INTRODUCTION. The purpose of this study is to report results from a prospective multicenter study of a bioresorbable type I collagen scaffold used to replace tissue loss following irreparable lateral meniscus injuries. METHODS. 49 non-consecutive patients (33M/16F; mean age 30.5 yrs, range 14.7–54.7 yrs) with irreparable lateral meniscus tears or loss requiring surgical treatment were prospectively enrolled at one of 7 EU centers. 11 patients (22%) had acute injuries of the lateral meniscus, while 38 (78%) had prior surgeries to the involved meniscus. Implantation of the LCMI (now Lateral Menaflex) was performed arthroscopically using an all-inside suturing technique (FASTFIX) combined with inside-out sutures in the more anterior meniscus aspect. Forty-three patients were evaluated with a 2 to 4-year follow-up (FU); mean FU duration was 45 months (range, 33–53 m). Patients were evaluated clinically and by self-assessment using Tegner activity and Lysholm function scores, as well as the Visual Analog Scales (VAS) for pain, and a satisfaction questionnaire. Evaluations were performed pre-operatively, 6 months, 1 year, 2 and 4 years after surgery. X-ray and/or MR-images were taken pre-operatively, and at 1 year and 2 years after surgery. RESULTS. At 3 months after surgery, all patients were able to return to activities of daily living without limitation. Post-op. mean values of all evaluated patients showed statistically significant improvement compared to the preoperative scores. Mean Tegner scores increased from 3.0 to 5.2 at 4 years (0.8 points less than the pre-injury “recall” value); mean Lysholm improved from 63 to 91; mean pain (VAS) decreased from 36 to 8. At the 4-year time point, 86% of the patients stated that they were satisfied with their results (compared to 78% at the one year FU time point). Function and pain scores improved continuously with the highest score at the latest FU evaluation. All data were statistically significant (p<0.001, except for Tegner with p=0.03). MRI examination revealed no changes to the articular cartilage and joint space; however, the newly formed tissue did not present a signal consistent with fully mature native meniscus tissue. Reoperations were necessary in 5 patients (10%) during the FU time period: 3 of the reoperations were for persistent swelling and pain, which were classified as related to the device (6%) and were treated by synovectomy and debridement. Patients recovered without sequelae. The re-op. rate in this series is comparable to re-op. rates reported after lateral meniscal repair. DISCUSSION. Based on available results with a minimum 2 year FU, 90% of the patients benefited from the Lateral Menaflex as evidenced by improved clinical outcomes associated with gains in activity and function. Longer-term FU continues to determine the extent and duration of the benefits observed

Purpose. to evaluate the kinematics of a knee with a polyurethane meniscal scaffold for partial meniscus defect substitution during flexion under weightbearing conditions in an upright MRI. In addition, radial displacement and the surface of the scaffold was compared to the normal meniscus. Materials and Methods. One cadaver with a normal lateral meniscus and medial scaffold in the left knee and with a normal medial meniscus and lateral scaffold in the right knee. The scaffolds were implanted to substitute a 3 cm meniscus defect in the posterior horn. The cadaver was scanned in an 0,7T open MRI with a range of motion from 0-30-60-90 to hyperflexion. Kinematics were evaluated on sagittal images by the following two parameters: the position of the femoral condyle, identified by the centre of its posterior circular surface, which is named the flexion facet centre (FFC), and the point of closest approximation between the femoral and tibial subchondral plates, the contact point (CP). Both were identified in relation to the posterior tibial cortex. The displacement, measured on coronal images, is defined as the distance between the tibial plateau and the outer edge of the meniscus. The surface was also measured on coronal slices and contains the triangular surface of the meniscus. Results. Medially from 0 degrees to hyperflexion the FFC does not move anteroposteriorly. Laterally the FFC moves 12 mm backwards. The CP moves 15 mm backwards both lateral and medial. The lateral femoral condyle does roll-back with flexion but the medial does not, so the femur rotates externally around a medial centre. By contrast, both medial and lateral contact points move back, roughly in parallel, from 0 degrees to hyperflexion. The kinematics of the involved compartment is not influenced by the presence of the scaffold compared to the controlateral normal compartment. The radial displacement remains stable during full flexion: both the normal and scaffold meniscus have no different (p > 0,05) position. Both for the normal and the scaffold meniscus there is no difference (p > 0,05) in surface; there is no compression of the meniscus during flexion. Conclusion. The polyurethane implant, indicated for partial meniscus defect substitution, has no effect on the normal kinematics of the knee. Additionally, the degree of flexion has no effect on the external displacement, the surface and compressibility of both the implanted scaffold and the meniscus