Relation between knee motion and ligament length patterns.

Fifteen knee specimens were tested in a 6°-of-freedom test machine using quadriceps force to drive continuous flexion-extension motion. Ten of the knees were again tested following isolated transaction of the anterior cruciate ligament. From transducer outputs, three-dimensional motion was determined.

The forces in a knee brace as a function of hinge design and placement.

Customized knee braces for three normal subjects were instrumented to monitor the forces and moments across the hinges as the subjects performed various activities. The forces and moments were taken to represent a mismatch between actual knee motion and the motion the brace sought to impose. The different hinge designs studied were fixed axis, gear-on-gear, rack-and-pinion, and natural 3-D; they showed only moderate differences in forces.

Three-dimensional dynamic motion analysis of the anterior cruciate ligament deficient knee joint.

Dynamic three-dimensional motion analyses of 15 fresh human knee joints subjected to combinations of flexion velocity and moment, internal and external femoral torque, and horizontal shear before and after sectioning the ACL were performed. ACL deficient specimens demonstrated marked anterior instability without rotational instability. The pivot shift phenomenon occurred with an isolated ACL deficiency and was the result of anterior instability.

The effects of knee brace hinge design and placement on joint mechanics.

A computer model of 23 knees was obtained by embedding, slicing and digitizing the bone outlines and ligament co-ordinates. Using co-ordinate transformations, various three-dimensional motions were imposed on the knees, and calculations made of femoral-tibial contact error, contact point locations and ligament lengths. Significant deviations in these parameters were noted for abnormal motions including the elimination of internal-external rotation and a-p displacement and the misplacement of a hinge producing correct motion.

Pendular model of paraplegic swing-through crutch ambulation.

Kinematics of swing-through crutch ambulation for an individual with complete T11-T12 spinal cord injury was examined and quantitative aspects of the body-swing phase used to formulate and evaluate a 3-link pendular model. Model simulation parallels measured kinematics when shoulder motion is forced to follow the measured motion while hips and crutch tips are free pivots. Shoulder control contributes to increased ground clearance, influences timing and stride length, and gives flowing gait.