Aim: To evaluate the repair of articular cartilage defects in the knee treated by autologous chondrocyte implantation (ACI), using arthroscopic assessment.

Method: One hundred and six articular cartilage defects in 79 knees of 77 patients were treated by ACI. The chondrocytes were injected beneath a periosteal flap (Brittberg et al, 1994).

Arthroscopy and removal of the metal implants were performed nine months following implantation. The ICRS score was used to assess the repairs.

Results: Of the 79 knees 43.5% of the lesions involved the patella, 35.2% the femoral condyles, 16.7% the trochlea, and 4.6% the tibial condyles. The average defect size was 254.65mm². It was found that 20% of knees had more than one defect. Associated biomechanical procedures were carried out in 88.7%.

Seventy lesions in 58 knees (56 patients) have been assessed; four eligible patients were not assessed arthroscopically. The ICRS scores (maximum 12) were: tibial condyle 11.5; patella 11.3; femoral condyle 11.0, and trochlea 10.7. Synovitis was markedly reduced in all knees with well-healed defects. Adhesions between the periosteal graft and the synovium caused a click in 11 patients, which was relieved by arthroscopic resection. Incomplete healing occurred in one patient with a wound dehiscence, in two following a fall in the post-operative period, and in one patient with a non-contained defect. Biopsies at arthroscopy showed predominantly hyaline cartilage.

Conclusions: We concluded that ACI was an effective method of repairing articular cartilage defects. In this series the results for the patella matched those for the femoral condyle, attributed to the simultaneous biomechanical correction of patellofemoral dysplasia. Stabilisation of the articular surface resulted in resolution of synovitis.