The autologous chondrocyte implantation (ACI) technique described by Peterson, which we adopted in 1997, is not suitable for an arthroscopic application. Since November 2000 we have been moving towards a system based on a solid collagenic scaffold (MACI^®, Verigen) which allowed us to develop an entirely arthroscopic procedure applicable to all knee joint areas.

A total of 47 patients (mean age 31 years), accounting for a total of 52 focal, non-degenerative chondral defects with an average size of 4.7 cm² (range: 3.2 – 6.2 cm²), have been treated arthroscopically. All were mobilised on the first and discharged on the second day after surgery. Partial weight-bearing was introduced after 4 weeks and increased to the full extent after 8 weeks. They were clinically evaluated by Modified Cincinnati, IKDC and Visual Analogue Scale (VAS). In two cases, after specific informed consent, an arthroscopic second look was performed1 year after surgery. The regeneration was assessed macroscopically (ICRS Cartilage Repair Assessment score) and histologically (histomorphometry and immunochemistry).

We re-assessed the first 30 knee joints with a mean follow-up of 23 months (min 12, max 36). Cincinnati Scores improved from 2.8±1.14 (baseline Clinician) to 9.4±0.73, and from 2.5±0.90 (baseline Patient) to 9.7±0.50 at 3 years, respectively. IKDC and VAS results paralleled the Cincinnati scores. The two second- lookprocedures performed showed a regenerated tissue assessed as normal according to ICRS, a finding also supported by the histological evaluation.

The arthroscopic technique can be considered an established approach for second-generation ACI application, even in case of multiple lesions, and mainly for medial femoral condyle localisations. Our approach, based on traditional arthroscopic tools and procedures, can be easily performed by other adequately trained surgeons, thanks to the optimal mechanical properties of the membrane, characterised by a high resistance to tears, also after prolonged exposure to the intra-articular perfusion fluids. From the surgical perspective, the procedure is easy and fast, also when compared to the open-ceiling techniques, and in particular for non-condylar localisations (patella, trochlea and tibial plate), with clinical and histological outcomes that seem comparable to those obtained with liquid-suspension systems.