Muscles generally insert into bones through tendons. Tendons have the ability to glide over bone and through tissue – and they are generally placed into two main categories, flexor and extensor. Flexor tendon injuries are classified into five zones: I through III include areas of the hand; IV consists of the wrist; and V involves the forearm.
Flexor tendon injuries have less impact on hand function, because there are several others to assist when one is damaged. But, there is only one extensor tendon responsible for the function of the second through the fifth finger, therefore an injury to this tendon has greater impact on hand function. These injuries are classified into eight zones – zones I through VI involve various areas of the hand, zone VII involves the wrist and multiple tendons, and zone VIII are injuries located in the distal forearm.
Tendon injuries are common and usually caused by accidents or high stress activity. In “open injuries,” glass or knives are usually involved. And “closed injuries” are often caused by sports that overstress the tendons without disrupting the skin.
The complete detachment of a tendon results in the loss of its function, which can be permanent if not repaired. Patients are usually aware when a tendon becomes detached and will experience difficulty moving a finger and pain when trying to use the tendon.
Understanding the activity that resulted in the tendon injury is important for a thorough assessment of the affected tendons and the extent of the damage. Once patient history is established the position of the injury (if a cut), the posture of the hand at rest, as well as passive and active movement are examined. In assessing passive movement, gentle pressure applied to each fingertip or the muscles in the forearm can identify a loss of tension or weakness of a joint. Also moving the wrist, which prompts finger movement, will indicate areas of weakness. In assessing active movement, patients are asked to use the tendon and affected joint while abnormalities are noted.
Treatment for tendon injuries depends on the zone classification and extent of the injury – and can consist of splinting, the use of absorbable sutures, or hand surgery.
Flexor tendon lacerations should be repaired within 12 hours of the injury, though it is possible to splint with the fingers flexed for delayed repair – up to four weeks. Particular care is taken in the repair of these tendons because the synovial sheaths increase the risk of infection.
Extensor tendon lacerations require special attention during surgical repair, because they often retract into the hand when they are cut.
Rehabilitation is an important part of any treatment for tendon damage. Following a tendon repair there is a risk that the repair adheres to the surrounding tissues – preventing the tendon from gliding properly. In order to avoid this, protected mobilization is used in conjunction with a series of exercises specific to the injured area.
Recovery and return to work depends on the severity of the injury and type of work. It can range from six to 12 weeks.