Primary synovial osteochondromatosis of a subdeltoid bursa

Abstract

Primary synovial osteochondromatosis (SOC) is known to be intra-articular and wherever it is observed outside a synovial joint, it is associated with the involvement of the nearby joint. Primary SOC has not been reported to involve a subdeltoid bursa. We present a case of a 52-year-old woman having a large number of loose bodies in a large tumor in the subdeltoid bursa. The swelling was first noticed by the patient 2 years back. Plain roentgenogram revealed soft tissue swelling only with no areas of calcification. On MRI, multiple nonosseous loose bodies were visualized in the bursa deep to the deltoid muscle. A surgical excision of subdeltoid bursa was done. A biopsy confirmed it to be cartilaginous loose bodies in synovial lining sugestive of metaplastic transformation of the synovial tissue.

Keywords: Subdeltoid bursa; extraarticular synovial osteochondromatosis; synovial osteochondromatosis.

Figure 1

(a) A clinical photograph showing big swelling on the outer aspect of the left shoulder and left upper arm (b) X-ray left shoulder showing a soft tissue swelling in the deltoid region; no point/area of calcification visible in the swelling (c) MRI coronal section through the shoulder joint shows multiple nonossified loose bodies deep into the deltoid muscle with subacromial extension. No loose body below the rotator cuff (d) Another MRI sagittal section through the material of the swelling, showing a large number of loose bodies deep into the deltoid muscle; none is ossified

Figure 2

Per-operative photograph showing (a) synovial sheath is visible from under the deltoid muscle which is retracted laterally (incision in line of the deltopectoral groove); (b) cartilaginous loose bodies coming out of the incidentally ruptured synovial bag; (c) innumerable loose bodies after removal

Figure 3

Histopathological micro-photograph: (a) black arrow denotes increased vascularity in the area of inflammation (granulation tissue); green arrow shows hyperplastic synovial lining; and blue arrow shows the early stage of development of the cartilaginous loose body which is still inside (b) chondrocytes in the hyaline cartilage (the blue thick arrow shows hyalinized tissue) (c) chondrocytes in lacunae inside the newly formed cartilage