Three dimensional patient-specific guides for guide pin positioning in reverse shoulder arthroplasty: An experimental study on different glenoid types.

INTRODUCTION: Incorrect positioning is one of the main factors for glenoid component loosening in reverse shoulder arthroplasty and component placement can be challenging. This study aimed to assess whether Patient-Specific Instrumentation (PSI) provides better guide pin positioning accuracy and is superior to standard guided and freehand instrumentation methods in cases of glenoid bone deformity. MATERIALS AND METHODS: Based on the Walch classification, five different scapula types were acquired by computed tomography (CT). For each type, two different surgeons placed a guide pin into the scapula using three different methods: freehand method, conventional non-patient-specific guide, and PSI guide. Each method was repeated five times by both surgeons. In these experiments, a total of 150 samples of scapula models were used (5 × 2 × 3 × 5 = 150). Post-operative CT scans of the samples with the guide pin were digitally assessed and the accuracy of the pin placement was determined by comparison to the preoperative planning on a three-dimensional (3D) model. RESULTS: The PSI method showed accuracies to the preoperative plan of 2.68 (SD 2.10) degrees for version angle (p < .05), 2.59 (SD 2.68) degrees for inclination angle (p < .05), and 1.55 (SD 1.26) mm for entry point offset (p < .05). The mean and standard deviation errors compared to planned values of version angle, inclination angle, and entry point offset were statistically significant for the PSI method for the type C defected glenoid and non-arthritic glenoid. CONCLUSION: Using the PSI guide created by an image processing software tool for guide pin positioning showed advantages in glenoid component positioning over other methods, for defected and intact glenoid types, but correlation with clinical outcomes should be examined.

Image processing methodology for patient-specific instrument design.

BACKGROUND: Patient-specific instrumentation (PSI) improves accuracy of surgical operations. PSI needs software for preoperative planning and instrument design. In this study, we explain the methodology of developing a software tool for PSI guide design and preoperative planning in reverse shoulder arthroplasty (RSA). METHODS: Approaches used to prepare input data, transform them into meaningful features and use of those features to create special guide geometries are explained by describing different algorithms and libraries. RESULTS: The developed software is tested on three different patients' data. Preoperative planning is performed and guides designed by software and the patients' bones are manufactured and tested for RSA. The method of building a software is presented to do the preoperative planning and designing specific guides for each patient are shown to be properly functional. CONCLUSIONS: This study proves processes in the development of the PSI software and the design of a specific guide for RSA.