Serial magnetic resonance imaging evaluation of the patellar tendon after posterior cruciate ligament reconstruction

Abstract

Purpose: Our purpose was to prospectively analyze serial changes in magnetic resonance imaging (MRI) signal of the bone–patellar tendon–bone autograft when used for posterior cruciate ligament (PCL) reconstruction and to retrospectively determine at mid-term follow-up the relationship between MRI graft appearance and clinical stability in patients who have undergone arthroscopic PCL reconstruction with a bone–patellar tendon–bone autograft. Type of Study: One prospective serial blinded study and 1 retrospective blinded study. Methods: The first part of the study focused on MRI scans obtained at 3, 6, 9, and 12 months postoperatively in a case series of 10 consecutive patients who underwent arthroscopically assisted PCL reconstruction (group A), and of 10 patients who underwent combined ACL-PCL arthroscopic reconstruction (group B). For the second part of the study, MRI scans were obtained in a retrospective series of 10 patients at mid-term follow-up after PCL arthroscopic reconstruction (group C). Signal intensity of 3 zones, corresponding to the proximal, middle, and distal intra-articular graft zones, was evaluated according to the Howell et al. classification. Fiber continuity assessment was performed using a modified Kühne et al. score. The signal intensity of the 3 zones was independently scored. Knee stability was clinically and instrumentally graded according to the IKDC evaluation form (group 4). A multivariance analysis and grouped t test were used for statistical evaluation. Results: In group A, the average MRI evaluation score was 7.65 ± 1.6 at 3 months, 3.8 ± 0.6 at 6 months, 4.75 ± 1 at 9 months and 6.25 ± 1.2 at 1 year. The portion of graft exiting the femoral tunnel exhibited increased signal and faster maturation than the tibial tunnel. In group B (combined ACL-PCL reconstruction), the graft showed slower graft healing with an average MRI score of 4.85 ± 0.7 at 3 months, 1.9 ± 0.7 at 6 months, 3.9 ± 0.9 at 9 months, and 5.3 ± 1.1 at 1 year. At 1 year follow-up, there was no correlation between MRI appearance and stability in group A, even with MRI findings of fiber continuity. However, at long-term evaluation (group C), a strict correlation between MRI appearance and achieved stability was found. Conclusions: The patellar tendon when used for PCL reconstruction requires more than 1 year to achieve a low-signal intensity over its entire course, and the distal zone near the tibial tunnel shows a slower healing process. MRI graft assessment is useful only 1 year or more following PCL reconstruction.