Thumb posture is a common difficulty in children with arthrogryposis. The thumb assumes a flexed (bent) posture at the metacarpophalangeal (MCP) joint and also may be adducted (tight towards the index finger). As the thumb is positioned across the palm, grasping with the fingers is a challenge (which is especially troublesome given that finger motion is already limited in many children).
There are several different strategies in the surgical correction of thumb position in arthrogryposis. However, the basic principles are to
1) widen the first web space (between the thumb and the index finger) and
2) correct the flexed position of the thumb.
Z- plasty (straightforward skin re- arrangement) can be considered in many conditions but is not our preferred choice for most children with arthrogryposis as a more significant correction of the skin deficit is required. We typically use a flap from the index finger that successfully deepens the web space in 3- dimensions and also allows exposure to address tight thenar musculature.
Correction of the flexed posture of the thumb may be accomplished with tendon transfer in those children with reasonable muscle quality or with a fusion of the MCP joint (technically not a fusion as would be performed in the adult but similar conceptually).
When successful, thumb surgery places the thumb into a position of function. This allows the best overall hand function and improves the ability to grasp large objects (think: soda can).
|Pre surgery right thumb|
|The arthrogrypotic right thumb is before surgery and the left has been treated with surgery|
|Palmar view of uncorrected and corrected arthrogrypotic thumbs|
|Flap placed to resurface web|
|See flap creation from index finger|
|Flap resurfacing first web space|