Abstract
INTRODUCTION: Rotational acetabular osteotomy (RAO) is an effective surgical technique for hip dysplasia that requires precise spherical osteotomy of the acetabulum. While curved osteotomes are commonly used, the quantitative relationship between osteotome design and its movement characteristics within bone remains poorly understood. This study aimed to analyze how osteotome shape parameters and insertion angles affect the trajectory of the osteotome tip using an optical navigation system. METHODS: Using sawbone models, we tested curved osteotomes with three different radii (R40, R45, R50mm) and two blade configurations (single-sided and double-sided). Osteotomes were inserted at three angles (30°, 45°, and 60°) relative to the bone surface. The osteotome tip trajectory was tracked using an optical navigation system (Vicra, NDI). We compared the actual trajectory with four predicted paths: circles tangent to the inner blade edge, outer blade edge, inner curve, and outer curve of the osteotome. Each condition was tested three times. RESULTS: For all osteotome designs and insertion angles, the actual trajectory most closely followed the circle tangent to the inner blade edge. At 45mm depth with R50 osteotome at 45° insertion angle, the mean deviation from this predicted path was 0.6±0.3mm. The second closest prediction was the inner curve path, with a deviation of 9.5±0.3mm. Similar patterns were observed across all radii and insertion angles, except for 30° insertion with single-sided osteotomes, which caused bone fracture. DISCUSSION: Despite the intuitive assumption that the osteotome would follow its curved shape, our findings demonstrate that the initial trajectory is primarily determined by the inner blade edge angle. This is likely due to the force distribution at the bone-blade interface during initial insertion. As insertion depth increases, the curved portion of the osteotome becomes more influential in guiding the trajectory. This understanding is crucial for preventing complications like intra-articular penetration or posterior column fracture, and could improve the accuracy of navigation-assisted RAO. CONCLUSION: The initial trajectory of curved osteotomes in RAO is predominantly influenced by the inner blade edge angle rather than the osteotome's overall curvature.