Baseline-to-loaded changes in regional tibial cartilage thickness, T1ρ and T2: Utilization of an MRI compatible loading device.

The objective of the study was to evaluate tibial cartilage thickness (TCT), T1ρ and T2 values within both loaded and baseline configurations in a cadaveric knee model using a 3D bone based tibial coordinate system. Ten intact cadaveric knees were mounted into an magnetic resonance imaging (MRI) compatible loading device. Morphologic and quantitative MRI (qMRI) images were acquired with the knee in a baseline configuration and after application of 50% body weight.

Patellar Fracture Forces Are Not Affected by Proximal Versus Distal Bone Block Anterior Cruciate Ligament Reconstruction Harvest Sites in a Cadaveric Model.

Purpose: To quantify the maximum load to fracture in patellae from which bone-patellar tendon-bone (BPTB) and bone-quadriceps tendon (BQT) autografts have been harvested for anterior cruciate ligament reconstruction in a cadaveric model.

Methods: Forty-six fresh-frozen patellae were isolated and divided into the BPTB harvest and BQT harvest groups with matching based on donor age and sex. Computed tomography scans were obtained to calculate bone mineral density (BMD) and patellar height, width, and thickness.

The Adductor Sling Technique for Pediatric Medial Patellofemoral Ligament Reconstruction Better Resists Dislocation Loads When Compared With Adductor Transfer at Time Zero in a Cadaveric Model.

Purpose: To characterize the ability of the intact medial patellofemoral ligament (MPFL) and the adductor transfer and adductor sling MPFL reconstruction techniques to resist subluxation and dislocation in a cadaveric model.

Methods: Nine fresh-frozen cadaveric knees were placed on a custom testing fixture with the femur fixed parallel to the floor, the tibia placed in 20° of flexion, and the patella attached to a load cell. The patella was displaced laterally, and subluxation load (in newtons), dislocation load (in newtons), maximum failure load (in newtons), patellar displacement at failure, and mode of failure were recorded.

Medial Meniscus Posterior Root Tears Lead to Changes in Joint Contact Mechanics at Low Flexion Angles During Simulated Gait.

Background: Previous biomechanical studies evaluating medial meniscus posterior root tears (MMPRTs) are limited to low loads applied at specified loading angles, which cannot capture the effects of MMPRTs during the multidirectional forces and moments placed across the knee during physiological activities.

Purpose: To quantify the effects of MMPRTs on knee joint contact mechanics during simulated gait.

Study Design: Controlled laboratory study.

Finite element modeling to predict the influence of anatomic variation and implant placement on performance of biological intervertebral disc implants.

Background: Tissue-engineered intervertebral disc (TE-IVD) constructs are an attractive therapy for treating degenerative disc disease and have previously been investigated in vivo in both large and small animal models. The mechanical environment of the spine is notably challenging, in part due to its complex anatomy, and implants may require additional mechanical support to avoid failure in the early stages of implantation. As such, the design of suitable support implants requires rigorous validation.

Proximal bone block with distal screw trajectory improves mechanical stability during distalization tibial tubercle osteotomy.

Purpose: The purpose of this study was to quantify differences in mechanical stability of a wedge-shaped distalization tibial tubercle osteotomy (TTO) with a standard technique, versus a modified technique with use of a proximal bone block and distally angled screw trajectory.

Methods: Ten fresh-frozen cadaver lower extremity specimens (five matched pairs) were utilized. Within each specimen pair, one specimen was randomly assigned to undergo a standard distalization osteotomy fixed with two bicortical 4.

Anteromedialization Tibial Tubercle Osteotomy Improves Patellar Contact Forces: A Cadaveric Model of Patellofemoral Dysplasia.

Background: Patellofemoral (PF) dysplasia is common in patients with recurrent patellar instability. Tibial tubercle osteotomy (TTO) is performed with goals of correcting patellar maltracking and redistributing contact forces across the PF joint. The biomechanical effects of TTO in the setting of PF dysplasia have not been quantified.

ACL transection results in a posterior shift and increased velocity of contact on the medial tibial plateau.

Our objective was to quantify the effect of ACL transection on dynamic knee joint contact force distributions during simulated gait. Given the prevalence of medial compartment osteoarthritis in un-reconstructed ACL ruptured knees, we hypothesized that changes in contact mechanics after ACL transection would be most prevalent in the medial compartment. Twelve human cadaveric knees were tested using a dynamic knee gait simulator which was programmed to mimic a clinical Lachman exam and gait.

Tekscan analysis programs (TAP) for quantifying dynamic contact mechanics.

This short communication provides details on customized Tekscan Analysis Programs (TAP) which extract comprehensive contact mechanics metrics from piezoelectric sensors in articulating joints across repeated loading cycles. The code provides functionality to identify regions of interest (ROI), compute contact mechanic metrics, and compare contact mechanics across multiple test conditions or knees. Further, the variability of identifying ROIs was quantified between seven different users and compared to an expert.

The Biomechanical Consequences of Arthroscopic Hip Capsulotomy and Repair in Positions at Risk for Dislocation.

Background: The effect of interportal (IP) capsulotomy, short T-capsulotomy, and long T-capsulotomy, and their repairs, on resistance to anterior and posterior "at risk for dislocation" positions has not been quantified.

Hypotheses: Our primary hypothesis was that an IP capsulotomy would have a minimal effect on hip resistive torque compared with both short and long T-capsulotomies in the at-risk dislocation positions. Our secondary hypothesis was that capsule repair would significantly increase hip resistive torque for all capsulotomies.

Dysplastic Patellofemoral Joints Lead to a Shift in Contact Forces: A 3D-Printed Cadaveric Model.

Background: The distribution of contact forces across the dysplastic patellofemoral joint has not been adequately quantified because models cannot easily mimic the dysplasia of both the trochlea and the patella. Thus, the mechanical consequences of surgical treatments to correct dysplasia cannot be established.

Purpose/hypothesis: The objective of this study was to quantify the contact mechanics and kinematics of normal, mild, and severely dysplastic patellofemoral joints using synthetic mimics of the articulating surfaces on cadavers.

Synthetic PVA Osteochondral Implants for the Knee Joint: Mechanical Characteristics During Simulated Gait.

Background: Although polyvinyl alcohol (PVA) implants have been developed and used for the treatment of femoral osteochondral defects, their effect on joint contact mechanics during gait has not been assessed.

Purpose/hypothesis: The purpose was to quantify the contact mechanics during simulated gait of focal osteochondral femoral defects and synthetic PVA implants (10% and 20% by volume of PVA), with and without porous titanium (pTi) bases. It was hypothesized that PVA implants with a higher polymer content (and thus a higher modulus) combined with a pTi base would significantly improve defect-related knee joint contact mechanics.

Meniscal repair: The current state and recent advances in augmentation.

Meniscal injuries represent one of the most common orthopedic injuries. The most frequent treatment is partial resection of the meniscus, or meniscectomy, which can affect joint mechanics and health. For this reason, the field has shifted gradually towards suture repair, with the intent of preservation of the tissue.

Analysis of the influence of species, intervertebral disc height and Pfirrmann classification on failure load of an injured disc using a novel disc herniation model.

Background Context: Annular repair devices offer a solution to recurrent disc herniations by closing an annular defect and lowering the risk of reherniation. Given the significant risk of neurologic injury from device failure it is imperative that a reliable preclinical model exists to demonstrate a high load to failure for the disc repair devices.

Purpose: To establish a preclinical model for disc herniation and demonstrate how changes in species, intervertebral disc height and Pfirrmann classification impacts failure load on an injured disc.

Comparison of biomechanical studies of disc repair devices based on a systematic review.

Background Context: A variety of solutions have been suggested as candidates for the repair of the annulus fibrosis (AF), with the ability to withstand physiological loads of paramount importance.

Purpose: The objective of our study was to capture the scope of biomechanical test models of AF repairs. We hypothesized that common test parameters would emerge.

Effect of interface mechanical discontinuities on scaffold-cartilage integration.

A consistent lack of lateral integration between scaffolds and adjacent articular cartilage has been exhibited in vitro and in vivo. Given the mismatch in mechanical properties between scaffolds and articular cartilage, the mechanical discontinuity that occurs at the interface has been implicated as a key factor, but remains inadequately studied. Our objective was to investigate how the mechanical environment within a mechanically loaded scaffold-cartilage construct might affect integration.

Self-assembled monolayers of phosphonates promote primary chondrocyte adhesion to silicon dioxide and polyvinyl alcohol materials.

The optimal solution for articular cartilage repair has not yet been identified, in part because of the challenges in achieving integration with the host. Coatings have the potential to transform the adhesive features of surfaces, but their application to cartilage repair has been limited. Self-assembled monolayer of phosphonates (SAMPs) have been demonstrated to increase the adhesion of various immortalized cell types to metal and polymer surfaces, but their effect on primary chondrocyte adhesion has not been studied.

Translating Orthopaedic Technologies Into Clinical Practice: Challenges and Solutions.

Despite the wealth of innovation in the orthopaedic sciences, few technologies translate to clinical use. By way of a 2-day symposium titled "AAOS/ORS Translating Orthopaedic Technologies into Clinical Practice: Pathways from Novel Idea to Improvements in Standard of Care Research Symposium," key components of successful commercialization strategies were identified as a passionate entrepreneur working on a concept aimed at improving patient outcomes and decreasing the cost and burden of disease; a de-risking strategy that has due recognition of the regulatory approval process and associated costs while maximizing the use of institutional, state, and federal resources; and a well thought-out and prepared legal plan and high quality, protected intellectual property. Challenges were identified as a lack of education on the scale-up and commercialization processes; few opportunities to network, get feedback, and obtain funding for early stage ideas; disconnect between the intellectual property and the business model; and poor adoption of new technologies caused in part by un-optimized clinical trials.

The Scaffold-Articular Cartilage Interface: A Combined In Vitro and In Silico Analysis Under Controlled Loading Conditions.

The optimal method to integrate scaffolds with articular cartilage has not yet been identified, in part because of our lack of understanding about the mechanobiological conditions at the interface. Our objective was to quantify the effect of mechanical loading on integration between a scaffold and articular cartilage. We hypothesized that increased number of loading cycles would have a detrimental effect on interface integrity.

Influence of the pericellular and extracellular matrix structural properties on chondrocyte mechanics.

Understanding the mechanical factors that drive the biological responses of chondrocytes is central to our interpretation of the cascade of events that lead to osteoarthritic changes in articular cartilage. Chondrocyte mechanics is complicated by changes in tissue properties that can occur as osteoarthritis (OA) progresses and by the interaction between macro-scale, tissue level, properties, and micro-scale pericellular matrix (PCM) and local extracellular matrix (ECM) properties, both of which cannot be easily studied using in vitro systems. Our objective was to study the influence of macro- and micro-scale OA-associated structural changes on chondrocyte strains.

Photocrosslinked tyramine-substituted hyaluronate hydrogels with tunable mechanical properties improve immediate tissue-hydrogel interfacial strength in articular cartilage.

Articular cartilage lacks the ability to self-repair and a permanent solution for cartilage repair remains elusive. Hydrogel implantation is a promising technique for cartilage repair; however for the technique to be successful hydrogels must interface with the surrounding tissue. The objective of this study was to investigate the tunability of mechanical properties in a hydrogel system using a phenol-substituted polymer, tyramine-substituted hyaluronate (TA-HA), and to determine if the hydrogels could form an interface with cartilage.

Reducing uncertainty when using knee-specific finite element models by assessing the effect of input parameters.

Little is known about knee-specific factors that influence contact mechanics. Finite Element (FE) models offer a powerful tool to study contact mechanics, but there often exists ambiguity in the exact values of the inputs (e.g.

Clinical platform for understanding the relationship between joint contact mechanics and articular cartilage changes after meniscal surgery.

Injury to the meniscus of the knee has been implicated as a significant risk factor for the subsequent development of osteoarthritis, but the mechanisms of joint degeneration are unclear. Our objective was to develop a clinically applicable methodology to evaluate the relationship of joint contact mechanics at the time of surgery to biological changes of articular cartilage as a function of time following surgery. A series of pre-, intra-, and post-operative protocols were developed which utilized electronic sensors for the direct measurement of contact mechanics, and advanced imaging to assess cartilage health.