Vagus nerve stimulation and drug reduction

The authors prospectively assessed drug reduction and patient satisfaction in 21 patients using vagus nerve stimulation (VNS) for refractory epilepsy and compared results to a case-matched control group with a mean follow-up of 13.2 months. Significant antiepileptic drug (AED) reduction occurred in 9/21 (42.9%) of VNS patients averaging 0.43 AED/patient, with dose reduction in four patients (19.0%). For 12/21 (57.1%) patients not reducing AED, dose reduction occurred in 6/21 (28.6%). Drug and dose reduction of AED is possible in patients using VNS for refractory epilepsy without loss of seizure control and with improved patient satisfaction.

Growth factor modulation of distraction osteogenesis in a segmental defect model

A model was established in 39 dogs to investigate the growth factor modulation of regenerate bone in distraction osteogenesis. A segment of the diaphysis of the radius was resected unilaterally. An osteotomy was made proximal to the segmental defect to create a transport segment. A monolateral external fixator was applied. After a latency period, the segment was transported across the defect. One week after the transport assembly contacted the distal pin clamp, an ipsilateral osteotomy of the proximal ulna was performed. In 20 dogs, transforming growth factor-beta was injected into the regenerate bone halfway through the transport period. Four dogs were sacrificed before docking, when the regenerate bone was still immature. In specimens harvested halfway through the transport period, evidence was found of intramembranous ossification during distraction. In specimens harvested after the transport assembly contacted the distal pin clamp, evidence was found that the mature regenerate formed by endochondral ossification. Therefore, a combined mechanism of ossification is proposed for this segmental defect model that includes mechanical stimulus for bone differentiation. The one-time administration of transforming growth factor-beta retarded the formation of a stable, united regenerate. It is concluded that transforming growth factor-beta caused an effect opposite to that which was desired.

Effect of immediate weightbearing on plated fractures of the humeral shaft

BACKGROUND

This study evaluated the effect of immediate weightbearing on fractures of the humeral shaft treated with dynamic compression plates.

METHODS

Eighty-three fractures met the inclusion criteria. The weightbearing status of the humerus was based on associated injuries and not the fracture pattern. There were no differences between the weightbearing and nonweightbearing groups in patient or fracture demographics.

RESULTS

Ninety-four percent of the fractures healed after the initial operation. Two in the nonweightbearing group and three in the weightbearing group required a second operation to achieve union. Alignment did not differ between the two groups. Immediate full weight. bearing had no effect on the union or malunion rate.

CONCLUSION

When indicated, open reduction and internal fixation of the diaphysis of the humerus, followed by immediate weightbearing through the involved humerus, is a safe and efficacious procedure.

A HECT domain ubiquitin ligase closely related to the mammalian protein WWP1 is essential for Caenorhabditis elegans embryogenesis

The highly conserved ubiquitin/proteasome pathway controls the degradation of many critical regulatory proteins. Proteins are posttranslationally conjugated to ubiquitin through a concerted set of reactions involving activating (E1), conjugating (E2), and ligase (E3) enzymes. Ubiquitination targets proteins for proteolysis via the proteasome and may regulate protein function independent of proteolysis. We describe the cloning and functional analysis of new members of the HECT domain family of E3 ubiquitin ligases. Murine Wwp1 encoded a broadly expressed protein containing a C2 domain, four WW domains, and a catalytic HECT domain. A Caenorhabditis elegans gene was cloned encoding a HECT domain protein (CeWWP1), which was highly homologous to murine and human WWP1. Disruption of CeWwp1 via RNA interference yielded an embryonic lethal phenotype, despite the presence of at least six additional C. elegans genes encoding HECT domain proteins. The embryonic lethality was characterized by grossly abnormal morphogenesis during late embryogenesis, despite normal proliferation early in embryogenesis. CeWWP1 must therefore have unique and nonredundant functions critical for embryogenesis.

Evaluation of recombinant human bone morphogenetic protein-2 as a bone-graft substitute in a canine segmental defect model

A study was performed in dogs to evaluate the dose-response characteristics and effectiveness of recombinant human bone morphogenetic protein-2 with a collagen sponge carrier in a segmental defect model. Twenty-seven dogs underwent bilateral radial osteotomies with creation of a 2.5-cm diaphyseal defect. All received autogenous cancellous bone graft in one defect and a collagen implant in the other. These implants contained recombinant human bone morphogenetic protein-2 at the following doses: group 1 at 0 microg (three dogs, 0 microg/ml total implant volume), group 2 at 150 microg (three dogs, 50 microg/ml), group 3 at 600 ,g (three dogs, 200 microg/ml), group 4 at 2,400 microg (three dogs, 800 microg/ml), group 5 at 0 microg (five dogs, 0 microg/ml), group 6 at 150 microg (five dogs, 200 microg/ml), and group 7 at 600 microg (five dogs, 50 microg/ml). The defects were stabilized with external fixators. The dogs in groups 1-4 were killed at 12 weeks postoperatively, and those in groups 5-7 were killed at 24 weeks postoperatively except for one dog in group 7, which was killed at 48 weeks. Evaluation included monthly radiographs, biomechanical testing, and nondemineralized histology. All 27 radii with autogenous cancellous bone graft and all 19 implants treated with recombinant human bone morphogenetic protein-2 achieved radiographic and histologic union and gross stability. The eight radii treated with collagen carrier alone went on to radiographic and histologic nonunion and were grossly unstable at death. A dose-dependent occurrence of cyst-like bone voids was noted radiographically and histologically. Biomechanical performance tended to be better at the lowest dose studied at 12 weeks, and all three doses performed better than the placebo (p < 0.05) at 12 and 24 weeks. By 24 weeks, radiolucent areas corresponding to histologic bone voids persisted radiographically, although there was evidence of early bone remodeling. This remodeling progressed to 48 weeks in the single animal followed to this time point, although bone voids remained. These radiologic findings were confirmed histologically. Recombinant human bone morphogenetic protein-2 in a collagen sponge carrier has significant osteoinductive activity in this canine segmental defect model. A dose-response relationship is evident, with heterotopic bone and cyst-like void formation at higher doses and a minimum effective dose of 0-150 microg. At 12 and 24 weeks postoperatively, biomechanical parameters achieved by defects treated with recombinant human bone morphogenetic protein-2 were comparable with those of autograft controls and were significantly stronger than those of the placebo (p < 0.05).

Tibial pilon fractures: a comparison of treatment methods

OBJECTIVE

This retrospective review of surgically treated distal tibia fractures was undertaken to determine whether treatment with open reduction and internal fixation (ORIF) was more efficacious in achieving fracture union than one of two external fixation methods.

METHODS

Of the 60 study patients with pilon fractures, 21 patients were treated with an ankle-spanning half-pin external fixator, 15 patients with a single-ring hybrid external fixator, and 24 patients with ORIF. The severity of injuries was similar across groups.

RESULTS

There was no significant difference in complication rates between groups, although two below-knee amputations were required in the ORIF group. A greater (p = 0.03) number of malunions occurred in the fractures treated with external fixation when compared with those treated with ORIF. Fractures in the external fixator groups showed this significant tendency to lose their initial adequate reduction, independent of bone grafting or fibula fixation. There was no significant difference between groups in the need for bone grafting. There was a trend for patients treated with a single ring hybrid frame to require late bone grafting for metaphyseal-diaphyseal nonunion.

CONCLUSION

External fixation offers advantages in the treatment of the soft-tissue injury associated with pilon fractures, but malunion continues to be a problem with this method of fixation.

Direct Evidence for Grain Boundary Potential Barrier Breakdown via In Situ Electron Holography

: Static and dynamic grain boundary potential barrier effects are directly observed at high spatial resolution for a varistor of model structure and chemistry. Grain boundary mechanisms for nonlinear electrical behavior are investigated for Nb-doped SrTiO(3) bicrystals by in situ high-resolution electron holography under applied current coupled with electrical measurements. For the static case, holography reveals a positive grain boundary barrier of about 0.45 V, which is indicative of positive grain boundary charge adjoined by negative space charge regions. Under high applied current, in situ holography records the breakdown of this grain boundary barrier in accord with the macroscopic varistor effect, which is reflected in bulk I-V experiments.

Synthesis and preclinical evaluation of glycoconjugate vaccines against group B Streptococcus types VI and VIII

Group B Streptococcus (GBS) types VI and VIII are prevalent among serotypes isolated from pregnant women in Japan. Maternal vaccination with a safe and effective GBS vaccine has been proposed as a rational approach to prevent neonatal GBS disease. Because antibody specific for the capsular polysaccharide (CPS) antigens of GBS is protective, vaccines were developed with purified type VI and VIII CPS coupled to tetanus toxoid. In rabbits the newly synthesized conjugate vaccines elicited high-titered, type-specific antibody that was opsonically active in vitro. Moreover, litters born to mice actively vaccinated with the conjugate vaccines, in contrast to uncoupled CPS or saline, were protected against an ordinarily lethal challenge of GBS of homologous serotype. GBS types VI and VIII conjugate vaccines of the design presented may be important components of a multivalent GBS vaccine for use in regions where these serotypes predominate.

A comprehensive prognostic index to predict survival based on multiple comorbidities: a focus on breast cancer

BACKGROUND

The presence of comorbidities often influences clinical decision-making, although many studies exclude patients with comorbid disease for the sake of analysis.

OBJECTIVES

The purpose of this study was to develop a Comprehensive Prognostic Index (CPI), designed specifically for breast cancer patients.

RESEARCH DESIGN

This study linked Medicare claims with the Kentucky Cancer Registry and developed two models based on 1 year survival; one focused on deaths caused by breast cancer and the other on deaths from all causes. Comorbidities were derived from inpatient and ambulatory claims for up to 2 years before the diagnosis of breast cancer.

SUBJECTS

Subjects included a cohort of 848 elderly women first diagnosed with breast cancer in the state of Kentucky in 1993.

MEASURES

Each model identified the comorbidities specific to breast cancer that were detrimental to survival, and generated a refined comorbidity index. The CPI integrated these measures with age and stage of cancer into a comprehensive prognostic index.

RESULTS

Nearly two-thirds of the patients had evidence of at least one comorbidity. Survival rates decreased with age, more advanced stage, and increased comorbidity burden, as expected. The interaction of comorbidity burden with either age or stage was particularly strong for the older and more advanced stage of cancer.

CONCLUSIONS

The CPI could be a useful tool in breast cancer intervention studies and a prognostic aid for clinicians.

Length of operative procedures: reamed femoral intramedullary nailing performed with and without a fracture table

OBJECTIVES

To determine whether performing reamed intramedullary nailing of the femur without the use of a fracture table decreases the length of operation.

DESIGN

Retrospective.

SETTING

Level 1 trauma center, Nashville. Tennessee.

PATIENTS/PARTICIPANTS

Consecutively treated patients with fractures of the femoral shaft were treated with intramedullary nails from June 1986 to March 1996.

INTERVENTION

Reamed intramedullary nailing of the femoral shaft was performed with the use of a fracture table or with the leg draped free on a radiolucent table.

MAIN OUTCOME MEASUREMENTS

Length of anesthesia time, prep and drape time (from the point the anesthetized patient is turned over to the surgeons until incision), and intramedullary nailing time (from incision until end of surgery) for reamed intramedullary nailing of the femoral shaft performed with and without the use of a fracture table were compared.

RESULTS

Univariate analysis showed statistically significant decreases in the length of prep and drape time, operative time, and anesthetic time when fractures were treated without the use of a fracture table. Multivariate analysis showed that use of a fracture table prolongs prep and drape time (plus twenty minutes), operative time (plus seventeen minutes), and anesthesia time (plus seventy-three minutes) when the covariates of age, sex, fracture location, learning curve, position of the patient, nail brand, and number of distal bolts are controlled.

CONCLUSIONS

Reamed intramedullary nailing of the femoral shaft performed without the use of a fracture table is significantly faster than when the procedure is performed with a fracture table.

Selective termination and elective reduction in twin pregnancies: 10 years experience at a single centre

Selective termination is employed in multifetal pregnancies, in the presence of an abnormal fetus, in order to improve the prognosis of the normal fetuses. The term elective reduction is used to describe reduction in twin pregnancies for maternal medical conditions, psychological, or socioeconomic reasons. The purpose of this study was to evaluate the factors that influence outcome in such pregnancies. Eighty-two twin pregnancies underwent selective termination (n = 59) or elective reduction (n = 23) over a 10-year period. Early procedures, performed < or = 14 weeks (n = 31), had a pregnancy loss of 9.7% and a mean procedure-to-loss interval of 4.1 +/- 2.8 weeks; mean birthweight was 3299 +/- 395 g in survivors, with a mean gestational age at delivery of 38.4 +/- 2.3 weeks. In comparison, procedures performed > 14 weeks (n = 51) had a pregnancy loss of 7.8%, with a procedure-to-loss interval of 1.2 +/- 0.6 weeks. Mean birthweight was 2577 +/- 999 g, with a mean gestational age at delivery of 35.7 +/- 5 weeks. In conclusion, outcomes were more favourable among patients who underwent a first trimester procedure. The slight increase in pregnancy loss may be attributed to a higher than expected rate of spontaneous abortions in the first trimester, as manifested by the higher procedure-to-loss interval after a first trimester procedure. These facts underscore the importance of early detection of fetal abnormalities in twin pregnancies by ultrasonography and chorionic villus sampling.

Antibody responses in invasive group B streptococcal infection in adults

Nonpregnant adults with group B streptococcus bacteremia were identified by active surveillance in three hospitals. Serum samples collected within 2 days of the time of blood culture were assayed for IgG antibodies to the capsular polysaccharide of the infecting strain: serotype Ia (3 isolates), III (5 isolates), or V (4 isolates). In 7 of 12 bacteremia episodes, the serum level of IgG to the infecting isolate was > or = 3.5 microg/mL, higher than the 1-2 microg/mL level thought to be protective in neonates. Among selected acute-phase sera, 4 of 5 that contained > or = 3.5 microg/mL specific IgG mediated efficient opsonophagocytic killing of the corresponding group B streptococcus isolate in vitro. High levels of specific antibodies during the acute phase of invasive group B streptococcus infection in nonpregnant adults may reflect a rapid antibody response to infection or, in some cases, may indicate that susceptibility is due to defects in other immune effectors.

Reamed intramedullary femoral nailing after induction of an "ARDS-like" state in sheep: effect on clinically applicable markers of pulmonary function

OBJECTIVES/HYPOTHESIS

At present, the optimal treatment for appropriately resuscitated, multiply injured patients includes fixation of long bone fractures within twenty-four hours of injury. This management approach has been shown to decrease the incidence of pulmonary complications, multiple organ failure, and death. Some investigators have hypothesized that acute reamed intramedullary nailing of the femur (RIMNF) may result in pulmonary dysfunction as a result of the pulmonary fat embolization generated during this procedure. Patients with concomitant thoracic trauma may be at particular risk for this potentially severe complication. In an attempt to determine whether RIMNF can be safely carried out regardless of the severity of a pulmonary injury, we monitored the pulmonary effects of RIMNF in sheep in which an acute respiratory disorder (ARDS)-like state had been induced. Our hypothesis was that, if the pulmonary fat embolization that occurs as a result of RIMNF has a clinically significant effect, it would be detectable in an animal model in which a severe lung injury had been induced prior to the start of RIMNF.

STUDY DESIGN

This was an acute experimental procedure performed on yearling sheep.

METHODS

Reamed intramedullary nailing of the femur was performed in two groups of instrumented sheep. The first group had no pulmonary injuries. The second group had an ARDS-like state induced by intravenous infusion of perilla ketone prior to RIMNF. Perilla ketone increases pulmonary microvascular permeability without changing filling pressures and is used to induce a model of human ARDS. Hemodynamic and oximetric parameters were measured or calculated, as was pulmonary dynamic compliance during the experiment.

RESULTS

Infusion of perilla ketone caused a significant pulmonary injury. RIMNF caused no additional significant effect on intrapulmonary shunt, mixed venous oxygen saturation, or dynamic compliance, which are clinically used to assess the severity of pulmonary dysfunction in injured patients.

CONCLUSIONS

The fat embolization that occurs during RIMNF in an appropriately resuscitated sheep has no clinically significant effect on pulmonary function, even in the setting of a severe pulmonary dysfunction.

Evaluation of bovine-derived bone protein with a natural coral carrier as a bone-graft substitute in a canine segmental defect model

The efficacy of a bone-graft substitute (bovine-derived bone protein in a carrier of natural coral) in the healing of a segmental defect of a weight-bearing long bone was evaluated. Twenty dogs, divided into two groups, underwent bilateral radial osteotomies with creation of a 2.5 cm defect. On one side of each dog, the defect was filled with autogenous cancellous bone graft. Contralateral defects received, in a blinded randomized fashion, cylindrical implants consisting of natural coral (calcium carbonate) or calcium carbonate enhanced with a standard dose of bovine-derived bone protein (3.0 mg/implant; 0.68 mg bone protein/cm3). The limbs were stabilized with external fixators, and all animals underwent monthly radiographs. They were killed at 12 (group 1) or 24 (group 2) weeks, and regenerated bone was studied by biomechanical testing and histology. Radiographic union developed in all 20 radii with autogenous cancellous bone grafts and in all 10 of the radii with the composite implants. None of the radii with implants of calcium carbonate alone showed radiographic evidence of union. This represented a statistically significant difference between implant types. In addition, calcium carbonate implants both with and without bone protein demonstrated radiographic evidence of near total resorption of the radiodense carrier by 12 weeks. This resorption facilitated radiographic evaluation of healing. Mean values for biomechanical parameters of radii with the composite implants exceeded those for the contralateral controls at 12 and 24 weeks; the difference was statistically significant at 12 weeks. Histology revealed scant residual calcium carbonate carrier at either time in the defects with calcium carbonate implants; however, a moderate amount was present in defects with the composite implants. In these specimens, the residual carrier was completely surrounded by newly formed bone that may have insulated the calcium carbonate from further degradation. The present study used a carrier of granular calcium carbonate reconstituted with bovine type-I collagen to deliver an osteoinductive protein to the defect site. This carrier is of nonhuman origin (eliminating the risk of disease transmission or antigenicity) and resorbs rapidly. In this model, bovine-derived bone protein in a natural coral carrier performed consistently better than the gold standard autogenous cancellous bone graft in terms of the amount of bone formation and strength of the healed defect. This may have implications for removal of hardware or resumption of weight-bearing in certain clinical situations. These data also indicate that coralline calcium carbonate alone represents a poor option as a bone-graft substitute in this critical-sized segmental defect model.

Bovine-derived bone protein as a bone graft substitute in a canine segmental defect model

OBJECTIVES

To evaluate the efficacy of a bone graft substitute in healing of a segmental defect of a weight-bearing long bone.

DESIGN

An established canine model was used to perform a blinded, prospective, randomized study of the performance of bone graft substitute implants. This performance was compared with that of an accepted treatment modality (autograft) in a paired fashion.

SETTING

An accredited animal research facility.

SUBJECTS AND INTERVENTION

Twenty-eight dogs underwent bilateral radial osteotomies with creation of a 2.5-centimeter defect. On one side, the defect in every dog was filled with autogenous cancellous bone graft (ABG). Contralateral defects received, in a blinded, randomized fashion, cylindrical implants of demineralized bone matrix (DBM) allograft or DBM plus a constant dose (3.0 milligrams) of bovine-derived bone protein (DBM + BP). The defects were stabilized by external fixation. Subjects underwent monthly radiographs and were killed at six, twelve, or twenty-four weeks. Regenerate bone was studied by biomechanical testing and histology. Six animals were studied to determine the dose-response characteristics of the protein preparation. Three received implants containing 0.3 milligram of BP (group 1) and three received 1.0 milligram of BP (group 2). These animals were killed at twelve weeks of follow-up.

RESULTS

All twenty-eight ABG radii (100 percent) progressed to radiographic union, as did thirteen of thirteen (100 percent) DBM + BP radii compared with only four of fifteen (27 percent) of DBM radii. The difference between union rates was statistically significant (p < 0.05). Mean values for most biomechanical parameters of DBM + BP radii exceeded those of their contralateral ABG controls at twelve and twenty-four weeks, whereas those for DBM implants did not. Histology revealed microscopic evidence of normal bone healing in all ABG and DBM + BP radii, whereas most DBM radii demonstrated nonunions. In the dose-response arm of the study, six of six ABG radii (100 percent) achieved union; zero of three (0 percent) of group 1 and two of three (67 percent) of group 2 radii achieved grossly stable unions. Biomechanical testing was consistent with radiographic results, indicating that the 3.0-milligram dose was the most effective of those studied.

CONCLUSIONS

The DBM + BP composite implants were more effective at healing critical-sized segmental defects than DBM alone in this canine model when a 3.0-milligram per implant dose of BP was used. Biomechanical and histologic properties of the regenerated bone formed by DBM + BP implants was comparable to that of cancellous autograft.

Operative treatment of fractures of the tibial plafond. A randomized, prospective study

We performed a randomized, prospective study to compare the results of two methods for the operative fixation of fractures of the tibial plafond. Surgeons were assigned to a group on the basis of the operation that they preferred (randomized-surgeon design). In the first group, which consisted of eighteen patients, open reduction and internal fixation of both the tibia and the fibula was performed through two separate incisions. An additional patient, who had an intact fibula, had fixation of the tibia only through an anteromedial incision. The second group consisted of twenty patients who were managed with external fixation with or without limited internal fixation (a fibular plate or tibial interfragmentary screws). Ten (26 per cent) of the thirty-nine fractures were open, and seventeen (44 per cent) were type III according to the classification of Rüedi and Allgöwer. There were fifteen operative complications in seven patients who had been managed with open reduction and internal fixation and four complications in four patients who had been managed with external fixation. All but four of the complications were infection or dehiscence of the wound that had developed within four months after the initial operation. The complications after open reduction and internal fixation tended to be more severe, and amputation was eventually done in three patients in this group. At a minimum of two years postoperatively (average, thirty-nine months; range, twenty-five to fifty-one months), the average clinical score was lower for the patients who had had a type-II or III fracture, regardless of the type of treatment. With the numbers available, no significant difference was found between the average clinical scores for the two groups. All of the patients, in both groups, who had had a type-II or III fracture had some degree of osteoarthrosis on plain radiographs at the time of the latest follow-up. With the numbers available, there was no significant difference between the two groups with regard to the osteoarthrotic changes. We concluded that external fixation is a satisfactory method of treatment for fractures of the tibial plafond and is associated with fewer complications than internal fixation.

The traumatic bunion

In seven cases of Lisfranc joint injury after trauma, bunion deformity developed. This "traumatic bunion" occurs over a prolonged period of time after injury. A high index of suspicion is needed to identify the deformity as being traumatic in origin. Injury about the first metatarsophalangeal joint complex may also contribute to this deformity. When recognized, it may need to be treated with a first metatarsal-cuneiform fusion and distal soft tissue realignment.

Porous ceramics as bone graft substitutes in long bone defects: a biomechanical, histological, and radiographic analysis

Three porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evaluation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight-bearing was achieved.

Cell growth rate regulates expression of group B Streptococcus type III capsular polysaccharide

The capsular polysaccharide (CPS) of group B streptococci (GBS) is an important virulence factor that also serves to protect cells from nonspecific host defense mechanisms. Expression of CPS by GBS, as with other encapsulated bacterial pathogens, is not constitutive but varies during growth in vitro and in primary cultures isolated from different sites of infection. Despite this understanding, little is known about regulation of this surface-expressed carbohydrate antigen in GBS. Here we report that expression of type III CPS by GBS strain M781 grown in continuous culture with a modified chemically defined medium is regulated by growth rate. Cells in steady state at mass doubling times (tds) of 0.8, 1.4, and 1.6 h expressed an average of sixfold more cell-associated CPS than did cells held at tds of 2.3 and 11 h. Strain M781 grown at a td of 1.4 h repeatedly produced more type III CPS than those held at a td of 11.0 h, even when limited for glucose, pyridoxamine, or thiamine. In our studies, > or = 93% of the total CPS expressed by strain M781 was cell associated. Strain M781 grown at a td of 11.0 h (i.e., lowered CPS expression) was susceptible to in vitro complement-mediated opsonophagocytosis and killing by human peripheral blood leukocytes, whereas cells grown at a td of 1.4 h (i.e., higher CPS expression) were not killed unless type III CPS-specific antibody was present. Factors that allow GBS to asymptomatically colonize women yet cause invasive infection to both mother and infant are poorly understood. Our results shed new light on parameters that regulate the pathogenic potential of GBS and may also serve as a way to discern more fully the genetics and biochemistry of GBS capsule synthesis.

Effects on pulmonary physiology of reamed femoral intramedullary nailing in an open-chest sheep model

We have recently developed an open-chest sheep model to monitor and study the effects of major orthopedic procedures on pulmonary physiology. In this pilot study, we focused on reamed intramedullary femoral nailing in animals without pulmonary injury. Details of the model are described herein. The control group consisted of sheep that underwent thoracotomy and invasive monitoring only, while the study group also underwent femoral osteotomy, reaming, and intramedullary nailing. Baseline, postthoracotomy, and post-reaming/nailing values were recorded for mean pulmonary arterial pressure, central venous pressure, left arterial pressure, dynamic compliance, arterial blood gas, mixed venous O2, cardiac index, and mean arterial pressure so that hemodynamic and oxygen transport data could be calculated. Postprocedure values were recorded at hourly intervals for 4 h. A physiologically stable, reproducible model was created. No statistically significant differences were found between the control and experimental groups, indicating no adverse effect of femoral reaming/nailing. In one animal, using echocardiography, pulmonary embolization was documented while reaming and inserting the intramedullary nail. Reamed femoral intramedullary nailing is not detrimental to sheep with otherwise normal lungs. This finding suggests that femoral reaming and nailing in trauma patients without associated pulmonary injuries and otherwise normal lungs may be carried out without risk of inducing significant respiratory complications.

Evaluation of ground cortical autograft as a bone graft material in a new canine bilateral segmental long bone defect model

The recent orthopaedic literature reflects a growing number of bone graft substitutes and osteogenic growth factors under investigation in a number of animal models. We attempted to establish a well-controlled, large animal model of a segmental defect in a weight-bearing long bone by developing a bilateral diaphyseal radial defect model in the canine. We also evaluated the effectiveness of ground cortical autograft as a graft material. Twenty-three adult mongrel dogs underwent bilateral radial osteotomies with creation of a 2.0-2.5-cm diaphyseal defect on each side. All dogs received cancellous autograft (CAN) on one side, nine received no graft material (DEF) on the opposite side, and 14 received morselized cortical autograft (CORT) on the opposite side. Radii were stabilized by external fixation. Animals were followed radiographically at 6-week intervals to evaluate the healing process. Thirteen dogs were sacrificed at short-term follow-up (8-12 weeks postsurgery) and 10 at long-term (16-24 weeks). Biomechanical torsion testing to failure and histological evaluation were performed on each defect. All CAN radii achieved union (100%) while only one of nine DEF radii (11%) and none of 14 (0%) of CORT radii achieved union. Statistically significant differences in biomechanical parameters between both test groups and their corresponding autograft control radii were found. Histology revealed fibrous nonunions in the DEF and CORT radii. These results demonstrate that the bilateral canine radial defect model represents a consistent and reproducible model for bone healing of segmental defects in weight-bearing long bones and that ground cortical autograft is an ineffective graft material.

Ipsilateral femoral neck and shaft fractures

Ipsilateral femoral neck and shaft fractures occur in 2.5% to 6% of femur fractures. The injury results from high energy trauma. Victims are usually young, with multiple associated injuries. The diagnosis of the neck fracture is delayed in 19% to 31% of patients. The neck fracture line is almost vertical and nondisplaced, or minimally displaced in 26% to 59% of cases. The shaft fracture is often midshaft and open, and/or comminuted in 47% to 67% of cases. Ipsilateral knee injuries occur in 20% to 40% of patients. Two major complications, osteonecrosis of the femoral head and nonunion of the neck, result from the neck fracture. Therefore, treatment of the neck fracture takes precedence. The rate of osteonecrosis is unknown, but probably is in the range of 4% to 22%. Union rate of the neck is high and related to stable, anatomic reduction. The timing of operative fixation often is dictated by the patient's status as a multiple trauma victim, but a delay of days to weeks in the fixation of the neck fracture does not seem to increase the complication rate. The goal of any treatment plan should be anatomic reduction of the neck fracture, and stable fixation of both fractures, so that the patient can be mobilized.

Purification of preparative quantities of group B Streptococcus type III oligosaccharides

Many bacterial capsular polysaccharides are regularly repeating units of oligosaccharides. Bacterial oligosaccharides have been used in neoglycoconjugate vaccines and as reagents in the study of specific antibody binding. Unfortunately, separation methods have not been adequate for the purification of preparative quantities of bacterial oligosaccharides. Here we describe a size-exclusion procedure that resulted in the resolution of group B Streptococcus type III oligosaccharides composed of 4-25 sugars.

Mechanical failures of intramedullary tibial nails applied without reaming

The clinical mechanical failures of small diameter intramedullary interlocking nails were evaluated to determine the relationship of failure modes to the type or location of tibial fractures. Methods were developed to duplicate failure modes in vitro in standardized tests to simulate the clinical situations. Where standard test methods were inadequate, new methods were developed to provide quantifiable, reliable methods of evaluating potential clinical performance. The modes and rates of mechanical failure in the clinical series were consistent among participating centers: (1) In diaphyseal fractures with secondary trauma, the intramedullary nail bent at the fracture site where the working length was unsupported; (2) failures that occurred several weeks after nailing were the result of fatigue fractures of the locking screws, usually at the distal end; and (3) nail and screw failures occurred most commonly in proximal and distal tibial fractures. The strength of the 8- and 9-mm sizes of Synthes and Russell-Taylor nails were comparable.