Triphalangeal Thumbs in the Pediatric Population: Long Term Outcomes Following Surgical Intervention

Phalanx of Supernumerary Digit of Hand

delta phalanx, thumb reconstructed, triphalangeal thumbs

A triphalangeal thumb is a thumb with three phalanges. The thumb often appears long and fingerlike, and can sometimes be in the same plane as the other fingers. Anatomically, the extra phalanx can have different shapes. Several classification systems have been used, but the simplest and most often used is the Wood (1976) classification by the shape of the extra phalanx. If the extra phalanx is triangularly shaped it is classified as a type I. Type II has a rectangular shaped extra phalanx but it has not developed as a full phalanx. Type III is a full extra phalanx.

A triphalangeal thumb is a thumb with three phalanges. The thumb often appears long and fingerlike, and can sometimes be in the same plane as the other fingers. Anatomically, the extra phalanx can have different shapes. Several classification systems have been used, but the simplest and most often used is the Wood (1976) classification by the shape of the extra phalanx. If the extra phalanx is triangularly shaped it is classified as a type I. Type II has a rectangular shaped extra phalanx but it has not developed as a full phalanx. Type III is a full extra phalanx. Different treatment strategies have been developed based on the type of triphalangeal thumb. This project looks specifically at type I, or a delta phalanx. The goals of surgery in any type are to reconstruct the anatomic deformity with a stable, functional thumb while providing an acceptable appearance. There is no consensus on how triphalangeal thumbs with a delta phalanx should be treated. Bunnell and Campbell in the 1940s advocated doing no surgery at all. Milch advocated excising the abnormal phalanx in the pediatric population but supporting non-operative treatment for the adult population. A potential unwanted result of excision has been an angulated joint. Buck-Gramcko proposed that excision of the delta phalanx combined with ligament reconstruction could give a better result than with excision alone. Hovius recommended different treatment based on the age of presentation. For patients less than 6 years, he advocated excision of a transverse oval piece of skin, resection of the extra phalanx with reconstruction of the radial collateral ligament at the new IP joint, and lengthening of the ulnar collateral ligament. For patients older than 6 years, he advocates partial resection of the extra phalanx with correction of the angle and arthrodesis of the DIP joint. Usually, collateral ligament reconstruction is not necessary in these cases. Horii et al reviewed 13 type I delta triphalangeal thumbs with no associated hand abnormalities. Surgical treatment for these patients consisted of excision of an accessory phalanx and the repair of the collateral ligament. The IP joint was temporarily fixed with Kirschner wires for 4-6 weeks. Mean follow-up was 8.9 years. All patients were satisfied with the improvement in appearance. The mean IP joint motion was 54 degrees. No patients complained of instability or pain in the IP joint. Only one patient had ten degrees of lateral bending. They recommend operating on these patients between ages 1-2 years, when the phalangeal epiphyses becomes clear. They felt that earlier excision allows for better joint adaptation. The children also will learn how to use their hands correctly. Recently it has been debated that it is beneficial to wait to operate on these children until they are older, and their bones and joints have matured. At that point, an osteotomy could be performed. Although these results have not been published yet, several well-respected hand surgeons have concluded that their outcomes have been better on patients who have had delayed surgery. In our institutions, children generally have their thumb reconstructed using a delta phalanx excision with repair of the ligament around 1 to 2 years.

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