A distal thumb defect is a defect far from the level of the interphalangeal joint of the thumb, including the proximal phalanx, the interphalangeal joint and the base of the terminal phalanx, and the defective tissue includes the ventral part of the finger, the phalanx, the nail bed, the nail root and the surrounding dorsal skin of the finger. It is generally accepted that the function of the thumb accounts for 40-50% of the total hand function, and most of the pinching, grasping and gripping functions of the hand are lost with complete defects, so reconstruction and functional reconstruction of the thumb after thumb defects are increasingly important. For distal thumb defects, despite the lack of thumb length, many important functions of the hand can still be performed, and some people even believe that a defect at the level of the interphalangeal joint has no effect on the function of the thumb. Therefore, reconstructive surgery of the distal thumb defect is not only based on the functional requirements of the hand, but the cosmetic aspects of the reconstructed thumb are particularly important. At the same time, the safety of the surgery and the effect on the function of the donor foot become factors that need to be carefully considered before surgery. Data and Methods I. General Data From October 2004 to May 2006, a total of 18 cases were operated. Among them, 14 cases were male and 4 cases were female, with an average age of 23.5 years (18-47 years). There were 7 left-sided cases and 11 right-sided cases. There were 6 cases of machine crush injury, 3 cases of heavy object injury, 3 cases of chainsaw injury, 2 cases of punching machine injury, 2 cases of shredder injury, 1 case of paper cutter injury, and 1 case of bottle press injury. The degree of distal thumb defect was based on the three-class, six-division method, with 5 cases of IA degree defect, 8 cases of IB degree defect, and 5 cases of IIA degree defect in the thumb. The time from surgery to injury ranged from 2 to 11 days, with an average of 4.9 days. 1. Incision design: The nail flap incision was designed according to the measured values of the middle nail, nail root, interphalangeal joint level circumference of the healthy thumb and the length of the thumb defect. The nail flap consists of the nail bed, 2/3 of the skin on the fibular side and 1/3 of the skin on the tibial side. A triangular flap is designed on the dorsal side of the toe with the tip of the flap exceeding the level of the reconstructed interphalangeal joint of the thumb. The proximal ends of the two ventral toe flaps are triangular in shape, and the two sides are dovetailed to form a palmar triangular flap. The donor foot is generally chosen ipsilateral, so that the peroneal flap with toe nerve is located on the opposite pinch side of the thumb, which facilitates good sensation of the pinched object. 2, nail flap cut: along the dorsum of the foot arc incision, lift the dorsum of the foot skin, separate to protect the flap reflux vein, retrograde separation to the beginning of the saphenous vein, ligated the other branches of the genus. The toe artery is first revealed at the toe web, the dorsal plantar artery and dorsalis pedis artery are revealed in a retrograde manner, and the flap is peeled and cut in a prograde manner. When separating the dorsal toe flap, pay attention to protecting the vascular bed to ensure the blood supply of the tibial flap. Bone treatment: Different treatment methods were used according to the degree of thumb bone loss. 5 patients with degree IIA loss were treated with iliac bone block implants, interphalangeal joint fusion, and nail flap with a small amount of nail bone in the nail ridge; 8 patients with degree IB loss were treated with interphalangeal joint preservation, iliac bone block implants, and nail flap with a small amount of nail bone in the nail ridge; 5 patients with degree IA loss were treated by cutting the end 1/2 of the toe bone without taking iliac bone graft. In five patients with IA degree defects, the end of the finger was cut to save two phalanges and no iliac bone graft was needed. The flap was fixed with a needle through the gristle. 4. Flap transfer shaping: The subcutaneous tunnel of the thumb was required to be spacious enough to prevent compression of the vascular tip. The skin of the lateral interphalangeal joint should be separated from the joint capsule because of the tightness of the skin. The skin of the thumb stump is cut longitudinally on the dorsal side of the palm and trimmed to fit precisely into the dorsal triangular flap of the nail. 5, vascular management: different vascular anastomoses were used according to the Gilbert typing of the dorsal metatarsal artery [8]. For type I (5 cases) and type II (9 cases) metatarsal dorsal arteries, 9 cases were separated to the dorsalis pedis artery and anastomosed with the dorsal carpal branch of the radial artery, and 5 cases were anastomosed with the main thumb artery. for type III (4 cases) metatarsal dorsal arteries, the plantar vessels were generally separated without cutting the transverse intermetatarsal ligament to reduce damage to the foot, and only the toe artery was separated and exposed, and the separation was done as proximally as possible to make the vessel caliber thicker and facilitate the anastomosis. 2 cases had good quality and good quality thumb arteries. In two cases, the thumb artery was of good quality and the pulsatile bleeding was normal, and the finger-toe artery was used for anastomosis; in two cases, the thumb artery was of poor quality, and the dorsalis pedis artery or vein graft was cut and anastomosed with the dorsal carpal branch of the radial artery. The distal flap vein was preserved as much as possible, sometimes it was more superficial and fine, and attention was paid to protection. The proximal end is separated to the beginning of the dorsalis pedis vein or saphenous vein, and anastomosed with the radial vein or cephalic vein of the dorsal palm. 6, nerve processing: when cutting the nail flap, take the peroneal toe nerve, peroneal deep nerve and dorsal toe nerve branches. The peroneal toe nerve is anastomosed with the ulnar finger nerve of the thumb, and the deep peroneal and dorsal toe nerves are anastomosed with the superficial branch of the radial nerve and the terminal branch of the lateral cutaneous nerve of the forearm. 7. The donor foot wound was covered with a skin graft taken from the thigh. The number of intraoperative vascular reanastomosis, the number of postoperative vascular re-exploration and anastomosis, and the postoperative observation of nail flap survival and flap healing were observed to evaluate the safety of the surgery. Long-term follow-up of 8 to 26 months was performed to observe the appearance of the thumb, measure the thumb joint mobility, sensation, grip strength and thumb pinch strength, and evaluate the function of the reconstructed thumb. The healing of the donor foot, toe mobility, gait, and bouncing were observed, and the changes in the weight-bearing area and center of gravity during static walking were analyzed by foot function assessment to evaluate the effect of surgery on the function of the donor foot. The patient’s satisfaction with the impact of the reconstructed bunion and foot function was determined by using the rating method. The above evaluation indexes were used to evaluate the safety of the surgery, the effect of the surgery and the negative impact. Results The nail flaps were all viable, and the stitch removal time was 15 to 18 days. Most patients had smooth healing of the incision, and one patient had a mild infection of the incision, which healed after dressing change. Another patient had partial necrosis of the skin strip on the tibial side of the flap, and the wound healed in the second stage after dressing change. One case was thrombosed due to poor quality of the anastomosis due to a mismatch in vessel diameter, and one case was thrombosed due to poor quality of the proximal phalangeal artery, and was revascularized with an anastomosis of the dorsal carpal branch of the radial artery. These two cases were both finger-toe artery anastomoses. The other case was due to arteriovenous misconnection. 1 case developed arterial crisis 4 hours after surgery and was reoperatively explored for thrombosis, which improved after reanastomosis, and this case was a case of anastomosis between the dorsal metatarsal artery and the main thumb artery. All reconstructed thumbs had good appearance, with some having mild nail deformity. The joint mobility of the reconstructed thumb with preserved interphalangeal joints reached 40º~75º (mean 60º). Grip strength: interphalangeal joint fusion reached 60% to 85% of the normal side, and those with preserved interphalangeal joints reached 70% to 90% of the normal side. Pinch strength: 65%~80% on the normal side for the interphalangeal joint fusion and 70%~85% on the normal side for the preserved interphalangeal joint. The patients’ satisfaction with the function of the reconstructed thumb ranged from 70 to 95 (average 86.2), and satisfaction with the appearance ranged from 75 to 95 (average 84.6). The area of the donor foot was 70%~100% (average 92.3%), and the necrotic part of the implant was healed by dressing exchange. 2 cases showed necrosis at the tip of the toe flap, which was mainly caused by the long end phalanx and the high tension of the skin strip after implantation. After healing, the patient’s gait and running and jumping were close to normal, and there was no significant pain. Analysis of foot function: There was no significant change in the weight-bearing area of the foot, and the standing weight-bearing area was mainly the belly of the toe, forefoot metacarpal and heel. The center of gravity in unipedal standing was mildly shifted outward or unchanged. The center of gravity of the body in forward and backward swing was located between the two feet or mildly shifted toward the healthy foot. Patient satisfaction with foot function was 80 to 95 (mean 88.3). Typical case of a male, 19 years old, with a disfiguring injury to the left thumb at the level of the base of the terminal phalanx distal to the paper cutter injury. The left modified nail flap graft was performed 11 days after the injury. The dorsal metatarsal artery was typed as type III, and the toe artery was anastomosed to the main thumb artery with the distal 1/2 of the terminal phalanx, the vein was anastomosed to the dorsal pedicle vein and the cephalic vein, the peroneal phalanx was anastomosed to the ulnar phalanx of the thumb, and the deep peroneal nerve was anastomosed to one of the superficial branches of the radial nerve. The dorsal skin defect of the donor toe was implanted, and the implant survived completely. At 10-month follow-up, the reconstructed thumb had a good appearance, with a discrimination of 5mm on the ulnar side and 7mm on the radial side, a pinch strength of 85% on the normal side, a grip strength of 90% on the normal side, an interphalangeal joint mobility of 75°, and a satisfaction score of 95. Donor foot The toe shortening was about 1cm, there was no foot pain, it did not affect the running and jumping function, and the walking gait was normal. The functional analysis of the foot showed no significant changes in the weight-bearing area of the donor foot, and the center of gravity was slightly shifted outward to the second and third toes; the change of the center of gravity in the anterior and posterior swing was smooth, and the center of gravity in walking was located at the midpoint between the two feet, with no significant deflection. The foot satisfaction score was 95. Discussion Reconstruction of thumb defects has been an issue of interest in the field of hand surgery due to the importance of thumb function. It is generally accepted that the ideal reconstructed thumb should have good joint movement and good stability, appropriate length to ensure good alignment with other fingers, good sensation and no pain, and an aesthetic appearance with a near normal nail profile. The reconstructed thumb meets the patient’s requirements to a large extent in terms of function and appearance. However, there are still some shortcomings in the original surgical approach. One of the biggest problems is the poor abrasion resistance of the implant area at the base of the toe, which affects the patient’s normal walking. In addition, necrosis often occurs in the donor implant area, resulting in the exposure of the toe bone, which may eventually require amputation of the toe, causing unnecessary losses. The existence of these unfavorable factors seriously affects the results of the surgery and restricts the promotion of the procedure. For the distal thumb defect, since the disabled thumb still has a certain functional length, in the past, patients mostly did not have the requirement for reconstruction. With the development of reconstructive techniques, more and more patients are requesting thumb revision. There are many factors that determine the need for thumb revision, including subjective factors such as the patient’s age, gender, marital status, occupation, cultural background, etc., and objective factors such as the success rate of surgery, the appearance and function of the reconstructed thumb, and the impact on foot function. These objective factors place higher demands on the technique and method of reconstructive surgery. The reconstructed thumb should not only have good function but also good appearance, and the impact of the surgery on the function of the donor foot also becomes an important reference in the selection of the surgical method. The ideal donor foot condition should have smooth implant survival, good skin texture and abrasion resistance in the functional weight-bearing area, which can bear the pressure of normal walking, no pain and normal gait. With the modified method of nail flap bunion reconstruction, the abrasion resistance of the skin is greatly improved because the normal skin of the weight-bearing area at the base of the toe is preserved. Patients can perform walking exercises early after surgery, which facilitates faster recovery of donor foot function. In addition, the toe neurovascular bundle on the tibial side of the toe flap is preserved, which greatly improves the sensation and blood supply of the flap and reduces the chance of flap necrosis. Of course, the surgical design should also pay attention to the ratio of the length and width of the sole of the toe skin strip, the protection of the neurovascular bundle in the skin strip during the surgical separation, and the appropriate pressure during the packing of the skin implant, etc., which can reduce the necrosis of the flap caused by improper surgery. In this group of cases, the functional evaluation of the donor foot and the observation of gait and bounce proved that the functional impact of the donor foot after surgery was small and the recovery was fast. On the one hand, it can reduce the chance of necrosis at the tip of the skin strip by reducing the suture tension of the flap, and on the other hand, the tip of the flap can be retained at the base of the toe to cover the stump of the toe bone and even partially cover the dorsal side of the terminal phalanx, which are the areas where skin necrosis is most likely to occur after free skin grafting, thus improving the chance of one-stage healing of the wound. The survival rate of the implants in this group was 92.3%, which was relatively satisfactory. It has been proved that the partial shortening of the terminal segment of the toe has no significant effect on the postoperative foot function. The removal of the nail ridge of the donor toe can reduce the resorption of the iliac bone implant; reduce the damage to the nail bed and the chance of nail deformity; preserve part of the bony skin ligament in the belly of the toe, the reconstructed finger belly has good stability and is conducive to grasping objects. For the defect far from the interphalangeal joint, 1/2 of the end phalanx (length about 1 cm) was cut instead of taking the iliac bone for bone grafting, which reduced the surgical injury caused by taking the iliac bone and simplified the operation. The treatment of blood vessels is the key to the smoothness and success of the operation. Different treatment methods are chosen according to the type of donor vessels and the vascular condition of the recipient area. Most of the reanastomoses and secondary surgical explorations of vessels in this group occurred in patients with toe-finger artery anastomoses, reminding us that prolonged operative time or secondary vascular exploration due to vessel quality often occurs. Therefore, the safety of the procedure can be improved by choosing a vessel with a thicker vessel diameter and jet bleeding as much as possible when conditions permit. For patients with type III dorsal metatarsal artery to reduce the foot impact, instead of splitting the transverse intermetatarsal ligament, the method of cutting the dorsalis pedis artery or vein graft is proven to be very safe, only to note that the plantar artery should be separated as proximally as possible to make the caliber of the vessel closer to the graft vessel and increase the safety of the procedure. Venous problems are the technical difficulties of distal bunion reconstruction. There are many variants of the dorsal toe vein, and many patients have a small dorsal toe vein diameter, which can be easily damaged by excessive dissection, as well as increasing the risk of venous embolism. More soft tissue around the vein when stripping is beneficial to increase the protection of the vessel and reduce the chance of venous crisis. In addition, at the level of the interphalangeal joint of the thumb, the skin is close to the subcutaneous tissue and joint capsule, and the subcutaneous tunnel space is limited, which easily causes compression of the vessel tip and increases the chance of vascular crisis. The above problem is well solved by designing a dorsal triangular flap to reach the proximal side of the interphalangeal joint and extending the dorsal triangular flap of the toe. On the one hand, it reduces the length of vein separation, decreases the risk of injury, and reduces the risk of embolization of fine veins due to the protection of the skin. In addition, the spaciousness of the subcutaneous tunnel is increased, making the procedure safer. It has been proven that adding a flap about 1 cm long does not increase the impact on the donor foot, so this is a good way to reduce the difficulty of the procedure and increase safety. The problem to be noted with the modified nail flap is that there is no toe nerve vascular bundle in the tibial flap, and the tibial flap is supplied with blood through the collateral circulation in the dorsal toe and nail fold, so care should be taken to protect the subcutaneous vascular network in the dorsal toe flap separation, otherwise there is a risk of partial necrosis of the flap. In addition, the quality of sensation in the tibial flap can be improved by repairing the dorsal toe nerve. Cases are completed by subacute surgery, i.e., within 2 weeks of injury, with most completed within a week. This timing allows for good preoperative preparation, both medical and psychological in many ways. Some injuries are heavily contaminated and are treated with a phase I debridement and dressing change for improved cleanliness, which can reduce the chance of infection. The case illustrates that modified method nail flap grafting is a safe method of thumb reconstruction with less impact on donor foot function. The selection of different treatment methods depending on the degree of thumb defect and vascularity can further reduce trauma, simplify the procedure, and increase its safety.