Bone Geometry, Density, Microstructure and Biomechanical Properties in the Distal Tibia in Patients with Primary Hypertrophic Osteoarthropathy Assessed by Second-Generation HR-pQCT.

Periosteosis refers to pathological woven bone formation beneath the cortical bone of the long bones. It is an imaging hallmark of primary hypertrophic osteoarthropathy (PHO) and also considered as one of the major diagnostic criteria of PHO patients. Up to date, detailed information on bone quality changes in long bones of PHO patients is still missing. This study aimed to evaluate bone microarchitecture and bone strength in PHO patients by using high resolution peripheral quantitative computed tomography (HR-pQCT). The study comprised 20 male PHO patients with the average age of 27.0 years and 20 age and sex-matched healthy controls. The areal bone mineral density (aBMD) was assessed at the lumbar spine (L1-L4) and hip (total hip and femoral neck) by dual-energy X-ray absorptiometry (DXA). Bone geometry, volumetric bone mineral density (vBMD), microstructure parameters at distal tibia were evaluated by using HR-pQCT. Bone strength was evaluated by the finite element analysis (FEA) based on HR-pQCT screening at distal tibia. Urinary PGE2, serum phosphatase (ALP), beta-C-telopeptides of type I collagen (β-CTX), soluble receptor activator of nuclear factor-kappaB Ligand (sRANKL), osteoprotegerin (OPG), and neuronal calcitonin gene-related peptide (CGRP) were investigated. As compared with healthy controls, PHO patients had larger bone cross-sectional areas, lower total, trabecular, and cortical vBMD, and compromising bone microstructures with more porous cortices, thinned trabeculae, reduced trabecular connectivity, and relatively more significant resorption of rod-like trabeculae at distal tibia. The apparent young's modulus was significantly lower in PHO patients. The concentration of PGE2 , biomarkers of bone resorption (β-CTX and sRANKL/OPG ratio) and the neuropeptide CGRP were higher in PHO patients versus healthy controls. PGE2 level correlated negatively with vBMD and estimated bone strength and positively with bone geometry at distal tibia. The present HR-pQCT study is the first one illustrating the microarchitecture and bone strength features in long bones.