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Biomedical subjects

K N An

Publications and source records attributed to K N An.

At least 253 records · Page 14Linked to original sources
PubMed1989

The effects of simulated unstable scaphoid fractures on carpal motion.

The kinematics of five fresh frozen wrist specimens were studied before and after a simulated scaphoid waist fracture. To determine the change in wrist motion and fracture site characteristics associated with an unstable wrist, the relative motion of each carpal bone was determined from the movement of implanted carpal markers on biplanar radiographs obtained in neutral and the four extreme wrist positions. The kinematics of the wrist in our specimens before the osteotomy were similar to previous studies. After the osteotomy, the proximal and distal segments of the scaphoid moved independently. The distal scaphoid assumed a relatively flexed stance and displayed increased motion. The proximal scaphoid fragment and lunate assumed a relatively extended stance and displayed less motion after the osteotomy. These kinematic abnormalities produced significant interfragmentary motion that would be expected to complicate normal fracture healing. The spontaneous collapse of the two scaphoid fragments produced a dorsal angulation or "humpback" deformity that simulated the clinical situation of displaced scaphoid nonunions. The scaphoid serves an important role maintaining normal alignment of the carpal bones and producing normal wrist motion.

Biomechanical Phenomena↗
PubMed1989

Functional anatomy of the human digital flexor pulley system.

The anatomy of 55 cadaver digits was studied, both statistically and with simulated active motion using weights attached to the flexor tendons. The modified description of Doyle and Blythe accurately described the anatomy observed. Serial pulley sectioning showed two types of bowstringing, both of which affected the relationship of tendon excursion to joint motion. The most constant, resulting in 15% loss of motion for a fixed tendon excursion, occurred over the concave surfaces of the proximal and middle phalanges. Bowstringing at the proximal interphalangeal joint was present only after 30 degrees of flexion had occurred, because of the convexity of the phalangeal condyles.

Anthropometry↗
PubMed1989

Reliability of carpal angle determinations.

The radioscaphoid, radiolunate, and radiocapitate angles of nine lateral projections of the wrist (three in flexion, three in extension, and three in neutral position) of three fresh cadaver specimens were measured. Seven orthopedic surgeons (six hand surgeons and one orthopedic surgeon) made the measurements with a standard goniometer using both the axial and tangential methods of angle determination. The overall standard deviation for all measurements was 5.2 degrees, and no significant difference in variability between axial and tangential methods was found. By comparing the same angles from different wrist positions, the amount of flexion-extension motion of the capitate, scaphoid, and lunate with respect to the radius was estimated. To assess the accuracy of such a method of carpal motion determination, a more accurate stereoradiographic method of analysis of carpal kinematics was utilized. The overall estimated error of this standard goniometric method of carpal motion determination averaged 7.4 degrees.

Anthropometry↗
PubMed1989

Wrist kinematics after limited intercarpal arthrodesis.

Two limited intercarpal fusions, scapho-trapezial-trapezoidal and scapho-capitate, were simulated in six fresh human cadaver wrists by means of two Herbert screws. By use of a biplanar radiographic measurement system, the relative kinematic behavior of selected carpal bones, before and after the simulated limited fusions could be analyzed. Both scapho-trapezial-trapezoidal and scapho-capitate fusions produced a similar reduction in global range of motion and comparable effects on the relative intracarpal motion. In both fusions, a significant reduction in relative motion at the lunocapitate joint was recorded. The scaphoid, being fused to the distal carpal row, was shown to lose its role in the adaptative mechanism that allows preservation of articular congruency to the always changing space between the distal carpal row and the radius. After both types of fusion, increased sliding motion of the lunate on the radius was found. These kinematic changes are likely to enhance shear stresses on the lunate and tension on the surrounding ligaments, potentially diminishing long-term functional results.

Arthrodesis↗
PubMed1989

Biomechanical study of tendon excursion of thumb muscles related to interphalangeal and metacarpophalangeal joint motion.

A biomechanical study of tendon excursion versus interphalangeal and metacarpophalangeal (MCP) joint motion relationships on extrinsic and intrinsic thumb muscles has been carried out. Continuous recording of excursion related to joint motion was obtained using a rotary potentiometer and an electrogoniometer. Functional activities of individual muscles were defined based on the excursion data. Moment arms of tendons were also derived. Flexor pollices longus and extensor pollices longus (EPL) tendons have a constant and linear relationship with flexion of the MCP joint. Extensor pollices brevis and flexor pollices longus contribute minimally in abduction-adduction. Extensor pollices longus is a secondary adductor of the joint. Abductor pollices brevis and adductor pollices transverse head are important in dynamic stabilization of the MCP joint and to keep EPL tendon in proper position through the balance of dorsal aponeurosis. This information enables pre-operative planning for functional reconstruction of the thumb, such as in tendon transfers, opponensplasty. MCP joint collateral ligament reconstruction and post-operative management after flexor tendon repair.

Biomechanical Phenomena↗
PubMed1988

Application of a magnetic tracking device to kinesiologic studies.

A magnetic position and orientation tracking system is currently available for the determination of the position and orientation of a sensor relative to a source by utilizing the principle of low-frequency magnetic field technology. The application of this system for biomechanical analysis of human movement is examined in this study. Studies of both planar particle motion and spatial rigid body motion based on Eulerian angle description and screw displacement axis description have been performed. The system has been found to be quite accurate and easy to use, and it would be a useful tool in kinesiologic research.

Biomechanical Phenomena↗
PubMed1988

Relative motion of selected carpal bones: a kinematic analysis of the normal wrist.

The relative motion of selected carpal bones and the radius was studied using five cadaver specimens labeled with metal markers to precisely quantitate their motions. Data was obtained by means of a combination of orthoradiography, sonic digitization, and computer analysis. We conclude that the wrist functions as two carpal rows with the distal row bones relatively tightly bound to one another and the proximal row bones less so but still moving together. Therefore, we theorize that the proximal row functions as a variable geometry intercalated segment between the distal row and the radius-triangular fibrocartilage.

Adult↗
PubMed1988

Three-dimensional geometric analysis of the metacarpophalangeal joint.

No prosthesis yet designed for replacement of the metacarpophalangeal (MCP) joint incorporates all considerations of anatomy and geometry of the natural joint to restore the normal kinematics. Loss of stability, recurrent deformity, and early loosening are persistent problems. In this study, a detailed three-dimensional geometric analysis of the MCP joint was performed. The sagittal contours of both metacarpal heads and base of the proximal phalanx under loaded and unloaded conditions were analyzed. The geometric parameters of the MCP joint articulating surfaces were analyzed, including the center and radius of curvature and the location and size of the contact area. The pressures on articulating surfaces during various hand functions were also established. These findings provided important information for better understanding the kinematics of finger joint articulation, as well as the cause of joint degeneration.

Adult↗
PubMed1988

Biomechanical studies of running suture for flexor tendon repair in dogs.

A new running-locking loop suture technique has been developed to increase tendon repair strength and to provide better tendon edge inversion. Biomechanical analysis documented the failure mechanism and the failure strength of various circumferential repair techniques. When compared with two well-known techniques, the simple circumferential running suture and Lembert running suture, the locking suture technique was shown to have 3.77 and 1.68 times greater tensile failure strength and 1.73 and 1.26 times greater stiffness than these traditional suture methods. A running peripheral locking suture may help augment the strength of tendon repair.

Animals↗
PubMed1988

Force transmission through the radial head.

A technique has been developed to study the transmission of axial force across the radiohumeral joint during simulated active motion of the elbow. Variations in the line of action and in the amount of muscle load, as well as in rotation of the forearm during flexion and extension of the elbow, were assessed. Consistent patterns of force transmission were demonstrated in the three specimens that were studied. The greatest force transmission occurred between zero and 30 degrees of flexion, and it consistently decreased with increased flexion. Force transmission was consistently greater in magnitude when the forearm was in pronation than when it was in supination. The varus-valgus pivot point with the elbow extended was established to closely approximate the line of action of the brachial muscle, which crosses near the center of the lateral portion of the trochlea.

Aged↗
PubMed1988

Strength function after elbow arthroplasty.

A prospective study of elbow strength after total elbow joint arthroplasty was conducted in 27 patients (31 procedures). In this overall group, flexion strength improved 92%, pronation, 63%, and supination, 69%. Grip strength improved 35%, but there was no mean improvement in extension strength among these patients. After 27 procedures for rheumatoid arthritis, the average strength improvement of all five functions was 71% compared to a 25% improvement in four patients with nonrheumatoid involvement. Placement of the prosthetic axis of rotation proximal or anterior to the normal axis was associated with consistently poorer strength. The sample was too small to distinguish performance among prosthetic types, but the triceps-sparing approach showed consistently better strength in extension (averaging 20%) than did the other exposures.

Arthritis↗
PubMed1987

Biochemical, histological, and biomechanical analyses of canine tendon.

To define the matrix composition and architecture of canine flexor tendon, and to correlate tissue structure with applied mechanical loading, five anatomical regions of flexor tendon were studied. Histologically, two prominent fibrocartilaginous areas were observed on concave aspects of the tendon. The location of the major fibrocartilaginous area at the metacarpophalangeal joint correlated well with the region predicted by biomechanical modeling to be under greatest compressive loads during standing and claw movement. Comparative biochemical analysis showed an elevated water content, a five-fold higher hexuronic acid content, and a larger hydroxylysine/hydroxyproline ratio in this region relative to that for more tendinous areas. The major glycosaminoglycan component of fibrocartilaginous areas was chondroitin sulfate, whereas in other areas dermatan sulfate and hyaluronic acid dominated. Cell density and DNA analyses indicated a slightly higher cellularity for fibrocartilaginous areas and the region of vinculum insertion. These data document the existence of discrete areas of specialization within the flexor tendon that appear to be an adaptation to nutritional and mechanical factors.

Animals↗
PubMed1987

Electromyographic analysis of muscles across the elbow joint.

An electromyographic (EMG) technique was developed to study simultaneously the eight major elbow muscles in five normal subjects. Recordings of EMG activity in elbow muscles were obtained while the elbow joint was subjected to resisted flexion, extension, abduction, and adduction functions. The results indicate that activity in the major elbow muscles is determined by the size of the resultant flexion and extension moments created about the elbow joint, but not by varus and valgus moments. These results support the hypothesis that determination of muscle force about a joint depends on joint constraint, namely, the degree of freedom, the resultant joint forces and moments due to externally applied load, and also the function of the muscle, i.e., the line of action of the muscle that crosses the joint. The data may be used to further refine the calculation of muscle force distribution across the elbow joint.

Adolescent↗
PubMed1987

Permeability of cortical bone of canine tibiae.

Movement of interstitial fluid in cortical bone is considered one of the important mechanisms affecting bone remodeling and fracture healing. To better understand such interstitial fluid movement, the hydrostatic permeability of cortical bone of the canine tibia was measured in this study. It was found that age has significant influence on permeability. The cortical bone permeability of puppy tibiae is six times higher than that of adult tibiae. Adult tibial cortex is impermeable unless the superficial layer of the periosteal cortex is removed. The permeability differs between regions and locations of the tibia. The pathways for such extravascular interstitial fluid movement were also identified to be primarily the haversian and Volkmann's canals and secondarily the canalicular and lacunar spaces. The high permeability of their cortical bone may explain the increase in periosteal new bone formation seen in puppies when a venous tourniquet is applied.

Aging↗
PubMed1987

The effect of scapholunate ligament section on scapholunate motion.

Although the scapholunate interosseous ligament has been studied anatomically and functionally by several investigators, its exact role in wrist kinematics is still controversial. We designed and executed an experimental study with four cadaver specimens to compare various carpal motions before and after section of this ligament. Our results suggest that injury to this structure significantly changes carpal motion especially between the scaphoid and lunate.

Humans↗