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. 2026 Jan 12;14(1):23259671251397650.
doi: 10.1177/23259671251397650. eCollection 2026 Jan.

Twelve-Month Maturation Timeline of Quadriceps Tendon Autograft Signal Intensity Ratio After ACL Reconstruction Surgery Using Magnetic Resonance Imaging

Daniel R Smith  1   2   3 , Kyle D Anderson  1   2   3 , Allen A Champagne  4 , Shayla M Warren  1   2   3 , Taylor M Zuleger  1   2   3   5 , Alexis B Slutsky-Ganesh  1   2   3   6   7 , Hung-I Hsiao  1   2   3   5 , Joseph D Lamplot  8 , Harris S Slone  9 , John W Xerogeanes  2   3 , Gregory D Myer  1   2   3   4   10 , Jed A Diekfuss  1   2   3   4
Affiliations

Twelve-Month Maturation Timeline of Quadriceps Tendon Autograft Signal Intensity Ratio After ACL Reconstruction Surgery Using Magnetic Resonance Imaging

Daniel R Smith et al. Orthop J Sports Med. .

Abstract

Background: Anterior cruciate ligament (ACL) injuries are among the most common sports-related injuries, accounting for about half of all knee injuries, and most athletes opt to undergo ACL reconstruction (ACLR). The quadriceps tendon (QT) ACLR has only recently been gaining popularity, and therefore few studies exist for evaluating the healing, or ligamentization, timeline of the QT autograft.

Purpose: To evaluate the signal intensity (SI) ratio of the tendon QT autograft after ACLR during the first postoperative year.

Study design: Case series; Level of evidence, 4.

Methods: A prospective case series of 19 athletes (mean age = 15.63 years) with ACL rupture who underwent ACLR with a QT autograft underwent knee magnetic resonance imaging (MRI) at 4 time points: presurgery (PRE), 3 months postoperative (3M), 6 months postoperative (6M), and 12 months postoperative (12M). SI ratio was calculated across different anatomic landmarks, specifically the intra-articular tissue of the native ACL of the contralateral knee from the PRE time point; the QT graft in the intra-articular space at 3M, 6M, and 12M time points; and the posterior cruciate ligament at each visit, to be used as a reference value and account for visit-to-visit variations in the MRI signal. Means of the SI ratio were calculated at the full graft level, as well as segmented into either 4 or 24 segments for analysis.

Results: At the full-graft level, there was a significantly higher SI ratio in the QT graft at 3M and 6M compared with the native contralateral ACL. By 12M, the full graft was most like the native contralateral ACL. Similarly at the 4 subsegment level, all regions except the distal segment had significantly higher SI ratios at 3M and 6M as compared with the native contralateral ACL. By 12M, all subsections of the graft were not significantly different from the native contralateral ACL.

Conclusion: The SI ratio of QT graft was increased at 3M and 6M after surgery and then returned close to that of the native ACL by 12M after surgery, which is largely consistent with the published maturational timeline of patellar tendon and hamstring tendon autografts.

Keywords: ACLR; MRI; QT autograft; SI ratio; anterior cruciate ligament; ligamentization.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: This work was partially funded by internal support from the Department of Orthopaedics at Emory University. G.D.M. has no direct conflicts of interest related to the current investigation. His institutions have received past and ongoing grant funding from the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases, the Department of Defense, the Department of Veterans Affairs (CReATE Motion Center), and the Arthritis Foundation Osteoarthritis Clinical Trial Network. He has also received industry-sponsored research support to his institution’s research related to injury prevention, sport performance, rehabilitation and surgical interventions including current funding from Arthrex Inc. for evaluation of ACL surgical techniques, GE Healthcare for MRI sequence development, and the National Basketball Association for validation of biomechanical models. His research program further benefits from philanthropic support from the Arthur M. Blank Family Foundation to advance dissemination and community-based translation of research discoveries. He also receives author royalties from Human Kinetics and Wolters Kluwer and is an inventor of biofeedback technologies (U.S. Patent 11350854B2; “Augmented and Virtual Reality for Sport Performance and Injury Prevention Application,” approved 6/7/2022, with associated software copyright), which have generated licensing royalties. J.A.D. receives royalties from Kendall Hunt Publishing Company. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto. Ethical approval for this study was obtained from Emory University (No. STUDY00002682).

Figures

The image displays 4D-sectioned views of the graft on the x-axis from 2.5 to 51.3, providing a detailed segmentation of the 3D representation of the graft, highlighting the native anterior cruciate ligament and intra-articular section of the quadriceps tendon graft at specific times.
Figure 1.
Representative slices of the segmentation of the (A) native anterior cruciate ligament and intra-articular section of the quadriceps tendon graft at (B) 3 months, (C) 6 months, and (D) 12 months. The segmented regions of the graft in 3-dimensional representation of the knee: (E) full graft, (F) 4-section graft (1-4), and (G) 24-section graft (1-24), where segments were generated along the length of the graft from distal (D) to proximal (P). DM, distal middle; PM, proximal middle.
Full Graft study on post-operative SI Ratio, comparing different time points with mean values and error bars, and noting significance in results.
Figure 2.
A comparison of signal intensity (SI) ratio values across the 3 graft time points (3, 6, and 12 months [M]) and the presurgery (PRE) contralateral native anterior cruciate ligament (ACL) (as represented by the dotted line). The asterisk indicates significance (P < .05) between the full quadriceps tendon autograft and the full PRE contralateral ACL at the respective time point. The individual dots represent the value for each of the 19 participants at each time point. The horizontal line and error bars represent the mean and SD, respectively.
The image compares the signal intensity (SI) ratio values of different graft sections, including distal, distal middle, proximal middle, and proximal, across three postoperative time points (3, 6, 12 months). It shows the signal intensity of these sections in relation to the ipsilateral preharvest quadriceps tendon, presurgery contralateral full anterior cruciate ligament, and individual values from 19 participants. Significance is noted with an asterisk at specific time points and sections. The right side of the image displays a 4-segment mask with different colors indicating each section.
Figure 3.
A comparison of the signal intensity (SI) ratio values of 4 sections of the graft: distal (Dis), distal middle (DM), proximal middle (PM), and proximal (Prox) across the 3 graft time points (3, 6, and 12 months [M]), and the segmented presurgery (PRE) contralateral native anterior cruciate ligament (ACL) (as represented by the dotted line for each of the four sections). The asterisk indicates significance (P < .05) between the QT autograft and the PRE contralateral ACL for a given segment at the respective time point. The individual dots represent the value for each of the 19 participants at each time point. The horizontal line and error bars represent the mean and SD, respectively.
The generated image shows a chart A with a graph of mean graft signal intensity ratio changes across 24 regions along the length of the graft, with error bars at each point for standard error. The graph shows variations from the distal to the proximal end of the graft with data points for PRE Native, 3M Graft, 6M Graft, and 12M Graft. Chart B displays a heat map of graft SI ratio differences between pre-surgery, 3 month, 6 months, and 12 months grafts, using a heat map on a single slice of a representative patient's graft mask.
Figure 4.
(A) The mean graft signal intensity (SI) ratio changes across 24 regions along the length of the graft, which shows variations from the distal to proximal end of the graft, with error bars at each point showing SE. (B) A visual representation of the graft SI ratio differences between time points across the graft using a heat map on a single slice of representative patient's graft mask. PRE, presurgery; M, month.
See this image and copyright information in PMC

References

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