Uptake of 17ß-trenbolone and subsequent metabolite trendione by the pinto bean plant (Phaseolus vulgaris).

Manure from livestock feeding operations is commonly applied to agricultural fields as an alternative to commercial fertilizers. Trenbolone acetate (TbA) is a synthetic growth promoter frequently utilized in beef cattle feeding operations. Metabolites of TbA can be present in manure and subsequently applied to fields. Fate ofTbA metabolites 17ß-trenbolone (17ßTb), 17α-trenbolone (17αTb), and trendione (TbO) have been assessed in manure and soils, but plant uptake in agricultural fields is not fully understood. The objective of this study was to investigate potential plant uptake and biotransformation of 17ßTb using the pinto bean plant (Phaseolus vulgaris). Vegetated (n=20) and control sands (n=16) were amended with 17ßTb at a level of 1µg/g once per week for a total of four weeks. Sand, above-ground plant portion and below-ground plant portion were collected each week and then analyzed for 17ßTb, 17αTb, and TbO. By week four, low concentrations of 17ßTb (10±4.9µg/g fresh weight) were taken up into the roots of plants and, to a much lesser extent, translocated throughout the plant (0.04±0.02µg/g fresh weight). Extensive transformation of 17ßTb to the metabolite trendione (TbO) occurred in vegetated sand, while minimal TbO was detected in control sand. These results suggest the biotransformation of 17ßTb to TbO is predominantly through microbial degradation. Trenbolone (Tb) metabolites can then be taken up into plants but remain concentrated in the roots with only slight translocation to above ground portions of the plant. After four weeks, maximum observed concentrations of total Tb (parent+metabolites) in fresh plant tissues were 33.0µg/g in roots and 0.25µg/g in leaves. No phytotoxicity was observed to pinto bean plants throughout the four week study.

Accumulation and effects of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) exposure in the green anole (Anolis carolinensis).

Environmental contamination by energetic compounds is an increasing international concern, although little is known of their accumulation in and affect on wildlife. Reptiles are often good models for contaminants studies due to natural history traits that increase their potential for exposure. We report a study to assess accumulation and effects of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, High Melting Explosive) in green anoles (Anolis carolinensis). Acute oral toxicity (LD(50)) was estimated to exceed 2000 mg/kg body weight in adult male and female anoles using a standard up-and-down method. Accumulation of HMX was assessed in adult females via dietary exposure and into eggs by two routes (directly from the soil and via maternal transfer). HMX readily accumulated into adult females in a dose-dependent manner and into eggs following both exposure pathways. However, total HMX in soil-exposed eggs was up to 40-times greater than those exposed via maternal transfer. Although there was a suggestion of an HMX-induced reduction in body weight in adult females, overall there were no effects observed over the 12 week exposure period. The only significant effect on eggs was a 50% reduction in hatching success for eggs exposed to 2000 mg/kg HMX in the soil during incubation. Growth and survival of hatchlings was not affected by HMX exposure. Our results demonstrate that HMX accumulates through the food chain and into eggs from the soil, but likely poses minimal threat to lizards except to hatching success in eggs incubated in soils with HMX levels near maximum environmental concentrations.

Does ultrasound correlate with surgical or histologic findings in greater trochanteric pain syndrome? A pilot study.

BACKGROUND: Greater trochanteric pain syndrome can be severely debilitating. Ideal imaging modalities are not established, treatments are not reliably evaluated, and the underlying pathology is not well understood. QUESTIONS/PURPOSES: Using surgical and histopathology findings as a gold standard, we therefore determined the positive predictive value of preoperative ultrasound assessment for greater trochanteric pain syndrome recalcitrant to nonoperative management. In addition, we report the outcomes of gluteal tendon reconstructive surgery using validated clinical and functional outcome tools and evaluate the contribution of the tendon and bursa to greater trochanteric pain syndrome. PATIENTS AND METHODS: We reviewed 24 patients who had combined gluteal tendon reconstruction and bursectomy. Preoperative ultrasound imaging was compared with surgical findings. In the absence of a greater trochanteric pain syndrome specific outcome tool, surgical outcomes for pain and function were assessed via a 100-mm visual analog scale, the modified Harris hip score, and the Oswestry Disability Index. Strength also was measured. The tendon and bursa tissue collected at surgery was histopathologically reviewed. RESULTS: In our small study, ultrasound had a high positive predictive value for gluteal tendon tears (positive predictive value = 1.0). Patients reported high levels of pain relief and function after surgery; tendon and bursa showed pathologic changes. CONCLUSIONS: Ultrasound appears to be clinically useful in greater trochanteric pain syndrome; reconstructive surgery seems to relieve pain and the histopathologic findings show tendinopathy and bursa pathology coexist in greater trochanteric pain syndrome. LEVEL OF EVIDENCE: Level IV, case series. See the Guidelines for Authors for a complete description of levels of evidence.

Short-term antidepressant treatment has long-lasting effects, and reverses stress-induced decreases in bone features in rats.

Antidepressants are among the most-prescribed class of drugs in the world and though weight gain is a common outcome of antidepressant treatment, that effect is not well understood. We employed an animal model comprised of 2 weeks of chronic restraint stress with antidepressant treatment, followed by diet-induced obesity. We showed that short-term antidepressant treatment had long-lasting effects, not only leading to weight gain, but also enhancing trabecular and cortical bone features in rats; therefore, weight gain in this model was different from that of the classic diet-induced obesity. Late in the post-restraint recovery period, antidepressant-treated animals were significantly heavier and had better bone features than saline-treated controls, when assessed in the distal femoral metaphysis. The propensity to gain weight might have influenced the rate of catch-up growth and bone allometry, as heavier animals treated with fluoxetine also had enhanced bone features when compared to non-stressed animals. Therefore, short-term antidepressant treatment ameliorated the long-term effects of stress on body growth and bone. Growth and bone structural features were associated with leptin levels, and the interaction between leptin levels and antidepressant was significant for bone mineral content, suggesting that short-term antidepressants in the context of long-term diet-induced obesity modified the role of leptin in bone formation. To our knowledge this is the first study reporting that short-term antidepressant treatment has long-lasting effects in restoring the effects of chronic stress in body weight and bone formation. Our findings may be relevant to the understanding and treatment of osteoporosis, a condition of increasing prevalence due to the aging population.

Elevated serum cardiac troponin I in older patients with hip fracture: incidence and prognostic significance.

INTRODUCTION: Cardiovascular complications are the main causes of morbidity and mortality in patients with osteoporotic hip fracture (HF). The aim of this prospective study was to evaluate the incidence and prognostic significance of elevated cardiac troponin I (cTnI) in the early peri-operative period in older patients with HF. MATERIALS AND METHODS: A blind evaluation of myocardial injury as detected by cTnI elevation in 238 consecutive older patients with low-trauma HF (mean age 81.9 +/- 7.8 (SD) years; 72% females). Data on demographic and clinical characteristics, in-hospital mortality, hospital length of stay and discharge destination were collected prospectively. Serum cTnI level was analysed from blood collected routinely in the first 72 h of hospital admission. RESULTS: Sixty-nine (29%) patients had elevated cTnI (>0.06 microg/l) but myocardial injury was clinically recognised in only 23 (33%) and only 24 (34.8%) had a history of coronary artery disease (CAD). Patients with elevated cTnI were significantly older, more often had American Society of Anaesthesiologist status score >or=3, a history of CAD or stroke and more often were current smokers than the patients without cTnI elevation. In multivariate regression analysis only age was an independent predictor of cTnI elevation. Patients with cTnI release were twice as likely to have a length of stay >or=20 days (P = 0.047) and 2.7 times more likely to be discharged to a long-term residential care facility (RCF) (P = 0.013). cTnI level >or=1 microg/l was a strong independent predictor of all-cause mortality with 98.3% specificity and 89.1% negative predictive value. CONCLUSION: Peri-operative myocardial injury is common in older HF patients but is frequently unrecognised clinically. Elevated blood cTnI level is an independent predictor of prolonged length of hospital stay (>or=20 days), need for long-term RCF and mortality (if cTnI >or=1 microg/l).

Quality of life after infection in total joint replacement.

PURPOSE: To compare the health-related quality of life and functional outcomes of patients with and without periprosthetic infection after total joint replacement (TJR). METHODS: 62 uncomplicated TJRs and 34 TJRs complicated with deep infection were compared using a visual analogue scale for satisfaction, the Western Ontario and McMaster Universities Osteoarthritis Index, Assessment of Quality of Life, and Short Form-36. RESULTS: Patients with complicated TJR had significantly poorer satisfaction in outcome (p<0.0001) and disease-specific functional outcomes (p<0.0001). Six of the 8 health-related quality-of-life scores were also significantly poorer (p<0.05). These results persisted after controlling for age, sex, and follow-up period in a multiple regression analysis. CONCLUSION: Infection following TJR reduces patient satisfaction and seriously impairs functional health status and health-related quality of life. When hospitals are balancing the costs of preventative measures with the costs of treating infection in TJR, the effect on patients' quality of life must be considered. Our findings argue strongly for allocation of health care resources to minimise the occurrence of infection after TJR.

Multi-slice ultrasound image calibration of an intelligent skin-marker for soft tissue artefact compensation.

In this paper, a novel multi-slice ultrasound (US) image calibration of an intelligent skin-marker used for soft tissue artefact compensation is proposed to align and orient image slices in an exact H-shaped pattern. Multi-slice calibration is complex, however, in the proposed method, a phantom based visual alignment followed by transform parameters estimation greatly reduces the complexity and provides sufficient accuracy. In this approach, the Hough Transform (HT) is used to further enhance the image features which originate from the image feature enhancing elements integrated into the physical phantom model, thus reducing feature detection uncertainty. In this framework, slice by slice image alignment and calibration are carried out and this provides manual ease and convenience.

Hospital effect on infections after four major surgical procedures: outlier and volume-outcome analysis using all-inclusive state data.

BACKGROUND: Hospital volume is known to have a direct impact on the outcomes of major surgical procedures. However, it is unclear if the evidence applies specifically to surgical site infections. AIMS: To determine if there are procedure-specific hospital outliers [with higher surgical site infection rates (SSIRs)] for four major surgical procedures, and to examine if hospital volume is associated with SSIRs in the context of outlier performance in New South Wales (NSW), Australia. METHODS: Adults who underwent one of four surgical procedures (colorectal, joint replacement, spinal and cardiac procedures) at a NSW healthcare facility between 2002 and 2013 were included. The hospital volume for each of the four surgical procedures was categorized into tertiles (low, medium and high). Multi-variable logistic regression models were built to estimate the expected SSIR for each procedure. The expected SSIRs were used to compute indirect standardized SSIRs which were then plotted in funnel plots to identify hospital outliers. FINDINGS: One hospital was identified to be an overall outlier (higher SSIRs for three of the four procedures performed in its facilities), whereas two hospitals were outliers for one specific procedure throughout the entire study period. Low-volume facilities performed the best for colorectal surgery and worst for joint replacement and cardiac surgery. One high-volume facility was an outlier for spinal surgery. CONCLUSIONS: Surgical site infections seem to be mainly a procedure-specific, as opposed to a hospital-specific, phenomenon in NSW. The association between hospital volume and SSIRs differs for different surgical procedures.

Does anterior cruciate ligament reconstruction restore normal knee kinematics?: A prospective MRI analysis over two years.

This prospective study used magnetic resonance imaging to record sagittal plane tibiofemoral kinematics before and after anterior cruciate ligament reconstruction using autologous hamstring graft. Twenty patients with anterior cruciate ligament injuries, performed a closed-chain leg-press while relaxed and against a 150 N load. The tibiofemoral contact patterns between 0 degrees to 90 degrees of knee flexion were recorded by magnetic resonance scans. All measurements were performed pre-operatively and repeated at 12 weeks and two years. Following reconstruction there was a mean passive anterior laxity of 2.1 mm (sd 2.3), as measured using a KT 1000 arthrometer, and the mean Cincinnati score was 90 (sd 11) of 100. Pre-operatively, the medial and lateral contact patterns of the injured knees were located posteriorly on the tibial plateau compared with the healthy contralateral knees (p=0.014), but were no longer different at 12 weeks (p=0.117) or two years postoperatively (p=0.909). However, both reconstructed and healthy contralateral knees showed altered kinematics over time. At two years, the contact pattern showed less posterior translation of the lateral femoral condyle during flexion (p<0.01).

Outcomes for older patients with hip fractures: the impact of orthopedic and geriatric medicine cocare.

OBJECTIVES: To assess the impact of a specifically designed model of orthopedic-geriatric cocare on hip fracture (HF) outcomes. SETTING: Tertiary teaching hospital (level I trauma center). DESIGN: Prospective observational study with a retrospective (historical) control. Data on 951 consecutive patients 60 years of age or older admitted to the authors' institution with a nonpathologic HF over a 7-year period (1995 to 2002) were analyzed. Between 1995 and 1997, medical problems were managed by a geriatric medicine (GM) consultation-only service (retrospective audit). In 1998, a GM registrar began overseeing daily medical care with weekly geriatrician consultant review (prospective study). Outcomes for 2 time periods were compared: a 3-year period before (no GM; 504 patients) and a 4-year period after (GM; 447 patients) the introduction of GM cocare. MAIN OUTCOME MEASUREMENTS: Postoperative medical complications, mortality, length of stay, discharge destination, use of thromboprophylaxis, and antiosteoporotic treatment. RESULTS: While comparing 2 periods (GM and no GM), significant reductions in postoperative medical complications and comorbid conditions (in total 49.5% vs. 71.0%, P<0.001) and mortality (4.7% vs. 7.7%, P<0.01) occurred and rehospitalization to medical wards within 6 months decreased (28% vs. 7.6%). However, no differences were observed in median length of hospital stay (10.8 vs. 11.0 days) or in discharge destination. Antiosteoporotic treatment (12% to 69%) and specific thromboprophylaxis (63% to 94%) increased in the GM period. CONCLUSIONS: Orthopedic-geriatric cocare for the older patients with HF was associated with significant reductions in morbidity and mortality, and increases in optimal postoperative care. Options for further improvement of orthopedic-GM cocare need to be investigated.

Factors predictive of patient outcome following total wrist arthrodesis.

AIMS: Total wrist arthrodesis (TWA) produces a spectrum of outcomes. We investigated this by reviewing 77 consecutive TWA performed for inflammatory and post-traumatic arthropathies, wrist instability and as a salvage procedure. PATIENTS AND METHODS: All operations were performed by a single surgeon using a specifically designed pre-contoured dorsally applied non-locking wrist arthrodesis plate at a single centre. RESULTS: Median post-operative Buck-Gramcko Lohman (BGL), Disabilities of the Arm, Shoulder and Hand and Patient Rated Wrist Evaluation scores at six years (interquartile range (IQR) 3 to 11) were 9 (IQR = 6 to 10), 19 (IQR = 7 to 45) and 13 (IQR = 1 to 31) respectively. Polyarticular inflammatory arthritis and female gender were associated with poorer patient-reported outcomes, although the effect of gender was partly explained by higher rates of inflammatory disease among women. Return to work was negatively influenced by workers' compensation and non-inflammatory wrist pathology. There was no difference in complication rates for inflammatory and non-inflammatory indications. TAKE HOME MESSAGE: Polyarticular inflammatory arthritis is a risk factor for adverse patient-reported outcomes in TWA. Furthermore, when compared with patients without inflammatory arthritis, dorsally applied pre-contoured plates can be used for wrist arthrodesis in patients with inflammatory arthritis without an increased risk of complications. Cite this article: Bone Joint J 2016;98-B:647-53.

Incidence and predictors of atrial flutter in the general population.

OBJECTIVES: The goal of our study was to determine the incidence and predictors of atrial flutter in the general population. BACKGROUND: Although atrial flutter can now be cured, there are no reports on its epidemiology in unselected patients. METHODS: The Marshfield Epidemiological Study Area (MESA), a database that captures nearly all medical care among its 58,820 residents was used to ascertain all new cases of atrial flutter diagnosed from July 1, 1991 to June 30, 1995. To identify predisposing risk factors, we employed an age- and gender-matched case-control study design using eight additional variables. RESULTS: A total of 181 new cases of atrial flutter were diagnosed for an overall incidence of 88/100,000 person-years. Incidence rates ranged from 5/100,000 in those <50 years old to 587/100,000 in subjects older than 80. Atrial flutter was 2.5 times more common in men (p < 0.001). The risk of developing atrial flutter increased 3.5 times (p < 0.001) in subjects with heart failure and 1.9 times (p < 0.001) for subjects with chronic obstructive pulmonary disease. Among those with atrial flutter 16% were attributable to heart failure and 12% to chronic obstructive lung disease. Three subjects (1.7%) without identifiable predisposing risks were labeled as having "lone atrial flutter." CONCLUSIONS: This study, the first population-based investigation of atrial flutter, suggests this curable condition is much more common than previously appreciated. If our findings were applicable to the entire U.S. population, we estimate 200,000 new cases of atrial flutter in this country annually. At highest risk of developing atrial flutter are men, the elderly and individuals with preexisting heart failure or chronic obstructive lung disease.

Paroxysmal supraventricular tachycardia in the general population.

OBJECTIVES: We sought to determine the epidemiology and clinical significance of paroxysmal supraventricular tachycardia (PSVT) in the general population. BACKGROUND: Current knowledge of PSVT has been derived primarily from otherwise healthy patients referred to specialized centers. METHODS: We used the resources of the Marshfield Epidemiologic Study Area, a region covering practically all medical care received by its 50,000 residents. A review of 1,763 records identified prevalent cases as of July 1, 1991 and all new cases of PSVT diagnosed from that day until June 30, 1993. A mean follow-up period of 2 years was completed in all incident patients. Patients without other cardiovascular disease were labeled as having "lone PSVT." RESULTS: The prevalence was 2.25/1,000 persons and the incidence was 35/100,000 person-years (95% confidence interval, 23 to 47/100,000). Other cardiovascular disease was present in 90% of males and 48% of females (p = 0.0495). Compared with patients with other cardiovascular disease, those with lone PSVT were younger (mean 37 vs. 69 years, p = 0.0002), had a faster PSVT heart rate (mean 186 vs. 155 beats/min, p = 0.0006) and were more likely to have their condition first documented in the emergency room (69% vs. 30%, p = 0.0377). The onset of symptoms occurred during the childbearing years in 58% of females with lone PSVT versus 9% of females with other cardiovascular disease (p = 0.0272). CONCLUSIONS: There are approximately 89,000 new cases/year and 570,000 persons with PSVT in the United States. In the general population, there are two distinct subsets of patients with PSVT: those with other cardiovascular disease and those with lone PSVT. Our data suggest etiologic heterogeneity in the pathogenesis of PSVT and the need for more population-based research on this common condition.

Development and validation of a VISA tendinopathy questionnaire for greater trochanteric pain syndrome, the VISA-G.

BACKGROUND: Greater trochanteric pain syndrome (GTPS) is common, resulting in significant pain and disability. There is no condition specific outcome score to evaluate the degree of severity of disability associated with GTPS in patients with this condition. OBJECTIVE: To develop a reliable and valid outcome measurement capable of evaluating the severity of disability associated with GTPS. METHODS: A phenomenological framework using in-depth semi structured interviews of patients and medical experts, and focus groups of physiotherapists was used in the item generation. Item and format clarification was undertaken via piloting. Multivariate analysis provided the basis for item reduction. The resultant VISA-G was tested for reliability with the inter class co-efficient (ICC), internal consistency (Cronbach's Alpha), and construct validity (correlation co-efficient) on 52 naïve participants with GTPS and 31 asymptomatic participants. RESULTS: The resultant outcome measurement tool is consistent in style with existing tendinopathy outcome measurement tools, namely the suite of VISA scores. The VISA-G was found to be have a test-retest reliability of ICC2,1 (95% CI) of 0.827 (0.638-0.923). Internal consistency was high with a Cronbach's Alpha of 0.809. Construct validity was demonstrated: the VISA-G measures different constructs than tools previously used in assessing GTPS, the Harris Hip Score and the Oswestry Disability Index (Spearman Rho:0.020 and 0.0205 respectively). The VISA-G did not demonstrate any floor or ceiling effect in symptomatic participants. CONCLUSION: The VISA-G is a reliable and valid score for measuring the severity of disability associated GTPS.

Risedronate treatment does not increase microdamage in the canine femoral neck.

Cortical and trabecular bone from the femoral neck of 24 adult female beagle dogs was examined for microdamage following 2 years of treatment with risedronate (NE-58095). Specimens of the femoral neck, sectioned between the femoral head and the intertrochanteric groove, were bulk stained in 1% basic fuchsin in graded alcohols and embedded in methylmethacrylate. Five transverse sections of 100 microns from each specimen were examined for microdamage and measurement of cortical and trabecular area, and three sections from each specimen were measured for calculation of trabecular and cortical bone activation frequency (Ac.f) and bone formation rate (BFR/BV) in the superior and anterior regions of the femoral neck. Although no statistical differences were observed among groups for numerical density or length of microcracks, Kruskal-Wallis analysis showed differences among groups for both cortical and trabecular bone area (p < 0.05). Ac.f was significantly lower in both cortical bone (p < 0.05) and trabecular bone (p < 0.005) of the femoral neck at all dosage levels. No significant difference was observed among groups for trabecular mean wall thickness. The hypothesis that microdamage accumulation increases following reduction in Ac.f was not supported for the canine femoral neck in this experiment. This result could be explained by the fact that microdamage does not accumulate following treatment; that transient increases in microdamage at the beginning of the study period had been repaired; or finally, that the canine femoral neck does not reflect weight-bearing conditions of clinical relevance to humans for assessment of microdamage.

The ferret as a small animal model with BMU-based remodeling for skeletal research.

UNLABELLED: The need exists for a small animal model with bone metabolic unit (BMU)-based remodeling to mimic the bone loss found in postmenopausal women. The purpose of this investigation was to evaluate the ferret as a potential model for skeletal research. Specifically, we determined whether the ferret: 1) exhibits evidence of BMU-remodeling, 2) has a skeletal response to parathyroid hormone (PTH) similar to other remodeling species, and 3) loses bone in response to reduced estrogen levels. METHODS: Using three sets of experiments, we determined the response of female ferrets to ovariectomy/light cycle manipulation or to administration of PTH. Scanning electron microscopy, light microscopy, determination of estrogen levels and/or single-photon absorptiometry (SPA) were used for evaluation. RESULTS: The ferret was found to exhibit BMU-based remodeling, and may therefore provide a small animal remodeling species for skeletal research. Ferrets reach skeletal maturity between four and seven months of age as evidenced by closure of the growth plate and maturation of trabecluae from thin rods to thick rods and plates. PTH treatment resulted in a marked increase in bone mass accompanied by the PTH-induced tunneling phenomenon known to occur in dogs and humans but not rats. The response to PTH supports the use of the ferret in studies of bone anabolic agents. Bone mass in the proximal tibia was significantly reduced when estrogen depletion was induced by either bilateral ovariectomy or short light/dark cycles (8 hour light, 16 hour dark). Maintenance of intact ferrets under short-light conditions mimiced ovariectomy in terms of serum estrogen levels, uterine weights, and tibial BMD.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric damage in the rat with nitrogen-containing bisphosphonates depends on pH.

BACKGROUND: The use of nitrogen-containing bisphosphonates (N-BPs) has been reported to be associated with gastrointestinal intolerance. The fasted, indomethacin-treated rat provides a model for assessing the gastrointestinal effects of these compounds. AIMS: The aims of this study were to elucidate the effect of pH on N-BP-induced gastric damage, and to evaluate the structure-activity relationship between N-BP anti-resorptive and gastric effects. METHODS: Fasted rats were dosed concomitantly with indomethacin (40 mg/kg, subcutaneously) and an N-BP (pamidronate, alendronate, or risedronate at 150 or 300 mg/kg, orally), with the N-BP dosing solutions adjusted to pH 2, 4 or 7. The aminopentane and aminohexane N-BPs (150, 225 or 300 mg/kg, orally) were only tested at pH 4 only. RESULTS: Nitrogen-containing bisphosphonate-induced gastric damage was pH-dependent, with increased damage at increasing pH. CONCLUSIONS: Gastric damage potential did not correlate with bone anti-resorptive effects, and the more potent anti-resorptive N-BPs were not necessarily more damaging to the stomach.

The influence of weight-bearing on the measurement of polyethylene wear in THA.

We have studied the influence of weight-bearing on the measurement of wear of the polyethylene acetabular component in total hip arthroplasty using two techniques. The measured vertical wear was significantly greater when radiographs were taken weight-bearing rather than with the patient supine (p = 0.001, method 1; p = 0.007, method 2). Calculations of rates of linear wear of the acetabular component were significantly underestimated (p < 0.05) when radiographs were taken supine. There are two reasons for this. First, a change in pelvic orientation when bearing weight ensures that the thinnest polyethylene is brought into relief, and secondly, the head of the femoral component assumes the position of maximal displacement along its wear path. Interpretation of previous studies on both linear and volumetric polyethylene wear in total hip arthroplasty should be reassessed in the light of these findings.

Results of revision total knee arthroplasty in the face of significant bone deficiency.

The successful approach to the failed knee with bone deficiency is dependent upon thorough planning prior to surgery in order to have the resources available in terms of adequate bone allograft and suitable revision implants. The approximate size of bone stock deficiency can be calculated from preoperative radiographs and similarly ligamentous incompetence can often be diagnosed clinically prior to surgery. Smaller defects of up to 1 to 1.5 cm in depth and localized in the main to a single side of the tibial plateau or to a single femoral condyle can be dealt with using smaller grafts that may be local autograft or allograft, or modular wedges. Larger tibial defects can be compensated for using conventional revision systems by thicker polyethylene and augmented baseplates, but once the flexion-extension gap reaches approximately 40 mm this is no longer possible and structural graft or customized componentry becomes necessary. Femoral defects larger than about 1 cm that cannot be made up by augments necessitate grafting. The need to use a large proximal tibial allograft also may dictate the operative approach used to expose the joint, especially in the situation of a multiply-operated tight knee. In such cases the use of a quadriceps turndown may be more advisable than the use of a tibial tubercle osteotomy as the osteotomy may well not have an adequate bed to heal to following the reconstruction. Several series have reported cases of patellar tendon avulsion and the clinical results following this complication usually are not satisfactory. Preoperatively it is important to identify, if possible, the case that is likely to require a more extended approach because of a tight soft tissue envelope. The reports of results of series of revision total knee arthroplasty in the setting of significant bone loss are at present confined to short-term followup. The clinical results of these series are satisfactory at this early point in time, but decision regarding the durability of reconstructions requiring major structural allografting awaits longer-term study. Of concern is the devastating complication of infection following such revision surgery, the risk of which is amplified in the setting of prior infection. In addition, the long-term viability of major structural grafts in the setting of loading is uncertain as the risk of graft collapse in the process of incorporation is not known. Notwithstanding these concerns, major grafting is sometimes the only recourse to achieve satisfactory revision of a failed arthroplasty. The use of such major grafts is therefore cautiously supported and because of the risks inherent in such surgery we believe that such surgery should be carried out in the setting of specialist interest units.

Antibiotic prophylaxis in low-risk cesarean section.

This prospective study was undertaken in an effort to evaluate the role of systemic antibiotic prophylaxis in elective abdominal delivery. Eighty-two patients undergoing elective cesarean section who were not in labor and who did not have ruptured membranes were assigned on a randomized, double-blind basis to receive a three-dose perioperative course of either placebo or ampicillin. Postoperatively, patients were evaluated for the development of infection-related complications. Patients in the antibiotic group experienced less febrile morbidity, had lower fever indices and developed fewer operative-site infections than did patients in the control group. No patient in either group, however, developed a potentially life-threatening infection, and all infected patients responded promptly to parenteral antibiotic therapy. Because of the limited morbidity associated with elective cesarean section in this patient population, it is concluded that the theoretical risks of antibiotic prophylaxis outweigh the expected benefits.