Measurement of Femoral neck and Leg Length in Total Hip Arthroplasty Based on Optical Positioning

In traditional total hip arthroplasty(THA), it is difficult to accurately measure the length of femoral neck when the replacement area is limited and deep. It may eventually lead to excessive difference in the length of two legs. This paper presents a method for measuring the length of femoral neck in THA based on optical positioning. During the operation, the end of the probe with a positioning ball was used to measure the length of the femoral neck in real time to assist surgeons in surgical decisionmaking. According to the comparison between the ideal length and the actual length, the femoral head prosthesis was reasonably selected for adjustment. As it is difficult to accurately and quickly measure the difference of two legs after the placement of prosthesis in traditional surgery, a spatial measurement method of medical anatomical points of two legs based on optical positioning is proposed. By measuring the length of the affected leg with a probe and comparing it with the length of the normal leg before operation, the feedback information of synchronous measurement is further verified. Experiments verify the feasibility of this method for the detection of leg length difference. The average error of these experimental measurements is within 1 mm.