The human hand has an extremely complex structure and offers numerous directions of movement to serve as a universal tool for our everyday life. The clenching of the fist, the careful picking up of a small object with two fingers, the strong grasping of the bicycle handle - our flexor tendons are responsible for all these movements.
Falls, bruises or deep cuts can result in an injury to the flexor tendons , which immediately severely limits hand function. This article deals with the anatomical significance of the flexor tendons, what happens when a tendon is ruptured and how a flexor tendon injury can be treated surgically and then therapeutically.
Hand Anatomy of the Flexor Tendons
The flexor tendons of the hand run along the underside of the forearm through the carpal tunnel and then radiate out to the fingertips. They transmit the force from the flexor muscle in the forearm to our fingers and thumb. The tendons are made of very tensile connective tissue and have a long healing time.
The thumb has one flexor tendon, the other fingers have two - one superficial and one deep. The deep flexor tendon flexes the last phalanx, while the superficial flexor tendon moves the middle joint between the first and second phalanx. The deep flexor tendon passes through the superficial one - which divides at the level of the first phalanx and then reattaches to the last phalanx.
The flexor tendons of the fingers: the superficial (turquoise) and deep flexor tendon (blue) run together. The tendons are surrounded by a tendon sheath that protects them from friction with the surrounding tissue. You can think of it like the cable in a bicycle brake: the brake cable is pulled through a tube that protects it from dirt, friction and erosion. In order for the cable or our tendon to slide through the tendon sheath without resistance, the sheath secretes synovial fluid.
The tendon with its tendon sheath is attached to the finger bones by ring ligaments . This ensures the guidance of the tendon along the finger even under tension. If the ligaments were missing, the tendon would move away from the finger when bent - it would look like the tendon of a taut bow.
Without the annular ligaments (blue) the flexor tendon would move away from the bone - the bowstring effect Torn flexor tendon - what to do in case of a flexor tendon injury on the finger
A flexor tendon tear occurs, for example, in the event of a fall in which the hand is very strongly overstretched in the direction of the back of the hand. More often, however, flexor tendon injuries result from deep cuts caused by knives, saws, an animal bite or falling into a shard. Crush injuries can also be associated with a flexor tendon rupture .
A deep cut on the finger or a suspected flexor tendon injury are emergencies and must be medically examined as soon as possible!
Whatever the cause of the injury, if you have a deep, gaping cut or suspect that flexion of one or more fingers may be restricted, seek urgent medical advice. Injury to a tendon is a medical emergency ! The sooner the remaining tendon stumps can be rejoined, the better the chances of healing.
In the case of a deep cut, a flexor tendon injury is suspected. Symptoms: How can I tell if my flexor tendon is injured?
If a flexor tendon is injured , flexion of the affected finger fails and it remains in an extended position. The muscle force can no longer be transferred to the bone in a movement. In an uninjured hand, the fingers form an even arc when the fingers are held in a relaxed position. If one of the fingertips falls out of line, there may be a tendon rupture.
Unlike the thumb, the fingers each have two flexor tendons. If the deep flexor tendon is injured, the finger end phalanx can no longer be actively flexed and remains in the extended position. However, a failure of the superficial tendon is often overlooked, as the deep tendon can partially compensate for the superficial tendon.
If a finger remains in the extended position, a flexor tendon injury may be the cause. But even if flexion is still possible, there may be a hidden injury to the superficial flexor tendon.
If both tendons are torn, both the end joint and the middle joint can no longer be bent. However, the metacarpophalangeal joint can still be bent even if both tendons are severed, as this movement is carried out by the muscles of the metacarpus.
How is an injury to the flexor tendon diagnosed?
If a flexor tendon injury is suspected, you should always seek medical attention. For an exact diagnosis, the individual joints are checked for their ability to bend and extend. In the case of a cut, the severed tendon may be directly visible in the wound. An X-ray image can clarify any bone injuries that may have been associated with the accident.
An incomplete transection is particularly difficult to identify because the bending function may still be preserved. If you want to be sure, an enlargement of the wound under local anaesthesia is necessary to be able to visually assess the condition of the tendon.
Flexor tendon surgery on the thumb or finger
Ideally, the operation is performed within the first 12 hours after the injury . The remaining tendon stumps are rejoined with a tendon suture . If a few days or even weeks pass between the rupture and the operation, a tendon suture is usually no longer possible. To regain the bending function, the much more complex tendon transplantation must be considered.
Every hour counts in flexor tendon surgery on the finger or thumb: the sooner the tendon is sutured, the better.
If there is a particularly large injury with heavy involvement of the surrounding nerves and blood vessels, a tendon suture is sometimes not possible. The surgeon may decide to perform the operation only after the wound has healed. Since the time window for a tendon suture has already passed, a tendon transplantation is performed: in a first operation, a silicone rod is inserted into the finger, around which the body forms a sliding channel. This is the replacement for the tendon sheath. In a second operation, the rod is removed again, a suitable tendon is taken from another part of the body and transplanted into the finger.
Flexor tendon physiotherapy - follow-up treatment after surgery
After surgery on the torn flexor tendon in the finger, the hand is usually placed in a Kleinert splint for six weeks: the hand is fixed in a flexed position so that the injured tendon is subjected to as little tension as possible. In addition, a rubber band is attached to the fingernail of the affected finger, which takes over the bending of the finger. This allows the tendon to heal while active stretching remains possible.
After six weeks, the splint can be removed, but the injured fingers must not yet be fully loaded. Twelve weeks after the injury, the operated flexor tendon is usually ready for use again.
Finger exercises are possible in the Kleinert splint: active stretching prevents adhesions. Moderate but regular movement is of enormous importance during the healing phase. Follow-up treatment in a hand therapy practice should be started as soon as possible after the operation - ideally within a few days. If there is insufficient movement, the tendon sheath secretes less synovial fluid and the passage of the tendon is impeded. The resulting adhesion must be prevented at all costs, as it is associated with long-term movement restrictions .
Only when the tendon regularly slides through the tendon sheath is sufficient synovial fluid secreted. In addition, since the accident rarely only injured the tendon, but all the surrounding tissue is in the healing process, adhesions between the different types of tissue can occur. These would also restrict the full range of movement after healing and can be prevented by specific exercises. Hand injury patients should follow the therapy plan as closely as possible to avoid both insufficient and excessive training.
Regular, controlled exercise is important to prevent adhesions and adhesions. Patients should follow their therapist's exercise plan.
In the case of adhesion or adhesions, another operation, tenolysis , may be necessary. This involves removing the surrounding tissue from the tendon with a scalpel. Since this second operation is followed by a renewed healing phase with the formation of more scar material, tenolysis is not always successful.
Daily training under therapeutic guidance in the splint and later with the free fingers is therefore of great importance in order to be able to restore the range of motion from before the injury. The motivated cooperation of the patients is required here: the therapy hours in the physiotherapy or occupational therapy practice are not sufficient, but independent training several times a day is also necessary at home.
Flexor tendon injury: what are the chances of complete healing?
The prognosis for flexor tendon injuries in the hand is very positive, but depends on some very important factors:
These 6 factors influence the prognosis for flexor tendon injuries:
The motivation of the hand-injured person to follow the training and therapy plan closely Time of surgery : the earlier the better, ideally 12 hoursStart of hand therapy after surgery: the sooner the better, ideally a few daysAge and state of health of the patientType of injury : a crush injury with heavy tissue involvement is more difficult to heal than a clean cut injury Family environment: support in everyday life and in the implementation of the therapy programme have a positive effect
We see: When it comes to healing flexor tendon injuries , the most important factors are speed of treatment and motivated cooperation on the part of the patient. If there are no complications, the full range of motion of the finger can be regained - and a strong grip is possible again.
Frequently asked questions
How does a flexor tendon injury occur in the finger?
A deep cut from a knife, saw or falling into a shard can sever a flexor tendon. An animal bite or a crush injury can also cause the injury. If you fall and hyperextend your hand strongly towards the back of the hand, a tendon rupture can also occur.
How do you recognise a flexor tendon injury?
If a flexor tendon in the finger is severed, it can no longer be actively flexed and remains in the extended position. However, incomplete tears or rupture of the superficial flexor tendon may remain undetected because the flexion movement does not completely cease.
What to do if a flexor tendon is torn?
A flexor tendon injury is an emergency because suturing of the remaining tendon stumps must be done as soon as possible. Therefore, if there is a large cut or a suspicion that a rupture may be present, medical advice should be sought urgently.
What is important in healing?
In the healing phase after a tendon suture or tendon transplant, regular therapy and training according to plan is one of the most important factors in restoring the original range of motion. This is where the patients' motivation is needed, as therapy sessions alone are usually not enough.
This article deals with a health topic, but is not suitable for self-diagnosis or the selection of a suitable therapy. The individual case can only be reliably diagnosed by medical expertise.
Sources
Waldner-Nilsson (ed.) (2013): Hand Rehabilitation. Volume 1 Fundamentals, Diseases. Heidelberg / Berlin: Springer-Verlag.
Schmidt, H-M. / Lanz, U. (1992): Surgical Anatomy of the Hand. Stuttgart: Thieme.
