Biomedical subjects

K N An

Publications and source records attributed to K N An.

At least 127 records · Page 7Linked to original sources

PubMed1997

Kinematics of the elbow during wheelchair propulsion: a comparison of two wheelchairs and two stroking techniques.

OBJECTIVE: The kinematics of the elbow joint were studied for two types of wheelchairs and during two types of propulsive strokes. PARTICIPANTS: Ten serially selected healthy volunteers propelled a standard and a lightweight wheelchair on a roller system with both circular and pumping strokes. DESIGN: Kinematic data for the wheelchair and the upper extremity were collected by an optical tracking system. These kinematic descriptors were subsequently time-normalized with a spline algorithm to provide a graphic description of the wheelchair strokes. MAIN OUTCOME MEASURES: Thirteen discrete variables were compared for the two chairs and the two propulsive strokes. RESULTS: Total elbow motion ranged from 60.9 degrees of flexion to 5.2 degrees of extension. Maximal elbow flexion velocity ranged from 515.4 degrees to 572.8 degrees per second. Kinematic differences between the two wheelchairs were minimal, with a trend for 8.3 degrees to 5.2 degrees more elbow flexion in the lightweight wheelchair (p < .05), depending on the stroke used. With the use of any one chair, the style of the stroke had no significant effect on elbow kinematics, but the use of a pumping stroke did decrease propulsion arc by 12 degrees to 14 degrees (p < .05). CONCLUSION: No major differences regarding elbow kinematics were seen between the two types of wheelchairs. The pumping-stroke technique resulted in a shortened handrim contact arc.

Adult↗

PubMed1997

Parameters for modeling the upper extremity.

The purpose of this paper was to provide parameters for the development of a musculoskeletal model of the upper extremity. Five upper extremity specimens were obtained from four fresh cadavers. Anthropometric measures were obtained for each cadaver. Segment inertial parameters were estimated for each specimen from anthropometric measures of the cadaver from which the specimen was obtained. The three-dimensional kinematics of the humerus, ulna, and radius in different movements of the glenohumeral, humeroulnar and ulnoradial joints were measured for each specimen using of the 3Space tracking system (Isotrack, Polhemus). The instantaneous rotation center of the glenohumeral joint and the instantaneous rotation axes of elbow flexion and forearm pronation were determined for each specimen from the kinematic data. The specimens were dissected and the muscle origins and insertions and bony structures needed in upper extremity modeling were digitized using the 3Space system. The shapes of muscle origins and insertions were estimated. Muscle length, volume and pennation angle were measured for the estimation of physiological cross-sectional areas of each muscle. The results, which are given for one specimen, showed that the rotation center of the glenohumeral joint was very close to the geometric center of the joint with a mean distance of 4 mm. The mean angle between the flexion-extension and pro-supination axes of the elbow joint was 94 degrees. The minimum distance between these two axes was about 4 mm.

Aged↗

PubMed1997

Normal kinematics of carpal bones: a three-dimensional analysis of carpal bone motion relative to the radius.

Normal carpal kinematics were studied in 22 cadaver specimens using a biplanar radiography method. The kinematics of the trapezium, capitate, hamate, scaphoid, lunate, and triquetrum were determined during wrist motion in sagittal and coronal planes. The results were expressed using the concept of the screw displacement axis and converted to describe the magnitude of rotation about and translation along three axes (X-axis: pronation-supination axis, Y-axis: flexion-extension axis, and Z-axis: radial-ulnar deviation axis) commonly used for the wrist. The orientation of these axes is expressed relative to the radius. Within the proximal carpal row, considerable differences of carpal behavior around the Y-axis were observed during sagittal plane motion of the wrist. The scaphoid exhibited the greatest magnitude of rotation, and the lunate the least. The magnitude of rotation of the carpal bones around the X-axis during sagittal plane motion of the wrist was small. The proximal carpal bones exhibited some ulnar deviation in 60 degrees of wrist flexion. During coronal plane motion of the wrist, the magnitude of radial-ulnar deviation of the distal carpal bones was mutually similar and generally of a greater magnitude than that of the proximal carpal bones. The proximal carpal bones experienced some flexion during radial deviation of the wrist and extension during ulnar deviation of the wrist. Translation was generally minimal in all carpal bones throughout wrist motion. This study reports results from the largest cadaver wrist kinematics study completed to date. The accuracy of the current method was improved when compared to previous studies. A sufficient number of specimens to allow statistical comparison was used and minimal interspecimen variability was noted. This study enabled a precise description of quantitative analyses of normal carpal kinematics relative to the radius.

Adult↗

PubMed1997

Influence of lateral release on patellar tracking and patellofemoral contact characteristics after total knee arthroplasty.

The influence of lateral release of retinaculum on patellofemoral kinematics and contact characteristics after total knee arthroplasty was investigated in vitro. Lateral release altered the patellar tracking in patellar flexion, rotation, tilting, and translation. The contact force was decreased at high flexion angles. The contact area was slightly decreased and the contact region shifted laterally on the patellar button and medially on the femoral component at most of the flexion angles. The results suggest that the lateral release in total knee arthroplasty can change some patellar tracking and patellofemoral joint contact characteristics.

Cadaver↗

PubMed1997

Mechanical behavior of the foot and ankle after plantar fascia release in the unstable foot.

The change in position of the bones of the foot was studied in three dimensions after plantar fascia release in intact and destabilized feet. Fifteen fresh-frozen human foot specimens were used. Physiologic loads of 445 newtons were applied axially to simulate standing at ease, and the three-dimensional position of tarsal bones was determined with a magnetic tracking device. The positions were presented in the form of screw axis displacements, quantitating rotation, and axis of rotation orientation. After fasciotomy in the six intact feet, significant differences in rotation were observed at the talotibial and calcaneotalar levels. After fasciotomy in the four unstable feet with three supporting elements sectioned, significant differences in position were observed at the talotibial joint and a significant decrease in arch height was observed. After fasciotomy in the five unstable feet with five supporting elements sectioned, significant differences in rotation were observed at the talotibial joint (mean, 5.5 +/- 1.6 degrees; P = 0.001), calcaneotalar joint (mean, 6.1 +/- 2.1 degrees; P = 0.003), and metatarsotalar level (mean, 9.3 +/- 4.1 degrees; P = 0.007). The average decrease in arch height was 7.4 +/- 4.1 mm (P = 0.015). Displacement of all joints tested occurred after fasciotomy, with rotation about all three axes. These changes in displacement were more pronounced in unstable or destabilized feet. The data suggest that operations involving fasciotomy affect arch stability and should not be performed in patients with evidence of concomitant pes planus deformity, because of the likelihood of further deformation.

Adult↗

PubMed1997

Effect of the posterior tibial tendon on the arch of the foot during simulated weightbearing: biomechanical analysis.

A cadaver study was performed to determine the effect of the posterior tibial tendon (PTT) on the stability of the foot in simulated midstance phase of gait. Thirteen fresh-frozen human foot specimens were used. Loads were applied axially and to each tendon. Three-dimensional positions of tarsal bones before and after tendon loading were determined with the use of a magnetic tracking device. Significant differences in tarsal bone positions were observed with application of loads to the Achilles, posterior tibial, flexor digitorum longus, peroneus longus, and peroneus brevis tendons at the metatarsotalar, calcaneotalar, and talotibial joints and in overall arch height. These tendon loads caused position changes toward arch flattening or mild pes planus deformity. Significant differences in tarsal bone positions were observed with PTT loading compared with no PTT loading in metatarsotalar, calcaneotalar, and talotibial levels as well as arch height. The PTT caused position changes toward restoring the arch alignment. These data suggest that the PTT is an important stabilizer of the arch of the foot.

Adult↗

PubMed1997

Kinematics and contact characteristics of the first metatarsophalangeal joint.

We studied six fresh frozen cadaver feet to define the three-dimensional motion of the hallux proximal phalanx in relation to the first metatarsal and to describe the contact features of the first metatarsophalangeal joint. Six tendons to the hallux were loaded to simulate dynamic loading of the hallux. A magnetic tracking system was used to monitor the three-dimensional movement of the proximal phalanx while the toe position was changed from a neutral position to full extension by adjusting the tendon loads. The average surface area was 0.38 +/- 0.08 cm2 in the neutral position; it decreased with toe extension and was the lowest (0.04 +/- 0.03 cm2) at the full extension position. Contact distribution of the proximal phalanx did not change substantially throughout the arc of motion. However, for the metatarsal articular surface, the contact distribution shifted dorsally with increasing degrees of extension. These data are consistent with the observation that chondral erosions associated with hallux rigidus and degenerative arthritis initially affect the dorsal articular surface of the metatarsal, and implant arthroplasty often fails from component loading dorsally. The current technique of determining joint contact characteristics is applicable not only for the first metatarsophalangeal joint but also other joints that have not been studied because of shortcomings with more conventional methods.

Aged↗

PubMed1997

Physiological elongation of ligamentous complex surrounding the hindfoot joints: in vitro biomechanical study.

Ligaments surrounding the hindfoot joints play an important role in hindfoot stability. This in vitro study investigated anatomical and biomechanical characteristics of nine major ligamentous structures, including length and orientation at neutral position and physiological elongation with the foot in five different positions relative to the neutral position. The results showed that ligament elongation depended on the ligament length, orientation in neutral position, and movement of bones to which they were attached.

Aged↗

PubMed1997

Stability of the arch of the foot.

We defined the relative contributions of six ligaments in stabilizing the arch of the foot: plantar aponeurosis, long-short plantar ligaments, plantar calcaneonavicular ligament (spring ligament), medial talocalcaneal ligament, talocalcaneal interosseous ligament, and tibionavicular portion of the deltoid ligament. Nineteen fresh-frozen human foot specimens were used. A load of 445 N was applied axially to simulate standing-at-ease posture. Three-dimensional positions of tarsal bones before and after ligament sectioning were determined with the use of a magnetic tracking device. The motions were presented in the form of screw axis displacements, quantitating rotation, and axis of rotation orientation. After sectioning one structure, the arch did not collapse on any specimen and there was no obvious change by visual inspection. There were, however, measurable changes in tarsal bone position. Metatarsal-to-talus total rotation difference was greatest with spring ligament and deltoid ligament sectioning, with an average of 2.1 degrees +/- 1.7 degrees and 2.0 degrees +/- 0.2 degree difference, respectively. Calcaneus-to-talus rotation difference was greatest with talocalcaneal interosseous ligament sectioning, with an average of 1.7 degrees +/- 1.5 degrees. The spring ligament, deltoid ligament, and talocalcaneal interosseous ligament were most important for arch stability.

Ankle Joint↗

PubMed1997

Subtalar arthrodesis versus flexor digitorum longus tendon transfer for severe flatfoot deformity: an in vitro biomechanical analysis.

We defined the mechanical behavior of the foot after an operation for treatment of the flatfoot deformity, subtalar arthrodesis, and compared results with those from flexor digitorum longus tendon transfer. Twelve fresh-frozen human foot specimens were used. Supporting elements were sectioned to create a flatfoot deformity. To simulate midstance phase of gait, loads were applied axially to the plantar foot and to five tendons. Reduction of deformity in metatarsal-talar, calcaneal-talar, and talar-tibial positions was achieved and was significantly greater after subtalar arthrodesis operation than after flexor digitorum longus transfer.

Adult↗

PubMed1997

Gliding resistance of extrasynovial and intrasynovial tendons through the A2 pulley.

The gliding ability of the flexor digitorum profundus tendon and of the palmaris longus tendon through the A2 pulley was compared, in terms of gliding resistance, with use of a system that we developed. Fourteen digits and the ipsilateral palmaris longus tendons from fourteen cadavera were used. The average gliding resistance at the interface between the palmaris longus tendon and the A2 pulley was found to be greater than that between the flexor digitorum profundus tendon and the A2 pulley under similar loading conditions. We concluded that the gliding ability of the palmaris longus tendon was inferior to that of the flexor digitorum profundus tendon in vitro.

Biomechanical Phenomena↗

PubMed1997

Gait abnormalities following resection of talocalcaneal coalition.

Eleven patients (fourteen feet) had resection of a coalition of the middle facet of the talocalcaneal joint because of symptoms that had been present for a mean of four years (range, 0.5 to nine years). The mean age at the time of the resection was seventeen years (range, thirteen to thirty-two years). Nine patients were male and two were female. Five feet had resection of the bone bridge with interposition of fat or tendon, and nine had resection without any interposed material. The mean duration of follow-up was six years (range, two to thirteen years). The clinical result was excellent for five feet, good for four, fair for three, and poor for two. Inversion was 8 +/- 4.5 degrees (mean and standard deviation) on the involved side and 17 +/- 6.2 degrees on the uninvolved side (p = 0.002). Three feet later had evidence of osteoarthrosis of the subtalar joint. Gait analysis demonstrated decreased motion of the hindfoot and the ankle, compared with that in normal subjects and with that in the contralateral (uninvolved) foot, in the sagittal and coronal planes during walking on a level surface. Motion was also reduced, particularly in the sagittal and coronal planes, during walking on a side slope. Ground-reaction forces (F8 and F9), temporal force factors (T2, T3, and T7), and the percentage of the gait cycle that consisted of the stance phase on the side-sloping walkway were different from those in normal subjects or in the uninvolved foot. These data indicate that, although most of our patients who had resection of a talocalcaneal coalition had a successful clinical result, most had a residual functional deficit.

Adolescent↗

PubMed1997

Subtalar joint stability. Talocalcaneal interosseous ligament function studied in cadaver specimens.

We used 6 fresh-frozen foot specimens to evaluate the contribution of the talocalcaneal interosseous ligament (IOL) in stabilizing the subtalar (talocalcaneal) joint. The tibia and ankle joint were secured, and the calcaneus was subjected to a bending and axial force applied circumferentially. The position of the calcaneus relative to the talus was monitored with a magnetic tracking system. Motion was recorded at every half degree in the 0 degree to 360 degrees arc before and after sectioning of the IOL. The results in the intact feet indicated that, with circumferential loading of the subtalar joint, there were two stable zones (supination stable zone, pronation stable zone) during which little displacement occurred and two transition zones during which the supination and pronation movement occurred. There was a greater degree of supination displacement after IOL sectioning (p = 0.008), but no pronation displacement. The IOL contributed substantially to subtalar joint stability, particularly in supination.

Aged↗

PubMed1997

Influences of cane length on the stability of stroke patients.

The purpose of this study was to investigate the influence of cane length on the standing and walking stability of stroke patients. Ten stroke patients were used as subjects and evaluated by using two different cane lengths based on the measurements of the distance from distal wrist crease to the ground (WC cane), and the distance from greater trochanter to ground (GT cane). Force plates were used to determine the center of pressure (COP). The maximum sways, the total travel distances, and the mean travel speeds of the COP were analyzed for each patient standing and walking with and without canes. It was found that the total travel distance and the mean travel speed of the COP in the medial-lateral (M-L) direction were significantly lower when standing with a cane than when standing without one. It was also found that the values of these parameters and the maximum sways of the COP in both anterior-posterior (A-P) and M-L directions were significantly lower when standing with the WC cane than when standing with the GT cane. No significant difference was found in the maximum M-L sway, the total travel distance, and the mean travel speed of the COP in walking. These results suggest that the standing stability of stroke patients is improved by using canes, especially by using a WC cane, although no significant influence of using canes on the walking stability was detected. Based on the results of this study, the vertical distance from the wrist crease to ground is recommended as the appropriate cane length for stroke patients.

Adult↗

PubMed1997

Intercarpal kinematics during wrist motion.

Twenty-two fresh cadaver specimens were analyzed using a three-dimensional biplanar roentgenographic kinematic technique to quantitate intercarpal motion. The large number of specimens provided substantial power to dramatically optimize the statistical significance of the measurements. It was confirmed that the bones of the distal carpal row behave as a single, functional unit with little intercarpal motion and are directly linked to movement of the third metacarpal. The scaphoid, lunate, and triquetrum exhibit significant "out of plane" motion, noted mainly in relation to the distal row bones. Measurable differences in the kinematics of the proximal row bones, relative to each other, were repeatedly defined.

Adult↗

PubMed1997

Boundary lubrication between the tendon and the pulley in the finger.

The lubrication mechanism between the human flexor digitorum profundus tendon and the A2 pulley was investigated in vitro. The gliding resistance at the interface between the tendon and the pulley increased significantly after the tendon had been treated with a hyaluronidase solution. Alcian-blue staining of the surface of the tendon before and after it was treated with hyaluronidase suggested the presence of hyaluronate complex. Alcian blue-positive and hyaluronidase-sensitive materials, such as hyaluronate or proteoglycan, in the synovial membrane and the matrix of the tendon, may act as a boundary lubricant, facilitating the gliding and reducing the resistance between the tendon and the pulley.

Alcian Blue↗

PubMed1997

Analysis of longitudinal arch supports in stabilizing the arch of the foot.

Two orthotic devices commonly prescribed as arch supports were studied to evaluate their efficacy in stabilizing the foot. Fourteen cadaveric feet were mounted in a loading frame, and an axial load of 222, 445, or 667 N was applied while three-dimensional positions of the talus, calcaneus, navicular, and first metatarsal were monitored with a magnetic tracking system. Feet were tested with and without the use of two commonly prescribed arch supports. The two indices used to assess arch stabilization were arch height and joint rotation. Joint rotations consistently increased on load application. Significant differences were observed with Inserts 1 and 2 in metatarsal talar abduction, dorsiflexion and eversion, calcaneal talar eversion, and talar tibial dorsiflexion. Arch height significantly increased with both inserts. Contrary to previously published results, the arch supports that were studied provided measurable improvement in arch stability in a simulated standing at ease position.

Biomechanical Phenomena↗

PubMed1997

Tensile stress of the lateral patellofemoral ligament during knee motion.

Abnormal patellar retinacular tension has been considered to result in patellar lateral subluxation/dislocation. In this study, an in vitro experimental model was developed to determine the tensile stress of the lateral patellofemoral ligament, the thickest portion of the retinaculum, under loading conditions simulating two knee motion patterns: passive knee motion and unweighted active knee extension. The results indicate that the tensile stress increased significantly before 30 degrees of knee flexion, which strongly supports the clinical findings that patellar subluxation/dislocation occurs at approximately 20 degrees to 30 degrees knee flexion angles.

Analysis of Variance↗