Background
Recent biomechanical studies reported that the stress on the graft of posterior cruciate ligament (PCL) increases as the posterior tibial slope (PTS) decreases in single-bundle (SB) and double-bundle (DB) PCL reconstructions. There is no long-term study about the clinical outcomes and graft survival rate of SB and DB PCL reconstruction based on the medial and lateral PTS measured by magnetic resonance images (MRI).
Hypothesis
We hypothesized that flattened medial and lateral PTS are associated with poor clinical outcomes and graft survival rate, at a minimum of 10-year follow-up after SB and DB PCL reconstructions.
Study Design: Cohort study; Level of evidence, 3.
Methods
In this cohort study, we retrospectively reviewed 46 patients (mean age, 28.8±9.9 years) and 39 patients (mean age, 28.6±8.7 years) who underwent primary SB and DB PCL reconstructions from 2000 to 2009, respectively. They were followed up for a minimum of 10 years. The medial and lateral PTSs were measured by preoperative MRI data. The patients were divided into two groups based on the cutoff values (medial PTS, <5.6° vs. >5.6°; lateral PTS, <3.8° vs. >3.8°) of both medial and lateral PTSs. Clinical scores (International Knee Documentation Committee subjective score, Lysholm score, and Tegner activity score), radiologic outcomes (side-to-side difference in stress radiographs and osteoarthritis progression), and PCL survival rate were compared between the groups at the last follow-up.
Results
Mean side-to-side difference in the stress radiographs after SB PCL reconstruction was significantly greater in patients with medial PTS <5.6° than in patients with medial PTS >5.6° (8.4±3.9 mm vs. 5.1±2.9 mm, p=.03), while lateral PTS subgroups after SB PCL reconstruction, both medial and lateral PTS subgroups after DB PCL reconstruction demonstrated no significant difference. The minimum 10-year graft survival rate was significantly lower in patients with medial PTS <5.6° than medial PTS>5.6° (68.4% vs. 92.6%, p=.029), and lateral PTS <3.8° than lateral PTS>3.8° (50.0% vs. 91.7%; p=.001) after SB PCL reconstruction, while there was no significant difference between two groups after DB PCL reconstruction.
Conclusions
Flattened medial PTS (<5.6°) is associated with an increased side-to-side difference on stress radiographs, and both flattened medial (<5.6°) and lateral (<3.8°) PTSs result in lower graft survival rate than medial (>5.6°) and lateral (>3.8°) PTSs at a minimum of 10-year follow-up after primary SB PCL reconstruction. In DB PCL reconstruction, both medial and lateral PTSs made no difference in clinical outcomes and survival rate at a minimum of 10-year follow-up.