Comparison of the regeneration of cartilage and the clinical outcomes after the open wedge high tibial osteotomy with or without microfracture: a retrospective case control study

Background: It is unclear whether postoperative outcomes are associated with the cartilage regeneration after open wedge high tibial osteotomy (OWHTO) combined with microfracture. The purpose of this study was to evaluate the regeneration of the articular cartilage, radiologic, and clinical outcomes after OWHTO with and without microfracture. Methods: Eighty-seven patients who underwent OWHTO from 2014 to 2015 were retrospectively included in this study. Fifty-seven OWHTOs with microfracture on medial femoral condyle (MFC) (group 1) and 30 OWHTOs without microfracture (group 2) were compared at a mean 2-year follow-up. The regeneration of the articular cartilage was evaluated using International Cartilage Repair Society (ICRS) grade on the second-look arthroscopy and the magnetic resonance observation of cartilage repair tissue (MOCART) score on magnetic resonance imaging (MRI). The weight-bearing line (WBL) ratio, hip-knee-ankle (HKA) angle, joint line convergence angle (JLCA) and Ahlback grade were evaluated. The clinical outcomes were evaluated using the Western Ontario and McMaster University (WOMAC) scores and the Knee Society (KS). Results: The articular cartilage in the MFC were regenerated in 67.8% of group 1 (43/57) and 58.6% of group 2 (16/30), respectively (p=0.014). However, change of the ICRS grades of the medial tibial plateau, lateral and patellofemoral compartments showed no statistical difference between the groups. Total MOCART score in group 1 was superior to that in the group 2 at postoperative 2years (41.818.6 vs. 31.8 +/- 19.8, p=0.023). Regarding MOCART score, microfracture was only effective in the defect filling and integration to the border zone of the MFC (p<0.001 and p=0.035, respectively). Other radiologic and clinical outcomes showed no statistical differences between the groups. Conclusion: Microfracture of the MFC during OWHTO only helped the filling of the degenerative cartilage defect and the integration of the cartilage with adjacent cartilage. However, the clinical and radiologic outcome could not be improved by mircrofracture in the OWHTO.