Summary

The ORKA-1 is a helpful tool for surgeons to estimate an individual patient’s likelihood of ACI survival.

Abstract

Background

The purpose of this study was first to validate the Oswestry Risk of Knee Arthroplasty index (ORKA-1) by applying it to an autologous chondrocyte implantation (ACI) patient cohort in the United States (US), and secondly, to determine predictive factors for the risk of ACI failure as defined by the senior author.

Methods

A total of 171 patients that underwent ACI were included to validate the ORKA-1 as all factors needed for calculation and outcomes were recorded. For cox regression analysis, 154 patients were included as they completed preoperative KOOS, Tegner, Lysholm, IKDC and SF-12 scores. Patient- and lesion-associated parameters were recorded for each patient.

Results

At final follow up (maximum of 10 years post-ACI), 19 patients (11.1%) underwent arthroplasty or osteochondral allograft transplantation (OCA) and a total of 27 patients (15.8%) were considered a failure by senior author’s definition. With arthroplasty or OCA as endpoint, mean survival time was not predicted by patient’s ORKA-1 (mean survival: risk-group 1 = 8.11 years; risk-group 5 = 8.71 years). With ACI failure as endpoint, the mean survival was 7.96 years in risk-group 1 and 5.4 years in risk-group 5. Cox regression analysis identified preoperative KOOS Sport/Recreation as the only significant predictive factor for ACI failure (p = 0.007).

Conclusion

The ORKA-1 is a helpful tool for surgeons to estimate an individual patient’s likelihood of ACI survival. However, the tool is less sensitive in terms of predicting subsequent knee arthroplasty as a specific endpoint when used on a US patient population.