Trapezium Fracture Associated with Thumb Carpometacarpal Joint Dislocation: A Report of Three Cases and Literature Review

Isolated trapezium fracture in combination with thumb carpometacarpal (CMC) joint dislocation is extremely rare, and no treatment consensus exists. Herein, we report 3 successfully treated cases of isolated trapezium fracture with thumb CMC joint dislocation. While good short-term results have been reported in the literature, the possibility of substantial ligament injuries that can lead to future instability of the thumb CMC joint must be noted. In order to obtain an excellent long-term clinical result, we propose the consideration of the anatomical repair of the CMC joint in terms of both bony and ligamentous structures in cases where instability remains after fracture fixation.


Introduction
Isolated fractures of the trapezium are rare injuries that account for 3-5% of all carpal fractures [1]. Pure carpometacarpal (CMC) dislocations of the thumb are also rare, accounting for less than 1% of all hand injuries [2]. Herein, we report 3 cases of isolated trapezium fracture with thumb CMC joint dislocation. Good short-term results were obtained; however, long-term complications must be noted. Optimal treatment for the injury considering the anatomical features of the thumb CMC joint is discussed.

Case 1.
A 20-year-old female presented to our hospital complaining of pain in her left thumb 2 days after a karate tournament. She had severe pain shortly after she guarded her face with her left forearm, and the opponent's kick directly hit the basal part of her left thumb. On physical examination, there was di use swelling and tenderness over her left thumb CMC joint. e range of motion (ROM) of her left thumb was limited due to strong pain. e plain radiograph revealed a trapezium body fracture and radial dislocation of the CMC joint (Figures 1(a) and 1(b)). Computed tomography (CT) showed collapse of the trapezium articular surface (Figures 1(c) and 1(d)). Open reduction and xation using Kirschner wire (K-wire) was performed 4 days after the initial injury. A radial approach was taken, and the radial joint capsule, along with the radial collateral ligament, was not torn. We incised the capsule and exposed the fracture. e collapsed articular surface was elevated, and β-tricalcium phosphate (β-TCP) was used to ll the subchondral bone loss, xed by K-wire (Figures 2(a) and 2(b)). Good stability was obtained by anatomical reduction of the fracture; therefore, we did not examine for a ligament injury. e rst and second metacarpals were temporarily xed by another K-wire. After 6 weeks of thumb spica immobilization, the intermetacarpal K-wire was removed, and active ROM exercises were started. ree months after the initial injury, she had returned to participating in karate. At the nal follow-up (2 years after the initial injury), the patient had full ROM in the CMC joint, without pain or instability. Plain radiograph showed a congruent CMC joint and trapezium fracture union. However, a hyperextension of the thumb metacarpophalangeal (MP) joint, a zigzag deformity, was revealed (Figures 2(c) and 2(d)), which is often seen in thumb CMC joint osteoarthritis.

Case 2.
A 17-year-old male presented to our hospital complaining of pain in his left thumb 2 days after a rugby match.
e injury involved a rugby-tackling accident; however, the details were not clear. On physical examination, there was di use swelling and tenderness over his left thumb CMC joint. e ROM of his left thumb was limited due to strong pain. e plain radiograph revealed a trapezium body fracture and dorsal dislocation of the CMC joint (Figures 3(a) and 3(b)). Open reduction and internal xation using double-thread headless screws (DTJ screw, Meira © , Nagoya, Japan) was performed 5 days after the initial injury. A dorsal approach was taken, and the dorsal joint capsule was not torn. Good reduction and xation was achieved using 2 DTJ screws. Good stability was obtained by anatomical reduction of the fracture; therefore, we did not examine for a ligament injury. e rst and second metacarpals were temporarily xed by K-wire (Figures 4(a) and 4(b)).
After 4 weeks of thumb spica immobilization, the intermetacarpal K-wire was removed, and ROM exercises were started. ree months after the initial injury, he had Seven days after the initial injury, the fracture was percutaneously xed with 2 headless screws (Acutrak 2 micro, Acumed © , Oregon, US). Good reduction was obtained by traction of the thumb and compression of the trapezium from the dorsal aspect. After screw xation, the CMC joint was highly stable. e rst and second metacarpals were temporarily xed by K-wire (Figures 6(a) and 6(b)). After 4 weeks of thumb spica immobilization, the intermetacarpal K-wire was removed, and ROM exercises were started. ree months after the initial injury, he had returned to playing rugby. At the nal follow-up (6 months after the initial injury), the patient had full ROM in the CMC joint, without pain or instability. Plain radiograph showed a congruent CMC joint and trapezium fracture union (Figures 6(c) and 6(d)).

Discussion
Given that isolated trapezium fracture and thumb CMC joint dislocation are rare injuries [1,2], the combination is extremely rare, with only 14 cases reported in the English literature [3][4][5][6][7][8][9][10][11][12][13][14][15]. Walker et al. [16] classi ed trapezium fractures into ve patterns (Figure 7). In previously reported cases, fracture patterns were either type IIa or IV. In the current study, the fracture pattern of case 1 was type V, and the fracture patterns of cases 2 and 3 were type IV. e mechanism underlying thumb CMC dislocation associated with isolated trapezium fracture is still controversial. Ramoutar et al. [3] indicated a direct dorsoradial impaction or indirect axial loading as mechanisms for the injury, which is consistent with case 1 in the current study. Kose et al. [4] reported either axial loading on a exed thumb or commissural shearing forces acting on the rst web space as the mechanism of injury, most likely consistent with the mechanism of the injury for cases 2 and 3 in the current study.
No consensus exists regarding optimal treatment for this rare injury. In previously reported cases, conservative therapy [4,5], closed reduction with K-wire xation [3,6,7], open reduction with K-wire xation [8][9][10], open reduction with internal xation [11][12][13]15], and closed reduction with external xation [14] were performed, and excellent results have been reported (Table 1) that treatment depends on the degree of instability and anatomic restoration after the rst reduction. Anatomically, the thumb CMC joint, with its unique articular shape, is stabilized by surrounding ligaments. e biconcave surfaces of the thumb CMC joint allow for a high degree of mobility but, on the other hand, are very unstable [17]. Su  direction during thumb abduction and adduction, while greater joint gliding occurs in the dorsal-volar and distalproximal directions during thumb exion and extension [18]. e ligaments providing stability to the joint are the anterior oblique ligament (AOL), intermetacarpal ligament (IML), dorsoradial ligament (DRL), posterior oblique ligament (POL), and ulnar collateral ligament (UCL) [19,20]. Historically, the AOL was considered to be the primary stabilizer of the thumb [21]. Bettinger et al. reported that the DRL and deep AOL play a substantial role in stabilizing the thumb CMC joint [20]. Recently, D'Agostino et al. concluded in their literature that DRL is the strongest and sti est ligament of the thumb CMC joint [22]. Considering these anatomical studies, when the thumb CMC joint dislocates, the condition of the DRL must be carefully evaluated.
McGuigan and Culp [23] reported that 5 out of 11 patients with an intra-articular trapezium fracture who underwent surgical treatment showed degenerative changes at long-term follow-up (mean, 47 months). Although thumb CMC dislocation was not included in their study, this result suggests that potential ligamentous injuries accompanied the intra-articular fracture, which led to substantial instability of the thumb CMC joint, resulting in osteoarthritis of the joint combined with articular cartilage injury. Case Reports in Orthopedics Although the fracture was anatomically reduced and the thumb CMC joint showed good stability clinically in case 1 of the current study, the radiographic nding at the 2-year follow-up showed a zigzag deformity of the joint. e articular cartilage injury combined with potential malfunctioning of DRL (primary stabilizer of the joint) may have led to this result. Although ligament reconstruction is currently thought to be too aggressive as the primary treatment for this injury [2], there is no consensus regarding optimal treatment. In the previously reported cases, Mody and Dias [8] and Roger et al. [15] treated their cases with ligament reconstruction in addition to K-wire or internal xation, due to obvious intraoperative instability of the CMC joint. In order to avoid long-term complications such as those seen as in the current case 1, we must strictly assess the instability of the joint. In patients with any degree of instability after fracture xation, we propose the consideration of open repair of the ligament for better stabilization of the thumb CMC joint. e articular cartilage injury alone may lead to Case Reports in Orthopedics osteoarthritis of the joint during long-term follow-up, and this must be thoroughly explained to patients with trapezium fracture and thumb CMC joint dislocation as well as with other joint intra-articular fractures.

Conclusion
We have successfully treated 3 cases of isolated trapezium fracture with thumb CMC joint dislocation. Similar to the current cases, good short-term results have been previously reported. However, in order to obtain an excellent long-term clinical result, we must consider the anatomical repair of the CMC joint in terms of ligamentous structures in cases where instability remains after fracture xation.

Conflicts of Interest
e authors declare that they have no con icts of interest.