Biomedical subjects

L F Draganich

Publications and source records attributed to L F Draganich.

At least 19 recordsLinked to original sources

PubMed2001

Motion of the whole body's center of mass when stepping over obstacles of different heights.

Tripping over obstacles and imbalance during gait were reported as two of the most common causes of falls in the elderly. Imbalance of the whole body during obstacle crossing may cause inappropriate movement of the lower extremities and result in foot-obstacle contact. Thus, this study was performed to investigate the effect of obstacle height on the motion of the whole body's center of mass (COM) and its interaction with the center of pressure (COP) of the stance foot while negotiating obstacles. Six healthy young adults were instructed to perform unobstructed level walking and to step over obstacles of heights corresponding to 2.5, 5, 10, and 15% of the subject's height, all at a comfortable self-selected speed while walking barefoot. A 13-link biomechanical model of the human body was used to compute the kinematics of the whole body's COM. Stepping over the higher obstacles resulted in significantly greater ranges of motion of the COM in the anterior-posterior and vertical directions, a greater velocity of the COM in the vertical direction, and a greater anterior-posterior distance between the COM and COP. In contrast, the motion of the COM in the medial-lateral direction was less likely to be affected when negotiating obstacles of different heights.

Accidental Falls↗

PubMed2001

The effects of antidepressants on obstructed and unobstructed gait in healthy elderly people.

BACKGROUND: Elderly patients treated with antidepressants for depression are at high risk for injury due to falling. The primary purpose of this study was to determine the effects of amitriptyline, desipramine, and paroxetine on the gait of healthy elderly subjects during unobstructed and obstructed (i.e., stepping over obstacles) gait. Psychomotor and mood tests were also performed. METHODS: A randomized, crossover, four-period, double-blind, placebo-controlled laboratory trial was performed. Twelve healthy elderly subjects (average age, 67 years; range, 65-72 years) were tested. Subjects were assigned the three antidepressant drugs or a placebo in a random order. Single doses of amitriptyline 50 mg, desipramine 50 mg, paroxetine 20 mg, or placebo were given 4 hours prior to gait testing. Temporal-distance measures and kinematics of the lower trailing limb (i.e., limb going over obstacle last) were obtained. RESULTS: Compared with placebo, amitriptyline significantly reduced gait velocity by as much as 8.0% (p = .028), cadence by as much as 4.9% (p = .012), angular velocity of hip flexion by as much as 10.0% (p = .004), and angular velocity of knee flexion by as much as 8.3% (p = 018) during the crossing strides when stepping over obstacles. Except for knee flexion angle, unobstructed gait was not affected. Amitriptyline affected integrative capacity of the central nervous system (CNS) and ability to concentrate as measured by psychomotor and mood tests. CONCLUSIONS: The results for amitriptyline suggest that the subjects slowed their obstacle crossing speeds as a result of reduced CNS integrative capacities. Neither paroxetine nor desipramine significantly affected gait, psychomotor function, or mood.

Affect↗

PubMed2001

The effects of adult acquired flatfoot deformity on tibiotalar joint contact characteristics.

Changes in the tibiotalar contact characteristics were investigated using eight fresh frozen cadaver ankle specimens to further develop an established model of the acquired flatfoot deformity. The deformity was simulated by sectioning the tendons and ligaments of the ankle and foot that normally support the longitudinal arch. Axial loads of 1,350 N were applied to the foot in a neutral position in both the intact specimen and flatfoot model. The flatfoot condition resulted in significant lateral shifts of 5.28 mm in global contact area and 11.26 mm in the location of peak pressure, and in a small but significant posterior shift of 1.14 mm in global contact area. The flatfoot condition also resulted in a significant, 35%, reduction in contact area. Significant increases in mean pressure, 14%, and peak pressure, 13%, were also found, but were not in proportion to the relatively large decrease in contact area. This suggests a transfer of load off of the talar dome. Increased loading of the lateral facet and fibula are suspected. The lateral shift in the contact region created a local increase in mean contact pressure that may be responsible for long term degenerative changes in patients with this deformity.

Adult↗

PubMed2000

The TRAC PS mobile-bearing prosthesis: design rationale and in vivo 3-dimensional laxity.

We present a posterior stabilized mobile-bearing prosthesis, TRAC PS, which has congruent contact from full extension to full flexion, allows for freedom of internal-external rotation, and has an automatic posterior shift in tibiofemoral contact on the tibia to maximize the quadriceps lever arm in flexion. TRAC PS has 2 radii of curvature in the sagittal plane, 1 for the distal femoral condyles and 1 for the posterior femoral condyles, as does the normal knee. The distal and posterior femoral condyles articulate congruently in the inner tracks or the outer tracks of the polyethylene bearing, respectively. Anterior or posterior sliding of the femoral condyles on the bearing or of the bearing on the tibial tray cannot occur, providing inherent anterior and posterior stability. Three-dimensional knee laxity testing was performed on 17 patients from 12 months to 25 months after total knee arthroplasty with the TRAC PS and on 18 healthy control subjects of similar ages. Normal ligament balancing and normal internal-external rotational laxity were achieved with the TRAC PS prosthesis. Anterior and posterior laxity in the patients with TRAC PS was significantly reduced compared with that of the control subjects.

Arthroplasty, Replacement, Knee↗

PubMed2000

The effects of transection and reconstruction of the ulnar collateral ligament complex on the position of the proximal phalanx of the thumb during simulated tip pinch.

Injuries to the ulnar collateral ligament (UCL) of the metacarpophalangeal joint of the thumb are common and may result in functional instability of the joint. Eight cadaveric hands were studied. Physiologic levels of muscle loads were applied to the extrinsic flexor tendon of the thumb to simulate tip pinch of the thumb. We investigated the effects of transection of the UCL and accessory UCL (UCL complex) with and without transection of the dorsal capsule and volar plate and of reconstruction of the UCL, for 2 surgical techniques, on the position of the proximal phalanx with respect to the thumb metacarpal. The spatial positions of the metacarpal and proximal phalanx were measured with a 6 degrees of freedom digitizing system for flexion angles from 0 degrees to 60 degrees in 15 degrees increments. Transection of the UCL complex, dorsal capsule, and volar plate (ulnar capsuloligamentous structures) of the metacarpophalangeal joint did not affect radioulnar deviation or radioulnar shift, but did produce significant increases in supination by 8 degrees and volar translation by 2 mm at 45 degrees and 60 degrees compared with those found for the intact joint. The UCL was reconstructed with a tendon graft using the autogenous extensor digiti quinti. The first surgical technique, a traditional technique, and the second surgical technique, a technique based on anatomy, returned the position of the proximal phalanx on the metacarpal head to normal, with the exceptions of volar translation of the proximal phalanx at 60 degrees and trends toward abnormal supination of the proximal phalanx for flexion angels of 45 degrees and 60 degrees.

Adult↗

PubMed2000

Effects of reconstructed radial collateral ligament on index finger mechanics.

Twenty fresh frozen hand specimens from cadavers were studied. Physiologic levels of extrinsic muscle loads were applied to the extrinsic flexor tendons of the index finger to simulate tip pinch of the finger on a fixed plate. The acute effects of transection of the radial collateral ligament and accessory radial collateral ligament (radial collateral ligament complex) with and without transection of the dorsal capsule and volar plate on the position of the proximal phalanx with respect to the metacarpal bone of the index finger were investigated. The acute effects of reconstruction of the radial collateral ligament, for each of two different surgical techniques, on the position of the proximal phalanx also were investigated. The spatial positions of the metacarpal bone and proximal phalanx were measured with a six-degree-of-freedom digitizing system for flexion angles from 0 degrees to 90 degrees in increments of 15 degrees. Transection of the radial collateral ligament complex resulted in significant increases in ulnar deviation (adduction) of the proximal phalanx and in volar translation. Additional transection of the dorsal capsule and volar plate caused significant increases in ulnar deviation, pronation, volar translation, and ulnar shift. The first surgical technique, one traditionally used to reconstruct the metacarpophalangeal joint of the thumb, failed to return the three-dimensional position of the proximal phalanx on the metacarpal head of the index finger to normal. The second surgical technique, based on anatomy, returned the position of the proximal phalanx to levels not statistically different from normal for most flexion angles.

Adult↗

PubMed1999

The effects of the rotating-hinge total knee replacement on gait and stair stepping.

We studied 7 younger and 5 older patients who had rotating-hinge total knee replacements, 10 patients who had semiconstrained total knee replacements, and 8 younger and 11 older healthy control subjects to determine the effects of the rotating-hinge device on gait and stair stepping. The younger patients with the rotating-hinge device had few significant differences from the younger control subjects during gait or stair stepping. The older patients with the rotating-hinge device had several significant differences from both the older control subjects and subjects with the semiconstrained device during gait and stair stepping. Nevertheless, the proportions of older patients with the 2 devices who were able to perform the step-on activity for the highest step were the same.

Adolescent↗

PubMed1998

Placing the trailing foot closer to an obstacle reduces flexion of the hip, knee, and ankle to increase the risk of tripping.

This study was performed to test the hypothesis that reducing the horizontal distance between the trailing foot (foot crossing the obstacle last) and obstacle, during stance just prior to stepping over the obstacle, would reduce flexion of the hip, knee, and ankle joints of the trailing limb when the toe is over the obstacle to reduce the vertical toe-obstacle clearance and increase the risk of tripping. Fourteen healthy young adults stepped over an obstacle of 51, 102, 153, and 204 mm height in a self-selected manner (i.e., toe-obstacle distance was not controlled) and for toe-obstacle distance targets of 10, 20, 30, and 40% of their step lengths measured during unobstructed gait. The reductions in toe-obstacle distance resulted in linear decreases in flexion of the hip, knee, and ankle when the toe was over the obstacle. Toe-obstacle clearance of the trailing limb decreased significantly as toe-obstacle distance decreased. The reductions in toe-obstacle distance led to contact of the trailing (but not the leading) foot with the obstacle, the closer the obstacle the greater the number of contacts. The reductions also resulted in linear decreases in swing time of the trailing limb from toe-off to when the toe was over the obstacle. The height of the hip was not affected by toe-obstacle distance. Angular velocity of knee flexion was found to increase linearly as toe-obstacle distance decreased and appears to be of primary importance in avoiding obstacle contact.

Accidental Falls↗

PubMed1998

Increasing quadriceps loads affect the lengths of the ligaments and the kinematics of the knee.

The relationships between the lengths of the ligaments and kinematics of the knee and quadriceps load, for low to physiologic levels of quadriceps loads, have not previously been studied. We investigated the effects of increasing levels of quadriceps force, necessary to balance increasing levels of externally applied flexion moments, on the kinematics of the tibiofemoral joint and on the separation distances between insertions of selected fibers of the major ligaments of the knee in twelve cadavera. Static measurements were made using a six-degree-of-freedom digitizer for flexion angles ranging from 0 to 120 deg in 15 deg increments. Quadriceps generated extension of the knee was performed by applying loads to the quadriceps tendon to equilibrate each of four magnitudes of external flexion moments equivalent to 8.33, 16.67, 25.00, and 33.33 percent of values previously reported for maximum isometric extension moments. The magnitude of quadriceps force increased linearly (p < 0.0001) as external flexion moment increased throughout the entire range of flexion. Anterior translation, internal rotation, and abduction of the tibia increased linearly (p < 0.0001, p < 0.001, p < 0.001) as external flexion moment and, hence, quadriceps load increased. For the fibers studied, the anterior cruciate ligament (p < 0.0076), posterior cruciate ligament (p < 0.0001), and medial collateral ligament (p < 0.0383) lengthened linearly while the lateral collateral ligament (p < 0.0124) shortened linearly as quadriceps load increased. Based on these results for low to physiologic levels of quadriceps loads, it is reasonable to assume that the ligament lengths or knee kinematics expected with higher quadriceps loads can be extrapolated.

Adult↗

PubMed1997

Minimum energy trajectories of the swing ankle when stepping over obstacles of different heights.

This study was performed to test the hypothesis that the motion of the lower extremities when stepping over obstacles is governed by the criterion of minimum mechanical energy. The trajectories of the swing ankle during level walking and when stepping over obstacles of 51, 102, 153, and 204 mm heights were predicted and measured for eight healthy young adults. The predictions were made with a planar, seven-link linkage model based on the criterion of minimum mechanical energy using the method of dynamic programming. When stepping over obstacles, the predicted trajectories of the swing ankle were just high enough for the swing toe to clear the obstacles. The clearances measured between the obstacle and toe were significantly larger than those predicted. When stepping over obstacles the levels of work required to generate the measured trajectories were significantly larger (p < or = 0.002) than those required to produce the predicted trajectories. The amount of work necessary to generate the measured or predicted trajectories increased linearly (significant at p < or = 0.022) with obstacle height and, except when predicting the trajectory for the lowest obstacle, was significantly greater than that required when walking on level ground (p < 0.02). Thus, conservation of energy was found to become a less dominant criterion for governing the motion of the body when crossing obstacles than when walking on level ground.

Acceleration↗

PubMed1997

Stepping over an obstacle increases the motions and moments of the joints of the trailing limb in young adults.

Tripping over obstacles is the most frequently mentioned causes of falls. Thus, this study was performed to test the hypotheses that when crossing obstacles, toe-obstacle clearance and the three-dimensional motions and moments at the hip, knee, and ankle of the trailing limb (limb crossing the obstacle last) increase with obstacle height. Data were collected using an optoelectronic digitizing system and force platform. Fourteen healthy young adults were tested during unobstructed level walking and when stepping over obstacles of 51, 102, 153, or 204 mm heights. Toe-obstacle clearances of the trailing foot increased from 31 mm during unobstructed gait to an average of 146 mm when stepping over obstacles of any of these heights. Obstacle height was not found to affect toe-obstacle clearance. When the toe of the trailing limb was over the obstacle, the flexion angles of the hip and knee increased linerly with obstacle height. Compared to flexion of the hip or ankle, flexion of the knee appears to be of primary importance when crossing obstacles with the trailing limb. The maximum extension moment at the hip joint during late stance decreased linearly with obstacle height. At the knee joint, the maximum flexion moment during early stance and the maximum adduction moment during late stance increased linearly with obstacle height. At the ankle joint, the maximum dorsiflexion moment during late stance increased linearly with obstacle height. These greater demands on motions and moments may affect the abilities of those elderly having decreased muscle strengths to step over obstacles.

Adult↗

PubMed1996

In vitro study of knee stability after posterior cruciate ligament reconstruction.

The effect of reconstructing the posterior cruciate ligament on anteroposterior laxity of the knee was evaluated in 7 cadaveric knees. A bone-patellar tendon-bone graft was used. Femoral pilot holes were drilled to locate the most isometric sites for attachment of the graft to the femur using an isometer. A tension of 89 N was set in the graft using a tensiometer with the knee in 90 degree flexion while applying an anterior drawer force of 156 N to the tibia. Posterior displacement of the knee was measured in 15 degree increments from O degree to 90 degrees in the intact knee, in the knee with the posterior cruciate ligament transected, and after reconstruction of the posterior cruciate ligament in response to 100 N of posteriorly applied force. Graft tension was nearly constant between 0 degrees and 90 degrees flexion, indicating the grafts to be isometric. The reconstruction reduced posterior translation of the tibia in the posterior cruciate ligament excised knee at all angles of flexion; the differences were statistically significant. The reconstruction returned posterior translation to levels not significantly different from those of the intact knee between 0 degrees and 45 degrees flexion but not in the greater angles of flexion tested.

Adult↗

PubMed1995

Predicting the kinematics and kinetics of gait based on the optimum trajectory of the swing limb.

An algorithm was developed to predict the minimum energy consumption trajectory of the swing limb. The method of dynamic programming, a multistage optimization method, was applied to generate the optimum trajectory of the swing ankle which minimized the mechanical energy required to generate the moments of the joints of the lower extremities during the single support phase of gait. Predictions and measurements of gait were compared for six healthy subjects. The predicted hip and knee flexion angles of the swing limb were not significantly different from those experimentally measured except for hip flexion at times greater than 75% of the swing period. The predicted ground reaction forces were not significantly different from the measured ground reaction forces. Furthermore, the moments about the joints were not significantly different from those computed using the measured ground reaction forces and kinematics of the limbs. The results of this study support the hypothesis that human gait is energy efficient.

Acceleration↗

PubMed1994

Knee laxity in symptomatic osteoarthritis.

Twenty-two patients with primary osteoarthritis (OA) of the knee were studied to determine the effects of OA on laxity of the knee joint. Laxity was measured with a Genucom Knee Analysis System. Ten knees had mild OA (> 50% preservation of joint space). Fifteen knees had moderate OA (some preservation of joint space, but < 50%). Eighteen knees had severe OA (no joint space). A group of 18 knees from 9 healthy (asymptomatic) subjects of ages similar to those of the OA patients were used as controls. Compared to control knees, severe OA knees had less total anteroposterior (AP) translation (12.2 versus 6.6 mm, p < 0.025) and less total tibial rotation (79 versus 59 degrees, p < 0.01). Compared to early OA knees, knees with severe OA had 57% less average total AP translation (15.2 versus 6.6 mm, p < 0.01), 31% less total varus/valgus rotation (15 degrees versus 10.4 degrees, p < 0.016), and 26% less total internal/external tibial rotation (80.1 degrees versus 59 degrees, p < 0.007). These data indicate that osteoarthritic knees tend to have less laxity than normal knees, probably because of a combination of contracture of the ligaments and pressure of osteophytes against ligaments and other capsular structures.

Aged↗

PubMed1994

Neuromechanics of the patellofemoral joint.

Patellofemoral joint pain is one of the most common ailments associated with visits to sports medicine clinics and can be disabling, although conservative clinical treatment has a reportedly very high success rate. Patellofemoral joint pain is often associated with improper tracking of the patella within the femoral trochlear notch. Improper tracking of the patella can be associated with increased patellofemoral contact pressures that may be a mechanical stimulus underlying patellar cartilage degeneration. In those cases in which anatomic anomalies and trauma may be excluded as the basis for improper tracking, attention is directed toward possible disruptions to the central nervous system control and contractile potential of the knee joint extensor musculature that underlies proper patellofemoral mechanics. This paper presents a review of three seminal components related to the neuromechanics of patellofemoral function; patellofemoral tracking, patellofemoral contact pressures, and neuromotor control of patellofemoral agonists. It is the intent of the authors to illuminate areas requiring further basic and clinical research and provide a point of departure for this work.

Biomechanical Phenomena↗

PubMed1992

Assessment of the posterior malleolus as a restraint to posterior subluxation of the ankle.

We assessed the function of the posterior malleolus, the anterior tibiofibular ligament, and the fibula with regard to posterior stability of the talus in ten ankles of cadavera. Posteriorly directed loads of as much as 200 newtons were applied. Two groups of ankles were tested; in the first group, three ankles in which the ligamentous and osseous structures were intact were tested after transection of the posterior capsule and after removal of 10, 20, 30, and 40 per cent of the articular surface of the distal end of the tibia from the posterolateral corner. In the second group, seven ankles were tested in the same sequence, but the anterior tibiofibular ligament and the fibula were transected before sectioning of the articular surface. Compared with the results for the intact ankle, the experiments on the first group demonstrated less than one millimeter of additional posterior translation of the talus after removal of as much as 40 per cent of the articular surface. In the second group, in which the anterior tibiofibular ligament and the fibula had been transected, significant posterior translation of the talus (more than three millimeters) occurred after removal of 30 per cent of the articular surface (p < 0.01). This represented a 160 per cent increase in translation compared with that in the intact ankle.

Aged↗

PubMed1991

Tensions in the anterior and posterior cruciate ligaments of the knee during passive loading: predicting ligament loads from in situ measurements.

Cruciate ligament tensions were predicted for anteroposterior (AP) tibial translation at 20 degrees, 30 degrees, 80 degrees, and 90 degrees of knee flexion based on in vitro measurements from six cadaver knees. A three-dimensional trigonometric equation was derived to calculate cruciate ligament tension as functions of AP force applied to the tibia and knee flexion angle (KFA). AP forces less than or equal to 150 N were applied. Ligament tension increased with applied AP force. The relationship between ligament tension and applied AP force appeared linear, but a Hotteling's T2 test failed to demonstrate a linear relationship. Tensions in the anterior cruciate ligament (ACL) attained magnitudes of approximately equal to 140 N. Tensions in the posterior cruciate ligament (PCL) attained magnitudes of approximately equal to 220 N. An analysis was performed to determine the sensitivity of ligament tension to hypothetical errors in the experimentally measured parameters used to compute ligament tension. The new method we report can be used to determine tensions in the ligaments of the knee or other joints for various loading conditions.

Adult↗

PubMed1991

The effects of resection of the proximal part of the fibula on stability of the knee and on gait.

We studied six patients to determine the effects of unilateral marginal resection of the proximal part of the fibula on stability of the knee and on gait. At the time of the operation, the fibular collateral ligament and the tendon of the biceps femoris were reattached, but no attempt was made to stabilize the fibula otherwise. The patients were tested an average of sixty-one months after operation. Stability of the knee was measured with an instrumented system. Gait was evaluated with an optical electronic three-dimensional digitizing system and a multicomponent force-platform. The gait of six healthy control subjects of similar age was also studied, and the reproducibility of measurements of stability of the knee was investigated in four healthy adults. There were significant differences between the side on which an operation had been done and the contralateral side with regard to the extent of anterior translation and of total anterior-posterior translation of the tibia at both 20 and 90 degrees of flexion of the knee, and in total varus and valgus rotation of the knee (the number of degrees from a position of maximum varus to one of maximum valgus angulation) at 20 degrees of flexion. The measurements of gait and of motion of the knee were found to be normal when compared with those in the control subjects. In the ground-reaction measurements, there were some significant differences from normal in the medial-lateral plane, but they were clinically unimportant. Resection of the proximal part of the fibula can lead to instability of the knee.

Adult↗