Abstract
Research Type:
Level 4 – Case series
Introduction/Purpose:
Minimal resection total ankle arthroplasty (TAA) systems are designed to improve osseous integration while limiting the bone removed from either the tibia or the talus. There is discussion in the literature regarding the increased incidence of tibial component lucency in the setting of large preoperative coronal plane deformity. In this study, we evaluated a consecutive series of minimal resection TAA with varying amounts of preoperative coronal plane deformity. This included patients without any deformity, mild deformity ( < 15 degrees), and severe deformity (> 15 degrees). The tibial component lucencies were identified in these patients with a minimum of one-year follow-up. Our primary aim was to identify if an increased preoperative tibiotalar angle was associated with increased postoperative tibial component lucency.
Methods:
A retrospective chart review of a single surgeon’s TAA procedures utilizing only the Cadence (Smith & Nephew, Massachusetts) prosthesis with both chamfer and flat cut talus components were identified. All patients were greater than 18 years old and underwent the procedure from January 1, 2018, through December 31, 2023. Exclusion criteria were less than 12 months of follow-up (20 pts) or poor-quality radiographs precluding accurate lucency analysis (5pts). For radiographic analysis, lucency was defined as a radiolucent line at the interface between the distal tibia and the tibial component that was greater than 0.5mm in thickness at any point in the defined zones (Figure 1).
The patient’s final follow-up radiograph, which was at least 12 months after the index procedure, was utilized for this analysis. Pre- and post-operative tibiotalar alignment was recorded. Other data points collected were age, sex, and weight.
Results:
59 ankles were analyzed. The mean follow-up was 30 months. 16 patients (27%) had no deformity. 29 patients (50%) had less than 15 degrees of angulation (average of 5.8 degrees varus, 6.9 degrees valgus), 14 patients (23%) had greater than 15 degrees of angulation (average of 19.9 degrees varus, 19.6 degrees valgus). Analysis between the three groups showed no significant differences in tibial interface lucency at any zone (p>0.05). In the no deformity group, 6/16 (38%) patients had lucency in one zone, 0/16 (0%) had lucency in two zones, and 9/16 (56%) had lucency in three or more zones. This was 4/29 (14%), 7/29 (24%), 11/29 (38%) in the mild deformity group and 0/14 (0%), 4/14 (29%), 7/14 (50%) in the severe deformity group respectively.
Conclusion:
Aseptic loosening in TAAs, evidenced by peri-implant lucency, is a known mode of failure. Recent literature suggests a preoperative coronal tibiotalar angle of greater than 15 degrees places the patient at higher risk of failure when using minimal resection TAA. In this study, there were no differences in the peri-implant lucency at the ten radiographic zones between the groups. This indicates that in our follow-up period, increased preoperative coronal plane deformity did not result in greater lucencies at the tibial bone-prosthesis interface. This challenges the belief that minimal resection TAA is not indicated in patients with larger coronal plane deformities.
AP and Lateral radiographic Zones analyzed for tibial bone-prosthesis lucency. A lucency >0.5mm at any location in a zone was deemed positive.