Ionizing radiation doses during lower limb torsion and anteversion measurements by EOS stereoradiography and computed tomography.

OBJECTIVES: To calculate and compare the doses of ionizing radiation delivered to the organs by computed tomography (CT) and stereoradiography (SR) during measurements of lower limb torsion and anteversion. MATERIALS AND METHODS: A Rando anthropomorphic phantom (Alderson RANDO phantom, Alderson Research Laboratories Inc., Stanford, Conn) was used for the dose measurements. The doses were delivered by a Somatom 16-slice CT-scanner (Siemens, Erlangen) and an EOS stereoradiography unit (EOS-Imaging, Paris) according to the manufacturers' acquisition protocols. Doses to the surface and deeper layers were calculated with thermoluminiscent GR207P dosimeters. Dose uncertainties were evaluated and assessed at 6% at k=2 (that is, two standard deviations). RESULTS: The absorbed doses for the principal organs assessed were as follows: for the ovaries, 0.1 mGy to the right ovary and 0.5 mGy to the left ovary with SR versus 1.3 mGy and 1.1 mGy with CT, respectively; testes, 0.3 mGy on the right and 0.4 mGy on the left with SR versus 8.5 mGy and 8.4 mGy with CT; knees, 0.4 mGy to the right knee and 0.8 mGy to the left knee with SR versus 11 mGy and 10.4 mGy with CT; ankles, 0.5 mGy to the right ankle and 0.8 mGy to the left with SR versus 15 mGy with CT. CONCLUSION: The SR system delivered substantially lower doses of ionizing radiation doses than CT to all the organs studied: CT doses were 4.1 times higher to the ovaries, 24 times higher for the testicles, and 13-30 times higher for the knees and ankles. The use of the SR system to study the torsion of lower limbs makes it possible to reduce the amount of medical irradiation that patients accumulate.

Reliability and diagnostic accuracy of qualitative evaluation of diffusion-weighted MRI combined with conventional MRI in differentiating between complete and partial anterior cruciate ligament tears.

OBJECTIVES: To assess the reliability and diagnostic accuracy of qualitative evaluation of apparent diffusion coefficient (ADC) mapping with magnetic resonance imaging (MRI) in differentiating between complete and partial anterior cruciate ligament (ACL) tears. METHODS: This prospective study protocol was approved by the institutional ethics review board and informed consent was obtained from all the patients. Eighty-five patients (35 women and 50 men, mean age 34.1 years) with recent (<4 months) knee trauma with suspected ACL injury underwent conventional MRI (T1-weighted and T2-weighted sequences with fat saturation) associated with ADC mapping. MR images were read qualitatively without and then with ADC mapping by three radiologists, with analysis of direct signs of a traumatic ACL tear and a second-reading. Dynamic X-rays (43 patients) or arthroscopies (42 patients) were used as reference standards. RESULTS: For complete ACL tear diagnosis (67 patients), sensitivity and specificity were 87% and 50% respectively with conventional MRI, and 96% and 94% respectively with ADC mapping (P < 0.01 for specificity). Inter-observer correlations between musculoskeletal radiologists were almost perfect (κ = 0.81) with ADC mapping and fair with conventional MRI on the second-reading. CONCLUSIONS: ADC mapping associated with conventional MR sequences is a reproducible method to better differentiate complete and partial ACL tears.

Evaluation of a new low-dose biplanar system to assess lower-limb alignment in 3D: a phantom study.

OBJECTIVE: Knee coronal alignment is routinely assessed on a full-length radiograph of the lower limbs. However, poor positioning of the knee during the procedure affects the accuracy of this kind of measurement, particularly in cases combining knee rotation and flexion. The purpose of this study was to assess the value of a three-dimensional assessment of the hip-knee-ankle (HKA) angle based on a biplanar radiographic system. MATERIALS AND METHODS: A biplanar slot scanning system was used to take radiographs of three lower-limb synthetic models with similar frontal deviation (5° valgus) but different flexion angulations (0°, 9°, and 18°). Biplane acquisitions were done with lower-limb axial rotations ranging from 20° of internal rotation to 20° of external rotation on each of the lower limb models. Three independent observers performed standard 2D measurements of the HKA angle from each anteroposterior (AP) image and also modeled the lower limb in 3D for each biplane acquisition with dedicated software. The HKA angle was automatically calculated from the 3D models. The results of the 2D and 3D techniques were compared. RESULTS: Axial rotation provoked 2D HKA measurement errors up to, respectively, 1.4°, 4.7°, and 6.8° for the lower extremities with 0°, 9°, and 18° flexion, while it never affected the 3D HKA measurement for more than 1.5°. Interobserver errors were 0.7° (SD = 0.5°) for the 2D measurements and 0.6° (SD = 0.4°) for the 3D measurements. CONCLUSIONS: The 3D modeling allows for a more accurate evaluation of coronal alignment compared to 2D, eliminating bias due to wrong knee positioning.

Arthroscopic treatment of localized pigmented villonodular synovitis of the knee.

PURPOSE: The purpose of this study was to review the outcome of the arthroscopic treatment of localized pigmented villonodular synovitis of the knee and to determine the recurrence rate with clinical and magnetic resonance imaging evaluation at midterm follow-up. METHODS: Thirty consecutive patients diagnosed with localized pigmented villonodular synovitis of the knee were treated arthroscopically between 1990 and 2008. Clinical assessment was made with the use of Lysholm Knee Scale, and radiologic assessment was done by plain radiographs and magnetic resonance imaging of the knee. Recurrence rate of the disease was also estimated. RESULTS: The average follow-up was 75 months (range 12-144). The median age of the patients was 46 years (range 23-71). Symptoms were discomfort of the knee (100%), swelling (90%), locking (50%), pain (10%) and palpable mass (15%). A history of knee trauma was present in 10% of the patients. The nodules were localized in the gutters (45%), suprapatellar pouch (26%), patellar fat pad (13%), posterior compartment of the knee (13%) and in the femoral notch (9%). The median Lysholm Knee Score was 56.5 (range 53-60) and 85.5 (83-88) preoperatively and at final follow-up, respectively. No postoperative complications occurred. CONCLUSIONS: Arthroscopy is a safe and effective procedure for the treatment of localized pigmented villonodular synovitis of the knee. Magnetic resonance imaging is essential to diagnose this pathologic condition and to define accurately its localization and treatment strategy.