E2b.3. BMD Evaluation: DXA measurements will be performed at the spine and dominant hip (contralateral hip in the presence of hardware in the dominant hip) using a GE Lunar Prodigy Instrument (GE medical Systems) at Grady Memorial Hospital. The DXA scanner is calibrated on a daily basis with the manufacturer's phantom according to manufacturer guidelines. Short-term root mean square coefficient of variation at our center is 1.1% at the lumbar spine and 1.5% at the total hip.