Twisting of patellar tendon grafts does not reduce their mechanical properties

The purpose of this study was to investigate whether the twisting of a patellar tendon (PT) graft improves or reduces its mechanical properties. Twenty-seven pairs of 10 mm cadaveric PT grafts were tested at a strain rate of 10% min(-1). For each pair, the left specimen served as an unmanipulated control while the right specimen was either left untwisted, twisted + 90 degrees, or twisted - 90 degrees. All avulsion failures were excluded from the data analysis, focusing only on pure in-substance tendon ruptures. Higher ultimate load values than previously reported were obtained for both the twisted and untwisted specimens, without a statistical significant difference between the two. The values obtained for the left and right specimens from Group A were 4014 +/- 319 and 3973 +/- 245 N, from Group B 3613 +/- 207 and 3891 +/- 14 N, and from Group C 3997 +/- 278 and 4415 +/- 507 N, respectively. Stiffness and failure strain were not influenced by the twisting. Neither the presence of a twist, nor the direction of the twist were found to increase the ultimate load of the 10 mm cadaveric patellar tendon graft. Therefore, recommendation for twisting cannot be assessed to its mechanical properties. (C) 1998 Elsevier Science Ltd. All rights reserved.