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PubMedDate not supplied

Influence of lumbar flexion on the position of the intercrestal line.

BACKGROUND AND OBJECTIVES: This study was performed to ascertain whether the position of the intercrestal line changes as a result of flexion of the lumbar spine. METHODS: Previously taken lumbar spine x-rays of 103 patients in the neutral and full-flexed positions were reviewed. In the lateral flexion images to compensate for the sagittal rotation of the pelvis during lumbar flexion and for the possible difference in the level between the two sides of the ilium when taking the lateral images, the intercrestal line was drawn as follows: a potential line, crossing the midpoint of the highest points of both iliums, should be perpendicular to the tangential line at the point of intersection of the potential line with the skin. The position of the intercrestal line in relation to the spinous process was determined on an imaginary line moved 1 cm toward the vertebral body from the tangential line on the 2 successive spinous processes, and the interspinous distance of L3-4 was measured on this imaginary line. RESULTS: With full-flexion of the lumbar spine, the position of the intercrestal line in relation to the spinous process [median (25th to 75th percentiles)] changed slightly from L4 (L4-L4-5) into L4-5 (L4-L4-5) (P <.001), but it remained at the same level in 58.3% of the patients (60/103). In no case was a change of more than 1 level observed. The interspinous width (mean +/- SD) of L3-4 increased from 6.5 +/- 2.4 mm to 13.2 +/- 4.4 mm (P <.001). CONCLUSION: When compared with the neutral position, the position of the intercrestal line usually does not change with full flexion of the lumbar spine, and even in cases in which change occurs, it does not move beyond the next level.

Adult↗
PubMed2005

Tracheobronchial haemorrhage in patients with neuromuscular disorders.

STUDY OBJECTIVES: Evaluation of different types of tracheostomy tubes in patients with neuromuscular disorders. DESIGN: Review of past charts of 49 patients with DMD. SETTING: Intensive care unit of Children's Hospital-Bambino Gesù Rome-Palidoro, Italy CONCLUSIONS: Our findings favour the use of flexible tracheostomy tubes in reducing the risk of developing tracheal haemorrhages.

Adult↗
PubMedDate not supplied

Distribution of anterior cortical shear strain after a thoracic wedge compression fracture.

BACKGROUND CONTEXT: Vertebral compression fractures (VCFs) are a common clinical problem and may follow trauma or be pathological. Osteoporosis increases susceptibility to fracture by reducing bone mass and weakening bone architecture. Approximately 2.5 million osteoporotic fractures occur worldwide annually, usually involving the vertebrae, wrist and hip. In the United States 700,000 VCFs occur annually, causing significant morbidity, mortality and economic burden. An initial VCF often leads to subsequent VCFs. The strain distribution along the anterior cortex, the major load-bearing pathway in flexion, may be predictive of impending VCF. Regions of high strain distribution are likely to experience secondary fracture. PURPOSE: To investigate the distribution of anterior cortical strain at, above and below an experimentally created index VCF to determine the vertebral body at risk of secondary fracture. STUDY DESIGN: In vitro experimental study using cadaveric thoracic spinal segments. METHODS: Seventeen thoracic spines underwent dual-energy X-ray absorptiometry (DEXA) to assess bone mineral density and were divided into T1-T3 (Subsegment 1), T4-T6 (Subsegment 2), T7-T9 (Subsegment 3) and T10-T12 (Subsegment 4). Rectangular rosette strain gauges were applied to the anterior cortices of the vertebrae of each subsegment (vertebrae in each specimen were denoted V1-superior, V2-intermediate and V3-inferior). V1 and V3 were partially embedded into polyester resin blocks, which were used to mount the specimens in a materials testing machine. Nondestructive predefect testing was performed in compression at 125 N and 250 N, followed by flexion at 1.25 Nm and 2.5 Nm. To ensure fracture reproducibility, V2 of each specimen had a trabecular defect created to a volume of 21.3+/-4.4% of the V2 centrum. Postdefect nondestructive compression and flexion were then performed in a manner similar to the predefect tests, followed by destructive testing in flexion. Anterior cortical shear strain on V1, V2 and V3, applied moments and applied flexion angle were all measured and analyzed. RESULTS: A VCF occurred in 55 of the 59 subsegments. Fifty-one VCF (93%) were seen in V2 and 4 VCF (7%) were seen in V1. After the creation of the trabecular defect, the shear strain on V2 increased, but a comparison of the postdefect with the predefect nondestructive tests showed no significant differences. The pre- and postdefect shear strain distribution in compression and flexion was V1strain>V3strain>V2strain. Shear strain at failure was highest on V2, and in all subsegments there were significant differences between V2 and V3 (p<.05). In all subsegments there were no significant differences between V2 and V1 (p>.05) at failure with the exception of Subsegment 1 where V2 and V1 were significantly different (p<.05). The predominant strain pattern at failure was (V2strain>V1strain>V3strain V2strain>>V3strain). Using shear strain as the codeterminant of peak moment with bending stiffness and applied angle at failure, the strain on V1 was the greatest predictor (p=.0084; R2=0.78). These findings suggest that the events leading to a secondary fracture probably start before the index VCF occurs and continue with loading beyond the index VCF. CONCLUSION: Anterior cortical strain is concentrated at the apex of a thoracic kyphotic curve. The vertebral body immediately above the index VCF has the next highest amount of strain and therefore the highest risk of secondary fracture.

Absorptiometry, Photon↗
PubMedDate not supplied

The multidirectional bending properties of the human lumbar intervertebral disc.

BACKGROUND CONTEXT: While the biomechanical properties of the isolated intervertebral disc have been well studied in the three principal anatomic directions of flexion/extension, axial rotation, and lateral bending, there is little data on the properties in the more functional directions that are combinations of these principal anatomic directions. PURPOSE: To determine the bending flexibility, range of motion (ROM), and neutral zone (NZ) of the human lumbar disc in multiple directions and to determine if the values about the combined moment axes can be predicted from the values about principal moment axes. STUDY DESIGN/SETTING: Three-dimensional biomechanical analysis of the elastic bending properties of human lumbar discs about principal and combined moment axes. METHODS: Pure, unconstrained moments were applied about multiple axes. The bending properties (flexibility, ROM, and NZ) of isolated lumbar discs (n=4 for L2/L3 and n=3 for L4/L5) were determined in the six principal directions and in 20 combined directions. The experimental values were compared with those predicted from the linear combination of the six principal moment axes. RESULTS: The maximum and minimum values of the biomechanical properties were found at the principal moment axes. Among combined moment axes, ROM and NZ (but not flexibility) values were predicted from the principal moment axis values. CONCLUSIONS: The principal moment axes coincide with the primary mechanical axes of the intervertebral disc and demonstrate significant differences in direction for values of flexibility, ROM, and NZ. Not all combined moment axis values can be predicted from principal moment axis values.

Humans↗
PubMed2006

Flexibility and conformational entropy in protein-protein binding.

To better understand the interplay between protein-protein binding and protein dynamics, we analyzed molecular dynamics simulations of 17 protein-protein complexes and their unbound components. Complex formation does not restrict the conformational freedom of the partner proteins as a whole, but, rather, it leads to a redistribution of dynamics. We calculate the change in conformational entropy for seven complexes with quasiharmonic analysis. We see significant loss, but also increased or unchanged conformational entropy. Where comparison is possible, the results are consistent with experimental data. However, stringent error estimates based on multiple independent simulations reveal large uncertainties that are usually overlooked. We observe substantial gains of pseudo entropy in individual partner proteins, and we observe that all complexes retain residual stabilizing intermolecular motions. Consequently, protein flexibility has an important influence on the thermodynamics of binding and may disfavor as well as favor association. These results support a recently proposed unified model for flexible protein-protein association.

Animals↗
PubMed2005

Influence of simulated clinical use on the torsional behavior of nickel-titanium rotary endodontic instruments.

OBJECTIVE: The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion. STUDY DESIGN: Thirty sets of 0.04 and 0.06 ProFile instruments in sizes #20, #25, and #30 were randomly divided into 3 groups: 1 contained 10 sets of new files, torsion tested to failure, while the other 2 groups, with 10 sets each, were first submitted to fatigue tests of up to one half and three fourths of their fatigue life, respectively, in geometrical conditions similar to those of the clinical practice and then torsion tested for rupture. RESULTS: Statistical analysis of the values obtained for the torque to failure and maximum angular deflection, using the Student t test at the 95% confidence level, showed that the cyclic deformation of instruments of up to one half and three fourths of their fatigue life gives rise to a significant reduction in these parameters. CONCLUSIONS: The simulated clinical use of ProFile instruments for shaping curved canals adversely affects their torsional properties.

Dental Alloys↗
PubMed2006

Cyclic fatigue of different nickel-titanium endodontic rotary instruments.

OBJECTIVE: A comparative study of the fatigue resistance of rotary nickel-titanium endodontic instruments was performed with the aim of assessing the influence of both instrument design and surface treatment on flexural fracture. STUDY DESIGN: To evaluate fatigue resistance of different rotary instruments, a total of 120 instruments were tested; these came from different sources: ProFile, RaCe, K3, Hero, and Mtwo. To compare the effect of electro-polishing procedures on fatigue resistance, a group of RaCe instruments (which are normally electro-polished) without surface treatment was used. A scanning electron microscope (SEM) study for each instrument was performed before and after fatigue study to determine the mode of fracture and the aspect of tips and cross-sectional surface areas. RESULTS: ProFile instruments gave the best values for fatigue resistance. It was seen that for RaCe instruments the surface treatment reduces the presence of micro-cracks, surface debris, and machining damage. CONCLUSIONS: This study shows that the instrument design often proves to be an important factor in the fatigue resistance of NiTi rotary instruments. In RaCe instruments the electro-polishing surface treatment increases the fracture-related fatigue resistance.

Analysis of Variance↗
PubMed2006

Utilization of waste glass in ECO-cement: strength properties and microstructural observations.

Waste glass creates a serious environmental problem, mainly because of the inconsistency of the waste glass streams. The use of waste glass as a finely ground mineral additive (FGMA) in cement is a promising direction for recycling. Based on the method of mechano-chemical activation, a new group of ECO-cements was developed. In ECO-cement, relatively large amounts (up to 70%) of portland cement clinker can be replaced with waste glass. This report examines the effect of waste glass on the microstructure and strength of ECO-cement based materials. Scanning electron microscopy (SEM) investigations were used to observe the changes in the cement hydrates and interface between the cement matrix and waste glass particles. According to the research results, the developed ECO-cement with 50% of waste glass possessed compressive strength properties at a level similar to normal portland cement.

Compressive Strength↗
PubMed1996

Randomized comparison of flexible versus nonflexible femoral sheaths on patient comfort after angioplasty.

Patients who undergo percutaneous transluminal coronary angioplasty (PTCA) by the femoral approach are usually required to lie flat in bed for 6 to 24 hours, which may result in significant discomfort. This study was performed to evaluate the safety and benefit of a flexible sheath that enables patients to sit at a 60-degree angle while the sheath is in place in the femoral artery. Sixty patients were randomly assigned to receive either flexible or nonflexible sheaths before PTCA. Patients with flexible sheaths were allowed to sit at an angle of 60 degrees after the procedure. Heparin management was the same in both groups. Frequency of calls to nurses for back pain was recorded for both groups. For analgesia, nalbuphine was administered in 2-mg increments. All sheaths were removed the day after the procedure. Femoral ultrasound was used to detect groin complications (hematoma, pseudoaneurysm, or arteriovenous fistula) and was performed in all patients. Baseline characteristics were similar in both groups. There were no differences in ease of sheath insertion or guide catheter movement through the sheaths. The arterial pressure waveform was not dampened in any of the flexible sheath patients while in the sitting position. Patients with flexible sheaths had fewer calls for back pain and required less nalbuphine than patients with nonflexible sheaths. Groin complications were similar in both groups. In conclusion, by allowing patients to sit up to an angle of 60 degrees, flexible sheaths have a beneficial effect in reducing back pain and the need for analgesics after PTCA.

Aged↗
PubMed1997

Effects of high-intensity strength training on quality-of-life parameters in cardiac rehabilitation patients.

Cardiac rehabilitation programs have not consistently been shown to improve the psychological well being of their patients. In our study of 38 cardiac patients (29 men and 9 women), a variety of quality-of-life parameters were assessed before and after they completed either 12 weeks of high-intensity strength training or flexibility training added to their outpatient cardiac rehabilitation aerobic exercise program. The strength-trained patients increased their self-efficacy scores for lifting (29% vs 4%, p <0.05), push-ups (65% vs. 17%, p <0.01), climbing (36% vs 0%, p <0.001), and jogging (100% vs -9%, p <0.001), when compared with the flexibility-trained patients. The strength group also had greater improvements in Profile of Mood States dimensions: total mood disturbance (123% vs 18%, p <0.05), depression/dejection (73% vs 15%, p <0.05), and fatigue/inertia (42% vs 3% p <0.05), than did the flexibility group. The Medical Outcome Survey Short Form 36 role emotional health domain scores were significantly improved in the strength group when compared with the flexibility group (64% vs 0%, p <0.05), and the role limitation scores improved in both groups. Increases in strength were associated with enhanced self efficacy and improved mood and well-being scores (n = 34, r = 0.30 to 0.53, p <0.05). High-intensity strength training added to a cardiac rehabilitation program of selected patients leads to improvements in quality-of-life parameters. These data, in conjunction with improvements in strength, strongly support the value of adding high-intensity strength training to cardiac rehabilitation programs.

Coronary Disease↗
PubMed2002

Flexible endorectal ultrasound for predicting pathologic stage of rectal cancers.

BACKGROUND: Endorectal ultrasound (ERUS) is an accurate method for preoperative staging of rectal cancers. Most often, a rigid 360-degree rotating probe is used. We studied whether flexible probes could attain equivalent accuracy for bowel wall penetration. METHODS: Forty-five patients were prospectively evaluated with flexible devices. Results were compared with 20 rigid and 10 flexible probe studies. To assess learning curves, we used logistic regression analysis and coefficients of correlation on accuracy data to compare ERUS accuracy with the number of examinations. RESULTS: Level of invasion was correct in 49%. Nodal examinations were correct in 78%. Learning curves leveled out at 100 examinations with 87% accuracy for the rigid probe (R = 0.46) and 77% for the flexible devices (R = 0.31). CONCLUSIONS: The coefficient of correlation for each method portends a more reliable learning curve for the rigid devices. Flexible devices were less accurate for level of invasion than the literature reported for rigid devices.

Adenocarcinoma↗
PubMed1997

Tricuspid valve repair with the Cosgrove-Edwards Annuloplasty System.

The technique of tricuspid valve repair with the Cosgrove-Edwards Annuloplasty System is described. This system provides a measured plication of the tricuspid valve annulus with a technique that is easily reproducible and permits physiologic motion of the tricuspid annulus.

Cardiac Surgical Procedures↗
PubMed1998

Biomechanical study of sternal closure using rigid fixation techniques in human cadavers.

BACKGROUND: We believe rigid plate fixation may be superior to wire fixation in sternal closure, as rigid fixation used in the craniofacial skeleton has shown greater stability, lower postoperative pain, and accelerated bone healing. We hypothesize that sterna fixed with titanium plates are more stable mechanically than sterna fixed with wires. METHODS: The sterna from human cadavers were used in this two-phased study. Phase I compared wires to four-hole titanium straight plates. Phase II compared wires to four-hole titanium custom H plates. The sterna were tested biomechanically using all fixation methods. RESULTS: Phase I showed no statistically significant difference in the stiffness or lateral displacement between the wired and straight plated sterna. Phase II showed a statistically significant greater stiffness (p < 0.05) and less lateral displacement (p < 0.05) in the custom plated sterna over the wired sterna. CONCLUSIONS: Our results showed that custom titanium H plates were superior to wire fixation. Furthermore, our results established the importance of plate configuration in sternal fixation. Our study may have beneficial clinical implications, as decreased motion at the sternotomy site could mean less postoperative pain, a decreased incidence of infection, and accelerated bone healing.

Aged↗
PubMed1998

Postimplantation leaflet cellularity of valve allografts: are donor cells beneficial or detrimental?

BACKGROUND: The theory that "viable" valve grafts have superior durability because the donor cell population of the leaflets survives implantation and functions normally, thus maintaining leaflet integrity, is still not definitively proven. The postulate has been investigated for grafts produced and used at Green Lane Hospital by examining a series of 155 removed at reoperation following up to 21.3 years of implantation. METHODS: Leaflet cellularity at explantation was assessed histologically. An additional 55 cases were also assessed by tissue culture. Cell origin for six positive cultures was determined by comparison of DNA of the culture with that of the recipient's blood cells. RESULTS: Grafts known to be nonviable at implantation lacked leaflet fibroblasts but sometimes showed ongrowth of fibrous tissue derived from the recipient's aorta. Grafts potentially viable at implantation showed three main patterns of fibroblastic growth: (1) relatively sparse, scattered cells; (2) focal hyperplastic growth with intervening acellular tissue that was prone to rupture; and (3) widely disseminated, vigorous growth causing abnormal thickening. The first pattern was associated with recipient cells, and both the second and third patterns were associated with nonrecipient cells. CONCLUSIONS: Donor cells surviving implantation do not maintain a normal leaflet architecture and may lead to failure by producing loss of leaflet flexibility.

Anti-Bacterial Agents↗
PubMed2003

Quantifying the magnitude of torque physiotherapists apply when stretching the hamstring muscles of people with spinal cord injury.

OBJECTIVE: To quantify the magnitude of stretch that physiotherapists apply to the hamstring muscles of people with spinal cord injury (SCI). DESIGN: Repeated-measures design. SETTING: SCI unit in Australia. PARTICIPANTS: Fifteen individuals with motor complete paraplegia or tetraplegia. INTERVENTION: Twelve physiotherapists manually administered a stretch to the hamstring muscles of each subject. The stretch was applied by flexing the hip with the knee extended. MAIN OUTCOME MEASURE: Applied hip flexor torque. RESULTS: Therapists applied median hip flexor torques of between 30 and 68Nm, although some torques were as large as 121Nm. The stretch applied by different therapists to any 1 subject varied as much as 40-fold. CONCLUSION: There is a large range of stretch torques provided by physiotherapists to patients with SCI. Some therapists provide stretch torques well in excess of those tolerated by individuals with intact sensation.

Activities of Daily Living↗
PubMed1996

Preloading and range of motion effect on plantarflexor muscle performance.

OBJECTIVE: To determine the effects of maximal preloading and range of motion (ROM) on the mechanical parameters of the plantarflexor muscles obtained while using the isotonic mode of testing of a Biodex dynamometer. DESIGN: A convenience sample of healthy subjects in the context of a descriptive comparative study. SETTING: Research laboratory in Canada. SUBJECTS: Fifteen volunteered subjects without history of injury or disorder to the right lower extremity. MEASUREMENTS: Four maximal isotonic tests were performed against a selected load of 27Nm. For the first two tests, the movement at the ankle ranged from -12 degrees (dorsiflexion) to +32 degrees (plantarflexion); one of these tests was preceded by a 2-second maximal preloading contraction, while the other was performed without preloading. For the other two tests, the ROM at the ankle was increased by 15 degrees of plantarflexion and thus ranged from -12 degrees to +47 degrees; again one of these tests was executed with preloading and the other without preloading. RESULTS: The four tests showed differences in the mechanical parameters (MANOVA p < .05). At angles of -10 degrees and +5 degrees, subjects produced higher torque and power but lower velocity values for the two tests preceded by a maximal preloading. The effect of ROM was demonstrated at +20 degrees where tests performed in a small amplitude reached a lower velocity than the corresponding tests performed in a larger amplitude. Based on the velocity profiles, the results also revealed that maximal preloading changed the selected isotonic movement of the Biodex dynamometer to an isoaccelerative movement characterized by high torque and power production. CONCLUSIONS: Isotonic assessment using the Biodex dynamometer provides different values of torque, velocity, and power depending on the testing conditions used. In clinical settings, it would be important to control these testing conditions.

Analysis of Variance↗
PubMed1997

Shoehorn-type ankle-foot orthoses: prediction of flexibility.

OBJECTIVE: To predict the factors affecting the flexibility of a shoehorn-type ankle-foot orthosis (AFO) in dorsiflexion and plantarflexion. DESIGN: Experimental assessment. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The dorsiflexion and plantarflexion angles of the ankle joints of the AFOs versus applied force were measured. RESULTS: The dorsiflexion and plantarflexion angles demonstrated significant negative linear correlations with the height of the AFO (p < .01), the height of the medial wall (p < .05), the height of the lateral wall (p < .01), the width of the narrowest area (p < .001), and the width of the ankle joint area (p < .001). The dorsiflexion angle also demonstrated a significant negative linear correlation with the curvature radius of the lateral trimline (p < .05) and the thickness of the plastic sheet (p < .05). Stepwise multiple regression analysis demonstrated that the width of the ankle joint area, the thickness of plastic sheet, and the height of the lateral wall significantly affected the dorsiflexion and plantarflexion angles (p < .001). CONCLUSION: The major predictor of flexibility in dorsiflexion and plantarflexion is the width of the ankle joint area, and the second predictor is the thickness of the plastic sheet in dorsiflexion and the height of the lateral wall in plantarflexion.

Ankle↗