A single intravenous administration of zoledronic acid prevents the bone loss and mechanical compromise induced by aromatase inhibition in rats.

Recent evidence has demonstrated that long-term estrogen deprivation using aromatase inhibitor therapy in postmenopausal women with breast cancer results in bone loss and increased fracture risk. Bisphosphonates are potent inhibitors of bone resorption and have demonstrated efficacy in preventing bone loss in postmenopausal women with low bone mineral density (BMD) and in patients with breast cancer receiving estrogen deprivation therapy. Therefore, this study investigated the effects of the bisphosphonate zoledronic acid on BMD and bone strength in rats treated with the aromatase inhibitor, letrozole. Peripheral quantitative computed tomography demonstrated that treatment of rats with daily oral letrozole (1 mg/kg) induced significant bone loss and cortical thinning compared with control animals (P < 0.01). A single prior intravenous dose of zoledronic acid dose dependently protected against letrozole-induced bone loss and cortical thinning, with the highest evaluated dose (20 microg/kg) resulting in BMD values that were not significantly different from controls over the 24 weeks of letrozole treatment. Furthermore, biomechanical testing of the distal femoral metaphysis demonstrated that zoledronic acid (20 microg/kg) significantly prevented the decrease in stiffness and elastic modulus induced by letrozole treatment. Taken together, these data support the use of zoledronic acid for the prevention of bone loss in women with breast cancer receiving aromatase inhibitor therapy.

Precise 3D skeletal kinematics using fast phase contrast magnetic resonance imaging.

PURPOSE: To examine the precision of cine-phase contrast (PC) magnetic resonance imaging (MRI) techniques as applied to the quantification of three-dimensional knee joint kinematics. MATERIALS AND METHODS: The knee joints of eight healthy volunteers were studied using three different dynamic, PC MRI protocols: cine-PC (one average), cine-PC (two averages), and cine-PC with segmented phase encoding (fast-PC). RESULTS: Fast-PC has comparable precision, shorter scan times, and improved subject interexam variability (SIEV) compared to cine-PC (two averages). Further, cine-PC (one average) has low precision and high SIEV, making fast-PC the preferred method of data acquisition. Specifically, the precision of fast-PC MRI in measuring knee joint kinematics ranged from 0.22 degrees -1.16 degrees. CONCLUSION: A cine-PC MRI technique utilizing segmented phase encoding (fast-PC MRI) acquires dynamic data at a faster rate than other PC imaging protocols, without compromising data precision. Being able to acquire precise 3D kinematics with shorter imaging times is critical if we are to use this technique to advance ongoing research in musculoskeletal kinematics.