Abstract
OBJECTIVES: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in treating symptomatic knee cartilage lesions. Rehabilitation is imperative to optimize outcome, though has been traditionally conservative. This study sought to investigate the 10-year outcomes of an accelerated return to full weight bearing (WB) after MACI. METHODS: This prospective randomized controlled trial (RCT) allocated 35 patients (37 knees) to a 6-week (n=18) or 8-week (n=19) return to full WB after MACI performed on the tibiofemoral knee joint (Figure 1). Patients were evaluated pre-operatively and at 1, 2, 5 and 10 years, via patient-reported outcome measures (PROMs) including the Knee Osteoarthritis Outcome Score (KOOS). Peak isokinetic knee extensor and flexor torque and single limb 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 post-operative timepoints to assess pertinent parameters of graft integrity as per the magnetic resonance observation of cartilage repair tissue (MOCART) system. A combined MRI Composite Score was also evaluated. RESULTS: At 10 years post-surgery, 31 patients (84%) were available for review, with 3 patients (6-week n=2, 8-week n=1) lost to follow up and 3 patients (6-week n=1, 8-week n=2) having already undergone total knee arthroplasty (TKA) before 10 years. All PROMs (apart from the Mental Component Subscale of the 36-item Short Form Health Survey, p=0.567) significantly improved (p<0.0001) over the 10-year period, with no group differences (p>0.05) observed. At 10 years, 93% (6-week) and 88% (8-week) of patients were satisfied with the overall outcome of their surgery. The peak knee extensor torque LSI significantly improved (p<0.0001) over time, with mean LSIs of 100.8% (6-week) and 99.1% (8-week) at 10 years. No group differences (p>0.05) were observed in hop test LSIs, with 10-year hop test LSIs ranging from 99.1% to 103.8%. No significant changes (p>0.05) 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=0.028) 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>0.05) were reported. At 10-years, one further graft (8-week) on MRI had failed and, combined with the three TKAs, an overall 10-year failure rate of 11.8% was observed. Figure 2 shows the MRI-progression of a successful graft through to 10 years post-surgery, while Figure 3 shows a failed graft at 10 years, despite encouraging graft status at 2 and 5 years post-surgery. CONCLUSIONS: MACI provided sustained clinical and MRI-based outcomes in most patients to 10 years post-surgery, with high satisfaction levels. The 6-week WB protocol did not jeopardize the early or longer-term graft outcome.