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PubMed2003

Correction of lumbosacral hyperlordosis in achondroplasia.

Anterior bulging of the abdomen and posterior protrusion of the buttocks are externally visible deformities reflecting lumbosacral hyperlordosis. Imbalance in pelvic femoral muscles may account for this posture. Despite the clinical significance of hyperlordosis, its surgical treatment has not been well-described. In the current preliminary study, the authors compare two techniques used at the authors' institution for lower limb lengthening, one of which affects the correction of lumbosacral hyperlordosis. Ten patients had bilateral lower extremity lengthening procedures. Seven patients had bilateral tibial lengthening and three patients had combined femoral and tibial lengthening. Ring external fixators were used. Correction of hyperlordosis was assessed by comparing four radiographs with measurements in the sagittal plane obtained preoperatively with those at the latest followup. In the femoral lengthening group, the average preoperative lumbar lordosis angle was 18 degrees, the lumbosacral joint angle was 12 degrees, the sacral inclination angle was 58.3 degrees, and the sacrohorizontal angle was 31 degrees. The mean changes at the latest followup were: lumbar lordosis angle (+1 degree), lumbosacral joint angle (+0.3 degrees), sacral inclination angle (-19 degrees), and sacrohorizontal angle (-15 degrees). In the tibia lengthening group, all parameters were relatively unaltered at the last followup compared with their preoperative levels. Tibial lengthening had no effect on lumbosacral hyperlordosis. However, femoral lengthening resulted in an improved apparent lumbosacral hyperlordosis, although the lumbar lordosis angle was not changed significantly. The change in sacrum tilting provides a likely explanation for the improvement in cosmetic hyperlordosis observed in patients who have had femoral lengthening.

Achondroplasia↗
PubMed2003

Management of fixed sagittal plane deformity: outcome of combined anterior and posterior surgery.

STUDY DESIGN: Retrospective study of consecutive patient series. OBJECTIVES: To review the radiographic and clinical results of patients with preoperative fixed sagittal imbalance treated with combined anterior and posterior arthrodesis, and to determine factors that predict clinical outcome. SUMMARY OF BACKGROUND DATA: Combined anterior and posterior arthrodesis of the spine is useful in the management of fixed deformity involving the coronal and sagittal planes. The specific indications for combined surgery in the patient with regional and global imbalance have not been well defined. METHODS: Retrospective review of 25 consecutive patients treated with combined anterior and posterior spinal arthrodesis. Inclusion criteria included a preoperative global sagittal imbalance of at least 5 cm. Outcome variables included radiographic measures of preoperative, postoperative, and follow-up films, and a clinical assessment using the Modified SRS Outcomes Instrument and a review of postoperative complications. RESULTS: Twenty-five consecutive cases were reviewed. Mean age was 58 years (range 38-77), and mean follow-up was 55 months (range 24-81) for clinical and 44.5 (range 24-81) months for radiographic outcome variables. The mean preoperative sagittal imbalance was 10.5 cm (range 5.2-23.3), which improved to 2.9 cm (range 0-12.6) after surgery, and was maintained as 3.3 cm (range 0-13.5) at follow-up. Mean lumbar lordosis was -23 degrees (range +40 to -47) before surgery, and increased to -42 degrees at follow-up (range -20 degrees to -60 degrees ), an increase of 19 degrees. Patients with preoperative regional hypolordosis in the lumbar spine that was corrected surgically had the highest postoperative scores. The mean score for patient satisfaction with surgical management was 4.45 (range 2.5-5). Correlation analysis of clinical outcome domains demonstrated that patient satisfaction correlated poorly with domains of pain (r = 0.37, P = 0.1) and function (r = 0.4, P = 0.09). Within the domains, self-image showed highest correlation with patient satisfaction (r = 0.65, P = 0.006) and total score (r = 0.89, P = 0.0001). CONCLUSIONS: Patients with global sagittal imbalance of the spine were effectively treated with a combined anterior and posterior arthrodesis as measured by radiographic parameters. Patient satisfaction with surgery, and overall clinical outcomes were best in cases that resulted in an increase in lumbar lordosis. The subset of patients with preoperative regional hypolordosis of the lumbar spine has better outcomes than those with preoperative lumbar lordosis in the physiologic range.

Adult↗
PubMed2004

Modeling of the sagittal cervical spine as a method to discriminate hypolordosis: results of elliptical and circular modeling in 72 asymptomatic subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects.

STUDY DESIGN: Computer analysis of digitized vertebral body corners on lateral cervical radiographs. OBJECTIVES: Using elliptical and circular modeling, the geometric shape of the path of the posterior bodies of C2-C7 was sought in normal, acute pain, and chronic pain subjects. To determine the least squares error per point for paths of geometric shapes, minor axis to major axis elliptical ratios (b/a), Cobb angles, sagittal balance of C2 above C7, and posterior tangent segmental and global angles. SUMMARY OF BACKGROUND DATA: When restricted to cervical lordotic configurations, normal, acute pain, and chronic pain subjects have not been compared for similarities or differences of these parameters. Conventional Cobb angles provide only a comparison of the endplates of the distal vertebrae, while geometric modeling provides the shape of the entire sagittal curves, the orientation of the spine, and segmental angles. METHODS: Radiographs of 72 normal subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects were digitized. For normal subjects, the inclusion criteria were no kyphotic cervical segments, no cranial-cervical symptoms, and less than +/- 10 mm horizontal displacement of C2 above C7. In pain subjects, inclusion criteria were no kyphotic cervical segments and less than 25 mm of horizontal displacement of C2 above C7. Measurements included segmental angles, global angles of lordosis (C1-C7 and C2-C7), height-to-length ratios, anterior weight bearing, and from modeling, circular center, and radius of curvature. RESULTS: In the normal group, a family of ellipses was found to closely approximate the posterior body margins of C2-C7 with a least squares error of less than 1 mm per vertebral body point. The only ellipse/circle found to include T1, with a least squares error of less than 1 mm, was a circle. Compared with the normal group, the pain group's mean radiographic angles were reduced and the radius of curvature was larger. For normal, acute, and chronic pain groups, the mean angles between posterior tangents on C2-C7 were 34.5 degrees, 28.6 degrees, and 22.0 degrees, C2-C7 Cobb angles were 26.8 degrees, 16.5 degrees, and 12.7 degrees, and radius of curvature were r = 132.8 mm, r = 179 mm, and r = 245.4 mm, respectively. CONCLUSIONS: The mean cervical lordosis for all groups could be closely modeled with a circle. Pain groups had hypolordosis and larger radiuses of curvature compared with the normal group. Circular modeling may be a valuable tool in the discrimination between normal lordosis and hypolordosis in normal and pain subjects.

Acute Disease↗
PubMed2005

Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position.

STUDY DESIGN: A prospective radiographic study of 160 volunteers without symptoms of spinal disease was conducted. OBJECTIVES: The objective of this study was to describe, quantify, and classify common variations in the sagittal alignment of the spine, sacrum, and pelvis. SUMMARY OF BACKGROUND DATA: Previous publications have documented the high degree of variability in the sagittal alignment of the spine. Other studies have suggested that specific changes in alignment and the characteristics of the lumbar lordosis are responsible for degenerative changes and symptomatic back pain. METHODS: In the course of this study, anteroposterior and lateral radiographs of 160 volunteers in a standardized standing position were taken. A custom computer application was used to analyze the alignment of the spine and pelvis on the lateral radiographs. A four-part classification scheme of sagittal morphology was used to classify each patient. RESULTS: Reciprocal relationships between the orientation of the sacrum, the sacral slope, the pelvic incidence, and the characteristics of the lumbar lordosis were evident. The global lordotic curvature, lordosis tilt angle, position of the apex, and number or lordotic vertebrae were determined by the angle of the superior endplate of S1 with respect to the horizontal axis. CONCLUSIONS: Understanding the patterns of variation in sagittal alignment may help to discover the association between spinal balance and the development of degenerative changes in the spine.

Adolescent↗
PubMed2005

Variation in surgical decision making for degenerative spinal disorders. Part II: cervical spine.

STUDY DESIGN: Survey-based descriptive study. OBJECTIVE: To study relationships between surgeon-specific factors and surgical approach to degenerative diseases of the cervical spine. SUMMARY OF BACKGROUND DATA: Geographic variations in the rates of cervical spine surgery are significant within the United States. Although surgeon density correlates with the rates of spinal surgery, other reasons for variation such as surgeon-specific factors are poorly understood. METHODS: A total of 22 orthopedic surgeons and 8 neurosurgeons of varied ages and geographic regions answered questions regarding the need for surgery, surgical approach, and use of fusion and instrumentation for 5 simulated cases. Cases included: (1) single-level disc herniation with osteophyte and radiculopathy, (2) single-level pseudarthrosis with axial neck pain, (3) multilevel stenosis with radiculopathy and neutral lordosis, (4) multilevel stenosis with myelopathy and neutral lordosis, and (5) multilevel stenosis with myelopathy and marked kyphosis. The effects of surgeon age and training background on surgical decision making were analyzed using an independent samples t test and Fisher exact test, respectively. RESULTS: The greatest agreement occurred for the single-level disc herniation, with all surgeons choosing an anterior discectomy, and 28 of the 29 respondents recommending fusion. Younger surgeons recommended instrumentation more often for all cases, reaching significance for the case of multilevel stenosis with myelopathy and neutral lordosis (Fisher exact test P = 0.02). Differences in recommendation for fusion, instrumentation, and the use of a posterior approach between orthopedic and neurosurgeons were limited. CONCLUSIONS: Variations in surgical procedures for cervical degenerative disease may depend on the clinical condition. Although this study found strong agreement in treatment approach to single-level disc herniation, significant variation was seen for the other degenerative conditions of the cervical spine. While differences in recommendation for fusion were not clearly associated with surgeon age, there was a trend toward the higher use of instrumentation by younger surgeons. Previously documented geographic variation may result in part from a lack of consensus regarding appropriate treatment techniques for certain degenerative conditions of the cervical spine, as well as surgeon-specific factors.

Adult↗
PubMed2004

Radiographic predictors of outcome after long fusion to L5 in adult scoliosis.

Radiographic factors that correlate with outcome following long posterior fusion to L5 for adult scoliosis were investigated. Measurement of thoracic, lumbar, and fractional lumbosacral curves, L5 obliquity, lumbar and L5-S1 lordosis, coronal balance, sagittal balance, and L5-S1 disc height were performed on preoperative, postoperative, and follow-up 36-in posteroanterior/lateral radiographs. Of 16 patients, 14 were female (88%) and 2 male (12%). Average follow-up was 32 months (8-78 months). Scoliotic curves demonstrated stable corrections; however, lumbar and L5-S1 lordosis decreased and sagittal decompensation worsened. Ten patients (62%) had no evidence of transitional degeneration. Six patients (38%) had radiographic evidence of L5-S1 degeneration, and three (19%) underwent revision. Patients with good preoperative sagittal balance, preserved lumbar lordosis, good postoperative fractional curve correction, and L5-S1 disc height preservation are most likely to benefit from posterior fusion to L5, avoiding sacral fusion, for adult scoliosis.

Adult↗
PubMed1992

Changes in the lumbosacral angle, sacral inclination and the curvature of the lumbar spine during aging.

Measurements of the curvature of the lumbar spine are useful in the investigations of low back pain. It is unclear whether the degree of lumbar lordosis, sacral inclination and lumbosacral angulation are the same for all normal adults. Radiographic studies were carried out on the lumbar spines of subjects aged 9-61 years. Mean and 95% tolerance ranges of the values of lumbar lordosis, lumbosacral angle and sacral inclination for adult age groups up to the sixth decade are given. The results showed that all three parameters varied steadily with age. The pattern of changes differed in males and females. Females had greater angles than males. Sacral inclination appeared to be a more important determinant of the degree of lumbar lordosis. All three parameters showed a tendency to decrease after the sixth decade. The significance of the findings is discussed.

Adolescent↗
PubMed1988

Curvature of the lumbar spine as a consequence of mechanical necessities in Japanese macaques trained for bipedalism.

If trained to walk bipedally at a juvenile age and over periods of some months or years, Japanese monkeys gradually acquire a pronounced lordosis of the lumbar spine. This lordosis persists even in the 'normal', pronograde posture of these animals. It is due to a relative increase of the ventral lengths of the vertebral bodies. This morphological change is clearly an adaptation to the mechanical necessities of the upright body posture. Our result is in complete accordance with the development of a lordosis in human children between 1 and 5 years, as described recently by others.

Animals↗
PubMed2005

Adaptive bone formation in acellular vertebrae of sea bass (Dicentrarchus labrax L.).

Mammalian bone is an active tissue in which osteoblasts and osteoclasts balance bone mass. This process of adaptive modelling and remodelling is probably regulated by strain-sensing osteocytes. Bone of advanced teleosts is acellular yet, despite the lack of osteocytes, it is capable of an adaptive response to physical stimuli. Strenuous exercise is known to induce lordosis. Lordosis is a ventrad curvature of the vertebral column, and the affected vertebrae show an increase in bone formation. The effects of lordosis on the strain distribution in sea bass (Dicentrarchus labrax L.) vertebrae are assessed using finite element modelling. The response of the local tissue is analyzed spatially and ontogenetically in terms of bone volume. Lordotic vertebrae show a significantly increased strain energy due to the increased load compared with normal vertebrae when loaded in compression. High strain regions are found in the vertebral centrum and parasagittal ridges. The increase in strain energy is attenuated by a change in architecture due to the increased bone formation. The increased bone formation is seen mainly at the articular surfaces of the vertebrae, although some extra bone is formed in the vertebral centrum. Regions in which the highest strains are found do not spatially correlate with regions in which the most extensive bone apposition occurs in lordotic vertebrae of sea bass. Mammalian-like strain-regulated bone modelling is probably not the guiding mechanism in adaptive bone modelling of acellular sea bass vertebrae. Chondroidal ossification is found at the articular surfaces where it mediates a rapid adaptive response, potentially attenuating high stresses on the dorsal zygapophyses.

Adaptation, Physiological↗
PubMed1991

Locomotor problems in infantile facioscapulohumeral muscular dystrophy. Retrospective study of 9 patients.

A retrospective study of 9 patients with infantile facioscapulohumeral muscular dystrophy defines orthopedic deformities and progression. Patients presented in the early months of life with facial diplegia. Sensorineural hearing loss occurred in 8 out of 9 with a mean onset at 5 (2-9) years. Walking began at the normal time, but worsened progressively, which was due mainly to gluteus maximus muscle weakness. Scapular winging, extreme lumbar lordosis, and foot drop were characteristic. The majority of patients (in this and other series) lose walking ability in the second decade. Efforts to control lumbar lordosis by bracing while the patients were still walking were ineffective. Control of lumbar lordosis after the patients are wheelchair-dependent is important.

Adolescent↗
PubMed2004

Three-level and four-level anterior cervical discectomies and titanium cage-augmented fusion with and without plate fixation.

OBJECT: Cage-assisted anterior cervical discectomy and fusion (ACDF) has proven to be a safe and effective procedure for the treatment of one- and two-level degenerative disc disease (DDD). To the authors' knowledge, clinical results after three- and four-level interbody cage-augmented ACDF have not been reported in the literature. The authors investigated the safety and effectiveness of titanium cages used in such procedures and evaluated the results in cases with or without plate fixation. METHODS: Fifty-six patients suffering from cervical DDD were divided into two groups. Group 1 included 32 patients who underwent titanium cage-assisted ACDF; Group 2 included 24 patients who underwent the same procedure, supplemented with plate fixation. The cervical DDD was confirmed by radiography and magnetic resonance imaging. The patients underwent radiographic evaluation to assess cervical lordosis, segmental height of cervical spine, the height of the foramina, and spinal stability. Neurological outcomes were assessed using the Japanese Orthopaedic Association (JOA) scores. Neck pain was graded using a 10-point visual analog scale (VAS). The follow-up period ranged from 13 to 28 months (mean 17.2 months). In both Groups 1 and 2 significant increase (p < 0.001) was demonstrated in the JOA scores (preoperatively 10.7 +/- 2.4 and 11.1 +/- 2, postoperatively 13.9 +/- 2.2 and 14.1 +/- 2.3, respectively) and VAS pain scores (preoperatively 8.8 +/- 0.9 and 8.5 +/- 1, postoperatively 3.1 +/- 2.1 and 2.8 +/- 1.8, respectively); however, there was no significant intergroup difference. A significant increase in the cervical lordosis, foraminal height, and segmental height was observed in both groups. Good stability of cage fusion was obtained in both groups 12 months postoperatively (90.6% in Group 1 and 91.7% in Group 2); however, there were no statistically significant intergroup differences. The complication rate in Group 2 was higher than that in Group 1. The hospital length of stay in Group 1 was significantly lower than in Group 2 (p < 0.001). CONCLUSIONS: Analysis of these findings demonstrated that titanium cage-assisted ACDF provided long-term stabilization, increased lordosis, increased segmental height, and increased foraminal height. In both groups good neurological outcomes were achieved and donor site morbidity was avoided. The lower complication rate and shorter hospital stay, however, make the cage-assisted fusion without plate fixation better than with plate fixation.

Adult↗
PubMed1999

Mechanisms of retrolisthesis in the lower lumbar spine. A radiographic study.

The study investigates lower lumbar segments with posterior vertebral shifts (retrolisthesis) with respect to the orientation of facet joints, disc height, lordosis of the lumbar spine, and orientation of vertebral endplates. Standing lumbar radiographs as well as CT and/or MRI investigations of 69 patients were analyzed. Data from patients with retrolisthesis (20 cases) were compared to data from patients with degenerative spondylolisthesis (DS, 23 cases), and from patients without signs of vertebral shifts (26 cases). The orientation of facet joints in segments with retrolisthesis was not different from segments without shifts, whereas the facet joints in patients with DS were oriented more sagittally. The overall lordosis of the lumbar spine and the endplate inclination were considerably reduced in patients with retrolisthesis, especially compared to those with DS. Disc height was comparable in retrolisthesis and DS, but was reduced compared to segments without shifts. The results support biomechanical considerations, that a retrolisthesis of a lower lumbar spine segment is correlated with a reduction of lumbar lordosis, endplate inclination, and segmental height.

Aged↗
PubMed1992

The etiology and pathogenesis of idiopathic scoliosis.

Idiopathic scoliosis is a complex three-dimensional deformity and in the thoracic region the essential lesion lies in the sagittal plane in the form of an area of inappropriate lordosis. The thoracic kyphosis is normally protected from buckling by being behind the axis of spinal column rotation but when the thoracic lordosis develops it brings the apical region anterior to this axis and thus under compression with resultant buckling failure of the spinal column. The condition of idiopathic thoracic scoliosis is the opposite to idiopathic hyperkyphosis (Scheuermann's disease), the latter being rotationally stable and not moving out of the sagittal plane. The two frequently co-exist in the same spine with thoracic hyperkyphosis above an area of lumbar lordo-scoliosis. There is a spectrum of normal lateral profile and flat backs at the one end are in danger of buckling (lordo-scoliosis) while round backs at the other end of the spectrum are in danger of being defined as Scheuermann's disease. There is no requirement for a specific pathological process. Engineers describe only two ways in which a flexible column can fall into mechanically-angular collapse (kyphosis) and column buckling (lordo-scoliosis). A number of factors favour column buckling (Euler's law) and thus the bigger a deformity the more likely it will be to continue progressing and the taller and more slender the column the more likely it will be to fail and this we see in our patients with idiopathic scoliosis. Not only is lordosis the essential lesion but it is also the primary abnormality which can be demonstrated in children before lateral curvature and rotation develop.

Adolescent↗
PubMed1986

The experimental basis of idiopathic scoliosis.

Idiopathic scoliosis is a complex three-dimensional deformity of the spine of which the scoliotic deformity and rotation are entirely secondary to an abnormality of shape in the median sagittal plane. In the thoracic region, there is a lordosis where a kyphosis should exist. In a controlled series of animal experiments using the growing New Zealand white rabbit as the model, idiopathic scoliosis can readily be produced if an asymmetric lordosis is created in the lower thoracic spine. Neither pure lordosis nor pure scoliosis produces the progressive idiopathic deformity. In the experimental animal when the normal thoracic kyphosis is reconstituted before maturity, the idiopathic deformity spontaneously improves. This lays the foundation for a more physiologic approach to treatment.

Animals↗
PubMed2002

Estrogen-induced dendritic spine elimination on female rat ventromedial hypothalamic neurons that project to the periaqueductal gray.

Neurons of the ventromedial hypothalamic nucleus (VMH) that project to the periaqueductal gray (PAG) form a crucial segment of the motor pathway that produces the lordosis posture, the hallmark of female rat sexual behavior. One suggested mechanism through which estrogen facilitates lordosis is by remodeling synaptic connectivity within the VMH. For instance, estrogen alters VMH dendritic spine density. Little is known, however, about the local VMH microcircuitry governing lordosis nor how estrogen alters synaptic connectivity within this local circuit to facilitate sexual behavior. The goal of this study was to define better the neuron types within the VMH microcircuitry and to examine whether estrogen alters synaptic connectivity, as measured by dendritic spine density, on VMH projection neurons. A retrograde tracer was injected into the PAG of ovariectomized rats treated with vehicle or estradiol. Retrogradely labeled VMH neurons were filled with Lucifer yellow, then immunostained for estrogen receptor-alpha (ER alpha). VMH neurons that project to the PAG had more dendrites than functionally unidentified neurons. Additionally, VMH projection neurons could be subdivided into those located within the cluster of ER alpha-containing neurons and those medial to the cluster. Estrogen decreased spine density by 57% on the long primary dendrites of VMH projection neurons located within the ER alpha cluster but not on projection neurons medial to the cluster. Only 4% of the VMH projection neurons expressed ER alpha. These results suggest that estrogen may facilitate sexual behavior by decreasing spines selectively, via an indirect mechanism, on a subset of VMH neurons that project to the PAG.

Animals↗
PubMed2003

Estrogen receptor-alpha is required for estrogen-induced mu-opioid receptor internalization.

Endogenous opioid circuits are pivotal for the regulation of sexual receptivity. Treatment of mice with morphine, a preferential mu-opioid receptor (MOR) agonist, severely attenuates lordosis. Estrogen induces internalization of MOR in cell groups of the limbic-hypothalamic lordosis-regulating circuit. Because rapid MOR internalization is mediated by estrogen release of endogenous opioid peptides, internalization has been used as a neurochemical signature of estrogen action in the central nervous system. Together these results indicate that estrogen induces a MOR mediated inhibition of sexual receptivity. To determine which estrogen receptor, estrogen receptor-alpha (ERalpha) or estrogen receptor-beta (ERbeta), mediates MOR internalization, ERalpha knockout (ERalphaKO), ERbeta knockout (ERbetaKO) and wild-type (WT) mice were used in the present study. WT, ERalphaKO and ERbetaKO mice had similar MOR distributions in the limbic-hypothalamic lordosis-regulating circuit. Estrogen treatment internalized MOR in the medial preoptic nucleus of ovariectomized WT and ERbetaKO, but not ERalphaKO mice. Treatment of ERalphaKO mice with the selective endogenous MOR ligand, endomorphin-1, induced levels of MOR internalization similar to WT mice suggesting that MOR in ERalphaKO mice could be activated and were probably functional. The results of the present experiments indicate that ERalpha is required for estrogen-induced MOR internalization and suggest that ERalpha can mediate rapid actions of estrogen.

Analgesics, Opioid↗
PubMed1994

Divergent axon collaterals originate in the estrogen receptive ventromedial nucleus of hypothalamus in the rat.

The ventromedial nucleus of the hypothalamus (VMH) plays a crucial role in the mediation of lordosis by integrating predominantly inhibitory limbic signals with cyclic variation of ovarian steroids and sending a stimulatory output to the midbrain, especially the periaqueductal gray (PAG). Tract-tracing studies have established projections of the VMH and Golgi studies have shown these neurons to frequently give rise to axon collaterals, but the anatomical pattern of shared projections has not been explored. We have used a combination of retrograde tracers to map VMH projections to the medial division of the medial preoptic nucleus (MPNm), posterodorsal division of the medial nucleus of the amygdala (MeApd), and the PAG. Neurons with dual projections were mainly confined to the VMHvl and represented 31%-37% of each projection subset. Neurons simultaneously projecting to the MPNm, MeApd, and PAG represented 7%-9% of each projection subset. By combining tract-tracing with steroid autoradiography, we found that approximately one-quarter of each projection subset in the VMHvl concentrated 3H-estradiol. Thus, some of the VMHvl neurons that communicate a facilitatory signal to the PAG may also act to stimulate lordosis through a feedback suppression of the net inhibition formed by efferent signals from the forebrain. The even distribution of estrogen binding among projection subsets suggests a lack of compartmentalization of estrogen-regulated processes that are relevant to lordosis.

Animals↗