That's my STYLEoideum - Symptomatic os styloideum in an adolescent male

Abstract

We present a 15-year-old male patient with persistent localized pain on the dorsal side of the left wrist between the base of the 2nd and 3rd metacarpal bones and over the third carpometacarpal joint. It was diagnosed as an accessory metacarpal bone -Os styloideum. This entity may be detected on plain radiographs and in ultrasound examination and is often asymptomatic. Symptomatic os styloideum occurs more frequently in the dominant hand and may be treated conservatively with corticosteroid infiltration. A palpable prominence on the dorsal side of the wrist and focal pain evoked anxiety of the adolescent patient who searched medical consultation. In the clinical examination, a bony protrusion was confirmed and different possible diagnoses have been considered. After treatment with a corticosteroid infiltration of the third carpometacarpal joint under fluoroscopy the pain resolved completely. We would like to draw attention of clinicians and radiologists to this rare anatomical variant that normally is asymptomatic, and therefore not immediately recognized. Acquaintance with this entity and its early detection may lead to conservative treatment instead of surgical excision. A comprehensive literature search, review and discussion about os styloideum are provided in the article.

Keywords: Carpe bossu; Os styloideum; carpal boss; computed tomography; ultrasound; wrist pain.

Figure 1

15-year-old male patient with symptomatic os styloideum (Non-enhanced CT of the wrist) TECHNIQUE: Non-contrast multislice CT (Somatom Definition Flash, Siemens). 100/Sn140 kV, 108/88 mAs. 0.6 mm slice thickness. CTDIvol 8.6 mGy. DLP 87 mGycm. CT axial (1a) and sagittal (1b) views. Os styloideum is visible on both reconstructions (arrows). It is located on the dorsal side of the wrist between the capitate and trapezoid and the base of the styloid process of the third metacarpal (arrows).

Figure 2

15-year-old male patient with symptomatic os styloideum (Ultrasound of the left hand) TECHNIQUE: 12 MHz linear transducer (Toshiba Amplio 500, Toshiba Medical Systems Corporation, Japan). Transverse (a) and longitudinal view (b). The left os styloideum is seen between the bases of the 2nd and 3rd metacarpals on both the longitudinal and transverse images.

Figure 3

15-year-old male patient with symptomatic os styloideum (Ultrasound of the right hand) TECHNIQUE: 12 MHz linear transducer (Toshiba Amplio 500, Toshiba Medical Systems Corporation, Japan). Transverse (a) and longitudinal view (b). The right os styloideum is also seen between the base of the 2nd and 3rd metacarpals on longitudinal and tranverse images, but is significantly smaller than the accessory ossicle on the left.