Poster 288: The Effect of Time Delay From Biopsy to Second-Stage Implantation on Return to Sport and Clinical Outcomes following Autologous Chondrocyte Implantation

Objectives: Expansion of chondral defect size and clinical outcomes in patients with cartilage lesions are thought to be modulated by several risk factors. Previous studies suggest that time delay until implantation may be a risk factor for an increase in the number and size of chondral lesions at the time of implantation. Reports on the effect of time delay on clinical outcomes, however, remain limited. Therefore, the purpose of this study was to evaluate the effect of time delay from cartilage biopsy to implantation on patient satisfaction, return to sport (RTS), and clinical outcomes following autologous chondrocyte implantation. Methods: A retrospective review was performed among patient who underwent autologous chondrocyte implantation (ACI) and matrix-associated autologous chondrocyte implantation (MACI) at a single institution between the years 2012 to 2020 with minimum 2-year clinical follow-up. Clinical outcomes were measured using the Visual Analog Scale (VAS) for pain and satisfaction and the Knee Injury and Osteoarthritis Outcome Score (KOOS; subscores: symptoms, pain, sport, and quality of life (QOL)). Time delay was calculated as the elapsed time between cartilage biopsy and implantation. Cartilage lesions were categorized based on the Outerbridge classification of chondral lesions. The number of high-grade lesions (Outerbridge grade 3 or 4) and size of lesions were analyzed at time of biopsy and implantation. T-tests or non-parametric tests and Chi-squared tests were used to analyze continuous variables and categorical variables, respectively. A one-way ANOVA was used to compare outcomes based on RTS status, using a post-hoc Tukey’s HSD test for multiple comparisons. Bivariate linear regression was used to determine the impact of the time interval from biopsy to implantation on the change in size of the largest high-grade lesion and RTS. Results: A total of 36 patients, mainly female (55.6%) aged 29.25 (± 9.49) with a mean follow-up of 6.51 ± 2.5 years were included in our analysis. Thirteen patients (36.1%) did not RTS. Of the 23 patients (63.9%) who returned to sport, 11 (30.6%) returned at their preoperative level or higher, and 12 (33.3%) returned at a lower level. VAS pain scores were significantly higher in patients who did not RTS vs those who did (42.85 vs. 9.35, p <0.001). All KOOS subscores (Symptom: 56.54 vs. 81.96, Pain: 72.22 vs. 91.74, Sports: 40.38 vs. 79.3, QOL: 35.58 vs. 70.38, p <0.001) were significantly lower in patients who did not RTS compared to those who returned. Increase in time delay from biopsy to implantation was associated with an increase in VAS pain score (OR [95% CI]; 1.42 [0.16 to 2.69], p=0.02) and inversely related to KOOS pain scores (OR [95% CI]; -1.01 [-1.83 to -0.01], p= 0.01. Furthermore, when comparing time from biopsy to implantation and expansion of the largest highgrade lesion, it was found that for every month increase in time, lesion surface area increased by 0.588 cm 2 ; however, this correlation did not reach significance (p=0.09). The number of high-grade lesions at time of implantation were significantly higher in those that returned to sport at a lower level than those who did not return (1.67 vs. 1.23, p=0.02). The average surface area of the defect at biopsy and implantation were 3.13 cm 2 and 4.38 cm 2 respectively. The number of patients who had an increase in the number of high-grade lesions from biopsy to implantation was significantly higher in those who returned to sport at a lower level compared to those who did not return (4 vs. 1, p=0.05). Logistic regression demonstrated no significant relationship between time interval and rate of return to sport (p=3.59). No other associations were observed between time from biopsy to implantation and clinical outcomes. Conclusions: An increase in time delay from biopsy to graft implantation is associated with worse pain after surgery. Both the number of high-grade lesions at the time of implantation and an increase in time delay were not associated with lower rates of return to sport. Further studies are needed to evaluate the effects of time delay until implantation and its potential role as a risk factor for worse clinical outcomes in patients undergoing autologous chondrocyte implantation procedures. [Table: see text]