Trigger Wrist Caused by Lumbrical Pathology: A small case series and Review of Literature

University of Connecticut – School of Medicine

Edward Hahn, Jr., M.D.1, Duffield Ashmead IV, M.D.2

1. Hand Surgery Fellow, Univ of Connecticut – School of Medicine, Dept of Orthopaedic Surg2. Program Director, Hand Surgery fellowship, Univ of Connecticut – School of Medicine, Dept of Orthopaedic Surg

Triggering at the wrist associated with finger motion is a rare occurrence, and should be differentiated from the wide variety of far more frequently encountered mechanical complaints at the wrist related to wrist motion. A recent case prompted us to revisit two earlier, similar cases for review, analysis and discussion.

Case Report #1:

A 43 year-old right hand dominant male, computer engineer, presented with a painless right mid-palmar mass. A “bump” in the area had been noted as early as 15 years earlier, but had seemed to resolve with local massage. By the time of presentation the patient had developed a triggering sensation in the area of his wrist and distal forearm with movement of his middle finger. Concurrently he had developed symptoms indicative of carpal tunnel syndrome evidenced by occasional numbness and tingling in the index and middle fingers. Physical examination revealed a discreet, non-tender, palpable mass of the right mid palm measuring approximately 2 cm in diameter. The mass appeared to be move proximally and distally with flexion and extension of the right middle finger, and specifically with the profundus tendon excursion. MRI imaging demonstrated a 1.1cm x 1.1cm x 4.3cm heterogeneously hyperintense T1 soft tissue mass in the area of the middle finger lumbrical muscle.

An open carpal tunnel decompression and surgical exploration was performed. The mass was not immediately appreciated. Careful dissection deep to the middle finger lumbrical muscle demonstrated an ill-defined multi-lobular fibrous neoplasm, which appeared to be arising at the interface of the lumbrical (Fig 1) and flexor profundus tendon (Fig 2 and 3). The lumbrical was easily distinguished from the tumor in-situ. Histologic examination concluded the tumor to be a fibroma.

Fig.1. Lumbrical (blue arrow) distorted by tumor

Fig. 2 and 3. Neoplasm dissected from the lumbrical (blue arrow) and seen attached to the flexor digitorum profundus tendon.

Fig 4. Neoplasm completely excised

Case Report #2:

A 52 year-old right hand dominant male, cardiac surgeon was evaluated for symptoms indicative of carpal tunnel syndrome, specifically episodic numbness and tingling in the area of the radial half of his right hand. Onset was approximately one year ago, and initially noted in the context of bicycling. After nearly one year, the paresthesia had progressed to be nearly constant. A nocturnal exacerbation had developed, requiring the patient to shake his hands to temporarily relieve the acute exacerbation. Also at this time, the patient developed a painful popping or triggering sensation with vigorous flexion and extension of the right index finger. On examination, a triggering phenomenon was demonstrated with vigorous fisting. Palpation of a low-pitched and impressive trigger phenomenon was appreciated at the radial margin of the carpal tunnel. Isolated testing of the index sublimis tendon failed to replicate this phenomenon, which suggested a profundus relationship.

Sensory exam demonstrated intact function with 2 point discrimination within 2-3mm. An open carpal tunnel decompression and surgical exploration was performed. A fusiform tumor was found arising at the lumbrical origin of the index profundus tendon. The tumor was carefully dissected free of the adjacent lumbrical and tenosynovial attachment. The fingers were passively ranged and demonstrated smooth and uninterrupted gliding excursion within the carpal tunnel. Histologic examination found the tumor to be consistent with a spindle cell lipoma. Post-operatively carpal tunnel symptoms and mechanical complaints resolved, and the patient was able to resume his duties as a cardiac surgeon. At long term follow-up there were no ongoing concerns.

Case Report #3:

A 41 year-old right hand dominant male presented with complaints of left wrist pain that developed after an altercation at his work as a corrections officer. He reported sharp pain at the mid volar wrist with rang of motion of middle and ring fingers. Physical exam findings were not very significant, and revealed mild tenderness at the level of the carpal tunnel. The patient demonstrated full range of motion of all digits, although resisted engagement of the middle and ring fingers elicited pain. The patient was treated for sprain of the left wrist that possibly involved intertendinous bands between the middle and ring finger flexors. Twelve weeks of conservative treatment modalities consisting of rest and limited physical engagement failed to relieve the discomfort, and in fact, the patient developed a precipitous increase in tenderness immediately proximal to the carpal tunnel. Interesting, he also developed an impressive wrist triggering, particularly palpable at the ulnar sided flexors, conceivably involving the ring and small finger flexor tendons. MRI imaging was not impressive, and merely demonstrated mild soft tissue edema surrounding the flexor tendons of the ring and small finger at the level of the carpal tunnel.

Operative exploration was undertaken to investigate the cause of the patient’s wrist triggering, and ill-defined wrist pain. A standard carpal tunnel incision was made and vital structures retracted and preserved. Examination of the flexor tendons revealed a polyp type mass measuring 1.5cm x 0.5cm x 0.5cm was noted to be involving the lumbrical and little finger profundus tendon, best visualized as the tendon was delivered from the carpal tunnel. This appeared to reflect that a tear in the small finger lumbrical occurred. The polyp was excised and tenolysis carried out from volar wrist crease to distal palmar crease, addressing adhesions between the ring and small finger profundus tendons and boggy tenosynovium. Histopathologic examination concluded the mass to be fibromyxoid tissue, with fibrin deposition, and granulation tissue.

Post-operatively, the patient’s wrist pain and mechanical complaints of triggering had resolved.

Discussion:

Wrist triggering is an unusual observation and requires a broad and thoughtful examination. The paucity of case reports speaks not only to the rarity of the phenomenon, but possibly an under-reporting as well. In fact, to the knowledge of the authors, these above case reports of wrist triggering due to lumbrical neoplasm would serve as the third, fourth, and fifth case reports respectively. Moreover, like most rare pathologies, under-reporting of this phenomenon can be attributed to the physician being unfamiliar with the pathology and the hallmark physical exam findings. This leads to a lack of detection and misdiagnosis of the pathology by the physician. This is evidenced by the existence of at least one case report in the literature in which a surgeon had been misled by a physical examination, and proceeded with annular 1 pulley release as an impulse response to triggering with finger motion, only to be unsatisfied and surprised to find persistent post-operative triggering.1 This serves as a reminder that the hand surgeon can be deceived by rare physical phenomenon and should always perform a comprehensive and thoughtful evaluation to avoid unnecessary morbidity.

Furthermore, if we consider the rarity of this phenomenon, we should perhaps consider employing classification systems that have been reported to help provide a consistent nomenclature as we move forward with future reporting. Ogino et al2 described various causes of wrist triggering and provided a classification: type 1 wrist trigger is due to finger movement; type 2 is due to wrist movement; type 3 is due to forearm pronation supination. Very few cases are found in the Western medical literature that report an intramuscular lumbrical neoplasm as a cause of wrist triggering phenomenon with finger motion. Berlund etal3 reported an intramuscular lipoma within the middle finger lumbrical muscle. Suematsu etal4 devised a classification system of wrist triggering based on the pathology of the flexor sheath. They describe type A – triggering due to neoplasm; type B- triggering due to anomalous lumbrical muscle belly; type C – neoplasm and lumbrical anomalous muscle belly. Hence, these classification systems would allow these three case reports to be described as a type 1A trigger wrist.

The primary objective of this presentation is to describe the unique and curious physical exam findings that are indicative of this rare, and potentially misleading phenomenon. This may conceivably expand upon the diagnostic astuteness of the hand surgery community, and ultimately provide better healthcare to our patients.

1. Takase K, Sato Y. Snapping wrist caused by synovial giant cell tumour and anomalous lumbrical muscle: A case report. J Hand Surg. 35(4); 320-321. 2010

2. Ogino T, Kato H, Ohshio, I, Trigger wrist induced by finger movement, Pathogenesis and differential diagnosis, Handchir Mikrochir Plast Chir 26(1):3-6, 1994

3. Berlund P, Kalamaras M, A Case report of trigger wrist associated with carpal tunnel syndrome caused by an intramuscular lipomas. Hand Surgery, 19(2):237-239, 2014

4. Suematsu N, Hirayama T, Takemitsu Y. Trigger wrist and flexor tenosynovitis. J Hand Surg 10B:121-123, 1985