What's the Diagnosis - Case 21

History 35 year old woman with increasing left foot pain.

What’s the Diagnosis - Case 21

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What’s the Diagnosis - Case 21

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Findings Radiographs demonstrate a soft tissue mass between the first two digits at the level of the metatarsal heads and extending distally. MRI demonstrates a fluid mass interposed between the first and second metatarsal heads containing a prominent amount of synovial proliferation/synovitis.

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Diagnosis: Tarsal Coalition In the forefoot, where the digital nerves traverse the deep transverse metatarsal ligament, there is often entrapment with fibrosis. This leads to a Morton’s neuroma.

However, also at this location is the intermetatarsal bursa, which usually contains a minimal amount of fluid. With irritation of the nerve or directly of the bursae, an increasing amount of fluid may yield a pathological intermetatarsal bursitis. This may contain synovitis, as is seen in this case. Intemetatarsal bursitis is frequently seen with an underlying Morton’s neuroma, but may be seen in isolation, also as seen in this case.

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Resources Intermetatarsal Spaces: Analysis with MR Bursography, Anatomic Correlation, and Histopathology in Cadavers.

Bossley CJ, Cairney PC. The intermetatarsophalangeal bursa: its significance in Morton’s metatarsalgia. J Bone Joint Surg Br 1980; 62-B:184-187.

Awerbuch MS, Shephard E, Vernon-Roberts B. Morton’s metatarsalgia due to intermetatarsophalangeal bursitis as an early manifestation of rheumatoid arthritis. Clin Orthop 1982; 214-221.

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What’s the Diagnosis - Case 21

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