Biomechanics Commons^™

Follow-Up Evaluation 2 Years After Acl Reconstruction With Bone–Patellar Tendon–Bone Graft Shows That Excessive Tibial Rotation Persists, Stavros Ristanis, Nikolaos Stergiou, Kostas Patras, Elias Tsepis, Constantina O. Moraiti, Anastasios D. Georgoulis

Journal Articles

Objective: To investigate in vivo if the increased tibial rotation found in anterior cruciate ligament (ACL)-deficient patients before surgery is restored 2 years after the reconstruction, during 2 high-demanding activities.

Design: Prospective follow-up study.

Setting: A gait analysis laboratory.

Participants: Nine subjects with unilateral ACL rupture, reconstructed with a bone–patellar tendon–bone (BPTB) graft, and 10 healthy control subjects.

Interventions: All the ACL-deficient patients underwent a unilateral ACL reconstruction after prereconstruction data acquisition.

Main Outcome Measurements: Using a 6-camera motion analysis system, kinematics were collected as subjects (1) descended from a stair and, after foot …

A Novel Approach To Measure Variability In The Anterior Cruciate Ligament Deficient Knee During Walking: The Use Of The Approximate Entropy In Orthopaedics, Anastasios D. Georgoulis, Constantina O. Moraiti, Stavros Ristanis, Nikolaos Stergiou

Journal Articles

Objective. The evaluation of variability of biological rhythmic activities through measures such as Approximate Entropy (ApEn) has provided important information regarding pathology in disciplines such as cardiology and neurology. This research lead to the “loss of complexity hypothesis” where decreased variability is associated with loss of healthy flexibility rendering the system more rigid and unable to adapt to stresses. ApEn as a measure of variability and complexity, correlates well with pathology while, in some cases, it is predictive of subsequent clinical changes. The study of human gait could benefit from the application of ApEn since it is also a …

An Improved Surrogate Method For Detecting The Presence Of Chaos In Gait, David J. Miller, Nikolaos Stergiou, Max J. Kurz

Journal Articles

It has been suggested that the intercycle variability present in the time series of biomechanical gait data is of chaotic nature. However, the proper methodology for the correct determination of whether intercycle fluctuations in the data are deterministic chaos or random noise has not been identified. Our goal was to evaluate the pseudoperiodic surrogation (PPS) [Small et al., 2001. Surrogate test for pseudoperiodic time series data. Physical Review Letters 87(18), 188,101–188,104], and the surrogation algorithms of Theiler et al. [1992. Testing for nonlinearity in time series: the method of surrogate data. Physica D 58(1–4), 77–94] and of Theiler and Rapp …

Recovery Of Postural Control After Cerebral Concussion: New Insights Using Approximate Entropy, James T. Cavanaugh, Kevin M. Guskiewicz, Carol Giuliani, Stephen Marshall, Vicki S. Mercer, Nikolaos Stergiou

Journal Articles

Context: The return-to-play decision after sport-related cerebral concussion depends in part on knowing when an athlete has fully recovered postural control after injury.

Objective: To describe the postconcussion recovery of postural control using approximate entropy (ApEn), a regularity statistic from nonlinear dynamics.

Design: Retrospective case series analysis.

Setting: Sports medicine research laboratory.

Patients or Other Participants: Collegiate athletes from whom center-of-pressure and symptom data were collected at preseason, less than 48 hours after injury, and 48 to 96 hours after injury.

Main Outcome Measure(s): Approximate entropy values reflecting the amount of randomness contained in center-of-pressure oscillations were calculated for anterior-posterior …

Sight-Reading Versus Repertoire Performance On The Piano: A Case Study Using High-Speed Motion Analysis, Brenda Wristen, Sharon Evans, Nikolaos Stergiou

Journal Articles

The purpose of the study was to examine whether differences exist in the motions employed by pianists when they are sight-reading versus performing repertoire and determine whether these differences could be quantified using high speed motion capture technology. A secondary question of interest was whether or not an improvement in the efficiency of motion could be observed between two sight-reading trials of the same musical excerpt. This case study employed a six digital infrared camera system (Motion Analysis, Inc.) to capture the motion of pianists playing two trials of a repertoire piece and two trials of a sight-reading excerpt. Angular …

Joint Kinetics Of The Ankle And Knee When Running Over Obstacles, Alan Hreljac, Nikolaos Stergiou, Shane D. Scholten

Journal Articles

When running over obstacles of increasing height, heelstrike runners switch to a forefoot landing pattern once a critical obstacle height is reached. The primary purpose of this study was to determine whether ankle or knee joint kinetic variables trigger the gait change from a heelstrike to a forefoot striking pattern as obstacle height increases. Ten subjects were filmed from the sagittal plane as they ran at their preferred running speed over a force platform during six obstacle height conditions ranging from 10% to 22.5% of standing height, as well as an additional baseline condition with no obstacle (0%). An inverse …

A Nonlinear Dynamic Approach For Evaluating Postural Control, James T. Cavanaugh, Kevin M. Guskiewicz, Nikolaos Stergiou

Journal Articles

Recent research suggests that traditional biomechanical models of postural stability do not fully characterise the nonlinear properties of postural control. In sports medicine, this limitation is manifest in the postural steadiness assessment approach, which may not be sufficient for detecting the presence of subtle physiological change after injury. The limitation is especially relevant given that return-to-play decisions are being made based on assessment results. This update first reviews the theoretical foundation and limitations of the traditional postural stability paradigm. It then offers, using the clinical example of athletes recovering from cerebral concussion, an alternative theoretical proposition for measuring changes in …

Excessive Tibial Rotation During High-Demand Activities Is Not Restored By Anterior Cruciate Ligament Reconstruction, Stavros Ristanis, Nikolaos Stergiou, Kostas Patras, Haris S. Vasiliadis, Giannis Giakas, Anastasios D. Georgoulis

Journal Articles

Purpose: Recent in vitro research has suggested that anterior cruciate ligament (ACL) reconstruction does not restore control of tibial rotation. The purpose of this study was to explore these findings in vivo and investigate rotational knee stability during landing and subsequent pivoting. Such an activity places higher demands on the knee, almost similar to those found during high-level sports.

Type of Study: Case control series study.

Methods: We assessed 11 patients who had undergone ACL reconstruction with the same arthroscopic technique using a bone–patellar tendon–bone graft, 11 ACL-deficient subjects who had sustained the injury more than 1 year prior to …

An Artificial Neural Network That Utilizes Hip Joint Actuations To Control Bifurcations And Chaos In A Passive Dynamic Bipedal Walking Model, Max J. Kurz, Nikolaos Stergiou

Journal Articles

Chaos is a central feature of human locomotion and has been suggested to be a window to the control mechanisms of locomotion. In this investigation, we explored how the principles of chaos can be used to control locomotion with a passive dynamic bipedal walking model that has a chaotic gait pattern. Our control scheme was based on the scientific evidence that slight perturbations to the unstable manifolds of points in a chaotic system will promote the transition to new stable behaviors embedded in the rich chaotic attractor. Here we demonstrate that hip joint actuations during the swing phase can provide …

Electromechanical Delay Of The Knee Extensor Muscles Is Not Altered After Harvesting The Patellar Tendon As A Graft For Acl Reconstruction: Implications For Sports Performance, Anastasios D. Georgoulis, Stavros Ristanis, Anastasios Papadonikolakis, Elias Tsepis, U. Moebius

Journal Articles

Although the scar tissue, which heals the donor site defect, has different elasticity from the neighbouring patellar tissue, it remains unclear if this scar tissue can lead to the changes of the electromechanical delay (EMD) of the knee extensor muscles. If such changes do exist, they can possibly affect both the utilization of the stored energy in the series elastic component, as well as the optimal performance of the knee joint movement. The purpose of this study was to investigate the influence of harvesting the patellar tendon during anterior cruciate ligament (ACL) reconstruction and the associated patellar tendon scar tissue …

Anterior Cruciate Ligament Reconstruction With A Quadrupled Hamstring Autograft Does Not Restore Tibial Rotation, Anastasios D. Georgoulis, Stavros Ristanis, Vasilis Chouliaras, Constantina O. Moraiti, Nikolaos Stergiou

Journal Articles

As a result of the morbidity associated with anterior cruciate ligament (ACL) reconstruction with a bone–patellar–tendon– bone graft, many orthopaedic surgeons prefer hamstrings as the graft for ACL reconstruction. However, this selection is not based on solid scientific evidence. In vitro research shows that this graft cannot restore control of tibial rotation. Our recent in vivo research work has also demonstrated the same result. In particular, patients undergoing ACL repair who were reconstructed with a quadrupled hamstring tendon graft showed excessive tibial rotation during a dynamic activity when compared with healthy control subjects. Although the hamstring tendon graft has a …

Using Three Dimensional Motion Capture Technology To Describe And Assess Piano Technique: A Case Study, Brenda Wristen, Nikolaos Stergiou, Sharon Evans

Journal Articles

The purpose of the study was to examine any differences that exist in the quality of motions employed by pianists when they are sight-reading versus performing repertoire. A secondary question of interest was whether or not an improvement in the efficiency of motion could be observed between two sight-reading trials of the same musical excerpt. While data analysis for the full study is ongoing, the following results from a case study are illustrative.

The Effect Of Anterior Cruciate Ligament Recontruction On Lower Extremity Relative Phase Dynamics During Walking And Running, Max J. Kurz, Nikolaos Stergiou, Ugo H. Buzzi, Anastasios D. Georgoulis

Journal Articles

The purpose of this investigation was to use relative phase dynamics to evaluate gait in individuals with a reconstructed anterior cruciate ligament (ACL) during walking and running. Relative phase dynamics can describe the coordination strategies between the interacting segments at the lower extremity. Ten subjects who had undergone ACL reconstruction using the central third of their patellar tendon and ten healthy controls walked and ran on a treadmill at a self-selected pace. Relative phase dynamics were calculated for the foot–shank and shank–thigh coordinative relation- ships. Statistical differences between the groups were noted for the foot– shank relationship (p<0.05) during both walking and running and for the shank–thigh relationship (p<0.05) during walking. Our results indicate that current ACL reconstructive techniques may result in altered relative phase dynamics. These changes in relative phase dynamics could be related to a loss of sensory information about joint position and velocity that is typically provided by the intact ACL. Additionally, relative phase adaptations could be a learned response from the early stages of postsurgical rehabilitation. Relative phase dynamics provide quantitative information about the dynamic status of the ACL-reconstructed knee that cannot be gained from the conventional time-series evaluation of gait analysis data. Relative phase dynamics measures should supplement the conventional gait analysis measures that are used today for the clinical evaluation of the functional dynamic stability of the reconstructed knee. The examination of relative phase dynamics could be clinically important for the quantification of new ACL surgical interventions and of patient performance at various stages of rehabilitation. Further research should incorporate relative phase dynamics to understand the influence of ACL reconstruction on coordination and functional patient outcomes.

Baseline Measures Are Altered In Biomechanical Studies, Nikolaos Stergiou, Melissa Scott

Journal Articles

The purpose of this investigation was to examine if baseline measures are altered between conditions in biomechanical studies and to determine the need for baseline measurements in biomechanics. Ten runners were asked to run at varying speeds and obstacle heights. Baseline measures were acquired between all conditions. Right lower extremity kinematic and kinetic data were collected for all baseline trials and evaluated by both a group and a single subject analysis. The group analysis revealed significant differences between baselines only for the obstacle perturbation. The single subject analysis indicated that baseline measures are altered in a greater degree for kinematics …

Robotic Surgery Training And Performance, Kenji Narazaki, D. Oleynikov, Nikolaos Stergiou

Journal Articles

Background: To understand the process of skill acquisition in robotic surgery and to allow useful real-time feedback to surgeons and trainees in future generations of robotic surgical systems, robotic surgical skills should be determined with objective variables. The aim of this study was to assess skill acquisition through a training protocol, and to identify variables for the quantification of proficiency.

Methods: Seven novice users of the da Vinci Surgical System engaged in 4 weeks of training that involved practicing three bimanual tasks with the system. Seven variables were determined for assessing speed of performance, bimanual coordination, and muscular activation. These …

A Template For The Exploration Of Chaotic Locomotive Patterns, Max J. Kurz, Nikolaos Stergiou, Jack Heidel, E. Terry Foster

Journal Articles

Inverted pendulum and spring-mass models have been successfully used to explore the dynamics of the lower extremity for animal and human locomotion. These models have been classified as templates that describe the biomechanics of locomotion. A template is a simple model with all the joint complexities, muscles and neurons of the locomotor system removed. Such templates relate well to the observed locomotive patterns and provide reference points for the development of more elaborate dynamical systems. In this investigation, we explored if a passive dynamic double pendulum walking model, that walks down a slightly sloped surface (γγ was increased, …

Three-Dimensional Kinematics Of The Tibiofemoral Joint In Acl-Deficient And Reconstructed Patients Shows Increased Tibial Rotation, Anastasios D. Georgoulis, Stavros Ristanis, Constantina O. Moraiti, Argyris Mitsou, Manfred Bernard, Nikolaos Stergiou

Journal Articles

The study of the altered knee joint movement patterns that follow anterior cruciate ligament (ACL) rupture can be very insightful in the development of prevention and therapeutic strategies concerning this injury. This can be achieved through three-dimensional kinematic analysis, because it provides an objective evaluation in vivo of the knee joint function. It has been demonstrated that ACL-deficient patients develop functional adaptations (ie, quadriceps avoidance gait) and walk with the knee in a more extended position to compensate for the ACL loss. Furthermore, it has been shown that ACL rupture results in anterior tibial translation and excessive tibial rotation while …

Detecting Altered Postural Control After Cerebral Concussion In Athletes With Normal Postural Stability, James T. Cavanaugh, Kevin M. Guskiewicz, Carol Giuliani, Stephen Marshall, Vicki S. Mercer, Nikolaos Stergiou

Journal Articles

Objective: To determine if approximate entropy (ApEn), a regularity statistic from non-linear dynamics, could detect changes in postural control during quiet standing in athletes with normal postural stability after cerebral concussion.

Methods: The study was a retrospective, case series analysis of centre of pressure (COP) data collected during the Sensory Organization Test (SOT) from NCAA Division I (USA) athletes prior to and within 48 h after injury. Subjects were 21 male and six female athletes from a variety of sports who sustained a cerebral concussion between 1997 and 2003. After injury, athletes displayed normal postural stability equivalent to preseason levels. …

The Effect Of The Walking Speed On The Stability Of The Anterior Cruciate Ligament Deficient Knee, Nikolaos Stergiou, Constantina O. Moraiti, Giannis Giakas, Stavros Ristanis, Anastasios D. Georgoulis

Journal Articles

Background. The reasons behind the development of future pathology in individuals with anterior cruciate ligament deficiency are unknown. This is due to the lack of appropriate methods to assess functional dynamic knee stability. In this study, we investigated the effect of walking speed on the functional dynamic stability of the anterior cruciate ligament deficient knee. We defined functional dynamic stability as local stability or the sensitivity of the knee to small perturbations. The natural stride-to-stride variations that exist during locomotion reflect exactly the presence of these perturbations. We hypothesized that speed will affect local stability in the deficient knee, …

The Effects Of Anterior Cruciate Ligament Reconstruction On Tibial Rotation During Pivoting After Descending Stairs, Stavros Ristanis, Giannis Giakas, Christos D. Papageorgiou, Constantina O. Moraiti, Nikolaos Stergiou, Anastasios D. Georgoulis

Journal Articles

Recent in vitro research suggests that ACL reconstruction does not restore tibial rotation. This study investigated rotational knee joint stability in vivo during a combined descending and pivoting movement that applies a high rotational load to the knee joint. We studied 20 ACL reconstructed patients (bone–patellar tendon–bone graft) and 15 matched controls with a six-camera optoelectronic system performing the examined movement. In the control group the results showed no significant differences in the amount of tibial rotation between the two sides. No significant differences were also found between the contralateral intact leg of the ACL group and the healthy control. …

Subtalar And Knee Joint Interaction During Running At Various Stride Lengths, Nikolaos Stergiou, Barry T. Bates, Max J. Kurz

Journal Articles

Background: It has been suggested that during running proper coordination between subtalar pronation/supination and knee flexion/extension via tibial rotation is important to attenuate ground reaction impact forces (GRIF). Lack of coordination over time may produce a wide range of injuries. It was hypothesized that increasing stride length would result in higher GRIF. It was also hypothesized that alterations in stride length would result in changes of the subtalar/knee coordination.

Methods: Six subjects ran under three different stride lengths (normal stride, understride and overstride) at their self-selected pace. Sagittal, rear view kinematic data and GRIF kinetic data were collected. The subtalar/knee …

The Aging Human Neuromuscular System Expresses Less Certainty For Selecting Joint Kinematics During Gait, Max J. Kurz, Nikolaos Stergiou

Journal Articles

This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty in selecting a joint range of motion during gait. Our results supported this hypothesis, and indicated that aged individuals demonstrated statistically less certainty for the knee (16.8%) and hip (24.6%). We suggest that neurophysiological changes associated with aging may result …

Compensatory Mechanisms In Anterior Cruciate Ligament Deficiency, Anastasios Papadonikolakis, Lance Cooper, Nikolaos Stergiou, Anastasios D. Georgoulis, Panayotis N. Coucacos

Journal Articles

The literature cites numerous studies involving the analysis of movement patterns in anterior cruciate ligament deficient (ACLD) patients. Although several in vivo biomechanical studies have shown that ACLD patients develop protective mechanisms against degenerative diseases, it seems that these adaptations fail to protect the knee from future pathology. Some authors state that ACLD patients adapt to the injury by avoiding quadriceps contraction during gait when the knee is near full extension. However, others have found increased hamstrings and decreased gastrocnemius activity, which normally contribute to the stability of the knee. It seems that further in vivo biomechanical investigation is required …

Nonlinear Dynamics Indicates Aging Affects Variability During Gait, Ugo H. Buzzi, Nikolaos Stergiou, Max J. Kurz, Patricia A. Hageman, Jack Heidel

Journal Articles

Objective. To investigate the nature of variability present in time series generated from gait parameters of two different age groups via a nonlinear analysis.

Design. Measures of nonlinear dynamics were used to compare kinematic parameters between elderly and young females.

Background. Aging may lead to changes in motor variability during walking, which may explain the large incidence of falls in the elderly.

Methods. Twenty females, 10 younger (20–37 yr) and 10 older (71–79 yr) walked on a treadmill for 30 consecutive gait cycles. Time series from selected kinematic parameters of the right lower extremity were analyzed using nonlinear dynamics. The …

Nonlinear Analysis Of The Development Of Sitting Postural Control, Regina T. Harbourne, Nikolaos Stergiou

Journal Articles

The development of sitting postural control in five normal infants was examined longitudinally at three stages of sitting: Stage 1, when infants could hold up their head and upper trunk, but could not sit independently; Stage 2, when infants began to sit independently briefly; and Stage 3, when infants could sit independently. Methods from nonlinear dynamics were used to analyze center of pressure (COP) data during sitting in terms of stability of the neuromuscular system (Lyapunov Exponent), movement dimensionality (Correlation Dimension), and complexity/regularity (Approximate Entropy). Results indicated significant changes in the nonlinear measures over time, with increased stability and increased …

The Spanning Set Indicates That Variability During The Stance Period Of Running Is Affected By Footwear, Max J. Kurz, Nikolaos Stergiou

Journal Articles

Sensory information the foot receives appears to be related to kinematic variability. Since footwear material densities affect sensory information, footwear may be an important factor that dictates variability. This study hypothesized that modifications in footwear would result in changes in kinematic variability during the running stance period. Subjects ran on a treadmill for three conditions: hard shoe, soft shoe and barefoot. The spanning sets of the mean ensemble curves of the knee and ankle changes for each condition were used to define variability. Variability was significantly larger in the barefoot condition in comparison with the two footwear conditions for both …

Three-Dimensional Tibiofemoral Kinematics Of The Anterior Cruciate Ligament-Deficient And Reconstructed Knee During Walking, Anastasios D. Georgoulis, Anastasios Papadonikolakis, Christos D. Papageorgiou, Argyris Mitsou, Nikolaos Stergiou

Journal Articles

Background: It is possible that gait abnormalities may play a role in the pathogenesis of meniscal or chondral injury as well as osteoarthritis of the knee in patients with anterior cruciate ligament deficiency.

Hypothesis: The three-dimensional kinematics of anterior cruciate ligament-deficient knees are changed even during low-stress activities, such as walking, but can be restored by reconstruction.

Study Design: Case control study.

Methods: Using a three-dimensional optoelectronic gait analysis system, we examined 13 patients with anterior cruciate ligament-deficient knees, 21 patients with anterior cruciate ligament-reconstructed knees, and 10 control subjects with uninjured knees during walking.

Results: Normal patterns of knee …

Spanning Set Defines Variability In Locomotive Patterns, Max J. Kurz, Nikolaos Stergiou, Daniel Blanke

Journal Articles

The purpose of the investigation was to use the spanning set methodology to quantify variability in locomotive patterns and to compare this method with traditional measures of variability. Subjects ran on a treadmill while sagittal plane kinematic data were collected with a high-speed (180 Hz) camera. Changes in variability were evaluated as the subject ran barefoot and in shoes. Mean ensemble curves for the knee angle during the stance period were created for each condition. From these curves, traditional measures of variability were calculated using the coefficients of variation (CVs), and the mean deviation (MD). Spanning set vectors were defined …

Frequency Domain Characteristics Of Ground Reaction Forces During Walking Of Young And Elderly Females, Nikolaos Stergiou, Giannis Giakas, Jennifer E. Byrne, Valerie Pomeroy

Journal Articles

Objective. To examine the frequency domain characteristics of the ground reaction forces of young and elderly females during free walking.

Design. Independent t-tests were used to examine the frequency content of all three components of the ground reaction force.

Background. Frequency domain analysis has the potential to assist in identifying changes in gait that may be masked in the time domain. No research has been done to identify changes in gait due to age-related impairments in the frequency domain.

Methods. Ten young and ten elderly females walked at a prescribed speed while ground reaction forces were collected via a …

Effect Of Normalization And Phase Angle Calculations On Continuous Relative Phase, Max J. Kurza, Nikolaos Stergiou

Journal Articles

The purpose of this investigation was to determine if phase plot normalization and phase angle definitions would have an affect on continuous relative phase calculations. A subject ran on a treadmill while sagittal plane kinematic data were collected with a high­ speed (180Hz) camera. Segmental angular displacements and velocities were used to create phase plots, and examine the coordination between the leg and thigh. Continuous relative phase was calculated with a combination of two different amplitude normalization techniques, and two different phase angle definitions. Differences between the techniques were noted with a root mean square (RMS) calculation. RMS values indicated …