This study found an association between ACS and age, sex, mechanism of injury, associated contiguous skeletal injury, and presence of a distal intra-articular fracture. The study did not highlight any soft tissue condition (closed fracture, open fracture Gustilo type 1, open fracture Gustilo type 2 and 3) as associated with ACS occurrence when tibia fractures were considered as a whole. However, after stratification by types of fractures, ACS occurrence was associated with open Gustilo type 2 and 3 injuries in proximal intra-articular fractures only.
The ACS occurrence rates found in this study fall within previously reported rates in the literature, which ranged from 0.7–12% for tibial plateau fractures (even as high as 53% for some higher-energy subgroups) [8–16], from 3–11.5% for tibial shaft fractures [8, 12, 13, 17–19], and from 2–12.5% for pilon tibial fractures [8, 13, 20]. For this reason, it can be assumed that the study cohort closely represents the habitual spectrum of tibia fractures, and that its results might be generalized to most tibia fracture patients.
In the past, there was a wrongly reassuring dogma assuming that an open fracture would protect from the occurrence of ACS by relieving the pressure inside the muscle compartments through the fascial tears. This was shown to be incorrect, as some studies reported ACS occurrences after open tibia fractures [11–13, 16–18, 21]. In the analysis without stratification by fracture type, we did not find any association between ACS occurrence and soft tissue condition. This is mainly due to the 120 distal intra-articular fractures included in the cohort, which had a significantly lower risk of ACS occurrence than other fracture types (3.3% vs. 10.4%; p = 0.014) and mitigated differences in the overall results. Indeed, our results showed that distal extra-articular fracture might be a protecting factor against ACS occurrence, when compared to a more proximal location. This finding might be explained by the fact that the distal tibia is surrounded by a less bulkier muscle mass, and that the energy released during trauma is transmitted into tendinous soft tissues rather than muscle, thus less likely leading to the potential development of ACS [19].
In the analysis by fracture types, ACS occurrence was associated with open Gustilo type 2 and 3 injuries in proximal intra-articular tibia fractures only, with a weak significance level (OR 3.39 (95% CI 1.01–11.42); p = 0.048). One previously published paper reported a significant linear association between occurrence of ACS and severity of open fracture in the univariate analysis, which failed to be confirmed after adjustment according to age and sex [11]. Another paper did not show any association between open fracture and ACS even in the univariate analysis [16]. Due to this weak evidence, one cannot definitively assume that an open skin lesion is associated with a higher risk of ACS occurrence in case of proximal intra-articular tibia fractures. However, the physician in charge should be aware of these findings, and should actively look for signs and symptoms of ACS development when treating open fractures.
No association with closed or any type of open injuries was highlighted for extra-articular tibia fractures. This means that open tibial shaft fracture was recognized neither as a risk factor nor as a protecting factor for ACS occurrence. This finding is in line with previously published research [13, 17–19]. However, two older publications recognized open tibial shaft fractures as positively associated with the occurrence of ACS, with open fracture severity directly proportional to ACS incidence [5, 21]. In this fracture type also, the physician in charge should be aware of these findings, and should actively look for signs and symptoms of ACS development.
There were not enough ACS cases (four) among distal intra-articular tibia fractures to draw any conclusions. The association of ACS with open fractures of the pilon tibial has not been investigated in a well-conducted study yet. To the best of the authors' knowledge, there is only one case-report available in the literature citing increased soft tissue damage as a potential risk factor for ACS occurrence after pilon tibial fracture; however in this paper, this statement was not evidence-based and it was not specified if increased soft tissue damage included open fractures [7].
Despite being the largest series to date analyzing the association between soft tissue injury and the development of ACS in tibia fractures, this paper suffers several limitations: 1) this study was prone to several biases inherent to its retrospective design, and to some inexactitude in patients’ charts that were reviewed to extract variables of interest; 2) ICP measurements, which would have been the gold standard to diagnose or exclude ACS, were performed only on a subset of patients, thus introducing the possibility of false positive or false negative diagnosis; however, we did not find any clinical records suspect of late ACS sequelae in the charts of patients that were not diagnosed with ACS, and every patient who underwent fasciotomy had pathological ICP values before fasciotomy, and/or presented muscle bulging or suffering at the time of fasciotomy; 3) the tibia fracture stratification that was used does not strictly follow the AO/OTA classification; however, we felt that an AO/OTA 41A2 or A3 fracture was closer to an AO/OTA 42 fracture than to an AO/OTA 41B or C fracture in terms of fracture line anatomy and absence of articular involvement, and we choose to stratify fractures following this method.