A biomechanical comparison of superior and anterior positioning of precontoured plates for midshaft clavicle fractures.

With recent studies suggesting improved outcomes in displaced midshaft clavicle fractures treated with open reduction and internal fixation, debate has increased over the preferred plate positioning. Biomechanical studies have yielded conflicting results and have been limited by the almost exclusive use of a simple transverse fracture model. We conducted a study to biomechanically compare superior and anterior plate positioning for clinically relevant midshaft clavicle fracture patterns.

Inflammatory response of intervertebral disc cells is reduced by fibrin sealant scaffold in vitro.

Intervertebral disc (IVD) degeneration is a complex process characterized by elevated concentrations of proinflammatory cytokines and proteolytic enzymes. Because of pro-healing constituents, we hypothesized that fibrin sealant (FS) can reduce inflammation and augment soft tissue healing within the damaged or degenerative IVD. To test this, human and porcine nucleus pulposus (NP) and annulus fibrosus (AF) cells were extracted from tissues and encapsulated into alginate beads (NP cells) and type I collagen sponges (AF cells).

Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.

Purpose: The purpose of this study was to compare the biomechanical properties of transosseous versus suture anchor repair of the subscapularis tendon. We also performed real-time measurement of contact area and pressure of the repair site under rotational loads.

Methods: Six paired human cadaveric shoulders were subjected to rotational loading after repair of the subscapularis tendon.

Disc arthroplasty design influences intervertebral kinematics and facet forces.

Background Context: Total disc replacement is a novel approach for dynamically stabilizing a painful intervertebral segment. While this approach is gaining popularity, and several types of implants are used, the effect of disc arthroplasty on lumbar biomechanics has not been widely reported. Consequently, beneficial or adverse effects of this procedure may not be fully realized, and data for kinematic optimization are unavailable.

The instant axis of rotation influences facet forces at L5/S1 during flexion/extension and lateral bending.

Because the disc and facets work together to constrain spinal kinematics, changes in the instant axis of rotation associated with disc degeneration or disc replacement may adversely influence risk for facet overloading and arthritis. The relationships between L5/S1 segmental kinematics and facet forces are not well defined, since previous studies have separated investigations of spinal motion and facet force. The goal of this cadaveric biomechanical study was to report and correlate a measure of intervertebral kinematics (the centrode, or the path of the instant axis of rotation) and the facet forces at the L5/S1 motion segment while under a physiologic combination of compression and anterior shear loading.

Biomechanically derived guideline equations for burst fracture risk prediction in the metastatically involved spine.

Methods to quantify burst fracture risk and neurologic deficit for patients with spinal metastases have not been well defined. This study aims to develop objective biomechanically based guidelines to quantify metastatic burst fracture risk. An experimentally validated finite element model of a human lumbar motion segment was used to simulate burst fracture.

Burst fracture in the metastatically involved spine: development, validation, and parametric analysis of a three-dimensional poroelastic finite-element model.

Study Design: A finite-element study and in vitro experimental validation was performed for a parametric investigation of features that contribute to burst fracture risk in the metastatically involved spine.

Objectives: To develop and validate a three-dimensional poroelastic model of a metastatically compromised vertebral segment, to evaluate the effect of lytic lesions on vertebral strains and pressures, and to determine the influence of loading and motion segment status (bone density, pedicle involvement, disc degeneration, and tumor size) on the relative risk of burst fracture initiation.

Summary Of Background Data: Finite-element analysis has been used successfully to predict failure loads and fracture patterns for bone.

Strain in the median and ulnar nerves during upper-extremity positioning.

The purpose of this study was to quantify the strain of the median nerve and the ulnar nerve throughout upper-extremity positioning sequences used by clinicians to evaluate nerve dysfunction. A microstrain gauge was used to quantify strain and digital calipers were used to assess nerve excursion in 4, fresh, intact cadavers. Data analysis of noncontinuous motion trials showed that the median nerve tension test caused a maximum summative strain in the median nerve at the carpal tunnel of 7.