Abstract
Restoration of ankle alignment is thought to be critical in total ankle arthroplasty (TAA) outcomes, but previous research is primarily focused on coronal alignment. The purpose of this study was to investigate the sagittal alignment of the talar component. The talar component inclination, measured by the previously-described gamma angle, was hypothesized to be predictive of TAA outcomes.
A retrospective review of the Canadian Orthopaedic Foot and Ankle Society (COFAS) database of ankle arthritis was performed on all TAA cases at a single center over a 11-year period utilizing one of two modern implant designs. Cases without postoperative x-rays taken between 6 and 12 weeks were excluded. The gamma angle was measured by two independent orthopaedic surgeons twice each and standard descriptive statistics was done in addition to a survival analysis. The postoperative gamma angles were analyzed against several definitions of TAA failure and patient-reported outcome measures from the COFAS database by an expert biostatistician.
109 TAA cases satisfied inclusion and exclusion criteria. An elevated postoperative gamma angle higher than 22 degrees was associated with talar component subsidence, defined as a change in gamma angle of 5 degrees or more between postoperative and last available followup radiographs. This finding was true when adjusting for age, gender, body mass index (BMI), and inflammatory arthritis status. All measured angles were found to have good inter- and intraobserver reliability.
Surgeons should take care to not excessively dorsiflex the talar cuts during TAA surgery. The gamma angle is a simple and reliable radiographic measurement to predict long-term outcomes of TAA and can help surgeons counsel their patients postoperatively.
