Neck Stability Research Articles

Deformation behavior of a NiCo multilayer with a modulated grain size distribution

In order to gain a fundamental understanding of the deformation behavior of multilayer architectures composed of a periodic layering of hard and soft structural features, NiCo samples possessing modulated nanocrystalline and coarse-grained microstructures were fabricated using pulsed electrodeposition. Scanning electron microscopy imaging confirmed that the samples possessed an alternating grain size distribution and the desired 1:1 thickness ratio of constitutive layers. Uniaxial tensile testing showed a rule of mixtures relationship in yield and ultimate tensile strengths for the multilayer with respect to reference samples. Notably, an increase in elongation to failure was observed in the multilayer when compared to the nanocrystalline reference. The gains in elongation were found to be associated with improved neck stability due to dislocation activity within the coarse-grained layers. The morphology of the fracture surface, considered together with the available mechanical data, electron micrographs and texture measurements, forms the basis of a multiscale deformation mechanism which describes a failure pathway for multilayer architectures with nanocrystalline and coarse-grained structural features.

The effects of isometric contraction of shoulder muscles on cervical multifidus muscle dimensions in healthy office workers

It is argued that cervical multifidus muscles (CMM) are responsible for providing neck stability. However, whether they are actually activated during the tasks performed by the upper extremities to the neck is still unknown. Therefore, the aim of this study was to examine the effects of isometric contraction of shoulder muscles on the dimensions of CMM. Twenty three healthy males voluntarily participated in this study. Ultrasonography imaging of CMM was conducted at rest and at 25%, 50%, 75%, and 100% of maximal voluntary contraction of shoulder muscles in 6 directions of shoulder movements. Anterior-posterior dimension (APD), lateral dimension (LD), shape ratio and multiplied linear dimension (MLD) of cervical multifidus were measured. The APD of CMM was increased while LD and shape ratio were decreased by shoulder muscles contraction (P < 0.01).

Path-Finding on the Microtubule

In long-range transport of cargo, prototypical kinesin-1 steps along a single protofilament on the microtubule, an astonishing behavior given the number of theoretically available binding sites on adjacent protofilaments. Using a laser trap assay, we analyzed the trajectories of several representatives from the kinesin-2 class on freely suspended microtubules, mimicking cargo transport as accurately as possible. In stark contrast to kinesin-1, heterodimeric kinesin-2 motors from diverse organisms displayed an astounding range of rotational pitches, expanding the list of torque generating kinesins to include processive representatives of the kinesin-2 family. We provide direct evidence that neck region of kinesin determines the torque generating properties by reversibly manipulating the properties of the neck of the human kinesin-1 and the heterodimeric kinesin-2 from sea urchin. Disrupting the stability of the neck by inserting flexible peptide stretches results in pronounced left-handed spiraling. Mimicking neck stability by crosslinking significantly reduces the spiraling of the motor up to the point of protofilament tracking.

Advanced core decompression, a new treatment option of avascular necrosis of the femoral head - a first follow-up

Aseptic necrosis of the femoral head (AVN) leads to destruction of the affected hip joint, predominantly in younger patients. Advanced core decompression (ACD) is a new technique that may allow better removal of the necrotic tissue by using a new percutaneous expandable reamer. A further modification is the refilling of the drill hole and the defect with an injectable, hard-setting, composite calcium sulphate (CaSO₄)-calcium phosphate (CaPO₄) bone graft substitute. Compression tests were performed on seven pairs of femoral cadaver bones. One femur of each pair was treated with ACD, while the opposite side remained untreated. Clinically, the postoperative outcome of 27 hips in 23 patients was performed by physical examination 6 weeks after ACD and at average follow-up of 9.69 months, and compared with the preoperative results. MRI was used to assess the removal of the necrotic tissue, any possible progression of AVN and evaluation of collapse. In the biomechanical analysis, the applied maximum compression force that caused the fracture did not significantly differ from the untreated opposite side. The overall results of postoperative physical examinations were significantly better than preoperatively. Five hips (18.5%) were converted to a total hip replacement. The follow-up MRIs of the other patients showed no progression of the necrotic area. The first follow-up results of ACD have been encouraging for the early stages of aseptic necrosis of the femoral head. In our opinion, an assured advantage is the high stability of the femoral neck after ACD, which allows quick rehabilitation.

Torque Generation of Kinesin Motors Is Governed by the Stability of the Neck Domain

In long-range transport of cargo, prototypical kinesin-1 steps along a single protofilament on the microtubule, an astonishing behavior given the number of theoretically available binding sites on adjacent protofilaments. Using a laser trap assay, we analyzed the trajectories of several representatives from the kinesin-2 class on freely suspended microtubules. In stark contrast to kinesin-1, these motors display a wide range of left-handed spiraling around microtubules and thus generate torque during cargo transport. We provide direct evidence that kinesin's neck region determines the torque-generating properties. A model system based on kinesin-1 corroborates this result: disrupting the stability of the neck by inserting flexible peptide stretches resulted in pronounced left-handed spiraling. Mimicking neck stability by crosslinking significantly reduced the spiraling of the motor up to the point of protofilament tracking. Finally, we present a model that explains the physical basis of kinesin's spiraling around the microtubule.

Biomechanical analysis of a novel femoral neck locking plate for treatment of vertical shear Pauwel's type C femoral neck fractures

BackgroundThe purpose of this study is to determine the biomechanical stability of a novel prototype femoral neck locking plate (FNLP) for treatment of Pauwels type C femoral neck fractures compared with other current fixation methods. MethodsForty femur sawbones were divided into groups and a vertical femoral neck fracture was made. Each group was repaired with one of the following: (CS) three parallel cancellous screws; (XCS) two cancellous lag screws into the head and one transverse lag screw into the calcar; and (FNLP) a novel FNLP with two 5.7mm locking, one lag screw into the calcar and two screws into the shaft; and (AMBI) a two-hole, 135° AMBI plate with a derotation screw. All groups were tested for change in axial stiffness over 20000 cycles, and rotational stiffness was measured before and after cyclic testing. A maximum load to failure test was also conducted. Results were compared with one-way analysis of variance (ANOVA) and Fisher protected least significant difference (PLSD). ResultsResults for axial stiffness show that AMBI, CS, XCS and FNLP are 2779.0, 2207.2, 3029.9 and 3210.7N-mmm−1, respectively. Rotational rigidity results are 4.5, 4.1, 17.1 and 18.7N-mmm−1. The average cyclic displacements were 0.75, 0.88, 0.80 and 0.65mm, respectively. Destructive failure loads for AMBI, CS, XCS and FNLP were 2.3, 1.7, 1.6 and 1.9kN, respectively. ConclusionsThe results of this experiment show statistically significant increases in axial stiffness for the FNLP compared with three traditional fixation methods. The FNLP demonstrates increased mechanical stiffness and combines the desirable features of current fixation methods.

Hip Fractures and the Contribution of Cortical Versus Trabecular Bone to Femoral Neck Strength

Osteoporotic fractures are caused by both cortical thinning and trabecular bone loss. Both are seen to be important for bone fragility. The relative contributions of cortical versus trabecular bone have not been established. The aim of this study was to test the contribution of cortical versus trabecular bone to femoral neck stability in bone strength. In one femur from each pair of 18 human cadaver femurs (5 female; 4 male), trabecular bone was completely removed from the femoral neck, providing one bone with intact and the other without any trabecular structure in the femoral neck. Geometrical, X-ray, and DXA measurements were carried out before biomechanical testing (forces to fracture). Femoral necks were osteotomized, slices were analyzed for cross-sectional area (CSA) and cross-sectional moment of inertia (CSMI), and results were compared with biomechanical testing data. Differences between forces needed to fracture excavated and intact femurs (DeltaF/F mean) was 7.0% on the average (range, 4.6-17.3%). CSA of removed spongiosa did not correlate with difference of fracture load (DeltaF/F mean), nor did BMD. The relative contribution of trabecular versus cortical bone in respect to bone strength in the femoral neck seems to be marginal and seems to explain the subordinate role of trabecular bone and its changes in fracture risk and the effects of treatment options in preventing fractures.

Stability of the upper neck during isometric neck exercises in rheumatoid arthritis patients with atlantoaxial disorders

Objective: To study the effect of isometric neck strength exercises on upper cervical stability in patients with rheumatoid arthritis (RA).Methods: Twenty patients with a mean (SD) age of 58 (9) years and duration of RA of 27 (10) years volunteered for the study. Lateral radiographs of the cervical spine were taken to measure the current atlantoaxial distance (AAD) in flexion and extension. Maximal isometric neck flexion and extension strength values were measured by a dynamometer. Thereafter, AADs were measured from radiographs taken at 80–90% resistance of maximal strength.Results: According to the full flexion radiographs at baseline, the patients were classified into three groups: eight patients without anterior atlantoaxial subluxation (aAAS) [AAD = 2.1 (2–3) mm], seven with unstable aAAS [AAD = 6.6 (5–8) mm], and five with stable aAAS [AAD = 5.5 (5–7) mm]. During resisted flexion the AAD decreased by 5 (3–7) mm (p<0.001) in the unstable aAAS group, while in the other two groups the changes were minor. During resisted extension the AAD increased by 3 (2–6) mm (p<0.001) in the cases with unstable aAAS only.Conclusion: Isometric exercising towards flexion decreases the AAD in cases with unstable aAAS. Submaximal loading of the neck extensors by pushing the back of the head against the resistance even in the neutral position of the cervical spine leads to a decrease in the width of the cervical spine canal and is not recommended in unstable aAAS.

Effect of Crystallization on High-Temperature Plastic Flow and Ductility in Pre-Annealed Zr-Al-Ni-Cu Bulk Metallic Glass

High-temperature plastic flow and tensile ductility in pre-annealed Zr65Al10Ni10Cu15 bulk metallic glass are examined in a supercooled liquid region. The specimen annealed at 673K for 1.8ks before the tensile test exhibits uniform deformation, and large elongation of 1100% is obtained in the tensile test at 673K and in a constant true strain rate of 1×10-2s-1. In the specimen, initial stress decreases in comparison with that of the specimen without annealing, but apparent strain hardening arise during deformation. SEM analysis after the deformation reveals that the cavitation is very limited even at the fracture tip. XRD and TEM analyses reveal that icosahedral phase is observed only in gage section but not in grip section after the deformation. The limited cavitation due to the accommodation of stress concentration through the grain boundary amorphous phase possibly makes a positive contribution to the large elongation in the annealed specimen, as well as the neck stability due to the strain hardening by the interaction between the icosahedral phase particles increasingly crystallized by the local strain.

Abdominal aortic aneurysm neck remodeling after open aneurysm repair

Proximal endovascular aortic graft fixation and maintenance of hemostatic seal depends on the long-term stability of the aortic neck. Previous investigations of aortic neck dilation mostly focused on the infrarenal aortic diameter. Fenestrated and branched stent grafts facilitate suprarenal graft fixation and may thereby improve the long-term integrity of the aortic attachment site. For these devices, the natural history of the suprarenal aortic segment is also of interest. We investigated the natural history of the supra- and infrarenal aortic segment after open abdominal aortic aneurysm (AAA) repair. For this retrospective analysis, we reviewed the preoperative and the initial postoperative as well as the most recent CT series that were obtained from 52 patients undergoing conventional repair of an infrarenal abdominal aortic aneurysm between January 1998 and December 2002. Measurements were performed using electronic calipers on a "split screen", allowing direct comparison of subsequent CT series at corresponding levels along the vessel. Main outcome measures were changes in postoperative measures of the supra- and infrarenal aortic diameters. The first postoperative exam was at a mean (+/-SD) of 7.0 +/- 3.5 months, and the final exams were at 44.4 +/- 21 months. Over this time period, the estimated rate of change in suprarenal diameter was 0.18 mm/ y with 95% confidence interval (CI) from 0.08 to 0.27. The estimated rate of change for the infrarenal diameter was 0.16 (95% CI: 0.05 to 0.27). A clinically relevant diameter increase of >or=3 mm was observed in seven patients (13%). There was evidence of larger diameter increases associated with larger AAA diameters (P = .003 and <.001 for suprarenal and infrarenal diameters), an inverted funnel shape (P = .002 and <.001), and marginal evidence of association with a history of inguinal hernia (P = .043 and .066). Although there is statistically significant evidence of increases in the supra- and infrarenal aortic diameters after conventional AAA repair, mean annual increases tended to be small and clinically relevant increases of 3 mm or more were observed in only a small proportion of cases.

Phosphorylation of Adult Type Sept5 (CDCrel-1) by Cyclin-dependent Kinase 5 Inhibits Interaction with Syntaxin-1

Increasing evidence implicates cyclin-dependent kinase 5 (Cdk5) in neuronal synaptic function. We searched for Cdk5 substrates in synaptosomal fractions prepared from mouse brains. Mass spectrometric analysis after two-dimensional SDS-PAGE identified several synaptic proteins phosphorylated by Cdk5-p35; one protein identified was Sept5 (CDCrel-1). Although septins were isolated originally as cell division-related proteins in yeast, Sept5 is expressed predominantly in neurons and is implicated in exocytosis. We confirmed that Sept5 is phosphorylated by Cdk5-p35 in vitro and identified Ser17 of adult type Sept5 (Sept5_v1) as a major phosphorylation site. We found that Ser17 of Sept5_v1 is phosphorylated in mouse brains. Coimmunoprecipitation from synaptosomal fractions and glutathione S-transferase-syntaxin-1A pulldown assays of Sept5_v1 expressed in COS-7 cells showed that phosphorylation of Sept5_v1 by Cdk5-p35 decreases the binding to syntaxin-1. These results indicate that the interaction of Sept5 with syntaxin-1 is regulated by the phosphorylation of Sept5_v1 at Ser17 by Cdk5-p35.

Cervicogenic dizziness – musculoskeletal findings before and after treatment and long-term outcome

Purpose. To explore musculoskeletal findings in patients with cervicogenic dizziness and how these findings relate to pain and dizziness. To study treatment effects and long-term symptom progress.Method. Twenty-two patients (20 women, 2 men; mean age 37 years) with suspected cervicogenic dizziness underwent a structured physical examination before and after physiotherapy guided by the musculoskeletal findings. Questionnaires were sent to the patients six months and two years after treatment.Results. Dorsal neck muscle tenderness and tightness was found in a majority of the patients. Zygapophyseal joint tenderness was found at all cervical levels. Cervical range of motion was equal to or larger than expected age and gender matched values. The cervico-thoracic region was often hypomobile. Most patients had postural imbalance. Dynamic stabilization capacity was reduced. Suboccipital muscles tightness correlated with posture imbalance and poor neck stability. The treatment resulted in reduced tenderness in levator scapula, high and middle paraspinal and temporalis muscles and zygapophyseal joints at C4-C7 and increased cervico-thoracic mobility. Reduction of middle paraspinal muscle tenderness correlated with neck pain relief. Postural alignment improved, as did dynamic stabilization in trunk, neck and shoulders. After 6 months, 13 of the 17 patients had still no or less neck pain and 14 had no or less dizziness. After 2 years, 7 patients had no or less neck pain and 11 no or less dizziness.Conclusion. Patients with suspected cervicogenic dizziness have some musculoskeletal findings in common. Treatment based on these findings reduces neck pain as well as dizziness long-term but some patients might need a maintenance strategy.

Hardening by Crystallization During Superplastic Flow in a Powder-metallurgy-processed Zr65Al10Ni10Cu15 Glass Metallic Alloy

The superplastic behavior of the Zr65Al10Ni10Cu15 glass metallic alloy produced by the powder metallurgy method was examined in the supercooled liquid region. A tensile elongation as large as 750% was obtained at 6.3 × 10−3 s−1 at 697 K. Large strain hardening took place during the course of deformation and systematic trend was observed in the hardening behavior. Plots of stress versus strain and strain rate versus stress at 697 K showed that Newtonian viscous flow governed the plastic flow until the onset of strain hardening. Microstructure and differential scanning calorimetry analyses as well as flow stress versus testing time curves provided consistent evidence that the strain hardening was induced by crystallization. Crystallization was enhanced in the gauge region (deformed region) as compared to the grip region (undeformed region). Crystallization is expected to decrease tensile ductility by decreasing the strain-rate-sensitivity value and increasing the degree of brittleness. Hardening by crystallization, however, can contribute to neck stability if crystallization is enhanced in the neck region. The strain hardening and plastic stability parameters were measured as a function of strain for different strain rates at 696 K. The strain hardening parameter remained highly positive until failure. Because of this, the neck stability parameter (I) could be I &lt; 0 in the entire hardening region. The contribution of hardening by crystallization to neck stability was found to be much more significant than that by grain growth in the superplastic metallic alloys. Reducing the specimen heating-and-holding time was suggested to promote superplasticity deformation without delaying initiation of crystallization. The largest tensile strain in the hardening region where crystallization may be obtained at the strain rates and temperatures where crystallization rate is controlled to be the lowest while maintaining I ≤ 0 throughout deformation.

High-Temperature Plastic Flow in Pre-Annealed Zr-Al-Ni-Cu Bulk Metallic Glass in a Supercooled Liquid Region

High-temperature plastic flow in pre-annealed Zr65Al10Ni10Cu15 bulk metallic glass is examined in a supercooled region, in order to clarify the effect of the change in microstructure on high-temperature plastic flow. The specimen without annealing exhibits significant necking, but the elongation of 550% is obtained in the tensile test at 673 K and in a constant true strain rate of 1 � 10 � 2 s � 1 . In contrast, the specimen annealed at 673 K for 1.8 ks before the tensile test exhibits uniform deformation, and large tensile ductility of 1100% is obtained. In the specimen, initial stress decreases in comparison with that of the specimen without annealing, but apparent strain hardening arise during deformation. XRD analysis reveals that no crystalline phase is detected in the specimen without annealing even after deformation. In contrast in the specimen annealed at 673 K for 1.8 ks, the peaks from icosahedral phase are observed only in gage section but not in grip section after deformation. Strain hardening due to the precipitation and growth of icosahedral phase, which is enhanced by deformation, must make a positive contribution to neck stability, and results in the large elongation in the annealed specimen.

Endoluminal repair of abdominal aortic aneurysm prevents enlargement of the proximal neck: a 9-year life-table and 5-year longitudinal study.

Endoluminal repair of abdominal aortic aneurysm (AAA) is predicated on stability of the proximal neck of the aneurysm. Reports on morphologic changes in the proximal neck after endoluminal repair of AAA have thus far been limited in duration to 3 years or less. The aim of this study was to document changes in diameter of the proximal neck of AAA in a group of patients who had undergone endoluminal repair between 5 and 9 years previously. Between May 1992 and December 1996, 61 patients with AAA were treated with endoluminal repair by the senior author. The following patients were excluded from the study group: those requiring primary conversion to open repair at the original operation (n = 8), those with false aneurysm (n = 1), and those with dissection in the proximal neck (n = 1). Fifty-one patients (48 men and three women) with a mean age of 71 years remained in the study group. The endoprostheses used were modified Parodi (n = 4), Endovascular Technologies (n = 14), White-Yu (n = 10), Stentor/Vanguard (n = 21), and Bard 1996 prototype (n = 2). Morphologic changes in the proximal aortic neck were studied with contrast computed tomographic scan with the methodology recommended by the Ad Hoc Committee for Standardized Reporting Practices for Endovascular AAA Repair (revised version). The maximum transverse diameter of the proximal neck was measured 1 cm below the most inferior renal artery. A Kaplan-Meier analysis was performed showing the proportion of patients at risk with a demonstrated enlargement of the neck at each interval of time compared with the predischarge computed tomographic scan. A longitudinal study of morphologic changes in the proximal aortic neck was also undertaken in 28 patients with successful endoluminal repair who survived 5 years. The Kaplan-Meier curve showed a probability of no dilatation of the proximal neck of 0.943 at 7 years after endoluminal AAA repair. Of 28 patients with 5 years of follow-up after discharge, only two had increases in the diameter of the proximal neck greater than 2 mm. The endograft in both patients had undergone migration before any proximal neck dilation. A paired t test showed that the overall average increase of 0.4 mm (standard error, 0.3 mm) in these 28 patients was not statistically significant (P =.23). A high probability (0.943 at 7 years) exists of no enlargement of the proximal neck of AAA after endoluminal repair. We hypothesize that endografts positioned correctly immediately below the renal arteries protect the proximal neck from dilatation in a manner that does not occur after open repair of AAA.

Percutaneous therapy of osteoid osteoma

Osteoid osteomas are tumors with intense clinical symptoms and extensive reactive bone changes far exceeding the volume of the lesion itself. Because of their small size they can be approached by minimally invasive surgical procedures. We treated ten symptomatic patients with osteoid osteomas (n 6 hip point, n 1 iliac bone, n 1 femoral diaphysis, n 2 tibial diaphysis) by excision of the nidus with a 3-mm Harlow-Wood needle using a percutaneous CT-guided approach. Seven patients with residual tumor were treated with either thermocautery (n 2) or sclerosis with 1 ml of 96% ethanol (n 5). Six patients had instant and constant relief (3 years' observation) of their pain. In two patients a second transcutaneous intervention was successful. Only two patients needed open resection. Compared with the invasive open resection of the tumors, sometimes even putting the stability of the femoral neck at risk, transcutaneous CT-guided enucleation of the nidus of the osteoid osteoma with additional sclerotherapy is a good alternative method, especially in the region of the femoral neck.

Observations and analysis of results in 131 cases of spasmodic torticollis after selective denervation.

In 131 patients treated exclusively by selective denervation during the past 10 years, all or almost all the abnormal movements of spasmodic torticollis were suppressed in 115 (88%) while preserving posture and mobility. This approach was also used in certain forms of adult-onset dystonia. An appreciable amount of abnormal movements remained in the other patients, either due to residual innervation or because of limitation of denervation necessary to preserve normal movements (laterocollis) or neck stability (retrocollis). A medio-lateral approach to the posterior cervical region in the sitting position using stimulation under light anaesthesia is recommended.

Rayleigh's criterion for the neck stability in heavy-ion reactions and fission.

Rayleigh's stability criterion for a cylinder of a classical, incompressible fluid against pinching is generalized to a fluid with a diffuse surface, appropriate in particular for applications in nuclear physics. The stability is governed by the wavelength of the perturbation and the surface thickness, both in comparison to the cylinder radius. The stability diagram is constructed.