Purpose or Case Report: Knee deformity is the most common and complex lower extremity abnormality associated with Thrombocytopenia Absent Radius (TAR) syndrome. Conventional pre-operative imaging includes radiographs and computed tomography (CT) for assessment of joint alignment. We report utilizing 3-D MRI series and manual segmentation on commeicially available software to create 3-D printed models for pre-operative planning in a TAR syndrome patient with largely unossified epiphyses who had unusually severe femoral anteversion and genu varum. We discuss the methods used for imaging and segmentation as well as the value and limitations of the 3D print in pre-operative planning for this case. Even with the limitations we encountered, better understanding of the spatial relationships and joint alignment was achieved with 3-D model generation and aided in planning for correction of the knee varus deformity and femoral torsion. In addition, the diagnostic MRI information provided the basis to forgo construction of cruciate ligaments at this stage due to an increased risk of failure related to severe joint deformity. Because the prognosis for TAR syndrome is good if the child survives the first 2 years, it is important that orthopedic interventions are well planned to give a good outcome. Utilization of advanced imaging tools such as 3D imaging and printing may aid in definitive surgical planning in complex cases such as this one, and MRI can be used to generate usable anatomical models for pre-operative planning in children with incompletely ossified epiphyses.
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