Anterior cruciate ligament grafts display differential maturation patterns on magnetic resonance imaging following reconstruction: a systematic review

  • Joseph A. Panos
  • Kate E. Webster
  • Timothy E. HewettEmail author



The appearance of anterior cruciate ligament (ACL) grafts on magnetic resonance imaging (MRI) is related to graft maturity and mechanical strength after ACL reconstruction (ACLR). Accordingly, the purpose of this review was to quantitatively analyze reports of serial MRI of the ACL graft during the first year following ACLR; the hypothesis tested was that normalized MRI signal intensity would differ significantly by ACL graft type, graft source, and postoperative time.


PubMed, Scopus, and CINAHL were searched for all studies published prior to June 2018 reporting MRI signal intensity of the ACL graft at multiple time points during the first postoperative year after ACLR. Signal intensity values at 6 and 12 months post-ACLR were normalized to initial measurements and analyzed using a least-squares regression model to study the independent variables of postoperative time, graft type, and graft source on the normalized MRI signal intensity.


An effect of graft type (P = 0.001) with interactions of graft type * time (P = 0.012) and graft source * time (P = 0.001) were observed. Post hoc analyses revealed greater predicted normalized MRI signal intensity of patellar tendon autografts than both hamstring (P = 0.008) and hamstring with remnant preservation (P = 0.001) autografts at postoperative month 12.


MRI signal varies with graft type, graft source, and time after ACLR. Enhanced graft maturity during the first postoperative year was associated with hamstring autografts, with and without remnant preservation. Serial MRI imaging during the first postoperative year may be clinically useful to identify biologically or mechanically deficient ACL grafts at risk for failure.

Level of evidence



Anterior cruciate ligament Magnetic resonance imaging Signal–noise-quotient Ligamentization 



Anterior cruciate ligament


Anterior cruciate ligament reconstruction


Magnetic resonance imaging


Bone–patellar tendon–bone graft


Hamstring graft


Hamstring graft with minimal debridement/remnant preservation surgical technique


Tibialis anterior graft


Quadriceps bone graft


Analysis of variance


Confidence interval


Signal-to-noise quotient


Author contributions

TEH conceived the study, participated in the critical evaluation of the data and drafting of the manuscript. KEW participated in the critical evaluation of the data and drafting of the manuscript. JAP conducted the literature review, performed the critical evaluation of the data, and participated in the drafting and revision of the manuscript.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.


Funding was provided by National Institute of Arthritis and Musculoskeletal and Skin Diseases (Grant Nos. R01AR55563, R01AR056259 and T32AR56950).

Ethical approval

Ethical approval was not required as this is a review of the literature not involving humans or animals.


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2019

Authors and Affiliations

  1. 1.Mayo Clinic Graduate School of Biomedical SciencesMayo ClinicRochesterUSA
  2. 2.Department of Physiology and Biomedical EngineeringMayo ClinicRochesterUSA
  3. 3.School of Allied HealthLa Trobe UniversityMelbourneAustralia
  4. 4.Department of Orthopedic SurgeryMayo ClinicRochesterUSA
  5. 5.Mayo Clinic Biomechanics Laboratories and Sports Medicine CenterMayo ClinicRochesterUSA
  6. 6.Department of Physical Medicine and RehabilitationMayo ClinicRochesterUSA

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