Poster 212: The Cartilage Early Return for Transplant (CERT) Score: Predicting Early Patient Election to Proceed with Cartilage Transplant Following Chondroplasty of the Knee

OBJECTIVES: Surgical management of articular cartilage lesions often includes a staging or index chondroplasty which allows for debridement of unstable chondral flaps, accurate measurement of the size and location of lesions, and evaluation of co-existing pathology that might require subsequent treatment. Some patients obtain meaningful symptomatic improvement from this staging procedure allowing a delay or avoidance of definitive treatment, while others have continued discomfort and elect to move forward with transplantation. The purpose of this study was to (1) identify risk factors associated with early election to proceed with subsequent cartilage transplantation after a staging chondroplasty within 6 months and (2) develop a risk calculator with pre-operative prognostic value for conversion. METHODS: A retrospective review of patients prospectively enrolled at the time of staging chondroplasty was performed, with early election defined as patient decision to proceed to cartilage transplantation within six months of chondroplasty. Cox proportional hazards analysis was used to determine univariate predictors of conversion, and a predictive calculator was formulated using stepwise regression employing the Akaike Information Criterion (AIC). Postoperative patient-reported outcomes were compared between failure and non-failure cohorts in the timepoints leading up to the mean decision time to validate that failure correlated with worse PROMs. RESULTS: Sixty-five patients (67 knees) were included for analysis, with an overall election rate of 29.9% within six months after chondroplasty. Condylar involvement, number of lesions, lesion topology, subchondral involvement, AMADEUS grade, history of prior surgery, indication for realignment osteotomy, and lower preoperative baseline functional assessment by IKDC, KOOS Pain, KOOS ADL, KOOS Jr, VR12 Mental, and VR12 Physical were significantly associated with greater univariate risk of early election to transplant (p≤0.04). Based on multivariate results, the final AIC-driven CERT score employed preoperative KOOS Pain Score, VR12 Physical Score, condylar involvement, and AMADEUS score to generate 0–7-point risk stratification system with a 3% early election to proceed to transplant risk in the 0–2-point score group, 33% risk in the 3–4-point group, and 79% risk in the 5+ point group (p < 0.01) and an overall AUC of 0.906 (p<0.01). By 6 weeks, early-electing patients demonstrated significantly worse pain (61.71±17.97 vs 77.03±14.79, p=.003), daily living (84.75±14.26 vs 67.55±20.69, p=.002), sports (57.36±22.94 vs 32.14±28.67, p=.002), and quality of life scores (49.31±21.27 vs 22.33±20.33, p=<.001). CONCLUSIONS: The risk of a given patient electing to proceed with a cartilage restoration procedure within 6 months after failing to derive therapeutic benefit from staging chondroplasty is closely and additively associated with pre-operative KOOS Pain Score, VR12 Physical Score, anatomic area involved, and lesion AMADEUS score. Clinical utilization of the CERT score can help guide patient conversations regarding expected benefit from chondroplasty and determination whether a single or two stage definitive procedure can be considered.