The nerves of the hand are bundles of nerve fibers of the peripheral nervous system, peripheral nerve axons, both myelinated and unmyelinated nerve fibers; the myelin sheath is not part of the neuron, it is composed of Schwann cells, each nerve fiber node is surrounded by a Schwann cell; the myelin sheath is regularly spaced into discontinuous knots called Ranviernode ( Ranviernode.) It allows for faster transmission of signals from the nerve.
I. Types of nerve injury
Seddon (1944) described three types of clinical nerve injury.
(a) neuropraxia: the nerve is temporarily blocked, paralyzed incomplete, there will be temporary impairment in function, but no evidence of nerve degeneration can be seen under the microscope, usually within a few weeks can be recovered quickly and completely. Stress is the most common cause of this injury.
(b) Axonal disruption injury (axonotemesis): The axon is injured/broken, but the surrounding connective tissue sheath retains its integrity and wartime degeneration occurs in the periphery. It usually takes several months for function to return. Compression injuries, traction, and compression are the most common causes.
(iii) Nerve dissection (neurotemesis): The nerve trunk is completely severed, which is the most severe nerve injury. It requires surgical repair and suturing before it can slowly regenerate and gradually regain function, but it takes longer.
Second, the surgical management of hand nerve rupture injury and operational treatment
Nerve ruptures in the hand can be classified as complete and partial lacerations; strains and contusions can also accompany lacerations. After nerve amputation due to trauma or other causes, nerve suture surgery (microsurgery) must be performed under a high-powered microscope. Four common nerve surgery suturing techniques include severed end suture, nerve bundle suture, nerve graft, and nerve canal splicing. In “dissection suture”, the two severed ends of the injured nerve trunk are flattened, and then the nerve epithelium and blood vessels of the two severed ends are aligned, and sutures are passed through the nerve epithelium of the two severed ends to close them. If the nerve bundles in the injured nerve trunk are sutured together with a microscopic technique, it is called “nerve bundle suture”. These two techniques are only applicable to damaged nerves with short fracture lengths. If the nerve break gap is larger, nerve grafting or neural tube splicing should be considered. A “nerve graft” is a procedure in which a segment of the nerve is taken from the nerve’s own body and grafted to the severed nerve site. “Nerve canal splicing” is a procedure in which a circular tube made of biomedical material is sewn into the severed ends of the nerve to guide and support the growth of the regenerated nerve fibers, while keeping the cells and secretions that hinder nerve regeneration outside the tube.
After the nerve is joined, the nerve fibers start to follow the path of the original nerve fibers and grow remotely at a rate of about 1mm per day. The regeneration of the nerve after joining varies from person to person, and the final result may not always be satisfactory. A neuroma is a mass of nerve fibers formed after a nerve injury, which can be painful when tapped or touched, or even “hypersensitive”, thus affecting the willingness of the patient to perform functional activities with the injured hand. Excessive growth of scars in the area of the suture may also prevent the nerve fibers from growing remotely.
After the nerve has been surgically sutured, the sensory axons would theoretically regrow and innervate the epidermal receivers over time. However, the regenerated sensory nerve axons may not be complete, resulting in some nerve fibers and receivers not regaining their original function or having abnormal function (hypersensitivity). Parry first proposed “sensory re-education” in 1966, and Dellon proposed “highly constructive sensory re-education” in 1974, dividing the program into early and late training, with the early phase based on vibraesthesia, the late phase on dynamic proprioception, and the late phase on sensory reactions. Both Parry and Dellon used stimulus localization and object recognition, focusing on the stimulus through visual cues, and when visuals were obscured, memory was used to achieve high cortical integration, with cases compensating for missing sensations by improving specific skills and generalizing to other sensory stimuli.
An important element of sensory reeducation is daily repetition, and many studies have shown that “sensory reeducation” is better in highly motivated cases. All programs emphasize repeated stimulation of the sensory receptors using a variety of different stimuli. The common training method is to first close the eyes (try to recognize the contact), then open them (see if the recognition is correct), and then close them again (if not correct, start again). In the training process to provide feedback, the length of training time must be limited to avoid excessive fatigue and excessive frustration. To prevent secondary injuries, training objects must not be potentially dangerous to non-sensory areas (e.g., sharp, temperature). In addition, home treatment programs should be provided to enhance learning during the treatment period.
”Desensitization” therapy is a treatment method to improve the threshold of sensory receptors and reduce the symptoms of hypersensitivity in cases with sensory hypersensitivity. The training method is different from “sensory reeducation” in that it uses the same training objects, but does not require the process of closing the eyes, and the order of using the training objects is different. The order of selecting the objects for “desensitization” treatment is from small to large sensitivity, while the order of selecting the objects for “sensory reeducation” is from large to small stimuli.
The following is a more detailed treatment for the three nerve disruptions in the hand.
(A) MedianNerveLesion
A tear of the median nerve at the wrist will result in low median nerve paralysis, affecting the innervated paired metacarpophalangeal muscles, abductor digiti minimi, index finger and middle finger earthworm muscles. Injury at or near the elbow affects the flexor digitorum profundus, all flexor digitorum superficialis, pronator teres, and pronator teres of the middle and index fingers, resulting in motor impairment.
The median nerve is the most important sensory nerve, which causes loss of movement of the thumb, index finger, middle finger, and radial side of the ring finger, so the injury can seriously affect hand function. In terms of movement, due to the lack of innervation of the abductor digiti minimi muscle and the opposite palmar thumb muscle, the interphalangeal muscle of the palm is atrophied and flattened, making it impossible to perform opposite palm movements. In this case, a shortopponeussplint can be used to maintain the thumb in an abducted palmar posture, so that the patient can have enough webspace when grasping in the future.
After a median nerve tear, motor recovery is earlier than sensory recovery. The purpose of teaching the patient to perform passive movement mobility is to maintain the mobility of the joint, such as maintaining the forearm rotation forward movement and thumb mobility. While waiting for sensory recovery, compensatory methods can be used, such as: visual cues, adaptive equipment to match the environment, grip adjustment, etc., to avoid injury and improve menu present.
(B) Ulnar nerve damage (UlnarNerveLesion)
If the ulnar nerve is damaged in the place of low ulnar nerve (such as: wrist), the sensation of the ulnar side of the ring finger and little finger will be lost, and the innervated inward little finger muscle, flexor little finger muscle, and the little finger muscle of the palm will be affected, thus losing the ulnar transversemetacarpal arch (ulnartransversemetacarpalarch), and making the palm surface of the hand flat; the dorsal and palmar interosseous muscles are not innervated because The dorsal and metacarpal interosseous muscles are not innervated, so there is no finger abduction or adduction; the earthworm muscles of the ring finger and little finger are affected and cannot be flexed at the metacarpophalangeal joint, so when the extrinsicextensor contracts, the metacarpophalangeal joint is over-extended and the interphalangeal joint is flexed, resulting in a clawhand, which also affects the fine motor skills.
Treatment methods are.
(1) Wearing anti-clawhand paraplint (MPblockingsplint) to maintain the metacarpophalangeal joints in a slightly flexed position to avoid over-extension of the metacarpophalangeal joints and pulling on the intrinsic muscles of the ring and little fingers.
(2) Teaching the case compensatory methods for sensory loss to avoid secondary injuries.
(3) Maintain passive mobility of the metacarpophalangeal joint under interphalangeal bone extension, taking care not to cause flexion contracture of the proximal interphalangeal joint. (Figure 4)
If the damaged ulnar nerve is injured near the high ulnar nerve (e.g., at the elbow), the flexor digitorum profundus and ulnar flexor carpi radialis of the ring and little fingers, which are innervated by it, will be affected. Although the claw-like hand of the ring and little fingers is less pronounced, it is important to note that the intrinsic muscles are affected so that they are unable to perform palmar movements. The treatment is the same as for low level ulnar nerve damage. However, if the flexor digitorum profundus is unable to perform the movement, it is necessary to teach the patient how to maintain the passive mobility of the interphalangeal joints of the ring and little fingers to avoid contracture.
(C) Radial Nerve Lesion
The radial nerve innervates the extensor muscles of the hand, and depending on the location of the injury, different extensor muscle groups will be paralyzed, and the wrist will drop, the thumb and fingers will drop, and the metacarpophalangeal joints will not be straightened, and other dropand phenomena will occur. Injury to the deepmotorbranch of the radial nerve is called posterior interosseous nerve palsy, and the function of the brachioradialis and radial extensor carpi radialis longus is usually unaffected. When the wrist is strained to straighten, there is a strong radial deviation of the wrist. This can affect the metacarpal and interphalangeal joint extension movements, as well as the ability to feel the back of the hand against the radial side. High radial nerve injury is often seen in cases of humeral fractures because the radial nerve courses from the back to the front of the humerus and is easily stretched when the humerus is fractured. This results in loss of sensory ability on the back of the hand against the radial side, and loss of function of the triceps muscle, but loss of function of the posterior rotators and wrist and finger extensors.
It is important to maintain the mobility of the joint during the recovery period while waiting for nerve regrowth or reconstructive surgery. Treatment involves maintaining wrist extension and avoiding a drooping wrist posture by using a static parapod, such as a vertical wrist parapod, with the wrist positioned at 30 degrees of extension and the fingers unrestricted. Another option is to wear a dynamicsplint, which lifts and straightens the wrist, fingers and metacarpophalangeal joints of the thumb, i.e., using a dynamicsplint device to open the fingers so that they can engage in functional gripping and grasping movements. This is an effective way to provide early functional hand movements for those who have to wait for a long period of nerve re-growth.
III. Conclusion
Nerve ruptures in the hand caused by external tears or lacerations usually require surgical repair by a hand surgeon in the visible position. For physical therapy, electrical stimulation can be used to prevent muscle atrophy. Moderate heat and physical therapy can promote blood circulation around the affected area and reduce local swelling and pain. During the rehabilitation process, appropriate paramedical support and exercises are used to maintain proper posture and maintain joint mobility to avoid twinning. Once the nerve growth is confirmed, the muscle strength, sensory and manipulative functions of the hand can be restored to a significant degree by following an appropriate sensory and motor training program.