Classification and injury biomechanics
Depending on the location, injuries are divided into metaepiphyseal and diaphyseal fractures (the latter can be transverse or oblique). The base of the first metacarpal is the most problematic area.
Two main types of intra-articular injuries in this area are distinguished:
- Bennett fracture-dislocation. This is a longitudinal avulsion of the palmar-ulnar margin. The biomechanics of displacement here is unique: the triangular fragment itself is firmly fixed by the ligamentous apparatus and remains in place, while the main body of the bone is dislocated and displaced proximally under the traction of the extensors and the abductor pollicis longus muscle.
- Rolando fracture. This is a more severe, comminuted injury of the articular surface.
Such injuries most commonly occur from direct physical impact to the base of the bone or as a result of a fall onto an outstretched thumb adducted toward the hand.
Clinical presentation and diagnostics
The patient complains of severe pain that blocks any active and passive movements. Examination of the hand reveals edema and a clear deformation in the area of the carpometacarpal joint, while the contours of the "anatomical snuffbox" are smoothed out. The firstเอง thumb itself is visually shortened and in a position of adduction and slight flexion.
During the physical examination, the physician identifies marked tenderness upon palpation and percussion of the base of the bone, as well as axial loading of the injured finger.
A pathognomonic clinical test for a Bennett fracture-dislocation is the "sled sliding" sign. If the surgeon presses distally on the prominent base of the bone, the bulge disappears (reduction occurs). However, as soon as the pressure is released, the bone instantly displaces back due to muscle traction. To finally confirm the diagnosis and assess displacement, radiography in two standard projections is mandatory.
Principles and techniques of treatment
The primary goal of therapy is the ideal alignment of articular surfaces. The procedure must be performed before muscle contracture develops (strictly within three days from the time of injury).
Closed manual reduction technique:
- Local anesthesia with a procaine solution is performed.
- The physician firmly immobilizes the patient's wrist joint.
- With one hand, the surgeon pushes the carpometacarpal joint in the ulnar direction.
- With the other hand, powerful traction is applied to the first thumb with its maximum abduction toward the radial side.
Following a successful maneuver, a plaster "pistol" splint is applied. To prevent secondary displacement of the bone, the surgeon forms a special indentation in the plaster over the snuffbox area while maintaining traction on the finger until the material completely hardens. The result is verified by a radiograph.
If the fragments are unstable or the control radiograph shows displacement, alternative methods are used:
- Skeletal traction. Performed via the distal phalanx using a special splint (for up to 3 weeks, followed by casting).
- Surgical intervention. Percutaneous osteosynthesis or transfixation (fixation to the adjacent second metacarpal bone) with Kirschner wires is used.
Rehabilitation period
Immediately after the removal of the fixation cast or apparatus, the functional recovery phase begins. The patient is prescribed a course of physical therapy (exercise therapy), massage, and physiotherapy, including therapeutic hand baths. With adherence to all recommendations, full working capacity and grip function return to normal within 6–8 weeks.
Briefly: answers to topical questions
What types of osteosynthesis are used for metacarpal fractures?
Percutaneous osteosynthesis and transfixation are used for metacarpal fractures.
- Percutaneous osteosynthesis — performed using one or two metal Kirschner wires.
- Transfixation — fixation of the injured bone to an adjacent one (e.g., the first metacarpal to the second) using two Kirschner wires.
These methods are indicated when it is impossible to maintain reduced fragments in the correct position, as well as when closed reduction or skeletal traction is ineffective.
What are the absolute indications for surgical treatment of metacarpal fractures?
Indications for surgical treatment of metacarpal fractures include the failure of conservative methods and the inability to maintain fragment position.
These include:
- Inability to perform closed manual reduction.
- Inability to maintain reduced fragments in the correct position.
- Ineffectiveness of reduction via skeletal traction when secondary displacement occurs.
- Failed attempts at fragment reduction in an intra-articular comminuted Rolando fracture (arthrodesis is indicated in this case).
What is the exact duration of plaster immobilization for a Bennett fracture?
The exact duration of plaster immobilization depends on the patient's age and the chosen treatment method.
- In children, the duration of immobilization is 10–14 days.
- In adults treated with skeletal traction, plaster immobilization is applied for an additional 1–3 weeks after the traction is removed (which is maintained for up to 3 weeks).
The exact duration of isolated plaster immobilization for adults is not specified in the text, but full working capacity returns in 6–8 weeks.
What types of fragment displacement are characteristic of metacarpal shaft fractures?
Angular and rotational fragment displacements are characteristic of metacarpal shaft fractures.
- Angular displacement — secondary displacement at an angle open toward the palmar side. It is caused by the pull of the interosseous and lumbrical muscles. Prominent fragments are palpable on the dorsal side of the hand, while a depression is noted on the palmar side.
- Rotational displacement — leads to disruption of the normal intersection of the axes of the fingers during flexion, resulting in impaired basic hand functions (gripping and opposition).
The "sled sliding" sign is easy to understand if you imagine muscle pull as gravity. The bone is easily reduced upon pressure, but as soon as you let go, it immediately "slides" back up like a sled down a hill.
Class and exam questions
What is the fundamental difference between Bennett and Rolando fractures?
Both injuries are intra-articular and located at the base of the first metacarpal. However, a Bennett injury is a fracture-dislocation with a single triangular fragment of the palmar-ulnar margin, whereas a Rolando fracture is a severe comminuted injury.
Why does the thumb appear shortened in a Bennett fracture-dislocation?
This occurs due to the proximal displacement of the metacarpal shaft. The powerful pull of the abductor pollicis longus and extensors pulls the bone toward the wrist joint.
Is it possible to perform reduction a week after the injury?
No, closed reduction must be performed within a maximum of 3 days. At later stages, persistent muscle contracture develops, and closed reduction of the bone is no longer possible.
What else to study on this topic
- Injury mechanisms and lunate fractures
- Duration of immobilization for fractures of other carpal bones (triquetrum, pisiform)
- Causes of aseptic necrosis after hand injuries
- Anatomical and biomechanical features of the foot structure
- Fractures of the talar neck and body: displacement specifics and risks
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