Letter to the editor
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LETTER TO THE EDITOR
Letter to the editor Emily L. Hampp1 · Michael A. Mont2 Received: 29 July 2020 / Accepted: 1 September 2020 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2020
To the Editor We have read the article by Seidenstein et al. [1] with great interest. Their study compared the accuracy and reproducibility of a recently introduced TKA robotic system to conventional instrumentation for bone resections. We want to congratulate the authors on providing an extensive cadaveric evaluation on the accuracy of a new robotic system. The study concludes that the novel TKA robotic system produced more accurate and reproducible bone resection angles (i.e., femur V/V, femur F/E, tibia V/V, tibia A/P and HKA) and resection levels (i.e., posterior femoral and proximal tibia) than conventional instrumentation. However, we have some comments regarding the data presented in Table 6 of the paper. Table 6 in Seidenstein et al. [1] lists other TKA robotic systems that compare bone resection accuracy and reproducibility results for femoral distal varus/valgus, femoral distal flexion/extension, tibial varus/valgus, and tibial anterior/posterior slope cuts with conventional instrumentation. However, this list does not address all potential femoral bone cut errors. The femoral anterior (internal/external and flexion/extension), femoral anterior chamfer (varus/valgus and flexion/extension), femoral posterior chamfer (varus/valgus and flexion/extension) and the femoral posterior (internal/ external and flexion/extension) cuts are additional degrees of freedom which may be considered and are presented in a least one other study [2]. It should be noted that we have not conducted a review of the other studies listed in Table 6, This comment refers to the article available online at https://doi. org/10.1007/s00167-020-06038-w. * Emily L. Hampp [email protected] Michael A. Mont [email protected] 1
Implant and Robotic Research, Stryker, Mahwah, NJ, USA
Department of Orthopaedic Surgery, Lenox Hill Hospital, Northwell Health, New York, NY, USA
2
and therefore, cannot comment on those measurements and the comparisons made. Furthermore, there are methodological differences between Seidenstein et al. [1] and a least one other study [2] in Table 6. In Hampp et al. [2], bone cut angles and final implant positions were measured and reported for the femur (coronal, transverse and sagittal planes) and tibia (coronal and sagittal planes) using a navigated planar probe along with a CT scan and fiducial markers. Fiducial markers are highly accurate markers that are rigidly attached to the bone prior to the preoperative CT (and remain in place throughout), which creates a ground truth registration from which all error can be measured, including bone registration error and bone cut error. Different rigid body trackers and a CT scan were used for the knee procedures (i.e., standard procedural trackers) and the accuracy measurements (i.e., fiducial markers). The fiducial markers allowed collection
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