To allow for a better understanding of the surgery for polydactyly of the thumb, the preoperative and postoperative photos have been uploaded to this page. These photos are taken with permission from the patients’ families, through their kind wish to help future patients. Therefore, please refrain from copying or reproducing the photos on this website.
In the surgery, reconstruction is carried out to regain the mechanical equilibrium of the thumb, whilst also considering the aesthetic outcome. The knowledge regarding the anatomy of the congenitally abnormal hand, the understanding of the biomechanics involved, and the reconstructive technique of the bone and soft tissues based on these factors differs between surgeons. The designing and suturing technique, and postoperative wound care all affect the aesthetic outcome of the surgery.
Especially, the types mentioned below require particular care.
(1) Wassel's type IV in which the two angled thumbs form a V shape require a high level of reconstructive technique and experience. In Wassel's types V and VI, adduction of the thumb and instability of the MP joint can be problematic. These types should be operated on by a hand surgeon who specialises in congenital hand abnormalities.
(2) Postoperatively in types I, II and III, tapering of the fingertip, asymmetrical appearance around the nail, exposure of palmar skin with fingerprint to the dorsal side, and presence of a linear scar on the dorsal side can be problematic. To overcome these issues, precise surgery needs to be carried out by combining the necessary parts from each finger to reconstruct a thumb of natural size, symmetry, and rounded shape.
Here, the Wassel's Classification (refer to the page on the classification of polydactyly of the thumb) has been applied, classifying the cases according to the level of duplication of the radial thumb, from level I to VI.
If the distal phalanx is bifid, the radial and ulnar nails will be fused, appearing as one wide nail. The surgery will leave the thumb on the ulnar side, but reduction or merging of the proximal phalanx may be necessary if it is wide. Aesthetically, the surgery is designed with the goal to leave no scar on the dorsal aspect of the thumb, form a symmetrical nail, and make the radial side of the fingertip round.
The angle of the distal phalanx, as well as the size and symmetry of the nails, are taken into account in deciding whether to leave the ulnar thumb or to carry out the Bilhaut procedure. If the nail is large and symmetrical, the thumb on the ulnar side (pinky side) is left. The ligament for the radial side of the thumb will be taken from the thumb on the radial side. Similarly to Wassel type I, aesthetically, the surgery is designed with the goal to leave no scar on the dorsal aspect of the thumb, form a symmetrical nail, and make the radial side of the fingertip round.
If the skeletal bifurcation occurs at the tip of the proximal phalanx, the nails are often small and asymmetrical and thus the Bilhaut procedure is considered. The joint of the merged nails will become less noticeable over time, but if it remains noticeable, corrective surgery can be carried out. The proximal phalanges will be merged as well. The surgery requires a high level of technique, so it is only recommended for surgeons who specialise in polydactyly of the thumb to operate on these cases.
A case treated with the Bilhaut procedure. The Bilhaut procedure is appropriate in cases where the two thumbs are of the same size. A single thumb is reconstructed by taking half the nail and bone from each thumb. The thumb was able to become the same size as on the other hand.
A large flat nail is reconstructed by joining the small nails from each thumb.
If the skeletal bifurcation occurs at the MP joint, the thenar muscles will need to be operated on. The surgery is relatively simple if the ulnar thumb is straight. It is necessary to ensure that the abductor pollicis brevis muscle is able to perform thumb opposition by internally rotating the thumb. On the other hand, if the joint is unstable and the thumb is angulated, the soft tissue will need to be adjusted. In such case, it is recommended to be treated by a specialist surgeon. Even if the finger is angulated, it can often be corrected to become straight by adjusting the soft tissues, and the need for osteotomy is carefully evaluated. If both thumbs are very slim, the Bilhaut procedure may be adopted, but it is extremely difficult to make the nail and scar neat, and there may be reduced range of movement and deviation at the IP joint.
A case treated with the ulnar thumb reconstruction procedure: This is appropriate in cases where one thumb is larger than the other. In this case, the ulnar thumb is reconstructed. To straighten the thumb, the course of the tendon will be centralized, and corrective osteotomy of phalanges will be indicated.
A case treated with the Bilhaut procedure: The Bilhaut procedure is appropriate in cases where the radial thumb and ulnar thumb are of similar size. A single thumb is reconstructed by taking half the nail and bone from each thumb. The thumb was able to become the same size as on the other hand.
The Bilhaut procedure undertaken for these cases require an exceptionally advanced level of technique. It should not be carried out unless the surgeon is highly experienced with this procedure.
If the thumb bifurcates at the level of the metacarpal bone, the abductor pollicis brevis muscle is hypoplastic and the force balance of thenar muscles is shifted towards an adduction/flexion position. Because of this, it is necessary to confirm if the first metacarpal bone is adducted using an X-ray. If narrowing of the first interdigital space is confirmed, interdigital space reconstruction will be carried out. In some cases, the abductor pollicis brevis muscle is short, and it may not be possible to transfer it, as done in Wassel's type IV. Depending on the postoperative course, osteotomy or opponensplasty may be carried out. Because cases of Wassel's types V and VI are relatively rare, it is recommended to be treated by a surgeon who is highly experienced with these cases.
The thumb is duplicated at the level of the carpometacarpal joint. In this type, the abductor pollicis brevis muscle is very hypoplastic and the balance of thenar muscles is shifted towards an adduction/flexion position. The first metacarpal bone is thus in an adducted position on X-ray. There are cases in which, on the ulnar (pinky side) thumb, the ligament on the ulnar side of the MP joint is loose, causing radial deviation of the thumb. As a result, although the space between the thumb and index finger may appear adequate, X-ray images demonstrate that the proximal phalanx and metacarpal bone are not aligned, as seen on the photos below. Due to narrowing of the first interdigital space, interdigital space reconstruction will need to be carried out. The adductor pollicis muscle may also need to be operated on. As the abductor pollicis brevis muscle is very small, the flexor pollicis brevis muscle will mainly be transferred. Depending on the postoperative course, osteotomy or opponensplasty may be carried out. Because cases of types V and VI are relatively rare, it is recommended to be treated by a surgeon who is highly experienced with these cases.