Patient and Chondral Defect-Specific Characteristics an Associated Matrix-Induced Autologous Chondrocyte Implantation...

Focal chondral defects in the knee lead to swelling, discomfort, and mechanical symptoms, resulting in disability and loss of function. Matrix-induced autologous chondrocyte implantation (MACI) has emerged as a viable treatment option, with satisfactory clinical outcomes reported compared with microfracture. Patient and lesion-specific variables associated with MACI after biopsy remain largely underreported.

To examine patient- and defect-specific characteristics associated with conversion to MACI after biopsy from a single institution.

Cohort study; Level of evidence, 3.

A retrospective chart review of prospectively collected data from June 2018 to March 2025 was performed. Inclusion criteria included patients ≥15 years of age with an arthroscopically confirmed focal International Cartilage Regeneration & Joint Preservation Society (ICRS) grade 2 to 4 knee chondral lesion undergoing chondral biopsy (phase 1). Patient and chondral defect characteristics were assessed using univariate and multivariate regression analyses to determine factors associated with conversion to MACI (phase 2).

A total of 104 patients (mean patient age, 31.4 ± 11.4 years) undergoing chondral biopsy were identified. MACI was performed in 28.8% (30/104) of patients at a mean of 9.8 ± 10.2 months from biopsy. Patients with a history of previous knee surgery (P = .003), patellar lesions (P = .014), and ICRS chondral defect grade ≥3 (P = .048) had a higher probability of undergoing MACI. Patients undergoing concomitant procedures during biopsy (P < .001), as well as patients with preoperative mechanical symptoms (P = .014), were less likely to undergo MACI. Multivariate logistic regression found that patellar lesions (OR, 18.85; 95% CI, 1.70-208.50; P = .017) were independently associated with a greater likelihood of conversion to MACI, while concomitant procedures during biopsy (OR, 0.22; 95% CI, 0.06-0.81; P = .022) were associated with a significantly lower likelihood of implantation.

MACI was performed in 28.8% of patients undergoing biopsy for symptomatic chondral lesions. Patients with patellar defects exhibited a significantly higher likelihood of MACI, with increased conversion rates associated with previous ipsilateral knee surgery and/or more advanced chondral defects. Patients undergoing concomitant procedures at biopsy were significantly less likely to require MACI, with lower conversion rates associated with a history of preoperative mechanical symptoms.