Carpometacarpal Joint Injuries: Bennett’s Fractures (Arthroscopic and Percutaneous Screw Technique)

52 Carpometacarpal Joint Injuries: Bennett’s Fractures (Arthroscopic and Percutaneous Screw Technique)

Joseph F. Slade III and John D. Mahoney

History and Clinical Presentation

An 18-year-old varsity field hockey player presented with pain in the base of her right thumb. She was injured in the course of a game.

Physical Examination

Inspection of the right hand revealed a swollen, obviously deformed thumb. The base of the thumb was tender to palpation. The skin was intact, with normal sensation over the surface of the thumb. Palpation of the carpometacarpal (CMC) joint did not reveal a step-off, but passive movement of the thumb elicited pain.

Diagnostic Studies

Radiographs demonstrated an oblique, intraarticular, displaced fracture of the base of the thumb metacarpal. To obtain a true lateral view of the joint, the hand was placed flat on the cassette and then pronated 15 to 20 degrees. The tube was directed obliquely 15 degrees distal to proximal, centering over the CMC joint.

Differential Diagnosis

Bennett’s fracture

Pure dislocation of the carpal metacarpal joint

Rolando’s fracture

Metacarpal shaft fracture

Carpal fracture

PEARLS

Malunion is present in a small minority of Bennett’s fractures managed surgically. These patients may be candidates for osteotomy or arthrodesis.
Nonunion is practically non-existent.
Reduction maneuvers may change the type of fracture; that is, a type I may become a type III on manipulation.

PITFALLS

The majority of patients treated conservatively will develop subluxation of the trapeziometa-carpal joint.
The superficial branch of the radial nerve may be injured in Bennett’s fracture. Careful neurological exam is warranted.
For fractures managed with K wires, use of a single K wire is often associated with K-wire migration, displacement, and pin tract infection.

Diagnosis

Bennett’s Fracture: Type III

The diagnosis in this case was Bennett’s fracture, type III, an oblique intraarticular fracture dislocation of the basal joint of the thumb metacarpal. The most common mode of injury is a motorcycle or bicycle accident, forcing the handlebar into the web space between the thumb and index finger. Other common causes include fights, sporting accidents, and falls on an outstretched hand. Generally, any trauma causing abduction and hyperextension of the thumb can cause a Bennett’s fracture. Most of the injuries (70–90%) occur in men, and the peak age incidence is 35 to 45 years. A classification scheme for Bennett’s fracture has been devised (Table 52–1).

**Table 52–1** **Classification of Bennett’s Fracture**
Fracture Type	Description
Type I	Distal fragment separation with preservation of continuity of the proximal joint surface
Type II	The opposite of type I, with proximal fragment separation, joint surface disruption, and preservation of the distal cortex
Type III	Most common (67% incidence), with total separation of the fragment

Surgical Management

We performed an arthroscopically assisted closed reduction and fixation with percutaneously placed cannulated screws. Four days after referral from the emergency department, the patient was taken to the 1-day surgery center for definitive management. The patient was placed supine, using general anesthesia, exsanguination of the arm, and tourniquet control. To begin, longitudinal traction was applied through a single finger trap to the thumb with 10–12 pounds of traction. A mini-fluoroscopy unit placed horizontally around the hand assisted in placement of percutaneous guidewires (Fig. 52–1

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