Metastatic lesions in the proximal femur can lead to a detrimental reduction in hip strength and subsequent pathologic fracture. Current methods for assessing pathologic hip fracture risk have been shown to be inadequate, and the conventional treatment for patients deemed to be at high risk—prophylactic surgical fixation, involving the placement of an orthopaedic implant, followed by separate post-operative radiation therapy treatments—is both highly invasive and inconvenient for the patient.

In this study, finite element models of cadaveric proximal femora were used to show that hip strength greatly depended (p<0.001) on the location of simulated metastatic lesions, modeled as spherical voids, within the femoral neck. These results indicate that defect location should be considered the primary risk factor for hip fracture, a finding that conflicts with current clinical practice and may help to improve the evaluation of hip fracture risk. As an alternative to conventional surgical fixation, we proposed a minimally-invasive technique, involving the injection of bone cement into regions of metastatic involvement, for repairing proximal femora at risk of pathologic fracture. Using mechanical testing and finite element models, the strength of cadaveric femora repaired with the proposed technique was demonstrated to be nearly completely restored to the strength of intact femora, indicating feasibility of the technique. Finally, radioactive bone cement was introduced as an alternative to conventional radiation therapy, and a radiation transport modeling method was developed for predicting the dose distribution in bone containing radioactive bone cement. The modeling method was shown to predict measured dose distributions within the experimental uncertainty, and will be a critical tool for further development of the technology.

The findings of this study may lead to a more reliable assessment of hip fracture risk due to metastatic lesions, leading to a reduction in patients suffering either a preventable hip fracture or undergoing unnecessary surgery. Additionally, for patients determined to be at high risk of fracture, the proposed repair technique, when combined with radioactive bone cement, would simultaneously address structural and radiation treatment requirements, resulting in a single, combined, minimally-invasive procedure that would greatly improve patient care and quality of life.