Aims

To investigate (1) The relationship between macroscopic grading and durability of cartilage repair following collagen-covered autologous chondrocyte implantation (ACI-C) in the knee; (2) The influence of histology on durability of cartilage repair; (3) The relationship between macroscopic appearance and histology of repair tissue.

Aim: To report the clinical and histological outcome of autologous chondrocyte implantation (ACI) using two techniques -collagen covered ACI or ACI-C and matrix carried ACI or MACI- over eight year period.

Patients and methods: One hundred and seventy one patients (61 ACI-C and 110 MACI) who underwent ACI were followed-up prospectively using both objective and patient reported clinical outcome measures. Biopsy of the repair tissue was performed in 115 patients.

The mean clinical follow-up was 39.4 months (13mths to 8 years) and the mean timing of biopsy was 14.8 months. The mean age at the time of surgery was 32 years (15 to 55 years). The site of defect was as follows: medial femoral condyle-95, lateral femoral condyle-25, trochlea-7, patella 27 and multiple sites- 12. The mean proportion of viable cells available for implantation was 96.3 % (range: 86 to 100) and the mean number of multiplication of cells during culture was 90 (range: 9 to 667).

Results: 79 % of patients had an improvement in clinical outcome, 5 % of patients had no difference and 16 % had deterioration in clinical outcome. Short Form 36 (SF-36) health survey assessments demonstrated significant improvements in both mental and physical component scores (p< 0.001). The number of patients who demonstrated hyaline-like, mixture of hyaline-like and fibrocartilage, fibrocartilagenous and fibrous tissue histology were 32, 22, 59 and 2 respectively.

The most favourable sites were lateral femoral condyle and trochlea where as the least favourable site was patella. There was no correlation between the mental score of patients and the final clinical result. Improvement in functional score was significantly higher among those who had a higher pre-operative function (p< 0.001). There were 7 patients who had previously failed micro-fracture and all of them obtained significant improvements in pain and function. Those who had a higher proportion of viable cells after cell culture demonstrated a tendency towards better outcome, but failed to reach statistical significance (p=0.14). There was no correlation between the number of cell multiplications at the time of cell culture and final clinical outcome (p=0.65). There was no significant difference in clinical outcome between the ACI- C and MACI techniques of ACI (p> 0.05).

Conclusion: Autologous chondrocyte implantation is a useful procedure for patients with symptomatic chondral defects of the knee and produces significant improvement in both objective and patient reported clinical outcome scores in up to 79 % of patients.