Development and validation of a 3D printed foot length scale for predicting intramedullary nail lengths for long bone fractures.

INTRODUCTION: The study aimed to develop and validate a 3D-printed foot length scale for predicting intramedullary nail lengths in long bone fractures. The device utilizes the European (EU) foot length scale and regression models derived from retrospective patient data to estimate nail lengths for the femur, tibia, and humerus. METHODS AND MATERIALS: The study involved two phases: (1) retrospective data collection and analysis to establish correlations between foot length and nail length, and (2) design, development, and validation of the 3D-printed device. Retrospective data were collected from 205 patients who underwent intramedullary nailing. The device was designed to measure foot length and estimate nail length based on the derived regression models. The device was prospectively validated in a clinical setting. RESULTS: The retrospective analysis showed strong correlations between foot length and nail length for the femur (R2 = 0.98), tibia (R2 = 0.91), and humerus (R2 = 0.85). The prospective validation demonstrated high accuracy of the device, with mean absolute errors (MAE) of 0.67 cm, 0.74 cm, and 0.62 cm for femur, tibia, and humerus nail length predictions, respectively. CONCLUSION: The 3D-printed foot length scale offers a practical and accurate method for predicting intramedullary nail lengths, potentially streamlining preoperative planning and improving surgical outcomes.