Anatomic changes and treatment strategy of crab claw like Polydactyly of the thumb

Abstract

Objective To observe the pathological anatomy of crab claw hke polydactyly of the thumb,analyze the possible mechanical mechanism and propose surgical strategies based on their treatment outcomes.Methods The intraoperative findings and X-ray morphology of 36 cases of crab claw hke polydactyly were analyzed.Based on the prevalent pathological deformity,modified Bilhaut-Cloquet technique was used to correct the deformity and reconstruct the thumb.Osteotomy and tendon insertion reattachment was done to re-align the axis.Results Crab claw hke polydactyly of the thumb had a typical 'S' shape and reverse 'S' shape appearance.There were different degrees of lateral angulations of both the IP joint and MP joint.In addition there was rotational deformity of the MP joint.The duplicate thumbs shared extensor and flexor tendons.The extensor tendon bifurcated at the level of the MP joint,while the flexor tendon bifurcated at the level of the IP joint.Both tendons terminated at the lateral aspect of the distal phalanx base.All the thenar muscles inserted at the radial side of the proximal phalanx base.Modified Bilhaut-Cloquet technique was used to correct the deformities.The result was satisfactory in 30 cases.Five cases were revised because of alignment shift.One case was revised because of double nail deformity.Conclusion The crab claw like polydactyly thumb is generally smaller than a normal thumb.The modified Bilhaut-Cloquet should be the major surgical procedure for reconstruction.Abnormal insertion of the tendons as well as bone and joim malformation are the two major causes for alignment shift.Osteotomy and tendon insertion reconstruction should be routinely adopted. Key words: Hand deformities, congenital; Surgical procedures, operative; Treatment outcome