Keywords
metacarpal hamate fracture dislocation - fourth and fifth carpometacarpal - hamate fracture
Introduction
An injury to the carpometacarpal joint of the ulnar edge hinders grip and fist strength, resulting in functional disability.[1]
[2]
[3] Unfortunately, these injuries are problematic entities in the clinical practice and a diagnostic challenge due to their complex anatomy and non-specific symptoms. Moreover, carpometacarpal joint lesions may occur in patients with other striking or life-threatening injuries,[4] and go unnoticed up to 71% of the time.[1] These factors delay the resolution of such injuries, leading to worse outcomes regarding pain and functionality..[5]
Hamate metacarpal dislocations encompass a spectrum of rare complex injuries, with an incidence of 0.2% to 1% of hand trauma.[4]
[5]
[6]
[7]
[8] Similarly, hamate fractures account for 2% of carpal fractures.[9]
[10] The coexistence of both injuries is even rarer, representing 10 to 15% of dislocated carpometacarpal fractures.[11]
[12]
The small casuistry on injuries to the carpometacarpal joint of the ulnar edge limits studies about them. Our goal was to address this rare lesion with significant challenges in its early diagnosis and no consensus regarding its optimal management. Therefore, this paper presents a group of patients treated for metacarpal hamate dislocation in a medical center and their functional outcomes and synthesizes recommendations from the current literature.
Materials and Methods
This study is descriptive. We retrospectively evaluated four patients older than 18 diagnosed with a carpometacarpal dislocation of the fourth and fifth fingers, surgically treated from 2017 to 2019, and who received no workers' compensation. All patients underwent surgery at the same medical center.
Demographic data included age, gender, dominant hand, mechanism of injury, injured side, time from accident to surgical intervention, type of injury according to imaging findings, and surgical management modality. We also analyzed the subjective functional outcomes and fist strength of our patients. All subjects signed an informed consent form for the use of this information.
Data were extracted from clinical records. Image analysis occurred using the institutional system. Functional diagnosis determination was based on the “Disabilities of the Arm, Shoulder, and Hand” (DASH) score adapted for the Chilean population. Measurement of fist strength used a dynamometer in kilograms and compared with the healthy hand. The statistical analysis employed median or mean values according to normal distribution and percentages. We excluded patients with less than 12 months of follow-up or incomplete imaging studies.
Data were extracted from clinical records. Image analysis occurred using the institutional system. Functional diagnosis determination was based on the DASH score adapted for the Chilean population. Measurement of fist strength used a dynamometer in kilograms and compared with the healthy hand. The statistical analysis employed median or mean values according to normal distribution and percentages. We excluded patients with less than 12 months of follow-up or incomplete imaging studies.
Results
Four of the seven patients identified completed the minimum follow-up of 12 months. The three remaining subjects opted out of the study before the cut-off period ([Table 1]). All patients were males with an average age of 39 years old (range, 33 to 55 years old). The dominant hand and the injured side were the right ones in all patients. All patients reported a fall from height with support on the back of the hand as an injury mechanism. Three patients had a single dislocation of the fifth metacarpal and a fracture of the base of the metacarpal bone with no fourth metacarpal involvement ([Fig. 1], [Fig. 2], [Fig. 3], and [Fig. 4]). One patient had an associated hamate body fracture with dislocation and fracture of the base of the fourth metacarpal and dislocation of the fifth metacarpal bone ([Fig. 3]). Three patients underwent preoperative assessment using computed tomography (CT) ([Fig. 2] and [Fig. 4]). The time from injury to surgery was 14, 30, 20, and 15 days respectively for cases 1, 2, 3 and 4. Patient 1 underwent a closed reduction, and the other three subjects underwent an open reduction through a dorsal approach. In all cases, definitive fixation used Kirschner wires. Patient 3, who presented a hamate body fracture, received a 2.7-mm screw as an additional osteosynthesis material. In all four cases, wrist immobilization occurred in 20 degrees of extension, while metacarpophalangeal bone immobilization occurred in 90 degrees of flexion. Removal of immobilization and Kirschner wires happened after six weeks. The average follow-up period was 38 months (16, 39, 49, and 49 months, respectively). The four patients had good functional outcomes, with a DASH score of 2.2, 4.5, 9, and 20.4, respectively, with full range of motion of the wrist and fingers compared with the contralateral one, no rotational alteration of the fingers, excellent grip strength compared with contralateral limb (92%, 102%, 100%, and 121% respectively) and complete resolution of pain. Final radiographic images revealed restoration of the involved carpometacarpal anatomy and joint congruity.
Fig. 1 Anteroposterior and oblique hand radiography at 30 degrees from patient 1. We suspect an injury at the base of the fifth metacarpal. A new anteroposterior and oblique radiography at 60 degrees confirmed the dislocation of the fifth metacarpal bone.
Fig. 2 Preoperative radiographs and computed tomography scans from patient 2.
Fig. 3 Preoperative, early postoperative, and late postoperative radiographs from patient 3.
Fig. 4 Preoperative radiograph and computed tomography scan from patient 4.
Table 1
|
Patient
|
Age (years)
|
Dominant side
|
Mechanism
|
MC injury
|
Hamate injury
|
CMC dislocation
|
Time to surgery
|
Surgical approach
|
Fixation
|
Initial CT scan
|
Follow-up CT scan
|
DASH score
|
Grip strength (%)
|
Follow-up
|
|
1
|
55
|
Right
|
Fall from height over the hand
|
Base of the fifth right finger
|
No
|
Fifth finger
|
14 days
|
Closed
|
KW
|
No
|
Yes
|
2.27
|
92
|
16 months
|
|
2
|
38
|
Right
|
Fall from height over the hand
|
Base of the fifth right finger
|
No
|
Fifth finger
|
30 days
|
Open
|
KW
|
Yes
|
Yes
|
4.54
|
102
|
39 months
|
|
3
|
33
|
Right
|
Fall from height over the hand
|
Base of the fourth right finger
|
Yes (body)
|
Fourth and fifth finger
|
20 days
|
Open
|
2.7-mm screw + KW
|
Yes
|
No
|
9
|
100
|
49 months
|
|
4
|
45
|
Right
|
Fall from height over the hand
|
Base of the fifth right finger
|
No
|
Fifth finger
|
15 days
|
Open
|
KW
|
Yes
|
No
|
20.45
|
121
|
49 months
|
Discussion
Hamate metacarpal dislocations cover a wide range of complex injuries, also known as carpometacarpal (CMC) dislocations of the fourth and fifth fingers, i.e., the ring and little fingers or ulnar fingers.[7]
They usually originate from hitting solid objects with the fist (54%) or high-energy mechanisms such as car accidents (23%) and falls from height (14%).[5]
The mechanism of injury involves an axial load through the fourth metacarpal, resulting in a fracture at the base of the bone. The sustained deforming force transfers to the fifth metacarpal through the intercarpal ligament with dorsal CMC ligament failure due to hamate avulsion and dislocation of the fifth metacarpal from its base towards the dorsal aspect. The degree of flexion of the fifth metacarpal at the time of injury determines the type and degree of hamate injury; a minimal flexion results in a coronal fracture.[5]
The clinical picture consists of pain, dorsoulnar deformity of the hand, epaulet sign, and eventual loss of function of the interosseous muscles due to compression of the ulnar nerve, especially in hamate fractures.[13]
[14]
[15]
The posteroanterior hand radiograph allows the evaluation of the three ulnar CMC joints and the contour of the hamate bone. Thirty degrees of supination isolate the radial rays (first and second CMC); 60 degrees of supination allow clear assessment of the fourth and fifth CMC; and lateral radiographs indicate the presence of dorsal or volar translation.[4]
[16]
A CT is advisable because of the joint involvement and the complexity of such injuries, as it improves the therapeutic approach.[13]
[17] Furthermore, CT is helpful in case of suspect injury persistence when radiographic findings are unremarkable.[4] Patients 2, 3, and 4 underwent an initial CT scan and an open reduction. CT probably guided the approach as it allowed the detailed visualization of joint involvement.
Non-surgical treatment is an option if displacement is minimal, which is rare since these fractures are often unstable due to the action of the flexor and extensor carpi ulnaris muscles, usually requiring surgery. Early diagnosed injuries can undergo closed reduction and percutaneous fixation. However, this approach can be difficult in dorsal CMC ligament interpositions and evolution times higher than three weeks. These cases require open reduction.[16]
[17] Fixation can use screws, Kirschner wires, or plates placed as a bridge.
The four patients received Kirschner wires for fixation. Immobilization occurred for six weeks to provide greater local stability. All showed excellent functional outcomes reflected in an average DASH score of 9 points, good grip strength, and full range of motion, even when the intervention occurred three weeks post-injury. The literature shows that consolidation often takes place with no recurrent instability, but surgery significantly reduces grip strength.[18] Other studies conclude a generally favorable prognosis in short and medium-term follow-up, regardless of the closed or open reduction method.[4] Inaccurate joint restoration, delayed treatment, concomitant neurological injuries, and secondary fracture displacement have been associated with worse outcomes as they increase the likelihood of postoperative pain, chronic deformity, malunion, and CMC osteoarthritis.[4]
[18]
[19]
[20]
Arthrodesis is a treatment option when the fifth CMC joint osteoarthritis conservative management is not feasible. It eliminates the primary cause of pain and significantly improves grip strength.[21]
[22] Other surgical treatment options include resection of the base of the fifth metacarpal with debridement of the CMC joint, interposition arthroplasty, and stabilizing arthroplasty[23] consisting of resection of the base of the fifth metacarpal and its fusion to the fourth metacarpal.[24]
The limitations of this study include its retrospective nature, the small number of patients, the loss of patients at follow-up, and the lack of an institutional management protocol. Our strengths include a long follow-up period of at least 16 months.
Based on the reviewed literature and the outcomes from our patients, we recommend a high index of suspicion for this low-frequency injury in patients with ulnar carpometacarpal pain after a consistent mechanism, such as a punch, a car accident, and a fall over the hand with an axial load on the metacarpal bones. It is critical to request appropriate imaging, including 30-degree and 60-degree oblique hand radiographs and CT for proper preoperative planning. We observed that using widely available minimal osteosynthesis elements can lead to excellent functional outcomes and high patient satisfaction, as reflected in the algorithm provided in [Figure 5].
Fig. 5 Treatment algorithm: Suspect of a carpometacarpal dislocation of the ulnar edge in patients with a consistent injury mechanism, such as a high-energy trauma, axial load on the metacarpal due to fist or fall, and symptoms like swelling and dorsoulnar hand pain. The first step is to request posteroanterior, oblique (at 30 and 60 degrees), and lateral radiographs of the involved hand. If a fracture-dislocation is present, request a hand computed tomography (CT) scan to define its configuration. When radiographic findings rule out the diagnosis, but the symptoms and mechanism of injury remain highly consistent, request a CT scan for better local visualization. In a positive diagnosis, the most common findings are joint incongruity and fracture instability. In this case, a surgical resolution will be necessary to reestablish the metacarpal height and the joint surface through general, open reduction and fixation with Kirschner wires, screws, plates, or a combination of these devices depending on the comminution degree, fragment size, and the ability to achieve metacarpal height.
In the long term, the goal is to establish whether these patients suffer more post-traumatic osteoarthritis than the general population. This information will come with extended follow-up periods.
