Teaching Case

A 15-year-old male presented with a painful soft-tissue swelling of the bilateral bimalleolar region.

A 15-year-old male figure skater presented with a painful soft-tissue swelling of the bilateral bimalleolar region. The pain had been present for two months and there was no history of trauma. MR imaging was performed and showed the presence of subcutaneous, focal soft-tissue masses of the bimalleolar region; the findings correlated to the level of the shoe rim, confirming the suspected MR imaging diagnosis of an impingement syndrome. The MR imaging study was performed using an RM scanner (0.2) with a dedicated coil. The examination consisted of T1- weighted spin-echo (SE), PD-weighted turbo-spin-echo (TSE), T2*-weighted gradient-echo (GE) and GE-STIR sequences, performed in the axial, sagittal and coronal planes.

Foot bursae are divided into anatomical bursae and acquired adventitial bursae, which commonly develop over the areas of bunion. There are many anatomical bursae in the foot that can occasionally be identified in patients on MR imaging, such as the bursae located on the medial and lateral plantar surfaces of the first and fifth metatarsals or the retrocalcaneal bursa, which is located between the calcaneus and the Achilles tendon. Anatomical bursae are closed sacs lined by a synovial-like membrane that contain synovial fluid and are subject to friction. Their purpose is to lessen normal friction and thus ease the motion that occurs between tendons, between the bones and skin, or between the tendons and ligaments. Bursae are found in numerous locations throughout the body and are classified according to their location, into deep bursae and subcutaneous bursae. The malleoli normally do not have anatomical bursae; malleolar adventitious bursae often result from abnormal contact pressure and shear forces that arise between the bony malleoli and the skater’s boot. The bony prominences of the malleoli have little inherent soft tissue to cushion them from this excessive pressure. The body responds to this abnormal stress by developing an adventitious bursa at this specific point and the newly developed adventitious bursae are suboptimal. These bursae develop by definition over time as a result of excessive pressure from ill-fitting skates. Adventitial bursae have a thinker fibrous wall than normal bursae and are more susceptible to inflammatory changes. Most bursitis cases can be categorized as aseptic bursitis, which can be labeled according to the cause as being traumatic, rheumatoid, metabolic, or neoplastic. The symptoms are related to the size and location of the bursitis, correlating to the focally painfull, clinically palpable soft-tissue mass. The bursae have a distinctive MR appearance, showing a homogeneous high signal intensity in relation to muscle on T2*-weighted GE and GE-STIR sequences, and appearing hypo-isointense on T1-weighted SE and PD-weighted TSE sequences. Bursitis must be differentiated from a soft-tissue tumor and a pseudotumor, for which the MR imaging technique plays a central role. Nonoperative measures usually provoke the best response in bursitis of the malleoli. The first-line treatment includes inspecting the skates for points that might be too tight around the malleoli. These areas can be stretched out using a ball-and-ring device that can be found at most shoe shops. The final nonoperative measure involves the cessation of skating. For patients who find no relief with the nonoperative measures mentioned, surgical excision is decisive.