Characteristics of bone turnover in the long bone metaphysis fractured patients with normal or low Bone Mineral Density (BMD).

João Costa-Rodrigues,Caner Takur,Paul Alfred Grützner,Thorsten Gühring,Christoph Wölfl,Daniela Schweppenhäuser,Leila Kolios,Ulrich Kneser,Bernd Höner

doi:10.1371/journal.pone.0096058

João Costa-Rodrigues, Caner Takur + Show 7 more

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https://doi.org/10.1371/journal.pone.0096058

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Abstract

The incidence of osteoporotic fractures increases as our population ages. Until now, the exact biochemical processes that occur during the healing of metaphyseal fractures remain unclear. Diagnostic instruments that allow a dynamic insight into the fracture healing process are as yet unavailable. In the present matched pair analysis, we study the time course of the osteoanabolic markers bone specific alkaline phosphatase (BAP) and transforming growth factor β1 (TGFβ1), as well as the osteocatabolic markers crosslinked C-telopeptide of type-I-collagen (β-CTX) and serum band 5 tartrate-resistant acid phosphatase (TRAP5b), during the healing of fractures that have a low level of bone mineral density (BMD) compared with fractures that have a normal BMD. Between March 2007 and February 2009, 30 patients aged older than 50 years who suffered a metaphyseal fracture were included in our study. BMDs were verified by dual energy Xray absorptiometry (DXEA) scans. The levels of BTMs were examined over an 8-week period. Osteoanabolic BAP levels in those with low levels of BMD were significantly different from the BAP levels in those with normal BMD. BAP levels in the former group increased constantly, whereas the latter group showed an initial strong decrease in BAP followed by slowly rising values. Osteocatabolic β-CTX increased in the bone of the normal BMD group constantly, whereas these levels decreased significantly in the bone of the group with low BMD from the first week. TRAP5b was significantly reduced in the low level BMD group. With this work, we conduct first insights into the molecular biology of the fracture healing process in patients with low levels of BMD that explains the mechanism of its fracture healing. The results may be one reason for the reduced healing qualities in bones with low BMD.

Highlights

Bone formation markers reflect the enzymatic activity of bone building cells, mostly osteoblasts, which are excess products from the bone formation process that are released during the breakdown of matrix components [1]
Until the fourth week after surgery, the bone specific alkaline phosphatase (BAP) levels in both groups showed a constant increase, with a maximum value of 16.1 mg/l in the low bone mineral density (BMD) group, which surpassed the maximum value of the control group significantly (9.5 mg/l)
Until the eighth postoperative week, a slight decrease was observed in the control group, while the levels of BAP in the low BMD group decreased slightly

Summary

Introduction

Bone formation markers reflect the enzymatic activity of bone building cells, mostly osteoblasts, which are excess products from the bone formation process that are released during the breakdown of matrix components [1]. Bone formation and resorption rates increase to repair the bone defect, and the accelerated bone metabolism can be detected using elevated serum levels of BTMs [5,6,7,8,9,10,11]. The elevation in BTMs may result from increased bone remodeling activity at the fracture sites or reflect accelerated bone resorption close to the fracture [12,13,14,15]. Diagnostic instruments that allow a dynamic insight into the fracture healing process and that may be used in collecting decision criteria for treatment of fractures and for monitoring the healing course are as yet unavailable [16]

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