The Thumb in Arthrogryposis

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

Central Deficiency, Severe

Central deficiency (cleft hand) may present in many different ways.  Sometimes, there is just long (or middle) finger absence and other times more than one digit may be missing.  The thumb- index web space is often affected, ranging from a mild narrowing to a complete syndactyly/ merging of the space.

In this young patient, both the long finger and the ring finger are completely absent.  There is a large cleft between the index finger and the small finger.  Finally, the thumb and the index finger are merged.

The primary functional limitation for this child is related to the lack of a thumb- index web space.  This affects large object grasp (think: soda can) and tip-to-tip pinch (think: manipulating beads).  In some children the large space between the index and small fingers (the cleft) can return some of this functionality, but certainly not all function.

Central Deficiency (cleft hand) with merged thumb and index finger.

Xray of central deficiency (cleft hand) with missing long and ring fingers.

If both the thumb and index finger have independent function on examination (can be difficult to assess), separation can be accomplished with reconstruction of the thumb- index web space.  This provides a thumb and two fingers.  It is important to note that reconstruction is not appropriate in all children with a limited number of digits and a number of factors should be considered including the opposite hand (i.e., whether it is affected).  Some families will favor a surgical approach while others may not.

Amniotic Constriction Band

The cause of amniotic constriction band is uncertain.  Some believe it is a developmental issue (a "dysplasia" resulting from abnormal development of the structures) and others believe that it is a "deformity" that results from banding or pressure on previously  normal structures.  Either way, at the time of birth, a variety of differences can be noted.

Banding, or ringing, of a finger, forearm, or leg can occur.  This is usually a problem only with appearance but deeper bands can also affect function.  Amputations (possibly from extremely tight bands or direct pressure in utero) can also occur.  The amputations usually affect fingers (or toes) or parts of fingers (or toes).  Finally, syndactyly (abnormal joining of the fingers) can also occur.  This type of syndactyly differs from other forms as the fingertips are joined whereas there are fenestrations (or holes) between the fingers closer to the hand.  Sometimes the tips of multiple fingers are joined together.  It is common for more than one extremity to be affected.

In the pictures below, the thumb and small finger are normal.  The index, long, and ring fingers are short due to amputations.  The long and ring fingers are syndactylized (joined at tip) but there is a fenestration between the digits.

Amniotic constriction band affecting short central fingers with a perforation (fenestration) between the fingers.

Palmar view of central digits affected by amniotic constriction band.