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PubMed2000

The biomechanical effect of postoperative hypolordosis in instrumented lumbar fusion on instrumented and adjacent spinal segments.

STUDY DESIGN: Change in lumbar lordosis was measured in patients that had undergone posterolateral lumbar fusions using transpedicular instrumentation. The biomechanical effects of postoperative lumbar malalignment were measured in cadaveric specimens. OBJECTIVES: To determine the extent of postoperative lumbar sagittal malalignment caused by an intraoperative kneeling position with 90 degrees of hip and knee flexion, and to assess its effect on the mechanical loading of the instrumented and adjacent segments. SUMMARY OF BACKGROUND DATA: The importance of maintaining the baseline lumbar lordosis after surgery has been stressed in the literature. However, there are few objective data to evaluate whether postoperative hypolordosis in the instrumented segments can increase the likelihood of junctional breakdown. METHODS: Segmental lordosis was measured on preoperative standing, intraoperative prone, and postoperative standing radiographs. In human cadaveric spines, a lordosis loss of up to 8 degrees was created across L4-S1 using calibrated transpedicular devices. Specimens were tested in extension and under axial loading in the upright posture. RESULTS: In patients who underwent L4-S1 fusions, the lordosis within the fusion decreased by 10 degrees intraoperatively and after surgery. Postoperative lordosis in the proximal (L2-L3 and L3-L4) segments increased by 2 degrees each, as compared with the preoperative measures. Hypolordosis in the instrumented segments increased the load across the posterior transpedicular devices, the posterior shear force, and the lamina strain at the adjacent level. CONCLUSIONS: Hypolordosis in the instrumented segments caused increased loading of the posterior column of the adjacent segments. These biomechanical effects may explain the degenerative changes at the junctional level that have been observed as long-term consequences of lumbar fusion.

Adult↗
PubMed2006

A clinical impact classification of scoliosis in the adult.

STUDY DESIGN: Multicenter, prospective, consecutive clinical series. OBJECTIVES: To establish and validate classification of scoliosis in the adult. SUMMARY OF BACKGROUND DATA: Studies of adult scoliosis reveal the impact of radiographic parameters on self-assessed function: lumbar lordosis and frontal plane obliquity of lumbar vertebrae, not Cobb angle, correlate with pain scores. Deformity apex and intervertebral subluxations correlate with disability. METHODS: A total of 947 adults with spinal deformity had radiographic analysis: frontal Cobb angle, deformity apex, lumbar lordosis, and intervertebral subluxation. Health assessment included Oswestry Disability Index and Scoliosis Research Society instrument. Deformity apex, lordosis (T12-S1), and intervertebral subluxation were used to classify patients. Outcomes measures and surgical rates were evaluated. RESULTS: Mean maximal coronal Cobb was 46 degrees and lumbar lordosis 46 degrees . Mean maximal intervertebral subluxation (frontal plane) was 4.2 mm (sagittal plane, 1.2 mm). In thoracolumbar/lumbar deformities, the loss of lordosis/higher subluxation was associated with lower Scoliosis Research Society pain/function and higher Oswestry Disability Index scores. Across the study group, lower apex combined with lower lordosis led to higher disability. Higher surgical rates with decreasing lumbar lordosis and higher intervertebral subluxation were detected. CONCLUSIONS: A clinical impact classification has been established based on radiographic markers of disability. The classification has shown correlation with self-reported disability as well as rates of operative treatment.

Adult↗
PubMed1987

The anatomy of spinal deformity: a biomechanical analysis.

The essential lesion in idiopathic scoliosis is a lordosis at the curve apex. For the rotational instability provided by a lordosis to progress, asymmetry must be present in another plane. A biomechanical analysis of spinal shape demonstrates a delicate balance between the median, transverse, and coronal planes. The normal cervical and lumbar lordosis which are inherently rotationally unstable are protected by: a) prismatic shaped vertebral bodies with their bases anterior, b) considerable available intersegmental flexion, and c) powerful posterior soft tissue support. In contrast, the thoracic vertebral bodies are shaped as prisms with their apices anterior. This rotationally unstable configuration is protected by a kyphosis with the axis of spinal rotation situated anteriorly. The thoracic vertebral prisms are asymmetric, their apices lying to the right of the median plane. In the presence of a lordosis the apices of the prisms will be directed toward the right producing a right-sided scoliosis. Any significant degree of left-sided coronal asymmetry can override the influence of the transverse plane and therefore left-sided curves are not uncommon. Thoracic idiopathic scoliosis is located at T8/T9 and the lordosis here is often an upward continuation of the normal lumbar lordosis such that the asymmetric thoracic prisms are no longer protected.

Biomechanical Phenomena↗
PubMed1991

Footwear and posture. Compensatory strategies for heel height.

The belief that wearing high-heeled shoes increases lumbar lordosis is firmly ingrained in clinical folklore. Proponents of negative heel footwear argue that because high positive heels increase the lumbar lordosis, negative heels will decrease the lumbar lordosis. Quantitative documentation of the assumption regarding high heels is not to be found in the literature, although sporadic attempts to prove this assumption have been made throughout the 20th Century. Although other effects, such as decreased gait speed and step length, and increased knee flexion at heel strike have been found in more than one study, no increase in lumbar lordosis has been found. Where an actual decrease in lordosis has been found, authors tend to explain it away as inconsistent with what every clinician feels that he or she has observed. We felt it appropriate, then, to conduct both a static and a dynamic study to assess the effects of heel height on lumbar spine and lower limb joint kinematics in the sagittal plane, as well as other strategies to compensate for heel height. The results indicate that the greatest compensation is at the ankle and knee. Where a significant effect occurred in the lumbar spine (males, dynamic study), high heels decreased the lumbar lordosis, i.e., resulted in less swayback rather than more.

Adolescent↗
PubMedDate not supplied

A retrospective consecutive case analysis of pretreatment and comparative static radiological parameters following chiropractic adjustments.

An investigation was undertaken to determine the effect of chiropractic adjustments on static radiological parameters. Standard plain film radiography was used. A retrospective consecutive case analysis approach was used for obtaining the data from the pretreatment and comparative posttreatment radiographs. Measurements for cervical lordosis, sacral base angle, lumbar lordosis, scapular angle, Cobb's angle and retrolisthesis of adjusted lumbar segments were determined by marking films in a blinded fashion. Intra- and interexaminer reliability for the measurement of cervical lordosis and retrolisthesis were determined to be excellent with a low standard error (Pearson's r range 0.89-0.97, p less than .001 for cervical lordosis and Pearson's r 0.74-0.90. p less than .001 for retrolisthesis). The data from pre- and comparative post-measurements of retrolisthesis showed a significant reduction of approximately 34%. No reduction was seen in a control group with retrolisthesis. No pre/post comparative changes were observed with cervical lordosis angle, sacral base angle, lumbar lordosis angle, scapular angle or Cobb's angle.

Adult↗
PubMed1996

Effects of androgens and estrogens on sexual differentiation of sex behavior, scent marking, and the sexually dimorphic area of the gerbil hypothalamus.

Mating, marking and the sexually dimorphic area (SDA) were studied in male gerbils that were castrated or sham-operated on the day of birth and in females given testosterone (T) propionate or oil 1 day later. Other females received dihydrotestosterone (DHT), R1881, estradiol benzoate (EB), R2858, DHT and EB, or DHT and R2858. Females and control males were castrated as adults. Then half of each group was given T and tested for marking and male sex behavior. They were still exposed to T at perfusion. The rest were given EB and progesterone and were tested for marking and lordosis. They were perfused 1 month after hormone treatment ended. Neonatal castration eliminated mounting, decreased T-induced marking and increased lordosis in males. Neonatal exposure to TP decreased lordosis and increased mounting, intromission patterns and T-induced marking in females. DHT and R1881 did not affect marking or mating when given alone. EB and R2858 decreased lordosis and increased mounting. DHT enhanced the former effect but not the latter. Only combined treatments increased T-induced marking. Total SDA volume was not affected by neonatal treatments, but "dark volume" was largest in control males. The SDA pars compacta (SDApc) was seldom seen in females unless they received steroid neonatally but was present in males that were castrated neonatally. SDApcs of neonatal castrates and steroid-treated females differed, though, from SDApcs of control males in that they were smaller in the absence of T and did not enlarge when exposed to T. Another cell group, the cmSDApc, was affected by T neonatally but was not seen consistently in either sex. SDApc volume correlated positively with T-induced marking and an index of male sex behavior. Both SDApc and cmSDApc volumes correlated negatively with lordosis. The correlations with marking and male sex behavior probably reflect constraints on sexual differentiation rather than causal relationships since these behaviors persist when the SDApc is gone. The effects of direct manipulations of the SDApc on lordosis have not been studied.

Androgens↗
PubMed1977

A comparative study of different amphetamines on copulatory behavior and stereotype activity in the female rat.

The influence of D- and L-amphetamine, fenfluramine, and p-chloroamphetamine on female copulatory behavior (lordosis response) and the induction of stereotype activity was compared. Lordosis response in the female rat has been shown to be inhibited by increased central nervous serotonergic (5-HT) as well as dopaminergic (DA) activity. A dose-dependent inhibitory effect on the estrogen- + progesterone-induced lordosis response in ovariectomized rats was demonstrated after treatment with the four amphetamines. In contrast, only D- and L-amphetamine induced a stereotype activity, which is considered to be mediated by DA mechanisms. A decrease in DA receptor activity, achieved by pimozide pretreatment, abolished the effect of D-amphetamine on lordosis behavior, but the effect of L-amphetamine was only slightly diminished and the action of fenfluramine and p-chloroamphetamine was unaffected. On the other hand, both L- and D-amphetamine-induced stereotype activity was prevented by pimozide treatment. The data suggest that the D-amphetamine effect on lordosis behavior is mediated by increased DA receptor activity. Although it induces stereotype activity by increased DA activity, L-amphetamine, like fenfluramine and p-chloroamphetamine, inhibits the lordosis response by some other action presumably related to serotonergic mechanisms.

Amphetamine↗
PubMed1987

Postnatal treatment of rats with adrenergic receptor agonists or antagonists influences differentiation of sexual behavior.

The aim of the study was to investigate the possible role of the adrenergic system in development and differentiation of neural centers controlling sexual behavior in adulthood. For this purpose normal and androgenized female rats were treated with the alpha 1-receptor antagonist prazosin, the alpha 2-receptor agonist clonidine, or the alpha 2-receptor antagonist yohimbine-HCl throughout the first week of life. In adulthood all animals were ovariectomized and, after appropriate hormone-priming, they were tested for the capacity to display female and male sexual behavior patterns. Alteration of adrenergic transmission during the critical postnatal period for sexual differentiation of neural centers resulted in significant changes in the capacity to express female lordosis behavior in adulthood. In nonandrogenized animals clonidine significantly reduced the capacity for lordosis behavior. In androgenized animals clonidine had the opposite effect; it attenuated the inhibitory effect of testosterone propionate (TP) on differentiation of lordosis behavior. Prazosin, which was without effect in nonandrogenized animals, also attenuated the inhibitory effect of TP on differentiation of lordosis behavior. Yohimbine was without effect in androgenized and nonandrogenized animals. There was no influence of any of the adrenergic drugs on differentiation of male sexual behavior. In conclusion, differentiation of lordosis behavior seems to be mediated or modulated via adrenergic transmission. The defeminizing effect of testosterone postnatally on the differentiation of lordosis behavior seems to be expressed via alpha 1-adrenergic transmission, and diminished adrenergic activity during the postnatal period seems to protect the developing brain against this effect of testosterone.

Adrenergic alpha-Agonists↗
PubMed1992

Mu-, delta-, and kappa-opioid receptor agonists selectively modulate sexual behaviors in the female rat: differential dependence on progesterone.

Previous studies suggested that opioid receptor agonists infused into the lateral ventricles can inhibit (through mu receptors) or facilitate (through delta receptors) the lordosis behavior of ovariectomized (OVX) rats treated with estrogen and a low dose of progesterone. The present study investigated the behavioral and hormonal specificity of those effects using more selective opioid receptor agonists. Sexually experienced OVX rats were implanted stereotaxically with guide cannulae aimed at the right lateral ventricle. One group of rats was treated with estradiol benzoate (EB, 10 micrograms) 48 hr and progesterone (P, 250 micrograms) 4 hr before testing, whereas the other group was treated with EB alone. Rats were infused with different doses of the selective mu-receptor agonist DAMGO, the selective delta-receptor agonist DPDPE, or the selective kappa-receptor agonist U50-488. The females were placed with a sexually vigorous male in a bilevel chamber (Mendelson and Gorzalka, 1987) for three tests of sexual behavior, beginning 15, 30, and 60 min after each infusion. DAMGO reduced lordosis quotients and magnitudes significantly in rats treated with EB and P, but not in rats treated with EB alone. In contrast, DPDPE and U50-488H increased lordosis quotients and magnitudes significantly in both steroid-treatment groups. Surprisingly, measures of proceptivity, rejection responses, and level changes were not affected significantly by mu or kappa agonists, although proceptivity and rejection responses were affected by DPDPE treatment. These results suggest that the effects of lateral ventricular infusions of opioid receptor agonists on the sexual behavior of female rats are relatively specific to lordosis behavior. Moreover, the facilitation of lordosis behavior by delta- or kappa-receptor agonists is independent of progesterone treatment, whereas the inhibitory effect of mu-receptor agonists on lordosis behavior may require the presence of progesterone.

Animals↗
PubMed1983

Melanocyte stimulating hormone and the inhibition of sexual behaviour in the female rat.

When administered to ovariectomized females, primed with oestradiol benzoate (OB) and progesterone, alpha-MSH increased lordosis behaviour in those rats that showed a low level of receptivity but in rats that were receptive it had an inhibitory effect. alpha-Melanocyte stimulating hormone also inhibited proceptive behaviour in these females. Luteinizing hormone releasing hormone (LHRH), on the other hand, failed to have a similar inhibiting effect although it did stimulate lordosis. While adrenalectomy failed to alter the stimulatory effect of alpha-MSH on lordosis it completely prevented the inhibitory actions of alpha-MSH on both lordosis and proceptive behaviour. Thus, while alpha-MSH may stimulate lordosis through a central action its inhibitory effects on lordosis and proceptive behaviour are probably mediated via the adrenal glands. Although alpha-MSH may stimulate the secretion of an adrenal steroid that blocks the facilitatory action of progesterone on female sexual behaviour the present results suggest that this inhibitory effect could be mediated by a catecholamine.

Adrenal Cortex Hormones↗
PubMed1984

Pharmacological and anatomical aspects of cholinergic activation of female sexual behavior.

Forebrain infusion of cholinergic agonists activated the sexual response, lordosis, in ovariectomized female rats that had been primed with a low dose of estrogen. Carbachol, an agonist with both muscarinic and nicotinic properties, and oxotremorine, an agonist with a primarily muscarinic action, produced dose-related increases in the frequency of lordosis elicited by stimulus male rats. This facilitation of lordosis was prevented when females were pretreated systemically with atropine or scopolamine, two muscarinic receptor antagonists. These results indicate that the effect of carbachol and oxotremorine on lordosis is mediated by cholinergic muscarinic receptors. The location of these receptors within the brain has not been identified. Ventricular infusion of carbachol was as effective as infusion directly into the medial preoptic area (POA) and more effective than infusion directly into the ventromedial hypothalamus (VMH). Furthermore, when carbachol or oxotremorine was delivered to the POA through cannulae angled to avoid traversing the lateral ventricles, no facilitation of lordosis was observed. These data suggest that muscarinic receptors stimulated by central infusion of cholinergic agonists may not be located in either the POA or the VMH, two regions traditionally implicated in the regulation of lordosis.

Animals↗
PubMed1976

Actions of repeated injections of LSD and apomorphine on the copulatory response of female rats.

LSD, a serotonin receptor stimulating agent, inhibits copulatory behavior (lordosis response) in the ovariectomized and estrogen + progesterone treated female rat. The same effect is obtained by apomorphine, a dopamine receptor stimulating compounds. The lordosis has been shown to be dependent on serotonin, but also dopamine has been implicated in its mediation. Tolerance develops to certain responses after repeated injections of LSD and in the present study the influence of apomorphine and LSD was compared, when given in repeated doses. Possible cross-tolerance between the two compounds was also tested on the frequency of lordosis responding in ovariectomized and hormone treated female rats. Tolerance to LSD develops over seven days, while the suppressing influence of apomorphine on lordosis in seven repeated doses is not significantly altered from that of a single dose. No cross-tolerance was observed on the lordosis response with either order of treatments. Repeated doses of LSD did not influence locomotor activity differently from a single dose, while repeated doses of apomorphine enhanced this response in comparison with the effect of an acute dose. These results indicate differential sensitivity to the repeated treatments and further support an interpretation of the LSD effects on lordosis responding to be primarily on serotonergic rather than dopaminergic receptors.

Animals↗
PubMed1983

Facilitation of estrogen-induced receptivity through metyrapone administration in ovariectomized rats.

Previously it has been established that adrenalectomy facilitates lordosis in estrogen-primed ovariectomized female rats and that corticosterone administration restores lordosis to preadrenalectomy levels. The present study examined the effects of an inhibitor of the synthesis of corticosterone, metyrapone, upon lordosis in ovariectomized females. In Experiment 1, chronic administration of moderate doses of metyrapone was found to facilitate lordosis. In Experiment 2, a single metyrapone administration at various doses and time intervals before testing had a mild facilitatory effect on lordosis. Experiment 3 compared the effects of metyrapone on ovariectomized and adrenalectomized-ovariectomized females. The absence of a facilitatory effect in adrenalectomized females suggests that the drug's effect on lordosis is mediated by its established inhibitory effects on 11 beta-hydroxylation in the adrenal. These data are consistent with indications that corticosterone titer modulates female receptivity.

Adrenalectomy↗
PubMed1991

Muscarinic receptor subtypes and sexual behavior in female rats.

Cholinergic muscarinic systems are involved in the regulation of female sexual behavior in rats and hamsters. This series of experiments was designed to determine whether sexual behavior in female rats is controlled preferentially by one of the traditional muscarinic receptor subtypes. Intraventricular infusion of the muscarinic antagonist scopolamine (10 micrograms bilaterally) which binds with high affinity to both M1 and M2 subtypes inhibited sexual behavior, as indicated by the incidence of lordosis, in ovariectomized rats treated with estrogen and progesterone. In contrast, the M1-selective antagonist pirenzepine failed to reduce the incidence of lordosis following intraventricular infusion (10 to 80 micrograms bilaterally). Biochemical analyses revealed that intraventricular infusion of scopolamine (10 micrograms bilaterally) inhibited both M1 and M2 binding in brain tissues while intraventricular infusion of pirenzepine (10 micrograms bilaterally) completely inhibited M1 binding without affecting M2 binding. Intraventricular infusions of the acetylcholinesterase inhibitor physostigmine (10 micrograms bilaterally), the cholinergic agonist carbachol (1 microgram bilaterally), and the muscarinic agonist oxotremorine-M (0.1 micrograms bilaterally) activated lordosis in ovariectomized females primed with low doses of estrogen. In contrast, the putative M1 agonist McN-A-343 failed to significantly increase lordosis following intraventricular infusions (1, 10, 20 micrograms bilaterally). According to biochemical results, the ability of these agents to activate lordosis in female rats was related to their affinities for M2 binding sites not M1 binding sites. In a final experiment, estrogen treatment of ovariectomized rats did not alter muscarinic subtype binding in several brain areas as measured by the M1-selective ligand [3H] pirenzepine and the M2-selective ligand [3H] oxotremorine-M. The results of these experiments confirm that muscarinic systems contribute to the regulation of lordosis in female rats and indicate that M2 binding sites rather than M1 binding sites may be a critical component of this regulation.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMedDate not supplied

Oxytocin facilitates the sexual receptivity of estrogen-treated female rats.

Oxytocin (OXY) and arginine-vasopressin (AVP) are widely distributed within the brain and have a number of behavioral effects resulting from central administration. We have previously found that central OXY administration accelerated the onset of maternal behavior in ovariectomized (OVXed) estrogen-treated nulliparous rats. We now report that intracerebroventricular (ICV) injections of OXY enhance lordosis behavior in OVXed estrogen-treated rats. After treatment with 0.15, 0.20, or 0.25 micrograms EB IM for three days, OXY (800 ng) infusion ICV on the fourth day produced a significant increase in lordosis behavior between 20 and 90 minutes after administration. Doses of OXY between 0.8 and 5 micrograms injected ICV significantly increased lordosis behavior in animals pretreated with 0.5 micrograms EB for three days. In other OVXed rats treated with 0.5 micrograms EB for three days, ICV injections of 1 micrograms OXY or an equimolar dose of AVP significantly increased lordosis while equimolar doses of ACTH1-10, ACTH4-10, arginine-vasotocin, GnRH and alpha-MSH did not significantly increase lordosis behavior over saline vehicle levels. ACTH1-24 significantly lowered lordosis quotients. We have concluded from these data that central administration of OXY (and possibly AVP) enhance female sexual receptivity. This effect is estrogen dependent, dose related and under our test conditions, specific to OXY and AVP.

Animals↗
PubMed1993

Female sexual behaviors in male rats with dorsal raphe nucleus lesions: treatment with p-chlorophenylalanine.

The effects of the serotonin-synthesis inhibitor, p-chlorophenylalanine (PCPA) on female sexual behaviors were examined in male rats with or without lesions (DRL) of the dorsal raphe nucleus, which contains a large number of serotonergic cell bodies. Estrogen-primed castrated males without brain surgery (control) showed extremely low levels of lordosis compared with females. On the other hand, DRL males displayed lordosis response more frequently than control males, but the lordosis quotient (LQ) in this group was lower than that in females. As well as DRL males, all PCPA-treated males showed lordosis, the mean LQ being comparable to the DRL group. Thus, the destruction of the dorsal raphe nucleus or the deprivation of serotonin by PCPA treatment facilitates manifestation of lordosis behavior in male rats. However, synergistic effect of DRL and PCPA treatments on female sexual behaviors have not been observed. The mean LQ in PCPA-treated male rats with DRL was almost the same as in DRL males or PCPA-treated males. These results suggest that the possible site of action of PCPA in regulating female sexual behavior in male rats is the serotonergic neurons in the dorsal raphe nucleus. Furthermore, the lordosis-facilitating effect of DRL is due to destruction of the serotonergic cell bodies in the dorsal raphe nucleus.

Animals↗
PubMed1981

Cholinergic influences on estrogen-dependent sexual behavior in female rats.

The ability of cholinergic agents to influence hormone-dependent sexual behavior in female rats was examined. In the first experiment, female sexual behavior, indicated by the incidence of lordosis, was significantly increased in estrogen-treated female rats following bilateral infusion of a cholinergic receptor agonist, carbachol (.5 microgram/cannula), into the medial preoptic area of the brain. Infusion of an artificial cerebrospinal fluid vehicle failed to facilitate lordosis. The incidence of lordosis was normally highest 15 min after carbachol infusion, began to wane by 45 min, and had returned to control levels by 90 min. Further, centrally administered carbachol activated lordosis at lower levels of estrogen priming than did systemically administered progesterone. In a second experiment, female rats, brought into sexual receptivity by administration of estrogen and progesterone, received preoptic infusions of an acetylcholine synthesis inhibitor, hemicholinium-3. Significant reductions in the incidence of lordosis were observed following bilateral infusion of hemicholinium-3 (1.25 microgram/cannula). This inhibition of lordosis was prevented when carbachol (.5 microgram/cannula) was infused along with hemicholinium-3. Results confirm the importance of cholinergic influences on sexual behavior in female rats.

Acetylcholine↗
PubMed2003

Sitting with adjustable ischial and back supports: biomechanical changes.

STUDY DESIGN: The seat and back contact force, pressure distribution, lumbar lordosis, and low back muscle activities associated with a new seat design with adjustable ischial support and backrest were investigated using kinematic, kinetic, electromyographic, and radiographic measurements. OBJECTIVES: To investigate the biomechanical effects of adjusting ischial and backrest supports during sitting. SUMMARY OF THE BACKGROUND DATA: Sitting may induce posterior rotation of the pelvis, reduction of lumbar lordosis, and increases in muscle tension, disc pressure, and pressure on the ischium and coccyx, which may be associated with low back pain. A device that reduces the ischial load and maintains lumbar lordosis may help increase seating comfort and reduce low back pain. METHODS: Fifteen office workers with no known low back pain history were tested. Contact pressure distributions, reaction forces between the buttock-thighs and seat and between the back and backrest, load carried by the seat pan and backrest, sacral inclination, lumbar lordosis, intervertebral space of lumbar spine, and muscular activity in stabilizing the trunk were measured for sitting with and without ischial support and with adjustable back support. RESULTS: When the ischial support was relieved, the center of the force on the seat and on the legs of the chair, and the peak center of pressure on the seat, were significantly (P < 0.002) shifted forward toward the thighs. The total contact area on the seat pan and on the backrest was significantly decreased and increased, respectively (P < 0.001). The sacral inclination, total and segmental lumbar lordosis, and lumbar spine disc height were significantly increased for sitting upright with backrest, with the lumbar curve close to that during standing. CONCLUSIONS: Sitting with reduced ischial support and fitted backrest to the lower spine altered the contact area, reduced peak pressure under the ischia, reduced muscular activity, maintained total and segmental lumbar lordosis, rotated the sacrum forward, and increased lumbar intervertebral disc heights, which could potentially reduce low back pain.

Adult↗