as his classical article gave a unified concept of compartment syndrome (2). He observed that the unified concept proposes that the underlying features of all compartment syndromes are the same, irrespective of aetiology or location. Increased tissue pressure is by definition the central pathogenic factor in compartment syndrome. Compartment syndrome is a significant clinical problem.

DEFINITION

Chronic compartment syndrome is “a reversible rise in tissue pressure to abnormal levels brought on by exertion and relieved by rest ... an increase in pressure within an enclosed space with potential to threaten perfusion and tissue viability” (8).

It is a condition in which increased pressure within a closed anatomical space compromises circulation and the tissues within the space. It is due primarily to a relative inadequacy of musculoskeletal compartment size that is compounded further by an increase in muscle volume with activity. It is estimated that skeletal muscles increase in volume during exercise by as much as 20%. The patient typically presents with pain on exercise, which is relieved by rest. The condition is also known as “recurrent compartment syndrome”, “exercise-induced

compartment syndrome”, “subacute compartment syndrome” and “exertional compartment syndrome”. Mubarak and Hargens prefer to describe it as “chronic compartment syndrome”, a term that is universally accepted and in common use (9).

INCIDENCE

Chronic compartment syndrome is much more common than the acute form, according to current literature. Several authors have reported a large series of patients with CCS: Reneman reported 61 patients (7), Sudman 51 patients (10), Detmer et al. 100 patients (11), and Allen and Barnes 110 patients (12).

It occurs predominantly in soldiers and individuals involved in sporting activities. The condition is frequently bilateral and is predominant in males, and people involved in running sports are widely represented. The syndrome is common in the

four lower leg compartments (Fig. 1), but it can also occur in compartments of the forearm and foot. Increasingly, other muscle compartments are involved and are reported as case histories.

PATHOPHYSIOLOGY All theories concerning the pathophysiology of CCS propose an increase in tissue pressure to a level that results in a compromise of muscle perfusion. This may be due to either excessive swelling of the muscles or insufficient compliance of the surrounding fascia.

Normal situation In normal exercising muscle, the capillary bed undergoes an increase in both surface area and filling pressure, causing an increase in resorption, with the result that the muscle increases in volume – by as much as 20% during vigorous exercise. Active muscle is not perfused during contraction. Relaxation allows adequate perfusion during the relaxation phase. Perfusion and function can be compromised if the pressure fails to fall to resting levels between contractions or the contraction is sustained.

Figure 1: Cross-section of the leg, showing the four compartments

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Abnormal situation In symptomatic situations, the factors responsible for an abnormal increase in pressure following exercise remain

speculative. Theories suggest that the elevated intramuscular pressure is initiated by arterial or venous occlusion or is due to increased interstitial fluid as a result of increased hyperosmolarity.

Tissue pressure

Increased tissue pressure may result from the following: n Limited or decreased compartment volume, as a result of tight, thickened fascia, arteriovenous (AV) fistula or constitutionally small space. This may mean a loss of elasticity and decreased compliance of the fascia, implying a greater resistance to the volume change required for exercising skeletal muscle, thus resulting in a tissue pressure rise. Detmer et al. published results of fasciotomies performed on 100 patients with CCS and at the time of surgery took 36 fascial biopsies (11). Fascial thickness was measured and found to be greater than 600 microns in 25 of the 36 patients; in some it was greater than 1200 microns. The significance of this is unconfirmed, as no information is available regarding the normal thickness of the fascia at this site. n Increased compartment content/ volume, due to muscle swelling, hypertrophy or anomalous muscle insertion. The increase in muscle volume produces a sufficient increase in pressure within the small unyielding compartments to limit venous outflow by a collapsing of the veins. This increases capillary resistance, induces arterial vasospasm, decreases capillary perfusion, and triggers extravasation of fluid into the compartment, which further increases compartment pressure and creates ischaemic pain and/or tissue destruction. Hargens et al., in their canine study, infused autologous plasma into the compartment in 1-ml aliquots and plotted the pressure change (13). They revealed a direct correlation between pressure and volume, depending largely on the initial compartment volume. They also showed that little, if any, fluid permeated the osseofascial boundaries in the lower leg and that hydrostatic pressures within one compartment are not transmitted to adjacent compartments. General principles suggest that the pressure and volume within a compartment are dependent on the compliance of

sportEX medicine 2009;40(Apr):16-22