Clinical and Radiological Outcomes at ≥10-Year Follow-up After Matrix-induced Autologous Chondrocyte Implantation in the Patellofemoral Joint

Abstract

Background: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in the treatment of knee cartilage defects, although limited research is available on its longer term (≥10 years) sustainability in the patellofemoral joint.

Purpose: To report the clinical and radiological outcomes at ≥10 years in a prospectively recruited cohort of patients undergoing MACI in the patellofemoral joint and compare outcomes in patients undergoing MACI on the patella versus the trochlea.

Study design: Case series; Level of evidence, 4.

Methods: The current study prospectively enrolled 95 patients who underwent patellofemoral MACI, of whom 29 (13 patella, 16 trochlea) underwent concomitant tibial tubercle osteotomy. Patients were assessed preoperatively and at 2, 5, and ≥10 years using a range of patient-reported outcome measures (PROMs) including the Knee injury and Osteoarthritis Outcome Score, the 36-item Short Form Health Survey, and the frequency and severity of knee pain as well as patient satisfaction, full active knee flexion and extension, and peak isokinetic knee extensor and flexor torques. High-resolution magnetic resonance imaging (MRI) was performed to assess pertinent graft parameters, as well as determine an overall MRI composite score, per the Magnetic Resonance Observation of Cartilage Repair Tissue scoring system. Results were analyzed according to the graft location (patella or trochlea).

Results: Of the 95 patients recruited, 82 patients (41 patella, 41 trochlea) were available for a clinical review at ≥10 years after surgery (mean follow-up, 11.9 years [range, 10-15 years]). For the whole patellofemoral MACI cohort, all PROMs significantly improved over time (P < .05), with no significant changes (P > .05) observed in any MRI-based score from 2 to ≥10 years after surgery. At ≥10 years, 90.2% (n = 74) were satisfied with MACI in relieving their knee pain, and 85.4% (n = 70) were satisfied with the improvement in their ability to participate in sports. No differences (P > .05) were observed in PROMs between those undergoing patellar MACI and those undergoing trochlear MACI, although a significant group effect was observed for limb symmetry indices of knee extensor (P = .009) and flexor (P = .041) strength, which were greater in those undergoing patellar (vs trochlear) MACI. No statistically significant differences (P > .05) were observed between patellar and trochlear grafts on any MRI-based measure. In the cohort assessed at ≥10 years after surgery, 4 patients (2 patella, 2 trochlea) demonstrated graft failure on MRI scans, although a further 3 patients (all trochlea) were omitted from the ≥10-year review for having already progressed to total knee arthroplasty.

Conclusion: Good clinical scores, high levels of patient satisfaction, and adequate graft survivorship were observed at ≥10 years after MACI on the patella and trochlea.

Keywords: clinical outcomes; magnetic resonance imaging (MRI); matrix-induced autologous chondrocyte implantation (MACI); patellofemoral joint.

Figure 1.

Flowchart demonstrating patients undergoing patellofemoral matrix-induced autologous chondrocyte implantation (MACI) who were enrolled in the study and were subsequently evaluated over the ≥10-year postoperative period. MRI, magnetic resonance imaging.

Figure 2.

Limb symmetry indices (LSIs) for knee extensor (quadriceps) strength in the patellar and trochlear groups, with a significantly higher LSI seen in the patellar group at 5 years and final follow-up (minimum, 10 years after surgery).

Figure 3.

Axial proton density–weighted fat-saturated magnetic resonance imaging of a graft (between white arrows) on the patella in a patient, demonstrating (A) the preoperative chondral defect and the graft at (B) 2 years, (C) 5 years, and (D) final follow-up (minimum, 10 years after surgery).

Figure 4.

Axial proton density–weighted fat-saturated magnetic resonance imaging of a graft (between white arrows) on the trochlea in a patient, demonstrating (A) the preoperative chondral defect and the graft at (B) 2 years, (C) 5 years, and (D) final follow-up (minimum, 10 years after surgery).