Autologous chondrocyte implantation (ACI) is a well-established cartilage repair procedure, however, numerous studies have shown higher ACI graft failure rates after prior marrow stimulation techniques (MST). The purpose of this study was to identify which factors may predict decreased graft survival after ACI among patients who underwent prior MST. A secondary aim was to investigate the specificity of these predictors.
In this review of prospectively collected data, we analyzed 38 patients who had failed prior MST surgery and subsequently underwent collagen covered ACI (case group). We divided our patient case group to graft failure ACI (n=8, 21%) and successful ACI (n=30, 79%). Fourteen clinical variables were categorized and analyzed to determine predictors for failure of the ACI graft. Preoperative magnetic resonance imaging (MRI) was used to evaluate the severity of subchondral bone marrow edema (BME) graded from I–absent to IV–severe, the presence of subchondral cyst, hypertrophic sclerosis, and intralesional osteophyte. The effects of these MRI findings on the graft survivor were also investigated. Concurrently, a control group, without prior MST was matched to investigate the specificity of the previously determined predictor.
In the case group, the presence of preoperative severe BME was significantly higher in patients with failed ACI as compared to patients with successful ACI (p<0.001). In the control group the presence of severe BME was not significantly different between the failure and successful group (p=0.747). ACI graft failure rate among patients with prior MST and preoperative grade IV BME was 83.7% at 5 years postoperatively resulting a significantly lower survival rate as compared to patients with prior MST and without severe BME (5-year graft failure rate=6.5%) (p < 0.001). Other parameters did not differ significantly.
The presence of grade IV BME after prior MST is a predictive factor for graft failure among patients who then underwent second-generation ACI.