Effect of Distal Tibial Cortical Bone Coverage in Rates of Total Ankle Arthroplasty Implant Subsidence, Loosening, Heterotopic Bone Formation and Clinical Outcomes

Abstract

Category: Ankle Arthritis Introduction/Purpose: Total ankle arthroplasty (TAA) has continued to increase in popularity as a treatment modality for ankle arthritis. Despite this increased popularity, continual updates to implant designs strive for improved outcomes. This has led to different implant design changes including an extended length tibial tray to offer more distal tibia cortical coverage. This study compares the rates of tibial component subsidence, tibial component loosening, heterotopic ossification (HO) formation, average post-operative range of motion (ROM), and patient reported outcome measures (PROMs) between two matched groups of patients who underwent TAA with Salto Talaris extended tibial tray components with full distal tibia cortical coverage and a group who underwent TAA with Salto Talaris traditional tibial tray components without full tibia cortical coverage. Methods: Patients who underwent TAA between January 2019 and February 2021 with Salto Talaris implants (Smith & Nephew, Memphis, TN) were included for review. Patients were matched into two groups for age, gender, and Body Mass Index (BMI). Group 1 consisted of patients who received TAA with the extended tibial tray implant and full distal tibia cortical coverage and Group 2 consisted of patients who received the standard tibial tray implant without full distal tibia cortical coverage. Preoperative and postoperative radiographs were analyzed for the presence of subsidence, loosening, HO formation. ROM was measured utilizing plantarflexion and dorsiflexion weight-bearing lateral radiographs. PROMs were also analyzed including the Veterans- RAND 12 (VR-12) Item Health Survey, Ankle Osteoarthritis Scale (AOS), Foot and Ankle Ability Measure (FAAM), Visual Analog Score (VAS), and Patient Satisfaction. Results: Sixty-one patients (36 males; 25 females) were matched between the two groups. The mean age was 66.9 years in Group 1 and 67.1 years in Group 2, with a mean follow-up of 15.6 months and 22.1 months, respectively. Mean BMI was 30.6 in Group 1 and 30.5 in Group 2. The post-operative VR-12 Physical score was significantly higher in Group 1 (49.2 vs 45.1, P=0.025). Group 1 also had a significantly lower post-operative VAS pain score (11.1 vs 21.2, P=0.012) as well as patient satisfaction (93.8 vs 85.2, P=0.018). Radiographically, the rate of subsidence was significantly lower in Group 1 (0% vs 16.4%, P=0.001) as well as the rate of HO formation (26.2% vs 67.2%, P<0.001). Group 1 had significantly greater post-operative plantarflexion (17.7 degrees vs 14.0 degrees, P=0.018). Conclusion: Early short-term results appear to indicate that utilizing TAA implants with an extended length tibial tray with full distal tibia cortical coverage is associated with less subsidence, less heterotopic ossification formation, greater post-operative plantarflexion, less pain and higher patient satisfaction. Future analysis with longer-term follow up as well as a larger patient cohort may help shed even more light into the efficacy of this new implant design.