Anatomy of the lower leg

The lower leg consists of four muscle compartments that are restricted by the fascia cruris, tibial bone, fibular bone, and an interosseous membrane (Fig. 1). The muscles in the anterior compartment (blue area in Fig. 1) induce dorsiflexion of the foot and contribute to inversion and eversion. The lateral compartment muscles (green) lead to plantarflexion and eversion, while contraction of the superficial posterior compartment (red) leads to plantarflexion and contributes to flexion of the knee joint. The deep posterior compartment (purple) contains the deep flexor muscles that plantarflex the foot and help with inversion. Recent magnetic resonance imaging (MRI) and perioperative findings confirm the existence of a fifth compartment containing the tibialis posterior muscle having a separate fascia [45, 46].

Fig. 1
figure 1

Cross section of the lower leg

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Definition and types of leg CECS

Recurrent exercise-induced pain and tightness in a portion of the leg due to elevated tissue pressure in a muscle compartment is termed “chronic exertional compartment syndrome” (CECS). There are three different locations of leg CECS [35]. In most individuals the syndrome affects the anterior tibialis muscle compartment (ant-CECS). This type is mostly isolated and bilateral. When individuals have a deep posterior (flexor) compartment syndrome (dp-CECS), symptoms are more often unilateral [44]. Lastly, CECS can occur in the lateral (peroneal) compartment (lat-CECS), which is frequently in concert with an ant-CECS [12]. In daily practice, a substantial portion of patients with CECS present with a combination of the three types (e. g., ant-CECS and lat-CECS), or they develop different types over time (e. g., dp-CECS followed by ant-CECS) [4].

Anterolateral-CECS, ant-CECS, or lat-CECS?

Confusion exists on the correct terminology for the different type(s) of CECS that can cause pain in the anterolateral leg. Some have considered an elevated intracompartmental pressure (ICP) in the anterior tibialis muscle sufficient evidence of a CECS and classify these cases simply as CECS [32]. However, it is now generally accepted that ant-CECS is a more appropriate term for the type of CECS associated with anterolateral leg pain [4]. Information on possibly elevated ICP in lateral compartments contributing to pain in these patients is seldomly provided. Therefore, a portion of these so-called ant-CECS patients may theoretically also harbor a concomitant lat-CECS. It is unclear whether, and to what extent, ant-CECS and lat-CECS are together present in patients with anterolateral pain. Some think that a lat-CECS is always combined with an ant-CECS [12, 32]. Others consider lat-CECS and ant-CECS as two separate entities [3, 22, 40]. These issues were circumvented by a proposal to use the somewhat awkward and not generally accepted term “anterolateral CECS” [32].

Several observations underlie this semantic confusion. Firstly, it was thought in earlier days that just one type of leg CECS existed, i.e., ant-CECS. Only later was it realized that leg CECS could also develop in other leg compartments. Secondly, most patients have great difficulty in pinpointing the exact area of pain. Only a minority is able to distinguish between the anterior compartment or the lateral compartment. Even a concise physical examination including palpation often does not identify the compartment(s) causing the pain. Moreover, patients are usually examined in resting conditions and not immediately after a provocative test. Thirdly, sports physicians preferentially limit invasive ICP measurements to the most accessible compartment of the leg, i.e., the anterior compartment. For reasons of safety, an ICP of the lateral compartment containing the profundal peroneal nerve may be avoided.

A recent study aimed to clarify this issue [39]. From a large general population, 73 individuals with anterolateral leg pain were selected who had undergone simultaneous ICP measurements in both the anterior and lateral compartments and had an elevated pressure in at least one compartment. Of these 73 patients, more than half (n = 42, 58%) had anterolateral pain due to elevated pressures in both compartments. A smaller portion had isolated ant-CECS (26%), whereas only 7% of the patients had isolated lat-CECS. The clinical relevance of this study is yet to be determined. One may argue that a simultaneous ICP of both compartments is justified in patients reporting a diffuse anterolateral pain and tightness suggesting CECS.

Milestones in ant-CECS

The first possible case of ant-CECS was documented in 1912. The English military surgeon Wilson wrote in his diary that he had severe pain in anterior portions of both legs while skiing during an Antarctic expedition. Symptoms intensified with each consecutive trip but always disappeared after rest. Over time, rest pain also emerged suggesting a gradual transition from a chronic to a subacute compartment syndrome. Unfortunately, all expedition members perished on their journey home and the presence of a CECS could not be confirmed [11].

In 1945, Horn described a 26-year-old previously healthy soldier with an acute painful state of the right leg that started immediately after an evening’s walk. In the months preceding this emergency he had noted pains in both legs during marching. On examination, the anterior portion of the right leg was stone hard. A surgical exploration via a fasciotomy revealed severe tibial muscle ischemia necessitating an extensive necrotectomy. In retrospect, he was likely suffering from ant-CECS that had turned into an acute compartment syndrome [15].

The first possible case of ant-CECS was documented in 1912

Eleven years later, Mavor diagnosed bilateral ant-CECS in a soccer player who was bothered with pain for over 2 years. He had several small muscle hernias in the anterior tibialis fascia that were considered spontaneous ruptures due to an elevated muscle compartment pressure. Mavor incised the muscle’s fascia including the hernias and closed the defect with a piece of fascia lata leading to a full recovery [20].

In 1975, Reneman presented the first case series of 61 (mostly military) patients with CECS. He demonstrated that the elevated ICP was normalized after diathermically cutting the anterior tibialis fascia with a thin metal wire. Symptoms persisted in patients who refrained from surgery [30].

Until 1976, a variety of invasive and occasionally irreproducible techniques were used for determination of muscle pressures. In that year, Mubarak introduced a wick-catheter technique that allowed for accurate and reproducible ICP measurements in a dog and a human model [24]. In 1987, Due and Nordstrand introduced an instrument termed a “fasciotome” that allowed for a quick and safe surgical opening of the fascia (fasciotomy) leading to pressure relief [9]. Pedowitz used the wick-catheter technique 3 years later to compare ICP values in ant-CECS patients with values of healthy individuals. He defined timed cut-off values before and after a provocative test suggesting CECS if pressures were beyond these thresholds. To this day, the Pedowitz criteria are still considered the gold standard [27].

Ant-CECS: who is at risk?

Exact CECS incidence rates in the general population are unknown. One study found that one in seven individuals who were evaluated for exercise-induced leg pain (ELP) had an ant-CECS [28]. Early reports suggested that CECS is predominantly found in young and healthy individuals, mainly in military personnel and athletes [19, 30]. However, more recent reports show that CECS can also be found in older and less active individuals [6, 10]. Gender distribution is more or less equal. Typical activities that may provoke ant-CECS are running, soccer, and skating [4]. Recently, a predictive model based on a large retrospective cohort of patients with ELP was proposed. Male gender, young age, bilateral symptoms, absent history of lower leg pathology, skating, and a tensed muscle compartment were identified as independent predictors for CECS [4].

Patient history in ant-CECS

A characteristic ant-CECS patient is a young individual who experiences exercise-induced pain and tightness. Cramps, muscle weakness, and altered foot skin sensation may also be reported. Additionally, some patients describe a sensation of “filling up” during sports leading to a rock hard and tense muscle. Over time, symptoms tend to start earlier during the provocative exercise necessitating premature termination of the sportive activities. The presence of pain and tightness is conditional for the diagnosis. A recent study of ant-CECS focusing on a variety of aspects in the patient history found that the incidence rate of pain and tightness during exercise was 100 and 96%, respectively. Contrary to popular beliefs, however, pain and tightness were also often experienced during resting conditions (85 and 81%, respectively), albeit at a lower intensity [39].

Physical examination in ant-CECS

Physical examination entails observation of the patient standing, walking, and running. A muscle herniation through a fascial defect may occasionally be visible during active extension. Firm palpation of the anterior tibialis or peroneal muscles may cause tenderness, possibly different from the contralateral side in a one-sided CECS. Palpation as well as active and passive range of motion and resistance tests should be performed before and after a provocative exercise such as a treadmill run. Since these symptoms are mostly nonspecific, physical examination is often normal in patients with ant-CECS. Therefore, the role of a physical examination in the management of CECS is not to confirm the diagnosis but to exclude concomitant entities other than CECS. A painful palpation of the distal posteromedial tibial rim in an ant-CECS patient may indicate a simultaneous medial tibial stress syndrome (MTSS, formerly “shin splints”; [23]). Tenderness of the distal flexor muscles just proximal to the medial malleolus suggests dp-CECS [46]. Hypoesthesia (occasionally hyperesthesia) of portions of the foot and/or distal portions of the leg indicate entrapment of branches of the common peroneal or tibial nerve [41]. Blanching of the foot sole or reduced arterial pulsations in prone position may indicate popliteal artery entrapment syndrome (PAES; [36]).

Dynamic ICP measurement

In patient with ELP with a suggestive history and physical examination, ant-CECS is confirmed using a dynamic ICP measurement. The ICP is measured at rest and after a provocative exercise (usually a treadmill run). Static ICP measurements are considered obsolete. A slit-catheter technique connected to an arterial line transducer system is currently regarded as most accurate for timed pressure measurements [2, 13]. In cases of bilateral complaints, values are obtained from the most symptomatic leg.

The most commonly used cut-off points are suggested by Pedowitz (rest pressure ≥20 mm Hg, ≥30 mm Hg 1 min after, or ≥20 mm Hg 5 min after a provocative exercise; [27]). However, threshold values as well as the validity of the technique itself are criticized [1]. Several reports indicate that an elevated pressure alone is not sufficient for the diagnosis [31]. Another group presented a potentially improved method and cut-off values, requiring confirmation in future studies [33].

Imaging and other techniques

The role of imaging for possible ant-CECS is limited. Near-infrared spectroscopy (NIRS) or MRI has a potential to confirm the diagnosis, but they are not used on a large-scale basis [37, 38]. Recently, MRI detected diffuse compartment edema in a patient with isolated lat-CECS who recovered following surgery [26]. Similar to the role of physical examination, imaging is predominantly indicated for exclusion of MTSS (bone scintigraphy, ultrasound), intermittent claudication (ankle–brachial index), PAES (Duplex), nerve entrapments (MRI), or stress fractures (plain X‑ray).

Diagnosis and differential diagnosis of ant-CECS

The diagnosis of ant-CECS is primarily based on a suggestive patient history. Physical examination and imaging are used to exclude concomitant or other entities causing ELP. The absolute role of the ICP analysis is controversial. Therefore, a patient suspected of having ant-CECS with a strongly suggestive history (pain and tightness during or shortly after exercise) but without any suggestive signs during physical examination or elevated ICP raises a diagnostic dilemma. As such, this patient may still undergo surgical treatment for CECS if conservative treatments fail.

The differential diagnosis of ant-CECS is extensive (Table 1). An elaborate patient history and a structured physical examination are pivotal to diagnose alternative pathologies or for guiding additional measurements/imaging. Some diagnoses are solely based on physical examination (fascial herniation, muscle/tendon injuries), while other entities may require additional imaging (PAES, stress fracture, peripheral artery disease).

Table 1 Differential diagnosis of chronic exertional compartment syndrome (CECS)
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Conservative treatment for ant-CECS

Evidence supporting the efficacy of conservative treatments for ant-CECS is scarce [29]. The most frequently used nonoperative treatments are rest, massage, stretching exercises, ice, or extracorporeal shockwave therapy. A long-term reduction of symptoms in the general population might not be attained. However, adverse effects are absent and thus a conservative regimen is often advised 3–6 months prior to considering surgery. Correction of foot overpronation and optimization of walking gait and shoes may help. Adopting a midfoot or forefoot strike resulted in fewer symptoms, a longer pain-free walking interval, and lowered ICP [7]. A 6-week forefoot running intervention in both a center-based and home-based setting led to similar improvements [14]. In an experimental setting, botulinum toxin A (Botox) injections were useful as pain disappeared in 15 of 16 patients, whereas ICP dropped by two thirds [16]. However, the long-term efficacy is unknown.

Surgery for ant-CECS

Surgery is offered to patients with ant-CECS who do not respond to conservative therapy. The fascia is either split (fasciotomy) or a strip thereof is removed (fasciectomy).

Fasciotomy in the early days was performed via a 10- to 15-cm longitudinal incision [25]. The introduction of a fasciotome reduced the size of the skin incision to 2 cm [9]. The technique that is proposed by Due is termed “semi-blind” as the subcutaneous advancement of the tip of the fasciotome does not occur under direct visualization. Potential disadvantages of this semi-blind approach are collateral muscle or nerve damage as the tip of the fasciotome may lose contact with the fascia during the pushing movement. A recent alternative to Due’s fasciotome is termed “FascioMax” [5]. This is a speculum-type instrument with two blades that are advanced in planes ventral and dorsal to the fascia (Fig. 2). By closing the blade, a hollow tube is formed allowing for a protected introduction of a thin fasciotome.

Fig. 2
figure 2

Fasciotomy for anterior chronic exertional compartment syndrome using the FascioMax. a Positioning of the speculum; b introduction of the fasciotome

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In the case of bilateral ant-CECS, both legs are operated in a one-stage procedure in day-care requiring approximately 20 min of operation time. A compressing bandage is applied for the first 24 h after which patients wear compressive stockings for 14 days. They refrain from sports but normal ambulation is recommended. Jogging is allowed from day 14 on.

For lat-CECS, two separate skin incisions are used that are located more dorsal compared with the fasciotomy for ant-CECS. The distal incision is placed over the location where the superficial peroneal nerve (SPN) may possibly exit the fascia avoiding any potential iatrogenic nerve damage. Recently, the assistance of an endoscope was proposed [17]. Although in theory this technique may improve outcome and reduce nerve injury rates, clinical results are not superior to those achieved with other techniques [18, 47].

Surgical complications and outcome

Complication rates of a fasciotomy are as high as 19% and include bleeding, SPN injury, and wound infection [8, 34, 42]. Long-term outcome largely depends on the definition of success and the expectations of the patient. Favorable outcomes vary between 50 and 100% in athletes and civilian populations. Success rates in military personnel are lower. For instance, nearly half of a military population who underwent fasciotomy reported recurrent symptoms, and one in four patients were not able to return to full activity [43]. In another study this number was even lower, as only 41% of military personnel who underwent elective fasciotomy were able to return to full military duty [21].

Persistent pain after CECS surgery: recurrence or concomitant disease?

A portion of ant-CECS patients might report residual symptoms within 3 months of surgery, or may have recurrent pain following an earlier successful fasciotomy. Persistent pain can be caused by either a concomitant disease such as MTSS or CECS in another compartment, or by insufficient surgical decompression. A recent study found that approximately one in four patients with persistent or recurrent pain after surgical treatment for CECS had residual or recurrent disease as demonstrated by pathologically elevated pressure in one or more compartments [40]. We therefore recommend a repeat ICP if history and physical examination are similar to the clinical picture prior to the fasciotomy. If history and physical examination differ from the preoperative situation, other entities such as dp-CECS, MTSS, intermittent claudication, PAES, nerve entrapments, or stress fractures must be excluded using the appropriate testing or imaging. When recurrent CECS is demonstrated, a fasciectomy is recommended. During this 30-min operation, a 5–7-cm-wide and 20–25-cm-long strip of fascia is excised (Fig. 3). The outcome is beneficial but a 15-cm incision is required.

Fig. 3
figure 3

Recurrent pain following fasciotomy for anterior chronic exertional compartment syndrome. a De novo fascial layer; b excision of strip of new and old fascia. Note superficial peroneal nerve at tip of scissors

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Conclusion

  • Pain and tightness in anterolateral portions of the leg are crucial for the diagnosis of ant-CECS.

  • Physical examination should be performed before and after a provocative treadmill test and may reveal a tender anterior tibialis muscle belly upon palpation.

  • An ICP measurement may support the diagnosis of ant-CECS.

  • Additional imaging is reserved for exclusion of concomitant entities such as artery or nerve entrapments.

  • Modification of the patient’s running technique may be successful.

  • A fasciotomy is considered in patients for whom conservative treatment has failed.

  • Recurrent disease may necessitate removal of a strip of the fascia.