■ Case Report Traumatic Volar Dislocation of the Trapezoid With Acute Carpal Tunnel Syndrome BRAD J. LARSON, MD; LANCE C. DELANGE, NP n 1869, W. Gay1 reported the first However, there was no intraneural hematoma case of a dislocation of the trapezoid. or obvious discontinuity of the nerve or ISince that time there have been Ͻ25 epineural sheath. With the median nerve care- reported cases in the literature.2-24 Most fully retracted, the trapezoid was identified dislocations are accompanied by a frac- through the same incision. To assist in reduc- ture of the adjacent carpals or tion, a dorsal incision was made overlying the metacarpals and usually are dorsal in trapezoid. Reduction was then obtained with direction. Palmar dislocation of the trape- the wrist in slight flexion, longitudinal traction zoid is distinctly more unusual, with Ͻ10 on the index and middle fingers, and volar reported cases.3, 4,6,22,24 A volar disloca- manipulation of the trapezoid. Reduction was tion with accompanying acute carpal tun- confirmed with fluoroscopy. Stabilization of nel syndrome has not been reported. This 1A 1B the trapezoid was performed with multiple K- article presents a case of volar dislocation wires (Figure 3). Figure 1: AP (A) and lateral (B) radiographs of the with acute carpal tunnel syndrome. Postoperatively the patient was placed into injured wrist. Note the proximal migration of the second metacarpal and absence of the trapezoid an initial thumb spica splint for 10 days, fol- CASE REPORT beneath it. The arrow on the lateral view points to lowed by a thumb spica short-arm cast for 4 A 21-year-old right-hand-dominant man the volarly displaced trapezoid. weeks. Postoperatively at 2 weeks, a CT scan sustained a traumatic injury to his right wrist confirmed reduction (Figure 4). Electro- in a high-speed four-wheel accident. The Clinical examination was notable for a diagnostic studies performed 6 weeks postoper- patient did not recall the exact mechanism of swollen, tender wrist. Any motion of the wrist atively confirmed evidence of a significant injury, but the vehicle reportedly went end- was painful, with significant discomfort on acute axonal injury to the median nerve. There over-end and he was thrown from the vehicle. motion of the radial 3 digits. Sensation was was no evidence of entrapment neuropathy of He sustained no other injuries, except to his decreased in the radial 3 digits and 2-point the ulnar nerve. Kirschner-wires were removed right wrist. discrimination was 7-10 mm. Motor testing at 6 weeks and the patient was started on range He presented to our clinic 2 days later with was significant for pain and was difficult to of motion and strengthening exercises. pain in the wrist and numbness in the hand. discern from neurologic injury. A clinical At 6 months follow-up the patient had Radiographs of the hand revealed a deformity diagnosis was made of acute traumatic carpal regained 80° of dorsi and 80° of volar flexion of the trapezoid (Figure 1). A computed tunnel syndrome. of his wrist, with a 90% return of grip tomography (CT) scan identified a palmarly The patient underwent an open carpal tun- strength. The dysesthesias in his radial 3 dig- dislocated trapezoid occupying the carpal tun- nel release through a standard volar incision. nel. Minute avulsion fragments were noted The median nerve was identified and found to From Alpine Orthopaedic Specialists, North from the trapezium and capitate, but no other have evidence of compression in the carpal Logan, Utah. significant carpal or metacarpal injuries were canal. The nerve was displaced volarly, having Reprint requests: Brad J. Larson, MD, 2380 identified (Figure 2). been stretched over the dislocated trapezoid. N 400 E, North Logan, UT 84341. FEBRUARY 2005 | Volume 28 • Number 2 165 ■ Case Report osseous anastomosis.30 The bone is stabi- lized by strong ligaments mostly palmar to all adjoining bones. This configuration and strong ligamentous attachments account for the rarity of the injury and the wedge shape for the preponderance of dorsal dislocation. Dorsal dislocation results from a blow to the distal end of the second metacarpal bone with the wrist in slight flexion. The second metacarpal bone acts as a lever to extrude the bone dorsally because of its 3A 3B 2 2,10,20 shape. It has been postulated that a Figure 3: Postoperative AP (A) and lateral (B) Figure 2: Axial CT scan view of the injured right strong pressure on both sides of the arch in radiographs of the injured wrist. The trapezoid has wrist. The dislocated trapezoid is volarly displaced been restored to its normal position with within the contents of the carpal canal. which the trapezoid plays the role of a key- restoration of the second metatarsal height. stone is necessary to dislocate it. Gripping a steering wheel has been reported as one the literature, however, most authors have its had resolved, 2-point discrimination was 5 mechanism causing this injury.20 reported reasonably good results. mm less in all digits, and he had no numbness Volar dislocation is rare because the Treatments used have included no reduc- tion,1,13,17 incomplete closed reduc- or pain with activity. Radiographs identified shape of the bone maintains its position. tion,11,14,16 complete closed reduc- good healing, with no evidence of avascular The mechanism of injury is less clear. It tion,10,16,21 open reduction,12,17,18 open necrosis, instability, or loss of reduction. has been proposed that a direct blow on reduction and fixation with K-wires or 2,4,6,9,19,20 the dorsum of the trapezoid flattens the staples, trapezoid excision, and limited fusion.2,22 Closed reduction is DISCUSSION carpal arch, increasing the space between generally advocated as the initial therapy, Because of its strong ligamentous sta- the trapezium and the capitate laterally, with open reduction reserved for irre- bility and relatively protected position and the second metacarpal and scaphoid ducible cases. No reduction17 and exci- 21 within the interlocking carpal geometry, longitudinally. This allows extrusion of sion result in proximal migration of the second metacarpal and are not indicated. the trapezoid is less commonly injured the trapezoid through the widened 25 6 Treatment for isolated dorsal trapezoid than any other carpal bone.6,25,26,27 When space. Rhoades and Reckling described dislocations may be performed closed. a forced extension of the wrist as the injured, there is a 70% associated ipsilat- This is accomplished by pulling the mechanism. eral arm injury.28 Trapezoid dislocations thumb and index finger longitudinally and The diagnosis of a trapezoid disloca- gently flexing the wrist with pressure on are often associated with injuries to the tion can be challenging, as it is un- the dislocated bone. Closed reduction is scaphoid, trapezium, and more commonly common and requires a strong clinical often stable and the wrist can be immobi- suspicion. Abnormal passive mobility of 10 the metacarpal bases. The trapezoid has lized in a cast. However, Ostrowski et the second metacarpal with mild limita- al2 reported a case of a dorsal dislocation been described as the keystone of the tion of flexion of the index finger are use- 2,7,21,26 20 that was treated by open reduction and proximal palmar arch. The bases of ful signs. capsular repair without internal fixation, the second and third metacarpals both Careful interpretation of the radi- which was then followed by early recur- ographs is essential after a careful clinical have multiple articular facets that are rent dorsal subluxation. This required history and examination. Sampson16 re- firmly attached to the carpus by strong repeat open reduction and a limited ported that the PA view is the most useful. intracarpal arthrodesis. Therefore, open ligaments; this means that a far greater However, obliques and carpal tunnel reduction may be necessary for unsuc- force is required to produce dislocation.29 views may also be of benefit. On a cessful or unstable reductions, and inter- straight posterior-anterior radiograph, the 2,6,9,20 The dorsal surface of this wedge-shaped nal fixation is recommended. In con- trapezoid is superimposed on the adjacent bone is approximately twice the size of trast, volar dislocations are virtually bones, either the scaphoid or second impossible to reduce because of the the palmar surface. Therefore, trapezoid metacarpal. The cavity of the trapezoid in webbed shape of the bone.9 Open reduc- dislocations are rare, especially when the distal carpal ray is empty. It can also tion through a dorsal approach, or at times be occupied by proximal migration of the volarly displaced. It receives its blood combined dorsal and volar approaches, secondary metacarpal or lateral migration has been reported. In our patient, volar supply through the dorsal and volar non- 10 of the trapezium. A CT scan is benefi- approach was necessary to adequately articulating surfaces where the ligaments cial in evaluating the position of the trape- decompress the median nerve. However, are inserted. The dorsal vessels supply the zoid and allowing the diagnosis of associ- visualization and soft-tissue interposition ated carpal or metacarpal injuries.2,6 dorsal 70% of the bone, and the palmar required a dorsal incision as well, with K- The treatment options have varied in supply the volar 30% with no intra- wire stabilization. 166 ORTHOPEDICS | www.orthobluejournal.com TRAUMATIC VOLAR DISLOCATION OF THE TRAPEZOID | LARSON ET AL However, because of the good reported 13. Frank J. Ontwrichting van het multangulum minus. Ned Tijdschr Geneeskd. 1925; results without fusion, we feel that 69:200-202. arthrodesis is an effective salvage proce- 14. Sheldon JG. Dorsal dislocation of the trape- dure that is indicated only for sympto- zoid.