Flexor Tendon Injuries

　　Tendon injuries in the hand are mostly open, with more traumatic factors such as cuts, and there are also electric saw injuries, crush injuries, etc., mostly caused by tendon rupture, resulting in corresponding symptoms. Among them, the surrounding tissue of the crush injury is severely contused, often accompanied by nerve, vascular, and bone and joint injuries, and attention should be paid to treatment.

　　This disease often occurs with nerve and vascular injuries or bone and joint injuries, and can also occur with closed tears, especially in patients with crush injuries, these complications are more likely to occur. Generally, after the rupture of the tendon, the corresponding joint will lose its function of movement. In addition, after surgery, this disease is also prone to the adhesion of tendons. Tendon nutrition, tendon healing, and tendon adhesion are a causal relationship. The more severe the destruction of tendon nutrition, the slower the tendon healing, and the more serious the adhesion will be, even leading to the collapse and atrophy of the sheath.

　　The main manifestation of this disease is the functional impairment of the corresponding region of the damaged flexor tendon:

　　1. The superficial flexor digitorum profundus tendon is ruptured, and the proximal interphalangeal joint of the corresponding finger cannot be flexed.

　　2. The flexor digitorum profundus tendon is ruptured, and the distal interphalangeal joint cannot be flexed.

　　3. Both the deep and superficial flexor tendons are ruptured, and the distal interphalangeal joints on both sides of the fingers cannot be flexed.

　　Since the intrinsic muscles of the hand are intact, the flexion of the metacarpophalangeal joints is not affected.

　　The prevention of flexor tendon injuries should pay attention to safety in production and life, avoid trauma, and ensure personal safety, which is the key to the prevention of this disease. In addition, it is also necessary to note that early functional exercise can promote endogenous healing and is an effective measure to prevent tendon adhesion. Early postoperative active extension and passive flexion movements can not only stimulate the maturation of the tendon wound and promote healing but also promote the early longitudinal arrangement of new fibers, which is conducive to the reshaping of the tendon scar, reduce the collapse and atrophy of the sheath, and accelerate the secretion of synovial fluid.

　　The diagnosis of flexor tendon injuries in clinical practice is not difficult. Based on the patient's history of trauma and the functional manifestations of the affected area, a diagnosis can generally be made without the need for other auxiliary examination methods. For some patients with incomplete tendon rupture, joint movement can appear normal, and resistance tests can be performed at this time, which are characterized by weakness and pain in the limbs and fingers, thereby making a diagnosis and adopting corresponding treatment methods.

　　Patients with flexor tendon injuries should eat more high-protein foods such as soybeans, lean meat, and at the same time, eat more calcium-rich and vitamin-rich foods such as milk, vegetables, and fruits, and eat less spicy and刺激性 foods.

　　The treatment of this disease varies according to the different injury regions.

　　1. Deep flexor tendon insertion area (Area I)The I region extends from the middle of the middle phalanx of the finger to the deep tendon insertion point. This region only contains the flexor digitorum profundus tendon, and early repair should be sought if it is ruptured, with direct suture of the ends. If the rupture occurs within 1 cm of the insertion point, the tendon end can be moved forward, that is, the distal segment is cut off, and the proximal end is re-attached to the insertion point.

　　2. Sheath Area (II Region): The II region extends from the beginning of the sheath to the attachment of the superficial flexor muscle of the finger (i.e., the middle of the middle phalanx). In this section, the deep and superficial flexor tendons are confined in a narrow sheath, and they are prone to adhesion after injury, which is difficult to treat and has poor results, hence the name 'No Man's Land'. Currently, it is generally advocated that if only the superficial flexor muscle tendon is pulled and ruptured, it should not be anastomosed to avoid adhesion; if both the deep and superficial tendons are ruptured simultaneously, only the deep tendons should be anastomosed, and the superficial tendons should be excised, retaining the sheath and pulley.

　　3. Palm Area (III Region): The III region extends from the distal side of the transverse ligament to the area where the tendons enter the sheath. On the radial side of the deep flexor tendons in the palm, there are lumbrical muscles attached, which limit the retraction of the proximal tendons after rupture. If both deep and superficial tendons are ruptured in the lumbrical muscle area, they can be anastomosed simultaneously, with the lumbrical muscles wrapping the deep tendons to prevent adhesion with the superficial tendons. From the lumbrical muscle to the sheath segment, only the deep tendons are anastomosed, and the superficial tendons are excised.

　　4. Carpal Tunnel Area (IV Region): Nine tendons and the median nerve are compressed in the carpal tunnel, with a small space. The median nerve is superficial, often injured simultaneously with the tendons. When treating, the transverse carpal ligament should be incised, only the deep tendons and the flexor pollicis longus tendons should be sutured, the superficial tendons should be excised to increase the space, and the median nerve must be anastomosed. The anastomotic site should not be on the same plane.

　　5. Forearm Area (V Region): The V region extends from the origin of the tendon to the proximal end of the carpal tunnel, that is, the lower 1/3 of the forearm. The flexor tendons in this area are protected by peritendinous tissue and surrounding soft tissue, with less chance of adhesion. If the flexor tendons are injured in this area, they should be sutured in full stage I, which usually has a good effect. However, when multiple flexor tendons are ruptured, it is necessary to avoid matching at the same level to reduce adhesion.

　　The rupture of the flexor pollicis longus tendon should also strive for stage I repair. At the level of the metacarpophalangeal joint, the tendon is trapped between two sesamoid bones, which is prone to adhesion. The rupture at this level does not directly suture the tendon, but resects the distal end, performs a tendon lengthening at the wrist, moves the distal end forward, and reattaches it to the insertion point. It is also possible to transfer the flexor digitorum profundus tendon to replace the flexor pollicis longus tendon. For ruptures within 1 cm of the insertion point, the method of anterior transfer of the tendon is usually adopted, but the tendon is not lengthened.