Hip Contact Forces in Asymptomatic Total Hip Replacement Patients

35 Background. Preclinical durability testing of hip replacement implants is standardised by 36 ISO-14242-1 (2002) which is based on historical inverse dynamics analysis using data 37 obtained from a small sample of normal healthy individuals. It has not been established 38 whether loading cycles derived from normal healthy individuals are representative of loading 39 cycles occurring in patients following total hip replacement. 40 Methods. Hip joint kinematics and hip contact forces derived from multibody modelling of 41 forces during normal walking were obtained for 15 asymptomatic total hip replacement 42 patients and compared to 38 normal healthy individuals and to the ISO standard for pre43 clinical testing. 44 Findings. Hip kinematics in the total hip replacement patients were comparable to the ISO 45 data and the hip contact force in the normal healthy group was also comparable to the ISO 46 cycles. Hip contact forces derived from the asymptomatic total hip replacement patients were 47 comparable for the first part of the stance period but exhibited 30% lower peak loads at toe48 off. 49 Interpretation. Although the ISO standard provides a representative kinematic cycle, the 50 findings call into question whether the hip joint contact forces in the ISO standard are 51 representative of those occurring in the joint following total hip replacement. 52