Acute knee trauma: role of ultrasound.

The purpose of this study was to determine the diagnostic accuracy of high spatial resolution ultrasonography (US) in the detection of lipohemarthrosis of the knee and to evaluate this sign as criteria of intra-articular fracture. Forty-eight patients with clinical suspicion of knee fracture were prospectively examined by conventional radiography, sonography examination and computed tomography (CT) within 48 h after trauma in order to depict direct (fracture line) and indirect (lipohemarthrosis) signs of intra-articular fracture. Lipohemarthrosis was defined as a multi-layered collection in the subquadricipital recess. CT was considered as the gold standard for both direct and indirect fracture criteria. CT imaging showed direct signs of intra-articular fracture in 31 patients (65%). Among these patients, 30 (97%) had a lipohemarthrosis. Conventional radiographs showed intra-articular fracture in 26 patients (54%). Among these, 18 (69%) had a lipohemarthrosis. Sonographic examinations could not depict any direct sign of intra-articular fracture but showed a lipohemarthrosis in 29 (93%) of patients with proven fracture via CT. This allowed the depiction of four out of five occult knee fractures. The sensitivity, specificity, positive predictive value, negative predictive value of sonography for the diagnosis of lipohemarthrosis was 97, 100, 100 and 94%, respectively, compared with 55, 100, 100 and 55% with conventional radiographs. Using lipohemarthrosis as criterion of fracture, the sensitivity, specificity, positive predictive value and negative predictive value of sonography for early detection of intra-articular knee fractures was 94, 94, 97 and 89%, respectively, compared with 84, 88, 93 and 75% with conventional radiographs. We concluded that, by showing lipohemarthrosis in the subquadricipital recess, high-resolution sonography is a reliable and accurate technique for the evaluation of intra-articular knee fractures.

Water excitation as an alternative to fat saturation in MR imaging: preliminary results in musculoskeletal imaging.

PURPOSE: To compare fat suppression methods by using spectrally selective fat saturation and section-selective water excitation in standard magnetic resonance (MR) imaging sequences used in day-to-day musculoskeletal practice. MATERIALS AND METHODS: Eighty-three patients underwent MR examination with a 1.5-T system. The two methods were compared by using three common sequences: T1-weighted spin-echo (SE) imaging performed after contrast material injection (n = 24), intermediate-weighted fast SE (n = 36) imaging, and T2-weighted fast SE (n = 36) imaging. Acquisition times of the sequences and signal-to-noise and contrast-to-noise ratios of bone, muscle, fat, and water for the two methods were compared quantitatively. Images were then qualitatively reviewed by two radiologists who were blinded to the type of fat suppression used. Image quality was scored according to four criteria (homogeneity of fat suppression, susceptibility and foldover artifacts, conspicuousness of lesion, and overall image quality) by using a five-point scale (0, bad; 1, poor; 2, fair; 3, good; and 4, excellent). A paired Student t test was used to compare the quantitative data, and a nonparametric paired-data Wilcoxon signed rank test was used for qualitative analysis. RESULTS: Water excitation allowed a substantial decrease in acquisition time (by up to 50%) for T1-weighted sequences. Quantitative measurements revealed a greater signal-to-noise ratio (P <.01) with water excitation for all three sequences, whereas the contrast-to-noise ratio was greater with water excitation only in intermediate-weighted sequences (P <.01). Qualitatively, water excitation proved statistically better than or equal to fat saturation for all criteria in all imaging sequences (P <.05). Mean scores of overall image quality ranged between 2.5 and 3.0 for fat saturation and 3.4 and 3.7 for water excitation, respectively (P <.05). CONCLUSION: Section-selective water excitation is faster than conventional fat saturation and produces images of better quality.

Occult fractures of the waist of the scaphoid: early diagnosis by high-spatial-resolution sonography.

OBJECTIVE: This study evaluated the diagnostic accuracy of high-spatial-resolution sonography in the diagnosis of occult fractures of the waist of the scaphoid. SUBJECTS AND METHODS: Sonography of the scaphoid bone with a 12-MHz transducer was performed in 54 patients with clinically suspected scaphoid fracture and normal findings on initial radiographs, including specific scaphoid images. Three levels of clinical suspicion were considered: high (20%), moderate (30%), and low (50%). Attention was paid to the continuity of the scaphoid cortex and to the surrounding soft tissues (i.e., hemarthrosis or hematoma). Data from early sonograms were then compared with the results of radiography repeated 10-14 days after the initial trauma. In cases of persistent suspicion despite normal findings on follow-up radiographs, the presence of fracture was evaluated on CT (four patients), MR imaging (one patient), or bone scanning (one patient). RESULTS: Follow-up examinations proved fracture of the scaphoid waist in five patients. In all patients, diagnosis of fracture was suspected on initial sonograms showing cortical disruption associated with soft-tissue abnormalities. There was one false-positive finding and no false-negative results. Using cortical disruption as a diagnostic criterion, we found the sensitivity, specificity, and accuracy of high-resolution sonography for the depiction of scaphoid fracture to be 100%, 98%, and 98%, respectively. Using soft-tissue abnormalities alone as a criterion, we found the sensitivity, specificity, and accuracy of high-resolution sonography to be 100%, 65%, and 68%, respectively. The overall prevalence of occult fracture was 9%, ranging from 3.7% for low suspicion to 27% for high suspicion of fracture. CONCLUSION: High-resolution sonography is a reliable and accurate method of evaluating occult fractures of the scaphoid waist. Cortical disruption is the diagnostic key. Soft-tissue abnormalities alone lack specificity.