The wrist has numerous described accessory ossicles, which are separate ossification centres that never fused to a neighbouring carpal bone. Clinically notable examples include the os centrale (between the capitate, scaphoid, and trapezoid, normally fused into the scaphoid in humans but separate in many other primates), the os styloideum (at the base of the second or third metacarpal), the os paratrapezium (beside the trapezium), and the os Gruberi (adjacent to the triquetrum). Most are incidental radiographic findings that rarely cause symptoms. The os styloideum can cause carpal boss syndrome, a painful dorsal midhand prominence at the second and third CMC joints.
| Articulations |
|
|---|---|
| Landmarks |
|
| Ossification | Accessory ossification centres that fail to fuse. Congenital variants present in a small percentage of the population. |
Carpal boss from an os styloideum or osteophyte at the second and third CMC joint dorsal margin produces a firm dorsal midhand mass that is often confused with a ganglion but is non-transilluminatable and non-fluctuant. Ultrasound confirms bony versus cystic nature. Symptomatic cases are managed with injection and occasionally surgical excision. After wrist trauma, an unexpected ossicle with smooth corticated margins is usually a variant, while CT or MRI showing cortical disruption or marrow oedema indicates a fracture.
Accessory carpal ossicles are often mistaken for chip fractures after wrist trauma; smooth corticated margins and bilateral presence point to a normal variant.
This website uses cookies to enhance your experience. Some are essential for site functionality, while others help us analyze and improve your usage experience. Please review your options and make your choice.
If you are under 16 years old, please ensure that you have received consent from your parent or guardian for any non-essential cookies.
Your privacy is important to us. You can adjust your cookie settings at any time. For more information about how we use data, please read our privacy policy. You may change your preferences at any time by clicking on the settings button below.
Note that if you choose to disable some types of cookies, it may impact your experience of the site and the services we are able to offer.
Some required resources have been blocked, which can affect third-party services and may cause the site to not function properly.
This website uses cookies to enhance your browsing experience and ensure the site functions properly. By continuing to use this site, you acknowledge and accept our use of cookies.
