Adrian E. Flatt

Kinematics of the wrist. I. An experimental study of radial-ulnar deviation and flexion-extension.

The kinematics of the wrist during radial-ulnar deviation and flexion-extension were studied in several ways. In six fresh cadaver wrists, the forearm was fixed in full pronation, each motion was constrained to one plane, and two metal markers were placed in each of the finger metacarpals, as well as in the radius and all of the carpal bones except the pisiform and greater multangular. Radial ulnar and flexion-extension movements in these wrists were studied roentgenographically. In the wrists of six normal volunteers, a similar roentgenographic analysis was carried out and the trajectories of wrist motions also were studied using light-emitting diodes. Finally, roentgenographic measurements were made on 100 wrists of normal subjects. From these studies, it was concluded that: (1) during each of these motions, rotation occurs about a fixed axis located within the head of the capitate, and the location of each axis is not changed by the position of the hand in either plane; (2) the distance from the base of the third metacarpal to the distal articular surface of the radius (the carpal height), measured along the proximally projected axis of the third metacarpal on posteroanterior roentgenograms, is constant throughout radial-ulnar deviation of the normal wrist and can be used as a measure of carpal collapse; and (3) the perpendicular distance of the fixed axis of rotation for radial-ulnar deviation from the distally projected longitudinal axis of the ulna can be used as a quantitative measurement of the amount of translation of the carpus in pathological conditions.

Kinematics of the wrist.

The wrist, or carpus, is a deformable anatomic entity composed of 8 small carpal bones (scaphoid, lunate, triquetrum, pisiform, hamate, capitate, trapezium and trapezoid) and the surrounding soft-tissue structures. These soft-tissue structures include the tendons that cross and/or attach within the carpus, and those ligamentous structures that connect the carpal bones to each other and to the bony elements of the hand and the forearm. The wrist functions both kinetically by transmitting forces from the hand to the forearm and vice versu, and kinematically by allowing for changes in the location and orientation of the hand relative to the forearm. In this biomechanical investigation, the behavior of the individual carpal bones is ignored and attention is focused on the overall kinematic behavior of the wrist. Review of the literature shows that there are identifiable trends in the evolution of our knowledge of the kinematics of the wrist. The study of wrist motion began in 1896 after the discovery of x-ray^.^ This initial study and subsequent covered many significant aspects of normal wrist movement. Efforts have been made to analyze kinematic motion of the wrist using various techniques such as stereo X-rays,21,22 plain

Kinematics of the wrist. Ii. Clinical applications.

A reproducible method of measuring carpal height and carpal-ulnar distance and expressing them as ratios of these distances to the length of the third metacarpal, as reported in a previous paper9, was applied to serial roentgenograms of seventeen patients with rheumatoid disease and six patients with Kienböcks disease. These ratios provide an accurate expression of the extent of carpal collapse and of ulnar translation. However, once carpal collapse has occurred, the trajectory of hand motion becomes flattened, and, as a result, the carpal height ratio will vary as the wrist moves from maximum radial to maximum ulnar deviation. These ratios may be of use in predicting a patients clinical course, but a larger clinical study is necessary before use of the measurements for this purpose can be recommended with assurance.

The influence of wrist position on the force produced by the finger flexors

Abstract This paper describes the design, instrumentation, procedures and results of a study of the influence of wrist position on the forces produced by the finger flexors at the middle and distal phalanges. Measurement at each phalangeal level was made on all four fingers simultaneously in each of five different wrist positions. Results of the study suggest that the percentage distribution of the total force produced by the finger flexors to each individual finger bear a constant relationship regardless of wrist position. The magnitude of the total force produced does vary with wrist position.

Biomechanical analyses of forearm pronation-supination and elbow flexion-extension

Abstract in an attempt to determine the optimal design characteristics of a total elbow endoprosthesis, we studied the normal kinematics of the forearm and elbow joint. An analytical model is presented utilizing a three-dimensional kinematic analysis of a linked two-rigid-body system. The results of the analytical study and those parameters not suited for analytical modeling were then tested and confirmed experimentally in fresh cadaver specimens. Normal range of motion of forearm pronation-supination and elbow flexion-extension are presented. Proximal and distal ulnar motion during pronation-supination and flexion-extension is shown using light emitting diode methodology. The longitudinal axis of the forearm and transverse axis of the elbow joint are defined. The normal carrying angle and how it varies during flexion-extension is also presented. Finally, an anatomical study displays photographically the geometry of the trochlea of the humerus and is correlated to our findings of a fixed center of rotation for flexion-extension.

Traumatic dislocation of the long-finger extensor tendon. A clinical, anatomical, and biomechanical study

Five cases of traumatic dislocation of the extensor tendon of the long finger are presented. The anatomical defect consists of loss of continuity between the radial intrinsic muscles and the extensor tendon. The extensor tendon of the long finger sits on top of the proximal portion of the transverse fibers where it is maintained by a relatively poor fibrous attachment. The force tending to displace the normally situated extensor ulnarward is greatest in full extension, decreases during the first 60 degrees of flexion, and subsequently increases as flexion increases from 60 to 90 degrees. The force required to prevent further ulnar dislocation is large once the tendon is displaced. Simple primary repair is usually satisfactory for traumatic dislocation of the extensor tendon.

The scapholunate ligament

The effects of scapholunate ligament sectioning on scaphoid and lunate bone three-dimensional kinematics were analyzed using a sonic digitizer method. Carpal bone motions were described using a screw displacement axis concept. After scapholunate ligament sectioning, few significant kinematic changes were observed in the orientation of the screw displacement axes or in carpal bone rotation about the screw displacement axes. The angles between the screw displacement axes of the scaphoid and lunate bones were only minimally affected, indicating that the two bones continued to track well relative to each other. The results indicate that sectioning of the scapholunate ligament does not result in a major disturbance of scaphoid and lunate bone motions.

The three-dimensional rotational behaviors of the carpal bones.

The rotational behaviors of the carpal bones of ten fresh cadaver forearms were determined using a three-dimensional sonic digitizer, as the hands were passively moved through planar constrained motions. Changing forearm orientation from supination to pronation results in an increase in the magnitudes of extension of the proximal and distal carpal row bones and a reduction in the magnitudes of flexion of the distal carpal row bones. The included angles between each carpal bone screw displacement axis (SDA) and third metacarpal SDA for corresponding intervals of motion are significantly greater than zero, regardless of forearm orientation. The included angles of the proximal carpal row bones are significantly greater than those of the distal carpal row bones during third metacarpal radial-ulnar deviation. The carpal bone rotation magnitudes are significantly attenuated relative to the prescribed rotation magnitudes of the third metacarpal, with the exception of the trapezoid during third metacarpal extension. The rotational attenuation is greatest in the proximal carpal row bones and is most pronounced during third metacarpal flexion-extension motion and ulnar deviation. Evidence from this investigation favors a carpal row concept of wrist motion, as opposed to a carpal column model.

Kinematic investigation of normal MCP joint

Abstract This investigation is an analytical and experimental study to quantitatively determine the kinematic behavior of the human metacarpophalangeal (MCP) joint. An in vivo study of the range of motion, and an in vitro study of the center of rotation, moment arm and tendon excursions are described. Various experimental techniques were employed. A specially designed finger experimenting apparatus was used in this investigation. Assuming the MCP joint to be an unknown joint mechanism which connects two rigid bodies, finger and metacarpal, the analysis of two rigid link kinematics is developed. In the study of kinematic behavior of the MCP joint, two motions are considered clinically significant: radial-ulnar deviation and flexion-extension motion.

Restoration of Rheumatoid Finger-joint Function: Interim Report on Trial of Prosthetic Replacement

Metallic hinged prostheses have been used in an attempt to restore some function to the metacarpophalangeal and proximal interphalangeal joints of fingers involved by rheumatoid arthritis. Indications for prosthetic replacement at the proximal interphalangeal joint are considered to be: (1) gross joint destruction, (2) persistent swan-neck deformity, and (3) ankylosis of the joint in a non-functional position. At the metacarpophalangeal joint the indications are considered to be: (1) gross joint destruction, (2) palmar dislocation of the joint, and (3) persistent ulnar drift combined with joint destruction or palmar dislocation. It is a prerequisite of prosthetic replacement that there be adequate muscle power to control the joint. Six cases are described and illustrated. Some typical complications, such as boutonniere deformity, fracture of the phalanges, and lack of voluntary control, are discussed. A total of fifty-seven prostheses have been placed at the present time. A table is presented giving the pertinent information concerning thirty-one prostheses which have been in place for six months or more.