L1 L2 Research Articles

Differentiating patients with radiculopathy from chronic low back pain patients by single surface EMG parameter

ABSTRACTThe classification potential of surface electromyographic (EMG) parameters needs to be explored beyond classification of subjects onto low back pain subjects and control subjects. In this paper, a classification model based on surface EMG parameter is introduced to differentiate low back pain patients with radiculopathy from chronic low back pain (CLBP) patients and control subjects. A variant of the Roman chair was used to perform static contractions, where subject's own upper body weight was used to induce muscle fatigue in low back muscles. Surface EMG signals were recorded over the paraspinal muscles at L1–L2 and L4–L5 interspace level. As a descriptor of spectral changes, the median frequency of the power spectrum (MDF) was estimated by use of Hilbert–Huang transform. Student's t-test detected that regression line slope of the median frequency is significantly different (p < 0.05) only between low back pain patients with radiculopathy and other two groups. There was no significant difference between CLBP patients and control subjects. The achieved overall accuracy of the implemented decision tree classification model was at best 86.8%. The results suggest possibility of differentiating low back pain patients to subgroups depending on clinical symptoms.

Biomechanical Comparison of Nucleotomy with Lumbar Spine Fusion versus Nucleotomy Alone: Vibration Analysis of the Adjacent Spinal Segments

This study aimed to investigate the effect of transforaminal lumbar interbody fusion (TLIF) with bilateral pedicle screw fixation (BPSF) on dynamic responses of the adjacent spinal segments to whole body vibration (WBV) after nucleotomy. A previously validated finite element model of an intact L1-sacrum lumbar spine was modified to simulate nucleotomy with and without TLIF and BPSF at L4–L5. Transit dynamic analyses were conducted on the nucleotomy alone and the fusion models under a vertical vibration load. The computed dynamic responses for the two models at adjacent levels were recorded and compared. The results showed that at level (L5–S1) below the denucleated disc, maximum response values of the disc bulge, annulus stress and intradiscal pressure decreased due to the fusion by 5.6%, 5.2% and 7.2%, and their vibration amplitudes decreased by 30.5%, 25.7% and 24.3%. At levels (L1–L2, L2–L3 and L3–L4) above the denucleated disc, maximum response values and vibration amplitudes of the strains and stresses also produced 5.2–8.9% and 25.9–29.7% deceases due to the fusion. It implies that after nucleotomy, application of the TLIF with BPSF might be helpful to prevent negative effects of the vertical WBV on adjacent disc levels.

Estimation of visceral fat in 9- to 13-year-old girls using dual-energy X-ray absorptiometry (DXA) and anthropometry.

SummaryObjectivesAccumulation of visceral fat (VF) in children increases the risk of cardiovascular disease and type 2 diabetes, and measurement of VF in children using computed tomography and magnetic resonance imaging (MRI) is expensive. Dual‐energy X‐ray absorptiometry (DXA) may provide a low‐cost alternative. This study aims to determine if DXA VF estimates can accurately estimate VF in young girls, determine if adding anthropometry would improve the estimate and determine if other DXA fat measures, with and without anthropometry, could be used to estimate VF in young girls.MethodsVisceral fat was measured at lumbar intervertebral sites (L1–L2, L2–L3, L3–L4 and L4–L5) using 3.0T MRI on 32 young girls (mean age 11.3 ± 1.3 years). VF was estimated using the GE CoreScan application. Measurement of DXA android and total body fat was performed. Weight, height and waist circumference (WC) measurements were also obtained.ResultsWaist circumference and body mass index were both strongly correlated with MRI, although WC was the best anthropometric covariate. Per cent fat (%fat) variables had the strongest correlation and did best in regression models. DXA %VF (GE CoreScan) and DXA android %fat and total body %fat accounted for 65% to 74% of the variation in MRI VF.ConclusionWaist circumference predicted MRI VF almost as well as DXA estimates in this population, and a combination of WC and DXA fat improves the predictability of VF. DXA VF estimate was improved by the addition of WC; however, DXA android %fat with WC was better at predicting MRI VF.

The Role of Linguistic Diversity in the Prediction of Early Reading Comprehension: A Quantile Regression Approach

ABSTRACTUsing classical and quantile regression analyses, we investigated whether predictor variables for early reading comprehension differed depending on language background and ability level in a mixed group of 161 monolingual (L1) and bilingual (L2) children in second grade (6–8 years). Although L2 readers scored lower on oral language skills and reading comprehension, the prediction of reading comprehension was similar for L1 and L2 readers. Classical regression identified decoding, vocabulary, and morphosyntactic knowledge as unique predictors with no interaction with language background. Quantile regression demonstrated that the prediction of reading comprehension differed across ability levels; decoding and morphosyntactic knowledge were consistently unique predictors, but vocabulary was uniquely related only for poor comprehenders and working memory only for good comprehenders. In both types of analysis, language background did not explain unique variance, indicating that individual differences in the predictor variables explained the L1–L2 performance gap in early reading comprehension across the ability range.

The Influence of Lexical Factors on Verbal Eojeol Recognition: Evidence from L1 Korean Speakers and L2 Korean Learners

The Influence of Lexical Factors on Verbal Eojeol Recognition: Evidence from L1 Korean Speakers and L2 Korean Learners

The influence of L1 Dutch and L2 English on L3 French: A longitudinal study

This longitudinal study investigates negative transfer from L1 Dutch and L2 English into L3 French in the first three years of French education in a Dutch/English secondary immersion school. We focus on two word order constructions in declarative root clauses where the three languages differ: V-to-C movement (+Dutch, −French) and V-to-T movement (−English, +French). The results of a grammaticality judgement task and a gap-filling task show that the L3 learners transfer a large amount from L1 Dutch in the initial stages of the first year of French education followed by a dramatic decline in the second and third year of French education. At the onset of L3 learning, L2 English is less activated; however, its influence intervenes and stays stable in later years of learning.

Patterns of Short-Term Phonetic Interference in Bilingual Speech

Previous research indicates that alternating between a bilingual’s languages during speech production can lead to short-term increases in cross-language phonetic interaction. However, discrepancies exist between the reported L1–L2 effects in terms of direction and magnitude, and sometimes the effects are not found at all. The present study focused on L1 interference in L2, examining Voice Onset Time (VOT) of English voiceless stops produced by L1-dominant Czech-English bilinguals—interpreter trainees highly proficient in L2-English. We tested two hypotheses: (1) switching between languages induces an immediate increase in L1 interference during code-switching; and (2) due to global language co-activation, an increase in L1-to-L2 interference occurs when bilinguals interpret (translate) a message from L1 into L2 even if they do not produce L1 speech. Fourteen bilinguals uttered L2-English sentences under three conditions: L2-only, code-switching into L2, and interpreting into L2. Against expectation, the results showed that English VOT in the bilingual tasks tended to be longer and less Czech-like compared to the English-only task. This contradicts an earlier finding of L2 VOT converging temporarily towards L1 VOT values for comparable bilingual tasks performed by speakers from the same bilingual population. Participant-level inspection of our data suggests that besides language-background differences, individual language-switching strategies contribute to discrepancies between studies.

The Role of Low-level First Language Skills in Second Language Reading, Reading-While-Listening and Listening Performance: A Study of Young Dyslexic and Non-dyslexic Language Learners

Abstract Our study investigated the differences in low-level L1 skills and L2 reading, listening, and reading-while-listening outcomes between young dyslexic and non-dyslexic Slovenian learners of English. The research, in which children completed four language assessment tasks in three modes in a carefully counter-balanced order, also examined the relationship between low-level L1 skills and L2 reading, listening, and reading-while-listening performance. The findings show that, in Slovenian, which is a transparent language, dyslexic students are behind their non-dyslexic peers in word-level L1 skills after five years of literacy instruction. The results also call attention to the fact that students with weak L2 reading and listening skills might not always be at risk of, or diagnosed as having, dyslexia. Importantly, the findings suggest that the accuracy and speed of real and non-word reading in L1 might serve as useful indicators of L2 reading difficulties of young language learners. Furthermore, L1 dictation tests were also found to yield diagnostic information on young L2 learners’ listening and reading-while-listening problems.

The influence of phoneme inventory on elicited speech errors in Arabic speakers of English

AbstractPrevious studies have shown that nonnative phonemic contrasts pose perceptual difficulties for L2 learners, but less is known about how these contrasts affect speech production in L2 learners. In the present study, we elicited speech errors in a tongue twister task investigating L1 Arabic speakers producing L2 English words. Two sets of word productions were contrasted: words with phonemic contrasts existing in both L1 Arabic and L2 English (e.g.tipvsdip, singvszing) or words with phonemic contrasts existing in English alone (pitvsbit, fatvsvat). Results showed that phonemic contrasts that do not exist in Arabic induced significantly more speech errors in L2 Arabic speakers of English compared to native English speakers than did phonemic contrasts found in both languages. Implications of these findings for representations in L2 learners are discussed.

A Mobile Outside-in Technique of Transforaminal Lumbar Endoscopy for Lumbar Disc Herniations.

Percutaneous endoscopic transforaminal lumbar discectomy (PETLD) has now become a standard of care for the management of lumbar disc disease. There are two techniques for the introduction of a working cannula with respect to disc-outside-in and inside-out. The aim of this prospective study is to describe the technical aspects of a novel mobile outside-in method in dealing with different types of disc prolapse. A total of 184 consecutive patients with unilateral lower limb radiculopathy due to lumbar disc prolapse were operated on with the mobile outside-in technique of PETLD. Their clinical outcomes were evaluated based on the type of disc prolapse they had, a visual analog scale (VAS) leg pain score, the Oswestry Disability Index (ODI), and the Macnab criteria. The completeness of the decompression was documented with a postoperative magnetic resonance imaging. The mean age of the patients was 50 ± 16 years and the male/female ratio was 2:1. The mean follow-up was 19 ± 6 months. A total of 190 lumbar levels were operated on (L1-L2: n = 4, L2-L3: n = 17, L3-L4: n = 27, L4-5: n = 123, and L5-S1: n = 19). Divided into types, the patient distribution was central: n = 14, paracentral: n = 74, foraminal: n = 28, far lateral: n = 13, superior-migrated: n = 8, inferior migrated: n = 38, and high canal compromise: n = 9. The mean operative time was 35 ± 12 (25 - 56) min and the mean hospital stay was 1.2 ± 0.5 (1-3) days. The VAS score for leg pain improved from 7.5 ± 1 to 1.7 ± 0.9. The ODI improved from 70 ± 8.3 to 23 ± 5. According to the Macnab criteria, 75 patients (40.8%) had excellent results, 104 patients (56.5%) had good results, and 5 patients (2.7%) had fair results. Recurrence (including early and late) was seen in 15 out of the 190 levels that were operated on (7.89%). This article presents a novel outside-in approach that relies on a precise landing within the foramen in a mobile manner and does not solely depend upon the enlargement of the foramen. It is more versatile in application and useful in the management of all types of disc prolapse, even in severe canal compromise and high migration.

Lumbar Interbody Fusion for Adjacent Segment Disease: An illustrative Case of The Transforaminal Approach (MIS-TLIF)

The scope of minimally invasive surgical (MIS) strategies for management of spinal pathology continues to expand. MIS transforaminal lumbar interbody fusion (TLIF) is an attractive alternative for the management of adjacent level disease. It minimizes approach related morbidities and provides anterior column support at a location where all 3 columns are affected by the adjacent segment degeneration (ASD).Our surgical technique involves the cannulation of the pedicles with K-wires. This is followed by a facetectomy and foraminal decompression with subsequent discectomy and endplate preparation. The cage is inserted followed by pedicle screw placement. To illustrate this technique, we present to you a case of a 56-year-old Female with previous L2–S1 successful arthrodesis, treated with MIS TLIF of L1–L2 for new adjacent segment disc herniation.This chapter describes the effective use of MIS TLIF in the treatment of adjacent segment disease and offers a unique strategy in management of this problem.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P7. Gravity line and sagittal alignment are both risk factors for increased rod stresses in long lumbopelvic fixation: A biomechanics study

BACKGROUND CONTEXT Posterior lumbopelvic fixation with iliac screws is a method that is commonly used for reconstructing the spine. However, clinically significant failure of lumbopelvic fixation (11.9%) and other complications such as pseudoarthrosis (observed in up to 50% of patients with rod failure) are possible, requiring revision surgery. With high rates of implant failure, questions remain regarding mechanical risk factors, or if there is any relationship between implant type, spinopelvic parameters, and failure to achieve fusion. PURPOSE The purpose of this study is to identify if—and to what extent—spinal-pelvic parameters play a role in construct failure using an in silico model. STUDY DESIGN/SETTING Finite element analysis. OUTCOME MEASURES Range of motion, rod stress or strain. METHODS Finite element models (T10-pelvis) were created to match the average spinal-pelvic parameters (pelvic tilt, sacral slope, and lumbar lordosis) of two cohorts of patients reported in the literature, major-failure (defined as pseudoarthrosis or rod fracture above S1) and nonfailure groups. In both groups, vertebral segments were modeled as three-dimensional solid elements. Intervertebral discs were structured as hyperelastic materials. The sacroiliac joint was modeled as articular cartilage contacts surrounded by six types of strong ligaments, depicted as spring elements. Pedicle screws with 5.5 mm diameters were modeled as titanium cylinders (yield strength=795 MPa). A moment load was applied at the T10 superior endplate to simulate gravimetric loading in a standing position. Both nonfailure and major-failure spines had a similar gravity line offset from the heels, as provided by the literature. A model validation was carried out to compare the range of motion of the intact spine unit with the experiments under 10Nm moment in flexion and extension. RESULTS Despite a fixed gravity line position relative to the heels, differences in spinopelvic parameters resulted in a neutral sagittal alignment in the nonfailure spine model, but produced a “sagittal forward” alignment of the major-failure spine model. In order for the latter to maintain sagittal balance, pelvic retroversion was reported and the major-failure spine was translated toward the heel by 10 mm to simulate that. As a result, the bending moment was approximately 17.3 Nm in the nonfailure group and 20.7 Nm in the major-failure group. Differences in loads produced 14 mm translation and 4.9° rotation for the major-failure group—18% and 14% higher, respectively, than in the nonfailure group (11.9 mm translation/4.3° rotation). Rod stresses were highest at L1–L2 and L4–L5. In the major-failure group, maximum stress (138.3 MPa) was observed at the left rod between L4 and L5. In the nonfailure group, maximum stress (115.4 MPa) was at the left rod surface between L1 and L2. High stress (141.0 MPa) was also observed in the right S1 screws in the major-failure group; it was 42% higher than the stress observed in the nonfailure group. CONCLUSIONS Due to compensatory differences in alignment of spinopelvic parameters between normal and failed spines, in the presence of a fixed gravity line, the major failure cohort in this study observed a 20% higher load and 18% greater instability. The higher load and instability further increased loading and mechanical demand on the posterior rods in the lower lumbar spine, further emphasizing the importance of proper sagittal alignment.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P37. QCT L1/L2 bone mineral density average: a useful bone quantity measure of the entire lumbosacral spine

BACKGROUND CONTEXT Quantitative computed tomography (QCT) of the lumbar spine is used as an alternative to DXA in assessing bone mineral density (BMD). Clinically, a BMD average of L1/L2 is commonly used as a surrogate marker for overall bone health. Since significant regional BMD differences within the spine have been described, it is unclear if the L1/L2 average is an accurate bone quantity measure of the entire lumbosacral spine. PURPOSE The aim of this study was to assess the agreement between the clinically used L1/L2 BMD average and the other lumbosacral vertebral levels. STUDY DESIGN/SETTING A quantitative computed tomography study. PATIENT SAMPLE A total of 296 consecutive patients undergoing posterior lumbar spinal fusion from 2014 to 2017 at a single, academic institution. OUTCOME MEASURES Bone mineral density. METHODS Patients that underwent posterior lumbar spinal fusion from 2014 to 2017 at a single, academic institution were included in this study. Subjects with missing preoperative lumbar spine CT imaging were excluded. Standard QCT measurements at the L1 and L2 vertebra and additional experimental measurements of L3, L4, L5 and S1 were performed. The correlations between L1–L2 average and the other vertebral bodies of the lumbosacral spine (L3, L4, L5, and S1) were evaluated. RESULTS A total of 296 patients (women, 55.4%) met inclusion criteria. The patient population was 88.5% Caucasian with a mean age of 63.1years and mean BMI of 28.0 kg/m2. The vertebral BMD values showed a gradual decrease from L1 to L3 and subsequently increased from L4 to S1 (L1=118.8 mg/cm3, L2=116.6 mg/cm3, L3=112.5 mg/cm3, L4=122.4 mg/cm3, L5=135.3 mg/cm3, S1=157.4 mg/cm3). Our data showed strong correlation between the L1/L2 average and the average of the other lumbosacral vertebrae (L3–S1) with a Pearson's correlation coefficient, r=0.85. We also analyzed the correlation between the L1/L2 average and each individual lumbosacral vertebra. Similar relationships were observed (r value, 0.67–0.87) with the strongest correlation between the L1/L2 average and L3. CONCLUSIONS Our data demonstrates considerable regional BMD throughout the lumbosacral spine. Nevertheless, there is high concordance between the clinically used L1/L2 BMD average and the BMD values in the other lumbosacral vertebrae. As the closest vertebra to the standard measurement site, L3 showed the strongest individual correlation to the L1/L2 average. Although still strongly correlated, Pearson's correlation coefficients were smaller for the L4, L5 and S1 vertebra. This might be of importance, since the majority of patients in our cohort underwent fusion procedures at L4–L5 (71.3%) and/or L5–S1 (44.9%). In summary, the L1/L2 BMD average is a useful bone quantity measure of the entire lumbosacral spine in patients undergoing posterior lumbar spinal fusion.

Language Dominance Affects Bilingual Performance and Processing Outcomes in Adulthood.

This study examines the role of language dominance (LD) on linguistic competence outcomes in two types of early bilinguals: (i) child L2 learners of Catalan (L1 Spanish-L2 Catalan and, (ii) child Spanish L2 learners (L1 Catalan-L2 Spanish). Most child L2 studies typically focus on the development of the languages during childhood and either focus on L1 development or L2 development. Typically, these child L2 learners are immersed in the second language. We capitalize on the unique situation in Catalonia, testing the Spanish and Catalan of both sets of bilinguals, where dominance in either Spanish or Catalan is possible. We examine the co-occurrence of Sentential Negation (SN) with a Negative Concord Item (NCI) in pre-verbal position (Catalan only) and Differential Object Marking (DOM) (Spanish only). The results show that remaining dominant in the L1 contributes to the maintenance of target-like behavior in the language.

STATISTICAL SENSITIVITY, COGNITIVE APTITUDES, AND PROCESSING OF COLLOCATIONS

AbstractFrequency and contingency (i.e., co-occurrence probability of words in multiword sequences [MWS]) are two driving forces of language acquisition and processing. Previous research has demonstrated that L1 and advanced L2 speakers are sensitive to phrasal frequency and contingency when processing larger-than-word units. However, it remains unclear whether such statistical sensitivity is robust across tasks and among subcategories of MWS. In addition, little is known about whether cognitive aptitudes can moderate such sensitivity. This study examined L1 and advanced L2 speakers’ statistical sensitivity to phrasal frequency and contingency as well as cognitive aptitudes’ moderating effects on such sensitivity when processing English adjective-noun collocations. Participants performed a phrasal acceptability judgment task (PJT). Meanwhile, their aptitude profiles were measured by six aptitude tests, which loaded separately onto implicit language aptitude, explicit language aptitude, and working memory capacity. Linear mixed-effects modeling revealed that both L1 and L2 English speakers were sensitive to phrasal frequency and contingency of collocations, although L2 speakers’ sensitivity was much stronger than that of L1 speakers. None of the aptitudes was found to moderate language users’ statistical sensitivity to either collocation frequency or contingency. Interestingly, disassociation patterns between the PJT performance and the involvement of implicit or explicit language aptitude among the L1 and L2 speakers were found. It was concluded that L1 and L2 speakers differed in terms of the way they processed the collocations, as well as the nature of their collocational knowledge.

High School Spanish Students and Foreign Language Reading Anxiety: Déjà vu All Over Again All Over Again

AbstractA unique anxiety for foreign language (L2) learning has been hypothesized to explain students’ problems with language learning. However, L2 anxiety instruments have been challenged on the grounds that they reflect students’ language learning ability and/or perceptions of their language learning skills. In this study, 266 U.S. high school students were administered measures of first language (L1) skills, L2 aptitude, and L2 achievement and followed through 2–3 years of Spanish courses. In 1st‐year Spanish, they were administered the Foreign Language Reading Anxiety Scale (FLRAS), divided into 3 anxiety groups, and compared on the L1 and L2 measures. Findings showed that the Low Anxiety group scored significantly higher than the High Anxiety group on all L1 and L2 measures, and significantly higher than the Average Anxiety group on most L1 and L2 measures at the end of 1st‐ and 2nd‐year Spanish. Students who completed 3rd‐year Spanish displayed either low or average anxiety on the FLRAS. Results revealed negative correlations between the FLRAS and all L1 and L2 measures. Correlations between the FLRAS and the L2 achievement measures increased over time. Findings show that the FLRAS is unlikely to be measuring anxiety for language learning but more likely to be a proxy for students’ levels of L1 skill, L2 aptitude, and L2 achievement.

Bioluminescence tomography with structural information estimated via statistical mouse atlas registration

Due to an ill-posed and underestimated characteristic of bioluminescence tomography (BLT) reconstruction, a priori anatomical information obtained from computed tomography (CT) or magnetic resonance imaging (MRI), is usually incorporated to improve the reconstruction accuracy. The organs need to be segmented, which is time-consuming and challenging, especially for the low-contrast CT images. In this paper, we present a BLT reconstruction method based on a statistical mouse atlas to improve the efficiency of heterogeneous model generation and the accuracy of target localization. The low-contrast CT image of the mouse was first registered to the statistical mouse atlas model with the constraints of mouse surface and high-contrast organs (bone and lung). Then the other organs, such as the liver and kidney, were determined automatically through the statistical mouse atlas model. The estimated organs were then discretized into tetrahedral meshes for BLT reconstruction. The linearized Bregman method was used to solve the sparse inverse problem of BLT by minimizing the regularization function (L1 norm plus L2 norm with smooth factor). Both numerical simulations and in vivo experiments were conducted, and the results demonstrate that even though the localization of the estimated organs may not be exactly accurate, the proposed method is feasible to reconstruct the bioluminescent source effectively and accurately with the estimated organs. This method would greatly benefit the bioluminescent light source localization for hybrid BLT/CT systems.

The Spoken Academic English of Dutch University Lecturers

ABSTRACTWhile English is used more and more at Dutch universities, it is subject to criticism, specifically regarding the lack of expressiveness. Our study described the differences in linguistic expressiveness between L1 spoken Dutch and L2 spoken English of nine Dutch university lecturers, by comparing their adjective and verb use mainly: variation of words used, frequencies, sophistication of word choice, and accuracy. It also looked at the views of the lecturers themselves on the richness of their language. Type/token ratio analyses showed that both the lectures in their L1 (Dutch) and those in their L2 (English) conformed to what may be expected in terms of variety of words used in academic lecturing. Frequency analyses for both L1 and L2 speech yielded remarkably comparable lists of highly frequently used, basic, commonly known words, and considerable lists of infrequently used, typically sophisticated and academic words. However, although the comparison of words, and in particular adjectives and verbs, suggested little to no difference between the L1 Dutch and L2 English of the speakers, a comparison of verbs in context showed that in L1 Dutch most common verbs were used in more elaborate and complicated idiomatic sentences.

Lumbar spinal stenosis in adult achondroplasia. An analysis of intervertebral disk alterations

Lumbar spinal stenosis is a major contributor to disability in adults with achondroplasia. It arises from congenital dysplasia and acquired degenerative changes. The aim of the study was to characterize degenerative changes of the intervertebral disk in adult achondroplasia patients with lumbar spinal stenosis and to identify factors associated with the process. The study was a case series of adult achondroplasia patients. Clinical parameters were recorded. Radiographs were used to analyze spino-pelvic parameters. MRI of the lumbar spine was used to measure antero-posterior diameter of the canal and disk degeneration using the Pfirrmann grading system. Comparisons were done using the Kruskal–Wallis test and correlations using the Spearman coefficient. Eighteen patients were included: age 37 ± 17, female 12, size 127 ± 7 cm, weight 57 ± 13 kg. All had symptoms due to lumbar spinal stenosis. Antero-posterior diameters of the spinal canal differed according to level ( P < 0.05). Lower values were observed at T12–L1, L1–L2 and L2–L3 levels. The lumbar spinal stenosis was maximal at L2–L3 (9.9 ± 1.8 mm). Degrees of disk degeneration also differed according to level ( P < 0.05). Higher degrees of degeneration were observed at L1–L2, L2–L3 and L3–L4 levels. Most advanced degenerative changes were observed at L2–L3 (2.9 ± 1.4). Correlation analysis between disk degeneration and spino-pelvic parameters found a significant relationship with thoraco-lumbar kyphosis at L2–L3 level (0.55). Correlation analysis between antero-posterior diameter of the spinal canal and the spino-pelvic parameters found a significant relationship with lumbar lordosis at T12–L1 (0.66) and L2–L3 (0.89) levels, and with thoraco-lumbar kyphosis at L1–L2 level (−0.55). Spinal stenosis and disk degeneration mainly involve the upper part of the lumbar spine in adult achondroplasia patients. Thoraco-lumbar kyphosis and lumbar lordosis are related with these processes. The findings may be of importance in rehabilitation and in early prevention of spinal stenosis in the course of achondroplasia.

Immiscibility of Liquid Phases and Liquid–Liquid Critical Phenomena in Aqueous Solutions of Sodium and Potassium Phosphates

Phase equilibria were studied in aqueous solutions of sodium and potassium phosphates at elevated temperatures (to 425°C) and pressures (to 63 MPa). Experimental data were obtained on the transformation of gas–liquid equilibria into heterogeneous equilibria of two liquid phases with increasing pressure, which ends in the critical phenomena of immiscibility (L1 = L2). Based on the experimental and literature data, it was concluded that the binary water–salt systems containing KH2PO4, K2HPO4, K3PO4, NaH2PO4, and Na2HPO4 are characterized by phase diagrams of the first type [1, 2], which have two critical invariant end points: N (G–L1 = L2) and R (G = L1–L2).