Guilherme C Gracitelli, Vinícius Y Moraes, Carlos ES Franciozi, Marcus V Luzo, João Carlos Belloti

Cartilage defects of the knee are often debilitating and predispose to osteoarthritis. Microfracture, drilling, mosaicplasty, and allograft transplantation are four surgical treatment options that are increasingly performed worldwide. We set out to examine the relative effects of these different methods. To assess the relative effects (benefits and harms) of different surgical interventions (microfracture, drilling, mosaicplasty, and allograft transplantation) for treating isolated cartilage defects of the knee in adults. We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, CENTRAL, EMBASE, MEDLINE, SPORTDiscus, LILACS, trial registers and conference proceedings up to February 2016. Any randomised or quasi-randomised trials that evaluated surgical interventions (microfracture, drilling, mosaicplasty, and allograft transplantation) for treating isolated cartilage defects of the knee in adults. At least two review authors independently selected studies, assessed risk of bias and extracted data. Intervention effects were assessed using risk ratios (RR) for dichotomous data and mean differences (MD) for continuous data, with 95% confidence intervals (CI). Data were pooled using the fixed-effect model, where possible. We included three randomised controlled trials comparing mosaicplasty versus microfracture for isolated cartilage defects in adults. Two trials were single-centre trials and one involved three centres. These small trials reported results for a total of 133 participants, of whom 79 (59%) were male. Mean participant age in the three trials ranged from 24.4 years to 32.3 years. All studies included grade 3 or 4 cartilage lesions (International Cartilage Repair Society (ICRS) classification). The defect area ranged from 1.0 cm² to 6.0 cm²; the mean area in all three trials was 2.8 cm². No trials of allograft transplantation or drilling were identified.All trials were judged as being at high or unclear risk of performance and reporting bias. We judged that the quality of evidence was very low for all outcomes. For individual outcomes, we downgraded the quality of evidence by one or two levels for risk of bias, one level for indirectness where there were data from a single-centre trial only, one or two levels for imprecision where there were wide confidence intervals and an insufficient number of events, and one level for inconsistency reflecting heterogeneity. This means that we are very uncertain about the estimates for all outcomes.There is very low quality evidence from one single-centre trial (57 participants), which included athletes only, that mosaicplasty resulted in higher patient-reported function scores (probably the IKDC 2000 subjective knee evaluation score) compared with microfracture (range 0 to 100; higher score = better function) at one year follow-up (MD 10.29 favouring mosaicplasty, 95% CI 7.87 to 12.71). Very low quality evidence from the same trial showed that this effect persisted in the long term at 10 years follow-up. However, there is very low quality evidence from the two other trials (72 participants) of little difference in patient-reported function, assessed via the Lysholm score (range 0 to 100; higher score = better function), between the two groups at long-term follow-up (MD -1.10 favouring microfracture, 95% CI -4.54 to 2.33). One trial (25 participants) provided very low quality evidence of no significant difference between the two groups in quality of life or pain at long-term follow-up. Pooled results for treatment failure - primarily symptom recurrence - reported at long-term follow-up (means ranging from 6.3 to 1.4 years) in the three trials (129 participants) favoured mosaicplasty (10/64 versus 20/65; RR 0.47, 95% CI 0.24 to 0.90). Based on an illustrative risk of 379 treatment failures per 1000 patients treated with microfracture, there is very low quality evidence that 201 fewer patients (95% CI 38 to 288 fewer) would have treatment failure after mosaicplasty. All three trials reported activity scores but due to clear statistical and clinical heterogeneity, we did not pool the long term Tegner score results. There was very low quality evidence from one study (57 participants) of higher Tegner scores - indicating greater activity - at intermediate-term and long-term follow-up in the mosaicplasty group; however, the between-group difference may not be clinically important. The other two trials provided very low quality evidence of no significant difference between the two groups in activity scores. We found no evidence from randomised controlled trials on allograft transplantation or drilling. The very low quality evidence from RCTs comparing mosaicplasty with microfracture is insufficient to draw conclusions on the relative effects of these two interventions for treating isolated cartilage defects of the knee in adults. Of note is that treatment failure, with recurrence of symptoms, occurred with both procedures. Further research is needed to define the best surgical option for treating isolated cartilage defects. We suggest the greatest need is for multi-centre RCTs comparing reconstructive procedures (mosaicplasty versus allograft transplantation) for large osteochondral lesions and reparative procedures (microfracture versus drilling) for small chondral lesions.