Correction of Talar Sagittal Alignment Using a Novel Biased Polyethylene Insert for a Fixed Bearing Total Ankle Arthroplasty

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Restoration of the sagittal plane alignment after total ankle arthroplasty (TAA) is important to improve patient outcomes and range of motion after TAA. The Cadence Total Ankle System is unique in that it has modular polyethylene components with both an anterior and posterior biased option that may improve reduction of the talus in the sagittal plane. As such, the purpose of this study is to evaluate the effectiveness of anterior and posterior biased polyethylene liners in improving sagittal component alignment and functional outcomes after TAA. Methods: This is a retrospective cohort study of consecutive patients that underwent TAA with the Cadence Total Ankle system using biased polyethylene liners with at least 12-months follow-up. All surgeries were performed by a single surgeon with extensive experience in TAA between July 2016 and November 2018. Patients underwent TAA in a standard fashion using an anterior approach, and then underwent clinical evaluation at standardized time points with administration of the Ankle Osteoarthritis Scale (AOS) and the Short Form Health Survey (SF-36). Radiographic outcomes included assessment of sagittal plane talar component alignment using the tibiotalar (TT) ratio and talar station at preoperative and 1-yr postoperative visits. Results: Our study included a total of 66 TAAs that required the use of a biased polyethylene liner. The most common biased polyethylene liner used was a posterior liner. In terms of the primary outcomes, which was radiographic sagittal talar alignment, patients demonstrated significant improvement in sagittal alignment using both the TT ratio and talar station. Overall, the proportion of patients that achieved neutral sagittal balance significantly improved from 25.76% to 50.00% postoperatively (χ2[df=1, n=66] = 18.24, p < < 0 .01). Anterior bias polyethylene liners were strongly associated with anterior preoperative alignment, while posterior bias polyethylene liners were strongly associated with neutral and posterior preoperative alignment (χ2[df=2, n=66] = 17.55, p < < 0 .01, V = 0.52). Conclusion: Sagittal talar translational deformities associated with end-stage ankle arthritis are common and should be corrected during TAA to improve kinematics and implant longevity. The Cadence TAA system has novel anterior and posterior biased polyethylene liners that may augment correction of sagittal talar deformities. This study demonstrates that biased liners are effective in correction of pathological sagittal talar deformities to near anatomic alignment clinical with significant improvement in functional outcomes.