Mamed Mesgarzadeh

Accuracy of MRI patterns in evaluating anterior cruciate ligament tears

Abstract The purpose of this study was to determine the different patterns of anterior cruciate ligament (ACL) tears on MRI and the prevalence and accuracy of these patterns. Images were obtained on high-tesla and low-tesla units and the results compared to determine whether field strength affects the interpretation using the grading system. In 172 patients who underwent knee MRI (109 knees with high-tesla units and 63 knees with low-tesla units) and arthroscopy, there was a total of 91 arthroscopically proven ACL tears. Five patterns of ACL tears were observed and designated as type 1 (diffuse increase in signal on T2-weighted images and enlargement of the ligament, 48%); type 2 (horizontally oriented ACL, 21%); type 3 (nonvisualization of the ACL, 18%); type 4 (discontinuity of the ACL, 11%); and type 5 (vertically oriented ACL, 2%). The positive predictive value (PPV) for type 2, 4, and 5 patterns was 100% for both field strengths; for type 3 PPV was just above 80% for both field strengths. The PPV value for type 1 was 90% for the high-tesla unit and 79% for the low-tesla, unit, which was not statistically significant. Combining the results of both field strengths, the overall sensitivity and specificity were 93% and 89%, respectively. Arthroscopic results were also used to determine the association between meniscal and ACL tears. Only 13% of ACL tears were isolated, the rest being associated with meniscal tears. Forty-five percent of medial meniscal and 50% of lateral meniscal tears were associated with an ACL tear, and 94% of ACLs were torn when both menisci were torn.

DIAGNOSTIC AND THERAPEUTIC FEATURES OF FACET AND SACROILIAC JOINT INJECTION: Anatomy, Pathophysiology, and Technique

A diagnosis of exclusion facet syndrome is considered one of the many genuine causes of low back pain. Using careful patient selection, percutaneous facet joint block is a useful diagnostic and therapeutic procedure in the management of lumbar facet syndrome. Sacroiliac joint syndrome appears to be a more tangible entity diagnostically and more amenable to injection. This article addresses the anatomy, pathophysiology, and salient radiographic features of the apophyseal joint, and describes the procedures and techniques for facet as well as sacroiliac joint injection.

Efficacy of limited CT for nonvisualized lower cervical spine in patients with blunt trauma

Records of 100 patients with blunt injury and nonvisualization of C7 and T1 on cross-table lateral and swimmers views were reviewed to evaluate the usefulness of limited computed tomographic (CT) scans in “clearing”1 the lower cervical vertebrae of injury. CT was deemed necessary and performed in all of these cases because the lower cervical spine could not be evaluated clinically or with plain radiographs. Ninety-seven of these 100 patients had normal findings on CT and only three patients showed cervical spine fractures. All three had isolated and stable fractures. Two of these patients had “clay-shoveler” fractures at C6 and C7, respectively, and one had a single laminar fracture at C7. All three patients were conservatively treated. This study emphasizes the value of clinical correlation in the evaluation of cervical spine trauma. When deemed necessary in symptomatic patients, CT is useful to exclude skeletal injury in the lower cervical spine thus avoiding delay in the patients workup and unnecessary hospitalization, and expediting patient discharge. Lack of pain and neurological findings in nonintoxicated, conscious, and alert patients is generally not associated with significant soft tissue or skeletal injury.

The role of magnetic resonance imaging in giant cell tumor of bone.

In six cases of giant cell tumor the magnetic resonance (MR) images obtained with various pulse sequences and field strengths were compared to the corresponding computed tomography (CT) scans and plain roentgenograms. MRI was superior to CT and plain films in demonstrating areas of tissue inhomogeneity within the tumor as well as soft tissue extension. CT was superior in demonstrating cortical thinning. Multiplanar imaging capability and visualization of articular cartilage may demonstrate intra-articular tumor spread. The characteristic MRI findings with short TR/TE (T1-weighting) and long TR/TE (T2-weighting) are described. We also describe one case where serial MR scans were used to assess response to therapy.

Femoral neck torsion angle measurement by computed tomography.

To establish the accuracy and reproducibility of measuring femoral neck torsion angles (FNTA) on CT images, this angle was measured on 12 dry femora directly on the gross specimens, on plain radiographs, and on CT images. The selection of the CT level, both at the femoral neck and the condyles, that may affect the measurement of FNTA was analyzed. The CT measurements of FNTA were found to have a reproducibility of 2.5 and 0° mean offset error when compared with readings on plain radiographs. A new CT method was developed to measure this angle particularly in patients with coxa valga in whom this measurement is difficult if not impossible to accomplish by current methods. For this purpose composite CT images were made of the femoral head and the femoral shaft, immediately below the lesser trochanter. On these images the line connecting the centers of the femoral head and shaft were inferred to represent the cervical plane. In comparison with the standard CT method, this new method had the same reproducibility, although it slightly overestimated this angle by 2°. This degree of error is negligible when compared with the normal variations of this angle, which ranges from −20 to + 38°. Furthermore, it compares favorably with the limited accuracy of derotational osteotomy surgery.

The semimembranosus-tibial collateral ligament bursa : anatomical study and magnetic resonance imaging

A bursa that was deep to the tibial collateral ligament and adjacent to the semimembranosus tendon was studied in fifty cadaveric knees; a vinyl solution was injected into four of the specimens in order to facilitate a study of the relationship between the bursa and its surrounding structures. The bursa had the shape of an inverted U: the superficial arm was an elliptical pocket that was located between the semimembranosus tendon and the tibial collateral ligament, and the deep arm was a triangular pocket that was located between the semimembranosus tendon and the medial tibial condyle. The bursa measured, on the average, twenty-one millimeters in its greatest anteroposterior dimension and ten millimeters in its greatest superoinferior dimension. Magnetic resonance images were made of two patients, and they showed fluid in the bursa.

The effect on medical metal implants by magnetic fields of magnetic resonance imaging

Forces and torques, due to a 0.3 Tesla magnetic field were evaluated on ten hip prostheses and ten hemostat clips. Measurements were performed with an instrument utilizing the movement of a laser beam caused by the deflection of a canti-lever. The results indicate effects, if any, to be smaller than the instruments sensitivity which, at its highest, was 7 mg of force and 125 mg·cm of torque.

The effect of magnetic resonance imaging on metal spine implants.

In Part 1 of this study, the forces and torques exerted on metallic spine implants by a 0.3-T magnetic field were evaluated using a cantilever system sensitive to forces as low as 250 mg and torques as low as 4 g/cm. Results Indicated that the 0.3-T magnification field did not cause forces or torques that could be measured within this range. It is concluded that patients with spine implants may safely undergo magnetic resonance scanning. In Part 2, the magnetic resonance scans from 33 patients (61 studies) then were reviewed to determine which, if any, parameters could be adjusted to minimize artifact. Magnetic power, slice thickness, plane of scan, and pulse sequence were considered. Plane of scan was found to be the most significant parameter in achieving useful studies, with the sagittal plane being the preferred orientation. Scans of patients who had posterior wiring were more likely to be useful, while scans of patients with spinal rods usually showed a large amount of artifact.

Case report 395

Fig. 1. A PA roentgenogram of the chest at the time of admission to the hospital shows considerable pleural thickening and infiltrate in the left upper lobe. Loss of volume of this segment of lung is reflected in the narrowing of the intercostal spaces and the marked buckling and displacement of the trachea to the left. The fight lung shows a few small linear densities in the lower 1/3. One of the densities may represent a somewhat depressed interlobar short fissure