Prolonged Standing-Induced Low Back Pain Is Linked to Extended Lumbar Spine Postures: A Study Linking Lumped Lumbar Spine Passive Stiffness to Standing Posture.

Postural assessments of the lumbar spine lack valuable information about its properties. The purpose of this study was to assess neutral zone (NZ) characteristics via in vivo lumbar spine passive stiffness and relate NZ characteristics to standing lumbar lordosis. A comparison was made between those that develop low back pain during prolonged standing (pain developers) and those that do not (nonpain developers). Twenty-two participants with known pain status stood on level ground, and median lumbar lordosis angle was calculated. Participants were then placed in a near-frictionless jig to characterize their passive stiffness curve and location of their NZ. Overall, both pain developers and nonpain developers stood with a lumbar lordosis angle that was more extended than their NZ boundary. Pain developers stood slightly more extended (in comparison to nonpain developers) and had a lower moment corresponding to the location of their extension NZ boundary. Overall, in comparison to nonpain developers, pain developers displayed a lower moment corresponding to the location of their extension NZ boundary which could correspond to greater laxity in the lumbar spine. This may indicate why pain developers have a tendency to stand further beyond their NZ with greater muscle co-contraction.

Coevolution between heat and cold tolerance in endotherms.

Whether the heat and cold tolerance of endotherms evolve independently or correlatively remains unresolved. Both physiological trade-offs and natural selection can contribute to a coevolutionary pattern of heat and cold tolerance in endotherms. Using a published database, we tested the correlation between upper and lower thermal limits across endothermic species with multi-response generalized linear mixed models incorporating phylogenies. We found a positive correlation between upper and lower thermal limits, which suggested a coevolutionary pattern of heat and cold tolerance. Specifically, this relationship between heat and cold tolerance is phylogenetically constrained for tropical endotherms but not for temperate endotherms. The correlated evolution between heat and cold tolerance may have a significant influence on endotherms' evolution and ecology and needs to be further investigated.

Biomechanical analysis of the door-shaped titanium plate in single-level anterior cervical discectomy and fusion.

BACKGROUND: Analyse and discuss the immediate stability of the cervical spine after anterior cervical discectomy and fusion using a door-shaped titanium plate and compare it with the traditional titanium plate, to provide biomechanical evidence for the rationality and effectiveness of the door-shaped titanium plate in clinical applications. METHODS: Ten adult goat C4/5 vertebral bodies were obtained, and models were prepared using denture base resin. Biomechanical experiments were performed on the specimens before internal fixation. MTS was used to conduct non-destructive biomechanical loading tests in six directions, including flexion, extension, left-right bending, and left-right torsion, recording the range of motion (ROM) and neutral zone (NZ) of each specimen. The specimens were then randomly divided into two groups: the study group was fixed with a door-shaped titanium plate, and the control group was fixed with a traditional titanium plate. ROM and NZ in each direction were measured again. After measurements, both groups were subjected to 0.5 Hz torsion loading with a torque of 2 N m for a total of 3000 cycles, followed by measuring ROM and NZ in six directions once more. RESULTS: Compared to before fixation, ROM and NZ in both groups significantly decreased in all six directions after fixation, with statistical significance (P < 0.05); after fixation, the study group showed slightly lower values for various mechanical reference parameters compared to the control group, with no statistical significance (P > 0.05); after 3000 torsional loads, both internal fixation groups showed increased ROM and NZ compared to after fixation but to a lower extent, and no screw or titanium plate loosening was observed. Compared to before fixation, the differences were still statistically significant (P < 0.05), with the study group having slightly lower ROM and NZ values in all directions compared to the control group, with no statistical significance (P > 0.05). CONCLUSION: The door-shaped titanium plate exhibits mechanical properties similar to the traditional titanium plate in all directions, and its smaller size and simpler surgical operation can be used for anterior cervical endoscopic surgery, reducing surgical trauma. It is clinically feasible and deserves further research and promotion.

Lower limb postures resembling sitting and standing alter lumbar angles along the passive stiffness curve.

In vivo lumbar passive stiffness is often used to assess time-dependent changes in lumbar tissues and to define the neutral zone. We tested the hypothesis that flexing the hips would alter tension in hip and spine musculature, leading to a more extended passive stiffness curve (i.e., right-shifted), without changes in lumbar stiffness. Twenty participants underwent side-lying passive testing with the lower limbs positioned in Stand, Kneel, and Sit representative postures. Moment-angle curves were constructed from the lumbar angles and the moment at L4/5 and partitioned into three zones. Partially supporting our hypothesis, lumbar stiffness within the low and transition stiffness zones was similar between the Stand and Sit. Contrary to our hypothesis, lumbar angles were significantly larger in the Sit compared to the Stand and Kneel postures at the first and second breakpoints, with average differences of 9.3° or 27.2% of passive range of motion (%PassRoM) in flexion and 5.6° or 16.6 %PassRoM in extension. Increased flexion in the Sit may be linked to increased posterior pelvic tilt and associated lower lumbar vertebrae flexion. Investigators must ensure consistent pelvis and hip positioning when measuring lumbar stiffness. Additionally, the adaptability of the neutral zone to pelvis posture, particularly between standing and sitting, should be considered in ergonomic applications.

Energetic costs of bill heat exchange demonstrate contributions to thermoregulation at high temperatures in toco toucans (Ramphastos toco).

Body temperature regulation under changes in ambient temperature involves adjustments in heat production and heat exchange rates between the animal and the environment. One mechanism involves the modulation of the surface temperature of specific areas of the body through vasomotor adjustment. In homeotherms, this thermoregulatory adjustment is essential for the maintenance of body temperature over a moderate temperature range, known as the thermal neutral zone (TNZ). The bill of the toco toucan (Ramphastos toco) has been described as a highly efficient thermal window and hypothesized to assist in the thermal homeostasis of this bird. Herein, we directly evaluated the contribution of heat exchange through the bill of the toco toucan and role of the bill in the delimitation of the TNZ. To do this, we measured metabolic rate (MR), via oxygen consumption, over a range of ambient temperatures from 0 to 35°C. MR measurements were made in birds with the bill intact and with the bill insulated. The limits of the TNZ did not differ between treatments, ranging from 10.8 to 25.0°C. The MR differed among treatments only at elevated temperatures (30 and 35°C), reaching 0.92±0.11 ml O2 g-1 h-1 (mean±s.d.) for the intact group and 1.13±0.13 ml O2 g-1 h-1 for the insulated group. These results indicate that although heat dissipation through the bill does not contribute significantly to widening of the TNZ, it may well be critically important in assisting body temperature regulation at higher temperatures extending above the upper limit of the TNZ.

Unveiling the Realm of Denture Fabrication: Revitalizing Aesthetics and Optimizing Efficiency for Geriatric Patients.

Disfigurement of the face has a significant impact not only on the appearance and function but also on the psychological well-being of an individual. Due to tooth loss, various psychological problems can occur. Dentures can help patients regain a sense of normalcy and also boost their confidence to live in society. Complete denture restores phonetics, esthetics, and mastication. A 63-year-old male patient reported to the Department of Prosthodontics with the chief complaint of total loss of teeth and wanted to get treated for the same. The purpose of this article is to describe changes in impression techniques, dental material, methodologies in teeth setting, and novel approaches to enhance the esthetics to optimize the results in a final complete denture. To reestablish the patient's masticatory, apparatus steps of complete denture fabrication were revisited accompanied by the modern application of innovative techniques with the base of historical concept.

How Does the Rib Cage Affect the Biomechanical Properties of the Thoracic Spine? A Systematic Literature Review.

The vast majority of previous experimental studies on the thoracic spine were performed without the entire rib cage, while significant contributive aspects regarding stability and motion behavior were shown in several other studies. The aim of this literature review was to pool and increase evidence on the effect of the rib cage on human thoracic spinal biomechanical characteristics by collating and interrelating previous experimental findings in order to support interpretations of in vitro and in silico studies disregarding the rib cage to create comparability and reproducibility for all studies including the rib cage and provide combined comparative data for future biomechanical studies on the thoracic spine. After a systematic literature search corresponding to PRISMA guidelines, eleven studies were included and quantitatively evaluated in this review. The combined data exhibited that the rib cage increases the thoracic spinal stability in all motion planes, primarily in axial rotation and predominantly in the upper thorax half, reducing thoracic spinal range of motion, neutral zone, and intradiscal pressure, while increasing thoracic spinal neutral and elastic zone stiffness, compression resistance, and, in a neutral position, the intradiscal pressure. In particular, the costosternal connection was found to be the primary stabilizer and an essential determinant for the kinematics of the overall thoracic spine, while the costotransverse and costovertebral joints predominantly reinforce the stability of the single thoracic spinal segments but do not alter thoracic spinal kinematics. Neutral zone and neutral zone stiffness were more affected by rib cage removal than the range of motion and elastic zone stiffness, thus also representing the essential parameters for destabilization of the thoracic spine. As a result, the rib cage and thoracic spine form a biomechanical entity that should not be separated. Therefore, usage of entire human non-degenerated thoracic spine and rib cage specimens together with pure moment application and sagittal curvature determination is recommended for future in vitro testing in order to ensure comparability, reproducibility, and quasi-physiological validity.

Even mild intervertebral disc degeneration reduces the flexibility of the thoracic spine: an experimental study on 95 human specimens.

BACKGROUND CONTEXT: Intervertebral disc degeneration represents one of multiple potential trigger factors for reduced passive spinal mobility and back pain. The effects of age-related degenerative intervertebral disc changes on spinal flexibility were however mainly investigated for the lumbar spine in the past, while intervertebral disc degeneration is also highly prevalent in the thoracic spine. PURPOSE: To evaluate the effect of the degeneration grade on the range of motion and neutral zone of the thoracic spine. STUDY DESIGN: Experimental study including combined radiological grading of intervertebral disc degeneration and biomechanical testing of 95 human thoracic functional spinal units (min. n=4 per level from T1-T2 to T11-T12) from 33 donors (15 female / 18 male, mean age 56 years, age range 37-80 years). METHODS: Degeneration grades of the intervertebral discs were assessed using the validated x-ray grading scheme of Liebsch et al. (0=no, 1=mild, 2=moderate, 3=severe degeneration). Motion segments were loaded with pure moments in flexion/extension, lateral bending, and axial rotation to determine range of motion and neutral zone at 5 Nm. RESULTS: All tested specimens exhibited degeneration grades between zero and two. Range of motion significantly decreased for grades one and two compared with grade zero in any motion direction (p<.05), showing the strongest decrease in extension comparing grade two with grade zero (-42%), while no significant differences were detected between grades one and two. Similar trends were found for the neutral zone with the strongest decrease in extension also comparing grade two with grade zero (-47%). Donor age did not significantly affect the range of motion, whereas the range of motion was significantly reduced in specimens from male donors due to the significantly higher degeneration grade in this study. CONCLUSIONS: Even mild intervertebral disc degeneration reduces the range of motion and neutral zone of the thoracic spine in any motion plane, whereas progressing degeneration does not further affect its flexibility. This is in contrast to the lumbar spine, where a more gradual decrease of flexibility was found in prior studies, which might be explained by differences between thoracic and lumbar intervertebral disc morphologies. CLINICAL SIGNIFICANCE: Thoracic intervertebral disc degeneration should be considered as one of multiple potential causal factors in patients showing reduced passive mobility and middle back pain.

A study to investigate the effectiveness of the application of virtual reality technology in dental education.

BACKGROUND: Today, the use of virtual reality (VR) technology as an educational tool in dental education has expanded considerably. This study was aimed to evaluate the effectiveness of using VR technology in teaching neutral zone and teeth arrangement. METHODS: This randomized trial was conducted at Kermanshah University of Medical Sciences, Iran in 2019. The study sample consisted of 50 six-year dental students who were randomly divided into experimental (n = 25) and control (n = 25) groups. Students' performance in both groups was assessed using tests. A questionnaire was used to assess the usability of VR technology and students' satisfaction with it. RESULTS: All faculty members confirmed the usability of VR technology in dental education. The majority of students (76%) were highly satisfied with the use of this technology in their learning process. The mean score of students was significantly higher in the experimental group (16.92 ± 1.12) than in the control group (16.14 ± 1.18). CONCLUSION: In general, it can be argued that VR technology is useful and effective in the teaching-learning process. Therefore, its use in medical and dental schools can play an effective role in creating a dynamic, attractive, and successful learning environment.

The Neutral Zone Approach with CAD-CAM Record Bases.

Lack of adequate retention, support, and stability in the complete denture can be attributed to a poor fit or incorrect shape of the polished surfaces. This article presents a case using the neutral zone technique effectively with the fabrication of computer-aided design and computer-aided manufacturing (CAD-CAM) record bases in an edentulous patient with severely resorbed alveolar ridges and discusses the overall treatment steps and clinical implications of this technique. A stable neutral zone and an accurate jaw relation were recorded using CAD-CAM record bases and stability of complete denture was optimized by arranging denture teeth and reforming polishing surfaces in the neutral zone. A new complete denture was fabricated for a patient with atrophic alveolar ridges by a technique utilizing the neutral zone with CAD-CAM record bases.

Effectiveness of denture space recording method in the prosthetic treatment of edentulous patients.

PURPOSE: To present a clinical rationale for the effectiveness of denture space recording methods for the prosthetic treatment of edentulous patients through a review of the literature. STUDY SELECTION: A total of 3167 studies were extracted from a search of four terms, namely denture space, neutral zone technique, flange technique, and piezography using PubMed and J-STAGE databases. A total of 57 documents that matched the inclusion and exclusion criteria were selected. RESULTS: From the extracted articles, the clinical application of denture space recording methods was found to be effective in edentulous patients with severe ridge resorption. The relationship between the labiolingual and buccolingual pressure in patients with neuromuscular problems or with mandibular or lingual defects differs from those without it, so a stable prosthesis can be easily fabricated by locating the neutral zone using denture space recording methods. CONCLUSION: The literature on denture space recording methods suggests that its application on challenging cases of edentulous patients is useful in providing prostheses with improved retention and stability.

Does the neutral zone quantification method matter? Efficacy of evaluating neutral zone during destabilization and restabilization in human spine implant testing.

Neutral zone (NZ) is an important biomechanical parameter when evaluating spinal instability following destabilizing and restabilizing events, with particular relevance for implant efficacy testing. It remains unclear what NZ calculation methods are most sensitive at capturing NZ changes across treatment conditions and a direct comparison is needed. The purpose of this study was to determine the most sensitive method at quantifying instability in human spines. Six cadaveric lumbar motion segments were subjected to a repeated measures implant testing schema of four sequential conditions: (1) Intact, (2) injury by herniation, (3) device implantation, (4) long-term cyclic fatigue loading. NZ was expected to increase after destabilization (steps 2 & 4) and decrease after restabilization (step 3). NZ methods compared in this study were: trilinear (TL), double sigmoid (DS), zero load (ZL), stiffness threshold (ST), and extrapolated elastic zone (EEZ). TL, ZL, and EEZ identified statistically significant NZ differences after each condition in flexion/extension and lateral bending. The ZL method also captured differences in axial rotation. All methods identified expected NZ changes after destabilization and restabilization, except DS in axial rotation. The TL, ZL, and EEZ methods were the most sensitive methods with this human cadaveric dataset. Future investigations comparing methods with additional datasets will clarify outcome generalizability and determine what curve profiles are most suitable for DS and ST methods. Understanding the applicability of NZ methods can enhance rigor and reliability of spinal instability measurements when quantifying the efficacy of novel implants and permits insight into clinically relevant biomechanical changes.

Exploring the influence of impact severity and posture on vertebral joint mechanics in an in-vitro porcine model.

To date, no in vitro studies have been conducted to explore lumbar soft tissue injury potential and altered mechanical properties from exposure to impact forces. After a motor vehicle collision (MVC), the cause of reported acute onset low back pain is difficult to associate with potential soft tissue strain injury sites including the facet joint and innervated facet joint capsule ligament (FJC). Thus, the purpose of this investigation was to quantify intervertebral anterior-posterior (AP) translation and facet joint capsule strain under varying postures and impact severities. Seventy-two porcine spinal units were exposed to three levels of impact severity (4 g, 8 g, 11 g), and posture (Neutral, Flexion, Extension). Impacts were applied using a custom-built impact track that replicated parameters experienced in low to moderate speed rear-end MVCs. Flexion-extension and anterior-posterior shear neutral zone testing were completed prior to impact. AP intervertebral translation and the strain tensor of the facet capsule ligament were measured during impacts. A significant main effect of collision severity was observed for peak AP intervertebral translation (4 g-2.8 ±0.53 mm; 8 g-6.4 ±2.9 mm; 11 g-8.3 ±0.45 mm) and peak FJC shear strain (2.37% strain change from 4 g to 11 g impact severity). Despite observed main effects of impact severity, no influence of posture was observed. This lack of influence of posture and small FJC strain magnitudes suggest that the FJC does not appear to undergo injurious or permanent mechanical changes in response to low-to-moderate MVC impact scenarios.

Ultrashort Implants, Alternative Prosthetic Rehabilitation in Mandibular Atrophies in Fragile Subjects: A Retrospective Study.

This study aimed to evaluate the effectiveness of using ultrashort implants in the rehabilitation of jaws of fragile patients. The aim of the study was to retrospectively evaluate the survival rate of full-arch prosthetic rehabilitation on ultrashort implants, length 4 mm, 4 mm in diameter in the premolar and canine area and 4.5 mm in diameter in the molar area, with the insertion torque of 60 Nw and immediate loading. Nineteen patients were evaluated for 3 years clinically and radiographically. The significant majority of the patients at the 3 year follow-up (T4) presented a stable and functional implant-supported prothesis, and the survival rate of the implants was 85%, with a loss of 16 implants on 114 implants. The combination of the innovative implant surfaces and the correct project of the prostheses, with the related implant connection, determined a different timing in the therapy, allowing to obtain an immediate loading, which is currently demanded by patients. This and recent reports on short and ultrashort implant usage in atrophic jaws offer a good solution in critical cases. In conclusion, within the limits of the study, the full-arch rehabilitation with immediate loading on ultrashort implants showed good results with few postoperative complications and related low biological cost.

Mechanical Consequence of Induced Intervertebral Disc Degeneration in the SPARC-Null Mouse.

Intervertebral disc (IVD) degeneration is associated with low back pain (LBP) and accompanied by mechanical changes to the spine. Secreted protein acidic and rich in cysteine (SPARC) is a protein that contributes to the functioning and maintenance of the extracellular matrix. SPARC-null mice display accelerated IVD degeneration and pain-associated behaviors. This study examined if SPARC-null mice also display altered spine mechanics as compared to wild-type (WT) mice. Lumbar spines from SPARC-null (n = 36) and WT (n = 18) mice aged 14-25 months were subjected to cyclic axial tension and compression to determine neutral zone (NZ) length and stiffness. Three separate mechanical tests were completed for each spine to determine the effect of the number of IVDs tested in series (one versus two versus three IVDs). SPARC-null spine NZs were both stiffer (p < 0.001) and smaller in length (p < 0.001) than WT spines. There was an effect of the number of IVDs tested in series for NZ length but not NZ stiffness when collapsed across condition (SPARC-null and WT). Correlation analysis revealed a weak negative correlation (r = -0.24) between age and NZ length in SPARC-null mice and a weak positive correlation (r = 0.30) between age and NZ stiffness in WT mice. In conclusion, SPARC-null mice had stiffer and smaller NZs than WT mice, regardless of the number of IVDs in series being tested. The increased stiffness of these IVDs likely influences mobility at these spinal joints thereby potentially contributing to low back pain.

Biomechanical Study of Posterior Dynamic Fixation at Atlantoaxial Joints / 医用生物力学

Objective To evaluate the influence of dynamic fixation (rotating and sliding pedicle screws) on stability of the atlantoaxial joint. Methods A series of in vitro biomechanical tests were performed using six fresh adult cervical spines (occipital bone-C4 segment) to simulate different conditions in surgery， including the intact state, the injury state, rigid fixation, rotating pedicle screw fixation, sliding pedicle screw fixation. The repeated measurement design was employed, and under intact, injury and different fixation states, the pure moment of 1.5 N·m in flexion-extension, left-right lateral bending, left-right axial rotation directions were applied using the spinal testing machine. The movement of atlantoaxial spine was measured consecutively by three-dimensional （3D） measurement system in order to analyze the range of motion (ROM) and neutral zone (NZ) of atlantoaxial joints. Results Under injury state, ROM of atlantoaxial joints was significantly larger than that under intact state during flexion, extension, lateral bending and rotation, leading to the instability of atlantoaxial joints. ROM of fixation segments was significantly reduced during flexion, extension, lateral bending and rotation after rigid and dynamic fixation. Compared with rigid fixation, dynamic fixation showed a significant ROM increase during lateral bending. NZs of fixation segments after dynamic fixation were significantly reduced. There were no significant ROM differences between rigid fixation and dynamic fixation. Conclusions The stability of atlantoaxial joints by dynamic fixation during flexion, extension and rotation was comparable to that by rigid fixation, but weaker during lateral bending. Dynamic screw fixation can maintain the relative stability of atlantoaxial joints.

Avian Surveys in the Korean Inner Border Area, Gimpo, Republic of Korea.

BACKGROUND: Birds are useful environmental indicators as their presence reflects the health of the food web. Bird occurrence, rarity and abundance are reliable indicators of ecosystem health. Monitoring of avian populations in the Republic of Korea (ROK) is a primary requirement due to plummeting populations and the risks to threatened species. The Ministry of Environment of ROK started conducting winter bird censuses in 1999, including inland areas and coast areas, such as Cheorwon, Yeoncheon, Junam Reservoir and Han River. Cheolwon, Yeoncheon and some extent islands in the West Sea have been survey extensively due to iconic bird species, such as White-naped Crane (Grus vipio) or Red-Crowned Crane (Grus japonensis) wintering there. However, the winter bird census has not covered Yu Islet, Han River Estuary. Yu Islet is located within the Han River Estuary, a protected wetland in the Neutral Zone between the two Koreas and north of Gimpo in the ROK. The Islet currently supports a large, mixed breeding colony of waterbirds, such as one of the nation's largest concentration of breeding Great Cormorants (Phalacrocorax carbo) and smaller numbers of breeding Black-faced Spoonbill (Platalea minor), Grey Heron (Ardea cinereal), Great Egret (Ardea alba) and Intermediate Egret (Ardea intermedia). Access to the area has long been restricted for military reasons, but recently, regular survey activity is possible supported by Gimpo City and the military base in Gimpo from November 2018. NEW INFORMATION: Here, we provide data demonstrating that Yu Islet is important for breeding for waterbirds; and that the northern Gimpo part of Han River Estuary is also internationally important for waterbirds during the migratory bird season, as defined by the Ramsar Convention (Ramsar 1971, RRC-EA 2017). In particular, four waterbird species were found during the survey in the Main Survey Area: Swan Goose (Anser cygnoides), Taiga Bean Goose (Anser fabalis), Tundra Bean Goose (Anser serrirostris) and Greater White-fronted Goose (Anser frontalis). Once considered widespread in East Asia and abundant, the world population of Swan Goose is now estimated at only 60,000 - 78,000 individuals (Wetlands International 2020) and the species is assessed by BirdLife International as globally Vulnerable (BirdLife International 2020). The 1,010 Swan Goose (Anser cygnoides) counted on the vegetated mudflats at Jogang-Ri in the Main Survey Area on 27 November 2018 represents more than 1% of the total world population of this species. Notably, it is also the highest count of this species in the ROK for at least a decade. The count confirms the continuing international importance of the Han River Estuary for the survival of the Swan Goose. The number counted in November had fallen to 250 by 28 December 2018; and none was recorded in the Main Survey Area in January or February 2019. Although searched for in March, none was noted during the northward migration either. The surveys also found small numbers of nationally-scarce Grey-capped Pygmy Woodpecker (Yungipicus canicapillus) in several areas of woodland surrounded by the Han River Estuary. By selecting the most species-rich count within a given month in each of the two survey sectors, the number of species we recorded ranged from a minimum 29 in January to a maximum of 65 in April 2019. Based on the species recorded, the survey area is clearly important for avian conservation. Its importance derives from the combination of the extensive areas of high-quality wetland and its geographic location within one of the Korea Peninsula's largest and most important remaining wetland ecosystems, the Han River Estuary. Our surveys resulted in the detection of a substantial number of bird species, especially in March and April when forest-breeding birds are more obviously vocal. The survey result is provided in the supplementary material (Suppl. material 1).

Is Neutral Zone, Patients Comfort Zone? A Feedback Review.

The technique of neutral zone is useful. It is the convergence of many concepts and ideas into a feasible and functional method. The technique aims to build a denture in accordance with the underlying oral structures that are formed by muscle function. It acts as an alternative technique in case of highly atrophic ridges. With a history of denture instability, it is most successful. This paper seeks to provide information with an enclosure of a patient input study to use the technique.

Passive stiffness characteristics and neutral zone quality of the scoliotic lumbar torso in the principle anatomical planes of motion.

BACKGROUND: The 1-10% prevalence rate of adult scoliosis frequently requires expensive therapy and surgical treatments and demands further research into the disease, especially with an aging population. Most studies examining the mechanics of scoliosis have focused on in vitro testing or computer simulations. This study quantitatively defined the passive stiffness properties of the in vivo scoliotic spine in three principle anatomical motions and identified differences relative to healthy controls. METHODS: Adult scoliosis (n = 14) and control (n = 17) participants with no history of spondylolisthesis, spinal fracture, or spinal surgery participated in three different tests (torso lateral side bending, torso axial rotation, and torso flexion/extension) that isolated mobility to the in vivo lumbar spine. The spinal stiffnesses and spinal neutral zone width were calculated. These parameters were statistically compared between factor of population and within factor of direction. FINDINGS: Torque-rotational displacement data were fit using a double sigmoid function, resulting an in excellent overall fit (Avg. R2 = 0.95). There was a significant interaction effect between populations when comparing axial twist neutral zone width vs. lateral bend neutral zone width and axial twist stiffness vs. lateral bend stiffness. The axial twist neutral zone width magnitude was significantly larger in scoliosis patients. INTERPRETATION: The present study is the first investigation to quantify the whole trunk neutral zone of the scoliotic lumbar spine. Future research is needed to determine if lumbar spine mechanical characteristics can help explain progression of scoliosis and complement scoliosis classification systems.