Computed Tomography of the Chest as a Screening Tool for Low Bone Mineral Density.

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 < .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).

Repeated Noise Exposure Does Not Reach Hazardous Levels During Total Joint Arthroplasty.

INTRODUCTION: Noise exposure is an occupational health concern for certain professions, especially military servicemembers and those using power tools on a regular basis. The purpose of this study was to quantify noise exposure during total hip arthroplasty (THA) and total knee arthroplasty (TKA) cases compared to the recommended standard for occupational noise exposure. MATERIALS AND METHODS: A sound level meter was used to record cumulative and peak noise exposure levels in 10 primary THA and 10 primary TKA surgeries, as well as 10 arthroscopy cases as controls. Measurements at the distance of the surgeon were taken in all cases. In TKA cases, measurements were taken at 3 feet and 8 feet from the surgeon, to simulate the position of the anesthetist and circulating nurse, respectively. RESULTS: Time-weighted average was significantly higher in THA (64.7 ± 5.2 dB) and TKA (64.5 ± 6.8 dB) as compared to arthroscopic cases (51.1 ± 7.5 dB, P < 0.001) and higher at the distance of the surgeon (64.5 ± 6.8 dB) compared to the anesthetist (52.9 ± 3.8 dB) and the circulating nurse (54.8 ± 11.2 dB, P = 0.006). However, time-weighted average was below the recommended exposure level of 85 dB for all arthroplasty cases. Peak levels did not differ significantly between surgery type or staff role, and no values above the ceiling limit of 140 dB were recorded. Surgeon's daily noise dose percentage per case was 1.78% for THA and 2.04% for TKA. CONCLUSION: Noise exposure in THA and TKA was higher than arthroscopic cases but did not exceed occupational standards. A daily dose percentage of approximately 2% per case indicates that repeated noise exposure likely does not reach hazardous levels in modern arthroplasty practice.

Cervical Spine Computed Tomography Hounsfield Units Accurately Predict Low Bone Mineral Density of the Femoral Neck.

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.

Low Revision Rates at 10 years for Metal on Metal Hip Implants in a Military Population.

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.

Combat-related acetabular fractures: Outcomes of open versus closed injuries.

INTRODUCTION: Since the onset of the Global War on Terror close to 50,000 United States service members have been injured in combat, many of these injuries would have previously been fatal. Among these injuries, open acetabular fractures are at an increased number due to the high percentage of penetrating injuries such as high velocity gunshot wounds and blast injuries. These injuries lead to a greater degree of contamination, and more severe associated injuries. There is a significantly smaller proportion of the classic blunt trauma mechanism typically seen in civilian trauma. METHODS: We performed a retrospective review of the Department of Defense Trauma Registry into which all US combat-injured patients are enrolled, as well as reviewed local patient medical records, and radiologic studies from March 2003 to April 2012. Eighty seven (87) acetabular fractures were identified with 32 classified as open fractures. Information regarding mechanism of injury, fracture pattern, transfusion requirements, Injury Severity Score (ISS), and presence of lower extremity amputations was analyzed. RESULTS: The mechanism of injury was an explosive device in 59% (n=19) of patients with an open acetabular fracture; the remaining 40% (n=13) were secondary to ballistic injury. In contrast, in the closed acetabular fracture cohort 38% (21/55) of fractures were due to explosive devices, and all remaining (n=34) were secondary to blunt trauma such as falls, motor vehicle collisions, or aircraft crashes. Patients with open acetabular fractures required a median of 17units of PRBC within the first 24h after injury. The mean ISS was 32 in the open group compared with 22 in the closed group (p=0.003). In the open fracture group nine patients (28%) sustained bilateral lower extremity amputations, and 10 patients (31%) ultimately underwent a hip disarticulation or hemi-pelvectomy as their final amputation level. DISCUSSION: Open acetabular fractures represent a significant challenge in the management of combat-related injuries. High ISS and massive transfusion requirements are common in these injuries. This is one of the largest series reported of open acetabular fractures. Open acetabular fractures require immediate damage control surgery and resuscitation as well as prolonged rehabilitation due to their severity. The dramatic number of open acetabular fractures (37%) in this review highlights the challenge in treatment of combat related acetabular fractures.