To the present knowledge, the present study represents the first attempt to develop and validate a nomogram specifically tailored to predict the risk of HCP in patients with isolated pilon fractures. The present investigation reveals an HCP incidence of 11.57%, with multifactorial analysis identifying several independent risk factors for this complication, including BMI, DVT, FB, use of dehydrating agents, duration of limb immobilization, and SII. The nomogram, constructed based on these six factors, demonstrated commendable performance metrics, achieving an AUC value of 0.842 (95% CI: 0.7931–0.8907), with a sensitivity of 72.1% and specificity of 87.8%. Importantly, both internal and external validation procedures underscored the robust consistency and reliability of this predictive model.

In a retrospective study of 1125 patients with tibial diaphyseal fractures, Babak Shadgan et al. found that the incidence of ACS was 7.73%, which was considerably lower than the 11.57% incidence of HCP in pilon fracture patients in the present study [17]. On one hand, such findings could be attributed to the inclusion of more patients due to the broader diagnostic criteria of HCP compared to ACS. On the other hand, it is plausible that the soft tissue surrounding the ankle joint is inherently dense, potentially predisposing it to the development of high compartment pressures following fracture. At the same time, in the TQP database, Carl Laverdiere et al. found that 0.7% of all the foot fractures required fasciotomies [18]. However, ankle fractures were not included in the study.

In contrast to simple ankle fractures, pilon fractures typically occur due to high-energy trauma involving substantial axial force. This force often results in the bursting of the tibial plafond over the talus [19]. Many physicians contend that high-energy trauma should be considered a risk factor for ACS. This belief stems from the understanding that the extensive soft tissue damage associated with high-energy transfer is likely to lead to increased necrosis, hypoxia, lactic acidosis, capillary leakage, and interstitial fluid accumulation, culminating in compartment swelling [20]. Therefore, this study specifically focused on patients with pilon fractures resulting from high-energy trauma to the ankle. Through clinical data analysis, it confirmed the decompressive effect of FB on HCP and, for the first time, identified the SII as a potential key indicator for predicting the development of HCP.

The popular belief is that ACS is more likely to occur in young males [17]. Park et al. [21] identified age as a significant risk factor, proposing that young males, owing to their typically larger muscle bulk, may also possess thicker fascia and inter-muscular septa, attributed to a higher collagen content. As such, even a slight increase in compartment volume could lead to a rapid rise in pressure. However, the present study findings contradict this assumption, revealing that women were equally susceptible to developing HCP following pilon fractures.

Undoubtedly, injuries affecting multiple anatomical sites can significantly disrupt the body’s homeostasis, triggering what is often referred to as a “chemical storm” characterized by systemic inflammatory response syndrome (SIRS) or compensatory anti-inflammatory response syndrome (CARS). Endothelial damage has been closely associated with the occurrence of ACS in such scenarios [22]. At the same time, SII was also identified as a significant risk factor for HCP in the present study. Several scholars have found that a single cell component or blood biochemical index does not have the optimal predictive ability. Therefore, the combined ratio of various indicators, such as neutrophil to lymphocyte ratio and platelet to lymphocyte ratio, has garnered significant attention in research. These composite indicators may offer greater value than individual cellular components or biochemical markers. SII, as a novel marker, incorporates lymphocytes, platelets, and neutrophils, enabling a more balanced and comprehensive evaluation of the immune and inflammatory response within the human body. Consequently, it holds more predictive value compared to previous single or dual-cell component ratios [23]. SII has unique advantages over other biomarkers, such as neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and C-reactive protein. Studies have indicated that SII appears to be less influenced by fluid load compared to the neutrophil to lymphocyte ratio and platelet to lymphocyte ratio [24]. Monitoring changes in cytokines in FB fluid and plasma, it was observed that different cytokine activity states occurred during different periods by Hou’s team. As HCP develops, there is a shift in the systemic inflammatory state from increased to decreased [25]. Given that most patients included in the present study were in the acute phase of trauma, it was observed that higher SII can serve as one of the indicators for early prediction of HCP. Such findings align with the results of previous studies.

While there is a risk of ACS associated with any form of pilon fracture, an open fracture is commonly perceived to have effectively decompressed the compartments, thus reducing the likelihood of ACS occurrence. The auto-decompression phenomenon observed in high-grade open fractures is hypothesized to create an effect akin to that of a fasciotomy [15, 20]. Nonetheless, the present study shows that ACS is just as likely to occur in open fractures as it is in closed fractures. These results are similar to those found by Park et al. [21].

In addition to SII, BMI, DVT, duration of limb immobilization, absence of FB, and absence of dehydrating agents were also considered as potential risk factors.This selection was driven by the dense nature of the tissue around the ankle joint, with each factor possibly affecting the pressure within the local fascial compartment. Hou’s team conducted an in-depth study of HCP. Their findings suggested that fracture blisters might signify a decrease in intrafascial pressure following traumatic injury. This pressure decrease can prevent the harmful cycle of ischaemia and hypoxia triggered by further elevation of intrafascial pressure, thus averting the development of severe intrafascial hypertension [26,27,28]. Simultaneously, Varela et al. reported that blister formation serves as one of the mechanisms for alleviating abnormally elevated pressure within a compartment [29]. In instances of high-energy fractures, DVT plays a significant role in impaired circulation, consequently elevating pressure within the fascial compartment and heightening the likelihood of HCP. Additionally, Due to the increased subcutaneous adipose tissue, individuals with obesity are at a higher risk of developing HCP following limb injuries compared to those with normal weight; this also explains why a high BMI is considered one of the risk factors for HCP.Prolonged use of limb fixation methods, including plaster casts, bandages, and splints, can result in fascial compartment compression and a decrease in content volume, which are recognized as common risk factors for HCP [30].Conversely, the use of dehydrating agents may alleviate pressure within the fascial cavity, thereby reducing the incidence of HCP. Research indicates that the application of dehydrating agents can markedly enhance the prognosis for patients with ACS [31].

Nomograms, commonly utilized in clinical predictive model research [32,33,34,35], leverage the predictive value of individual risk factors to present final predictions visually. In the present study, a nomogram aimed at aiding clinicians in assessing the risk of HCP in recently admitted patients with pilon fractures was successfully developed and validated. The nomogram incorporates six predictors derived from routinely collected clinical data, readily available within a few hours of admission. The utilization of the nomogram expedites the identification of patients at an elevated risk of HCP. Clinicians can readily ascertain the predictive probability for each variable by drawing vertical lines corresponding to the variable outcomes and then aggregating these values to calculate the associated risk.

The present study offers notable scientific insights, including the formulation of a nomogram and its thorough validation through internal assessments. Nevertheless, it is crucial to recognize several limitations. Firstly, the present study’s retrospective nature inherently introduces the risk of selection bias, which cannot be avoided. Secondly, certain variables that could potentially influence the incidence of HCP were either not recorded or not measured, such as the duration of limb immobilization. Thirdly, there is an urgent need to clarify the diagnostic criteria for HCP. Although the STIC Monitor was used in the present study, significant discrepancies in measured results of fascial compartment pressure persisted among patients. Additionally, the clinical data used to construct and validate the nomogram was derived from a single healthcare centre. As such, caution is warranted when generalizing the findings to more diverse populations and regions. It is imperative to underscore the importance of prospective observational studies that encompass data from multiple centres. Such an approach would facilitate a more comprehensive evaluation of the clinical applicability of the proposed model.