Total Disk Replacement Adjacent to a Multilevel Fusion in the Cervical Spine: A Biomechanical Motion Analysis.

Objective: Cervical total disk replacement (TDR) has emerged as a motion-preserving alternative to anterior cervical diskectomy fusion (ACDF). Biomechanical studies have demonstrated that the TDR preserves motion at the diseased segment and minimizes motion and stress at adjacent segments compared with fusion. There has been growing interest in performing a TDR adjacent to a cervical fusion.

Biomechanical Strength of Retrograde Fixation in Proximal Third Scaphoid Fractures.

Current techniques for fixation of proximal pole scaphoid fractures utilize antegrade fixation via a dorsal approach endangering the delicate vascular supply of the dorsal scaphoid. Volar and dorsal approaches demonstrate equivalent clinical outcomes in scaphoid wrist fractures, but no study has evaluated the biomechanical strength for fractures of the proximal pole. This study compares biomechanical strength of antegrade and retrograde fixation for fractures of the proximal pole of the scaphoid.

The combination of tibial anterior translation and axial rotation into a single biomechanical factor improves the prediction of patient satisfaction over each factor alone in patients with ACL reconstructed knees.

Purpose: The purpose of this study was to identify biomechanical factors, in both reconstructed and healthy knees, that correlate with patient satisfaction after ACL reconstruction.

Methods: Seventeen patients who had undergone unilateral ACL reconstruction were reviewed 9 years post-op. Patients completed subjective questionnaires and underwent manual knee laxity testing (Lachman-Trillat, KT-1000, and pivot shift) and automated laxity testing.

Is It "In" or "Out"? The Optimal Fluoroscopic Views for Intraoperative Determination of Proper Lateral Mass Screw Placement.

Study Design: Cadaveric.

Objective: Determine optimal fluoroscopic views for detecting cervical lateral mass screw (LMS) violations.

Summary Of Background Data: Single plane intraoperative x-rays are commonly used but frequently inadequate due to its complex trajectory.

High-intensity stretch treatment for severe postoperative adhesive capsulitis of the shoulder.

Background: Some patients with postoperative adhesive capsulitis reach a plateau in their recovery with a standard protocol of physical therapy (PT), which puts them at risk for further surgical intervention.

Objectives: We aimed to evaluate therapy for postoperative adhesive capsulitis of the shoulder in 2 groups of patients: (1) those who used a high-intensity stretch (HIS) device after reaching a plateau in their recovery with a standard protocol of traditional PT (PT+HIS) and (2) those who showed no plateau in their recovery with a standard protocol of traditional PT alone (PT only).

Methods: We retrospectively reviewed the records for 60 patients (51 males; mean age 46.

Biomechanical effects of rotator interval closure in shoulder arthroplasty.

Background: Subscapularis dysfunction remains a significant problem after shoulder arthroplasty. Published techniques have variable recommendations for placing a rotator interval closing suture in attempts to off-load the subscapularis repair site, the implications of which have yet to be examined in the literature. The goals of this study were to investigate the biomechanical benefit of the rotator interval closing suture on the subscapularis repair strength and to analyze the effect on shoulder range of motion.

The effect of capacitively coupled (CC) electrical stimulation on human disc nucleus pulposus cells and the relationship between CC and BMP-7.

Purpose: An in vitro study using human intervertebral disc nucleus pulposus cells to evaluate the effects of CC stimulation on disc-matrix macromolecule production.

Methods: Nucleus pulposus cells were cultured in alginate beads and treated with CC stimulation. The effect of BMP on CC stimulation of the cells was evaluated by applying a BMP blocker (noggin) or by applying additional BMP-7 to the culture.

Improving Spanning-Knee External Fixator Stiffness: A Biomechanical Study.

The purpose of this study was to test and compare external fixator construct stiffness using pin-to-bar clamps or multipin clamps across 2 external fixation systems. Constructs were tested with 8-mm and 11-mm-diameter bar systems and pin-to-bar or multipin clamps. Three construct designs were tested: construct 1 with a single crossbar and pin-to-bar clamps, construct 2 with 2 crossbars and pin-to-bar clamps, and construct 3 with 2 crossbars and multipin clamps.

A biomechanical comparison of 360° stabilizations for corpectomy and total spondylectomy: a cadaveric study in the thoracolumbar spine.

Background: To date, there has been no adequate biomechanical model that would allow a quantitative comparison in terms of stability/stiffness between a corpectomy with the posterior column preserved and a total spondylectomy with the posterior column sacrificed. The objective of this study was to perform a biomechanical comparison of 360° stabilizations for corpectomy and total spondylectomy, using the human thoracolumbar spine.

Methods: Five human cadaveric thoracolumbar spines (T8-L2) were tested according to the following loading protocol: axial compression, flexion, extension, lateral bending to the right and left, and axial rotation to the right and left.

Two fixation methods for acromioclavicular joint reduction during coracoclavicular ligament reconstruction: a biomechanical analysis.

One specimen from each of six pairs of cadaveric shoulders underwent a semitendinosus coracoclavicular ligament reconstruction with a hook plate used for acromioclavicular joint reduction, while on the other specimen a polydioxanone (PDS) suture braid was utilized. Cyclical loading followed by maximal load-to-failure testing was performed. Displacement during cyclical loading, loads to 50% and 100% displacement, stiffness, and maximal load to failure were determined for all specimens.

The effect of hubbing on the pull-out strength of lateral mass screws in the cervical spine: a biomechanical experiment.

Study Design: This was a cadaveric biomechanical experiment.

Objective: To compare the pull-out strength of polyaxial screws that are either hubbed or not hubbed when inserted into the lateral mass.

Summary Of Background Data: It has been shown in a study on pedicle screws in the thoracic spine that "hubbing" the head of the screw against the dorsal laminar cortex results in significantly lower pull-out strength of the screws.

Comparison of screw trajectory on stability of oblique scaphoid fractures: a mechanical study.

Purpose: To determine whether a screw placed perpendicular to the fracture line in an oblique scaphoid fracture will provide fixation strength that is comparable with that of a centrally placed screw.

Methods: Oblique osteotomies were made along the dorsal sulcus of 8 matched pairs of cadaveric scaphoids. One scaphoid from each pair was randomized to receive a screw placed centrally down the long axis.

Arthroscopic repair of triangular fibrocartilage tears: a biomechanical comparison of a knotless suture anchor and the traditional outside-in repairs.

Purpose: To compare the biomechanical strength of a knotless suture anchor repair and the traditional outside-in repair of peripheral triangular fibrocartilage complex (TFCC) tears in a cadaveric model.

Methods: We dissected the distal ulna and TFCC from 6 matched cadaveric wrist pairs and made iatrogenic complete peripheral TFCC tears in each wrist. In 6 wrists, the TFCC tears were repaired using the standard outside-in technique using 2 2-0 polydioxane sutures placed in a vertical mattress fashion.

Bone morphogenetic protein-7 antagonizes tumor necrosis factor-α-induced activation of nuclear factor κB and up-regulation of the ADAMTS, leading to decreased degradation of disc matrix macromolecules aggrecan and collagen II.

Background Context: Tumor necrosis factor-α (TNF-α) is a regulatory cytokine that can increase the activity of enzymes such as ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs), which degrade disc matrix. ADAMTS are enzymes that break down disc matrix and thereby mediate disc degeneration. Bone morphogenetic protein-7 (BMP-7), on the other hand, stimulates synthesis of the disc extracellular matrix and is a potential therapeutic molecule for the treatment of disc degeneration.

Link protein N-terminal peptide binds to bone morphogenetic protein (BMP) type II receptor and drives matrix protein expression in rabbit intervertebral disc cells.

Intervertebral disc (IVD) degeneration and associated spinal disorders are leading sources of morbidity, and they can be responsible for chronic low back pain. Treatments for degenerative disc diseases continue to be a challenge. Intensive research is now focusing on promoting regeneration of degenerated discs by stimulating production of the disc matrix.

The effect of pedicle screw redirection after lateral wall breach--a biomechanical study using human lumbar vertebrae.

Background Context: Currently, pedicle screw segmental fixation of the spine is considered a standard of care for a number of conditions. Most surgeons employ a free-hand technique using various intraoperative modalities to improve pedicle screw accuracy. Despite continued improvements in technique, pedicle breach remains a frequent occurrence.

Microendoscopic lateral decompression for lumbar foraminal stenosis: a biomechanical study.

Study Design: A biomechanical study.

Objective: How much of the facet joint and the pars interarticularis (PI) can be removed in microendoscopic lateral decompression (MELD) for lumbar foraminal stenosis (LFS)?

Summary Of Background Data: MELD is a surgical modality for patients with LFS. In severe degenerative cases, unilateral facet joint resection or unilateral removal of the lateral part of the PI are sometimes needed to decompress the nerve root adequately.

A novel low-molecular-weight compound enhances ectopic bone formation and fracture repair.

Background: Use of recombinant human bone morphogenetic protein-2 (rhBMP-2) is expensive and may cause local side effects. A small synthetic molecule, SVAK-12, has recently been shown in vitro to potentiate rhBMP-2-induced transdifferentiation of myoblasts into the osteoblastic phenotype. The aims of this study were to test the ability of SVAK-12 to enhance bone formation in a rodent ectopic model and to test whether a single percutaneous injection of SVAK-12 can accelerate callus formation in a rodent femoral fracture model.

Changes of number of cells expressing proliferation and progenitor cell markers with age in rabbit intervertebral discs.

Basic knowledge about the normal regeneration process within the intervertebral disc (IVD) is important to the understanding of the underlying biology. The presence of progenitor and stem cells in IVD has been verified. However, changes of number of progenitor and stem cells with age are still unknown.

ISSLS Prize winner: Effect of link protein peptide on human intervertebral disc cells.

Study Design: An in vitro study using human intervertebral disc cells.

Objective: To evaluate the effect of link protein peptide (LPP) on the expression of disc extracellular matrix macromolecules sulfated glycosaminoglycan, aggrecan, and collagen II. To determine the effect of LPP on catabolic regulators and to compare LPP with both BMP2 and BMP7 in terms of osteoinductivity.

A biomechanical study of two different pedicle screw methods for fixation in osteoporotic and nonosteoporotic vertebrae.

In reconstruction of the osteoporotic spine, patients often show poor outcome because of pedicle screw failure. This study used osteoporotic and nonosteoporotic vertebrae to determine the difference in fixation strength between pedicle screws inserted straight forward and pedicle screws inserted in an upward trajectory toward the superior end plate (i.e.

Pulsed Electromagnetic Field (PEMF) plus BMP-2 upregulates intervertebral disc-cell matrix synthesis more than either BMP-2 alone or PEMF alone.

Study Design: An in vitro study using human intervertebral disc (IVD) cells.

Objectives: To determine if pulsed electromagnetic field (PEMF) plus bone morphogenetic protein (BMP)-2 could upregulate IVD-cell matrix synthesis more than either BMP-2 alone or PEMF alone.

Summary Of Background Data: BMP-7 and BMP-2 can both upregulate IVD-cell matrix synthesis.

The effect of spinal shortening after total en bloc spondylectomy: a biomechanical study in the thoracic spine.

Study Design: A biomechanical study using human cadaveric thoracic spine specimens.

Objective: To evaluate and compare the biomechanical effects of spinal shortening and cross-links in reconstruction after total en bloc spondylectomy (TES).

Summary Of Background Data: There have been no studies that have examined the biomechanical effects of spinal reconstruction after multilevel TES or the biomechanical effects of spinal shortening in reconstruction after TES.

E-cadherin upregulates expression of matrix macromolecules aggrecan and collagen II in the intervertebral disc cells through activation of the intracellular BMP-Smad1/5 pathway.

E-cadherin is a transmembrane protein that mediates cell-cell adhesion and cell-matrix interaction. Although the E-cadherin has been shown to mediate a broad-ranging cellular signals and functions, its effects on matrix metabolism of intervertebral discs (IVDs) are unknown. In this study, we investigated the effects of E-cadherin on IVD matrix synthesis using pharmacological and molecular biology methods.