volar metacarpal phalangeal joint
Volar Metacarpal Phalangeal Joint Dislocation: A Rare and Often Missed Injury I
From the Departments of Emergency Medicine* and Orthopedics,t Medical College of Wisconsin, Milwaukee.
Stephen W Hargarten, MD, MPH* Douglas P Hanel, MDt
Received for publication July 31, 1991. Revision received May 18, 1992. Acceptedfor publication May 20, 1992.
Volar metacarpal phalangeal joint dislocations are rare injuries. We could find only eight cases reported, with none in the emergency medicine literature. We present a case report and describe the biomechanics and radiographic findings of this injury. [Hargarten SW, Hanel DP: Volar metacarpal phalangeal joint dislocation: A rare and often missed injury. Ann EmergMed.September 1992;21:1157-1159.] INTRODUCTION Acute injuries of the hand account for 5% to 20% of emergency department visits each year. 1,2 Lacerations, fractures, contusions, and dislocations accounted for 83% of the hand injuries in one study. 1 Volar dislocation of the metacarpal phalangeal joint is a rare, easily overlooked injury, especially when it involves the small finger. 3-7 In the following case study, an example of a volar dislocation of the small finger metacarpal phalangeal joint is presented. Despite acute physical and radiographic evaluation, this injury eluded diagnosis for a number of weeks. The presentation, biomechanics, and diagnostic signs of this injury are presented. CASE REPORT A 66-year-old physician struck the ulnar aspect of his flexed right fist against a door frame while attempting to break a fall. He noted immediate tenderness in the small finger metacarpal phalangeal region and presented to the ED for evaluation. Physical examination revealed limitation in metacarpal phalangeal joint motion, moderate tenderness, and minimal swelling. The interphalangeal joints had normal mobility, and the neurovascular examination was normal. Radiographs taken in posteroanterior, lateral, and oblique projections were interpreted as normal by both the emergency and radiology staff physicians (Figure 1A, B, and C). The patient was splinted in a position of comfort and advised to follow up appropriately. The pain and limitation of motion persisted, and after four weeks he sought the advice of a hand surgeon in the Department of Orthopedic Surgery. Repeat examination of the metacarpal phalangeal joint revealed a fixed flexion contracture of 45 ° and no
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active motion. The proximal interphalangeal joint had developed a 40 ° flexion contracture and active flexion to 100°. Radiographs directed at the small £mger demonstrated a volarly dislocated metacarpal phalangeal joint (Figure 2A, B, and C). Open reduction and metacarpal phalangeal joint reconstruction restored 65 ° of active flexion. The proximal interphalangeal joint contracture remained unchanged, and the patient declined further corrective intervention. After one year, the patient has a stable metacarpal phalangeal joint and mild joint discomfort.
DISCUSSION Solar dislocations of the small finger metacarpal phalangeal joint are extremely rare. There are eight reported cases of this injury in the orthopedic, hand, and trauma literature. 3-7 There are no references to this injury in the emergency medicine literature. Frazier et al 1 described 1,164 emergency mtients with hand injuries. Only three of the cases had Figure I.
Radiographs of the small finger on day of injury A. Posteroanterior projection B. Obliqueprojection C. Lateral projection
metacarpal phalangeal joint dislocations. Dislocation type was not described. There is some difference of opinion regarding the mechanism of injury. Renshaw and Louisa suggested that hyperextension of the metacarpal phalangeal joint resulted in interposition of the volar plate between the metacarpal and proximal phalanx, thus preventing reduction. In contradistinction, Moneim6 reported that the mechanism of injury is a fall onto the dorsum of the hand, resulting in acute flexion of the metacarpal phalangeal joint. Wood and Dobyns5 suggested that the mechanism of injury is hyperflexion of the metacarpal phalangeal joint with proximal translation of the proximal phalanx, with the dorsal joint capsule as the structure preventing reduction. The history as well as the operative findings in our case are in agreement with those of Moneim6 and Wood and Dobyns. 5 Prompt referral for consideration of open reduction is indicated for optimal results. However, delay in diagnosis is a common problem with this injury. Of the nine reported Figure 2.
Radiographs of the small finger three weeks after injury A. Obliqueprojection demonstrates solar dislocation of the metacarpal phalangeal joint. B. Lateral projection demonstrates volar dislocation of the proximal phalanx at the metacarpal phalangeal joint (arrows outline the metacarpal head and base of the proximal phalanx). C. Posteroanterior projection demonstrates cartilage narrowing and metacarpal phalangeal joint subluxation.
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cases (ours included), six were missed on initial evaluation. Physical examination should heighten suspicion of subluxation by demonstrating decreased range of motion and swelling and tenderness on the volar aspect of the affected joint. The importance of prompt detection of this injury is underscored in this case by the limited functional motion of the small Finger metacarpal phalangeal joint and persistent flexion contracture of the proximal interphalangeal joint. After reviewing this case, we believe that the diagnosis Could have been made from the initial radiographs if the following subtle findings had been noted: On posteroanterior projection, the metacarpal phalangeal joint space is narrowed in comparison with the adjacent metacarpal phalangeal joints (Figure 1A); on oblique projection, the relationship between the small finger metacarpal head and the proximal phalanx is incongruous compared to adjacent joints (Figure 1B); on lateral projection, the metacarpal phalangeal joint is volarly subluxed (Figure 1C). This latter finding is obscured because of underpenetration of the small Finger metacarpal phalangeal joint and overlap of the adjacent metacarpal heads. SUMMARY
REFERENCES 1. Frazier WH, Miller H, Fox RS, et al: Hand injuries: Incidence and apidemiology in an emergency service. JACEP 1978;7:265-268. 2. Clark DP, Scott RN, Anderson IWR: Hand problems in an accident and emergency department. J Hand Surg 1985;3:297-299. 3. McLaughlin E: H complex "locked" dislocation of the metacarpal phalangeal joints. J Trauma 1965:5:683-688. 4. Renshew TS, Louis BS: Complexvelar dislocation of the metacarpalphalangeal joint: A case report. J Trauma 1973;13:1086-1088. 5. Wood MB, Dobyns JH: Chronic complex velar dislocation of the metacarpalphalangeal joint. J Hand Surg 1981;6:73-76. 6. Moneim MS: Velar dislocation of the metacarpalphalangeal joint: Pathologic anatomy and report of two cases. Clin Orthop 1983;173:186-189. 7. Betz RB, Browne EZ, Perry GB, et al: The complex velar metacarpalphalangeal joint dislocation: A case report and review of the literature. J Bone JointSurg 1982:64A:13741375. Address for reprints: Stephen W Hargarten, MD, MPH Department of Emergency Medicine Medical College of Wisconsin 8700 West Wisconsin Avenue Milwaukee, Wisconsin 53226
Volar metacarpal phalangeal joint subluxation and dislocation are rare injuries. Prompt recognition, appropriate referral, and therapy can improve the outcome of this injury. After one-year follow-up, the patient reported limited active flexion and mild joint discomfort.
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