In 2021, type 2 diabetes was estimated to be 537 million worldwide (1), affecting one in every 11 adults (2). Diabetes and its complications pose a great threat to global health. Among them, approximately 19-34% of individuals with diabetes (3) will develop foot vasculopathy and neuropathy due to poor blood glucose control, leading to peripheral circulation blockage, foot deformities, and subsequent uneven pressure distribution on the feet. Coupled with diminished protective sensation, this cascade ultimately leads to skin ulceration, necrosis, and secondary infections. Simultaneously, due to compromised lower limb blood supply in patients and aggravated tissue damage from infections, this eventually leads to prolonged non-healing of diabetic foot ulcer (DFU) (4). Moreover, more than 15% of DFUs eventually necessitate amputation (3).

Although amputation surgery can enable patients to quickly return to normal life after surgery (5), it is associated with a high post-surgery recurrence rate, and the long-term prognosis is poor (6). Furthermore, the patients strongly desire limb preservation, making amputation surgeries difficult to carry out. The currently common clinical treatment methods include debridement, off-loading surgery, free flap transplantation, and vacuum sealing drainage. However, as these conventional methods often fail to enhance blood supply to lower limbs, patients’ ulcers often encounter challenges in achieving smooth healing. Although percutaneous transluminal angioplasty can restore patency in some major lower limb vessels, it cannot reconstruct the peripheral microcirculation, leading to limited effectiveness (7). At present, surgeons and DFU patients are faced with the problem that patients cannot achieve definite curative effects after paying huge medical expenses.

How to reconstruct or restore the blood perfusion to the distal limb is the key to the treatment of DFU. Wolff J (8) discovered that normal bone tissue possesses compensatory capability, allowing it to maintain dynamic metabolic equilibrium when subjected to external forces. Ilizarov G A (9) proposed the law of tension stress: giving suitable stretch stress to bone can stimulate the active growth of local tissues of the body, facilitate the restoration of microcirculation, subsequently augmenting local blood supply. Based on the above theory, Ilizarov G A designed and developed tibial cortex transverse transport (TTT) to address bone nonunion and found that TTT has the effect of promoting blood vessels and tissue regeneration (10). Subsequently, numerous researchers’ studies further affirmed the role of TTT in reconstructing local and distant tissue microcirculation and restoring blood supply (11). Hua et al. (12) took the lead in introducing TTT into the treatment of DFU, and reduced the corticotomy area of the original surgical method (5.0cm×1.5cm). Recent studies have shown that compared with conventional surgical treatment, TTT is more helpful for wound healing and limb salvage in DFU patients (13, 14). However, extensive osteotomy can result in excessive damage to the surrounding soft tissues, increasing the risk of bone flap necrosis and tibial fractures. Moreover, the angiogenic promotion effect does not intensify as the osteotomy area increases. In this study, to reduce the related complications caused by tibial osteotomy, we further reduced the osteotomy area by switching to two rectangular bone windows (1.5cm×1.5cm). The aim of this study is to assess the short-term effectiveness of modified TTT in managing DFU and to ascertain the occurrence of associated complications, thereby laying the groundwork for the surgical management of DFU.

DFU is not only impose a significant financial burden due to the high treatment costs but also present a formidable challenge in terms of management, frequently culminating in non-traumatic amputations. At present, it is generally believed that diabetic foot ulcer is the joint result of vascular and neurological diseases of the lower limbs. Eighty percent of DFU patients undergoing amputation are related to foot ischemia (19), and small artery occlusion is the main cause of foot perfusion defects (20). Due to the poor vascular condition of lower limbs and the limited self-repair ability of the body, it is difficult to heal the wound by local debridement and dressing change alone. Studies have shown that after standard surgical treatment (21) (including decompression, infection control, revascularization, and wound debridement), the healing rate of ulcers within 1 year is 77%, and the recurrence rate are 40%, 60%, and 65% in 1, 3 and 5 years, respectively (22). It can be seen that although conventional surgery can heal the wound, the postoperative recurrence rate and amputation rate are still high due to the lack of intervention for the ischemic condition of the lower limbs of patients. Hence, the central challenge in the treatment of DFU lies in the restoration of blood supply to the distal foot, enhancement of microcirculation, and optimization of oxygen metabolism in neighboring tissues, all while conducting comprehensive debridement of infected tissue.

In the 1980s, Ilizarov introduced the Principle of Tension Stress: giving an appropriate stretch stress to the bone can stimulate the active growth of local tissues in the body, promote the rejuvenation of microcirculation and increase local blood supply. Subsequently, Ilizarov proposed TTT based on this theory and took the lead in applying this technique to the clinical treatment of bone nonunion, which achieved good therapeutic results. Later, Hua and his colleagues implemented this approach in the management of DFU and observed the postoperative ulcer healing rate was 96.3% and the 2-year recurrence rate was 2.9% (23). The therapeutic efficacy of TTT is evidently superior to conventional surgical treatment approaches. Further research found that TTT can improve the expression levels of angiopoiesis related factors and tissue repair-associated factors in the patients’ serum, consequently promoting angiogenesis (24–26). In addition, TTT also has a stimulating effect on immune cells. TTT has the ability to facilitate the transition of M1 macrophages into M2 macrophages during the wound healing proliferation phase, thereby promoting the polarization balance of macrophages and the reconstruction of anti-inflammatory function, and accelerating wound healing (27). Furthermore, VEGF-A released by M2 macrophages can also promote angiogenesis, guiding Schwann cells along neovascularization and inducing axonal regeneration, thereby improving patients’ neurological function (27). In this study, the osteotomy site was in the tibial diaphysis, but it was manifested as healing of foot ulcers (13, 14, 23, 28). This suggests that TTT can elicit a systemic response. This phenomenon may be related to the mobilization of bone marrow stem cells by TTT, which promotes the migration of stem cells to the site of injury, restores vascular endothelial function, and promotes angiogenesis (29). In addition, the occurrence of systemic reactions may be related to circulating cytokines produced by mechanical stimulation (30). TTT can provide effective pain relief. The decrease in VAS scores in patients after surgery is attributed to the reestablishment of collateral circulation in the foot and the reduction of intramedullary pressure through fenestration, which alleviates vascular spasms.

The modified TTT procedure used two small rectangular bone windows of 1.5cm×1.5cm, which reduced the overall bone window area. Small bone windows have significant advantages, including avoiding extensive periosteal stripping, reducing necrosis of free bone fragments, and maximizing the tibial stability and biomechanical integrity. The average incidence of postoperative tibial fractures using the traditional large area of osteotomy method was 2.6% (31). However, during the three-month follow-up period, no patient in our study experienced tibial fracture. Despite our follow-up period was relatively short, the complications related to TTT predominantly occur between 3 to 12 weeks postoperatively (31). Therefore, our record of complication rates remains valid. In comparison to the conventional osteotomy method, patients who underwent the modified TTT procedure had a significantly lower incidence of postoperative tibial fractures. This finding underscores the importance of reducing the dimensions of the osteotomy area is one of the key factors in preventing fractures, which is consistent with the views expressed by Wang et al. (31). It should be emphasized that the size of the tibial bone window is not entirely determined and can be appropriately reduced for patients with a shorter stature. In addition, due to the smaller osteotomy area, patients can engage in weight-bearing activities shortly after surgery, which serves to mitigate the risk of deep vein thrombosis formation in the lower limb. The postoperative ulcer healing rate in patients who underwent the modified TTT was 95.83%, and there was an increase in the ABI of the patients after treatment, consistent with findings from previous studies (13, 14, 23, 28). This indicates that reducing the size of the bone windows does not appear to weaken the subsequent traction’s stimulating effect on the periosteum, which is consistent with the findings of Kostopoulos et al.’s study (32). These results tentatively indicate the potential application of this technique for tissue regeneration therapy in smaller bone areas, such as the craniofacial region. However, further experimental studies are also necessary to validate these findings.

By transporting the bone blocks, the foot microcirculation and inflammatory balance were reconstructed. However, the efficacy of modified TTT should not be overstated. At the end of the follow-up of this study, there were still 4 patients whose wounds had not healed completely, and 3 patients underwent amputation due to the progression of local infection. And patients with DFU remain compromised static balance and alterations in plantar load distribution of the lower limbs following surgery. As can be seen from these adverse cases, DFUs are the result of multiple factors and cannot be expected to be completely cured by surgery alone. Thus, attention to patients’ self-management is crucial. Additionally, bone transport should be accompanied by thorough debridement, professional wound care, anti-infection treatment, static standing balance training, and blood glucose control.

It is worth noting that modified TTT is not a universal solution for all patients with DFU. Patients with mild ulcers often heal with conventional treatment and do not need modified TTT treatment. The effectiveness of TTT appears to be limited in individuals with severe or complete occlusion of the main vessels supplying the ankle. This limitation can be attributed to factors such as oxidative stress, impaired endothelial function, and regeneration defects commonly observed in diabetic patients. These factors collectively pose challenges for the regeneration and remodeling of large blood vessels through TTT, and the role of TTT in the reconstruction of middle and large vessels still requires further investigation.

The primary limitations of this study encompass the following aspects: Firstly, one major limitation of this study is the retrospective design of the study. Secondly, given the relatively recent emergence of this technique, our research was designed to evaluate the short-term therapeutic outcomes of modified TTT. In the future, we will conduct long-term large-sample controlled clinical trials on the basis of the original research to further clarify the therapeutic effect of modified TTT, and provide more reliable basis for limb salvage treatment of DFU.

Modified TTT can effectively improve the foot microcirculation of patients, promote wound healing, and significantly reduce the amputation rate. After reducing the osteotomy area, the incidence of local tibial complications was reduced. In the future, more large-scale clinical trials are needed to further evaluate its efficacy. In addition, related experiments based on modified TTT are needed to explore its local biomechanical characteristics and related mechanisms.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by Beijing Chaoyang Hospital Human Research Ethics Committee. The studies were conducted in accordance with the local legislation and institutional requirements. The ethics committee/institutional review board waived the requirement of written informed consent for participation from the participants or the participants’ legal guardians/next of kin because Beijing Chaoyang Hospital Human Research Ethics Committee has confirmed that the need for consent to participate was deemed unnecessary according to national regulations and approved to access the patient date used in this research.

JL: Conceptualization, Formal analysis, Investigation, Methodology, Writing – original draft. XY: Writing – original draft. ZX: Data curation, Writing – original draft. YW: Methodology, Writing – original draft. FP: Data curation, Writing – original draft. LZ: Data curation, Formal analysis, Writing – original draft. ML: Validation, Writing – original draft. MS: Formal analysis, Writing – original draft. XD: Methodology, Supervision, Writing – review & editing. HZ: Data curation, Supervision, Writing – review & editing.