Abstract
Research Type:
Level 4 – Case series
Introduction/Purpose:
Computer-Assisted Surgical (CAS) systems have demonstrated efficacy in enhancing the accuracy of joint arthroplasty resections, reduction of outliers, and improvement in the targeted alignment of orthopedic implants. Total ankle arthroplasty (TAA) treats end-stage ankle osteoarthritis, and contemporary TAA techniques have yielded favorable clinical outcomes, establishing them as a viable alternative to ankle arthrodesis. The alignment of implants during TAA is challenging due to limited surgical exposure and reliance on fluoroscopic guidance. To address these limitations, a TAA application for a CAS system was developed. The accuracy and precision of the newly developed TAA CAS system was previously assessed relative to anatomic landmarks. The primary objective of this study was to compare the accuracy of a conventional technique alongside the CAS system using the same method.
Methods:
TAA was performed by a board-certified, fellowship-trained orthopedic surgeon on twelve artificial ankle joint specimens using conventional instrumentation. Surgical technique was standardized for all specimens. Scans of each of the twelve specimens were performed before TAA using a structured light industrial scanner (Metrascan, Black Elite) used for assessing surface profiles. Bone resections were performed using conventional cutting guides and positioning jigs in conjunction with fluoroscopy. Resections on the talus included a flat cut with three degrees of freedom (e.g. varus, slope, and cut height), whereas tibial resections included distal and medial cuts with five degrees of freedom (e.g. varus, slope, axial rotation, medial offset and cut height). The resected bones were scanned and subsequently overlaid with the initial model using an open-source cloud fitting software (CloudCompare) to evaluate the discrepancy between the actual and planned resections. Finally, conventional results were compared to CAS results from the previously executed study.
Results:
Tibial deviations from plan and 95% confidence intervals were compared: varus error was 1.18°±0.50° for conventional and 0.22°±0.56° for CAS, closed slope error was -2.38°±0.78° for conventional and -0.50°±0.53° for CAS, internal rotation error was -0.31°±2.45° for conventional and -0.10°±0.69° for CAS, cut height error was 0.58mm±0.49mm for conventional and 0.14mm±0.48mm for CAS, and mediolateral position error was 0.32mm±1.45mm for conventional and 0.15mm±0.59mm for CAS. For the talus: varus error was 0.15°±1.05° for conventional and -0.24°±0.79° for CAS, slope error was -4.12°±1.27° for conventional and -1.32°±0.55° for CAS, and cut height error was 0.58mm±0.49mm for conventional and 0.14mm±0.48mm for CAS. The mean and 95% confidence intervals of all parameters were within 2mm and 2° except for tibial closed slope, tibial internal rotation and talar slope.
Conclusion:
The accuracy and precision of resections using the CAS system was increased compared to conventional instrumentation when combining all parameters with an average absolute accuracy of 0.48°±0.62° and 0.31mm±0.47mm with CAS and 1.63°±1.21° and 0.76mm±0.73mm for the conventional instrumentation (tibia and talus resections, respectively). The CAS system helped to reduce outliers of the tibial slope/rotation and talar slope parameters. In conclusion, the conventional instrumentation provided acceptable levels of accuracy and precision while the CAS system was able to improve accuracy and precision while reducing outliers without the need of fluoroscopy for positioning of the instrumentation.
