The normal intracompartmental pressure (ICP) is less than 10 mm Hg. Elevated compartment pressure occurs when either the contents of an osseofascial compartment increase in volume or when the compartment itself reduces in volume (e.g., after a circumferential deep burn, or secondary to external constriction). In compartment syndrome, elevated interstitial pressure overwhelms perfusion pressure. As the ICP rises, venous pressure rises. When venous pressure is higher than capillary perfusion pressure, the capillaries collapse. The accepted threshold above which there is occlusion of capillary flow is 30 mm Hg, or a relative difference between the ICP and the diastolic blood pressure of less than 30 mm Hg. Both of these are very important parameters to be aware of.1–3
scenario? The anterior compartment is most likely to be involved in a lower limb compartment syndrome. McQueen et al1 reviewed 59 cases of leg compartment syndrome that included both open and closed tibial injuries. They found that all cases involved the anterior compartment but only 18 involved all four compartments. For ICP monitoring, the anterior compartment is easy to access. The deep posterior compartment is probably the most difficult to reliably decompress but is the second most at-risk compartment. In 6 of the 59 cases, the lateral compartment was also involved, and in 5 cases the deep posterior compartment was also involved. The deep posterior compartment is probably the most difficult to reliably assess and is the second most at-risk compartment. A more recent study by McQueen et al retrospectively reviewed 1,407 patients who had sustained an open tibial shaft fracture, in order to identify predictors of compartment syndrome. Their analysis showed that the main predictor was age, with males between the ages of 12 and 29 to be most at risk. They did not comment on the compartment involved in this study; however, they postulated that the increased risk in younger patients is due to the increased physical size of muscles in this patient group. The anterior compartment may be most at risk of developing compartment syndrome because it is a particularly tight compartment with well-developed musculature. The close proximity to the tibia is also likely to be a factor.2
Compartment syndrome affects the deep muscles of the volar compartment (flexor digitorum profundus and FPL) most significantly. They are more susceptible to damage, since they are compressed against the radius, the ulna, and interosseous membrane (Fig. 91.1). A retrospective study on acute compartment syndrome of the forearm in 93 patients by Duckworth et al1 showed that the volar compartment was most commonly decompressed (99% of cases), and this included the carpal tunnel in around half of these cases. The decision on which compartment to decompress was based on clinical examination and intracompartmental measurement. The most common complication was a neurological deficit (18%) followed by contracture (4%). Muscle necrosis with associated weakness was observed in around 3% of cases in this series.
The six Ps (pain, pallor, poikilothermia, pressure, paralysis/paresthesias, pulselessness) are useful to consider in suspected compartment syndrome. They must be placed in the context of the injury and patient history. Pain is the single most important early finding and will be disproportionate to the expected pain from injury and exacerbated by passive extension of the affected compartmental muscles. Progressive loss of nerve function begins with sensory nerves and progresses to motor nerves and is usually a later sign. Pulselessness is another late sign of compartment syndrome, and if present early in the episode, a vascular injury or occlusion is more likely to be the underlying cause. The presence of one of the six Ps alone remains a poor indicator of compartment syndrome. When more than two features coexist in the lower leg, the likelihood increases to above 90%.1
Pain on passive stretch of the muscles in a compartment is one of the cardinal signs of compartment syndrome. Patients who suffer a high-voltage electrical injury are at risk of developing acute compartment syndrome. The bone has a high resistance and becomes disproportionately hot during electrical current conduction. The surrounding muscle is damaged by both the electrical current itself and the heat from the underlying bone. This leads to a massive amount of swelling, which may result in compartment syndrome. An ICP reading of 30 mm Hg (not 20 mm Hg) or above would indicate a compartment syndrome, as would a series of rising pressure readings in association with clinical signs. Tingling in the median nerve distribution can be an early indicator of rising pressure in the volar compartment of the forearm, but the strongest indication in this scenario is the pain on passive muscle stretch. The presence Fig. 91.1 Cross-sectional view of the right proximal forearm. Flexor digitorum profundus muscle Medial surface of ulna Flexor pollicis longus muscle Lateral surface of radius of radius and ulna fractures indicates that significant force has been applied to the arm, increasing the risk of elevated compartment pressures, but this is not necessarily an indication for decompression in isolation.1–3
output. This man has several features of missed compartment syndrome, with a high-risk mechanism of injury. The elevated CPK/CK levels are concerning, and it is important to maintain good diuresis and monitor renal function while he clears myoglobinuria to avoid renal injury. Unfortunately, the window of opportunity to decompress his forearm has passed. Late decompression converts a closed injury with nonviable muscle into an open injury with little additional benefit, running the risk of secondary infection, compartmentectomy, and, in some case series, death. If he still had worsening or static levels of pain, this might indicate viable muscle that could still be salvaged, but as his pain has largely subsided this does not apply. Ultrasonography is not helpful in the diagnosis of compartment syndrome, although it can help eliminate other diagnoses. In the absence of raised CPK/CK, but with a swollen limb, a scan may be indicated to exclude deep venous thrombosis or other soft-tissue swelling. A key step in the management of patients with missed compartment syndrome is to ensure physical therapy commences early to minimize swelling, stiffness, and long-term dysfunction.1,2
The two-incision approach to leg fasciotomy involves a posteromedial incision combined with either a lateral or anterolateral incision (Fig. 91.2). This access facilitates decompression of the two posterior and anterior/lateral compartments, respectively.1 The medial incision is generally placed 1 to 2 cm posterior to the tibial border to preserve perforating skin vessels from the posterior tibial artery that may be required for local transposition flaps. The incision passes into the superficial posterior compartment and dissection continues around the soleus to access the deep compartment. During this dissection, care must be taken to avoid damage to the posterior tibial neurovascular bundle. The lateral incision is placed anterior to the fibula border and the first compartment entered would be either the lateral or anterior depending on the incision location; therefore, the peroneal or anterior compartment muscles (not FHL) would be seen first. The anterolateral incision is commonly placed 2 cm posterior to the lateral tibial border, and the first muscle encountered in this approach is the tibialis anterior as the anterior compartment is entered. Dissection then continues subfascially in a lateral direction toward the peroneal septum, which is then divided to release the lateral compartment. The superficial and deep peroneal nerves lie within these two compartments (depending on the level) but are unlikely to be damaged using these approaches. The interosseous membrane, separating the anterior and deep posterior compartments, does not need to be divided.
The anterior compartment of the leg contains the anterior tibial vessels and deep peroneal nerve. There is no anterior tibial nerve. It also contains the following four muscles: the tibialis anterior; the extensor hallucis longus; the extensor digitorum longus; and the peroneus tertius, which runs with the digitorum longus (Fig. 91.3). The saphenous nerve is located on the medial aspect of the leg and lies superficial to the leg compartments. The superficial peroneal nerve is located in the lateral compartment along with peroneus longus and brevis, emerging superficially at the junction of the middle and distal third of the leg. The tibial nerve is located in the posterior compartment with the posterior tibial vessels, the gastrocnemius, soleus, tibialis posterior, and the long flexors.1,2 Fig. 91.2 Incisions and anatomic structures for leg fasciotomies. Anterolateral incision Anterior tibial artery and vein and deep peroneal nerve Peroneal artery and vein Posterior tibial artery and vein and tibial nerve Posteromedial incision Superficial posterior Peroneal compartment Deep posterior Fig. 91.3 Cross-section of the lower leg. Tibialis anterior muscle Anterior tibial artery and vein and deep peroneal nerve Extensor digitorum longus muscle Peroneus brevis muscle Extensor hallicus longus muscle Peroneus longus muscle Peroneal artery and vein Gastrocnemius muscle Tibialis posterior muscle Flexor digitorum longus muscle Posterior tibial artery and vein Soleus muscle Flexor hallicus longus muscle
The foot is considered to have either four or nine compartments (depending on how they are classified), all of which can be decompressed using a single medial incision along the plantar border of the first metatarsal (Fig. 91.4).1–3 The arm is considered to have two or three compartments (anterior, posterior, +/− deltoid) that are usually decompressed through one medial, or two (medial and posterolateral) incisions (see Fig. 91.6, Essentials of Plastic Surgery, third edition).4 The hand is normally considered to have 10 compartments and is commonly decompressed using two dorsal and two volar incisions. The dorsal incisions are placed over the index and ring metacarpals, while the volar incisions are placed on the ulnar and radial borders of the glabrous palmar skin (see Fig. 91.8, Essentials of Plastic Surgery, third edition).5 Fig. 91.4 Foot fasciotomy by medial incision. To decompress the four compartments of the foot using a medial approach, an incision is made along the plantar border of the first metatarsal, allowing access to all four compartments. The incision can be extended proximally if the posterior tibial neurovascular bundle requires decompression as well. Medial Incision Central Lateral The anterior and posterior thigh compartments are decompressed using a lateral incision. A separate medial incision is required for decompression of the medial compartment (see Fig. 91.5, Essentials of Plastic Surgery, third edition).6 The common options for decompression of the four-leg compartments include combined medial and lateral incisions or a single lateral approach.