A cadaveric survey exploring bias, and tissue type of the rectus capitis posterior the variation, prevalence, sex soft-tissue bridge between minor and the posterior atlanto-occipital membrane

The purpose of this investigation was to determine the variation, prevalence, tissue type, and sex bias in the soft-tissue bridge between rectus capitis posterior minor (RCPMi) and the posterior atlanto-occipital membrane (PAO). Seventy-five cadavers (27 females and 48 males) were surveyed using a traditional layering dissection of the posterior cervical musculature. When RCPMi was revealed, its superior attachment was detached and the muscle was reflected inferiorly to determine if it was attached to the underlying PAO. If a soft-tissue bridge was identified, the fibers found within the bridge were classified by visual inspection into three categories: tendon-like, muscle-like, and fascia-like. A fourth category of no attachment was also noted. These results show that RCPMi was present bilaterally in 93% of all cadavers surveyed (89% of the female cadavers and 96% of the male cadavers). On the right side, a soft-tissue bridge was present 67% in males and 78% in females. On the left side, the soft-tissue bridge was present in 69% of the males and in 82% of the females. The number of male cadavers possessing tendon fibers in a soft-tissue bridge was 56% on the right side and 55% on the left side. in females, the number of cadavers possessing tendon fibers in a soft-tissue bridge was 44% on the right side and 64% on the left side. In males, muscle fibers were present in the soft-tissue bridge 34% of the cadavers on the right side and in 36% on the left. In females, muscle fibers were found in the soft-tissue bridge in 43% of the cadavers on the right and in 36% on the left. A Pearson Chi-square test (p<.05) was performed to determine: 1) if gender was associated with the presence of the soft-tissue bridge and 2) if a fiber type within a soft-tissue bridge, as denoted by the authors, was associated with gender. The results of the Chi-square analyses indicated that there were no significant associations of gender in either test.