Radiological and histological analysis of two replaced interphalangeal joints with active subchondral bone resorption in erosive hand osteoarthritis: a novel mechanism?

The aim of this study was to describe the histological features of erosive hand osteoarthritis (EHOA), which is considered an aggressive subset of hand osteoarthritis (OA) characterized by severe local inflammation and degeneration of the distal and proximal interphalangeal joints. Two patients with EHOA underwent replacement with a cement-free press fit ceramic prosthesis of a proximal interphalangeal joint (PIPJ). Clinical and radiological data were collected and histological examination was performed. Radiological examination with histological correlation showed complete erosion of the articular cartilage with focal presence of peripheral fibrocartilaginous resurfacing, sclerosis, and remodeling of the exposed bone, osteoclastic activity with resorptive lacunae in the subchondral bone and around degenerative fibromyxoid pseudocysts, coarse trabeculation of the cancellous bone, and marginal osteophytes. The synovial membrane showed non-specific mild hypertrophy and mildly cellular fibromyxoid stroma. The histological findings in patients with EHOA suggest a pathogenesis of cartilage resorption from the subchondral bone, via osteoclastic-mediated activity and formation of periarticular reactive fibrocartilaginous proliferation with partial resurfacing of the articular surface.