What are anatomical compartments?

The concept of anatomical compartments in the limb is attributed to Enneking. The idea is that these osteofascial envelopes tend to contain the growth of sarcomas and therefore consideration should be given to removing the whole compartment when operating. Furthermore, it is obvious that biopsies should not cross (and therefore contaminate) uninvolved compartments. Where these barriers are obvious, for example in the thigh, the tumour is said to be in an intracompartmental site. Other sites with less obvious barriers (for example the popliteal fossa) are classified as extracompartmental.

This concept is used in the MSTS staging system and the classification of surgical margins.

Examples of intra- and extracompartmental sites:

Intracompartmental sites Extracompartmental sites
Intra-articular
Superficial to deep fascia
Osteofascial compartments Extrafascial planes or spaces
– Ray of hand or foot – Mid- and hindfoot
– Posterior calf – Popliteal space
– Anterolateral leg – Groin/femoral triangle
– Anterior thigh – Intrapelvic
– Medial thigh – Mid hand
– Posterior thigh – Antecubital fossa
– Buttocks – Axilla
– Volar forearm – Periclavicular
– Dorsal forearm – Paraspinal
– Anterior arm – Head and neck
– Posterior arm
– Periscapular

Tumours which arise within a compartment and expand outside it are also classified as extracompartmental. For example, an osteosarcoma of the distal femur with an associated soft tissue mass would be classified as an MSTS 2B if not metastatic.

 

Limitations of this approach include the fact that although the margins of a compartment might be clear in an axial section, often the superior and inferior limits of the compartment are less well defined.

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