Total Ankle Arthroplasty Radiographic Alignment Comparison Between Patient- Specific Instrumentation and Standard Instrumentation
Mario Escudero, MD
Department of Orthopaedics
Universidad de Chile
The advances in Total Ankle Arthroplasty (TAA) have been substantial in implant design and operative technique. One recent innovation is patient-specific instrumentation (PSI). PSI uses a preoperative computed tomographic (CT) scan and generates cutting blocks specific to each patient’s anatomy as well as a modifiable operative plan. TAA with PSI has several published advantages compared with standard instrumentation (SI) including cost-effectiveness, decreased operative time, and reduced radiation exposure without increasing osteolysis risk from more soft-tissue dissection.1–3
So far, two studies have analyzed the tibial component alignment of PSI compared with SI,(3,4) but there are no reports in the literature that also consider the talar component alignment and the overall alignment of the TAA. Our study attempts to determine if alignment differs between TAA with the INFINITY Total Ankle System (Wright Medical Technology, Memphis, TN) with and without the Prophecy (Wright Medical Technology) PSI system.
We found that TAA radiographic coronal alignment is accurately reproduced with both PSI and SI techniques. Regarding sagittal alignment, we found a relatively low rate of acceptable values for the analyzed parameters; anatomic sagittal distal angle (aSDTA) and lateral talar station (LTS). We hypothesize that these findings could be explained by the fact that the tibial component sagittal plane positioning in both SI and PSI cases is referenced from the mechanical axis rather than the tibial anatomical axis and the design of the INFINITY Total Ankle System, that appears to shift anteriorly the talar center of rotation by a few millimeters on average.
Our study suggests that PSI is unnecessary for experienced surgeons to achieve satisfactory TAA alignment. However, PSI has other advantages that are useful for experienced and inexperienced surgeons. The enrollment of cases performed by less experienced surgeons performing PSI could provide more information regarding the utility of PSI and the generalizability of our findings.
- Daigre J, Berlet G, Dyke BV, Peterson KS, Santrock R. Accuracy and Reproducibility Using Patient-Specific Instrumentation in Total Ankle Arthroplasty. Foot & Ankle International. 2017;38(4):412-418. doi:10.1177/1071100716682086
- Escudero MI, Symes M, Bemenderfer TB, et al. Does Patient-Specific Instrumentation Have a Higher Rate of Early Osteolysis Than Standard Referencing Techniques in Total Ankle Arthroplasty? A Radiographic Analysis. Foot & Ankle Specialist. Published online February 13, 2019:1938640019828069. doi:10.1177/1938640019828069
- Hamid KS, Matson AP, Nwachukwu BU, Scott DJ, Mather RC, DeOrio JK. Determining the Cost-Savings Threshold and Alignment Accuracy of Patient-Specific Instrumentation in Total Ankle Replacements. Foot & Ankle International. 2017;38(1):49-57. doi:10.1177/1071100716667505
- Saito GH, Sanders AE, O’Malley MJ, Deland JT, Ellis SJ, Demetracopoulos CA. Accuracy of Patient-Specific Instrumentation in Total Ankle Arthroplasty: a Comparative Study. Foot and Ankle Surgery. Published online February 16, 2018:1-28. doi:10.1016/j.fas.2018.02.008