Three-dimensional ultrasound and intraoperative navigation: A new application in femoral osteotomies.

Aim: As precise operative central is difficult to achieve, the accuracy of femoral osteotomies can only be estimated. Therefore, a computer-assisted u ltrasound navigation system was developed in order to apply an on-line cont rol for femoral osteotomies. Method: Three ultrasound emitters were fixed o n a triangle. The exact position of triangles could be determined by measur ing the time the ultrasound beam takes to reach microphones positioned in a frame. With a reference triangle fixed distally to the osteotomy and a sec ond triangle fixed on the surgical chisel the exact correction angle can be determined three-dimensionally. Results: A high degree of accuracy was fou nd in both laboratory trials and in simulation trials using pig femurs. The deviation of measured values compared to a laser beam control was less tha n 0.5 degrees. Conclusion: The system was introduced into our operating the atre as an optimised control device that can provide excellent support to t he surgical procedure.