Preserving the abductor mechanism in robotic THR: the influence of stem design and cutterpath.

The tip of the greater trochanter is the attachment site for the abductor muscles of the hip joint. Its preservation in robotic and conventional THR is important for normal gait. The effect of different stem designs and robotic cutterpaths on the preservation of the trochanter tip is examined.One anatomical stem, one straight stem, and one stem specifically designed for robotic THR were implanted virtually in CT scans of osteoarthrotic hip joints using the Torch preoperative planning unit (URS-ortho). In transverse sections of the trochanter tip, dimensions of the trochanter area removed by the milling tool were recorded for each stem design and different cutterpaths (3-axis versus 5-axis m…