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

Corrective osteotomies are the indicated treatment for complex forearm malunions. The use of 3D computer-assisted preoperative planning offers significant advantages, such as improved comprehension of the multiplanar deformity and high accuracy. However, the clinical application of computer-assisted preoperative planning methods is limited due to the considerable time, effort, and expertise required. This emphasizes the necessity for a tool that can generate clinically feasible osteotomy plans, complying with patient-specific anatomical reconstruction goals. To address this challenge, this research developed an automatic planning tool for corrective osteotomies of radius malunions, requiring minimal user interaction. By automatically registering the pathological and contralateral bone models, the tool provides insight into the degree and nature of the deformity. An Evolutionary Algorithm is implemented to optimize patient-specific osteotomy plans by minimizing bone protrusion near the osteotomy plane. The automatic planning tool yields patient-specific osteotomy plans including the osteotomy plane location and orientation, as well as the required reduction of the distal part after the osteotomy cut. These plans ensure accurate alignment of both the proximal and distal radial joint surfaces. The developed tool was validated on 15 patient cases. The osteotomy plans generated by the automatic tool were compared to those planned manually in the past. Objective validation, based on residual alignment errors of the entire radius bone, often favored the manual planning approach. However, the automatic tool consistently provided osteotomy plans with more accurate alignment of the distal joint surface. Additionally, a blinded qualitative validation was conducted with a highly experienced orthopedic surgeon, who rated all osteotomy plans on a scale of 1 to 10. The results indicated that the automatic tool is not yet capable of generating osteotomy plans with feasibility scores equivalent to manual planning. However, the feasibility scores differed by only one point on most patient cases. The main areas that require improvement to consistently produce clinically feasible osteotomy plans include the incorporation of osteosynthesis plate fixation, consideration of the relationship with the ulna, and the option for double-cut osteotomies. In conclusion, the developed tool is capable of generating clinically feasible osteotomy plans, serving as a valuable starting point for patient-specific plans that can be further refined manually.

Introduction
Implementing a three-dimensional (3D) planning and printing lab in hospitals can offer multiple benefits for both healthcare professionals and patients. The aim of this master’s thesis is to support the initiation of a 3D lab in the Albert Schweitzer hospital through three topics: a workflow proposal for development of anatomical models, a survey study investigating the added value of these models in collaboration with the department of orthopedics and a business case outlining three potential scenarios of implementation.

Methods
A hospital-specific workflow was established by incorporating existing literature and identifying the key stages, materials, hardware, software, roles and responsibilities for development and 3D printing of anatomical models. A survey study was conducted using a questionnaire containing Likert and categorical scales. Anatomical models for orthopedic cases were produced and utility of each model was evaluated with the participation of orthopedic surgeons. The business case included a cost-benefit analysis for the three scenarios: in-house 3D printing of anatomical models (scenario 1), 3D printing of orthopedic surgical guides for total knee arthroplasty (scenario 2) and 3D printing of orthognathic anatomical models and wafers (scenario 3).

Results
A 15-step workflow was created covering all stages from image acquisition to delivery of the anatomical model. 30 orthopedic cases were included for the survey study. A total of three orthopedic surgeons participated in the study and agreed that 3D printed models provide additional information during the process of preoperative planning (rated 3.4/5), might enhance surgical outcomes and efficiency (rated 3/5 and 3.2/5, respectively) and can reduce average operative time with several minutes. These advantages were particularly evident in hip revision and ankle/foot cases, whereas conventional hip cases benefited the least. Cost-benefit analyses in the business case demonstrated cost-savings in scenarios 2 and 3 for in-house planning and printing over outsourcing of these tasks, considering a 5-year period.

Conclusion
This work presents a clear and implementable workflow for the development of 3D printed anatomical models. These models can function as a valuable tool in the process of preoperative planning of orthopedic surgery and hold potential for other applications. To optimize financial benefits, it is recommended to initiate a 3D lab with the in-house production of orthopedic surgical knee guides. Future work should explore the demand for 3D printing in other departments to further optimize the usefulness of a 3D lab in this hospital.