Flexor Tendon Injury

　　The flexor tendons have deep and superficial groups, originating from the forearm, passing through the carpal tunnel, palm, and flexor sheath tube, and ending respectively at the base of the distal phalanx and the proximal ridge of the middle phalanx. The entire tendons are surrounded by loose connective tissue, which not only nourishes the tendons but also facilitates the sliding of the tendons in them, and is known as the peritenon or peritendinous tissue.

　　Tendons are the transmission devices of joint movement and an important link for the normal function of the hand. After the injury of the flexor tendons, hand flexion and extension function and other functions are often lost.

　　The causes of flexor tendon injury are mostly caused by cutting and piercing injuries.

　　Pathogenesis

　　After the external rupture of the tendon, due to the contraction of the muscle, the proximal end retracts, and can even retract very far, such as when the proximal phalanx is cut, the distal end can retract back to the palm. When the finger is injured, the finger often presents a flexed and gripping shape, and after the joint is extended, the distal end moves forward again after the injury, making it difficult to find both ends during surgery, and it is also difficult to repair. After suturing, due to tension, the sutured area may separate and form a gap, affecting healing.

　　It has been controversial whether the blood vessels that cannot be seen in the tendons can heal on their own like other tissues after being cut. The theory of exogenous healing dominated for a long time, which holds that tendons lack the ability to heal themselves and must be repaired by the surrounding richly vascularized tissues, allowing granulation tissue to grow into them. Especially in the sheath area, the sheath affects the growth of granulation tissue, and part of it must be removed to allow the tendon to heal. Scar formation leads to tendinous adhesion, which is an inevitable consequence after the repair of the tendons, affecting the sliding function of the tendons. Therefore, in the sheath area, especially in the II area, the initial treatment is limited to the repair of the surrounding skin and soft tissues, and late-stage tendon transplantation is used to reconstruct the flexion function of the fingers. If initial repair is to be done, it is limited to neat, non-contaminated cuts, removing part of the sheath, and excising the proximal palmar flexor tendon while suturing the deep flexor tendon to reduce adhesion and preserve the function of movement. If both the deep and superficial flexor tendons are repaired, the mutual adhesion will have a more serious impact on the function, resulting in the opposite effect.

　　The injury of flexor tendons is mainly caused by traumatic factors, and the diagnosis can be made based on the patient's history of trauma, clinical symptoms, and examination.

　　This disease often combines nerve and vascular injuries or bone and joint injuries, and can also occur in closed tears, especially in patients with compression injuries, where 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 prone to complications such as tendinous adhesion. Tendon nutrition, tendon healing, and tendinous adhesion are causal relationships; the more severe the destruction of tendon nutrition, the slower the tendon healing, and the more serious the tendinous adhesion will be. Even the collapse and atrophy of the sheath may occur.

　　Hand tendon injuries are mostly open, with incision injuries being more common. They often occur with nerve and vascular injuries or bone and joint injuries, and can also occur with closed tear injuries.

　　Clinical manifestations:

　　General symptoms of tendon injury include local pain, swelling, tenderness, and occasionally subcutaneous hemorrhage. If the tendon injury is severe or ruptured, the function at that location will be weakened or lost.

　　The main manifestation of flexor tendon injury is the functional disorder of the corresponding area of the injured flexor tendon:

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

　　2. The deep flexor tendon is ruptured, manifested as the inability to flex the distal interphalangeal joint.

　　3. Both the superficial and deep flexor tendons are ruptured, and both the proximal and distal interphalangeal joints cannot be flexed.

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

　　Division of flexor tendon areas:

　　Due to the special anatomical structure of the flexor tendons in different parts, the principles and methods of treatment are not the same. According to the Verdan classification, they can be divided into 5 areas.

　　I Area: From the stopping point of the superficial flexor muscle of the finger middle phalanx to the stopping point of the deep flexor muscle of the distal phalanx, for the thumb, it is from the middle of the proximal phalanx to the stopping point of the flexor pollicis longus tendon.

　　II Area: From the middle of the middle phalanx to the metacarpal neck, commonly known as 'no man's land' (no man's land).

　　III Area: 'Palm area', i.e., from the metacarpal neck to the distal edge of the transverse carpal ligament.

　　IV Area: Carpal tunnel area.

　　V Area: Forearm area.

　　The flexor pollicis longus tendon is also divided into 5 areas:

　　I Area: Attachment point of the flexor pollicis longus tendon.

　　II Area: From the proximal phalanx neck to the metacarpal neck, i.e., the sheath area.

　　III Area: Large thenar muscle area.

　　IV Area: Carpal tunnel area.

　　V Area: Forearm area.

　　The injury of flexor tendons is mainly caused by traumatic factors, and the diagnosis can be made based on the patient's history of trauma, clinical symptoms, and examination.

　　Therefore, in terms of prevention, attention should be paid to production and life safety, avoiding trauma, and ensuring personal safety is the key to preventing this disease.

　　In addition, it is important 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, while protecting the wound, can stimulate the maturation of the tendon wound and promote healing, and also promote the early longitudinal arrangement of new fibers, which is beneficial for the reshaping of the tendon scar, reducing the collapse and atrophy of the sheath, and accelerating the secretion of synovial fluid.

　　Hand tendon injuries are mostly open, with incision injuries being more common. They often occur with nerve and vascular injuries or bone and joint injuries, and can also occur with closed tear injuries.

　　The diagnosis of flexor tendon injuries in clinical practice is not difficult. Based on the patient's trauma history and functional manifestations at the affected site, a diagnosis can generally be made without the need for other auxiliary examination methods.

　　For patients with incomplete tendon ruptures, joint movement may appear normal. At this time, an anti-resistance test can be performed, which manifests as weakness and pain in the limbs and fingers, thereby enabling diagnosis and the adoption of corresponding treatment methods.

　　Patients with flexor tendon injuries should prioritize light and balanced diets.

　　This condition usually requires immediate surgical repair, and normal eating can be resumed within 2-3 days after surgery. The diet should be reasonable according to the patient's taste and avoid greasy, sour, and spicy foods.

　　In the later stage, it is appropriate to provide foods rich in collagen fibers, such as bone soup, cartilage, and milk rich in protein, which can promote recovery.

　　At the same time, the Chinese medicine advocated ox tendons and pork tendons cooked until soft and eaten with the meat also have a good effect on promoting the recovery of the disease.

　　During the treatment period, spicy and刺激性 food should be avoided, as well as alcohol.

　　The injury of flexor tendons is mainly caused by traumatic factors, and the diagnosis can be made based on the patient's history of trauma, clinical symptoms, and examination.

　　The treatment of this disease varies with the different areas of injury:

　　1. Tendon suture method

　　(1) Requirements for tendon suture:

　　① The suture method for tendon suture should be simple, practical, have good tensile strength, and have little impact on the blood circulation of the tendon ends.

　　② Abide by non-traumatic operation techniques, make the suture site smooth, and avoid long-term exposure.

　　③ Select non-traumatic tendon suture lines with good tensile properties and few tissue reactions. Tendon suture should use a round needle to reduce damage to the tendons.

　　(2) Tendon suture method:

　　① One-end suture method for tendon ends: Suitable for fresh tendon rupture suture, or suture of tendons with equal diameters.

　　A. Bunnell suture method: Sutured with double straight needles and polyester monofilament thread (3-0), as shown in the figure. This method is complex to operate and has an impact on the blood circulation of the tendons, and is now basically not used.

　　B、'8' shape suture method: Sutured with a single needle monofilament (3-0) thread, as shown in the figure. This method is simple to operate, but the tensile strength at the suture site of the tendons is weak.

　　C、Extraction wire method: Select 36#～38# wire or 5-0 non-traumatic wire tendon suture line, suture the near end of the tendon with an '8' shape, pass through the far end of the tendon and out through the skin, and fix it on the skin surface with a button to reduce the tension at the junction of the tendon ends. After 4 weeks, cut the wire under the button with scissors and pull the wire out from the near end.

　　D、Kessler suture method: Sutured with double straight needles and polyester thread (5-0), as shown in the figure. This method has strong tensile strength and can be used for tendon suture within the tenosynovium, with controlled early passive activity using supports. The improved Kessler method adds a ring of intermittent suture around the suture site of the tendons based on the original method to strengthen the local tensile strength and make the suture site smooth and flat.

　　E、Kleinert suture method: Sutured with 3-0 non-traumatic straight needle monofilament thread, the suture method is simple, has strong tensile strength, and has little interference with the blood circulation of the tendon ends. To make the suture site smooth and have better tensile strength, intermittent sutures are made around the periphery.

　　F、Becker suture method: The tendons are cut into a bevel, sutured with 5-0 non-traumatic monofilament thread, and stitched intermittently. This method has strong tensile strength, as there are many suture lines, the tendons need to overlap, and the length of the tendons is affected. It is suitable for heterotopic tendon suture.

　　G、Intramuscular suture method: The tendons at both ends are sutured with a single needle circular non-invasive suture line, and the loops at the entry and exit points are sutured and fixed with an '8' shape. Most of the suture lines are embedded in the tendons.

　　H. Tsuge suture method: Straight needle suture line (3-0 or 5-0), cross a needle about 1.0 cm from the tenotomy end, pull the needle out and then insert it into the loop. Tighten the suture to hold a little tenon adventitia and tenon bundle, then insert the needle longitudinally into the tenon and pull the needle line out from the palmar side of the tenotomy end, then insert the needle into the opposite end, enter the needle at the palmar side, exit the needle 1.0 cm from the end, pull the suture line to align the tenon ends, cut one of the threads, cross a needle at the exit point, and tie the ends of the cut thread.

　　② Tendon end-side suture method:

　　A. When a dynamic muscle tendon is transferred to multiple tendons, the weaving method should be used for suture.

　　B. Tendons with unequal diameters can also be sutured using the weaving method.

　　C. Tendons with equal diameters can also be sutured using the weaving method.

　　③ Fish mouth suture method: Used for the transplantation of tendons with different diameters.

　　④ Tendon-bone suture method: Suitable for suturing tendons that are inserted into bones.

　　There are various methods of tendon suture, each with its own advantages and disadvantages. Regardless of the method used, it is necessary to strive for simplicity of operation, high tensile strength, minimal interference with the blood circulation of the tendon ends, and a smooth and flat suture site. The specific method should be selected according to the actual situation.

　　2. Fresh flexor tendon repair

　　Although there are still different practices, the basic approach has been unified to perform regular surgery during emergencies.

　　Wound debridement: To facilitate operation, an extended incision is required, with Z-shaped or continuous serrated incisions made on the finger and palm, and longitudinal Z-shaped incisions on the wrist and forearm. The deep tissues should be fully exposed to investigate the condition of various tissue injuries. In addition to the tendons, the tenosynovium itself, nerves, and blood vessels should also be clearly identified and treated simultaneously. After the rupture of the flexor tendons, due to the extension of the finger joints, the distal ends retract towards the distal side. Generally, the finger joints are flexed to the angle of injury so that the distal ends can be exposed at the wound. The proximal ends often retract further. If the long tendon loop is intact and continuous, the long tendon loop can limit the retraction. If it is ruptured near the attachment point of the long tendon loop, the proximal end can retract very far. In case of a rupture in area Ⅱ, it can retract to the palm, and in area Ⅲ, it can retract into the carpal tunnel. First, the wrist and metacarpophalangeal joints should be passively flexed, and the flexor muscles of the forearm should be massaged to allow the ruptured tendons to slide forward to the vicinity of the rupture. To facilitate observation or surgical operation, the tenosynovium should be incised in the shape of an 'L', and the transverse ligament in the carpal tunnel can also be incised at one end. It is forbidden to use hemostats blindly in the sheath tube or palm passage, which may cause injury and lead to extensive adhesions postoperatively, seriously affecting function. After finding the distal ends, repair should be performed according to different areas.

　　Area Ⅰ: Refers to the rupture of the deep flexor or hallux longus flexor tendons near the short tendon loop, which can be directly sutured using the Kessler method. If the retraction is far, the tendinous ends can be sutured with an '8' shape using a wire drawing method, with the wire tail exiting from the lateral aspect of the distal phalanx near the nail, twisted and tied on a rubber pad to prevent retraction of the proximal tendons. Then, the tendons are sutured end-to-end, or the distal flexor tendons can be split into two, with the proximal tenon head inserted between them for a mattress suture; or a groove can be made on the metacarpal bone at the insertion of the deep flexor tendon, lift the bone slice, embed the tenon head into the bone groove, and then suture the tendons.

　　Ⅱ Area: The principle has changed, the forbidden area has been broken, and primary repair is the most satisfactory treatment. The 'Z' shaped incision is used to expose the flexor tendon sheath, protecting the固有血管 and nerve bundles. If there is a nerve rupture, it is repaired together with the completion of the tendon suture.

　　An L-shaped incision is made near the wound end of the synovial sheath, and the synovial sheath of the cruciate ligament part is cut as much as possible to avoid the annular ligament part. The triangular flap is sutured with a traction line to open it, so that the internal structure of the tube can be seen. Bend all the joints and press the muscle belly to make the distal ends of the two tendons slide out of the synovial sheath opening separately. Observe the injury condition and debridement. First, the proximal flexor tendon is brought out. To prevent retraction, an injection needle can be used to cross the synovial sheath at 1.5 to 2 cm from the proximal side to secure it. The deep and superficial tendons should be kept together to prevent hindrance to the blood supply. First, a half Kessler suture or other suture method can be used on the deep tendon, and the thread end is led out from the broken end as a traction point. The superficial tendon should be repaired according to the location of the break in the Camper's cross. If the break is beyond the cross, the two tendons are sutured separately in an '8' shape; if the break is near the cross, Kessler suture method can be used. It is necessary to make the surface smooth. If the superficial tendon cannot be repaired, its proximal segment can be cut off; the distal end should be preserved as the posterior tendon bed for the deep tendon's sliding. If the superficial tendon is too short, it often causes hyperextension deformity at the proximal interphalangeal joint after surgery. After the repair of the superficial tendon is completed, repair the deep tendon. Regardless of the suture method used, the depth should be kept on the palmar side half. The knot is buried in the tendon, and the surface is sutured with 9-0 monofilament nylon thread in an interrupted manner to make it smooth. The synovial sheath should also be sutured meticulously. After removing the injection needle, flex the wrist 30°, then gently flex and extend each joint of the fingers to see if the sutured tendons can pass through the repaired part of the synovial sheath. Maintain the position of the wrist and fingers, do not allow the suture to pull the tendon apart. Repair the nerve and suture the skin. Stick a shirt collar hook on the nail, and fix it with a Kleinert activity splint.

　　If the synovial sheath is broken and cannot be repaired, some people use autologous or heterologous biological materials or synthetic materials for repair, and the effectiveness varies. Alternatively, the damaged part of the synovial sheath can be removed. Generally, the A2 and A4 annular ligaments should be partially preserved as much as possible to maintain their pulley function. If the injury is in the proximal part of the II Area, the A1 pulley can be removed without hindrance, just like the anterior shift of the III Area.

　　Ⅲ Area: The repair of the tendons and the digital common nerve is easy and effective, and the suture site is wrapped with the蚓状肌 to prevent adhesion.

　　Ⅳ Area: The tendons are within the carpal tunnel, where a total of 9 tendons and the median nerve pass through. A Z-shaped incision is made on the skin, the transverse carpal ligament is cut from one end, the deep flexor and the flexor pollicis longus tendons are repaired, and a segment of the superficial flexor tendon is resected from both the proximal and distal ends to prevent adhesion. If only the superficial layer of the flexor tendon is ruptured, the entire repair is done, the median nerve is sutured, and the transverse carpal ligament does not need to be sutured back, so no bowstring formation will occur.

　　V area: From the origin of the tendons to the entry into the carpal tunnel, there is peritendinous tissue surrounding them. In case of any rupture, all should be repaired. If the median or ulnar nerves are damaged, they should also be repaired, and controlled activities should be performed after surgery.

　　3. Tendon repair in all areas

　　(1) Tendon repair in the I area: The proximal end of the flexor digitorum profundus in the I area is damaged, and due to the tenodesis and lumbrical muscles at the site of the rupture, the retraction distance will not be much.

　　① Direct suture of the tendon ends or advancement of the proximal tendon end surgery: If the proximal end of the flexor digitorum profundus has sufficient length and the distal end is longer than 1 cm, the ends can be sutured directly. If the distal end is shorter than 1 cm, the residual tendons at the distal end can be excised, and the proximal end can be advanced to reconstruct the insertion point. If the proximal end retracts too much and the deep tendons can no longer pass through the bifurcation of the superficial flexor tendons, the insertion point of the superficial flexor tendons can also be advanced and sutured with the distal end of the flexor digitorum profundus. After the advancement of the tendon ends, due to the high tension, the extension of the injured finger may be limited in the early stage, which can be corrected after appropriate functional exercise.

　　② Tendon fixation: After the flexor digitorum profundus in the I area is ruptured, the distal end is longer than 1 cm, but the proximal end retracts too much and cannot be sutured directly. If the superficial flexor tendons function well, tenodesis can be performed, that is, the distal end is fixed on the middle phalanx bone, so that the distal interphalangeal joint is in a functional position, which is convenient for stable pinching.

　　③ Distal interphalangeal joint fusion: If the proximal end of the flexor digitorum profundus has shortened or is damaged, and the superficial flexor tendons function normally, and the distal interphalangeal joint has poor passive movement or there is also damage to the joint, interphalangeal joint fusion in the functional position can be performed, which is reliable for restoring the pinch function of the injured finger.

　　(2) Tendon repair in the II area: The superficial flexor tendons in the II area do not need to be repaired. The deep flexor tendons can compensate for most of the function. If the deep flexor tendons are damaged and the superficial flexor tendons function normally, distal interphalangeal joint fusion or tenodesis can be performed. If both the deep and superficial flexor tendons are ruptured, free tendon transplantation or tenodesis should be performed to reconstruct the function of the deep flexor tendons.

　　(3) Tendon repair in the III area: The tendons are damaged for a short period of time, and the proximal part retracts to the palm or wrist. Whether it is the superficial or deep flexor tendons, they can be sutured directly. If the damage is prolonged and only the superficial flexor tendons are damaged, no repair is required. If the deep flexor tendons or both the superficial and deep flexor tendons are damaged, free tendon transplantation can be performed to reconstruct the function of the deep flexor tendons. When the superficial and deep flexor tendons are damaged at different levels, the proximal longer tendons can be sutured with the distal end of the flexor digitorum profundus to restore its function.

　　(4) Tendon repair in the IV area: There are many tendons in the carpal tunnel, and the repair of the flexor digitorum profundus and the long flexor tendons of the thumb should be the main focus. When free tendon transplantation is required, the sutured part of the tendons should be located within the III and V areas.

　　(5) Tendon repair in the V area: Tendons with no defects can be sutured directly if damaged, and the superficial and deep flexor tendons and the long flexor tendons of the thumb, the flexor tendons of the wrist should be repaired separately. When the tendons are ruptured at different levels, and cannot be sutured directly due to shortening or defects, the proximal longer tendons can be transposed to the distal end of the flexor digitorum profundus.

　　(6) Repair of the flexor pollicis longus tenosynovium: When the flexor pollicis longus tenosynovium is injured in any area, direct suture should be performed when the ends are not significantly shortened. If the tenosynovium or muscle is slightly shortened, it can be overcome by the wrist joint flexion. After surgery, through functional exercise, the hand can recover to the normal sliding range. The suture points of the tendons should avoid the metacarpophalangeal joint and wrist joint, otherwise adhesion is easy to occur. When there is a tendinous defect, methods such as tenosynovial extension, transplantation, and transposition can be used for repair. When all the above methods cannot be implemented, interphalangeal joint tenosynovial fixation surgery or joint fusion surgery can be performed.

　　① Extension of the flexor tendons: The flexor pollicis longus tenosynovium is a unipennate muscle, with a longer tenosynovium on the lateral side, which can be extended in a 'Z' shape to extend the tendons, so as to directly suture the ends or reconstruct the tenosynovium insertion point.

　　② Transposition of the superficial flexor tenosynovium of the ring finger: The superficial flexor tenosynovium and the flexor pollicis longus are synergistic muscles. The superficial flexor tenosynovium is cut from the proximal margin of the short tendon group, and the muscle tendon is pulled out from the proximal end of the wrist band, and then transposed to the flexor pollicis longus tenosynovium through the carpal tunnel.

　　4. Pulley Reconstruction Surgery

　　If the A2 and A4 pulleys are still present after the tenosynovial injury, the basic finger flexion function can be guaranteed. If these two annular ligaments are destroyed, the flexor tendons will become弓弦状, greatly affecting the flexion function of the fingers. If necessary, reconstruction can be performed during the second stage of tenosynovial repair.

　　The material for reconstructing the pulley can be taken from the longitudinal half split of the palmaris longus tenosynovium or other tendons, and the soft tissue and extensor tendons are separated from the finger bone laterally until they can be surrounded to communicate with both sides. In hand surgery instruments, the pulley forceps have a head shaped like a large semicircular arc hook, which is convenient for blunt tissue separation. The tendons are pulled back to the opposite side after wrapping around, with the tendinous sheath tissue facing towards the center, tightened and sutured, and the sutured area turned to the dorsal extensor tendons above.

　　5. Free Tenosynovium Transplantation

　　Free tenosynovium transplantation surgery is suitable for repairing tendinous defects in various areas of the hand, but it is more commonly used for repairing tendinous defects in the finger sheath.

　　6. Donor Tendons for Free Tenosynovium Transplantation

　　The palmaris longus tenosynovium, extensor digitorum longus tenosynovium, tibialis posterior tenosynovium, extensor indicis proprius tenosynovium, and superficial flexor tenosynovium of the finger can all be used as tenosynovium for transplantation. The palmaris longus tenosynovium is flat and long, up to 15cm can be cut, and it is the first choice for transplantation. The extensor digitorum longus tenosynovium is longer and flat, with more tenosynovial intertubercular syndesmosis, often cutting the extensor tendons of the second to third toes. The tibialis posterior tenosynovium is the longest tenosynovium in the body, twice the length of the palmaris longus tenosynovium, with a presence rate of 93%. Due to the difficulty in checking whether the tenosynovium is absent before surgery and its deep position, it is not easy to cut, so it is used less now. The extensor indicis proprius tenosynovium is rarely used for free tenosynovial transplantation, as it is short, usually only 8cm can be cut, and the superficial flexor tenosynovium is thicker and larger, which is easy to adhere after transplantation and is used less.

　　7. Adjustment of Transplanted Tenosynovial Tension

　　Excessive tenosynovial tension leads to limited finger extension; insufficient tension results in incomplete finger flexion. Appropriate adjustment of tenosynovial tension is an important factor for achieving good function after tenosynovial transplantation. Adjust the tension of the tenosynovium by taking the rest position of the adjacent finger as a reference, and the position of the affected finger after tenosynovial transplantation should be slightly greater than the flexion degree of the rest position of the adjacent finger.

　　If the proximal end of the tendon is adherent near the original wound or the injury time is short, and there is no significant change in the muscle tension of the broken tendon, the degree of finger flexion of the transplanted tendon can be adjusted to be consistent with the adjacent finger at rest. If the injury time is long and the muscle has contracted, the muscle tension is felt to be greater when pulling the broken end, the tension of the tendon transplantation should be appropriately relaxed, that is, the position of the injured finger is slightly extended from the rest position after the suture of the tendon, in order to avoid the finger from not being completely extended after surgery. When the muscle has atrophy due to disuse, the muscle tension is relaxed when pulling the tendon, and the tension of the transplanted tendon should be slightly tighter to avoid incomplete finger flexion after surgery, and also weak in strength.

　　8, Staged flexor tendon surgery

　　For fingers with poor blood circulation, more scars, or those not suitable for free tendon transplantation in the first stage, a staged tendon transplantation can be performed.

　　(1) First-stage surgery: Implant a silicone rubber strip as a tendon substitute into the prepared site for tendon transplantation, fix the distal end to the base of the distal phalanx, and place the proximal end in the tissue of the palm or forearm. After the wound heals, perform passive finger extension and flexion exercises, and gradually form a false sheath around the silicone strip.

　　(2) Second-stage surgery: After two months of inserting the silicone rubber strip, remove the implant and perform tendon transplantation within the artificial sheath.

　　9, Rehabilitation after flexor tendon repair

　　Adhesions are prone to occur after flexor tendon repair, and adhesions are the most important complication affecting function, followed by joint stiffness of the fingers. The best way to avoid adhesions and joint stiffness is to move. To date, no suture material or suture method can allow patients to flex their fingers autonomously early without causing rupture. Currently, various anti-adhesion drugs and membranes are being tested, and the possibility of preventing adhesions and other complications is not yet sufficient to widely promote various methods. In China, the most useful methods are controlled active movement (Kleinert method) and continuous passive movement, or a combination of both.

　　Kleinert restrictive dynamic splinting method: After surgery, the wrist joint is fixed at 45° with a dorsal plaster splint, and the metacarpophalangeal joint is flexed at 60°. Its length extends beyond the fingertips, and a collar hook is glued to the nail with 502 glue. A rubber band is hung, and a safety pin is tied to the wrist band, hanging the other end of the rubber band. Under its elasticity, the affected finger maintains a passive flexion position. Starting from the second day, active finger extension exercises are performed 50 times per hour, and the interphalangeal joints are flexed passively, each joint flexed separately, as well as combined flexion, 5 times per hour. Due to the restriction of the dorsal plaster, the repaired flexor tendons slide within the sheath without being pulled apart under tension. The range of motion and frequency of practice are adjusted according to the severity of the injury and the patient's tolerance to pain. If there is more than 20° of insufficient extension at the proximal interphalangeal joint in the fourth week, an aluminum splint with a sponge pad is tied on the palmar side of the finger at night, fixing it in a straight position. In the fifth week, remove the splint for 2 hours a day, performing 10 times of wrist joint extension and flexion, and 10 times of finger comprehensive extension and flexion (40°～60°). In the sixth week, perform the full range of extension and flexion. In the seventh week, remove the dorsal splint and gradually perform resistance joint activities until a complete recovery is achieved by the twelfth week, during which physical therapy is indispensable.

　　Continuous passive movement, equipped with a commercially available CPM device, initially using Type I, slowly traction the fingers' extension and flexion while keeping the wrist flexed. After 4 weeks, switch to Type II, with coordinated extension and flexion of the fingers and wrist. China is currently in the trial production and trial operation stage, lacking mature experience.

　　Rehabilitation medicine in China is still in its early stage of development. Many hospitals and centers lack regular guidance from specialized physical therapists, which greatly reduces the efficacy of flexor tendon surgery.

　　10. Flexor Tendon Release Surgery

　　In the era when the theory of external healing was dominant, tendon healing inevitably resulted in adhesion. With the current surgical methods and postoperative rehabilitation routine treatment, the adhesion and severity of tendons after repair have been greatly reduced, but different authors still report that 15% to 41% of patients need to undergo secondary release surgery. Whether a tendon release surgery is needed and whether it can achieve a good result requires a detailed examination by experienced specialist doctors to decide. Blind exploration may sometimes lead to excessive stripping, causing ischemic necrosis of the tendons, spontaneous rupture during exercise, or increased trauma and heavier adhesions.

　　The timing of tendon release should be after the tendons have healed, the wounds have softened, and the adhesions and scars have been reshaped through physical therapy. For those with joint rigidity, tendon release is ineffective; for those with joint stiffness, it should be performed when the joint has a larger range of motion. It is generally believed that tendon repair should be released after 3 months postoperatively, and tendon transplantation should be released after 6 months postoperatively.

　　Tendon release surgery requires patient cooperation in movements, and can be performed under local anesthesia plus intravenous anesthesia. The surgery must be performed in a venous drainage state, with a full course of saw-toothed incisions on the fingers, and all restrictive adhesions are removed systematically, while blood supply and the gliding mechanism are preserved, with the minimum retention of the A2 and A4 annular ligaments. After the gliding mechanism is reconstructed, the function will decrease. If the superficial flexor tendons are shallow and the deep flexor tendons are heavily adhered, it is difficult to make both tendons effectively movable or to prevent re-adhesion. In such cases, the superficial tendons may be excised, and the deep tendons retained. Sometimes the superficial tendons slide well, but the deep tendons are heavily adhered, making it difficult to become mobile. In such cases, the distal interphalangeal joint may be fixed or fused in the functional position. Postoperative rehabilitation is very important for the recovery of function.

　　Research on the application of drugs, placing biomembranes or synthetic interposition membranes to prevent recurrence is endless, but it has not been recognized by the public.