T2-relaxation time of cartilage repair tissue is associated with bone remodeling after spongiosa-augmented matrix-associated autologous chondrocyte implantation.

OBJECTIVE: To investigate whether T2 relaxation time measurements of cartilage repair tissue and structural changes of the knee joint are associated with subchondral bone architecture after spongiosa-augmented matrix-associated autologous chondrocyte implantation (MACI). DESIGN: Both knees of 25 patients (25.5 ± 7.8y; 10 women) were examined preoperatively and 2.7 years after unilateral spongiosa-augmented MACI with 3T magnetic resonance (MR) imaging. Cartilage composition was assessed using T2 relaxation time measurements, subchondral trabecular bone microstructure was quantified using a 3D phase-cycled balanced steady state free-precision sequence. Structural knee joint changes were assessed using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). The Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score was used for the postoperative description of the area that underwent MACI. Correlations were assessed using Spearman's rank correlation coefficients. RESULTS: Hypertrophy of the cartilage repair tissue was found in 2 of 25 patients, both after a MACI procedure at the patella, 21 patients showed congruent filling. In subchondral bone of the cartilage repair compartment, apparent trabecular thickness was significantly higher in compartments with elevated cartilage T2 (n = 17; 0.37 ± 0.05 mm) compared to those showing no difference in cartilage T2 compared to the same compartment in the contralateral knee (n = 8; 0.27 ± 0.05 mm; P = 0.042). Significant correlations were found between the overall progression of WORMS and the ipsilateral vs contralateral ratio of average trabecular thickness (r = 0.48, P = 0.031) and bone fraction (r = 0.57, P = 0.007). CONCLUSIONS: After spongiosa-augmented MACI, T2 values of cartilage repair tissue and structural knee joint changes correlated with the quality of the underlying trabecular bone.

Sandwich Technique for Large Osteochondral Lesions of the Knee.

OBJECTIVE: To evaluate whether a sandwich technique procedure for large osteochondral lesions (OCL) of the medial femur condyle reduces clinical symptoms and improves activity level as well as to assess repair tissue integration on MRI over 2 years. DESIGN: Twenty-one patients (median age: 29 years, 18-44 years) who received matrix-associated autologous chondrocyte transplantation (MACT) combined with cancellous bone grafting at the medial femur condyle in a 1-step procedure were prospectively included. Patients were evaluated before surgery (baseline) as well as 3, 6, 12, and 24 months postoperatively, including clinical evaluation, Lysholm score, Tegner Activity Rating Scale, and MRI with Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score and a modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). RESULTS: Seventeen patients were available for the 24-month (final) follow-up (4 dropouts). Lysholm significantly improved from 48 preoperatively stepwise to 95 at final follow-up (P < 0.05). Tegner improvement from 2.5 at baseline to 4.0 at final follow-up was not significant (P = 1.0). MOCART score improved significantly and stepwise from 65 at 3 months to 90 at 24 months (P < 0.05). Total WORMS improved from 14.5 at surgery to 7.0 after 24 months (P < 0.05). Body mass index and defect size at surgery correlated with total WORMS at final follow-up (P < 0.05) but did not correlate with clinical scores or defect filling. CONCLUSION: MACT combined with cancellous bone grafting at the medial femoral condyle reduces symptoms continuously over 2 years. A 1-step procedure may reduce perioperative morbidity. However, despite improvements, patients' activity levels remain low, even 2 years after surgery.