Excursion of the flexor digitorum profundus tendon: a kinematic study of the human and canine digits.

The most common problem following primary flexor tendon repair is the failure of the tendon apparatus to glide, secondary to the formation of adhesions. Early motion following tendon repair has been shown to be effective in reducing adhesions between the tendon and the surrounding sheath. Therefore, it is important to determine the amount of flexor tendon excursion along the digit during joint motion. In this study, the excursion between the flexor digitorum profundus (FDP) tendon and the sheath was examined in both human and canine digits. Based on roentgenographic measurements and joint kinematic analysis, the motion of the bones, the FDP tendon, and the sheath were measured with respect to joint rotations. It was found that the canine flexor tendon apparatus behaved similarly to that of the human for the motions studied. The amount of tendon excursion was very small in regions distal to the joint in motion (approximately 0.1 mm/10 degrees of joint rotation). There was little displacement of the sheath (0.2-0.3 mm), except at the metacarpal joint region during metacarpophalangeal (MCP) joint motion and at the proximal interphalangeal (PIP) joint region during PIP joint motion. Tendon excursion relative to the tendon sheath was the largest in zone II during PIP joint rotation (1.7 mm/10 degrees of joint rotation). These results suggest that PIP joint motion may be most effective in reducing adhesions following tendon repair in zone II.

A rigid-body method for finding centers of rotation and angular displacements of planar joint motion.

A rigid-body method for determining the center of rotation (CR) and the angular displacement in a plane is developed. A comparison of this method to the graphical method of Reuleaux (Theoretische Kinematik: Grundzüge einer Theorie des Maschinenwerens, 1875) is found to have fewer constraints while meeting or exceeding the Reuleaux method in accuracy. The rigid-body method is not constrained by the location of the markers, as they can be placed radially or juxtapositioned about the CR. Magnitude of the rotation angle does not affect the accuracy in calculating the rotation angle. When applying both methods to locate the CR in a simulated knee joint, a substantial decrease in error is found with the new method. In a comparison of optimal marker angles used to locate the CR and find the angular displacement, the rigid-body method is found to be more accurate in both the mean and range of error. Effects of parameters specified by Panjabi (J. Biomechanics 12, 911-920, 1979) are applied to both methods. Results are then used in setting up guidelines for increasing accuracy with the rigid-body method.

The excursion and deformation of repaired flexor tendons treated with protected early motion.

A canine flexor tendon repair model was used to study the magnitude of early tendon excursion, the consistency of tendon gliding, and the amount of repair site elongation when protected early motion techniques were used. Tendon excursion of 3.8 +/- 1.1 mm was maintained with limited passive flexion and extension movements on a consistent basis throughout the first 14 days. There was no significant repair site deformation in 11 of 12 tendons and little variation in the range of tendon gliding during this period.