Technical note: the “double eye” technique as a modification of autologous chondrocyte implantation for the treatment of retropatellar cartilage defects

Retropatellar cartilage defects treated with autologous chondrocyte implantation (ACI) are still associated with inferior clinical outcome compared to defects being located on the femoral condyles. This is partly because of the biomechanical characteristics of the patellofemoral section of the joint, in which, in contrast to the medial or lateral compartments of the knee joint, prejudicial shearing forces are dominant. The patellar ridge has a particularly important role in the reduction of these shearing forces. The double eye technique was developed as a modification of ACI with preserving the important patellar ridge for the treatment of retropatellar cartilage defects extending beyond the patellar ridge and involving the medial and lateral retropatellar facets. This technique provides for a separate reconstruction of the medial and the lateral facets by means of ACI, but the ridge region is preserved to maintain the original thickness of cartilage at this point. The present paper describes the “double eye” technique as a modification of autologous chondrocyte transplantation (ACI) for treatment of cartilage defects of the patella, that involve both lateral and medial facets, and gives first clinical results of 11 patients. The average follow-up was 41.6 (±15.0) months, and the average age at diagnosis was 40.4 (±10.1) years. The Lysholm score, the subjective IKDC score, and the ICRS score were the instruments used to measure the outcome. This paper focuses on the introduction of the double eye technique with preservation of the patella ridge in the treatment of retropatellar cartilage lesion. Nevertheless, first clinical results of 11 patients are given, with an average Lysholm score of 75 (±14) points and an average subjective IKDC score of 60 (±14). Objective evaluation according to the criteria of the IKDC score showed very good or good treatment results in 9 of the 11 cases, with only 2 poor results. In conclusion, with the double eye modification presented in this paper, the potential for successful results in the treatment of combined cartilage defects of the medial and lateral facets of the patella is high; it takes into account the specific biomechanical properties of the patella ridge. The procedure needs further evaluation in clinical studies involving larger numbers of patients so that the indications can be determined more precisely.