Purpose: The study looked at different suturing configurations for hamstring reconstruction of the ACL to ensure that all four limbs of the graft were evenly tensioned at the time of insertion.

Method: Calf hoof flexor tendons were used as an animal model for the four strands of a “hamstring” ACL graft. They were sutured together at one end, which was clamped rigidly in a test rig. The free ends were then sutured altogether, in doubles or singly using 2 Ethibond. Miniature Variable Resistance Reluctance Transducers (DVRT) were then inserted into the tendons. The tendon construct was then loaded to 100N in 5N increments (with an initial I5N preload).

One hundred Newtons was decided on as the maximum force following measurements in theatre showing a force of approximately 75N were applied to a hamstring ACL graft at the time of fixation in the tibial tunnel. The DVRT’s allowed accurate assessment of the Load/Displacement of each tendon in the construct to be assessed. Repeatability experiments on the DVRT’s were performed. Ten specimens were prepared which were all tested in the different suturing configurations. Each test was repeated three times on each construct.

Results: The results showed that those tendons sutured all together did not load evenly with only one or two of the tendons in the construct showing any displacement throughout the loading cycle. When sutured as pairs, one of the tendons in each pair showed immediate displacement with the other tendon also showing displacement early in the loading cycle. When sutured individually the tendons all showed evidence of displacement early in the loading cycle, therefore showing more even tensioning and load sharing.

Conclusion: We recommend the use of singly sutured hamstring tendons in ACL reconstruction to allow more even tensioning and load sharing therefore reducing the risk of construct rupturing.