APPROACH TO THE LATERAL (THENAR) MIDPALMAR SPACE

USES

This approach is used for decompression of midpalmar abscesses, or to access the index flexor tendons in zone 3 or the origin of the transverse head of the adductor pollicis from the volar shaft of the third metacarpal.

ADVANTAGES

This is the most direct approach to the lateral (thenar or radial) midpalmar space.

DISADVANTAGES

Proximal extension of the incision must be done carefully, as the recurrent motor branch of the median nerve lies near the proximal extent of the incision. This approach only decompresses the lateral (radial) midpalmar space. The medial (ulnar) midpalmar space must be opened through a separate incision.

STRUCTURES AT RISK

The digital nerves to the index and long finger are at risk, as is the recurrent motor branch of the median nerve.

TECHNIQUE

The skin incision lies just ulnar to the thenar crease and parallels the thenar crease. Bluntly dissect through the palmar fascia overlying the flexor tendons to the index finger. Identify the digital nerves and vessels lying alongside the flexor tendons. Open the interval between the flexor tendons and the ulnar neurovascular bundle. The thenar midpalmar space is the potential space below the index and long flexors and above the adductor pollicis muscle. Often, when decompressing a lateral midpalmar space abscess, a separate dorsal incision along the radial border of the index metacarpal should be done to address potential collar button abscesses.

TRICKS

Retract the index flexors and the lumbrical radially to minimize injury to the lumbrical and to provide better access to the origin of the transverse head of the adductor pollicis.