gms | German Medical Science

Objectives/Interrogation: Ulna dimelia is a rare congenital disorder, presenting with mirror hand, a term that describes the clinical presentation of this condition. But not all patients present with symmetry. There are numerous variations of digits in this condition, mostly seven fingers are present. The normal pre-axial or radial structures, like thumb, index, trapezium, scaphoid and radius are missing and the radius is replaced by a second ulna.

As genetic knowledge about limb bud formation increases, there is still a paucity of data regarding optimal treatment of this condition.

Methods: Problems that need to be taken into account in the treatment of mirror hands with ulnar dimelia are:

Limited elbow movement, decreased pro-/supination of the forearm, flexion contracture of the wrist with radial deviation, absent or weak extensor tendons, supernumerous digits but absent thumb, absent first webspace and thenar, thus no opposition, furthermore there may be syndactyly, divergent metacarpals and/or a palmar cleft.

In order to achieve an optimal functional outcome with an aesthetically pleasing, or at least inconspicuous, result one has to combine multiple steps of treatment that should be carefully planned and combined, if feasible, in order to minimize patient and his family's burden.

The authors present their experience in treating several cases including the treatment protocol that developed over time as well as intraoperative steps and long-term follow-up.

Results and Conclusions: Our treatment strategies are derived from experience with congenital disorders. This knowledge lead to optimisation of the treatment of mirror hand. Furthermore experience with our own cases and their follow-up improved our strategy. The rarity of this congenital anomaly prevents feasibility of randomized controlled trials, because even if those would be ethically accepted, there would not be enough statistical power to those studies due to the limited number of cases. Thus the best available evidence is level IV.

The first step is adequate diagnosis, clinical and radiologic examination. When elbow flexion is feasible, which is mostly the case in young babies, the deviated wrist is splinted to correct deviation. The next step is a 3-dimensional distraction, similar to radial club hand treatment and thereafter a modified centralization. Thereafter a modified pollicisation with a reasonable compromise between form and function follows. Later a modified resection arthroplasty of one of the olecranons is helpful in improving pro-/ supination.