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SICOT e-Newsletter

Issue No. 47 - August 2012

Worldwide News

Review of "Minimum ten-year results of a prospective randomised study of autologous chondrocyte implantation versus mosaicplasty for symptomatic articular cartilage lesions of the knee"

Ashley Brown

Minimum ten-year results of a prospective randomised study of autologous chondrocyte implantation versus mosaicplasty for symptomatic articular cartilage lesions of the knee Bentley G, Biant LC, Vijayan S, Macmull S, Skinner JA, Carrington RW. J Bone Joint Surg Br. 2012 Apr;94(4):504-9. Autologous chondrocyte implantation (ACI) and mosaicplasty are methods of treating symptomatic articular cartilage defects in the knee. This study represents the first long-term randomised comparison of the two techniques in 100 patients at a minimum follow-up of ten years. The mean age of the patients at the time of surgery was 31.3 years (16 to 49); the mean duration of symptoms pre-operatively was 7.2 years (9 months to 20 years). The lesions were large with the mean size for the ACI group being 440.9 mm² (100 to 1050) and the mosaicplasty group being 399.6 mm² (100 to 2000). Patients had a mean of 1.5 previous operations (0 to 4) to the articular cartilage defect. Patients were assessed using the modified Cincinnati knee score and the Stanmore-Bentley Functional Rating system. The number of patients whose repair had failed at ten years was ten of 58 (17%) in the ACI group and 23 of 42 (55%) in the mosaicplasty group (p < 0.001). The functional outcome of those patients with a surviving graft was significantly better in patients who underwent ACI compared with mosaicplasty (p = 0.02).

Review:

Articular cartilage lesions of the knee in young patients can have profound consequences, including chronic knee pain, reduced knee function and early onset osteoarthritis. Autologous chondrocyte implantation (ACI) and mosaicplasty are two methods used to treat articular cartilage lesions in young and middle-aged patients. Bentley et al’s paper is one of the first of its kind, prospective, randomised, comparative study of the two methods with medium-term follow-up.

With a sample size of 100, and minimum ten-year follow-up, this study favours the use of ACI over mosaicplasty for isolated articular cartilage lesions of the knee greater than 100 mm². ACI was found to have a failure rate at 10 years of just 17% compared with 55% in the mosaicplasty group, as well as a significantly better functional knee score. Variables including, age, sex, aetiology, site of lesion, and duration of symptoms were not found to have any significant effect on outcome.

Interestingly, the lesions treated in this study were chronic (mean duration of symptoms prior to surgery of 7.2 years), with a mean number of previous operations of 1.5. The recent literature suggests that primary articular cartilage lesions show better outcomes for those that are treated within one year of injury. While we should aim to treat articular cartilage lesions within the first year, this study demonstrates that even patients with large chronic lesions can benefit from ACI.

Two variables that the authors did not analyse in relation to outcome were the size of lesion (range 100 - 2000 mm²) and the number of previous operations (range 0 to 4); both of these variables may have influenced outcome. The authors also used two different materials for the membrane in ACI (porcine collagen membrane or autologous periosteum) - again, it would have been useful to determine if this had any influence on outcome in the ACI group.

The study only included isolated articular cartilage lesions of the knee. The aetiology of nearly half (46%) of these lesions was traumatic. However, traumatic knee injuries resulting in articular cartilage lesions often have other associated intra-articular injuries, such as ligament or meniscal injuries. Injury to these structures has been shown to influence outcome of articular cartilage lesions.

The authors used two different functional knee scores; the modified Cincinnati rating system and the Stanmore-Bentley functional rating system - neither of these are validated for cartilage repair studies. They found significantly better scores for the modified Cincinnati rating system in the ACI group compared to mosaicplasty group, but no significant difference with the Stanmore-Bentley system.

In summary, this study favours the use of ACI over mosaicplasty for large, chronic, isolated articular cartilage lesions of the knee in the short- and medium-term. Ongoing follow-up of these patients will allow us to see if repair of these lesions reduces the development of early-onset osteoarthritis.