Lower Lordosis Research Articles

Correction of Spinal Sagittal Alignment after Posterior Lumbar Decompression: Does Severity of Central Canal Stenosis Matter?

This study adopted a retrospective study design. Our study aimed to investigate the impact of central canal stenosis severity on surgical outcomes and lumbar sagittal correction after lumbar decompression. Studies have evaluated sagittal correction in patients with central canal stenosis after lumbar decompression and the association of stenosis severity with worse preoperative sagittal alignment. However, none have evaluated the impact of spinal stenosis severity on sagittal correction. Patients undergoing posterior lumbar decompression (PLD) of ≤4 levels were divided into severe and non-severe central canal stenosis groups based on the Lee magnetic resonance imaging (MRI) grading system. Patients without preoperative MRI or inadequate visualization on radiographs were excluded. Surgical characteristics, clinical outcomes, and sagittal measurements were compared. Multivariate logistic regression was performed to determine the predictors of pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence minus lumbar lordosis (PI-LL). Of the 142 patients included, 39 had severe stenosis, and 103 had non-severe stenosis. The mean follow-up duration for the cohort was 4.72 months. Patients with severe stenosis were older, had higher comorbidity indices and levels decompressed, and longer lengths of stay and operative times (p <0.001). Although those with severe stenosis had lower lordosis, lower SS, and higher PI-LL mismatch preoperatively, no differences in Delta LL, SS, PT, or PI-LL were observed between the two groups (p >0.05). On multivariate regression, severe stenosis was a significant predictor of a lower preoperative LL (estimate=-5.243, p =0.045) and a higher preoperative PI-LL mismatch (estimate=6.192, p =0.039). No differences in surgical or clinical outcomes were observed (p >0.05). Severe central lumbar stenosis was associated with greater spinopelvic mismatch preoperatively. Sagittal balance improved in both patients with severe and non-severe stenosis after PLD to a similar degree, with differences in sagittal parameters remaining after surgery. We also found no differences in postoperative outcomes associated with stenosis severity.

FRI381 Melanocortin 4 Receptor Signaling In Sim-1 Neurons Permits Sexual Receptivity In Female Mice

Abstract Disclosure: M.T. Harberson: None. E. Semple: None. J.W. Hill: None. Female sexual dysfunction affects approximately 40% of women in the United States, yet few therapeutic options exist for these patients. The melanocortin system is a new treatment target for hypoactive sexual desire disorder (HSDD), but the neuronal pathways involved are unclear. In this study, female MC4R knockout mice lacking melanocortin 4 receptors (MC4Rs) paired with males were found to approach males less and have reduced receptivity to copulation, as indicated by a low lordosis quotient. The mice were then bred to express MC4Rs exclusively on Sim1 neurons (tbMC4RSim1 mice) or on oxytocin neurons (tbMC4ROxt mice). Lordosis behavior was normalized in tbMC4RSim1 mice and improved in tbMC4ROxt mice. In contrast, approach behavior was unchanged in tbMC4RSim1 mice but greatly increased in tbMC4ROxt animals. The changes were independent of melanocortin-driven metabolic effects. These results implicate MC4R signaling in Oxt neurons in appetitive behaviors and MC4R signaling in Sim1 neurons in female sexual receptivity, while suggesting melanocortin-driven sexual function does not rely on metabolic neural circuits. Presentation: Friday, June 16, 2023

Low pelvic incidence with low lordosis and distal apex of lumbar lordosis associated with higher rates of abnormal spinopelvic mobility in patients undergoing THA.

The risk factors for abnormal spinopelvic mobility (SPM), defined as an anterior rotation of the spinopelvic tilt (∆SPT) ≥ 20° in a flexed-seated position, have been described. The implication of pelvic incidence (PI) is unclear, and the concept of lumbar lordosis (LL) based on anatomical limits may be erroneous. The distribution of LL, including a unusual shape in patients with a high lordosis, a low pelvic incidence, and an anteverted pelvis seems more relevant. The clinical data of 311 consecutive patients who underwent total hip arthroplasty was retrospectively analyzed. We analyzed the different types of lumbar shapes that can present in patients to identify their potential associations with abnormal pelvic mobility, and we analyzed the potential risk factors associated with a ∆SPT ≥ 20° in the overall population. ΔSPT ≥ 20° rates were 28.3%, 11.8%, and 14.3% for patients whose spine shape was low PI/low lordosis (group 1), low PI anteverted (group 2), and high PI/high lordosis (group 3), respectively (p = 0.034). There was no association between ΔSPT ≥ 20° and PI ≤ 41° (odds ratio (OR) 2.01 (95% confidence interval (CI)0.88 to 4.62), p = 0.136). In the multivariate analysis, the following independent predictors of ΔSPT ≥ 20° were identified: SPT ≤ -10° (OR 3.49 (95% CI 1.59 to 7.66), p = 0.002), IP-LL ≥ 20 (OR 4.38 (95% CI 1.16 to 16.48), p = 0.029), and group 1 (OR 2.47 (95% CI 1.19; to 5.09), p = 0.0148). If the PI value alone is not indicative of SPM, patients with a low PI, low lordosis and a lumbar apex at L4-L5 or below will have higher rates of abnormal SPM than patients with a low PI anteverted and high lordosis.

Melanocortin 4 receptor signaling in Sim-1 neurons permits sexual receptivity in female mice

Female sexual dysfunction affects approximately 40% of women in the United States, yet few therapeutic options exist for these patients. The melanocortin system is a new treatment target for Hypoactive Sexual Desire Disorder (HSDD), but the neuronal pathways involved are unclear. In this study, female MC4R knockout mice lacking melanocortin 4 receptors (MC4Rs) paired with males were found to approach males less and have reduced receptivity to copulation, as indicated by a low lordosis quotient. The mice were then bred to express MC4Rs exclusively on Sim1 neurons (tbMC4RSim1 mice) or on oxytocin neurons (tbMC4ROxt mice). Lordosis behavior was normalized in tbMC4RSim1 mice and improved in tbMC4ROxt mice. In contrast, approach behavior was unchanged in tbMC4RSim1 mice but greatly increased in tbMC4ROxt animals. The changes were independent of melanocortin-driven metabolic effects. These results implicate MC4R signaling in Oxt neurons in appetitive behaviors and MC4R signaling in Sim1 neurons in female sexual receptivity, while suggesting melanocortin-driven sexual function does not rely on metabolic neural circuits. R01HD081792 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Melanocortin 4 receptor signaling in Sim1 neurons permits sexual receptivity in female mice.

Female sexual dysfunction affects approximately 40% of women in the United States, yet few therapeutic options exist for these patients. The melanocortin system is a new treatment target for hypoactive sexual desire disorder (HSDD), but the neuronal pathways involved are unclear. In this study, the sexual behavior of female MC4R knockout mice lacking melanocortin 4 receptors (MC4Rs) was examined. The mice were then bred to express MC4Rs exclusively on Sim1 neurons (tbMC4RSim1 mice) or on oxytocin neurons (tbMC4ROxt mice) to examine the effect on sexual responsiveness. MC4R knockout mice were found to approach males less and have reduced receptivity to copulation, as indicated by a low lordosis quotient. These changes were independent of body weight. Lordosis behavior was normalized in tbMC4RSim1 mice and improved in tbMC4ROxt mice. In contrast, approach behavior was unchanged in tbMC4RSim1 mice but greatly increased in tbMC4ROxt animals. The changes were independent of melanocortin-driven metabolic effects. These results implicate MC4R signaling in Oxt neurons in appetitive behaviors and MC4R signaling in Sim1 neurons in female sexual receptivity, while suggesting melanocortin-driven sexual function does not rely on metabolic neural circuits.

Low lordosis is a common finding in young lumbar disc herniation patients

PurposeThe sagittal alignment of the lumbar spine and pelvis can be classified into several subtypes. It has been suggested that the risk of developing certain pathologies, such as a lumbar disc herniation (LDH) is affected by spinal sagittal profiles. The main aim of this study was to investigate the sagittal profile in young patients surgically treated for a lumbar disc herniation and if a discectomy would alter the sagittal parameters.MethodsSixteen active young patients (mean age 18.3 ± 3.2 SD) with a lumbar disc herniation having a discectomy were included. A classification according to Roussouly of the sagittal parameters was made by two senior spinal surgeons, both pre-operatively and post-operatively on radiographs. The distribution of sagittal parameters and spinopelvic profiles were analysed and compared to a previous established healthy normal population.ResultsThis series of active young patients with LDH exhibited a low lumbar lordosis dominance, with Roussouly sagittal profiles type 1 and type 2 accounting for more than 75% of the examined patients. An analysis of the erect radiographs revealed no significant changes in the post-operative sagittal profile.ConclusionsThis study showed that sagittal spinal alignment according to Roussouly in a young population with LDH is skewed compared with a normal population cohort. Furthermore, the lack of post-operative correction is suggestive of a non-ephemeral response to a LDH. Roussouly type 2 spinal sagittal profile may be a risk factor in young individuals suffering a disc herniation.

Retrospective Review of Immediate Restoration of Lordosis in Single-Level Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Comparison of Static and Expandable Interbody Cages.

Sagittal alignment is an important consideration in spine surgery. The literature is conflicted regarding the effect of minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) on sagittal parameters and the role of expandable cage technology. To compare lordosis generated by static and expandable cages and to determine what factors affect postoperative sagittal parameters. Preoperative regional lordosis (RL), segmental lordosis (SL), and posterior disc height (PDH) were compared to postoperative values in single-level MI-TLIF performed using expandable or static cages. Patients were stratified based on preoperative SL: low lordosis (<15 degrees), moderate lordosis (15-25 degrees), and high lordosis (>25 degrees). Regression analyses were conducted to determine factors associated with postoperative SL and PDH. Of the 171 patients included, 111 were in the static and 60 in the expandable cohorts. Patients with low preoperative lordosis experienced an increase in SL and maintained RL regardless of cage type. Those with moderate to high preoperative lordosis experienced a decrease in SL and RL with the static cage, but maintained SL and RL with the expandable cage. Although both cohorts showed an increase in PDH, the increase in the expandable cohort was greater. Preoperative SL was predictive of postoperative SL; preoperative SL, preoperative PDH, and cage type were predictive of postoperative PDH. Expandable cages showed favorable results in restoring disc height and maintaining lordosis in the immediate postoperative period. Preoperative SL was the most significant predictor of postoperative SL. Thus, preoperative radiographic parameters and goals of surgery should be important considerations in surgical planning.

279. Cervical corpectomy vs 2-level discectomy: a comparative study of 100 patients

BACKGROUND CONTEXT Surgical treatment of cervical spine degenerative pathology involving 2 levels can be performed anteriorly through a double discectomy or through a corpectomy. It is not clear, however, what is the capacity of each technique in the restoration of cervical lordosis and what is its effect over time. PURPOSE Compare the 2 techniques with respect to clinical and radiographic results, namely in the restoration and maintenance of sagittal cervical balance. METHODS Clinical files and radiographs of patients submitted to a 2-level discectomy (Group A) or a 1-level corpectomy (Group B) were evaluated retrospectively in the treatment of degenerative cervical disease between 2010 and 2017. Radiological parameters were measured (C2-C7 sagittal Cobb, regional cervical lordosis and graft collapse) preoperatively, after 3-6 weeks and at the last follow-up. Patient variables, surgery and perioperative parameters (length of stay, blood loss, surgical time and complications) were compared. RESULTS A total of 100 patients (43 men and 57 women) with a mean age of 60.4 years (40-86) were included. Average follow-up of 3.5 years (8 months-7.3 years). Group A: 18 patients, mean age 60.3, 39% (n = 7) with radiculopathy and 61% (n = 11) with myelopathy; Group B: 82 patients, mean age 61.4; 69.5% (n = 56) with myelopathy, 30.5% (n = 25) with radiculopathy. There was no statistically significant difference between the 2 groups regarding length of hospital stay, blood loss or surgical time. Patients submitted to a corpectomy had a lower lordosis than those who underwent discectomy at 2 levels (p = 0.083). However, the gain of lordosis with surgery was similar in both groups, 7.8° in Group B and 6,1° in Group A (p = 0.582). After surgery, there was a progressive loss of lordosis gain mainly in the first 6 weeks but without significant differences between the groups. (p = 0.08 at 6 weeks and p = 0.690 at the last follow-up). CONCLUSIONS In the presence of myelopathy, corpectomy was the preferred surgical option. Preoperatively, these patients had a lower degree of lordosis than those operated by radiculopathy. Both surgical options allowed an equivalent gain in lordosis, which was partially lost during follow-up. There were no advantages of one surgical technique over the other in lordosis gain. Therefore, the decision on the technique to be used must be based on factors other than the concern with the gain of lordosis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

X-ray parameters of low segmental lordosis of lumbar spine and their relation with sacral and pelvic tilt in frontal plane in patients with sacroiliac joint dysfunction

X-ray parameters of low segmental lordosis of lumbar spine and their relation with sacral and pelvic tilt in frontal plane in patients with sacroiliac joint dysfunction

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT Sagittal alignment is becoming an increasingly important consideration in minimally invasive spine surgery. Single level minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) can have immediate impact on segmental and regional sagittal parameters. PURPOSE The purpose of this study was to compare immediate restoration of segmental (SL) and regional lordosis (RL) after single level MIS TLIF using an expandable or static interbody cage. STUDY DESIGN/SETTING All patients underwent single level MIS TLIF using tubular retractor and bilateral pedicle screw fixation with interbody cage. Measurements of preoperative RL and SL were made and compared with post operative values. Patients were divided into 3 groups based on their preoperative SL: low lordosis ( 25°). Mann Whitney u test was used to determine statistical significance of results PATIENT SAMPLE Patients who underwent single level MIS TLIF. OUTCOME MEASURES Segmental and regional lordosis after single level MIS TLIF using an expandable or static interbody cage METHODS A retrospective review of prospectively collected data on patient undergoing single level MIS TLIF using expandable or static interbody cages was performed. All patients underwent single level MIS TLIF using tubular retractor and bilateral pedicle screw fixation with interbody cage. Measurements of preoperative RL and SL were made and compared with post operative values. Patients were divided into 3 groups based on their preoperative SL: low lordosis ( 25°). Mann Whitney u test was used to determine statistical significance of results. RESULTS A total of 114 patients were included with 57 patients in the expandable cohort and 53 in the static cohort. The expandable cohort had an average age of 64 (37–86) and 34 females. The static cohort had an average age of 58 (24–80) and 27 females. In the expandable cage cohort, patients who had low lordosis preoperatively had a statistically significant increase in postoperative SL (p CONCLUSIONS This study compares the immediate impact of MIS TLIF using expandable or static cages on segmental lordosis of the lumbar spine. Our findings suggest that while cage type does not impact postoperative lordosis, a patient's preoperative lordosis can. Specifically, those patients with low lordosis preoperatively (>15°) have the highest likelihood of achieving statistically significant improvement in segmental lordosis while those with moderate (15–25°) or high (>25°) lordosis preoperatively may experience no change or even a loss of lordosis postoperatively.

Effects of inter-individual lumbar spine geometry variation on load-sharing: Geometrically personalized Finite Element study

There is a large, at times contradictory, body of research relating spinal curvature to Low Back Pain (LBP). Mechanical load is considered as important factor in LBP etiology. Geometry of the spinal structures and sagittal curvature of the lumbar spine govern its mechanical behavior. Thus, understanding how inter-individual geometry particularly sagittal curvature variation affects the spinal load-sharing becomes of high importance in LBP assessment. This study calculated and compared kinematics and load-sharing in three ligamentous lumbosacral spines: one hypo-lordotic (Hypo-L) with low lordosis, one normal-lordotic (Norm-L) with normal lordosis, and one hyper-lordotic (Hyper-L) with high lordosis in flexed and extended postures using 3D nonlinear Finite Element (FE) modeling. These postures were simulated by applying Follower Load (FL) combined with flexion or extension moment. The Hypo-L spine demonstrated stiffer behavior in flexion but more flexible response to extension compared to the Norm-L spine. The excessive lordosis stiffened response of the Hyper-L spine to extension but did not affect its resistance to flexion compared to the Norm-L spine. Despite the different resisting actions of the posterior ligaments to flexion moment, the increase of disc compression was similar in all the spines leading to similar load-sharing. However, resistance of the facet joints to extension was more important in the Norm- and Hyper-L spines which reduced the disc compression. The spinal curvature strongly influenced the magnitude and location of load on the spinal components and also altered the kinematics and load-sharing particularly in extension. Consideration of the subject-specific geometry and sagittal curvature should be an integral part of mechanical analysis of the lumbar spine.

Revisiting the neural role of estrogen receptor beta in male sexual behavior by conditional mutagenesis

Estradiol derived from neural aromatization of gonadal testosterone plays a key role in the perinatal organization of the neural circuitry underlying male sexual behavior. The aim of this study was to investigate the contribution of neural estrogen receptor (ER) β in estradiol-induced effects without interfering with its peripheral functions. For this purpose, male mice lacking ERβ in the nervous system were generated. Analyses of males in two consecutive tests with a time interval of two weeks showed an effect of experience, but not of genotype, on the latencies to the first mount, intromission, pelvic thrusting and ejaculation. Similarly, there was an effect of experience, but not of genotype, on the number of thrusts and mating length. Neural ERβ deletion had no effect on the ability of males to adopt a lordosis posture in response to male mounts, after castration and priming with estradiol and progesterone. Indeed, only low percentages of both genotypes exhibited a low lordosis quotient. It also did not affect their olfactory preference. Quantification of tyrosine hydroxylase- and kisspeptin-immunoreactive neurons in the preoptic area showed unaffected sexual dimorphism of both populations in mutants. By contrast, the number of androgen receptor- and ERα-immunoreactive cells was significantly increased in the bed nucleus of stria terminalis of mutant males.These data show that neural ERβ does not play a crucial role in the organization and activation of the neural circuitry underlying male sexual behavior. These discrepancies with the phenotype of global ERβ knockout models are discussed.

ASSOCIATION OF SPINOPELVIC PARAMETERS WITH THE LOCATION OF LUMBAR DISC HERNIATION

Objective:To associate spinopelvic parameters, pelvic incidence, sacral slope, pelvic tilt and lumbar lordosis with the axial location of lumbar disc herniation.Methods:Retrospective study, which evaluated imaging and medical records of 61 patients with lumbar disc herniation, who underwent surgery with decompression and instrumented lumbar fusion in only one level. Pelvic incidence, sacral slope, pelvic tilt and lumbar lordosis with simple lumbopelvic lateral radiographs, which included the lumbar spine, the sacrum and the proximal femur. The affected segment was identified as the level and location of lumbar disc herniation in the axial plane with MRI scans.Results:Of 61 patients, 29 (47.5%) had low lumbar lordosis; in this group 24 (82.8%) had central disc herniation, 4 (13.8%) had lateral recess disc herniation and 1 (3.4%) had extraforaminal disc herniation (p&lt;0.05). Of the 61 patients, 18 (29.5%) had low sacral slope; of this group 15 (83.3%) had central disc herniation and 3 (16.7%) had disc herniation in lateral recess (p&lt;0.05).Conclusions:There is a trend towards greater load distribution in the anterior region of the spine when the spine has hypolordotic curve. This study found an association between low lordosis and central disc herniation, as well as low sacral slope and central disc herniation.

Anterior Cervical Discectomy and Fusion Alters Whole-Spine Sagittal Alignment.

PurposeAnterior cervical discectomy and fusion (ACDF) has become a common spine procedure, however, there have been no previous studies on whole spine alignment changes after cervical fusion. Our purpose in this study was to determine whole spine sagittal alignment and pelvic alignment changes after ACDF.Materials and MethodsForty-eight patients who had undergone ACDF from January 2011 to December 2012 were enrolled in this study. Cervical lordosis, thoracic kyphosis, lumbar lordosis, sagittal vertical axis (SVA), and pelvic parameters were measured preoperatively and at 1, 3, 6, and 12 months postoperatively. Clinical outcomes were assessed using Visual Analog Scale (VAS) scores and Neck Disability Index (NDI) values.ResultsForty-eight patients were grouped according to operative method (cage only, cage & plate), operative level (upper level: C3/4 & C4/5; lower level: C5/6 & C6/7), and cervical lordosis (high lordosis, low lordosis). All patients experienced significant improvements in VAS scores and NDI values after surgery. Among the radiologic parameters, pelvic tilt increased and sacral slope decreased at 12 months postoperatively. Only the high cervical lordosis group showed significantly-decreased cervical lordosis and a shortened SVA postoperatively. Correlation tests revealed that cervical lordosis was significantly correlated with SVA and that SVA was significantly correlated with pelvic tilt and sacral slope.ConclusionACDF affects whole spine sagittal alignment, especially in patients with high cervical lordosis. In these patients, alteration of cervical lordosis to a normal angle shortened the SVA and resulted in reciprocal changes in pelvic tilt and sacral slope.

Ivermectin reduces sexual behavior in female rats

Ivermectin (IVM) is an antiparasitic drug that is widely used in domestic animals. In mammals, IVM acts as a γ-aminobutyric acid (GABA) receptor agonist. This neurotransmitter plays an important role in the regulation of female sexual behavior. The present study investigated the effects of therapeutic (0.2mg/kg) and high (1.0mg/kg) IVM doses on female sexual behavior in physiological and pharmacological conditions. Female rats in estrus or treated with estradiol valerate to induce sexual behavior 24h before the experiments were used. Ivermectin was administered 15min before the sexual observations. The number of lordosis events in 10 mounts was recorded to calculate the lordosis quotient. The intensity of lordosis (0 [no lordosis], 1 [low lordosis], 2 [normal lordosis] and 3 [exaggerated lordosis]) was scored. In estrus and hormonal treated female rats, both IVM doses decreased the intensity of the lordosis reflex and the percentage of females that presented high levels of lordosis (exaggerated lordosis). However, the number of females that presented lordosis was unaltered. We conclude that in both hormonal conditions, 0.2mg/kg IVM treatment reduced female sexual behavior and the execution of the lordosis reflex. The present results may be useful for avoiding the side effects of this drug in veterinary practice.

Sociosexual behaviours in cycling, intact female rats (Rattus norvegicus) housed in a seminatural environment

Groups of 3 males and 4 females were housed in a seminatural environment for a period of 8 days. Female sociosexual behaviours were recorded and analysed from the beginning of behavioural oestrus (defined as the first lordosis response observed in the environment) until the end of oestrus (defined to occur at the moment of a lordosis that was not followed by another one within 60 min). The duration of behavioural oestrus varied between 4.05 and 10.87 h, with a mean of 7.41 ± 0.49 h. In order to analyse changes in behaviour during oestrus, the entire period was divided in 5% segments for each female. The frequency and/or duration of some behaviours changed during the period of oestrus, while others remained stable. Most remarkable among the latter are the frequency of lordosis and the lordosis quotient. From the start of oestrus until the end, the females responded with lordosis to every male mount. Rejections were most frequent at the beginning of the period of oestrus. Then there was a decline, and thereafter rejections remained at a low level, even when the end of oestrus was approached. Paracopulatory behaviours reached a maximum towards the end of the first quarter of the oestrus period. There was no evident decline at the end of oestrus. Females having a high frequency of lordosis showed more paracopulatory behaviours and were pursued more by the males than females with low lordosis frequency. When the behaviour of females with a large number of offspring was compared to that of females with a low number of offspring, no difference in sexual behaviours was found. Comparisons between the females’ behaviour in response to preferred (either defined as the male producing the largest number of lordosis responses or as the male that was most sniffed by the female) and non-preferred males revealed a few minor differences. Location of behaviour was also analysed. Comparisons were made between the environment’s open area and burrow and between different sectors in these parts. Some important differences were found. This is the first detailed description of female rat sociosexual behaviour during the entire period of behavioural oestrus in a seminatural environment.

Cervical myelopathy due to degenerative spondylolisthesis

Objective. To investigate clinical-radiological features of cervical myelopathy due to degenerative spondylolisthesis (DSL).Methods. A total of 448 patients were operated for cervical myelopathy at Nishitaga National Hospital between 2000 and 2003. Of these patients, DSL at the symptomatic disc level was observed in 22 (4.9%) patients. Clinical features were investigated by medical records, and radiological features were investigated by radiographs.Results. Disc levels of DSL were C3/4 in 6 cases and C4/5 in 16 cases. Distance of anterior slippage was 2 to 5 mm (average 2.9 mm) in flexion position. Space available for the spinal cord (SAC) was 11 to 15 mm (average 12.8 mm) in flexion position and 11 to 18 mm (average14.6 mm) in extension position; 11 cases were reducible and 11 cases were irreducible in extension position. Myelograms demonstrated compression of spinal cord by the ligamentum flavum in extension position. Compression of spinal cord was not demonstrated in flexion position. C5-7 lordosis angle was lower than control. C5-7 range of motion (ROM) was reduced compared to controls. These alterations were statistically significant.Conclusions. DSL occurs in the mid-cervical spine. Lower cervical spine demonstrated restricted ROM and lower lordosis angle. Pathogenesis of cervical myelopathy due to DSL is compression of spinal cord by the ligamentum flavum in extension position and not by reduced SAC in flexion position.

Progesterone and 3α,5α-THP enhance sexual receptivity in mice.

Progesterone (P) and its metabolites' effects on sexual receptivity (lordosis) of mice was examined. P dosages that produced normal circulating concentrations of P and 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) enhanced lordosis of ovariectomized, sexually experienced C57BL/6J (C57), +/+ C57BL/6Jx129SvEv (C57x129), and -/- C57BL/6Jx129SvEv (PRKO) mice. Only C57 and C57x129 mice had increases in progestin receptor (PR)-immunoreactivity (PR-IR) in the hypothalamus. RU38486, a PR antagonist, attenuated lordosis of C57 and C57x129, but not PRKO, mice; epostane, a progestin biosynthesis inhibitor, reduced plasma progestins; and finasteride, a P metabolism inhibitor, reduced plasma 3alpha,5alpha-THP and attenuated lordosis of all mice. For sexually naive mice, greater lordosis on initial sexual experience corresponded to greater concentrations of plasma and central progestins and increased central binding of a GABAA agonist, muscimol, compared with that seen in mice with lower lordosis on initial mating. Thus, P-facilitated receptivity in mice involves P and 3alpha,5alpha-THP and their actions at PRs and GABAA receptors.

Lordosis in male rats: The facilitatory effect of mesencephalic dorsal raphe nucleus lesion

The dorsal raphe nucleus was destroyed (DRL) by a radiofrequency lesion generator in castrated male rats, and lordosis behavior was observed. Five weeks after the surgery, all animals were implanted with two Silastic tubes containing estradiol (E2). Behavioral tests were started 2 days after implantation of E2 and carried out every other day for 16 days. Castrated control and sham-operated control males showed low incidence of lordosis and low lordosis quotient (LQ) throughout the tests, whereas all the DRL males displayed lordosis and the mean LQ of the group was significantly higher than that of control groups, but lower than that of an ovariectomized female group. These results suggest that the dorsal raphe nucleus plays an important role in inhibiting lordosis in male rat brain.

Progesterone inhibition of sexual behavior is accompanied by an activation of aggression in female Syrian hamsters

Previous studies have shown that progesterone can have biphasic activational and inhibitory roles in the regulation of sexual behavior in female Syrian hamsters. The purpose of this study was to determine whether these biphasic effects on sexual behavior are mirrored in a reciprocal regulation of aggression. Ovariectomized female Syrian hamsters were treated with estradiol followed 2 and 3 days later by either 1) two oil injections (O-O), 2) an oil and a progesterone injection (O-P), 3) a progesterone and oil injection (P-O), or 4) two progesterone injections (P-P). Females were tested for aggression and sexual behavior in conjunction with these hormone treatments. On the final test session, P-P females had significantly lower lordosis durations than did O-P females, confirming the progesterone inhibition of sexual behavior previously reported. Without hormone treatment all females showed high baseline levels of aggression. On the last behavioral test, aggression in O-O females and P-O females was comparable to their baseline levels of aggression. In contrast, aggression in P-P females was significantly higher than the baseline levels of aggression. These results suggest that like its effects on sexual behavior, progesterone can have both inhibitory and activational effects on aggression in female Syrian hamsters.