The trapezium has a key role in the function of the thumb with the carpometacarpal saddle joint accounting for 60° of flexion/extension, 60° radial abduction, and 10° adduction available to the thumb. The volar ridge serves as an attachment for the radial aspect of the transverse carpal ligament and provides a groove for the path of the flexor carpi radialis tendon (Figure 5). The flexor carpi radialis tendon and flexor pollicis long tendons pass just ulnar to the ridge, whereas the superficial palmar branch of the radial artery passes just radial.
Illustration depicting the transverse cross section through the distal carpal row (TM = triquetrum, TD = trapezoid, C = capitate, H = hamate, TQ = triquetrum) highlighting the relationship of the hook of the hamate (black diamond) and the ridge of the trapezium (black star) to the surrounding tissue (1 = ulnar artery, 2 = motor branch of ulnar nerve, 3 = sensory branch of ulnar nerve, 4 = flexor carpi radialis tendon).
On examination, swelling and ecchymosis about the thenar eminence may be present. Pain will be present with metacarpophalangeal joint range of motion and wrist dorsiflexion and radial deviation. In addition to the standard radiographs, the Bett view isolates the articular surfaces. For this view, the hand is semipronated, the elbow is elevated relative to the wrist, and the thumb is abducted and extended. The carpal tunnel view is useful for evaluating the trapezium ridge. Noncontrast CT is advisable if no fracture is seen on the radiographs but index of suspicion is high or if needed for further fracture classification such as with severe comminution.
There are several patterns of injury to the trapezium that can be grouped grossly into trapezial body fractures and ridge fractures. These have been previously classified as types 1 through 5 by Walker et al (Table 1). Nondisplaced fractures of the body are treated with short arm-thumb spica casting for 4 to 6 weeks. Trapezium body fracture displacement is associated with carpometacarpal dislocation and should be managed aggressively. Displaced body fractures with minimal comminution should undergo closed versus open reduction and internal fixation. The volar-radial approach, as originally described by Wagner, is useful for fracture reduction and fixation. Bone loss from impaction should be restored with bone graft (cancellous allograft versus distal radius autograft). For proximal migration of the radial fragment and attached metacarpal, the thumb can be distracted to maintain length and a Kirschner wire can be placed through the first and second metacarpals or from the first metacarpal into the carpal bones (Figure 6). Fractures of the ridge can be treated with a removable wrist splint for comfort. Patients should be educated that during the healing process there can be notable tenderness over the ridge, which lasts for several months.
Fluoroscopic radiograph demonstrating pin orientation of a trapezium body fracture with CMC dislocation now after open reduction and pin fixation.
High-energy trapezium fractures can lead to carpometacarpal (CMC) joint instability and result in notable functional impairment. However, studies have found that appropriately treated fractures have reasonably good outcomes. McGuigan and Culp reviewed 11 patients with high-energy intra-articular trapezium fractures and found that at an average 4-year follow-up, grip strength, and pinch strength were equivalent to the uninjured side, and all patients continued working at their chosen occupation. Notably, five patients had radiographic evidence of trapeziometacarpal arthritis. This demonstrates the high prevalence of posttraumatic arthritis in even appropriately managed trapezium fractures.
J Am Acad Orthop Surg. 2020;28(15):e651-e661. © 2020 American Academy of Orthopaedic Surgeons