SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Lordosis

28

The purpose of this study is to review our operative experience of congenital kyphosis or kyphoscoliosis undergoing either pedicle subtraction osteotomy (PSO) or posterior vertebral column resection (pVCR) according to certain criteria we have established.

Concepts: Vertebral column, Scoliosis, According to Jim, Vertebra, Skeletal disorders, Lordosis, Kyphosis, Kyphoscoliosis

28

STUDY DESIGN.: Meta-analysis on mid- to long-term outcomes in adolescent idiopathic scoliosis after instrumented posterior spinal fusion. OBJECTIVE.: To compare mid- to long-term outcomes and complications of the most commonly used instrumentation systems in adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA.: A meta-analysis of mid- to long-term results of different methods of instrumentation, including the most currently used all-pedicle screw construct, is lacking. METHODS.: A structured literature review was conducted for studies concerning management of patients with adolescent idiopathic scoliosis with instrumented posterior fusion. Pooled means, standard deviations, and sample sizes were either identified or calculated on the basis of the results of each study. RESULTS.: Meta-analyses were performed on outcomes from 27 studies. Overall, 1613 patients who had been treated with Harrington rods, 361 patients who had undergone Cotrel-Dubousset instrumentation, and 298 patients who managed with all-pedicle screw constructs were reviewed. The mean follow-up was 14.9 years. Cotrel-Dubousset and pedicle screw instrumentations achieved a significantly greater degree of correction of the thoracic curve than Harrington rods (40.3° vs. 14.7°; P < 0.001 and 21.9° vs. 14.7°; P = 0.005, respectively). Cotrel-Dubousset technique achieved a significantly higher degree of correction than all-pedicle screw construct in both the thoracic (40.3° vs. 21.9°, respectively; P < 0.001) and lumbar curves (37.2° vs. 16°, respectively; P < 0.001). Similarly, Cotrel-Dubousset construct achieved a greater correction of both thoracic kyphosis (33.5° vs. 23°, respectively; P < 0.001) and lumbar lordosis (46° vs. 50.7°, respectively; P = 0.002) than pedicle screws. All-pedicle screw fixation was associated with the lower risk of pseudarthrosis, infection, neurological deficit, and reoperation. CONCLUSION.: This study confirms the negative effect of Harrington rods on sagittal alignment. We further found that the degree of correction in the coronal and sagittal planes was higher after Cotrel-Dubousset instrumentation than all-pedicle screw fixation. All-pedicle screw constructs offered the lower risk of mid- to long-term complications and revision surgery.

Concepts: Vertebral column, Scoliosis, Lordosis, Spinal fusion, Kyphosis, Scheuermann's disease, Kyphoscoliosis, Harrington implant

28

Neutral sitting postures encouraging lumbar lordosis have been recommended in the management of sitting-related low back pain (LBP). However, prolonged lordotic sitting postures can be associated with increased fatigue and discomfort. This pilot study investigated whether changing the type of chair used in sitting can reduce the effort of maintaining a neutral sitting posture. The muscle activation of six trunk muscles was recorded using surface electromyography in 12 painfree participants. Participants were facilitated into a neutral sitting posture for 1min on both a standard backless office chair and a dynamic, forward-inclined chair (Back App). Lumbar multifidus activity was significantly lower on the Back App chair (p=0.013). None of the other five trunk muscles measured demonstrated a significant difference in activity between the chairs. There was no significant difference (p=0.108) in the perceived effort of maintaining the neutral sitting posture on the two chairs. This study suggests that the lumbar multifidus activation required to maintain a neutral sitting posture can be reduced by considering the type of chair used. The mechanism through which the Back App chair reduces lumbar multifidus activation is unclear, but the greatest difference between chairs is the degree of hip flexion. The ability to maintain a neutral lumbar posture with less lumbar multifidus activation is potentially advantageous during prolonged sitting. Further investigations of the effects of chair design on longer duration sitting, and among LBP subjects, are warranted.

Concepts: Spinal disc herniation, Low back pain, Muscle, Electromyography, Sitting, Lordosis, Chair, Office chair

27

Trunk balance in upright stance expresses an individual postural strategy found on anatomic and functional parameters. The “pelvic vertebra” is an essential transitional region for the coherence of spinal parameters (notably, lumbar lordosis and thoracic kyphosis) and pelvic parameters (sacral slope, pelvic tilt and incidence). Deterioration of this postural harmony is often associated with spinal aging, maladjusted spinal arthrodeses, or mechanical abnormalities of the hip joints. Spinal surgeons are aware of the importance of detecting and analyzing sagittal imbalance, whether compensated or not. The influence of the hip joint, however, is underestimated and poorly objectified on conventional imaging, as are its interrelations with overall lower-limb posture. Currently, hip surgeons focus basically on the pelvis as bone reference in planning implantation, peroperative adjustment and failure analysis. The antero-posterior (AP) pelvic view is the gold standard, with lateral views being little used. Influenced by the classic anatomic attitude in favor of transverse slices in dorsal decubitus, CT is considered the reference method for “horizontal” assessment of the hip joint. The present study draws attention to a more global vision of the pelvic and subpelvic regions in the sagittal balance of the trunk, relying on the sitting as well as the standing posture, as both involve subtle mechanisms of adaptation governed by the pelvic incidence angle.

Concepts: Osteoporosis, Vertebral column, Hip, Pelvis, Human anatomy, Sacrum, Lordosis, Obturator internus muscle

4

Background context Prolonged microgravity exposure is associated with localized low back pain and an elevated risk of post-flight disc herniation. Though the mechanisms by which microgravity impairs the spine are unclear, they should be foundational for developing in-flight countermeasures for maintaining astronaut spine health. Because human spine anatomy has adapted to upright posture on Earth, observations of how spaceflight affects the spine should also provide new and potentially important information on spine biomechanics that benefit the general population. Purpose This study compares quantitative measures of lumbar spine anatomy, health, and biomechanics in astronauts before and after six months of microgravity exposure on board the International Space Station (ISS). Study Design Prospective longitudinal study. Sample Six astronanut crewmember volunteers from the National Aeronautics and Space Administration (NASA) with six month missions aboard the ISS. Outcome Measures For multifidus and erector spinae at L3-L4, measures include: cross-sectional area (CSA), functional cross-sectional area (FCSA), and FCSA/CSA. Other measures include: supine lumbar lordosis (L1-S1), active (standing) and passive (lying) flexion-extension range of motion (FE ROM) for each lumbar disc segment, disc water content from T2-weighted intensity, Pfirrmann grade, vertebral endplate pathology, and subject-reported incidence of chronic low back pain or disc injuries at one-year follow-up. Methods 3T MRI and dynamic fluoroscopy of the lumbar spine were collected for each subject at two time points: approximately 30 days before launch (pre-flight) and one day following six months spaceflight on the ISS (post-flight). Outcome measures were compared between time points using paired t-tests and regression analyses. Results Supine lumbar lordosis decreased (flattened) by an average of 11% (p=0.019). Active FE ROM decreased for the middle three lumbar discs (L2-L3: -22.1%, p=0.049; L3-L4: -17.3%, p=0.016; L4-L5: -30.3%, p=0.004). By contrast, no significant passive FE ROM changes in these discs were observed (p>0.05). Disc water content did not differ systematically from pre- to post-flight. Multifidus and erector spinae changed variably between subjects, with five of six subjects experiencing an average decrease 20% for FCSA and 8-9% for CSA in both muscles. For all subjects, changes in multifidus FCSA strongly correlated with changes in lordosis (r(2)=0.86, p=0.008) and active FE ROM at L4-L5 (r(2)=0.94, p=0.007). Additionally, changes in multifidus FCSA/CSA correlated with changes in lordosis (r(2)=0.69, p=0.03). While multifidus-associated changes in lordosis and ROM were present amongst all subjects, only those with severe, pre-flight endplate irregularities (2 of 6 subjects) had post-flight lumbar symptoms (including chronic low back pain or disc herniation). Conclusions We observed that multifidus atrophy, rather than intervertebral disc swelling, associated strongly with lumbar flattening and increased stiffness. Because these changes have been previously linked with detrimental spine biomechanics and pain in terrestrial populations, when combined with evidence of pre-flight vertebral endplate insufficiency, they may elevate injury risk for astronauts upon return to gravity loading. Our results also have implications for deconditioned spines on Earth. We anticipate that our results will inform new astronaut countermeasures that target the multifidus muscles, and research on the role of muscular stability in relation to chronic low back pain and disc injury.

Concepts: Spinal disc herniation, Low back pain, Lumbar vertebrae, Vertebral column, Vertebra, Intervertebral disc, International Space Station, Lordosis

4

OBJECTIVE: To study the immediate effect of posteroanterior mobilization on back pain and the associated biomechanical changes in the lumbar spine. DESIGN: An experimental between-group study. SETTING: A biomechanics laboratory PARTICIPANTS: Nineteen low back pain subjects and twenty healthy subjects participated in this study. INTERVENTIONS: Three cycles of 60 seconds, Grade III posteroanterior mobilization was applied at the L4 level in people with or without back pain on one occasion. MAIN OUTCOME MEASURES: Pain intensity, active lumbar range of motion, the magnitude of the posteroanterior mobilization loads, bending stiffness of the lumbar spine and the lordotic curvature of the lumbar spine before and after three cycles of posteroanterior mobilization. RESULTS: The magnitude of pain of the patients was found to decrease significantly after posteroanterior mobilisation treatment. There was also a significant decrease in the bending stiffness of the lumbar spine of the patients, which was derived from the posteroanterior load and the associated change in spine curvature. The stiffness was restored to a level which was similar to that of the asymptomatic subjects. Strong correlation was found between the magnitude of pain and the bending stiffness of the spine before (r = 0.89) and after posteroanterior mobilization (r = 0.98). CONCLUSIONS: Posteroanterior mobilization was found to bring about immediate desirable effects in reducing spinal stiffness and the magnitude of back pain. The restoration of the mechanical properties of the spine may be a possible mechanism which explains the improvement in pain after manual therapy.

Concepts: Spinal disc herniation, Low back pain, Lumbar vertebrae, Vertebral column, Scoliosis, Acupuncture, Massage, Lordosis

3

Clinicians regard lumbar lordotic curvature (LLC) with respect to low back pain (LBP) in a contradictory fashion. The time-honored point of view is that LLC itself, or its increment causes LBP. On the other hand, recently, the biomechanical role of LLC has been emphasized and loss of lordosis is considered a possible cause of LBP. The relationship between LLC and LBP has immense clinical significance, since it serves as the basis of therapeutic exercises for treating and preventing LBP.

Concepts: Spinal disc herniation, Low back pain, Back pain, Massage, Lordosis

2

The incidence of congenital spine deformities, including congenital scoliosis, kyphosis and lordosis, may be influenced by the in utero mechanical environment, and particularly by fetal movements at critical time-points. There is a limited understanding of the influence of fetal movements on spinal development, despite the fact that mechanical forces have been shown to play an essential role in skeletal development of the limb. This study investigates the effects of muscle forces on spinal curvature, vertebral segmentation and vertebral shape by inducing rigid or flaccid paralysis in the embryonic chick. The critical time-points for the influence of fetal movements on spinal development were identified by varying the time of onset of paralysis. Prolonged rigid paralysis induced severe defects in the spine, including curvature abnormalities, posterior and anterior vertebral fusions and altered vertebral shape, while flaccid paralysis did not affect spinal curvature or vertebral segmentation. Early rigid paralysis resulted in more severe abnormalities in the spine than later rigid paralysis. The findings of this study support the hypothesis that the timing and nature of fetal muscle activity are critical influences on the normal development of the spine, with implications for the understanding of congenital spine deformities. This article is protected by copyright. All rights reserved.

Concepts: Developmental biology, Vertebral column, Scoliosis, Spina bifida, Copyright, Lordosis, Kyphosis, Botulism

2

Flattening of the preimplantation rod contour in the sagittal plane influences thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery. The effects of multilevel facetectomy and screw density on postoperative changes in spinal rod contour have not been documented. This study aimed to evaluate the effects of multilevel facetectomy and screw density on changes in spinal rod contour from before implantation to after surgical correction of thoracic curves in patients with AIS prospectively. The concave and convex rod shapes from patients with thoracic AIS (n = 49) were traced prior to insertion. Postoperative sagittal rod shape was determined by computed tomography. The angle of intersection of the tangents to the rod end points was measured. Multiple stepwise linear regression analysis was used to identify variables independently predictive of change in rod contour (Δθ). Average Δθ at the concave and convex side were 13.6° ± 7.5° and 4.3° ± 4.8°, respectively. The Δθ at the concave side was significantly greater than that of the convex side (P < 0.0001) and significantly correlated with Risser sign (P = 0.032), the preoperative main thoracic Cobb angle (P = 0.031), the preoperative TK angle (P = 0.012), and the number of facetectomy levels (P = 0.007). Furthermore, a Δθ at the concave side ≥14° significantly correlated with the postoperative TK angle (P = 0.003), the number of facetectomy levels (P = 0.021), and screw density at the concave side (P = 0.008). Rod deformation at the concave side suggests that corrective forces acting on that side are greater than on the convex side. Multilevel facetectomy and/or screw density at the concave side have positive effects on reducing the rod deformation that can lead to a loss of TK angle postoperatively.

Concepts: Regression analysis, Linear regression, Vertebral column, Scoliosis, Lordosis, Kyphosis, Scheuermann's disease, Kyphoscoliosis

1

Because of genetic heterogeneity present in idiopathic scoliosis, we previously defined clinical subsets (a priori) from a sample of families with idiopathic scoliosis to find genes involved with spinal curvature. Previous genome-wide linkage analysis of seven families with at least two individuals with kyphoscoliosis found linkage (P-value = 0.002) in a 3.5-Mb region on 5p13.3 containing only three known genes, IRX1, IRX2, and IRX4 In this study, the exons of IRX1, IRX2, and IRX4, the conserved noncoding elements in the region, and the exons of a nonprotein coding RNA, LOC285577, were sequenced. No functional sequence variants were identified. An intrafamilial test of association found several associated noncoding single nucleotide variants. The strongest association was with rs12517904 (P = 0.00004), located 6.5 kb downstream from IRX1 In one family, the genotypes of nine variants differed from the reference allele in all individuals with kyphoscoliosis, and two of three individuals with scoliosis, but did not differ from the reference allele in all other genotyped individuals. One of these variants, rs117273909, was located in a conserved noncoding region that functions as an enhancer in mice. To test whether the variant allele at rs117273909 had an effect on enhancer activity, zebrafish transgenesis was performed with overlapping fragments of 198 and 687 bp containing either the wild type or the variant allele. Our data suggests that this region acts as a regulatory element; however, its size and target gene(s) need to be identified to determine its role in idiopathic scoliosis.

Concepts: DNA, Gene, Genetics, Allele, Scoliosis, Lordosis, Kyphosis, Kyphoscoliosis