Cochrane in CORR®: Surgical Interventions (Microfracture, Drilling, Mosaicplasty, and Allograft Transplantation) for Treating Isolated Cartilage Defects of the Knee in Adults

Importance of the Topic

Focal cartilage defects of the knee represent one of the most challenging clinical problems encountered by orthopaedic surgeons. Left untreated, continued repetitive loading can result in early onset post-traumatic arthritis, a devastating prospect for those young, active patients who are frequently diagnosed with these lesions [3].

Marrow stimulation techniques such as microfracture and drilling are widely used for treatment of focal cartilage defects of the knee [2, 13]. Marrow stimulation, however, has its limitations; namely, the durability of the resultant fibrocartilage, inconsistent pain relief with larger, less-contained defects, and an increased risk of failure—namely the need for revision surgery—with subsequent autologous chondrocyte implantation [9, 10, 12]. In this context, it is not surprising that some clinicians have turned to osteochondral autograft (mosaicplasty) and allograft as alternative treatment options. Although more complex and costly, these options allow for potential restoration of hyaline cartilage to defects [6].

This systematic review and meta-analysis evaluated surgical treatment of focal cartilage defects in the knee, and included three randomized trials that compared microfracture to mosaicplasty in 133 participants [5, 7, 14]. The authors, however, could not draw any conclusion regarding the treatment effect of these interventions, and no studies evaluating drilling or osteochondral allograft transplantation met inclusion criteria.

Upon Closer Inspection

The low-quality evidence for all the outcomes in this review reflects the presence of important methodological shortcomings. The trial by Lim and colleagues [7] failed to ensure allocation concealment and may not have reported all collected patient-reported outcomes. Gudas and colleagues [5] did not state how or if patients were blinded, nor if treatment allocation was concealed. Additionally, the outcome assessors were not blinded in the study by Ulstein and colleagues [14]. These methodical shortcomings are important to note as they may lead to the apparent benefit of an intervention to be exaggerated. Overall, due to high risk of bias of the included trials, as well as inconsistency and imprecision across the study results, the authors could not draw conclusions on the relative effects of mosaicplasty and microfracture for treating isolated cartilage defects of the knee in adults.

The inclusion of only three studies highlights the difficulty in studying patients with focal cartilage defects. Cartilage defects are rarely uniform in size, shape, severity, or location. Furthermore, these patients frequently undergo multiple additional procedures to address concomitant pathology. Such a multitude of confounding variables results in increased study heterogeneity and makes performing randomized trials difficult, and this difficulty is compounded when one tries to pool the results of randomized trials into a meta-analysis. Coupled with the relatively low incidence of focal chondral lesions and the long-term followup required to judge the efficacy of cartilage restoration treatment, it is not surprising that in the current review so few studies met inclusion criteria.

Take-home Messages

This Cochrane review of randomized clinical trials seems premature, due to the low number of studies, the overall poor methodological quality of the included studies, and the insufficient evidence to draw any conclusions regarding the use of microfracture versus mosaicplasty for the treatment of focal cartilage lesions in the adult knee [4]. The included studies, however, represent the best available evidence, and do provide some insight regarding treatment of cartilage lesions in the knee. For example, the study by Gudas and colleagues [5], although performed in a younger and more-active population compared to the other randomized clinical trials, did show improved patient functional scores and higher rates of continued athletic activity with mosaicplasty. Although lower overall activity levels are expected in older patients, these results echo the findings of the recent meta-analyses, both of which included randomized and observational studies [1, 6]. Pooled results in this Cochrane review also found a considerably lower rate of symptom recurrence in patients treated with mosaicplasty at 10 years [4]. Given the well-reported decline in the durability of fibrocartilage at 2 years, this is an expected result, but in conjunction with the previous findings mosaicplasty may be a more favorable option in the young, active patient [6, 12].

The most important finding of this Cochrane review is the need for large, well-designed, and appropriately executed randomized clinical trials. Long-term followup of at least 10 years tracking both clinical outcomes and radiologic progression of osteoarthritis will be of paramount importance. The consensus statement among the International Cartilage Repair Society and contributing authors is an important first step in ensuring high methodological standards and uniform objective evaluation of patient outcomes in future studies [11]. With the continued increase in the surgical treatment of focal cartilage defects, the recruitment time for such trials should decrease [8].