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PubMed1991

Electrophysiological actions of oxytocin on hypothalamic neurons in vitro: neuropharmacological characterization and effects of ovarian steroids.

Oxytocin (OT) neurotransmission in the brain has a facilitatory effect on sexual receptivity in rats. This effect of OT is dependent on priming by ovarian steroids, estrogen and progesterone. These steroids modulate OT binding in specific brain nuclei, including the ventrolateral portion of the ventromedial hypothalamic nucleus (vlVMN). In the present study, single-unit activity was recorded from the vlVMN in hypothalamic slices to characterize the electrophysiological actions of OT. To examine the effects of ovarian steroids on OT actions, we used brain slices prepared from ovariectomized rats either treated with estrogen or not, and some slices were treated with progesterone in vitro. OT had little modulatory action on neuronal responses to other agents, but affected the activity of large numbers of vlVMN units. Of those neurons affected, 94% responded with excitation. This predominant stimulatory action of OT is consistent with its lordosis-facilitating effect, because increases in the activity of VMN neurons are generally associated with the facilitation of lordosis. Pharmacological analyses with selective OT agonists and antagonists as well as structurally related peptides showed that the excitatory action of OT is mediated by OT receptors. Estradiol modulated several aspects of OT transmission. First, it increased neuronal responsiveness to OT, especially at the lowest concentration used (0.2 nM). In addition, it caused neuronal responses to OT to correlate significantly with responses to acetylcholine and norepinephrine, which also can act on the ventromedial hypothalamus to facilitate lordosis. Finally, estradiol enhanced the excitability of laterally projecting neurons, which have been implicated in lordosis. In estrogen-pretreated slices, addition of progesterone in vitro caused little further effect on responses of individual neurons to exogenous OT. Altogether, the present electrophysiological findings are consistent with the hypothesis that estrogen potentiates OT action by increasing functional OT receptors preferentially in lordosis-relevant neurons, thereby enabling OT to efficiently facilitate female reproductive behavior.

Acetylcholine↗
PubMed1978

Androgenic influences on feminine sexual behavior in male and female rats: defeminization blocked by prenatal antiandrogen treatment.

The prenatal influence of androgen on the development of female sexual behavior in rats was investigated. The nonsteroidal antiandrogen, flutamide (4'-nitro-3'-trifluoromethylisobutyrylanilide; SCH), was administered to pregnant female rats from days 10--22 of gestation in dosages of either 1 mg/mother-day or 5 mg/mother-day. Males and females were gonadectomized in adulthood and tested for the display of lordosis in response to estradiol benzoate (EB) alone or EB with progesterone (P). Males exposed prenatally to either the 1- or 5-mg dosage of flutamide exhibited significantly higher lordosis quotients than controls when given EB alone. The addition of P was without effect in all male groups with regard to estrogen-induced lordosis. Females exposed prenatally to flutamide had significantly higher lordosis quotients than controls when given either 0.175 or 0.25 micrograms EB daily for 3 days. Addition of P to EB treatment significantly facilitated lordosis display in control and flutamide-treated females. The increase of feminine sexual behavior in both males and females of feminine sexual behavior in both males and females resulting from prenatal antiandrogen treatment suggests that androgen, prenatally, inhibits development of female sexual behavior. This androgenic inhibition of sexual receptivity (defeminization) seems to be related to the animal's sensitivity to estrogen in adulthood.

Anilides↗
PubMed1986

Sex-dependent differences in estrogen regulation of choline acetyltransferase are altered by neonatal treatments.

We investigated whether estrogenic actions of testosterone during development which mediate the suppression of feminine reproductive behavior and cyclic gonadotropin secretion also contribute to reported sex differences in the induction of choline acetyltransferase (ChAT) after estrogen priming in the diagonal band region of the preoptic area. Newborn female rats received estradiol (E2 females); newborn males received 1,4,6-androstatrien-3,17-dione (ATD), an inhibitor of aromatase (ATD males); and some of both sexes received vehicle treatment (control). In adulthood, feminine sexual behavior (lordosis) was tested after E2 plus progesterone priming. The neonatal treatments reversed the sex-specific response pattern; E2 females were defeminized and displayed minimal lordosis, as did control males, while ATD males showed maximal lordosis, as did control females. E2 was then administered, and ChAT activity was measured in the horizontal and vertical nuclei of the diagonal bands (hDB and vDB, respectively). Controls exhibited the normal sex-specific response to E2. Females showed increased ChAT activity in the hDB and unaltered activity in the vDB: males had unaltered ChAT activity in the hDB and decreased activity in the vDB. In neonatally treated males and females, ChAT activity after E2 administration was not altered from the normal sex-specific pattern in the hDB, i.e. all females showed increased hDB ChAT after E2, and no male responded. In the vDB, groups defeminized in terms of lordosis (E2 females and control males) showed higher ChAT activity in the absence of E2 priming, and E2 treatment decreased vDB ChAT in these groups. In addition, ATD males showed a unique response to E2 in the vDB, namely increased ChAT activity. Although neonatal E2 and ATD treatments did not completely reverse the sex-specific pattern of E2 priming on ChAT activity, the results obtained suggest that a net increase in diagonal band cholinergic function, as indexed by increased ChAT activity after E2 priming, may contribute to the ability of hormones to induce lordosis and/or LH surges.

Androstatrienes↗
PubMed1993

Sagittal configuration of spinal curvature line in sportsmen using Moire technique.

A separate moire photograph of 380 men's back was taken. Using a micro-computer the sagittal configuration of the spinal curvature line was reconstructed based on the moire fringe on the back. Then the sagittal configuration of this line was compared among groups according to their sports: rugby, soccer, kendo, swimming, yachting, four track and field events (sprinting, distance running, jumping, and throwing), body-building as well as non-athletic men. Distance runners and sprinters had a greater degree of thoracic kyphosis and greater degree of lumbar lordosis, while non-athletes had a smaller degree of both kyphosis and lordosis. Swimmers, bodybuilders, rugby and soccer players had partial lordosis. The degree of lumbar lordosis of swimmers and bodybuilders was less than average while the degree of thoracic kyphosis was ordinary and the degree of thoracic kyphosis of rugby and soccer players was less than average while the degree of lumbar lordosis was ordinary.

Adult↗
PubMed2002

Early results using the Atlantis anterior cervical plate system.

OBJECT: The authors present a retrospective review of 77 patients in whom they performed anterior cervical discectomy and fusion (ACDF) in the treatment of radiculopathy and/or myelopathy. In all cases anterior interbody fusion was performed using the Atlantis locking plate system to treat the degenerative disease. METHODS: There were 41 men and 36 women (mean age 53.8 years), and 24 active cigarette smokers (31%) in the group. All patients presented with signs and symptoms of cervical radiculopathy and/or myelopathy, and magnetic resonance imaging or computerized tomography myelography demonstrated evidence of radicular and/or spinal cord compression at one or more cervical levels. Thirty-one patients underwent single-level ACDF, 20 patients underwent multilevel ACDF without posterior instrumentation, in eight patients one- to four-level corpectomies were supplemented with posterior fixation, 12 patients underwent single-level corpectomy, and six patients underwent multilevel corpectomy with no posterior instrumentation. The mean follow-up period was 15.33 months; overall good-to-excellent outcome was seen in 75% of patients; osseous fusion was demonstrated in 93.5%. In all patients except three, fibular allograft was used as graft material. The degree of overall cervical lordosis was measured at the last follow up and was compared with normal values obtained in age-matched individuals. In addition, the degree of cervical lordosis at fusion levels was compared with overall cervical lordosis. In patients in all five of the aforementioned categories significantly less lordosis was demonstrated than in age-matched controls. In patients who underwent single-level ACDF, single-level corpectomy, and multilevel ACDF significantly less lordosis was observed at the fusion segment than that in the overall cervical spine. Complications included one episode of chronic anterior wound drainage treated with intravenous antibiotic medication and one postoperative posterior wound infection, which required reoperation and intravenous antibiotic medication. Two cases (2.6%) of anterior screw backout and/or breakage were identified. One patient died of unrelated causes within 3 months of operation. CONCLUSIONS: These initial results indicate that use of the Atlantis plate system for anterior cervical arthrodesis produces fusion rates and clinical outcomes that are comparable with those obtained using other locking plating systems. It has the unique advantage, however, of providing the surgeon with the choice of fixed, variable, or hybrid screw constructs as a way of tailoring screw angles to individual anatomical/biomechanical needs.

Adult↗
PubMed1977

The effects of different amphetamines on copulatory behaviour and stereotype activity in the female rat, after treatment with monoamine depletors and synthesis inhibitors.

The effects of treatment with alpha-methyl-p-tyrosine (alphaMPT), parachlorophenylalanine (pCPA) and reserpine in combination with D- or L-amphetamine on copulatory behaviour and stereotype activity was studied in estrogen + progesterone treated ovariectomized rats. In doses which clearly prevented D- and L-amphetamine-induced stereotype activity alphaMPT or pCPA did not influence the effect of D- and L-amphetamine on lordosis response. Reserpine treatment decreased the enhanced stereotype activity after D- and L-amphetamine but did not decrease the effect on the copulatory behaviour. Pretreatment with pCPA or reserpine clearly reduced the effect of fenfluramine on the lordosis response. It is suggested that different mechanisms of action are involved in the D-amphetamine effect on the lordosis response and on stereotype activity. The present data give further evidence that the lordosis inhibitory effect of fenfluramine is mediated by 5-HT-mechanisms. The mechanism by which L-amphetamine inhibits the lordosis response seems to be different from both the action of fenfluramine and the effect of D-amphetamine.

Amphetamines↗
PubMed2003

[Physiological value of pelvic and spinal parameters of sagital balance: analysis of 250 healthy volunteers].

PURPOSE OF THE STUDY: Sagital balance of the spine is a fundamental element necessary for understanding spinal disease and instituting proper treatment. The aim of this prospective work was to establish the physiological values of pelvic and spinal parameters of sagital balance of the spine and to investigate their interactions. MATERIAL AND METHOD: Pelvic and spinal parameters were measured on the standing radiographs of 250 healthy volunteers. The following parameters were measured on lateral views including the head, the spine and the pelvis: lumbar lordosis, thoracic kyphosis, sagital tilt at T9, sacral inclination, pelvic incidence, pelvic version, intervertebral angulation, and the vertebral cuneiformization from T9 to S1. These measurements were taken after digitalization of the radiographs. Two types of analysis were performed: a descriptive univariate analysis to characterize the angular parameters and multivariate analysis (correlation, principal component analysis) to detail the relative variations of these parameters. RESULTS AND DISCUSSION: Mean values were: maximal lumbar lordosis 61 +/- 12.7 degrees, maximal thoracic kyphosis 41.4 +/- 9.2 degrees, sacral inclination 44.2 +/- 8.5 degrees, pelvic version 13 +/- 6 degrees, pelvic incidence 55 +/- 11.2 degrees, sagital tilt at T9 10.5 +/- 3.1 degrees. There was a strong correlation between sacral inclination and pelvic incidence (r=0.86), pelvic version and pelvic incidence (r=0.66), lumbar lordosis pelvic incidence pelvic version and thoracic kyphosis (r=0.9) and finally between pelvic incidence and the following parameters: sagital tilt at T9, sacral inclination, pelvic version, lumbar lordosis, and thoracic kyphosis (r=0.98). The relations between the different parameters studied demonstrated that saggital tilt at T9, which reflects spinal balance, is determined by three independent factors. The first is a linear combination of pelvic incidence, lumbar lordosis, and sacral inclination. The second is pelvic version. The third is thoracic kyposis. CONCLUSION: This work provided a useful tool for analyzing and understanding anteroposterior imbalance in patients with spinal disease and also a means of calculating corrections to be made with treatment, established from the linear regression equations which were elaborated.

Adult↗
PubMed1991

Low lumbar burst fractures. Comparison among body cast, Harrington rod, Luque rod, and Steffee plate.

Burst fracture of the low lumbar spine are rare and have not been well delineated in the literature. Thirty-one low lumbar burst fractures (L3-L5) were treated from 1981 through 1989. Average follow-up for 27 of the 31 patients was 46 months. Persistent complaints of back pain seemed to be found more in patients with long instrumentation and fusion and in patients with loss of lordosis. Conservative treatment of low lumbar burst fractures with body cast is a viable option in the neurologically intact patients with minimal height loss and minor angulation. If surgery is chosen, short rigid instrumentation (eg, transpedicular device) is best in accomplishing shorter fusion, maintaining vertebral height, and restoring lumbar lordosis. Harrington distraction rods improve vertebral height but produce loss of lumbar lordosis. Luque rods do not restore vertebral height and are only moderately effective in restoring lumbar lordosis. If patients are neurologically impaired in association with low lumbar burst fractures, posterior decompression by laminotomy or a transpedicular approach is generally effective. Maintaining vertebral height and restoring lumbar lordosis may be important in the prevention of disability from back pain.

Back Pain↗
PubMed1979

Potentiation of D- and L-amphetamine effects on copulatory behavior in female rats by treatment with alpha-adrenoreceptor blocking drugs.

The influence of noradrenergic mechanisms on the effects of D- and L-amphetamine on lordosis behavior and stereotype activity was studied in ovariectomized estrogen + progesterone treated rats. Phenoxybenzamine, phentolamine and prazosin, which all block alpha-adrenergic receptors potentiated the inhibitory effect of D-amphetamine on lordosis behavior. Phenoxybenzamine and prazosin also potentiated the effect of L-amphetamine, while phentolamine did not increase the effect. No augmented effect of D- or L-amphetamine was obtained on stereotype activity after pretreatment with phenoxybenzamine or phentolamine. L-propranolol, which blocks beta-adrenergic receptors and pimozide, a dopamine receptor blocker did not influence the effect of D- or L-amphetamine on lordosis behavior. Clonidine an alpha-receptor stimulant drug inhibited lordosis response in estrogen treated rats. This is probably due to a presynaptic effect, decreasing the release of NA from nerve terminals. The possibility that D- and L-amphetamine activates a NA system which influences lordosis behavior either by a direct facilitation or by decreasing the activity of an inhibitory serotonergic system is discussed.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

The impact of breast size on the vertebral column: a radiologic study.

BACKGROUND: Macromastia usually is associated with the physical and psychological symptoms reported comprehensively by many studies. Reduction mammoplasty seems to be the most reasonable solution for these symptoms, and many articles have reported improvement of these complaints after surgery. Some authors have postulated that the anatomic mechanisms of postural aberrations are heavy breasts and related pain symptoms. However, limited numbers of studies have tried to explain the effect of the heavy breasts on the vertebral column. METHODS: This study enrolled 100 females in four groups according to their breast cup sizes (groups A, B, C, D). All four groups were compared with each other statistically using one-way analysis of variance (ANOVA) followed by a post hoc test according to the body mass index (BMI) as well as the thoracic kyphosis, lumbar lordosis, and sacral inclination angles. RESULTS: The BMI was significantly higher in the D cup-sized breast group. There was a statistically significant difference between groups A and D in terms of the thoracic kyphosis and the lumbar lordosis angles, and between groups B and D in terms of the lumbar lordosis angle. No statistically significant difference was detected between the groups in terms of the sacral inclination angle. CONCLUSION: Breast size seems to be an important factor that affects posture, especially the thoracic kyphosis and lumbar lordosis angles.

Adolescent↗
PubMed2002

Clinical outcome and radiographic results after operative treatment of Scheuermann's disease.

The aim of this prospective study was to evaluate radiographic findings, patient satisfaction and clinical outcome, and to report complications and instrumentation failure after operative treatment of Scheuermann's disease using a combined anterior and posterior spondylodesis. The loss of sagittal plane correction after removal of the posterior instrumentation was analysed. The indication for surgery was a thoracic kyphosis greater than 60 degrees in adolescents and adults with persistent back pain, which failed to respond to conservative treatment. Thoracic kyphosis and lumbar lordosis angles were measured by the Cobb method at preselected time points and at final follow-up. Sagittal plane alignment was measured as translation. The validated Scoliosis Research Society Instrument (SRSI) questionnaire was sent to all patients at follow-up. P-values were calculated using the Wilcoxon signed rank test (P<0.05 is significant). Between October 1987 and August 1999, 23 consecutive patients underwent operative treatment. The median follow-up was 75 months (range 25-126 months). Median preoperative thoracic kyphosis was 70 degrees (range 62 degrees-78 degrees) and median preoperative lumbar lordosis was 68 degrees (range 54 degrees-84 degrees). Immediate postoperative median thoracic kyphosis was 39 degrees (range 28 degrees-54 degrees) (P<0.05) and immediate postoperative median lumbar lordosis was 49 degrees (range 35 degrees-63 degrees) (P<0.05). These significant corrections were maintained at early follow-ups conducted 1 year and 2 years postoperatively. At final follow-up, the median thoracic kyphosis had significantly increased, to 55 degrees (range 36 degrees-65 degrees) (P<0.05 relative to immediate postoperative value), and the median lumbar lordosis had increased to 57 degrees (range 44 degrees-70 degrees) (P<0.05). The late deterioration of correction in the sagittal plane was mainly caused by removal of the posterior instrumentation, and occurred despite radiographs, bone scans and thorough intra-operative explorations demonstrating solid fusions. The median SRSI score was 83 points (range 55-106). There was no significant correlation between the radiographic outcome and the SRSI score (P>0.05). Our series showed relatively fair outcome after operative treatment in Scheuermann's disease. Therefore, the indication for surgery in patients with Scheuermann's disease can be questioned.

Adolescent↗
PubMed2007

Sagittal balance of the pelvis-spine complex and lumbar degenerative diseases. A comparative study about 85 cases.

Retrospective analysis of the spino-pelvic alignment in a population of 85 patients with a lumbar degenerative disease. Several previous publications reported the analysis of spino-pelvic alignment in the normal and low back pain population. Data suggested that patients with lumbar diseases have variations of sagittal alignment such as less distal lordosis, more proximal lumbar lordosis and a more vertical sacrum. Nevertheless most of these variations have been reported without reference to the pelvis shape which is well-known to strongly influence spino-pelvic alignment. The objective of this study was to analyse spino-pelvic parameters, including pelvis shape, in a population of 85 patients with a lumbar degenerative disease and compare these patients with a control group of normal volunteers. We analysed three different lumbar degenerative diseases: disc herniation (DH), n = 25; degenerative disc disease (DDD), n = 32; degenerative spondylolisthesis (DSPL), n = 28. Spino-pelvic alignment was analysed pre-operatively on full spine radiographs. Spino-pelvic parameters were measured as following: pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, thoracic kyphosis, spino-sacral angle and positioning of C7 plumb line. For each group of patients the sagittal profile was compared with a control population of 154 asymptomatic adults that was the subject of a previous study. In order to understand variations of spino-pelvic parameters in the patients' population a stratification (matching) according to the pelvic incidence was done between the control group and each group of patients. Concerning first the pelvis shape, patients with DH and those with DDD demonstrated to have a mean pelvic incidence equal to 49.8 degrees and 51.6 degrees, respectively, versus 52 degrees for the control group (no significant difference). Only young patients, less than 45 years old, with a disc disease (DH or DDD) demonstrated to have a pelvic incidence significantly lower (48.3 degrees) than the control group, P < 0.05. On the contrary, in the DSPL group the pelvic incidence was significantly greater (60 degrees) than the control group (52 degrees), P < 0.0005. Secondly the three groups of patients were characterized by significant variations in spino-pelvic alignment: anterior translation of the C7 plumb line (P < 0.005 for DH, P < 0.05 for DDD and P < 0.05 for DSPL); loss of lumbar lordosis after matching according to pelvic incidence (P < 0.0005 for DH, DDD and DSPL); decrease of sacral slope after matching according to pelvic incidence (P = 0.001 for DH, P < 0.0005 for DDD and P < 0.0005 for DSPL). Measurement of the pelvic incidence and matching according to this parameter between each group of patients and the control group permitted to understand variations of spino-pelvic parameters in a population of patients.

Adult↗
PubMed2005

Lordotic vertebrae in sea bass (Dicentrarchus labrax L.) are adapted to increased loads.

Lordosis in fish is an abnormal ventral curvature of the vertebral column, accompanied by abnormal calcification of the afflicted vertebrae. Incidences of lordosis are a major problem in aquaculture and often correlate with increased swimming activity. To understand the biomechanical causes and consequences of lordosis, we mapped the morphological changes that occur in the vertebrae of European sea bass during their development from larva to juvenile. Our micro-CT analysis of lordotic and non-lordotic vertebrae revealed significant differences in their micro-architecture. Lordotic vertebrae have a larger bone volume, flattened dorsal zygapophyses and extra lateral ridges. They also have a larger second moment of area (both lateral and dorso-ventral) than non-lordotic vertebrae. This morphology suggests lordotic vertebrae to be adapted to an increased bending moment, caused by the axial musculature during increased swimming activity. We hypothesize the increase in swimming activity to have a two-fold effect in animals that become lordotic. The first effect is buckling failure of the axial skeleton due to an increased compressive load. The second effect is extra bone deposition as an adaptive response of the vertebrae at the cellular level, caused by an increased strain and strain rate in these vertebrae. Lordosis thus comprises both a buckling failure of the vertebral column and a molecular response that adapts the lordotic vertebrae to a new loading regime.

Adaptation, Physiological↗
PubMedDate not supplied

Sitting biomechanics part I: review of the literature.

OBJECTIVE: To develop a new sitting spinal model and an optimal driver's seat by using review of the literature of seated positions of the head. spine, pelvis, and lower extremities. DATA SELECTION: Searches included MEDLINE for scientific journals, engineering standards, and textbooks. Key terms included sitting ergonomics, sitting posture, spine model, seat design, sitting lordosis, sitting electromyography, seated vibration, and sitting and biomechanics. DATA SYNTHESIS: In part I, papers were selected if (1) they contained a first occurrence of a sitting topic, (2) were reviews of the literature, (3) corrected errors in previous studies, or (4) had improved study designs compared with previous papers. In part II, we separated information pertaining to sitting dynamics and drivers of automobiles from part 1. RESULTS: Sitting causes the pelvis to rotate backward and causes reduction in lumbar lordosis, trunk-thigh angle, and knee angle and an increase in muscle effort and disc pressure. Seated posture is affected by seat-back angle, seat-bottom angle and foam density, height above floor, and presence of armrests. CONCLUSION: The configuration of the spine, postural position, and weight transfer is different in the 3 types of sitting: anterior, middle, and posterior. Lumbar lordosis is affected by the trunk-thigh angle and the knee angle. Subjects in seats with backrest inclinations of 110 to 130 degrees, with concomitant lumbar support, have the lowest disc pressures and lowest electromyography recordings from spinal muscles. A seat-bottom posterior inclination of 5 degrees and armrests can further reduce lumbar disc pressures and electromyography readings while seated. To reduce forward translated head postures, a seat-back inclination of 110 degrees is preferable over higher inclinations. Work objects, such as video monitors, are optimum at eye level. Forward-tilting, seat-bottom inclines can increase lordosis, but subjects give high comfort ratings to adjustable chairs, which allow changes in position.

Biomechanical Phenomena↗
PubMed1997

Hypolumbarlordosis: a predisposing factor for preeclampsia.

OBJECTIVE: The aim of this research was to study the relationship between lumbar lordosis and preeclampsia. STUDY DESIGN: We studied lumbar lordosis of 52 primipara patients with pregnancy-induced hypertension and 59 normal primipara pregnant women. We determined the lumbar lordotic deviation (LLD) from lumbar lordosis measurement device in the lateral recumbent position and standing position. Roll-over test was performed for both groups. Resistance index (RI) of internal iliac artery was also measured by color Doppler sonography. RESULTS: The LLD was 33 +/- 6.1 degrees week 20-29 and 34 +/- 6.9 degrees week 30-40, respectively. In patients with preeclampsia, the LLD was 19.8 +/- 6.3 degrees week 20-29, 21.3 +/- 7.9 degrees week 30-40. The LLD in patients with preeclampsia was significantly lower than in the normal pregnant women. The LLD correlated to the increase diastolic pressure after roll-over test significantly. Hypolumbarlordosis was frequently associated with high resistance of peripheral vessel. CONCLUSIONS: We conclude that hypolumbarlordosis is frequently associated with preeclampsia. It is also closely related to the mechanism for positive roll-over test and increase of resistance of vessels. As lumbar lordosis does not change greatly in individuals before pregnancy, hypolumbarlordosis may be a predisposing factor for preeclampsia.

Adult↗
PubMedDate not supplied

Evaluation and analysis of patient outcomes with an intrasegmental fixation system in lumbar spinal fusion.

BACKGROUND CONTEXT: A new spinal fixation system with polydirectional screws and modular links with interconnecting radial serrations has been developed. The system allows the linking of multiple points of fixation, two points at a time (intrasegmental fixation), thus eliminating the need for intraoperative contouring of rods or plates. PURPOSE: Evaluation of this new type of spine system was done through biomechanical studies, analysis of lumbar lordosis preservation postoperatively, and multicenter review of patient outcomes with a minimum of 1 year follow-up. STUDY DESIGN/SETTING: Biomechanical studies of the spine system were performed according to American Society for Testing and Materials (ASTM) standards. To evaluate the maintenance of lordosis, radiographs from the first 119 patients were reviewed by the authors. Analysis of patient outcomes consisted of a review of the first 259 patients who underwent spinal fusion surgery with the new spine system. PATIENT SAMPLE: Evaluation of patient outcomes consisted of 122 men and 137 women with an average age of 50+/-13 years (range, 22-96 years) and a mean follow-up of 20+/-6 months (range, 12-54 months). The patient population was at high risk for fusion failure, with 127 smokers (49%), 141 who had previous spine surgery (54%), 22 with osteoporosis (8%), 63 were obese (24%), and 32 with diabetes (12%). One hundred two patients (39%) had a one-level fusion, 105 patients (41%) had two levels fused, and 52 patients (20%) had three or more levels fused. The majority of patients (66%) were covered under workers' compensation. OUTCOME MEASURES/METHODS: Radiographic fusion was deemed successful when the presence of trabecular bridging bone from transverse process to transverse process was observed, as well as no fixation failure nor radiographic evidence of screw loosening. Clinical success was rated excellent, good, fair, or poor depending on the patients pain level, function, and pain medication intake. RESULTS: Biomechanical studies of this intrasegmental fixation system have shown it to be strong under both static and fatigue testing, with exceptional strength in compression bending. In evaluating preservation of lumbar lordosis, no statistically significant loss of lordosis was observed. Overall, radiographic fusion was noted in 229 of 259 patients (88%) and did not differ significantly (p>.10) by the number of levels fused. Clinically, 69 patients (27%) had an excellent result, 111 patients (43%) had a good result, 50 patients (19%) had a fair result, and 29 patients (11%) had a poor result. The high rate of successful patient outcomes did not differ significantly (p>.10) by the number of levels fused, or other patient or surgical variables, except for the satisfaction level of workers' compensation versus nonworkers' compensation. One hundred of 118 patients (85%) who were working before surgery returned to work at an average 9+/-4 months postoperatively (range, 2-20 months). The use of direct current (DC) stimulation in this population was reserved for patients with one or more risk factors for fusion failure and was noted to be of benefit. There were no recorded intraoperative complications, but postoperatively 5 device and 19 non-device-related complications (9%) were noted, which is comparable to other lumbar fusion series. CONCLUSIONS: The results of these analyses show consistent patient outcomes regardless of the number of levels fused with an intrasegmental system. This may be attributable to the increased biomechanical strength of the system at each segment, coupled with the ability of intrasegmental fixation to maintain sagittal plane balance through preservation of the patient's lordotic curve.

Adult↗
PubMed1989

Changes in the pharyngeal airway in relation to extension of the head.

In a sample of 20 adults the associations between cervical lordosis, craniocervical inclination, position of the hyoid bone and cross-sectional dimensions of the pharyngeal airway were studied. Lateral skull radiographs were obtained in natural head posture and also at 20 degrees extension with the subjects' teeth in the intercuspal position. Cervical lordosis was measured from the second to the sixth vertebra and the position of the hyoid bone was calculated in horizontal and vertical directions. The dimensions of the free airway were measured between the dorsal tongue surface and the posterior pharyngeal wall and at the level of the second and fourth vertebra. A change from natural head posture to 20 degrees extension resulted in an increase in cervical lordosis and craniocervical inclination, changed position of the hyoid bone and increased cross-sectional dimensions of the pharyngeal airway. The changes in lordosis produced by changing natural head posture to 20 degrees extension showed significant correlations with the size of changed craniocervical inclination and free airway.

Adult↗
PubMed1996

Overpowering the crankshaft mechanism. The effect of posterior spinal fusion with and without stiff transpedicular fixation on anterior spinal column growth in immature canines.

STUDY DESIGN: This experimental study was designed to test the hypothesis that posterior spinal fusion and internal fixation, using a stiff transpedicular construct, would withstand additional anterior column growth without the need for an anterior procedure and would prevent the development of deformity secondary to asymmetric growth of the anterior column in the immature canine model. OBJECTIVES: This model revealed that a mechanical epiphysiodesis of the anterior spinal column can be created through a posterior approach in an immature growing animal using a stiff transpedicular construct. These results were correlated to the crankshaft mechanism clinically to provide a possible rationale for transpedicular posterior spinal instrumentation and fusion, without a concomitant anterior procedure, in immature patients. SUMMARY OF BACKGROUND DATA: All operative immature canines underwent posterior fusion of L1-L5 vertebral bodies with autogenous iliac crest bone graft. Instrumented canines underwent the additional placement of transpedicular screws at L1, L3, and L5 as well as 3/16-inch rods and a transverse connector. Previous studies have revealed that continued anterior spinal column growth after posterior arthrodesis causes a resultant deformity in quadrupeds. No previous study has assessed whether a transpedicular construct can overpower the anterior spinal growth plate in an immature growing model. METHODS: Twenty-five skeletally immature canines were randomized into four groups: control, fusion only, screw and fusion, and instrumentation and fusion. Disc space growth, vertebral body growth, and sagittal plane angulation were the variables analyzed. Management response variables were visualized graphically and radiographically. RESULTS: Posterior tethering and anterior column growth occurred in the noninstrumented fusion groups, producing substantial lordosis. Anterior column growth was arrested in the instrumented canines as demonstrated by decreased vertebral body length, disc space narrowing, and, most importantly, prevention of lordosis. CONCLUSIONS: The present study confirmed that in immature canines anterior column growth continues after posterior fusion without instrumentation. The magnitude of this growth, combined with a posterior tether, is sufficient to cause significant lordosis. The results are the first to document that a stiff posterior spinal instrumentation system is sufficient to overpower the residual anterior growth centers, even in the presence of a posterior tether (fusion mass). This technique creates a mechanical epiphysiodesis evidenced by arresting vertebral body length, narrowing disc space, and preventing lordosis, thus thwarting the deformity-producing mechanism without an additional anterior procedure.

Age Factors↗