Vol. 5, Issue 10 (2019)
Heterotopic ossification of the hip: A systemic review
Author(s): Dr. Mark Wilson, Dip Anat Trauma, Dr. Per Prisell
Abstract: Introduction/aims: Ectopic bone formation (heterotopic ossification) is associated with major hip surgery, including total hip replacement, hip resurfacing arthroplasty and pelvic trauma surgery and occurs in up to half of cases. It was hypothesised that increasing grades of heterotopic ossification is associated with increasingly deleterious effects on clinical hip function following arthroplasty. Methods: A Systematic Review was performed to examine ectopic bone formation following hip arthroplasty and to determine its effect on function in the post-operative setting. Search terms were “Ectopic bone”, “Heterotopic ossification (HO)”, “Brooker classification”, “Arthroplasty” and “Harris Hip Score”. Fifty-five studies were identified. Exclusion criteria: non-English language; case studies; book chapter reviews. Forty-four studies were deemed suitable for inclusion, including select ‘classic’ papers. A search was made of MEDLINE via Pubmed, MEDLINE via Ovid SP, EMBASE via Ovid SP, CENTRAL, and Web of Science for identifying reports of randomised controlled trials, cohort studies and reviews. Results: The amount of bone deposited in the gluteal muscles varies from small islands to widespread bridging ossification. The underlying basis of heterotopic ossification seems to be related primarily to systemic factors, as well as gender, surgical trauma and concurrent anti-inflammatory use. Radiotherapy has a role in prophylaxis in high risk groups only, given its inherent risks. Conclusion: The surgical technique and the local tissue trauma moderate both the occurrence and amount of heterotopic ossification, but the condition does not seem to cause pain or decrease hip muscle strength. There is a limitation on hip mobility in cases with significant amounts of ectopic bone formation (Brooker grades III-IV), but not in lesser grades. There is insufficient clinical correlation between function and the Brooker stage.