Nerve injuries may involve the major nerves of the arm and forearm, the median, ulnar and radial nerves, and also the smaller nerve branches in the hand and fingers, the digital nerves. Nerves are very delicate structures and while a nerve can of course be injured by a laceration, injury may also occur as a result of a 'crush' type injury or contusion; in the later two situations, the nerve is not divided, but function may be completely lost.
A careful examination, testing sensation (feeling) and the function of muscles in the hand / upper limb will identify which nerve has been damaged, and the level along the nerve that this has occurred (if this is not obvious from the site of a wound). In some cases a nerve test is required to determine the severity of a nerve injury and predict whether it will recover without surgical intervention.
When a laceration has occurred in the vicinity of a nerve and the nerve is clearly not functioning normally, surgical exploration is required. There is often damage to other structures such as tendons, blood vessels and muscles as well as the nerve. Exploration involves making an incision long enough to properly see the nerve and adjacent structures and repairing these if they have been damaged. Repair of nerves requires miocrosurgical skills; a microscope or high powered loupes (magnifying surgical glasses) is used; the stitches are far finer than a human hair for repairing a digital nerve. This surgery is exacting and should only be done by someone with microsurgical training who frequently does this type of work. A good result from a nerve repair will only occur if it has been done meticulously.
After surgery a protective splint is usually worn to protect the healing nerve.
A nerve in some ways functions like an electric wire, passing signals along the very fine nerve fibres. The difference is that if an electric wire is repaired, it will immediately work again; this does not happen with a nerve. The outer sheath (equivalent to the plastic around the wire) is repaired by the surgeon; the nerve fibres then have to re-grow from the point that the nerve has been cut. This is a very slow process, nerve fibres grow perhaps 1mm per day! It is very important, while an injured nerve is recovering, to make sure that joints remain supple, and (in the case of the larger nerves in the arm and forearm) that muscles are strengthened as the re-growing nerve fibres reach them. This involves a hand therapy programme that my expert therapists will provide.
Digital nerve injury
The most commonly injured nerves are the digital nerves in the fingers or thumb. The digital nerves function is to transmit information about what the fingers are touching to the brain. There are two digital nerves to each finger that pass along either side of the finger and are responsible for the feeling on that side of the finger or thumb. A laceration to the finger may cut the digital nerve and this will cause altered feeling or numbness on that side of the finger, particularly the pulp (pad) of the finger. It is important to have good feeling in the tips of the fingers – to perform delicate tasks, and to know if something hot or sharp is being touched.
Digital nerve injuries are in most cases explored under local anaesthetic as a day case procedure. A soft dressing (in some cases a plastic splint) is worn for about 10 days after surgery, then the hand can start to return to light use.