Pisiform fractures are rare, although they are highly associated with fractures elsewhere in the wrist and hand. The pisiform is a pea-shaped sesamoid bone within the flexor carpi ulnaris tendon and rests on the volar surface of the triquetrum.
Examination will reveal a swelling of the hypothenar eminence and tenderness over the pisiform. The pisiform can be consistently palpated by finding the palmar prominence formed at the ulnar base of the hypothenar eminence. Flexion and ulnar deviation of the wrist will activate the flexor carpi ulnaris (FCU) and can be painful if a fracture is present. Radiographic views for the pisiform fractures should include the 45° supinated oblique view and the carpal tunnel view. Fractures typically take on three patterns: sagittal, transverse, and comminuted (Table 1). The classic low energy fall pins the pisiform between the impacting surface and the triquetrum, resulting in a sagittal fracture line (Figure 10). A similar mechanism with higher energy will result in fracture line propagation and comminution. Alternatively, a strong pull by the FCU can result in a transverse avulsion fracture. Nondisplaced fractures are managed with 3 to 6 weeks of ulnar gutter cast immobilization. At the surgeon's discretion, severely displaced pisiform fractures can be managed initially with pisiformectomy and FCU repair, given the high risk of nonunion. Patients with symptomatic nonunion should undergo pisiformectomy, which has been shown to have good outcomes without notable functional impairment.
Axial CT imaging of a sagittal pisiform fracture with minimal displacement. (Reproduced with permission from Kaewlai R, Avery L L, Asrani A V, et al: Multidetector CT of carpal injuries: Anatomy, fractures, and fracturedislocations. RadioGraphics 2008; 28:1771–1784. With permission from the Radiological Society of North America.)
Outcomes data on pisiform fractures are limited, given the rarity of the injury. However, sequelae of the injury are generally limited and well tolerated. Nonunion of the pisiform is the most cited complication, which often remains asymptomatic. Symptomatic nonunions respond well to excision. Palmieri reported on five patients with symptomatic pisiform nonunions, and after surgical excision, all patients were able to return to work with a symptomatic relief.
J Am Acad Orthop Surg. 2020;28(15):e651-e661. © 2020 American Academy of Orthopaedic Surgeons