Bisphosphonate treatment affects trabecular bone apparent modulus through micro-architecture rather than matrix properties.

Bisphosphonates are emerging as an important treatment for osteoporosis. But whether the reduced fracture risk associated with bisphosphonate treatment is due to increased bone mass, improved trabecular architecture and/or increased secondary mineralization of the calcified matrix remains unclear. We examined the effects of bisphosphonates on both the trabecular architecture and matrix properties of canine trabecular bone. Thirty-six beagles were divided into a control group and two treatment groups, one receiving risedronate and the other alendronate at 5-6 times the clinical dose for osteoporosis treatment. After one year, the dogs were killed, and samples from the first lumbar vertebrae were examined using a combination of micro-computed tomography, finite element modeling, and mechanical testing. By combining these methods, we examined the treatment effects on the calcified matrix and trabecular architecture independently. Conventional histomorphometry and microdamage data were obtained from the second and third lumbar vertebrae of the same dogs [Bone 28 (2001) 524]. Bisphosphonate treatment resulted in an increased apparent Young's modulus, decreased bone turnover, increased calcified matrix density, and increased microdamage. We could not detect any change in the effective Young's modulus of the calcified matrix in the bisphosphonate treated groups. The observed increase in apparent Young's modulus was due to increased bone mass and altered trabecular architecture rather than changes in the calcified matrix modulus. We hypothesize that the expected increase in the Young's modulus of the calcified matrix due to the increased calcified matrix density was counteracted by the accumulation of microdamage.

Contact stresses in the glenoid component in total shoulder arthroplasty.

Several studies of retrieved glenoid components from total shoulder arthroplasty show an erosion of the rim, surface irregularities, component fracture and wear resulting from polyethylene deformation in vivo. Particles resulting from polyethylene wear might be one of the reasons for the very high rate of glenoid component loosening found clinically. Because wear can be the result of high contact stresses, the aim of this study is to find out whether or not contact stresses are high enough to cause wear of the glenoid component and what influence the component type and geometry have on polyethylene contact stresses for different humerus abduction angles. Elasticity theory is used in a parametric study of contact stresses in several glenoid component designs. A finite element method is used to confirm the accuracy of the analytical solution. The analysis shows that the peak stress generated in glenoid components under conditions of normal living can be as high as 25 MPa; since this exceeds the polyethylene yield strength, wear and also cold flow of the components can be expected. It is predicted that more conforming components have lower contact stresses, which might result in lower wear rate and less cold flow. It is also found that a metal-backed component promotes higher contact stresses than an all-polyethylene component with the same total thickness, therefore it can be expected that metal-backed components have inferior wear properties.

Yield of vancomycin-resistant enterococci and multidrug-resistant Enterobacteriaceae from stools submitted for Clostridium difficile testing compared to results from a focused surveillance program.

It has been suggested that a method of performing surveillance for vancomycin-resistant enterococci (VRE) is to screen specimens submitted for Clostridium difficile testing. We compared this approach to our focused surveillance program of high-risk units during October 1997 to compare the yield of VRE and multidrug-resistant Enterobacteriaceae (MDRE) with both methods. Of the stools submitted for C. difficile testing, 14% were positive for VRE or MDRE, whereas rectal swabs from routine surveillance yielded 11% VRE- or MDRE-positive results. Although stools submitted for C. difficile testing resulted in a higher percentage of positive cultures, 14 VRE- and 2 MDRE-positive patients from our high-risk population were missed because many patients had no stool submitted for C. difficile testing. Therefore, while screening stools submitted for C. difficile testing cannot replace our focused surveillance program, it appears advantageous to assess these stools at various intervals to detect new patient reservoirs of drug-resistant organisms that may benefit from routine surveillance cultures.

Modified lapidus procedure for the treatment of hypermobile hallux valgus.

The intermediate outcome of patients who underwent a modified Lapidus procedure for the treatment of hallux valgus secondary to a hypermobile first ray was evaluated with an outcome tool to determine if their pain and functional status were improved. We evaluated 31 feet in 26 patients who underwent a modified Lapidus procedure. All working patients (100%) returned to full-time work. Six patients were retired and one was unemployed prior to surgery. There was an average of eight months until sports or unlimited activities were performed, and an average 16 weeks until conventional shoes could be worn. All patients but one (96%) were satisfied with the surgery and knowing their results would have the surgery again. Postoperative pain relief satisfaction was totally satisfied in 19 patients, satisfied with reservations in six patients, and not satisfied in one patient. Postoperative appearance satisfaction was totally satisfied in 21 patients and satisfied with reservations in five patients. Postoperative joint motion was no noticeable stiffness in 22 patients, noticeable stiffness but not bothersome in three patients, and stiffness that impairs activity in one patient (two feet). In the radiographic measurements, there was an average improvement of 10 degrees in the hallux valgus angle, 10 degrees in the intermetatarsal angle, two degrees in the lateral metatarsal-floor angle and two grades in the sesamoid position. Complications experienced were five recurrent deformities, two metatarsalgias, and one deep vein thrombosis. One of the five recurrences became symptomatic and required a revision.

Mechanical properties of brain tissue in-vivo: experiment and computer simulation.

Realistic computer simulation of neurosurgical procedures requires incorporation of the mechanical properties of brain tissue in the mathematical model. Possible applications of computer simulation of neurosurgery include non-rigid registration, virtual reality training and operation planning systems and robotic devices to perform minimally invasive brain surgery. A number of constitutive models of brain tissue, both single-phase and bi-phasic, have been proposed in recent years. The major deficiency of most of them, however, is the fact that they were identified using experimental data obtained in vitro and there is no certainty whether they can be applied in the realistic in vivo setting. In this paper we attempt to show that previously proposed by us hyper-viscoelastic constitutive model of brain tissue can be applied to simulating surgical procedures. An in vivo indentation experiment is described. The force-displacement curve for the loading speed typical for surgical procedures is concave upward containing no linear portion from which a meaningful elastic modulus might be determined. In order to properly analyse experimental data, a three-dimensional, non-linear finite element model of the brain was developed. Magnetic resonance imaging techniques were used to obtain geometric information needed for the model. The shape of the force-displacement curve obtained using the numerical solution was very similar to the experimental one. The predicted forces were about 31% lower than those recorded during the experiment. Having in mind that the coefficients in the model had been identified based on experimental data obtained in vitro, and large variability of mechanical properties of biological tissues, such agreement can be considered as very good. By appropriately increasing material parameters describing instantaneous stiffness of the tissue one is able, without changing the structure of the model, to reproduce experimental curve almost perfectly. Numerical studies showed also that the linear, viscoelastic model of brain tissue is not appropriate for the modelling brain tissue deformation even for moderate strains.

Persistent contamination of fabric-covered furniture by vancomycin-resistant enterococci: implications for upholstery selection in hospitals.

Vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens in hospitals throughout the United States. An increasing concern with respect to VRE dissemination is survival on, and potential transmission from, environmental surfaces within health care institutions. Therefore, we assessed survival of VRE on fabric chairs in an attempt to determine the optimal upholstery for the health care setting. VRE was identified on 3 of 10 seat cushions sampled, including 2 chairs in a room of a patient with known VRE. After performing simulated contamination experiments, all samples were positive at 72 hours and 1 week after inoculation. Contamination of the upholstery could be prevented by placing a sheet folded 4 times or a bath blanket folded in half on the seat cushion. In conclusion, VRE are capable of prolonged survival on fabric seat cushions and can be transferred to hands. Environmental surfaces such as chairs may serve as a potential reservoir for nosocomial transmission of VRE, and an easily cleanable, nonporous material is the preferred upholstery in hospitals.

Triple arthrodesis in adults using rigid internal fixation: an assessment of outcome.

The intermediate outcome of patients who underwent a triple arthrodesis for the treatment of adult foot disorders was evaluated with an outcome tool to determine if their pain and functional status were improved. We evaluated 63 feet in 57 patients who underwent a triple arthrodesis using rigid internal fixation for the treatment of hindfoot deformities associated with symptomatic arthrosis. Twenty-four men and thirty-three women, with an average age of 54 years, were evaluated. The average follow-up was 30 months. Multiple diagnoses contributed to hindfoot deformities with secondary arthrosis. Iliac crest bone graft was used in 56 of 63 cases (89%). Percutaneous heel cord lengthening was done in 53 of 63 cases (84%). Twenty-four of the thirty patients (80%) returned to work. Twenty-five patients were retired and two were unemployed before surgery. All patients except two (97%) were satisfied with the surgery and would have the surgery again. The average American Orthopaedic Foot and Ankle Society Ankle-Hindfoot preoperative score was 28 points, and the average postoperative score was 81 points (P < 0.0001). In the radiographic measurements, there was an average improvement of 12 degrees in the lateral talometatarsal angle, 7 degrees in the lateral talocalcaneal angle, and 10 degrees in the AP talometatarsal angle (P < 0.0001). Complications experienced included two varus malunions, two valgus malunions, two nonunions, two deep vein thromboses, one distal fibula stress fracture, and one wound infection. Of the 26 feet in 22 patients with mortise views available, 10 feet (38%) had evidence of ankle arthrosis and 19 feet (73%) had some degree of talar tilt postoperatively.

The prognostic value of quantitative bone scan in knee osteochondritis dissecans. A preliminary experience.

We reviewed the records of 12 patients ages 9 to 16 years with knee osteochondritis dissecans. All patients had clinical histories and examinations, four radiographic views of the knee, and technetium-99m diphosphonate quantitative bone scans. Scan results (symmetric, increased, or decreased activity), clinical course, healing time, and final outcome were correlated to determine the prognostic value of the scan. We divided the patients into those with open physes (distal femoral and proximal tibial) and those with closed physes. Four of the six patients with open physes had increased activity on the bone scan. All four of these knees healed with nonsurgical treatment. The other two patients had decreased activity on bone scan, and both required surgical treatment after nonsurgical treatment failed. Of the six patients with closed physes, all had increased activity on the bone scan, but only two patients had healing of the osteochondral lesion without surgery. Quantitative bone scanning had a 100% predictive value for the prognosis in osteochondritis dissecans patients with open physes, but for those with closed physes the predictive value was less. Because the natural history in the adolescent group is less predictable, it is in this group that the quantitative scan would be most helpful. In this small group of patients, quantitative bone scanning had limited prognostic value.

The Omaha System: a model for describing school nurse case management.

Case management is a key role for school nurses to employ in effecting positive outcomes for students in both health and education. The purpose of this paper is to describe the Omaha System and demonstrate its usefulness as a tool for school nurse case management. A case study model was used to analyze the practice of a single school nurse. During the 1995-1996 school year, the Omaha System helped a school nurse to identify students' health problems utilizing the Problem Classification Scheme, and the Intervention Scheme helped identify the nursing interventions employed. The Problem Rating Scale for Outcomes is also discussed in relation to this particular school nurse's practice.

Subtalar distraction bone block fusion: an assessment of outcome.

Twenty-nine feet in 28 patients who underwent subtalar distraction bone block fusion for the treatment of subtalar deformities associated with symptomatic arthrosis were evaluated. All patients were assessed with the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale score. Eighteen men and 10 women with a mean age of 44 years were evaluated. The mean follow-up was 33 months. Subtalar arthrosis was secondary to trauma in 27 of 29 feet (93%) with os calcis fractures in 19, subtalar dislocations in 5, and talus fractures in 3. Eighteen of the 28 patients (64%) returned to either full- or part-time work. The change in the mean AOFAS Ankle-Hindfoot Scale score from 25 preoperatively to 75 postoperatively was statistically significant (P < 0.0001). The radiographic analysis of the pre- and postoperative standing lateral radiographs showed an average increase of 8 mm in hindfoot height, 9 degrees in lateral talocalcaneal angle, and 11 degrees in lateral talar declination angle that were statistically significant (P < 0.0001). All patients but one (96%) were satisfied. Complications included four nonunions, two varus malunions, one metatarsal stress fracture, and one medial plantar nerve paresthesia. Each nonunion occurred in patients who smoked.

A selected annotated bibliography on midwives and family planning. Part I.

PIP: This short and concise collection of publications on the topic of midwifery and family planning is published in 2 parts (Part 2 appears in the Fall 1977 issue of Journal of Nurse-Midwifery). Information and titles for this bibliography were gleaned from printed indexes and university medical center libraries. The entries cover the last 20 years only. Material included is accessible to English-speaking audience by design. Excluded are government documents, pamphlets, in-house reports, theses, dissertations, preprints, and any other item not easily obtained by professionals. Part 1 of the bibliography printed here covers the following topics: 1) professional goals and philosophy of midwives; 2) education of midwives regarding family planning practice; 3) education of patients in family planning; and 4) midwives' practice with specific birth control methods.^ieng

A selected annotated bibliography on midwives and family planning. Part II.

PIP: This collection of titles and annotations on the topics of midwifery and family planning is published in 2 parts (part 1 appears in the Summer 1977 issue of Journal of Nurse-Midwifery). Titles were compiled for this bibliography from medical indexes and university medical center libraries. Entries cover only the last 10 years. Foreign language material is excluded, along with any material inaccessible to the English-speaking professional. Also excluded are government documents, pamphlets, in-house publications, theses, dissertations, preprints, and any other item not easily obtained. Part 2 of the bibliography printed here covers the following topics: 1) midwives involvement in the practice of family planning in various clinical settings; and 2) midwives and family planning in various geographical areas.^ieng