The first finger column, where the thumb is located, accounts for 40% of the function of the whole hand. The main mechanism is that the thumb can make axial movements perpendicular to the palm of the hand, so that the thumb is opposite to the other fingers, thus producing grasping and pinching movements. The anatomical basis for this action is multifaceted, with three osteoarticular bases.
1, the first carpometacarpal joint is a saddle joint, which produces abduction, rotation forward and flexion when opposing the palm.
2, the metacarpophalangeal joint of the thumb is a flexion garrison joint, which produces radial deviation, rotation forward and flexion against the palm.
3. The interphalangeal joint is a hinge joint, which produces flexion when palmar. Due to the unequal size of the distal condyle of the proximal phalanges, there is mild rotation of the terminal phalanges when accompanied by flexion. The soft tissue base is the stable structure of the joint capsule and ligaments of the first carpometacarpal joint and metacarpophalangeal and interphalangeal joints.
The power base of the thumb to palm has always been controversial. Duchenne believes that it is the short thumb extensor, short thumb flexor, and thumb to palm muscles; Kaplan believes that in addition to the above muscles, the long thumb extensor and short thumb extensor also play a role; Grant believes that the thumb to palm is a circular movement, with abduction produced by the short thumb extensor and assisted by the adductor muscles, rotation forward produced by the short thumb flexor and thumb to palm muscles, and rotation forward produced by the short thumb flexor and thumb to palm muscles. He considers the superficial head of the thumb flexor and the thumb palmar muscle as a functional unit, which he calls the “anterior thumb unit”. From the above arguments, we can see that the thumb-to-palm is mainly a synergistic effect of the short thumb extensor and thumb-to-palm muscles and other external and internal muscles that end at the first finger row. There are many reasons for the loss of thumb-to-palm function, including loss of function of the greater interosseous muscle due to peripheral nerve injury in the upper extremity, especially median nerve injury, injury to muscles or bone joints due to trauma, and congenital deficiency of the interosseous muscle. The loss of thumb-to-palmar function has a great impact on hand function, so it is necessary to reconstruct thumb-to-palmar function. The complexity of the anatomical structure of thumb-to-palmar function makes us only partially reconstruct thumb-to-palmar function, i.e., simulating the action of the short thumb extensor and thumb-to-palmar muscles. According to the conditions of bone and soft tissue, we can classify the thumb-to-palm function reconstruction into dynamic and static.
For those with normal bone and joint structures and good soft tissue conditions, the main choice is dynamic thumb-to-metacarpal reconstruction, including the selection of the power muscle, the treatment of the stopping point and the direction of tendon travel.
(A) Selection of power muscles.
As early as 1924, Bunnell proposed the use of tendon transfer to reconstruct thumb-to-metacarpal function, and proposed the basic principles of tendon transfer, namely, adequate muscle strength of the donor muscle, as single function as possible, and a suitable glide range. This principle has been accepted over the years, and numerous scholars have devised various methods to achieve this goal accordingly.
Selection of extrinsic muscles.
There are numerous options for the power of extrinsic muscle displacement, and almost all muscles of the forearm can be used as a power source in the literature; the specific procedure should be selected according to the specific circumstances of the case, tissue conditions, and level of operation.
1 , palmaris longus: Camitz first used this muscle as a power source in 1929. The long palmar muscle and the short thumb are synergistic muscles, and there is little damage to the donor area after displacement, so it has become a more common method, but because the tendonous part of the muscle is displaced to the palmar tendon membrane behind the transverse wrist, the palmar tendon membrane needs to be removed during surgery, which is traumatic to the palm. The long palmar muscle is innervated by the median nerve along with the short thumb extensor muscle, so if the nerve is damaged at a high position, the muscle will be affected as well.
2. Superficial flexor muscle of middle and ring finger: Royle designed this method in 1938. The middle and ring finger flexor superficialis muscles are independent, with long tendon structure and functional compensation of the flexor digitorum profundus muscle, so the impact on the donor area after excision is small. The two muscles are innervated by the median nerve, and if the nerve is damaged in a high position, the two muscles are also affected.
3. Intrinsic extensor of the index finger: Burkhalter used this muscle as a motive force in 1973. This muscle is innervated by the radial nerve and is not affected by the median nerve injury. After excision, it is compensated by the extensor digitorum generalis and has little effect on the donor area.
4, ulnar extensor carpi radialis: Phalen used this muscle as a power in 1969. Baker believes that a transposition of the ulnar extensor carpi radialis will result in radial deviation during dorsal wrist extension.
5. Radial extensor carpi radialis longus and shortus: Henderson designed this method in 1962, this muscle is innervated by the radial nerve and is not affected by median nerve injury. Baker et al. cut the tendon from the stop point and cut the tendon part longitudinally to the tendon ventral junction and then cut half of it as the source of tendon graft.
6, Intrinsic extensor of the little finger: Schneider used this muscle as a motive force in 1969. This muscle has the same advantages as the intrinsic extensor of the index finger.
7.Extensor digitorum longus: Riley used this muscle as a motive force in 1980. This muscle is innervated by the radial nerve and is not affected by median nerve injury. It has a long tendon structure and does not require grafting, but it has a large impact on thumb extension after excision.
8, flexor hallucis longus: Baeyer designed this method in 1931. Keeping the starting and ending points of the flexor digitorum longus unchanged, the tendons of zones I-III were freed, the proximal phalanges of the thumb were truncated, and the flexor digitorum longus tendon was placed between the extensor digitorum longus tendon and the proximal phalanges from the radial-palmar side of the metacarpal head around the metacarpophalangeal joint and then the phalanges were fixed. The authors concluded that this approach avoids tendon grafting, preserves the tendon origin to avoid loss of function in the donor area, and resets the tendon to produce a thumb-to-palm-like motion, which may be an option when no other power is available.
9, Brachioradialis: Henderson designed this method in 1962. The brachioradialis is innervated by the radial nerve and is not affected by median nerve injury, but the tendon portion is not long and requires tendon grafting.
10, ulnar flexor carpi radialis: Bunnell designed this method in 1938. The muscle is innervated by the ulnar nerve and is not affected by median nerve injury, and the radial flexor carpi radialis muscle is compensated after excision, which has little effect on the donor area.
Selection of intrinsic muscles.
Because of the large difference in the starting and ending point travel between the extrinsic muscle and the short thumb extensor muscle, in terms of biomechanics, the extrinsic muscle is a large muscle, and it is not easy to balance and regulate the force with it instead of the small muscle, and the stroke is long and vulnerable to soft tissue conditions and pulley structure, so some scholars seek to replace the thumb-to-palm function with the intrinsic muscle. The intrinsic muscle replaces the intrinsic muscle, which has a similar starting and ending point structure, without the influence of longer muscle pull and free tendon graft, and the tension is easy to adjust and easy to cortical reinnervation, so the intrinsic muscle transposition has become a hot spot for research in recent years.
1. Thumb flexor: In 1996, Zhu Wei conducted an anatomical study of the thumb flexor instead of the thumb flexor, and concluded that the thumb flexor is anatomically adjacent to the thumb flexor and is a synergistic muscle with the thumb flexor, and the starting point of the thumb flexor is more on the midline of the palm than the thumb flexor. When the deep branch of the ulnar nerve is paralyzed, the deep head of the thumb flexor can still function, and the superficial head of the thumb flexor is not easily separated from the deep head and has a common stop. Biomechanically, shifting the stop point increases the angle between the thumb flexor and the thumb adductor by 6° under normal conditions, thus allowing the shifted thumb flexor to exert a more direct force in the palmar direction than the other intrinsic and extrinsic muscles. Therefore, the thumb flexor stop is designed to be fixed to the abductor stop through the deep surface of the thumb abductor muscle to perform the palmar function.
2, Adductor digiti minimi: This method was first created by Huber in 1921 for the treatment of median nerve injuries, and was used by Litte in 1963 for the treatment of thumb dysplasia, with some authors refining the surgical technique later. The thumb abductor muscle originates from the radial half of the distal radial aspect of the transverse carpal ligament, with its fibers crossing the metacarpophalangeal joint on the radial side, and the tendon attaches to the radial capsule with two stops, one at the radial seed bone and the other at the dorsal extensor tendon expansion of the thumb, which is innervated by the median nerve. One ends at the ulnar side of the base of the proximal phalanx of the little finger, and the other ends at the expansion of the extensor tendon, which is innervated by the deep branch of the ulnar nerve and supplied by the ulnar artery; the similar origin and termination structures of these two muscles and their different innervation provide the anatomical basis for reconstruction.
The earliest surgical approach had two incisions, one at the ulnar border of the lesser trochanter, extending from the flexor dermatome of the proximal interphalangeal joint of the little finger to the flexor dermatome of the carpal joint; in this incision the adductor digiti minimi muscle was revealed, both stops of the ADM were severed and freed proximally, the neurovascular tip was freed proximally, and its doughy attachment was lifted in order to obtain sufficient mobility, and an ulnar flexor carpal muscle was isolated from the The second incision was made on the radial side of the thumb at the level of the metacarpophalangeal joint, and a subcutaneous tunnel was made between the two incisions, with the ADM folded approximately 170 degrees and passed through the subcutaneous tunnel to suture the end of the ADM to the end of the thumb abductor.
In 1977, Ogin thought that this method was not satisfactory in appearance, as the supplemental interosseous muscle was more ulnar than normal, so he improved the method by freeing a 2-3 cm cord from the ulnar flexor carpi radialis at the proximal end of the ADM and separating it from the ulnar flexor carpi radialis and fixing it to the long palmar muscle or, if the long palmar muscle was absent, to the transverse carpal ligament, so that the displaced muscle was closer in kinetics to the short thumb palmar muscle, and the postoperative appearance was closer to that of the short thumb palmar muscle. and the postoperative appearance is closer to normal.
Although the tunnel is wide enough in most cases, some patients still have limited motion due to the tunnel, so in 2003 Osam et al. modified it to an island flap displacement of the ADM with cutaneous fascia by designing a shuttle incision in the ADM distal to the ulnar side of the proximal phalanx of the little finger and proximal to the transverse carpal ligament, and in this incision the ADM is free The other incision was made at the level of the transverse thumb metacarpophalangeal joint and extended to the proximal third of the first metacarpal, and the proximal skin was lifted to transpose the ADM skin island flap.
The ADM transposition reconstructs the thumb abduction and allows the atrophied or deficient greater trochanter to be replenished; there is little loss of function in the donor area. In particular, its function of improving appearance cannot be replaced by other surgeries; therefore, this method is an excellent treatment for congenital thumb hypoplasia or congenital pisiformis deficiency, and is also a good option for median nerve injury when other muscles are difficult to transpose or when the patient has requirements for appearance.
Free muscle as power.
This method was designed by Shengxiu Zhu et al. in 1981. The proximal end of the muscle is sutured to the transverse carpal ligament and the distal end is penetrated into the radial bone hole at the base of the proximal phalanx of the thumb, and the neurovascular and vascular nerves of the recipient area are anastomosed separately to re-establish blood flow and innervation. This method is mainly used for neuromuscular defects in the greater interphalangeal area caused by firearm injuries, and can repair the defect and reconstruct movement at the same time.
(B) Treatment of the stop point In order to achieve the function of the thumb to the palm, the stop point of the displaced tendon should be as close as possible to the stop point of the short thumb extensor muscle, and the treatment of the stop point can be divided into three types: single tendon bundle, double tendon bundle and natural stop point.
1, Single tendon bundle stop: the single tendon is first sutured to the thumb flexor at the radial capsule attachment of the metacarpophalangeal joint, and then sutured to the extensor digitorum communis tendon through the dorsal extensor tendon expansion of the thumb; or a hole is drilled in the base of the proximal phalanx of the thumb from the dorsal ulnar side to the radial metacarpal side, and the tendon bundle is passed through the hole and sutured to itself.
2. Double tendon bundle stop.
(1) Brand procedure: the distal end of the tendon is divided into two bundles, one bundle is sutured with the short thumb extensor muscle and then crosses the metacarpophalangeal joint and sutured with the extensor digitorum longus tendon; the other bundle is sutured with the thumb adductor muscle at the stop of the ulnar joint capsule of the metacarpophalangeal joint after crossing the dorsal extensor tendon expansion of the thumb, this technique can stabilize the metacarpophalangeal joint and is suitable for those with complete loss of interphalangeal muscle function and unstable metacarpophalangeal joint.
(2) Royle-Thompson technique: A hole is drilled in the coronal plane of the first metacarpal neck, and a tendon bundle is passed through this hole and sutured to another tendon bundle that reaches the base of the proximal phalanges through a subcutaneous tunnel, allowing for mild rotation of the metacarpophalangeal joint without causing flexion.
(3) Riordan’s procedure: Two tendon bundles are woven through each other at the stop of the short thumb extensor muscle and the extensor digitorum longus tendon bundle distal to the MP, which facilitates end-joint extension of the flexion deformity of the interphalangeal joint of the thumb.
(4) Littler procedure: The two tendon bundles pass through the short thumb extensor hallucis muscle stop area and then fold back and suture to themselves.
However, some scholars believe that the double stop structure has the effect of one stop shielded by the other stop and does not achieve the ideal state.
3.Natural stops.
(1) Thumb extensor tendon stop: Phalen believed that the thumb extensor tendon has a stop structure on the dorsal side of the base of the proximal phalanx of the thumb, and when the tendon is pulled in a suitable direction, it can produce a similar effect to that of the thumb on the palm, so they designed to preserve the thumb extensor tendon stop structure, cut it off at the tendon ventral junction, pass it through a subcutaneous tunnel at the metacarpophalangeal joint to the palmar side, pull it in the direction of the douglas, and suture it to the displaced power tendon. The problem of insufficient length of the power tendon can be solved, and at the same time there is a stop point.
(2) Thumb extensor tendon stop: This method is based on the same principle as above and designed by Bo Zhandong in 2003.
(C) Direction and slide direction
(1) Make a subcutaneous tunnel between the wrist incision and the MP incision of the thumb, and the power tendon reaches the stop point through the tunnel.
(2) Changing the direction of power through the pulley structure Through the analysis of the thumb to palm action and anatomical structure, we know that the main action of the thumb to palm is abduction and rotation. When the muscle contracts, it can directly pull the first metacarpal to abduct and rotate forward, which mainly plays the role of rotating forward and flexing the carpometacarpal joint at the same time. Therefore, the single power of displacement needs to take into account the function of both muscles to have a better effect on the palmar. In a study by Qingtai Li et al [19], it was found that for those who chose flexor tendons as the power tendon, such as the long palmar muscle and the superficial flexor of the finger, the postoperative alignment angle was normal in very few cases, accounting for only 16%. After surgery, the radial abduction angle of the thumb improved more than before surgery, with an average angle of about 40°, but the anterior rotation and flexion angles of the thumb were insufficient. The difference in the anterior rotation angle was even greater, with an average difference of 30° to 40°. After surgery, the patient’s thumb and index finger were still pinched “laterally”, and when pinched with the middle finger, only the tips of the fingers were in contact with each other. About 84% of the patients could not complete the pinching action with the ring and little finger, or could only barely touch the fingertip, mainly because the direction of these tendons and the first metacarpal angle is small, and the rotation of the front effect is poor. If the extensor tendon is chosen as the driving tendon displacement (e.g., ulnar carpal extensor, intrinsic extensor of the index finger, etc.), the postoperative results of thumb to palm function are better than those with flexor tendons. The radial abduction angle of the thumb improved to 45°, and the anterior rotation angle also improved, but was still 20°-30° worse than the healthy side. The thumb can be pinched with the middle finger, but the ring and little finger are still pinched laterally. The reason for this is that the extensor muscle in the direction of displacement travels more on the ulnar side than the flexor, which is more in line with the mechanics.
In 1938, Bunnell proposed that the direction of force is best when the stop is in line with the bean bone, and Cooney et al. came to a similar conclusion, so the direction of muscle force should be changed by making a pulley structure near the bean bone. The subcutaneous tunnel at the distal edge of the bean bone can be used as a glide structure, or the distal end of the ulnar flexor carpal tendon can be cut in half longitudinally and used as a glide at the attachment of the bean bone.
2.Methods of reconstruction of the carriage
(1) Reconstruction of the carriage with the bean bone and ulnar flexor carpal tendon: cut 1/2 of the tendon at 4 cm from the stop of the ulnar flexor carpal muscle, separate it to the bean bone, wrap this tendon strip around to form a ring, and pass the transplanted tendon through this tendon ring as the carriage structure.
(2) Reconstruction of the carriage with the palmar tendon membrane and the palmaris longus tendon: the palmaris longus tendon was cut at 4 cm from the transverse carpal stripe, separated to the transverse carpal ligament, and this tendon strip was encircled into a loop, and the transplanted tendon passed through this tendon loop as the carriage structure.
(3) Reconstruction of the pulley with the palmar tendon membrane and the sheath of the flexor tendon: the superficial flexor tendon of the ring finger was taken together with its tendon sheath, and the ligament was partially excised at the proximal edge of the transverse carpal ligament to create a window, and the tendon sheath was sutured to this window as a pulley.
Sakellarides believes that the reconstructed tendon glide will gradually lax over time.
II. Static thumb-to-palm functional reconstruction can be considered when there is no available muscle as a power source, or when there is a deformity, injury, or stiffness of the carpometacarpal joint of the thumb.
1. Bone grafting between the 1st and 2nd metacarpal bones of the thumb in the opposite metacarpal position; place the thumb in the opposite metacarpal position and implant a triangular iliac bone block between the 1st and 2nd metacarpal bones, or cut holes on the opposite sides of the 1st and 2nd metacarpal bones, trim the bone grafting strips into a mortise and tenon shape and insert them into the holes of the 1st and 2nd metacarpal bones, and stiffen the thumb in the opposite metacarpal position after bone healing.
2, the first metacarpal rotation osteotomy: the first metacarpal osteotomy, distal rotation anterior-posterior fixation, can be used as a power on the metacarpal reconstruction before the inadequate function of rotation.