Articular cartilage lesions cause pain and decreased mobility, affecting the working capacity and quality of life. To date, cartilage defects have been treated by different strategies, including debridement and lavage, microfracture, osteochondral autograft transplantation, osteochondral allograft transplantation, autologous chondrocyte implantation, and stem cell transplantation. Debridement and lavage are procedures of the oldest technique and typically reserved for low- demand older patients with small lesions (<2 to 3 cm²) Bert and Maschka, 1989Federico and Reider, 1997Freedman et al., 2004Owens et al., 2002. Current research has suggested that the best candidates for debridement and lavage are those who suffer from mechanical symptoms (Moseley et al., 2002). Meanwhile, for patients with small to moderate sized lesions (1 to 5 cm²), microfracture is a suitable treatment. The microfracture process helps stimulate fibrocartilage in-growth into the chondral defect to cover the underlying bone Freedman et al., 2004Gill and Macgillivray, 2001Steadman et al., 2003. The procedure is performed by creating tiny fractures in the subchondral bone plate.

Moreover, osteochondral autograft plugs have been investigated as a means to restore cartilage defects. Osteochondral autograft transplantation has been most commonly applied to treat symptomatic lesions Freedman et al., 2004Hangody et al., 2001. The greatest advantage of osteochondral autografts is the use of live hyaline cartilage. This technique results in cartilage that is most similar to the injured cartilage. However, this technique also has disadvantages, namely donor site morbidity (pain and new cartilage defect), technical difficulty and risk of cartilage or bone collapse.

Fresh osteochondral allograft transplantation entails the implantation of a cadaveric osteochondral graft into the cartilage defect Aubin et al., 2001Bugbee, 2000Garrett, 1994. This technique can be used for large articular cartilage defects (from 3 cm² up to an entire hemicondyle). The major advantage of osteochondral allografts is the ability to replace large osteochondral defects in a single-stage procedure.

Currently, autologous cultured chondrocyte implantation has also been explored for the treatment of cartilage defects. In this technique, a small piece of cartilage is harvested arthroscopically. Chondrocytes from the sample are isolated and grown expanded in culture over several weeks. In the next step, millions of autologous cultured cartilage cells are suspended in a solution of fibrin glue and later implanted into cartilage defects Peterson et al., 2000. This technique is usually considered for intermediate to high-demand patients who have failed arthroscopic debridement or microfracture Brittberg et al., 1994Chu et al., 1999Gillogly et al., 1998.

Stem cell transplantation is currently another promising therapy for osteoarthritis and cartilage defects. Some recent studies have shown that autologous adipose stem cell transplantation can improve osteoarthritis Bui et al., 2014. Combination of stem cell transplantation and microfracture have also proven to be better than microfracture alone Nguyen et al., 2016. However, similar to osteochondral allograft transplantation and autologous chondrocyte implantation, stem cell transplantation is expensive but yields promising results in clinical trials.

In this study, we aim to investigate the application of osteochondral transplantation to treat cartilage defects of osteoarthritic knee.

Hangody et al. recommended the use of OAT only for patients <40 years of age; there have been relative contraindications in patients ranging from 40-50 years of age, and contraindications in those >50 years of age Hangody et al., 2001. Kish et al., 1999 as well as Marcacci et al., 2005 have also reported better results in younger patients. However, Chow et al. have found that age is not a factor which limits the procedure; old people with chondral defects and a stable knee joint can achieve good results Chow et al., 2004. In our study, we also found in patients with a mean age of 55 ± 8 years old, clinical results as well as pain scores improved at 12 and 18 months post-operation. In a recent study, mosaicplasty for treatment of cartilage defects demonstrated promising results. In a multi-center study, Hangody et al. showed that mosaicplasty was better than other cartilage repair methods, including debridement, subchondral penetration and abrasion arthroplasty Hangody et al., 2001. Similarly, Krych et al. saw better activity levels after osteochondral autograft transfer mosaicplasty than after microfracture Krych et al., 2012.

Several other studies have also demonstrated improved results after mid-term and long-term follow-up. Randomized studies with a control group have been performed. Horas et al. Horas et al., 2003 and Dozin et al. Dozin et al., 2005 concluded that the clinical outcome of mosaicplasty was equivalent to autologous chondrocyte implantation, with a high rate of hyaline cartilage. However, after early- stage promising results, Solheim et al. Solheim et al., 2010 showed that there is a gradual reduction of efficacy after 10 to 14 years of follow-up; 40% of the 73 cases had poor outcome, and good outcome was often seen in younger patients with defect size <3 cm². In a study of 52 patients at 37 months follow-up, Jakob et al. found that the method was limited by the defect size and the number of plugs taken at the donor site Jakob et al., 2002. Marcacci et al. studied 30 patients and confirmed better outcome was associated with small defect size and with only 1-3 plugs Marcacci et al., 2005.

In our study, after the 12 month follow-up period, the percentage with good and excellent Lysholm score was 50.8%. The percentage having knee with normal or mild inflammation on the OKS scale was 95.1%, and the rate of mild pain or no pain on the VAS scale was 93%. Although the Lysholm scale results was lower than previous studies, the results of the VAS scores and OKS scores were equivalent to what other authors, such as Marcacci et al., 2005 and Jakob et al., 2002 have published. The reason for the lower Lysholm scale scores in this study may be due to the fact that the patients in our study included those with knee osteoarthritis.

Osteochondral autograft transplantation for isolated cartilage defects with < 2-3 cm² lesion area in young people requiring high activity is nothing controversial. In our study, osteochondral autograft transplantation for grade III/IV cartilage defects with 1-3 cm² lesion area on the weight‐bearing surfaces of femoral condylar in older adults with osteoarthritis is an expanded indication to delay knee replacement surgery. Initial results showed good results with lesion area of ≤ 3 cm² at 12 months post-operation and similar results in the 18 months post-operative group. In studies by Hangody et al., the authors only performed OAT for cartilage defect sizes from 1-4 cm², although it can be applied as a temporary method for 8 cm² cartilage defects Hangody et al., 2001.

In this study, we compared the results in two groups of lesion defects: <2 cm² and 2-3 cm². We saw good results in both groups; there was no correlation between lesion size and clinical results. Marcacci et al. observed better results with smaller-sized lesions Marcacci et al., 2005, but other authors have found Jakob et al., 2002, as we did too, that there are no statistically significant correlation between clinical outcome and lesion size.

With the development of diagnostic imaging devices, MRI provides not only a non-invasive means to diagnose cartilage lesions but also a reliable tool for monitoring and evaluating results of articular cartilage lesion treatment. In particular, 3D MOCART is a good scale and most often used for evaluating results of OAT by MRI Marlovits et al., 2006Marlovits et al., 2004. 3D MOCART scale assesses many variables, including: degree of repair filling, integration of the cartilage repair tissue to the border zone, structure of the surface, structure of the whole repair tissue, and signal intensity. Thus, the scale can be used to evaluate the effectiveness, success or failure of treatment.

Rate of complete defect fill after 1 year according to research by Zak et al. is 50% Zak et al., 2014. In our study, this rate was only 8%; most cases (80%) had defect fill from 50% to <100%. We found intact surface rate of cartilage after 1 year to be 28%; Zak group’s found it to be 70% Zak et al., 2014. This difference may be due to parameters in other studies which are not seen in osteoarthritis patients. The majority of patients in our study are older and osteoarthritic thus MRI results after 1 year were worse. However, the rate of complete bone interface was 72% and we did not have any complete delamination case, meaning that all plugs were stable and in place.

The average MOCART score after 12 months in our study was 62.4 points, not too much lower than 75 points in Zak et al.’s study Zak et al., 2014 and Krusche-Mandl et al.’s study Krusche-Mandl et al., 2012. We also did not find a correlation between MOCART score and function scores or VAS scores.

Concerning the correlation between MOCART score and clinical outcome, Krusche-Mandl et al. did not find any correlation between MOCART score and Lysholm, IKDC or VAS scores Krusche-Mandl et al., 2012. Tetta et al. also found that there is only a correlation with the IKDC scale but not with the Tegner scale Tetta et al., 2010. A recent meta-analysis study also found that there is not enough evidence to confirm a correlation between morphological results of MRI and clinical outcome Wakitani et al., 2002.

Ensuring the matching between plugs and the receiving site to create a smooth cartilage surface is a challenge in the OAT technique. Chow et al. showed that harvesting and transplanting of osteochondral plugs should be perpendicular to cartilage surface; in fact, wrong angle placement will reduce efficacy Chow et al., 2004. Marcacci et al. also agreed with this assessment after 3 of their cases failed and were related to the surface matching problem Marcacci et al., 2005. Hangody and Fules also emphasized the importance of matching between plugs and the receiving location Hangody et al., 2001. Therefore, in our study, we carefully performed the OAT procedure, and only 1 case without matching after transplantation had to be replaced with another plug.

OAT procedure under arthroscopy was investigated as a treatment for osteoarthritis patients with grade III/IV cartilage defects (1-3 cm² lesion area) and showed promising initial results. OAT is an accepted and trusted method in the treatment of 1-3 cm² cartilage defects, helping to delay knee replacement surgery. There is no correlation between 3D MOCART and functional outcome, or to post-operative pain score. OAT under arthroscopy may be a promising procedure for the treatment of knee articular cartilage defects since it is a minimally invasive, low-priced, and one-stage procedure which yields some efficacy and few complications.

OAT: autologous osteochondral transplantation

OKS : Oxford Knee Score

LFC : Lateral femoral condyle

MOCART :Magnetic resonance observation of cartilage repair tissue

All patients gave informed consent and the studies were approved by the Committee of Department of Science and Technology, Ho Chi Minh city, Viet Nam.

BHTK: collected, analyzed, data and wrote the manuscript; MTV, NDT, LTV, NPT: collected data, write the draft of manuscript; HNT: diagnosis, evaluated clinical scores; performed MRI evaluation. All authors approved this manuscript