Morphometric Study and Clinical Significance of Muscle/Tendon Ratio of Palmaris Longus

Abstract

Hypothesis- Is there a functional relevance of relative length of muscle to tendon ratio in Palmaris longus muscle? Material and Methods Material for the present study consisted of 36 detached upper limbs of different age groups. The limbs used were those available in the Anatomy department at AIIMS, New delhi. The length and width of the PL-Muscle Belly (PL-MB) and PL-Tendon (PL-T) were measured with the help of centimeter scale and a thread. The unpaired t test was used to study the significance of the differences in right and left Palmaris longus muscle (PL). Muscle belly length (MBL): It is the dimension taken in Proximal-Distal plane from the medial epicondyle of the humerus to the musculotendinous junction. Tendon Length (TL): The point of measurement taken for the tendon is in Proximal-Distal plane from the musculotendinous junction to its distal attachment. Muscle belly width (MBW): It is the dimension taken in Medio-lateral plane at the maximum width of the muscle belly. Summary of Results Various parameters that includesmean of length of total muscle, muscle belly, tendon and relative ratio of belly length with respect to tendon length were calculated and tabulated. These data were compared with previous literatures. Among 36 specimens, we found absence of PL in 6 specimens. This is more common on left side as per previous literature. In the present study, this preference was not seen. It was found that relative ratio of M/T was lesser on left side (0.66) than right side (0.92) indicating towards lesser muscle mass in left upper limbs. This increased tendon length indicates differential evolution of PL in both limbs. Conclusion- Currently, PL has clinical significance in surgery as it has tendon transfer applicability. Further evaluation of M/T ratio of this muscle in large sample size and also in living subjects may give new clues in understanding the evolution pattern of PL and its relevance to dexterity. It may also be useful to correlate the same with the occupation of the individuals.