摘要:

Study DesignIn vitrobiomechanical testing was performed using a simulated vertebral body bone graft instrumented with strain gauges. Strains were recorded from various locations on the graft during axial compressive loading. Comparisons were made of the strain patterns recorded before and after application of two different anterior plates.ObjectivesTo quantify the changes in axial compression experienced by the strut graft in the presence of an anterior plate.Summary of Background DataThe use of anterior instrumentation to augment anterior thoracolumbar grafting offers the potential advantage of saving additional motion segments while being performed in a single-stage surgery. Several biomechanical studies have compared the anteriorly grafted and instrumented spine to the compressive axial stiffness and torsional rigidity of the intact spine. No previous study has addressed the loading patterns experienced by the graft before and after plating.MethodsAnterior spinal plates of two designs (Amset ALPS Anterior Locking Plate System; AMS, Hayward, California; Anterior Thoracolumbar Locking Plate System; Synthes Spine, Paoli, Pennsylvania) were evaluated to determine the axial compressive forces experienced by the bone graft before and after application of the plates. Bovine spines harvested from 8- to 12-week-old calves were used for testing. All plates were tested in axial compression to 500 N. Simultaneous recordings were made of the axial strains on the simulated bone graft and the load applied to the construct. Comparisons were made of the strain through the graft without any instrumentation (graft alone, or baseline), with the plate applied, and after removal of the caudal screws (dynamization).ResultsWith the application of the ALPS plate, the compressive strain through the graft adjacent to the plate averaged 77% of the graft alone construct (range, 39% to 158%). After application of the Synthes plate, the compressive strain through the graft adjacent to the plate averaged 34% of the graft alone construct (range, -14% to 97%). Once the caudal screws were removed, the dynamized construct allowed near-baseline compression through the graft.ConclusionsAlthough the literature indicates that the anteriorly instrumented spine may restore the overall spinal structure to near-normal resistance to rotation and flexion forces, the current study demonstrates that a significant amount of compression through the graft is lost by its application. This decreased axial loading further supports the concept of device-related osteopenia observed clinically with such devices.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignThe stiffness of the hemipelvis during simulated physiologic loading and the bone deformation in the remaining posterior ilium after the harvest of increasing sizes of corticospongious bone graft were compared with values in intact bone.ObjectivesTo quantify the biomechanical effects of the removal of bone grafts from the posterior ilium and to relate the size of graft removed to the stiffness of the hemipelvis and deformation of the remaining bone.Summary of Background DataBone fractures and pelvic instability have been reported to complicate graft harvest from the posterior iliac crest. There is no quantitative data relating graft size to the mechanical properties of the remaining ilium.MethodsSeven cadaveric hemipelves were loaded with a materials testing machine through the superior sacrum while supported at the acetabulum and stabilized with a cable fixed to the ilium. Force and displacement histories and deformation in the greater sciatic notch were recorded for the intact bone and after removal of corticospongious bone graft in 1.5-cm increments from the posterior iliac crest.ResultsIf the length of the removed corticospongious bone graft exceeded 3.0 cm, the stiffness of the posterior pelvic ring decreased, and deformation in the remaining bone increased substantially.ConclusionsRemoval of bone graft in excess of 3 cm from the posterior ilium increases the risk of iatrogenic fatigue fracture.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignAn axial rotation tester was designed and fabricated for the study. This allowed stabilization of seated subjects (hip down) and coupling of shoulders, permitting axial rotation and coupled lateral flexion. Using this device, a “flexion-extension free” axial rotation was executed for studying its characteristics.ObjectivesTo determine the mechanism of initiation, sustenance, and execution of axial rotation. This was planned to be done by determining the phasic relationship of various torso muscles in the initiation, execution, and termination of axial rotation. Another objective was to determine the total and relative contribution of torso muscles in axial rotation and the small segments of these activities.Summary of Background DataThere only are a few studies conducted on axial rotation. Generally, these have investigated isometric maximal voluntary contraction in neutral or prerotated postures. The two studies that have reported isokinetic axial rotation have investigated maximal efforts. No study in literature has reported initiation, termination, and execution of unresisted normal velocity axial rotation.MethodsFifty healthy young subjects executed a full cycle of axial rotation, starting from neutral position to their extreme left, continuing to their extreme right, and finally moving to the neutral posture in one smooth motion without stopping anywhere. The electromyographic results of external obliques, internal obliques, rectus abdominis, pectoralis major, erectores spinae at T10and L3, and latissimus dorsi were measured bilaterally simultaneously during this trunk rotation. The timing and relative magnitude analyses were done to determine the global and individual muscle contributions in axial rotation. The correlation between electromyographic and angular displacement, and nonlinear curve fitting regression analyses were performed to decipher individual muscles behavior.ResultsThe pattern of muscle activation was variable. However, contralateral external obliques, ipsilateral erector spinae, and latissimus dorsi became active before other muscles. These were agonists and the others were antagonists or stabilizers. The agonists contributed 65% of the total electromyographic output, whereas antagonists and stabilizers contributed 35%. The muscle activities during onset and offset periods were biphasic with significantly different slopes.ConclusionsIt was concluded that the axial rotation is achieved through the activities of agonists, and return to neutral position is because of elastic recoil controlled by agonistic muscles. A range of approximately 10-15° on either side of the anatomical midsagittal plane involves little muscle effort, but beyond this region, the osteoligamentous structures become stiff and require increasing effort to execute axial rotation.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignThe authors investigated the positions of dorsal root ganglia and the relation of the location to symptoms and to the effects of nerve root infiltration in the cervical spine anatomically and clinically.ObjectivesTo clarify normal variation of positions of dorsal root ganglia and the relation of the location of dorsal root ganglia to symptoms and to the effects of nerve root infiltration.Summary of Background DataThe dorsal root ganglia of the spinal nerve has attracted much attention as an important structure in the mechanisms of radicular symptoms in the lumbar spine. Although the position of the dorsal root ganglia in the lumbar spine has been classified recently, there are few reports regarding the dorsal root ganglia in the cervical spine.MethodsThe positions of dorsal root ganglia were divided into two types: proximally situated and distally situated. The positions of dorsal root ganglia in the anatomic and clinical cases were compared. The relation of the positions of dorsal root ganglia to symptoms and to the clinical effects of nerve root infiltration were analyzed.ResultsThere was no statistically significant difference in positions of dorsal root ganglia in C6 nerve roots between anatomic and clinical cases. In addition, there was no relation between symptoms and the positions of dorsal root ganglia in clinical cases. However, there was a significant difference in positions of dorsal root ganglia in C7 nerve roots between anatomic and clinical cases. Nerve root infiltration was significantly more effective in the distally situated type of dorsal root ganglia.ConclusionsThis study defined the normal variation of the positions of dorsal root ganglia. The results strongly suggest that some attention should be paid to the position of dorsal root ganglia in the diagnosis and treatment of cervical radiculopathy.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignData were obtained in a Danish cross-sectional postal survey and compared with information from four methodologically similar studies conducted in some of the Nordic countries between 1977-1985.ObjectivesThe objectives were to estimate the life-time cumulative incidence and the 1-year period prevalence of low back pain in the general population, to study whether there are any differences in the occurrence of low back pain according to age and sex, and to investigate whether low back pain is on the increase.Summary of Background DataThe prevalence of low back pain commonly is thought to be high, but estimates differ considerably between studies. It is also not known whether low back pain is more common in men or women or in certain age groups, and it is unclear whether the prevalence of low back pain has increased in the past years.MethodsPrevalence estimates were established in a current study, and results then were adjusted to suit the age and sex criteria of four previous studies.ResultsBetween 60-65% of 30- to 50-year-old men and women living in the Nordic countries reported at least one incident of low back pain during their lifetime, based on the information from four studies with a total sample size of 3513. The most likely 1-year period prevalence estimate is between 44-54%, based on two studies and a total sample of 2035 individuals. There was no consistent evidence favoring higher figures with increasing age or relating to any of the genders. No clearly observed time-related trend was noted.ConclusionsWhen data were examined from five methodologically similar studies on the 30- to 50-year-old Nordic population, there was reasonable consistency of prevalence figures. Thus, approximately 66% report having had low back pain at least sometime during their lifetime and approximately 50% sometime during the preceding year, with no significant differences relating to age or sex. The best method to investigate whether low back pain is on the increase might be through replicate studies.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignThis case-control study was undertaken to determine if relatives of patients who had been admitted for surgery for degenerative disc disease-related problems were at increased risk for lower back pain or sciatica.ObjectivesTo determine if familial factors play a role in placing a person at risk for development of degenerative disc disease of the lumbar spine.Summary of Background DataIt is known that smoking and various occupational factors can place a person at risk for degenerative disc disease problems. It is not known if a familial predisposition may also exist.MethodsThe family members and relatives of 65 patients who had undergone surgery for lumbar degenerative disc disease were interviewed with a standardized questionnaire and compared with a control group of 67 patients who had been admitted to hospital for non-spine-related orthopedic procedures. The same interview and standardized questionnaire was used for both groups by a single observer.ResultsIn the study group of 65 patients who had undergone surgery for degenerative disc disease, 44.6% were noted to have a positive family history, whereas 25.4% of the patients in the control group had a positive family history. Eighteen and one-half percent of relatives in the study group had a history of having spinal surgery, compared with only 4.5% of the control group.ConclusionsThe results indicate that a familial predisposition to degenerative disc disease can exist along with other risk factors.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignSixty radiographs were measured on two separate occasions by three physicians using four different techniques to evaluate the reliability and reproducibility of the measurement of lumbar lordosis.ObjectiveTo evaluate clinical methods of measuring lumbar lordosis, determining intraobserver and interobserver reliability.Summary of Background DataSeveral different methods are used to measure lumbar lordosis. The reliability and reproducibility of these has not been well studied.MethodsSixty lateral full spine radiographs were obtained, labeled, and the lumbar lordosis measured independently by three practitioners who routinely perform these measurements. Four measurement techniques were used. These included measurements from the inferior endplate of T12 to the superior endplate of S1; the superior endplate of L1 to the superior endplate of S1; the inferior endplate of T12 to the inferior endplate of L5; and the superior endplate of L1 to the inferior endplate of L5. The measurements then were repeated after relabeling.ResultsIntraobserver reliability coefficients ranged from 0.83 to 0.92, indicating excellent reproducibility. Ninety-two percent of repeat measures were within 10°. High overall and pairwise agreement among the three observers also was present; the interobserver reliability coefficients ranged from 0.81 to 0.92.ConclusionsThe measurement of lumbar lordosis is reproducible and reliable if the technique is specified and one accepts 10° as acceptable variation. Factors that affect the reproducibility of measurement include end vertebra selection (especially with transitional segments) and vertebral endplate architecture.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignThis study was a retrospective anatomic correlation of intervertebral disc dimensions with current surgical guidelines.ObjectivesTo develop safer guidelines for disc instrumentation.Summary of Background DataAnterior perforation of the anulus fibrosus and injury to intra-abdominal structures is a known complication of lumbar discectomy. Coplanar magnetic resonance imaging of the lumbar intervertebral discs could decrease the rate of complication using axial T1-weighted scans.MethodsThree measurements through the intervertebral discs of the lumbar spine were taken in 50 patients. These were correlated with current surgical guidelines for lumbar instrumentation.ResultsMost of the measurements exceeded the current suggested guidelines for instrumentation at 3 cm.ConclusionsCurrent guidelines for introduction of instruments into the lumbar disc spaces should be reevaluated. Appropriate measurements should be made on an individual basis.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Study DesignData from a retrospective cohort study of people with adolescent idiopathic scoliosis were combined with information on full-spinal radiographs to estimate contemporary x-ray doses and lifetime risks for development of cancer.ObjectivesTo project the lifetime risk for development of cancer from diagnostic radiographs for people with adolescent idiopathic scoliosis.Summary of Background DataAlthough a twofold excess risk for breast cancer has been reported for women treated for scoliosis between 1925 and 1965, information on the cancer risks associated with scoliosis management today is sparse. Specifically, there is a lack of up-to-date information on the number of spinal radiographs taken, the organ-specific x-ray doses from current radiographic techniques, and the projected cancer risks.MethodsThe cohort consisted of subjects with adolescent idiopathic scoliosis who were referred to the scoliosis clinic of a large pediatric hospital between 1965 and 1979 in Montreal, Quebec, Canada. Based on radiographic equipment and practices implemented in 1982, organ-specific x-ray doses to the thyroid gland, female breast, respiratory organs, digestive organs, and bone marrow were calculated using Monte Carlo methods. These doses were incorporated into a life table procedure to calculate theoretic lifetime cancer risks. For all organs except the thyroid gland, dose-response models from the United States National Academy of Sciences Fifth Committee on the Biological Effects of lonizing Radiation were used. For thyroid cancer, a risk model was derived from a study of thyroid cancer incidence after x-ray treatment for tinea capitis.ResultsThe average number of spinal radiographs was 12 for women (80% anteroposterior or posteroanterior) and 10 for men (78% anteroposterior or posteroanterior). Cumulative x-ray doses were in general higher in adolescents who were referred as younger teenagers than at later ages, and doses increased with the size of the spinal curve. Depending on the age at referral and curve size, the total excess lifetime cancer risks were calculated to range from 42 to 238 cases per 100,000 women and 14 to 79 cases per 100,000 men. For subjects who underwent surgery (those exposed to the highest doses), the lifetime number of cancer cases over and above background was almost as great as the number of thyroid cancers that would occur in the absence of radiation exposure. If the anteroposterior view was replaced by the posteroanterior view, a three- to sevenfold reduction in cumulative doses to the thyroid gland and the female breast would be achieved, yielding three- to fourfold reductions in the lifetime risk of breast cancer and a halving of the lifetime risk of thyroid cancer.ConclusionsThe cancer risks from full-spinal radiographs for scoliosis are not negligible and can be reduced from one half to three quarters if the anteroposterior view is replaced with the posteroanterior view.

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0362-2436    

出版商:OVID    

年代:1996

数据来源: OVID