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PubMed1976

Lordosis behaviour in male, female and androgenized female rats.

Sex differences in the lordodis response of adult rats to ovarian hormones were studied in a series of experiments. Male rats were less sensitive to oestradiol benzoate (OB, a single injection of 10, 100 or 1000 mug/kg or seven daily injections of 2, 10, or 50mglkg)then were female rats. Oestradiol benzoate-primed (10 mglkg)female, but not male, rats showed dose-dependent responses to progesterone (0-4, 2-0 or 10-0 mg/kg/. male rats responded clearly to progesterone (2 mg/rat) only when primed with a high dose of OB (100 mug/rat). Display of the whole pattern of female sexual behaviour was induced in male rats by treatment with 100 mug OB and 2 mg progesterone. Female rats treated with 1 mg testosterone propionate (TP) on day 4 of life, ovariectomized as adults and tested under the same endocrine conditions as the rats described above, retained behavioural OB sensitivity but responded poorly to progesterone. Evidence is presented that ovarian secretions during development significantly modify the response of neonatally TP-treated and normal female rats to OB in adulthood.

Animals↗
PubMed1980

Absence of a diurnal rhythm in lordosis behaviour induced by oestrogen in gonadectomized rats.

Gonadectomized rats bearing s.c. Silastic capsules containing crystalline oestradiol-17 beta diluted with cholesterol, or oestradiol-17 beta dissolved in sesame oil were tested for the presence of a diurnal rhythm in the display of lordotic behaviour. In experiment 1, female rats received four consecutive tests at intervals of 8 h in a lighting regimen of 12 h light: 12 h darkness beginning 4, 14 and 28 days after implantation of 5 mm capsules of oestradiol. After a single test on day 4, male rats were tested on days 14-15 only, at the same times as the female rats. Female animals were tested while vaginal-cervical stimulation was prevented by vaginal masking beginning 35 days after implantation of oestradiol. In experiment 2, lordotic responsiveness of female rats was assessed beginning 4 days after implantation of oestradiol once on each of 3 consecutive days, with each test occurring at a different time of day. Finally, in experiment 3, female rats were tested as in experiment 1 beginning 4 dys after implantation of lower threshold amounts of oestradiol in oil-filled capsules. In no experiment were changes in lordotic behaviour observed as a function of the time of day. These findings failed to support recent reports of a sexually dimorphic rhythm in lordotic responsiveness to oestradiol in the rat.

Animals↗
PubMed2000

Congruent spinopelvic alignment on standing lateral radiographs of adult volunteers.

STUDY DESIGN AND OBJECTIVES: Radiographs of 75 healthy volunteers were measured to decide parameters and ranges for "congruent" sagittal spinopelvic alignments using the pelvic radius technique. A subset of 30 of the volunteers subsequently had a second radiograph to assess for changes in the repeated measurements. SUMMARY OF BACKGROUND DATA: Measurement of spinal alignment is important. Radiographic parameters for "congruent" spinopelvic balance over the hips and changes in sagittal spinal alignments over time have not been defined. Measurement techniques for spinal alignments and to quantitate pelvic morphology need to be standardized. METHODS: The 75 volunteers (44 men/31 women, mean age 39 years, range, 20 to 63 years) had 36-inch standing lateral radiographs of the thoracolumbar spine and pelvis taken that included both hips. Thirty volunteers (19 men/11 women) had a second radiograph taken 5 to 6 years later. Radiographic measurements were made using the pelvic radius technique. This required locating a midpoint between the approximate centers of both femoral heads to establish a pelvic hip axis. A line between the hip axis and the posterior superior corner of S1 for the pelvic radius was drawn and measured for length. Angles were measured from the pelvic radius to tangents along the vertebral endplates on the 105 films with an electronic digital readout device. These angles included PR-S1 for pelvic morphology and PR-T12 for total lumbopelvic lordosis. A pelvic angle was measured from a vertical line through the hip axis to the pelvic radius. This angle gave the sagittal alignment for the pelvis over the hips. Longitudinal measurements between radiographs were compared for minimum and maximum change. Significant statistical correlations for the measurements were carefully studied to determine potentially important clinical relationships. In addition, thoracic kyphosis/lumbar lordosis ratios were assessed. RESULTS: The most constant measurement with the least change on the repeated radiographs was that for pelvic morphology (PR-S1 angle) followed by length of the pelvic radius, pelvic alignment over the hips (pelvic angle), and total lumbopelvic (PR-T12) and lumbosacral (T12-S1) lordosis. Other longitudinal measurements, including those for thoracic kyphosis and spinal balance by a plumbline, showed greater change. Measurements for pelvic morphology by the pelvic radius technique were correlative with standing total lumbosacral lordosis, regional lumbopelvic lordosis, pelvic alignment, pelvic radius length, and gender (P< or = 0.006 for each). The correlations between total and regional lumbopelvic lordosis and pelvic alignment measurements were even higher(P<0.0001). Of possible clinical importance was the finding that standard measurements for lordosis were dependent on individual pelvic morphology quantitated by the pelvic radius technique. CONCLUSIONS: In all of the sagittally balanced subjects studied, "congruent" spinopelvic alignment on all 105 standing lateral radiographs could be defined by four parameters using the pelvic radius technique: total lumbopelvic lordosis (PR-T12), incorporating complementary angles for lumbosacral lordosis (T12-S1), and pelvic morphology (PR-S1 angle) that summarily were always between -69 degrees to -116 degrees (+/-3 degrees ); centered pelvic alignment over the hips, as determined by the pelvic angle, that was always between -3 degrees to -32 degrees (+/-2 degrees ); compensated spinal balance, with a sagittal plumbline from the center of the T4 body always posterior to the hip axis as well as the center of the L4 vertebral body; and a concordant T4-T12 kyphosis/PR-T12 lordosis ratio that was always negative and between 0.15 to 0.75. [Key words: congruent alignment, pelvic radius technique, pelvic morphology, lumbopelvic lordosis, lumbosacral lordosis]

Adult↗
PubMed1982

Responses of medullary reticulospinal and other reticular neurons to somatosensory and brainstem stimulation in anesthetized or freely-moving ovariectomized rats with or without estrogen treatment.

The medical medullary reticular formation (mMRF) is probably involved in controlling lordosis, a feminine mating reflex which requires both estrogen priming and appropriate somatosensory input(s). We have recorded single-unit activity of antidromically identified reticulospinal (RS) and unidentified (UI) neurons in mMRF of ovariectomized rats with or without estrogen treatment to investigate neurohormonal mechanisms regulating lordosis. The units were recorded in both acute and chronic preparations, the latter involving implanted "floating" wire electrodes to allow the influence of estrogen on a particular unit to be followed for several days. A substantial number of RS and UI units in both acute and chronic preparations were either excited or inhibited by a lordosis-eliciting somatosensory stimulation, indicating that the lordosis-eliciting sensory inputs did reach mMRF. The majority of these units responded promptly to the stimulation, and could participate in triggering the short-latency lordosis reflex. Electrical stimulation of several brainstem locations revealed that there was an extensive and specific convergence on mMRF neurons between inputs from the lordosis-eliciting stimulation and mesencephalic central gray, which has been shown to relay lordosis-inducing estrogen influence from hypothalamus to lower brainstem. Therefore, mMRF neurons can receive both the estrogen influence and the lordosis-eliciting inputs and integrate them. Although no apparent estrogen influence was detected in chronic preparations, statistical comparisons of results from acute preparations with or without estrogen treatment suggest that estrogen can increase the proportion of the neurons excited by the lordosis-eliciting stimulation and facilitate neuronal excitability. Both effects are consistent with the prevailing notion that the net lordosis-inducing influence of estrogen is facilitatory, and they may be mechanisms for making lordosis elicitable.

Animals↗
PubMed2001

The sagittal profile of the cervical and lumbosacral spine in Scheuermann thoracic kyphosis.

The sagittal profiles of the cervical and lumbar spine have not been studied in Scheuermann kyphosis. The purpose of this study was to investigate these profiles. Standing lateral radiographs of the spine in 34 children with Scheuermann kyphosis were reviewed. Cervical lordosis, lumbar lordosis, thoracic kyphosis, sagittal vertebral axis, and sacral inclination were measured. The relations between these variables were explored using the Pearson correlation. The average patient age was 15.5 +/- 1.8 years, thoracic kyphosis was 65 degrees +/- 12 degrees, lumbar lordosis 71 degrees +/- 13 degrees, and cervical lordosis 4 degrees +/- 15 degrees (Cobb angle), and 9 degrees +/- 14 degrees (posterior vertebral body angle [PVBA]). No correlations were noted between cervical lordosis and thoracic kyphosis. Correlations were noted between cervical lordosis and lumbar lordosis (r2 = 0.17, Cobb angle; r2 = 0.16, PVBA) and between cervical lordosis and the residual sagittal difference (thoracic kyphosis minus lumbar lordosis; r2 = 0.32, p = 0.001 [Cobb angle], and r2 = 0.19, p = 0.01 [PVBA]). In Scheuermann kyphosis, the flexible cervical and lumbar spine is linked by the intermediate rigid thoracic segment. As the residual sagittal difference becomes more kyphotic, lordosis of the cervical spine increases as the patient strives to maintain a forward visual gaze.

Adolescent↗
PubMed2002

Sagittal plane correction in idiopathic scoliosis.

STUDY DESIGN: Patients with idiopathic scoliosis who had undergone posterior fusion by means of posterior multisegmented hook instrumentation were studied retrospectively. OBJECTIVES: To present the changes in projected thoracic hypokyphosis and the behavior of lumbar lordosis within and below the fusion. SUMMARY OF BACKGROUND DATA: Scoliosis is a three-dimensional deformity of the spine. The idiopathic cases usually exhibit a flattening of the sagittal curves, which had further deteriorated when the Harrington technique was used. The consequences included the flat back, angular increase of the lumbar lordosis below the fusion, and low back pain. Previous studies showed no or only moderate correction of thoracic hypokyphosis when using Cotrel-Dubousset instrumentation or its modifications were used. Harrington rod systems resulted in decreased lumbar lordosis in the fusion area and increased lordosis below the fusion. No background data were found concerning the effects of multisegmented hook instrumentation on the lumbar spine within and below the fusion. METHODS: For this study, 306 patients with idiopathic scoliosis who had undergone posterior spinal fusion with multisegmented hook systems using the derotation maneuver were analyzed after a mean follow-up period of 5 years and 4 months. The coronal plane curvature, the sagittal plane projection of the thoracic kyphosis, and the lumbar lordosis within and below the fusion were evaluated. RESULTS: The average coronal plane correction was 67.1%. Analysis of the sagittal contours demonstrated that the preoperative thoracic hypokyphosis (less than 20 degrees between T4 and T12) increased by an average of 12 degrees, and that 55.1% of hypokyphotic backs were corrected to the normal range (20 degrees to 40 degrees ). In patients with frank lordosis (kyphosis less than 10 degrees ), the degree of correction was higher (average, 16 degrees ), but complete correction was achieved in only 38.5% of the cases. In patients with mild lordosis (kyphosis between 10 degrees and 20 degrees ), the average correction was 8 degrees, and 71.3% of the patients were in the normal range after surgery. The normal preoperative thoracic kyphosis was preserved in 81.3% of the cases. In the lumbar area, the Cotrel-Dubousset instrumentation was capable of correcting the preoperative hypolordosis (less than -20 degrees between L1 and L5) in 94.4% of the cases. The normal preoperative lordosis (-20 degrees to -60 degrees ) was preserved in 97.9% of the cases. The hyperlordosis was corrected in all cases. Analysis of the data in terms of lower fusion limit showed that the lower the caudal hook, the greater the increase in the segmental lordosis within the fusion, without any increase distal to the fusion. No segmental hyperlordosis was observed below the fusion. CONCLUSIONS: The Cotrel-Dubousset technique ensures considerable sagittal correction of the spine. In the course of scoliosis correction, it is possible to preserve the normal preoperative sagittal profile of the spine, to correct the slightly flattened thoracic kyphosis, to increase materially the kyphosis of the frankly hypokyphotic spine, to preserve or restore normal lumbar lordosis in a considerable percentage of the cases, to avoid angular segmental hyperlordosis at the level of the first disc below the fusion, and to avoid retrolisthesis of the last fused vertebra.

Adolescent↗
PubMed2003

Influence of cage geometry on sagittal alignment in instrumented posterior lumbar interbody fusion.

STUDY DESIGN: Retrospective radiographic evaluation of the sagittal alignment of the lumbar spine in patients undergoing short-segment instrumented posterior lumbar interbody fusion with cage systems of different shape. OBJECTIVES: To determine whether rectangular and wedge-shaped cages have a different influence on the sagittal alignment of the lumbar spine in patients undergoing short-segment instrumented posterior lumbar interbody fusion. SUMMARY OF BACKGROUND DATA: Previous studies of sagittal alignment after posterior lumbar interbody fusion have focused on the impact of intraoperative patient, hip, and knee positioning, as well as instrumentation characteristics on sagittal posture. The influence of the cage shape on indexes of total and segmental sagittal alignment of the lumbar spine is yet unknown. METHODS: Forty-two patients having undergone instrumented short-segment posterior lumbar interbody fusion were reviewed retrospectively. Twenty-two patients (12 women and 10 men, 38-78 years of age) had posterior lumbar interbody fusion with rectangular cages. The fused segments were: 4 at L3-L4, 16 at L4-L5, 11 at L5-S1. Thirteen patients had single- and nine patients double-level fusion. Twenty patients (8 women and 12 men, 34-81 years of age) had posterior lumbar interbody fusion with wedge-shaped cages. The fused segments were: 4 at L3-L4, 15 at L4-L5, 11 at L5-S1. Ten patients had single- and 10 patients double-level fusion. Cages were packed with cancellous bone from the posterior iliac crest and/or bone fragments harvested by laminectomy. All patients had additional pedicle screw fixation. Pre- and postoperative standing lateral radiographs were assessed for segmental and lumbar lordosis as well lumbar and sacral tilt. Data were analyzed with repeated measures analysis of variance. RESULTS The mean follow-up period was 18 months with a minimum follow-up period of 14 months. Mean segmental lordosis of the fused segments showed significant changes between the two implant groups (P < 0.05). Segmental lordosis decreased in the rectangular cage group from 10 degrees to 2 degrees at L3-L4, from 10 degrees to 5 degrees at L4-L5, and from 9 degrees before to 6 degrees after fusion surgery at L5-S1. In the wedge-shaped cage group, segmental lordosis increased from 4 degrees to 7 degrees at L3-L4, from 2 degrees to 8 degrees at L4-L5, and from 9 degrees to 17 degrees at L5-S1. Analysis of changes in lumbar lordosis and lumbar and sacral tilt did not show significant differences though opposite trends: lumbar lordosis decreased from 55 degrees to 48 degrees in the rectangular cage group and increased from 45 degrees to 53 degrees in the wedge-shaped cage group. Lumbar tilt measured 98 degrees before and 102 degrees after surgery in the rectangular cage group and 97 degrees before and 94 degrees after surgery. Sacral tilt measured 44 degrees before and 40 degrees after surgery in the rectangular cage group and measured 42 degrees before and 45 degrees after surgery in the wedge-shaped cage group. CONCLUSIONS: The cage geometry has a significant impact on the alignment of the lumbar spine after instrumented posterior lumbar interbody fusion. With rectangular cages, lumbar lordosis and segmental lordosis of the segments fused decrease; sagittal balance is maintained by compensatory changes of the sacral tilt. Wedge-shaped cages significantly increase segmental lordosis, enhance lumbar lordosis, and therefore should be preferred for restoring sagittal alignment in instrumented posterior lumbar interbody fusion procedures.

Adult↗