Helical CT Scan Evolution of Periprosthetic Cysts of a Stainless Steel DLC Coated Total Ankle Arthroplasty at Four Years Apart and Survival at 13 Years
Authors: Lucas Julien , Fourgeaux Antoine 
Published: September 2018

Category: Ankle Introduction/Purpose: Total ankle arthroplasty (TAA) is the alternative to tibio-talar fusion in the non-conservative operative treatment of osteoarthritis. It preserves joint range of motion and prevents adjacent joints while improving quality of life and relief. Long-term studies frequently show the presence of periprosthetic cysts, which is linked to an increased risk of revision, pain or lameness. In 2012, a stainless steel, DLC coated, TAA was subjected to a clinical review and a CT scan analysis. The main objective of this study was to analyze periprosthetic cysts evolution (numbers and volumes) on helical CT scans at 4 years apart of this same cohort of patients. The secondary objective was to present clinical results and survival curve of the implant. Methods: We retrospectively reviewed the cohort of 68 cases from 2012. The average follow-up was 13 ± 6 years. 42 CT analysis of the Periprosthetic cysts, were performed at the last follow-up and compared to the 2012 analysis. Cysts were classified in 3 groups (A: 0-200mm2, B: 200-400mm2, C:> 400 mm2) distributed over 7 areas. Numbers, locations and sizes were listed. The functional evaluation was performed in 2012 and at the last follow-up with the American Orthopedic Foot and Ankle Society Ankle and Hindfoot Score (AOFAS-AHS) and with the range of motion. TAR survival at 5 years were calculated for the 68 patients, and for the last 34 to avoid the learning curve effect. Two end points were defined: revision or removal of the implant for any reasons and revision or removal of the implant for aseptic loosening. TAR survival at 10 years was also analyzed thanks to the long follow-up. Results: Cysts size and prevalence were not significantly different at 4-year apart (p> 0.05). No type C cysts were revealed. The mean AOFAS-AHS was 77.6 ± 15.4 [38-98] in 2012 and stable at 75 ± 18.2 [16-97] at the last follow-up. Pre-operative ankle range of motion and at the last follow-up were not significantly different. The 5-year survival for the last 34 cases were 85.2% [73.2; 97.2] for any cause of revision and 90.7% [80.7; 100] for aseptic loosening. The 10-year survival for the last 34 cases were 77.1% [67.3; 87.4] for any cause of revision and 85.4% [73.4; 98.4] for aseptic loosening. Between 2012 and 2016, one case was revised for aseptic loosening of the talar component and two cases needed fusion. Conclusion: This study shows no significant increase of cysts volume or number at 4-year apart with a stainless steel, DLC coated TAA. The clinical results and 5-year survival are similar to those in the literature. The strength of this study is its mean follow-up greater than 13 years which allowed a 10-year survival and a long-term CT scan analysis. The implant design (spherical tibial component, dual curvature PE insert, trochlear-shaped talar component), its materials (DLC coated stainless steel) and its fixation (alumina coating) ensure long-term similar clinical results, with no break after 5-year survival, and stability of cysts prevalence and size.