Reamed locked intramedullary nailing for studying femur fracture and its complications.

Morbidity associated with femur fractures in polytrauma patients is known to be high. The many unsolved clinical questions include the immunological effect of the fracture and its fixation, timing of fracture fixation, management of fracture non-union, effect of infection and critical size of bone defects. The aim of this study was to establish a clinically-relevant and reproducible animal model with regards to histological, biomechanical and radiological changes during bone healing. A custom-designed intramedullary nail with interlocking system (RabbitNail, RISystem AG, Davos Platz, Switzerland) was used for fixation, following femur fracture. New Zealand White rabbits were assigned to two groups: 1. closed fracture model (CF; non-survival model: n = 6, survival model: n = 3) with unilateral mid-shaft femur fracture created by blunt force; 2. osteotomy model (OT; survival model: n = 14) with unilateral transverse osteotomy creating femur fracture. There were no intraoperative complications and full-weight bearing was achieved in all survival rabbits. Significant periosteal reaction and callus formation were confirmed from 2 weeks postoperatively, with a significant volume formation (739.59 ± 62.14 mm3) at 8 weeks confirmed by micro-computed tomography (µ-CT). 2 months after fixation, there was no difference between the osteotomised and contralateral control femora in respect to the maximum torque (3.47 ± 0.35 N m vs. 3.26 ± 0.37 N m) and total energy (21.11 ± 3.09 N m × degree vs. 20.89 ± 2.63 N m × degree) required to break the femur. The data confirmed that a standardised internal fixation technique with an intramedullary nail for closed fracture or osteotomy produced satisfactory bone healing. It was concluded that important clinically-relevant studies can be conducted using this rabbit model.

Bisphosphonate-ciprofloxacin bound to Skelite is a prototype for enhancing experimental local antibiotic delivery to injured bone.

BACKGROUND: The risk of osteomyelitis after open bone fracture may be reduced by locally applied antibiotics. ENC-41-HP (E41), which comprises ciprofloxacin linked to a 'bone seeking' bisphosphonate, loaded on to carrier Skelite calcium phosphate granules (E41-Skelite) has favourable in vitro characteristics for application to wounded bone. This study assessed E41-Skelite in a rat model of acute tibial osteomyelitis. METHODS: Mechanically induced tibial troughs were contaminated with approximately log10 4 colony forming units (c.f.u.) of Staphylococcus aureus (Cowan 1 strain) 'resistant' to E41 (minimum inhibitory concentration 8-16 microg/ml), lavaged and packed with Skelite alone, or with E41-Skelite slurry. Animals were killed at 24 h (n = 62), 72 h (n = 46) or 14 days (n = 12), and each tibia was assessed for S. aureus load (c.f.u./g tibia) and histological appearance (14 days only). RESULTS: At 24 and 72 h, the tibias of rats treated with E41-Skelite (n = 54) had a significantly lower mean (s.e.m.) load of S. aureus than animals that received Skelite alone (n = 54): log10 3.6(0.2) versus 6.4(0.1) c.f.u./g respectively at 24 h (P < 0.001, Mann-Whitney rank sum test) and log10 4.4(0.2) versus 6.6(0.1) c.f.u./g at 72 h (P < 0.001). At 14 days, E41-Skelite-treated tibias had fewer bacteria, no signs of osteomyelitis and histological signs of healing. CONCLUSION: E41-Skelite, a prototype granulated topical antibiotic delivery system, reduced the development of infection in experimental bone wounds.

Effect of the wicking behavior of multifilament sutures.

The purpose of this study was to compare the wicking propensity of multifilament sutures. Dexon II, Vicryl, and black silk suture (BSS) were dipped in saline or soaked for 48 h, then suspended on a microscope slide. Fluorescein isothiocyanate-dextran (FITC-D) was placed at the suture mid points, and its movement was observed using fluorescence microscopy. The experiment was repeated, replacing the FITC-D with mixture of S. salivarius and saline, incubating the suture specimens in culture medium, and evaluating microbial growth. Dipped sutures showed FITC-D movement in the Dexon II group only. All 48-h soaked sutures demonstrated FITC-D movement with significant (p < 0.005) differences in mean times: BSS 179 +/- 42 s; Vicryl 120 +/- 26 s; and Dexon II 32 +/- 2 s. Dexon II suture demonstrated wicking of S. salivarius, whereas Vicryl and BSS did not (p < 0.05). These results suggest that BSS and Vicryl sutures do not wick as readily as Dexon II does.

A comparison of laterally condensed gutta-percha, thermoplasticized gutta-percha, and mineral trioxide aggregate as root canal filling materials.

The purpose of this study was to evaluate the potential of using mineral trioxide aggregate as a root canal filling material by comparing its apical sealing ability with that of laterally condensed gutta-percha with sealer and high-temperature thermoplasticized gutta-percha with sealer in extracted bovine teeth. Sixty bovine incisors with single canals were prepared in a standard manner using LightSpeed instruments, randomly divided into three groups of 20 teeth, and obturated. The sealing ability of each technique was assessed by immersion in 1% methylene blue dye for 3 days. The teeth were cleared, and the linear extent of dye penetration was measured with a stereomicroscope. Data were analyzed by the Kruskal-Wallis one-way ANOVA followed by Dunn's test. Canals filled with laterally condensed gutta-percha or thermoplasticized gutta-percha showed significantly less apical dye penetration than canals obturated with mineral trioxide aggregate (p < 0.001). There was no significant difference in leakage between the laterally condensed group and the thermoplasticized group. The results suggest that gutta-percha obturation may provide an apical seal that is superior to MTA.

The effect of various intracanal oxidizing agents on the push-out strength of various perforation repair materials.

OBJECTIVE: The purpose of this study was to determine the effect of intracanal oxidizing agents on the strength of materials used to repair root perforations. STUDY DESIGN: Standardized perforations in bovine root samples were repaired with mineral trioxide aggregate (MTA), Super-EBA cement (S-EBA), or intermediate restorative material (IRM). After 7 days, 10 samples from each group were tested for push-out strength with an Instron machine (controls). The remaining samples were immersed in NaOCl, sodium perborate mixed with saline (SPB+S), Superoxol (SO), sodium perborate mixed with Superoxol (SPB+SO), or saline for 7 days to investigate the effect of irrigating and walking bleach compounds on the perforation repair materials. Push-out strength values were compared with those of the dry materials to determine whether any loss of integrity had occurred. RESULTS: MTA was statistically significantly less resistant across conditions to displacement than S-EBA or IRM. IRM was consistent across treatment conditions, whereas S-EBA lost strength when exposed to NaOCl, SPB+S, or SPB+SO. Exposure to SPB+S had the greatest effect on all 3 materials. CONCLUSIONS: IRM performed consistently as a perforation repair material despite exposure to oxidizing agents, whereas MTA was less resistant to dislodgement than either IRM or S-EBA and was more affected than IRM by sodium perborate-containing bleaching solutions.

Antimicrobial activity of several calcium hydroxide preparations in root canal dentin.

The purpose of this study was to evaluate the antimicrobial activity of several calcium hydroxide (Ca(OH)2) preparations in root canal dentin infected with Enterococcus faecalis. Roots of extracted bovine incisors were prepared to standardized cylindrical test specimens of 5 mm in height; the smear layer was removed, and the specimens were incubated for 24 h at 37 degrees C in bacteriological culture medium that contained 7.0 x 10(4) colony forming units per milliliter of E. faecalis. The specimens were mounted in individual 4-mm diameter culture wells, and the test material was applied to fill the canal lumen. There were five treatment groups: group 1, a thick mixture of Ca(OH)2 USP (1.0 g/ml H2O); group 2, a thin mixture of Ca(OH)2 USP (0.1 g/ml H2O); group 3, Pulpdent TempCanal paste; group 4, sterile H2O (positive control); and group 5, 25 dentin specimens in sterile, uninoculated brain-heart infusion broth that were included as negative controls. Quantitative microbiological analysis of dentin at various depths was completed after 24 h. All groups showed a significant (p < 0.001) decrease in numbers of E. faecalis in all depths of dentin compared with the control. Groups 2 and 3 demonstrated significantly greater antimicrobial activity (73%-86% reduction) at all depths of dentin tested compared with group 1 (13%-26%) (p < 0.05). These results suggest that Ca(OH)2 can decrease the numbers of E. faecalis at all depths of dentinal tubules within 24 h and that thin preparations of Ca(OH)2 may be more effective in the elimination of E. faecalis from dentinal tubules than thick preparations.

Determination of periodontal ligament cell viability in long shelf-life milk.

The purpose of this study was to determine the ability of long shelf-life milk to serve as a temporary storage medium for the maintenance of periodontal ligament (PDL) cell viability on avulsed teeth. PDL cells were plated onto 24-well culture plates and allowed to attach for 24 h. Minimal Essential Medium was replaced with regular pasteurized milk (refrigerated milk), long shelf-life milk (Parmalat), or Save-A-Tooth. Tap water served as the negative control, and Minimal Essential Medium served as the positive control. The tissue culture plates were incubated at 37 degrees C for 1, 2, 4, or 8 h. Cell viability was determined using a cell proliferation assay (CellTiter 96 AQ Assay) and absorbance read at 490 nm. ANOVA indicated that all media performed significantly better than tap water at all time periods. At 8 h, PDL cell viability in regular pasteurized milk and long shelf-life milk were significantly greater than in Save-A-Tooth (p < or = 0.001). There was no significant difference between regular pasteurized milk and long shelf-life milk at any time period. These results suggest that long shelf-life milk, which has the advantage of not requiring refrigeration, is as effective a storage medium for avulsed teeth as regular pasteurized milk and more effective than Save-A-Tooth.

Asthma training in third-year medical students.

To assess the educational experiences of physicians-in-training with asthma patients, we had medical students complete asthma surveys at the beginning and end of their internal medicine clerkship (IMC). At the beginning of the IMC, all students received a 1-hr asthma lecture and half of the students received a compilation of pocket cards containing many of the algorithms from the National Heart, Lung, and Blood Institute asthma guidelines. We found that students had relatively few encounters with asthmatic patients during the IMC. Students were good judges of asthma severity but performed poorly on survey questions pertaining to asthma treatment. Confidence in treating and assessing patients improved by the end of the IMC, but remained low. We conclude that the usual 1-hr lecture and limited contact with asthma patients during the IMC may be in adequate to train students to care for patients with asthma.

The effect of growth temperature on Staphylococcus aureus binding to type I collagen.

Many strains of Staphylococcus aureus produce a collagen-binding surface protein that could enable these strains to colonize tissues such as bone. Previous studies indicated that the expression of the collagen receptor varies with growth conditions. We report here that the growth temperature influences the ability of some S. aureus strains to produce this receptor. S. aureus isolates from human, osteomyelitic bone were grown at 37 degrees C and 42 degrees C and tested for agglutination of collagen-coated latex beads. Binding by 42 degrees C grown cells was significantly reduced in five of the seven isolates studied, including a complete loss of collagen binding in three of these isolates. In an 125I-collagen-binding assay, the binding ability of one of these isolates, strain #16, was 20-fold lower if grown at 42 degrees C. Reduced collagen binding by this isolate could be demonstrated after only two cell divisions at 42 degrees C and the cells regained the ability to bind collagen when shifted back to 37 degrees C. Sodium dodecyl sulfate (SDS)-PAGE confirmed the presence of proteins at 117 kDa in strain #16 and 135 kDa in SMH which were absent following growth at 42 degrees C. Chicken IgG, specific for the 117 kDa protein, was found to react in immunoblot assays with these proteins as well as a protein of 135 kDa extracted from S. aureus Cowan 1. The antibody did not react with proteins extracted from non-binding strains. Strains #15 and #21, collagen-binders at both 37 degrees C and 42 degrees C, produced immunoreactive proteins at 110 and 135 kDa, respectively, in lysates from cells grown at both temperatures. Antibody against a recombinant form of a previously characterized collagen receptor was used to confirm cross-reactivity with these novel collagen receptors. These data suggest that the ability to produce the collagen receptor is temperature sensitive in some S. aureus strains associated with osteomyelitis. It is proposed that a better understanding of the environmental effects on collagen receptor production could enhance our understanding of staphylococcal infections in bone and joints.

In vitro study of the effect of photodynamic therapy on pituitary adenomas.

Photodynamic therapy (PDT) has been employed in the management of recurrent cerebral gliomas, but its activity against pituitary adenomas has not been specifically studied. An in vitro study of the effects of PDT against a variety of pituitary adenomas was conducted. It was found that PDT using haematoporphyrin derivative as a photosensitizer showed dose dependent activity against a variety of pituitary adenomas. The activity of PDT against pituitary adenomas should be investigated further and may hopefully provide a useful form of adjuvant therapy for preventing recurrence of micro-invasive pituitary adenomas or dealing with established recurrence after surgery and radiotherapy.

Use of uncalibrated biplanar radiography for the measurement of skeletal coordinates around the shoulder girdle.

Mechanical modelling of the musculoskeletal system is dependent upon information regarding the bony attachments of the relevant muscles; in order to study the biomechanics of the shoulder girdle the authors have identified the muscle attachments in three embalmed cadavers. A simple biplanar radiographic technique was then used to determine the attachment coordinates using frames of reference defined for each bone. This technique, using hand positioning without special fixtures was believed to be sufficiently accurate, bearing in mind the likely degree of biological variation. In order to test this assumption, the accuracy of the technique has been studied by measuring the agreement between the two measurements of the common coordinate in the pairs of radiographs. It was found that for the trunk, the errors in the common coordinate were always less than the natural variation; for the scapula they were of a similar magnitude but, for the humerus, the measurement errors frequently exceeded the variation in the coordinates of muscle attachments. It was concluded that, in general, uncalibrated biplanar radiography was sufficiently accurate for the determination of the spatial coordinates of muscle attachments.

The current cost of nuclear medicine.

In the light of the control of expenditure and changes in radiopharmaceutical costs, changes in study protocols, new investigation procedures and inappropriate placing in Korner categories, the BNMS Council set up a working party to derive an agreed set of costings for Nuclear Medicine techniques. Using data from three hospitals with additional information from another nine, we have agreed the 1988 cost of individual nuclear medicine procedures in the UK. These figures include staffing (radiopharmacy, nursing, physics, medical including consultant), radiopharmaceuticals and other consumables, indirect costs (secretarial, administrative, portering), variable overheads (service contracts, stationery) and fixed overheads (rates, lighting, heating, building and engineering). Capital costs, equipment and buildings were not included. Because figures include salary and overhead costs they are difficult to compare with the majority of other previous nuclear medicine costings, apart from Bretland et al., or with data for other imaging modalities. Comparison of these costings with Korner schedules shows marked overlap between the Korner groups. Such groups therefore form a poor method of costing nuclear medicine procedures. We propose alternative groupings.

An antibiotic resistant experimental model of Pseudomonas osteomyelitis.

We report a model of chronic Pseudomonas aeruginosa osteomyelitis in the rat that was reproducible, simple and inexpensive. No promoting agent was required to cause infection. Infected animals yielded consistent pseudomonal colony counts (log): 4.98 +/- 0.32 (SD)/g cortical tibia (n = 16). The 95% confidence interval of the mean was 4.83-5.14. The inoculum required to infect 50% of challenged rats (ID50) was log 4.0; the ID 100 was log 6.4. Ceftazidime (50 mg/kg/8 h, subcutaneously), alone and in combination with tobramycin (40 mg/kg/12 h, subcutaneously), produced no significant change in quantitative bacterial count or gross bone pathology when used to treat established disease.

The promotional effect of bone wax on experimental Staphylococcus aureus osteomyelitis.

The consequences of using surgical bone wax are not well studied. We evaluated the infection-promoting potential of sterile bone wax in a rat model of chronic Staphylococcus aureus osteomyelitis. The addition of bone wax greatly reduced the quantitative bacterial inoculum (log colony-forming units) required to establish chronic osteomyelitis in 50% and 100% of challenged animals. The 50% infection rate was reduced from log 6.9 to 2.6 and the 100% infection rate from 8.2 to 4.4, respectively (p less than 0.015, t test for parallelism). Separate experiments were done 10 to 30 minutes after inoculation with only log 6.4 staphylococci. Tibiae of animals that received bone wax yielded more organisms than those that did not (log 2.76 +/- 0.68 versus 1.72 +/- 0.94, p less than 0.01). At 24 hours quantitative colony counts were not significantly different whether animals received wax or not (log 5.02 +/- 0.42 versus 4.43 +/- 0.65, p greater than 0.09). These studies suggest that the routine surgical use of bone wax should be reassessed.

Binding of a Staphylococcus aureus bone pathogen to type I collagen.

We contrasted the collagen-binding potential of the experimental osteomyelitis pathogen, Staphylococcus aureus strain SMH, to several other strains. These included Cowan 1 (binder), Wood 46 (non-binder) and six capsular variants. These measurements were made using an 125I-collagen binding assay. Formalin-killed S. aureus SMH strongly bound commercial type I iodinated collagen (dissociation constant, Kd = 2 x 10(-9) M). The extent of binding was similar to Cowan 1. Binding was saturable and not inhibited by 100 mM solutions of D-glucose, D-galactose, D-mannose, methyl-alpha-L-fucopyranoside, L-hydroxyproline or L-glycine. D-lactose gave moderate inhibition of binding to collagen, and L-fucose was strongly inhibitory. Trypsinized SMH did not bind collagen. None of four Ruthenium-red-staining staphylococci (encapsulated) avidly bound type I collagen. The encapsulated Smith strain, for example, did not bind to collagen but its capsule-negative variant, Smith compact, showed extensive binding. Three of five non-encapsulated S. aureus were strong collagen binders. These data suggest that the prototype bone pathogen binds to the major protein component of bone's extracellular matrix. Collagen-binding is promoted by protein adhesin(s), not capsule. The latter, in fact, appeared to interfere with this interaction. Binding was inhibited by solutions containing the simple monosaccharide, L-fucose.

Treatment of chronic experimental Staphylococcus aureus osteomyelitis with LY146032 and vancomycin.

LY146032 and vancomycin were compared as therapeutic agents in the treatment of chronic Staphylococcus aureus osteomyelitis in the rat. Quantitative cultures disclosed that one of 16, none of 16 and two of 17 tibiae were sterile from the control LY146032, and vancomycin groups, respectively. From positive cultures, geometric mean staphylococcal CFU per gram of bone were as follows: control, 5.13 +/- 1.58; LY146032, 5.36 +/- 0.43 (p = 0.57); and vancomycin, 4.33 +/- 1.73 (p = 0.078). Mean gross pathology was decreased significantly in both treatment groups. LY146032 was no more effective than vancomycin in reducing bacterial counts.

In vivo glycocalyx expression by Staphylococcus aureus phage type 52/52A/80 in S. aureus osteomyelitis.

Osteomyelitic rat tibiae were examined by scanning electron microscopy for the extracellular glycocalyx of Staphylococcus aureus. S. aureus and fractured tibiae from normal rats were incubated together in vitro and examined similarly. Low magnification of endosteal Haversian portals from tibiae studied in vivo and in vitro disclosed adherent S. aureus exuding glycocalyx that buried the organism in dense, coccoid-studded biofilms. The biofilm became progressively more dense over time in vitro and was exuberant at day 70 in vivo. S. aureus incubated in vitro without tibiae disclosed no glycocalyx. Bone chips studied in vitro disclosed staphylococci more commonly near the endosteal Haversian portals than on the intervening endosteal surfaces (mean +/- SE, 280 +/- 75 vs. 12 +/- 3 per 2,500-micron 2 field; P less than .002 by Student's t test). Organisms within ostia were not counted, although they occluded 10%-40% of the ostium. Staphylococci were adherent to exposed woven material, perhaps collagen.

Synergism between Bacteroides fragilis and Staphylococcus aureus in experimental tibial osteomyelitis.

We explored the potential role of microbial synergy in an experimental rat osteomyelitis model. Osteomyelitis was assessed by gross pathologic conditions and quantitative cultivation of rat tibiae for the implanted organisms 21 days after challenge. When Staphylococcus aureus was used alone, the 50% infective dose (ID50) and the 100% infective dose (ID100) were 400 and 25,000 colony-forming units (CFU), respectively. When Bacteroides fragilis was inoculated alone, the ID50 was 150,000 organisms, and the ID100 was not confidently determined. Subinfectious numbers of B. fragilis added to the staphylococcal inocula yielded an ID100 as low as 20 staphylococci. Mixed inocula with 20 or 200 staphylococci and increasing numbers of B. fragilis yielded a dose-dependent increase in the number of staphylococci isolated from osteomyelitic tibiae. Multiple linear regression analysis confirmed the two inocula and their interaction to be significantly predictive of the 21-day quantitative assessment of staphylococci (r = 0.80). Synergy was most striking at low bacterial inocula. When even large numbers of S. aureus were added to B. fragilis, the B. fragilis inoculum required to initiate B. fragilis osteomyelitis was essentially unchanged. We conclude that small numbers of B. fragilis allow remarkably low numbers of S. aureus (20 or 200 CFU) to establish osteomyelitis in the rat.