Size 3-0 polydioxanone was used as a single strand, single braid (3 strands), or double braid (6 strands) to create six suture material-pattern combinations for equine tenorrhaphy: single-strand locking loop, single-braid locking loop, double-braid locking loop, single-strand three-loop pulley, single-braid three-loop pulley, and double-braid three-loop pulley. Maximum load to failure for the single-strand locking loop (46.1 +/- 2.9 newtons [N]) was less than for all other sutures (range, 103-155 N). The load required to form a 2 mm gap between tendon ends was greater for the single-braid three-loop pulley (66.7 +/- 6.9 N) and double-braid three-loop pulley (85.4 +/- 17.7 N) than any other sutures. The load required to produce a 10 mm gap was least for the single-strand locking loop (34.3 +/- 3.9 N) and greatest for the double-braid three-loop pulley (131.5 +/- 27.5 N). Gap between tendon ends at maximum load was greater for the single-braid (18.1 +/- 0.9 mm) and double-braid (19.2 +/- 2.2 mm) locking loops than for any other sutures. Suture material broke in 53% of the locking-loop tests but in only 17% of the three-loop pulley tests. Tendon matrix disruption accounted for 43% of the locking-loop failures and 77% of the three-loop pulley failures. The three-loop pulley pattern provided more support, less tendon distraction, and less tendon matrix constriction and distortion than the locking-loop pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Healing of transected superficial digital flexor tendons was evaluated mechanically and histologically in eight horses. Tendons sutured with polyglyconate had higher loads at failure than nonsutured tendons at weeks 5 and 9. The tendon stress at failure (force per unit area) was higher in the sutured tendons at week 5 but not at week 9, reflecting the increased size of the scar at week 9. Histologically, scars after tenorrhaphy were consistently more mature than nonsutured tenotomy scars. The mean maturity score for sutured tendons was higher than for nonsutured tendons at weeks 5 and 9. Overall, these data support tenorrhaphy with absorbable suture.

A realistic and adaptive viscoelastic model for prediction of transient wound roll stress distributions is presented. The web material is taken to be orthotropic with a nonlinear radial stiffness dependent upon interlayer pressure. Viscoelastic behavior is represented by a generalized Maxwell model for creep written as a convolution integral. Numerical solutions to the resulting integral boundary value problem give both initial and transient stress distributions within the wound roll. The model is successfully compared to the analytical solution for a simple case of isotropy as well as to published works on this topic. In contrasting the solutions, the advantages and adaptability of this formulation will be readily seen.

A simple algorithm has been developed for predicting traction in web handling applications. Minimal traction exists when the minimum air film height between the roller and web is greater than three times the rms roughness of the two surfaces in contact. Classical foil bearing theory modified for permeable surfaces is used to determine the air film height. A piecewise linear solution using squeeze film theory is also used to account for side leakage. The minimum air film height is a function of web tension, web and roller velocity, air viscosity, web width, web permeability and roller radius. The algorithm is applicable for permeable and nonpermeable webs. Values obtained from the algorithm can be used to predict if sufficient traction is available between the web and roller for a given set of physical and operating parameters. Traction values can also be used as input for winding, wrinkling, and spreading models.

Models which can be used to calculate the internal stresses within wound rolls of web material have all been confirmed to the center winding technique to date. The mechanism by which a nip roller can increase the wound in tension in the outer layer of the wound roll is presented. Results of this work have been used to establish new winding models which can accurately predict the internal stresses within a center wound roll with an impinged nip.