Pilot study of total knee arthroplasty planning by use of 3-D ultrasound image volumes.

The incidence of Total Knee Arthroplasties (TKA) is increasing. The main problem is the correct placement of especially the femoral prosthesis. Pre-operative planning and intra-operative realization relies on lower limb X-rays and extra- or intramedullary devices. This may lead to implant displacements. We generated virtual models of the distal femur for 10 knee joints. In a free-hand sweep we recorded 3-D US image volumes, which typically took 90 sec. The bony structures were detected automatically in the US-images and then appeared as curvilinear lines. Spatially arranged these lines formed femur models, which were used for the placement of a femoral prosthesis in an interactive computer-based 3-D planning. The automatic image segmentation took about 45 minutes. Its analysis showed correct detection of the bone surface. The interactive planning took 5-10 minutes. The investigation demonstrates that 3-D US can provide data of position and size of bony structures. Bone models created by analysis of 3-D US image volumes are useable for simulation of TKA implantations.