An 85 year old gentleman presented with no movement in the left hip following a left total hip replacement.
An 85 year old gentleman underwent a left total hip replacement in 1997 due to osteoarthritis. He had Paget’s disease but was otherwise fit and well with no other medical problems. Three years following the procedure, he found that movements of the hip were painless but markedly limited. A plain AP radiograph showed heterotopic bone formation around the hip and the decision was made to try and excise this in 2000. Prior to excision, he was reviewed by the bone biochemistry team who treated him with etidronate to reduce the chances of recurrence of ectopic bone. Post operatively he did well but movements at the hip over the next twelve months gradually decreased to the point where no movement was possible. The plain radiograph opposite demonstrates grade IV heterotopic ossification with no evidence of wear of the hip prosthesis. Despite the hip fusing, the patient was pain free and happy with the outcome of his total hip replacement.
Heterotopic ossification develops most commonly amongst males and in patients with ankylosing spondylitis, hypertrophic osteoarthritis or post traumatic osteoarthritis. The cause is unknown but it seems to occur more commonly after procedures where there is substantial soft tissue stripping or considerable bone resection1. Calcification can usually be identified as early as three weeks on plain radiograph and can progress to extensive bone formation within three months. However, the bone doesn’t normally mature until nine to twelve months. The Brooker Classification describes the extent of bone formation and it is described as follows2 , I Islands of bone within soft tissues, II Bone spurs from the proximal femur or pelvis with at least 1cm between opposing bone surfaces, III Bone spurs from the proximal femur or pelvis with less than 1cm between the opposing bone surfaces, IV Ankylosis. Histologically, the tissue is indistinguishable from that seen in myositis ossificans. The condition is usually painless but may restrict motion. Operative removal is rarely indicated and excision is difficult as the normal landmarks are usually obscured and abnormal bone is fragile and not easily removed from the surrounding soft tissue but successful outcomes following surgical excision when combined with radiotherapy have been described3. Recurrence is also common. Bisphosphonates have been advocated in the treatment of heterotopic ossification especially in Paget’s disease but these merely delay the mineralisation of osteiod4. Non steroidals and indomethacin have been shown to reduce formation of heterotopic bone in a number of studies5. Radiation therapy has also been reported as effective in preventing severe heterotopic bone formation but treatment needs to be given within three days of surgery6.
Grade IV heterotopic ossification of the left hip
According to the provided hip joint X-ray images:
Considering the postoperative timeline and the propensity in male patients, along with the presence of ossification in the soft tissue, heterotopic ossification is the most common possibility. This condition may be related to extensive manipulation of soft tissue or bone during surgery, leading to progressively developing ossification that can limit joint mobility.
Periprosthetic infection can also cause local soft tissue abnormalities or bony changes, but it typically presents with noticeable pain, swelling, and abnormal laboratory values (e.g., CRP, ESR). On imaging, it may show destructive bony changes or bone resorption around the prosthesis. Although the risk is relatively low here, it still needs to be ruled out.
In cases of prosthetic loosening, X-rays often show radiolucent lines or significant bone lysis around the femoral stem of the prosthesis. Currently, no such obvious findings are observed, so the likelihood of prosthetic loosening is relatively low.
Taking into account the patient’s advanced age, male sex, the common occurrence of postoperative heterotopic ossification, and the marked ossification in the soft tissue around the hip joint seen on imaging, the most likely diagnosis is Postoperative Heterotopic Ossification (HO).
For further clarification, CT or MRI can be used to better assess the extent of soft tissue and bony involvement, and laboratory tests (e.g., complete blood count, inflammatory markers) can help rule out infection. If necessary, a histopathological examination may be performed for definitive confirmation.
Rehabilitation exercises should be individualized and follow a gradual, safe progression. Recommendations include:
If persistent pain, swelling, or difficulty in movement occurs during rehabilitation, seek medical evaluation promptly.
Disclaimer: This report provides a reference for medical analysis and does not replace an in-person consultation or professional medical advice. If you have further questions or changes in your condition, please consult a specialist.
Grade IV heterotopic ossification of the left hip
