That’s my STYLEoideum- It is not always desirable to be unique, at least anatomically. Os styloideum

Posted By Tilo Niemann
That’s my STYLEoideum- It is not always desirable to be unique, at least anatomically. Os styloideum

Case Report We report the case of a 15-year-old male patient that was admitted to our hospital for persistent localized pain on the dorsal site of the left adominant wrist. Clinical assessment and physical examination revealed punctual localized pain on the dorsal aspect of the left wrist between the base of the 2nd and 3rd metacarpal bones over the third carpometacarpal joint. Inspection showed a slight localized protrusion, asymmetry and concomitant tenderness but no relevant swelling, no other signs for infection. The mobility and strength of the wrist and fingers was symmetrical to the opposite site. There was no history of trauma or prior operation. The sensations of pain occurred mostly when lifting heavy objects. According to his mother he had recently grown noticeably. Basing on clinical symptoms and assessment a slight insertional tendinitis of extensor carpi radialis longus/brevis muscle or a carpe bossu were suspected. To rule out fracture and for the purpose of accurate distinction of the lesion a native multi-slice CT (Siemens Somatom Definition Flash, Siemens Medical Solutions, Germany) of the left wrist was performed. The images revealed no fracture and normal alignment of the carpal bones. An accessory round osseous structure between the dorsal aspect of the capitate and trapezoid bones and the radial aspect of the base of the third metacarpal bone with pseudoarticulation was detected. To determine if the accessory bone was present in the opposite wrist, a further verifying ultrasound examination with the use of a 12 MHz linear transducer (Toshiba Amplio 500, Toshiba Medical Systems Corporation, Japan) was performed. Ultrasonography revealed additional bones on the base of the metacarpal II and III bones on both sides. However, the accessory bone was significantly larger in the left wrist. A corticosteroid infiltration of the third carpometacarpal joint under fluoroscopy resolved pain completely within a few days, verifying the carpe bossu causing the patients clinical symptoms. Discussion An accessory bone called os styloideum is a rare anatomical variant in the construction of a carpometacarpal joint with an incidence of 0.3-1.6% [1]. It is located between the capitate and trapezoid and the bases of second and third metacarpals, and is also called “ninth carpal bone” [1]. Furthermore, in the orthopaedic jargon terms like “carpe bossu” or “carpal boss” stand for the pain in the dorsum of the wrist, thus correlate with the location of the os styloideum [2-4]. Mostly, os styloideum disappears during fetal development while its occurrence is explained as an embryologic developmental variant resulting from non-fusion of the primordial cartilaginous units [5]. Routinely the way from clinical symptoms to the conclusive diagnosis leads through the CT or ultrasound examination to rule out differential diagnoses [6]. A palpable bony prominence on the dorsal site of the wrist in the clinical examination and concomitant

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