Proximal femur strength, cortical thickness and bone structure in Klinefelter syndrome

Enrico Schileo; Alberto Ferlin; Ilaria Palmadori; Fulvia Taddei; Alessandro Coran; Sigurdur Sigurdsson; Vilmundur Gudnason; Tamara Harris; Carlo Foresta

doi:10.1530/endoabs.37.EP280

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Endocrine Abstracts (2015) 37 EP280 | DOI: 10.1530/endoabs.37.EP280

ECE2015 Eposter Presentations Calcium and Vitamin D metabolism (96 abstracts)

Proximal femur strength, cortical thickness and bone structure in Klinefelter syndrome

Enrico Schileo ² , Alberto Ferlin ¹ , Ilaria Palmadori ² , Fulvia Taddei ² , Alessandro Coran ¹ , Sigurdur Sigurdsson ³ , Vilmundur Gudnason ³ , Tamara Harris ⁴ & Carlo Foresta ¹

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¹Department of Medicine, University of Padova, Padova, Italy; ²Istituto Ortopedico Rizzoli, Bologna, Italy; ³Icelandic Heart Association, Kópavogur, Iceland; ⁴National Institute on Aging, Bethesda, Maryland, USA.

Introduction: Klinefelter syndrome patients (KS) frequently show low bone mass, which could have multiple aetiologies. The structural basis of low bone mass and its consequences on bone strength are almost not known, but analogies in bone microstructure and strength between KS and ageing women have proposed by studying distal tibia by HRpQCT. The aim of this study was to compare proximal femur strength and bone structure of KS with elderly women and men.

Patients and methods: Proximal femur QCT analysis was performed on 18 KS (mean age 44±8 years) and compared with 89 elderly women (76±6 years) and 39 elderly men (79±5 years). QCT-based estimates of proximal femur strength were obtained with a personalized Finite Element procedure previously validated in-vitro and in-vivo under loading conditions corresponding to ten fall directions to span accidental conditions. Bone structure analysis included trabecular and cortical volumetric bone mineral density (Tb.vBMD, Ct.vBMD), and cortical thickness (Ct.Th.), mapped to 18 sectors covering the whole femoral neck. Femoral neck length and cross-sectional area were calculated.

Results: KS and women had similar bone strength (KS: 2981±514 N, W: 2822±627 N, Mann–Whitney P=0.14), both significantly lower (P<0.001) than elderly men (4176±985 N). Bone cortex was significantly thinner in KS patients with respect to women (P<0.05 in 13 out of 18 sectors). Ct.vBMD was equivalent in KS and women, whereas Tb.vBMD was instead higher in KS (P=0.003). Femoral neck was significantly larger in KS patients (CSA 25% higher, P<0.001).

Conclusion: We showed for the first time that, at proximal femur, KS and elderly women are similar in terms of bone strength. This similarity emerged however from different structural traits: KS had thinner femoral neck cortex, partially compensated by a denser trabecular compartment and larger bone dimensions (i.e. higher moments of area and bone mass).