Department of Mechanical, Industrial and Manufacturing Engineering

Research Interests

Dr. Hefzy's experimental and modeling research activities are in the areas of orthopedic biomechanics and rehabilitation engineering with a focus on the knee joint. Teaming with the Department of Rehabilitative Medicine at MCO, they have active funding from the NSF to work with engineering senior students designing and constructing devices to aid physically disabled individuals. Presently, Dr. Hefzy is actively involved in the following research projects:

1) Biomechanics of the knee joint in Deep Flexion

It is estimated that about half million total knee replacements (TKR) surgical interventions are being performed annually worldwide. In general, this operative treatment modality is prescribed for older patients (average age 55 years) and has been found to improve function and to decrease or eliminate pain resulting from Osteoarthritis (OA). Because of this success, it has been suggested to consider TKR as an option when treating younger and more active patients. However, such an attempt will place increased mechanical demands on the prosthesis that exceed the design limits of most of the currently available devices. Young and active patients are expected to perform activities that require the knee to be maximally flexed such as squatting and deep knee bending. Since none of the presently commercially available TKR allows for deep flexion, none of them will have an acceptable outcome to young and active patients.

A solution to this problem is the development of a TKR implant that would provide for full flexion of the knee. However, this is limited by the present state-of-the-art of knee mechanics, which does not provide an accurate understanding of how this joint functions in deep flexion in normal individuals. Our understanding of the complex three-dimensional dynamic tibio-femoral and patello-femoral motions past 140 degrees of knee flexion is limited. The purpose of this study is to determine the three-dimensional six-degree-of-freedom patello-femoral and tibio-femoral joint motions and loading during activities requiring deep knee flexion.

2) Three-dimensional Anatomic Dynamic Mathematical Modeling of the Human Knee Joint to include patello-femoral and tibio-femoral articulations

Mathematical modeling has been recognized as an effective and inexpensive tool by which one can obtain a better understanding of the complicated mechanical behavior of the substructures which comprise the human musculoskeletal system including the knee joint. The effectiveness of these models in predicting in-vivo behavior depends on their level of accuracy and sophistication. Interestingly, most of the mathematical models that have been developed to study the human knee are either for the tibio-femoral or the patello-femoral joint. Also, most of these models are static or quasi-static in nature and, therefore, do not predict the effects of inertial loads that occur in many locomotion activities. In a recent article: "Review of Knee Models: 1996 Update", it has been concluded that the current state-of-the-art for knee modeling can be summarized as follows:

i) Not a single dynamic comprehensive anatomically based mathematical three-dimensional model of the knee joint that includes both tibio-femoral and patello-femoral joint has yet been developed

ii) The only anatomically based mathematical three-dimensional dynamic model of the tibio-femoral joint is the one presented most recently by our group as part of this research activities.

The purpose of the present phase of this continuing project is to extend our modeling activities by performing a three-dimensional anatomical dynamic modeling of the knee to include both tibio-femoral and patello-femoral joints. Model calculations will be used to determine the response of normal knees under different dynamic loading conditions and following common reconstruction procedures.

3) Design experiences for engineering undergraduate students to design and build devices to aid the disabled

This research activity is part of a funded project from the National Sciences Foundation to work with engineering senior students to construct custom designed devices for physically disabled individuals attending the Inpatient Rehabilitation Unit and Rehabilitation Services at the Medical College of Ohio (MCO). As part of their training and education, senior mechanical engineering students at The University of Toledo are required to complete a capstone design course. During this one semester course, these students design, construct and test an original or a custom-modified device to meet design objectives specified by a customer. The goal of these projects is to assist disabled individuals to enjoy life and to reach toward their maximum potential. Furthermore, these projects enhance the education of student engineers through the experience of designing and building devices to meet a real need with feedback on how well the device satisfies that need.

4) Assessing the Lunge Exercise as a rehabilitation regiment for quadriceps strengthening

The Lunge can be described as an exercise in which a person step forward with one foot and gradually bends the front knee and hip. Physical therapists and athletic trainers are often prescribing this exercise as a rehabilitation regiment for quadriceps strengthening. Furthermore, Lunge is an activity performed in sports like fencing. Pushing objects can also be considered one form of lunging. Lunging can be performed in different forms including lunging anteriorly, posteriorly, anterolaterally, laterally, and posterolaterally. Very little information are available to assess and quantify the biomechanics of the lunge exercise. The purpose of this study is to study the mechanics of this rehabilitation activity.

Last Updated: 7/18/17