Introduction. Bone tissue engineering approaches are an emerging strategy to treat bone defects, and commonly involve the delivery of osteogenic cells and/or drugs via a porous scaffold. We have been exploring an alternative injectable approach for drug delivery that would obviate the need for invasive surgery. Hypothesis. Sucrose Acetate Isobutyrate (SAIB) is a sucrose-based ester that is a highly viscous semi-solid. Diluting SAIB with 10–20% ethanol markedly reduces its viscosity, with ethanol diffusing rapidly after in vivo injection. This phase transitioning property makes SAIB an ideal candidate for bone tissue engineering. Materials and methods. The capacity of SAIB to act as a delivery system for recombinant human BMP-2 (rhBMP-2) was tested in a mouse ectopic bone formation model. In this model SAIB was used to deliver 0 to 10μg rhBMP-2. Next, SAIB was compared with porous collagen scaffold used clinically to delivery rhBMP-2 in a head-to-head trial. Commercial SAIB and SAIB produced in-house were also compared. Bone volumes were quantified by μCT. Discussion. Bone was found to form with as little as 2μg rhBMP-2 when delivered with SAIB. Injected SAIB also showed minimal inflammatory response and rapid breakdown, with bone formation occurring between one and two weeks. Conclusion. SAIB was found to be an effective delivery system for rhBMP-2 with translational utility. Future work will be required to examine the upscaling of this delivery system

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