Ultrafast nonlinear optical studies of silicon nanowaveguides

Results of a self-consistent ultrafast study of nonlinear optical properties of silicon nanowaveguides using heterodyne pump-probe technique are reported. The two-photon absorption coefficient and free-carrier absorption effective cross-section were determined to be 0.68cm/GW, and 1.9x10(-17) cm2, respectively and the Kerr coefficient and free-carrier-induced refractive index change 0.32x10(-13) cm2/W, and -5.5x10(-21) cm3, respectively. The effects of the proton bombardment on the linear loss and the carrier lifetime of the devices were also studied. Carrier lifetime reduction from 330ps to 33ps with a linear loss of only 14.8dB/cm was achieved using a proton bombardment level of 10(15)/cm2.

Can the reparability of meniscal tears be predicted with magnetic resonance imaging?

BACKGROUND

Historically, magnetic resonance imaging (MRI) has been very useful in diagnosing meniscal tears but not as valuable in predicting whether a meniscal tear is reparable. Given that several recent studies suggested that MRI can be used to predict tear reparability, the topic has resurfaced as a controversy in the orthopaedic and radiology literatures.

HYPOTHESIS

Experienced musculoskeletal radiologists can use MRI to predict the reparability of meniscal tears with good to excellent accuracy using the same arthroscopic criteria used by surgeons intraoperatively.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

Fifty-eight patients with meniscal tears treated with repair were matched by age and sex with 61 patients with tears treated with meniscectomy. Two senior musculoskeletal radiologists independently and blindly reviewed preoperative MRI of these 119 meniscal tears. Using established arthroscopic criteria, the radiologists were asked to grade each tear 0 to 4, with 1 point for each of the following: a tear larger than 10 mm, within 3 mm of the meniscosynovial junction, greater than 50% thickness, and with an intact inner meniscal fragment. Only a tear with a score of 4 would be predicted to be reparable.

RESULTS

The 2 radiologists' ability to correctly estimate reparability was poor, with 58.0% and 62.7% correct predictions (κ = 0.155 and 0.250, respectively). Interrater reliability assessment showed that the raters agreed on a score of 4 (reparable) versus <4 (not reparable) 73.7% of the time (κ = 0.434) but came to identical scores only 38.1% of the time (κ = 0.156). Determining the status of the inner fragment was the most predictive individual criterion and the only one to reach statistical significance (χ(2) = 14.9, P <.001).

CONCLUSION

Magnetic resonance imaging is not an effective or efficient predictor of reparability of meniscal tears with the current arthroscopic criteria.

Accuracy of magnetic resonance imaging in determining the presence and size of recurrent rotator cuff tears

We attempted to assess the accuracy of magnetic resonance imaging (MRI) in determining the size of recurrent cuff tears in correlation with size measured at surgery. Thirty-seven shoulders in 33 patients who had reoperation for a presumed failed rotator cuff repair were retrospectively evaluated. All patients had preoperative MRI, the results of which were read by a musculoskeletal radiologist to determine the presence of a tear and to estimate its size. All tears were measured intraoperatively in sagittal and coronal planes. Thirty-three shoulders had recurrent tears of the rotator cuff, and MRI correctly identified the presence of 30 of them. MRI correctly identified only 1 of the 4 patients without a recurrent tear of the cuff. The correlation coefficient for MRI accurately defining the size of cuff tears was 0.46. The sensitivity of MRI for the diagnosis of retear was 91%, and the specificity was 25%. MRI is accurate in diagnosing a recurrent full-thickness cuff tear in postsurgical shoulders. However, it is relatively inaccurate in correctly defining the size of the tear. MRI also has a tendency to overdiagnose cuff tears in postsurgical patients with continued pain and symptoms.

Quality of life assessment in elite collegiate athletes

The objectives of this study were to establish baseline Medical Outcomes Study Short Form Health Survey (SF-36) data for Division I collegiate athletes and to determine the effects of injury severity and training time. All participating athletes (N = 562) at a major university were evaluated with the SF-36. Regression analysis was performed to identify predictive factors. When the men without injury were compared with a previously established norm group, there was a significant increase in the role emotional score. In the women without injury there were significant increases in mental component summary, physical function, role emotional, mental health, and vitality scores when compared with the norm group. Serious injury was a predictor of lower scores in all domains, whereas minimal injury was predictive of lower physical component summary, role physical, bodily pain, social function, and general health scores. Increased training time was predictive of higher mental component summary, role physical, vitality, and general health scores. Elite collegiate athletes scored differently from previously established age-matched norms, and injury was a strong predictor of lower scores.

Biomechanics of the coracoclavicular ligament complex and augmentations used in its repair and reconstruction

Augmentation is a well-accepted and common component of coracoclavicular ligament repairs and reconstructions. The purpose of this study was to examine and compare the strength, stiffness, and mode of failure of the coracoclavicular ligament complex and four different augmentation techniques in cadaveric shoulders. There was no significant difference in the mean failure load between the intact ligament complex (724.9+/-230.9 N) and augmentations performed with braided polydioxanone (PDS) (676.7+/-115.4 N) or braided polyethylene placed through (986.1+/-391.1 N) or around (762.7+/-218.2 N) the clavicle. The mean failure load for augmentations using a 6.5-mm cancellous screw through the clavicle and into a single cortex of the coracoid (390.1+/-253.6 N) was significantly lower than that for the intact coracoclavicular ligaments. There was no difference in mean stiffness between the intact coracoclavicular ligament complex (115.9+/-36.2 N/mm) and the braided polyethylene augmentations placed through (99.8+/-22.2 N/mm) or around (90.0+/-25.5 N/mm) the clavicle. Polydioxanone augmentations were significantly less stiff (27.4+/-3.3 N/mm) than the intact complex, while screw augmentations were significantly stiffer (250.4+/-88.2 N/mm). There were no significant differences in strength or stiffness of braided polyethylene reconstructions placed around or through a drill hole in the clavicle.