Typical Patterns of Communication between palmar bursae.

Typical Patterns of Communication between palmar bursae.

Communication between the radial bursa and the FPL tendon sheath is the rule, reported in 100% of cases in both anatomic and imaging studies. Communication between the ulnar bursa and the FD5 tendon sheath is slightly less common, occurring in approximately 80% of persons. Communication between the ulnar and radial bursae at the level of the carpal tunnel is common, occurring in 50%-100% of persons. An ‘intermediate bursa’ consisting of accessory synovial sacs along the FD2 tendon has been identified as a site of communication between the radial and ulnar bursae (8a).

Cadaveric section through the carpal tunnel depicting communication of the radial bura (blue dotted lines) and the ulnar bursa (yellow dotted lines). Green gelatin, previously injected into the FPL tendon sheath at the level of the proximal phalanx, is seen within both the radial and ulnar bursae.

A fat-suppressed T1-weighted post-contrast coronal image of the hand at the level of the carpal tunnel in a 58-year-old woman with horseshoe abscess due to tuberculosis. Note involvement of the the FPL (short arrow) and FD5 (long arrow) tendon sheaths. The digital flexor sheaths of FD2, FD3, and FD4 are spared (arrowheads).