Abstract
Background:
The true incidence and primary predictors of foot compartment syndrome remain controversial. Our aim was to better define the overall incidence of foot compartment syndrome in relation to the frequency and location of various foot injuries. We hypothesized that (1) the incidence would increase in proportion to the number of anatomic locations of injury, (2) the incidence would be higher in association with hindfoot and crush injuries compared with any other injury categories, and (3) not only would the incidence associated with calcaneal fractures be lower than the often quoted 10% but foot compartment syndrome would also be fairly uncommon after such fractures.
Methods:
The National Trauma Data Bank was used to identify patients who had undergone a fasciotomy for the treatment of isolated foot compartment syndrome. Strict inclusion and exclusion criteria were used to identify only patients with foot injuries who had undergone fasciotomy for foot compartment syndrome.
Results:
Three hundred and sixty-four patients with an isolated foot compartment syndrome were identified. The highest incidence of foot compartment syndrome was seen in association with a crush mechanism combined with a forefoot injury (18%, nineteen of 106), followed by an isolated crush injury (14%, twenty-three of 162). Only 1% (thirty-two) of 2481 patients with an isolated calcaneal fracture underwent fasciotomy. An increase in the number of anatomic locations of injury did not appear to correspond to an increased incidence of foot compartment syndrome.
Conclusion:
Our results demonstrate that injuries involving a crush mechanism, either in isolation or in combination with a forefoot injury, should raise suspicion about the possibility that a foot compartment syndrome will develop.
Level of Evidence:
Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.
Trauma to the foot has long been recognized as a cause of foot compartment syndrome, a serious complication first described by Bonutti and Bell1 in a 1986 case report and later by Myerson in 1987 and 19882,3. Untreated or delayed management of foot compartment syndrome can lead to substantial long-term disability, so a prompt diagnosis is required. A high index of suspicion is often necessary for patients at risk for developing foot compartment syndrome on the basis of the history and physical examination findings. To our knowledge, a stratification of injury patterns in the foot corresponding to the relative risk of foot compartment syndrome has not been defined. The inability to clearly predict patients at risk necessitates more reliance on serial physical examinations and has promoted a more reactive, rather than a proactive, clinical approach.
Foot compartment syndrome should be suspected after any substantial foot injury. As pointed out by Myerson and Manoli, the diagnosis should be based foremost on the development of disproportionate or uncontrollable pain in the presence of typical physical findings such as severe swelling, ecchymosis, pain with passive motion of the toes, decreased sensation, or obvious structural deformity2-4. If time permits, intracompartmental pressure measurements are recommended to confirm the diagnosis4,5. Abnormal clinical examination findings and elevated compartmental pressure measurements are useful and relatively reliable diagnostic tools when used together. Elevated pressure measurements alone, however, may not accurately reflect the presence of compartment syndrome, particularly when the physical examination findings do not correlate with these measurements6.
To date, calcaneal fracture is the only specific type of foot injury that has a clearly established relationship with an evolving foot compartment syndrome (a 10% incidence4), although high-energy crush injuries have also been associated with compartment syndrome1,7-9. Foot compartment syndrome has been documented after other injury types such as Lisfranc fracture-dislocations and multiple metatarsal and phalangeal fractures, but, as is the case for crush injuries, the actual incidence associated with these other injury patterns remains poorly understood8. Patients can also develop concurrent compartment syndrome of the foot and leg in the presence of multiple lower-extremity fractures as a result of communication between the calcaneal compartment and the deep posterior compartment of the leg10,11. Open fractures do not preclude the possibility of foot compartment syndrome12.
The most common sequelae of a missed foot compartment syndrome are intrinsic minus claw toe deformities, due to either intrinsic muscle weakness or contracture of the quadratus plantae within the calcaneal compartment1,9,11,13-15. Following a compartment syndrome, cavus deformity may also result from fibrosis of the plantar foot structures or a concurrent compartment syndrome in the leg16. Currently, the specific patterns of foot injury that pose the highest risk of foot compartment syndrome remain unknown. Our purpose in performing this study was to better define the overall incidence of foot compartment syndrome in relation to the frequency and location of various foot injuries.
We hypothesized that (1) the incidence of foot compartment syndrome would increase in proportion to the number of anatomic locations of injury involved, (2) the incidence of foot compartment syndrome would be higher in association with hindfoot and crush injuries compared with other injury categories, and (3) not only would the incidence associated with calcaneal fractures be lower than the often quoted 10% but foot compartment syndrome would also be fairly uncommon after such fractures.
The primary data source for this study was the National Trauma Data Bank (NTDB), which is published by the American College of Surgeons and serves as a public resource to enhance trauma care through research. We used version 7.0, which contains data from 2002 through 2008, to identify a target population of patients with isolated foot injuries or fractures who had undergone fasciotomy for the treatment of a compartment syndrome of the foot.
Several ICD-9 (International Classification of Diseases, Ninth Revision) diagnostic codes were used to search the data bank to identify the at-risk target population. The AppendixAppendix lists these codes, which include all patterns of foot injury that may result in compartment syndrome. The codes were then separated into four categories on the basis of either the anatomic location of injury or whether the injury was caused by a crush mechanism. While ICD-9 codes 958.90 and 958.92 identify patients with compartment syndrome and traumatic compartment syndrome of the lower extremity, respectively, these codes were not populated in the NTDB. As an alternative, the procedure code 83.14 (defined in the NTDB as “fasciotomy”) was used to determine which patients in the cohort underwent fasciotomy of any extremity, presumably for the diagnosis of compartment syndrome.
Since the 83.14 code does not discriminate between anatomic sites of fasciotomy, the procedure codes involving injuries to the femur, tibia, or fibula that may have been associated with compartment syndrome were considered exclusion criteria in our cohort in order to isolate foot fasciotomies. This step eliminated patients who had thigh or leg compartment syndrome or who might have developed foot compartment syndrome as a result of injury to the tibia or fibula. Procedures in the upper extremities that might have been associated with upper-extremity compartment syndrome requiring fasciotomy were also eliminated. The AppendixAppendix summarizes the exclusion procedure codes that were used to isolate patients who had had fasciotomy only of the foot for a presumed foot compartment syndrome.
Patient demographics such as age, sex, race, mechanism of injury, Injury Severity Score (ISS), length of hospital stay, and time of arrival in the emergency room were recorded. The regional location of the hospitals in the United States (Northeast, South, Midwest, and West) and the types of hospitals (teaching versus nonteaching and trauma-level designation) were also recorded.
Two cohorts were generated for comparison: (1) patients with foot injuries who had undergone a fasciotomy for a presumed foot compartment syndrome and (2) patients with similar injury patterns who had not undergone a fasciotomy. Additionally, an attempt was made to determine any effect of patient demographics and hospital factors on the fasciotomy rate.
Statistical Analysis
Basic descriptive statistics means, standard deviations, and rates associated with the independent and foot compartment syndrome outcome variables were used to describe the sample and to summarize the univariate relationships between foot compartment syndrome and the selected predictors and covariates.
Differences in foot compartment syndrome rates were evaluated with use of Poisson regression with log link modeling using the GENMOD and GLIMMIX procedures available in SAS 9.2 software. These models produce unadjusted foot compartment syndrome rates and the relative risk of foot compartment syndrome when demographic factors are evaluated one at a time and produce adjusted foot compartment syndrome rates and relative risks of foot compartment syndrome when all demographic factors are considered in the model simultaneously.
Source of Funding
There was no external funding source for this study.
More than 1.1 million entries in the National Trauma Data Bank, version 7.0, were screened. The total number of patients with isolated foot injuries in the NTDB was 18,676 as determined by our inclusion and exclusion criteria. Of these patients, 364 (overall incidence, 2%) had a fasciotomy of the foot for a presumed foot compartment syndrome, based on procedure code 83.14 and with use of our exclusion criteria.
The average age of patients undergoing fasciotomy for foot compartment syndrome was thirty-eight years. Most patients sustaining foot injuries were male (68%, 12,701 patients) and white (71%, 13,272 patients). The average ISS for the cohort was 10.7 ± 4. The mean length of hospital stay was 7.3 days, and the mean time in the intensive care unit was two days. In the cohort of patients undergoing fasciotomy, 83% were male and 71% were white.
Fifty-nine percent of the patients had the fasciotomy in hospitals in the Northeast and South (34% and 25%, respectively), 23% had it in the Midwest, and the remainder had it in the West.
Fasciotomy Rates Based on Categories of Injury
Of the 18,676 patients with isolated foot injuries, 8749 (47%) had involvement of the forefoot. The number of patients with an isolated forefoot injury was 6714 (36%), which was the largest group in the forefoot category (6714 of 8749). Isolated forefoot injuries resulted in a fasciotomy rate of 1.6%.
Hypothesis 1: Individual fasciotomy rates following injuries of the forefoot, the midfoot, and the hindfoot were comparable. Combining the anatomic locations of injury (levels of involvement) did not appear to increase the rates of fasciotomy (Table I). For example, only 4% (eleven) of the 279 patients with combined forefoot, midfoot, and hindfoot injuries underwent a fasciotomy for a presumed foot compartment syndrome, whereas 6% (forty-two) of the 722 patients with combined forefoot and midfoot injuries underwent such a fasciotomy.
Hypothesis 2: A crush mechanism of injury was one of the most important factors in the development of a foot compartment syndrome. Of the 162 patients with an isolated crush mechanism, 14% (twenty-three) underwent a fasciotomy for a presumed foot compartment syndrome. Furthermore, 18% (nineteen) of the 106 patients who had a forefoot injury combined with a crush mechanism of injury underwent a fasciotomy for a presumed foot compartment syndrome (Table I). However, less than 1% (sixty-seven) of the 7008 patients with an isolated hindfoot injury underwent such a fasciotomy.
Hypothesis 3: Of the 2481 patients with an isolated calcaneal fracture in the entire cohort, only 1% (thirty-two) underwent a fasciotomy for foot compartment syndrome.
Injury Patterns in the Fasciotomy Group
The most common injury pattern in patients undergoing fasciotomy involved the forefoot (Table II). Almost one-third (109; 30%) of the patients who underwent a foot fasciotomy in this study had a noncrush injury isolated to the forefoot. If the injury category (location of fracture or injury as defined in the AppendixAppendix) included at least the forefoot, along with other areas in the foot, this rate increased to almost two-thirds (213; 59%) of all patients treated with a fasciotomy. Combined injuries involving both the forefoot and the midfoot were present in 12% of the fasciotomy group. Sixty-two percent of the injuries in the forefoot associated with a foot compartment syndrome were metatarsal fractures (Table III). An isolated midfoot injury was present in 4% (fourteen) of the 364 patients who underwent fasciotomy, and an isolated hindfoot injury was present in 18% (sixty-seven) of these 364 patients. Furthermore, 48% (thirty-two) of the sixty-seven isolated hindfoot injuries in patients who developed a foot compartment syndrome were calcaneal fractures (Table III).
General crush injuries represented another significant predictor of foot compartment syndrome requiring fasciotomy. Fifty patients (14%) in the fasciotomy group had a crush mechanism as part of their injury pattern. Of these patients, twenty-three (6%) had an isolated crush injury with no fractures in the foot.
Patients with injury patterns resulting in fasciotomy were compared with those with similar patterns who did not undergo fasciotomy. The relative risk of a patient undergoing fasciotomy when he or she had a forefoot injury, compared with one who did not have a forefoot injury, was 1.5, when adjusted for significant patient and hospital variables as indicated below. The adjusted relative risk of a crush mechanism leading to fasciotomy was 1.7. The relative risk of a patient with a hindfoot injury undergoing fasciotomy was 1.9, when similarly adjusted, but an isolated calcaneal fracture did not significantly increase the risk of a fasciotomy (relative risk = 0.55).
Patient and Hospital Variables
Age, sex, and the region of the country, when unadjusted and adjusted for each other, all individually affected fasciotomy rates. The length of stay in the hospital differed between patients who underwent a fasciotomy and those who did not when stratified for similar injury patterns. These differences were all significant (p < 0.05), as demonstrated in Table IV. Certain patient and hospital factors such as race, time of arrival into the emergency department, ISS, and type of hospital did not significantly affect fasciotomy rates (p > 0.1), with the number of patients studied.
The true incidence and primary predictors of foot compartment syndrome remain unknown. Foot compartment syndrome has been reported to develop in approximately 10% of patients who have sustained a calcaneal fracture4. Other injury patterns such as Lisfranc fracture-dislocations and metatarsal fractures have also been reported to cause foot compartment syndrome8. Ojike et al., in a recent review of the literature involving thirty-nine patients, reported that crush injury to the foot was the most common cause of foot compartment syndrome7. We conducted the present study to better define the overall incidence of foot compartment syndrome in relation to the frequency and location of various foot injuries to increase surgeons’ awareness of and improve their ability to anticipate, diagnose, and appropriately manage patients at risk for foot compartment syndrome. To our knowledge, this study represents the largest reported series of patients treated with fasciotomy for presumed foot compartment syndrome.
Our first hypothesis stated that an increase in the number of anatomic locations of injury would result in higher rates of compartment syndrome. This was not supported by the results as indicated in Table I. For example, the incidence of fasciotomy associated with combined forefoot and midfoot injuries was higher than that associated with a combined forefoot, midfoot, and hindfoot injury pattern.
Our second hypothesis stated that the incidence of foot compartment syndrome following crush injuries would be higher than that in any other category of injury. Our data supported this hypothesis. Patients with an isolated crush injury, or a crush injury in combination with a forefoot injury, had the highest rate of fasciotomy. Hence, foot crush injuries should be considered an important predisposing factor in the development of foot compartment syndrome; the presence of a crush mechanism almost doubles the relative risk of developing a foot compartment syndrome. These injuries should raise the vigilance of the treating physician regarding the development of foot compartment syndrome in a trauma patient. These results echo those of Ojike et al.7, who reported that a crush mechanism was the major factor predicting the development of compartment syndrome. However, the number of patients with combined midfoot and crush injuries and the number with combined forefoot, midfoot, and crush injuries were not large enough for us to draw any applicable conclusions despite the high rates of fasciotomies (Table I).
Our second hypothesis also stated that the incidence of foot compartment syndrome after hindfoot injuries would be higher than that after an injury in any other zones. The data did not support this hypothesis. Isolated hindfoot injuries comprised a significant percentage of the injury patterns in the fasciotomy group (18%), but only 1% of all hindfoot injuries were followed by the development of a foot compartment syndrome. This rate was lower than those in other injury groups. Also, isolated injury to the forefoot accounted for almost one-third of the foot compartment syndromes identified in this study. We theorize that this finding may be related to disruption of the intermetatarsal arterial branches, which exit from dorsal to plantar through the interosseous space, leading to extensive bleeding, swelling, and increased intracompartmental pressures. Additional study will be required to investigate this hypothesis. Another explanation could be that, from an anatomic perspective, the fascial compartments in the forefoot are more prone to the development of compartment syndrome by virtue of structure or location.
Our third hypothesis was that the incidence of foot compartment syndrome associated with calcaneal fractures would be lower than the often-quoted 10% and that foot compartment syndrome would be fairly uncommon following these fractures. We found that only 1% of the patients with an isolated calcaneal fracture underwent fasciotomy for a presumed foot compartment syndrome, which supported our hypothesis. This rate is much lower than the 10% rate reported by Myerson and Manoli4. Furthermore, calcaneal fractures represented <50% of the hindfoot injuries in the fasciotomy group. This suggests that other injuries in the hindfoot, as listed in the AppendixAppendix, should also raise suspicion about foot compartment syndrome in a symptomatic patient.
There are several limitations of this study. Before we began the study, the NTDB was queried with use of ICD-9 codes 958.90 and 958.92 (compartment syndrome and traumatic compartment syndrome of the lower extremity, respectively) to determine the incidence of patients who had a diagnostic code for compartment syndrome documented in the data bank. One limitation of the study was that we could not find any patients with codes for these diagnoses, which we believe was a reporting error and a limitation of the data bank. Hence, the procedure code 83.14 (defined by the NTDB as fasciotomy) was used as a surrogate to isolate patients of interest. Patients with possible fasciotomy procedures in other parts of the body were eliminated with our exclusion criteria as documented in the Materials and Methods section. We then made the assumption that the remaining patients with diagnoses of isolated foot injury who had undergone a fasciotomy procedure did so for a foot compartment syndrome.
A second limitation of the study is that the results that we document are based on data obtained from the NTDB and thus depend on the quality of data entered into that database. Users cannot independently verify the accuracy of the data or confirm compliance with reporting. While we identified a large cohort of patients with foot injuries, we were able to isolate only 364 who had had a foot fasciotomy performed for a foot compartment syndrome on the basis of our stringent exclusion criteria. We believe that this may represent under-reporting and/or nonreporting of data of patients from the various participating institutions who developed foot compartment syndrome following foot injuries. Koval et al.17 documented this issue previously in a study in which they utilized the same data bank.
A final limitation of this study is that some multiply injured patients with concomitant foot injuries resulting in foot compartment syndrome might have been eliminated on the basis of our exclusion criteria. This is reflected by the majority of our patients having a low ISS score. We believe, nonetheless, that we managed to effectively isolate patients with foot compartment syndrome resulting from foot injuries only.
In conclusion, our study shows that a crush mechanism of injury, either in isolation or in combination with injury to other areas of the foot such as the forefoot, results in the highest incidence of foot compartment syndrome requiring fasciotomy. Combined injuries to the forefoot and midfoot are also risk factors for the development of foot compartment syndrome. A better understanding of these relationships should help the treating physician predict and diagnose foot compartment syndrome in patients with these injury patterns.
Tables showing the diagnostic codes that defined the cohort of interest and the NTDB procedure codes that served to exclude patients from the foot fasciotomy cohort are available with the online version of this article as a data supplement at jbjs.org.
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Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.