Calcif Tissue Int (1992) 50:507-510
Calcified Tissue International 9 1992 Springer-Verlag New York Inc.
The Effect of Overlying Calcification on Lumbar Bone Densitometry Paul J. Drinka, 1'2'3 Arthur A. DeSmet, 3 Steven F. Bauwens, 4 and Alice Rogot s tWisconsin Veterans Home, King, Wisconsin 54946; 2Veterans Administration Medical Center; and 3University of Wisconsin, Madison; 4Managed Care Resources, Inc., Chesapeake, Virginia; and 5Medical Biostatistics Center, University of Wisconsin, Madison, Wisconsin, USA Received August 13, 1991, and in revised form November 14, 1991
S u m m a r y . W e studied bone mineral density (BMD) of the spine using dual p h o t o n absorptiometry, as well as standard anterior-posterior and lateral lumbar spine X-ray film in 113 ambulatory elderly male v o l u n t e e r s with a mean age of 72 years (range 66--91 years). E a c h subject had three measurements taken for lumbar v e r t e b r a e 1 through 4: B M D , length of aortic calcification (AC), and degenerative facet sclerosis graded 0-3. A separate statistical model was fit to B M D for each v e r t e b r a using analysis of covariance. A C did not contribute significantly to B M D . B M D was increased by 0.280.03 g/cm 2 (L1-L4) with a sclerosis score of 2, and by 0.470.25 g/cm 2 with a sclerosis score of 3, P < 0.001. The association between increased BMD and overlying facet sclerosis may be related to the bone density within the sclerosis itself or to an association b e t w e e n degenerative joint disease and a generalized increase in subchondral bone.
Key words: B o n e d e n s i t o m e t r y - M a l e s - F a c e t
sclerosis-
Aortic calcification.
Minimal data h a v e b e e n published regarding the association b e t w e e n d e g e n e r a t i v e sclerosis, aortic calcification (AC), and lumbar bone mineral density (BMD) in elderly patients. Previous authors h a v e e m p h a s i z e d the effects of osteophytes in the intervertebral space related to degenerative disk disease [1-3]. In contrast, w e studied the effects of overlying facet sclerosis, as well as v a s c u l a r calcification by analyzing the relationship b e t w e e n lumbar B M D on dual photon absorptiometry and m e a s u r e s of overlying degenerative facet sclerosis and A C f r o m lumbar radiographs in 113 elderly male volunteers. W e then fit a m o d e l to the data to estimate the a m o u n t that B M D was e l e v a t e d in relationship to overlying calcification.
Subjects and Methods Subjects A letter of invitation was sent to every male, age 65 years or older, living in Dane County, Wisconsin, and registered with the Wm. S. Middleton Memorial Veterans Hospital Outpatient Department. The letter informed the veteran that we were interested in studying bone health and osteoporosis. A total of 520 letters were sent; 113 ambulatory males volunteered to participate. The group receiving the
Offprint requests to: P. J. Drinka, Wisconsin Veterans Home, King, WI 54946
letters (n = 520) had a mean age of 73.2 + 4.6 years, with a range of 66-96. The group studied had a mean age of 71.9 + 5.8 years with a range of 66-91. When these two groups were submitted to a t test, there was no significant difference between their ages. Of our study sample, all but one were white. They were not socially isolated, as 87% lived with a spouse. Only seven patients (6%) had alcohol abuse documented on their medical record. The men were questioned regarding their self-reported alcohol intake. Of the 113 men studied, 32 men (27.5%) did not drink alcohol. The mean frequency of alcohol intake for those who drank alcohol was 14.4 (-+ 11.7 S.D.) times per month. The mean number of alcoholic drinks on each occasion was 2.1 (-1.2 SD). The group means are within the range of socially acceptable alcohol use. We calculated an alcoholic drink as one 12-oz. beer or one 30-cc shot. Nutritionally, none of our subjects weighed less than 5% below ideal body weight (ibw = 50 kg + 2.3 kg for every 1 inch above 5 ft). The mean albumin level was 4.33 g/dl (NL: 3.5-5.5 g/dl), with a range of 3.7-5.2 g/dl. Even the lowest albumin level was within the normal range.
Methods Standard anterior-posterior (AP) and lateral lumbar spine radiographs were obtained and quantitatively assessed by one of the authors who was blind to BMD. Each lumbar vertebra was evaluated for the presence of sclerosis projected over each vertebral body. This included the density due to facet joint sclerosis, discogenic sclerosis, and osteophytes, but was primarily from degenerative joint disease of the facets graded primarily on the AP film. The AP film was used to estimate sclerosis because tissue thickness is more uniform over the spine on the AP projection compared with the lateral projection. On the lateral projection, the ilia overlie L4 and L5, making these areas seem more dense than the upper vertebrae. The AP projection is also that used by the bone densitometer so the superimposed bony structures on the AP radiograph reflect the bone summed by the densitometer. The following grading system was used to quantitate the sclerosis: grade 0 = no sclerosis, grade 1 = mild increase in bone density, grade 2 = increased bone density such that central vertebral density approached the density of compact or cortical bone, and grade 3 = marked sclerosis such that no bone detail could be seen through the increased density. In addition, the total length of AC over each vertebral level was measured on the lateral film using a standard millimeter ruler. The precision of this method of measurement was within 1%. BMD of the spine was measured by dual-photon absorptiometry using a 1 Ci Gd153 source (Lunar Dp3, Lunar Corporation, Madison, WI). BMD was measured as bone mass per unit projected area (g/cmz) for each vertebra, 1 through 4. The precision of this method was 2%. Thus, each subject had three measurements taken for each lumbar vertebra 1 through 4: BMD from dual photon densitometry, length of aortic calcification (AC), and sclerosis score from the lumbar X-ray film. A separate statistical model was fit to BMD for each vertebra using analysis of covariance (ANCOVA). The initial model for BMD included aortic calcification and sclerosis score.
508
P.J. Drinka et al.: Overlying Calcification and Densitometry
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Calcified Tissue International 9 1992 Springer-Verlag New York Inc.
The Effect of Overlying Calcification on Lumbar Bone Densitometry Paul J. Drinka, 1'2'3 Arthur A. DeSmet, 3 Steven F. Bauwens, 4 and Alice Rogot s tWisconsin Veterans Home, King, Wisconsin 54946; 2Veterans Administration Medical Center; and 3University of Wisconsin, Madison; 4Managed Care Resources, Inc., Chesapeake, Virginia; and 5Medical Biostatistics Center, University of Wisconsin, Madison, Wisconsin, USA Received August 13, 1991, and in revised form November 14, 1991
S u m m a r y . W e studied bone mineral density (BMD) of the spine using dual p h o t o n absorptiometry, as well as standard anterior-posterior and lateral lumbar spine X-ray film in 113 ambulatory elderly male v o l u n t e e r s with a mean age of 72 years (range 66--91 years). E a c h subject had three measurements taken for lumbar v e r t e b r a e 1 through 4: B M D , length of aortic calcification (AC), and degenerative facet sclerosis graded 0-3. A separate statistical model was fit to B M D for each v e r t e b r a using analysis of covariance. A C did not contribute significantly to B M D . B M D was increased by 0.280.03 g/cm 2 (L1-L4) with a sclerosis score of 2, and by 0.470.25 g/cm 2 with a sclerosis score of 3, P < 0.001. The association between increased BMD and overlying facet sclerosis may be related to the bone density within the sclerosis itself or to an association b e t w e e n degenerative joint disease and a generalized increase in subchondral bone.
Key words: B o n e d e n s i t o m e t r y - M a l e s - F a c e t
sclerosis-
Aortic calcification.
Minimal data h a v e b e e n published regarding the association b e t w e e n d e g e n e r a t i v e sclerosis, aortic calcification (AC), and lumbar bone mineral density (BMD) in elderly patients. Previous authors h a v e e m p h a s i z e d the effects of osteophytes in the intervertebral space related to degenerative disk disease [1-3]. In contrast, w e studied the effects of overlying facet sclerosis, as well as v a s c u l a r calcification by analyzing the relationship b e t w e e n lumbar B M D on dual photon absorptiometry and m e a s u r e s of overlying degenerative facet sclerosis and A C f r o m lumbar radiographs in 113 elderly male volunteers. W e then fit a m o d e l to the data to estimate the a m o u n t that B M D was e l e v a t e d in relationship to overlying calcification.
Subjects and Methods Subjects A letter of invitation was sent to every male, age 65 years or older, living in Dane County, Wisconsin, and registered with the Wm. S. Middleton Memorial Veterans Hospital Outpatient Department. The letter informed the veteran that we were interested in studying bone health and osteoporosis. A total of 520 letters were sent; 113 ambulatory males volunteered to participate. The group receiving the
Offprint requests to: P. J. Drinka, Wisconsin Veterans Home, King, WI 54946
letters (n = 520) had a mean age of 73.2 + 4.6 years, with a range of 66-96. The group studied had a mean age of 71.9 + 5.8 years with a range of 66-91. When these two groups were submitted to a t test, there was no significant difference between their ages. Of our study sample, all but one were white. They were not socially isolated, as 87% lived with a spouse. Only seven patients (6%) had alcohol abuse documented on their medical record. The men were questioned regarding their self-reported alcohol intake. Of the 113 men studied, 32 men (27.5%) did not drink alcohol. The mean frequency of alcohol intake for those who drank alcohol was 14.4 (-+ 11.7 S.D.) times per month. The mean number of alcoholic drinks on each occasion was 2.1 (-1.2 SD). The group means are within the range of socially acceptable alcohol use. We calculated an alcoholic drink as one 12-oz. beer or one 30-cc shot. Nutritionally, none of our subjects weighed less than 5% below ideal body weight (ibw = 50 kg + 2.3 kg for every 1 inch above 5 ft). The mean albumin level was 4.33 g/dl (NL: 3.5-5.5 g/dl), with a range of 3.7-5.2 g/dl. Even the lowest albumin level was within the normal range.
Methods Standard anterior-posterior (AP) and lateral lumbar spine radiographs were obtained and quantitatively assessed by one of the authors who was blind to BMD. Each lumbar vertebra was evaluated for the presence of sclerosis projected over each vertebral body. This included the density due to facet joint sclerosis, discogenic sclerosis, and osteophytes, but was primarily from degenerative joint disease of the facets graded primarily on the AP film. The AP film was used to estimate sclerosis because tissue thickness is more uniform over the spine on the AP projection compared with the lateral projection. On the lateral projection, the ilia overlie L4 and L5, making these areas seem more dense than the upper vertebrae. The AP projection is also that used by the bone densitometer so the superimposed bony structures on the AP radiograph reflect the bone summed by the densitometer. The following grading system was used to quantitate the sclerosis: grade 0 = no sclerosis, grade 1 = mild increase in bone density, grade 2 = increased bone density such that central vertebral density approached the density of compact or cortical bone, and grade 3 = marked sclerosis such that no bone detail could be seen through the increased density. In addition, the total length of AC over each vertebral level was measured on the lateral film using a standard millimeter ruler. The precision of this method of measurement was within 1%. BMD of the spine was measured by dual-photon absorptiometry using a 1 Ci Gd153 source (Lunar Dp3, Lunar Corporation, Madison, WI). BMD was measured as bone mass per unit projected area (g/cmz) for each vertebra, 1 through 4. The precision of this method was 2%. Thus, each subject had three measurements taken for each lumbar vertebra 1 through 4: BMD from dual photon densitometry, length of aortic calcification (AC), and sclerosis score from the lumbar X-ray film. A separate statistical model was fit to BMD for each vertebra using analysis of covariance (ANCOVA). The initial model for BMD included aortic calcification and sclerosis score.
508
P.J. Drinka et al.: Overlying Calcification and Densitometry
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