Slender tibias show less remodeling, increased stiffness vs. robust bones

Similar findings across genders indicate that osteoblasts, osteoclasts may modulate tissue quality.

SAN DIEGO — New research examining young adult human tibias shows that tissue quality varies with bone size. Researchers believe that the findings may help explain why patients with more slender bones have an increased fracture risk.

In an analysis of tibias obtained from 31 donors, investigators discovered that more slender bones had increased bone mineral content and decreased remodeling, which produced stiffer, less ductile tissue with increased damageability.

"The mechanical implication may be the advantage that the bones are stiff and strong for day-to-day activity, but these relationships may make the bones more susceptible to fracture under extreme loading conditions," said Steven M. Tommasini, MS, at the Orthopaedic Research Society annual meeting, here.

The findings mirror other animal studies, which have linked the level of organ function with bone morphology and tissue quality, he noted.

There were no differences in the relationship between size and stiffness across genders.

"The males and females showed similar tissue-level mechanical properties despite dimorphic growth patterns, suggesting that both sexes share a common biological or adaptive mechanism in constructing bone matrix. It also implies that osteoblasts and osteoclasts are not only capable of modulating bone morphology, but also tissue quality," Tommasini said.

The investigators measured the mechanical properties of tibias collected from 17 men and 14 women. They determined tissue strength through four-point bending and measured tissue level modulus, work to failure and postyield strain. The level of damageability was also assessed using four-point bending tests.

An analysis of ash content revealed a positive correlation between bone slenderness and the amount of remodeling, but a negative correlation between bone slenderness and ash content.

"Thus, narrow or more slender tibias had increased mineral content and decreased amounts of remodeled tissue, whereas wider, more-robust tibias had a decreased mineral content and an increased amount of remodeled tissue," Tommasini said.

For more information:
Tommasini SM, Nasser P, Hu B, et al. Of mice, men and women: the relationship between bone morphology and tissue quality. #186. Presented at the Orthopaedic Research Society 53rd Annual Meeting. Feb. 11-14. 2007. San Diego.