Objective: To investigate survival of cartilage repair in the knee by microfracture (MFX; n = 119) or mosaicplasty osteochondral autograft transfer (OAT; n = 84).
Design: For survival analyses, "failure" was defined as the event of a patient reporting a Lysholm score <65 or undergoing an ipsilateral knee replacement. The Kaplan-Meier method was used for construction of a survival functions plot for the event "failure." Log rank (Mantel-Cox) test was used for comparison of survival distributions in the 2 groups.
Results: The long-term failure rate (62% overall) was significantly higher in the MFX group (66%) compared with the OAT group (51%, P = 0.01). Furthermore, the mean time to failure was significantly shorter (P < 0.001) in the MFX group, 4.0 years (SD 4.1) compared with the OAT group, 8.4 years (SD 4.8). In the OAT group, the survival rate stayed higher than 80% for the first 7 years, and higher than 60% for 15 years, while the survival rate dropped to less than 80% within 12 months, and to less than 60% within 3 years in the MFX group, log rank (Mantel-Cox) 20.295 (P < 0.001). The same pattern was found in a subgroup of patients (n = 134) of same age (<51 years) and size of treated lesion (<500 mm2), log rank (Mantel-Cox) 10.738 (P = 0.001). The nonfailures (48%) were followed for median 15 yeas (1-18 years).
Conclusions: MFX articular cartilage repairs failed more often and earlier than the OAT repairs, both in the whole cohort and in a subgroup of patients matched for age and size of treated lesion, indicating that the OAT repair is the more durable.
Level of evidence: Therapeutic study, Level III.
Keywords: articular cartilage defects; knee; microfracture; mosaicplasty; survival analyses.