|
Year |
2001 |
|---|---|
|
Question Number |
221. |
|
Category |
Select |
Question
A 25-year-old construction worker reports a mass on the dorsum of his hand that is painful with strenuous use. Examination reveals a 4-x2- x 1-cm soft mass that overlies the proximal portions of the index and middle metacarpals. It moves with flexion and extension of those digits, becomes firmer with forceful grasp, and does not transilluminate. What is the most likely diagnosis?
1. Dorsal wrist ganglion
2. Extensor tenosynovitis
3. Giant cell tumor of the tendon sheath
4. Carpal boss
5. Anomalous extensor muscle
Figures
Answer (click for answer)
Answer: 5
Anomalous extensor muscles of the hand are not uncommon. Well-recognized anomalies include anomalous extensor indicis proprius (aEIP), extensor digitorum brevis manus (EDBM), extensor medii proprius (EMP), and extensor indicis et medii communis (EIMC). aEIP and EDBM may occasionally give rise to dorsal wrist pain and the diagnosis is often confused especially in the presence of other findings such as a ganglion.
AEIP
The origin of and insertion of the aEIP are the same as the EIP, but it’s muscle belly passes beyond the fourth compartment during full flexion of the wrist. There is a 4% incidence reported by anatomic studies. The aEIP may undergo considerable tenosynovial proliferation around its bulky musculotendinous portion secondary to constriction within the confines of the fourth dorsal compartment. This results in dorsal wrist pain that is aggravated by activities and localizes over the EIP musculotendinous junction and the tendons of the EDC within the fourth dorsal compartment. Pain is characteristically elicited by extension of the index finger against resistance with the wrist in flexion (the extensor indicis proprius test); absence of pain during this test rules out this condition.
EDBM
The extensor digitorum brevis manus muscle(EDBM) reported incidence in dissection studies is between 1% and 9%. It occurs bilaterally in approximately one third of cases and there is no difference in the incidence between the right and left hands or between genders. In contrast to the aEIP, the proximal belly of the EDBM always lies distal to the distal edge of the extensor retinaculum. It becomes more prominent and firm or painful when the wrist is slightly flexed and the finger fully extended or with the finger actively extended against resistance. Absence of transillumination or fluctuation and a negative aspiration test are sometimes misleading because a ganglion may occasionally coexist. A clinical diagnosis of EDBM can be made without surgical exploration and can be confirmed by EMG. The EDBM usually causes little or no pain. However, resistive extension of the fingers may cause pain in the hands with the EDBM or pain maybe reproduced with patients pushing the palm against a table with extension of the wrist. Virtually all patients who have required surgery have been manual workers. When the muscle is present bilaterally, symptoms usually occur in the dominant hand.
Dorsal wrist pain should only be attributed to anomalous extensor muscles if the following conditions are met: (1) the symptoms are intermittent and occur only after repeated movements that involve the anomalous muscle mass traversing the dorsal compartments, (2) the pain can be documented on active resistive extension, (3) the presence of an anomalous muscle has been proven either by operative intervention or imaging, (4) there are no associated conditions such as a ganglion that are treated at the same time, and (5) surgical decompression of the fourth dorsal compartment (for aEIP) or surgical reduction of the muscle belly (for EDBM) leads to symptomatic relief.
Giant Cell Tumor of the Tendon Sheath: These occur on the palm side of the finger, usually to people over the age of 30, somewhat more often to women than men (ratio of 3:2). A giant cell tumor is a slowly enlarging painless mass. Sometimes patients will have limited tendon function due to adhesions.
Carpal boss: Located at the base of the second and third metacarpals on the surface of the hand. Usually affecting people between the ages of 30 and 50 and most common in women. There is a slight bump due to a bony ossicle/bone spur.
Ganglia: Soft tumor cysts arising from joint capsules or tendon sheaths, filled with fluid. Depending on their size and location, ganglion cysts can result in limited joint motion. Clinically, ganglion cysts will transilluminate.
Reference: Tan ST, Smith PJ: Anomalous extensor muscles of the hand: A review. J Hand Surg Am 1999;24:449-455
Doyle JR: Extensor tendons: Acute injuries, in Green DP, Hotchkiss RN, Pederson WC (eds): Green’s Operative Hand Surgery, ed 4. New York, NY, Churchill Livingstone, 1999, pp 1950-1987.