Mechanical behavior of two hamstring graft constructs for reconstruction of the anterior cruciate ligament

Citation
J. Hoher et al., Mechanical behavior of two hamstring graft constructs for reconstruction of the anterior cruciate ligament, J ORTHOP R, 18(3), 2000, pp. 456-461
Citations number
42
Categorie Soggetti
da verificare
Journal title
JOURNAL OF ORTHOPAEDIC RESEARCH
ISSN journal
07360266 → ACNP
Volume
18
Issue
3
Year of publication
2000
Pages
456 - 461
Database
ISI
SICI code
0736-0266(200005)18:3<456:MBOTHG>2.0.ZU;2-6
Abstract
We compared the mechanical behavior of two common hamstring graft construct s that are frequently used for reconstruction of the anterior cruciate liga ment-Graft A: quadrupled semitendinosus tendon fixed with titanium button/p olyester tape and suture/screw post, and Graft B: a double semitendinosus a nd double gracilis tendon fixed with a cross pin and two screws over washer s. The experimental protocol used to evaluate each graft construct included stress relaxation (with and without preconditioning), cyclic loading, and a tensile load-to-failure test. The amount of stress relaxation without pre conditioning was 60.6% for Graft A and 53.8% for Graft B. With precondition ing, it significantly decreased (p < 0.05) to 38.7 and 42.3%. respectively. Elongation of the graft construct in response to 100 cycles of loading (20 -150 N) was 1.8 and 0.6% of the original length for Grafts A and B, respect ively. However, after a series of five cyclic loading tests, the residual p ermanent elongation for each construct was 3.8 +/- 1.2 and 0.3 +/- 0.2 mm, a significant difference (p < 0.05) between the two graft constructs. Furth er analysis found more than 90% of the permanent elongation in the proximal and distal regions of Graft A, which consisted of polyester tape tied to a titanium button (proximal) and sutures tied around a screw post (distal). The tensile load-to-failure tests also revealed significant differences (p < 0.05) between the two graft constructs. Linear stiffness was 32 +/- 1 and 119 +/- 19 Nmm and ultimate load was 415 +/- 36 and 658 +/- 128 N for Craf ts A and B, respectively. For Graft A, the polyester tape consistently fail ed; for Graft B, slippage or tearing from the washers was the mode of failu re. We conclude that a quadruple-hamstring graft Fixed over a cross pin pro ximally and with metal washers distally (Graft B) has less permanent elonga tion in response to cyclic loading and has structural properties superior t o those of a graft construct that includes suture and tape material (Graft A). The large permanent elongation following repetitive loading of a graft construct with tape and suture material during the early postoperative peri od is of concern.