In the clinic, bone disease and treatment are usually evaluated using bone remodelling markers and bone density measurements. In some cases where local microstructural changes occur, however, these measures might not be able to capture the actual effects. In a previous study, vibration therapy in osteopenic girls with adolescent idiopathic scoliosis (AIS) showed no effect on distal tibia bone density and microstructure although this would have been expected at this load-bearing site. Recently, an image analysis approach was developed to determine local sites of bone remodelling in patients based on high-resolution peripheral quantitative computed tomography. For the purpose of this study, we applied the newly developed image analysis method to the follow-up scans of five osteopenic AIS patients receiving vibration therapy and three controls receiving observation only. In agreement with the clinical outcome, we did not find any difference in global bone remodelling measures between the groups. However, the local visualisation of bone remodelling sites indicated cortical drift, where bone was added on the outside and removed on the inside of the cortex in the treatment group whereas this was less pronounced or even the other way around in the control group. Such a drift might increase mechanical integrity without affecting global bone density or microstructural parameters and thus is only detectable with a local measurement. However, results should be interpreted with caution as they are limited by a small number of subjects and confounded by growth in the still growing subjects. Most of the subjects showed considerable bone turnover, which in one severe case complicated accurate registration of the follow-up images. Nevertheless, we conclude the image analysis approach for local bone remodelling is promising for evaluating disease and treatment in more detail and using a more local approach.
Disclosure: Bert van Rietbergen is a consultant for Scanco Medical AG. The other authors declare that they have no competing interests.