Flexor Tendon Injury
The anatomy of the palm is complex. Each individual finger is bent using two flexor tendons; one deep and one surface. The fingers’ flexor tendons in the palm run through tunnels called tendon sheaths. These sheaths have a mucous-like lining that allows the tendons to easily glide through them. Additionally, the tendons are rigged through a pulley system on the bones that enables them to keep their intended path when under tension. After an injury, the flexor tendons tend to adhere to their sheath, which adversely affects their function. Therefore, special surgical techniques are conucted and considerable attention paid to aftercare following such an injury.
Indicative of tendons being involved in a hand injury is an unnatural stretching of the finger. Depending on the extent of injury, the patient may no longer be able to bend the middle or end finger joints actively. In such a case, immediate surgical suturing of the tendon is strived for. In cutting injuries, even if the size of the wound itself is minimal, all underlying and neighbouring structures should either be clinically or intraoperatively verified as clearly uninjured.
In order to prevent tendons adhering to their sheaths after suturing, the tendons must be made mobile soon after surgery. However, at the same time, the tendons are not able to take any weight or load and in practice 10% of cases will tear again if prematurely put under stress. Bending of the finger without active pulling on the tendons is therefore carried out post-operatively using various principles as follows:
Kleinert Dynamic Splinting
One option is the aftercare of the operated finger using a Kleinert dynamic splint. Using this, the wrist joint is held in a lightly flexed position in a plaster splint and the finger is held in mid-flexion by elastic attached to the fingernail. If the patient actively extends the finger, then the elastic will pull the finger to its original half-flexed position without the patient using force. The use of the splint should begin on the first day post-op and extension should be limited to the constraints of the splint. It is important that the patient regularly releases the finger from the elastic during the day and especially during the night otherwise flexion contracture of the affected finger can occur, which is difficult to rehabilitate.
Early active motion
A further mobility option is called "early active motion", in which the patient learns under guidance, and with the wrist joint in a relief position, how to actively and carefully steer the tendons in order to mobilize them without load.
An additional form of therapy is called "passive motion", in which the tenodesis effect of the wrist is exploited in order to induce passive mobilisation of the finger. When we gently lift our wrist up (extend it), the fingers naturally curl and when we flex the wrist, the fingers naturally stretch. In this way it is possible to achieve good gliding of the tendons without putting them under stress.
It is rare for the finger to be passively moved solely by the physiotherapist or patient. Should these exceptional circumstances arise, the healthy fingers must also be brought into flexion in order to prevent tension on the tendons.
The patient's cooperation during post-operative care is crucial for the success of the surgery. If, despite intensive post-operative physiotherapy, the tendons show signs of adhesion, then this can only be surgically eliminated 3-6 months later in a procedure called tenolysis. Any load on the tendons will be only possible 6 weeks at the earliest after suturing. The tendons are usually fully functional under load after approximately 3 months.
Two-Stage Tendon Grafting
If direct suturing of the tendon is not possible, and if both flexor tendons in a finger or if the long flexor tendon of the thumb is also torn, other methods of flexor tendon reconstruction are turned to. In a tendon graft, a tendon from the calf or forearm is transplanted in the hand and sutured to the stump of the torn tendon and fixed through the bone (transosseous) at the distal phalanx of the finger (fingertip), or sutured to both torn stumps (single stage tendon graft). The results, however, are not as promising as when there has been immediate suturing of a clean cut. This is because it is common for ruptures to occur at the repair sites and the chances of adhesion are increased, which leads to persistent incorrect flexion of the finger.
Because injury of the tendon sheaths or adhesion usually also exists, the reconstructive surgery is carried out in two stages. Initially, a silicone rod is implanted, which acts as a place holder for the missing tendon. Sheath-like tissue then builds around it over the next 6-8 weeks. After 2-3 months the tendon can be grafted as above into the newly formed canal created by the implant.
More on tendon injuries in
Hand Surgery at a Glance