Advisor Information
Nicholas Stergiou
Location
Dr. C.C. and Mabel L. Criss Library
Presentation Type
Poster
Start Date
3-3-2017 10:45 AM
End Date
3-3-2017 12:00 PM
Abstract
After anterior cruciate ligament (ACL) rupture most will undergo reconstructive surgery. Within the first year after surgery 25% of patients will re-tear their ACL. Most of those injured attempt to return to sports which include running and cutting. The ability to produce appropriate ground reaction forces may be crucial for the successful return to sports without re-injury. Understanding stability of multidirectional ground reaction force (mGRF) production in healthy and ACL reconstructed (ACL-r) patients can lend insight to the high instance of re-injury. Typically, stability has been measured using linear analyses, but these analyses cannot capture the subtle time varying changes that can occur. Recently, research using nonlinear techniques, such as the Lyapunov exponent (LyE), have been able to overcome these issues. Recent studies using this measure to quantify the stability of knee flexion during gait found that there are significant increases in LyE measured after ACL injury and reconstruction when compared to healthy control subjects. The purpose of this study was to understand the ability of those with ACL reconstruction to produce specific mGRFs stably. We hypothesized that there would be more instability, noted by greater LyE values, after ACL reconstruction when compared to healthy uninjured controls. Secondarily, we hypothesized that LyE values measured during the medial/lateral (ML) task would be greater compared to the anterior/posterior (AP) task. Our study included 7 (2M) healthy uninjured individuals and 2 (1M) who have undergone ACL reconstruction. We provided visual feedback of GRF production in the AP and ML direction to the subjects. LyE requires two input parameters time lag (tau) and embedding dimension (m), used to transform the AP and ML GRF into phase space. LyE was calculated using the Wolf algorithm. Largest LyE in bits/sec was reported as it indicates maximum divergence/instability of force production. ACL-r subjects had larger LyE values when compared to healthy uninjured controls. Additionally, the uninvolved limb of ACL-r subjects exhibited larger LyE values when compared to healthy uninjured controls. When comparing the ML and AP task there were no differences in all three limbs: healthy, involved, and uninvolved. While there was instability between groups there was no instability specific to direction of force production.
Included in
Biomechanics and Biotransport Commons, Other Biomedical Engineering and Bioengineering Commons
ACL Reconstruction Results in Alterations for Force Control Variability During Multidirectional Force Production
Dr. C.C. and Mabel L. Criss Library
After anterior cruciate ligament (ACL) rupture most will undergo reconstructive surgery. Within the first year after surgery 25% of patients will re-tear their ACL. Most of those injured attempt to return to sports which include running and cutting. The ability to produce appropriate ground reaction forces may be crucial for the successful return to sports without re-injury. Understanding stability of multidirectional ground reaction force (mGRF) production in healthy and ACL reconstructed (ACL-r) patients can lend insight to the high instance of re-injury. Typically, stability has been measured using linear analyses, but these analyses cannot capture the subtle time varying changes that can occur. Recently, research using nonlinear techniques, such as the Lyapunov exponent (LyE), have been able to overcome these issues. Recent studies using this measure to quantify the stability of knee flexion during gait found that there are significant increases in LyE measured after ACL injury and reconstruction when compared to healthy control subjects. The purpose of this study was to understand the ability of those with ACL reconstruction to produce specific mGRFs stably. We hypothesized that there would be more instability, noted by greater LyE values, after ACL reconstruction when compared to healthy uninjured controls. Secondarily, we hypothesized that LyE values measured during the medial/lateral (ML) task would be greater compared to the anterior/posterior (AP) task. Our study included 7 (2M) healthy uninjured individuals and 2 (1M) who have undergone ACL reconstruction. We provided visual feedback of GRF production in the AP and ML direction to the subjects. LyE requires two input parameters time lag (tau) and embedding dimension (m), used to transform the AP and ML GRF into phase space. LyE was calculated using the Wolf algorithm. Largest LyE in bits/sec was reported as it indicates maximum divergence/instability of force production. ACL-r subjects had larger LyE values when compared to healthy uninjured controls. Additionally, the uninvolved limb of ACL-r subjects exhibited larger LyE values when compared to healthy uninjured controls. When comparing the ML and AP task there were no differences in all three limbs: healthy, involved, and uninvolved. While there was instability between groups there was no instability specific to direction of force production.