BACKGROUND: Preoperative three-dimensional (3D) planning has become the standard of care for complex orthopedic procedures. Quantitatively evaluating whether the preoperative plan is successfully performed remains a challenge due to the lack of standardized measurements, which makes comparison across studies difficult. Therefore, standardized measurements are required to close the feedback loop to improve upon our procedures and achieve safer or closer resections.

OBJECTIVE: This present study investigates the best suitable standardized approach for evaluating the procedural accuracu of the achieved plane compared to the preoperative plan, and to assess the achieved results in complex orthopedic procedures, with a main focus on bone tumor resections.

DESIGN: This single-centre retrospective cohort study included 10 patients who underwent complex orthopaedic procedures (7 oncological, 3 non-oncological), between 2021 and 2024, with a total of 28 cutting planes in patients and 17 in allografts. All patients had a 3D planned surgical approach with digital visualization and patient-specific instruments (PSIs). The achieved planes were determined using four methods (mesh, normal vector, manual and point cloud) and the procedural accuracy was assessed by multiple linear and angular outcome measures (distance between points, center of grafity (COG)-to-COG, COG-to-plane, angle between normal vectors and pitch and roll angles).
RESULTS: The mesh and point cloud methods were superior in terms of ease of use and objectivity, with the point cloud method being the most accessible due to the lack of segmentation requirements. The point cloud method performed comparably to the mesh method for linear and angular deviations, with a mean deviation within 0.8 mm (millimeters) and 0.2 degrees for roll and pitch angles in patient cases. The average flatness according to the corrected ISO-1101 standard was 2.5 mm, and a surgical margin difference of 1 mm was observed. Significant differences were observed between the COG-to-COG approach and other linear approaches for both methods, and between the corrected and non-corrected ISO-standards for the mesh method.

CONCLUSION: The point cloud method appeared to be a good alternative to the mesh method for identifying the achieved plane in bone (tumor) resections. Furthermore, the average outcomes observed in this study provide a useful baseline for assessing procedural accuracy in complex orthopaedic procedures using 3D planning and computer assisted surgery (CAS). Further research with larger sample sizes is needed to validate these findings.

KEYWORDS: bone resection, computer-assisted surgery, linear deviation, angular deviation, cutting plane, procedural accuracy