Comparison of Sagittal Subluxation in Two Different Three-Component Total Ankle Replacement Systems

Abstract

Background: Malalignment following total ankle arthroplasty (TAA) has been reported in 4% to 45% of patients. However, all reports to date have been related to coronal deformity. This study compared sagittal malalignment between the Mobility and Hintegra total ankle systems and assessed the positional stability of the implant components over time. Methods: The study included 50 cases each of total ankle replacement arthroplasty with the Hintegra and Mobility total ankle systems performed between May 2008 and June 2010. The Mobility group included 24 men and 25 women, and the mean age was 60.3 years (range, 50.7-70.0 years). The Hintegra group included 25 men and 25 women, and the mean age was 59.8 years (range, 50.8-68.7 years). The 2 groups did not differ in terms of gender (P = .76) or age (P = .77). Three independent observers with different levels of training evaluated the radiographs and performed the measurements independently. Each observer evaluated the radiographs twice at a 6-week interval to determine the intraobserver reliability, and the anteroposterior offset ratio was evaluated. Results: The anteroposterior offset ratio intra-and interobserver reliabilities all showed good or excellent levels of agreement in the Hintegra total ankle system and the Mobility total ankle system. With respect to the stability of sagittal translation of the talus, the Mobility system (0.08 +/- 0.07 immediately, 0.0 +/- 0.07 at 6 weeks postoperatively, and 0.01 +/- 0.07 at 1 year postoperatively) was better than the Hintegra system (0.20 +/- 0.08 immediately, 0.18 +/- 0.11 at 6 weeks postoperatively, and 0.15 +/- 0.10 at 1 year postoperatively) (P < .0001). Conclusions: The Mobility system had less sagittal malalignment of the talus than the Hintegra system. Consequently, when treating ankles in patients with osteoarthritis using the Hintegra system, one must pay careful attention to sagittal malalignment during surgery.