From Planning to Navigation: A Decade of Progress in Computer-Assisted Lower Limb Deformity Correction

Computer-assisted techniques for corrective osteotomies of the lower extremities began to gain significant traction around 2015 with the introduction of 3D-printed, patient-specific instruments. Balgrist University Hospital was among the pioneers in this field, developing innovative solutions in the last decade that are now applied in clinical practice. My talk will trace the evolution of computer-assisted surgery for deformity correction in the lower extremities, emphasizing key advancements that have shaped the current state-of–the-art in research and treatment. In preoperative 3D planning, each step of the surgery is simulated using 3D models of the patient's anatomy to accurately quantify the parameters relevant for navigation. The simplest and most common approach involves a purely static, geometric analysis of the bone anatomy. However, with the integration of biomechanical models, we are transitioning to functional planning, emphasizing the restoration of biomechanical functionality of the joint or limb. Advances in diagnostic imaging are further enhancing 3D planning capabilities, enabling 3D reconstructions from low-dose CT or 2D X-rays to minimize radiation exposure, as well as multimodal data fusion for the integration of soft tissue and cartilage structures. Patient-specific instruments (PSI) continue to be the primary tool for accurate, navigated execution of 3D-planned corrective osteotomies. They integrate seamlessly into surgical workflows and are particularly effective for stabilizing bone fragments in situ. Today's PSI portfolio covers nearly all extra- and intra-articular corrections for the foot, knee, and hip, including highly complex procedures such as femoral head reduction osteotomies. However, a major limitation of PSI remains their lack of adaptability, as corrections are pre-determined with little possibility for intraoperative adjustments. This limitation has revitalized research into optically-guided osteotomies, driven by emerging technologies like augmented reality. Despite its potential, computer-assisted corrective osteotomies have not yet been established as the standard of care. Future research should therefore also focus on reducing costs and effort, simplifying workflows, and broadening the technology's applications.