Surgical treatment of acute arch dissection.

OBJECTIVES: Acute type A arch dissections are rare and no consensus has been reached on their surgical treatment. We studied perioperative risk factors for mortality in arch dissection patients. METHODS: Between October 1995 and October 2001, 108 patients with acute type A dissection were operated on, of whom 16 had acute arch dissections. Their mean age was 58 +/- 9 (44-77). Surgery involved total arch replacement in 4, hemiarch replacement in 10, and intimal tear repair with pledgeted sutures and ascending aortic replacement in 2. RESULTS: One patient who underwent total arch replacement died intraoperatively due to bleeding. Both patients who underwent ascending aortic replacement and primary repair of arch tears died 2 days postoperatively, 1 due to bleeding, and the other due to multiorgan failure. In-hospital mortality was thus 18.75%, or 3 of 16. All 3 had cardiac tamponade preoperatively. The 13 survivors were discharged after a mean hospital stay of 11 +/- 6 days. Mean follow-up was 38 +/- 25 months, from 3 months to 6 years. One patient died due to graft infection 3 months postoperatively, but the remaining 12 remain in good condition. Univariate predictors of in-hospital mortality were the type of surgery (primary intimal tear repair) (p = 0.027) and preoperative cardiac tamponade (p = 0.007). CONCLUSION: Surgical treatment of acute type A-arch dissections can be done with reasonable mortality and mid-term survival comparable with those of other subgroups with acute type A dissection. As with series of arch dissections, our patient population is too small to draw specific conclusions, but our experience leads us to conclude that the sites of intimal tears should be resected in acute type A arch dissection.     

Predictive value of conventional computed tomography in determining proximal extent of abdominal aortic aneurysms and possibility of infrarenal clamping

The present study aimed to evaluate the diagnostic reliability of computed tomography in determining the proximal extent of abdominal aortic aneurysms and the possibility of infrarenal clamping. Preoperative computed tomographic findings, together with the operative data for 95 patients, were retrospectively analyzed in light of the operative findings. Eighty-nine (93.68%) of the patients were men and 6 (6.32%) were women, with a mean age of 66.27 +/- 18.14 years. Diagnosis of infrarenal aneurysm by computed tomography was confirmed at the time of surgery in 91 (95.79%) of 95patients. The negative-predictive value of computed tomography in detecting supra-aneurysmal renal arteries was found to be 95.79%. The specificity was 98.91%. Infrarenal cross-clamping was performed in 59 (62.11%) of 95 patients, whose aortic segments between the renal artery orifices and the proximal borders of the aneurysms had a mean length of 26.4 +/- 7.11 mm by computed tomography Suprarenal clamping was required in 36 (37.89%) of the 95 patients, whose aortic segments had a mean length of 12.7 +/- 3.48 mm. We conclude that conventional computed tomography is reasonably accurate in determining the proximal extent of abdominal aortic aneurysms. Although there is a high rate of error in determining the possibility of infrarenal clamping when no specific measurements are taken, infrarenal clamping can be planned when measurement by computed tomography shows a length of > or = 26 mm between the renal arteries and the proximal extent of the aneurysm. In patients with shorter aortic segments, suprarenal aortic clamping should be considered.     

The Otto Aufranc Award: Demineralized Bone Matrix Around Porous Implants Promotes Rapid Gap Healing and Bone Ingrowth

Background  

Noncemented revision arthroplasty is often complicated by the presence of bone implant gaps that reduce initial stability and biologic fixation. Demineralized bone matrix has osteoinductive properties and therefore the potential to enhance gap healing and porous implant fixation.     

Effect of noninvasive low intensity ultrasound on bone growth into porous-coated implants

Noninvasive low intensity ultrasound has been shown to be an effective means of accelerating bone fracture healing in both animal and clinical studies. An in vivo canine study was designed to determine if noninvasive low intensity ultrasound could influence the rate and extent of bone growth into porous-coated implants. Twenty-two pairs of fully porous transcortical implants were inserted bilaterally into the femora of 12 dogs. In each dog, one femur served as a control and the other was subjected to daily ultrasound stimulation for 2, 3, or 4 weeks. Overall, the ultrasound-stimulated implants demonstrated an 18% increase in bone ingrowth compared with their contralateral controls (p = 0.02). Noninvasive low intensity ultrasound had its greatest effect in the first 2–3 weeks of stimulation. At 2 and 3 weeks, the ultrasound-stimulated implants showed 21 and 16% more ingrowth than their respective contralateral controls. Because noninvasive low intensity ultrasound had a positive effect on bone ingrowth in this experimental investigation, further research is suggested to assess the clinical potential for application to noncemented porous-coated total joint replacements.     

Ultrastructure of Mutants of Streptococcus mutans with Reference to Agglutination, Adhesion, and Extracellular Polysaccharide

An electron microscopic study of S. mutans 6715-13 wild type and representatives of three distinct classes of glucan synthesis-defective mutants (which fail to form adherent microbial plaques but agglutinate normally in the presence of exogenous glucans) disclosed the presence of two sucrose-dependent, glucanase-sensitive, extracellular components. In the wild type, these extracellular glucans had predominantly fibrillar (with some globular) morphologies. However, in the mutant strains, there was a consistent reduction in or loss of the fibrillar components and dramatic increases in globular forms. A cell surface-associated fuzzy coat was consistently seen, and it was neither sucrose-dependent nor glucanase-sensitive. The data indicated that in vitro and in vivo adhesion and virulence at smooth tooth surfaces (all these properties dramatically reduced in the mutants) were causally and functionally related to the extracellular, fibrillar, glucan component, whereas in vitro glucan-mediated agglutination may be related to the cell-associated surface fuzzy coat.     

Motor evoked potentials from transcranial stimulation of the motor cortex in humans

Electrical monitoring of the motor system offers the potential for the detection of injury, the diagnosis of disease, the evaluation of treatment, and the prediction of recovery from damage. Existing evoked potentials monitor one or another sensory modality, but no generally usable motor monitor exists. We have reported a motor evoked potential using direct stimulation of the spinal cord over the motor tracts in cats and in humans. To achieve a less invasive monitor, we used transcranial stimulation over the motor cortex in the cat, thus stimulating the motor cortex. We report here the initial application of this method to humans. A plate electrode over the motor cortex on the scalp and a second electrode on the palate direct a mild current through the motor cortex which will activate the motor pathways. This signal can be recorded over the spinal cord. It can elicit contralateral peripheral nerve and electromyographic signals in the limbs or movements when the appropriate stimulation parameters are used. In clinical use to date, this has been more reliable than the somatosensory evoked potential in predicting motor function in patients where the two tests differed. It offers a number of possibilities for the development of valuable brain and spinal cord monitoring techniques, but requires further animal studies and clinical experience. Studies to date have not demonstrated adverse effects, but evaluation is continuing.