Summary

This study showed that good mid-term outcomes of atelocollagen-associated autologous chondrocyte implantation applied new tissue-engineering technology to create a cartilage-like tissue in a three-dimensional culture for the repair of chondral defects of the knee, however the graft detachment was subsequently treated with graft removal in one knee.

Abstract

Introduction

Atelocollagen-associated autologous chondrocyte implantation (ACI) is applied new tissue-engineering technology to create a cartilage-like tissue in a three-dimensional culture using atelocollagen gel. We reported the prospective multicenter clinical trial of atelocollagen-associated ACI for the repair of chondral defects of the knees. However, the mid- or long-term results of this ACI procedure remains unclear. The purpose of this study was to evaluate the mid-term clinical outcomes and complications in patients undergoing atelocollagen-associated ACI for the repair of chondral defects of the knee.

Method

Between 2004 and 2016, twelve consecutive patients (12 knees) who underwent atelocollagen-associated ACI were enrolled prospectively in this study. This study design had been accepted by the institutional review board clearance in our hospital. There were 7 men and 5 women with a mean age of 35.7 years (range: 15-68 years) at time of surgery. The causes of the osteochondral defect were trauma in six knees, osteochondritis dissecans in five knees and spontaneous osteonecrosis of the knee (SONK) in one knee. The lesions were located at the medial femoral condyle in seven knees, and at lateral femoral condyle in five knees. In surgical procedure, the patients underwent a two-stage procedure that included cartilage harvest and subsequent implantation of autologous chondrocytes embedded in atelocollagen gel covered by a sutured periosteal flap. Concerning the combined surgery, ACL reconstruction was performed in two knees, iliac bone graft in one knee, osteochondral autologous transplantation (OAT) in one knee and lateral meniscus reconstruction in one knee. We used the following clinical and MRI evaluation scales for preoperative and latest follow-up periods after surgery (mean 8 years, range: 2-13 years): Lysholm score, Knee injury and Osteoarthritis Outcome Score (KOOS) and MR observation of cartilage repair tissue (MOCART) score. The Student t-test was used to determine the significance of the differences. The significance level was set at p=0.05.

Results

The size of chondral defect averaged 4.5 cm2 (range: 4-6 cm2). The Lysholm score significantly improved from 65 to 90 points (p<0.001). Regarding KOOS, all five subscale scores improved significantly (p<0.05). In MRI evaluation, we confirmed integration to border zone and subchondral bone, but thickening of the graft was confirmed in 2 cases. MOCART score improved significantly from 10 to 83 points (p<0.001). In one case treated with OAT previously for osteochondritis dissecans, the graft was detached at 8 months after the implantation, and arthroscopic debridement was required. In this case, osteosclerosis of the subchondral bone was observed and histologically detached graft fragment consisted of fibrous tissue and cartilage-like tissue. In another case with SONK of the medial femoral condyle, total knee arthroplasty was performed 8 years after surgery. In the four cases, a needle biopsy was performed at the site of chondral implantation. We confirmed cartilage-like tissue with a proteoglycan-rich matrix pathologically and good bound of grafted tissue to the subchondral bone, but that consisted of just monolayer different from four layers in normal hyaline cartilage.

Conclusions

This study showed that good and excellent mid-term outcomes of atelocollagen-associated ACI. However, the treatment failure was subsequently treated with graft removal in one patient who had a marked hypertrophic response at the grafted site and then detachment of approximately half of the graft. This case had been performed OAT previously, so the reason of detachment was thought to be osteosclerosis of the subchondral bone for implantation.