Two-Year Follow-up Study on Clinical and Radiological Outcomes of Polyurethane Meniscal Scaffolds

Background: Little is known about radial displacement (RD) of polyurethane (PU) scaffolds, intended for partial meniscus defect substitution; no data are available on whether rim thickness influences RD and whether RD correlates with clinical outcome scores. Hypotheses: The meniscus is not extruded preoperatively, but RD occurs after scaffold implantation. A thicker rim will limit RD, and there is no correlation between RD and clinical outcome. Study Design: Case series; Level of evidence, 4. Methods: Twenty-six patients were implanted with a PU scaffold (8 lateral, 18 medial). Radial displacement (mm) was evaluated on magnetic resonance images preoperatively and at 3 months, 1 year, and 2 years postoperatively. At each time point, it was determined whether a correlation existed between the rim and RD. Clinical outcome was determined using a visual analog scale (VAS) for pain as well as the Lysholm knee scoring scale, Knee Injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) score. Results: Radial displacement of lateral scaffolds was not significantly different (P = .178) either preoperatively (mean +/- SD, 3.42 +/- 0.99 mm) or at 3 months (4.82 +/- 0.59 mm), 1 year (4.55 +/- 0.87 mm), or 2 years postoperatively (4.10 +/- 0.93 mm). No correlation was observed between the rim and lateral RD at all time points. Medial scaffold RD increased significantly (P < .001) from preoperative values (2.17 +/- 0.84 mm) to those at 3 months (4.25 +/- 0.89 mm), 1 year (4.43 +/- 1.01 mm), and 2 years postoperatively (4.41 +/- 0.96 mm). A strong negative correlation between medial RD and the rim was observed at all time points. There was no significant correlation between clinical outcome scores and RD, either preoperatively or postoperatively. Conclusion: This study demonstrated that limited medial meniscal RD was present preoperatively but increased by 2 mm after scaffold implantation. Lateral RD was also present preoperatively but did not increase after scaffold implantation. Importantly, a strong negative correlation was found between the rim and postoperative medial RD; a thicker rim limited RD. However, in the lateral compartment, rim thickness did not correlate with RD because RD was already strongly present preoperatively. Finally, no correlations were observed between scaffold RD and clinical outcome scores, either preoperatively or postoperatively.