Correction of Talar Sagittal Alignment in Total Ankle Replacement using Cadence Biased Polyethylene Insert
Authors: Kayum Shahin , Khan Ryan M. , Daniels Timothy R. 
Published: November 2020

Category:

Ankle; Ankle Arthritis

Introduction/Purpose:

The success of total ankle arthroplasty (TAA) depends on many factors, including patient selection, prosthetic design, soft tissue balancing, severity of joint deformity, and component position. Malposition of the components increases contact pressures and diminishes prosthesis survival / patient outcomes; therefore, anatomic alignment of the prosthesis is desirable. Sagittal malalignment of the talar component is common and has been associated with lower outcome scores. Cadance Total ankle system is unique in that it has modular polyethene components with both an anterior and posterior biased option that may help improve reduction of the talus in the sagittal plane. The purpose of this study is to evaluate the effectiveness of anterior and posterior biased polyethylethene liners in improving sagittal component alignment in patients with preoperative sagittal translational deformities

Methods:

This is a prospective radiographic and clinical study of patients that underwent TAA with the CadenceTM 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 December 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-26). Radiographic outcomes included assessment of sagittal plane component alignment using the tibiotalar (TT) ratio and tibial-axis-to-lateral-process distance at preoperative and at postoperative visits.

Results:

The cohort included a total of 7O TAA which demonstrated pre-operative sagittal talar malalignment and/or intra- operative sagittal instability where a biased polyethylene liner was inserted. Preoperative talar sagittal translation was 54 anterior, 6 posterior and 10 were neutral. 30 anterior biased polyethylene and 40 posterior biased polyethylene were used. Sagittal translation decreased from an average 4.2 mm to 0.8 mm. The T-T ratio averaged 40.8 +- 10.8 % on preoperative x-ray and 38.1 +- 3.6 % on postoperative. The pre and post-operative pain and disability scores displayed statistically significant improvements wherein AOS pain scores decreased 25.28 +- 14.34 points from an average of 45.86 points while AOS disability scores decreased -30.11 +- 22.70 from an average of 56.15 points.

Conclusion:

Sagittal translational deformities associated with end-stage ankle arthritis are common and should be corrected during TAA to improve loading kinematics and implant longevity. The Cadence TAA has anterior and posterior biased polyethylene liners that help to correct sagittal talar translational deformities. This study demonstrates that biased liners are effective in improved postoperative clinical outcomes with significant correction of pathological sagittal translation to near anatomic alignment.