Complex regional pain syndrome type 1 (CRPS-1) is a clinical syndrome characterised by pain that is disproportionate to the inciting event (e.g. a fracture), oedema, decreased function, changes in skin colour and bone loss. Although Südeck proposed an inflammatory origin over a century ago, the pathophysiology is still unknown. Current hypotheses include neurological, vasomotor and immune dysfunctions. In two recently published papers we reported that the healing process of stable distal radius fractures can be assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT) in combination with finite element analysis (FEA). A 54-year old postmenopausal patient who was included in this study developed CRPS-1 during fracture healing. HR-pQCT scans of the fractured wrist of this patient were performed at 12, 23, 45 and 86 days and 26 months post-fracture according to the study protocol and showed a remarkable decrease in trabecular density, first detected six weeks post-fracture (fifth percentile), along with a decrease in trabecular number, which persisted at 26 months. There was an initial temporary strong increase in markers of bone formation and resorption. Surprisingly, the coronal cross-sections revealed dramatic resorption of trabecular bone proximal, but not distal of the fracture line. In contrast, the cortical region healed normally as the fracture gaps were bridged and cortical thickness increased. This resulted in restoration of bone stiffness as estimated with FEA at 26 months similar to patients without CRPS-1. These results, though from a single patient, illustrate the possible role of HR-pQCT in the early identification of CRPS-1 related bone loss and could identify patients at risk for developing CRPS-1. The anatomical localisation of trabecular bone changes in the diaphysis and proximal of the fracture site suggests involvement of the vasculature of the nutrient artery in the resorption process.
Disclosure: P.C. Willems is a board member of the Dutch Spine Society (association of spine surgeons). J.J. Arts is a board member of workgroup Biotechnology of the Dutch Orthopedic Association (NOV). B. van Rietbergen is a consultant for Scanco Medical AG. This work was supported by the Weijerhorst Foundation (grant number WH2).