Development of small bone implants using a mean shape bone in a porcine model for carpal bone replacement

The development of innovative small bone replacements for the human wrist has been partially limited by the lack of a suitable preclinical animal model. This study explores the feasibility of using the Yucatan minipig (YMP) as a preclinical model for small bone replacement. Implants for the radial carpal bone (RCB), homologous to the human scaphoid, were developed for a pilot in vivo animal study. RCB size (volume, bounding box dimensions) was quantified (n = 35), and relationships between animal age, weight, and RCB volume were investigated. Bounding box dimensions were also analyzed relative to RCB volume. A mean-shaped RCB model was generated using ShapeWorks Studio and scaled to create a set of implants. These implants were evaluated in a pilot in vivo study, where the distances between the explanted bone surface and both the predicted and surgeon-selected implant surfaces were recorded for each animal. Predicted implant distances (0.8 ± 0.2 mm), were larger (p < 0.001) than surgeon-selected implant distances (0.4 ± 0.1 mm) in three animals. In one animal, the predicted implant distances (0.3 ± 0.2 mm) were smaller (p < 0.0001) than the surgeon-selected implant distances (0.5 ± 0.3 mm). The set of implants generated provided the surgeon with options suitable for the range of animals in the in vivo study. This study presents a novel approach to generating small bone replacements by scaling a mean-shaped bone in a porcine model and further evaluates the YMP as a preclinical model for small bone replacement in the human wrist.