Measurement of Intraoperative Range of Motion of Total Hip Arthroplasty Using an Inertial Measurement Unit Based Smart Trial System: an in Vitro Validation Experiment

Intraoperative detection of hip Range of Motion ( ROM ) is the basis for prediction of postoperative functional limits allowed for patients’ daily living. Although computer navigation system for Total Hip Arthroplasty ( THA ) has improved the accuracy of intraoperative ROM evaluation, it has not been able to gain popularity because of its complex and time-consuming procedures. We preliminarily developed a Inertial Measurement Unit based Hip Smart trial system ( IMUHS ) that is easy and simple to use. An in vitro validation experiment was conducted using radiopaque sawbones with imaging measurement method as the reference standard. The validity of measuring ROM in the three axes was as follows: 4.36±4.93°forflexion and extension, 1.75 ± 5.21°for adduction and abduction, and 6.42 ± 4.32°for internal and external rotation( p = 0.059 ~ 0.550 ). The ICC values of measuring ROM in all three axeswere 1.00. As measuring ROM is the basis for evaluating direction of impingement, subluxation and dislocation, the IMUHS is a promising development direction of THA computer assisted surgery.