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Notchplasty, resection of bone from the roof and lateral side of the inter-condylar notch, is frequently performed during anterior cruciate ligament (ACL) reconstruction to avoid abrasion or deflection of the ACL graft by the femur (graft impingement). Graft impingement can develop months after the initial reconstruction despite adequate notchplasty. Such impingement has recently been attributed to fibrocartilage overgrowth of the notchplasty site. The objectives of this study were to evaluate the MR appearance of the notchplasty site immediately after surgery and 6 months later and to investigate whether cartilage overgrowth of the notchplasty site can be detected with MR imaging.Thirty-three patients who underwent bone-tendon-bone autograft ACL reconstruction had MR scans of the intercondylar notch 6 months after surgery. Twenty-five of these patients also had MR scans in the immediate postoperative period. The appearance of the notchplasty site and evidence for cartilage overgrowth of the notchplasty site were evaluated. Arthroscopic correlation was available for six patients.On MR images, the margins of the notchplasty site were identified in all patients. Contour of the notchplasty site along the lateral notch wall was frequently concave toward the notch, a finding not commonly seen in an unoperated notch. Six months later, the shape of the notchplasty site had not changed, but evidence for recortication of the notchplasty site (seen as a layer of signal void 0.5-1.5 mm in thickness over the previously exposed cancellous bone) was seen in 94% of the patients. Additionally, a second layer of signal void, 1-5 mm in thickness with signal intensity identical to that of hyaline cartilage, was seen overlying the notchplasty site in 64% of patients. Arthroscopic correlation available in six patients suggested that this second layer represented fibrocartilage overgrowth of the notchplasty site.Characteristic changes of the intercondylar notch after notchplasty can be seen on MR images. This preliminary study also suggests that a thin layer of cortical bone forms over the notchplasty site in most patients within 6 months of surgery. Perhaps more significantly, overgrowth of the notchplasty site by fibrocartilage may also be detected in some patients. Further experience is needed to determine whether MR imaging is a useful method for identifying cartilage overgrowth after notchplasty.

Objective. —To test the hypothesis that a reduction of 1000 ppm or more of lead in soil accessible to children would result in a decrease of at least 0.14 μmol/L (3 μg/dL) in blood lead levels. Setting. —Urban neighborhoods with a high incidence of childhood lead poisoning and high soil lead levels. Design. —Randomized controlled trial of the effects of lead-contaminated soil abatement on blood lead levels of children followed up for approximately 1 year after the intervention. Patients. —A total of 152 children less than 4 years of age with venous blood lead levels of 0.34 to 1.16 μmol/L (7 to 24 μg/dL). Children were largely poor and had a mean age at baseline of 32 months, a mean blood lead level of 0.60 μmol/L (12.5 μg/dL), and a median surface soil lead level of 2075 ppm. Interventions. —Children were randomized to one of three groups: the study group, whose homes received soil and interior dust abatement and loose paint removal; comparison group A, whose homes received interior dust abatement and loose paint removal; and comparison group B, whose homes received only interior loose paint removal. Main Outcome Measures. —Change in children's blood lead levels from preabatement levels to levels approximately 6 and 11 months after abatement. Results. —The mean decline in blood lead level between preabatement and 11 months after abatement was 0.12 μmol/L (2.44 μg/dL) in the study group (P=.001), 0.04 μmol/L (0.91 μg/dL) in group A (P=.04), and 0.02 μmol/L (0.52 μg/mL) in group B (P=.31). The mean blood lead level of the study group declined 0.07 μmol/L (1.53 μg/dL) more than that of group A (95% confidence interval [CI], -0.14 to -0.01 μmol/L [-2.87 to -0.19 μg/dL]) and 0.09 μmol/L (1.92 μg/dL) more than group B (95% CI, -0.16 to -0.03 μmol/L [-3.28 to -0.56 μg/dL]). When adjusted for preabatement lead level, the 11-month mean blood lead level was 0.06 μmol/L (1.28 μg/dL) lower in the study group as compared with group A (P=.02) and 0.07 μmol/L (1.49 μg/dL) lower than in group B (P=.01 ). The magnitude of the decline independently associated with soil abatement ranged from 0.04 to 0.08 μmol/L (0.8 to 1.6 μg/dL) when the impact of potential confounders, such as water, dust, and paint lead levels, children's mouthing behaviors, and other characteristics, was controlled for. Conclusions. —These results demonstrate that lead-contaminated soil contributes to the lead burden of urban children and that abatement of lead-contaminated soil around homes results in a modest decline in blood lead levels. The magnitude of reduction in blood lead level observed, however, suggests that lead-contaminated soil abatement is not likely to be a useful clinical intervention for the majority of urban children in the United States with low-level lead exposure. (JAMA. 1993;269:1647-1654)

Etude de la pyrolyse du (E)-methyl-2 phenyl-2 neopentyl-3 dibenzo [5,6:7,8] sila-2bicyclo [2.2.2] octane en presence de methoxy trimethyl silane

The reaction of two equivalents of vinyldimethylethoxysilane or vinyldimethylmethoxysilane with hydrocarbon soluble alkyllithium reagents; t -BuLi, s -BuLi, or n -BuLi; in hexane at low temperature gives high yields of 1,1-dimethyl-2-alkyl-4-(dimethylalkoxysilyl)silacyclobutanes. With methyl- or phenyllithium substituted vinylsilanes are obtained. The stereochemistry of the silacyclobutanes is assigned on the basis of Si-29 and H-1 NMR. For vinyldimethylethoxysilane the ratio of cis to trans silacyclobutane is about 57 43 , and is independent of the alkyllithium reagent used. In the reaction of vinyldimethylmethoxysilane with t -BuLi a sol70 30 ratio of the cis and trans silacyclobutane is obtained. A pathway is proposed which is consistent with the stereochemical results and with the products isolated in the reaction run in THF.

Translation diffusion coefficients have been measured for oxyhemoglobin A and oxyhemoglobin S over the concentration range 0.1–37 g/dl by means of photon correlation spectroscopy. The solutions were 0.1 M in KCl and in each case the pH was adjusted to the isoelectric point of the hemoglobin species present. No significant differences were found between the HbA and HbS results; and after correction to water at 20°C, the diffusion coefficients could be described by the equation where Do = (6.93 ± 0.06) × 10−7 cm2/sec and c ids the concentration in units of g/dl. No evidence was found for the aggregation of oxy-HbS at high concentrations which was reported by Lindstrom et. al. [(1976) Biophys. J.16, 679–689].