Schimoler Patrick J, Braun David T, Miller Mark Carl, Akhavan Sam
Department of Orthopaedic Surgery, Allegheny General Hospital, Pittsburgh, Pennsylvania, U.S.A.; Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A.
Department of Orthopaedic Surgery, Allegheny General Hospital, Pittsburgh, Pennsylvania, U.S.A.
Arthroscopy. 2015 Jun;31(6):1091-6. doi: 10.1016/j.arthro.2015.01.013. Epub 2015 Mar 19.
This study sought to compare the strength of quadrupled hamstring tendon (QHT) grafts of 6 to 9.5 mm in clinical diameter with that of 10-mm bone-patellar tendon-bone (BPTB) grafts.
Twenty cadaveric semitendinosus and gracilis tendons were combined into QHT grafts. These were sized using a standard graft-sizing device and an area micrometer, yielding grafts ranging from 6 to 9.5 mm in diameter. The grafts were tested to failure. Five 10-mm BPTB grafts were also sized and tested.
Clinical sizing did predict the strength of the graft but not profoundly. As a material alone, without consideration of fixation in bone tunnels, QHT grafts were stronger than BPTB grafts. Graft strength decreased with size, but a linear relation between strength and diameter (r(2) = 0.715, P < .001) was found to be as good as the expected quadratic fit (r(2) = 0.709). Compared with BPTB grafts, even the smallest QHT grafts (diameter <6.5 mm) were still significantly stronger than 10-mm BPTB grafts (P = .004). The elastic moduli of the QHT and BPTB grafts were 761 ± 187 MPa and 615 ± 403 MPa, respectively; elongations at failure were 12.0% ± 2.0% and 7.5% ± 1.6%, respectively; and failure stresses were 105 ± 18 MPa and 50 ± 14 MPa, respectively.
This work shows that a clinical size of QHT grafts of 6 mm in diameter is not a concern regarding the strength itself. For a possible lower-end prediction of acceptable size, assuming that a gracilis-semitendinosus graft would have only the stress of the weakest measured QHT graft of 88 MPa, a graft of 5.5 mm in diameter would suffice, having more strength in newtons than the average patellar tendon.
Clinically sized QHT grafts have a higher failure strength than 10-mm patellar tendon grafts. Therefore the strength of the graft cannot account for the higher clinical failure rates of smaller hamstring grafts in active patients in clinical studies.
本研究旨在比较临床直径为6至9.5毫米的四倍绳肌腱（QHT）移植物与10毫米髌腱-骨（BPTB）移植物的强度。
将20条尸体半腱肌和股薄肌腱组合成QHT移植物。使用标准移植物尺寸测量装置和面积测微计对这些移植物进行尺寸测量，得到直径范围为6至9.5毫米的移植物。对移植物进行破坏测试。还对5条10毫米的BPTB移植物进行尺寸测量和测试。
临床尺寸确实能预测移植物的强度，但预测程度不深。仅作为一种材料，不考虑在骨隧道中的固定情况，QHT移植物比BPTB移植物更强。移植物强度随尺寸减小而降低，但发现强度与直径之间的线性关系（r² = 0.715，P <.001）与预期的二次拟合关系（r² = 0.709）一样好。与BPTB移植物相比，即使是最小的QHT移植物（直径<6.5毫米）仍显著强于10毫米的BPTB移植物（P =.004）。QHT和BPTB移植物的弹性模量分别为761±187兆帕和615±403兆帕；破坏伸长率分别为12.0%±2.0%和7.5%±1.6%；破坏应力分别为105±18兆帕和50±14兆帕。
这项研究表明，直径6毫米的临床尺寸QHT移植物在强度方面本身无需担忧。对于可接受尺寸的可能下限预测，如果假设股薄肌-半腱肌移植物仅具有所测量的最弱QHT移植物88兆帕的应力，那么直径为5.5毫米的移植物就足够了，其以牛顿为单位的强度比平均髌腱更大。
临床尺寸的QHT移植物具有比10毫米髌腱移植物更高的破坏强度。因此，移植物的强度不能解释临床研究中活跃患者中较小绳肌移植物较高的临床失败率。
