Sections show fibromyxoid, edematous stroma and skeletal muscle heavily infiltrated by dense sheets of neutrophils, lymphocytes, plasma cells, and foamy histiocytes. Prominent vascular proliferation, congestion, fresh hemorrhage, and focal hemosiderin deposits are present. The acute-on-chronic inflammatory exudate surrounds degenerating, necrotic fibroconnective tissue and muscle fibers, forming an abscess wall. Cancellous bone fragments show thin, remodeled trabeculae with focal loss of osteocytes within lacunae, indicating ischemic necrosis. The intertrabecular marrow spaces are expanded and replaced by a dense neutrophilic exudate, fibrinous debris, vascular congestion, and focal marrow fibrosis. No granulomas or neoplastic cells are identified.
Synovial membrane biopsy; right-sided developmental dysplasia of the hip (DDH) complicated by severe superior-anterior displacement of the right femoral head, early (grade 1) avascular necrosis, and an active/residual inflammatory process.
Two soft tissue and bone fragments collectively measured 3x2.5x1.5 cm, totally embedded.
Right hip joint capsule, periarticular soft tissue, and femoral head bone (debridement):