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Femoral trabecular patterns in asymptomatic spinal osteoporosis and femoral neck fracture
Clin. Radiol. (1974)25, 243-246 FEMORAL TRABECULAR PATTERNS IN ASYMPTOMATIC SPINAL OSTEOPOROSIS AND FEMORAL NECK FRACTURE J. D E Q U E K E R , K. G A U T A M A and Y. S. R O H
Section of Rheumatology, Academic Hospital PelIenberg and University Psychiatric Hospital Lovenjoel, University of Leuven, Belgium The femoral trabecular pattern grading system and its changes with age, osteoporosis, vertebral collapse and with femoral neck fracture have been evaluated. The technique was found to be simple and reproducible. A large proportion of normal subjects maintain a normal pattern (Grades 6, 5 and 4) through the seventh and eighth decades. However, the majority of females investigated with vertebral collapse also had a normal trabecular pattern. Thus, grading of the trabecular pattern of the upper femur is of only limited use in the assessment of total bone mass. The authors found that the trabecular pattern grade was consistently low in females with fractures of the femoral neck. They suggest that the method is of value in screening subjects liable to such fractures.
SEVERALinvestigators have shown that the changes in the trabecular patterns of the femoral neck are related to the degree of osteoporosis. Hall (1961) radiographically examined 30 cadaveric femora and divided them into normal, osteoporotic and severely osteoporotic groups on the basis of the trabecular patterns. Singh et al. (1970) investigated the trabecular patterns in the upper end of the femur and the clinical and histological evidence of osteoporosis in 35 patients. They recognised 6 different trabecular patterns representing the degree of bone loss. The radiographic grades ranged from six for normals to one for severe osteoporotics. The present study is a critical evaluation of Singh's grading system and its usefulness in the estimation of bone mass in normal and pathological conditions. MATERIAL AND METHODS Antero-posterior radiographs of the hip were assessed for changes in the trabeculae in definite areas in the proximal end of the femur according to the criteria of Singh et al. (1970) (Fig. 1). Two authors independently graded 47 hips and compared the results in order to test the accuracy of the method. The correlation coefficient between the values of two observers was r=0.842. In Fig. 2 the frequency distribution of trabecular pattern grades made by two observers is shown. There was no systematic + or - difference in the values obtained between the two observers. The intra observer error was found to be very low. One
observer repeated the grading of 72 hips on the same radiographs three months later. The correlation coefficient between repeated gradings by one observer was r = 0.920. SUBJECTS The X-ray files of a large psychiatric hospital for females were used to find cases in whom radiographs of the hips, dorsal or lumbar spine were available. Subjects were divided into three groups: the 'normal' group consisted of 57 subjects, aged 20-83 years, who had no wedging at the dorsal spine or biconcavity at the lumbar spine; the asymptomatic vertebral collapse group, 33 subjects aged 47-86 years; and the femoral neck fracture group, 21 subjects aged 50-82 years. Patients with X-ray evidence of Pagets' disease or osteoarthrosis of the hips were excluded. RESULTS Fig. 3 represents the records of trabecular pattern grading according to age groups for 57 normal females. Although no significant age influence on trabecular pattern grade was found, a low trabecular pattern (grade 3) was found in 16.6% of the age group 40-59 years, and 12% in the age group 60-83 years. In the youngest age group nearly all subjects had a trabecular grade 6or5. In Fig. 4 the trabecular pattern gradings of females with asymptomatic vertebral collapse and 243
244
CLINICAL
RADIOLOGY
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z
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FEMORAL T R A B E C U L A R P A T T E R N IN ASYMPTOMATIC S P I N A L OSTEOPOROSIS
245
Trabecular pattern grading
% 80-
..°
68.1
70
60
,°o°°°
r = 0.642
50 /,o
3
30" I'/.I
20"
2
10.6
10" -2
-1
0
*1
*2
1 --
I
I
I
20-3g
/,0-59
60-83
Age groups
FEMALES FIG. 2 Frequency distribution of gradings for femoral trabecular pattern made by two observers on films of 47 hips.
femoral neck fractures are compared with a control group. In the control group 1 2 ~ had a low trabecular pattern grading (grading 3-2-1), compared with 45.4 ~ of the asymptomatic vertebral collapse group and 95-2~ of the femoral neck fracture cases. DISCUSSION The trabecular pattern index is based on the structure rather than on the amount of trabecular bone in the proximal femur. This index thus indicates whether the structure of bone present in a specific individual is normal for him or not. Because each individual enters young adult life with an index that is grade 6 or 5, subsequent loss of bone structure can be easily assessed. The reproducibility is good and the inter-observer error of estimation is found to be low. The variability of changes in trabecular structure with age is not constant, and increases with age as Singh et al. (1972) have shown. A large proportion of normal subjects maintain normal trabecular structure (grade 6-5-4) through the seventh and eighth decades. This finding is in contrast to the bone atrophy
FIG. 3 Trabecular pattern gradings of the upper end of the femur for 57 'normal' female subjects, according to age.
with ageing of cortical bone, where there is no marked increase in variability as age progresses and where most people with ageing are observed to have a decreased bone mass ( G a r n e t al., 1967; Exton-Smith et al., 1969; Dequeker, 1972). Although the grading of trabecular pattern of the upper end of the femur is a simple and reproducible method, its value for an overall assessment of trabecular bone mass has been overstated. This investigation could not confirm the high correlation between axial osteoporosis and trabecular pattern as reported by Singh et al. (1972). 54~o of the vertebral collapse patients had a 'normal' trabecular pattern which indicates that the trabecular pattern grading does not discriminate spinal osteoporosis at an individual level from normal. In other words the trabecular pattern grading is of little help in establishing the presence or severity of osteoporosis. Other authors also report the poor resolution of this technique. Mielke et al. (1972) found that changes in the trabecular bone of the femur are distinct from changes in femoral cortex and trabecular ash density in the same sample. Kranendonk et aI. reported that the trabecular pattern of the proximal
246
CLINICAL RADIOLOGY
Trabacular pattern grade
6 5 l,
3
.e*eee
*=e
lloo
12.1%
12.4%
2
Qoololl
45& % QI
92.8% 60-89
n=2/.
20-59
normal
47- 86 Asymptomatic vertebral collapse n = 33
n=33
60-82 Femoral neck fracture n =14
FEMALES FIG. 4 Trabecular pattern gradings of the upper end of the femur for 57 'normal' subjects, 33 asymptomatic vertebral collapse cases and 21 femoral neck fracture cases. femur is n o t correlated with b o n e mass measured at the radial mid-shaft with a 1751 p h o t o n absorptiometry method. The finding of a consistently low trabecular p a t t e r n grade in 21 cases of femoral neck fracture confirms the data of Singh et al. (1972), who f o u n d that all their 12 patients with pathological fracture of the femoral neck were grade 3 or below. Since i n cases with femoral neck fracture a clear separation with n o r m a l controls is achieved, the trabecular p a t t e r n grading is of particular value for screening cases liable to sustain a femoral neck fracture.
REFERENCES DEQUEKER, J. (1972). Bone loss in normal and pathological conditions. Leuven University Press, Leuven, p. 214. EXTON-SMITH, A. N., MILLARD, P. H., PAYNE, P. R. &
WHEELER, E. (1969). Pattern of development and loss of bone with age. Lancet, 2, 1154-1157. GARN, S. M., ROHMANN, C. G. & WAGNER, B. (1967). Bone loss as a general phenomenon in man. Fed. Proc., 26, 1729-1738. HALL, M. C. (1961). The trabecular patterns of the neck of the femur with particular reference to changes in osteoporosis. Canadian Medical Association Journal, 85, 1141-1144. KRANENDONK,D. H., JURIST, J. M. & GUN LEE, H. (1972). Femoral trabecular patterns and bone mineral content. Journal of Bone and Joint Surgery, 54A, 1472-1478. MIELKE, J. H., ARMELAGOS,G. J. & VAN GERVAN, D. P. (1972). Trabecular involution in femoral heads of a prehistoric (X-group) population from Sudanese Nubia. American Journal of Physical Anthropology, 36, 39-44. SINGH, M., NAGRATH,A. R. & MAINI,P. S. (1970). Changes in trabecular pattern of the upper end of the femur as an index of osteoporosis. Journal of Bone and Joint Surgery, 52A, 457-467. SINGH, M., RIGGS, B. L., BEABOUT, J. W. t~ JOWSEY, J. (1972). Femoral trabecular index for evaluation of spinal osteoporosis. Annals of Internal Medicine, 77, 63-67.
Section of Rheumatology, Academic Hospital PelIenberg and University Psychiatric Hospital Lovenjoel, University of Leuven, Belgium The femoral trabecular pattern grading system and its changes with age, osteoporosis, vertebral collapse and with femoral neck fracture have been evaluated. The technique was found to be simple and reproducible. A large proportion of normal subjects maintain a normal pattern (Grades 6, 5 and 4) through the seventh and eighth decades. However, the majority of females investigated with vertebral collapse also had a normal trabecular pattern. Thus, grading of the trabecular pattern of the upper femur is of only limited use in the assessment of total bone mass. The authors found that the trabecular pattern grade was consistently low in females with fractures of the femoral neck. They suggest that the method is of value in screening subjects liable to such fractures.
SEVERALinvestigators have shown that the changes in the trabecular patterns of the femoral neck are related to the degree of osteoporosis. Hall (1961) radiographically examined 30 cadaveric femora and divided them into normal, osteoporotic and severely osteoporotic groups on the basis of the trabecular patterns. Singh et al. (1970) investigated the trabecular patterns in the upper end of the femur and the clinical and histological evidence of osteoporosis in 35 patients. They recognised 6 different trabecular patterns representing the degree of bone loss. The radiographic grades ranged from six for normals to one for severe osteoporotics. The present study is a critical evaluation of Singh's grading system and its usefulness in the estimation of bone mass in normal and pathological conditions. MATERIAL AND METHODS Antero-posterior radiographs of the hip were assessed for changes in the trabeculae in definite areas in the proximal end of the femur according to the criteria of Singh et al. (1970) (Fig. 1). Two authors independently graded 47 hips and compared the results in order to test the accuracy of the method. The correlation coefficient between the values of two observers was r=0.842. In Fig. 2 the frequency distribution of trabecular pattern grades made by two observers is shown. There was no systematic + or - difference in the values obtained between the two observers. The intra observer error was found to be very low. One
observer repeated the grading of 72 hips on the same radiographs three months later. The correlation coefficient between repeated gradings by one observer was r = 0.920. SUBJECTS The X-ray files of a large psychiatric hospital for females were used to find cases in whom radiographs of the hips, dorsal or lumbar spine were available. Subjects were divided into three groups: the 'normal' group consisted of 57 subjects, aged 20-83 years, who had no wedging at the dorsal spine or biconcavity at the lumbar spine; the asymptomatic vertebral collapse group, 33 subjects aged 47-86 years; and the femoral neck fracture group, 21 subjects aged 50-82 years. Patients with X-ray evidence of Pagets' disease or osteoarthrosis of the hips were excluded. RESULTS Fig. 3 represents the records of trabecular pattern grading according to age groups for 57 normal females. Although no significant age influence on trabecular pattern grade was found, a low trabecular pattern (grade 3) was found in 16.6% of the age group 40-59 years, and 12% in the age group 60-83 years. In the youngest age group nearly all subjects had a trabecular grade 6or5. In Fig. 4 the trabecular pattern gradings of females with asymptomatic vertebral collapse and 243
244
CLINICAL
RADIOLOGY
U
z
~
H ~,.., U
Z
¢/
O
~,~ 6 0
~
e
Q
U
z 0
Q
c~
o~
.~ ,~-,4
FEMORAL T R A B E C U L A R P A T T E R N IN ASYMPTOMATIC S P I N A L OSTEOPOROSIS
245
Trabecular pattern grading
% 80-
..°
68.1
70
60
,°o°°°
r = 0.642
50 /,o
3
30" I'/.I
20"
2
10.6
10" -2
-1
0
*1
*2
1 --
I
I
I
20-3g
/,0-59
60-83
Age groups
FEMALES FIG. 2 Frequency distribution of gradings for femoral trabecular pattern made by two observers on films of 47 hips.
femoral neck fractures are compared with a control group. In the control group 1 2 ~ had a low trabecular pattern grading (grading 3-2-1), compared with 45.4 ~ of the asymptomatic vertebral collapse group and 95-2~ of the femoral neck fracture cases. DISCUSSION The trabecular pattern index is based on the structure rather than on the amount of trabecular bone in the proximal femur. This index thus indicates whether the structure of bone present in a specific individual is normal for him or not. Because each individual enters young adult life with an index that is grade 6 or 5, subsequent loss of bone structure can be easily assessed. The reproducibility is good and the inter-observer error of estimation is found to be low. The variability of changes in trabecular structure with age is not constant, and increases with age as Singh et al. (1972) have shown. A large proportion of normal subjects maintain normal trabecular structure (grade 6-5-4) through the seventh and eighth decades. This finding is in contrast to the bone atrophy
FIG. 3 Trabecular pattern gradings of the upper end of the femur for 57 'normal' female subjects, according to age.
with ageing of cortical bone, where there is no marked increase in variability as age progresses and where most people with ageing are observed to have a decreased bone mass ( G a r n e t al., 1967; Exton-Smith et al., 1969; Dequeker, 1972). Although the grading of trabecular pattern of the upper end of the femur is a simple and reproducible method, its value for an overall assessment of trabecular bone mass has been overstated. This investigation could not confirm the high correlation between axial osteoporosis and trabecular pattern as reported by Singh et al. (1972). 54~o of the vertebral collapse patients had a 'normal' trabecular pattern which indicates that the trabecular pattern grading does not discriminate spinal osteoporosis at an individual level from normal. In other words the trabecular pattern grading is of little help in establishing the presence or severity of osteoporosis. Other authors also report the poor resolution of this technique. Mielke et al. (1972) found that changes in the trabecular bone of the femur are distinct from changes in femoral cortex and trabecular ash density in the same sample. Kranendonk et aI. reported that the trabecular pattern of the proximal
246
CLINICAL RADIOLOGY
Trabacular pattern grade
6 5 l,
3
.e*eee
*=e
lloo
12.1%
12.4%
2
Qoololl
45& % QI
92.8% 60-89
n=2/.
20-59
normal
47- 86 Asymptomatic vertebral collapse n = 33
n=33
60-82 Femoral neck fracture n =14
FEMALES FIG. 4 Trabecular pattern gradings of the upper end of the femur for 57 'normal' subjects, 33 asymptomatic vertebral collapse cases and 21 femoral neck fracture cases. femur is n o t correlated with b o n e mass measured at the radial mid-shaft with a 1751 p h o t o n absorptiometry method. The finding of a consistently low trabecular p a t t e r n grade in 21 cases of femoral neck fracture confirms the data of Singh et al. (1972), who f o u n d that all their 12 patients with pathological fracture of the femoral neck were grade 3 or below. Since i n cases with femoral neck fracture a clear separation with n o r m a l controls is achieved, the trabecular p a t t e r n grading is of particular value for screening cases liable to sustain a femoral neck fracture.
REFERENCES DEQUEKER, J. (1972). Bone loss in normal and pathological conditions. Leuven University Press, Leuven, p. 214. EXTON-SMITH, A. N., MILLARD, P. H., PAYNE, P. R. &
WHEELER, E. (1969). Pattern of development and loss of bone with age. Lancet, 2, 1154-1157. GARN, S. M., ROHMANN, C. G. & WAGNER, B. (1967). Bone loss as a general phenomenon in man. Fed. Proc., 26, 1729-1738. HALL, M. C. (1961). The trabecular patterns of the neck of the femur with particular reference to changes in osteoporosis. Canadian Medical Association Journal, 85, 1141-1144. KRANENDONK,D. H., JURIST, J. M. & GUN LEE, H. (1972). Femoral trabecular patterns and bone mineral content. Journal of Bone and Joint Surgery, 54A, 1472-1478. MIELKE, J. H., ARMELAGOS,G. J. & VAN GERVAN, D. P. (1972). Trabecular involution in femoral heads of a prehistoric (X-group) population from Sudanese Nubia. American Journal of Physical Anthropology, 36, 39-44. SINGH, M., NAGRATH,A. R. & MAINI,P. S. (1970). Changes in trabecular pattern of the upper end of the femur as an index of osteoporosis. Journal of Bone and Joint Surgery, 52A, 457-467. SINGH, M., RIGGS, B. L., BEABOUT, J. W. t~ JOWSEY, J. (1972). Femoral trabecular index for evaluation of spinal osteoporosis. Annals of Internal Medicine, 77, 63-67.