The triquetrum has three facets for articulation with the lunate, hamate, and pisiform bones on the radial, distal, and volar borders, respectively. The proximal-ulnar edge of the triquetrum articulates with the triangular fibrocartilage complex near the ulnar styloid. Its articulation with the lunate is stabilized by the lunotriquetral (LT) interosseous ligament, which has three components (volar, intercalated, and dorsal). The volar LT ligament is the most important for stability, and fractures to the volar-radial triquetrum put the wrist at risk for volar intercalated segmental instability (VISI).
On examination, the ulnar and dorsal aspects of the hand may demonstrate swelling and ecchymosis. Radial deviation and flexion of the wrist aids in palpation, with the triquetrum found just distal to the ulnar styloid. Pain with flexion/extension is common with triquetral fractures. Additional imaging should include the 45° pronated oblique radiograph which silhouettes the dorsal-ulnar border of the triquetrum. Dorsal cortical comminution is evident on this view and on the lateral radiograph with a classic finding termed the "pooping duck sign" (Figure 2). Fractures of the volar aspect of the triquetrum are difficult to evaluate with radiographs, therefore CT may be necessary. When ligamentous stability is a concern, such as with volar-radial fragments, MRI can evaluate for peritriquetral soft-tissue injury.
Lateral wrist radiograph demonstrating the "pooping duck" sign, indicative of a dorsal cortical triquetrum fracture (arrow).
The most common fracture pattern is a dorsal cortical fracture, which in isolation can be treated as a wrist sprain.[8,9] Notably, although the dorsal intercarpal ligament and the dorsal radiocarpal ligament insert on the dorsal triquetrum, the location of the dorsal fragments is typically proximal and ulnar to the insertions of the dorsal intercarpal/dorsal radiocarpal, and therefore, the body of the triquetrum and the wrist maintains stability. The second most common are triquetral body fractures (Figure 3), which are more ominous and require careful clinical consideration (Table 1). Important patterns to recognize are transverse fractures, which are associated with perilunate fracture-dislocations (Figure 4), and palmar cortical fractures, which can be a sign of avulsion of the LT ligament, putting the wrist at risk for VISI deformity.
Lateral hand radiograph and CT imaging of a triquetrum body fracture with mid carpal joint subluxation (white arrows).
Posteroanterior and lateral hand radiographs demonstrating a transtriquetral transstyloid dorsal perilunate fracture-dislocation. (Reproduced with permission from Leung YF, IP SPS, Wong A et al: Trans-triquetral dorsal perilunate fracture dislocation. J Hand Surg Eur 2007;32:647–648.)
Stable small dorsal fragment fractures can be treated with a splint or cast immobilization for 3 to 4 weeks, followed by removable wrist brace support and progressive wrist motion. These injuries have a notable chance of progressing to painless fibrous nonunion, which will likely remain asymptomatic and not require further treatment. Stable nondisplaced body fractures and volar cortex fractures can be treated with cast immobilization for 4 to 6 weeks with good outcomes. Displaced triquetral body fractures should undergo closed reduction with pinning versus open reduction and internal fixation. All cases that demonstrate ligamentous instability should be treated with open reduction and internal fixation. If the integrity of the LT ligament is disrupted, the lunotriquetral joint should be pinned in a reduced position and ligamentous repair should be attempted.
Early intervention for triquetrum fractures may mitigate its complications. The position in the ulnar column highlights the triquetrum's role in carpal stability. Therefore, missed body fractures that cause instability lead to functional impairment and have an increased risk for nonunion. Malunions are also a concern and predispose patients to developing posttraumatic arthritis. Both complications can be avoided with surgical fixation that maintains appropriate reduction. Pisotriquetral arthritis with volar cortex fractures may develop, which can be managed with pisiform excision.
J Am Acad Orthop Surg. 2020;28(15):e651-e661. © 2020 American Academy of Orthopaedic Surgeons