Biomedical subjects

Jeff Houck

Publications and source records attributed to Jeff Houck.

9 recordsLinked to original sources

PubMed2006

Comparison of foot kinematics between subjects with posterior tibialis tendon dysfunction and healthy controls.

STUDY DESIGN: A 2 x 4 mixed-design ANOVA with a fixed factor of group (posterior tibialis tendon dysfunction [PTTD] and asymptomatic controls), and a repeated factor of phase of stance (loading response, midstance, terminal stance, and preswing). OBJECTIVE: To compare 3-dimensional stance period kinematics (rearfoot eversion/inversion, medial longitudinal arch [MLA] angle, and forefoot abduction) of subjects with stage II PTTD to asymptomatic controls. BACKGROUND: Abnormal foot postures in subjects with stage II PTTD are clinical indicators of disease progression, yet dynamic investigations of forefoot, midfoot, and rearfoot kinematic deviations in this population are lacking. METHODS: Fourteen subjects with stage II PTTD were compared to 10 control subjects with normal arch index values. Subjects were matched for age, gender, and body mass index. A 5-segment, kinematic model of the leg and foot was tracked using an Optotrak Motion Analysis System. The dependent kinematic variables were rearfoot inversion/eversion, forefoot abduction/adduction, and the MLA angle. An ANOVA model was used to compare kinematic variables between groups across 4 phases of stance. RESULTS: Subjects with PTTD demonstrated significantly greater rearfoot eversion (P = .042), MLA angle (P = .008) and forefoot abduction angles (P < .005) during specific phases of stance. Subjects with PTTD demonstrated significantly greater rearfoot eversion (P<.004) and MLA angles (P < .009) by 6.2 degrees and 8.0 degrees, respectively, during loading response when compared to controls. During preswing, the subjects with PTTD demonstrated a significantly greater MLA angle (P < .002) and a forefoot abduction angle (P<.001) which exceeded that of the controls by 10.0 degrees. CONCLUSIONS: The abnormal kinematics observed at the rearfoot, midfoot, and forefoot across all phases of stance implicate a failure of compensatory muscle and secondary ligamentous support to control foot kinematics in subjects with stage II PTTD.

Biomechanical Phenomena↗

PubMed2006

Accelerated fracture healing.

Acceleration of the fracture healing process would have far-reaching benefits for both civilians and military personnel. Decreasing the time to return to complete function would reduce medical costs, enhance quality of life by decreasing pain and increasing mobility, accelerate the return of professional athletes to their sport, and decrease the time for military recruits to enter active duty after injuries incurred in basic training. Moreover, augmenting the healing process may prevent the long-term disability caused by fracture nonunion. Currently available pharmaceutical agents may allow us to realize this goal. However, these agents need to be tested in prospective randomized clinical trials.

Bone Density Conservation Agents↗

PubMed2005

Rabbit knee joint biomechanics: motion analysis and modeling of forces during hopping.

Although the rabbit hindlimb has been commonly used as an experimental animal model for studies of osteoarthritis, bone growth and fracture healing, the in vivo biomechanics of the rabbit knee joint have not been quantified. The purpose of this study was to investigate the kinematic and kinetic patterns during hopping of the adult rabbit, and to develop a model to estimate the joint contact force distribution between the tibial plateaus. Force platform data and three-dimensional motion analysis using infrared markers mounted on intracortical bone pins were combined to calculate the knee and ankle joint intersegmental forces and moments. A statically determinate model was developed to predict muscle, ligament and tibiofemoral joint contact forces during the stance phase of hopping. Variations in hindlimb kinematics permitted the identification of two landing patterns, that could be distinguished by variations in the magnitude of the external knee abduction moment. During hopping, the prevalence of an external abduction moment led to the prediction of higher joint contact forces passing through the lateral compartment as compared to the medial compartment of the knee joint. These results represent critical data on the in vivo biomechanics of the rabbit knee joint, which allow for comparisons to both other experimental animal models and the human knee, and may provide further insight into the relationships between mechanical loading, osteoarthritis, bone growth, and fracture healing.

Animals↗

PubMed2004

Validity and comparisons of tibiofemoral orientations and displacement using a femoral tracking device during early to mid stance of walking.

First, this study compares tibiofemoral motion during walking using a new femoral tracking device (FTD) and bone mounted markers in a single subject (n=1). The results suggest errors of <3 degrees in tibiofemoral angles using the FTD method over the first 85% of stance. Second, this study compares tibiofemoral angles and displacement during walking using the FTD method and a modified Helen Hayes method to track the femur in 13 subjects (n=13). The results suggest similar tibiofemoral angles in the sagittal and frontal planes using the two methods (average root mean square (RMS) differences <3.6+/-1.5 degrees ), and a large decrease in the transverse plane angles (average RMS differences=6.5+/-1.9 degrees ) and estimates of tibiofemoral displacement (P<0.05) using the FTD method. The FTD method presents a practical alternative to recording tibiofemoral transverse plane angles and displacement over the first 85% of stance.

Adult↗

PubMed2003

Associations of knee angles, moments and function among subjects that are healthy and anterior cruciate ligament deficient (ACLD) during straight ahead and crossover cutting activities.

The objective of this study was to compare knee angles and moments of healthy subjects (n=20) and subjects that were anterior cruciate ligament deficient (ACLD) (n=16) during stepping and crossover cutting activities. Subjects that were ACLD were separated into high (n=7) and low (n=9) functioning groups based on knee functional ratings. Knee angles and moments were estimated using three dimensional motion tracking and force plate data. The results suggest that knee angle and moment data were associated with level of functioning of ACLD subjects. Primarily knee frontal and transverse plane moments distinguished the stepping and crossover cut activities. Only some of the findings for the ACLD group were attributed to increasing knee stability.

Aged↗

PubMed2003

Muscle activation patterns of selected lower extremity muscles during stepping and cutting tasks.

Lower extremity muscle activations during crossover and side step cut tasks are hypothesized to play an important role in controlling knee motion, and therefore, impact the design of knee injury prevention and rehabilitation programs. However, the contribution of lower extremity muscles to frontal and transverse plane moments during cutting tasks is unclear. The purpose of this study was to compare the muscle activation patterns of selected lower extremity muscles (vastus lateralis, medial/lateral hamstrings and medial/lateral gastrocnemius) of subjects performing a stepping down and side step cut, a stepping down and crossover cut and an equivalent straight ahead task. Ground reaction force was used to determine the cut angle, stance time and compare the lower limb loading during each task. Electromyography data during all tasks were normalized to the average activation during the straight ahead tasks to determine relative changes in muscle activation between the straight ahead and different cut styles (crossover and side step). There were no differences in the pattern of muscle activation of the vastus lateralis, or lateral hamstring muscles when comparing the cutting tasks to the equivalent straight ahead task. However, the crossover cut task resulted in significantly higher muscle activation of the medial hamstrings and lateral gastrocnemius muscles relative to both the side step cut and straight ahead tasks. These results suggest the medial/lateral hamstrings and medial/lateral gastrocnemius play a role in transverse and frontal plane control during cut tasks.

Adult↗

PubMed2003

Self-reported giving-way episode during a stepping-down task: case report of a subject with an ACL-deficient knee.

STUDY DESIGN: Case report. OBJECTIVE: To describe the knee kinematics and moments of a giving-way trial of a subject with an anterior-cruciate-ligament- (ACL) deficient knee relative to his non-giving-way trials and to healthy subjects during a step-down task. BACKGROUND: Episodes of giving way are believed to damage joint structures, therefore treatments aim to prevent giving-way episodes, yet few studies document giving-way events. METHODS: The giving-way trial experienced by a 32-year-old male subject with ACL deficiency during a step-down task was compared to his non-giving-way trials (n = 5) and data from healthy subjects (n = 20). Position data collected at 60 Hz were combined with anthropometric data and ground reaction force data collected at 300 Hz to estimate knee displacement and 3-dimensional angles and net joint moments. RESULTS: The knee joint displacement was higher during the giving-way trial: from 4% to 32% of stance, reaching 9.0 mm at 18% of stance as compared to 1.6 +/- 0.7 mm for the non-giving-way trials. After 4% of stance, the knee flexion angle of the giving-way trial was 6.6 degrees higher than the non-giving-way trials and was associated with a higher knee extension moment. The knee frontal plane moment was near neutral during early stance of the giving-way trial in contrast to the non-giving way and healthy subjects which demonstrated a knee abduction moment. CONCLUSIONS: The response of this subject to the giving-way event suggests that higher knee flexion angles may enhance knee stability and, in reaction to the giving-way event, that knee extension moment may increase.

Adult↗

PubMed2002

Variations in the relationship between the frequency content of EMG signals and the rate of torque development in voluntary and elicited contractions.

Our purpose was to characterize the relationship between EMG mean power frequency (MPF) or median frequency (MF) and rate of torque development in voluntary ballistic and electrically elicited isometric contractions. Twenty-three healthy adults participated in two sets of experiments performed on elbow flexor muscles. For Experiment 1, subjects were asked to generate voluntary ballistic contractions by reaching four different target torque levels (20, 40, 60 and 100% of the maximal voluntary contraction (MVC)) as fast as they could. For Experiment 2, electrical (M-waves) and mechanical (twitches) responses to electrical stimulation of the nerves supplying the biceps brachii and brachioradialis muscles were recorded with the subjects at rest and with a background isometric contraction of 15% MVC. MPF, MF and rate of torque development (% MVC/s) were calculated for both voluntary and elicited contractions. Significant positive correlations were observed between MPF and rate of torque development for the voluntary contractions, whereas significant negative correlations were observed between the two variables for elicited contractions. This suggests that factors other than muscle fiber composition influence the frequency content of EMG signals and/or the rate of torque development, and that the effect of these factors will vary between voluntary and elicited contractions.

Adult↗

PubMedDate not supplied

Effects of childhood obesity on three-dimensional knee joint biomechanics during walking.

Despite the increasing percentages of children who are overweight, few studies have investigated their gait patterns. The purpose of this study was to quantify the three-dimensional knee joint kinematics and kinetics during walking in children of varying body mass and to identify effects associated with obesity. Three-dimensional kinematics and kinetics were collected from children of normal weight and overweight during normal gait using surface-mounted infrared emitting diodes and a force plate. The overweight group walked with a significantly lower peak knee flexion angle during early stance, and no significant differences in peak internal knee extension moments were found between groups. However, the overweight group showed a significantly higher peak internal knee abduction moment during early stance. These data suggest that although overweight children may develop a gait adaptation to maintain a similar knee extensor load, they may not be able to compensate for alterations in the frontal plane, which may lead to increased medial compartment joint loads. Therefore, assuming that the development of varus angular deformities of the knee joint and, in the longer term, medial compartment osteoarthritis are influenced by cumulative stress, this study supports the understanding that childhood obesity may impart a greater risk for the development of these diseases.

Biomechanical Phenomena↗