Patients' Evaluation of Family Planning Services: The Case of Inner-City Clinics

During bone regeneration, mechanical loading is believed to be responsible for provoking bone formation, however previous investigations into tissue level loading have been limited to crosssectionalstudies and relied upon idealized models for mechanics.By applying in vivo time-lapse micro-computed tomography (microCT) in concert with imaged based micro-finite element (microFE) analysis we have overcome these limitations and have identified an association between tissue loading and bone formation during fracture healing.A femoral defect of 1.24SD = 0.13 mm was created in five female mice (C57BL/6); the femur was first stabilized with an external fixator (MouseExFix, RISystem, Switzerland). Weekly scans wereperformed using microCT imaging (vivaCT 40, Scanco Medical, Switzerland) over a period of 6 weeks, resulting in a series of timelapsed images. We determined sites of mineralization by registeringand overlaying images from the second and third week. Combining this with microFE (Parosol) simulations based upon images of the second week, we separated strains in volumes where mineralization occurred, from volumes where no change occurred.To assess the efficacy of strain as a predictor of mineralization, receiver operating characteristic analysis was used. The optimum strain level correctly predicted 60SD= 9 % of the mineralization which occurred,and the final state for 86SD= 4 % of the entire volume.We have for the first time, quantitatively demonstrated that an association exists between local tissue strain and bone formation during fracture healing. This could be used to determine the optimalstiffness for biomaterials intended to promote bone healing.