R. Andresen

Relationship Between Structural Parameters, Bone Mineral Density and Fracture Load in Lumbar Vertebrae, Based on High-Resolution Computed Tomography, Quantitative Computed Tomography and Compression Tests

Abstract: Different noninvasive techniques for the assessment of the individual fracture risk in osteoporosis are introduced, and the relation between structural properties of high-resolution computed tomography (HR-CT) images of vertebral bodies, their bone mineral density (BMD) and the fracture load is analyzed. In 24 unfractured lumbar vertebrae with different degrees of demineralization from six specimens, the trabecular and cortical BMD was determined using quantitative CT. A lateral X-ray image revealed the number of fractures in the entire spine. A structural analysis of spongy and cortical bone was performed based on the HR-CT images. In the spongiosa, the fractal dimension was calculated as a function of the threshold value. In the cortical shell, the maximum number of clusters of low BMD was determined at varying threshold values. After the CT measurements the vertebrae were excised and compressed until fractured. On the basis of the spongiosa BMD and the number of fractures, 3 cases were found to be severely osteoporotic; the other 3 cases showed osteopenia. The average fracture loads were determined as 3533 N for the non-osteoporotic cases (range 2602–5802 N) and 1725 N for the osteoporotic cases (range 1311–2490 N). The parameters were determined as follows: average spongiosa BMD 115.2 mg/ml (101.8–135.3 mg/ml) for the non-osteoporotic cases, 46.2 mg/ml (34.8–57.6 mg/ml) for the osteoporotic cases; average cortical BMD 285.1 mg/ml (216.4–361.9 mg/ml) for the non-osteoporotic cases, 136.1 mg/ml (142.5–215.2 mg/ml) for the osteoporotic cases; spongiosa structure: average 0.5 (range 0.32–0.75) for the non-osteoporotic cases, average 1.05 (range 0.87–1.24) for the osteoporotic cases; cortical structure: average 81 (range 55–104) for the non-osteoporotic cases), average 136 (range 102–159) for the osteoporotic cases. Single parameters (BMD and structure) and weighted sums of these parameters were correlated with the fracture load, resulting in correlation coefficients of rsBMD= 0.82 (spongiosa BMD), rcBMD= 0.82 (cortical BMD), rsStr=–0.75 (spongiosa structure) and rcStr=–0.86 (cortical structure). The weighted sum of cortical and spongiosa BMD resulted in rBMD= 0.86, of cortical and spongiosa structure in rStr=–0.86. A weighted combination of all four parameters correlates with the fracture load at r4= 0.89, all correlations being statistically significant (p<0.0001). The four individual parameters show only a slight overlap between non-osteoporotic and osteoporotic subjects. The high correlation of the cortical BMD and the structural parameter in cortical bone indicates the important contribution of the cortical shell to vertebral stability. A weighted sum of multiple parameters results in a higher correlation with the fracture load and does not show an overlap between the two groups. It is best suited to estimate the individual fracture risk. The presented methods are generally applicable in vivo; and allow an improvement of the diagnosis of osteoporosis compared with the measurement of the BMD alone.

BONE MINERAL DENSITY AND SPONGIOSA ARCHITECTURE IN CORRELATION TO VERTEBRAL BODY INSUFFICIENCY FRACTURES

Objective: the clinical value of spinal quantitative CT (sQCT) and the structural patterns of the vertebral bone were studied Material and Methods: sQCT was performed on 246 patients with a mean age of 57 years for whom conventional lateral radiographies of the thoracic and lumbar spine were available. All patients were suffering from back pain of unknown etiology. the bone mineral density (BMD) of the midvertebral section of 3 lumbar vertebral bodies was determined by means of single-energy-(SE)-weighted QCT (85 kV). Spongiosa architecture and density profile analyses were made in the axial images. This was contrasted to BMD values ascertained in SE QCT. the mean BMD was compared to the number of fractures and the patients were divided into three groups: group I — no fracture; group II — one fracture; and group III 1 fracture Results: the mean BMD was: 134.3 (74.1–187.5) mg hydroxyapatite (HA)/ml in group I; 79.6 (58.6–114.3) mg HA/ml in group II; and 52.4 (13.1–79.1)mg HA/ml in group III. A significant deterioration in spongiosa structure was found with increasing demineralization: strongly rarefied patterns predominated in the fracture groups II and III Conclusion: sQCT provides a good risk assessment of the occurrence of vertebral body insufficiency fractures

MR Diagnosis of Retropatellar Chondral Lesions under Compression A Comparison with Histological Findings

Purpose: The aim of the study was to improve the chondromalacia patellae (CMP) diagnosis by MR imaging under defined compression of the retropatellar cartilage, using a specially designed knee compressor. The results were compared with histological findings to obtain an MR classification of CMP. Method: MR imaging was performed in in vitro studies of 25 knees from cadavers to investigate the effects of compression on the retropatellar articular cartilage. The results were verified by subsequent histological evaluation. Results: There was a significant difference in cartilage thickness reduction and signal intensity behaviour under compression according to the stage of CMP. Conclusion: Based on the decrease in cartilage thickness, signal intensity behaviour under compression, and cartilage morphology, the studies permitted an MR classification of CMP into stages I—IV in line with the histological findings. Healthy cartilage was clearly distinguished, a finding which may optimize CMP diagnosis.

Assessment of the penile vascular system with color-coded duplex sonography and pharmacocavernosometry and -graphy in impotent men

Objective: to examine the extent to which color-coded duplex sonography permits complete clarification of vessel-dependent erectile dysfunction (ED). Material and Methods: A total of 215 patients with ED were examined All patients underwent pharmacocolor-coded duplex sonography (PHCCDS; 20 μg of prostaglan-din El, PGE1, intracavernosally) as well as pharmacocavernosometry and -graphy (PHCM and PHCG; 20 μg of PGEl intracavernosally). the penile vessels were visualized, i.e. the dorsal arteries, the cavernosal arteries, and the anastomoses between them, as well as the venous pathways. Peak flow and end-diastolic flow in all arteries and, when present, anastomoses were determined after stimulation. Induction flow to achieve maximal tumescence/rigidity as well as maintenance flow were determined during PHCM. Finally, for the morphological visualization of the cavernous body and possible venous insufficiencies, a radiography in 2 planes was produced with infusion of a water-soluble contrast medium. Results: in 145 patients with a grade 0-III tumescence after stimulation with 20 μg of PGEI, PHCCDS revealed an end-diastolic flow of >5 cm/s, with a peak flow velocity >25 cm/s in the 2 cavernosal and 2 dorsal arteries. the deep dorsal vein of the penis was visualized in 110 of these 145 patients with a blood flow >5 cm/s, and in 35 cases with a blood flow <5 cm/s. Venous drainage to the corpus spongiosum was visualized in 80 patients with a blood flow >10 cm/s. All patients had a pathologically increased induction (normal value <100 ml/min) and maintenance venous flow (normal value <10 ml/min) in the PHCM as well as venous drainage in the PHCG. Sixty patients with a tumescence grade of IV-V (rigidity) had a peak flow velocity clearly >25 cm/s, an end-diastolic flow <5 cm/s in the 2 cavernosal and 2 dorsal arteries in the PHCCDS, as well as induction values <100 ml/min and maintenance flow values <10 ml/min in the PHCM, without visible insufficient efferent venous pathways on the PHCG. in 29 patients (13.5%) hemodynamically active anastomoses perforating the tunica albuginea could be detected. Ten patients with a tumescence grade of III had a peak flow velocity <25 cm/s and an end-diastolic flow <5 cm/s without venous leakage in PHCM and PHCG. Conclusion: PHCCDS allows for the assessment of arterial flow disorder as well as of venous leakage in ED. PHCM and PHCG should only be carried out in patients in whom surgical or radiological interventional procedures at the efferent venous pathways are planned.

Projecting the sulcal pattern of human brains onto a 2D plane--a new approach using potential theory and MRI.

A new method is introduced to project the sulcal pattern of the brain surface onto a 2D plane. Twin brains are compared against each other using the planar representation. We obtained T1-weighted Flash-3D MRI volumes from 14 male twins (seven monozygotic, seven dizygotic) with 3 mm-thick coronal slices. The projection is based on potential theory: A virtual electrostatic field is calculated between the area of the segmented brain and a surrounding spherical electrode. Field lines starting from each border point of the segmented brain follow the gradient towards the sphere, leading to field line concentrations due to the underlying sulci. The unwrapped sphere surface with the number of field lines per area unit is used as the 2D representation of the sulcal pattern. The resulting brain projections show a distinctive pattern, and a visual assignment of the twin pairs from the unsorted set is possible because of a high similarity of the patterns between twin pairs. Global correlation coefficients for each pair of maps yield significantly higher values for matching monozygotic twin pairs (mean = 20.2, range 12.3-25.6) than for unmatched pairs (mean = 13.0, range 1.1-28.5). As a conclusion, our method allows us to map the location and depth of the sulci on a 2D plane. The resulting maps allow quantitative inter-individual comparisons on the entire brain or parts of the brain surface.

The current state of osteoporosis diagnostics using spinal QCT

Urinary pyridinium crosslisks (XL) are considered valid markers of bone resorption, and various methods have been introduced for the quantitative determination of total, free and peptide bound XL forms. However, the generation and metabolism of these various molecular derivates, and their clinical significance has not been studied in detail. We therefore determined total and free urinary XL in a set of 240 healthy individuals (10 males and 10 females in each age bracket; see table 1). XL were measured by reverse-phase ion-paired HPLC with (total XL) and without hydrolysis (free XL) as described previously. Bound crosslinks were calculated from the difference of total and free XL compunds. All values were corrected by urinary creatinine measured with the standard Jaffe technique. Results are shown for DPD only in fig. and table I.

Computerized analysis of gray-value profiles in spongy and cortical bone. Clinical experience.

RATIONALE AND OBJECTIVES Osteoporosis is characterized by a loss of bone mineral density and deterioration of structure. The authors present a structural parameter for the quantitative assessment of osteoporotic changes in vertebral bone. METHODS In 40 patients without or with known osteoporotic fractures, spongiosa and cortical bone mineral density was measured in lumbar vertebrae 1 to 3 by quantitative CT. Additional axial high-resolution CT slices were obtained for the structural analysis. In the spongiosa, the gray-value profile along a horizontal line in the CT slice was used, whereas in the cortical shell a profile was obtained from the cortical ridge. Both profiles were intersected with a horizontal line of variable position, and the maximum number of intersections was determined. RESULTS The maximum number of intersections is significantly higher in cases with fractures (spongiosa 48.6, cortical shell 77.3) than in cases without fractures (spongiosa 42.1, cortical shell 62.4). It also correlates with bone mineral density and age. CONCLUSIONS The presented method shows significantly different numeric results for patients with and without osteoporotic fractures. The analysis is easy to perform and provides additional information on the bone structure that may be used in combination with bone mineral density measurements.