Clinical evaluation of scoliosis during growth: description and reliability

The clinical evaluation, even today, remains a central point in the diagnosis, prognostic definition and treatment prescription regarding scoliosis. The clinical evaluation of a scoliotic patient has been established for a long time, but it has not been standardized. The aim of the present work is to report the most common clinical measures for the assessment of scoliosis, explain the usefulness of each clinical measurement, and report the repeatability and limits in order to help the physician in making appropriate clinical choices.

METHODS

The height of the hump, the angle of trunk rotation, the sagittal and frontal profiles, and the Trunk Aesthetic Clinical Evaluation (TRACE) have been fully described, and their reliability and repeatability have been assessed.

RESULTS

The measures analyzed showed good reliability and repeatability on the intra-operator basis. The inter-operator repeatability is usually not that good.

CONCLUSION

The main measures of the clinical assessment of scoliotic patients have been tested, and their reliability has been evaluated. The knowledge of measurement error, as well as intra- and inter-operator reliability, are essential for the clinical evaluation and treatment of scoliosis. This is an unavoidable basis for decision making in the assessment and the treatment of scoliosis.

Ultrasound femoral anteversion (FAV) and tibial torsion (TT) after school screening for adolescent idiopathic scoliosis (AIS)

Torsion and counter-torsion in the spine are features of the three-dimensional deformity of adolescent idiopathic scoliosis, Vertebral axial rotation has recently been found in the normal adult thoracic spine. Torsion in the lower limbs, femora and tibiae is a feature of normal human skeletal postnatal development. In recent years, femoral anteversion (FAV) and tibial torsion (TT) have been studied in normal children by imaging techniques, especially ultrasound. This paper reports summaries of the application of real-time ultrasound to FAV and TT of normal children and scoliosis school screening referrals. In the scoliosis girls and boys, the FAV decrease and FAV asymmetry compared with normals may result from abnormally increased femoral detorsion maturationally earlier with left-right asynchrony which, if repeated as a growth plate anomaly in the trunk (spine and/or periapical ribs), might initiate the AIS deformity, given other requirements. In scoliosis boys relative to girls, the TT decrease without asymmetry may result from sexually dimorphic maturation at knee tibial growth plates ? maturationally delayed TT with left-right synchrony.

Bone quality: the material and structural basis of bone strength

The material composition and structural design of bone determine its strength. Structure determines loads that can be tolerated but loads also determine structure. Bone modifies its material composition and structure to accommodate loads by adaptive modeling and remodeling. Adaptation is successful during growth but not aging because accumulating insults, including a reduction in the volume of bone formed in the basic multicellular unit (BMU), increased resorption in the BMU, increased remodeling rate in midlife in women and in some men because of sex hormone deficiency, and in both sexes in old age as a consequence of secondary hyperparathyroidism and reduced periosteal bone formation, all of which compromises the material composition of bone and its structure. An understanding of the mechanisms of adaptation and failed adaptation provides rational approaches to interventions that can prevent or restore bone fragility.

Concepts on the pathogenesis of adolescent idiopathic scoliosis. Bone growth and mass, vertebral column, spinal cord, brain, skull, extra-spinal left-right skeletal length asymmetries, disproportions and molecular pathogenesis

There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). Encouraging advances thought to be related to AIS pathogenesis have recently been made in several fields including anthropometry of bone growth, bone mass, spinal growth modulation, extra-spinal left-right skeletal length asymmetries and disproportions, magnetic resonance imaging of vertebral column, spinal cord, brain, skull, and molecular pathogenesis. These advances are leading to the evaluation of new treatments including attempts at minimally invasive surgery on the spine and peri-apical ribs. Several concepts of AIS are outlined indicating their clinical applications but not their research potential. The concepts, by derivation morphological, molecular and mathematical, are addressed in 15 sections: 1) initiating and progressive factors; 2) relative anterior spinal overgrowth; 3) dorsal shear forces that create axial rotational instability; 4) rotational preconstraint; 5) uncoupled, or asynchronous, spinal neuro-osseous growth; 6) brain, nervous system and skull; 7) a novel neuro-osseous escalator concept based on a putative abnormality of two normal polarized processes namely, a) increasing skeletal dimensions, and b) the CNS body schema - both contained within a neuro-osseous timing of maturation (NOTOM) concept; 8) transverse plane pelvic rotation, skeletal asymmetries and developmental theory; 9) thoraco-spinal concept; 10) origin in contracture at the hips; 11) osteopenia; 12) melatonin deficiency; 13) systemic melatonin-signaling pathway dysfunction; 14) platelet calmodulin dysfunction; and 15) biomechanical spinal growth modulation. From these concepts, a collective model for AIS pathogenesis is formulated. The central concept of this model includes the body schema of the neural systems, widely-studied in adults, that control normal posture and coordinated movements with frames of reference in the posterior parietal cortex. The escalator concept has implications for the normal development of upright posture, and the evolution in humans of neural control, the trunk and unique bipedal gait.

[Vertebral column growth in children after surgical correction of severe kyphosis in tuberculosis spondylitis]

The growth of the unit of vertebrae and intact vertebrae outside and within the instrumental fixation area was studied in children operated on for tuberculosis spondylitis complicated by severe kyphotic deformity. There was a considerable growth retardation of blocked vertebrae after radical spinal repair from the growth of intact vertebrae. Instrumental fixation of the vertebral column after its radical reconstruction causes no considerable retardation of the vertical growth of intact vertebral bodies; however, it leads to the advanced growth of their anterior versus posterior portions, which mediates a supplementary self-correction of residual kyphosis during growth. When compression implants are presented in the body for 2 years or more, most children develop degeneration of intervertebral risks within the fixation area.

Etiologic theories of idiopathic scoliosis. Somatic nervous system and the NOTOM escalator concept as one component in the pathogenesis of adolescent idiopathic scoliosis

There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). In recent years encouraging advances thought to be related to the pathogenesis of AIS have been made in several fields. After reviewing concepts of AIS pathogenesis we formulated a collective model of pathogenesis. The central concept of this collective model is a normal neuro-osseous timing of maturation (NOTOM) system operating in a child's internal world during growth and maturation; this provides a dynamic physiological balance of postural equilibrium continuously renewed between two synchronous, polarized processes (NOTOM escalator) linked through sensory input and motor output, namely: 1) osseous escalator-increasing skeletal size and relative segmental mass, and 2) neural escalator - including the CNS body schema. The latter is recalibrated continuously as the body adjusts to biomechanical and kinematic changes resulting from skeletal enlargement, enabling it to coordinate motor actions. We suggest that AIS progression results from abnormality of the neural and/or osseous components of these normal escalator in time and/or space - as asynchrony and/or asymmetries - which cause a failure of neural systems to control asymmetric growth of a rapidly enlarging and moving adolescent spine. This putative initiating asymmetric growth in the spine is explained in separate papers as resulting from dysfunction of the hypothalamus expressed through the sympathetic nervous system (leptin-sympathetic nervous system concept for AIS pathogenesis). In girls, the expression of AIS may result from disharmony between the somatic and autonomic nervous systems - relative postural maturational delay in the somatic nervous system and hypothalamic dysfunction in the autonomic nervous system, with the conflict being fought out in the spine and trunk of the girl and compounded by biomechanical spinal growth modulation.

Intervertebral disc changes in an animal model representing altered mechanics in scoliosis

The intervertebral discs become wedged and narrowed in a scoliosis curve, and this may be due in part to altered biomechanical environment. To study this, external rings were attached by percutaneous pins transfixing adjacent vertebrae in 5-week-old Sprague-Dawley rats and four permutations of mechanical conditions (4 groups of animals) were compared: (A) 15 degrees Angulation, (B) Angulation with 0.1 MPa Compression, (C) 0.1 MPa Compression, and (D) Reduced mobility. These altered mechanical conditions were applied for 5 weeks. After 5 weeks, disc narrowing at the intervention levels was evident in micro-CT images. Average disc space loss as a percent of the initial values over the 5 weeks was 19%, 28%, 22% and 20% four groups listed above. Increased lateral bending stiffness relative to within-animal controls was also observed at all groups. The minimum stiffness was recorded at an angle close to the in vivo value, indicating that angulated discs had adapted to the imposed deformity. In the angulated and compressed discs there was a small difference in the amount of collagen crimping in the disc annuli between concave and convex sides. All experimental interventions produced substantial changes in the intervertebral discs of these growing animals. 'Reduced mobility' was present in all interventions, and the changes in the discs with reduced mobility alone were comparable with those in loaded and angulated discs. This suggests that imposed reduced mobility is the major source of disc changes, and may be a factor in disc degeneration in scoliosis. Further studies are in progress to characterize gene expression, matrix protein synthesis and composition in these discs.

Mechanical modulation of spinal growth and progression of adolescent scoliosis

It is unclear why some children with a small magnitude scoliosis at the onset of the adolescent growth spurt develop a progressive curve. Normally the skeleton grows symmetrically, presumably because genetic and epigenetic factors regulating growth to maintain growth symmetry despite activities and environmental factors causing asymmetrical loading of the spine. This chapter reviews the recently published data relating to the notion that progression of scoliosis is a result of biomechanical factors modulating spinal growth ('vicious cycle' theory). Quantitative data exist for the key variables in an analysis of scoliosis curve progression. In a predictive model of the evolution of scoliosis simulating the 'vicious cycle' theory, and using these published data, a small lateral curvature of the spine can produce asymmetrical spinal loading that causes asymmetrical growth and a self-perpetuating progressive deformity during skeletal growth. This can occur if the neuromuscular control of muscle activation is directed at minimizing the muscular stress (force per unit cross section), although other activation strategies may produce differing spinal growth patterns. Mechanical modulation of vertebral growth is a significant contributor to the progression of an established scoliosis deformity. Quantitative simulation of this mechanism demonstrates how therapeutic interventions to alter neuromuscular control of trunk muscles or otherwise modify spinal loading may alter the natural history of progression.

Stature and growth compensation for spinal curvature

Spinal curvatures alter measured stature and may influence the evaluation of skeletal maturity and growth based on stature measurements.

METHODS

A dataset of calibrated measurements of vertebral positions of 407 radiographs in the frontal plane, together with clinically measured Cobb angles was used to determine the difference between spinal length and spinal height ('height loss') as a function of Cobb angles for radiographs indicating both single (N=182) and double (N=225) curves.

RESULTS

An apparently quadratic relationship: Height loss (mm)=1.0+0.066*Cobb+0.0084*Cobb*Cobb was found between height loss and each patient's mean Cobb angle for double curves. There was close agreement of the regression coefficients for single and double curves, and the present findings were very similar to the relationship reported by Ylikoski (Eur Spine J, 2003, 12:288-291). The relationships differed substantially from those proposed by Bjure (Clin Orthop, 1973 93:44-52) and by Brookenthal (SRS Exhibit 15, 2002).

DISCUSSION AND CONCLUSIONS

The findings of the present study indicate that height loss (in mm) occurring with a 10 degrees increase in mean Cobb angle (for two curves) would be 1.1+0.16 times the mean Cobb angle (in degrees). For example, for a Cobb angle change from 30 to 40 degrees, the expected height loss would be 1.1+35*0.16 mm=6.7 mm. This assumes that height loss occurs only as a result of altered curvature, without alteration in disc height associated with an increase in scoliosis.

Pediatric scoliosis and kyphosis

Pediatric spinal deformity is a common manifestation of multiple disorders. The clinical picture varies depending on the age at presentation, the severity of the curve at the time of diagnosis, and the underlying cause. Knowledge of the natural history of these varied conditions, the dynamics of growth in the developing spine, and normal axial skeletal biomechanics are fundamental in planning an appropriate treatment. Furthermore, in many instances the spinal anomaly is just part of the problem in a globally affected patient. Treatment alternatives must be judged based on their capacity to positively alter the natural course of the disease and provide a long-standing solution into a patient's adulthood.

Bony-tailed tadpoles: the development of supernumerary caudal vertebrae in larval megophryids (Anura)

The axial skeleton in most anuran families consists of <or=9 presacral vertebrae, a single sacral vertebra, and the urostyle. Tadpoles from one anuran family, the Megophryidae, deviate, however, from this pattern in bearing supernumerary vertebral centra in their tails. At least 5 of 11 genera from this Asian family share this character: Leptobrachella (approximately 30 caudal centra), Leptolalax (5-6), Megophrys (11-15), Ophryophryne (11-14), and Xenophrys (>or=7). Tadpoles from each genus are typically found in streams, where their extended caudal skeleton anchors muscles that facilitate tadpoles wiggling between plant debris and rocks or even burrowing into the stream bed. The extra centra of megophryids ossify differently in each genus. In Leptobrachella and Ophryophryne, the caudal centra ossify around the entire notochord, whereas in Megophrys and Xenophrys each develops from dorsal and ventral pairs of ossifications that expand to meet each other. The evolutionary loss of caudal centra, an apomorphic anuran trait, is reversed in larval megophryids and confirms that the machinery for caudal vertebral development has been retained in some modern anurans. A likely driving force in the reappearance of the trait in megophryids is the selective pressure associated with a riparian lifestyle.

Spinal sonography in newborns and infants--Part I: method, normal anatomy and indications

Spinal sonography can be performed in newborns and young infants as long as the vertebral arches are not completely ossified. With high resolution linear transducers (>10 MHz), excellent detailed images of the spine may be obtained from the base of the skull to the caudal end of the thecal sac. Sagittal and axial sections are performed routinely. Beside the spinal cord, the dorsal and ventral nerve roots and the cauda equina can be shown. The medullary conus normally ends above the level of L2/L3. Lower positions are suspective of tethered cord. M-mode sonographic examinations reveal oscillations of the cord due to respiration and the pulse cycle. Colour Doppler sonography displays the epidural venous plexus as well as the central branches of the anterior spinal artery. Normal variants are transient widening of the central canal, terminal ventricle and asymmetric nerve roots. Indications for spinal sonography are midline cutaneous markers in the lumbosacral region, subcutaneous masses, foot abnormalities, anorectal and genitourinary malformations and neurological abnormalities of the lower extremities. All these clinical symptoms are suspicious of spina bifida occulta and tethered cord which should be ruled out by spinal sonography.

Vitamin K deficiency inhibits mineralization and enhances deformity in vertebrae of haddock (Melanogrammus aeglefinus L.)

Vitamin K has been known to regulate bone formation through osteocalcin synthesis by osteoblasts, which is important for mineralization and bone structure. The mechanism underlying the relationship of vitamin K with the changes of microanatomy is not fully understood, and our goal is to test whether bone deformities develop in association with vitamin K deficiency. Fish were fed a semi-purified diet containing either devoid (0.00 mg/kg diet) or adequate (40.0 mg/kg diet supplemented but 20.8 mg/kg analyzed) levels of vitamin K (menadione sodium bisulphite) for 20 weeks. At the end of 8 and 20 weeks, fish were subjected to gross examination and X-ray, and mineral content of the vertebrae was measured. The vertebrae were also subjected to histological, histomorphometric and enzyme histochemical examinations to determine the bone formation and resorption. Vitamin K deficiency primarily decreased bone mineralization and subsequently a decrease in bone mass thus resulted in an increased susceptibility to bone deformity. The occurrence of bone deformities coincided with an increased amount of osteoid tissue and decreased bone mineral content. Number of osteoblasts and osteoclasts were not affected by dietary vitamin K. In conclusion, vitamin K deficiency can impair bone mineralization and enhances bone deformities.

Abnormal vertebral segmentation and the notch signaling pathway in man

Abnormal vertebral segmentation (AVS) in man is a relatively common congenital malformation but cannot be subjected to the scientific analysis that is applied in animal models. Nevertheless, some spectacular advances in the cell biology and molecular genetics of somitogenesis in animal models have proved to be directly relevant to human disease. Some advances in our understanding have come through DNA linkage analysis in families demonstrating a clustering of AVS cases, as well as adopting a candidate gene approach. Only rarely do AVS phenotypes follow clear Mendelian inheritance, but three genes-DLL3, MESP2, and LNFG-have now been identified for spondylocostal dysostosis (SCD). SCD is characterized by extensive hemivertebrae, trunkal shortening, and abnormally aligned ribs with points of fusion. In familial cases clearly following a Mendelian pattern, autosomal recessive inheritance is more common than autosomal dominant and the genes identified are functional within the Notch signaling pathway. Other genes within the pathway cause diverse phenotypes such as Alagille syndrome (AGS) and CADASIL, conditions that may have their origin in defective vasculogenesis. Here, we deal mainly with SCD and AGS, and present a new classification system for AVS phenotypes, for which, hitherto, the terminology has been inconsistent and confusing.

Flexible non-fusion scoliosis correction systems reduce intervertebral rotation less than rigid implants and allow growth of the spine: a finite element analysis of different features of orthobiom

The orthobiom non-fusion scoliosis correction system consists of two longitudinal rods, polyaxial pedicle screws, mobile and fixed connectors and a cross-connector. The mobile connectors can move along and around the rod, thus allowing length adaptation during growth. The aim of this study was to determine the effects of different features of this novel implant on intervertebral rotations, to calculate the movement of the mobile connectors along the rods for different loading cases and to compare the results with those of a rigid implant construct. A finite element analysis was performed using six versions (M1-M6) of a three-dimensional, nonlinear model of a spine ranging from T3 to L2. The models were loaded with pure moments of 7.5 N m in the three main anatomical planes. First, the validated intact model (M1) was studied. Then, the orthobiom implant system was inserted, bridging the segments between T4 and L1 (M2). The effect of pedicle screws only in every second vertebrae was investigated (M3). For comparison, three connection variations of screws and rods were investigated: (1) an implant with rigid screws and mobile connectors (M4), (2) an implant with non-locking polyaxial screws and fixed connectors (M5) and (3) a completely rigid implant construct (M6). For flexion, extension and lateral bending, intervertebral rotation was reduced at all implant levels due to the implants. A rigid implant construct (M6) and an implant with non-locking polyaxial screws and fixed connectors (M5) led to the strongest reduction of intervertebral rotation. The orthobiom non-fusion implant system (M2, M3) allowed much more intervertebral rotation than a rigid implant (M6). Differences in intervertebral rotations were small when polyaxial screws were placed at every second level only (M3) instead of at every level (M2). For axial rotation, intervertebral rotation was strongly reduced by a rigid implant construct (M6) and by an implant with rigid screws and mobile connectors (M4). For rotation, an implant with non-locking polyaxial screws (M2, M3, M5) led to nearly the same intervertebral rotations as in an intact spine without an implant (M1). The predicted maximum translation of the mobile connectors along the rod was 4.2 mm for extension, 3.1 mm for lateral bending, 1.6 mm for flexion and 0.8 mm for axial rotation. The movement of the connectors was highest for those closest to the ends of the rods. With rigid screws, the maximum translation was significantly reduced. This study, conducted under a load-controlled loading protocol, showed that intervertebral rotation was reduced much less by the non-fusion orthobiom system than by a rigid implant. The mobile connectors moved considerably along the rod when the spine was bent. It can be expected that the connectors also move along the rod as the adolescent grows, possibly leaving the discs intact until the patient is fully grown.

Analysis and simulation of progressive adolescent scoliosis by biomechanical growth modulation

Scoliosis is thought to progress during growth because spinal deformity produces asymmetrical spinal loading, generating asymmetrical growth, etc. in a 'vicious cycle.' The aim of this study was to test quantitatively whether calculated loading asymmetry of a spine with scoliosis, together with measured bone growth sensitivity to altered compression, can explain the observed rate of scoliosis progression in the coronal plane during adolescent growth. The simulated spinal geometry represented a lumbar scoliosis of different initial magnitudes, averaged and scaled from measurements of 15 patients' radiographs. Level-specific stresses acting on the vertebrae were estimated for each of 11 external loading directions ('efforts') from published values of spinal loading asymmetry. These calculations assumed a physiologically plausible muscle activation strategy. The rate of vertebral growth was obtained from published reports of growth of the spine. The distribution of growth across vertebrae was modulated according to published values of growth sensitivity to stress. Mechanically modulated growth of a spine having an initial 13 degrees Cobb scoliosis at age 11 with the spine subjected to an unweighted combination of eleven loading conditions (different effort direction and magnitude) was predicted to progress during growth. The overall shape of the curve was retained. The averaged final lumbar spinal curve magnitude was 32 degrees Cobb at age 16 years for the lower magnitude of effort (that produced compressive stress averaging 0.48 MPa at the curve apex) and it was 38 degrees Cobb when the higher magnitudes of efforts (that produced compressive stress averaging 0.81 MPa at the apex). An initial curve of 26 degrees progressed to 46 degrees and 56 degrees, respectively. The calculated stresses on growth plates were within the range of those measured by intradiscal pressures in typical daily activities. These analyses predicted that a substantial component of scoliosis progression during growth is biomechanically mediated. The rationale for conservative management of scoliosis during skeletal growth assumes a biomechanical mode of deformity progression (Hueter-Volkmann principle). The present study provides a quantitative basis for this previously qualitative hypothesis. The findings suggest that an important difference between progressive and non-progressive scoliosis might lie in the differing muscle activation strategies adopted by individuals, leading to the possibility of improved prognosis and conservative or less invasive interventions.

Dorsal arthrodesis of thoracic spine and effects on thorax growth in prepubertal New Zealand white rabbits

STUDY DESIGN

Dorsal arthrodesis of thoracic spine in a prepubertal New Zealand White rabbit model.

OBJECTIVE

Evaluating the consequences of dorsal arthrodesis on the growth of the spine, sternum, and thorax in prepubertal rabbits, through the study of CT scans.

SUMMARY OF BACKGROUND DATA

Vertebral arthrodesis in the treatment of progressive idiopathic scoliosis in prepubertal patients is not ideal, but is still a choice in treating major deformities of the spine. Postoperative assessment of spinal deformity is essential, feasible, and recordable through CT scans.

METHODS

Twelve female rabbits, 9 weeks old, were subjected to surgery for dorsal arthrodesis of the upper thoracic spine. Surgery involved the implant of 2 "C"-shaped titanium bars, which were placed beside the spinous processes of the thoracic vertebrae. Three CT scans were performed, 10 (T1), 55 (T2), and 139 (T3) days after surgery. Measures were obtained by Myrian Pro software for 3 different groups: G1 with complete fusion, G2 with incomplete fusion, and G3 sham-operated.

RESULTS

The average of the dorsoventral/laterolateral thoracic diameter ratio at fused levels is lower than 1 in G1 as well as in G2; on the contrary, in G3 is higher than 1. The average growth of the sternum length between T1 and T2 and between T2 and T3 is minor in G1 than in G2 and G3. The dorsal and ventral lengths of thoracic vertebral bodies in the spinal segment D1-D6 is smaller in G1 and G2 than in G3, whereas no differences were observed between the 3 groups in the D7-D12 segment without arthrodesis.

CONCLUSION

Dorsal arthrodesis in prepubertal rabbits changes thoracic growth patterns. In operated rabbits, the dorsoventral thoracic diameter grows more slowly than the laterolateral thoracic diameter. The sternum as well as the lengths of thoracic vertebral bodies in the spinal segment D1-D6 grow less. The crankshaft phenomenon is evident at the fused vertebral levels where there is a reduction of thoracic kyphosis.

Histologic, risser sign, and digital skeletal age evaluation for residual spine growth potential in Chinese female idiopathic scoliosis

STUDY DESIGN

A prospective study.

OBJECTIVE

To ascertain the correlation between histologic grades (HGs) of vertebral growth plates and Risser grades as well as DSA stages in the Chinese female idiopathic scoliosis (IS) patients; to identify whether digital skeletal age (DSA) is a reliable indicator for accurate evaluation of the spinal residual growth potential.

SUMMARY OF BACKGROUND DATA

DSA is considered one of the more important indicators for representing the peak height velocity (PHV) typically and predicting spinal growth potential. The correlation between HGs of growth plates and DSA stages in IS patients is unclear.

METHODS

Thirty-nine Chinese female patients were available for this study. Superior and inferior growth plates were obtained at each level when anterior approach surgeries were performed. Histologic examinations were conducted after the specimens were processed. Of these patients, 28 cases were evaluated by DSA stages in this study. Correlations between histologic grades, Risser grades, menarchal status, and chronologic age were analyzed in 39 patients. Correlations between histologic grades, DSA, menarchal status, and chronologic age were analyzed in 28 patients.

RESULTS

There was a negative correlation between the following: HGs and Risser grades in 39 patients (r = -0.645, P = 0.000-0.05), HGs and menarchal status in patients in Risser 4 (r = -0.710, P = 0.002-0.05), HGs and DSA stages in 28 cases (r = -0.541, P = 0.003-0.05), and HGs and menarchal status in patients in DSA Stage III (r = -0.591, P = 0.006-0.05). Statistical significance of growth activity of growth plates was found between patients in Risser Grades 0 to 1 and those in Risser Grades 2 to 5 (P = 0.020-0.05) and patients in DSA Stage II and those in DSA Stage III (P = 0.014-0.05).

CONCLUSION

DSA may be a reliable indicator for predicting the spinal residual growth potential in IS patients, but it should be correlated with menarchal status and chronologic ages.

Nuclear factor I X deficiency causes brain malformation and severe skeletal defects

The transcription factor family of nuclear factor I (NFI) proteins is encoded by four closely related genes: Nfia, Nfib, Nfic, and Nfix. A potential role for NFI proteins in regulating developmental processes has been implicated by their specific expression pattern during embryonic development and by analysis of NFI-deficient mice. It was shown that loss of NFIA results in hydrocephalus and agenesis of the corpus callosum and that NFIB deficiency leads to neurological defects and to severe lung hypoplasia, whereas Nfic knockout mice exhibit specific tooth defects. Here we report the knockout analysis of the fourth and last member of this gene family, Nfix. Loss of NFIX is postnatally lethal and leads to hydrocephalus and to a partial agenesis of the corpus callosum. Furthermore, NFIX-deficient mice develop a deformation of the spine, which is due to a delay in ossification of vertebral bodies and a progressive degeneration of intervertebral disks. Impaired endochondral ossification and decreased mineralization were also observed in femoral sections of Nfix-/- mice. Consistent with the defects in bone ossification we could show that the expression level of tetranectin, a plasminogen-binding protein involved in mineralization, is specifically downregulated in bones of NFIX-deficient mice.

Simulation of progressive spinal deformities in Duchenne muscular dystrophy using a biomechanical model integrating muscles and vertebral growth modulation

BACKGROUND

Ninety percent of Duchenne muscular dystrophy patients develop scoliosis in parallel with evident muscular and structural impairment. Altered muscular spinal loads acting on growing vertebrae are likely to promote a self-sustaining spinal deformation process. The purpose of this study was to simulate the effect of asymmetrical fat infiltration of the erector spinae muscles combined with vertebral growth modulation over a period of growth spurt.

METHODS

A finite element model of the trunk was built. It integrates (1) longitudinal growth of vertebral bodies and its modulation due to mechanical stresses, (2) muscles and control processes generating muscle recruitment and forces. Three different impairments of the erector spinae muscles were considered and their actions over 12 consecutive cycles representing a span of 12 months were analyzed.

FINDINGS

When asymmetrical muscle degeneration was simulated and weaker erector spinae muscles were located on the convex side of the curve, mild scoliosis (Cobb angle of 8-19 degrees ) was induced in the frontal plane and the kyphosis increased from 72 degrees to 110 degrees in all simulations. Those changes were accompanied by a substantial increase of muscle activity in the Rectus Abdominus and Obliquus Internus.

INTERPRETATION

Scoliosis as documented in the literature were induced through an asymmetrical activity in the erector spinae muscles and it can be hypothesized that the Rectus Abdominus and Obliquus Internus have a role in maintaining balance and counteracting against spine torsion. This study demonstrated the feasibility of the modeling approach to investigate a musculo-skeletal deformation process based on a neuromuscular deficit.

[Experimental study on controlling unilateral spine growth by shape memory alloy staple]

OBJECTIVE

To observe the effects that shape memory alloy (SMA) staples implanted to the lateral aspect of the thoracic vertebrae on spinal growth in goats.

METHODS

Sixteen goats (age 2 - 3 months) were divided into 3 groups: six in single staple group; six in double staples group and four in control group. Single staples group underwent right-side thoracotomy for exposing the thoracic spine through the eighth rib. Five SMA staples were placed laterally into vertebral bodies of T(6 - 11) spanning discs. Double staples group underwent the same operation. Laterally directed 10 SMA staples were placed into vertebrae of T(6 - 11) spanning discs and two staple spanning each disc. The last four goats in control groups just only underwent right-side thoracotomy. In the next 4 months after operation, radiographs were taken to observe the spinal growth every month.

RESULTS

The radiographic analysis demonstrated scoliosis of 12.83 degrees +/- 12.17 degrees in single staple group and 12.00 degrees +/- 3.22 degrees in double staple group after 2 months of the operation. Cobb angle of 6.00 degrees +/- 4.94 degrees and 25.17 degrees +/- 3.71 degrees were observed in the two groups respectively after 4 months of operation, as compared with 0 degrees in the control groups. Only 2 goats developed kyphosis.

CONCLUSIONS

Compression between vertebral bodies by SMA staples can depress spinal growth in the same side and greater compression result in larger curves.

Effects of 17alpha-ethinylestradiol and bisphenol A on vertebral development in the fathead minnow (Pimephales promelas)

Growth, reproductive ability, and metabolic functions may be impaired by disruption of early endocrine patterning. Natural and synthetic estrogens detected in surface waters have been linked to reproductive endocrine signaling disruption in several species. The present study characterizes the nonreproductive morphological endpoint of vertebral anomalies in fish exposed to environmental estrogens. Estrogen is a proliferation-inducing compound in osteoblasts, regulating cartilage and bone deposition during development in vertebrates. The hypothesis for the present work is that xenobiotics with estrogenic activity adversely impact vertebral bone formation. Fathead minnows (Pimephales promelas) were exposed to 0.1 to 100 microg/L 17alpha-ethinylestradiol (EE2) and 0.1 to 1,000 microg/L bisphenol A (BPA) from egg stage (24 h postfertilization) to 25 to 26 d posthatch. Fish were measured for length and analyzed microscopically to determine degree of skeletal development (developmental score) and the occurrence of spinal abnormalities, including vertebral compression, bone fusion, and spinal curvatures. Fish length and developmental score were inversely related to vertebral malformations in exposed fish. Skeletal developmental was affected significantly in EE2-exposed fish: Vertebral malformations were observed in up to 62% of fish in a nonmonotonic dose-response. However, BPA did not significantly impair skeletal development or induce vertebral malformations. The bioassay results suggest vertebral bone development is a potential endpoint of endocrine disruption from potent estrogenic compounds in surface waters.

A novel locus on the X chromosome regulates post-maturity bone density changes in mice

Two mouse strains, AKR/J and SAMP6, were assessed longitudinally for bone mineral density of the spine. They displayed very different time courses of bone accrual, with the SAMP6 strain reaching a plateau for vertebral BMD at 3 months, whereas AKR/J mice continued to increase spine BMD for at least 8 months. Among 253 F(2) progeny of an AKR/JxSAMP6 cross, at 4 months of age, the BMD variance was 5-6% of the mean, vs. 15% for weight. Variance increased with age for every parameter measured, and was generally higher among males. The ratio of 6-month/4-month spine BMDs, termed DeltasBMD, had a normal distribution with 5.7% variance, and was largely independent of spine BMD (R=-0.23) or body weight (R=-0.12) at maturity. Heritability of the DeltasBMD trait was calculated at 0.59. Genetic mapping identified two significant loci, both distinct from those observed for BMD at maturity--implying that different genes regulate skeletal growth vs. remodeling. A locus on the X chromosome, replicated in two mouse F(2) populations (P<10(-4) for combined discovery and confirmation), affects age-dependent BMD change for both spine and the full skeleton. Its position agrees with a very narrow region identified by association mapping for effects on lumbar bone density in postmenopausal women [Parsons CA, Mroczkowski HJ, McGuigan FE, Albagha OM, Manolagas S, Reid DM, et al. Interspecies synteny mapping identifies a quantitative trait locus for bone mineral density on human chromosome Xp22. Hum Mol Genet 2005;14:3141-8]. A second locus, on chromosome 7, was observed in only one cross. Single-nucleotide polymorphisms (SNPs) are highly clustered near these loci, distinguishing the parental strains over only limited spans.