68 Part I Chapter 3 Thus, partial or subtotal meniscectomy is only done in patients with unrepairable, complex, mostly degenerative meniscal lesions [19]. In most cases the injured meniscus is repaired using sutures or suture devices [17]. Different suture techniques such inside-out, outside-in and all-inside are available. Meniscal substitution using biocompatiblemeniscus scaffolds made fromcollagen or polyurethane and meniscal allograft transplantation are possible treatment options in patients after partial or total meniscectomy [20]. The most common problems arise frommisjudgment of meniscal tissue quality. Only with a reasonable meniscus quality suturing is successful. For meniscal substitution and allograft transplantation fixation remains a significant source of failure [17]. Cartilage repair Cartilage repair is more than just surface repair. One has to differentiate between chondral and osteochondral lesions. In chondral lesions only the surface is affected. In osteochondral lesions the lesions reach into the subchondral bone. For chondral lesions chondroplasty, microfracturing, mosaicplasty with autograft or allograft and autologous chondrocyte implantation (ACI) are available. For osteochondral lesions the knee surgeon can choose from a variety of surgical treatment options such as Pridie drilling, open or arthroscopic fixation using screws or pins, excision of the osteochondral fragment, microfracturing without or with membrane coverage, osteochondral grafting (with autograft or allograft), and autologous chondrocyte implantation (ACI) [21-24]. However, a common reference technique has yet to be found (Figure 1). The decision on which treatment to choose depends on the size, the location and degree of cartilage lesions [24]. In addition, associated problems such as meniscal tears, alignment issues or ligamentous stability have to be addressed [24]. Figure 1 SPECT/CT arthrography of the knee in a 24-year-old male patient with an OD, which was fixed with a screw 4 months before the examination (an osteotomy was also performed). Bone SPECT/CT was performed to investigate whether the OD defect was properly fixed and to exclude free bodies. The OD was found to be fixed adequately in situ with physiological high uptake 4 months after fixation (arrow) and no corpus liberumwas visualized. (A) SPECT, (B) CT, and (C) fused SPECT/CT. OD, osteochondritis dissecans. Image courtesy of Prof. Dr K. Strobel (Lucerne, Switzerland).