Biomechanical properties and thermal characteristics of frozen versus thawed whole bone.

Biomechanics research often requires cadaveric whole bones to be stored in a freezer and then thawed prior to use; however, the literature shows a variety of practices for thawing. Consequently, this is the first study to report the mechanical properties of fully frozen versus fully thawed whole bone as 'proof of principle'. Two groups of 10 porcine ribs each were statistically equivalent at baseline in length, cross-sectional area, and bone mineral density.

Experimental Validation of the Radiographic Union Score for Tibial Fractures (RUST) Using Micro-Computed Tomography Scanning and Biomechanical Testing in an in-Vivo Rat Model.

Background: The Radiographic Union Score for Tibial fractures (RUST) and the modified version of the system, mRUST, are popular standards for assessing fracture-healing progress with use of radiographs. To our knowledge, this is the first study to experimentally validate the ability of RUST and mRUST to accurately assess bone-healing progression with use of both micro-computed tomography (micro-CT) scanning and biomechanical testing.

Methods: Adult male rats (n = 29) underwent osteotomy with a midshaft fracture gap repaired with use of a polyetheretherketone plate.

Biomechanical Testing of a 3-Hole Versus a 4-Hole Sliding Hip Screw in the Presence of a Retrograde Intramedullary Nail for Ipsilateral Intertrochanteric and Femur Shaft Fractures.

Objective: The goal of this study was to compare a 3-hole versus a 4-hole sliding hip screw (SHS) in the presence of a retrograde intramedullary (RIM) nail for fixing intertrochanteric and comminuted midshaft femur fractures.

Methods: Mechanical tests were performed on 10 matched pairs of human cadaveric femurs that were osteotomized and then fixed using a 3-hole SHS versus the traditional "gold standard" 4-hole SHS in the presence of an RIM nail.

Results: Data showed no differences between the 3-hole SHS with RIM nail versus 4-hole SHS with RIM nail for stiffness (281 ± 127 vs.

Estimating the density of femoral head trabecular bone from hip fracture patients using computed tomography scan data.

The purpose of this study was to compare computed tomography density (ρ ) obtained using typical clinical computed tomography scan parameters to ash density (ρ ), for the prediction of densities of femoral head trabecular bone from hip fracture patients. An experimental study was conducted to investigate the relationships between ρ and ρ and between each of these densities and ρ and ρ . Seven human femoral heads from hip fracture patients were computed tomography-scanned ex vivo, and 76 cylindrical trabecular bone specimens were collected.

3D atlas-based registration can calculate malalignment of femoral shaft fractures in six degrees of freedom.

Objective: This study presents and evaluates a semi-automated algorithm for quantifying malalignment in complex femoral shaft fractures from a single intraoperative cone-beam CT (CBCT) image of the fractured limb.

Methods: CBCT images were acquired of complex comminuted diaphyseal fractures created in 9 cadaveric femora (27 cases). Scans were segmented using intensity-based thresholding, yielding image stacks of the proximal, distal and comminuted bone.

Biomechanical measurements of stopping and stripping torques during screw insertion in five types of human and artificial humeri.

During orthopedic surgery, screws are inserted by "subjective feel" in humeri for fracture fixation, that is, stopping torque, while trying to prevent accidental over-tightening that causes screw-bone interface failure, that is, stripping torque. However, no studies exist on stopping torque, stripping torque, or stopping/stripping torque ratio in human or artificial humeri. This study evaluated five types of humeri, namely, human fresh-frozen (n = 19), human embalmed (n = 18), human dried (n = 15), artificial "normal" (n = 13), and artificial "osteoporotic" (n = 13).

Biomechanical measurements of stiffness and strength for five types of whole human and artificial humeri.

The human humerus is the third largest longbone and experiences 2-3% of all fractures. Yet, almost no data exist on its intact biomechanical properties, thus preventing researchers from obtaining a full understanding of humerus behavior during injury and after being repaired with fracture plates and nails. The aim of this experimental study was to compare the biomechanical stiffness and strength of "gold standard" fresh-frozen humeri to a variety of humerus models.

Biomechanical measurements of cortical screw purchase in five types of human and artificial humeri.

Humerus shaft fracture fixation is largely dependent on cortical screw purchase in host bone. Only 2 prior studies assessed cortical screw purchase in human humeral shafts, but were of very limited scope and did not fully assess humerus material properties. Also, no studies evaluated the human dried or artificial humeri both commercially available from Sawbones.

The biomechanical effect of artificial and human bone density on stopping and stripping torque during screw insertion.

Orthopedic surgeons apply torque to metal screws manually by "subjective feel" to obtain adequate fracture fixation, i.e. stopping torque, and attempt to avoid accidental over-tightening that leads to screw-bone interface failure, i.

Can fluoroscopy-based computer navigation improve entry point selection for intramedullary nailing of femur fractures?

Background: The entry point is crucial to an accurate reduction in femoral nailing. Fluoroscopy-based navigation was developed to aid in reducing femur fractures and selecting entry points.

Questions/purposes: We asked: (1) Can the piriformis fossa (PF) and tip of the greater trochanter (TT) be identified with high reproducibility? (2) What is the range of nonneutral images clinically acceptable for entry point selection? (3) Does navigation improve accuracy and precision of landmarking the TT and PF? And (4) does off-angle fluoroscopy within the acceptable range affect landmark accuracy?

Methods: Three orthopaedic surgeons digitized the PF and TT under direct visualization on 10 cadaveric femurs, quantifying the reproducibility of the targeted PF and TT landmarks.

Biomechanical measurements of surgical drilling force and torque in human versus artificial femurs.

Few experimental studies have examined surgical drilling in human bone, and no studies have inquired into this aspect for a popular commercially-available artificial bone used in biomechanical studies. Sixteen fresh-frozen human femurs and five artificial femurs were obtained. Cortical specimens were mounted into a clamping system equipped with a thrust force and torque transducer.

Can a semi-automated surface matching and principal axis-based algorithm accurately quantify femoral shaft fracture alignment in six degrees of freedom?

Accurate alignment of femoral shaft fractures treated with intramedullary nailing remains a challenge for orthopaedic surgeons. The aim of this study is to develop and validate a cone-beam CT-based, semi-automated algorithm to quantify the malalignment in six degrees of freedom (6DOF) using a surface matching and principal axes-based approach. Complex comminuted diaphyseal fractures were created in nine cadaveric femora and cone-beam CT images were acquired (27 cases total).

Biomechanical measurements of cortical screw stripping torque in human versus artificial femurs.

Femur fracture plates are applied using cortical bone screws. Surgeons do this manually by subjective 'feel' without monitoring torque. Few studies have quantified stripping torque in human bone.

Biomechanical measurements of axial crush injury to the distal condyles of human and synthetic femurs.

Few studies have evaluated the 'bulk' mechanical properties of human longbones and even fewer have compared human tissue to the synthetic longbones increasingly being used by researchers. Distal femur fractures, for example, comprise about 6% of all femur fractures, but the mechanical properties of the distal condyles of intact human and synthetic femurs have not been well quantified in the literature. To this end, the distal portions of a series of 16 human fresh-frozen femurs and six synthetic femurs were prepared identically for mechanical testing.

Computer navigation in the reduction and fixation of femoral shaft fractures: a randomized control study.

Objectives: We investigated the accuracy of reduction of intramedullary nailed femoral shaft fractures in human cadavers, comparing conventional and computer navigation techniques.

Methods: Twenty femoral shaft fractures were created in human cadavers, with segmental defects ranging from 9 to 53 mm in length (Winquist 3-4, AO 32C2). All fractures were fixed with antegrade 9 mm diameter femoral nails on a radiolucent operating table.

High-viscosity cement significantly enhances uniformity of cement filling in vertebroplasty: an experimental model and study on cement leakage.

Study Design: Experimental study using a laboratory leakage model.

Objective: To examine the working hypothesis that high-viscosity cements will spread uniformly, thus significantly reducing the risk of leakage.

Summary Of Background Data: In vertebroplasty, forces that govern the flow of bone cement in the trabecular bone skeleton are an essential determinant of the uniformity of cement filling.