The lateral femoral notch sign: a reliable diagnostic measurement in acute anterior cruciate ligament injury.

PURPOSE: To describe the validity and inter- and intra-observer reliability of the lateral femoral notch sign (LFNS) as measured on conventional radiographs for diagnosing acute anterior cruciate ligament (ACL) injury. METHODS: Patients (≤ 45 years) with a traumatic knee injury who underwent knee arthroscopy and had preoperative radiographs were retrospectively screened for this case-control study. Included patients were assigned to the ACL injury group (n = 65) or the control group (n = 53) based on the arthroscopic findings. All radiographs were evaluated for the presence, depth and location of the LFNS by four physicians who were blind to the conditions. To calculate intra-observer reliability, each observer re-assessed 25% of the radiographs at a 4-week interval. RESULTS: The depth of the LFNS was significantly greater in ACL-injured patients than in controls [median 0.8 mm (0-3.1 mm) versus 0.0 mm (0-1.4 mm), respectively; p = 0.008]. The inter- and intra-observer reliabilities of the LFNS depth were 0.93 and 0.96, respectively. Secondary knee pathology (i.e., lateral meniscal injury) in ACL-injured patients was correlated with a deeper LFNS [median 1.1 mm (0-2.6 mm) versus 0.6 mm (0-3.1 mm), p = 0.012]. Using a cut-off value of 1 mm for the LFNS depth, a positive predictive value of 96% was found. CONCLUSION: This was the first study to investigate the inter- and intra-observer agreement of the depth and location of the LFNS. The depth of the LFNS had a very high predictive value for ACL-injured patients and could be used in the emergency department without any additional cost. A depth of > 1.0 mm was a good predictor for ACL injury. Measuring the depth of the LFNS is a simple and clinically relevant tool for diagnosing ACL injury in the acute setting and should be used by clinicians in patients with acute knee trauma. LEVEL OF EVIDENCE: Diagnostic study, level II.

Opportunistic screening for osteoporosis on routine computed tomography? An external validation study.

OBJECTIVES: Opportunistic screening for osteoporosis using computed tomography (CT) examinations that happen to visualise the spine can be used to identify patients with osteoporosis. We sought to verify the diagnostic performance of vertebral Hounsfield unit (HU) measurements on routine CT examinations for diagnosing osteoporosis in a separate, external population. METHODS: Consecutive patients who underwent a CT examination of the chest or abdomen and had also received a dual-energy X-ray absorptiometry (DXA) test were retrospectively included. CTs were evaluated for vertebral fractures and vertebral attenuation (density) values were measured. Diagnostic performance measures and the area under the receiver operator characteristics curve (AUC) for diagnosing osteoporosis were calculated. RESULTS: Three hundred and two patients with a mean age of 57.9 years were included, of which 82 (27%) had osteoporosis according to DXA and 65 (22%) had vertebral fractures. The diagnostic performance for vertebral HU measurements was modest, with a maximal AUC of 0.74 (0.68 - 0.80). At that optimal threshold the sensitivity was 62% (51 - 72%) and the specificity was 79% (74 - 84%). CONCLUSIONS: We confirmed that simple trabecular vertebral density measurements on routine CT contain diagnostic information related to bone mineral density as measured by DXA, albeit with substantially lower diagnostic accuracy than previously reported. KEY POINTS: • We externally validated the value of vertebral trabecular bone attenuation for osteoporosis • These diagnostic performance measures were, however, substantially lower than previously reported • This information might be useful when considering the implementation of opportunistic osteoporosis screening.

Intravenous contrast injection significantly affects bone mineral density measured on CT.

OBJECTIVE: The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. METHODS: One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1). RESULTS: CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25% false negatives. CONCLUSIONS: Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT. KEY POINTS: • Routine CT may gain a role in bone attenuation measurements for osteoporosis • Contrast media injection has substantial influence on CT-derived bone density • Contrast-enhanced CT leads to underestimation of osteoporosis compared to unenhanced CT • Adjusting for contrast injection phase may improve CT screening protocols for osteoporosis.