John Leicester Williams

The University of Memphis | U of M · Department of Biomedical Engineering

Background. It is known that reserve zone (RZ) chondro-cytes regulate the organization of the physis and that chondrocyte primary cilia (PC) act as mechanotransducers. Objective. To explore if physeal loading-induced strains in RZ chondrocyte PC can enable cells to sense whether the physis is subjected to increasing or decreasing levels of compress...

OBJECTIVE: The purpose of this narrative review is to summarize what is currently known about the structural, chemical, and mechanical properties of cartilage-bone interfaces, which provide tissue integrity across a bimaterial interface of 2 very different structural materials. Maintaining these mechanical interfaces is a key factor for normal bon...

The role of the growth plate reserve zone is not well understood. It has been proposed to serve as a source of stem cells and to produce morphogens that control the alignment of clones in preparation for the transition into the proliferative zone. We hypothesized that if such a role exists, there are likely to be mechanoregulatory stimuli in cellul...

The capital femoral physis is a growth plate located between the head of the femur and femoral neck, which forms a temporary joint where growth plate cartilage is converted to bone by endochondral ossification. The bone‐cartilage‐bone interface develops a unique radial pattern of interdigitating mammillary processes that interlock the femoral head...

Background. The subchondral epiphyseal bone plate between the epiphysis and the growth plate cartilage is formed by an unknown process. Objective. To examine if reserve zone chondrocytes could be involved in the development of the subchondral epiphyseal bone plate, by relating their intracellular stress-strain state to mechanobiological tissue diff...

Long bones grow by a process in which chondrocytes within growth plate cartilage near the bone ends synthesize and mineralize a cartilaginous matrix that serves as a template for bone cells. The growth plate consists of several distinct zones, including a reserve zone (RZ) that lies between the epiphyseal subchondral bone plate and the proliferativ...

The increasing accessibility of low-cost, desktop scanners has provided researchers with the means to acquire 3D geometric data that can be used to create digital archives of archaeological artifacts, such as bones, for geometric morphometric study in the fields of osteology and forensic anthropology. However, the process of digitizing and assessin...

Background: Despite our knowledge of several biomechanical risk factors related to anterior cruciate ligament (ACL) injury, such as decreased knee flexion, increased knee abduction, and increased hip flexion, adduction and internal rotation during walking, jogging, and landing from a jump, the incidence of ACL tears remains high. Quantifying variab...

The physis, or growth plate, is a layer of cartilage responsible for long bone growth. It is organized into reserve, proliferative and hypertrophic zones. Unlike the reserve zone where chondrocytes are randomly arranged, either singly or in pairs, the proliferative and hypertrophic chondrocytes are arranged within tubular structures called chondron...

In young growing vertebrates, the head of the femur is attached to the neck by a cartilaginous joint comprised of growth cartilage with an interdigitating arrangement of various size undulations, called mammillary processes, and a perichondrium. Occasionally the joint separates, a condition known as slipped capital femoral epiphysis (SCFE). It has...

The proximal tibial growth plate of yearling domestic cattle is characterized by a 0.5-1 mm undulating layer that forms bone as the animal grows. Growth plate mammillary processes form an interlocking interface of hills and valleys that continues to evolve as the bone grows in length and circumference. Metaphyseal mammillary processes are formed by...

Figure 2. Experimental (solid lines) and model (dashed lines) results of the tooth analog study.

Figure 1. Experimental (markers) and model (dashed lines) results of the shrinkage stress study. Nominal tensile stress = tensile force divided by cross-sectional area.

To download: https://rdcu.be/5ghw Growth plate chondrocytes are responsible for bone growth through proliferation and differentiation. However, the way they experience physiological loads and regulate bone formation, especially during the later developmental phase in the mature growth plate is still under active investigation. In this study a previ...

The focus of this study is to characterize the development of mammillary processes in the capital femoral physis of the domestic pig, expanding on the work of Tayton[1] and Liu[2]. The literature currently lacks a comprehensive characterization of the complete topography of this joint, which may offer better insight into the role mammillary process...

Uneven and excessive compressive loading of the growth plate has been implicated as one of the contributors to tibia vara or adolescent Blount’s disease and possibly to idiopathic scoliosis. Therefore, investigating how compression affects the growth plate at the microscale level is important if we are to understand how compressive forces are trans...

Background This bilateral squat study tests whether people with anterior cruciate ligament (ACL) reconstruction have symmetric three-dimensional ground reaction forces (GRFs) and symmetric anterior–posterior (AP) translation rates of the femur with respect to the tibia when compared with healthy control subjects. We hypothesized that there would b...

The objective of this study was to describe how tibiofemoral internal/external rotation varies in patients after total knee arthroplasty (TKA) when compared with control participants during a sit-to-stand (STS) maneuver. Motion analysis was used to measure internal/external knee rotation during STS in the control and TKA groups. Fourteen participan...

An orthopaedic knee prosthesis includes a femoral component having a condyle surface. The condyle surface is defined by one or more radii of curvatures, which are controlled to reduce or delay the onset of anterior translation of the femoral component relative to a tibial bearing.

In the immature tibia, the tibial tuberosity lies anterior to the proximal tibial epiphysis from which it is separated by an epiphyseal plate, which runs perpendicular to the proximal tibial epiphyseal plate and merges with the articular cartilage in the knee joint (Fig. 1). This growth plate has been referred to as a ‘cartilage bridge’ [1] and it...

In previous studies, the tensile strength of growth plate cartilage microstructures was shown to vary with location within a given growth plate, with growth plate thickness, and with collagen content. In the present study we compared the strength and microstructure of growth cartilage from two different growth plates (capital femoral and greater tr...

The polyethylene bearing on the tibial side of a total knee replacement (TKR) is subjected to large forces from the metal femoral component while allowing the required motions of rolling, gliding and rotation. Over time the polyethylene bearing surface topography is expected to undergo change due to creep and wear. We hypothesized that changes in s...

The physis, or growth plate, is a complex disc-shaped cartilage structure that is responsible for longitudinal bone growth. In this study, a multi-scale computational approach was under-taken to better understand how physiological loads are experienced by chondrocytes embedded inside chondrons when subjected to moderate strain under instantaneous c...

Introduction: The growth plate (GP) is responsible for longitudinal bone growth through chondrocyte proliferation, differentiation, swelling, matrix mineralization and apoptosis. The physiological mechanisms governing this growth are not well known, but mechanical factors are known to play a role [1]. Mechanobiological bone growth theories [2, 3] h...

Obesity is associated with increased risk of total hip arthroplasty (THA) dislocation. Differences in kinematics and kinetics at the hip during activities of daily living such as sit-to-stand (STS) may contribute to this risk. Nine high body mass index (BMI) subjects (mean BMI 31.2) and ten normal BMI control subjects (mean BMI 22.1) were analyzed...

Balancing a varus knee has traditionally been accomplished by releasing portions of the medial soft-tissue sleeve off the proximal tibia. More recently, a “pie-crusting” (PC) technique for balancing has been described. In a biomechanical cadaver study we compared PC to traditional release to determine their relative effects on flexion and extension...

The objective of this study was to design and validate a unique bioreactor design for applying spatially selective, linear, cyclic strain to degradable and non-degradable polymeric fabric scaffolds. This system uses a novel three-clamp design to apply cyclic strain via a computer controlled linear actuator to a specified zone of a scaffold while is...

Worldwide in 2008, more than 1.4 billion adults, age 20 and older, were overweight. Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health. The World Health Organization defines overweight as having a body mass index (BMI) greater than or equal to 25 kg/m2 and obese as a BMI greater than or equal to 30 k...

Soft tissue balancing is an important part of every total knee arthroplasty (TKA) surgery. Traditionally, balancing the varus knee has been approached by releasing portions of the medial soft tissue sleeve in a sub-periosteal nature off of the proximal tibia, but this may lead to undue laxity or residual pain about the area where the release was pe...

Introduction: During every total knee arthroplasty (TKA) surgery, an arthrotomy, or incision, is made vertically along the medial side of the knee joint capsule in order to gain access to the joint. After surgery, it is important to correctly repair this arthrotomy to seal the joint capsule. Surgeons attempt to close the arthrotomy with the medial...

The growth plate is a thin layer of cartilage sandwiched between epiphyseal and metaphyseal bone and is the location of active bone growth during childhood. It is subjected to large compressive and shear forces while pro-tecting its resident chondrocytes from damage. We believe that computational modeling can help us better un-derstand how the macr...

Same as United States Patent US8187335B2

An orthopaedic knee prosthesis includes a tibial bearing and a femoral component configured to articulate with the tibial bearing. The femoral component includes a posterior cam configured to contact a spine of the tibial bearing and a condyle surface curved in the sagittal plane. The radius of curvature of the condyle surface decreases gradually b...

Computational mechanics methods, such as finite element analysis or multibody dynamics, are usually employed toward the end of the design phase of a total joint implant system. It is of greater benefit, however, to utilize these methods early in the design process as a benchmarking tool to compare competitive products, as a screening tool to elimin...

The main goals of anterior cruciate ligament reconstruction (ACLR) are to restore knee function and prevent development of osteoarthritis (OA). However, the incidence of early-onset OA remains higher in patients following ACLR [1]. To our knowledge, the tibiofemoral joint (TFJ) force during gait has not been studied as a possible contributory facto...

The main goals of anterior cruciate ligament reconstruction (ACLR) are to restore knee function and prevent develop-ment of osteoarthritis (OA). However, the incidence of early-onset OA remains higher in patients following ACLR. The purpose of this study was to compare the computed tibiofemoral joint (TFJ) forces and muscle forces of ACLR knees to...

The next generational leap in computer navigation will hopefully aid surgeons in personalizing surgical techniques to patients’ individual anatomical variables to optimize outcomes. To effectively use the information obtained in the operating room, a multitude of kinematic variables must be conveyed to the orthopedic surgeon in a usable and coheren...

Assessment of patient function after TKA often focuses on implant alignment and daily activity capabilities, but the functional results and kinematics of the TKA are not easily predicted by some of these parameters during surgery. We asked whether differences in implant alignment in the transverse plane may affect fluorokinematics and be one of the...

An orthopaedic knee prosthesis includes a femoral component having a condyle surface. The condyle surface is defined by one or more radii of curvatures, which are controlled to reduce or delay the onset of anterior translation of the femoral component relative to a tibial bearing.

This study compared the gait of 10 subjects with unilateral anterior cruciate ligament (ACL) reconstruction to a group of 12 height- and weight-matched control subjects. The analysis was based on knee flexion, adduction, and internal rotation angles and moments. The objective was to use principal component analysis (PCA) to identify knees of the AC...

A knee replacement system includes a proximal tibial posterior camming portion defined by a first radius of curvature with a first origin in a first medio-lateral plane, a distal tibial posterior camming portion defined by a second radius of curvature with a second origin in a second medio-lateral plane, an anterior femoral camming portion of a pos...

An orthopaedic knee prosthesis includes a tibial bearing and a femoral component configured to articulate with the tibial bearing. The femoral component includes a condyle surface curved in the sagittal plane. The radius of curvature of the condyle surface decreases gradually between early-flexion and mid-flexion. Additionally, in some embodiments,...

A knee replacement system includes a femoral component including a lateral condylar articulating portion and a medial condylar articulating portion, a tibial tray including an upper articulating surface, and a tibial insert including (i) a first articulating portion for articulating with the lateral condylar articulating portion with a first condyl...

ACL reconstructed knees analyzed in early flexion displayed a 5-fold greater rate of change in posterior tibial translation in the reconstructed knee relative to the contralateral side than did a similar comparison of normal knees (p = 0.01). The relative rate of change of external rotation of the tibia with respect to the femur appeared to be 3 ti...

Computer-assisted surgery has focused on alignment of implants and soft tissue balancing but the end results during surgery as they pertain to long-term function of the implants are not yet realized. One parameter that continues to be variable despite the use of computer navigation is the placement of the implants in the transverse plane. The objec...

Histologic analysis of the posterior cruciate ligament has been reported in the normal and osteoarthritic knee but not after cruciate-retaining (CR) total knee arthroplasty (TKA). Retention of the posterior cruciate ligament during TKA has been debated as to whether it is beneficial in stability and function. If the presence of mechanoreceptors is...

1. ABSTRACT Rotational alignment of the femoral component is believed to be critical to satisfactory outcome and rotational malalignment has been observed to occur in 10-30% of patients. The objective of this work was to develop and explore simulations of a lunge manoeuvre often performed in fluoroscopic studies of total knee arthroplasty (TKA) pat...

Polyethylene wear after a total knee arthroplasty is inevitable. The effects of the wear particles on the surrounding soft tissue causing inflammatory responses and eventual aseptic loosening are well documented, but the biomechanical changes from polyethylene wear have been less understood. This study investigated how wear from a retrieved polyeth...

One of the common reasons for early revision or poor outcome in total knee arthroplasty is due to patellar maltracking, loosening, or pain. The analysis of how the patellofemoral mechanism operates and wears in vivo has not been a focus of many retrieval studies. This paper describes the wear pattern observed on patellar buttons from well-functioni...

The conventional approach to measuring structural parameters in trabecular bone rests on stereology from optical images, derived from sections of embedded bone. In order to provide data that are statistically representative of a sufficiently large volume, multiple sections need to be analyzed in each of the three orthogonal planes. In this work, an...

Paradoxical anterior translation has been reported to occur to varying degrees in total knee replacement devices. Although it has been observed in most fluoroscopic studies of posterior cruciate retaining devices, is not clear what design attributes might be contributing to this undesirable kinematic outcome. We compared simulations of a double leg...

Paradoxical anterior translation of the femur (undesirable anterior motion of the femoral side of the knee relative to the tibia) has been observed in patients with posterior cruciate ligament (PCL) retaining total knee devices in which the ACL is absent. Simulations of a double leg squat of several total knee implant designs were compared using me...

A new approach for the quantitative analysis of trabecular microstructure, based on high-field proton nuclear magnetic resonance (NMR) imaging, is presented. NMR is ideal because it provides high contrast between the marrow proton signal and the bone, which appears with background intensity. Images from 1 cm3 defatted specimens of trabecular bone,...

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

This computational study examines a rotating-platform TKA design in a weight-bearing functional activity (deep knee bending) to explore theoretical differences in wear-related contact parameters page 162 ISBN: 978-84-691-2464-2

The purpose of this study was to examine the influence of variability in bone properties and loading on peri-implant crestal and cancellous bone strains using a probabilistic approach, in combination with finite element (FE) analysis. Oblique occlusal loading was applied to a single endosseous implant embedded in a two-dimensional (2-D) FE model of...

Rigid immobilization of the cervical spine in children is normally accomplished with a halo ring attached to the skull with pins. Concern exists about the risk of halo pin complications in small children due to their diminished skull thickness. More data are needed on biomechanical properties of the immature skull and on safe levels for halo pin pe...

Slipped capital femoral epiphysis was produced in 9 matched pairs of fresh-frozen pig femurs (1-year-old pigs) by twisting the femoral head about the femoral neck axis. Each matched pair was fixed with a single steel cannulated screw on one side and 2 screws contralaterally, after which the perichondrium was removed before retesting. Double-screw f...

A 2-D finite element model of growth plate cartilage enabled the strains in and around chondrocytes in each growth plate cartilage zone to be estimated in relation to the nominal strain imposed on a tensile test coupon, consisting of bone-cartilage-bone and harvested from the greater trochanter. High tensile strains were predicted in regions where...

Our aim was to analyze and compare systematically the relative and interactive effects of implant diameter, length, and taper on calculated crestal bone strains. Three-dimensional finite-element models were created of a 20-mm premolar section of the mandible with a single endosseous implant embedded in high- or low-density cancellous bone. Oblique...

Polymerization shrinkage of dental restorative composites causes interfacial stress as well as residual stress within the body of the restoration. These residual stresses have been associated with a decrease in physical properties and void formation. Aim: The purpose of this study was to develop a finite element approach which could predict the for...

The purpose of this paper is to apply a finite deformation, elastic/viscoplastic approach to predict curing stresses in three light-cured dental composites, using Perzyna’s theory. Time-dependent constitutive parameters were obtained from mercury dilatometry, dynamic mechanical analysis and constrained shrinkage strerss testing. The numerical appro...

This is the first study to directly compare microstructural tensile properties of different growth plates in the same bone. Despite large differences in growth plate and reserve zone thicknesses, we found that the two growth plates in the proximal femur had similar mechanical properties.

We hypothesized that this cartilage bridge would be particularly resistant to shear stress due to the expected tension in the patellar tendon, which inserts into the tuberosity. To test this hypothesis, we compared two different directions of shear, one related to an upward directed force on the tuberosity and the other to a downward force. We also...

PMT-type halo pins were driven into 43 samples of skull bone taken from eight fetal calf skulls (30-39 week gestational age). Bi-linear force-penetration curves were obtained, consisting of a low initial stiffness region, associated with elastic deformation of the diploë, and a secondary linear region with high stiffness, associated with consolidat...

Introduction: Polymerization shrinkage associated with restoration failure remains one of the major performance factors preventing the universal use of dental composite restorative materials. Since the developing stress state at the bonded tooth-composite interface cannot be measured directly, finite element modeling is an attractive investigative...

The objective of this study was to use finite-element analysis to model tensilometer tests of polymerizing dental composites. A typical sample in polymerization shrinkage stress tests is shaped like a flat disk, that is, has a high aspect ratio (ratio of diameter to height). In the experimental literature it is implied that the induced stress state...

The aim of this study was to introduce design optimization of an endosseous dental implant in order to minimize cortical bone strains at the crest of the implant/bone interface. Linear elastic p-version finite element analysis was used to find the optimal design in four different two-dimensional finite element models of the mandibular bone: model 1...

The aim of this study was to compare implant-bone interface stresses and peri-implant principal strains in anisotropic versus isotropic three-dimensional finite element models of an osseointegrated implant in the posterior mandible. We obtained anisotropic (transversely isotropic) elastic constants for mandibular bone and derived equivalent isotrop...

Slipped capital femoral epiphysis (SCFE) is the most common hip disorder affecting adolescent children [1]. The etiology is not fully understood but thought to be multifactorial, related to both biological and biomechanical factors [2]. SCFE occurs when the epiphysis of the proximal femur slips in relation to the metaphysis through the growth plate...

The variable outcome of physeal distraction has raised questions as to the mechanism by which bone lengthening is achieved. Is it by stretching of the matrix or does it stimulate growth? In order to explore the contribution of matrix stretching, we sought to answer the following questions in an animal model: (a) Are the tensile properties of the la...

In the developing proximal tibial epiphysis the anterior ossifying tibial tuberosity is separated from the secondary ossification center of the tibial epiphysis by a bipolar growth plate known as the 'cartilage bridge.' We tested the fracture toughness of the central part of this growth cartilage in 18-week old calves in the direction perpendicular...

It has been proposed that physeal compression due to trauma can crush the germinal layer and cause growth arrest (1). Such a crush injury is not visible on a roentgenogram and is classified as a Type V injury (1). Others maintain that compression leaves the germinal layer intact and crushes the metaphyseal trabeculae and zone of provisional calcifi...

We computed the bone-implant interface stresses for a bullet-shaped dental implant in the human mandible under combined vertical and horizontal loading. We also calculated the principal strains in the bone surrounding the implant. Two cases were compared: One in which the bone was considered to have isotropic elastic constants and the other in whic...

The elastic moduli have not been reported for cancellous bone from the edentulous mandible. Accurate values are needed for finite element modeling of the mandible. The aim of this study was to determine elastic modulus values in three orthogonal directions for cancellous bone taken from an edentulous jaw and to relate these values to apparent densi...

Understanding growth plate behavior under hyperphysiologic loads is relevant to understanding growth arrest following physeal injury and growth abnormalities such as tibia vara. We determined the compressive properties of 29 samples of bone-growth plate cartilage-bone a 12-18 month old bovine proxima! tibial physis. Physeal samples (7mm x 7mm x 4-l...

Slipped capital femoral epiphysis involves the gradual displacement of the femoral head relative to the neck. Mapy theories have arisen to explain this slip. Frequently cited etiological faclors include increases in physeal thickness and inclination. Slipped epiphysis has been postulated to result from shear overload that causes separation through...

The American Society of Mechanical Engineers ASME-PUBLICATIONS-BED-Vol. 42: 579-580 ISBN No. 0-7918-1611-7

Slipped capital femoral epiphysis involves the gradual displacement of the femoral head relative to the neck. Many theories have arisen to explain this slip. Frequently cited etiological factors include increases in physeal thickness and inclination. Slipped epiphysis has been postulated to result from shear overload that causes separation through...

Bioengineering Division. ASME-PUBLICATIONS-BED-Vol. 39: 265-266 ISBN No. 0-7918-1582-X ISSN No. 0360-9960 The American Society of Mechanical Engineers

To compare monofilament wire versus braided cable for stabilizing transverse patella fractures using the modified AO tension band technique. A randomized blocked (paired) study comparing two fixation methods. Statistical analysis was performed using a nested repeated measures analysis, followed by Bonferroni post hoc testing. Seven paired embalmed...

The objective of this study was to examine how changes in glenohumeral joint conformity and loading patterns affected the forces and strains developed at the glenoid. After removal of soft tissue (muscles, ligaments, and labrum), force-displacement data were collected for both natural and prosthetically reconstructed joints. Joints were shown to de...