Andrew T Mahar

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STUDY DESIGN In vitro biomechanical investigation using human cadaveric cervical spines. OBJECTIVE Evaluate differences in biomechanical stability between typical lateral mass screw + rod constructs compared to transfacet screw fixation with and without rods. SUMMARY OF BACKGROUND DATA Lateral mass screw + rod constructs have reported efficacious(More)
STUDY DESIGN Normal cohort evaluation of the accuracy of existing methods for radiographic measurement of sagittal spinal balance. OBJECTIVES To examine the validity and reliability of sagittal vertical axis measurements during a variety of standing positions commonly used while obtaining lateral thoracolumbar spine radiographs. SUMMARY OF THE(More)
Knee prosthetic designs that increase quadriceps moment arm can reduce quadriceps tension and patellofemoral compressive forces. Six knees from cadavers were tested on the Oxford knee rig, which simulates closed chain knee extension under load. Three conditions were tested sequentially for each knee: Normal, Control (implanted with the Osteonics 7000 knee(More)
Femoral head coverage achieved with an acetabular osteotomy for hip dysplasia is achieved by acetabular rotation that can be restricted by osteotomy orientation and soft tissue attachments to the acetabular fragment. Procedures that allow excess rotation or motion in an undesirable direction (especially external rotation) may have undesirable consequences.(More)
Flexion-extension radiographs are commonly used to assess lumbar fusion. Recommended criteria for solid fusion have varied from 1 to 5 degrees of angular motion between vertebrae. Notwithstanding this wide variation, the validity of these criteria have never been biomechanically tested. As a preliminary and initial step, it was the authors' purpose to(More)
The purpose of this study was to compare the biomechanical stability of triple innominate osteotomies fixed with either bioabsorbable or stainless steel screws. Triple innominate osteotomies were performed on composite hemipelves and fixed with either three 4.5-mm bioabsorbable screws or three stainless steel 4.5-mm screws. Two screws were placed from the(More)
STUDY DESIGN Biomechanical evaluation of sacropelvic fixation strategies as they apply to neuromuscular scoliosis. OBJECTIVES The primary objective was to compare the rigidity of 2 methods of sacropelvic fixation (Galveston vs. Colorado II). The secondary objective was to evaluate the effect on construct rigidity by adding a pair of L1 pedicle screws to a(More)
BACKGROUND Little evidence is available addressing biomechanical properties of posterior distraction forces and their effects on anterior spinal column in the growing rod technique. The question is often asked if posterior distraction forces may be kyphogenic. The goal of this study is to determine whether posterior distraction forces transmitted anteriorly(More)
STUDY DESIGN In vitro biomechanical investigation of lumbosacropelvic spinal instrumentation. OBJECTIVE Determine whether unilateral iliac fixation, with or without an L6 to S1 interbody graft, provides equivalent biomechanical stability compared with bilateral iliac fixation. SUMMARY OF BACKGROUND DATA Recent clinical evidence has shown improved(More)
OBJECT Biomechanical testing and fluoroscopic imaging were used to study an extension-limiting device that has been developed to support and cushion the facet complex. It is a titanium screw-based system with a polycarbonate-urethane bumper that lies against the inferior articular process and is anchored into the pedicle by the screw for posterior dynamic(More)