Histomorphometric analysis of patients with femoral neck fracture and 25-hydroxyvitamin D deficiency: a cross-sectional study.

Introduction: Vitamin D deficiency causes osteoporosis, bone mineralization disorders, and osteomalacia. Osteomalacia is diagnosed using blood biochemical tests, clinical symptoms, and imaging; however, accurate detection of mineralization disorders requires tissue observation. We investigated the prevalence of bone mineralization disorders and their relationship with serum 25-hydroxyvitamin D (25OHD) levels in patients with untreated osteoporosis with femoral neck fractures.

Materials and methods: A non-demineralized specimen was prepared from the femoral head removed during surgery in 65 patients. Bone histomorphometry of cancerous bone in the femoral head center was conducted. Osteoid volume per bone volume (OV/BV) and osteoid thickness (O.Th) were measured as indicators of mineralization disorder.

Results: The mean serum 25OHD level (11.9 ± 5.7 ng/mL) was in the deficiency range (< 12 ng/mL). There were no clinically diagnosed cases of osteomalacia (OV/BV > 10% and O.Th > 12.5 µm); however, one case of mineralization disorder, considered histologically pre-osteomalacia (OV/BV > 5% and O.Th < 12.5 µm), was observed (OB/BV, 17.6%; O.Th, 12.3 µm). Excluding this case, those with severe (25OHD < 12 ng/mL, at risk of osteomalacia; n = 39) and non-severe deficiency (25OHD ≥ 12 ng/mL; n = 25) did not significantly differ in OV/BV (%; 0.77 ± 0.54 vs. 0.69 ± 0.38, p = 0.484) or O.Th (µm; 5.32 ± 1.04 vs. 5.13 ± 0.78, p = 0.410). Further, 25OHD and OV/BV were not significantly correlated (R = - 0.124, p = 0.327).

Conclusion: This is the first study in the twenty-first century to examine serum 25OHD concentrations and bone mineralization disorders in Japanese patients with osteoporosis. The results indicate that vitamin D deficiency does not necessarily cause bone mineralization disorders and rarely leads to osteomalacia.