The fibularis digiti quinti tendon: A cadaveric study with anthropological and clinical considerations.

In addition to the fibularis longus and brevis muscles, a number of anomalous muscles or tendons can arise from the lateral compartment of the leg. The authors describe a bilateral and robust fibularis digiti quinti (FDQ) tendon present in the foot of a 99-year-old female cadaver, present the incidence of this tendon in a cohort of 26 cadavers dissected by podiatric-medical students for a lower-extremity anatomy course, and discuss the anthropological and clinical significance of the findings. In these specimen, the FDQ tendon arose from the fibularis brevis tendon proximal to the lateral malleolus, but did not separate completely from the fibularis brevis tendon until passing through the inferior fibular retinaculum. On the lateral dorsum of the foot, the FDQ passed through a third fibular retinaculum formed by the fibularis tertius tendon, and inserted onto the extensor sling of the fifth digit. This case specimen is designated as an example of the fully present category. Of the 52 limbs dissected, 17 limbs (33%) showed a fully present FDQ, while 20 limbs (38%) exhibited an FDQ in a rudimentary form. Thus, 71% of the limbs showed some presence of the FDQ. Because human bipedality requires less dexterity than that of nonhuman primates in the routine use of their hindlimbs, the authors interpret the high variability of the FDQ, including its absence in many feet, as a relaxation of natural selection maintaining this trait since the divergence of humans from African apes.