• Jay R Ebert, Michael Fallon, Timothy R Ackland, Gregory C Janes, and David J Wood.
• School of Human Sciences (Exercise and Sport Science), University of Western Australia, Crawley, Western Australia, Australia.
• Am J Sports Med. 2020 Jan 1; 48 (1): 133-142.

BackgroundLonger term outcomes after matrix-induced autologous chondrocyte implantation (MACI) are lacking, while early postoperative weightbearing (WB) management has traditionally been conservative.PurposeTo investigate the longer term clinical and radiological outcomes after an 8-week (vs 12-week) WB protocol after MACI.Study DesignRandomized controlled trial; Level of evidence, 1.MethodsA randomized study design allocated 70 patients to an 8- (n = 34) or 12-week (n = 36) approach to full WB after MACI of the medial or lateral femoral condyle. Patients were evaluated preoperatively; at 3, 12, and 24 months after surgery; and at 5 and 10 years after surgery. At 10 years (range, 10.5-11.5 years), 60 patients (85.7%; 8 weeks: n = 29; 12 weeks: n = 31) were available for review. Clinical outcomes included patient-reported outcomes, maximal isokinetic knee extensor and flexor strength, and functional hop capacity. High-resolution magnetic resonance imaging (MRI) was undertaken to assess the quality and quantity of repair tissue per the MOCART (magnetic resonance observation of cartilage repair tissue) system. A combined MRI composite score was also evaluated.ResultsClinical and MRI-based scores for the full cohort significantly improved (P < .05) over the 10-year period. Apart from the Tegner activity score, which improved (P = .041), as well as tissue structure (P = .030), which deteriorated, there were no further statistically significant changes (P > .05) from 5 to 10 years. There were no 10-year differences between the 2 WB rehabilitation groups. At 10 years, 81.5% and 82.8% of patients in the 8- and 12-week groups, respectively, demonstrated good-excellent tissue infill. Graft failure was observed on MRI at 10 years in 7 patients overall, which included 4 located on 10-year MRI (8 weeks: n = 1; 12 weeks: n = 3) and a further 3 patients (8 weeks: n = 1; 12 weeks: n = 2) not included in the current analysis who proceeded to total knee arthroplasty. At 10 years, 93.3% of patients were satisfied with MACI for relieving their pain, with 83.3% satisfied with their ability to participate in sport.ConclusionMACI provided high satisfaction levels and tissue durability beyond 10 years. The outcomes of this randomized trial demonstrate a safe 8-week WB rehabilitation protocol without jeopardizing longer term outcomes.

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