Plaster of Paris as an osteoconductive material for interbody vertebral fusion in mature sheep.

STUDY DESIGN: In adult female sheep, histologic and biomechanical criteria were used to determine whether the osteoconductive performance of plaster of paris would promote the incorporation of the tubular titanium mesh implants used for interbody vertebral fusions. OBJECTIVES: To compare the osteogenicity of plaster of paris with that of autogenous iliac crest bone and bone marrow 6 months after they were loaded into tubular titanium mesh cages and implanted as L3-L5 bridges after L4 corpectomies. SUMMARY OF BACKGROUND DATA: One of the aims of surgery for vertebral pathology is to stabilize the spine by interbody fusions. The morbidity associated with the use of iliac crest autograft bone for fusion grafts prompted trials using plaster of paris as an osteoconductive substrate. METHODS: The total volume of bone that invested the L3-L5 mesh cages after 6 months was quantitated by computed tomography scans. All specimens subsequently were cut into fusion mass segments for biomechanical testing in flexion, extension, compression, and torsion, and then embedded in plastic for sectioning and histomorphometry to determine the trabecular bone volume within the titanium mesh. RESULTS: In each experimental model, implants of plaster of paris were the osteoconductive equal of autogenous iliac crest bone/marrow preparations. The volumes of bone formed around and within the titanium mesh were identical, and the tissues were biomechanically indistinguishable. A partial mechanism was determined by modifying the system for midshaft femoral defects. CONCLUSIONS: In the sheep, a tubular titanium mesh packed with plaster of paris forms an osteoconductive conduit to achieve a biomechanically stable interbody lumbar vertebral fusion.

Percutaneous dissolution of gallstones.

Contact dissolution with MTBE is an effective and safe method to treat symptomatic patients with cholesterol gallstones. Personnel, time, and safety factors have limited widespread use of the procedure. With current competing methods to treat gallstones, it is likely that MTBE use will be reserved for those patients who elect percutaneous therapy due to fear of surgery or anesthesia and in those elderly patients who are compromised by underlying medical conditions.

Increased blood levels of methyl tert-butyl ether but not of ethyl propionate during instillation with contact gallstone dissolution agents in the pig.

We performed experiments in anesthetized piglets with two cholesterol gallstone solvents, methyl tert-butyl ether and ethyl propionate, to determine whether blood levels of either solvent would increase during gallbladder instillation of these solvents under conditions simulating gallstone dissolution. The solvent was oscillated rapidly in and out of the gallbladder with a computer-controlled syringe pump; intraluminal pressure was set below the leakage pressure, and oscillating volume was set below the leakage volume to decrease loss of solvent into the intestine. Blood levels were measured with gas chromatography. Six piglets received methyl tert-butyl ether, and six piglets received ethyl propionate. During 2 hr of instillation with methyl tert-butyl ether, blood levels increased steadily to concentrations averaging 0.3 ml/L blood at 2 hr; during a 6-hr period of instillation, blood levels rose to above 0.4 ml/L blood. Replacement of methyl tert-butyl ether with saline solution in the gallbladder caused blood levels to decline gradually; plasma levels decreased by half in 90 min. In contrast, when ethyl propionate was infused for 2 or 6 hr, blood levels remained below the detection limit, probably because of high first-pass hepatic extraction. We conclude that, under conditions simulating those likely present in patients undergoing contact dissolution of gallbladder stones, the two solvents differ: Ethyl propionate is removed so rapidly from blood that its levels remain undetectable, whereas methyl tert-butyl ether levels in blood (and, presumably, peripheral tissues) increase continuously.(ABSTRACT TRUNCATED AT 250 WORDS)

Contact dissolution of cholesterol gallstones with organic solvents.

Contact dissolution of cholesterol gallstones with organic solvents is emerging as a rapid, safe, alternative treatment for symptomatic cholesterol gallbladder stones. Placement of a percutaneous transhepatic catheter into the gallbladder is a rapid and safe technique. The availability of safe, effective cholesterol solvents and solvent transfer devices means that cholesterol gallbladder stones can be eliminated rapidly and safely by CDOS, without the risk of general anesthesia or surgical dissection of the gallbladder bed. Patients with single gallstones are better candidates for CDOS than are patients with multiple gallstones because recurrence after dissolution is less common. Contact dissolution may well be judged the treatment of choice by the medical-surgical gallstone management team in some patients.

Continuous speech recognition in MR imaging reporting: advantages, disadvantages, and impact.

OBJECTIVE: Our objective was to describe our experience with a commercially available continuous speech recognition system, highlighting the advantages, disadvantages, and costs compared with those of conventional transcription for MR imaging reports. MATERIALS AND METHODS: Data from 5072 reports generated in our MR imaging section during a 9-month period after the implementation of a commercial continuous speech recognition system were compared with 4552 reports produced during the same period 1 year earlier. Information pertaining to the use of continuous speech recognition, report turnaround time, word recognition rate, report appearance, and equipment costs was collected. RESULTS: After its system installation, continuous speech recognition was used to dictate 81.8% of all reports. The mean report turnaround time decreased from 87.8 to 43.6 hr, and report availability at 24 hr increased from 10.5% to 62.5%. The system was found to have an average word recognition accuracy of 92.7% for spontaneous dictation. Mean report length declined from 95 to 60 words, with an increase in spacing errors from 0.3 to 8.0 per 1000 words and a decrease in spelling errors from 3.0 to 0.8 per 1000 words. Initial hardware and software costs were approximately $10,000, compared with a yearly cost of $12,000 for human transcription. CONCLUSION: Although the technology is still evolving and was evaluated in its earliest implementation stages, continuous speech recognition nonetheless markedly improved report turnaround time and proved cost-effective.

Magnetic resonance imaging of the upper airway. Effects of propofol anesthesia and nasal continuous positive airway pressure in humans.

BACKGROUND: Anesthetic agents inhibit the respiratory activity of upper airway muscles more than the diaphragm, creating a potential for narrowing or complete closure of the pharyngeal airway during anesthesia. Because the underlying mechanisms leading to airway obstruction in sleep apnea and during anesthesia are similar, it was hypothesized that anesthesia-induced pharyngeal narrowing could be counteracted by applying nasal continuous positive airway pressure (CPAP). METHODS: Anesthesia was induced in ten healthy volunteers (aged 25-34 yr) by intravenous administration of propofol in 50-mg increments every 30-s to a maximum of 300 mg. Magnetic resonance images of the upper airway (slice thickness of 5 mm or less) were obtained in the awake state, during propofol anesthesia, and during administration of propofol plus 10 cm nasal CPAP. RESULTS: Minimum anteroposterior diameter of the pharynx at the level of the soft palate decreased from 6.6 +/- 2.2 mm (SD) in the awake state to 2.7 +/- 1.5 mm (P < 0.05) during propofol anesthesia and increased to 8.43 +/- 2.5 mm (P < 0.05) after nasal CPAP application. Anteroposterior diameter of the pharynx at the level of the dorsum of the tongue increased from 7.9 +/- 3.5 mm during propofol anesthesia to 12.9 +/- 3.6 mm (P < 0.05) after nasal CPAP. Pharyngeal volume (from the tip of the epiglottis to the tip of the soft palate, assuming this space to be a truncated cone) significantly increased from 2,437 +/- 1,008 mm3 during propofol anesthesia to 5,847 +/- 2,827 mm3 (P < 0.05) after nasal CPAP application. CONCLUSIONS: In contrast to the traditional view that relaxation of the tongue causes airway obstruction, this study suggests that airway closure occurs at the level of the soft palate. Application of nasal CPAP can counteract an anesthesia-induced pharyngeal narrowing by functioning as a pneumatic splint. This is supported by the observed reduction in anteroposterior diameter at the level of the soft palate during propofol anesthesia and the subsequent increase in this measurement during nasal CPAP application.

Percutaneous intraluminal US in the gallbladder and bile ducts.

The authors describe their initial experience with a dedicated intraluminal ultrasound (US) device that was coupled to a catheter and introduced percutaneously into the gallbladder and/or bile ducts. Access was created with interventional radiologic techniques in 22 patients and at laparoscopy in four patients. Thirty-one examinations in 26 patients revealed information on normal anatomy, pathologic processes, and responses to therapy. The pathologic processes seen included bile duct and gallbladder debris, stones, ductal strictures, and tumors. Additional information provided with this technique over other diagnostic studies included differentiation of intraluminal filling defects, examination of areas inaccessible to conventional imaging, and observations about the walls of the ducts and gallbladder. Percutaneous US examination of metallic stents within the bile ducts and of filling defects in the ducts at laparoscopic cholecystectomy was of particular interest and altered subsequent therapy. The procedure is simple, straightforward, and devoid of complications. While refinements and improvements are needed, this diagnostic technique holds promise.

Effect of replacement therapy with cholylsarcosine on fat malabsorption associated with severe bile acid malabsorption. Studies in dogs with ileal resection.

The efficacy of cholylsarcosine, a synthetic deconjugation-resistant and nonsecretory conjugated bile acid analog for the treatment of fat malabsorption caused by severe bile acid malabsorption, was assessed in an animal model. In two dogs, the ileum and ileocecal valve were resected, causing severe diarrhea, steatorrhea, bile acid malabsorption, and progressive weight loss. Cholylsarcosine was administered as the water-soluble sodium salt by mixing with the dog food. Various doses were explored as well as varying intakes of dog food. Fat absorption was assessed by gravimetric measurement of fecal fat; a nonabsorbable recovery marker (polyethylene glycol mol wt 4000) was used to correct for incomplete fecal collections. Cholylsarcosine caused a 5- to 30-fold increase in fat absorption but had no significant effect on weight loss or fecal weight. Duodenal content was collected during digestion of a meal via a surgically placed Thomas cannula; the aspirates were dilute, acidic, and had a low bile acid concentration. The bile acid concentration increased modestly when cholylsarcosine was administered, but remained below the critical micellization concentration. The results indicate that oral administration of cholylsarcosine improved dietary fat absorption in a canine model of severe bile acid malabsorption with associated steatorrhea and bile acid deficiency in the proximal small intestine. Studies with this compound in patients with nutritional problems because of steatorrhea and severe bile acid malabsorption appear warranted.

Successful topical dissolution of cholesterol gallbladder stones using ethyl propionate.

Topical dissolution of cholesterol gallbladder stones using methyl tert-butyl ether (MTBE) is useful in symptomatic patients judged too ill for surgery. Previous studies showed that ethyl propionate (EP), a C5 ester, dissolves cholesterol gallstones rapidly in vitro, but differs from MTBE in being eliminated so rapidly by the liver that blood levels remain undetectable. Our aim was to test EP as a topical dissolution agent for cholesterol gallbladder stones. Five high-risk patients underwent topical dissolution of gallbladder stones by EP. In three patients, the solvent was instilled via a cholecystostomy tube placed previously to treat acute cholecystitis; in two patients, a percutaneous transhepatic catheter was placed in the gallbladder electively. Gallstone dissolution was assessed by chromatography, by gravimetry, and by catheter cholecystography. Total dissolution of gallstones was obtained in four patients after 6-10 hr of lavage; in the fifth patient, partial gallstone dissolution facilitated basketing of the stones. In two patients, cholesterol dissolution was measured and averaged 30 mg/min. Side effects were limited to one episode of transient hypotension and pain at the infusion site; no patient developed somnolence or nausea. Gallstone elimination was associated with relief of symptoms. EP is an acceptable alternative to MTBE for topical dissolution of cholesterol gallbladder stones in high-risk patients. The lower volatility and rapid hepatic extraction of EP suggest that it may be preferable to MTBE in this investigational procedure.

Acute effects of topical methyl tert-butyl ether or ethyl propionate on gallbladder histology in animals: a comparison of two solvents for contact dissolution of cholesterol gallstones.

Experiments were performed in anesthetized rabbits and piglets to assess gallbladder mucosal injury during irrigation with methyl tert-butyl ether, a C5 ether, or ethyl propionate, a C5 ester--two organic solvents used in the contact dissolution of cholesterol gallstones. In 44 New Zealand White rabbits, the gallbladder was exposed to individual solvents or saline solution through a transhepatic catheter for 2 hr. Gallbladders were then harvested and fixed immediately or after a recovery period of 1, 4 or 8 days. Tissue sections were examined under light microscopy, and severity of injury was graded with predefined criteria by two pathologists blinded to the animals' treatment regimens. Histological assessment showed severe mucosal injury such as necrosis of the cells at the villus tips immediately after 2 hr of exposure to either solvent. After 4 days, injury had decreased significantly; after 8 days, complete mucosal healing had taken place. A similar study was performed in 32 piglets. Solvent or saline solution was oscillated in and out of the gallbladders of these piglets with a computer-controlled syringe pump at a pressure less than the leakage pressure of the gallbladder. Histological assessment was performed on tissue samples obtained immediately after the procedure or 8 days later. Both solvents caused severe mucosal injury; however, after 8 days complete mucosal healing had occurred, so that gallbladders exposed to solvent were indistinguishable from gallbladders exposed to saline solution, which was used as control. We conclude that both methyl tert-butyl ether and ethyl propionate cause moderate to severe epithelial injury but that the gallbladder epithelium regenerates within a few days.(ABSTRACT TRUNCATED AT 250 WORDS)

Torsional injury resulting in disc degeneration: I. An in vivo rabbit model.

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.