Extension Stiffness Research Articles

Metacarpophalangeal joint stiffness. Still a challenge for the hand surgeon?

ObjectivesThe aim of this study is to analyse the outcomes of the surgical treatment of metacarpophalangeal stiffness by dorsal teno-arthrolysis in our centre, and present a review the literature. Material and methodsThis is a retrospective study of 21 cases of metacarpophalangeal stiffness treated surgically. Dorsal teno-arthrolysis was carried out on all patients. A rehabilitation programme was started ten days after surgery. An evaluation was performed on the aetiology, variation in pre- and post-operative active mobility, complications, DASH questionnaire, and a subjective satisfaction questionnaire. ResultsThe mean age of the patients was 36.5 years and the mean follow-up was 6.5 years. Of the 21 cases, the most common cause was a metacarpal fracture (52.4%), followed by complex trauma of the forearm (19%). Improvement in active mobility was 30.5°, despite obtaining an intra-operative mobility 0–90° in 80% of cases. Mean DASH questionnaire score was 36.9 points. The outcome was described as excellent in 10% of our patients, good in 30%, poor in 40%, and bad in the remaining 20%. There was a complex regional pain syndrome in 9.5% of cases, and intrinsic muscle injury in 14.3%. ConclusionBecause of its difficult management and poor outcomes, surgical treatment of metacarpophalangeal stiffness in extension is highly complex, with dorsal teno-arthrolysis being a reproducible technique according to our results, and the results reported in the literature.

Rigideces metacarpofalángicas en extensión. ¿Un desafío para el cirujano de mano?

ObjectivesThe aim of this study is to analyse the outcomes of the surgical treatment of metacarpophalangeal stiffness by dorsal teno-arthrolysis in our centre, and present a review the literature. Material and methodsThis is a retrospective study of 21 cases of metacarpophalangeal stiffness treated surgically. Dorsal teno-arthrolysis was carried out on all patients. A rehabilitation programme was started ten days after surgery. An evaluation was performed on the aetiology, variation in pre- and post-operative active mobility, complications, DASH questionnaire, and a subjective satisfaction questionnaire. ResultsThe mean age of the patients was 36.5 years and the mean follow-up was 6.5 years. Of the 21 cases, the most common cause was a metacarpal fracture (52.4%), followed by complex trauma of the forearm (19%). Improvement in active mobility was 30.5°, despite obtaining an intra-operative mobility 0-90° in 80% of cases. Mean DASH questionnaire score was 36.9 points. The outcome was described as excellent in 10% of our patients, good in 30%, poor in 40%, and bad in the remaining 20%. There was a complex regional pain syndrome in 9.5% of cases, and intrinsic muscle injury in 14.3%. ConclusionBecause of its difficult management and poor outcomes, surgical treatment of metacarpophalangeal stiffness in extension is highly complex, with dorsal teno-arthrolysis being a reproducible technique according to our results, and the results reported in the literature.

Right-Left Differences in Knee Extension Stiffness for the Normal Rat Knee: In Vitro Measurements Using a New Testing Apparatus.

Knee stiffness following joint injury or immobilization is a common clinical problem, and the rat has been used as a model for studies related to joint stiffness and limitation of motion. Knee stiffness measurements have been reported for the anesthetized rat, but it is difficult to separate the contributions of muscular and ligamentous restraints to the recorded values. in vitro testing of isolated rat knees devoid of musculature allows measurement of joint structural properties alone. In order to measure the effects of therapeutic or surgical interventions designed to alter joint stiffness, the opposite extremity is often used as a control. However, right-left stiffness differences for the normal rat knee have not been reported in the literature. If stiffness changes observed for a treatment group are within the normal right-left variation, validity of the results could be questioned. The objectives of this study were to utilize a new testing apparatus to measure right-left stiffness differences during knee extension in a population of normal rat knees and to document repeatability of the stiffness measurements on successive testing days. Moment versus rotation curves were recorded for 15 right-left pairs of normal rat knees on three consecutive days, with overnight specimen storage in a refrigerator. Each knee was subjected to ten loading-unloading cycles, with the last loading curve used for analysis. Angular rotation (AR), defined here as the change in flexion-extension angle from a specified applied joint moment, is commonly used as a measure of overall joint stiffness. For these tests, ARs were measured from the recorded test curves with a maximum applied extension moment of 100 g cm. Mean rotations for testing days 2 and 3 were 0.81-1.25 deg lower (p < 0.001) than for day 1, but were not significantly different from each other. For each testing day, mean rotations for right knees were 1.12-1.30 deg greater (p < 0.001) than left knees. These right-left stiffness differences should be considered when interpreting the results of knee treatment studies designed to alter knee stiffness when using the opposite extremity as a control.

Biomechanical Comparison of Spinopelvic Fixation Constructs: Iliac Screw Versus S2-Alar-Iliac Screw

Study DesignBiomechanical cadaveric study. ObjectiveTo compare the biomechanical properties of the iliac and S2-Alar-Iliac (S2AI) screw in a similar spinopelvic fixation construct. Summary of Background DataSpinopelvic fixation is used in the correction of pelvic obliquity, high-grade spondylolisthesis, and long spinal fusions. With the development of pedicle screw fixation, the iliac screw has been used as an anchor point to the pelvis. The associated morbidity with this fixation has led to the development of the S2AI screw. Many studies have examined the biomechanical properties of iliac and S2AI screws; however, a direct comparison has not been performed. MethodsEight cadaveric spines were instrumented with pedicle screws bilaterally at L5 and S1. Four specimens were further instrumented with iliac screws placed with a starting point at the posterior superior iliac spine, and four specimens were instrumented with S2AI screws placed with a starting point 1 mm inferolateral to the S1 foramen. Screws were connected with 6.35 mm rods. Subfailure testing was performed by loading at 1°/second to a torque of 10 Nm in four directions: left bending, right bending, extension, and flexion. Specimens then underwent a monotonic load to failure under flexion at a rate of 1°/second. ResultsThere were no significant differences for torsional stiffness in extension, flexion, left bending, or right bending between S2AI and iliac screw constructs. There were no significant differences in S2AI versus iliac screws for failure torque (30.9 ± 12.00 Nm vs. 22.61 ± 6.25 Nm) and yield torque (11.86 ± 0.41 Nm vs. 12.01 ± 1.70 Nm). ConclusionIliac screws have been associated with increased dissection, wound complications, an additional construct failure point, and hardware prominence. The S2AI screw was developed as an alternative and has been associated with less morbidity. The iliac and S2AI screw demonstrate no statistical difference in stiffness and load-to-failure in a spinopelvic fixation model. Level of EvidenceLevel V.

L’arthrogrypose : manifestations cliniques et prise en charge

Arthrogryposis is a condition existing at birth, seen in different diseases that have in common the existence of multiple joint stiffness. The clinical presentation is diversified and the functional prognosis depends on the etiology, which makes therapeutic options different from one case to another. The objective of this study was to describe clinical manifestations observed in arthrogrypotic patients and show the different therapeutic methods and functional results. This was a retrospective study over a period of 12 years from 2000 to 2012, based on clinical examinations of 23 patients with arthrogryposis. The mean age of the patients was 6.6 years. The four limbs were involved in 19 cases and only the lower limbs in four cases. The etiology was amyoplasia in nine patients, distal arthrogryposis in three, peripheral neuropathy in two, and muscular atrophy in one infantile patient. Foot deformities were observed in 22 cases, with 25 talipes equinovarus deformities (clubfoot), six convex feet, and five valgus feet. The Ponseti method was applied in 12 clubfeet with recurrence in eight cases. The other clubfeet had functional treatment and necessitated surgical release in 11 cases. Deformation of the knee was seen in 15 patients, flessum in 16 knees, restriction of flexion in eight cases, genu recurvatum in three, stiffness in extension in two, and agenesis of the patella in one case. Surgical treatment was carried out in only one case. Other cases of deformity of the knee were treated by rehabilitation with slight improvement. Deformation of the hip was seen in 15 patients, with 16 hips dislocated and four hips in flessum. The dislocation of the hip was treated orthopaedically in two cases and surgically in six cases, with reduction in all cases but persistence of stiffness. Involvement of the shoulders was observed in eight cases, the elbow in seven cases, the wrist in ten cases, and the fingers in 16 cases. The treatment was based on physical therapy and orthotics in all cases, and improvement was better in the wrist and fingers. Arthrogryposis has different clinical presentations. Successful treatment is not constant. Multidisciplinary care is necessary and should be early and continued in order to gain the maximum autonomy and facilitate patients' social integration.

In vitro biomechanical evaluation of four fixation techniques for distractive–flexion injury stage 3 of the cervical spine

Purpose. Anterior plate fixation has been reported to provide satisfactory results in cervical spine distractive flexion (DF) injuries stages 1 and 2, but will result in a substantial failure rate in more unstable stage 3 and above. The aim of this investigation was to determine the biomechanical properties of different fixation techniques in a DF-3 injury model where all structures responsible for the posterior tension band mechanism are torn.Methods. The multidirectional three-dimensional stiffness of the subaxial cervical spine was measured in eight cadaveric specimens with a simulated DF-3 injury at C5–C6, stabilized with four different fixation techniques: anterior plate alone, anterior plate combined with posterior wire, transarticular facet screws, and a pedicle screw–rod construct, respectively.Results. The anterior plate alone did not improve stability compared to the intact spine condition, thus allowing considerable range of motion around all three cardinal axes (p > 0.05). The anterior plate combined with posterior wire technique improved flexion–extension stiffness (p = 0.023), but not in axial rotation and lateral bending. When the anterior plate was combined with transarticular facet screws or with a pedicle screws–rod instrumentation, the stability improved in flexion–extension, lateral bending, and in axial rotation (p < 0.05).Conclusions. These findings imply that the use of anterior fixation alone is insufficient for fixation of the highly unstable DF-3 injury. In these situations, the use of anterior fixation combined with a competent posterior tension band reconstruction (e.g. transarticular screws or a posterior pedicle screws–rod device) improves segmental stability.

Development of a new suturing technique for tendon graft preparation: An animal cadaver study

BackgroundThis study should analyze ten different suturing techniques for tendon graft preparation to allow the development of an entirely new suturing technique. MethodsExtensor tendon grafts of fattening bulls' forelegs were sutured with Ethibond Excel size three (six metric) fibers (Ethicon, Somerville, New York, USA). The tendon/suture complexes were biomechanically tested with a hydraulic testing machine applying traction according to a standardized protocol. The testing was observed to find out why the failure at the maximum traction load occurred. The mean values for the maximum tension and extension stiffness were recorded for each suturing technique. FindingsAn entirely new suturing technique was developed based on the observations and biomechanical results. The newly developed suture was also tested and provided a higher traction stability than the other ten techniques that had been evaluated. Compared to the other ten techniques the new technique was ranked 3rd in terms of extension stiffness and reached 10.3N/mm. InterpretationThe new technique evolved in the course of this study provided promising results. Therefore this study provides initial evidence that this technique could be useful in clinical routine.

Field Application of Cable Tension Estimation Technique Using the h-SI Method

This paper investigates field applicability of a new system identification technique of estimating tensile force for a cable of long span bridges. The newly proposed h-SI method using the combination of the sensitivity updating algorithm and the advanced hybrid microgenetic algorithm can allow not only avoiding the trap of local minimum at initial searching stage but also finding the optimal solution in terms of better numerical efficiency than existing methods. First, this paper overviews the procedure of tension estimation through a theoretical formulation. Secondly, the validity of the proposed technique is numerically examined using a set of dynamic data obtained from benchmark numerical samples considering the effect of sag extensibility and bending stiffness of a sag-cable system. Finally, the feasibility of the proposed method is investigated through actual field data extracted from a cable-stayed Seohae Bridge. The test results show that the existing methods require precise initial data in advance but the proposed method is not affected by such initial information. In particular, the proposed method can improve accuracy and convergence rate toward final values. Consequently, the proposed method can be more effective than existing methods in terms of characterizing the tensile force variation for cable structures.

Modeling and Identification of Asymmetric Hysteresis in Smart Actuators: a Modified Maxwell-slip Model Approach

This paper proposes a modified Maxwell-slip (MS) model to capture convex and/or concave asymmetric hysteresis in smart actuators. The original MS model can only capture antisymmetric hysteresis. To overcome this limitation, generalized elasto-slide operators (ESOs) are constructed to replace MS elements. Each ESO is characterized by its spring extension stiffness constant, maximum extension, compression stiffness constant, and maximum compression. A procedure is also proposed to identify the model parameters. Simulation and experimental results show that the proposed model is capable of reproducing convex and/or concave asymmetric hysteresis and improving the fit between the modeling and experimental results.

Biomechanical comparison of an interspinous fusion device and bilateral pedicle screw system as additional fixation for lateral lumbar interbody fusion

BackgroundThis investigation compares an interspinous fusion device with posterior pedicle screw system in a lateral lumbar interbody lumbar fusion. MethodsWe biomechanically tested six cadaveric lumbar segments (L1–L2) under an axial preload of 50N and torque of 5Nm in flexion–extension, lateral bending and axial rotation directions. We quantified range of motion, neutral zone/elastic zone stiffness in the following conditions: intact, lateral discectomy, lateral cage, cage with interspinous fusion, and cage with pedicle screws. FindingsA complete lateral discectomy and annulectomy increased motion in all directions compared to all other conditions. The lateral cage reduced motion in lateral bending and flexion/extension with respect to the intact and discectomy conditions, but had minimal effect on extension stiffness. Posterior instrumentation reduced motion, excluding interspinous augmentation in axial rotation with respect to the cage condition. Interspinous fusion significantly increased flexion and extension stiffness, while pedicle screws increased flexion/extension and lateral bending stiffness, with respect to the cage condition. Both posterior augmentations performed equivalently throughout the tests except in lateral bending stiffness where pedicle screws were stiffer in the neutral zone. InterpretationA lateral discectomy and annulectomy generates immediate instability. Stand-alone lateral cages restore a limited amount of immediate stability, but posterior supplemental fixation increases stability. Both augmentations are similar in a single level lateral fusion in-vitro model, but pedicle screws are more equipped for coronal stability. An interspinous fusion is a less invasive alternative than pedicle screws and is potentially a conservative option for various interbody cage scenarios.

Biomechanical Evaluation of 5 Fixation Devices for Proximal Interphalangeal Joint Arthrodesis

To determine in a cadaver model which, among 5 fixation methods for proximal interphalangeal (PIP) joint arthrodesis, has the greatest stiffness. Thirty-five cadaver digits were randomly assigned to 1 of 5 fixation groups: oblique K-wire with coronal intraosseous wiring, tension-band wire (TBW), dorsal plate, intramedullary linked screw (IMS), and 90/90 wiring (90/90W). Testing was done by applying bending moments to the PIP joint in the sagittal and frontal planes. The force/displacement curves were used to estimate the stiffness of each construct. Ultimate strength was determined by loading to failure in extension. The IMS had significantly higher stiffness than all wiring constructs in all planes of motion and significantly greater stiffness in extension than the dorsal plate. The IMS stiffness exceeded 10 N/mm across all bending directions and showed an ultimate strength of 21 N. The plate demonstrated higher stiffness in radial bending than the oblique K-wire with coronal intraosseous wiring and TBW. There were no differences in stiffness between the IMS and plate in all modes of testing except extension. Load-to-failure testing of the devices showed the IMS device to be significantly stronger than the TBW, 90/90W, and plating constructs. The IMS resisted larger bending moments than all wiring constructs and showed the greatest ultimate strength when compared with 3 of the tested arthrodesis techniques. The plate was significantly better than 2 of the wiring constructs, but only in radial bending. No differences were found between the, TBW, and 90/90W when compared with each other. The stiffness necessary for a successful PIP joint fusion has not been quantified, but according to this study, the IMS was the most favorable biomechanical construct for initial stability.

A cadaveric analysis of cervical fixation: the effect of intermediate fixation points and dynamization in multilevel cervical fusions.

The authors conducted a study to compare biomechanical effects on the cervical spine of bridging fixation and intermediate fixation techniques, in both fixed and dynamic modes. A biaxial, servohydraulic machine biomechanically tested 23 human cervical spines for stiffness and strain in compression, extension, flexion, and lateral bending through 3 specimen states: 1) intact, 2) defect (corpectomy and discectomy), and 3) grafting with plate application in 1 of 4 constructs: C3-7 dynamized long strut (DLS), C3-7 fixed long strut (FLS), C3-5-7 dynamized multisegment (DMS), and C3-5-7 fixed multisegment (FMS). Compared with FMS, FLS had significantly greater strain in extension (at C-3 and at the rostral and caudal parts of the graft) and in lateral bending (at C-3 and at the caudal part of the graft). Fixed (FLS and FMS) constructs had greater flexion stiffness than did dynamized (DLS and DMS) constructs and showed a trend toward greater lateral bending stiffness. Instrumentation revealed greater extension strain with the long fixed (FLS and DLS) constructs than with the multifixed (FMS and FMS) constructs at the rostral and caudal parts of the graft but no significant differences between the dynamized (DLS and DMS) and fixed (FLS and FMS) constructs. Multisegmental fixation provided greater stabilizing forces than did bridging constructs for both dynamized and fixed plates. Use of multisegmental fixation can potentially decrease strain at the screw-plate interface and reduce the rate of hardware failure.

Polimiosite por Neospora caninum em um filhote de golden retriever – relato de caso

Neosporosis is a disease caused by the protozoan Neospora caninum that can lead to neurological signs and death in dogs. There are not many reports of this disease in Brazil. The aim of this paper is to describe a case of neosporosis in a young male golden retriever that presented limited mobility, pain and spasticity of the hind limbs. Result of serodiagnosis (IIF-IgG) was positive for Neospora (titer of 6400). The presence of clinical signs associated with high serology titers allowed the presumptive diagnosis of neosporosis. Antimicrobial therapy with trimethoprim sulfamethoxazole and pyrimethamine was instated for 120 days. The animal was monitored during this period and also underwent to physiotherapy sessions. There was partial improvement, although muscle contracture remained. This disease should be considered an important differential diagnosis in young dogs with extension stiffness and contracture of the hind limbs.

Finite Element Based Nonlinear Normalization of Human Lumbar Intervertebral Disc Stiffness to Account for Its Morphology

Disc degeneration, usually associated with low back pain and changes of intervertebral stiffness, represents a major health issue. As the intervertebral disc (IVD) morphology influences its stiffness, the link between mechanical properties and degenerative grade is partially lost without an efficient normalization of the stiffness with respect to the morphology. Moreover, although the behavior of soft tissues is highly nonlinear, only linear normalization protocols have been defined so far for the disc stiffness. Thus, the aim of this work is to propose a nonlinear normalization based on finite elements (FE) simulations and evaluate its impact on the stiffness of human anatomical specimens of lumbar IVD. First, a parameter study involving simulations of biomechanical tests (compression, flexion/extension, bilateral torsion and bending) on 20 FE models of IVDs with various dimensions was carried out to evaluate the effect of the disc's geometry on its compliance and establish stiffness/morphology relations necessary to the nonlinear normalization. The computed stiffness was then normalized by height (H), cross-sectional area (CSA), polar moment of inertia (J) or moments of inertia (Ixx, Iyy) to quantify the effect of both linear and nonlinear normalizations. In the second part of the study, T1-weighted MRI images were acquired to determine H, CSA, J, Ixx and Iyy of 14 human lumbar IVDs. Based on the measured morphology and pre-established relation with stiffness, linear and nonlinear normalization routines were then applied to the compliance of the specimens for each quasi-static biomechanical test. The variability of the stiffness prior to and after normalization was assessed via coefficient of variation (CV). The FE study confirmed that larger and thinner IVDs were stiffer while the normalization strongly attenuated the effect of the disc geometry on its stiffness. Yet, notwithstanding the results of the FE study, the experimental stiffness showed consistently higher CV after normalization. Assuming that geometry and material properties affect the mechanical response, they can also compensate for one another. Therefore, the larger CV after normalization can be interpreted as a strong variability of the material properties, previously hidden by the geometry's own influence. In conclusion, a new normalization protocol for the intervertebral disc stiffness in compression, flexion, extension, bilateral torsion and bending was proposed, with the possible use of MRI and FE to acquire the discs' anatomy and determine the nonlinear relations between stiffness and morphology. Such protocol may be useful to relate the disc's mechanical properties to its degree of degeneration.

Knee Extension and Stiffness in Osteoarthritic and Normal Knees: A Videofluoroscopic Analysis of the Effect of a Single Session of Manual Therapy

Descriptive biomechanical study using an experimental repeated-measures design. To quantify the response of participants with and without knee osteoarthritis (OA) to a single session of manual physical therapy. The intervention consisted primarily of joint mobilization techniques, supplemented by exercises, aiming to improve knee extension. While manual therapy benefits patients with knee OA, there is limited research quantifying the effects of a manual therapy treatment session on either motion or stiffness of osteoarthritic and normal knees. Methods The study included 5 participants with knee OA and 5 age-, gender-, and body mass index-matched healthy volunteers. Knee extension motion and stiffness were measured with videofluoroscopy before and after a 30-minute manual therapy treatment session. Analysis of variance and intraclass correlation coefficients were used to analyze the data. Participants with knee OA had restricted knee extension range of motion at baseline, in contrast to the participants with normal knees, who had full knee extension. After the therapy session, there was a significant increase in knee motion in participants with knee OA (P = .004) but not in those with normal knees (P = .201). For stiffness data, there was no main effect for time (P = .903) or load (P = .274), but there was a main effect of group (P = .012), with the participants with healthy knees having greater stiffness than those with knee OA. Reliability, using intraclass correlation coefficient model 3,3, for knee angle measurements between imaging sessions for all loading conditions was 0.99. Reliability (intraclass correlation coefficient model 3,1) for intraimage measurements was 0.97. End-range knee extension stiffness was greater in the participants with normal knees than those with knee OA. The combination of lesser stiffness and lack of motion in those with knee OA, which may indicate the potential for improvement, may explain why increased knee extension angle was observed following a single session of manual therapy in the participants with knee OA but not in those with normal knees. Videofluoroscopy of the knee appears reliable and relevant for future studies attempting to quantify the underlying mechanisms of manual therapy. J Orthop Sports Phys Ther 2014;44(4):273-282. Epub 25 February 2014. doi:10.2519/jospt.2014.4710.

The effect of design parameters of interspinous implants on kinematics and load bearing: an in vitro study

A number of concepts with controversy approaches are currently discussed for interspinous stabilization (IPS). However, comparative biomechanical studies among the different systems are rare. Nevertheless, it remains unclear which biomechanical characteristics are influenced by different design features of these implants, such as implant stiffness or an additional tension band. Therefore, the aim of the present study was to compare different interspinous implants to investigate the biomechanical impact of IPS implant design on intersegmental kinematics, such as range of motion, neutral zone, center of rotation (COR), as well as load transfer like intradiscal pressure (IDP), to gain additional experience for clinical indications and limitations. Twelve human lumbar spine specimens were tested in a spine loading apparatus. In vitro flexibility testing was performed by applying pure bending moments of 7.5 Nm without and with additional preload of 400 N in the three principal motion planes. Four interspinous implants, Coflex "COF" (Paradigm Spine, Germany), Wallis "WAL" (Abbott Laboratories, France), DIAM "DIA" (Sofamor Danek, France) and InterActiv (Aesculap AG, Germany) with two treatment options (without dorsal tensioning "IAO" and with dorsal tensioning "IAM") were consecutively tested in comparison to the native situation "NAT" and to a defect situation "DEF" of the functional spinal unit. The tested IPS devices are comprised of a compression stiffness range of 133 to 1,674 N/mm and a tensile stiffness range of 0-39 N/mm. Range of motion, neutral zone, center of rotation and intradiscal pressure were analyzed for all instrumentation steps and load cases. For the IPS, we found a correlation between compression stiffness and stabilization in extension. Here, the system with the lowest stiffness, DIA, displayed nearly no stabilization of the treated segment, whereas the system with the highest stiffness, WAL and COF, was most pronounced. This applies also for the correlation between device stiffness and IDP. In flexion only the degree of stabilization is in correlation with the tensile stiffness, whereas the IDP stays constant and is not affected by the different tensile stiffness. IPS is not able to stabilize in the frontal and transversal plane. Furthermore IPS does not substantially alter the location of the COR.

Feasibility and biomechanical performance of a novel transdiscal screw system for one level in non-spondylolisthetic lumbar fusion: an in vitro investigation

Background contextThe bilateral pedicle screw system (BPSS) is currently the “gold standard” fusion technique for spinal instability. A new stabilization system that provides the same level of stability through a less invasive procedure will have a high impact on clinical practice. A new transdiscal screw system is investigated as a promising minimally invasive device. PurposeTo evaluate the feasibility of a novel transdiscal screw in spinal fixation as an alternative to BPSS, with and without an interbody cage, in non-spondylolisthesis cases. Study designAn in vitro biomechanical study in lumbar cadaveric spines. MethodsTwelve lumbar cadaveric segments (L4–S1) were tested under flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Six treatments were simulated as follows: (1) intact, (2) bilateral facetectomy at L4–L5, (3) transdiscal screw system, (4) BPSS, (5) BPSS with transforaminal lumbar interbody cage, and (6) transdiscal screws with transforaminal interbody cage. Specimens were randomly divided into two testing groups: Group 1 (n=6) was tested under the first five conditions, in the order presented, whereas Group 2 (n=6) was tested under the first, second, third, fourth, and sixth conditions, with the fourth condition preceding the third. Range of motion (ROM) and neutral zone stiffness (NZS) were estimated and normalized with respect to the intact condition to explore statistical differences among treatments using non-parametric approaches. ResultsSignificant differences in FE ROM were observed in the pedicle screws-cage condition with respect to the facetectomy (p<.01), the pedicle screw (p=.03), and the transdiscal screw (p<.02) conditions. All fixation constructs significantly restricted LB and AR ROM (p<.01) with respect to facetectomy. In terms of stiffness, the pedicle screw and the transdiscal screw systems increased (p<.01) LB and AR NZS with respect to facetectomy. The pedicle screws-cage condition significantly increased flexion and extension stiffness with respect to all other conditions (p<.05). However, LB NZS for the pedicle screws-cage and the transdiscal screws-cage condition could not be explored due to a testing order bias effect. There was not enough evidence to state any difference between the pedicle and transdiscal screw conditions in terms of ROM or NZS. ConclusionsTransdiscal and pedicle screw systems showed comparable in vitro biomechanical performance in the immediate stabilization of a complete bilateral facetectomy. The pedicle screws-cage condition was the most stable in FE motion; however, comparison with respect to the transdiscal screws-cage condition could not be investigated.

헬리콥터 무베어링 로터 허브 복합재 유연보 피로 안전수명 해석

After we designed Bearingless rotor hub system for 7,000lb class helicopter, flexbeam fatigue analysis was conducted for validation of requirement life time 8,000 hours. sectional structural analysis method applying elastic beam model was used. Fatigue analysis for two sections of flexbeam which were expected to weak to fatigue damage from result of static analysis was conducted. Extension, bending and torsion stiffness of flexbeam section shape was calculated using VABS for structure analysis. S-N curve of two composite material which composed flexbeam was generated using wohler equation. Load analysis of bearingless rotor system was conducted using CAMRAD II and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used flexbeam fatigue safe life analysis.

Dynamic Biomechanical Examination of the Lumbar Spine with Implanted Total Spinal Segment Replacement (TSSR) Utilizing a Pendulum Testing System

BackgroundBiomechanical investigations of spinal motion preserving implants help in the understanding of their in vivo behavior. In this study, we hypothesized that the lumbar spine with implanted total spinal segment replacement (TSSR) would exhibit decreased dynamic stiffness and more rapid energy absorption compared to native functional spinal units under simulated physiologic motion when tested with the pendulum system.MethodsFive unembalmed, frozen human lumbar functional spinal units were tested on the pendulum system with axial compressive loads of 181 N, 282 N, 385 N, and 488 N before and after Flexuspine total spinal segment replacement implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5°; resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and bending stiffness (N-m/°) was calculated and compared for each testing mode.ResultsThe total spinal segment replacement reached equilibrium with significantly fewer cycles to equilibrium compared to the intact functional spinal unit at all loads in flexion (p<0.011), and at loads of 385 N and 488 N in lateral bending (p<0.020). Mean bending stiffness in flexion, extension, and lateral bending increased with increasing load for both the intact functional spinal unit and total spinal segment replacement constructs (p<0.001), with no significant differences in stiffness between the intact functional spinal unit and total spinal segment replacement in any of the test modes (p>0.18).ConclusionsLumbar functional spinal units with implanted total spinal segment replacement were found to have similar dynamic bending stiffness, but absorbed energy at a more rapid rate than intact functional spinal units during cyclic loading with an unconstrained pendulum system. Although the effects on clinical performance of motion preserving devices is not fully known, these results provide further insight into the biomechanical behavior of this device under approximated physiologic loading conditions.

Dynamic Biomechanical Examination of the Lumbar Spine With Implanted Total Disc Replacement Using a Pendulum Testing System

Biomechanical cadaver investigation. To examine dynamic bending stiffness and energy absorption of the lumbar spine with and without implanted total disc replacement (TDR) under simulated physiological motion. The pendulum testing system is capable of applying physiological compressive loads without constraining motion of functional spinal units (FSUs). The number of cycles to equilibrium observed under pendulum testing is a measure of the energy absorbed by the FSU. Five unembalmed, frozen human lumbar FSUs were tested on the pendulum system with axial compressive loads of 181 N, 282 N, 385 N, and 488 N before and after Synthes ProDisc-L TDR implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5º resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and bending stiffness (N·m/º) was calculated and compared for each testing mode. In flexion/extension, the TDR constructs reached equilibrium with significantly (P < 0.05) fewer cycles than the intact FSU with compressive loads of 282 N, 385 N, and 488 N. Mean dynamic bending stiffness in flexion, extension, and lateral bending increased significantly with increasing load for both the intact FSU and TDR constructs (P < 0.001). In flexion, with increasing compressive loading from 181 N to 488 N, the bending stiffness of the intact FSUs increased from 4.0 N·m/º to 5.5 N·m/º, compared with 2.1 N·m/º to 3.6 N·m/º after TDR implantation. At each compressive load, the intact FSU was significantly stiffer than the TDR (P < 0.05). Lumbar FSUs with implanted TDR were found to be less stiff, but absorbed more energy during cyclic loading with an unconstrained pendulum system. Although the effects on clinical performance of motion-preserving devices are not fully known, these results provide further insight into the biomechanical behavior of these devices under approximated physiological loading conditions.