Introduction

Compartment syndrome is defined as an increased pressure in a space surrounded by non-expandable structures. Various body regions, including the visceral cavity as well as upper and lower extremities can be affected. While an acute compartment syndrome (ACS) represents an emergency requiring immediate surgical release, a chronic compartment syndrome develops over a longer time period. The ACS of the foot represents a severe complication following fractures, soft tissue trauma or vascular lesions resulting in a reperfusion injury [1]. Immediate dermatofasciotomy to release the affected compartments is required to preserve anatomic structures and thus function of the extremity. Without adequate therapy long-term sequelae consist of contractures due to muscle necrosis and consecutive conversion to fibrosis leading to impaired function [1].

The current understanding on the pathophysiology of compartment syndromes includes two complementary theories: “arterio-venous gradient theory” as well as an “ischemia/reperfusion syndrome”. Increasing intracompartmental pressure leads to decreased blood flow as well as supply and consequently tissue oxygen saturation. Decreased oxygen delivery results in a metabolic deficit and consequently tissue necrosis.

While compartment syndrome of the lower leg was already described in 1958 [2], ACS of the foot was only mentioned in case reports [3, 4] until the detailed description and therapeutic intervention were published in 1988 [5]. Although the overall incidence is low, a high rate of missed ACS of the foot following calcaneal fractures was described [5] suggesting a relevant underestimation of the true incidence of ACS. A high level of suspicion for the development of ACS of the foot is required in patients with crush injuries to the lower extremity with or without fractures [6].

The aim of the current study was to describe injury mechanisms leading to and treatment of ACS of the foot.

Methods

Study design

A retrospective analysis of all patients treated at a level I trauma center between 1 December 2000 and 30 September 2007 was performed. All patients diagnosed and/or treated with an acute compartment syndrome of the foot were identified using our hospital information system. The study was approved by the university ethical committee.

Mechanism of injury, additional injuries and clinical course

Patients’ records were analyzed and mechanisms of injury as well as concomitant injuries were documented. Injury distribution was determined with the 2005 revised edition of the Abbreviated Injury Scale (AIS) and summarized to the Injury Severity Score (ISS) reflecting the overall injury severity as described earlier [7].

Neurological and vascular status on admission as well as treatment and complications during the clinical course was evaluated.

Statistical methods

The data were analyzed using the statistical package for the social sciences (SPSS; version 19; IBM Inc., Somers, NY, USA). Incidences are presented with counts and percentages, while continuous values are presented as mean ± standard deviation (SD).

Results

Patient’s characteristics

In the current study, 31 patients (33 feet) with complete data sets were included; 21 were males. Mean age of included patients at time of injury was 33.8 ± 16.9 years. In seven patients, a work-related injury occurred with employer’s liability insurance coverage. One patient was transferred to our medical center 1 day after an emergency surgical release in an external institution.

While the majority of included patients suffered from a high-energy injury mechanism approximately 20 % of included patients developed an ACS of the foot following a low-energy accident. The mechanisms of injury are illustrated in Fig. 1.

Fig. 1
figure 1

Mechanism of injury

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Local and concomitant injuries

All but one of included patients developed an ACS of the foot due to a local fracture. In one patient with a diaphyseal tibial fracture an ACS of the lower leg and foot developed. An open fracture was present in one case. In 17 patients, the ACS developed due to a single injury. Multiple injuries with a mean ISS of 19.5 ± 11.0 were diagnosed in 14 patients.

The right foot was affected in 13 cases; an ACS was diagnosed on the left side in 16 patients. Two patients had an ACS at both feet.

In 22 patients, a fracture of the tarsus was present, forefoot fractures were diagnosed in 4 and ankle fractures in 7 patients. A combined injury was seen in seven cases, nine patients suffered from a luxation fracture.

Diagnostics and therapy

An acute compartment syndrome of the foot was clinically diagnosed in 19 patients. When the surgeon in charge was uncertain about the presence of a compartment syndrome, invasive measurement of intracompartmental pressure was performed (n = 12) with a commercially available device (Stryker, Duisburg, Germany) as described earlier [8]. A pressure difference of <30 mmHg to the diastolic blood pressure was defined as indication for a surgical release [1].

Surgical release was initiated directly after diagnosis with ACS, while development of ACS was variable following trauma (see Table 1). In all patients, a dermatofasciotomy was most frequently performed with 2 dorsal incisions over the second and fourth metatarsals. Temporary closure was either achieved by covering the wounds with artificial skin (Epigard®, Orthomed, Wien, Austria) or by negative-pressure wound therapy (VAC®, KCI, San Antonio, Texas, USA). These devices were regularly changed in the operation room until swelling subsided and a definitive wound closure was possible. The mean number of surgeries until definitive wound closure was 3.3 ± 2.4.

Table 1 Time until diagnosis
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During the clinical course, six superficial and one deep infections developed. In two patients, secondary amputations due to complex injuries of the proximal leg were necessary.

Mean in-patient time was 39.9 ± 33.4 days, patients with multiple injuries had a total length of stay of 46.7 ± 28.8 days.

Discussion

Mechanism of injury

In general, a compartment syndrome can develop either due to increased content of the compartment or decreased intracompartmental volume and external pressure or compression. In the current study, only trauma-related ACS of the foot was included. In a previous publication, 6 % of patients with foot injuries caused by motorcycle accidents developed an ACS of the foot [9]. To date, studies describing detailed injury mechanisms are not available. In the current cohort, most ACSs were caused by motor vehicle accidents and falls from height leading to additional major injuries. Interestingly, nearly 20 % of the patients developed an ACS of the foot following a low-energy mechanisms underlining the importance of a careful clinical examination even in patients suffering from minor trauma.

Diagnosis

Various devices for intracompartmental pressure measurement are available. For the current study, a system using the piezoelectric effect was applied. A previous survey by Sterk et al. [10] showed that these systems are widely applied in Germany. However, only every second surgeon does perform invasive measurements in patients with suspected acute compartment syndrome [10, 11]. One can assume that in centers with a device available measurement is performed in the majority of patients. In patients with reduced vigilance or under analgetic therapy common clinical findings may be masked. Thus, pressure measurement serves as a helpful tool for diagnosing ACS in those patients. Nevertheless, a liberal decision for surgical release is recommended since long-term consequences of a neglected ACS outweigh the perioperative risk of dermatofasciotomy.

To date, it remains unclear at which intracompartmental pressure tissue damage occurs, while it seems reasonable to consider the individual blood pressure as a parameter for tissue perfusion. In our study, a threshold of <30 mmHg between diastolic blood pressure and intracompartmental pressure was defined as an indication for surgical release. This value was shown to be safe in neglecting acute compartment syndrome [12] although other values considering mean arterial pressure or absolute intracompartmental pressure are common [10].

Additional imaging-based diagnostics like ultrasonography, computed tomography or magnetic resonance imaging have been shown to provide a poor correlation with intracompartmental pressure and, therefore, are inappropriate for diagnosing an acute compartment syndrome [13–16].

A diagnosis based on a clinical examination is favored by a large number of physicians [10, 11]. Measurement of pressure requires consideration of all compartments on risk. While only four compartments are present in the lower leg, the existence of up to 10 compartments in the foot is discussed in the current literature [17]. In the present study, a dermatofasciotomy of the calcaneal compartment was not performed, while clinical impression of an adequate release as described earlier was present.

As previously shown [12, 18], development of an ACS may occur in association with an open fracture proving incomplete decompression.

Treatment

Treatment of ACS aims at immediate decompression of all affected compartments to restore adequate perfusion and consecutive tissue oxygenation to prevent long-term sequelae, i.e., claw toe deformities. Surgical techniques for adequate release are inconsistent in the current literature referring to the disputable numbers of foot compartments that need to be decompressed. In 1990, in a publication, nine compartments in foot were described. It is debatable whether all compartments are of clinical relevance since the barrier between the superficial and the calcaneal compartment was incompetent after a pressure of 10 mmHG. Although multiple approaches are described in the current literature [4, 5, 19–21], a combined dorsal and medial-plantar approach is most frequently used [1, 22]. In the present study, surgical decompression was performed via two dorsal approaches: medial of the second metatarsal and lateral of the fourth metatarsal not considering a calcaneal compartment. However, in all cases, the surgeon’s evaluation showed adequate pressure release.

While approximately two-thirds of all included patients presented with an ACS within the first day, in 13 patients ACS developed after 24 h following injury. This finding underlines the requirement of serial examinations focusing on the development of an ACS in patients at risk [1].

Temporary wound closure is an essential step during the treatment of patients with ACS following dermatofasciotomy. While conventional wound dressings or artificial skin was routinely used for wound coverage 20 years ago the introduction of negative-pressure wound therapy represents the actual standard therapy in western countries. It was previously shown that negative-pressure wound therapy decreased requirement of complex reconstructive procedures [23, 24]. Still, definitive wound closure should be achieved as soon as possible to avoid infectious complications. While we achieved a definitive closure at a mean of three additional surgeries, the incidence of superficial infections was rather high with nearly 20 %. This finding may be explained by the concomitant soft tissue injuries accompanying the documented fractures of the investigated feet requiring additional debridements. Especially after delayed treatment, a high incidence of infections with amputation required was described [25]. However, in the current study, only two amputations due to severe injuries of the leg, but not the foot were necessary.

Conclusion

Acute compartment syndrome of the foot has a low incidence. Since one-fifth of all affected patients suffer from low-energy trauma mechanisms a thorough clinical examination must be performed. Immediate and adequate surgical decompression is necessary to prevent long-term sequelae. No specific surgical approaches can be recommended based on the current literature.