Fingertip injury represents the most common injury of the hand , which is defined as a distal injury of the flexor digital tendon and extensor tendon insertion . In the management of a fingertip injury, although it is essential to maintain the length, preserve the nail and the appearance, the main goal of treatment is to ensure the durability of the fingertip and painless at the skin. Therefore, the treatment must be individualized based on several patient-related factors and unique trauma characteristics .
For those injured fingers with bone exposure and local soft tissue defects, stump revision (i.e., phalangeal shortening and direct suture) is the simplest and fastest way to recovery, which can be performed under local anesthesia in the emergency room . However, this operation shortens the phalange and adversely affects the appearance and function of the affected finger. With the advancement of medical technology, stump revision is no longer a common approach to manage tissue defects . Compared with stump revision,, given that our method demonstrated a similar length of operative time and difficulty while retaining the length and function of the affected finger.
At present, the “V-Y” advancement flap  is widely performed in the management of fingertip injuries. “V-Y” flap is best used for transverse or anticlinal fingertip amputation and is suitable for injury to any finger. The contraindications of applying this flap include oblique metacarpal fingertip amputation and extensive palmar soft tissue defects. The edge of the wound is at the bottom of a distal triangle of the flap, and the apex of the flap can be extended to the transverse striation of the distal interphalangeal joint. During the operation, the skin and subcutaneous tissues should be incised first, including the fiber septum, and injury to the neurovascular bundle should be avoided. The flap can be advanced 1 cm to the distal end and form a "Y" shape repair. With this method, the maximum advancement distance of the skin flap is limited to 3–4 mm  and the skin flap area provided are often inadequate. Moreover, the incision of this operation is made at the finger pulp and the postoperative scar is located at the middle of the finger pulp, which may affect the sensory function. On the other hand, the most widely used transfer flap, the “V-Y” flap is widely used, but its shortcomings still need to be further improved. The parallelogram transfer method allows a longer transfer distance of the transposition flap. In our practice, the residual skin was trimmed and flipped over. The transverse width of the flap was abandoned and the longitudinal length of the flap was obtained. The defects were evenly distributed on each side of the parallelogram to achieve sufficient transfer distance to cover the exposed bone and tissues.
This article provided a detailed description of a modified flap for the surgical management of fingertip defects. The transfer flap was incised closely to the bone surface of the distal phalanx, and the interphalangeal artery was not damaged during stripping [16, 17], which is key to flap survival. Venous outflow is maintained by venules and capillaries in the perivascular adipose tissues through a retrograde fashion . Therefore, if the interphalangeal artery is well protected during the flap design, the flap survival can be assured more confidently, as evidenced in our analyses that all our parallelogram flaps had survived postoperatively.
The reconstructive surgery for fingertip injury aims to obtain stable tissue coverage, achieve acceptable appearance, restore sensitivity, maintain finger length and resume normal physical activity promptly. After a careful preoperative design of the parallelogram flap, postoperative skin flap contracture is less likely to occur, given that the turning over of the flap provides more coverage area than the “V-Y” flap. Furthermore, the incision of the parallelogram flap is distributed at both sides of the fingertip, and therefore the scar is at the sides of the finger. In this way, we abandon the finger’s width and retain the length, successfully achieving the purpose of the operation.
The practice of sensory or non-sensory reconstruction of fingers remains controversial and debatable among hand surgeons. Studies have reported an average of 10 mm in the static two-point discrimination test when a "senseless" reverse digital artery island flap has been performed[20, 21]. Conversely, other studies have demonstrated a normal static two-point discrimination test (1-5mm) following neurovascular island flaps [22, 23]. The findings of these studies indicate a reduced ability of flaps to restore sensation in the absence of nerve connections [24–26]. By performing free flap surgery, the digital nerve can usually be preserved. We demonstrated that our operative method provided a good sensory reconstruction of fingers, leading to satisfactory recovery in the finger movement, strength, etc.
There were limitations to our parallelogram flap. In particular, this flap would not be applicable when there were multiple skin defects at the donor site, or the required transfer distance was more than 6-7mm. In this instance, the skin flap adjacent to the finger or a reverse-flow island flap can be considered. Though the outcomes of our parallelogram flaps appeared encouraging, the results were limited by the absence of comparative analysis with other surgical methods.
In conclusion, for the fingertip injuries requiring less than 7 mm in the transfer distance, the parallelogram flap we have proposed results in favorable outcomes, including a high flap survival rate, acceptable appearance and optimal function of fingers.