Lateral Curvature Of Spine Research Articles

Trainability of functional deficits in adults with scoliosis.

Scoliosis is an understudied diagnosis of a lateral spinal curvature, and is classified with a diagnostic feature of a curve exceeding 10 degrees. Most commonly, there is no known cause and the onset occurs in adolescence. Our laboratory has previously reported on baseline functional data in adults with Adolescent Idiopathic Scoliosis (AIS). The purpose of this follow-up study is to determine the change over time in patients who were treated for scoliosis in an out-patient orthopedic physical therapy clinic. Fourteen patients were treated for an average of 6.75 weeks, resulting in 12 treatments. Patients were assessed for improvements in lumbar strength, rotational strength/symmetry, pain, and functional index (Oswestry questionnaire). Strength and range of motion (ROM) of the trunk were measured and treated on MedX spinal dynamometers. During initial evaluation, 70.4% of the patients expressed spinal pain. Typical pain improved in 72.7% of patients; peak pain was improved in 50% of patients. The perceived functional index demonstrated that 58.3% of patients reported improved function. Initially, patients’ trunk rotation strength was reported at 28.3% below average. Following therapy, patients’ rotation strength improved on the left by 26.7% and 36.4% on the right, bringing strength closer to established norms while improving bilateral strength balance (i.e., reducing strength asymmetry). We conclude that adults with AIS may benefit from specific trunk strengthening interventions that improve strength, strength symmetry, pain, and self-perceived disability.

Effects of asymmetric loading on lateral spinal curvature in young adults with scoliosis: A preliminary study.

Usual guidelines recommend symmetric load carriage over asymmetric load carriage. Whether this recommendation is valid for subjects with asymmetric body alignment, such as those with scoliosis, remains unclear. Scoliosis is both a subject-dependent and time-variant condition. Interventions are generally employed to prevent the abnormal spinal curvature from progressing. To investigate the effects of an asymmetric load carriage on lateral spinal deformity in participant with scoliosis. Repeated measure and single-case experimental designs Methods: Photogrammetry was employed to measure the scoliotic curvature changes in thoracic and lumbar regions without a load (0%) and with a single-strap cross-chest bag loaded at 2.5%, 5%, 7.5%, 10% and 12.5% of body weight. Statistical tests and programming models were adopted to determine the loading conditions (placement and weight of the bag) with optimal and minimal corrections of the affected and unaffected scoliotic spinal regions, respectively. Significant short-term postural correction of scoliosis was achieved through applying an asymmetric load on the ipsilateral shoulder relative to the apex location of the major scoliotic curve. A subject-specific optimal loading configuration was determined using a programming model. The results suggest that the application of a properly controlled asymmetric load carriage might be possible for reducing scoliotic spinal curvature. Further study of the long-term effects of subject-specific optimal asymmetric load carriage on scoliotic spinal curvatures is warranted. Clinical relevance Short-term reduction of scoliotic spinal curvatures under asymmetric load carriage was demonstrated. Thoracic curvatures could be reduced when asymmetric loading was applied on the ipsilateral shoulder relative to the scoliotic apex. Multiobjective programming was applied to determine the optimal weight of asymmetric load for participant with scoliosis.

PREVALENCE OF ADOLESCENT IDIOPATHIC SCOLIOSIS AMONG PRIMARY AND SECONDARY GIRLS SCHOOLS OF SIKANDERABAD, KARACHI, PAKISTAN

BACKGROUND AND OBJECTIVES Scoliosis is the deviation in the lateral curvature of spine. This study aimed to estimate the prevalence of idiopathic scoliosis among the school going female population of Sikanderabad, Karachi, Pakistan between the ages of 11 to 20 years. STUDY DESIGN Cross-sectional study. STUDY SETTINGS AND PARTICIPANTS Study was conducted at Sikanderabad, Karachi, Pakistan. Adolescent female population of primary and secondary schools between the ages of 11-20 years were the targeted population. METHOD Data was collected by observation of the posture, palpation of spine and questionnaire. Examination was carried out by dividing the thoracic spine into three segments i-e; upper, middle and lower thoracic spine. Adam’s forward bending test was used to assess the three segments of spine and the results were confirmed by using a scoliometer. Data was analyzed by using SPSS version 20. RESULTS The total sample consisted of 226 students. The mean age estimated was 13.61 with ±2.10 and the overall prevalance of idiopathic scoliosis was 21.16%. Lower thoracic region was founded the most affected. CONCLUSION Study confirmed that scoliosis is prevalent in females especially in the lower thoracic region of spine and the mean age group affected is 13.6 1 years.

Scoliosis surgery, predictors and outcomes in a tertiary care hospital, Riyadh, KSA

Background: Scoliosis is a back deformity, defined as structural lateral curvature of spine more than 10° (cobb angle) with rotation. Surgical intervention has better radiographic and clinical outcomes for the patients. However, it’s not indicated in all cases and it’s associated with certain complications. Methods: This is case series study which tracked subjects with scoliosis surgery. We investigated the data of all scoliosis surgery cases in our institution from 2009 to 2016 with internal board review approval. A data collection form was used to extract the data from the charts which included some demographic data such as age, gender, and date of birth, and indication of the procedure were included. Perioperative data such as operative time, blood loss, and perioperative death were estimated. Also, post-operative complications were included. Length of stay in hospital was calculated. Preoperative and postoperative recorded x-rays were interpreted and recorded. All of the reviewed data were coded and expelled into Excel sheet. Statistical package for social sciences (SPSS) version 22 was used for data analysis. Categorical variables were described by frequencies and percentages. Unpaired t-test was used to compare the pre and post-operative outcomes. Results: The mean age for the patients' who underwent the surgery is 17.7 (range, 8-56 years). 39% (32) of the sample is male and 61% (50) is female. The mean blood loss was 482.3 mL (range, 200-2900 mL) with the mean days of stay in hospital was 10 days (range, 4-90 days). The mean operative time was 250 minutes (range, 130-360 minutes). The most common indications for the surgery where neuromuscular scoliosis 36 (43.9%), idiopathic scoliosis 32 (39%). The mean cobb angel was 65° (range, 40°-116°) preoperatively and cobb angel of 16.1° (range, 0-87°) (P

Characteristics of the Spinal Alignments and Spinal Muscles in Male University Kendo Players

Purpose: Low back pain in kendo players is characterized by its development in the left lumbar area during stepping. The purpose of this study is to examine the factor and obtain indicators of physical therapy. Background: No paper has been published in English dealing with sport-associated disorders in Kendo practitioners. The present study was undertaken to provide information for overseas physicians and therapists involved in the care of Kendo practitioners, regarding the lower pack pain encountered in these individuals. Methods and measures: The subjects were 20 out of 37 male kendo players of the university from whom consent was obtained after explanation of the major purpose of the present study. We evaluated the spinal alignments using spinal X-ray pictures and spinal muscles by lumbar MRI (a ratio of the multifidus muscle to the major psoas muscle). Results: For the lateral spinal curvatures during stepping motion, all 20 players showed convex lateral curvatures in the left lumbar spine and the right thoracic spine. The average value of the lumbar flexure degrees was 27.5 ± 5.50 in standing and 39.0 ± 2.30 in stepping, showing a significant increase in stepping compared to standing (p<0.01). There was a significant negative correlation that when the ratio of the multifidus muscle to the major psoas muscle was low, the degree of change of the lumbar flexure was high (p<0.01). Conclusions: It was indicated that selective training of the multifidus muscle and increasing the amount of the muscle led to the prevention of low back pain.

Treatment of Early Onset Scoliosis - An Early Experience of Growing Rod Insertion and Lengthening

Introduction Early onset scoliosis normally found in children from the age of birth till 10 years old with female preponderance. Any lateral spinal curvature of 10 degrees or more by reference to Cobb's angle measurement is diagnosed as scoliosis. The deformities is three dimensional thus affecting spinal growth in multiple planes. Scoliosis has been classified based on it's underlying causes such as congenital, idiopathic and also secondary causes as neuromuscular scoliosis or syndromic scoliosis. Material and Methods A retrospective study of patients seen in Orthopedic and Traumatology department of Hospital Kuala Lumpur. The age of patients ranges from 8 to 13 years old and are diagnosed with scoliosis regardless of the etiology. Twenty two patient (nine males, thirteen females) whom underwent surgical intervention are the subjects of this study. Spine correction details includes Cobb'sangle, T1-S1 length, Coracoid Height Difference (CHD), Clavicle Ribcage intersection point Difference(CRID), Clavicular Tilt Angle Difference(CTAD), Vertebral height, Apex distance from CSVL and rate of lengthening were collected. Data were then statistically analyzed. Results The results obtained after data analysis were as followes: Mean age of surgery is 11.1(between 13 and 7.7). Improvement of Cobb's angle immediately post op is 33.71%(between 54.55 and 15.56). Final improvement is 48.66 (between 69.09% and 27.59%). T1S1 length improved immediately post operatively by 12.28% and at final lengthening was 26.41%. An improvement of shoulder CHD immediately post op by 38.33% and at final by 51.96% was observed. Balance CRID improve post operatively 35.21% and final 31.86%. Balance CTAD showed improvement post operatively by 24.38% and final by 23.64%. Overall shoulder balance improved post operatively by 32.64% and final was 35.72%. Reduction of coronal distance immediate postoperatively by 36.30% and final at 54.89%. Conclusion Growing rod is not only one of the best option to prevent the progression of curvature, it is also a good method in correcting the co-existing curvature. With a good correction of curvature, it will facilitate in achieving the maximal correction for definitive fusion later. The outcome of our center is comparable with the results published by other international studies. Treatment of Early Onset Scoliosis with growing rod technique is safe and effective.

Body Composition, Muscle Quality and Scoliosis in Female Collegiate Gymnasts: A Pilot Study.

Research has demonstrated an elevated prevalence of body weight concerns and scoliosis among female gymnasts. The purpose of the current pilot study was to evaluate the utility of ultrasonography and dual-energy X-ray absorptiometry (DXA) as practical imaging modalities to measure body composition and spinal curvature variables that may correlate with performance in female collegiate gymnasts (n=15). DXA was used to evaluate body composition and lateral spinal curvature, utilizing a modified Ferguson method. Echo intensity (EI) and cross-sectional area (CSA) of the vastus lateralis were determined from a panoramic cross-sectional ultrasound image. For returning athletes (n=9), performance scores from the previous season were averaged to quantify performance. The average performance score was correlated with lean mass of the arms (R=0.714; P=0.03) and right leg (R=0.680; P=0.04). Performance was not correlated with total mass, fat mass or body fat percentage (P>0.10). Scoliosis was identified in 3 of 15 scans (20%). Echo intensity and CSA of the vastus lateralis were inversely correlated with each other (R=-0.637, P=0.01), but not with other measures of body composition or performance. Results suggest that limb LBM may be a determinant of gymnastics performance, and DXA may provide important health and performance-related information for female collegiate gymnasts.

Freehand three-dimensional ultrasound system for assessment of scoliosis

SummaryBackground/ObjectiveStanding radiograph with Cobb's method is routinely used to diagnose scoliosis, a medical condition defined as a lateral spine curvature > 10° with concordant vertebral rotation. However, radiation hazard and two-dimensional (2-D) viewing of 3-D anatomy restrict the application of radiograph in scoliosis examination.MethodsIn this study, a freehand 3-D ultrasound system was developed for the radiation-free assessment of scoliosis. Bony landmarks of the spine were manually extracted from a series of ultrasound images with their spatial information recorded to form a 3-D spine model for measuring its curvature. To validate its feasibility, in vivo measurements were conducted in 28 volunteers (age: 28.0 ± 13.0 years, 9 males and 19 females). A significant linear correlation (R2 = 0.86; p < 0.001) was found between the spine curvatures as measured by Cobb's method and the 3-D ultrasound imaging with transverse process and superior articular process as landmarks. The intra- and interobserver tests indicated that the proposed method is repeatable.ResultsThe 3-D ultrasound method using bony landmarks tended to underestimate the deformity, and a proper scaling is required. Nevertheless, this study demonstrated the feasibility of the freehand 3-D ultrasound system to assess scoliosis in the standing posture with the proposed methods and 3-D spine profile.ConclusionFurther studies are required to understand the variations that exist between the ultrasound and radiograph results with a larger number of volunteers, and to demonstrate its potential clinical applications for monitoring of scoliosis patients. Through further clinical trials and development, the reported 3-D ultrasound imaging system can potentially be used for scoliosis mass screening and frequent monitoring of progress and treatment outcome because of its radiation-free and easy accessibility feature.

Automatic analysis of the trunk thermal images from healthy subjects and patients with faulty posture

BackgroundThis paper presents an automatic method for assessing temperature distribution on the patient׳s back using thermal imaging. It discusses the advantages and disadvantages of thermal imaging and presents an algorithm for image analysis and processing that runs automatically and reproducibly. MethodThe proposed new method of image analysis relates to automatic and reproducible analysis of temperature distribution on the patient׳s back. It includes the following steps: (1) detection of the external contours of the human body, (2) identification and recognition of the position of the arms, hips and shoulders, (3) application of a mesh having a fixed number of fields (which automatically adapts to the size of the patient׳s back), (4) analysis of the paraspinal muscles. These steps are preceded by image pre-processing. ResultsBased on a thermal image, this new fully automated algorithm enables to: (1) evaluate temperature distribution in the paraspinal area; (2) pre-assess the degree of lateral spinal curvature in screening, and (3) evaluate anomalies (deviations from the norm) in temperature distribution. The algorithm was practically implemented in Matlab Image Processing Toolbox.

Ultrasound Volume Projection Imaging for Assessment of Scoliosis.

The standing radiograph is used as a gold standard to diagnose spinal deformity including scoliosis, a medical condition defined as lateral spine curvature > 10°. However, the health concern of X-ray and large inter-observer variation of measurements on X-ray images have significantly restricted its application, particularly for scoliosis screening and close follow-up for adolescent patients. In this study, a radiation-free freehand 3-D ultrasound system was developed for scoliosis assessment using a volume projection imaging method. Based on the obtained coronal view images, two measurement methods were proposed using transverse process and spinous profile as landmarks, respectively. As a reliability study, 36 subjects (age: 30.1 ±14.5; male: 12; female: 24) with different degrees of scoliosis were scanned using the system to test the inter- and intra-observer repeatability. The intra- and inter-observer tests indicated that the new assessment methods were repeatable, with ICC larger than 0.92. Small intra- and inter-observer variations of measuring spine curvature were observed for the two measurement methods (intra-: 1.4 ±1.0° and 1.4 ±1.1°; inter-: 2.2 ±1.6° and 2.5 ±1.6°). The results also showed that the spinal curvature obtained by the new method had good linear correlations with X-ray Cobb's method (R2 = 0.8, p < 0.001, 29 subjects). These results suggested that the ultrasound volume projection imaging method can be a promising approach for the assessment of scoliosis, and further research should be followed up to demonstrate its potential clinical applications for mass screening and curve progression and treatment outcome monitoring of scoliosis patients.

Detection of Adolescent Idiopathic Scoliosis among Nepalese Children Through the School Screening Program

Introduction: Idiopathic Adolescent Scoliosis (IAS) is the commonest type of scoliosis without any known cause. There has been studies in different countries and population on IAS; and its prevalence rate varies for different population. There has been no reported study done in Nepal on prevalence of adolescent idiopathic scoliosis (AIS). The aim of this study was to detect and evaluate the prevalence of idiopathic adolescent scoliosis in school children in different parts of Nepal. Methods: This was a descriptive cross sectional study conducted at five schools from different geographical parts of Nepal, from January 2010 to December 2010. Scoliosis screening was done in 5 schools from different geographical locations of Nepal. Children (from grade 6 to 10; age more than 10 years) with positive Adam’s forward bending test and scoliometer angle of 5 degrees or more were subjected for radiographic evaluation of the spine. The criterion for the diagnosis of scoliosis was detection of Cobb’s angle of more than 10 degrees. Evaluation of scoliosis according to the age, gender, ethnic group, spinal region and magnitude of curve was done. Results: Out of 1094 children screened, 31 (2.83%) were referred for radiological evaluation; and 12 of them had lateral spinal curvature of more than 10 degrees. Hence the prevalence of scoliosis was 1.09%. The girl to boy ratio of distribution of scoliosis was 3:1 for larger curves of more than 20 degrees. Maximum number of scoliosis cases was seen in girls of 13 years, and the right sided thoracic scoliosis was most common. There is no ethnic predominance of scoliosis. Conclusion: Prevalence of idiopathic scoliosis among school children who need treatment in Nepal is low; however, school screening program has its epidemiological value. DOI: http://dx.doi.org/10.3126/noaj.v3i2.9514 NOAJ July-December 2013, Vol 3, Issue 2, 14-19

The influence of lateral spinal curvature on range of motion

Methods Height, body mass, spacing between hands, and length of the upper limbs were measured in all of the examinees. Lateral spinal curvature was identified using a bob (plummet) and clinical examination. Examinees performed five spinal flexibility tests: right and left lateral mobility test, forward bending test, shoulder static flexibility test, and neck and trunk static flexibility test. Results gathered using a bob (plummet) and clinical examination were compared to the results of flexibility tests. Difference between these methods in children with, and without, lateral spinal curvature was determined with statistical Ttest. Medcalc program was used for statistics. Statistical significance was affirmed at p=0.01 level.

Some Possibilities of Correction and Compensation in Body Posture Regulation Among Children and Adolescents with Low Degree Scoliosis

Postural alignments, secondary curves of spine and tendency to unequal body weight distribution are the compensatory mechanisms in scoliosis, eventually leading to disturbances in the regulation of body posture. The pathological pattern of incorrect posture, evokes a vicious circle of causes and effects, which probably includes alterations in body weight distribution to both feet. To examine the role of equal weight loading of both feet in posture regulation among children and adolescents with low-degree scoliosis. A total of 115 participants, aged 7-19 years, were divided into three groups: low degree scoliosis (10-26⁰ Cobb; n = 56), scoliotic posture (5-9⁰; n = 29), and without lateral spine curvature (n = 30). Three measurements of body arrangement and the weight distribution on feet were simultaneously taken using the photogrammetry and the podographic platform: in a free standing position, while attempt to correct body arrangement and with equal loading of both feet. Unequal weight distribution was observed in free standing position in patients with scoliosis. Attempts to correct body arrangement worsened existing disproportion, especially in the left-side curvatures. Equal feet loading lead to the body disarrangement, even among non - scoliotic subjects. In subjects with low degree scoliosis the compensatory changes in the spatial arrangement of the body are usually accompanied by asymmetric distribution of foot pressure and the active attempt to correct the curvature enhances this asymmetry. Attempts to maintain symmetrical distribution of body weight result in significant deterioration of the posturometric parameters even in non-scoliotic subjects.

Some possibilities of correction and compensation in body posture regulation among children and youth with low degree scoliosis

Materials and methods A total of 115 participants, aged 7-19 years, were divided into three groups: low degree scoliosis (10-26° Cobb; n = 56), scoliotic posture (5-9°; n = 29), and without lateral spine curvature (n = 30). Three measurements of body arrangement and the weight distribution on feet were simultaneously taken using the photogrammetry and the podographic platform: in a free standing position, while attempt to correct body arrangement and with equal loading of both feet. Results Unequal weight distribution was observed in free standing position in patients with scoliosis. Attempts to correct body arrangement worsened existing disproportion, especially in the left-side curvatures. Equal feet loading lead to the body disarrangement, even among non – scoliotic subjects. Conclusions In subjects with low degree scoliosis the compensatory changes in the spatial arrangement of the body are usually accompanied by asymmetric distribution of foot pressure and the active attempt to correct the curvature enhances this asymmetry. Attempts to maintain symmetrical distribution of body weight result in significant deterioration of the posturometric parameters.

Scoliosis Imaging: What Radiologists Should Know

Scoliosis is defined as a lateral spinal curvature with a Cobb angle of 10° or more. This abnormal curvature may be the result of an underlying congenital or developmental osseous or neurologic abnormality, but in most cases the cause is unknown. Imaging modalities such as radiography, computed tomography (CT), and magnetic resonance (MR) imaging play pivotal roles in the diagnosis, monitoring, and management of scoliosis, with radiography having the primary role and with MR imaging or CT indicated when the presence of an underlying osseous or neurologic cause is suspected. In interpreting the imaging features of scoliosis, it is essential to identify the significance of vertebrae in or near the curved segment (apex, end vertebra, neutral vertebra, stable vertebra), the curve type (primary or secondary, structural or nonstructural), the degree of angulation (measured with the Cobb method), the degree of vertebral rotation (measured with the Nash-Moe method), and the longitudinal extent of spinal involvement (according to the Lenke system). The treatment of idiopathic scoliosis is governed by the severity of the initial curvature and the probability of progression. When planning treatment or follow-up imaging, the biomechanics of curve progression must be considered: In idiopathic scoliosis, progression is most likely during periods of rapid growth, and the optimal follow-up interval in skeletally immature patients may be as short as 4 months. After skeletal maturity is attained, only curves of more than 30° must be monitored for progression.

Is there a relationship between foetal position and both preferred lying posture after birth and pattern of subsequent postural deformity in non-ambulant people with cerebral palsy?

A pattern of postural deformity was observed in a previous study that included an association between direction of spinal curvature and direction of windsweeping with more windswept deformities occurring to the right and lateral spinal curvatures occurring convex to the left. The direction of this pattern was found to be associated with preferred lying posture in early life. The aim of this study was to test the association between foetal position and both the preferred lying posture after birth, and the direction of subsequent postural deformity in non-ambulant children with cerebral palsy (CP). A retrospective cohort study was carried out involving 60 participants at level five on the gross motor function classification for CP. Foetal position during the last month of pregnancy was taken from antenatal records and parents were interviewed to identify preferred lying posture in the first year of life. At the time of the physical assessment ages ranged from 1 year and 1 month to 19 years with a median age of 13 years and 1 month. Foetal presentation was found to be associated with the preferred lying posture with participants carried in a left occipito-anterior/lateral position more likely to adopt a supine head right lying posture, and vice versa. An association was also observed between the foetal position and asymmetrical postural deformity occurring later in life with participants carried in a left occipito-anterior/lateral presentation more likely to have a convex left spinal curve, a lower left pelvic obliquity, and a windswept hip pattern to the right. Clinicians should be aware of the association between foetal presentation, asymmetrical lying posture, and the direction of subsequent postural deformity for severely disabled children. A hypothesis is described that might help to explain these findings.

Patterns of postural deformity in non-ambulant people with cerebral palsy: what is the relationship between the direction of scoliosis, direction of pelvic obliquity, direction of windswept hip deformity and side of hip dislocation?

Objective: To investigate: (a) associations between the direction of scoliosis, direction of pelvic obliquity, direction of windswept deformity and side of hip subluxation/ dislocation in non-ambulant people with cerebral palsy; and (b) the lateral distribution of these postural asymmetries. Design: Cross-sectional observational study. Setting: Posture management services in three centres in the UK. Subjects: Non-ambulant people at level five on the gross motor function classification system for cerebral palsy. Main measures: Direction of pelvic obliquity and lateral spinal curvature determined from physical examination, direction of windswept hip deformity derived from range of hip abduction/adduction, and presence/side of unilateral hip subluxation defined by hip migration percentage. Results: A total of 747 participants were included in the study, aged 6—80 years (median 18 years 10 months). Associations between the direction of scoliosis and direction of pelvic obliquity, and between the direction of windswept hip deformity and side hip subluxation/dislocation were confirmed. A significant association was also seen between the direction of scoliosis and the direction of the windswept hip deformity (P<0.001) such that the convexity of the lateral spinal curve was more likely to be opposite to the direction of windsweeping. Furthermore, significantly more windswept deformities to the right (P = 0.007), hips subluxed on the left (P = 0.002) and lateral lumbar/lower thoracic spinal curves convex to the left (P = 0.03) were observed. Conclusions: The individual asymmetrical postural deformities are not unrelated in terms of direction and not equally distributed to the left/right. A pattern of postural deformity was observed.

Factors of Thoracic Cage Deformity That Affect Pulmonary Function in Adolescent Idiopathic Thoracic Scoliosis

This clinical study examined the association between pulmonary function and thoracic cage deformities in scoliosis. To determine the factors in spinal and thoracic cage deformities that affect pulmonary function in scoliosis. Pulmonary function in scoliosis has generally been evaluated in terms of lateral spinal curvature. No previous report has evaluated changes in pulmonary function taking into consideration measurements reflecting not only spinal curvature but also thoracic cage deformities, although scoliosis is a three-dimensional deformity. A total of 109 patients (mean age, 14.2 years) with adolescent idiopathic right thoracic scoliosis (mean lateral spinal curvature, 37.7 degrees) had full assessment of pulmonary function and a radiographic evaluation from radiographs of the whole spine, Moiré topography, and thoracic computed tomography. Multiple regression analysis (stepwise method) was performed at each vertebral level from T3-T12 to identify the factor that most strongly affects %VC. The correlation coefficient was highest at T9 and next highest at T8, with values of 0.641 (r2 = 0.411, P < 0.0001) and 0.625 (r2 = 0.390, P < 0.0001), respectively. At T9, multiple regression analysis showed that the sagittal diameter of the thoracic cage and the total lung area were identified as factors that most strongly affect %VC. Similarly, the sagittal diameter of the thoracic cage and the rotation angle to the sagittal plane were identified at T8. The factors that reduced %VC were the sagittal diameter of the thoracic cage, total lung area and vertebral rotation at the T8 and T9 levels.

Multiple linear regression with some correlated errors: Classical and robust methods

In this paper we consider classical and robust methods of estimation and diagnostics for the multiple linear regression model when some of the errors are correlated. This work was motivated by the analysis of a medical data set, from an observational study aimed at identifying factors affecting the outcome of a surgical method for the correction of scoliosis (abnormal lateral spinal curvature). There are 392 observations but some of them are on the same patient (double curves). It seems adequate to consider a multiple linear regression model but, since it is not desirable to discard the double curves, the assumption of non-correlated errors is clearly violated, and this is indeed confirmed by related diagnostics on the residuals (Durbin-Watson test). A more appropriate model retains the linear structure but allows for non-null correlation between the errors on the same patient. We propose two different procedures for the estimation of the parameters of the linear model and the correlation parameters: maximum likelihood assuming normal errors and a robustified version obtained by plugging-in results from robust linear regression. The latter procedure is designed to be resistant to outlying observations or error distributions with heavy tails and has produced the most satisfactory results for the analysed data set.

Sublethal effects of lead on northern leopard frog (Rana pipiens) tadpoles

Northern leopard frogs (Rana pipiens) were exposed to environmentally relevant concentrations of lead in water (3, 10, and 100 microg/L as lead nitrate) from the embryonic stage to metamorphosis. Survival, growth, deformity, swimming ability, metamorphosis, and lead tissue concentrations were evaluated. Tadpole growth was significantly slower in the early stages (Gosner stages 25-30) in 100 microg/L treatment. More than 90% of tadpoles in the 100 microg/L treatment developed lateral spinal curvature, whereas almost all the tadpoles in the other groups were morphologically normal. Spinal deformity was associated with abnormal swimming behavior. Maximum swimming speed of tadpoles in the 100 microg/L treatment was significantly lower than that in the other groups. No significant effect of lead exposure was found on percentage metamorphosis, snout-vent length, mortality, and sex ratio of metamorphs. Time to metamorphosis was delayed in 100 microg/L treatment. Lead tissue concentrations in the tadpoles ranged from 0.1 to 224.5 mg/kg dry mass, were positively related to lead concentrations in the water, and fell within the range of tissue concentrations of wild tadpoles found in previous studies. According to our results, the current U.S. Environmental Protection Agency freshwater-quality chronic criterion for lead (2.5 microg/L) is appropriate to protect northern leopard frog larvae.