Assessment of the medial head of the gastrocnemius muscle in functional compression of the popliteal artery

Objective: Nonfunctional popliteal entrapment is due to embryologic maldevelopment within the popliteal fossa. Functional entrapment occurs in the apparent absence of an anatomic abnormality. Gastrocnemius hypertrophy has been associated with the latter. Both forms of entrapment may cause arterial injury and lower limb ischemia. This study assessed the attachment of the medial head of the gastrocnemius muscle in healthy occluders and healthy nonoccluders. Methods: provocative tests were used to identify, 58 nonoccluders and 16 occluders. Ten subjects from each group underwent magnetic resonance imaging evaluation of the popliteal fossa. The medial head of the gastrocnemius muscle attachment was assessed in the supracondylar, pericondylar, and intercondylar areas. Results: In the occluder group, significantly more muscle was attached towards the femoral midline (supracondylar), around the lateral border of the medial condyle (pericondylar), and within the intercondylar fossa. Conclusion: The more extensive midline position of the medial head of the gastrocnemius in occluders is likely to be a normal embryological variation. Forceful contraction results in compression and occlusion of the adjacent popliteal artery. The clinical significance of these anatomic variations remains unclear. However, these new observations may provide insight for future analysis of the causes and natural history of functional compression and the potential progression to clinical entrapment. (J Vasc Surg 2008;48:1189-96.)