What causes compression of blood vessels and nerves in compartment syndrome?

The correct choice highlights the role of fascia in compartment syndrome. Fascia is a fibrous tissue surrounding muscles, nerves, and blood vessels, which confines them within a specific compartment. In normal circumstances, the fascia can expand to some extent; however, in compartment syndrome, the fascia does not expand appropriately due to various reasons such as injury or swelling. When there is injury or inflammation, the pressure within the compartment can increase significantly. If the fascia is rigid and unable to accommodate this pressure increase, it leads to compression of the adjacent blood vessels and nerves, resulting in pain, decreased blood flow, and potentially nerve damage.

The other choices touch on various contributing factors to increased pressure in a compartment. While expansion of fascia due to injury can lead to localized swelling, it’s the failure of the fascia to expand (i.e., the rigidity of the compartment) that directly causes the compression of critical structures inside. Similarly, excessive fluid buildup or internal bleeding can contribute to increased compartmental pressure but are more about what causes that pressure rather than the primary mechanism at play when discussing the rigidity of the fascia itself. Thus, the lack of expansion of the fascia is central to understanding the pathology of compartment syndrome.