RESUMEN
BACKGROUND AND PURPOSE: THA changes the pattern of strain distribution in the proximal femur. We quantified the changes in BMD for 5 years after insertion of the cemented Exeter stem in women. METHODS: 18 women aged 55-79 years, undergoing unilateral THA with the cemented Exeter stem, were included in the study. The BMD was measured in 7 femoral regions of interest according to Gruen, and the contralateral hip and spine using dual-energy X-ray absorptiometry postoperatively, at 18 and at 60 months of follow-up. Results were tested using Wilcoxon matched-pairs signed-rank test. RESULTS: During the first 18 months, a significant decrease in BMD was seen in zones 2, 3, 6, and 7. No significant changes were seen in zones 4 and 5, in the contralateral hip, or at the spine. In zone 1, there was a small but significant rise in BMD. From 18 to 60 months, we observed a statistically significant rise in BMD in all zones except 4 and 7. Despite this, the total periprosthetic BMD decreased during the follow-up relative to the immediate postoperative situation. There was no significant reduction in BMD in the contralateral hip. In the spine, we observed a significant rise in BMD. INTERPRETATION: 18 months after THA, BMD had decreased in Gruen zones 2, 3, 6, and 7. The bone loss was similar to that seen after other implants and appears to be related to the changes in stress pattern within the proximal femur. At 5 years, BMD had increased again in these zones. It remained lower than baseline, however.
Asunto(s)
Artroplastia de Reemplazo de Cadera/efectos adversos , Densidad Ósea , Falla de Prótesis , Absorciometría de Fotón , Anciano , Artroplastia de Reemplazo de Cadera/métodos , Cementación , Femenino , Fémur , Estudios de Seguimiento , Articulación de la Cadera , Humanos , Persona de Mediana Edad , Estudios Prospectivos , Factores de TiempoAsunto(s)
Artroplastia de Reemplazo de Cadera , Densidad Ósea , Fémur/patología , Prótesis de Cadera/efectos adversos , Anciano , Artroplastia de Reemplazo de Cadera/métodos , Cementos para Huesos , Resorción Ósea/etiología , Femenino , Fémur/fisiopatología , Estudios de Seguimiento , Humanos , Persona de Mediana EdadRESUMEN
RANKL (receptor activator of NF-kappaB) is a potent physiological inducer of osteoclastogenesis. Its actions are blocked by the decoy receptor osteoprotegerin (OPG), and treatment with OPG blocks bone resorption in postmenopausal women. Both positive and negative associations between serum OPG and bone mineral density (BMD) have been reported in the literature. We hypothesized that decreased OPG production relative to RANKL within bone itself could lead to increased risk of osteoporotic fracture. We included ten women with hip fracture (age 76.3 +/- 8.0 years, N.S, : hip BMD 0.686 +/- 1.3 g/cm2, P < 0.05) and 24 women with osteoarthrosis of the hip (age 72.8 +/- 7.2 years, hip BMD 0.832 +/- 1.1 g/cm(2)). Transiliac biopsies were obtained at the time of surgery. Total RNA was extracted from biopsies and reverse-transcribed. Real-time quantification of mRNA was performed with a SYBR Green I real time PCR assay, calculating relative gene expression with normalization of results for beta actin mRNA. Actin normalized mRNA levels for OPG and interleukin (IL)-6 were significantly lower in fracture patients, with a significantly higher RANKL/OPG ratio in patients with fractures. There was no significant difference in tumor necrosis factor (TNF), IL-1, IL-1ra, or IL-7 expression. IL-6 mRNA levels were lower in fracture patients (P < 0.05). The effect of increased RANKL/OPG ratio (Z = 2.08, P < 0.05) on fracture risk was additive to that of hip BMD T score (Z = -1.95, P < 0.05) when assessed using logistic regression. Elderly women with hip fractures exhibit an increased RANKL/OPG mRNA content of iliac bone. This is associated with increased fracture susceptibility, which is not in itself explained by low BMD.