The distally based peroneal artery perforator-plus fasciocutaneous flap is not only has the characteristics of the distally pedicled sural fasciocutaneous flap,but also has the unique characteristics of dual blood supply and venous outflow from the perforator and fascial pedicle [13，14]. However, the reliability of these flaps remains the main concern. The highest necrosis (including complete and partial) rate of the distally based sural flap was 35.7% (25/70) . In the last decade, various necrosis rates of the distally based sural flap in studies with relative large sample sizes (n ≥ 40) were reported to be 3.9% (2/51) by Asʼadi et al. , 8.3% (13/156) by Gill et al. , 8.8% (9/102) by Dhamangaonkar et al. , 11.8% (9/76) by Herlin et al. , 17.2% (15/87) by Raza et al.  , 20.5%(9/44) by Dai et al. , 22.3%(33/148) by Schmidt et al. , 30.6%(36/85) by Perumal et al. . In the present study, the sample size was relatively large and there were no cases of complete necrosis of the flap. Forty-seven (83.9%) flaps completely survived within one stage, while the other eight (14.3%) defects were reconstructed using the DPAPF flaps with simple skin grafting or suturing in the second stage, only one (1.7%) remnant defect was covered with a local flap. The results suggest that the DPAPF flaps are relatively reliable for reconstructing the defects in the distal forefoot. Once partial necrosis of the flap occurred, the remnant defects in most cases were covered successfully with a simple procedure. The DPAPF flap is particularly suited for the reconstruction of the defects over the distal forefoot for physicians who are not experienced with using free flaps or patients who are not eligible for undergoing reconstruction with a free flap[ 23，24].
The defects over the distal forefoot are more distal than those over other parts of the foot. Covering the soft tissue defects in this region is difficult. Zgonis et al. and Gözü et al. utilized the cross-leg reverse sural artery flap to reconstruct the defects over the distal forefoot in small sample size [7, 8]. However, it isn’t an optimal choice because the prolonged postoperative immobilization of both lower limbs and the unavoidable reoperations is a great inconvenience for patients.Zhu et al. reconstructed the defect over the forefoot using 5 types of free flaps for 41 patients, and two flaps were lost by repeat exploration . Free flap can be used to reconstruct larger defects，however the procedure has some disadvantages, such as time limitation, requirement of additional equipment, increased technical complexity, sacrificing of the main vessel, trained microsurgeons and teams, postoperative monitoring requirements, and the need for a relatively longer learning curve，and there is always a risk of reexploration.
When the DPAPF flap is designed to reconstruct the defect over the distal forefoot, the contour and location of the defect in every case is invariable. Thus, length of the fascial pedicle and total length of the flap are subject to the height of pivot point. The higher the pivot point is, the longer are the fascial pedicle and the flap needed. Li et al. considered that reverse sural neurofasciocutaneous flaps with the pivot point of 5–7 cm above the lateral malleolus were not able to repair middle and distal foot injuries, and they advised that the defects in the region should be covered with the flaps with lower pivot points . By the anatomical study, Zhang et al. found the length and the outer diameter of the perforator located at the lower pivot point were shorter and smaller, and the perforator can still nourish a sizeable distally based flap for foot and ankle coverage . However, the length and diameter of the perforator located at 5-7 cm above the tip of lateral malleolus are larger, which is helpful for avoiding the excessive torsion of the perforator and the flap blood supply.
Based on our previous study, partial necrosis rates of reverse sural artery flaps increased significantly when LWR was of 5:1 or more skin island width was 8 cm or more, or the top-edge of the flap was located in the 9th zone . In the current study, the proportions of the aforementioned first two unfavorable conditions were 82.1% and 76.8%, respectively; the top-edge of the flaps was located in the 8th zone (66.1%) or the 9th zone (33.9%); the mean of length of fascial pedicle and skin island, total length, and the LWR were more than those parameters which reported by Wei et al.. Despite so many unfavorable conditions, the survive rate of the DPAPF flaps was relative higher, and the only remnant defect (1.8%) was repaired using a local flap. The outcome of the DPAPF flaps for repairing the defects over the distal forefoot was acceptable. The reason why the DPAPF flaps can survive longer and more reliably is that an average of 3.2 true anastomoses connect the perforators without change in the caliber on the posterior calf, which are parallel to the sural nerve . Compared with the survival flaps, the constitute ratios of the two indicators (LWR of 5:1 or greater and skin island width ≥ 8 cm) were not significantly different in the partial necrosis flaps (p > 0.05). partial necrosis rate of the DPAPF flaps located in the 8th zone (5.4%) was significantly lower than that of the flaps located in the 9th zone (36.8%) (p < 0.05). The finding suggest that the DPAPF flaps with the top edge in the 8th zone were safer and more reliable in repairing the defects of the distal forefoot. It is consistent with both our previous research  and the “Surgical Unsafe Zone” reported by Mojallal et al. .
As mentioned above, the partial necrosis rate of the DPAPF flaps was most associated with the top-edge of the flap. By fixing the ankles in dorsiflexion, in the setting of invariable the skin island and the pivot point, the length of the fascial pedicle was reduced about 2.35 cm on average, and the total length of the flap was simultaneously shortened by the same amount. Meanwhile, the top-edge of the flaps was descended by the procedure; otherwise, the proportion of flaps with the top edge in the 9th zone would be higher, even the proximal border of some flaps would beyond the popliteal crease. The external fixation device is a device that prevents complications of distally based sural flaps and facilitates postoperative care [15, 28]. However, it requires an additional nail for external fixation nursing care during the postoperative fixation period, and it increases the financial burden on the patients. Pallua et al. introduced the concept of reconstructing the defects in the distal forefoot using pedicle flaps and fixing the feet using a cast . We did not use this approach because of difficulties in changing the dressings and the high risk of pressure sores of the heel. In the present study, the ankle was fixed in dorsiflexion using a Kirschner wire, which is cheaper and requires a more convenient dressing and nursing care. There was no case of infection of the ankle or nail. After three weeks of the operation, the Kirschner wire was pulled out after confirming the stability of the flaps. The period of ankle fixation was short; therefore, the function of the ankle was not affected.
Width of fascial pedicle is associated with arterial supply  and venous drainage . When the DPAPF flap was utilized to repair the defect over the distal forefoot, if the dimension of the skin island was larger, the fascial pedicle should be widened appropriately. This tip was also helpful for reducing the LWR to prevent complications of the flaps to some extent.
The mean duration of DPAPF flap elevation was approximately 30 minutes, which highlights that the flap can be elevated easily and quickly, and the defects over the distal forefoot can be covered without microsurgical techniques and sacrificing major arteries of the lower extremities. The disadvantage was that the donor sites were closed by resurfacing with a skin graft, which may be related to the relatively larger dimensions of the defects. In the present study, although a follow-up of eight weeks or three months was enough [8, 1711, 20], we evaluated the reconstruction outcomes of the DPAPF flaps over more than 6 months of follow-up. The reconstruction outcomes were very satisfactory with only 2/48 cases having evaluated fair outcomes.
To the best of our knowledge, this is the first study to introduce the reconstruction of the defects over the distal forefoot with DPAPF flaps with the largest number of patients. A randomized controlled trial was not possible because this study was a retrospective review, which is a major limitation of the study. Further studies with larger ssample sizes are required to improve the success rate of DPAPF flaps in the reconstruction of defects over the distal forefoot.