Implant placement accuracy in total knee arthroplasty: validation of a CT-based measurement technique

Abstract

Background: The primary goal of many computer-assisted surgical systems like robotics for total knee arthroplasty (TKA) is to accurately execute a preoperative plan. To assess whether the preoperative plan was executed accurately in 3D, one option is to compare the planned and postoperative implant placement using a preoperative and postoperative CT scan of the patient's limb. This comparison requires a 3D-to-3D surface registration between the preoperative and postoperative 3D bone models and between the planned and postoperative 3D implants. Hence, the present study aimed at validating this measurement technique by determining (I) the anatomical regions that result in the lowest 6-degree of freedom (DoF) errors for 3D-to-3D surface registration of bone models, (II) the 6-DoF errors for 3D-to-3D surface registration of the implant models, and (III) the 6-DoF of the complete measurement technique.Methods: Four different regions of the femur were tested to determine which one would result in the most accurate 3D-to-3D registration of the bone models using 12 cadaveric lower limb specimens. Next, total knee arthroplasties were performed on six specimens, and the accuracy of the 3D-to-3D implant registration was evaluated against a gold standard registration performed using fiducial markers. Results:The most accurate 3D-to-3D bone registration was obtained when using the largest anatomical regions available after TKA, being the full 3D femur model or the femur model without the distal femur which resulted in root mean square errors within 0.2 mm for translations and 0.2° for rotation. The accuracy of the 3D-to-3D femoral and tibial implant registration was within 0.7 mm for translations and 0.4°-0.6° for rotations, respectively. The accuracy for the overall procedure was within 0.9 mm and 0.6° for both femur and tibia when using femoral regions resulting in accurate 3D-to-3D bone registration. Conclusions:In conclusion, this measurement technique can be used in applications where measurement errors up to 0.9 mm in translations and up to 0.6° in rotations in component placement are acceptable.

Accuracy of intraoperative bone registration and stereotactic boundary reconstruction during total knee arthroplasty surgery

“…36 While the CT-based measuring technique was questioned, Campanelli et al demonstrated that the measurement error of this technique was maximum 0.9 mm and 0.6°. 37 Because the impact of cutting errors was excluded in the work of Dahabreh et al, the mismatch could be a result of intraoperative registration errors as confirmed by our results. Given the observed errors and the cumulative behaviour in the surgical procedure, the intraoperative registration error should not be neglected and can be relevant for the total implant positioning error.…”

“…While the CT‐based measuring technique was questioned, Campanelli et al. demonstrated that the measurement error of this technique was maximum 0.9 mm and 0.6° 37 . Because the impact of cutting errors was excluded in the work of Dahabreh et al., the mismatch could be a result of intraoperative registration errors as confirmed by our results.…”

Image-Free Robotic-Assisted Total Knee Arthroplasty Improves Implant Alignment Accuracy: A Cadaveric Study

“…0.6 mm, which is finer than most clinical imaging protocols. Likewise, implant-induced metal artifacts cause uncertainty in alignment measures [24,25]. A study by Sires and Wilson [17] found absolute differences between resection angles measured intraoperatively and the corresponding implant alignments measured using a CT scan ranged from 1.09 ± 0.75 to 1.97 ± 1.41 for tibial coronal and sagittal alignment, respectively, with 9% of the accuracy measurements deviating by >3 .…”

Improved accuracy of implant placement with an imageless handheld robotic system compared to conventional instrumentation in patients undergoing total knee arthroplasty: a prospective randomized controlled trial using CT‐based assessment of radiological outcomes

“…These studies reported comparable or decreased number of outliers with RATKA. However, in those studies, the accuracy and measurements were performed on standardized radiographs, which introduces a low reproducibility with known inaccuracies when compared with CT‐based measurements [5, 8]. To the best of our knowledge, the present trial is the first study that used CT‐based measurement techniques to determine implant placement accuracy for TKA with the use of 3D‐to‐3D surface registration between the perioperative planned and postoperative achieved implant placement in a prospective RCT comparing image‐free RATKA with CTKA.…”