Acute os styloideum injury in an elite athlete

Fracture of an aberrant os styloideum: a unique case report

Several accessory bones can be found around the wrist, which may pose a diagnostic challenge. Hereby, we report a unique case of a traumatic fracture of an aberrant os styloideum in a 66-year-old male. The patient presented with a swollen dominant right hand and a hematoma on its anterior and posterior aspects, as a result of a fall on an outstretched hand. The diagnosis was based on a CT scan, which showed a fractured accessory bone between the distal portion of the capitate bone and the base of the third metacarpus. Due to its typical location, the ossicle was identified as os styloideum. The patient was treated conservatively and the symptoms subsided on a short forearm cast after 2 weeks. At a 12-month follow-up, no other episodes were declared. Strong anatomical knowledge and sharing of such cases is essential for proper diagnosis and treatment of this very rare condition.

MRI of a painful carpal boss: variations at the extensor carpi radialis brevis insertion and imaging findings in regional traumatic and overuse injuries

OBJECTIVE

To report patterns of MRI findings involving carpal boss and extensor carpi radialis brevis (ECRB) tendon insertion in individuals with overuse-related or post-traumatic wrist pain.

MATERIALS AND METHODS

Eighty-four MRI cases with carpal bossing between December 2006 and June 2015 were analyzed by two fellowship-trained musculoskeletal radiologists. The following MRI findings were reviewed: type of carpal bossing (bony prominence, partial coalition, os styloideum), insertion of ECRB tendon (to the 3rd metacarpal, to carpal boss or to both), bone marrow edema (BME), insertion site, and tenosynovitis/tendinosis of ECRB tendon. Clinical information on wrist pain was available on 68 patients.

RESULTS

Fused carpal bossing was detected in 21%, partial coalition in 35%, and os styloideum in 44% of the cases. Regional BME was observed in 64% of the cases. When BME specifically at the carpal boss was assessed, 78% of stable and 50% of unstable bosses showed BME (p = 0.035). ECRB tendon inserted on a carpal boss in 20%, on the 3rd metacarpal bone in 35%, and on both sites in 45% of the cases. As BME at the carpal boss was assessed, BME was detected at the respective insertion sites in 71%, 35%, and 66% of the cases (p = 0.015). Dorsal wrist pain was associated with BME as 75% of the patients had regional BME in the vicinity of the carpal boss (p = 0.006).

CONCLUSION

A spectrum ranging from complete fusion of a boss to an entirely unfused os styloideum exists with a variable ECRB insertional anatomy. BME at the carpal boss is a consistent MRI finding.

MRI diagnosis of carpal boss and comparison with radiography

Background A carpal boss is a potentially painful bony mass in the region of the second or third carpometacarpal joint. The combination of clinical examination and radiography is usually sufficient for the diagnosis. Purpose To determine whether magnetic resonance imaging (MRI) examination of the quadrangular joint can assist the diagnosis of persistent pain near a carpal boss. Material and Methods Fifty-seven patients with a carpal boss were retrospectively reviewed using MRI and conventional radiographs and compared to an asymptomatic control group. Results MRI demonstrated a variable morphology and a variety of bone and soft tissue abnormalities associated with carpal boss. Bone marrow edema around the quadrangular joint shows a significant correlation (Fisher's exact test: P < 0.001) and a positive correlation (Pearson's test r = 0.632, significant at the 0.01 level [two-tailed]) with a painful carpal boss. Conclusion MRI offers detailed examination of bone and soft tissue abnormalities associated with a carpal boss. Local bone marrow edema strongly correlates with a painful carpal boss.

Prevalence of Os Styloideum in National Hockey League Players

BACKGROUND

Os styloideum describes an accessory carpal ossicle between the trapezoid, the capitate, and the second and third metacarpals. Injuries to this tissue have been described as part of the carpal boss syndrome. While the etiology of os styloideum remains uncertain, it may represent a physiologic response to altered loading forces in the wrist, similar to the development of cam-type deformity in the hips of ice hockey players or the Bennett lesion in the shoulders of baseball pitchers.

HYPOTHESIS

Professional hockey players will have a higher prevalence of os styloideum compared with the general population.

STUDY DESIGN

Case series.

LEVEL OF EVIDENCE

Level 4.

METHODS

A retrospective review of 16 professional hockey players from 4 different National Hockey League (NHL) teams who underwent unilateral imaging of the wrist was performed. Seventeen wrists were reviewed for the presence of os styloideum.

RESULTS

Thirteen of 16 players (81%) had an os styloideum, representing an increased prevalence compared with the general population. Previous clinical and cadaveric studies estimated a general prevalence of up to 19% ( P < 0.001). For the 10 players who had their leading wrist scanned, 9 had an os styloideum (90%). Ten of 11 (91%) players demonstrated a bone marrow edema pattern within the metacarpal and the os styloideum on magnetic resonance imaging. There was no significant association between the presence of an os styloideum and the player's position, leading wrist, or years in the league.

CONCLUSION

There appears to be an increased prevalence of os styloideum among NHL players, and team physicians should consider this finding while formulating a differential diagnosis for dorsal wrist pain.

CLINICAL RELEVANCE

This study identified NHL players as having an increased prevalence of os styloideum compared with the general population. By doing so, these findings represent an opportunity to enhance our understanding of the etiology, clinical significance, and treatment of os styloideum.

Imaging Findings at the Quadrangular Joint in Carpal Boss

A carpal boss was initially described as a bony, sometimes painful mass at the quadrangular joint. Clinical examination and plain radiography will usually reveal the diagnosis. US and CT may add information. MRI may illustrate a variable bony morphology and additional bony and soft tissue pathologies. Bone marrow edema shows a significant correlation with a painful carpal boss. Hence, MRI may be of additional diagnostic value in patients with persistent pain and preoperatively. This paper presents a review of the anatomy and pathology in carpal boss. The merit of each imaging modality - in particular MRI - is mentioned.

Achados de imagem por tomografia computadorizada e ressonância magnética do os styloideum em atleta sintomático

Os styloideum é um ossículo acessório, imóvel, localizado dorsalmente no carpo, que representa uma variante anatômica. A associação entre os styloideum e dor no punho é conhecida clinicamente como "carpal boss syndrome". Os autores relatam um caso de os styloideum com edema ósseo trabecular no estudo por ressonância magnética em atleta jovem tenista, com revisão da literatura deste achado.

[Numerical variants and congenital fusions of carpal bones]

The number of carpal bones may be increased or decreased by the fact of anatomical variants or true congenital anomalies. Numerical increment arises from additional or from split bones. Over twenty accessory carpal bones have been described but the commonest are the os centrale carpi, the os radiale externum, the triangular bone and the styloideum bone. Additional carpal bones usually result from a failure of fusion of their ossification centers. A congenital origin is not clearly established for all these ossicles. The scaphoid and lunate may split into two or three bones and several cases of bipartite hamulus of the hamatum have been reported. A carpus with only seven bones results from the congenital absence of a normal bone, which mainly affects the scaphoid, lunate and triquetrum, or from a synostosis between two carpal bones, usually the lunate and triquetrum. Congenital fusions originate from an absence of joint cavitation into the embryo and chondrification of the joint interzone. Numerical carpal variants are uncommon as independent entities but occur with a relative high frequency in association with complex malformations of the hand. These anomalies are detectable on plain radiographs of the wrist, but CT-scan and MR-Imaging are useful to differentiate bipartite and accessory bones from carpal fractures or posttraumatic injuries, carpal fusions having to be distinguished from bony ankylosis.