Some effects of basic multicellular unit-based remodelling on photon absorptiometry of trabecular bone

Area of Science:

• Biophysics
• Bone Physiology
• Medical Imaging

Background:

• Photon absorptiometry is a common method for estimating bone mass.
• Bone turnover, remodelling space, and undermineralized bone can influence mineral content.
• Previous assumptions about measurement errors may be underestimated.

Purpose of the Study:

• To develop algorithms and an algebra for estimating the effects of bone turnover on bone mass.
• To quantify the impact of remodelling space, undermineralized bone, and surface-to-volume ratio on trabecular bone mass estimation.
• To explain discrepancies in osteoporosis treatment efficacy.

Main Methods:

• Development of algorithms based on published histomorphometric data and other evidence.
• Algebraic modeling of bone turnover, remodelling space, and mineral content.
• Analysis of potential errors in photon absorptiometry measurements.

Main Results:

• Algorithms suggest bone mineral content can differ from true bone mass by over 40% in extreme cases, and 5-15% commonly.
• High bone turnover can lead to underestimation of true bone mass.
• Reduced bone turnover can cause apparent gains in bone mass due to mineral return to remodelling spaces.
• Bone mineral changes can take 6 months to over 3 years to reach steady states after remodelling challenges.
• A real increase in bone volume can appear as no gain or initial loss via absorptiometry.

Conclusions:

• Bone turnover significantly affects the accuracy of bone mass estimation by photon absorptiometry.
• The magnitude of errors (5-15%) is larger than previously assumed.
• These factors may explain the long-term failure of some osteoporosis treatments.
• The dynamic nature of bone remodelling can mask or mimic changes in bone mass, impacting treatment assessment.