Injury of polyester grafts by vascular clamps

Protected vascular clamps are not new. Clamp associated damage of human arteries has already been published over 20 years ago. The necessity of protective clamps seems to have been forgotten. In our explant archive (230 explants) we have observed an accumulation of graft ruptures in the groin (13 of 25 ruptures). We presume a multifactorial process. Clamp damage could be part of it. The aim of this study is to prove the clamp induced damage of polyester vascular grafts and to examine whether protected clamps can reduce this. METHOD: Five unprotected (Aesculap(R) FB512R, FB502, FB517, Ulrich CC1235, CV3535) and 5 protected vascular clamp types (Aesculap(R) FB667, FB668, Edwards(R) - formally Baxter(R) - Fogarty(R) CV5050, CV5201, Edwards(R) Cosgrove(R) CV1033) were tested. A longitudinal burst test was performed after maximal clamp closure on 6 different, multifilament polyester yarns of 2 different vascular grafts manufacturers (B. Braun(R), Edwards(R)). RESULTS: The yarn tests with protected clamps showed no difference to those of the unclamped yarns. After clamping with unprotected vascular clamps the stress-strain-diagrams differed significantly. The mean, maximum burst strength was up to 75 % lower. Video documentation revealed filament ruptures. Damage of the yarn surface was seen on a simple woven graft in scanning electron microscopy (SEM). DISCUSSION: The application of unprotected vascular clamps on polyester vascular grafts is common in Germany (56 %). The observed damage of multifilament polyester yarns makes it necessary to re-consider the use of unprotected vascular clamps. The benefit for biological vessels has already been shown.     

Frame dislocation of body middle rings in endovascular stent tube grafts.

OBJECTIVES: To understand the cause, and propose a mechanism for frame dislocation in endovascular grafts. MATERIALS AND METHODS: Five tube grafts were explanted due to secondary distal leakage 15-21 months after operation. One bifurcated graft was removed during emergency operation after aortic rupture caused by secondary leakage. A second bifurcated graft was harvested from a patient with thrombotic occlusion of one limb, who died after transurethral prostatic resection. The inside of the grafts were examined endoscopically. The stent was inspected after removal of the fabric, broken ligatures were counted and examined by scanning electron microscopy. The fabric strength was tested by probe puncture. RESULTS: We found 17-44% of the stent ligatures of the body middle rings to be loose. The knots were intact. Degradation of the polyester textile was not observed. CONCLUSIONS: Continuous movements in the grafted aorta and blood pressure impose permanent stress to the stent frame and the polyester fabric resulting in morphological changes in the body middle ring of grafts. The clinical implications of the suture breakages are unknown although they may be related to distal secondary leakage in tube grafts.     

Placement of pedicle screws using different navigation systems. A laboratory trial with 12 spinal preparations

A well-known problem occurring with thoracolumbar spondylodesis is the perforation of pedicle screws through the pedicle wall. It occurs in up to 40% of the implanted screws. To reduce this problem, computed tomography (CT)-based navigation systems have been introduced, which allow the surgeon multidimensional control of the screw position in virtual reality and real time during insertion. In the recent past, fluoroscopy-based navigation systems have also been built. We inserted 77 pedicle screws in human lumbar cadaveric spine specimens either without navigation, with CT-based navigation, or with fluoroscopy-based navigation. In the critical sizes of pedicles between 6.5 and 9 mm, we found the best results with CT-based navigation, but there was no significant difference between the three methods. The minimal pedicle and the screw diameters should be reported in every study on pedicle screw misplacement and spine navigation since they represent the most important factor in pedicle wall perforations.     

Bone-patellar tendon-bone grafts for anterior cruciate ligament reconstruction: an in vitro comparison of mechanical behavior under failure tensile loading and cyclic submaximal tensile loading

BACKGROUND: Secure fixation is an important factor in the success of anterior cruciate ligament reconstruction. HYPOTHESIS: There is no difference in the mechanical behavior of reconstructions from method of fixation or method of testing. STUDY DESIGN: Controlled laboratory study. METHODS: Anterior cruciate ligament reconstructions were performed with bone-patellar tendon-bone grafts in 48 human cadaveric knees. Three different fixation methods (Endobutton, interference screw, suture-post fixation) were compared under failure tensile loading and cyclic submaximal tensile loading. RESULTS: No difference was observed in ultimate load among the three techniques. Stiffness of the grafts was significantly lower for the suture technique than for the interference screw technique. Cyclic loading revealed significantly different failure rates: 0% of the Endobutton, 38% of the interference screw, and 100% of the suture-post groups. The relative movement of the femoral bone plug and the migration of the bone plug out of the femoral canal were lowest in the interference screw group. CONCLUSIONS: The suture-post fixation is not recommended. The interference screw technique showed the best results, but results were age-dependent, suggesting its best use is in younger patients. The Endobutton technique is recommended for older patients. Clinical Relevance: Results of testing are useful to the surgeon in making a choice of reconstruction technique.     

Partial withdrawal of levothyroxine treated disease leads to brain activations and effects on performance in a working memory task: A pilot study

Hypothyroidism is associated with memory impairments. The present study aimed to evaluate the effects of partial withdrawal of levothyroxine on working memory tasks and brain function. Fifteen subjects under long‐term levothyroxine substitution as a result of complete hypothyroidism participated in the present study. Functional magnetic resonance imaging (MRI) was performed using a working memory task (n‐back task) and neuropsychological tests were performed before and 52‐54 days after the induction of subclinical hypothyroidism by reducing the pretest levothyroxine dosage by 30%. Reaction time of subjects under partial levothyroxine withdrawal was significantly longer and less accurate with respect to solving the working memory tasks. Functional MRI revealed significant activation changes after medication withdrawal in the cerebellum, insula, parietal, frontal, temporal and occipital lobes, lingual gyrus, and the cuneus. Partial withdrawal of levothyroxine may lead to deficits in a working memory task and to an activation of brain areas associated with working memory ability.     

New directions in research on assertive community treatment

Evaluation of assertive community treatment programs has demonstrated that they are highly effective in reducing the need for psychiatric hospitalization of chronic mentally ill patients. However, the programs also tend to cost more than traditional outpatient care, and their impact on other areas of patient functioning is not clear. The authors believe more rigorous studies of the programs are needed before policymakers can properly evaluate their role in the overall mix of services. Future studies should extend previous research by comparing the programs to current state-of-the-art treatment in community mental health centers or county mental health programs; assessing the total system costs of assertive community treatment programs, as well as the amount of cost shifting by payers; analyzing outcomes of clients in mature programs over longer time periods; standardizing the measurement of various client outcomes; and determining the impact of individual program elements--alone and in combination--on different subgroups of clients.     

Horizontal and Vertical Integration-Diversification in Rural Hospitals: A National Study of Strategic Activity, 1983–1988

Abstract: This study examines both the magnitude of and factors influencing the adoption of 13 horizontal and vertical integration and diversification strategies in a national sample of 797 U.S. rural hospitals during the period 1983–1988. Using organization theory, hypotheses were posed relating environmental and market factors, geographic location, and hospital characteristics to the adoption of horizontal and vertical integration and diversification. Results indicate that only one of 13 strategies was adopted by more than 50 percent of all rural hospitals during the study period, and that most of the directional hypotheses were not confirmed using Cox's proportional hazards models. In particular, environmental and market factors were unrelated to the strategies studied. Issues of methodology and theory are discussed; however, during an historically turbulent period, both relatively low levels of rural hospital strategic activities and lack of predictive power of the theory suggest caution in relying heavily on a policy for rural hospital survival that is dependent on individual market-oriented strategic behavior.