Early and Delayed Meniscal Shrinkage After Fresh-Frozen Lateral Meniscal Allograft Transplantation: Magnetic Resonance Imaging Study With a Midterm Follow-up

Abstract

To evaluate whether fresh-frozen meniscal allograft shrinkage occurs only during the first year of the early remodeling period or progresses over the delayed period of midterm years and to determine whether these changes were associated with certain clinical and radiologic outcomes. We retrospectively reviewed meniscal allograft transplantations (MATs) performed by 1 senior surgeon (S-I.B.) using fresh-frozen allograft from 2008 to 2013. The inclusion criteria were the patients who had midterm follow-up magnetic resonance imaging (MRI) scans between 3 and 6years after isolated lateral MATs. We excluded the graft tears found on the 1-year or midterm MRI scans. MATs were indicated for the treatment persistent compartmental pain in young to middle-aged, physically active patients who had well-aligned nonarthritic joint without ligament insufficiency. The meniscal width of the transplants at the midbody and posterior horn was measured on day 2 (as a reference), at 1year (after early remodeling period), and after 3 to 6years (delayed period) postoperatively. Joint space width changes during each interval were measured on 45° flexion posteroanterior views. The Lysholm score and Tegner activity scale were used to evaluate clinical outcomes. Eighty-four isolated lateral MATs with the midterm MRI scans were identified. Of these, 17 graft tears were found; therefore, we analyzed 67 patients (32 male and 35 female patients) with a mean age of 30.9years (range, 15-52years). The mean relative meniscal width at the midbody decreased to 93.7% (95% confidence interval [CI], 91.8%-95.6%; P < .001) at 1year postoperatively and to 88.0% (95% CI, 85.6%-90.3%; P < .001) at the midterm follow-up of 4.0 ± 1.0years. The posterior horn shrank less than the midbody during the same period (96.0%; 95% CI, 94.8%-97.1%) at 1year (P < .001) and 92.5% (95% CI, 91.0%-94.1%) at the last follow-up (P < .001). Although there was no severe shrinkage (>50% of the initial size), the incidence of moderate (25%-50%) changes at the midbody increased from 1 (1.5%) at 1year to 5 (7.5%) at the last follow-up, respectively. We could not find any significant positive correlations between the relative meniscal width and patient-reported outcomes or joint space width changes after 1year or at the last follow-up. Shrinkage of fresh-frozen meniscal transplants occurred during both the early remodeling and delayed midterm periods. Although the changes were greater in the midbody than in the posterior horn, the overall changes were less than those of the previous studies using cryopreserved grafts. We could not find that the meniscal shrinkage over the midterm period were significantly associated with inferior outcomes in this series. Level IV, therapeutic case series.