Summary

Larger defect size and an initial plan for subsequent MACI were significant predictors of a patient proceeding with the MACI procedure.

Abstract

OBJECTIVES: Repair of articular cartilage defects presents a significant challenge in orthopedics. Matrix-Induced Autologous Chondrocyte Implantation (MACI) is an advanced intervention aimed at treating articular cartilage defects. Despite its growing application, the decision-making process for undergoing MACI remains complex and multifaceted. This study aimed to identify predictive variables influencing the likelihood of undergoing MACI following an articular cartilage biopsy.

Methods

This retrospective chart review included 254 patients who underwent articular cartilage biopsy from 2017 to 2022. Patients who underwent MACI were categorized as the MACI group, while those who did not were categorized as the non-MACI group. Univariate analysis was performed for each independent variable. Stepwise binary logistic regression analysis was employed to evaluate predictors of undergoing MACI. Variables evaluated include patient age at biopsy, sex, BMI, pain level, intra-operative total cartilage defect size, and concomitant injuries. Provider intention was also considered as a predictor, categorizing patients into three groups according to pre-operative notes: incidental findings at the time of surgery (G1), plan for post-biopsy reassessment of symptoms (G2), and staged intention to treat the cartilage defect (G3). Model selection was performed to maximize goodness of fit according to the Hosmer-Lemeshow test, Nagelkerke R² value, and Specificity/Sensitivity Contingency Table. In addition to objective predictors of MACI, data on subjective factors influencing the decision-making process for MACI was collected. These patients were classified into one or more of the following categories based on the reasons documented: time of year, life events, social circumstances, insurance approval, financial concerns, work-related issues, personal preferences, comorbid conditions, seeking a second opinion, surgeon's recommendations, alternative treatments explored, symptom improvement, lack of follow-up, and other factors.

Results

The study included 254 patients, 142 men (55.9%) and 112 women (44.1%), with an average age of 27.7±9.2 years (range, 14-59 years) and BMI of 27.9±5.3 kg/m² (range, 15.7-42.6 kg/m²). The average total defect area was 6.0±3.6 cm² (range, 1.0-21.5 cm²). A total of 80 out of 254 patients (31.5%) underwent the MACI procedure. There was a significant difference in the total cartilage defect area between the non-MACI (5.5±3.3 cm2) and MACI (7.0±3.9 cm2) group (p=0.003).There was a significant difference in initial intent to perform MACI between the two groups (p<0.001). Younger patient age was a marginally non-significant trend towards proceeding with MACI. (non-MACI 28.3±9.6 years; MACI 26.4±8.2 years, p=0.057). The final regression model included patient age at the time of biopsy (OR =-0.041, p=0.064), gender (OR =0.229, p=0.516), initial intention group (direct intention OR=2.848, p<0.001; incidental finding OR=0.364, p=0.747; postoperative reassessment OR=reference, p<0.001), total defect size (OR=0.130, p=0.011), BMI (OR =0.057, p=0.100), and pain level (OR =0.042, p=0.649). This model demonstrated a strong predictive accuracy (87.9% Specificity, 72.5% Sensitivity) and strong fit to the data (Hosmer and Lemeshow test, p = 0.558). Controlling for other predictors in the model, each 1 cm² increase in defect size corresponded to a 13.8% increase in the likelihood of undergoing MACI. Of the 174 patients who did not proceed with the MACI procedure, the 69.5% cited symptom improvement as their reasoning for not progressing with the subsequent surgery. This decision influence was followed by surgeon’s recommendation to not undergo MACI (14.2%), inconvenient time of year (13.2%), disruptive life event(s) (7.5%), and comorbid condition(s) (6.9%).

Conclusions

Larger defect size and an initial plan for subsequent MACI were significant predictors of a patient proceeding with the MACI procedure. Younger patient age carried a marginally non-significant trend towards proceeding with MACI