Campanelli Valentina, Lozano Rocio, Akhlaghpour Hosna, Brar Abheetinder S, Maislin David, Nedopil Alexander J, Zuhars Joel
THINK Surgical, Inc., Fremont, CA, USA.
Biomedical Statistical Consulting, Wynnewood, PA, USA.
Quant Imaging Med Surg. 2020 Feb;10(2):475-484. doi: 10.21037/qims.2020.01.02.
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.
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.
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.
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.
许多计算机辅助手术系统（如用于全膝关节置换术（TKA）的机器人技术）的主要目标是准确执行术前计划。为了评估术前计划是否在三维空间中得到准确执行，一种方法是使用患者肢体的术前和术后CT扫描来比较计划的和术后的植入物位置。这种比较需要在术前和术后的三维骨模型之间以及计划的和术后的三维植入物之间进行三维到三维的表面配准。因此，本研究旨在通过确定（I）导致骨模型三维到三维表面配准的六自由度（DoF）误差最低的解剖区域，（II）植入物模型三维到三维表面配准的六自由度误差，以及（III）完整测量技术的六自由度，来验证这种测量技术。
使用12个尸体下肢标本测试股骨的四个不同区域，以确定哪个区域能实现骨模型最准确的三维到三维配准。接下来，对六个标本进行全膝关节置换术，并将三维到三维植入物配准的准确性与使用基准标记进行的金标准配准进行比较。
使用TKA后可用的最大解剖区域，即完整的三维股骨模型或不含股骨远端的股骨模型时，获得了最准确的三维到三维骨配准，其平移的均方根误差在0.2mm以内，旋转的均方根误差在0.2°以内。三维到三维股骨和胫骨植入物配准的准确性分别为平移在0.7mm以内，旋转在0.4°-0.6°以内。当使用能实现准确的三维到三维骨配准的股骨区域时，股骨和胫骨整个手术过程的准确性分别在0.9mm和0.6°以内。
总之，这种测量技术可用于在组件放置中平移测量误差高达0.9mm、旋转测量误差高达0.6°可接受的应用中。
