Improved Postoperative Radiographic Alignment Associated with Patient-Specific Instrumentation in Total Ankle Arthroplasty

Category: Ankle Arthritis; Ankle Introduction/Purpose: The rate of total ankle arthroplasty (TAA) is projected to continue to increase globally over the next several decades. While the most significant predictor of complications after total ankle arthroplasty is implant malalignment, intra-operative evaluation of alignment can be technically challenging to achieve. Patient-specific instrumentation (PSI) was designed to improve the accuracy of implant positioning in TAA. Therefore, we sought to compare radiographic alignment and postoperative function in patients who underwent TAA with PSI guides versus standard instrumentation. Methods: We retrospectively reviewed 75 ankles who underwent TAA using PSI compared to 80 ankles who underwent TAA without PSI. Demographics, radiographic alignment, range of motion (ROM), complications, and postoperative American Orthopaedic Foot and Ankle Society (AOFAS) scores were compared. All patients had minimum 1-year follow-up. Demographics were similar between cohorts, including gender (p=0.176), body mass index (p=0.914), laterality (p=0.847), preoperative diagnosis (p=0.126), and history of diabetes mellitus (p=0.665), although patients in the PSI group were older (mean=68.56 versus 64.75, p=0.014) and had a higher American Society of Anesthesiologists score (mean=2.37 versus 2.15, p=0.003). Preoperative dorsiflexion (mean=9.09° versus 8.79°, p=0.762), plantarflexion (mean=29.59° versus 27.50°, p=0.152), and total ROM (mean=38.68° versus 36.29°, p=0.260) were similar between cohorts. The PSI cohort had more preoperative talar tilt (mean=7.48° versus 4.38°, p=0.004), but similar coronal angle (mean=-2.39° versus -0.09°, p=0.242) and sagittal translation (mean=3.14° versus 1.30°, p=0.085). Results: Postoperative coronal angle (mean=0.27° (range=-8.16°-5.42°) versus 1.38° (range=-4.19°-9.14°), p=0.006) and sagittal angle (mean=-1.99° (range=-9.01°-3.94°) versus -4.51° (range=-13.0°-2.0°), p< 0.001) were more accurate and had a narrower range with the PSI guides compared to the manual guides. Postoperative ROM was similar between the PSI and manual groups, including dorsiflexion (mean=10.27° versus 10.83°, p=0.549), plantarflexion (mean=29.27° versus 29.83°, p=0.607), and total ROM (mean=39.54° versus 40.67°, p=0.496). Patients with PSI had improved AOFAS alignment scores (mean=9.73 versus 8.89, p=0.005), but there were similar AOFAS pain (mean=29.32 versus 31.51, p=0.125), function (mean=40.48 versus 38.79, p=0.281), and total scores (mean=79.52 versus 79.19, p=0.897) between cohorts. There were similar numbers of patients who required revision (1.33% versus 7.50%, p=0.144) or irrigation and debridement (4.00% versus 5.00%, p=1.000) between cohorts. Conclusion: PSI is associated with more accurate postoperative coronal and sagittal alignment compared to manual instrumentation TAA. While patients with PSI had decreased AOFAS alignment scores, both cohorts had similar postoperative range of motion and overall AOFAS scores. While there were a similar number of revisions and irrigation and debridement procedures in each cohort, this retrospective review was limited to shorter term follow-up. Further research is needed to determine if the improved alignment with the use of PSI implants is associated with better survivability long term.