Development of a novel augmentation pattern of femoroplasty to prevent osteoporotic hip fracture

Abstract

Osteoporotic hip fractures cause a high rate of morbidity and mortality as well as imposing a heavy burden on the social medical system. The current preventive methods include physical exercises, the use of hip protectors, and an array of pharmacological agents. However, there are many issues associated with the use of such methods, for example cost, side effects, and patient compliance. So, a huge number of patients still develop osteoporotic hip fractures. A logical solution to the problem of osteoporotic hip fractures is the development of a prophylactic surgical intervention to increase the strength of proximal femora and protect the proximal femur. This technique should be safe and only minimally invasive, and should be applied in patients with high risk of hip fractures. Femoroplasty, the injection of bone cement into the proximal femur to augment femoral strength and to prevent fracture, is an option with great potential. There have been some biomechanical studies on the prophylactic augmentation of hips by injecting cement into proximal femora. In these studies, a considerable amount of cement was injected. This has the undesirable effect of disturbing the entire bony architecture, the surrounding biological environment, and the blood supply to the femoral head. Together with the heat released during cement polymerisation, this may potentially cause femoral head necrosis. Therefore, a well-directed and controlled cement augmentation at strategic areas is necessary to both minimise interference with the biology and maximise the mechanical benefit. Besides, as a medical technique, the safety issues should be comprehensively investigated before clinical application. However, up to now, there is no in vivo study has been done to evaluate the safety of femoroplasty. Due to limited resources of cadaveric femora and the divergence of femur specimens, a patient-specific computer tomography (CT) based finite element model of the femur was successfully established and verified by cadaveric femora. Then, using this model, we: 1) precisely predicted the risk area of the proximal femur when falling in order to plan preventive intervention; 2)developed a novel augmentation pattern of femoroplasty to protect the osteoporotic hip. Lastly, the safety issues related to femoroplasty were comprehensively evaluated in an animal model. The finite element analysis (FEA) results showed that the medial aspect of the femoral neck or slightly distal were at risk of fracture when falling on the greater trochanter. Based on the results, five different augmentation patterns were designed, simulated, and compared in FEA. We found that augmentation at the calcar femorale was significantly more effective than the other patterns. After that, a preliminarily animal study was conducted to evaluate the safety issues related to the surgical procedures for femoroplasty. During the whole surgery and short-term follow-up study, no complications and no side-effects were observed. In conclusion, a novel augmentation pattern was developed using the patient-specific CT-based FEA model of the femur. The surgical procedures for femoroplasty were provisionally found to be both feasible and safe.