The tongue has various and complex functions that play important roles in swallowing and speech.
With the development of functional microsurgery, various pedicled tissue flaps have been used to repair and reconstruct the shape and function of the tongue. These flaps were initially developed to simply fill the dead cavity and close the wound to maximize the recovery of various functions of the tongue.
In 1984, Song [14] reported the first clinical application of ALTP. ALTP has many advantages: it has a long vascular pedicle, it remains in the same position, it only slightly affects the function of the donor area, and it can be taken from a donor area that can provide a large amount of tissue. It can repair a large tongue defect combined with a pharyngeal defect. It has a large vascular diameter and is easy to anastomose; the distance between the donor area and the recipient area is large, and the operation can be carried out in two areas at the same time. The wound at the donor area can be directly sutured, and its location can be hidden. The branches of the lateral femoral cutaneous nerve and the motor nerve of the flap are left intact, so the sensory and motor nerves of the tongue can be anastomosed after transplantation, which is helpful to restore the sensory function of the flap and increase the ability of the reconstructed tongue to move.
However, ALTP also has some limitations; for example, it can lead to skin flap necrosis, infection, unsatisfactory postoperative function and appearance. To reduce the occurrence of complications and obtain better postoperative reconstruction results, previous studies have proposed various approaches to tongue reconstruction, but their design is complex, making them difficult to apply in clinical practice [15]. As shown in Fig. 5, we aimed to design a new type of ALTP flap that ensures functional and morphological recovery in patients with half-tongue defects, has the simplest design possible, and is easy to use. Both flaps showed good performance immediately after tongue reconstruction, but in long-term follow-up, traditional ALTP showed hypertrophy of the tongue and this affected the tongue function (Fig. 4), which did not seem to occur in the L-shaped flap group (Fig. 3).
Based on the extensive and favourable characteristics of the ALTP, we designed an L-shaped flap that was modified according to the shape of the half-tongue defect undergoing repair, making the best use of the tissue in the donor area after radical operations for tongue cancer and achieving good recovery of the function of the tongue while preserving as much of the tissue in the donor area as possible.
Sufficient tissue volume is very important during tongue reconstruction to avoid restricting the activity of the remaining tissue in the body of the tongue. Preservation of the donor site tissue and avoidance of invalid trauma are also important for the function and appearance of the donor sites. Currently, there are many methods used to locate the perforators, such as Doppler ultrasound, CTA, and MRA [16,17,18,19]. Because of the high cost and long scanning time required for MRA, we used three other methods to locate the perforator. A smartphone-compatible thermal imaging camera [10] was used in the new L-type flap group, Doppler ultrasound was used in 5 patients, and CT was used in 2 patients in the traditional flap group. Almost all of the positions of the perforating branches in the patients were consistent with the preoperative scan positions, except for one patient in the traditional group for whom a replacement of the perforator was not found during the operation. In addition, there were also patients who needed to undergo tissue clipping before donor suturing. We found that there was no significant difference between the infrared method and other methods in terms of the operation time and the accuracy in finding perforating branches Intraoperatively. Except for one patient who required a changed in the position of the flap, all of the flaps were obtained within 30 to 40 min.
In the L-shaped group, the recovery of the donor site was better than that of the traditional flap group. We sutured points E and B in pairs, and the rest of the points were sutured in sequence with the new pairs. This approach reduced the pressure required during placing the sutures, and the L-shaped design reduced the need for trimming the tissue before stitching. In our study, there were no cases of donor site invalid trauma in the L-shaped flap group. Hence, the L-shaped design was conducive to restoration of the donor site. In the traditional group, two patients had scar hyperplasia in the donor area, one of which affected leg movement. In contrast, 15 patients did not have invalid wounds in the donor area, and no patients had scar hyperplasia or other complications, such as motor and sensory impairment, at the postoperative follow-up.
The L-shaped defects in the donor area were easily closed and sutured. Inaddition to improvements at the donor area, our main innovation is in the flap design, which was selected according to the shape of the half-tongue defect. Compared with the traditional flap that adopts the shape of a circle and square, this flap has an L-shaped design, is better shaped to rebuild the tongue frenum, and has less adhesion and more mobility. In some patients who underwent traditional flap repair, the effect of the immediate repair was acceptable. However, because the flap shape was not completely aligned with the defect shape, it was found that the tip of the tongue was pushed towards the healthy side by the hypertrophic flap, the range of movement was limited, and the vocal and swallowing functions were affected.
The tip of the tongue is lined with fungous papillae containing taste buds that can detect sweetness, and the tip of the tongue is important for the pronunciation of certain words. Therefore, for tumours located in the middle and posterior lingual margins, we preserved the tongue tip in the safe area during the resection. After follow-up of the L-flap group, We found that there was no significant difference in the impact on taste, swallowing or speech between the two groups (P > 0.05), but it should be noted that all of the patients in the tip-preserving group retained their ability to taste on the tip of the tongue, while 3 patients with standard hemilingual resection had partial or complete loss of taste at the tip of the tongue (Additional file 7: Supplemental Table S4).
The MDADI was used to evaluate postoperative swallowing function [20,21,22,23,24]. The results show that the L-shaped group was superior to the traditional group in terms of dysphagia and language function.
In summary, the L-shaped flap can maximize the use of flap tissue to treat tongue defects, and L-shaped flap repair is associated with fewer complications in the donor and recipient areas and better postoperative recovery of swallowing and language functions than traditional flap repair. Due to the small number of cases in this study, more studies need to be conducted to verify the findings. In future work, we will increase the sample size and carry out additional research to improve postoperative functional recovery and reduce the occurrence of complications.