Virtually all types of collagenous tissues have been transferred in and around the knee joint for intra-articular and extra-articular ligament reconstructions. However, the mechanical properties (in particular, strength) of such grafts have not been determined in tissues from young adult donors, where age and disuse-related effects have been excluded. To provide this information, we subjected ligament graft tissues to high-strain-rate failure tests to determine their strength and elongation properties. The results were compared with the mechanical properties of anterior cruciate ligaments from a similar young-adult donor population. The study indicated that some graft tissues used in ligament reconstructions are markedly weak and therefore are at risk for elongation and failure at low forces. Grafts utilizing prepatellar retinacular tissues (as in certain anterior-cruciate reconstructions) and others in which a somewhat narrow width of fascia lata or distal iliotibial tract is utilized are included in this at-risk group. Wider grafts from the iliotibial tract or fascia lata would of course proportionally increase ultimate strength. The semitendinosus and gracilis tendons are stronger, having 70 and 49 per cent, respectively, of the initial strength of anterior cruciate ligaments. The bone-patellar tendon-bone graft (fourteen to fifteen millimeters wide, medial or central portion) was the strongest, with a mean strength of 159 to 168 per cent of that of anterior cruciate ligaments.

Patellar tendon-bone units, based on grip-to-grip motions, were found to be three to four times stiffer than similarly gripped anterior cruciate ligaments, while gracilis and semitendinosus tendon preparations had values that were nearly identical to those of anterior cruciate ligaments. Fascia lata and patellar retinacular graft tissues showed much lower stiffnesses than did the anterior cruciate ligaments.

CLINICAL RELEVANCE:​ The surgeon controls the mitial structural properties of a ligament reconstruction by the type and size of graft selected. The data reported here for the initial mechanical properties of grafts allows a more rigorous evaluation of other biological grafts, not previously available. Weaker grafts, which are more apt to fail prematurely than those of greater strength, probably also require longer postoperative protection to allow time for remodeling. The longer protection times may not allow for increased graft strength. One note of caution is also required:​ if wider distal iliotibial-tract grafts are used to increase initial strength, iliotibial tract function may be adversely affected Tissues of greater width also require larger drill-holes if bone fixation is used, and therefore additional time may be required for bone ingrowth and graft incorporation. Use of a bone-tendon-bone graft has a distinct theoretical advantage for earlier graft incorporation at the fixation site and higher initial graft strength, thereby allowing earlier motion of the knee and shorter periods of disuse and immobility.