Hashemi, Javad

In this thesis, adaptations were made on the Hybrid Cadaveric System to
accommodate new testing ramifications. The tests simulated dynamic loading (jump
landings) from a 1ft. height with various degrees of valgus (fixed hamstring and
quadricep forces) and various Quadricep (Q) and Hamstring (H) forces (fixed degrees of
valgus) to determine how the Anterior Cruciate Ligament (ACL) and Medial Collateral
Ligament (MCL) behave. The tests performed included 0Q 0H, 100Q 0H, 300Q 0H,
300Q 100H, and 5°, 15°, 25° of valgus. To determine the strain behavior of the ACL and
MCL a variety of equipment was used, including electromagnetic force plate to take
impact reading, cables used to create loading on the quadriceps and hamstrings, and two
Differential Variance Resistance Transducers (DVRTs). These ultimately generated ACL
and MCL strain allowing for a variety of strain comparisons under various circumstances.
It was concluded that in a few cases there were statistically significant differences in
strain for the ACL and MCL when applying various quadricep and hamstring forces (fixed valgus). It was also found that only statistical significance was present in ACL
strain when comparing degrees of valgus (fixed quadricep and hamstring forces). The
research concluded that muscle activation reduces strain on the ACL and MCL in these
testing scenarios. It was also established that degrees of valgus effects the ACL but is
negligible for the MCL. However, due to complications and variables, further testing is
needed to increase accuracy and supply more definitive results.

In this dissertation, the design and development of a hybrid robotic system that
simulates dynamic biomechanical tasks of the lower extremity with emphasis on knee
and hip joints are presented. The hybrid system utilizes a mechanical hip and a cadaveric
knee/ankle component and can accelerate the whole complex towards the ground. This
system is used to simulate complex athletic movements such as landing from a jump at
various anatomical orientations of the lower extremity with muscle action. The dynamic
response of the lower extremity is monitored and analyzed during impulsive contact
between the ground and the cadaveric leg. The cadaveric knee is instrumented to measure
strain of the Anterior Cruciate Ligament (ACL) during simulated high impact sports
activities. The mechanical hip allows various kinematics of the hip including flexion as
well as abduction. In addition to the flexion and abduction of the mechanical hip, the
controlled flexion and extension of the cadaveric knee allows for simulation of complex
tasks such as landing from a jump. A large number of tests were performed at various anatomical positions utilizing this device to simulate landing from a jump. ACL strain
was measured during these tasks using a Differential Variance Resistance Transducer
(DVRT). Ground Reaction Force and muscle forces were measured and monitored using
AmCell load cells recorded using the LabView software. one-inch and 6-inch jump
landing heights were used for all the simulations. The tests were performed at differing
angles of hip flexion (0°, 30°, 45°, 60°) and at two different ankle positions. Plantar
flexion and flat-footed landing conditions were simulated and compared in all degrees of
hip flexion. These tests were repeated with and without hip abduction in order to study
the effects of these landing positions on ACL strain. Hip flexion was found to effect ACL
strain: as angle of hip flexion increases, ACL strain decreases. This occurred in both
abducted and non-abducted hip positions. Ankle landing position had an effect only in
small drop heights, while hip abduction had an effect in large drops. Future tests must be
completed to further study these effects. These studies showed that the robotic system can
simulate dynamic tasks, apply muscle forces, and move the cadaveric tissue in three
dimensional biomechanical positions.

The Anterior Cruciate Ligament (ACL) resists excessive anterior translation and
internal rotation of the tibia during athletic activities and stabilizes the knee. In the US,
annually, over 200,000 cases of ACL disruption are reported. The impact on the quality of life of the subject and its cost to healthcare is tremendous. The objectives of this study were to determine any significant associations between the size of the tibial eminence and ACL injury and to develop a finite element model for structural analysis. The results suggest that the size of the tibial eminence plays a role in loading the ACL and is therefore a risk factor. In addition to the epidemiological analysis, a finite element model of the knee was developed that with added modifications can be used for complex knee loading situations. The results in this thesis may be used to develop strategies for ACL injury prevention and rehabilitation.