Abstract
BACKGROUND: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in treating symptomatic knee cartilage lesions. Rehabilitation is imperative to optimize outcome, although it has been traditionally conservative. PURPOSE: To investigate the longer term clinical and radiological outcome of MACI and investigate any differences in outcome between patients randomized to a 6-week (vs 8-week) return to full weightbearing (WB) after MACI. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: A total of 35 patients were recruited into the study, though 37 knees (i.e. two patients had both knees inlcuded at different timepoints) were independently evaluated preoperatively and at 1, 2, 5, and 10 years after surgery. A comparison was made between recruited knees prospectively randomized to a 6-week (n = 18) or 8-week (n = 19) return to full WB after MACI. Patient-reported outcome measures (PROMs) were assessed utilizing the Knee injury and Osteoarthritis Outcome Score. Peak isokinetic knee extensor and flexor torque and single-leg hop capacity (single horizontal, lateral, and medial hop tests for distance) were assessed, with limb symmetry indices (LSIs) calculated. High-resolution magnetic resonance imaging (MRI) was undertaken at all postoperative time points to assess pertinent parameters of graft integrity as per the MOCART (magnetic resonance observation of cartilage repair tissue) system. A combined MRI composite score was also evaluated. RESULTS: At 10 years after surgery, 31 knees (84%) were available for review, with 3 knees (6 weeks, n = 2; 8 weeks, n = 1) lost to follow-up and 3 knees (6 weeks, n = 1; 8 weeks, n = 2) having already had total knee arthroplasty (TKA) performed before 10 years. All PROMs (apart from the Mental Component Summary of the 36-item Short Form Health Survey [P = .57]) significantly improved (P < .0001) over the 10-year period, with no group differences (P > .05) observed. At 10 years, overall satisfaction was reported as 93% (6 weeks) and 88% (8 weeks). The peak knee extensor torque LSI significantly improved (P < .0001) over time, with mean LSIs of 100.8% (6 weeks) and 99.1% (8 weeks) at 10 years. No group differences (P > .05) were observed in hop test LSIs, with 10-year hop test LSIs ranging from 99.1% to 103.8%. No significant changes (P > .05) were observed for any graft parameter, or the MRI composite score, from 1-year to final 10-year review. Apart from a significant group effect (P = .03) for graft tissue intensity in favor of the 6-week group suggesting repair tissue more reflective of native cartilage, no other MRI-based differences (P > .05) were reported. At 10 years, 1 further graft (8 weeks) on MRI had failed and, combined with the 3 TKAs, an overall 10-year failure rate of 11.8% was observed. CONCLUSION: MACI provided sustained clinical and MRI-based outcomes in most patients to 10 years after surgery, with high satisfaction levels. The 6-week WB protocol did not jeopardize the early or longer term graft outcome.