Transtibial tunnel reconstruction is one of the classical surgical techniques for posterior cruciate ligament (PCL) reconstruction. However, this surgical technique inevitably produces the "killer turn" effect. Specifically, during the transtibial tunnel reconstruction, there is a sharp tunnel edge at the exit of the tibial tunnel, and the graft has a large stress at this edge, which leads to the failure of transplantation due to the repeated friction between the graft and the tunnel edge. The "killer turn" effect may lead to the "residual laxity", thus resulting in postoperative knee instability, affecting the long-term efficacy of reconstructive surgery and reducing the postoperative satisfaction of patients. In recent years, many scholars have proposed a series of improved techniques for PCL reconstruction in dealing with the "killer turn" effect, including tibial inlay technique and improved transtibial tunnel technique. The authors review the formation mechanism of "killer turn" effect and methods to eliminate or reduce the effect, in order to provide a reference for improving the effect in PCL reconstruction.

Objective:To explore the clinical application of lateral thoracic artery perforator flap in repairing local defect after breast conserving surgery.Methods:The clinical data of 48 breast cancer patients planned to finish breast conserving surgery were retrospectively analyzed. The patients were divided into plastic breast-conserving group and routine breast conserving group. In the plastic breast-conserving group, 24 patients local defect repaired with the lateral thoracic artery perforator flap. In the routine breast conserving group, 24 patients local defect repaired with the fascial flap around the cutting edge. The operation related indexes and cosmetic effect from two groups were compared.Results:Both groups of patients successfully completed breast conserving surgery. The plastic breast-conserving group patients had significantly increased in operation time, operative blood loss, incision length and drainage tube indwelling time compared with the routine breast conserving group; the differences were statistically significant ( t=6.99, 9.37, 21.74, 8.80, P<0.05). The rate of secondary surgery enlarged was lower than fhat in the routine breast conserving group, and the difference was statistically significant (χ 2=4.76, P<0.05). There were 3 cases in the plastic breast conserving group and 1 case in the conventional breast conserving group. The skin at the edge of the flap was ischemic necrosis in the 4 cases, which healed after dressing change and drainage, and there was no significant difference ( P>0.05). The evaluation of postoperative cosmetic effect showed that the excellent and good rate of the observation group was 91.7%, compared with the routine breast conserving group (58.3%); the difference was statistically significant (χ 2=7.11, P<0.05). All patients were followed up for average 24 months, and local recurrence and distant metastasis were not observed. Conclusions:The lateral thoracic artery perforator flap for filling local defects in the lateral quadrant or central region of breast cancer is feasible, easy to operate, hides incision scar, better cosmetic effect and worthy of clinical promotion.