Suture Purchase Research Articles

Influence of Core Suture Purchase Length on Strength of Four-Strand Tendon Repairs

Recently the length of core suture purchase has been identified as a variable affecting the strength of tendon repairs. The influence of the length of the core suture purchase on the strength of multistrand locking and grasping suture repairs, however, has not been studied extensively in transversely lacerated tendons. We assessed the effects of the length of the core suture purchase on the strength of three 4-strand grasping or locking repair techniques. Seventy-four fresh adult pig flexor tendons were cut transversely and repaired with 1 of 3 methods: double-modified Kessler, locking cruciate, and modified Savage. Each method was assessed using 2 different lengths of core suture purchase (1.0 and 0.4 cm). The tendons were subjected to a linear noncyclic load-to-failure test in a tensile testing machine. We recorded the forces required for gap formation, ultimate strength, stiffness of the tendon, and the mode of repair failure. The resistance to gap formation, the ultimate strength of all 3 repairs, and the stiffness of the tendons with the double-modified Kessler and modified Savage repairs decreased significantly as the length of core sutures decreased from 1.0 to 0.4 cm. Locking and grasping repairs had a similar decrease in strength when the purchase was decreased from 1.0 to 0.4 cm. All tendons with modified Savage repairs with 1.0-cm purchase failed by suture breakage and tendons with 0.4-cm purchase failed predominantly by pullout. The length of core suture purchase significantly affects the strength of these 4-strand tendon repairs. The forces required for gap formation and the ultimate failure of repairs with 0.4-cm purchase were 20% to 45% lower than those of the repairs with 1.0-cm purchase. Locking repairs did not show a greater capacity to offset the decrease in strength than grasping repairs when the length of core suture purchase was decreased from 1.0 to 0.4 cm. Our study indicates that the length of suture purchase directly influences the strength of both locking and grasping core tendon repair methods.

Core Suture Purchase Affects Strength of Tendon Repairs

It generally is considered that a certain distance should be maintained between the site of the tendon-suture junction and the laceration level of the tendon. In this study we assessed how the length of core suture purchase may affect the repair strength of transversely cut tendons using a 2-strand modified Kessler method and a 4-strand circle-locking method. Seventy-four fresh pig flexor tendons were transected. Fifty-eight tendons were divided into 4 groups and repaired with a 2-strand grasping repair technique with the core suture purchase in the tendon stump ranging from 0.4 to 1.2 cm. Sixteen tendons were repaired with a 4-strand circle-locking tendon-suture repair technique. The core suture purchase of these tendons was 0.4 and 1.0 cm, respectively. The tendons were subjected to a linear, noncyclic, load-to-failure test in a tensile testing machine. The forces measured for initial gap formation, 2-mm gap formation, and ultimate strength were recorded for each repair. The resistance to gap formation and ultimate strength of 2-strand grasping technique repairs increased significantly as the suture purchase increased from 0.4 to 0.7, 1.0, and 1.2 cm although strength remained constant from 0.7 to 1.2 cm. The strength of 4-strand circle-locking repairs with a suture purchase of 1.0 cm was statistically greater than that of the repairs with a suture purchase of 0.4 cm. For both the 2-strand grasping and 4-strand circle-locking repair methods, the length of core suture purchase significantly influences the resistance to 2-mm gap formation and the ultimate strength of repairs in transversely lacerated flexor tendons. We determined that the optimal length of purchase is between 0.7 and 1.0 cm and that increased length of purchase from 0.7 to 1.2 cm does not increase the strength of the repair. Core suture purchase length of 0.4 cm or less results in significantly weaker repairs.

Locking repairs for obliquely cut tendons: Effects of suture purchase and directions of locking circles

Oblique cuts in tendons weaken conventional repairs but locking sutures improve the repair strength of the tendon. In this study we assessed how suture purchase and direction (or type) of locking sutures affect the repair strength. Ninety-three fresh pig flexor tendons were transected obliquely (45 degrees to the long axis of the tendon) and repaired with either a locking Kessler repair (with perpendicular or horizontal locking circles) or a locking cruciate method (with oblique locking or perpendicular locking circles). The suture purchase in the short side of the tendon stump with a perpendicular locking Kessler repair ranged from 0.3 to 1.2 cm. The gap formation and ultimate strength were measured to compare the biomechanical performance for each repair. The repair strength increased significantly as the suture purchase increased from 0.3 to 1.0 cm in oblique tendon lacerations, with a suture span of 1.0 cm being the strongest. The strength decreased significantly when the span was 1.2 cm. The repairs with horizontal locking sutures were significantly weaker than those with perpendicular locking sutures. The locking cruciate repair with the perpendicular locking circles had strength identical to that of the cruciate with oblique locking circles. Both suture purchase and the direction of locking circles affect the repair strength remarkably. For locking repairs the suture purchase of 1.0 cm in an obliquely cut tendon produced the highest strength; the repairs with a purchase less than 0.4 cm had significantly reduced strength. The strength of the repairs with locking circles perpendicular to the long axis of the tendon was significantly greater than that of the repairs with locking circles parallel to the long axis of the tendon.

The effect of increased peripheral suture purchase on the strength of flexor tendon repairs

Purpose: Previous studies have hypothesized unequal load sharing between peripheral and core sutures in flexor tendon repairs. Most commonly peripheral sutures are placed very near the repair site and characteristically fail before the core strands. We hypothesized that placement of the peripheral sutures farther from the repair site would better optimize load sharing and resist suture pullout, yielding a stronger overall repair. Methods: To test the hypothesis we developed a mathematical model of the load sharing between core and peripheral sutures. By using this model we predicted that placement of peripheral sutures 2 mm from the repair site would optimize the balance of load between core and peripheral sutures. We then divided and repaired 27 flexor digitorum profundus tendons in 6 ways (core plus peripheral or peripheral sutures only at 1 mm, 2 mm, or 3 mm from the repair site). Tendons were clamped to a custom-built linear loading machine and distracted to failure. Results: There was a clinically and statistically significant increase in strength with an increased distance of the peripheral suture from the repair site showing that core sutures augmented by a 2-mm peripheral repair were stronger than those performed with 1-mm peripheral repairs (50.8 vs 37.1 N). Conclusions: A peripheral stitch placement approximately 2 mm from the repair site represents a simple modification that can significantly increase the ultimate strength of flexor tendon repairs. (J Hand Surg 2003;28A:464-468. Copyright © 2003 by the American Society for Surgery of the Hand.)