Evaluating Bone Remodelling: Does How We Calculate Ratios Matter?

In our latest study, we explored a simple methodological question: does the way we calculate Haversian canal-to-osteon ratios influence our interpretation of bone remodelling activity? As it turns out, the answer is yes. A small difference in analytical approach can produce noticeably different biological conclusions.

Why study Haversian canal-to-osteon ratios?
Bone is constantly being renewed through the activity of Basic Multicellular Units (BMUs), which remove old bone and replace it with new tissue. In cortical bone, this process creates secondary osteons surrounding central Haversian canals. The relative size of these structures provides valuable information about bone remodelling, bone quality, and conditions associated with ageing, disease, biomechanics, and lifestyle. Researchers often use the ratio of Haversian canal area to secondary osteon area as an indicator of the balance between bone resorption and bone formation. Higher ratios generally suggest proportionally larger canal space and less lamellar bone deposition, while lower ratios indicate relatively greater bone formation.

Two common ways to calculate the ratio
We compared two methods commonly used in histological research. Pooling involves measuring all Haversian canals and osteons separately, calculating the mean for each, and then deriving a ratio from those averages. Pairing involves measuring each Haversian canal together with its corresponding osteon, calculating an individual ratio for every remodelling event, and then averaging those ratios. Although both methods aim to describe the same biological process, they are mathematically distinct and do not necessarily yield the same result.

What we did
To investigate this issue, we analysed 551 secondary osteons from femoral midshaft histology slides representing 38 young and middle-aged women from a medieval English skeletal collection. We then calculated Haversian canal-to-osteon ratios using both pooling and pairing approaches and compared the outcomes statistically. 

What we found
Across the sample, the pooling method generally produced lower ratio values than the pairing method. This pattern was observed not only in the full sample but also across age and socioeconomic subgroups. Importantly, the differences between methods were statistically significant and were not explained by the number of osteons measured in each individual. These findings suggest that the choice of averaging technique can directly affect how we interpret bone remodelling. In many cases, pooling implied thicker lamellar bone and therefore greater bone formation during BMU activity, whereas pairing suggested relatively less bone formation per remodelling event.

Why does this matter?
The implications extend beyond statistics. Researchers use these ratios to investigate ageing, osteoporosis, menopause-related bone loss, activity patterns, biomechanics, and socioeconomic influences on skeletal health. If different calculation methods produce different ratio values, they may also lead to different biological interpretations. We found that pooling tends to place greater weight on larger osteons, which can skew the resulting ratio. By contrast, pairing treats each individual remodelling event equally and preserves information at the level of individual BMUs. This makes paired data more biologically informative and more flexible for future analyses that might incorporate additional variables such as osteocyte density or mineralisation patterns. 

Balancing efficiency and precision
There is, however, a practical trade-off. Pooling is generally faster and easier because it requires less data management and fewer calculations. This can be advantageous when dealing with large datasets or when only summary measurements are available. Pairing requires additional effort during data collection and analysis, but it provides greater analytical precision and richer biological information. 

Our take-home message
Our study demonstrates that pooling and pairing are not interchangeable approaches for calculating Haversian canal-to-osteon ratios. While pooling remains useful and efficient, pairing provides a more precise representation of individual bone remodelling events. We therefore encourage researchers to be explicit about which method they use and to consider how that choice may influence biological interpretations and comparisons between studies. Ultimately, methodological transparency is essential if we want bone histology to continue providing reliable insights into health, ageing, and skeletal adaptation in both modern and past populations.

Paper reference here and well done to our post-doc Karen Cooke for leading the study and Honours student Isabella Pearce for collecting part of the data!

Cooke, K. M., Pearce, I., R Claire, A., Louys, J., Mahoney, P., & Miszkiewicz, J. J. (2026). Evaluating Haversian canal-to-osteon ratios for reconstructing bone remodelling activity. Journal of Bone and Mineral Metabolism.