In-vitro comparison of LC-DCP- and LCP-constructs in the femur of newborn calves - a pilot study.

Background: To compare the biomechanical in-vitro characteristics of limited-contact dynamic compression plate (LC-DCP) and locking compression plate (LCP) constructs in an osteotomy gap model of femoral fracture in neonatal calves. Pairs of intact femurs from 10 calves that had died for reasons unrelated to the study were tested. A 7-hole LC-DCP with six 4.

The influence of different osteosynthesis configurations with locking compression plates (LCP) on stability and fracture healing after an oblique 45° angle osteotomy.

Background: Locking compression plates are used in various configurations with lack of detailed information on consequent bone healing.

Study Design: In this in vivo study in sheep 5 different applications of locking compression plate (LCP) were tested using a 45° oblique osteotomy simulating simple fracture pattern. 60 Swiss Alpine sheep where assigned to 5 different groups with 12 sheep each (Group 1: interfragmentary lag screw and an LCP fixed with standard cortex screws as neutralisation plate; Group 2: interfragmentary lag screw and LCP with locking head screws; Group 3: compression plate technique (hybrid construct); Group 4: internal fixator without fracture gap; Group 5: internal fixator with 3mm gap at the osteotomy site).

Mechanical anchorage and peri-implant bone formation of surface-modified zirconia in minipigs.

Aim: To test the hypothesis that peri-implant bone formation and mechanical stability of surface-modified zirconia and titanium implants are equivalent.

Materials And Methods: Twelve minipigs received three types of implants on either side of the mandible 8 weeks after removal of all pre-molar teeth: (i) a zirconia implant with a sandblasted surface; (ii) a zirconia implants with a sandblasted and etched surface; and (iii) a titanium implant with a sandblasted and acid-etched surface that served as a control. Removal torque and peri-implant bone regeneration were evaluated in six animals each after 4 and 13 weeks.

Prediction of dental implant torque with a fast and automatic finite element analysis: a pilot study.

Objectives: Despite its importance, implant removal torque can be assessed at present only after implantation. This paper presents a new technique to help clinicians preoperatively evaluate implant stability.

Study Design: Planning software has been combined with an in-house finite element solver.

Quantifying the influence of bone density and thickness on resonance frequency analysis: an in vitro study of biomechanical test materials.

Purpose: Resonance frequency analysis (RFA) offers the opportunity to monitor the osseointegration of an implant in a simple, noninvasive way. A better comprehension of the relationship between RFA and parameters related to bone quality would therefore help clinicians improve diagnoses. In this study, a bone analog made from polyurethane foam was used to isolate the influences of bone density and cortical thickness in RFA.

Viscoelastic properties of the ovine posterior spinal ligaments are strain dependent.

Background: The biomechanical role of the posterior spinal ligaments for spinal stability has been stated in previous studies. The investigation of the viscoelastic properties of human lumbar spinal ligaments is essential for the understanding of physiological differences between healthy and degenerated tissues. The stress-relaxation behavior of biological tissues is commonly described with the quasi-linear viscoelastic model of Fung, which assumes that the stress-relaxation response is independent of the applied strain.

Biomechanical analysis of torsion and shear forces in lumbar and lumbosacral spine segments of nonchondrodystrophic dogs.

Objective: To determine stiffness and load-displacement curves as a biomechanical response to applied torsion and shear forces in cadaveric canine lumbar and lumbosacral specimens.

Study Design: Biomechanical study.

Animals: Caudal lumbar and lumbosacral functional spine units (FSU) of nonchondrodystrophic large-breed dogs (n=31) with radiographically normal spines.

Comparative biomechanical investigation of a modular dynamic lumbar stabilization system and the Dynesys system.

The goal of non-fusion stabilization is to reduce the mobility of the spine segment to less than that of the intact spine specimen, while retaining some residual motion. Several in vitro studies have been conducted on a dynamic system currently available for clinical use (Dynesys). Under pure moment loading, a dependency of the biomechanical performance on spacer length has been demonstrated; this variability in implant properties is removed with a modular concept incorporating a discrete flexible element.

Biomechanical analysis of the three-dimensional motion pattern of the canine cervical spine segment C4-C5.

Objective: To study the kinematics of cervical spine segment C(4)-C(5) and its association with disc dimensions and the coupled motion (CM) in relation to primary motion (PM).

Study Design: Cadaveric biomechanical study.

Animals: Cadavers of large breed dogs (>20 kg; n=11).

A robust and accurate two-stage approach for automatic recovery of distal locking holes in computer-assisted intramedullary nailing of femoral shaft fractures.

It has been recognized that one of the most difficult steps in intramedullary nailing of femoral shaft fractures is the distal locking - the insertion of distal transverse interlocking screws, for which it is necessary to know the positions and orientations of the distal locking holes (DLHs) of the intramedullary nail (IMN). This paper presents a robust and accurate approach for solving this problem based on two calibrated and registered fluoroscopic images. The problem is formulated as a two-stage model-based optimal fitting process.

Vertebral endplate trauma induces disc cell apoptosis and promotes organ degeneration in vitro.

There is a major controversy whether spinal trauma with vertebral endplate fractures can result in post-traumatic disc degeneration. Intervertebral discs, which are adjacent to burst endplates, are frequently removed and an intercorporal spondylodesis is performed. In any case, the biological effects within the discs following endplate fractures are poorly elucidated to date.

Accurate and reliable pose recovery of distal locking holes in computer-assisted intra-medullary nailing of femoral shaft fractures: a preliminary study.

Objective: One of the difficult steps in intra-medullary nailing of femoral shaft fractures is distal locking - the insertion of distal interlocking screws. Conventionally, this is performed using repeated image acquisitions, which leads to considerable irradiation of the patient and surgical team. Virtual fluoroscopy has been used to reduce radiation exposure, but can only provide multi-planar two-dimensional projection views.

Minimizing errors during in vitro testing of multisegmental spine specimens: considerations for component selection and kinematic measurement.

Apparatus-induced artifacts may invalidate standard spine testing protocols. Kinematic measurements may be compromised by the configuration of motion capture equipment. This study has determined: (1) the influence of machine design (component friction) on in vitro spinal kinetics; (2) the sensitivity of kinematic measurements to variations in the placement of motion capture markers.