Impact of degenerative radiographic abnormalities and vertebral fractures on spinal bone density of women with osteoporosis

ABSTRACT CONTEXT: Measurements of bone density taken by dual-energy x-ray absorptiometry are the most accurate procedure for the diagnosis of osteoporosis. This procedure has the disadvantage of measuring the density of all mineral components, including osteophytes, vascular and extra vertebral calcifications. These alterations can influence bone density results and densitometry interpretation. OBJECTIVE: To correlate radiography and densitometry findings from women with osteoporosis, analyzing the influence of degenerative processes and vertebral fractures on the evaluation of bone density. DESIGN: Retrospective study. SETTING: Osteoporosis outpatients’ clinic at Hospital das Clínicas, Universidade Estadual de Campinas. PARTICIPANTS: Ninety-six postmenopausal women presenting osteoporosis diagnosed by bone density. MAIN MEASUREMENTS: Bone mineral density of the lumbar spine and femoral neck were measured by the technique of dual-energy x-ray absorptiometry, using a LUNAR-DPX densitometer. Fractures, osteophytes and aortic calcifications were evaluated by simple x-rays of the thoracic and lumbar spine. RESULTS: The x-rays confirmed vertebral fractures in 41.6%, osteophytes in 33.3% and calcifications of the aorta in 30.2%. The prevalence of fractures and aortic calcifications increased with age. The mean bone mineral density was 0.783g/cm and the mean T-score was −3.47 DP. Neither fractures nor aortic calcifications had significant influence on bone mineral density (P = 0.36 and P = 0.09, respectively), despite the fractured vertebrae having greater bone mineral density (P < 0.02). Patients with lumbar spine osteophytes showed greater bone mineral density (P = 0.04). Osteophytosis was associated with lumbar spine bone mineral density after adjustment for fractures and aortic calcifications by multiple regression (P = 0.01). CONCLUSION: Osteophytes and lumbar spine fractures can overestimate bone density interpretation. The interpretation of densitometry results should be carried out together with the interpretation of a simple lumbar spine x-ray in elderly women.


Impact of degenerative radiographic abnormalities and vertebral fractures on spinal bone density of women with osteoporosis
Hospital das Clínicas, Faculty of Medicine Sciences, Universidade Estadual de Campinas, Campinas, Brazil.

INTRODUCTION
Osteoporosis is considered to be a public health problem due to high morbidity and mortality rates caused by fractures, particularly in elderly women.In Brazil it is estimated that osteoporosis affects around 35% of women over 45 years old. 1 Today, measurements of bone mineral density (BMD) taken by dualenergy x-ray absorptiometry (DXA) are the most accurate procedure for the diagnosis of osteoporosis. 2However, measurements taken by DXA are two-dimensional and when made with an anterior-posterior projection, the most used incidence, this procedure has the disadvantage of measuring the density of all the mineral components encountered in the x-ray pathway, including osteophytes and vascular and extra-vertebral calcifications.It has been shown in some studies that these alterations can influence bone mineral density results when the measurements taken are from regions with a degenerative process. 3,4 study on bone mineral density in men with osteophytes was carried out by Ito et al.  (1993), in which the results from DXA and quantitative computerized tomography (QCT) were compared.It concluded that QCT is more precise because it provides only trabecular measurements without the addition of osteophytes.4 Studies made by Orwoll et al.  (1990) and Masud et al. (1993) showed that men with lumbar spine osteophytes had 15% to 24% greater bone mineral density when compared with those without osteophytes.3,5 Due to the superposition of the aorta in relation to the lumbar spine, some studies have speculated that the presence of aortic calcifications can overrate lumbar spine bone mineral density.3,[6][7][8] Vertebral fractures, particularly vertebral collapses, can also increase bone mineral density measurements of the affected vertebrae.As they are denser than the adjacent ones, they can be detected by the decrease in vertebral height or by the heterogeneity of density measured in adjacent vertebrae.9 The objective of this study was to correlate radiography and densitometry findings from women with osteoporosis, analyzing the influence of osteophytes, aortic calcifications and vertebral fractures, with regard to lumbar spine bone mineral density.

METHODS
A retrospective investigation was made of 96 postmenopausal outpatients with osteoporosis who had been followed up at the osteoporosis outpatients' clinic at Hospital das Clínicas, UNICAMP.All of them had osteoporosis that was diagnosed using dualenergy x-ray absorptiometry (DXA) in an anterior-posterior projection, according to the World Health Organization criteria. 2Bone mineral density was measured using a LUNAR-DPX densitometer (LUNAR Corporation, USA).The coefficient of variation was 2% for the lumbar spine.
Simple lumbar spine x-rays in lateral and anterior-posterior projections were analyzed by two investigators.In these, they would assess each vertebra with regard to osteophytes, aortic calcifications and vertebral fractures.Vertebral fractures were defined as being present when there was a reduction in vertebral height greater than 20% in comparison with the heights of the adjacent vertebrae. 10,11he statistical analysis was done using the mean bone mineral density in absolute values (g/cm 2 ) and in relation to young-adult values (T-score).Comparisons of means were carried out using the Student t test.Multiple regression analysis was done to analyze the association between degenerative abnormalities, fractures and bone mineral density.In the statistical analysis the level of significance was set at p < 0.05.The statistical analysis was done using the SAS statistics package (NC, USA).
The distribution of the radiographic alterations, based on age groups, showed a significant increase in the frequency of fractures (P = 0.019) and in aortic calcifications (P = 0.001) with increasing age.With regard to osteophytes, there was no significant increase (Table 1).
The comparison of mean lumbar spine bone mineral density (g/cm 2 ) with regard to the presence or absence of fractures, osteophytes or aortic calcifications is shown in Table 2.
Patients with osteophytes had higher mean bone mineral densities (P = 0.04).There was no significant difference in the mean bone mineral density in patients with vertebral fractures or vascular calcifications, in comparison to those with no radiological alterations (Figure 1, Figures 2A and 2B).
A later, more detailed bone mineral density analysis of each vertebra from L1 to L4 was carried out, in which they were compared with the corresponding vertebrae without fractures.This comparison of mean bone mineral density for each fractured vertebra with a non-fractured one showed an increase of bone mineral density varying from 4% to 17%.The mean bone mineral density of fractured lumbar vertebrae was significantly greater than for those with no fracture (P < 0.02) (Table 3, Figure 1, Figures 2A and 2B).
When potential confounders such as fractures and aortic calcifications were considered in multiple regression, an association between osteophytes and bone mineral density was revealed (P = 0.0174) (Table 4).

DISCUSSION
The prevalence of alterations in our sample was high when compared with other studies and this increased with age.Dawson-Hughes & Dallal analyzed the impact of radiographic alterations with regard to loss of spinal bone mass in a group of 293 postmenopausal women with no fractures, finding a 2% prevalence for osteophytes and 11% for aortic calcifications. 12Another study found a 69% prevalence of osteophytes in men and women with a mean age of 69 years. 13hese differences may be due to the diversity in the characteristics of the population studied, which was made up only of postmenopausal women presenting a densitometry diagnosis of osteoporosis, of which 40% had vertebral fractures.
The influence of osteophytes on bone  ) ) ) 5][16] Studies analyzing the intensity of osteophytes have shown that the greater the intensity of this abnormality, the higher the increase in bone mineral density is. 3 It is clear that osteophytes can lead to an apparent increase in bone mineral density, although it is not clear whether this increase is associated with a decrease in fractures.

X-ray X-ray X-ray X-ray X-ray
With regard to calcification of the abdominal aorta, the results from this study are similar to those presented by other investigators, who likewise did not find that this type of calcification influenced bone mineral density evaluated by densitometry. 8,17evertheless, some studies have observed that large calcifications can cause a discrete increase in bone mineral density in the affected area, although this influence is small. 3,7Despite the controversies, aortic calcifications seem to have a much smaller effect on vertebral bone mineral density, due probably to the fact that these vascular deposits have less mineral density. 3he incidence of lumbar fractures in the study population was 24%, which was similar to the 20% found by other investigators. 13It was observed that the prevalence of thoracic and lumbar spine fractures increased from 22.5%, in the under 60-year age group, to 40% in women over 70 years of age.Other studies have shown that the prevalence, type and number of vertebral deformities increase with age and are more prevalent in women. 18- 20However, the actual prevalence reported depends not only on the age and sex of the population measured but also upon the method of fracture definition. 13The criterion used for defining vertebral fractures in this study was a reduction in vertebral height greater than 20%, in comparison with the height of adjacent vertebrae.However, many authors do not consider this criterion to be ideal, as these parameters can vary along the spine and the presence of any degenerative change can confound measurements in adjacent vertebrae, leading to a false fracture diagnosis. 13,21hen comparing bone mineral density in patients with or without fractures it was observed that the patients with vertebral fractures had a lower mean bone mineral density than was found in the group of patients without fractures.This was to be expected, as a lower bone mineral density means a higher risk of fracture.Analyzing each one of the vertebrae (L1 to L4), comparing bone mineral   density in fractured vertebrae to nonfractured ones, an increase in bone mineral density was found in the fractured ones, varying from 4% to 17%.Some authors have shown that the bone mineral density of vertebrae with old fractures has an increase of around 16%, and that differences in adjacent vertebrae that are greater than 10% should be analyzed cautiously and sometimes even eliminated from a mean bone mineral density study. 9hese results show that degenerative processes, particularly osteophytes and fractures, can hinder the interpretation of bone densitometry of the spine and may even in some cases overestimate the measurements of bone mass in the affected areas.To reduce these effects, it is suggested that, for more elderly patients, densitometry results should be accompanied by an x-ray of the lumbar spine region, particularly in patients over 70 years of age, as these alterations are more frequent at this age.
of bone density taken by dual-energy x-ray absorptiometry are the most accurate procedure for the diagnosis of osteoporosis.This procedure has the disadvantage of measuring the density of all mineral components, including osteophytes, vascular and extra vertebral calcifications.These alterations can influence bone density results and densitometry interpretation.Bone mineral density of the lumbar spine and femoral neck were measured by the technique of dual-energy x-ray absorptiometry, using a LUNAR-DPX densitometer.Fractures, osteophytes and aortic calcifications were evaluated by simple x-rays of the thoracic and lumbar spine.

Figure 1 .
Figure 1.Lumbar spine x-ray showing lumbar fracture in L 2 and multiple and large osteophytes.

Figure 2 (
Figure 2 (A).Spine bone density showing an increase in BMD caused by loss of vertebral heights in L 2 and osteophytes in L 1 -L 3 .(B).Femoral bone density in the same patient showing marked osteoporosis.

Table 1 . Radiological abnormalities of the lumbar spine in women with osteoporosis, according to age group (n = 96)
P * Fisher test.

Table 4 . Factors associated with lumbar spine bone mineral density by multiple regression analysis
r 2 = 0.08.