40 First Metacarpal Base Fractures (Bennett and Rolando Fractures)
Bennett and Rolando fractures are intra-articular fracture dislocations of the base of the first metacarpal that can be treated with several surgical techniques including fixation with Kirschner wires, interfragmentary screws, plate osteosynthesis, and arthroscopically assisted fixation.
A number of techniques for reduction and stabilization of first metacarpal base fractures exist including fixation with Kirschner wires, interfragmentary screws, plate osteosynthesis, and arthroscopically assisted fixation.
40.2 Key Principles
Bennett and Rolando fractures are intra-articular fracture dislocations of the base of the first metacarpal which are displaced due to the pull of the abductor pollicis longus (APL) and adductor pollicis muscles. These fractures occur when an axial compressive load is directed through a partially flexed first metacarpal shaft. As a result, a fragment of the palmar articular lip of the metacarpal remains is reduced to the trapezium via its attachment to the volar beak ligament, while the remainder of the metacarpal subluxes in a proximal-dorsal-radial direction and adducts from the deforming forces of the APL and adductor pollicis muscles, respectively. Key principles include reestablishing alignment of the first metacarpal base on the trapezium and restoring articular congruity.
The fixation method in Bennett fractures depends upon the size of the marginal palmar fragment that remains attached to the intact volar beak ligament. In fractures where the palmar fragment is small and unable to accommodate screws, K-wire fixation is preferred. When the palmar fragment is larger (usually at least 1/3 of the articular surface), two interfragmentary screws can be placed across the fracture. Rolando fractures are three-part/comminuted, complete intra-articular fractures that usually require plate fixation.
Nondisplaced and stable fractures can be immobilized in a cast for 4 to 6 weeks.
Surgery is indicated for fractures that are displaced, unstable, subluxed, or open.
Malunited fractures require a corrective osteotomy.
Chronic injuries showing evidence of arthrosis in the carpometacarpal (CMC) joint require a fusion or an arthroplasty.
40.6 Special Considerations
A computed tomography scan can help in determining the size of the palmar articular fragment, supplement preoperative planning in comminuted fractures, and identify associated injuries such as a fracture to the triquetrum. Arthroscopically assisted fixation can increase the accuracy of the reduction of the articular surface through direct visualization of the joint.
40.7 Special Instructions, Positioning, and Anesthesia
The patient is positioned supine with the arm on a hand table.
Fluoroscopy should be available to judge the accuracy of reduction and placement of implants.
Options for anesthesia include general anesthesia, sedation and local, regional block, or local injection depending on surgeon and patient preference.