Palmar Dislocation of the Trapezoid with Associated Carpometacarpal Injuries: Two Case Reports and Literature Review

Abstract

Purpose

Palmar dislocation of the trapezoid is an exceptionally rare injury, typically resulting from high-energy wrist trauma, and is frequently associated with complex carpal or carpometacarpal fractures.

Materials and methods

We report 2 cases of palmar trapezoid dislocation following motorcycle accidents. In both patients, the injury was associated with multiple fractures and carpometacarpal dislocations. Open reduction via a dorsal approach with temporary Kirschner-wire fixation and ligamentous repair was performed.

Results

At final follow-up, anatomical reduction was maintained in both cases without radiological signs suggestive of trapezoid avascular necrosis on radiographs and computed tomography. Functional outcomes were influenced by the severity of associated injuries. A review of the literature identified eight previously reported cases, most treated with open reduction via a dorsal approach. Trapezoid excision, described in earlier reports, was associated with less favorable outcomes due to secondary dorsal migration of the second metacarpal.

Conclusions

Palmar trapezoid dislocation remains difficult to diagnose because of its rarity and frequent association with complex carpometacarpal injuries. Early recognition and open reduction via a dorsal approach allow stabilization of the central column and ligament repair. Trapezoid avascular necrosis is theoretically possible; however, available anatomical and clinical data suggest that it appears to be uncommon. Functional outcomes appear to depend more on the severity of associated carpal and carpometacarpal injuries than on the trapezoid dislocation itself.

Type of study/level of evidence

Case report, level IV.

Most published cases of traumatic trapezoid dislocation describe dorsal dislocations.^1,2 Palmar dislocations are even rarer and usually occur in the context of high-energy wrist trauma, often associated with carpal and/or carpometacarpal fractures or dislocations.2, 3, 4

We report 2 complex cases of palmar trapezoid dislocation following high-energy motorcycle accidents. In the first case, associated injuries included a displaced Schernberg V scaphoid fracture involving the trapezium and first metacarpal, a displaced hamate fracture, and dorsal carpometacarpal dislocations of four long fingers. In the second case, associated injuries included dorsal dislocation of the second carpometacarpal joint, dorsal fracture-dislocation of the fourth metacarpal base, and ipsilateral both-bone forearm fractures.

Given the rarity of palmar trapezoid dislocations, we also performed a focused literature review using the PubMed database. The search was conducted using the following keywords: “trapezoid dislocation” and “palmar trapezoid dislocation.” Only articles published in English and reporting clinical cases of trapezoid dislocation were included. Reference lists of relevant articles were also screened to identify additional cases. Studies describing either dorsal dislocations or those that did not clearly specify the direction of dislocation were excluded. No formal systematic review methodology was applied because of the limited number of reported cases.

Materials and Methods

Written informed consent was obtained from both patients for publication of this case report and the accompanying images.

Case report 1

A 69-year-old man had a complex left wrist injury following a motorcycle accident. On admission, clinical examination revealed a swollen, painful wrist with dorsal abrasions and intact neurovascular status.

Initial radiographs demonstrated palmar dislocation of the trapezoid associated with dorsal dislocation of the second carpometacarpal joint and a Schernberg V scaphoid fracture (Fig. 1A). Complementary computed tomography (CT) scan confirmed additional dorsal dislocations of the third to the fifth carpometacarpal joints and a displaced hamate fracture (Fig. 1B).

Figure 1.

A Anteroposterior and lateral radiographs obtained at admission demonstrating palmar dislocation of the trapezoid (white arrow). B Three-dimensional CT reconstruction (anterior and oblique three-quarter views) illustrating the spatial displacement of the trapezoid within the central column. The trapezoid is highlighted in yellow.

Surgery was performed 15 hours after injury under locoregional anesthesia. Closed reduction was unsuccessful, and open reduction was undertaken through combined volar and dorsal approaches. The volar approach first allowed assessment of the carpal tunnel and exclusion of median nerve compression. A dorsal approach centered on the second carpometacarpal joint revealed the trapezoid dislocated into the carpal tunnel with complete avulsion of the dorsal ligaments. The trapezoid was repositioned anatomically and stabilized with a 1.2-mm (0.047 in) Kirschner wire, followed by repair of the radioscaphocapitate ligament (Fig. 2). The scaphoid and hamate fractures were fixed with screws, and the carpometacarpal dislocations were reduced and stabilized with Kirschner wires through dorsal intermetacarpal approaches.

Figure 2.

Postoperative anteroposterior and lateral radiographs demonstrating reduction of the palmar dislocation of the trapezoid, reduction of the carpometacarpal dislocations, and internal fixation of the scaphoid and hamate.

After surgery, the wrist was immobilized for 6 weeks. Kirschner-wire removal was performed at 3 months, and physiotherapy was initiated at 6 weeks.

Case report 2

A 49-year-old man was admitted after a high-energy motorcycle accident with complex trauma of the left upper limb. Clinical examination revealed a severe dorsal degloving wound with intact neurovascular status. Radiographs and CT demonstrated palmar trapezoid dislocation and associated injuries including dorsal dislocation of the 2nd carpometacarpal joint, dorsal fracture-dislocation of the 4th metacarpal base, ipsilateral both-bone forearm fracture, and elbow dislocation (Fig. 3A, B).

Figure 3.

A Anteroposterior and lateral radiographs at admission. The white arrow indicates palmar dislocation of the trapezoid; B coronal, sagittal, and axial CT scans at admission showing palmar dislocation of the trapezoid. M2, second metacarpal; TZO, trapezoid.

Surgical management included wound debridement, plating of the forearm fractures, and a dorsal approach to the second carpometacarpal joint. The trapezoid was found completely enucleated into the carpal tunnel with avulsion of its dorsal ligaments (Fig. 4). Anatomical reduction was achieved, stabilized with Kirschner wires, and dorsal ligamentous repair. The fourth metacarpal base fracture-dislocation was also reduced and stabilized. Kirschner wires were removed at 2 months, and physiotherapy was initiated.

Figure 4.

Dislocated trapezoid within the carpal tunnel, removed through an open reduction via a dorsal approach. Avulsion of capsuloligamentous structures.

Results

Case report 1

At 18 months, the patient showed partial functional recovery, with wrist stiffness (flexion/extension 40°/5° vs contralateral 80°/70°), persistent pain, a Disabilities of the Arm, Shoulder, and Hand score of 61.4/100, but full thumb opposition (Kapandji score 10/10). Radiographs and CT confirmed anatomical reduction. Degenerative changes were present, including subchondral sclerosis and joint space narrowing, consistent with posttraumatic remodeling. No radiological signs suggestive of trapezoid avascular necrosis (AVN) were observed at final follow-up; however, early or subclinical AVN cannot be definitively excluded in the absence of magnetic resonance imaging (Fig. 5A, B).

Figure 5.

A Anteroposterior and lateral radiographs; B frontal and sagittal CT scans at 18 months showing degenerative changes of the carpometacarpal, radiocarpal, and midcarpal joints.

Case report 2

At 15 months, persistent stiffness of the third to fifth metacarpophalangeal joints required teno-arthrolysis. At 24 months, functional recovery was satisfactory for daily activities, with satisfactory wrist range of motion (flexion/extension 50°/40° vs contralateral 80°/70°), no pain, a Disabilities of the Arm, Shoulder, and Hand score of 25/100, and full thumb opposition (Kapandji score 10/10). Degenerative changes were present, including subchondral sclerosis and joint space narrowing, consistent with posttraumatic remodeling. No radiological signs suggestive of trapezoid AVN were observed at final follow-up; however, early or subclinical AVN cannot be definitively excluded in the absence of magnetic resonance imaging (Fig. 6A, B).

Figure 6.

Anteroposterior and oblique radiographs A and coronal, sagittal, and axial CT scans B at 18 months showing degenerative changes of the carpometacarpal joints, trapeziometacarpal osteoarthritis, and no radiological signs suggestive of AVN. M2, second metacarpal; TZO, trapezoid.

Discussion

Palmar dislocation of the trapezoid is a rare carpal injury with only a limited number of cases reported to date (Table).1, 2, 3, 4, 5, 6, 7, 8 Its rarity is explained by the specific anatomy of the trapezoid, a short, wedge-shaped bone locked as a “keystone” within the distal carpal row and stabilized by thick interosseous and capsuloligamentous structures. The palmar ligaments are described as stronger than the dorsal ligaments, contributing to its intrinsic stability.1, 2, 3^,5

Table.

Review of published cases of palmar trapezoid dislocation

No.	Author	Mechanism	Associated Injuries	Surgical Approach	Trapezoid Dislocation Treatment	Follow-up (mo)	Outcomes
1	Lewis5	Crush	CMC 2–3 dislocations	Dorsal	Trapezoid excision	36	Proximal migration M2
2	Rhoades and Reckling2	Motorcycle accident	Multiple fractures	Dorsal	ORIF + pinning	12	AVN
3	Dunkerton and Singer6	Sports	CMC 2 dislocation	Dorsal	ORIF + pinning	2	Good
4	Taylor and Shakespeare7	Bicycle accident	Galeazzi + CMC 4 fracture-dislocation	Dorsal	ORIF + pinning	3	Good
5	Koenig and West1	Fall	CMC 2–4 dislocations, triquetral fracture	Dorsal	ORIF + pinning	NR	Residual proximo-dorsal trapezoid subluxation
6	Larson and Delange8	Car accident	Acute CTS	Dorsal	ORIF + pinning	6	Good
7	Calfee et al4	Mountain biking	Scaphoid and hamate fracture	Dorsal	ORIF + screw fixation	7	Mild stiffness
8	Montanari et al3	Crush injury	CMC 2–4 dislocations + acute CTS	Dorsal	ORIF + pinning	24	Good
9	Present study (2024) (n = 2)	Motorcycle accident	Case 1: Scaphoid + hamate fractures + CMC 2–5 dislocations Case 2: Both-bone forearm fracture + CMC 2–4 dislocations	Dorsal (both cases)	ORIF + pinning + ligament repair	18–24	Mild stiffness (case 1); Good (case 2)

CMC, carpometacarpal; ORIF, open reduction and internal fixation; CTS, carpal tunnel syndrome; NR, not reported.

Biomechanically, palmar trapezoid dislocation is thought to result from high-energy trauma, either through forced wrist hyperextension or a direct dorsal impact producing a palmar tilt of the trapezoid.¹ Unlike the first and ulnar carpometacarpal joints, which allow greater mobility, the trapezoid-second metacarpal complex forms a rigid central column. Disruption of this column requires substantial energy and is almost invariably associated with concomitant carpal or metacarpal injuries. Failure of the dorsal ligaments may allow enucleation and palmar extrusion of the trapezoid into the carpal tunnel, as observed in our two cases and previously reported.³ The proposed biomechanical sequence is illustrated in Figure 7.

Figure 7.

Theoretical schematic representation of the mechanism leading to palmar trapezoid dislocation. A A direct dorsal force (blue arrow) applied to the second metacarpal produces a palmar tilt of the trapezoid. B Enucleation and palmar extrusion of the trapezoid into the carpal tunnel. D, dorsal; P, palmar; R, radius; L, lunate; S, scaphoid; Tz, trapezoid; T, trapezium; M1, first metacarpal; M2, second metacarpal.

More than 80% of reported cases were associated with fractures or carpometacarpal fracture-dislocations, confirming that isolated palmar trapezoid dislocation is exceptional. Frequently associated lesions include fracture of the scaphoid, hamate, trapezium, or metacarpal bases, and acute median nerve compression has occasionally been described.³ These complex injury patterns may delay trapezoid dislocation diagnosis, particularly in polytrauma settings.⁵

In both of our patients, open reduction of the trapezoid via a dorsal approach with temporary pin fixation achieved satisfactory anatomic reduction allowing concomitant ligament repair. No radiological signs suggestive of AVN were observed on radiographs and CT at late follow-up. Although osteonecrosis has been considered a potential complication,^6,7 only a single well-documented case has been reported in the literature. This low incidence is consistent with anatomical data on carpal vascularization indicating that 70% of the trapezoid’s blood supply arises from dorsal branches, mainly from the radial artery,^9,10 which may explain the low incidence of AVN despite palmar dislocation.

There is currently no therapeutic consensus for the management of palmar trapezoid dislocations, given the small number of published cases. All reported cases were treated using a dorsal approach, with variable follow-up durations. Open reduction through a dorsal approach has been required in all reports after failure of closed maneuvers. Stabilization is typically achieved using temporary Kirschner-wire fixation between the trapezoid and the second metacarpal or capitate, combined with dorsal ligament repair.4, 5, 6, 7, 8 In older reports, trapezoid excision was proposed in chronic or irreducible cases. However, this strategy was associated with proximal migration of the second metacarpal, loss of grip strength, and carpometacarpal instability.⁵ Preservation of the trapezoid through anatomical reduction appears preferable to maintain central column stability.

Functional outcomes largely depend on the severity of associated injuries rather than on the trapezoid dislocation itself. In our series, postoperative stiffness and degenerative changes were observed, reflecting the high-energy nature of trauma. Despite these sequelae, anatomical reduction was maintained in both cases.

In summary, complete palmar dislocation of the trapezoid is a rare injury, almost always secondary to high-energy trauma and associated with complex carpometacarpal injuries. It should be systematically suspected in the setting of severe wrist trauma with central column disruption. Open reduction via a dorsal approach with temporary stabilization should be preferred over excision, as it restores anatomical relationships and avoids long-term instability. Both patients and surgeons should be aware of possible sequelae, especially stiffness and posttraumatic arthritis, which remain frequent because of the severity of associated injuries.

Conflicts of Interest

No benefits in any form have been received or will be received related directly to this article.