Functional anatomy and biomechanics of the meniscus

The meniscus is no longer considered the evolutionary remnant in the knee joint.Rather, it is now well established as an important structure that is integral to the complex biomechanics and proper functioning of the knee. The medial and lateral menisci form two crescent-shaped wedges of fibrocartilage between the femoral condyles and tibial plateaus.The knee joint biomechanics are based on a complex interaction of these intra-articular structures. The functions ascribed to the menisci include load transmission, shock absorption, stability, proprioception, joint lubrication, and joint nutrition. Load transmission generally is accepted as one of its primary functions. The menisci transmit a portion of the axial forces across the knee joint by converting this load into “hoop stresses.” This is accomplished by their unique shape, composition, and anatomic attachments. The menisci are relatively mobile structures and their motion during knee flexion also is determined by their shape and soft tissue attachments/constraints. Preservation of the meniscal functions is essential, and the authors review the basic anatomic and biomechanical concepts necessary to understand techniques for repair and restoration of these functions.     

Assessment of the spatial occurrence of childhood leukaemia mortality using standardized rate ratios with a simple linear Poisson model.

Reports of a suspected cluster of childhood leukaemia cases in West Central Phoenix have led to a number of epidemiological studies in the geographical area. We report here on a death certificate-based mortality study, which indicated an elevated rate ratio of 1.95 during 1966-1986, using the remainder of the Phoenix standard metropolitan statistical area (SMSA) as a comparison region. In the process of analysing the data from this study, a methodology for dealing with denominator variability in a standardized mortality ratio was developed using a simple linear Poisson model. This new approach is seen as being of general use in the analysis of standardized rate ratios (SRR), as well as being particularly appropriate for cluster investigations.     

Near visual acuity: a simple measure of practical significance in insulin-treated diabetic patients.

The value of measuring near visual acuity as a predictor of loss of independence in administering insulin and monitoring blood or urine glucose has been assessed in 110 insulin-treated diabetic patients. Near visual acuity was simple to measure in the clinic setting, and correlated well with 6 m acuity. Fourteen patients depended on an assistant either to draw up the correct dose of insulin (n = 12), inject the insulin (n = 7) or to monitor blood or urine glucose (n = 12). Of these 14 patients only one, who was demented, had near visual acuity better than N.12. Two other patients had near visual acuity N.12 or worse and yet were independent of help. One had severe visual impairment and used a pen-injector and a meter with speech synthesizer, and the other had near visual acuity of N.12. Impairment of near visual acuity to N.12 or worse is associated with loss of independence in insulin-treated diabetes. Measurement of near visual acuity could be useful in predicting independence of insulin-treated patients.     

Cine CT for attenuation correction in cardiac PET/CT.

In dual-modality PET/CT systems, the CT scan provides the attenuation map for PET attenuation correction. The current clinical practice of obtaining a single helical CT scan provides only a snapshot of the respiratory cycle, whereas PET occurs over multiple respiratory cycles. Misalignment of the attenuation map and emission image because of respiratory motion causes errors in the attenuation correction factors and artifacts in the attenuation-corrected PET image. To rectify this problem, we evaluated the use of cine CT, which acquires multiple low-dose CT images during a respiratory cycle. We evaluated the average and the intensity-maximum image of cine CT for cardiac PET attenuation correction. METHODS: Cine CT data and cardiac PET data were acquired from a cardiac phantom and from multiple patient studies. The conventional helical CT, cine CT, and PET data of an axially translating phantom were evaluated with and without respiratory motion. For the patient studies, we acquired 2 cine CT studies for each PET acquisition in a rest-stress (13)N-ammonia protocol. Three readers visually evaluated the alignment of 74 attenuation image sets versus the corresponding emission image and determined whether the alignment provided acceptable or unacceptable attenuation-corrected PET images. RESULTS: In the phantom study, the attenuation correction from helical CT caused a major artifactual defect in the lateral wall on the PET image. The attenuation correction from the average and from the intensity-maximum cine CT images reduced the defect by 20% and 60%, respectively. In the patient studies, 77% of the cases using the average of the cine CT images had acceptable alignment and 88% of the cases using the intensity maximum of the cine CT images had acceptable alignment. CONCLUSION: Cine CT offers an alternative to helical CT for compensating for respiratory motion in the attenuation correction of cardiac PET studies. Phantom studies suggest that the average and the intensity maximum of the cine CT images can reduce potential respiration-induced misalignment errors in attenuation correction. Patient studies reveal that cine CT provides acceptable alignment in most cases and suggest that the intensity-maximum cine image offers a more robust alternative to the average cine image.     

Prostate development in prune belly syndrome (PBS) and posterior urethral valves (PUV): etiology of PBS--lower urinary tract obstruction or primary mesenchymal defect?

Prune belly syndrome (PBS) has been recognized since 1950 as the triad of absent abdominal wall musculature, undescended testes, and urinary tract anomalies. The etiology, however, remains uncertain. Theories of mesenchymal maldevelopment, obstruction, and genetic origin have been proposed. To evaluate the role of lower urinary tract obstruction as it relates to prostatic development and PBS, we studied the lower urinary tract of 15 cases of PBS, 8 cases of posterior urethral valves (PUV), and 34 age-matched controls. It is generally accepted that prostatic growth and development are dependent on mesenchymal-epithelial interactions. We evaluated the mesenchymal and epithelial differentiation and relationships, and found distinctly different and consistent abnormalities between PBS and PUV as compared with one another and controls. The findings suggest that in PBS, prostatic growth and development are hindered because of destruction or absence of the appropriate primitive mesenchyme. Our studies could not definitely exclude very early obstruction as a cause of the findings because of lack of appropriate fetal material.     

Circulating antibodies to lung protein(s) in patients with cryptogenic fibrosing alveolitis.

BACKGROUND--It has been hypothesised that cryptogenic fibrosing alveolitis has an immunological pathogenesis mediated by T lymphocytes. It is, however, recognised that patients may show dysregulation of the humoral immune system and that the presence of large numbers of B lymphocytes in open lung biopsies may be associated with a poor prognosis. Evidence of a role for the humoral immune system in the pathogenesis of cryptogenic fibrosing alveolitis has been suggested, but attempts to demonstrate circulating immunoglobulin to antigen within the lung have been inconclusive. METHODS--Plasma samples from 22 patients with cryptogenic fibrosing alveolitis, 22 patients with sarcoidosis, and 17 healthy controls were screened by SDS-PAGE and Western blotting for the presence of autoantibodies to lung proteins derived from cryptogenic fibrosing alveolitis, sarcoid and control lung tissue, as well as four normal non-pulmonary tissues. Possible site(s) of target protein(s) within the lung tissue were identified by immunohistochemical examination using IgG purified from the plasma of six patients and two controls. RESULTS--Eighteen of the plasma samples from patients with cryptogenic fibrosing alveolitis had reactive IgG to lung protein(s) in the 70-90 kDa molecular weight range compared with five of 18 plasma samples from patients with sarcoidosis and one of 17 controls. Plasma from patients with cryptogenic fibrosing alveolitis recognised antigen(s) of the same molecular weight in control and sarcoid lung tissue, but not non-pulmonary tissues, with a similar frequency. Immunohistochemical staining of cryptogenic fibrosing alveolitis biopsy material using IgG purified from plasma samples from patients with cryptogenic fibrosing alveolitis, but not control samples, revealed fine linear positivity in the lung parenchyma in a pattern suggestive of reaction with alveolar lining cells. The pattern was cytoplasmic/membranous and not nuclear. CONCLUSIONS--Patients with cryptogenic fibrosing alveolitis have a high frequency of plasma IgG autoantibodies to protein(s) within lung tissue associated with alveolar lining cells. This is believed to be the site where immunological injury occurs in cryptogenic fibrosing alveolitis, but the significance of these antibodies to the aetiology and pathogenesis is as yet unclear.     

Prostate Development in Prune Belly Syndrome (PBS) and Posterior Urethral Valves (PUV): Etiology of PBS-Lower Urinary Tract Obstruction or Primary Mesenchymal Defect?

Prune belly syndrome (PBS) has been recognized since 1950 as the triad of absent abdominal wall musculature, undescended testes, and urinary tract anomalies. The etiology, however, remains uncertain. Theories of mesenchymal maldevelopment, obstruction, and genetic origin have been proposed. To evaluate the role of lower urinary tract obstruction as it relates to prostatic development and PBS, we studied the lower urinary tract of 15 cases of PBS, 8 cases of posterior urethral values (PUV), and 34 age-matched controls. It is generally accepted that prostatic growth and development are dependent on mesenchymal-epithelial interactions. We evaluated the mesenchymal and epithelial differentiation and relationships, and found distinctly different and consistent abnormalities between PBS and PUV as compared with one another and controls. The findings suggest that in PBS, prostatic growth and development are hindered because of destruction or absence of the appropriate primitive mesenchyme. Our studies could not definitely exclude very early obstruction as a cause of the findings because of lack of appropriate fetal material.