Summary

The cartilage repair after OWHTO with autologous osteochondral transplantation in cases with spontaneous osteonecrosis of the knee was good/excellent in more than 90% and significantly better than in cases with osteoarthritis.

Abstract

Introduction

The study compared cartilage repair outcomes in cases of opening-wedge high tibial osteotomy(OWHTO) with autologous osteochondral transplantation(AOT) for spontaneous osteonecrosis of the knee(SONK) patients with varus malalignment and medial knee osteoarthritis(OA).

Materials And Methods

Total of 146 OA and 33 SONK patients were treated by OWHTO with AOT with a follow-up of over 4 years, and among them, a case-control study was conducted on 26 matched cases each of OA and SONK patients. There were 13 male and 13 female patients in each group, with a mean age of 67.7 years at the time of surgery. The cartilage lesion area was 536 mm2 in the OA group and 482 mm2 in the SONK group, with 3.3 and 3.0 grafts used on average, respectively. Cartilage repair at the second-look arthroscopy was evaluated using the ICRS cartilage repair assessment score.

Results

During the follow-up, two cases in each group dropped out and underwent joint replacement surgery, but the rest were able to continue with their daily lives. The cartilage repair score at the second-look arthroscopy was 8.5 points in the OA group and 10.1 points in the SONK group, with 65% of the OA group and 92% of the SONK group achieving “nearly normal” or higher repair grades, indicating significantly better outcomes in the SONK group. The most significant difference was yielded in subscore of the degree of fibrocartilage growth around the plugs. We examined which factor most affected the cartilage repair score among sex, age, body mass index, lesion size, and OA grade. Factor influencing cartilage repair in OA group was the lesion size of cartilage injury. On the other hand, postoperative OA grade significantly affected the cartilage repair in the SONK group.

Discussion

Although OA and SONK have similar pathologies, the lesions in SONK often involve depressed areas with osteochondral defects, while OA lesions are characterized by widespread cartilage wear and flattening. The successful restoration of near-normal cartilage surface shape through autologous osteochondral transplantation in the SONK group may have contributed to improvements in OA grade and, consequently, influenced cartilage repair outcomes. This study also examined the factors affecting cartilage repair outcomes and clinical symptoms, in order to clarify the indication of this cartilage repair procedure.