ORIGINAL ARTICLE Bone structure assessed by HR-pQCT, TBS and DXL in adult patients with different types of osteogenesis imperfecta R. Kocijan 1 & C. Muschitz 1 & J. Haschka 1 & D. Hans 2 & A. Nia 1 & A. Geroldinger 3 & M. Ardelt 4 & R. Wakolbinger 1 & H. Resch 1 Received: 5 January 2015 /Accepted: 27 April 2015 # International Osteoporosis Foundation and National Osteoporosis Foundation 2015 Abstract Summary Bone microarchitecture by high-resolution periph- eral quantitative computed tomography (HR-pQCT) was assessed in adult patients with mild, moderate, and severe osteogenesis imperfecta (OI). The trabecular bone score (TBS), bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA), and dual X-ray and laser (DXL) at the calcaneus were likewise assessed in patients with OI. Tra- becular microstructure and BMD in particular were severely altered in patients with OI. Introduction OI is characterized by high fracture risk but not necessarily by low BMD. The main purpose of this study was to assess bone microarchitecture and BMD at different skeletal sites in different types of OI. Methods HR-pQCT was performed in 30 patients with OI (mild OI-I, n =18 (41.8 [34.7, 55.7]years) and moderate to severe OI-III-IV, n =12 (47.6 [35.3, 58.4]years)) and 30 healthy age-matched controls. TBS, BMD by DXA at the lumbar spine and hip, as well as BMD by DXL at the calca- neus were likewise assessed in patients with OI only. Results At the radius, significantly lower trabecular parameters including BV/TV (p =0.01 and p <0.0001, respectively) and trabecular number (p <0.0001 and p <0.0001, respectively) as well as an increased inhomogeneity of the trabecular network (p <0.0001 and p <0.0001, respectively) were observed in OI-I and OI-III-IV in comparison to the control group. Similar re- sults for trabecular parameters were found at the tibia. Micro- structural parameters were worse in OI-III-IV than in OI-I. No significant differences were found in cortical thickness and cor- tical porosity between the three subgroups at the radius. The cortical thickness of the tibia was thinner in OI-I (p <0.001), but not OI-III-IV, when compared to controls. Conclusions Trabecular BMD and trabecular bone micro- structure in particular are severely altered in patients with clin- ical OI-I and OI-III-IV. Low TBS and DXL and their signifi- cant associations to HR-pQCT parameters of trabecular bone support this conclusion. Keywords Bone microstructure . DXA . DXL . HR-pQCT . Osteogenesis imperfecta . TBS Introduction Osteogenesis imperfecta (OI) is a hereditary disorder caused by a defect in collagen type I or by proteins interacting with collagen type I [1]. OI is characterized by increased bone fragility, recurrent fractures, and extraskeletal manifestations, such as dentinogenesis imperfecta, hearing impairment, or blue sclerae [2]. To date, 12 types of autosomal and recessive OI have been identified through genetic testing [3–5]. More than 1500 mutations in COL1A1 or COL1A2, the two encoding genes for collagen type I, have been identified for autosomal-dominant OI. In contrast, rare recessive OI forms are caused by deficiency of proteins such as CRTAP, LEPR E1, PPIB, FKBP10, and SERPINH1 [1]. OI can be further divided into four subtypes based upon clinical and * R. Kocijan roland.kocijan@bhs.at 1 Medical Department II, St. Vincent Hospital Vienna, Medical University of Vienna, Stumpergasse 13, 1060 Vienna, Austria 2 Department of Bone and Joint Diseases, Center for Bone Diseases, Lausanne University Hospital, Lausanne, Swizerland 3 Center for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria 4 Department of General, Visceral and Vascular Surgery, University of Jena, Jena, Germany Osteoporos Int DOI 10.1007/s00198-015-3156-4