Computational analysis of electrical stimulation to promote tissue healing for hernia repair at varying mesh placement planes.

Development of a tear in the abdominal wall allowing for protrusion of intra-abdominal contents is known as a hernia. This can cause pain, discomfort, and may need surgical repair. Hernias can affect people of any age or demographic.

A preliminary viability study of an electrically active hernia mesh on mouse fibroblasts.

Hernias occur when part of an organ, typically the intestines, protrudes through a disruption of the fascia in the abdominal wall, leading to patient pain, discomfort, and surgical intervention. Over one million hernia repair surgeries occur annually in the USA, but globally, hernia surgeries can exceed 20 million. Standard practice includes hernia repair mesh to help hold the compromised tissue together, depending on where the fascial disruption is located and the patient's condition.

Design considerations for piezoelectrically powered electrical stimulation: The balance between power generation and fatigue resistance.

Quality and timing of bone healing from orthopedic surgeries, especially lumbar spinal fusion procedures, is problematic for many patients. To address this issue, clinicians often use electrical stimulation to improve surgery success rates and decrease healing time in patients with increased risk of pseudarthrosis, including smokers and diabetics. Current invasive electrical stimulation devices require an implantable battery and a second surgery for removal.

Integration of clinical perspective into biomimetic bioreactor design for orthopedics.

The challenges to accommodate multiple tissue formation metrics in conventional bioreactors have resulted in an increased interest to explore novel bioreactor designs. Bioreactors allow researchers to isolate variables in controlled environments to quantify cell response. While current bioreactor designs can effectively provide either mechanical, electrical, or chemical stimuli to the controlled environment, these systems lack the ability to combine all these stimuli simultaneously to better recapitulate the physiological environment.

Management of single-level thoracic disc herniation through a modified transfacet approach: A review of 86 patients.

Background: Symptomatic thoracic disc herniation (TDH) is rare and does not typically resolve with conservative management. Traditional surgical management is the transthoracic approach; however, this approach can carry significant risk. Posterolateral approaches are less invasive, but no single approach has proven to be more effective than the other results are often dependent on surgeon experience with a particular approach, as well as the location and characteristics of the disc herniation.

Moment-rotation behavior of intervertebral joints in flexion-extension, lateral bending, and axial rotation at all levels of the human spine: A structured review and meta-regression analysis.

Spinal intervertebral joints are complex structures allowing motion in multiple directions, and many experimental studies have reported moment-rotation response. However, experimental methods, reporting of results, and levels of the spine tested vary widely, and a comprehensive assessment of moment-rotation response across all levels of the spine is lacking. This review aims to characterize moment-rotation response in a consistent manner for all levels of the human spine.

Analysis of how compliant layers and encapsulation affect power generated from piezoelectric stacked composites for bone healing medical devices.

Use of piezoelectric materials to harvest energy from human motion is commonly investigated. Traditional piezoelectric materials are inefficient at low frequencies but composite structures can increase efficiency at these frequencies. Compliant layer adaptive composite stack (CLACS) is a new piezoelectric PZT (lead zirconate titanate) structure designed for orthopedic implants to use loads generated during walking to provide electrical stimulation for bone healing.

Stacked PZT Discs Generate Necessary Power for Bone Healing through Electrical Stimulation in a Composite Spinal Fusion Implant.

Electrical stimulation devices can be used as adjunct therapy to lumbar spinal fusion to promote bone healing, but their adoption has been hindered by the large battery packs necessary to provide power. Piezoelectric composite materials within a spinal interbody cage to produce power in response to physiological lumbar loads have recently been investigated. A piezoelectric macro-fiber composite spinal interbody generated sufficient power to stimulate bone growth in a pilot ovine study, despite fabrication challenges.

The rib cage stiffens the thoracic spine in a cadaveric model with body weight load under dynamic moments.

The thoracic spine presents a challenge for biomechanical testing. With more segments than the lumbar and cervical regions and the integration with the rib cage, experimental approaches to evaluate the mechanical behavior of cadaveric thoracic spines have varied widely. Some researchers are now including the rib cage intact during testing, and some are incorporating follower load techniques in the thoracic spine.

Influence of Sequential Ponte Osteotomies on the Human Thoracic Spine With a Rib Cage.

Study Design: Biomechanical cadaveric study.

Objectives: The purpose of this study was to determine the change in range of motion (ROM) of the human thoracic spine and rib cage due to sequential Ponte osteotomies (POs).

Summary Of Background Data: POs are often performed in deformity correction surgeries to provide flexibility in the sagittal plane at an estimated correction potential of 5° per PO, but no studies have evaluated the biomechanical impact of the procedure on a cadaveric model with an intact rib cage.

Effect of follower load on motion and stiffness of the human thoracic spine with intact rib cage.

Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive follower preload. However, dynamic mechanical testing using both the rib cage and follower load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive follower preloads was performed.

Effects of follower load and rib cage on intervertebral disc pressure and sagittal plane curvature in static tests of cadaveric thoracic spines.

The clinical relevance of mechanical testing studies of cadaveric human thoracic spines could be enhanced by using follower preload techniques, by including the intact rib cage, and by measuring thoracic intervertebral disc pressures, but studies to date have not incorporated all of these components simultaneously. Thus, this study aimed to implement a follower preload in the thoracic spine with intact rib cage, and examine the effects of follower load, rib cage stiffening and rib cage removal on intervertebral disc pressures and sagittal plane curvatures in unconstrained static conditions. Intervertebral disc pressures increased linearly with follower load magnitude.

Mechanical analysis of the human cadaveric thoracic spine with intact rib cage.

The goal of this study was to characterize the overall in-plane and basic coupled motion of a cadaveric human thoracic spine with intact true ribs. Researchers are becoming increasingly interested in the thoracic spine due to both the high prevalence of injury and pain in the region and also innovative surgical techniques that utilize the rib cage. Computational models can be useful tools to predict loading patterns and understand effects of surgical procedures or medical devices, but they are often limited by insufficient cadaveric input data.

Grade 1 spondylolisthesis and interspinous device placement: removal in six patients and analysis of current data.

Background: In the treatment of patients with Grade 1 spondylolisthesis, the use of interspinous devices has been controversial for nearly a decade. Several authors have suggested that Grade 1 spondylolisthesis be considered a contraindication for interspinous device placement.

Methods: We removed interspinous devices in six symptomatic Grade 1 spondylolisthesis patients and analyzed pertinent literature.

Mechanical Contribution of the Rib Cage in the Human Cadaveric Thoracic Spine.

Study Design: An in vitro biomechanical human cadaveric study of T1-T12 thoracic specimens was performed with 4 conditions (with and without rib cage, instrumented and uninstrumented) in flexion-extension, lateral bending, and axial rotation.

Objective: The objective was to understand the influence of the rib cage on motion and stiffness parameters of the human cadaveric thoracic spine. Hypotheses tested for overall motion in all modes of bending for both uninstrumented and instrumented specimens were (i) in-plane range of motion and neutral and elastic zones will be greater without the rib cage, (ii) neutral and elastic zone stiffness values will be different for specimens without the rib cage, and (iii) out-of-plane rotations will be different for specimens without the rib cage.

Composite piezoelectric spinal fusion implant: Effects of stacked generators.

Spinal fusion surgeries have a high failure rate for difficult-to-fuse patients. A piezoelectric spinal fusion implant was developed to overcome the issues with other adjunct therapies. Stacked generators were used to improve power generation at low electrical load resistances.

Evaluation of apparent fracture toughness of articular cartilage and hydrogels.

Recently, biomaterials-based tissue-engineering strategies, including the use of hydrogels, have offered great promise for repairing articular cartilage. Mechanical failure testing in outcome analyses is of crucial clinical importance to the success of engineered constructs. Interpenetrating networks (IPNs) are gaining more attention, due to their superior mechanical integrity.

Theoretical model of a piezoelectric composite spinal fusion interbody implant.

Failure rates of spinal fusion are high in smokers and diabetics. The authors are investigating the development of a piezoelectric composite biomaterial and interbody device design that could generate clinically relevant levels of electrical stimulation to help improve the rate of fusion for these patients. A lumped parameter model of the piezoelectric composite implant was developed based on a model that has been utilized to successfully predict power generation for piezoceramics.

Mechanical testing of hydrogels in cartilage tissue engineering: beyond the compressive modulus.

Injuries to articular cartilage result in significant pain to patients and high medical costs. Unfortunately, cartilage repair strategies have been notoriously unreliable and/or complex. Biomaterial-based tissue-engineering strategies offer great promise, including the use of hydrogels to regenerate articular cartilage.

Porosity of neat and composite bone cement mantles.

The effect of fiber additions to bone cement on femoral cement mantle porosity was determined. Eighteen porcine femurs were implanted with a cemented prosthesis. Three cement types were used: as-received cement, cement with untreated polyethylene terephthalate fibers, and cement with treated polyethylene terephthalate fibers.

Fracture toughness and fatigue crack propagation rate of short fiber reinforced epoxy composites for analogue cortical bone.

Third-generation mechanical analogue bone models and synthetic analogue cortical bone materials manufactured by Pacific Research Laboratories, Inc. (PRL) are popular tools for use in mechanical testing of various orthopedic implants and biomaterials. A major issue with these models is that the current third-generation epoxy-short fiberglass based composite used as the cortical bone substitute is prone to crack formation and failure in fatigue or repeated quasistatic loading of the model.

Fatigue performance of composite analogue femur constructs under high activity loading.

Synthetic mechanical analogue bone models are valuable tools for consistent analysis of implant performance in both equilibrium and fatigue biomechanical testing. Use of these models has previously been limited by the poor fatigue performance when tested under realistic service loads. An objective was to determine whether a new analogue bone model (Fourth-Generation) using enhanced analogue cortical bone provides significantly improved resistance to high load fracture and fatigue as compared to the current (Third-Generation) bone models in clinically relevant in situ type testing of total hip implants.

Elastic anisotropy of bone and dentitional tissues.

The calculation of the scalar compressive and shear anisotropy factors developed for single crystal refractory compounds has been adapted to the anisotropic elastic stiffness coefficients determined by a number of ultrasonic measurements of bone based on transverse isotropic symmetry. Later, this work was extended to include the ultrasonic measurements of bone based on orthotropic symmetry. Recently, the five transverse isotropic elastic constants for both wet and dry human dentin were determined using resonant ultrasound spectroscopy.