Frequency of the palmaris longus tendon in North American Caucasians.

The palmaris longus tendon was reported absent in North American Caucasians 24.4% of the time in one or both arms, by Thompson in 1921. Some studies have described its absence as being more frequent in females, and its bilateral absence more frequent than its unilateral absence. This study randomly evaluated 200 Caucasian patients (100 of each sex), seen in an office or hospital setting, for the presence of the palmaris longus tendon. It was absent in one extremity in 3% of the patients. Two and one-half percent of the patients had bilateral absence for a 5.5% total overall absence. This study demonstrated that absence of the palmaris longus tendon in North American Caucasians was considerably lower than reported by Thompson in his report in 1921.