Improving diagnostic efficiency: analysis of pelvic MRI versus emergency hip aspiration for suspected hip sepsis.

BACKGROUND: Accurately diagnosing and treating childhood hip sepsis is challenging. Adjacent bone and soft-tissue infections are common and can lead to delayed and inappropriate treatment. This study evaluated the effect of early advanced imaging (bone scan, magnetic resonance imaging) in the management of suspected hip sepsis. METHODS: A retrospective review of pediatric patients admitted between 2003 and 2009 with suspected hip sepsis was performed. Patients were classified into 2 categories: group I-immediate hip aspiration or group II-advanced imaging performed before intervention. RESULTS: In total, 130 patients (53 in group I and 77 in group II) were included. No significant differences were found between the groups with regard to laboratory values, temperature, number of anesthetics, and length of hospital stay. However, patients in group I were younger than in group II (5.4 vs. 7.3 y, P=0.02) and more patients in group I were unable to bear weight on the affected limb compared with group II (83% vs. 61%, P=0.009). In group I, 36 patients (68%) had a septic hip compared with 35 patients (45%) in group II. In group I, 16 patients (30%) required reoperation versus 13 (17%) patients in group II. Results from the multivariate analysis demonstrated that reoperation was required 2.8 times (95% confidence interval, 1.12-6.78) more often in group I as compared with group II (P=0.03). CONCLUSIONS: Advanced imaging performed before hip aspiration improves diagnostic efficacy and may decrease the need for reoperation. LEVEL OF EVIDENCE: III.

EOS imaging of the human pelvis: reliability, validity, and controlled comparison with radiography.

BACKGROUND: The EOS technique represents a unique imaging modality combining low radiation exposure with high image quality. As its applications for pelvic imaging may increase with time, we performed a pilot study to evaluate the validity and reliability of this technique for the assessment of gross pelvic and acetabular morphology. METHODS: Consecutive conventional and EOS radiographs of a human cadaveric pelvis were made in 5° intervals of sagittal tilt and axial rotation (range, -15° to 15° for each). Six measurements were made on each image: (1) the vertical distance between the sacrococcygeal joint and the upper border of the pubic symphysis, (2) the horizontal distance between the midpoints of these structures, (3) the distance between the anterior superior iliac spines, (4) the distance between the facets of S1, (5) the Sharp angle, and (6) the Tönnis angle. Coxa profunda and crossover signs were also evaluated. The findings of the two imaging techniques were correlated with each other and with true linear measurements made on the cadaveric pelvis. All measurements were performed by two independent observers, and one observer repeated all measurements to assess reproducibility. Both observers were blinded to the true linear measurements made on the pelvis. RESULTS: There was a strong correlation between the results of the conventional and EOS radiography (Pearson correlation coefficient, 0.644 to 0.998), and both modalities had high intraobserver and interobserver reproducibility (intraclass correlation coefficient, 0.795 to 1.000). Intraobserver and interobserver agreement on the presence of coxa profunda were both 100%. Intraobserver agreement (96.2%) and interobserver agreement (92.3%) on the presence of the crossover sign were marginally lower. Linear measurements differed significantly between the two modalities because of distortion caused by magnification effects in the conventional radiographic imaging (p < 0.05). CONCLUSIONS: The EOS imaging technique proved reliable for the assessment of gross pelvic and acetabular morphology, and it may be an alternative to current radiography for primary imaging in the pediatric population and potentially in adults as well. This study did not evaluate the ability of EOS imaging to detect subtle radiographic anatomic abnormalities.

Acetabular version on magnetic resonance imaging: analysis of two different measuring techniques.

BACKGROUND: Both increased anteversion and retroversion of the acetabulum can lead to clinical problems. Although computed tomography (CT) is the gold standard in acetabular version imaging, magnetic resonance imaging (MRI) is becoming increasingly popular. We conducted this retrospective study to answer the following questions: 1) can the bony landmarks necessary to outline and measure acetabular version on MRI be consistently and reproducibly identified; 2) are soft-tissue (labral) landmarks comparable to bony landmarks for the measurement of acetabular version? METHODS: Twenty-nine MRI torsional profile examinations were studied. A total of 232 readings (116 each for right and left sided acetabulae) were involved. Acetabular anteversion angle (AAA) was measured using two different methods (i.e. bony acetabulum landmarks and labrum), by two investigators, at two separate times. RESULTS: Mean age was 13 years, 8 months with a range of 14 years. There were 12 male patients and 17 female. It was possible to consistently identify bony and labral landmarks in all MR images. AAA measurements using both methods were consistent and reproducible. When comparing the two methods to each other we found them to be in excellent agreement with an ICC of 0.943 (95% confidence interval, 0.927 to 0.956), 37% of all readings were in perfect agreement and 97% were within 5 degrees. The mean difference in measurement between methods was 1.34 degrees. CONCLUSION: Measurement of acetabular version using MRI remains consistent independent of the method used (bone versus labrum). MRI can provide adequate information for calculating acetabular version.

CT and MRI lower extremity torsional profile studies: measurement reproducibility.

BACKGROUND: Assessment of lower extremity (LE) torsional profile using computed tomography (CT) imaging is a well-recognized imaging method that supplements the clinical examination. Magnetic resonance imaging (MRI) is another advanced imaging modality that can be used as an alternative, since there are many growing concerns of radiation exposure with traditional CT studies, particularly in the skeletally immature population. METHODS: Sixty-two patients between the ages of 7 and 19 years were included. Thirty-four had CT and 28 had MRI for assessment of LE torsional profile. All patients had clinical evidence of torsional malalignment. CT and MR images were randomized and de-identified. Two observers measured femoral anteversion and tibial torsion based on previously published methodologies. This exercise was repeated 2 weeks later and the data were tabulated and statistical analysis was performed. Radiation exposure for the patients studied by CT was estimated. RESULTS: The mean age of the patients was 14.4 years (range 9.5-18.9 years) and 13.8 years (range 7.3-18.9 years) for the CT and MRI groups, respectively. Inter-observer reliability for both CT and MRI studies were excellent. The intra-class correlation coefficient (ICC) for femoral anteversion and tibial torsion studied by CT and MRI for both observers at both times were excellent. The radiation exposure for CT examination averaged 0.3-0.5 mSv, compared to none with the MRI method. CONCLUSIONS: MRI provides a reproducible method for assessing the torsional profile in children and adolescents using similar anatomic landmarks for measurements as those used on CT torsional profile. In circumstances where MRI methods are readily available (and affordable), the CT torsional profile can be replaced with MRI methods, in the current era of growing concerns of radiation hazards and increasing awareness about radiation safety. LEVEL OF EVIDENCE: Diagnostic Level III.