Description
Background: Matrix-induced autologous chondrocyte implantation (M-ACI) has shown promising functional results and low failure rates in the medium to long term. However, studies investigating the outcome of ACI in adolescents report a concerning rate of graft failure resulting in the need for surgical revision in 20 to 69% after 1st generation ACI, while the results of M-ACI are only reported in the medium term or in the absence of a valid comparison group.
Objectives:
-Evaluation of long-term survival and patient-reported outcome (PRO) of adolescents after matrix-induced ACI (M-ACI) at long-term follow-up
-Compare clinical and radiographic outcomes after M-ACI in adolescents with a Propensity Score Matched (PSM) cohort of adults
Hypothesis:
Adolescents have comparable long-term functional and radiographic outcomes with low rates of graft failure.
Methods: Prospectively collected data of adolescents younger than 17 years at the time of surgery treated with M-ACI (Novocart 3D®, TETEC AG, Germany) for focal cartilage damage ICRS grade III and IV were included. A total of 23 adolescent patients could be identified and were matched to 23 adult patients with a minimum age of 18 years using 1:1 nearest neighbor propensity score matching (PSM) for baseline characteristics (Figure 1). The tolerance for matching was set at 0.01, resulting in similar baseline characteristics.
Demographics, complications, revisions, and PROMs were assessed preoperatively and at 1, 2, and >5 years postoperatively. Clinical outcome was assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and its previously published Patient Acceptable Symptomatic State (PASS) and Minimal Clinically Important Difference (MCID). Area Measurement And Depth & Underlying Structures (AMADEUS) and Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) 2.0 Knee Score was used to evaluate MRI results by two blinded orthopedic surgeons.
Results: After a mean follow-up of 8.2 years (5.4-11.9), 46 individuals (23 in each group) could be matched for similar baseline characteristics (n.s.). A total of 12 adolescent patients had open growth plates at the time of surgery, 5 were partially open, and 6 patients had closed growth plates.
Adolescents had a slightly worse preoperative clinical status compared to adults. This trend changed in favor of the adolescents, especially in the long term, with adolescents being significantly more likely to achieve PASS at 96 months compared to adults (Table 1). This trend was also reflected in the differences in ΔKOOS between the two groups, which became clinically meaningful at long-term follow-up. KOOS subscale analysis showed that adolescents benefit from M-ACI compared to adults, particularly in symptom improvement (59.2±9.8 vs. 53.7±13.4), pain reduction (86.2±19.2 vs. 78.4±18.4), activities of daily living (93.4±13.5 vs. 86.2±16.2), and quality of life (70.1±27.6 vs. 55.9±16.0). The differences in KOOS subscores at 12, 24, and 96 months are shown in Figure 2 in relation to the PASS.
Intraclass correlation coefficients showed excellent intraobserver (0.96 [0.91-0.99; 95% CI]) and good interobserver (0.89 [0.65-0.96; 95% CI]) reliability of the radiographic assessment. While preoperative AMADEUS scores were slightly worse in adolescents, this ratio changed in favor of adolescents, with the difference between groups peaking at 24 months (Figure 3). Notably, adolescent patients had persistently high MOCART scores at 24 and 96 months (83.2±11.5 and 80.3±16.3; p=(n.s.)). None of the patients in the adolescent group showed graft hypertrophy or required revision at the current follow-up.
Conclusion: Third generation M-ACI is a highly effective treatment for chondral and osteochondral defects in adolescent patients with low revision rates and high patient satisfaction at 96 months.
-Adolescents benefit particularly in terms of symptom improvement, pain relief, activities of daily living and quality of life (p<0.05).
-Radiographic evaluation has demonstrated that M-ACI is effective in preventing OA in an adolescent population with consistently high MOCART scores over the long term.
-Orthopaedic surgeons should be less concerned about the previously reported high revision rates for 1st generation ACI in adolescents.
-Surgeons, legislators and health insurers should consider expanding the indication to include adolescent M-ACI patients in order to avoid failures due to less reliable cartilage regeneration techniques.
