Heterotopic Ossification of the Hip : Wheeless' Textbook of Orthopaedics

- See: Total Hip Replacement Menu
            - Heterotopic Ossification

- Discussion:
- typically develops on x-ray 3-8 wks postop in pericapsular area of the affected hip joint;
- over all incidence is 50% (1/3 of these are clinically significant);
- risk factors:
- male gender (uncommon in females);
           - active AS;
- DISH
- post traumatic arthritis;
- heterotrophic osteoarthritis
- previous HO;
- previous hip fusion;
- Paget's disease
- Parkinson's disease
- excessive osteophytosis or enthesiopathic radiographic changes on AP of pelvis;
- head injury and/or spinal cord injury;

- Brooker Classification:
- based on an AP radiograph;
- this classification has been criticized because bone which appears to be bridging may actually be located
either anterior or posterior to the hip, and thus does not cause significant loss of ROM;
- class:
- class I: represents islands of bone w/in soft tissues about hip
- class II: inclues bone spurs in pelvis or proximal end of femur leaving at least 1 cm between the opposing bone surfaces;
- class III: represents bone spurs that extend from pelvis or the proximal end of femur, which reduce the space between the opposing bone surfaces to less than 1 cm;
- class IV: indicates radiographic ankylosis of the hip;

- Non Operative Treatment:
- NSAIA:
- indomethacin 25 mg PO tid for 3-6 months;

    - total joint arthroplasty:
- given one month preoperatively and 3 months postoperatively;
- some argue that NSAIDS should only be used with cemented implants;
                 - references:
                          - Heterotopic ossification: Pathophysiology, clinical features, and the role of radiotherapy for prophylaxis.
                          - Non-steroidal anti-inflammatory drugs for preventing heterotopic bone formation after hip arthroplasty
                          - A systematic survey of 13 randomized trials of non-steroidal anti-inflammatory drugs for the prevention of heterotopic bone formation after major hip surgery.

- acetabular fractures:
- some controversy as to whether indomethacin actually reduces HO;
- in the study by Matta and Siebenrock (1997), indomethacin was not effective for preventing ectopic bone formation;
- references:
- Prevention of heterotopic ossification by nonsteroid antiinflammatory drugs after total hip arthroplasty.
- The use of indomethacin to prevent the formation of heterotopic bone after total hip replacement. A randomized, double-blind clinical trial.
- Effect of aspirin on heterotopic ossification after total hip arthroplasty in men who have osteoarthrosis.
- The use of aspirin to prevent heterotopic ossification after total hip arthroplasty. A preliminary report.
- Heterotopic bone formation after noncemented total hip arthroplasty. Location of ectopic bone and the influence of postoperative antiinflammatory treatment.
- Does indomethacin reduce heterotopic bone formation after operations for acetabular fractures? A prospective randomised study.

    - Etidronate:
- theoretically works by delaying mineralization of osteoid
- diphosphonates do not prevent heterotopic bone formation in lab animals but they do delay of mineralization of osteoid;
- delay in mineralization caused by diphosphanates are reversed when the disphosphonates are discontinued;
- reference:
- Results of the administration of diphosphonate for the prevention of heterotopic ossification after total hip arthroplasty.
- Radiation Therapy:
- single does of 700 to 800 cGy can be given preoperatively or on POD 1;
- XRT given preoperatively better eliminates patient discomfort;
- a relative contra-indication of XRT may be posterior hip dislocation w/ femoral head frx, since there is a theoretical risk of contributing to AVN or non-union;
- cost: $ 2,000 to 2,500;
- references:
- Radiation-blocking shields to localize periarticular radiation precisely for prevention of heterotopic bone formation around uncemented total hip arthroplasties.
- The use of radiation to discourage ectopic bone. A nine year study in surgery about the hip.
                 - The prevention of heterotopic ossification in high-risk patients by low-dose radiation therapy after total hip arthroplasty.
- Prevention of heterotopic ossification with irradiation after total hip arthroplasty: Radiation therapy with a single dose of 800 centigray administered to a limited field.
                 - The prevention of heterotopic ossification in high-risk patients by low-dose radiation therapy after total hip arthroplasty.

- Operative Resection:
- main disadvantage is risk of recurrence heterotopic ossification;
- if hetertopic ossfication has caused the loss of motion, consider allowing process to mature (sharp cortical and trabecular markings) before operative resection;
- some recommend waiting 12 months before operative resection;
- once serial radiographs have shown that the ossification is mature w/ sharp peripheral edges and no indication of expansion, resection is considered;
- bone scans and alkaline phosphatase may not be helpful in predicting maturity of the ossification

Serum alkaline phosphatase as an indicator of heterotopic bone formation following total hip arthroplasty.

Ectopic bone formation after total hip arthroplasty.

Erythrocyte sedimentation rate and heterotopic bone formation after cemented total hip arthroplasty.

Heterotopic ossification around the hip in spinal cord-injured patients. A long-term follow-up study.

Prevention of heterotopic ossification with irradiation after total hip arthroplasty. Radiation therapy with a single dose of eight hundred centigray administered to a limited field.

Radiation therapy to prevent heterotopic ossification after cementless total hip arthroplasty.

Total hip arthroplasty. The role of antiinflammatory medications in the prevention of heterotopic ossification.

Periarticular heterotopic ossification after total hip arthroplasty for primary coxarthrosis.

Heterotopic ossification as a complication of acetabular fracture. Prophylaxis with low-dose irradiation.

Prophylaxis with indomethacin for heterotopic bone. After open reduction of fractures of the acetabulum.

Surgical approaches for resection of heterotopic ossification in traumatic brain-injured adults.

Periarticular heterotopic ossification after total hip arthroplasty. Risk factors and consequences.