Association Between Tunnel Position, Tunnel Angle, Graft Signal Intensity, and Graft Thickness in the Reconstructed Posterior Cruciate Ligament

Background: An appropriate tunnel position, tunnel angle, and tunnel-graft angle are important factors for maintaining the stability and mechanical properties of a posterior cruciate ligament (PCL) graft. Purpose: To evaluate the association between tunnel position, tunnel angle, graft signal intensity ratio (SIR), and graft thickness after remnant-preserving PCL reconstruction. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Included were patients who had undergone remnant-preserving single-bundle PCL reconstruction using a tibialis anterior allograft between March 2014 and September 2020 and who had minimum 12-month postoperative magnetic resonance imaging scans. Tunnel position and angle were evaluated via 3-dimensional computed tomography, and their association with graft SIR on both the femoral and the tibial sides was determined. Graft thickness and SIR at 3 areas of the graft were evaluated and compared, and their association with tunnel-graft angle was also determined. Results: Overall, 50 knees (50 patients; 43 male, 7 female) were included. The mean time to postoperative magnetic resonance imaging was 25.8 ± 15.8 months. The mean SIR of the graft’s midportion was higher compared with that of the proximal and distal portions ( P = .028 and P < .001, respectively), and the SIR of the proximal portion was higher compared with that of the distal portion ( P = .002). The femoral tunnel-graft angle was more acute than the tibial tunnel-graft angle ( P = .004). A more anteriorly and distally located femoral tunnel led to a less acute femoral tunnel-graft angle ( P = .005) and a decreased SIR of the proximal portion ( P = .040), and a more laterally located tibial tunnel was associated with a less acute tibial tunnel-graft angle ( P = .024) and a reduced SIR of the distal portion ( P = .044). The mean thicknesses of the graft’s midportion and distal portion were larger than that of the proximal portion ( P < .001). The SIR of the graft’s midportion was positively correlated with its thickness ( r = 0.321; P = .023). Conclusion: The SIR of the proximal portion of the graft around the femoral tunnel was higher than that of the distal portion around the tibial tunnel. An anteriorly and distally positioned femoral tunnel and a laterally positioned tibial tunnel resulted in less acute tunnel-graft angles that were associated with decreased signal intensity.