Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “stability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources
PubMed2001

Merits and limitations of the mode switching rate stabilization pacing algorithms in the implantable cardioverter defibrillator.

BACKGROUND: The 7250 Jewel AF Medtronic model of ICD is the first implantable device in which both therapies for atrial arrhythmias and pacing algorithms for atrial arrhythmia prevention are available. Feasibility of that extensive atrial arrhythmia management requires correct and synergic functioning of different algorithms to control arrhythmias. METHODS AND RESULTS: The ability of the new pacing algorithms to stabilize the atrial rate following termination of treated atrial arrhythmias was evaluated in the marker channel registration of 600 spontaneously occurring episodes in 15 patients with the Jewel AF. All patients (55+/-15 years) had structural heart disease and documented atrial and ventricular arrhythmias. Dual chamber rate stabilization pacing was present in 245 (41 %) of episodes following arrhythmia termination and was a part of the mode switching operation during which pacing was provided in the dynamic DDI mode. This algorithm could function as the atrial rate stabilization pacing only when there was a slow spontaneous atrial rhythm or in presence of atrial premature beats conducted to the ventricles with a normal AV time. In case of atrial premature beats with delayed or absent conduction to the ventricles and in case of ventricular premature beats, the algorithm stabilized the ventricular rate. The rate stabilization pacing in DDI mode during sinus rhythm following atrial arrhythmia termination was often extended in time due to the device-based definition of arrhythmia termination. This was also the case in patients, in whom the DDD mode with true atrial rate stabilization algorithm was programmed. CONCLUSIONS: The rate stabilization algorithms in the Jewel AF applied after atrial arrhythmia termination provide pacing that is not based on the timing of atrial events. Only under certain circumstances the algorithm can function as atrial rate stabilization pacing. Adjustments in availability and functioning of the rate stabilization algorithms might be of benefit for the clinical performance of pacing as part of device therapy for atrial arrhythmias.

Adult↗
PubMed2005

The stability of vocational interests from early adolescence to middle adulthood: a quantitative review of longitudinal studies.

The present meta-analysis examined the stability of vocational interests from early adolescence (age 12) to middle adulthood (age 40). Stability was represented by rank-order and profile correlations. Interest stability remained unchanged during much of adolescence and increased dramatically during the college years (age 18-21.9), where it remained for the next 2 decades. Analyses of potential moderators showed that retest time interval was negatively related to interest stability and that rank-order stability was less stable than profile stability. Although cohort standings did not moderate stability, interests of the 1940s birth cohort were less stable than those of other cohorts. Furthermore, interests reflecting hands-on physical activities and self-expressive/artistic activities were more stable than scientific, social, enterprising, and clerical interests. Vocational interests showed substantial continuity over time, as evidenced by their higher longitudinal stability when compared with rank-order stability of personality traits. The findings are discussed in the context of psychosocial development.

Adolescent↗
PubMed2006

Three-month stability of delay and probability discounting measures.

Psychopharmacologists are interested in delay and probability discounting because the tendency to discount the value of future and uncertain rewards has been linked with drug dependency. However, relatively little is known about the long-term stability of discounting measures typically studied in clinical psychopharmacology. To evaluate the stability of discounting over a 3-month period, the authors compared points of subjective equality (indifference points) with those collected from the same subjects 3 months earlier. Seven delay periods, ranging from 1 week to 25 years, and 7 probability values, ranging from .95 to .05, were assessed in an undergraduate sample (n=22, delay discounting; n=18, probability discounting). The authors examined both differential stability (stability of individual differences) and absolute stability (stability of the group mean) of delay and probability discounting measures as well as their respective indifference points. The results demonstrate that standard delay and probability discounting parameters (e.g., hyperbolic k and area under the curve) had both differential stability and absolute stability across 3 months. Moreover, most indifference points in the delay and probability discounting tasks demonstrated both differential and absolute stability. All together, these results suggest that delay and probability parameters are stable enough to predict future behavior, such as substance abuse. Additional findings indicated that a hyperbolic function fitted the data better than an exponential function and that delay and probability discounting parameters were not significantly correlated.

Adult↗
PubMed2001

Functional stability re-training: principles and strategies for managing mechanical dysfunction.

Functional stability is dependent on integrated local and global muscle function. Mechanical stability dysfunction presents as segmental (articular) and multi-segmental (myofascial) dysfunction. These dysfunctions present as combinations of restriction of normal motion and associated compensations (give) to maintain function. Stability dysfunction is diagnosed by the site and direction of give or compensation that relates to symptomatic pathology. Strategies to manage mechanical stabililty dysfunction require specific mobilization of articular and connective tissue restrictions, regaining myofascial extensibility, retraining global stability muscle control of myofascial compensations and local stability muscle recruitment to control segmental motion. Stability re-training targets both the local and global stability systems. Activation of the local stability system to increase muscle stiffness along with functional low-load integration in the neutral joint position controls segmental or articular give. Global muscle retraining is required to correct multisegmental or myofascial dysfunction in terms of controlling the site and direction of load that relates to provocation. The strategy here is to train low-load recruitment to control and limit motion at the site of pathology and then actively move the adjacent restriction, regain through range control of motion with the global stability muscles and regain sufficient extensibility in the global mobility muscles to allow normal function. Individual strategies for integrating local and global recruitment retraining back into normal function are suggested.

Activities of Daily Living↗
PubMed2003

Maintenance and regulation of mRNA stability of the Saccharomyces cerevisiae OLE1 gene requires multiple elements within the transcript that act through translation-independent mechanisms.

The Saccharomyces cerevisiae OLE1 gene encodes a membrane-bound Delta-9 fatty acid desaturase, whose expression is regulated by unsaturated fatty acids through both transcriptional and mRNA stability controls. In fatty acid-free medium, the mRNA has a half-life of 10 +/- 1.5 min (basal stability) that drops to 2 +/- 1.5 min when cells are exposed to unsaturated fatty acids (regulated stability). A deletion analysis of elements within the transcript revealed that the sequences within the protein-coding region that encode transmembrane sequences and a part of the cytochrome b5 domain are essential for the basal stability of the transcript. Deletion of any of the three essential elements produced unstable transcripts and loss of regulated instability. By contrast, substitution of the 3'-untranslated region with that of the stable PGK1 gene did not affect the basal stability of the transcript and did not block regulated decay. Given that Ole1p is a membrane-bound protein whose activities are a major determinant of membrane fluidity, we asked whether membrane-associated translation of the protein was essential for basal and regulated stability. Insertion of stop codons within the transcript that blocked either translation of the entire protein or parts of the protein required for co-translation insertion of Ole1p had no effect. We conclude that the basal and regulated stability of the OLE1 transcript is resistant to the nonsense-mediated decay pathway and that the essential protein-encoding elements for basal stability act cooperatively as stabilizing sequences through RNA-protein interactions via a translation-independent mechanism.

3' Untranslated Regions↗
PubMed2005

The manganese-stabilizing protein is required for photosystem II assembly/stability and photoautotrophy in higher plants.

Interfering RNA was used to suppress the expression of two genes that encode the manganese-stabilizing protein of photosystem II in Arabidopsis thaliana, MSP-1 (encoded by psbO-1, At5g66570), and MSP-2 (encoded by psbO-2, At3g50820). A phenotypic series of transgenic plants was recovered that expressed high, intermediate, and low amounts of these two manganese-stabilizing proteins. Chlorophyll fluorescence induction and decay analyses were performed. Decreasing amounts of expressed protein led to the progressive loss of variable fluorescence and a marked decrease in the fluorescence quantum yield (F(v)/F(m)) in both the absence and the presence of dichloromethylurea. This result indicated that the amount of functional photosystem II reaction centers was compromised in the plants that exhibited intermediate and low amounts of the manganese-stabilizing proteins. An analysis of the decay of the variable fluorescence in the presence of dichlorophenyldimethylurea indicated that charge recombination between Q ((A-)) and the S(2) state of the oxygen-evolving complex was seriously retarded in the plants that expressed low amounts of the manganese stabilizing proteins. This may have indicated a stabilization of the S(2) state in the absence of the extrinsic component. Immunological analysis of the photosystem II protein complement indicated that significant losses of the CP47, CP43, and D1 proteins occurred upon the loss of the manganese-stabilizing proteins. This indicated that these extrinsic proteins were required for photosystem II core assembly/stability. Additionally, although the quantity of the 24-kDa extrinsic protein was only modestly affected by the loss of the manganese-stabilizing proteins, the 17-kDa extrinsic protein dramatically decreased. The control proteins ribulose bisphosphate carboxylase and cytochrome f were not affected by the loss of the manganese-stabilizing proteins; the photosystem I PsaB protein, however, was significantly reduced in the low expressing transgenic plants. Finally, it was determined that the transgenic plants that expressed low amounts of the manganese-stabilizing proteins could not grow photoautotrophically.

Arabidopsis↗
PubMed2001

Product development: using a 3D computer model to optimize the stability of the Rocket powered wheelchair.

A three-dimensional (3D) lumped-parameter model of a powered wheelchair was created to aid the development of the Rocket prototype wheelchair and to help explore the effect of innovative design features on its stability. The model was developed using simulation software, specifically Working Model 3D. The accuracy of the model was determined by comparing both its static stability angles and dynamic behavior as it passed down a 4.8-cm (1.9") road curb at a heading of 45 degrees with the performance of the actual wheelchair. The model's predictions of the static stability angles in the forward, rearward, and lateral directions were within 9.3, 7.1, and 3.8% of the measured values, respectively. The average absolute error in the predicted position of the wheelchair as it moved down the curb was 2.2 cm/m (0.9" per 3'3") traveled. The accuracy was limited by the inability to model soft bodies, the inherent difficulties in modeling a statically indeterminate system, and the computing time. Nevertheless, it was found to be useful in investigating the effect of eight design alterations on the lateral stability of the wheelchair. Stability was quantified by determining the static lateral stability angles and the maximum height of a road curb over which the wheelchair could successfully drive on a diagonal heading. The model predicted that the stability was more dependent on the configuration of the suspension system than on the dimensions and weight distribution of the wheelchair. Furthermore, for the situations and design alterations studied, predicted improvements in static stability were not correlated with improvements in dynamic stability.

Computer Simulation↗
PubMed1990

Detyrosination of alpha tubulin does not stabilize microtubules in vivo.

The relationship between alpha tubulin detyrosination and microtubule (MT) stability was examined directly in cultured fibroblasts by experimentally converting the predominantly tyrosinated MT array to a detyrosinated (Glu) array and then assaying MT stability. MTs in mouse Swiss 3T3 cells displayed an increase in Glu immunostaining fluorescence approximately 1 h after microinjecting antibodies to the tyrosinating enzyme, tubulin tyrosine ligase. Detyrosination progressed to virtual completion after 12 h and persisted for 30-35 h before tyrosinated subunits within MTs were again detected. The stability of these experimentally detyrosinated MTs was tested by first injecting either biotinylated or Xrhodamine-labeled tubulin and then measuring bulk turnover by hapten-mediated immunocytochemistry or fluorescence recovery after photobleaching, respectively. By both methods, turnover was found to be similarly rapid, possessing a half time of approximately 3 min. As a final test of MT stability, the level of acetylated tubulin staining in antibody-injected cells was compared with that observed in adjacent, uninjected cells and also with the staining observed in cells whose MTs had been stabilized with taxol. Although intense Glu staining was observed in both injected and taxol-treated cells, increased acetylated tubulin staining was observed only in the taxol-stabilized MTs, indicating that the MTs were not stabilized by detyrosination. Together, these results demonstrated clearly that detyrosination does not directly confer stability on MTs. Therefore, the stable MTs observed in these and other cell lines must have arisen by another mechanism, and may have become posttranslationally modified after their stabilization.

Alkaloids↗
PubMed2001

Posterior-stabilized and cruciate-retaining total knee replacement: a randomized study.

A randomized controlled study was done to compare the clinical, radiographic, and quality of life outcomes between posterior-stabilized and cruciate-retaining primary total knee implants. One hundred forty-three patients were enrolled in the study. Patients ranged in age from 57 to 89 years, had a primary diagnosis of osteoarthritis, and an intact functioning posterior cruciate ligament. Patients were excluded if they had a flexion contracture greater than 15 degrees, a varus deformity greater than 20 degrees, or a valgus deformity greater than 15 degrees. Patients were randomized to one of two study groups, posterior-stabilized AMK total knee implants (76 patients) or cruciate-retaining AMK total knee implants (67 patients). One hundred eight patients have had a minimum 2-year followup including 57 patients in the posterior-stabilized group and 51 patients in the cruciate-retaining group. Seventy-three patients have had a minimum 3-year followup including 37 patients in the posterior stabilized group and 36 patients in the cruciate-retaining group. The overall total Knee Society clinical rating score at 2 years averaged 157.1 points in the posterior-stabilized group and 156.5 points in the cruciate-retaining group. At 3 years, the scores averaged 156.8 points in the posterior-stabilized group and 163.5 points in the cruciate-retaining group. The range of motion component of the Knee Society score averaged 113.6 degrees for the posterior-stabilized group and 108.5 degrees for the cruciate-retaining group at 2 years, and 108.3 degrees in the cruciate-retaining group and 108.5 degrees in the posterior-stabilized group. Based on the various parameters analyzed, there were no notable differences between the groups with a posterior-stabilized and a cruciate-retaining total knee implant at 2 years. This trend seemed to be the same at 3 years.

Aged↗
PubMed2002

Dynamic glenohumeral stability provided by three heads of the deltoid muscle.

The deltoid is a large bulky muscle, comprising approximately 20% of the shoulder muscles. Therefore, the function of the deltoid as a stabilizer is thought to be significant. The current authors quantified dynamic glenohumeral stability provided by three heads of the deltoid by a new biomechanical parameter, the dynamic stability index. The dynamic stability index considers not only the force vectors generated by individual shoulder muscle, but also the concavity compression mechanism. The higher the dynamic stability index, the greater the dynamic stability. The deltoid generated significant shear force and compressive force in the position of anterior shoulder instability. The deltoid provided dynamic stability with the arm in the scapular plane and only decreased the stability of the shoulder with the arm in the coronal plane. The mid and posterior heads should be strengthened vigorously in anterior shoulder instability in conservative and operative treatment, because they provide more stability generating higher compressive force and lower shear force than the anterior head. Scapular muscles should be balanced to avoid the vulnerable glenohumeral position where the arm is extended beyond the scapular plane. Anatomic reattachment of the detached labrum onto the glenoid rim in the anterior instability is important to enhance the effect of compressive force component generated by the muscles.

Aged↗
PubMed1989

Static stability as a predictor of overturn in fatal motor vehicle crashes.

Fatal Accident Reporting System (FARS) files for the years 1981-1984 were examined for rollover crash involvement of 15 utility and passenger vehicle make-models for which static stability values (1/2 track width divided by height of center of gravity) were published. The values ranged from highs of 1.57-1.62 for the pre-1979 Ford LTD, the pre-1979 Chevrolet Nova, and the pre-1982 Pontiac Firebird to lows of 1.01-1.07 for the Jeep CJ-5 and CJ-7 and the pre-1978 Ford Bronco. Rollover as the first harmful event and as the most harmful event per 100,000 vehicles registered was strongly predicted by stability. Stability was unrelated to nonrollover crashes. The low-stability vehicles were much more likely to roll over on the road rather than after leaving the road. Other road, driver, and environmental risk factors recorded in the FARS files were not correlated to stability in such a way as to explain the high rollover of low-stability vehicles. Using Federal Highway Administration vehicle mileage estimates, calculations were made of the mileages under various conditions which the vehicles with low stability values would have to have been driven if mileage or hazardous-condition differences rather than stability differences accounted for their substantially higher fatal rollover fatal crash rates. This analysis indicates that fatal rollover rates of low-stability vehicles could not have occurred at reasonable mileage.

Accidents, Traffic↗
PubMed1988

Spinal stabilization of vertebral column tumors.

An analysis of indications, techniques, results of stabilization and decompression of 100 consecutive spinal tumour cases was carried out. Localized metastatic disease is best operated anteriorly. Primary malignancies are best treated with en bloc resection. Pain relief in metastatic disease is achieved by rigid stabilization. The unstable spine secondary to benign or malignant disease often requires stabilization for alleviation of pain; 132 stabilization procedures were performed in 100 patients. There were nine benign and 91 malignant tumors including 71 metastatic. Indications for stabilization were pathological fracture or following decompression. Anterior approaches including implant stabilization were used in those with metastatic disease limited to one to two levels or where significant kyphosis existed. Posterolateral decompression with Luque rod stabilization was indicated where disease was more widespread. In metastatic disease acrylic cement was used both anteriorly and posteriorly together with implant stabilization. Eighty-one percent had good to excellent relief of pain; 68 patients had neurological deficits. Significant neurological return was achieved in 40% of posterior decompressions and 71% of anterior decompressions in metastatic disease. All patients with benign tumors have solid fusions. In malignant disease the use of cement provided stability without loss of fixation in 87 of 91 procedures. Complications were 4% infection and failure of two Harrington rods without wiring, one Luque rod and two anterior constructs. The average longevity of patients treated for metastatic disease was 11.3 months.

Equipment Failure↗
PubMed1999

Stabilizing potential of anterior cervical plates in multilevel corpectomies.

STUDY DESIGN: An in vitro investigation of three-dimensional kinematics of cervical spine models of one- and three-level corpectomy with anterior plate fixation. OBJECTIVES: To evaluate the capability of an anterior plate to stabilize the reconstructed cervical spine under simulated physiologic motions, and to study the effects of fatigue loading. SUMMARY OF BACKGROUND DATA: Clinical studies have found high failure rates of multilevel anterior cervical plate fusions, indicating suboptimal stabilization. However, no biomechanical studies have been done to investigate the stabilizing capabilities of long-plate instrumentations in corpectomy models. METHODS: Seven fresh human cadaveric cervical spine specimens (C2-T1) were used. Flexibility tests consisted of flexion, extension, and bilateral torsion, and lateral bending, each with a pure moment of 0.25, 0.5, 0.75, and 1.0 Nm. Stabilizing potential indices [(MotionIntact-MotionInstrumented)/MotionIntact] for ranges of motion and neutral zones obtained from the flexibility tests, were measured when the specimen was intact and after one-level (C5) and three-level (C4, C5, and C6) corpectomies and anterior plate stabilizations). The stabilizing potential indices were re-measured after a 1000-cycle fatigue loading (1 Nm flexion and extension moments at C5 vertebra at 0.14 Hz). RESULTS: The differences in stabilizing potential indices of range of motion and neutral zone between one-level and three-level plates were not significant before fatigue. However, after fatigue, the stabilizing potential indices significantly decreased (P < 0.05) for the three-level model, but not for the one-level plate model. CONCLUSIONS: The capability of an anterior cervical plate to stabilize the spine after three-level corpectomy was significantly reduced with fatigue loading.

Adolescent↗
PubMed2000

The role of bone graft force in stabilizing the multilevel anterior cervical spine plate system.

STUDY DESIGN: The role of bone graft force in stabilizing an instrumented cervical spine was evaluated for one-level and three-level corpectomy models using in vitro experiments. OBJECTIVES: To investigate the role of bone graft force in enhancing stability of anterior cervical plate, and to study effects of fatigue loading. SUMMARY OF BACKGROUND DATA: The anterior cervical plate system is used widely in stabilizing the cervical spine after spinal corpectomy and grafting. Many factors such as applied screw torque, screw pullout force, plate strength, plate geometry, and type of bone graft have been studied. However, the role of bone graft in stabilizing the anterior plate system has not been explored. METHODS: Two models (one-level and three-level) incorporating corpectomy, strut graft, and anterior plate were constructed from eight human spine specimens (C2-T1). The flexibility of an intact specimen and two constructs with graft forces of 0 N and 100 N was determined. A flexibility test, simulating physiologic loads, consisted of pure moments of flexion, extension, lateral bending, and axial torques up to 1 Nm. For each moment, range of motion and neutral zone were determined. The stability potential index was defined as the decrease in motion caused by instrumentation, as compared with intact motion. A larger stability potential index indicates a more stable spinal construct. Repeated measures analysis of variance was used to determine the significant changes. RESULTS: In both models, bone graft force increased during extension, decreased during flexion, and showed minor changes during axial torsion and lateral bending. Higher bone graft force increased stability potential index-neutral zone and stability potential index-range of motion in the three-level model in all directions, but only in flexion-extension in the one-level model. Fatigue loading decreased bone graft force to a greater extent in the three-level model. CONCLUSIONS: In the corpectomy-graft-anterior-plate model, graft force decreased in flexion and increased in extension. Higher graft force increased and fatigue decreased stability of the spinal construct in the three-level model.

Adolescent↗
PubMed2006

Gender and limb differences in dynamic postural stability during landing.

OBJECTIVE: To determine if gender and limb dominance affect dynamic postural stability and vertical ground reaction force data during jump landings. Secondary objective was to assess the reliability of the dynamic postural stability index (DPSI). DESIGN: A mixed model (2 genderx2 limb) repeated measures design was used to determine the effects of gender and limb dominance on dynamic postural stability. Subjects were required to perform a two-legged jump to a height equivalent of 50% of their maximum vertical leap, land on a single-leg and balance for three seconds. SETTING: Sports Medicine Research Laboratory. PARTICIPANTS: Forty healthy subjects (20 men, 20 women) participated in this investigation. MAIN OUTCOME MEASURES: The DPSI and its directional components quantified dynamic postural stability during a single-leg jump landing. Normalized vertical ground reaction force data quantified energy absorption. RESULTS: DPSI values revealed that females had significantly different dynamic postural stability as compared to males in the vertical plane [T (78)=-4.2, P<0.01], and in the composite score (dynamic postural stability index) [T (78)=-6.3, P<0.01]. In addition, females had significantly higher peak vertical ground reaction forces [T (78)=-13, P=0.01] than males. The DPSI also showed excellent reliability (ICC=0.96), with a 95% confidence interval ranging from 0.94 to 0.97. CONCLUSIONS: The results indicate that females have higher dynamic postural stability scores in the vertical direction as well as the composite score. This suggests that females used different dynamic postural stability strategies than males. There were no side-to-side dynamic postural stability differences between healthy contralateral limbs.

Adult↗
PubMed2005

Posterior instrumentation reduces differences in spine stability as a result of different cage orientations: an in vitro study.

STUDY DESIGN: A multisegmental cadaveric spine model was used to quantify the load-displacement behavior of intact spine specimens, specimens injured and stabilized using Bagby and Kuslich (BAK) cages as lumbar interbody fusion devices with or without posterior instrumentation across two levels. OBJECTIVES: To compare the stabilities imparted by the cages placed using an oblique and conventional posterior approaches and to determine the effects of supplementary posterior instrumentation. SUMMARY OF BACKGROUND DATA: The BAK cage as posterior lumbar interbody fusion (PLIF) has been used to restore disc height, reduce morbidity, provide immediate stability to the patients, and enhance fusion rates. The obliquely inserted BAK cage has the advantages of reducing exposure and precise implantation. The biomechanical efficacy of this procedure is sparse, especially in comparison to the PLIF with and without posterior instrumentation. METHODS: Nine fresh human ligamentous spines (L2-S1) were affixed within a testing frame for determining their load-displacement behaviors. Load testing in clinically relevant modes was performed sequentially for the intact and the following procedures across the L4-S1 segment: posterior destabilization, stabilization using two parallel BAK cages (CBAK group) or one oblique BAK cage (OBAK group), further stabilization with posterior instrumentation, and finally cyclic loading in flexion-extension. Spatial positions of the LEDs attached to vertebral bodies were recorded using a three-dimensional motion measurement system. RESULTS: When used alone to restore stability, the orientation of the cage affected the outcome. In flexion OBAK orientation and in extension CBAK orientation provided better stability (decrease in motion with respect to intact case), compared with the other orientation. In lateral bending, CBAK orientation was found to be better than OBAK. In axial mode, CBAK orientation was effective in both directions while OBAK was effective only in right axial rotation. With the supplementary posterior fixation, the differences in stability resulting from the orientations were not noticeable at all, both before and after cyclic tests. CONCLUSIONS: Owing to the differences in the surgical approach and the amount of dissection, the stability for the cages when used alone as a function of cage orientation was different. These subtle differences were reduced by the use of posterior fixation device, underscoring the importance of using instrumentation when cages are used as PLIFs. However, the oblique insertion may be more favorable since it requires less exposure, enables precise implantation, and is less expensive, especially when used with supplementary instrumentation.

Aged↗
PubMed2005

Biomechanical analysis of rigid stabilization techniques for three-column injury in the lower cervical spine.

STUDY DESIGN: Comparison of nondestructive multidirectional flexibility in groups of specimens receiving two different posterior instrumentation constructs with or without anterior plating. OBJECTIVE: To compare stability after a three-column injury stabilized posteriorly by lateral mass screws-rods at C5-C6 and pedicle screws-rods at C7 ("LLP") or by pedicle screws-rods at C5-C6-C7 ("PPP"), and to compare posterior, anterior, and combined anterior-posterior fixation. SUMMARY OF BACKGROUND DATA: Pedicle screws resist pullout better than lateral mass screws, but little research has compared the stability of pedicle screws to that of lateral mass screws used within constructs. METHODS: Fourteen human cadaveric C4-T1 specimens were tested intact, posteriorly instrumented (7 LLP and 7 PPP), anteriorly instrumented, or with combined (anterior-posterior) instrumentation. Nonconstraining, nondestructive torques induced flexion, extension, lateral bending, and axial rotation while angular motion was recorded optically. RESULTS: Posterior, anterior, and combined instrumentation each significantly improved stability (P < 0.05). Combined fixation provided significantly better stability than either anterior or posterior instrumentation alone. In no loading mode and in no testing condition was any parameter significantly different between LLP and PPP. Posterior instrumentation provided significantly better stability than anterior instrumentation. CONCLUSIONS: Anterior plate and posterior screw-rod fixation alone improve stability in a two-level, three-column cervical injury model. Combined fixation further improves stability. There is little discernible difference in immediate postoperative stability between posterior rod constructs combining lateral mass and pedicle screws and those using only pedicle screws.

Adult↗
PubMed2006

Evaluation of transitional implant stabilized overdentures: a case series report.

Transitional implants (TI) can immediately improve the stability and retention of existing unstable mandibular complete dentures. This study evaluated the improvement of mandibular complete denture stability and retention with the use of TI. Three TIs were placed in the intraforaminal region of the edentulous mandible of seven patients (three men, four women; mean age 69.7 years). The patients' existing mandibular complete dentures were immediately modified to TI-stabilized overdentures. Their masticatory movements (mandibular movements during mastication) were measured using a commercially available tracking device (BioPACK, Bioresearch, Japan), both before TI placement and about 1 month after delivery of the TI-stabilized overdentures. The mean time of each chewing phase (opening, closing, and occluding) and coefficients of variation were calculated. The patients also completed a questionnaire about the foods they could chew and indicated on a 100 mm Visual Analog Scale (VAS) their personal levels of comfort, ease of chewing, speech, and stability. For masticatory movements, there were no significant differences (P > 0.05) between the TI-stabilized overdentures and existing complete dentures. However, the number of foods that could be chewed increased, and the stability and comfort were reported as improved with the TI-stabilized overdentures. Using TIs, the stability and comfort of the existing mandibular complete dentures studied in this report could be immediately improved.

Aged↗