The Effect of Presence of Palmaris Longus and Fifth Superficial Flexor Tendons on Median Nerve Surface Area; A Cross-sectional Study with Sonography

Abstract: Background & Aims: Sonography has enjoyed much attention as a noninvasive diagnostic tool for carpal tunnel syndrome in recent years. The aim of the present study was to assess the effect of anatomic variations of existence or absence of palmaris longus and fifth superficial flexor tendons on the sonographic measurement of median nerve surface area in healthy individuals’ wrists. Methods: 93 volunteers without any symptoms related to carpal tunnel syndrome underwent clinical evaluation for determining presence of tendons in both wrists and also, sonographic measurement of median nerve surface area. Results: In 22 of 186 hands (11.82%), there was absence of the palmaris longus tendon and absence of the fifth flexor was noted in 8 (4.30%). The median nerve surface area in the hands without palmaris longus was meaningfully less than the hands with it (P = 0.025), while the difference in the median nerve surface area was not statistically significant regarding the presence of the fifth flexor (P = 0.324). Conclusion: Based on the findings of the present study, it seems that the median nerve surface, area as a sonographic finding, is probably related to presence or absence of the palmaris Longus tendon. So, those hands with the tendon present have larger surface areas. Also, it seems that this sonographic finding is not dependent on the presence of fifth superficial flexor tendon. Keywords: Carpal tunnel syndrome, Ultraonography, Tendon variatio

An assessment of the effects of variations in the Palmaris longus tendon and the fifth superficial flexor digitorum on pinch and grip strength

INTRODUCTION: The effect of the absence or presence of the Palmaris longus tendon on pinch and grip strength was investigated in this study. Similarly, the effect of the presence or absence of the fifth superficial flexor digitorum on grip strength in the hand was studied. The aim of the present study was to assess the combined effect of these anatomical variations on pinch and grip strength. MATERIALS AND METHODS: In this cross-sectional study, 523 volunteers and their 1046 hands were enrolled. Each hand was assessed for the presence or absence of the Palmaris longus tendon and for variations in the fifth superficial flexor digitorum function. Then the grip and pinch power of the hands were measured with the Jammar Dynamometer. RESULTS: The presence or absence of Palmaris longus had no effect on grip strength in the individuals studied. Likewise, variations in fifth superficial flexor digitorum function had no effect on grip and pinch strengths. But the results of statistical testing showed the effect of the presence of Palmaris longus on pinch strength (25.38 lbs in hands with Palmaris present vs 24.43 lbs in hands without Palmaris). Pinch and grip power was higher in men than in women and in the right hand than in the left. CONCLUSION: Based on the findings of the present study, it seems that absence of the Palmaris longus tendon is associated with a reduction in pinch strength but has no effect on grip strength, and the variations in the fifth superficial flexor digitorum (flexor digitorum superficialis, or FDS) have no effect on pinch and grip strengths. © 2020 - IOS Press and the authors. All rights reserved