Study Design: A retrospective cohort. Objective: The objective of this study to determine the correlation between Hounsfield unit (HU) measurements from the C4 vertebral body and dual-energy x-ray absorptiometry (DXA) T-score. Summary of Background Data: Recent attention has turned to the utilization of HU measurements from computed tomography (CT) as a potential screening method for low bone mineral density (BMD). We hypothesized that cervical spine CT HU measurements will correlate with BMD measurements conducted with DXA scans of the femoral neck. Material and Methods: Patients with cervical CT and femoral neck DXA scans at 1 institution were included in the study. HUs were manually measured from the cancellous bone in the C4 vertebrae by 1 author blinded to DXA scans. HU measurements were compared with femoral neck DXA T-scores for the entire population. Results: A total of 149 patients with 149 cervical CT and femoral neck DXA scans were included in the study. The low BMD group (osteoporotic and osteopenic combined) showed a significant difference in HU compared with the normal groups within the study (P<0.0001). A low BMD screening value of 447 HU captured over 95% of patients with low BMD within our study and provided a sensitivity of 92% and negative predictive value of 82.1%. The male and female intrasex analysis demonstrated a significant difference between the low BMD and normal BMD groups with P=0.001 and P=0.0001, respectively. Conclusions: HU measurements taken from the C4 vertebral body on CT scan correlate with low BMD of the femoral neck as determined by DXA scan T-scores. Screening values of 447 HU captured 95% of patients with low BMD, with a high degree of sensitivity, and negative predictive value of 80%. Utilization of cervical spine HU as a screening method provides a simple, quick, and easily assessable screening tool for assessing low BMD. Level of Evidence: Level III—diagnostic.

Introduction Prior to being largely abandoned due to unacceptably high failure rates and the adverse physiologic reactions to metal ions, metal-on-metal (MoM) total hip arthroplasty (THA) and hip resurfacing (HR) were in widespread use throughout the USA, and the potential benefit of decreased volumetric wear rates made it of particular interest to those who serve a young active population, such as military surgeons. The aim of our study was to determine the revision rate of metal on metal hip implants performed at our military institution and obtain current patient reported outcomes from this cohort. Materials and Methods We conducted a retrospective review of patients who underwent MoM total hip arthroplasty (THA) or hip resurfacing (HR) at our institution from 2006 to 2012. Revision status and component type were determined, and patients were contacted to obtain current HOOS JR scores. Results We identified 103 THAs in 88 patients and 38 HRs in 33 patients, with mean follow up of 10.2 years. Average age at time of surgery was 48 years, and 85% of the patients were male. The mean HOOS JR score in the THA and HR groups were 84.9 ± 17.6 and 75.8 ± 24.9, respectively (p = 0.38), and were not significantly lower in those who were revised. Two THA revisions occurred for metallosis and one for aseptic loosening of the femoral component. One HR revision occurred for breach of the anterior femoral neck, and one occurred for heterotopicossification. Conclusions Revision rates of MoM THA and HR in this young, predominantly male population were 2.9% and 5.3%, respectively, and patients maintained generally good hip-specific outcomes.

Introduction Computed tomography (CT) Hounsfield units (HU) recently emerged as a promising screening tool for low bone mineral density (BMD). We hypothesized that CT HU measurements of the thoracic spine would significantly and positively correlate with dual X-ray absorptiometry (DXA) BMD scans of the femoral neck. Materials and methods The study included patients with DXA scans and thoracic CT scans at the Walter Reed National Military Medical Center. One author, blinded to the DXA scans, measured HU from the cancellous bone in T4 vertebrae. Another author statistically compared femoral neck DXA T-scores to the CT HU measurements. Results The study included 145 patients with CT scans and femoral neck DXAs. The osteoporotic and osteopenic groups had a significant difference in HU measurements compared to the normal group within the study (P &lt; .0001 and .002, respectively). A low BMD screening value of 231 HU provided a sensitivity of 90.1% and negative predictive value of 85.7%. Conclusion Thoracic vertebrae HU measurements correlate with a low BMD of the femoral neck as determined by DXA T-scores. A high sensitivity and negative predictive value was achieved with a screening value of 231 HU. Utilization of chest or thoracic spine CT imaging as a screening method provides a quick and available screening tool for assessing low BMD in patients with these scans. Level of Evidence: III (Diagnostic)