SLR - August 2011 - Stacie Buck
Reference: Lee K, Cho Y, Park J, Song E, Yoon T, Seon J. Heterotopic Ossification After Primary Total Ankle Arthroplasty. The Journal of Bone and Joint Surgery 2011; 93:751-8.
Scientific Literature Review
Reviewed by: Stacie Buck, DPM
Residency Program: University Hospitals Richmond Medical Center/Ohio College of Podiatric Medicine
Podiatric Relevance:
This article examines the prevalence and location of heterotopic ossification after primary total ankle arthroplasty using the HINTEGRA implant. Predisposing factors and clinical outcomes are also evaluated, as well as the development of a new classification system for heterotopic ossification of the ankle joint.
Methods:
This is a retrospective study of eighty ankles status post total ankle arthroplasty using the cementless, mobile-bearing HINTEGRA implant. All patients were followed postoperatively at one, three, six, twelve, and twenty-four months. Radiographs were used to identify any heterotopic ossification that formed and the location of the ossification was also noted. A modification of the existing Brooker classification (originally used for hip replacements) was designed. Class 0 was defined as no heterotopic ossification; Class 1 as islands of bone in the ankle soft tissue; Class 2 as bone spurs from the tibia or talus reducing the joint space by <50%; Class 3 as reducing the joint space by >50%, and Class 4 as a continuous bridging bone between the tibia and talus. Sex, BMI, preoperative diagnosis, prior ankle surgery, operative time, and pre and postoperative ankle joint motion and AOFAS ankle-hindfoot score were compared in the patients with and without ossification using an independent t test and Fisher exact test.
Results:
The overall prevalence of heterotopic ossification in this study was 25% following ankle arthroplasty with the posterior aspect of the ankle being the most common site. Most of the cases of ossification were initially noticed at the three month follow-up and considered a Class 4. There was no significant difference comparing the groups with and without ossification in sex, age, BMI, preoperative diagnosis, previous ankle surgery, preoperative ankle motion, or preoperative AOFAS score. In the heterotopic ossification group, the mean operative time was significantly higher and the postoperative ankle joint motion and postoperative AOFAS score was significantly lower compared to the group without ossification. Eight of the eighty ankles had symptomatic heterotopic ossification.
Conclusions:
When evaluating for heterotopic ossification, CT scans were found to be more precise than radiographs, but the modified Brooker classification system was found to be reliable. Heterotopic ossification following ankle implant arthroplasty using an HINTEGRA implant yields a poor clinical outcome with reduced ankle joint range of motion during a two year follow-up. Predisposing factors are thought to be an inappropriate sized tibial component, posttraumatic arthritis prior to surgery, and excessive soft tissue dissection (likely leading to a longer operating time).