Background: Heterotopic ossification following lower-limb joint arthroplasty is a challenging clinical problem. No comprehensive study has been conducted on heterotopic ossification after total ankle arthroplasty, to our knowledge. The purpose of this study was to evaluate the prevalence and location of heterotopic ossification after primary total ankle arthroplasty, predisposing factors, and effects on clinical outcomes, and to develop a method of classification.
Methods: Eighty ankles in eighty patients with a primary total ankle arthroplasty were followed for a mean (and standard deviation) of 31.9 ± 11.3 months (range, twenty-four to sixty-five months). The prevalence and location of heterotopic ossification, predisposing factors, and outcomes were analyzed, and a method of classification was developed.
Results: Twenty (25%) of the eighty ankles demonstrated postoperative heterotopic ossification, with the majority of the cases in the posterior aspect of the ankle. The heterotopic ossification was Class I in four cases (20%); Class II, in five (25%); Class III, in four (20%); and Class IV, in seven (35%). Symptomatic heterotopic ossification was reported in eight patients (10%), and two required surgical resection because of intractable pain. Ankles that developed heterotopic ossification had significantly longer operative times, less postoperative motion, and lower American Orthopaedic Foot & Ankle Society ankle-hindfoot scores at the six, twelve, and twenty-four-month follow-up examinations (p < 0.05 for all).
Conclusions: This study demonstrates that the prevalence of heterotopic ossification following primary total ankle arthroplasty is considerable, and that heterotopic ossification is associated with reduced ankle motion and a poor clinical outcome at a mean of two years postoperatively. Care is needed to attempt to reduce the occurrence of heterotopic ossification.