Browsing by Person "Polak, F. J."

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Anthropometry and allometry in girls with right thoracic adolescent idiopathic scoliosis (AIS).
(ISO Press, 1997) Cole, A. A.; Burwell, R. G.; Kirby, Alanah; Polak, F. J.; Webb, J. K.; Diab, K. M.; Sevastik, J. A.
Body mass index of girls in health influences menarche and skeletal maturation: a leptin-sympathetic nervous system focus on the trunk with hypothalamic asymmetric dysfunction in the pathogenesis of adolescent idiopathic scoliosis?
(2008) Burwell, R. G.; Aujla, R. K.; Kirby, Alanah; Dangerfield, P. H.; Moulton, A.; Cole, A. A.; Polak, F. J.; Pratt, R. K.; Webb, J. K.
Lower body mass index (BMI) and lower circulating leptin levels have been reported in girls with AIS. In this paper we evaluate skeletal sizes and asymmetries by higher and lower BMI subsets about the means for each of three groups of girls age 11-18 years: 1) normals, 2) school screening referrals, and 3) preoperative girls. Higher and lower BMI subsets, likely to have separated subjects with higher from those with lower circulating leptin levels, identify: 1) girls with relatively earlier and later menarche; 2) trunk width size greater in the higher than in the lower BMI subset, of all three groups; 3) abnormal upper arm length (UAL) asymmetries (right minus left) in the lower BMI subset of the preoperative girls; and 4) in thoracic AIS of screened and preoperative girls, Cobb angle and apical vertebral rotation each significantly and positively correlate with UAL asymmetry in the lower BMI subset but not in the higher BMI subset. In preoperative girls, the lower BMI subset shows the combination of relatively reduced pelvic width and abnormal UAL asymmetry, suggesting that both are linked to lower circulating leptin levels. An earlier puberty with hormonal changes provides a plausible explanation for the larger trunk width at the shoulders and pelvis especially at the younger ages in the higher BMI subsets. At the shoulders, this widening is driven by the ribcage which, in human evolution was acquired with decoupling of head and trunk movements required for efficient bipedal gait. The UAL asymmetry patterns within the groups and BMI subsets are not explained by hormonal mechanisms. It is hypothesized that 1) normal trunk widening of the thoracic cage by hormones in human adolescence is supplemented via the sympathetic nervous system under leptin-hypothalamic control influenced by energy stores (metabolic fuel); and 2) hypothalamic dysfunction with altered hypothalamic sensitivity to leptin through a SNS-driven asymmetric effect may create skeletal length asymmetries in upper arms, ribs, ilia and vertebrae, and initiate AIS. Additional mechanisms acting in the spine and trunk may be required for AIS to progress including 1) somatic nervous system dysfunction, 2) biomechanical spinal growth modulation, and 3) osteopenia.
Etiologic theories of idiopathic scoliosis: neurodevelopmental concept of maturational delay of the CNS body schema (body-in-the-brain)
(IOS Press, 2006) Burwell, R. G.; Freeman, B. J. C.; Dangerfield, P. H.; Aujla, R. K.; Cole, A. A.; Kirby, Alanah; Polak, F. J.; Pratt, R. K.; Webb, J. K.; Moulton, A.; Dangerfield, P. H.; Uyttendaele, D.
Several workers consider that the etiology of adolescent idiopathic scoliosis (AIS) involves undetected neuromuscular dysfunction. During normal development the central nervous system (CNS) has to adapt to the rapidly growing skeleton of adolescence, and in AIS to developing spinal asymmetry from whatever cause. Examination of evidence from (1) anomalous extra-spinal left-right skeletal length asymmetries, (2) growth velocity and curve progression, and (3) the CNS body schema, parietal lobe and temporoparietal junction, led us to propose a new etiologic concept namely of delay in maturation of the CNS body schema during adolescence. In particular, the development of an early AIS deformity at a time of rapid spinal growth the association of CNS maturational delay results in the CNS attempting to balance a lateral spinal deformity in a moving upright trunk that is larger than the information on personal space (self) already established in the brain by that time of development. It is postulated that the CNS maturational delay allows scoliosis curve progression to occur - unless the delay is temporary when curve progression would cease. The putative maturational delay in the CNS body schema may arise (1) from impaired sensory input: (2) primarily in the brain; and/or (3) from impaired motor output. Oxidative stress with lipid peroxidation in the nervous system may be involved in some patients. The concept brings together many findings relating AIS to the nervous and musculo-skeletal systems and suggests brain morphometric studies in subjects with progressive AIS.
Girls with right thoracic adolescent idiopathic scoliosis (AIS): lower body mass index (BMI) and evidence suggesting an inverse relation between sympathoactivation and somatotropic (GH/1GF) secretions
(IOS Press, 2010-07-10) Burwell, R. G.; Aujla, R. K.; Grevitt, M. P.; Randell, T. L.; Dangerfield, P. H.; Cole, A. A.; Kirby, Alanah; Polak, F. J.; Pratt, R. K.; Moulton, A.; Webb, J. K.; Aubin, Carl-Eric; Labelle, Hubert; Moreau, Alain; Stokes, Ian A. F.
Introduction: Relatively lower but not higher BMI was associated with left-right skeletal asymmetries in 1)preoperative AIS girls, upper arm length asymmetry (UALA), 2) normal adolescent girls and boys, trunk asymmetry; and 3) normal juvenile girls, skeletal sizes for age associated withUALA. Objectives: In girls with right thoracic AIS to evaluate the effect of lower and higher BMI upon the relation of curve severity to UALA. Material and Methods: Data from girls with right thoracic AIS (n=110, preoperative n=77, screened n=33) including Cobb angle, apical vertebral rotation (AVR) and UALA (right minus left, mm), are evaluated by higher (n-57) and lower (n=53) BMI relative to median values (mean BMIs 21.8 and 17.3 respectively, p<0.001). Results: Mean Cobb angles and UALA are not significantly different between lower and higher BMI. Mean AVR in the lower BMI subset is significantly less than in the higher BMI subset. Cobbangle and AVR each correlate significantly with UALA in girls with lower but not higher BMI. Conclusion: In accordance with our double neuro-osseous theory for AIS pathogenesis in girls, we postulate that lower BMI girls with presumptively lower circulating leptin levels, have relatively more sympathoactivation causing the skeletal asymmetries and less somatotropic secretions. From previous findings of younger preoperative girls with higher BMI showing early skeletal overgrowth, such girls may have relatively more somatotropic secretions and less sympathoactivation. Significance: This putative inverse relation for AIS is in accordance with several medical conditions showingan inverse relationship between sympathoactivation and GH/1GF secretions.
Leg-arm length ratios correlate with severity of apical vertebral rotation in girls after school screening for adolescent idiopathic scoliosis (AIS): a dynamic pathomechanism in the initiation of the deformity?
(IOS Press, 2008) Burwell, R. G.; Aujla, R. K.; Kirby, Alanah; Dangerfield, P. H.; Moulton, A.; Freeman, B. J. C.; Cole, A. A.; Polak, F. J.; Pratt, R. K.; Webb, J. K.; Dangerfield, P. H.
There is increasing support for the view that the unique human bipedalism and the erect posture are prerequisites for the pathogenesis of adolescent idiopathic scoliosis (AIS). How human bipedalism may contribute to the pathogenesis of AIS is not clear. In normal humans, axial rotations and counter-rotations of the trunk are carried out frequently and forcibly in activities that are not performed by quadrupeds. Some workers have analysed gait in AIS subjects, others have studied torsions in lower limb bones, but there are only two reports on leg-arm ratios in relation to AIS. In this paper, leg-arm ratios studied in relation to the spinal deformity in scoliosis screening referrals, reveal a highly significant correlation with the apical vertebral rotation but not the Cobb angle of the scoliosis curves. We suggest that leg-arm proportions and movements during gait involving pelvi-spinal axial rotations and thoracic counter-rotations contribute a dynamic pathomechanism to early AIS from whatever cause and involving the thoracic cage. Curve progression needs other mechanisms that may include a central nervous system failure to control structural asymmetry of vertebral axial rotation, and biomechanical spinal growth modulation.
Preliminary study of a new real-time ultrasound method for measuring rib rotation and spinal rotation in scoliosis.
(IOS Press, 1997) Kirby, Alanah; Aujla, R. K.; Burwell, R. G.; Cole, A. A.; Moulton, A.; Polak, F. J.; Webb, J. K.; Diab, K. M.; Sevastik, J. A.
Preoperative Girls with Adolescent Idiopathic Scoliosis (AIS): Systemic Skeletal Overgrowth Patterns Probably Hormonally-driven Revealed in Higher and Lower Body Mass Index (BMI) Subsets
(IOS Press, 2010-07-10) Burwell, R. G.; Aujla, R. K.; Grevitt, M. P.; Randell, T. L.; Dangerfield, P. H.; Cole, A. A.; Kirby, Alanah; Polak, F. J.; Pratt, R. K.; Moulton, A.; Webb, J. K.; Aubin, Carl-Eric; Labelle, Hubert; Moreau, Alain; Stokes, Ian A. F.
Introduction: Evidence suggests that extraspinal general skeletal overgrowth in AIS girls is associated with the relative anterior spinal overgrowth (RASO) giving such overgrowth pathogenetic significance. Objectives: To compare skeletal sizes for age of preoperative AIS/normal girls by higher and lower BMI subsets relative to median values in a cross-sectional study. Materials and Methods: Preoperative (n=122) and normal girls (n=274) age 11-18 years were measured using the Holtain equipment. BMI was weight in kg/stature in meters2 corrected for scoliosis. Skeletal sizes for each of stature, sitting height, subischial height, trunk widths (biacromial and biiliac) and limb segment lengths bilaterally (upper arm, forearm-with-hand, tibia, and foot) were compared within each BMI subset (ANOVA correcting for age). Spinal deformity was measured. Menarcheal age was recorded. Results: With relatively higher BMIs, preoperative girls from 11 years have larger skeletal segments than normals, decreasing to normal size by 16 years, in each of 11 skeletal segments, six in paired limb bones but not feet. BMIs and menarcheal ages are similar. With relatively lower BMIs, two growth phases are evident: early with skeletal sizes of preoperatives mostly similar to normals; and late, larger than normals. Menarche in preoperatives is later than normals but not statistically significant. Conclusion: Overall, preoperative girls show skeletal overgrowth patterns which are systemic, probably hormonally driven, for the relatively higher BMI subset somatotropic (growth hormone/IGF) axis, and the relatively lower BMI subset, estrogen. Significance: Circulating hormones in AIS girls by relatively higher and lower BMI need study, leading to possible medical therapy.
The posterior skeletal thorax: rib-vertebral angle and axial vertebral rotation asymmetries in adolescent idiopathic scoliosis.
(IOS Press, 2008) Burwell, R. G.; Aujla, R. K.; Freeman, B. J. C.; Dangerfield, P. H.; Cole, A. A.; Kirby, Alanah; Polak, F. J.; Pratt, R. K.; Moulton, A.; Dangerfield, P. H.
The deformity of the ribcage in thoracic adolescent idiopathic scoliosis (AIS) is viewed by most as being secondary to the spinal deformity, though a few consider it primary or involved in curve aggravation. Those who consider it primary ascribe pathogenetic significance to rib-vertebra angle asymmetry. In thoracic AIS, supra-apical rib-vertebra angle differences (RVADs) are reported to be associated with the severity of the Cobb angle. In this paper we attempt to evaluate rib and spinal pathomechanisms in thoracic and thnoracolumbar AIS using spinal radiographs and real-time ultrasound. On the radiographs by costo-vertebral angle asymmetries (rib-vertebral angle differences RVADs, and rib-spinal angle differences RSADs), apical vertebral rotation (AV) and apical vertebral translation (AVT) were measured; and by ultrasound, spine-rib rotation differences (SRRDs) were estimated. RVADs are largest at two and three vertebral levels above the apex where they correlate significantly and positively with Cobb angle and AVT but not AVR. In right thoracic AIS, the cause(s) of the RVA asymmetries is unknown: it may result from trunk muscle imbalance, or from ribs adjusting passively within the constraint of the fourth column of the spine to increasing spinal curvature from whatever cause. Several possible mechanisms may drive axial vertebral rotation including, biplanar spinal asymmetry, relative anterior spinal overgrowth, dorsal shear forces in the presence of normal vertebral axial rotation, asymmetry of rib linear growth, trunk muscle imbalance causing rib-vertebra angle asymmetry weakening the spinal rotation-defending system of bipedal gait, and CNS mechanisms.
Ultrasound femoral anteversion (FAV) relative to tibial torsion (TT) is abnormal after school screening for adolescent idiopathic scoliosis (AIS): evaluation by two methods
(IOS Press, 2008) Burwell, R. G.; Aujla, R. K.; Kirby, Alanah; Moulton, A.; Dangerfield, P. H.; Freeman, B. J. C.; Cole, A. A.; Polak, F. J.; Pratt, R. K.; Webb, J. K.; Dangerfield, P. H.
In the scoliotic spine, torsion is generally evaluated in relation to axial rotation of the apical vertebra. In the lower limbs, the changes in torsion by age of femoral anteversion (FAV) relative to tibial torsion (TT) have been studied in dried bones, normal growing subjects and adults and subjects with osteoarthritis of the hip or the knee. This paper reports the application of real-time ultrasound to FAV and TT in normal children age 11-18 years and in scoliosis screening referrals with particular reference to how FAV relates to TT as 1) ratios, and 2) tibio-femoral index (TFI) of torsion, calculated as TT minus femoral FAV. The FAV/TT ratio findings show an abnormal normal relationship of FAV to TT both proximo-distally and in left-right asymmetry. These may express torsional abnormalities in femoral and/or tibial growth plates with left-right asynchrony suggesting the possibility of similar torsional abnormalities in vertebral end-plates and/or rib growth plates initiating the deformity of AIS. TFI of the right limb in the scoliosis girls is greater than in the normals that is interpreted as resulting from earlier skeletal maturation of FAV. FAV/TT ratios and TFI are unrelated to the spinal deformity (Cobb angle and apical vertebral rotation) except for boys where TFI is associated with apical vertebral rotation. FAV/TT ratios may be a more accurate method estimating the relationship of FAV to TT. than TFIs.
Upper arm lengths suggest transient asymmetry associated with right thoracic adolescent idiopathic scoliosis (RT-AIS) of girls with implications for pathogenesis and estimation of linear skeletal overgrowth
(IOS Press, 2012-07) Burwell, R. G.; Aujla, R. K.; Grevitt, M. P.; Randell, T. L.; Dangerfield, P. H.; Cole, A. A.; Kirby, Alanah; Polak, F. J.; Pratt, R. K.; Webb, J. K.; Moulton, A.; Grivas, T.; Kotwicki, T.
The International Research Society of Spinal Deformities (IRSSD) promotes a multidisciplinary approach to scoliosis and spinal problems, with a strong emphasis on research in the field of etiology, as well as the clinical effectiveness of a wide range of interventions. The society has been active in one form or another for three decades, encouraging open discussion in all areas related to spinal deformities. The International Research Society of Spinal Deformities (IRSSD) promotes a multidisciplinary approach to scoliosis and spinal problems, with a strong emphasis on research in the field of etiology, as well as the clinical effectiveness of a wide range of interventions. The society has been active in one form or another for three decades, encouraging open discussion in all areas related to spinal deformities. This current overview of topics related to spinal deformities provides the opportunity for readers to learn more about the latest developments in this field, and it contributes to the advancement of study and research into spinal deformities for the benefit of patients.