Palmaris Longus Muscle Variations: Clinical Significance and Proposal of New Classifications.

BACKGROUND: The palmaris longus muscle is one of the most variable muscles in the human body and there have been numerous variations reported. The different palmaris longus variations are interesting not only from an anatomical point of view, but they could also have definite clinical significance. AIM: The aim of this study was to examine the different types of variations of palmaris longus muscle in the Bulgarian population. MATERIALS AND METHODS: Over a period of 15 years, 56 formol-carbol fixed human cadavers were studied to investigate the different variations of palmaris longus muscle (PLM). RESULTS: Various anatomical variations of PLM have been reported: absence (2.68%); reversed palmaris longus coexisting with an additional abductor digiti minimi muscle (0.89%); digastric (0.89%); palmaris longus with intermediate muscle belly (1.79%) and duplication (1.79%). CONCLUSIONS: To reveal the wide variety of the types of palmaris longus muscle and their importance for clinical practice, we make a brief literature review concerning the different types of variations, their role in the median and ulnar neuropathy in the wrist or as structures simulating a soft tissue tumour and the application of palmaris longus tendon in plastic and reconstructive surgery as grafting material. We also present new systematic anatomical and clinical classifications of palmaris longus variations by dividing them into two simple groups.