Fibroblast orientation to stretch begins within three hours.

Most connective tissue cells align in response to stretch. Previous studies have shown these responses occur within 12-14 h of initiation of stretch, but do not identify the time at which this orientation occurs, nor whether the orientation continues after cessation of stretch. To ascertain the earliest times at which fibroblast orientation occurs, we cultured primary human fibroblasts on deformable culture dishes and stretched (1 Hz, 8% uniaxial strain) them for up to 24 h.

Posterior atlantoaxial fixation: biomechanical in vitro comparison of six different techniques.

Study Design: Six different techniques for atlantoaxial fixation were biomechanically compared in vitro by nondestructive testing.

Objective: To evaluate the immediate three-dimensional stability of a new atlas claw combined with transarticular screws and alternative techniques for transarticular screw fixation in comparison with established techniques.

Summary Of Background Data: Posterior transarticular screw fixation in combination with wire-bone graft constructs is frequently used for C1-C2 fixation.

Monitoring and healing analysis of 100 tibial shaft fractures.

Background: We assessed the value of measuring biomechanical stiffness by assessing the fixator's external deformation as an objective means for monitoring fracture healing and determining the postoperative treatment regime, as compared to clinical and radiographic means of evaluation.

Patients And Methods: One hundred patients with tibial shaft fractures managed by unilateral external fixation had their fracture stiffness monitored. Stiffness was measured and clinical and radiological examinations were performed every 3-4 weeks.

[Intramedullary femoral osteosynthesis with the "rendezvous procedure". A new philosophy of retrograde intramedullary nailing].

Objective: The disadvantages of retrograde intramedullary nailing are the necessity of explanting the nail through the knee and the occasional difficulties with proximal interlocking. The new retrograde intramedullary nail includes the following innovations: The nail is inserted into the medullary canal beyond the great trochanter, so that a proximal aiming device can be used. The nail is removed through the proximal opening.

Effects of one-plane and two-plane external fixation on sheep osteotomy healing and complications.

Objectives: Comparison of one-plane and two-plane external fixation in terms of successful healing, incidence of complications, and biomechanical stability in a sheep model.

Background: Rigid fixation is preferred in open and comminuted fractures with a reduced blood supply, preventing infection and healing delay, but more often a flexible device is recommended even in unfavourable healing conditions.

Methods: The left tibiae of fifteen sheep were osteotomized and laterally fixed with a four-screw unilateral fixator frame (axial stiffness 183 N/mm) to a 3 mm gap size.

The traumatic spondylolisthesis of the axis. A biomechanical in vitro evaluation of an instability model and clinical relevant constructs for stabilization.

Objective: Stepwise destabilization of the traumatic spondylolisthesis C2 with an increasing anterior defect of C2-C3 was investigated. The three-dimensional stabilizing capabilities of posterior transpedicle screw osteosynthesis and two anterior plate systems C2-C3, the H-plate and the titanium locking plate were tested.

Design: A biomechanical in vitro study was performed using a standardized experimental protocol in a spine tester.

A scanning electron microscopy study of human osteoblast morphology on five orthopedic metals.

Despite the long-standing use of metals as orthopedic implants there still are unsolved problems with these materials and open questions about their behavior in a biological environment. Cell-culture studies provide a useful tool for investigations. In addition to the determination of biochemical or molecular biological parameters, the morphology of adhering cells reflects their interaction with the substrata.

Correlation of bone mineral density with strength and microstructural parameters of cortical bone in vitro.

The aim of this study was to evaluate the influence of microstructural parameters, such as porosity and osteon dimensions, on strength. Therefore, the predictive value of bone mineral density (BMD) measured by quantitative computed tomography (QCT) for intracortical porosity and other microstructural parameters, as well as for strength of cortical bone biopsies, was investigated. Femoral cortical bone specimens from the middiaphysis of 23 patients were harvested during total hip replacement while drilling a hole (dia.

[Dislocation tendency, stabilizing effect and sintering tendency of different lumbar vertebrae cages in an in vitro experiment].

For biomechanical purposes, interbody fusion cages should not dislocate, should provide high stability, and should have a low subsidence risk. Zientek (Marquardt Medzintechnik), Stryker (Stryker Implants), and Ray lumbar interbody fusion cages (Surgical Dynamics) were tested in this study. They were implanted by pairs from a posterior approach without further stabilization.

[Stabilizing effect and sintering tendency of 3 different cages and bone cement for fusion of cervical vertebrae segments].

Important requirement for spinal fusion devices for segment are that they provide sufficient stability and guarantee a low subsidence risk. An important requirement for spinal fusion devices for segments are that they provide sufficient stability and guarantee a low subsidence risk. Therefore, in the following in vitro study, the stabilizing effect and subsidence tendency of cervical fusion cages and bone cement were investigated during cyclic loading.

[Effect of artificial disk nucleus implant on mobility and intervertebral disk high of an L4/5 segment after nucleotomy].

This study investigated whether after a nucleotomy and implantation of a prosthetic disk nucleus (PDN) the original height and mobility of an L4/L5 disk can be restored. Compared to the intact state (100%), nucleotomy increased the median values of the normalized range of motion (ROM) in flexion/extension to 118%, lateral bending to 112%, and axial rotation to 121%. PDN implantation reduced ROM to 102%, 88%, and 90%.

From sulfoxide precursors to model oligomers of conducting polymers.

The gas-phase internal elimination (E(i)) reaction of the sulfoxide (-SO-CH(3)) precursors of ethylene and model oligomers of PPV and PITN has been investigated by means of Hartree-Fock, Møller-Plesset (second and fourth order), and Density Functional Theory (B3LYP, MPW1K) calculations. Considerable differences between the obtained ground state and transition state geometries and the calculated activation energies are observed from one approach to the other, justifying first a careful calibration against the results of a benchmark CCSD(T) study of the E(i) reaction leading to ethylene. In comparison with the CCSD(T) results, as well as with available experimental data, DFT calculations along with the MPW1K functional are found to be a very appropriate choice for describing the E(i) pathway.

[MACS-TL polyaxial screw XL. A new concept for increasing stability of ventral spondylodesis in the presence of dorsal injuries].

The influence of additional dorsal structure damage on anterior stabilization of thoracolumbar fracture is still unknown. Screw cement enhancement is a possibility to reinforce the stability of anterior instrumentation. A new anchorage system has been developed for fixation of anterior stabilization devices, adapted through geometric optimization and the possibility of optional additional cementation after screw insertion in cases of poor bone quality.

[MAC-TL twin screw. A new thoracoscopic implantable stabilization system for treatment of vertebral fractures--implant design, implantation technique and in vitro testing].

Due to the lack of an appropriate instrumentation system for minimally invasive procedures to treat spinal fracture, a new thoracoscopically implantable stabilization system was developed. This report describes the new implant design and implantation technique. In a biomechanical in vitro study, an anterior corpectomy model representing the worst case of burst fracture instability was simulated, and the primary stability parameters of the new system were evaluated in comparison to a dorsal stabilization system.

[Neon--a new angle-stable implant system for dorsal occipitocervical instrumentation. Biomechanical comparison with established systems].

Posterior instrumentation of the occipitocervical spine is well-established for different indications. The aim of this study was to evaluate whether posterior internal fixation of the occipitocervical spine with the new implant system improves primary biomechanical stability. Primary stability was significantly increased in all load cases with the new modular implant system compared to the other implant systems.

Proliferation of human-derived osteoblast-like cells depends on the cycle number and frequency of uniaxial strain.

We tested the hypothesis whether the number of applied load cycles and the frequency of uniaxial strain have an effect on proliferation of human bone derived osteoblast-like cells. A new approach was developed in order to differentiate between the effects of frequency and the effects of cycle number and strain duration. Monolayers of subconfluently grown cells were stretched in rectangular silicone dishes with cyclic predominantly uniaxial movement along there longitudinal axes.

Prediction of cortical bone porosity in vitro by microcomputed tomography.

The high importance of intracortical porosity for mechanical strength of cortical bone has been established. The contribution of other parameters of microstructure such as osteon dimensions for strength is in discussion. The aim of this study was to evaluate the predictive value of microcomputed tomography (mCT) for porosity and other microstructural parameters of cortical bone in cortical bone biopsies.

Primary stability in cementless femoral stems: custom-made versus conventional femoral prosthesis.

Objective: To compare a custom-made femoral stem with a conventional cementless stem for initial stability in human femurs.

Design: The bone-femoral prosthesis interface motion was measured in vitro using displacement transducers. Combined axial and torsional loads simulating single-leg stance, loading were applied.

Pullout test with three lumbar interbody fusion cages.

Study Design: In vitro biomechanical testing was performed on 12 cadaveric human lumbar spines.

Objective: To determine the initial dislocation resistance, as quantified by the pullout force of three different cage designs.

Summary Of Background Data: Interbody cage devices frequently are used as stand-alone cages in the surgical treatment of degenerative conditions in the lumbar spine.

A modified hip screw incorporating injected cement for the fixation of osteoporotic trochanteric fractures.

Objective: To evaluate a modified sliding hip screw for the fixation of trochanteric fractures that provides increased fixation strength in osteoporotic bones and allows for the safe intraoperative application of bone cement.

Design: Biomechanical cadaver study.

Materials: Unstable trochanteric fractures were simulated by osteotomy in nine pairs of cadaveric femurs and stabilized by a standard sliding hip screw randomly assigned to the left or right femur.

Mechanically simulated muscle forces strongly stabilize intact and injured upper cervical spine specimens.

Although muscles are assumed to be capable of stabilizing the spinal column in vivo, they have only rarely been simulated in vitro. Their effect might be of particular importance in unstable segments. The present study therefore tests the hypothesis that mechanically simulated muscle forces stabilize intact and injured cervical spine specimens.

Resistance of the lumbar spine against axial compression forces after implantation of three different posterior lumbar interbody cages.

Background: The aim of using interbody fusion cages is to distract the degeneratively decreased disc height to decompress the neural structures in the intervertebral foramina and allow bony fusion. Prerequisite for a successful fusion therapy is a high resistance against subsidence and breakage.

Method: Three types of implants, a cylindrical threaded titanium cage (Ray) (1c), a bullet shaped PEEK cage (Stryker) (1a) and a rectangular titanium cage with an endplate anchorage device (Marquardt) (1b) were implanted in eight monosegmental lumbar spine specimens (L 2/3 and L 4/5).

The effect of micromovement on callus formation.

Micromovement at fracture sites is known to promote callus formation and bridging of the bony fragments. The present study was conducted to identify the suitable amount of micromovement, and to analyze the location and timing of callus proliferation. A standardized transverse osteotomy, in the right metatarsus of 32 sheep, was used as a fracture model.

In vivo investigations on composites made of resorbable ceramics and poly(lactide) used as bone graft substitutes.

Porous composites made of poly(L, DL-lactide) (PLA) and alpha-tricalcium phosphate (alpha-TCP) or the glass ceramic, GB14N, respectively, were investigated in a loaded implant model in sheep. Six, 12 and 24 months after implantation histological and biomechanical evaluation were performed and compared to autogenous bone transplants. No significant differences were observed between the composites.

Resorbable polymer fibers for ligament augmentation.

Resorbable augmentation devices for cruciate ligament surgery have been developed to temporarily protect healing tendon grafts or sutured ligaments against high tensile loads during the postoperative healing period. Materials available at present [e.g.