From the Guidelines
Heterotopic ossification (HO) of the hip is a condition where bone tissue forms outside of the skeleton, in soft tissues such as muscles, tendons, and ligaments, often as a result of trauma, injury, or surgery.
Key Characteristics
- HO can occur after major hip procedures and fractures, with varying incidence rates reported in different studies 1
- The condition can lead to significant disability and reduced mobility, as seen in patients with fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder characterized by progressive HO 1
- HO can be triggered by various factors, including soft tissue injury, intramuscular injections, viral infections, and muscular stretching or fatigue 1
Diagnosis and Treatment
- Diagnosis of HO can be made through clinical evaluation and radiological findings, with confirmatory genetic testing available for FOP 1
- Treatment options for HO are limited, but may include non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids to reduce inflammation and tissue edema 1
- Preventative management is crucial, with prophylactic measures against falls, respiratory decline, and viral infections essential for patients with FOP 1
Clinical Trials and Research
- Clinical trials for novel treatments in FOP and other rare diseases are critical for developing effective therapies, with special considerations needed to ensure patient safety and accommodate the unique needs of these patients 1
From the Research
Definition of Heterotopic Ossification (HO)
- Heterotopic ossification (HO) is defined as the presence of bone in soft tissue where bone normally does not exist 2, 3, 4, 5, 6
- It is a condition characterized by the presence of mature lamellar bone and often bone marrow in soft tissues surrounding a major joint 6
Causes and Risk Factors
- The acquired form of HO most frequently is seen with either musculoskeletal trauma, spinal cord injury, or central nervous system injury 2
- Patients who have recently undergone total hip arthroplasty or have paraplegia after spinal cord injury are at risk for HO 2
- Hip ankylosis, male gender, and previous history of HO are said to be risk factors with a significant level 5
- The implant of a non-cemented prosthesis seems to be associated with a greater incidence of HO 6
Diagnosis
- The fever, swelling, erythema, and occasional joint tenderness seen in early HO can be difficult to distinguish from cellulitis, osteomyelitis, or thrombophlebitis 2
- Bone scanning and other imaging tests frequently are used to distinguish between these diagnostic possibilities 2
- The Brooker classification that divides HO into four grades is the most commonly used for diagnosis 5
- A bone scan can be used as a confirmation test 5
Treatment and Prophylaxis
- Either a nonsteroidal antiinflammatory drug (such as indomethacin), a diphosphonate (such as ethane-1-hydroxy-1-diphosphate), or local radiation therapy is recommended as treatment or prophylaxis for HO 2
- Pharmacotherapy with NSAIDs (non steroid anti-inflammatory drugs) and radiotherapy are the two primary methods of preventing heterotopic ossification 3
- Symptomatic heterotopic ossifications are treated by extracorporeal shock wave therapy (ESWT) and surgery, followed by NSAID pharmacotherapy or radiotherapy 3
- The most effective prophylactic treatment is radiotherapy or administration of nonsteroidal anti-inflammatory drugs 5