Differential Arterial Supply of the ACL and PCL Revealed by 7T-qMRI, Histology, and Micro-CT.

BACKGROUND

Qualitative anatomical studies have reported ligament-specific differences in vascular organization in the anterior and posterior cruciate ligaments (ACL and PCL).

PURPOSE: (1) To quantitatively map the regional arterial vascular supply of the ACL and PCL across standardized anatomical regions using 7-Tesla quantitative magnetic resonance imaging (7T-qMRI), histology, and high-resolution computed tomography (micro-CT) in a fresh-frozen human cadaveric model; and (2) to directly compare vascular distribution patterns between cruciate ligaments.

STUDY

DESIGN

Descriptive laboratory study.

METHODS

Seven fresh-frozen human cadaveric knee specimens (mean ± SD age, 41.9 ± 15.5 years) underwent pre- and postcontrast 7T-qMRI to quantify ligamentous vascularity by measuring contrast enhancement. Ligament zones were categorized based on relative distance from distal insertion as follows: 1 (≥90%), 2 (>75% to 90%), 3 (>25% to 75%), 4 (>10% to 25%), and 5 (≤10%). Subsequent quantitative algorithm-based histologic analysis with hematoxylin and eosin staining followed, and an additional specimen underwent micro-CT (98 μm) for qualitative assessment.

RESULTS

7T-qMRI found relative arterial contributions as follows: for the ACL, zone 1, 10.2%; zone 2, 25.9%; zone 3, 24.8%; zone 4, 10.3%; and zone 5, 17.6%. For the PCL, zone 1, 9.3%; zone 2, 13.2%; zone 3, 16.7%; zone 4, 21.8%; and zone 5, 39.5%. Analysis revealed significant differences in overall contribution within soft tissue zones between the ACL and PCL (8.3% vs 27.1%; P = .02). Zone-by-zone analysis identified significant interligament differences in zone 2 and zone 4 (P = .046 for both). Both tibial entheses (ACL, 87.7%; PCL, 76.9%) demonstrated higher vascularity compared with the femoral (ACL, 12.3%; PCL, 23.1%) (ACL, P = .02; PCL, P = .87). A 3-zone 7T-qMRI and histologic sensitivity analysis confirmed the distribution pattern.

CONCLUSION

This study demonstrates a distinct, region-specific arterial distribution in the ACL and PCL. The ACL exhibited predominantly proximal vascular supply, whereas the PCL showed greater distal and overall arterial contribution. These quantitative differences in vascular organization provide a biological basis that may help explain ligament-specific healing behavior.

CLINICAL RELEVANCE: This study establishes 7T-qMRI as a methodology for quantitative comparison of vascularity between the ACL and PCL to support future translational studies investigating the relationship between vascular supply, ligament-specific healing patterns, and injury-specific treatment strategies.