**3. Cartilage replacement techniques**

#### **3.1 Chondrocyte autograft transfer and mosaicplasty**

The description of the technique using osteochondral autografts for the treatment of joint defects was firstly studied by Pap and Krompecher [40]. Later, Wagner and Muller in Germany used the posterior part of the femoral condyle as an osteochondral autograft [41, 42]. Motions came in the 1990s by Matsusue in Japan and Hangody and colleagues in Hungary [43, 44].

 The osteochondral plugs are harvested from non-weight-bearing areas and are transplanted into a small osteochondral defect. A larger lesion is filled in with multiple cylinders; it is also possible to transfer the posterior femoral condyle. Due to multiple cylinders, the gaps between the plugs produce an irregular articular surface.

The main indications for mosaicplasty include the chondral or focal osteochondral lesion in a stable knee, with lesions smaller than 22 mm in diameter and no more than 10 mm in depth.

The main benefits of this technique are that it is a single-stage procedure and there is rapid subchondral bone healing with restoration of native type II hyaline cartilage at the articular surface.

In a series by Hangody et al. with 57 patients and follow-up of more than 3 years, reported 91% good to excellent results with a mosaicplasty [45]. Gudas et al. in a prospective randomized study showed better clinical-functional and MRI results after 3 years for osteochondral transplants than for microfracture surgery [46].

Most of the studies showed good to excellent results in the short and long term, with a greater return to athletic activity when compared to microfracture [47–54].

Major complications of the osteochondral graft include donor site morbidity such as patellofemoral arthritis, fibrocartilage hypertrophy of the donor area, and unsatisfactory filling of the cartilage defect (especially with grafts > 8 mm in diameter) [49, 52, 54–56].
