Bone remodeling markers: assessment of fracture risk and fracture risk reduction

The clinical contribution of cortical porosity to fragility fractures

Cortical bone is not compact; rather it is penetrated by many Haversian and Volkmann canals for blood supply. The lining of these canals are the intracortical bone surfaces available for bone remodeling. Increasing intracortical bone remodeling increases cortical porosity. However, cortical bone loss occurs more slowly than trabecular loss due to the fact that less surface per unit of bone matrix volume is available for bone remodeling. Nevertheless, most of the bone loss over time is cortical because cortical bone constitutes 80% of the skeleton, and the relative proportion of trabecular bone diminishes with advancing age. Higher serum levels of bone turnover markers are associated with higher cortical porosity of the distal tibia and the proximal femur. Greater porosity of the distal radius is associated with higher odds for forearm fracture, and greater porosity of the proximal femur is associated with higher odds for non-vertebral fracture in postmenopausal women. Measurement of cortical porosity contributes to fracture risk independent of areal bone mineral density and Fracture Risk Assessment Tool. On the other hand, antiresorptive treatment reduces porosity at the distal radius and at the proximal femoral shaft. Thus, porosity is a substantial determinant of the bone fragility that underlies the risk of fractures and may be a target for fracture prevention.

Bone turnover markers are associated with higher cortical porosity, thinner cortices, and larger size of the proximal femur and non-vertebral fractures

Bone turnover markers (BTM) predict bone loss and fragility fracture. Although cortical porosity and cortical thinning are important determinants of bone strength, the relationship between BTM and cortical porosity has, however, remained elusive. We therefore wanted to examine the relationship of BTM with cortical porosity and risk of non-vertebral fracture. In 211 postmenopausal women aged 54-94 years with non-vertebral fractures and 232 age-matched fracture-free controls from the Tromsø Study, Norway, we quantified femoral neck areal bone mineral density (FN aBMD), femoral subtrochanteric bone architecture, and assessed serum levels of procollagen type I N-terminal propeptide (PINP) and C-terminal cross-linking telopeptide of type I collagen (CTX). Fracture cases exhibited higher PINP and CTX levels, lower FN aBMD, larger total and medullary cross-sectional area (CSA), thinner cortices, and higher cortical porosity of the femoral subtrochanter than controls (p≤0.01). Each SD increment in PINP and CTX was associated with 0.21-0.26 SD lower total volumetric BMD, 0.10-0.14 SD larger total CSA, 0.14-0.18 SD larger medullary CSA, 0.13-0.18 SD thinner cortices, and 0.27-0.33 SD higher porosity of the total cortex, compact cortex, and transitional zone (all p≤0.01). Moreover, each SD of higher PINP and CTX was associated with increased odds for fracture after adjustment for age, height, and weight (ORs 1.49; 95% CI, 1.20-1.85 and OR 1.22; 95% CI, 1.00-1.49, both p<0.05). PINP, but not CTX, remained associated with fracture after accounting for FN aBMD, cortical porosity or cortical thickness (OR ranging from 1.31 to 1.39, p ranging from 0.005 to 0.028). In summary, increased BTM levels are associated with higher cortical porosity, thinner cortices, larger bone size and higher odds for fracture. We infer that this is produced by increased periosteal apposition, intracortical and endocortical remodeling; and that these changes in bone architecture are predisposing to fracture.

Effect of three doses of conjugated estrogens/medroxyprogesterone acetate on biomarkers of bone turnover and cartilage degradation in postmenopausal women: The Pan-Asia Menopause (PAM) study

OBJECTIVE

To assess the effects of three doses of continuously combined conjugated estrogens (CE) and medroxyprogesterone acetate (MPA) on bone turnover and cartilage degradation markers in early postmenopausal Asian women (mean age 53.6 years).

METHODS

A total of 1028 women were randomly allocated to receive treatment with either 0.625/2.5, 0.45/1.5, or 0.3/1.5 mg CE/MPA for 6 months. End-points were the percent change from baseline in markers of bone resorption (alpha alpha CTX, beta beta CTX), bone formation (osteocalcin), and cartilage degradation (CTX-II).

RESULTS

The 0.45/1.5 mg and the 0.625/2.5 mg doses elicited comparable responses as measured by the biomarkers. Women with high rates of bone or cartilage turnover at baseline responded with larger changes to the effects of CE/MPA.

CONCLUSIONS

Lowering the commonly used dose of 0.625 mg CE + 2.5 mg MPA to 0.45 mg CE + 1.5 mg MPA does not significantly alter the inhibitory effect on bone and cartilage turnover in Asian women.

An outcome measure for Japanese people with chronic low back pain: an introduction and validation study of Japan Low Back Pain Evaluation Questionnaire

STUDY DESIGN

Development of a nationwide patient-based outcome measure for patients with chronic low back pain (CLBP).

OBJECTIVE

The purpose of this study was to develop and introduce a new means of measuring outcomes for Japanese individuals with CLBP (the Japan Low Back Pain Evaluation Questionnaire [JLEQ]), and to examine its validity and reliability by comparison with the Roland-Morris Disability Questionnaire (RDQ).

SUMMARY OF BACKGROUND DATA

CLBP is a serious problem affecting the health and welfare of workers, especially laborers. The severity and disability it causes vary depending on cultural background and the psycho-emotional aspect of the patients.

METHODS

The following items were tested for the JLEQ and the RDQ using psychometric analyses: content validity, construct validity, criterion validity, internal-consistency reliability, and test and retest reliability.

RESULTS

A total of 195 patients with CLBP participated in this study. There were no floor and ceiling effects in the JLEQ. Cronbach's alpha coefficient was 0.971 and 0.893 for the JLEQ and RDQ, respectively. The test-retest interclass correlation coefficient in the JLEQ was 0.886, indicating good test-retest reliability. Categorical principal component analysis showed that the construct structure consisted of 3 item clusters in the JLEQ. The factor loading patterns indicated that the JLEQ items were separated into 3 domains, i.e., a moderately loaded group, a less loaded group, and psychological conditions. The degree of correlation between the question items in the JLEQ and RDQ was evaluated using Akaike Information Criteria.

CONCLUSION

The JLEQ was shown to be a valid and reliable questionnaire scale for measurement of patient-based outcomes in CLBP patients.

Disordered osteoclast formation in RAGE-deficient mouse establishes an essential role for RAGE in diabetes related bone loss

The mechanisms underlying diabetes-mediated bone loss are not well defined. It has been reported that the advanced glycation endproducts (AGEs) and receptor for AGEs (RAGEs) are involved in diabetic complications. Here, mice deficient in RAGE were used as a model for investigating the effects of RAGE on bone mass. We found that RAGE-/- mice have a significantly increased bone mass and bone biomechanical strength and a decreased number of osteoclasts compared to wild-type mice. The serum levels of IL-6 and bone breakdown marker pyridinoline were significantly decreased in RAGE-/- mice. RAGE-/- mice maintain bone mass following ovariectomy, whereas wild-type mice lose bone mass. Furthermore, osteoclast-like cells do express RAGE mRNA. Our data therefore indicate that RAGE serves as a positive factor to regulate the osteoclast formation, directly implicates a role for RAGE in diabetes-promoted bone destruction, and documents that the AGE-RAGE interaction may account for diabetes associated bone loss.