[Biochemical bone resorption markers during the healing of osteoporotic fractures]

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

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.

Characteristics of bone metabolism markers during the healing of osteoporotic versus nonosteoporotic metaphyseal long bone fractures: a matched pair analysis

PURPOSE

The activity and metabolism of fracture healing can be monitored quantitatively by measuring bone turnover markers (BTMs) in serum or urine. However, in osteoporotic bone, the exact metabolism processes during the healing of metaphyseal fractures remain unknown. There is no diagnostic approach which currently allows dynamic insight into the fracture healing processes in order to monitor the progression of healing and to assist in therapeutic decision making.

METHODS

Between March 2007 and February 2009, 30 patients over 50 years of age who suffered a metaphyseal fracture were included in our study. The levels of the osteoanabolic marker BAP (bone-specific alkaline phosphatase) and osteocatabolic marker β-CTX [crosslinked C-(CTX)-telopeptide-of-type-I-collagen] were monitored during the fracture healing of osteoporotic and nonosteoporotic fractures for a duration of 8 weeks.

RESULTS

After an initial decrease of BAP in the first week, the BAP level steadily increased through the fourth week in both groups. The levels of BAP in the osteoporotic group surpassed the healthy group. β-CTX steadily increased in healthy bone up to the fourth week; in osteoporotic bone, β-CTX first increased and, thereafter, decreased from the first week onwards.

CONCLUSIONS

In this work, the first molecular biological aspects of osteoporotic fracture healing have been uncovered, helping to explain the mechanisms of delayed fracture healing in osteoporotic bone. The early decrease of reduced β-CTX as well as elevated BAP during the healing process may be the first aspects within the delayed healing of osteoporotic bone. Further studies are necessary in order to achieve more detailed insight to fracture healing and to ascertain the progression of fracture healing as being essential (criteria) for therapeutic decision making.