Infrequent Adventitious Bursitis Associated with A Palpable Metatarsal Mass: Series of Cases

Abstract

Category: Midfoot/Forefoot Introduction/Purpose: Adventitious bursae are structures that appear in adulthood, as a mechanism for protection. It may develop at sites where subcutaneous tissue (ST) is exposed to friction and high pressure. In the forefoot, adventitious bursitis is usually adjacent to bony prominences of the metatarsal heads and is one of the causes of forefoot pain. There are different stages of the pathology, at the beginning there is a small bursa without cavity, subsequently this cavity will gradually acquire a larger size, until becoming independent. The degeneration of the connective tissue which is the characteristic of the adventitious bursa. Figure 1.We present four cases of adventitious bursitis in patients who complained of a fluctuating mass on the forefoot associated with localized pain on palpation and pressure. Methods: We reviewed the cases of 4 patients treated by one of us (MGSA) for forefoot pain associated with a palpable mass. We obtained the information from the medical records: clinical presentation, radiographs, ultrasound, magnetic resonance imaging (MRI), treatment, histological diagnosis (if it was available) and outcomes. Pain was assessed with visual analog scale (VAS). Results: The four patients complained of a mass on the forefoot associated with pain. The skin was normal with no signs of infection. Ultrasound and MRI showed heterogeneous images in the ST in high pressure areas. Patients were diagnosed according to the previous studies and treated conservatively. The treatment consisted of cryotherapy and walker boot until they had shoe insoles with metatarsal olive in order to unload the metatarsus. Forefoot pain improved markedly from an initial VAS of 8.5 to 3.5 in the first month and the palpable mass decreased. Except in one patient whose studies were not conclusive and mass does not decrease in size and she required an excisional biopsy. The anatomopathological diagnosis was consistent with adventitial bursitis. Conclusion: Adventitious bursitis of the plantar forefoot is not a frequent pathology and it can be confused with a foreign body granuloma, localized infection or a tumoral mass among other possible diagnoses due to the clinical and imaging presentations. It is important to take this diagnosis into account when dealing with metatarsalgia and have fluent communication with the radiologist in order to avoid an unnecessary surgery and to establish the appropriate treatment to improve the symptoms.