Examining the effects of prenatal alcohol exposure on performance of the sustained attention to response task in children with an FASD.

Prenatal alcohol exposure (PAE), the leading known cause of childhood developmental disability, has long-lasting effects extending throughout the lifespan. It is well documented that children prenatally exposed to alcohol have difficulties inhibiting behavior and sustaining attention. Thus, the Sustained Attention to Response Task (SART), a Go/No-go paradigm, is especially well suited to assess the behavioral and neural functioning characteristics of children with PAE. In this study, we utilized neuropsychological assessment, parent/guardian questionnaires, and magnetoencephalography during SART random and fixed orders to assess characteristics of children 8-12 years old prenatally exposed to alcohol compared to typically developing children. Compared to neurotypical control children, children with a Fetal Alcohol Spectrum Disorder (FASD) diagnosis had significantly decreased performance on neuropsychological measures, had deficiencies in task-based performance, were rated as having increased Attention-Deficit/Hyperactivity Disorder (ADHD) behaviors and as having lower cognitive functioning by their caretakers, and had decreased peak amplitudes in Broadmann's Area 44 (BA44) during SART. Further, MEG peak amplitude in BA44 was found to be significantly associated with neuropsychological test results, parent/guardian questionnaires, and task-based performance such that decreased amplitude was associated with poorer performance. In exploratory analyses, we also found significant correlations between total cortical volume and MEG peak amplitude indicating that the reduced amplitude is likely related in part to reduced overall brain volume often reported in children with PAE. These findings show that children 8-12 years old with an FASD diagnosis have decreased amplitudes in BA44 during SART random order, and that these deficits are associated with multiple behavioral measures.

[Assessment of Work Engagement in Patients with Hematological Malignancies: Psychometric Properties of the German Version of the Utrecht Work Engagement Scale 9 (UWES-9)]. / Erfassung von Arbeitsengagement bei Patienten mit hämatologischen Malignomen: Die psychometrischen Eigenschaften der deutschen Version der Utrecht Work Engagement Scale 9 (UWES-9).

OBJECTIVE: Our purpose was the psychometric evaluation of the German version of the Utrecht Work Engagement Scale-9 (UWES-9), a self-assessment tool measuring work-related resources consisting of 9 items. METHODS: Based on a sample of 179 patients with hematological malignancies in in-patient and rehabilitative oncological settings, we tested the dimensional structure by confirmatory and explorative factor analysis. We further evaluated reliability, item characteristics, and construct validity of the UWES-9. RESULTS: The confirmatory factor analysis showed acceptable fit for both a 1-dimensional factor structure and the original 3-factor model. Based on an explorative principal component analysis, we were able to replicate the 1-dimensional factor accounting for 67% of the total variance and showing very high internal consistency (α=0.94) and high factor loads (0.73-0.88). The construct validity was further supported by significant positive correlations between work engagement and meaning of work, corporate feeling, commitment to the workplace, and job satisfaction. CONCLUSION: The German version of the UWES-9 shows good psychometric qualities in measuring dedication to work in patients with hematological malignancies in in-patient and rehabilitative oncological settings.

Pressure load-sensing assessments of the right ventricular outflow tract and main pulmonary artery.

Surgical repairs for congenital right ventricular outflow tract disease have commonly required multiple procedures because of hemodynamic failures from previous operations. Over the past decade, the percutaneous placement of stented valve prostheses in a failed right ventricular outflow tract conduit to restore acceptable pulmonary valve function has produced acceptable results; however, the incidence of stent fractures post-implantation in these stented valve prostheses has aroused concerns. In order to investigate this problem, sequential, pressure load-sensing assessments throughout the right ventricular outflow tract and into the main pulmonary artery would be required to effectively evaluate the degree of physiological loading along these sites. Customarily, to perform these assessments, multiple cardiopulmonary bypass procedures, as well as multiple pulmonary arteriotomies would be required, both of which carry their own risks. Owing to these risks, we developed a successful surgical technique for sequential load-sensing evaluations throughout the right ventricular outflow tract and main pulmonary artery using a single cardiopulmonary bypass session and one pulmonary arteriotomy. This technique successfully provided a means to prevent multiple arteriotomies and bypass sessions without complications while obtaining reproducible data in evaluating pressure load-sensing states throughout the right ventricular outflow tract and main pulmonary artery in adult sheep.

[Therapeutic application of mesenchymal stromal cells in autoimmune disease: rationale and initial clinical experience]. / Therapeutische Anwendung mesenchymaler Stromazellen bei Autoimmunerkrankungen: Rationale und erste klinische Erfahrungen.

Mesenchymal stromal cells (MSC) are characterized by their proliferative capacity, their phenotype and their ability to multipotent differentiation. However, little is known about their function and characteristics in vivo. MSC posses a tropism for injured tissues. Numerous investigations of MSC in different model systems suggest an immunosuppressive potential, although the results are in part contradictory. Apparently, MSC exert these effects on nearly all cells in the immune system. However, the relevance and mechanisms of these phenomena in vivo are not clear. The clinical effectiveness of allogeneic MSC in the treatment of refractory graft-versus-host disease has raised hopes that MSC could offer a new concept for the therapy of other immune-mediated disorders. However, before MSC are introduced in clinical practise, several important questions as to their side effects have to be addressed. This includes the possibility that MSC may contribute to the induction of malignant diseases.

Quantification of active caspase 3 in apoptotic cells.

We describe an enzyme-linked immunosorbent assay (ELISA) for quantifying relative amounts of active caspase 3 in apoptotic cells. Covalent modification of caspase 3 active sites with a biotinylated inhibitor differentiates active from latent caspases. Capture on an ELISA plate with an antibody specific for caspase 3 makes the assay specific for caspase 3. Detection is with horseradish peroxidase (HRP)-conjugated streptavidin that binds to the biotinylated inhibitor covalently bound to caspase 3. Using the assay we detected 6.6 ng active caspase 3 per 10(6) apoptotic staurosporine-treated Jurkat cells. Specificity of the assay for caspase 3 was demonstrated by lack of signal with purified caspases 2, 7, 8, and 10 that were modified by a biotinylated inhibitor. Specificity was also demonstrated by lack of signal with apoptotic MCF-7 cells which do not express caspase 3. The ability to discriminate between active and latent caspase 3 was shown by Western blotting with HRP-streptavidin and anti-caspase 3. Although latent caspase 3 was captured it was not covalently modified with the biotinylated inhibitor. The basic principle of using a covalent inhibitor to identify active enzymes and an antibody to differentiate between enzymes with similar activities has potential for quantifying active members of many classes of enzymes.

Quantitative analysis of discontinuous EEG in premature and full-term newborns during quiet sleep.

To assess the spatio-temporal structure of discontinuous EEG tracing in mature and immature newborns, we analysed mean spectral power in frequency bands between 0.8 and 16.8 Hz in 6 full-term newborns and 7 premature newborns < 32 weeks of conceptional age. The most striking results showed a significantly higher mean spectral power for the first half of bursts than for the second half recorded in > 2.8-14.8 Hz frequency bands. This pattern was more pronounced in premature than in full-term newborns. No clear differences were observed in comparisons between the first and the second half of the interburst periods. In addition, as far as mid and high frequency band spectra were considered, the mean spectral power of burst was, in both groups, higher in the right as compared to the left occipital regions.

The natural history of asymptomatic thoracic disc herniations.

STUDY DESIGN: Magnetic resonance imaging was used to determine the natural history of asymptomatic thoracic disc herniations. OBJECTIVES: To determine whether thoracic disc herniations change in size over time. SUMMARY OF BACKGROUND DATA: Based on previous work by the authors of the present study, the incidence of asymptomatic thoracic disc herniations is approximately 37%. The natural history of thoracic disc herniations is unknown. The natural history of lumbar and cervical disc herniations in symptomatic individuals who become asymptomatic has been shown in multiple studies frequently to result in a decrease in size of the herniation. METHODS: Twenty patients with 48 asymptomatic thoracic herniations previously diagnosed with magnetic resonance imaging underwent repeat magnetic resonance imaging using sagittal T1-weighted spine echo and axial multiplanar gradient refocused images at each thoracic disc level from T1 to T12 for a mean follow-up period of 26 months. Midsagittal canal diameter was recorded, and disc herniation square area was measured using a computer-assisted digitizing program. Disc herniations were categorized according to percentage of canal compromise. The change in size of the disc herniations over time was analyzed. RESULTS: All patients remained asymptomatic during the follow-up period. A total of 48 disc herniations were identified from the original magnetic resonance images. There were 21 small (0-10% canal compromise) disc herniations, 20 medium (> 10-20%) disc herniations, and seven large (> 20%) disc herniations. Of the 21 small disc herniations, 18 showed no significant change in size, whereas three showed a measurable increase in size. Of the 20 medium-sized disc herniations, 16 showed either a small or no change in size, one showed a significant increase in size, and three showed a significant decrease in size. Of the seven large disc herniations, three demonstrated no change in size, and four demonstrated a significant decrease in size. In addition, five new disc herniations were detected in four patients; one was small, and four were moderate in size. CONCLUSIONS: Based on the results of this study, the authors believe that asymptomatic disc herniations may well exist in a state of relative flux, yet exhibit little change in size and remain asymptomatic. There was a trend, however, for small disc herniations either to remain unchanged or increase in size and for large disc herniations often to decrease in size.

Rotational changes of the vertebral pelvic axis after sublaminar instrumentation in adolescent idiopathic scoliosis.

STUDY DESIGN: The authors studied the rotational effect of sublaminar wiring on the spinal pelvic axis on 20 patients who were being treated for adolescent idiopathic scoliosis. OBJECTIVES: To determine if sublaminar wiring effectively derotates the scoliotic spine. SUMMARY OF BACKGROUND DATA: The correction of the rotational deformity in adolescent scoliosis via sublaminar wiring is not well quantified in the literature. The derotation maneuver of Cotrel-Dubousset has been shown to produce variable and unpredictable amounts of axial derotation. METHODS: Twenty patients who underwent posterior spine fusion for adolescent idiopathic scoliosis were evaluated using computed tomography scans and plain radiography before and after surgery and at a subsequent follow-up examination (average time of follow-up examination, 35 months after surgery). The degree of angle of vertebral rotation about the sagittal plane and that relative to the pelvis were measured before and after surgery and at a follow-up examination. RESULTS: The primary thoracic curves were not derotated significantly relative to the pelvis with sublaminar wiring. Primary thoracolumbar curves instrumented on the convexity with pedicle screws were derotated significantly relative to the pelvis (P = .001). The average initial correction was 57%. On final follow-up examination, the correction was 24% (18 of 20 twenty individuals lost axial correction by an average of 34%). In nine of 20 patients the spine was more rotated, relative to the pelvis, than it had been before surgery. No coronal or sagittal decompensation was seen in any curve type. CONCLUSIONS: Coronal and sagittal plane correction of scoliotic curves may be achieved with sublaminar instrumentation. The ability to derotate axially the scoliotic spine appears to be variable, however, and, in most cases, curve-type dependent. Over time, much correction appears to be lost, and in many patients the scoliosis actually becomes worse than it was before surgery. Nonetheless, the apical derotation that takes place appears to be reasonably true: the percent correction of angle of rotation about the sagittal plane and the percent correction of angle of rotation about the sagittal plain relative to the pelvis were closely correlated. Derotation forces applied to the instrumented spine do not appear to be transmitted to more distal segments.

Magnetic resonance imaging and biological changes in injured intervertebral discs under normal and increased mechanical demands.

STUDY DESIGN: An animal model was used to examine the short-term tissue response to changes in the mechanical environment after the structure (disc) is mechanically injured. OBJECTIVES: To observe changes in an injured intervertebral disc and the corresponding motion segment when the mechanical demands of the disc were increased by fusion of the adjacent motion segments. SUMMARY OF BACKGROUND DATA: Disc degeneration has been modeled in animals by producing a tear in the anulus via laminectomy, laparotomy, or posterolaterally. Methods of altering and quantifying the mechanics of the intervertebral joint by use of internal fixation and fusion in the canine have been developed. METHODS: Eight dogs divided into two groups (a study and a control group) had anular stab wounds (L2-L3). The study group was surgically instrumented posteriorly from L3 to L7. Magnetic resonance imaging studies were conducted for all animals before and periodically after the surgical procedures. At the end of the study, the segments were processed histologically and biochemically. RESULTS: Anular bulging was seen on magnetic resonance imaging in all control animals 4 months after injury and did not progress out until 6 months after injury. Similar changes were seen in study animals, but 75% were herniated by 6 months. Histologic changes correlated with magnetic resonance imaging changes. No significant difference in water or proteoglycan content of the disc tissue between groups was found. CONCLUSIONS: Progression from the bulging of the anulus to herniation was not evident in damaged discs not subjected to adjacent fusions. No change in water or proteoglycan content as a function of altered mechanical state was found, suggesting the short-term effect of the altered mechanics is on the mechanical structure and not on the cells or extracellular matrix.

Effect of sacral and iliac instrumentation on strains in the pelvis. A biomechanical study.

STUDY DESIGN: This study is a biomechanical study on human cadaver pelves using strain gauges to measure strains at different locations in response to different load states. OBJECTIVES: To examine the changes in strains, at different sites on the pelvis, and after instrumentation of the lumbosacral joint and the lumbosacroiliac joint. SUMMARY OF BACKGROUND DATA: Pelvic girdle pain after long instrumented fusions to the sacrum has been described and studied along with sacroiliac and pubic instability. Fractures of the pelvic rami or the iliac wing have been reported in patients after surgical fusions that incorporated the sacrum and sacroiliac joint. METHODS: Pelves with lumbar spine attached had three axis rosette strain gauges cemented to specific sites on the pelves (ilium [correction of ileum] and rami). Specimens were tested in different configurations involving lumbosacral and sacroiliac instrumentation. Iliac bone harvest was also tested. Strain values were computed and compared for each configuration. RESULTS: The "Galveston" and "sacral" instrumentation configurations caused significant stress shielding in pelves under all compression loads applied. Axial rotations on the instrumented specimens caused higher strains at all sites. Harvesting of bone from the ilium did not alter the strains seen at the different sites. CONCLUSIONS: This study suggests significant stress shielding provided by sacro and sacroiliac instrumentation systems, supporting the possibility of development of device-related osteopenia that may predispose patients to late, insufficiency-type fractures as their activity increases. The rigid instrumentation of the lumbosacral spine was found to increase the stress during torsion, which may lead to failure during activity.

Effect of patient position on the sagittal-plane profile of the thoracolumbar spine.

Although the normal sagittal profile of the thoracolumbar spine has been described, this has been obtained primarily by using young individuals standing. We sought to describe the sagittal profile of the thoracolumbar spine in an older population in the supine cross-table lateral position compared with that standing. We enrolled 50 volunteers with no history of back pain or spine deformity and 50 matched subjects with mechanical back pain (LBP) only. Lateral radiographs of the thoracolumbar spine (T10-S1) in both standing and cross-table supine positions were obtained. Lordosis from L1 to S1, kyphosis from T10 to L1, and the changes seen moving from the supine position to standing were calculated. There were few differences comparing the two groups in either the standing or cross-table supine position, or when changing positions. Within each group, however, there were small, but significant, differences in the midlumbar and thoracolumbar spine when comparing supine versus standing. Both asymptomatic individuals and those with a history of LBP demonstrated similar small but statistically significant increases in lumbar lordosis and thoracolumbar kyphosis when standing versus supine. The clinical significance of these findings remains to be determined.

Thoracic volume changes in scoliosis surgery.

STUDY DESIGN: Eighteen patients with adolescent idiopathic scoliosis treated with ISOLA instrumentation and 13 treated with Cotrel-Dubousset instrumentation were studied before and after surgery with computed tomography scans. OBJECTIVES: To analyze and compare the immediate change in chest volume of patients treated with the derotation method of Cotrel-Dubousset versus the sublaminar wire translational technique of ISOLA. SUMMARY OF BACKGROUND DATA: Previous literature suggests a small but variable improvement in pulmonary function with the use of Harrington instrumentation when treating adolescent idiopathic scoliosis. The effect of modern instrumentation techniques on chest volume and ultimately pulmonary function has not been determined. METHODS: An axial computed tomography slice was made through each vertebral body from T3 to T10. Using a technique of spine curve measurements, the cross-sectional area at each level was computed, and from the height measured, the volume of the thoracic cage was computed. RESULTS: Single thoracic curves (King-Moe Type III) managed with ISOLA sublaminar instrumentation showed a statistically significant increase in chest volume when compared with other curve types and when compared with all curves managed with Cotrel-Dubousset. Seventeen of 18 patients treated with ISOLA instrumentation gained chest volume, whereas half of those treated with Cotrel-Dubousset actually lost volume. CONCLUSIONS: ISOLA instrumentation and sublaminar wiring appears to increase the chest volume in patients with adolescent idiopathic scoliosis. Its clinical significance remains to be determined.

Kinematics of the canine lumbar intervertebral joint. An in vivo study before and after adjacent instrumentation.

STUDY DESIGN: In vivo, canine lumbar spine intervertebral motion was measured before and after instrumentation of caudal segments. The three-dimensional kinematics of the intervertebral joint were described using helical axes and Fourier series. OBJECTIVE: The in vivo three-dimensional kinematics of the intervertebral joint were measured and described. An animal model where intervertebral motion could be repeatedly changed was developed. SUMMARY OF BACKGROUND DATA: The kinematics of intervertebral joints have been described from results of extensive in vitro testing, some limited in vivo testing, and clinically by evaluation of flexion/extension films. In the canine, in vivo intervertebral motion has been described previously, but the method possessed some measurement artifact. METHODS: In vivo, four canines had motion data collected (L2-L3) while the animals walked on a treadmill. L3 To L7 were instrumented in all of the animals and motion testing was repeated 1 and 12 weeks later. Helical axes of motion were determined for each gait cycle. Fourier series were fit to the motion data, helical axis parameters, and Fourier coefficients were all statistically compared (pre- and postinstrumentation). RESULTS: Vertebral rotations (coronal plane) and excursion of the L2/3 facet increased significantly (P < 0.01) after caudal instrumentation. Helical axes were oriented in a ventral direction and only the angle of rotation about the axis changed significantly (P < 0.05) after instrumentation of caudal segments. The Fourier coefficients (amplitudes) showed a significant (P < 0.05) increase in the coronal plane rotations only, after adjacent instrumentation. CONCLUSION: The in vivo kinematics of the intervertebral joint have been completely defined in this study. Some motion characteristics compare very well to human motion. Since motion at an intervertebral joint now can be repeatedly altered, this animal model shows promise as a useful tool for investigation of tissue response to changes in motion at a joint.

An improved technique for measuring in vivo intervertebral motion in the canine.

STUDY DESIGN: An experimental animal study using an established technique for measuring in vivo motion in canines was designed to improve measurement techniques and to eliminate the effects of the instrument mounting technique on the tissue and subsequently on the motion being measured. OBJECTIVES: The purpose of this study was to improve a technique for measuring in vivo intervertebral motion in canines, so that the measuring technique did not affect the motion being measured. SUMMARY OF BACKGROUND DATA: Biplanar radiography has been used to measure in vivo intervertebral motion, but involves radiation exposure and expensive equipment. Electromechanical devices have been used more recently but have had significant effects on the motion over extended time periods. METHODS: Intervertebral motion was measured using an instrumented spatial linkage in eight adult canines divided into two groups that differed regarding the method of "mounting pin" placement. Group I had open surgical placement of the pins and Group II had pins placed into the spinous processes. After pin implantation, the instrumented spatial linkage was attached and motion data were recorded during walking. This testing sequence was repeated 3 weeks later. Animals were killed and intervertebral and facet motion were calculated from the experimental data and compared statistically. RESULTS: Facet motion decreased 1 to 3 weeks after pin implantation for animals of group I (3.4 +/- 0.2 mm to 1.1 +/- 0.3 mm), whereas the facet excursion of animals in Group II showed no change (3.0 +/- 0.2 mm and 3.1 +/- 0.3 mm). CONCLUSIONS: A new method of measuring in vivo intervertebral motion in canines has been developed and shown to have no significant affect on the segment mechanics.

Biomechanical analysis of facet and graft loading in a Smith-Robinson type cervical spine model.

OBJECTIVE: This study determined the effect of change in graft height on the forces across a Smith-Robinson graft as well as across the posterior elements of the same motion segment. STUDY DESIGN: The study utilizes a strain gauge technique for the measurement of facet joint loading and a subminiature load cell for the measurement of graft loads. SUMMARY OF BACKGROUND DATA: A number of cases of Smith-Robinson procedures have had some form of collapse of the interspace and graft material after surgery. Some patients with collapse of the graft go on to have prolonged sclerotomal-type pain or pseudarthrosis. The appropriate amount of distraction is not well defined in the literature and may affect the outcome. METHODS: Cervical spines (C5-C6) were instrumented by placing strain gauges bilaterally on the pedicles of C6 (to measure the forces across the posterior elements). A miniature load cell with matching metallic shims was used to measure the force across the graft site and to distract the segment. Forces across the posterior elements and the graft site were measured, during flexion loading, and compared as the disc space was distracted. RESULTS: The ratio of posterior element load to graft load with increasing disc space distraction significantly decreased from 1.06 +/- 0.65 (1.4 mm distraction) to 0.30 +/- .13 (4.6 mm distraction) (P < .03). The posterior element load decreased significantly after the same distraction, from 46.1 +/- 22.0 to 18.7 +/- 9.7 N/Nm (P < .05). CONCLUSIONS: In spondylotic specimens (4-5 mm disc heights) disc space distraction in excess of 3.0 mm from preoperative height caused a significant decrease in both the ratio of posterior element to graft loading and posterior element loads. These findings may help explain recent clinical reports of a limit of effective disc space distraction.

Comparison of in vivo and in vitro adjacent segment motion after lumbar fusion.

STUDY DESIGN: For in vitro studies, there is no basis for choosing a "load control study" over a "displacement control" study. This study qualitatively compared results from in vitro and in vivo tests, allowing the authors to address the experimental assumptions that in vitro testing contributes to the understanding of the in vivo condition. OBJECTIVES: To compare motion changes at segments adjacent to fusions for in vitro and in vivo tests. SUMMARY OF BACKGROUND DATA: Investigators have measured the effects of spinal fusions on the adjacent segment in a human cadaver model and found greater adjacent facet joint load after fusions. Others have found significant increases in motion and facet loads at segments adjacent to in vitro lumbosacral and long fusions, when the same range of motion was repeated before and after immobilization of lumbar segments. METHODS: L2-L3 motion was measured in vitro by an instrumented spatial linkage under load and displacement control before and after immobilization of segments (L3-L7). In vivo, L2-L3 motion was measured while animals walked on a treadmill. L3-L7 was fused and the L2-L3 motion testing was repeated. The change in in vivo adjacent segment motion was qualitatively compared with the in vitro change under "load" and "displacement" control. RESULTS: Under "load" control, in vitro facet motion did not significantly change after immobilization, whereas under "displacement" control, the facet motion significantly increased from 2.2 +/- 0.4 mm to 4.1 +/- 0.6 mm. Post-instrumentation, in vivo L2-L3 facet motion increased significantly. This change in vivo related better to the changes seen in the in vitro "displacement" control test than to the in vitro "load" control test.

Description and application of instrumented staples for measuring in vivo bone strain.

In vivo bone strain measurements using strain gages cemented to bony surfaces with cyanoacrylate polymers are limited in duration due to debonding of the gages from bone. As an alternative to the bone bonded strain gages, a technique was developed in which strain gages were first bonded to miniature staples and then the staples embedded into bone. The instrumented staples may be calibrated so that staple strain is directly proportional to bone strain. The method was first validated by comparing the staple output with cemented surface strain gages. Comparison of instrumented staples to cemented strain gages revealed only a 3% deviation from linearity during longitudinal bending; the staples were insensitive to transverse loading. The instrumented staples were then applied to the in vitro canine lumbar spine to determine L2-3 facet loads. Load testing, repeatibility of facet calibration, and validity testing of the in vitro instrumented staples were found to be comparable to that of the previous cemented strain gage techniques. In vivo facet joint application of the instrumented staples for periods of greater than 5 weeks gave load measurements comparable to our previous short-term in vivo studies obtained with cemented strain gages. The advantages of the instrumented staples are a more secure bonding to the bone, and less traumatic surgery for fixation.

Sacral screw loads in lumbosacral fixation for spinal deformity.

Fixation to the sacrum and pelvis is a problem in the operative treatment of spinal deformity. Previous testing of pedicle screws address axial pull-out strength, yet how screws are loaded in vivo remains unknown. The goals of this study were to determine the loads experienced by sacral screws when loaded as part of Cotrel-Dubousset (CD) sacral instrumentation and whether different anterior grafting methods would effect screw loads. Sacral screws were modified to become transducers capable of measuring axial and bending loads. The screw transducers were incorporated into the sacral fixation of CD instrumentation in seven calf spines. Specimens were loaded to simulate flexion. The sacral screws carried axial loads (1.1 N/[Nm of load]) and bending moments (1.1 Nm/[Nm of load]). The results suggest bending of the sacral screws may be important in their failure, and screw loading was not dependent on graft types used.

The effects of immobilization of long segments of the spine on the adjacent and distal facet force and lumbosacral motion.

Long levels of spinal instrumentation and fusion are common in surgery for spinal deformity. The effect on the remaining mobile segments is not well understood. The changes in lumbar facet loading and lumbosacral motion were evaluated as the number of immobilized levels increased. Four fresh canine cadaveric spines from T6 to sacrum were used. Lumbosacral motion was measured with an instrumented spatial linkage device, and facet loads were measured at L1, L4, and L7 using a strain gauge technique. Lumbosacral motion and facet loading were significantly increased (P < 0.05) after immobilization of proximal segments, and the amount of the increase was dependent on the number of immobilized segments (P < 0.05). This indicates that immobilization of long segments of the spine influences the remaining mobile segments by increasing the load and motion not only at the immediately adjacent segment but also at the distal segments.