Transfer accuracy and precision scoring in planar bone cutting validated with ex vivo data

Abstract

The use of interactive surgical scenarios for virtual preoperative planning of osteotomies has increased in the last 5 years. As it has been reported by several authors, this technology has been used in tumor resection osteotomies, knee osteotomies, and spine surgery with good results. A digital three-dimensional preoperative plan makes possible to quantitatively evaluate the transfer process from the virtual plan to the anatomy of the patient. We introduce an exact definition of accuracy and precision of this transfer process for planar bone cutting. We present a method to compute these properties from ex vivo data. We also propose a clinical score to assess the goodness of a cut. A computer simulation is used to characterize the definitions and the data generated by the measurement method Keywords: osteotomy; cut; accuracy; precision; clinical score Clinical Background and Related WorkComputer-Assisted Preoperative Planning in bone surgery is becoming more common everyday. Its use has been reported in knee osteotomy, 1 mandibular reconstruction, 2 spine surgery, 3 foot and ankle surgery, 4 and tumor resection. 5 The existence of virtual osteotomy planning opens the possibility of measuring the discrepancies that occur in the transfer from the target to the executed osteotomies. These discrepancies are very common since many factors add random variations and biases to the surgical process: CT/MR imaging errors, three-dimensional modeling and segmentation omissions and the inherent inaccuracies of surgical tools and actions. Even though the evaluation of transfer accuracy (ACC) and precision (PRC) in bone cutting is a key application in orthopedics, there is no consensus about their definition in the field of planar osteotomies, neither there is an established method to measure them nor a score to assess them. 6 In recent years, several research groups have approached the accuracy and precision estimation problem in bone cutting. Barrera et al. 7 introduced a way to evaluate planar osteotomies in total knee replacement using translational and rotational errors of the executed plane measured against the target plane. More recently, Cartiaux et al. 8 proposed a method based in the ISO 1101:2004 standard for geometrical tolerancing to evaluate differences between a cutting plane and a target plane. Their work shows that it is possible to express the most significant translational and rotational errors using only the location parameter (L) defined in the mentioned ISO standard. For experimental data gathering, a test bed with a block simulating bone tissue is used, and errors are estimated with a coordinate measuring machine set in the same frame of reference. Dobbe et al. 9 propose a method to measure and estimate the normal of an executed plane. This normal is used to compute the dihedral angle with the target plane, that is decomposed in sagittal and coronal plane angles. Then a distance error between the target and executed plane is computed taking the Euler distance between the centroids of the cross ...

Virtual Planning and Allograft Preparation Guided by Navigation for Reconstructive Oncologic Surgery

“…We previously shaped the allograft manually by a trial-anderror process once the defect had been created, leading to potential anatomic inaccuracies between the sculpted allograft and the recipient site. In recent years, bone tumor resections guided by computer navigation have been reported [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Navigation can be a useful tool to improve allograft shaping to match with the recipient site and the alignment.…”