autografts in separations >3 cm.2  One hypothesis for this decreased efficacy is that since the currently-FDA-approved conduits do not provide an environment that promotes nerve cell and tissue regeneration due to a lack of biologically friendly materials.  What our research project seeks to accomplish is to develop a conduit with regeneration-promoting biomaterial in order to facilitate regrowth across distances greater than >3 cm with an end goal of around 10 cm.  The biomaterial we have chosen is magnesium for a couple reasons.  First is that we want a material that is biodegradable to eliminate the need for a second surgery to remove the graft and to minimize the amount of foreign substance (such as silicone) being inserted into the body.  Second is that other materials that take longer to be absorbed by the body can cause inflammation which would hinder the regeneration progress of the injured tissue.5

The ground work for this project has already been set, with several proof-of-concept papers already published by our lab. One demonstrates that implanted conduits made of poly(caprolactone) (PCL, a biomaterial) and the regenerated nerves associated with them can be imaged with micro-CT, meaning that progress can be visualized.  Another shows that magnesium appears to be very effective in promoting nerve regeneration in rat peripheral nerves with minimal side effects, though regain of function was not directly studied. This was done by microsurgery to cut the rat sciatic nerves to a separation of about 2 cm (a distance proportional to about the 10 cm that we are hoping to achieve in future human trials), implanting the magnesium conduits, and giving the rats 6 weeks to recover.  Afterwards, nerve regrowth was imaged with micro-CT with promising results.  Regain of function was not directly studied, but muscle mass distal to the lesion was studied and the magnesium device was seen to have greater muscle mass than compared to other conduit materials.5

Currently, this project is in the process of gathering data more points using the discussed experimental design to give our study more power.  Future goals of this project are to quantify the regain of muscle function.  The results currently seen are extremely promising and we hope they will help further the field’s exploration of magnesium-based nerve conduits and we are optimistic that the use of magnesium conduits in peripheral nerve repair will become a leading method in the operating room.