Delayed Diagnosis of Dislocation of All Four Ulnar Carpometacarpal Joints. Surgical Treatment Strategy and Challenges.

Abstract

Background  Carpometacarpal dislocations are rare injuries whose diagnosis is often missed initially. These injuries can be treated conservatively, as long as an anatomical closed reduction is achieved. However, in most cases, open reduction followed by internal or external fixation is necessary to reach a stable anatomical reduction.

Case Description  A 32-year-old male was referred to our institution due to excess swelling of his right hand, 2 months after a motorcycle crash he sustained. During our imaging workup, a dorsal carpometacarpal dislocation of all four ulnar metacarpals was found accompanied by a fracture of the base of the fifth metacarpal. An open reduction was achieved using Kirschner wires and a small plate for arthrodesis of the fifth carpometacarpal joint. The postoperative follow-up on the 3rd, 6th, and 12th month was uncomplicated. The range of motion and grip strength was satisfactory on the 3rd month and almost full on the 6th month compared to the unaffected side.

Literature Review  Carpometacarpal dislocations are rare hand injuries. They are often the result of a high-energy injury and their diagnosis is usually delayed or missed. The main reasons are the excessive pain and swelling of the hand which make the initial clinical examination difficult and the overlapping of the metacarpals on the X-ray, which make the radiological diagnosis challenging.

Case Relevance  A delayed diagnosis needs urgent open surgical treatment to achieve an anatomical reduction due to the interposition of soft tissue, bony fragments, and newly formed callus. Diagnosis and treatment of these injuries demands a high clinical suspicion from the traumatologist. The role of computed tomography scan is invaluable and open reduction is the mainstay of treatment for the cases that are diagnosed late.

Carpometacarpal (CMC) dislocations are rare injuries whose diagnosis is often missed on initial presentation (< 1% of all hand injuries). ^{1 2 3} They are usually the result of a high-energy mechanism of injury like direct punching, falls from a height, motorcycle and car crashes, and vehicle-pedestrian collisions. Unfortunately, the diagnosis of these injuries is often omitted or delayed. A delayed treatment, however, is associated with poorer outcomes in terms of hand function, pain, and posttraumatic arthritis. Early diagnosis of CMC dislocation can, in some cases, lead to a successful closed reduction, with or without percutaneous fixation and cast immobilization. Open reduction and internal fixation are usually necessary to achieve a stable anatomical reduction, especially in late diagnoses. The treatment strategy is affected by the time passed until the surgery, the stability of the reduction, the severity and type of injury, and whether an anatomical reduction can be achieved with a closed reduction.

We report the rare case of a neglected dorsal dislocation of all four ulnar CMC, accompanied by a fracture of the base of the fifth metacarpal. The diagnosis was set 2 months postinjury. A closed reduction attempt was unsuccessful, while callus formation was obvious around the base of the dislocated fifth metacarpal. Thus, open reduction and internal fixation was the optimum treatment.

The purpose of this report is to highlight the diagnostic and operative difficulties regarding the treatment of neglected CMC dislocations and review the literature in order to provide a rationale for their surgical management.

Case Presentation

A 25-year-old male was referred to our institution due to excessive swelling and persistent pain of his right hand 2 months after a motorcycle crash. After the accident, he was admitted in the intensive care unit for a week and was operated for a Lisfranc injury of his right foot in another institution. Our radiological workup (X-rays, a thin slices computed tomography [CT] scan of the hand) revealed a dorsal CMC dislocation of all four ulnar metacarpals, along with a fracture of the base of the fifth metacarpal ( Figs. 1 2 3 ). A closed reduction was attempted at first but was unsuccessful, possibly due to the callus formed on the fracture site and the stiffness of the hand. The patient was taken to the operation room and an open reduction was attempted. A single curved dorsal incision was used. Extensive dorsal ligamentous releases and an osteotomy of the callus around the base of the 5th metacarpal were utilized to achieve reduction. Interposed soft tissues and bony fragments were removed. Under fluoroscopic control, volarly directed pressure on the base of the 2nd and 4th metacarpals held the reduction in place, which was stabilized using two crossing 1.5-mm Kirschner wires (K-wires) ( Fig. 4 ). Due to severe intra-articular comminution of the base of the 5th metacarpal ( Fig. 3 ) arthrodesis of the 5th CMC joint was performed, restoring the alignment and enhancing the stability of the fifth ray of the hand. A square four-hole plate (TriLock Gridplate 1.3 mm, Medartis, Switzerland) was employed and the base of the metacarpal was fused to the hamate. The capsule was sutured back. Anatomic reduction was attained with no residual subluxation in the C-arm check ( Fig. 5 ).

Fig. 1.

( A , B ) Preoperative radiograph. Dorsal dislocation of all four ulnar carpometacarpal (CMC) joints with evident callus around the base of the fifth metacarpal (blue arrow).

Fig. 2.

( A-H ) Three dimensional view computed tomography 3D reconstruction of the hand ( A , B ) and thin slice computed tomography scan (sagittal views C , D and coronal views E - H ). Focusing on the comminution of the base of the 5th metacarpal. Due to the extensive fracture comminution, fixation with K-w was not sufficient to maintain the reduction of the 5th ray and thus the application of the plate was necessary.

Fig. 3.

( A – E ) Three-dimensional (3D) view (computed tomography 3D reconstruction) of the hand revealing the dorsal carpometacarpal (CMC) dislocation and the fracture of the base of the fifth metacarpal.

Fig. 4.

( A , B ) Intraoperative view of the hand. ( A ) Open reduction of the fifth metacarpal base with the aid of a reduction clamp (arrow). ( B ) Stabilization of the rest of the metacarpals with 1.5 mm Kirschner wires.

Fig. 5.

( A , B ) Postoperative view of the hand. Two Kirschner wire (K-wire) are used to maintain the reduction of the 2nd-4th metacarpals while a plate is used to fix the 5th carpometacarpal joints.

The postoperative course was uncomplicated. The hand was immobilized with a cast for 6 weeks, when the K-wires were removed and physical therapy was initiated. The wound healing was normal and no signs of infection were observed. The range of motion and grip strength were satisfactory on the 3rd month and full on the 6th month compared to the unaffected side (0 score in the Disabilities of Arm, Shoulder and Hand questionnaire) ( Fig. 6 ). The patient was pain-free during his everyday activities and was very satisfied with the result ( Fig. 7 ).

Fig. 6.

( A , B ) 6th Postoperative month-anatomical reduction.

Fig. 7.

( A , B , C ) Full grip strength and range of motion in the 6th postoperative month follow-up visit.

Discussion

The incidence of CMC joint injuries is estimated between 0.2 and 1% of all hand injuries, while dislocation of all four ulnar metacarpals is rarer. ^{1 2 3 4} To our knowledge, the presented case is the first report in literature of an all four ulnar CMC joint dislocation that was diagnosed and treated in such a chronic setting.

CMC fracture dislocations are categorized by fracture location, direction of dislocation, and the number of the displaced fragments. Dorsal, volar, and divergent CMC dislocations have been reported, with the first, as in our case, being much more frequent. ^{5 6 7} The injury pattern is mainly determined by the direction of the force to the metacarpals and the position of the wrist during the impact. ⁸ Dorsal dislocations are commoner as the stronger static restraints (dorsal ligaments) and dynamic stabilizers (wrist extensors) cause the failure of bone dorsally, followed by rupture of the volar ligaments. ⁹ The 2nd and 3rd metacarpals form a rigid central unit fixed to the carpus, providing a rotation center around which the mobile thumb and moderately mobile 4th and 5th metacarpals move, providing spatial adaptation for the palm. The key of the 4th and 5th metacarpal mobility is the “saddle joint” configuration between their base and the hamate. Thus, the higher degrees of freedom in motion render them more prone to CMC injuries than the radial more stable rays. ^{10 11 12}

A high-energy mechanism of injury is usually needed for the disruption of the strong ligamentous support of the CMC joint, consisted of a system of four ligaments, namely the dorsal metacarpal, the volar metacarpal, and the two sets of interosseous ligaments. ^{8 13 14 15} The most common causes are a blow with clenched fist (about half of the patients in three case series in literature), a fall from height, and car and motorcycle accidents. ^{2 5 9 16}

CMC dislocations are notoriously overlooked injuries during the initial evaluation (up to 71% according to Henderson and Arafa). ¹⁷ The main reasons for that is the excessive swelling and pain that makes clinical examination of the hand difficult, the serious concomitant injuries that may distract the attention of the clinician, and the overlapping of the metacarpals on the lateral X-ray, which make its interpretation challenging.

A proper radiological evaluation should include a standard posteroanterior (PA), a true lateral, a semi-pronated, and a semi-supinated view. ¹⁸ In order to minimize the incidence of overlooked CMC dislocations, multiple projections are necessary. ^{3 19} On routine PA view, attention should be focused on the three carpal arcs of Gilula, the “parallel M” lines described by Fisher et al, the metacarpal cascade lines, as well as the “oblique metacarpal line” described by Chmell et al. ²⁰ Many authors focus on the crucial role of an adequate true lateral radiograph. ^{1 21 22 23} The articular surfaces should be parallel, with a uniform joint space, and there should be no bony overlaps. ^{9 20 24 25 26 27 28}

In recent years, the role of a thin slice CT scan has been pointed out, as it can confirm the diagnosis in difficult cases, provide a better assessment of the joint surfaces and concomitant fractures, and help in the preoperative planning. ^{5 8 18 19 22} In our case, the diagnosis was set by the true lateral view. The CT scan confirmed the dislocation and depicted precisely the fracture of the 5th metacarpal base. It revealed the pattern of a “baby or mirrored Bennett” fracture (fracture-dislocation of the base of the 5th metacarpal where the radial part of the base stays in place through ligamentous connections and the ulnar part dislocates proximally due to the pull of the extensor carpi ulnaris tendon, a similar pathomechanism of injury to the Bennett fracture of the thumb metacarpal). That prepared us for the need of extensive debridements and intraoperative callus osteotomies to aid the reduction and dictated the use of a dorsal buttress plate for stabilization of the fifth ray. ^{18 29 30}

Currently, there is no widely accepted treatment strategy for these rare injuries. The decision between conservative and surgical treatment depends on the chronicity and the pattern of the injury, the presence of other concomitant fractures, and the ability to achieve a stable anatomical reduction by closed means. Consensus exists across literature, however, that the main goal of the treatment is to restore the articular anatomy, avoid further displacement, and preserve mobility and functional status in a painless hand in order to prevent posttraumatic arthritis. ^{9 11}

When diagnosed early, there seems to be a role for closed reduction and cast immobilization in the definitive treatment of CMC dislocation. ^{23 31 32} A successful closed reduction is usually possible, when attempted within the first 10 days of the injury. ¹⁷ In these cases, close follow-up with plain radiographs at a weekly interval are imperative for the first 2 weeks, as redislocation is common. ^{9 19}

However, conservative treatment has also been disputed, as it may lead to subtle malreduction and worse long-term functional results. ^{19 33} Therefore, the vast majority of the CMC dislocations is nowadays treated with open reduction and hardware stabilization. ^{2 16 19} The main indications for operative treatment are open fracture dislocations, persistent joint instability despite closed reduction efforts, significant intra-articular damage, concomitant fractures to the carpal or metacarpal bones, ⁵ avulsion fractures of the extrinsic extensor tendons, ⁹ and neglected dislocations.

Delayed diagnosis necessitates operative intervention, as good exposure of the injury site is mandatory to remove scar tissues and callus, clear interposed soft tissues and bony fragments, release capsule contractures and, thus, achieve anatomic or near anatomic reduction, and avoid residual subluxation. Delayed treatment can result in neurovascular injuries due to edema and prolonged compression. ^{2 13} Our patient was treated 2 months postinjury. In literature we found three cases of 4th and 5th CMC dorsal dislocation, diagnosed late (two patients with a 2 months' delay and one on the 11th week postinjury), that were successfully treated operatively with open reduction and internal fixation with good results. ^{17 34}

The CMC joints are approached through longitudinal or curved incisions over the dorsum of the hand (one or two are usually sufficient for adequate exposure). The dorsal approach provides good exposure to all the CMC joints, leaving a wide skin bridge at the same time to avoid skin complications. The injured metacarpals and carpal bones can be visualized, debrided, and reduced. ⁹ Multiple methods of fixation have been recommended including K-wires, mini screws, and dorsal buttress plating. ¹⁸ K-wire fixation is the most widely used method of fixation. Transfixation of the affected CMC joints and transverse fixation of metacarpals have been described. ⁵ In multiple joint dislocations, some authors accentuate the role of fixation of the third CMC joint (keystone) to aid the reduction and stabilization of the subsequent neighboring joints. ⁹ The CMC joint capsule should be sutured back for improved stability. ⁹ In recent years, dorsal buttress plating has provided good results especially in the case of comminuted CMC joint fracture dislocations. ^{9 35}

CMC dislocations are infrequent hand injuries, whose diagnosis is usually delayed or missed. Their diagnosis on initial patient examination is challenging. The role of the CT scan is essential for late diagnoses. Delayed diagnosis requires urgent open surgical treatment to achieve an anatomical reduction due to the interposition of soft tissue and bony fragments. The diagnosis and treatment of these injuries demand a high clinical suspicion from the orthopedist. Multiple fixation methods provide stability after an anatomical reduction, including classic K-wire fixation but also novel strategies using dorsal low profile buttress plates. Anatomical reduction is necessary in order to ameliorate the functional outcomes and avoid late postoperative complications owing to residual subluxation.

Funding Statement

Funding None declared.