Engineering Commons^™

Balance Assessment Using A Smartwatch Inertial Measurement Unit With Principal Component Analysis For Anatomical Calibration, Benjamin M. Presley, Jeffrey C. Sklar, Scott J. Hazelwood, Britta Berg-Johansen, Stephen M. Klisch

Biomedical Engineering

Balance assessment, or posturography, tracks and prevents health complications for a variety of groups with balance impairment, including the elderly population and patients with traumatic brain injury. Wearables can revolutionize state-of-the-art posturography methods, which have recently shifted focus to clinical validation of strictly positioned inertial measurement units (IMUs) as replacements for force-plate systems. Yet, modern anatomical calibration (i.e., sensor-to-segment alignment) methods have not been utilized in inertial-based posturography studies. Functional calibration methods can replace the need for strict placement of inertial measurement units, which may be tedious or confusing for certain users. In this study, balance-related metrics from a smartwatch …

Baseball Pitching Arm Three-Dimensional Inertial Parameter Calculations From Body Composition Imaging And A Novel Overweight Measure For Youth Pitching Arm Kinetics, Dalton J. Jennings, Scott K. Reaves, Jeffrey Sklar, Colin Brown, John Mcphee, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

Many baseball pitching studies have used inverse dynamics to assess throwing arm kinetics as high and repetitive kinetics are thought to be linked to pitching injuries. However, prior studies have not used participant-specific body segment inertial parameters (BSIPs), which are thought to improve analysis of high-acceleration motions and overweight participants. This study's objectives were to (1) calculate participant-specific BSIPs using dual energy X-ray absorptiometry (DXA) measures, (2) compare inverse dynamic calculations of kinetics determined by DXA-calculated BSIPs (full DXA-driven inverse dynamics) against kinetics using the standard inverse dynamics approach with scaled BSIPs (scaled inverse dynamics), and (3) examine associations between …

Knee Angles After Crosstalk Correction With Principal Component Analysis In Gait And Cycling, Jordan Skaro, Scott J. Hazelwood, Stephen M. Klisch

Biomedical Engineering

Principal component analysis (PCA) has been used as a post-hoc method for reducing knee crosstalk errors during gait analysis. PCA minimizes correlations between flexion–extension (FE), abduction–adduction (AA), and internal–external rotation (IE) angles. However, previous studies have not considered PCA for exercises involving knee flexion angles that are greater than those typically experienced during gait. Thus, the goal of this study was to investigate using PCA to correct for crosstalk during one exercise (i.e., cycling) that involves relatively high flexion angles. Fifteen participants were tested in gait and cycling using a motion analysis system. Uncorrected FE, AA and IE angles were …

Inverse Dynamics Analysis Of Youth Pitching Arm Kinetics Using Body Composition Imaging, Jay A. Sterner, Scott K. Reaves, Arnel L. Aguinaldo, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

This study’s objectives were to: (1) assess whether dual energy X-ray absorptiometry (DXA)-mass inverse dynamics (ID) alters predictions of youth pitching arm kinetics and (2) investigate correlations between kinetics and body composition. Eighteen 10- to 11-year-olds pitched 10 fastballs. DXA scans were conducted to obtain participant-specific upper arm, forearm, and hand masses. Pitching arm segment masses and kinetics calculated with scaled and DXA masses were compared with paired t-tests and correlations were investigated with linear regression. Hand (p < 0.001) and upper arm (p < 0.001) DXA masses were greater, while forearm (p < 0.001) DXA masses were lesser, than their scaled masses. Shoulder compressive force (p < 0.001), internal rotation torque (p < 0.001), and horizontal adduction torque (p = 0.002) increased when using DXA masses. Shoulder compressive force correlated with body mass (p < 0.001) and body mass index (BMI; p = 0.002) and elbow varus torque correlated with body mass (p < 0.05). The main conclusions were that (1) using participant-specific mass ratios leads to different predictions of injury-related pitching arm kinetics and, thus, may improve our understanding of injury risk factors; and (2) pitching arm kinetics were correlated with body composition measures and a relatively high total body mass and/or BMI may increase shoulder and/or elbow injury risk.

Knee Joint Biomechanics In Transtibial Amputees In Gait, Cycling, And Elliptical Training, Greg Orekhov, A. Matt Robinson, Scott J. Hazelwood, Stephen M. Klisch

Biomedical Engineering

Transtibial amputees may experience decreased quality of life due to increased risk of knee joint osteoarthritis (OA). No prior studies have compared knee joint biomechanics for the same group of transtibial amputees in gait, cycling, and elliptical training. Thus, the goal of this study was to identify preferred exercises for transtibial amputees in the context of reducing risk of knee OA. The hypotheses were: 1) knee biomechanics would differ due to participant status (amputee, control), exercise, and leg type (intact, residual) and 2) gait kinematic parameters would differ due to participant status and leg type. Ten unilateral transtibial amputee and …

Quantifying Proliferative And Surface Marker Heterogeneity In Colony‐Founding Connective Tissue Progenitors And Their Progeny Using Time‐Lapse Microscopy, Edward Kwee, Gerald M. Saidel, Kimerly Powell, Christopher M. Heylman, Cynthia A. Boehm, George F. Muschler

Biomedical Engineering

Connective tissue progenitors (CTPs) are defined as the heterogeneous population of tissue‐resident stem and progenitor cells that are capable of proliferating and differentiating into connective tissue phenotypes. The prevalence and variation in clonal progeny of CTPs can be characterized using a colony formation assay. However, colony assays do not directly assess the characteristics of the colony‐founding CTP. We performed large, field‐of‐view, time‐lapse microscopy to manually track colonies back to the founding cells. Image processing and analysis was used to characterize the colonies and their founding cells. We found that the traditional colony‐forming unit (CFU) assay underestimates the number of founding …

Effects Of Game Pitch Count And Body Mass Index On Pitching Biomechanics In 9-To 10-Year-Old Baseball Athletes, Jim D. Darke, Eshan M. Dandekar, Arnel L. Aguinaldo, Scott J. Hazelwood, Stephen M. Klisch

Biomedical Engineering

Background: Pitching while fatigued and body composition may increase the injury risk in youth and adult pitchers. However, the relationships between game pitch count, biomechanics, and body composition have not been reported for a study group restricted to 9-to 10-year-old athletes.

Hypothesis: During a simulated game with 9-to 10-year-old athletes, (1) participants will experience biomechanical signs of fatigue, and (2) shoulder and elbow kinetics will correlate with body mass index (BMI).

Study Design: Descriptive laboratory study. Methods: Thirteen 9-to 10-year-old youth baseball players pitched a simulated game (75 pitches). Range of motion and muscular output tests were conducted before and …

Effects Of Game Pitch Count And Body Mass Index On Pitching Biomechanics In 9- To 10-Year-Old Baseball Athletes, Scott Hazelwood, Jim D. Darke, Eshan M. Dandekar, Arnel L. Aguinaldo, Stephen M. Klisch

Biomedical Engineering

Background:

Pitching while fatigued and body composition may increase the injury risk in youth and adult pitchers. However, the relationships between game pitch count, biomechanics, and body composition have not been reported for a study group restricted to 9- to 10-year-old athletes.

Hypothesis:

During a simulated game with 9- to 10-year-old athletes, (1) participants will experience biomechanical signs of fatigue, and (2) shoulder and elbow kinetics will correlate with body mass index (BMI).

Study Design:

Descriptive laboratory study.

Methods:

Thirteen 9- to 10-year-old youth baseball players pitched a simulated game (75 pitches). Range of motion and …

Elbow And Shoulder Joint Torques Are Correlated With Body Mass Index But Not Game Pitch Count In Youth Baseball Pitchers, Jim Douglas Darke, Eshan M. Dandekar, Arnel Aguinaldo, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

The number of ulnar collateral ligament (UCL) reconstructive (i.e. “Tommy John”) surgeries performed on youth baseball pitchers have more than doubled since 2000 [1]. Routinely pitching while fatigued is considered a leading factor associated with UCL injuries; adolescent pitchers who had elbow or shoulder surgery were 36 times more likely to have routinely pitched with arm fatigue [1]. MLB/USA Baseball Pitch Smart guidelines limit 9-10 yr. old pitchers to a maximum 75 pitches per game, a figure based on long-term studies related to injury prevention [2]. Several studies have shown that pitching kinematics (e.g. elbow flexion/extension and pronation/supination, scapulothoracic internal-external …

Knee Biomechanics During Cycling Are Similar For Normal Weight And Obese Subjects, Juan D. Gutierrez-Franco, Jordan Skaro, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

Osteoarthritis (OA) is a degenerative disease of cartilage and bone tissue, and is linked to more than 70% of total hip and knee replacements [1]. In 1994 the direct and indirect costs of OA in the United States were $155 billion [2] and in 2006 OA resulted in approximately $10.5 billion in hospital charges [3]. Obesity is a risk factor for OA [1, 3, 4], likely due to increased knee loading [5, 6] and varus malalignment [7] in gait. Seated cycling has been recommended as a weight-loss exercise with lower knee loads than walking or jogging [8]. However, lack of …

Principal Component Analysis Of Gait And Cycling Experiments: Crosstalk Error Reduction And Corrected Knee Axes, Jordan Skaro, Harsh Goel, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

Crosstalk is a leading source of error in motion analysis [1-2]. Due to incorrect flexion axis direction that develops from marker placement error, crosstalk results in a strong, anatomically incorrect correlation between flexion-extension (FE) and adduction-abduction (AA) motions [1-2]. Thus, crosstalk limits the ability of biomechanical models to reflect the “true” motion of the knee. Principal Component Analysis (PCA) has been proposed as a post-hoc correction for crosstalk in prior gait studies [1-2]; however, previous studies have not proposed a method to determine PCA corrected knee axes. Further, it is not clear how PCA should be implemented in motion analysis …

Emg-Driven Inverse Dynamic Analysis Of Knee Contact Forces During Gait And Cycling Using Opensim, Megan V. Pottinger, Katherine Mavrommati, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

Joint contact forces determine the loading experienced by cartilage tissue and, thus, may be used to predict risk of cartilage tissue damage and osteoarthritis (OA). Participating in low impact and/or non-weight bearing activities such as cycling may help reduce knee OA risk by limiting forces exerted during exercise [1]. Cycling is a common recommendation for rehabilitative or fitness sustainment exercise for select patients [1]. Although knee joint contact forces have been directly measured in gait and cycling using instrumented knee implants [2,3] and calculated in gait using EMG-driven analysis [4]; they have not been calculated in cycling using EMG-driven analysis. …

Three-Dimensional Adult Cardiac Extracellular Matrix Promotes Maturation Of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes, Ahsley H. Fong, Mónica Romero-López, Christopher M. Heylman, Mark Keating, David Tran, Agua Sobrino, Anh Q. Tran, Hiep H. Pham, Cristhian Fimbres, Paul D. Gershon, Elliot L. Botvinick, Steven C. George, Christopher C.W. Hughes

Biomedical Engineering

Pluripotent stem cell-derived cardiomyocytes (CMs) have great potential in the development of new therapies for cardiovascular disease. In particular, human induced pluripotent stem cells (iPSCs) may prove especially advantageous due to their pluripotency, their self-renewal potential, and their ability to create patient-specific cell lines. Unfortunately, pluripotent stem cell-derived CMs are immature, with characteristics more closely resembling fetal CMs than adult CMs, and this immaturity has limited their use in drug screening and cell-based therapies. Extracellular matrix (ECM) influences cellular behavior and maturation, as does the geometry of the environment—twodimensional (2D) versus three-dimensional (3D). We therefore tested the hypothesis that native …

Label-Free Imaging Of Metabolism And Oxidative Stress In Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes, Rupsa Datta, Christopher M. Heylman, Steven C. George, Enrico Gratton

Biomedical Engineering

In this work we demonstrate a label-free optical imaging technique to assess metabolic status and oxidative stress in human induced pluripotent stem cell-derived cardiomyocytes by two-photon fluorescence lifetime imaging of endogenous fluorophores. Our results show the sensitivity of this method to detect shifts in metabolism and oxidative stress in the cardiomyocytes upon pathological stimuli of hypoxia and cardiotoxic drugs. This non-invasive imaging technique could prove beneficial for drug development and screening, especially for in vitro cardiac models created from stem cell-derived cardiomyocytes and to study the pathogenesis of cardiac diseases and therapy.

Automated Detection And Analysis Of Depolarization Events In Human Cardiomyocytes Using Madec, Agnieszka F. Szymanska, Christopher M. Heylman, Rupsa Datta, Enrico Gratton

Biomedical Engineering

Optical imaging-based methods for assessing the membrane electrophysiology of in vitro human cardiac cells allow for non-invasive temporal assessment of the effect of drugs and other stimuli. Automated methods for detecting and analyzing the depolarization events (DEs) in image-based data allow quantitative assessment of these different treatments. In this study, we use 2-photon microscopy of fluorescent voltage-sensitive dyes (VSDs) to capture the membrane voltage of actively beating human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs). We built a custom and freely available Matlab software, called MaDEC, to detect, quantify, and compare DEs of hiPS-CMs treated with the β-adrenergic drugs, propranolol and …

Supervised Machine Learning For Classification Of The Electrophysiological Effects Of Chronotropic Drugs On Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes, Christopher Heylman, Rupsa Datta, Agua Sobrino, Steven George, Enrico Gratton

Biomedical Engineering

Supervised machine learning can be used to predict which drugs human cardiomyocytes have been exposed to. Using electrophysiological data collected from human cardiomyocytes with known exposure to different drugs, a supervised machine learning algorithm can be trained to recognize and classify cells that have been exposed to an unknown drug. Furthermore, the learning algorithm provides information on the relative contribution of each data parameter to the overall classification. Probabilities and confidence in the accuracy of each classification may also be determined by the algorithm. In this study, the electrophysiological effects of β–adrenergic drugs, propranolol and isoproterenol, on cardiomyocytes derived from …

Design And Implementation Of An Instrumented Pedal For Cycling Biomechanics Research, Luke I. Kraemer, Juan D. Gutierrez-Franco, Jake E. Deschamps, Karim C. Dudum, Eshan M. Dandekar, Scott Hazelwood, Hemanth Porumamilla, Stephen M. Klisch

Biomedical Engineering

Cycling is a common, low-impact activity used for recreation, exercise, and rehabilitation. Knee joint loading can be predicted using inverse dynamic analyses of pedal load cell and kinematic data measured during cycling biomechanics experiments. Several studies have successfully measured foot loading at the pedals, e.g. by using custom instrumented pedal spindles outfitted with strain gauges and a potentiometer to measure crank angle [1-3]. Such designs are relatively complex, requiring difficult machining and component fabrication, and require post-processing of strain gauge data.

The long-term goal of this study is to calculate knee joint loading and, ultimately, cartilage tissue stress to provide …

Human Knee Joint Finite Element Model Using A Two Bundle Anterior Cruciate Ligament: Validation And Gait Analysis, Nicholas A. Czapla, Meghan K. Sylvia, Zachary F. Lerner, David J. Tuttle, Otto J. Schueckler, S. J. Hazelwood, Stephen M. Klisch

Biomedical Engineering

Anterior cruciate ligament (ACL) deficient individuals are at a much higher risk of developing osteoarthritis (OA) compared to those with intact ACLs, likely due to altered biomechanical loading [1]. Research indicates the ACL is comprised of two “bundles”, the anteromedial (AM) and posterolateral (PL) bundles [2]. Although the function of both bundles is to restrain anterior tibial translation (ATT), each bundle has their own distinct range of knee flexion where they are most effective [3].

Articular cartilage contact stress measurements are difficult to measure in vivo. An alternative approach is to use knee joint finite element models (FEMs) to predict …

Development Of A Human Knee Joint Finite Element Model To Investigate Cartilage Stress During Walking In Obese And Normal Weight Adults, Meghan K. Sylvia, Nicholas A. Czapla, Zachary F. Lerner, David J. Tuttle, Otto J. Schueckler, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

Osteoarthritis (OA) is a degenerative condition characterized by the breakdown and loss of joint articular cartilage. While the cause of OA is not precisely known, obesity is a known risk factor [1]. Particular effort has gone towards understanding the relationship between obesity and knee OA because obesity is more strongly linked to OA at the knee than at any other lower extremity joint [2]. Although the relationship between obesity and knee OA is well established, the mechanism of pathogenesis is less understood. Excess body weight generates greater joint contact forces at the knee. However, obese individuals alter their gait, resulting …

Using Opensim To Predict Knee Joint Moments During Cycling, Karim C. Dudum, Jake E. Deschamps, Juan D. Gutierrez-Franco, Luke I. Kraemer, Alejandro M. Gonzalez-Smith, Eshan M. Dandekar, S. J. Hazelwood, Stephen M. Klisch

Biomedical Engineering

Cycling is a relatively low impact activity conventionally recommended as a rehabilitative or fitness sustaining exercise for patients at a high risk for knee osteoarthritis (OA) [1,2]. Expanding our understanding of knee joint loads is necessary to develop and improve evidence-based prescriptions for cycling as a rehabilitative and fitness therapy that limits the risk for knee OA.

OpenSim (www.simtk.org) is an open source biomechanical analysis software that can partition predictions of external joint loads (or net muscle moments) into muscle and joint contact loads [3]. Joint contact loads more accurately represent cartilage tissue loading and hence risk for cartilage damage …

Modeling And Experimental Methods To Predict Oxygen Distribution In Bone Defects Following Cell Transplantation, Christopher M. Heylman, Sharon Santoso, Melissa D. Krebs, Gerald M. Saidel, Eben Alsberg, George F. Muschler

Biomedical Engineering

We have developed a mathematical model that allows simulation of oxygen distribution in a bone defect as a tool to explore the likely effects of local changes in cell concentration, defect size or geometry, local oxygen delivery with oxygen-generating biomaterials (OGBs), and changes in the rate of oxygen consumption by cells within a defect. Experimental data for the oxygen release rate from an OGB and the oxygen consumption rate of a transplanted cell population are incorporated into the model. With these data, model simulations allow prediction of spatiotemporal oxygen concentration within a given defect and the sensitivity of oxygen tension …

A Strategy For Integrating Essential Three-Dimensional Microphysiological Systems Of Human Organs For Realistic Anticancer Drug Screening, Christopher Heylman, Agua Sobrino, Venktesh S. Shirure, Christopher Cw Hughes, Steven C. George

Biomedical Engineering

Cancer is one of the leading causes of morbidity and mortality around the world. Despite some success, traditional anticancer drugs developed to reduce tumor growth face important limitations primarily due to undesirable bone marrow and cardiovascular toxicity. Many drugs fail in clinical development after showing promise in preclinical trials, suggesting that the available in vitro and animal models are poor predictors of drug efficacy and toxicity in humans. Thus, novel models that more accurately mimic the biology of human organs are necessary for high-throughput drug screening. Three-dimensional (3D) microphysiological systems can utilize induced pluripotent stem cell technology, tissue engineering, and …

A Biomechanical Comparison Of Three Spondylolysis Repair Techniques In A Calf Spine Model, R. Roberto, B. Dezfuli, C. Deuel, S. Curtiss, S. Hazelwood

Biomedical Engineering

Summary of background data: Previous work has demonstrated the efficacy of lumbar pedicle screw hook rod (PSHR) techniques and the Buck screw in the stabilization of spondylolysis. The mechanical behavior of lower profile cervical implants used to create PSHR, hybrid cable plate constructs, and titanium miniplating has not previously been described.

Methods: Calf lumbar spines (L2-L6) were utilized for testing (n = 27). Intervertebral rotation was measured in the intact spines across the L4-5 segment before and after creation of bilateral pars interarticularis defects. Defects were then stabilized with one of three repair techniques, PSHR, miniplate, or …

Slowing The Onset Of Hypoxia Increases Colony Forming Efficiency Of Connective Tissue Progenitor Cells In Vitro, Christopher M. Heylman, Tonya N. Caralla, Cynthia A. Boehm, Thomas E. Patterson, George F. Muschler

Biomedical Engineering

Background: Survival and colony formation by transplanted tissue derived connective tissue progenitor cells (CTPs) are thought to be important factors in the success of clinical tissue engineering strategies for bone regeneration. Transplantation of cells into defects larger than a few millimeters expose cells to a profoundly hypoxic environment. This study tested the hypothesis that delaying the onset of hypoxia will improve the survival and performance of CTPs in vitro.

Methods: To mimic declines seen in an avascular in vivo bone defect, colony forming efficiency by marrow derived nucleated cells was assessed under osteogenic conditions. Variation in the rate of …

The 4+1 Program And Distance Learning Meeting Objectives And Outcomes, Daniel W. Walsh, Lanny Griffin, Robert S. Crockett

Biomedical Engineering

Graduate engineering education is a key to the maintenance of U.S. competitiveness in the world market. The world has been an extremely dynamic engine during the last fifty years, and we have witnessed a dramatic change in the world order. The change has been evolutionary in many cases, but events in Eastern Europe, the Middle East and the erstwhile Soviet Union are only slightly less cataclysmic than the Second World War. In a world where strength is measured in terms of the financial resource, the technological ability and the intellectual capability of a populace Japan, China, India and the EEC …

Polymeric Splint And Rapid-Setting Polyurethane, Lanny Griffin, Dane Robert Jones

Biomedical Engineering

A splint includes a first container capable of being wrapped about an item to be supported and a second container capable of containing a multiple part mixture during a mixing operation. The second container being capable of delivering the mixture into the first container, wherein the mixture hardens to form a support structure. A method for using the splint is also disclosed.

The Biomechanics Of Varied Proximal Locking Screw Configurations In A Synthetic Model Of Proximal Third Tibial Fracture Fixation, Philip R. Wolinsky, Douglas Dennis, Brett D. Crist, Shane Curtiss, Scott J. Hazelwood

Biomedical Engineering

Objective: To determine if 1) angularly stable devices created by compressing (‘‘locking’’) proximal locking screws to intramedullary nails using end caps or compression screws or 2) increasing the number of proximal screws from two to three increases the stiffness of intramedullary constructs that stabilize proximal third tibia fractures in a nonosteopenic bone model.

Methods: Four proximal locking screw configurations were examined in a synthetic composite tibia model with a 2-cm gap simulating a comminuted proximal third tibia fracture with no bony contact: 1) two proximal screws not compressed to the nail; 2) one of two proximal screws compressed to …

The Effect Of Cox-2 Specific Inhibition On Direct Fracture Healing In The Rabbit Tibia, David J. Hak, Kurt S. Schulz, Behrang Khoie, Scott J. Hazelwood

Biomedical Engineering

Objective: The purpose of this study was to evaluate the effect of Cox-2 administration on direct (primary) fracture healing.

Methods: A transverse tibial osteotomy was created in adult male rabbits and rigidly fixed in compression using a 2.7-mm dynamic compression plate. Animals were randomized to receive either rofecoxib (12.5 mg orally per day) or placebo. Animals were killed at 4 weeks and fracture healing assessed by mechanical testing.

Results: There were no significant differences between the control and Cox-2 treated animals in terms of mechanical strength at 4 weeks. There was a high complication rate of peri-implant fractures …

Arteriogenesis And Ischemia Impair Functional Vasodilation In Resistance Arteries, Trevor Cardinal, Joseph S. Zhu, Kyle R. Struthers, Thomas J. Kesler, Matthew D. Yocum

Biomedical Engineering

No abstract provided.

Differential Regulation Of Immature Articular Cartilage Compressive Moduli And Poisson's Ratios By In Vitro Stimulation With Igf-1 And Tgf-Β1, Gregory M. Williams, Kristin J. Dills, Christian R. Flores, Michael E. Stender, Kevin M. Stewart, Lauren M. Nelson, Albert C. Chen, Koichi Masuda, Scott J. Hazelwood, Stephen M. Klisch, Robert L. Sah

Biomedical Engineering

Mechanisms of articular cartilage growth and maturation have been elucidated by studying composition-function dynamics during in vivo development and in vitro culture with stimuli such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta 1 (TGF-β1). This study tested the hypothesis that IGF-1 and TGF-β1 regulate immature cartilage compressive moduli and Poisson’s ratios in a manner consistent with known effects on tensile properties. Bovine calf articular cartilage from superficial-articular (S) and middle-growth (M) regions were analyzed fresh or following culture in medium with IGF-1 or TGF-β1. Mechanical properties in confined (CC) and unconfined (UCC) compression, cartilage matrix composition, and explant …