Extra-articular ankylosis is due to bridging heterotopic ossification. The underlying joint is preserved. The elbow, shoulder and hip are most commonly affected. Interestingly, these joints can be affected regardless of the site of injury.
The earliest radiographic manifestation of extra-articular ankylosis is periarticular calcification that may progress to heterotopic ossification. Extra-articular ankylosis usually responds to physical therapy and surgical excision.
Intra-articular ankylosis (shown above) occurs within the joint and most commonly occurs at the interphalangeal joints. Intra-articular ankylosis results in serious functional and cosmetic problems and is not as easily treated as the extra-articular type. Treatment options include arthrodesis, osteotomy, arthroplasty, or amputation.
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