Importance and vulnerability of the world's water towers.

Mountains are the water towers of the world, supplying a substantial part of both natural and anthropogenic water demands1,2. They are highly sensitive and prone to climate change3,4, yet their importance and vulnerability have not been quantified at the global scale. Here we present a global water tower index (WTI), which ranks all water towers in terms of their water-supplying role and the downstream dependence of ecosystems and society. For each water tower, we assess its vulnerability related to water stress, governance, hydropolitical tension and future climatic and socio-economic changes. We conclude that the most important (highest WTI) water towers are also among the most vulnerable, and that climatic and socio-economic changes will affect them profoundly. This could negatively impact 1.9 billion people living in (0.3 billion) or directly downstream of (1.6 billion) mountainous areas. Immediate action is required to safeguard the future of the world's most important and vulnerable water towers.

Correlation of fetal ventricular size and need for postnatal cerebrospinal fluid diversion surgery in open spina bifida.

OBJECTIVES: Open spina bifida is a common cause of hydrocephalus in the postnatal period. In-utero closure of the fetal spinal defect decreases the need for postnatal cerebrospinal fluid (CSF) diversion surgery. Good prenatal predictors of the need for postnatal CSF diversion surgery are currently lacking. In this study, we aimed to assess the association of fetal ventriculomegaly and its progression over the course of pregnancy with the rate of postnatal hydrocephalus requiring intervention. METHODS: In this retrospective study, fetuses with a prenatal diagnosis of open spina bifida were assessed longitudinally. Ventricular diameter, as well as other potential predictors of the need for postnatal CSF diversion surgery, were compared between fetuses undergoing prenatal closure and those undergoing postnatal repair. RESULTS: The diameter of the lateral ventricle increased significantly throughout gestation in both groups, but there was no difference in maximum ventricular diameter at first or last assessment between fetuses undergoing prenatal closure and those undergoing postnatal repair. There was no significant difference in the rate of progression of ventriculomegaly between the two groups, with a mean progression rate of 0.83 ± 0.5 mm/week in the prenatal-repair group and 0.6 ± 0.6 mm/week in the postnatal-repair group (P = 0.098). Fetal repair of open spina bifida was associated with a lower rate of postnatal CSF diversion surgery (P < 0.001). In all subjects, regardless of whether they had prenatal or postnatal surgery, the severity of ventriculomegaly at first and last assessments was associated independently with the need for postnatal CSF diversion surgery (P = 0.005 and P = 0.001, respectively), with a greater need for surgery in fetuses with larger ventricular size, even after controlling for gestational age at assessment. CONCLUSIONS: In fetuses with open spina bifida, fetal ventricular size increases regardless of whether spina bifida closure is performed prenatally or postnatally, but the need for CSF diversion surgery is significantly lower in those undergoing prenatal repair. Ventriculomegaly is associated independently with the need for postnatal CSF diversion in fetuses with open spina bifida, irrespective of timing of closure. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

TROPHY registry - status report.

INTRODUCTION: The TROPHY registry has been established to conduct an international multicenter prospective data collection on the surgical management of neonatal intraventricular hemorrhage (IVH)-related hydrocephalus to possibly contribute to future guidelines. The registry allows comparing the techniques established to treat hydrocephalus, such as external ventricular drainage (EVD), ventricular access device (VAD), ventricular subgaleal shunt (VSGS), and neuroendoscopic lavage (NEL). This first status report of the registry presents the results of the standard of care survey of participating centers assessed upon online registration. METHODS: On the standard of treatment forms, each center indicated the institutional protocol of interventions performed for neonatal post-hemorrhagic hydrocephalus (nPHH) for a time period of 2 years (Y1 and Y2) before starting the active participation in the registry. In addition, the amount of patients enrolled so far and allocated to a treatment approach are reported. RESULTS: According to the standard of treatment forms completed by 56 registered centers, fewer EVDs (Y1 55% Y2 46%) were used while more centers have implemented NEL (Y1 39%; Y2 52%) to treat nPHH. VAD (Y1 66%; Y2 66%) and VSGS (Y1 42%; Y2 41%) were used at a consistent rate during the 2 years. The majority of the centers used at least two different techniques to treat nPHH (43%), while 27% used only one technique, 21% used three, and 7% used even four different techniques. Patient data of 110 infants treated surgically between 9/2018 and 2/2021 (13% EVD, 15% VAD, 30% VSGS, and 43% NEL) were contributed by 29 centers. CONCLUSIONS: Our results emphasize the varying strategies used for the treatment of nPHH. The international TROPHY registry has entered into a phase of growing patient recruitment. Further evaluation will be performed and published according to the registry protocol.

Understanding osteoporosis and fractures: an introduction to the use of qualitative research.

BACKGROUND: Qualitative research has been recognized in recent years as a field of inquiry used to understand people's beliefs, attitudes, behaviors, culture or lifestyle. While quantitative results are challenging to apply in everyday practice, the qualitative paradigm can be useful to fill in a research context that is poorly understood or ill-defined. It can provide an in-depth study of interactions, a way to incorporate context, and a means to hear the voices of participants. Understanding experiences, motivation, and beliefs can have a profound effect on the interpretation of quantitative research and generating hypotheses. In this paper, we will review different qualitative approaches that healthcare providers and researchers may find useful to implement in future study designs, specifically in the context of osteoporosis and fracture. METHODS: We will provide insight into the qualitative paradigm gained from the osteoporosis literature on fractures using examples from the database Scopus. Five prominent qualitative techniques (narratives, phenomenology, grounded theory, ethnography, and case study) can be used to generate meanings of the social and clinical world. DISCUSSION AND CONCLUSION: We have highlighted how these strategies are implemented in qualitative research on osteoporosis and fractures and are anchored to specific methodological practices. We focus on studies that explore patient psychosocial experiences of diagnosis and treatment, cultural boundaries, and interprofessional communication. After reviewing the research, we believe that action research, that is not frequently used, could also effectively be used by many professions to improve programs and policies affecting those dealing with osteoporosis issues.

Isolated left innominate vein aneurysm: a rare cause of mediastinal widening.

Mediastinal widening in an adult is mostly nodal in origin. Occasionally vascular aneurysms may be the underlying cause, in which case the aorta or its branches are most frequently involved. Thoracic venous aneurysms, on the other hand, have been reported only in anecdotes, with fusiform aneurysm of the superior vena cava being the commonest. Isolated aneurysms involving the brachiocephalic/innominate vein are extremely rare. We describe detection of a saccular aneurysm of the innominate vein, as the underlying cause of mediastinal widening seen on a chest radiograph in a 42-year-old asymptomatic woman. The characteristic radiological findings of thoracic venous aneurysms are described with particular reference to the importance of multiplanar computed tomography in such settings. Also discussed is the role of imaging in the diagnosis and guiding the management of this rare entity.

Outcome assessment in hip fracture: evaluation of the practicality of commonly-used outcomes in hip fracture studies.

INTRODUCTION: Elderly patients are at a major risk for a first hip fracture. The decrease in bone mineral density may account for 60-85% of the variability in fracture risk. Other contributing factors for hip fractures include cognitive impairment as well as impaired mobility and visual depth perception. Dizziness and poor or fair self-perceived health care characteristics are predictive of a second hip fracture. In general, patients over the age of 65 years admitted to a geriatric rehabilitation unit after proximal hip fracture have complex multiple interacting pathologies with 78% having significant co-morbidity. Because of the added co-morbidity, we believed that the choice of outcome assessment in hip fracture studies would reflect the practical qualities of an instrument. The purpose of our study was to evaluate the practicality of functional outcome instruments found in the current literature in the elderly following postoperative hip fracture. METHODS: We coded the instruments according to the International Classification of Functioning, Disability and Health conceptual framework. 24 different instruments measuring Body Function, 13 instruments evaluating Activity and Participation and 8 composite scores were identified. Practicality was evaluated using four dimensions: respondent burden, examiner burden, score distribution and format compatibility. RESULTS: All instruments evaluating Body Function were performance-based and used exclusively in rehabilitation trials. Performance-based instruments also correlated with a high score in examiner and respondent burden. Surgical trials mostly adopted the Harris hip score which was rated low in examiner and respondent burden. The SF-36 was rated with an adequate score distribution but low in format compatibility. DISCUSSION AND CONCLUSION: An instrument with low respondent burden and minimal examiner burden demonstrated better potential for being applicable in randomized trials with elderly hip fracture patients presenting with co-morbidities. In the future we believe that practical qualities should also be considered when developing or utilizing instruments.

Predictive Value of MRI in Diagnosing Brain AVM Recurrence after Angiographically Documented Exclusion in Children.

BACKGROUND AND PURPOSE: MRI is routinely performed following brain AVM after treatment in children. Our aim was to determine the predictive values of contrast-enhanced MR imaging and TOF-MRA for brain AVM recurrence in children, compared with conventional angiography and the role of 3D rotational angiography-MR imaging fusion in these cases. MATERIALS AND METHODS: We included all pediatric patients with brain AVMs during an 18-year period with angiographically documented obliteration after treatment. Patients underwent 3T MR imaging, including contrast-enhanced MR imaging, TOF-MRA, and conventional angiography, with a subset undergoing 3D rotational angiography. The predictive values of contrast-enhanced MR imaging and TOF-MRA for brain AVM recurrence were determined. CTA sections reconstructed from 3D rotational angiography were coregistered with and fused to 3D-T1WI for analysis. RESULTS: Thirty-nine children (10.8 ± 3.9 years of age; range, 2-17 years; male/female ratio, 19:20; mean Spetzler-Martin grade, 1.9 ± 0.6) met the inclusion criteria. Of these, 13 had angiographically confirmed brain AVM recurrence, 8 following surgery and 5 following embolization. Sensitivity, specificity, and positive and negative predictive values for recurrence were the following: contrast-enhanced MR imaging: 84.6%, 38.5%, 40.7%, 81.8%; TOF-MRA: 50.0%, 96.1%, 85.7%, 79.3%; both: 75.0%, 90.9%, 85.7%, 83.3%. 3D rotational angiography-MR imaging fused images confirmed or excluded recurrence in all available cases (13/13). Embolization-only treatment was a significant predictor of recurrence (OR = 32.4, P = .006). MR imaging features predictive of recurrence included a tuft of vessels on TOF-MRA and nodular juxtamural/linear enhancement with a draining vein on contrast-enhanced MR imaging. CONCLUSIONS: MR imaging is useful for surveillance after brain AVM treatment in children, but conventional angiography is required for definitive diagnosis of recurrence. TOF-MRA and contrast-enhanced MR imaging provide complementary information for determining brain AVM recurrence and should be interpreted in conjunction. 3D rotational angiography-MR imaging fusion increases the diagnostic confidence regarding brain AVM recurrence and is therefore suited for intraoperative neuronavigation.

Ultrasound assisted synthesis of methyl butyrate using heterogeneous catalyst.

Ultrasound assisted esterification of butyric acid with methanol was investigated in an ultrasound irradiated isothermal batch reactor using acid ion-exchange resin (amberlyst-15) as a catalyst. Effect of parameters such as temperature (323-353 K), catalyst loading (0-8.5%w/w), alcohol to acid ratio, M (2-6), ultrasound power (0-145 W), duty cycle (0-85%) and amount of molecular sieves added (0-11%w/w) on the rate of reaction was studied. At optimized parameters, a maximum conversion of 91.64% was obtained in 120 min in presence of ultrasound. Experimental kinetic data were correlated by using Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHH W) models taking into account reverse reaction. Studies showed that single site LHHW with reactants and products both adsorbing on catalyst surface was most suited for the obtained experimental data. Activation energy determined based on heterogeneous kinetics was in the range 49.31-57.54 kJ/mol while it was 18.29 kJ/mol using homogeneous model.

Effectiveness of feature groups for automated pairwise leukocyte class discrimination.

Automated blood cell differentials using statistical classification techniques have been implemented in several commercial machines. The machine-derived features used to classify leukocytes resemble the descriptors used by humans performing visual classification, e.g. size, content, shape, color, and texture. However, because of our crude modeling of vision there is no universally accepted measure of characteristics such as shape, color, or texture. One expects, therefore, that features which are powerful discriminators for humans may perform poorly when quantified by machine, while other parameters may be more precisely measured automatically and so prove more useful in cell classification. This paper reports the results of a feature evaluation study for automated discrimination between all pairs of a large set of leukocyte classes consisting of both normal and abnormal types. To provide a framework for comparing automated feature ordering with the ranking attached by medical technologists, the machine-derived features were divided into six groups: size and content, mean and mode, cytoplasm/nucleus comparison, contrast and texture, color, and nuclear shape. A sequential procedure was used to select the best five-feature set from each group and the globally best five-feature set for each pairwise classification. The results illustrate the strengths and weaknesses of machine-derived descriptors for each type of decision.

Serial magnetic resonance imaging findings for a spontaneously resolving spinal subdural hematoma: case report.

OBJECTIVE AND IMPORTANCE: Spinal subdural hematoma (SSDH) is a rare entity, and cases are usually managed as surgical emergencies. We describe a patient with a SSDH who demonstrated incomplete clinical resolution with nonsurgical management, despite continued anticoagulation treatment. We provide the most complete demonstration of the magnetic resonance imaging (MRI) characteristics of a large SSDH from its initiation to its radiological resolution. CLINICAL PRESENTATION: A 61-year-old woman developed a large SSDH as a complication of a lumbar puncture. Her only neurological deficit was urinary retention. INTERVENTION: Because of the extensiveness of the hematoma and the relative neurological preservation of the patient, she was treated conservatively. Serial MRI scans were obtained at 4, 7, 13, and 25 days. The evolution of deoxyhemoglobin in the hematoma to methemoglobin was observed. By 25 days, MRI scans showed virtual resolution. CONCLUSION: SSDHs undergo MRI signal changes that are similar to those of brain hematomas. In certain cases, even large SSDHs demonstrate swift and dramatic spontaneous resolution, despite continued anticoagulation treatment. This report suggests that there is a role for conservative management for selected cases of SSDHs.

Lumboperitoneal shunting: a retrospective study in the pediatric population.

There is a shortage of data concerning the long-term follow-up of patients with lumboperitoneal (LP) shunts, especially in the pediatric population. A retrospective study of 143 patients who underwent LP shunting between 1974 and 1991 was therefore performed. The mean age at the time of shunt insertion was 3.3 years (range, 18 d to 17.8 yr), and the indication for shunting was: hydrocephalus (81%), cerebrospinal fluid fistula (12%), and pseudotumor cerebri (7%). The mean follow-up time was 5.7 years (range, 5 d to 17.5 yr), and during this period, there were five deaths of which one was shunt related (2.5 yr post-shunt insertion). Of the types of LP shunt used during the study period, the T-tube shunt (101 patients) fared significantly better (P = 0.003) than the percutaneous type (42 patients), and the overall survival characteristics for the T-tube shunt approximated those seen for ventriculoperitoneal shunts, with a 50% probability of remaining free of malfunctions for 5 years. A high rate of migration (19%) was partially responsible for the poor performance of the percutaneous-type shunts. By the end of the study, 40 patients (28%) had been converted to ventricular shunts, and this rate of conversion was similar for both shunt types. LP shunts have certain advantages over other forms of cerebrospinal fluid diversion and were successfully used for various clinical conditions during this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Incidence of silent hemorrhage and delayed deterioration after stereotactic brain biopsy.

OBJECT: Many neurosurgeons routinely obtain computerized tomography (CT) scans to rule out hemorrhage in patients after stereotactic procedures. In the present prospective study, the authors investigated the rate of silent hemorrhage and delayed deterioration after stereotactic biopsy sampling and the role of postbiopsy CT scanning. METHODS: A subset of patients (the last 102 of approximately 800 patients) who underwent stereotactic brain biopsies at the Toronto Hospital prospectively underwent routine postoperative CT scanning within hours of the biopsy procedure. Their medical charts and CT scans were then reviewed. A postoperative CT scan was obtained in 102 patients (aged 17-87 years) who underwent stereotactic biopsy between June 1994 and September 1996. Sixty-one patients (59.8%) exhibited hemorrhages, mostly intracerebral (54.9%), on the immediate postoperative scan. Only six of these patients were clinically suspected to have suffered a hemorrhage based on immediate postoperative neurological deficit: in the remaining 55 (53.9%) of 102 patients, the hemorrhage was clinically silent and unsuspected. Among the clinically silent intracerebral hemorrhages, 22 measured less than 5 mm. 20 between 5 and 10 mm, five between 10 and 30 mm, and four between 30 and 40 mm. Of the 55 patients with clinically silent hemorrhages, only three demonstrated a delayed neurological deficit (one case of seizure and two cases of progressive loss of consciousness) and these all occurred within the first 2 postoperative days. Of the neurologically well patients in whom no hemorrhage was demonstrated on initial postoperative CT scan, none experienced delayed deterioration. CONCLUSIONS: Clinically silent hemorrhage after stereotactic biopsy is very common. However, the authors did not find that knowledge of its existence ultimately affected individual patient management or outcome. The authors, therefore, suggest that the most important role of postoperative CT scanning is to screen for those neurologically well patients with no hemorrhage. These patients could safely be discharged on the same day they underwent biopsy.

Cerebrospinal fluid shunt infection: a prospective study of risk factors.

OBJECT: Hydrocephalus is a common condition of childhood that usually requires insertion of a cerebrospinal fluid (CSF) shunt. Infection is one of the most devastating complications that may arise from the presence of CSF shunts. In this study, the authors prospectively analyzed perioperative risk factors for CSF shunt infection in a cohort of children. METHODS: Between 1996 and 1999, 299 eligible patients underwent CSF shunt operations (insertions and revisions) that were observed by a research nurse at a tertiary care pediatric hospital. Several perioperative variables were recorded. All cases were followed postoperatively for 6 months to note any development of CSF shunt infection. A Cox proportional hazards model was used to analyze the relationship between the variables and the development of shunt infection. Thirty-one patients (10.4%) experienced shunt infection. Three perioperative variables were significantly associated with an increased risk of shunt infection: 1) the presence of a postoperative CSF leak (hazard ratio [HR] 19.16, 95% confidence interval [CI] 6.96-52.91); 2) patient prematurity (< 40 weeks' gestation at the time of shunt surgery: HR 4.72, 95% CI 1.71-13.06), and 3) the number of times the shunt system was inadvertently exposed to breached surgical gloves (HR 1.07, 95% CI 1.02-1.12). CONCLUSIONS: Three variables associated with an increased incidence of shunt infection have been identified. Changes in clinical practice should address these variables, as follows. 1) Great care should be taken intraoperatively to avoid a postoperative CSF leak. 2) Alternatives to placement of a CSF shunt in premature infants should be studied. 3) Surgeons should minimize manual contact with the shunt system and consider the use of double gloves.

Imaging correlates of successful endoscopic third ventriculostomy.

OBJECT: The goal of this study was to determine and compare imaging correlates in pediatric patients who underwent successful or failed endoscopic third ventriculostomies (ETVs). To this end, the authors measured ventricular size changes and the presence of cerebrospinal fluid (CSF) flow void in both groups of children following ETV. METHODS: Images obtained in children with hydrocephalus immediately before and at least 30 days after having undergone ETV were reviewed by four independent observers (two blinded and two nonblinded). Each observer independently measured the frontal and occipital horn ratio ([FOR], a reliable and valid measure of ventricular size) and provided a subjective assessment of the presence of a flow void at the ETV site, the degree of periventricular edema, and the amount of CSF over the cerebral hemispheres. There were 29 children whose mean age was 6.6 years at the time of ETV and who had a mean postoperative follow-up period lasting 1.6 years. Postoperatively, the mean reduction in ventricular size (as measured using the FOR) was 7% (95% confidence interval [CI] 3-11%) in cases that were deemed failures (eight patients) and 16% (95% CI 12-20%) in clinically successful cases (21 patients). This reduction was significantly greater in cases of clinical success compared with those that were deemed failures (p = 0.03, t-test). There were no substantial differences between blinded and nonblinded assessments. Flow void was present in 94% of successes and absent in 75% of failures (p = 0.01, Fisher's exact test). The other subjective assessments were not significantly different between the groups of successes and failures. CONCLUSIONS: Ventricular size appears to be somewhat reduced in both groups of patients who underwent clinically successful and failed ETV; however, the reduction is significantly greater among clinically successful cases. The presence of a flow void also appears to correlate with clinical success and its absence with clinical failure.

Malignant transformation of ganglioneuroma into spinal neuroblastoma in an adult. Case report.

Ganglioneuroma is generally considered to be a benign tumor and potentially surgically curable. The authors present a case of a 21-year-old woman who underwent resection of a retroperitoneal ganglioneuroma and developed spinal neuroblastoma 11 years later. She has survived 10 more years with only recent development of metastases. To the authors' knowledge, this is the first report of malignant transformation of a ganglioneuroma into a neuroblastoma. Also, such long-term survival in an adult with spinal neuroblastoma has not been reported previously. This case raises the possibility of a dedifferentiating potential for ganglion cells in a ganglioneuroma or the presence of a long-term, quiescent form of neuroblastoma.

Primary cerebellar glioblastomas multiforme in children. Report of four cases.

Primary cerebellar glioblastomas multiforme are exceedingly rare in children. The authors therefore retrospectively characterized the clinical behavior and pathological features of these tumors. A review of the database at the Hospital for Sick Children, Toronto, Canada revealed four patients with cerebellar tumors that displayed significant pleomorphism, hypercellularity, mitoses, and necrosis with pseudopalisading. The authors performed a detailed clinical, radiological, histological, and immunohistochemical analysis of the tumors in these four children (three boys and one girl; average age at presentation 7 years; range 21 months-15 years). Magnetic resonance imaging and computerized tomography most commonly revealed a large lesion with minimal edema, inhomogeneous contrast enhancement, and a discrete border. Tumor resection was subtotal in one patient and gross total in three patients. Immunostaining of the tumor cells with antisera to glial fibrillary acidic protein and vimentin was positive in varying degrees. Initial adjuvant therapy consisted of local radiation only (one patient), chemotherapy only (one patient), and radiation and chemotherapy (one patient). One patient received no adjuvant therapy. Tumor recurrence was documented in all patients: two local recurrences (at 3.5 and 7 months), one spinal recurrence (at 14 months), and one local recurrence with ventricular and spinal spread (at 8 months). Ultimately, three of the four patients developed leptomeningeal tumor spread. Patient follow up ranged from 8 to 17 months (mean 12.5 months). Three patients were dead at last follow up with a mean survival of 15 months. The prognosis for patients with cerebellar glioblastomas is extremely poor, and the tumor has a tendency for cerebrospinal fluid dissemination. The optimal management of patients harboring of these difficult-to-treat tumors, including the role of craniospinal radiation and chemotherapy, has not yet been achieved.

Tonsillar herniation: the rule rather than the exception after lumboperitoneal shunting in the pediatric population.

Although the development of tonsillar herniation (acquired Chiari malformation) in association with lumboperitoneal (LP) shunting is well recognized, it has previously been considered rare. In order to ascertain the incidence of this complication after LP shunting, the authors undertook a retrospective study of all patients in whom this form of shunt had been inserted between 1974 and 1991 at The Hospital for Sick Children, Toronto. In the 143 patients, the mean age at insertion was 3.3 years and the indications for shunt placement were hydrocephalus (81%), pseudotumor cerebri (7%), cerebrospinal fluid fistula (6%), and posterior fossa pseudomeningocele (6%). The mean follow-up period was 5.7 years, during which time there was one shunt-related death due to unsuspected tonsillar herniation. Five other patients developed symptomatic tonsillar herniation treated by suboccipital decompression. Review of all computerized tomography (CT) scans not degraded by artifact showed evidence of excess soft tissue at the level of the foramen magnum in 38 (70%) of 54 patients so studied. In order to confirm that this CT finding represented hindbrain herniation, sagittal and axial magnetic resonance (MR) images were obtained for 17 asymptomatic patients and revealed tonsillar herniation (range 2 to 21 mm) in 12 (70.6%). In addition, some of these asymptomatic patients had evidence of uncal herniation and mesencephalic distortion. Similarities and distinctions are drawn between the morphological changes occurring after LP shunting and those seen in association with the Chiari I and II malformations. Although less than 5% of this study population required treatment for tonsillar herniation, the incidence of this complication was high in asymptomatic patients; MR imaging surveillance for patients with LP shunts is therefore recommended.

Meta-analyses in orthopaedic surgery. A systematic review of their methodologies.

BACKGROUND: The number and quality of well-designed scientific studies in the orthopaedic literature are limited. The purpose of this review was to determine the methodological qualities of published meta-analyses on orthopaedic-surgery-related topics. METHODS: A systematic review of meta-analyses was conducted. A search of the Medline database provided lists of meta-analyses in orthopaedics published from 1969 to 1999. Extensive manual searches of major orthopaedic journals, bibliographies of major orthopaedic texts, and personal files identified additional studies. Of 601 studies identified, forty met the criteria for eligibility. Two investigators each assessed the quality of the studies under blinded conditions, and they abstracted relevant data. RESULTS: More than 50% of the meta-analyses included in this review were published after 1994. We found that 88% had methodological flaws that could limit their validity. The main deficiency was a lack of information on the methods used to retrieve and assess the validity of the primary studies. Regression analysis revealed that meta-analyses authored in affiliation with an epidemiology department and those published in nonsurgical journals were associated with higher scores for quality. Meta-analyses with lower scores for quality tended to report positive findings. The meta-analyses that focused upon fracture treatment and degenerative disease (hip, knee, or spine) had significantly lower mean quality scores than did meta-analyses that examined thrombosis prevention and diagnostic tests (p < 0.05). CONCLUSIONS: The majority of meta-analyses on orthopaedic-surgery-related topics have methodological limitations. Limitation of bias and improvement in the validity of the meta-analyses can be achieved by adherence to strict scientific methodology. However, the ultimate quality of a meta-analysis depends on the quality of the primary studies on which it is based. A meta-analysis is most persuasive when data from high-quality randomized trials are pooled.