Case 3 : Polydactyly of thumb
Surgeon: Malika Rumpradit, MD
Thai girl 7 years old presents with duplication of right thumbs since birth. She can use her hand well for grasping and pinching small object by her radial side thumb.
She is right hand dominant.
No family history of congenital defect.
Left hand: Duplication of thumbs.
: The ulnar side is slightly larger than the radial side but both thumbs are smaller compare to the right thumb.
: Both thumbs have normal nails.
: Normal function in key grip, precision pinch with dominant of radial side thumb.
: No sensory impairment.
Right hand: Normal.
Lower extremity: Grossly normal.
Head and neck: No anomaly.
Other systems: Within normal limit.
Figure 1. Preoperation
Film left hand: The phalanges are duplicate and articulating on the common broad metacarpal head.
: The metacarpal bone is single.
Figure 2. Film left hand , AP and oblique view.
Polydactyly of left thumb, Wassel Type IV.
Abation of radial thumb and collateral ligament reattachment.
After the general anesthesia with endotracheal tube was satisfied. The left arm was prepped and draped as usual. The tourniquet was raised to 200 mm.Hg.The incision was done at the dorsal surface between both thumbs.
The intrinsic muscles, Adductor pollicis muscle and Abductor pollicis brevis muscle, and the radial and ulnar collateral ligament were identified. The extra phalanges was removed .The radial collateral ligament was reattached to the base of proximal phalanx. The tendon of Abductor pollicis brevis muscle was advanced to the extensor tendon by vicryl 5-0 for centralization and stability of thumb. The skin was closed with nylon 6-0.
Figure 3. Postoperation
The most widely used classification scheme for congenital malformations of the upper extremity was proposed by Swanson and accepted by The American Society for Surgery of the Hand (ASSH) and IFSSH. The deformities are classified into 7 groups.
1. Failure of formation of parts
2. Failure of differentiation (separation) of parts
4. Overgrowth (Gigantism)
5. Undergrowth (hypoplasia)
6. Congenital constriction band syndrome
7. Generalized skeletal abnormalities
Polydactyly means digital duplication and is the second most common congenital hand anomaly. It is classified in duplication group believed to result from a cleaving insult to the limb bud or the ectodermal cap during embryological differentiation in 25- 50 day.
Polydactyly of the thumb (preaxial polydactyly) is the common congenital anomaly accounted for 6.6% of all hand deformities. It is most common in the Whites and Asians.
Figure 4. Wassel’s classification
Wassel (1969) classified thumb polydactyly into 7 types. This patient is classified in Type IV. It represents duplication of both phalanges and common boarded metacarpal head and is the most common types ,seen in 50% of patients.
The aims of treatment are:
1. Restoration of basic functions of a normal hand.
2. Unrestricted growth
2. Acceptable appearance
The timing of surgery is important. Early surgery requires great care because the hand is very small. The hand rapidly increases in size during the first 4 years. In case of polydactyly the surgery is suggested to perform in 1-3 years of age. By this time the hand is larger, the anesthesia is easier and the surgical dissection is more predictable.
The prime function of thumb is to be in opposition against the other digits and the prerequisites for stable pinch, especially a stable metacarpophalangeal ulnar collateral ligament. The ulnar side of the thumb should be preserved by this reason. Fortunately the radial side is usually the more hypoplasic allowing conservation of the ulnar part and its important ulnar collateral ligament.
In this case, the radial thumb is sacrificed by the two digits are almost equal in size. This preserves the normal sensation on the important ulnar side of the thumb and maintain stability in pinch by undisturbed the ulnar collateral ligament of the metacarpophalangeal joint. The Abductor pollicis brevis muscle reinsertion is required and the intact ligament of the deleted digit is used to reconstruct the radial collateral ligament. The parent should be advised that the remaining part is always hypoplasic compare to the other side .
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