An isolated, closed, complex dislocation of the metacarpophalangeal joint of the long finger: a unique case

A rare case of closed isolated dislocation of the third metacarpophalangeal joint of the hand

Metacarpophalangeal joint [MCP] dislocations of the index, little and thumb are common; that of the middle finger is very rare. In all the literature consulted only five cases of isolated closed dorsal dislocation of the MCP joint of the middle finger have been reported. Hyperextension of MCP joint is the mechanism of injury. We are herewith reporting a case of isolated MCP dislocation of the middle finger. One of our medical students while driving a motorcycle fell down on the road and sustained lacerated wound over the hypothenar area of the left hand. There was prominence of the head of the third metacarpal on the volar aspect and the base of the proximal phalanx was prominent dorsally. MCP dislocation of the middle finger was our clinical diagnosis which was confirmed by the radiograph. The patient had reported within 60 min of the accident. There was no tendon injury. Wound debridement was done, wound was extended to the back of the middle finger. The volar plate which was interposed between the head of the metacarpal and the base of the proximal phalanx was repositioned and the dislocation was reduced. Reduction was stable and the patient was reviewed after 14 months. The function of the hand is satisfactory. The case is presented for its unique presentation. This is the sixth case of isolated dislocation of the MCP joint of the middle finger.

A cadaver model that investigates irreducible metacarpophalangeal joint dislocation

PURPOSE

Controversy exists over the pathologic anatomy of irreducible dorsal metacarpophalangeal (MCP) dislocation. The aim of this work is to develop a cadaveric model of MCP joint dislocation that closely simulates the clinical situation and to study the structures around the MCP joint and their contribution to irreducibility of the dislocation.

METHODS

Nine fresh-frozen cadaveric specimens were amputated at the radiocarpal joint and stabilized in a specially formulated fixture. The dislocation was created by an impact load delivered by a servohydraulic testing machine, at a displacement rate of 1000 mm/s and with a maximum displacement of 60 mm. An irreducible dislocation was successfully created in 6 index fingers. An attempt at closed reduction was followed by a dissection of the dislocated joint.

RESULTS

In the 6 examined specimens, the flexor tendons were ulnar to the joint in all cases, the radial digital nerve was superficial (5 cases) or radial (5 cases) to the metacarpal head, and the lumbrical was usually radial (5 of 6 cases) to the joint. Division of the superficial transverse metacarpal ligaments, natatory ligaments, flexor tendons, or lumbricals does not aid reduction of the dislocation. Division of the volar plate was necessary for reduction of the dislocation in all 6 cases, whereas division of the deep transverse metacarpal ligaments does not allow reduction of the dislocation.

CONCLUSIONS

We present a model for creating an irreducible MCP joint dislocation using an impact load that simulates the clinical situation. The volar plate is the primary structure preventing reduction of the dislocation. Division of the deep transverse metacarpal ligament is not effective in reducing the dislocation. The flexor tendons, lumbricals, superficial transverse metacarpal ligament and natatory ligaments do not contribute to irreducibility. The anatomy of the structures surrounding the MCP joint is variable, and careful dissection to prevent iatrogenic injuries is mandatory.

Dorsal approach for open reduction of complex metacarpophalangeal joint dislocations

The metacarpophalangeal (MP) joint is resistant to injury due to its strong capsuloligamentous structures, which include the volar plate and deep transverse metacarpal and collateral ligaments. Complex MP joint dislocations are, by definition, irreducible by closed means and require open reduction, as the volar plate becomes entrapped between the metacarpal head and proximal phalanx. The dorsal approach may offer the following advantages: 1) reduced risk to palmarly displaced neurovascular structures, 2) facilitated management of osteochondral fractures, and 3) full exposure of the volar plate. However, the dorsal approach requires splitting of the volar plate for adequate reduction, which may delay recovery.

MR imaging of the metacarpophalangeal joints of the fingers: evaluation of 38 patients with chronic joint disability

OBJECTIVE

To report the MR imaging findings of painful injured metacarpophalangeal (MCP) joints of the fingers.

DESIGN AND PATIENTS

MR imaging of 39 injured MCP joints in 38 patients was performed after a mean delay of 8.8 months. The MR images were obtained with the fingers in extended and flexed positions using T2-weighted and T1-weighted sequences before and after intravenous injection of a gadolinium compound. Ten patients were treated surgically. Mean clinical follow-up was 1.8 years.

RESULTS

Tears of the collateral ligaments were the most common lesion (30/39), most being radial in location. Contrast-enhanced axial T1-weighted images with the MCP joint in a flexed position showed these lesions optimally. Ten tears were partial and 20 were complete. In 13 patients, MR images showed 17 associated lesions including injuries of the extensor hood (10/17), interosseous tendon (3/17), palmar plate (3/17), and an osteochondral lesion (1/17). Sagittal MR images were essential to highlight palmar plate tears.

CONCLUSION

Partial or complete tears of the collateral ligaments are prevalent MR imaging findings in patients with chronic disability resulting from injuries to the MCP joints. Although conservative treatment generally is sufficient for isolated injuries of the collateral ligaments, surgical repair is often required in cases of more extensive injuries. MR imaging may clearly delineate associated lesions of and about the MCP joints.

A dislocated finger

Images

Scissoring deformity after closed reduction of a dorsal subluxation of the MP joint of the middle finger

A rare case of scissoring deformity after closed reduction of a dorsal subluxation of the MP joint of the middle finger is reported. The aetiology and treatment of this deformity are presented along with a modified classification of dorsal dislocations and subluxations of the MP joint.

An isolated complex dorsal dislocation of the MP joint of the ring finger

A rare case of isolated complex dorsal dislocation of the MP joint of the ring finger is described. Differences in the pathological findings between dislocations of the ring finger and other digits are discussed.