Morphological study of plantaris muscle

Abstract

Plantaris (PM) arises from the lower part of the lateral supracondylar line and the oblique popliteal ligament. It has a small fusiform belly ending in a long slender tendon, and crosses obliquely, in an infero-medial direction, between gastrocnemius and soleus and is inserted into the calcaneous, just medial to the tendo-calcaneous tendon. Functionally, it is of less importance as a plantar flexor and is considered to be a vestigial muscle. The plantaris muscle shows variations like total absence, either unilaterally or bilaterally. In this present study, tendinous origin of the muscle in a single specimen was demonstrated along with usual morphological study of PM. Material and Method: During regular routine dissection in the department, the popliteal region and posterior compartment of leg from both sides of 18 adult human cadavers (36 inferior extremities) were displayed. Dissection of plantaris muscle from its origin to insertion was done and measurements were taken with the help of measuring tape and photographed for records. Observations were analyzed and discussed. Results and Conclusion:In this present study, unilateral and bilateral absence of plantaris muscle was found in 8.33% and 2.77% of cases; it had a tendinous origin in 2.63% and in majority of cases (88.88%) the usual origin and insertion of the plantaris muscle were demonstrated. A unique case, the tendinous origin of plantaris muscle, was demonstrated which showed an intermediate state between the usual type (small muscle belly with long tendon) and complete absence of muscle, suggesting that during the evolution process, the welldeveloped state of the muscle in monkeys gradually become a vestigial entity in human being.