Fig. 4From: Multiple drilling is not effective in reducing the rate of conversion to Total hip Arthroplasty in early-stage nontraumatic osteonecrosis of the femoral head: a case-control comparative study with a natural courseA Survival analysis of conversion to THA between patients who underwent multiple drilling combined with and without autogenous bone grafting (P = .373, Kaplan-Meier method with log-rank test). Depending on the different extent of necrotic lesion in ONFH patients who underwent multiple drilling, B the survival analysis showed a significant difference in patients with necrotic lesion < 15% (P = .007) and no significant difference in patients with necrotic lesion of 15–30% (C) or > 30% (D) (P = .453 and .657, respectively)Back to article page