Grafts for ACL Reconstruction Go Under the Microscope in a Study from Japan

One of the continuing debates in anterior cruciate ligament reconstruction is the choice of the graft to replace the torn ACL.

In most cases, autografts are generally considered to be a more suitable choice than allografts, but then the question becomes: What is the optimal tendon for the autograft?

Scientists at Osaka Metropolitan University in Japan investigated the issue by evaluating the microscopic anatomy of 2 popular grafts for ACL reconstruction, the quadriceps tendon-patellar bone (QTB) graft and the bone-patellar tendon-bone (BPTB) graft.

Their findings have been published in The American Journal of Sports Medicine.

Study Methodology

The research team evaluated the relative suitability of QTB and BPTB grafts by comparing their similarity to the ACL at the femoral insertion site. The researchers removed ACLs, QTBs, and BPTBs from 20 paired human cadaveric knees, stained histologic specimens with Masson trichrome and toluidine blue, and then examined the tendons under the microscope.

The ACLs and graft tendons were measured for:

  • Insertion width and thickness
  • Ligament attachment angle
  • Graft bending angle (GBA)
  • Angle corresponding to the GBA (cGBA)

In addition, 18 living patients had CT scans done on their operated knee to evaluate GBA 1 week after ACL reconstruction with either a QTB or BTPB graft.

Study Findings

Statistical analysis showed that:

  • The insertion width and thickness of the QTB grafts were greater than for the ACL, while those of the BTBP grafts were significantly smaller than the ACL.
  • Greater similarity in ligament attachment angle was observed between the ACL and QTB grafts than between the ACL and BTBP grafts.
  • The difference between the GBA and the cGBA was also significantly smaller in the QTB grafts than in the BTPB grafts, suggesting that the former does not bend as much as the latter. This results in a lower risk of excessive stress on the insertion site and, therefore, a lower probability of graft damage.

The study findings suggest that the QTB graft may allow for a more anatomic ACL reconstruction, contributing to potential improvement in ACL injury treatment.

“Our results show that the QTB graft had greater similarity to the ACL at the femoral insertion site, indicating it as a more suitable option for ACL reconstruction,” concluded first author Takuya Kinoshita, MD.

“We hope to verify this advantage of QTB grafts through clinical results in the future.”


Kinoshita T, Hashimoto Y, Iida K, Nakamura H. ACL graft matching: cadaveric comparison of microscopic anatomy of quadriceps and patellar tendon grafts and the femoral ACL insertion site. Am J Sports Med. 2022 Sep;50(11):2953-2960. doi: 10.1177/03635465221110895. Epub 2022 Aug 1.


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