Polydactyly is a common congenital disorder of the hand with the highest incidence in Asians, and in China, compound thumb deformity is the most common polydactyly. The thumb plays an important role in the hand, and surgery is needed to improve the appearance and function of the finger as much as possible. The treatment principle is to remove the poorly shaped and poorly functioning side of the thumb, reconstruct the thumb to preserve its shape, and improve the function of the finger body. The Wassel IV type is the most common type, with about 50% of the thumbs sharing a common joint. Due to the complex anatomy of Wassel IV, the incidence of secondary deformity and functional limitation after treatment is high, which seriously affects the outcome of the surgery.
The Wassel IV type, in which both thumbs share a common joint, is the most common type, accounting for approximately 50% of cases. Due to the complex anatomy of Wassel IV, the incidence of secondary deformities and functional limitations after surgical treatment is high, which seriously affects the surgical outcome. The secondary deformities after surgery are common: finger axis deviation, joint stiffness, finger weakness, tiger mouth stenosis, postoperative scar, scar contracture, nail deformity, and continued growth of the excised finger, which require reoperation after the first surgery.
1.Selecting the timing of surgery
The period of 6 months after birth is the time to establish the basic functions of the hand. Due to the existence and continuous growth of the radial compound thumb, the thumb’s internal deformity is greatly affected, and the poor function of the child’s thumb to the palm, holding objects mainly relies on the internal thumb to hold objects, which affects the function of the finger body. At the same time, with the development of society and the progress of living standards, some parents are ashamed to bring their children to public places, which reduces the opportunities for children to contact with the outside world, and as they grow older, children themselves find that their fingers are different from others, so children and parents are prone to a series of psychological barriers. Nowadays, most of the parents of the children ask for early surgical treatment if they can tolerate general anesthesia without affecting the health of the children.
As a result, the timing of surgery for compound thumb deformity is becoming earlier and earlier. However, the younger the child is, the more delicate and incomplete the finger structure is, and the more difficult it is to recognize the abnormal anatomy, which increases the difficulty of surgery and the incidence of secondary deformity after surgery, so the timing of surgery is very important. It is currently considered that for simple duplicated thumb deformities, such as floating thumb, it can be resected at 6 months, and for complex duplicated thumb deformities requiring metacarpal osteotomy orthopedic cases, it is based on the time of appearance of the thumb ossification center [8]. The selection of the timing of surgery based on this has an objective nature. In the case of type IV, surgery should be performed at the age of 1 year because the ossification center of the terminal phalanx of the thumb appears at 1.5 years of age and the ossification center of the proximal phalanx appears at 1 year of age. needs to be performed within 1 year of age.
2. Selection of finger body for resection
Before the surgery, we should perfect the 1:1 ratio X-ray examination of both hands, perform compound thumb typing, and evaluate the development of the bone and joint. We will assess the degree of difference from the healthy side of the finger, measure the circumference of the finger at the level of the interphalangeal joint, measure the opening angle of the thumb, assess the stability and mobility of the joint, and assess the degree of deviation of the skeletal axis. Based on the above assessment, we will determine which side of the thumb to keep. If the developmental difference between the two thumbs is large, the thumb with poor relative appearance development, poor function or 3 phalanges will be removed. If the difference in appearance and function between the two thumbs is not obvious and the choice is difficult, the radial side is usually chosen to be removed to ensure the integrity and aesthetics of the tigers.
3.Analysis of secondary deformity types and causes
Many parents do not know enough about polydactyly and the risks of surgery, but they are eager to restore the normal appearance and function of their children’s fingers as soon as possible, and often have high expectations for the whole treatment process and results. Therefore, we need to fully understand the possible secondary deformities before surgery and inform the parents in detail so that they can objectively understand the disease and subjectively be prepared to treat the whole treatment process correctly. As doctors, we need to analyze in detail the possible causes of secondary deformities and reduce the factors that cause secondary deformities in the treatment process.
The analysis is as follows.
(1) Skewed finger body axis
(1) The finger bones of the child are not well developed, and after the osteotomy, the longitudinal axis and force line deviation gradually appear during the growth of the finger body. Therefore, it is necessary to choose the appropriate timing for surgery.
(2) If the longitudinal axis and force line are not osteotomized or not effectively corrected during surgery, the epiphysis of the finger bone is damaged, so the X-ray of both hands (1:1 ratio) should be checked before surgery, i.e., the X-ray equal to the actual size of the hand, and the size, position and angle of the osteotomized finger body should be measured before surgery.
(iii) Failure to provide exact fixation after osteotomy
The osteotomy requires strong internal fixation with a kerf pin. When surgically corrected, minor longitudinal deviation or angulation problems, the angle of deviation will become larger as the child grows. Therefore, it is very important to correct the ulnar radial deviation during surgery with the use of a Kirschner pin fixation. After surgery, external fixation with a cast is required for 4 weeks, and after the fracture heals, the kerf pins are removed, and then the brace fixation is continued for 3 months. Studies have shown that brace fixation, which can limit the lateral deviation of the finger body, can also move the interphalangeal and metacarpophalangeal joints and prevent joint stiffness.
④Tendon ligament factor
Nguyen Ngoc Hung described that when reconstructing the thumb abductor stop, a proximal basal cartilage block was preserved on the thumb abductor muscle of the radial finger, and a correspondingly sized and shaped cartilage block was made at the proximal base of the ulnar finger. After osteotomy, the cartilage block and the tendon stop were reconstructed in the corresponding position of the ulnar finger to strengthen the stability of the reconstructed thumb abductor stop. Salama and Weissman (1975) described an anomalous connection of the long thumb flexor and extensor tendons on the radial side of the thumb, and Miura (1977) noted that in polydactyly, the stops of the long thumb flexor and extensor tendons were deviated from the center of the base of the distal phalanx.
In the Wassel IV-D thumb, a new study by Nan found that there was no slide structure, the attachment point of the long flexor thumb tendon was on the radial side, the long extensor thumb tendon bifurcated at the level of the metacarpophalangeal joint, and the flexor tendon bifurcated at the level of the proximal phalanx in the proximal middle third, without a sheath. If these abnormal anatomic structures are not correctly recognized and treated, the continued abnormality of the tendon dynamics may lead to postoperative instability and angular deformity of the metacarpophalangeal and interphalangeal joints, i.e., Zigzag deformity, and Scott HK believes that osteotomy is not effective in correcting the Zigzag deformity and proposes tendon stop reconstruction and arthroplasty, which would be more effective than osteotomy. Nan Guoxin suggested to create a flexor hallucis longus tendon carriage during surgery, borrowing the displaced part of the tendon sheath, i.e., the fibrous membrane attached between the two proximal phalanges, cutting down from the radial finger, wrapping around the ulnar flexor hallucis longus tendon and turning it to the ulnar side, and suturing it.
Xu Yun-lan also found that the lateral deviation of the thumb joint was mostly due to the abnormal position of the tendon stop. He believed that the timing of wedge osteotomy should be delayed because of the imperfect bone development in young children. Therefore, he used the radial thumb flexor tendon to cross the ulnar flexor tendon and reconstructed the flexor tendon stop on the ulnar side of the base of the radial phalanx, so that the IP joint has two tendon stops to balance the muscle force and correct the lateral deformity of the joint.
⑤ Joint stiffness
It is often seen after Bilhaut-Cloquet surgery. Due to the unevenness of the re-formed joint, it makes the joint poorly aligned and affects the normal gliding of the joint. In addition, postoperative functional exercise is one of the important factors in improving joint mobility. Proper functional exercise is beneficial to the establishment of hand function, promotes the development of soft tissues such as muscles and tendons of the affected finger and bone shaping, and reduces the limitation of joint movement caused by contracted adhesions of ligaments and tendons.
(6) Tiger mouth stenosis
The main reason is that the gap between the ulnar thumb metacarpal and the second metacarpal is too small, and the effective opening of the tiger’s mouth is not performed during the orthopedic treatment, which aggravates the narrowing of the tiger’s mouth after surgery. In addition, if reconstruction of the thumb abductor stop and metacarpal osteotomy of the ulnar thumb are not performed, the narrowing of the tiger’s mouth may also be aggravated and the function of the thumb to the palm may be affected.
(7) Nail deformity
Nail deformities include small nail shape, split nail, and asymmetric nail contour. These deformities are often caused by the Bilhaut-Cloquet method. The causes of deformities include poorly designed nail bed excision, too tight nail bed sutures, inadequate skeletal closeness, unequal size of the primary nails of the two fingers, unequal merging, and mismatch between the width of the terminal phalanx and the reconstructed nail. Therefore, many scholars nowadays adopt the modified Bilhaut-Cloquet method, in which the nail, nail bed, and phalanges of the polydactyly are excised and an appropriately sized skin flap is preserved and combined with the preserved thumb to improve the shape of the thumb. The orthopedic thumb has a slightly smaller phalanx but better function and appearance and avoids nail deformity. The traditional Bilhaut-Cloquet method is only used to treat cases where two nails are joined or when the length and width of the preserved nail is less than 80% of that of the healthy finger, and advocates the use of 7-0 to 9-0 non-invasive sutures for suturing the nail bed. abid has adopted a modified method that preserves both the nail of the dominant finger, usually the radial side, and removes the middle part of the proximal phalanges of both fingers, combined, and the end phalanges are osteotomized, so that the complete nail of one side can be preserved and deformity can be avoided.
(8) Postoperative scarring
Nowadays, parents of children are more and more demanding about the appearance of the finger body, and if the finger body scar is obvious after surgery, it will definitely affect the surgical result. Moreover, postoperative scar contracture can cause joint contracture deformity and restricted movement. Therefore, it is important to reduce the formation of postoperative scars. When designing the incision, not only should we consider ensuring sufficient skin coverage of the preserved finger body to prevent postoperative scar contracture, but also the concealment of the postoperative scar. The flap design of the surgery can be done with a shuttle or ping pong racket-shaped incision to ensure that the radial incision is longer than the ulnar incision; for longer incisions, a Z-shaped incision is used to prevent the formation of linear scar. The incision suture is biased to the palmar side as much as possible, with as fine a needle and thread as possible and tension-free suture, either 7-0 or 5-0 cosmetic thread.
⑨ Continued growth of the excised finger
When removing the compound thumb, the epiphysis of the proximal phalanx of the compound thumb is not removed together, resulting in continued growth of the residual part of the epiphysis, local augmentation and lateral deviation of the thumb. In the case of the radial duplicated thumb, the corresponding articular surface of the metacarpal head was not removed, resulting in secondary deformity due to enlargement of the metacarpal head after surgery. The treatment is to remove the residual epiphysis or hypertrophic articular surface on the radial side of the metacarpophalangeal joint of the thumb and reconstruct the stop of the short thumb extensor muscle. In the case of the radial bulge of the metacarpophalangeal joint with ulnar deviation of the thumb, it is necessary to perform metacarpal osteotomy in addition to removal of part of the articular surface to completely correct the deformity.
4.The choice of surgical method
According to the cause of the secondary deformity after surgery, we choose the appropriate surgical method according to the type of deformity. There are three types of surgical methods: excision of the redundant finger combined with tendon ligament reconstruction, with or without wedge osteotomy; Bilhaut-Cloqllet surgery; and modified Bilhaut-Cloqllet surgery. The Wassel type IV also involves a large number of bones. Moreover, Wassel type IV involves both the interphalangeal and metacarpophalangeal joints, which can have serious consequences if dysfunction occurs at the same time.
Therefore, when choosing the surgical approach, for subtypes 1 and 2, resection of the redundant finger combined with tendon and ligament reconstruction, with or without wedge osteotomy, for types 3 and 4, if the difference between the two sides of the finger body is large, resection of the redundant finger is chosen. -In the case of subtype 4, where the development of the bones and joints on both fingers is significantly abnormal, a modified Bilhaut-Cloqllet procedure is performed to replace the bones with soft tissue merging to reduce complications such as bone discontinuity and joint ankylosis, and at the same time, tendon transfer and soft tissue narrowing on the convex side are used to achieve satisfactory surgical results and maximize the reconstruction of an aesthetic and functional thumb. Marie Maillet does not recommend a one-stage osteotomy.
Tien believes that surgery in infancy and early childhood should focus on soft tissue surgery to promote the development and recovery of the thumb, and that osteotomies are not recommended to prevent damage to the epiphysis and affect bone development. We believe that skin and soft tissue release, tendon reconstruction, and joint fixation can achieve good results for those with less severe skeletal deformities, but not for those with severe skeletal deformities, and suggest that skin and soft tissue release, tendon reconstruction, and joint fixation should be performed in one stage to improve the appearance of the affected hand, and then, when the child is older than 3 years old, Osteotomy is performed.
The thumb plays an important role in the normal life and work of people, so the treatment of repetitive thumb deformities is particularly important. The treatment should not only remove the redundant knuckles, but also objectively improve the thumb axis, stability and mobility of the metacarpophalangeal and interphalangeal joints, carpometacarpal joint mobility, and grip strength, and subjectively obtain a satisfactory thumb shape and contour of the thumb, reduce scarring, and nail deformity. Therefore, it is difficult to obtain satisfactory treatment results of the duplicated thumb. We have to carefully choose a reasonable treatment plan according to the specific conditions of the patient’s duplicated thumb in order to obtain the most satisfactory results.