In Silico Model for Aseptic Loosening Prediction in Cementless Hip Stems: A Design of Experiments

Hip arthroplasty is a common orthopedic surgery. Cementless hip prostheses are currently more common, especially in young and active patients. The number of procedures and revisions is expected to increase with life expectancy. Aseptic loosening (AL) is the main cause of failure. Osteoinductive coatings improve long-term implant stability by enhancing osseointegration. This study aimed to develop a computational framework for predicting AL, considering both the biomechanical factors involved in the osseointegration process and the biological response to osteoinductive materials. A finite element model of a human femur implanted with a cementless hip stem was coupled with a Finite State Machine to simulate osseointegration and tissue fibrotization. The osteoinductive coating was modeled by adjusting the maximum gap at the bone-implant interface that can be bridged by newly formed bone, as well as the bone growth rate. To explore population variability, a total of 27 cases were simulated, including three different stem sizes, initial stem fit, and loading conditions. For each case, both uncoated and hydroxyapatite (HA)-coated stems were evaluated. Overall, this modeling framework was able to predict improved osseointegration with the osteoinductive coating at two years of follow-up. In two cases, the HA coating prevented AL, which occurred for the uncoated stem. Osseointegration patterns were consistent with previously reported data. The availability of this pipeline enables the simulation of large virtual cohorts and, therefore, the development of an In Silico technology for stem design to estimate the risk of AL associated with different designs and/or specific coatings.