Referred pain patterns of the third and fourth dorsal interosseous muscles.

BACKGROUND Myofascial pain (MP) is a common disorder that can involve any skeletal muscle in the human body. There are no published reports of the referred pain patterns of the third and fourth dorsal interosseous muscles. OBJECTIVE To investigate the referred pain patterns of the third and fourth dorsal interosseous muscles. STUDY DESIGN Prospective evaluation. SETTING Academic medical center. METHODS Twenty healthy adults participated in the study. Needle placement and injection of 0.2 mL 6% hypertonic saline solution into the midpoint of the interosseous muscles were performed under ultrasonographic (US) guidance. After the injections, the participants were instructed to wait until they felt the most pain and then draw a pain diagram. This drawing was transferred to the computer for analysis. RESULTS The referred pain distributions for the third dorsal interosseous muscle were as follows: the interdigital space of the third and fourth fingers, 80%; the distal phalanx of the third and fourth fingers, 45%; and the ulnar side of the palm, 55%. Three and 6 participants reported pain on the volar side of the wrist and in the fifth finger, respectively. The referred pain distributions for the fourth dorsal interosseous muscle were as follows: the interdigital space of the fourth and fifth fingers, 80%; the hypothenar area, 65%; and the distal phalanx of the fourth and fifth fingers, 60%. Seven and 3 participants also reported pain on the ulnar side of the wrist and the ulnar side of the forearm, respectively. LIMITATION This study is limited by its small sample size. CONCLUSION Referred pain patterns of the third and fourth interosseous muscles resemble the pain experienced in C7 or C8 radiculopathies or the ulnar neuropathy. Thus, identification of the third and fourth interosseous muscle trigger point should be considered when patients experience pain on the ulnar aspect of the hand and wrist.