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Thenar Space

spatium thenaris

The thenar space is the radial potential space in the deep palm, bounded medially by the oblique septum (midpalmar septum) running to the middle finger metacarpal, laterally by the thenar muscles (adductor pollicis and flexor pollicis brevis), anteriorly by the flexor tendons to the index finger, and posteriorly by the adductor pollicis fascia. It is separate from the midpalmar space by the oblique septum.

Region: Hand & Wrist

Clinical Relevance

Clinical Notes

Thenar space infection from puncture wounds or web space infection spreading radially produces a tense, tender thenar eminence swelling with the thumb held in abduction (characteristic posture from adductor pollicis distension). Drainage requires both dorsal and palmar incisions to adequately decompress the space. Thenar space infections are uncommon compared to midpalmar space infections because the radial space is more enclosed. Untreated thenar space infection can produce finger web space involvement and dorsal hand oedema.

Pathology

Common Injuries & Conditions

Thenar Space Infection from Penetrating Hand Wound

Puncture wound to the thenar eminence or index finger web introduces organisms into the thenar space, producing characteristic abducted thumb posture, tense thenar swelling, and pain reproduced by passive thumb adduction; surgical drainage through longitudinal palmar and dorsal incisions at the web space decompresses the radial deep palmar space.