The Use of the Skeletal Burden Score for Predicting Physical Outcomes in Patients with Fibrous Dysplasia

Evaluating the extent of fibrous dysplasia (FD) is crucial for understanding the disease’s severity, monitoring its progression, and effectively managing and treating its complications. The skeletal burden score (SBS) is the sole tool available for assessing FD severity that is unaffected by aging or the use of bisphosphonate treatment for bone pain. However, due to the rarity of FD and its diverse manifestations, there are a limited number of studies that have focused on the utilisation of SBS in the assessment of FD involvement.

This thesis presents a collection of original studies focusing on the applicability of SBS. The first two chapters were systematic reviews. The first one, investigated the SBS association with the quality of life (QoL) measures in FD patients. The second systematic review investigated the diagnostic accuracy of cross-sectional imaging modalities for the diagnosis of FD. We also measured the clinicians’ knowledge and use of SBS through an internationally disseminated online survey.

The core research of this thesis involved conducting a multicentre study of FD/MAS patients from five collaborating sites in the United Kingdom and Saudi Arabia. The collected data were analysed to investigate three primary aims. First aim was to evaluate the agreement among five radiologists in measuring the SBS from bone scintigraphy scans presented in two different image formats. Second aim, to examine the quality of life (QoL) and highlighted the factors that influenced it, and to assess the relationship between SBS with the reported QoL and bone pain of the patient cohort. The third aim was to compare FD involvement on bone scintigraphy and whole-body magnetic resonance imaging (WB-MRI) scans. Also to evaluate the reliability of the SBS measured from WB-MRI scans, a novel approach.

Our longitudinal study highlighted the negative impact of FD on the QoL, in particular patients with extensive FD involvement. In addition, the SBS of the legs and pelvis compartments demonstrated a stronger correlation with the physical health domains of QoL than the total SBS. Excellent intra- and inter-reader agreement was observed among the readers and in using bone image formats. Also, good SBS reliability when measured from WB-MRI. Further research is required to validate our findings regarding the applicability of SBS on WB-MRI in a larger cohort.

Our findings offer insights into the accessibility of SBS for assessing the FD skeletal extent. This study aligns with the current international FD guidelines, emphasising the importance of using SBS to assess disease extent, and manage its complications to preserve physical health and QoL.