PMC4382757_01
Types of thumb duplication and level of bifurcation according to Wassel's classification. DP = Distal phalanx, IPJ = Interphalangeal joint, PP = Proximal phalanx, MPJ = Metacarpophalangeal joint, M = Metacarpal, and CMJ = Carpometacarpal joint.
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F2
Ulnar-side thumb had flexion deformity of interphalangeal and metacarpophalangeal joints [Figure 2].
42-year-old man with isolated left-hand duplicated thumb. Clinical photo of the left hand (a) side view shows pre-axial polydactyly, (b) front view shows the extra digit is mildly hypoplastic, has flexion deformity of interphalangeal joint (black arrow), and hyperextension of metacarpophalangeal joint (dotted arrow) (swan neck deformity). Ulnar-side thumb has flexion deformity of interphalangeal and metacarpophalangeal joints (white arrow).
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F3
Plain radiographs showed duplicated phalanges with bifid first metacarpal [Figure 3].
42-year-old man with isolated left-hand duplicated thumb. Plain radiographic image shows duplicated phalanges with bifid first metacarpal. Swan neck deformity is observed as hyperextension of metacarpophalangeal joint (white arrow) and flexion deformity of interphalangeal joint (dotted arrow). Ulnar-side thumb is articulated with the metacarpal head and has flexion deformity of interphalangeal and metacarpophalangeal joints (arrowhead).
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F4
A sesamoid bone adjacent to the metacarpophalangeal joint of radial-side thumb was observed on the axial and coronal reformatted CT images [Figure 4].
42-year-old man with isolated left-hand duplicated thumb. (a and b) Coronal reformatted consecutive CT images show the proximal (p) and distal (d) phalanges of the radial thumb. A sesamoid bone (s) is also observed. (b) CT image shows swan neck deformity as hyperextensionof metacarpophalangeal joint (dotted arrow) and flexion deformity of interphalangeal joint (arrow). (c) CT image shows the proximal phalanx articulates with the first metacarpal (arrow). (d) CT image shows the articulation between proximal phalanx and first metacarpal (arrow). M = First metacarpal, P = Proximal phalanx, D = Distal phalanx, PP = Proximal phalanx of the ulnar-sided thumb, S = Sesamoid bone.
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F5
Three-dimensional (3D) reformatted CT images showed the general view of the articulations and abnormal bones [Figure 5].
42-year-old man with isolated left-hand duplicated thumb. (a) Three-dimensional reformatted CT images show the articulations of radial-side and ulnar-side thumbs. The radial-side thumb has hyperextension of metacarpophalangeal joint (white arrow) and flexion deformity of interphalangeal joint (dotted arrow). (b) Ulnar-side thumb has flexion deformity of interphalangeal and metacarpophalangeal joints (arrowhead).
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F6
Ulnar- and radial-side flexor pollicis longus tendons inserted into the palmar aspects of the distal phalanges as seen on the coronal multiplanar reformatted and axial CT images [Figure 6]. Transverse interconnecting fibers were observed between the radial- and ulnar-side flexor pollicis longus tendons [Figure 6]. Abductor pollicis brevis intrinsic muscle inserted into radial aspect of the proximal phalanx of radial-side thumb [Figure 6].