The carpal boss: a review of different sonographic findings

Abstract

Carpal boss is an uncommon condition whose incidence is underestimated and that is frequently confused with other causes of development of tumor-like lesions on the dorsum of the wrist. From the clinical point of view, the main obstacle to its recognition is the nonspecificity of symptoms, frequently attributed to dorsal ganglion cysts, since both conditions share a similar location on the dorsum of the wrist. The assessment by ultrasonography allows for a correct diagnosis and appropriate management, with better chances of resolution of the clinical complaint and lower probability of iatrogenic worsening of the lesion. The present review is aimed at describing the different sonographic findings of carpal boss.

Keywords: Carpal boss; Cyst; Ganglion; Ultrasonography; Wrist.

Figure 1

Transducer positioning for longitudinal carpal boss evaluation.

Figure 2

Carpal boss (acquired presentation). Longitudinal image demonstrating the capitate bone (cap), metacarpal bone (met) and osteophytes on the margins of the metacarpal joint (arrowheads), the latter, secondary to osteoarthrosis. The bone prominence determined by the osteophytes characterizes the acquired carpal boss.

Figure 3

Carpal boss (congenital presentation). A: Longitudinal image demonstrating os styloideum (arrow head), corresponding to the palpable clinical finding. Also, observe the capitate (cap) and metacarpal (met) bones forming the carpometacarpal joint. B: Lateral radiography confirming the presence of an accessory ossicle.

Figure 4

Carpal boss (mixed presentation). A: Longitudinal image demonstrating the capitate bone (cap), the metacarpal bone (met) and the osteophyte on the carpal margin of the carpometacarpal joint (arrow). Also, note the presence of os styloideum (arrowhead). The combination of acquired and congenital findings characterizes the mixed presentation of carpal boss. B: Clinical presentation demonstrating a prominence of stony consistency on the dorsal aspect of the metacarpophalangeal joint of the third digit (arrowheads).