H. Imhof

Subchondral bone and cartilage disease: a rediscovered functional unit.

Imhof H, Sulzbacher I, Grampp S, Czerny C, Youssefzadeh S, Kainberger F. Subchondral bone and cartilage disease: A rediscovered functional unit. Invest Radiol 2000;35:581–588. ABSTRACT.The role of subchondral bone in the pathogenesis of cartilage damage has likely been underestimated. Subchondral bone is not only an important shock absorber, but it may also be important for cartilage metabolism. Contrary to many drawings and published reports, the subchondral region is highly vascularized and vulnerable. Its terminal vessels have, in part, direct contact with the deepest hyaline cartilage layer. The perfusion of these vessels accounts for more than 50% of the glucose, oxygen, and water requirements of cartilage. Bony structure, local metabolism, hemodynamics, and vascularization of the subchondral region differ within a single joint and from one joint to another. Owing to these differences, repetitive, chronic overloading or perfusion abnormalities may result in no pathological reaction at all in one joint, while in another joint, these same conditions may lead to osteonecrosis, osteochondritis dissecans, or degenerative changes. According to this common etiological root, similar pathological reactions beginning with marrow edema and necrosis and followed by bone and cartilage fractures, joint deformity, and insufficient healing processes are found in osteonecrosis, osteochondritis dissecans, and degenerative disease as well.

MR contrast arthrography (MRA) in osteochondrosis dissecans

Osteochondrosis dissecans (OCD) is a lesion that characteristically affects the articular cartilage and subchondral bone with the potential of fragmentation and separation. Exact assessment of cartilaginous and subchondral bony changes is mandatory for the planning of adequate treatment. Therefore, we examined 25 knees using spin echo (SE) and gradient echo (GE) sequences on a 1.5 T superconducting unit prior to and following intraarticular administration of 40 ml of a 2 mmol/L Gd-DTPA solution (MR arthrography). For evaluation (staging) a modified Clanton and DeLee scheme was employed. Verification by arthroscopy or arthrotomy was available in 24 cases. A correct diagnosis of OCD with regard to its type prior to intraarticular injection of Gd-DTPA was possible in 39.3% using T1-weighted SE sequences and in 57.4% on GE sequences. After intraarticular administration of Gd-DTPA, the rate of correct diagnoses improved to 92.9% on T1-weighted SE sequences and 100% on GE sequences. Magnetic resonance arthrography appears to be helpful for the exact assessment of the articular cartilage overlying OCD lesions as well as for the differentiation between partial and complete separation of cartilaginous or osteocartilaginous fragmentations.

The role of relaxation times in monitoring proteoglycan depletion in articular cartilage.

Various proton relaxation times (T2, T1ρ, and gadolinium‐diethylene triamine pentaacetic acid [Gd‐DTPA]‐enhanced T1) were measured in articular cartilage in vitro at 3 T to assess their role in visualizing proteoglycan depletion. Cartilage‐bone specimens were obtained from patients who underwent total joint replacement and got a double dose of Gd‐DTPA 2 hours prior surgery. In these specimens, regions of mechanically undamaged cartilage having a decreased content of proteoglycans showed about 15% lower T1 values compared with apparently normal cartilaginous tissue. The expected increase of the T2 relaxation time was not observed in these regions. On the other hand, the T2 and, to a lower degree, T1 relaxation times were found to be increased in regions of cartilage fibrillation. The T1ρ relaxation times obtained were slightly longer than the corresponding T2 values, but both parameters showed almost identical spatial distributions. J. Magn. Reson. Imaging 1999;10:497–502.

MRI visualization of proteoglycan depletion in articular cartilage via intravenous administration of Gd-DTPA.

The effect of intravenous administration of gadolinium diethylenetriamine-pentaacetic acid (Gd-DTPA) on MR images was studied in vitro, using pathologic osteochondral specimens removed during surgery for total endoprosthesis, and in vivo, on a group of volunteers. In ex vivo specimens, lesions of different shape having lower T1 were detected which corresponded to areas with depleted proteoglycans found histologically. In vivo experiments on young volunteers showed that the time course of cartilage enhancement was different for different anatomies. The time for maximum enhancement ranged from 45 min for the ventral femoral condyle to 270 min for patellar cartilage.

Postcontrast Mr Arthrography in Assessment of Cartilage Lesions

Objective Although MR has been proven effective in evaluating many components of the musculoskeletal system, including ligaments, fibrocartilage, muscle, and bone marrow, its role in the evaluation of articular cartilage remains controversial. Recent studies have demonstrated that intraarticular injection of Gd-DTPA [MR arthrography (MRA)] improves the detection of cartilage abnormalities in cadaveric specimens. The aim of this study was to determine the efficacy of MRA for the detection of naturally occurring cartilage lesions in a clinical population. Materials and Methods Sixty knees of 58 patients were studied with a three-dimensional (3D) T2*-weighted GE sequence (FISP) both before and after and a Tl-weighted (TlW) SE sequence after the intraarticular injection of a 2 mmol/L Gd-DTPA solution. All knees subsequently underwent arthroscopy or arthrotomy. Results The MRA sequences performed significantly better (k = 0.85) than the routine FISP sequences (k = 0.39) in both the detection and the staging of cartilage abnormalities. The MRA FISP sequence (k = 0.91) performed slightly better than the MRA TlW sequence (k = 0.85), but there was no statistically significant difference between the two sequences. No complications from the intraarticular injection of contrast material occurred. Conclusion Therefore, MRA appears to be an effective and safe method for the evaluation of articular cartilage abnormalities.

Impact of Spinal Degenerative Changes on the Evaluation of Bone Mineral Density with Dual Energy X-Ray Absorptiometry (DXA)

Abstract. The purpose of this study is to evaluate degenerative factors in a postmenopausal patient group and differentiate the influence on bone mineral density (BMD) measurements by dual-energy X-ray absorptiometry (DXA). The patients and methods included an investigation of 144 postmenopausal women (mean 63.3 years) with PA-DXA of the spine. Degenerative factors (osteophytes, osteochondrosis, scoliosis, and vascular calcification) were evaluated from plain lumbar radiographs, their estimated probability was analyzed as a function of age, and their influence on BMD measured by PA-DXA was determined. The results of the study revealed osteophytes in 45.8%, vascular calcifications in 24.3%, scoliosis in 22.2%, osteochondrosis in 21.5%. The estimated probability for degenerative factors increased from 35 to 80% in the 55- to 70- year age group. Osteophytes and osteochondrosis were associated with up to a 14% increase in BMD values (P < 0.001). Vascular calcifications showed a positive trend, whereas scoliosis did not show a discernible influence.We concluded that degenerative factors, except for scoliosis, showed an influence on BMD as measured by DXA. Their prevalence increased rapidly between 55 and 70 years of age. Interpretation of PA-DXA spine data for subjects of or above this age range should be complemented by plain film radiographs.

Dental CT: imaging technique, anatomy, and pathologic conditions of the jaws

Abstract. In addition to conventional imaging methods, dental CT has become an established method for anatomic imaging of the jaws prior to dental implant placement. More recently, this high-resolution imaging technique has gained importance in diagnosing dental-associated diseases of the mandible and maxilla. Since most radiologists have had little experience in these areas, many of the CT findings remain undescribed. The objective of this review article is to present the technique of dental CT, to illustrate the typical appearance of jaw anatomy and dental-related diseases of the jaws with dental CT, and to show where it can serve as an addition to conventional imaging methods in dental radiology.

Importance of subchondral bone to articular cartilage in health and disease.

The almost absolute barrier to diffusion of nutrients between articular cartilage and subchondral bone does not exist. These anatomic regions represent a functional unit. Repetitive overloading in degenerative disease leads primarily to lesions in the subchondral region (including vessels), which in turn impede flow of nutrition to articular cartilage. As a result, in degenerative joint disease the subchondral region shows reactive enhanced vascularization and heightened metabolism with insufficient repair. In aging, however, vascularization and metabolism are decreased; no repair takes place. In many cases, MRI allows visualization of these subchondral abnormalities. It also demonstrates the basic similarities of degenerative osteoarthritis, osteochondritis dissecans, and avascular necrosis. These different entities may have the same basic etiology but with different disease severity.

Brain shape in human microcephalics and Homo floresiensis

Because the cranial capacity of LB1 (Homo floresiensis) is only 417 cm3, some workers propose that it represents a microcephalic Homo sapiens rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological H. sapiens specimen that, like LB1, represents an ≈3-foot-tall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1s with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1s having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.

MR imaging of meniscal subluxation in the knee.

Purpose: The aim of this study was to establish diagnostic criteria for meniscal subluxation, and to determine whether there was any connection between meniscal subluxation and other common meniscal and knee-joint abnormalities. Material and Methods: The normal position of the meniscal body was assessed in 10 asymptomatic volunteers. MR signs of meniscal subluxation were evaluated retrospectively in 60 symptomatic patients with pain in the knee, impaired mobility, and/or joint swelling who had no clear diagnosis after the evaluation of case history, clinical examination, and radiography. The criterion for subluxation of the meniscus was defined as a distance of ≥3 mm between the peripheral border of the meniscus and the edge of the tibial plateau. Results: In the volunteers, the mean distance from the medial meniscus to the edge of the tibial plateau was 0.07 mm, and that from the lateral meniscus was 0 mm. In 55 symptomatic patients without meniscal subluxation, the mean distance from.the meniscus to the edge of the tibial plateau was 0.27 mm. Five patients (8%) had evidence of meniscal subluxation, 4 in the medial meniscus and one in the lateral meniscus. The most commonly associated knee abnormality was joint effusion in 5 knees and osteoarthritis in 2 knees. Conclusion: Meniscal subluxation was not a rare finding with MR imaging in patients with painful knees. Meniscal subluxation was associated with other knee abnormalities such as joint effusion or osteoarthritis.