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, 7 (3), 2325967119832594
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Computed Tomography Assessment of Anatomic Graft Placement After ACL Reconstruction: A Comparative Study of Grid and Angle Measurements

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Computed Tomography Assessment of Anatomic Graft Placement After ACL Reconstruction: A Comparative Study of Grid and Angle Measurements

Anagha P Parkar et al. Orthop J Sports Med.

Abstract

Background: The anatomic placement of anterior cruciate ligament (ACL) grafts is often assessed with postoperative imaging. In clinical practice, graft angles are measured to indicate anatomic placement on magnetic resonance imaging, whereas grid measurements are performed on computed tomography (CT). Recently, a study indicated that graft angle measurements could also be assessed on CT. No consensus has yet been reached on which measurement method is best suited to assess anatomic graft placement.

Purpose: To compare the ability of grid measurements and angle measurements to identify anatomic versus nonanatomic tunnel placement on CT performed in patients undergoing ACL reconstruction.

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

Methods: A total of 100 knees undergoing primary reconstruction with a hamstring graft (HAM group), 91 undergoing reconstruction with a bone-patellar tendon-bone graft (BPTB group), and 117 undergoing revision ACL reconstruction (REV group) were assessed with CT. Grid measurements of the femoral and tibial tunnels and angle measurements of grafts were performed. Graft placement, rated as anatomic or nonanatomic, was assessed with both methods. Pearson chi-square, analysis of variance, Kruskal-Wallis, and weighted kappa tests were performed as appropriate.

Results: The grid assessment classified 10% of the HAM group, 4% of the BPTB group, and 17% of the REV group as nonanatomic (P < .001). The angle assessment classified 37% of the HAM group, 54% of the BPTB group, and 47% of the REV group as nonanatomic. The weighted kappa between angle measurements and grid measurements was low in all groups (HAM: 0.009; BPTB: 0.065; REV: 0.041).

Conclusion: The agreement between grid measurements and angle measurements was very low. The angle measurements seemed to overestimate nonanatomic tunnel placement. Grid measurements were better in identifying malpositioned grafts.

Keywords: anterior cruciate ligament; graft angles; grid measurement; tunnel position.

Conflict of interest statement

The authors declared that there are no conflicts of interest in the authorship and publication of this contribution. 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.

Figures

Figure 1.
Figure 1.
(A) Femoral tunnel measurement according to Bernard and Hertel, as depicted on 3-dimensional computed tomography (CT) after reconstruction with a hamstring graft. The graft tunnel center is 27% in the femoral deep-shallow direction and 35% in the femoral high-low direction (anatomic placement). (B) Tibial tunnel measurement according to Stäubli and Rauschning. The graft tunnel center is 46% in the tibial anterior-posterior direction (anatomic placement). (C) Coronal angle measurement on CT (example of reconstruction with a bone–patellar tendon–bone graft), measured at 80° (nonanatomic placement). (D) Sagittal angle measurement, measured at 60° (nonanatomic placement).
Figure 2.
Figure 2.
(A) Distribution of femoral and tibial tunnel placement between the 3 study groups. Differences in the mean (B) coronal angle and (C) sagittal angle between the 3 study groups. Blue line = hamstring; red line = bone–patellar tendon–bone; yellow line = revision anterior cruciate ligament reconstruction.
Figure 3.
Figure 3.
(A) Distribution of femoral and tibial tunnel placement in revision anterior cruciate ligament reconstruction. Differences in the mean (B) coronal angle and (C) sagittal angle in the revision group. Green line = anteromedial portal approach; orange line = transtibial approach.
Figure 4.
Figure 4.
(A) The graft tunnel aperture in reconstruction with a hamstring graft; the aperture center is the same as the graft center (arrow). (B) The graft tunnel aperture looks larger in reconstruction with a bone–patellar tendon–bone graft, but the graft is actually placed slightly deeper than the aperture center (arrow).

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