Systemic patterns of trabecular bone across the human and chimpanzee skeleton

Area of Science:

• Paleoanthropology
• Comparative Anatomy
• Skeletal Biology

Background:

• Trabecular bone architecture is linked to skeletal loading and varies across primate species with different lifestyles.
• Systemic factors like genetics, hormones, diet, and activity levels also influence bone structure, complicating functional interpretations.
• Understanding variability in trabecular bone is crucial for interpreting its relationship with joint loading and function.

Purpose of the Study:

• To investigate trabecular bone structure across the entire skeleton of humans and chimpanzees.
• To differentiate between systemic and local loading influences on bone architecture.
• To identify skeletal features that may reflect joint function.

Main Methods:

• A whole-region analysis was applied to micro-computed tomographic scans of human and chimpanzee skeletons.
• Quantified trabecular bone volume fraction (BV/TV), degree of anisotropy (DA), and trabecular thickness (Tb.Th).
• Examined skeletal sites including humeral and femoral heads, metacarpal and metatarsal heads, distal tibia, talus, and thoracic vertebra.

Main Results:

• Chimpanzees exhibited significantly higher bone volume fraction (BV/TV) than humans across most sites, indicating systemic differences.
• Differences in BV/TV between forelimbs and hindlimbs did not consistently correlate with locomotor loading.
• No clear systemic differences in the degree of anisotropy (DA) were found, suggesting it may reflect joint loading.

Conclusions:

• Systemic factors play a significant role in determining interspecific differences in trabecular bone structure.
• Trabecular bone volume fraction (BV/TV) differences between humans and chimpanzees are largely unrelated to local loading.
• The degree of anisotropy (DA) may be a more reliable indicator of joint loading and function in comparative skeletal studies.