Isolated dislocation of the carpometacarpal (CMC) joint of the hand is a rare injury. While the dislocation can be dorsal or palmar, dorsal dislocation is more common. Palmar dislocations can be either ulnopalmar or radiopalmar. There are very few reports of isolated radiopalmar dislocations of the fifth CMC joint in the English-language literature.1-3 We present a case of delayed presentation and management of radiopalmar dislocation of the fifth CMC joint. The patient provided written informed consent for print and electronic publication of this case report.
Case Report
A 42-year-old man presented with polytrauma to our emergency department. He was stabilized initially, and open fractures were treated by débridement and external fixator application. During an examination 3 days after admission, swelling was noted in the right hand. On further study, there was splaying of the fifth digit and tenderness over the fourth and fifth CMC joints (Figure 1). No abnormal mobility or crepitus could be elicited. Plain radiographs of the right hand in anteroposterior and lateral views revealed radiopalmar dislocation of the fifth CMC joint (Figure 2). It was decided to reduce the dislocation immediately after the patient was declared fit for surgery.
Under axillary block, closed reduction was unsuccessful. Open reduction of the fifth CMC joint was performed through a dorsal incision. The base of the fifth metacarpal bone was found to be stripped of soft-tissue attachments and lying in a radiopalmar location. Reduction, which was checked under image intensifier, was found to be satisfactory (Figure 3). Reduction was stabilized by passing a smooth Kirschner wire (K-wire) from the fifth metacarpal to the hamate bone. After achieving hemostasis, the wound was closed in layers and a below-elbow splint was applied. The perioperative period was uneventful, and sutures were removed on postoperative day 10. The K-wire was removed after 4 weeks, and radiographs showed satisfactory position of the fifth CMC joint. Gentle active and passive mobilization of fingers and wrist were started. The patient had regained good function of the wrist and fingers 2 months after surgery (Figure 4).
Discussion
Carpometacarpal joint dislocations are uncommon injuries and account for less than 1% of hand injuries.4 They are classified as dorsal and volar (palmar) dislocations. Dorsal dislocations of the CMC joints occur more frequently than do volar dislocations, mainly affecting the fourth and fifth digits.5 Isolated volar or palmar dislocation of the fifth CMC joint is an uncommon injury that was first reported in 1918 by McWhorter.6 In 1968, Nalebuff7 classified the volar dislocations into 2 groups according to the direction of the displacement of the fifth metacarpal base: radiopalmar and ulnopalmar. Berg and Murphy8 found the hook of the hamate to deviate the metacarpal bone to either the ulnar or radial side. Tearing of all ligament and tendon attachments of the base of the fifth metacarpal results in radiopalmar dislocation.7 The attachments of ligaments and tendons remain intact in the ulnopalmar dislocation.7
The clinical features of this injury are pain and swelling about the base of the fifth metacarpal and axial deformity of the little finger with apparent shortening. The deep motor branch of the ulnar nerve lies volar to the fifth CMC joint as it courses around the hook of the hamate. It is vulnerable to injury in both dorsal9,10 and volar11 CMC dislocations. For radiologic evaluation, in addition to standard anteroposterior and lateral radiographs, a lateral view in 30º pronation of the hand can provide an improved view of the fifth CMC joint, as suggested by Bora and Didizian.12
The treatment of ulnopalmar dislocation has evolved. Ulnopalmar dislocations have been successfully treated by closed reduction without fixation,8 and by open reduction and K-wire fixation.3,7,13
Radiopalmar dislocations are inherently unstable because of the tearing of all ligament and tendon attachments of the base of the fifth metacarpal.7 In our case of radiopalmar dislocation, diagnosis was delayed and attempts at closed reduction were unsuccessful. Therefore, it was treated by open reduction and K-wire fixation. In our case, open reduction and K-wire fixation for radiopalmar dislocation of the fifth CMC joint provided promising results.
Conclusion
Radiopalmar dislocation of the fifth CMC joint is a rare injury, and very few cases have been reported in the English-language literature. We report one such case, which was successfully treated with open reduction and K-wire fixation.