Acta med. scand. Vol. 198, pp. 453454, 1975
Skeletal Status in Patients with Rheumatoid Arthritis Claus Christiansen and Paul R ~ d b r o From the Departments of Clinical Chemisfr.v and Clinical Physiology, Glostrup Hospital. and the Depariment of Clinical Physiology, Alhorg Syyehus S y d , Alborg, Denmark
ABSTRACT. The total body calcium - estimated from the bone mineral content in the distal part of the forearm, measured by means of photon absorptiometry - has been determined in 15 patients with rheumatoid arthritis. None of the patients were treated with steroids and all were relatively mobile. The results indicate that osteoporosis is uncommon in such patients.
Recent investigations have postulated that osteoporosis, estimated from X-ray pictures, is a common phenomenon in patients with rheumatoid arthritis (1, 8, 9). The etiology of bone loss is not understood but an explanation is often sought in various multiple factors such as immobilization, treatment with corticosteroids or other anti-inflammatory agents. However, the specific role of each factor is poorly defined and it is still not clear whether rheumatoid arthritis in itself leads to osteoporosis. We have investigated the bone mineral content (BMC) in a group of relatively mobile patients with rheumatoid arthritis (without corticosteroid treatment) in order to investigate whether and to what degree rheumatoid arthritis in itself leads to osteopenia. We studied this by measuring the BMC in the distal part of the forearm by photon absorptiometry. This parameter is well correlated to total bone calcium (3, 4, 5, 6). MATERIAL AND METHODS Eleven women and four men, aged 26-59 years (mean 46), consented to the study. All patients had rheumatoid arthritis defined according to the American Rheumatism Association criteria. Mean duration of the illness was 9.5 years (range i 1 4 2 ) . Nobody was being or had been treated with corticosteroids and all were receiving one or two anti-inflammatory agents, such as acetyl salicylate or phenylbutazone. They were all relatively mobile patients.
BMC was determined by direct photon absorptiometry on both forearms (Fig. I ) . Antebrachium is fixed in a plexiglass container filled with distilled water. Water is used, since it has nearly the same coefficient of absorption as plexiglass and soft tissue. The source of radiation (25 mCi and the detector are fixed in holders on either side of the bones to be examined. A mechanical scanner displaces the detector and the source perpendicular to the longitudinal axis of the bones. The transmission of photons through the bones depends on the BMC. Cameron et al. (2) showed a direct relation between the absorption of photons from 1251 and BMC. In our modified version of the method (3), the BMC is expressed in arbitrary units as a mean value of six scans from each forearm. The coefficient of variation of duplicate measurements in the same patient on different days is of the order 3 4 %. BMC of the forearm is fairly well correlated to the body’s total calcium content (3, 4, 5, 6). The BMC value in each patient was compared with the values in a group of 127 normal subjects matched for age and sex (4), in such a way that the patient’s value was classified using the mean and S.D. in the corresponding age- and sexdependent subgroup. Furthermore, the patient’s BMC value was expressed as a percentage of the corresponding normal mean,
RESULTS The percental value of BMC in the patients did not correlate significantly to the duration of illness, and the patients were accordingly considered as a sample of the population of “relatively mobile rheumatoid arthritis patients without corticosteroid treatment”. The BMC values in the patients scattered around the corresponding normal mean, and n o patient had a BMC value lower than the normal range (mean + 2 S.D.). The group mean for the 15 patients amounted to 94% (S.D. 18%) of the corresponding normal mean. This is not significantly different from the normal mean (100%. S.D. 16%), according to either the t-test for differences between averages or Wilcoxon’s test. Acra med. scand. 198
454 C. Christansen and P R ~ d h r o plexiglass qontainer
b
Fig. I . Principle for the measurement of bone mineral content by direct photon absorptiometry on t h e forearm. (a) Section through system showing plexiglass container, and U-shaped holder, with radioactive source and detector. ( h ) System seen from volar surface showing scanning movements of source and detector.
DISCUSSION The results indicate, in spite of the relatively few patients, that osteoporosis in rheumatoid arthritis is unusual in relatively mobile patients treated with “ordinary” anti-inflammatory drugs. Mueller and Jurist (7) found in six patients treated with corticosteroids that the BMC (investigated with almost the same technique, radius alone being studied with a non-scanning procedure) was significantly decreased to nearly 70% of the value in six matched controls without steroid treatment. Furthermore, they found that the mean BMC in 20 patients with rheumatoid arthritis without steroids did not differ significantly from the mean in 20 matched controls. The patients’ BMC amounted t o 95% of the corresponding normal mean. The present study confirms these findings, our mean value amounting to 94 % of normal.
Acta rned. scand. 198
From these two recent studies it is tempting to conclude that rheumatoid arthritis in ifself does not lead t o significant osteoporosis. However, further studies are clearly necessary to test whether and to what degree osteoporosis is found in this disease. A question of particular interest is the part played by immobilization in the development of osteoporosis in rheumatoid arthritis. AC K N OW L EDG EM EN T This study was supported by a grant from Carl J . Beckers Fond.
REFERENCES I . Bjelle, A. & Nilsson, B.: Osteoporosis in rheumatoid arthritis. Calcif. Tissue Res. 5: 327, 1970. 2. Cameron, J. R., Mazess, R. 9 . & Sorenson, J. A,: Precision and accuracy of bone mineral determination by direct photon absorptiometry. Invest. Radiol. 3: 141, 1968. 3. Christiansen, C. & Rsdbro, P.: Estimation of total body calcium from the bone mineral content of the forearm. To be published. 4 - Bone mineral content and estimated total body calcium in normal adults. To be published. 5. Cohn, S. H . , Ellis, K. J., Wallach, S.. Zanzi, I., Atkins, H . L. & Aloia, J . F.: Absolute and relative deficit in total-skeleton calcium and radial bone rninera1 in osteoporosis. J . nucl. Med. 15:428, 1974. 6 . Mazess, R . B.: Estimation of bone and skeletal weight by direct photon absorptiometry. Invest. Radiol. 6: 52, 1971. 7. Mueller. M. N. & Jurist, J . M.:Skeletal status in rheumatoid arthritis. Arthr. and Rheum. 16: 66,1973. 8. Saville, P. & Karmosh, 0.: Osteoporosis of rheumatoid arthritis. Influence of age, sex and corticosteroids. Arthr. and Rheum. 10:423, 1967. 9. Soila, P.: Roentgen manifestations of adult rheumatoid arthritis. Acta rheum. scand., Suppl. I , 1958.
Skeletal Status in Patients with Rheumatoid Arthritis Claus Christiansen and Paul R ~ d b r o From the Departments of Clinical Chemisfr.v and Clinical Physiology, Glostrup Hospital. and the Depariment of Clinical Physiology, Alhorg Syyehus S y d , Alborg, Denmark
ABSTRACT. The total body calcium - estimated from the bone mineral content in the distal part of the forearm, measured by means of photon absorptiometry - has been determined in 15 patients with rheumatoid arthritis. None of the patients were treated with steroids and all were relatively mobile. The results indicate that osteoporosis is uncommon in such patients.
Recent investigations have postulated that osteoporosis, estimated from X-ray pictures, is a common phenomenon in patients with rheumatoid arthritis (1, 8, 9). The etiology of bone loss is not understood but an explanation is often sought in various multiple factors such as immobilization, treatment with corticosteroids or other anti-inflammatory agents. However, the specific role of each factor is poorly defined and it is still not clear whether rheumatoid arthritis in itself leads to osteoporosis. We have investigated the bone mineral content (BMC) in a group of relatively mobile patients with rheumatoid arthritis (without corticosteroid treatment) in order to investigate whether and to what degree rheumatoid arthritis in itself leads to osteopenia. We studied this by measuring the BMC in the distal part of the forearm by photon absorptiometry. This parameter is well correlated to total bone calcium (3, 4, 5, 6). MATERIAL AND METHODS Eleven women and four men, aged 26-59 years (mean 46), consented to the study. All patients had rheumatoid arthritis defined according to the American Rheumatism Association criteria. Mean duration of the illness was 9.5 years (range i 1 4 2 ) . Nobody was being or had been treated with corticosteroids and all were receiving one or two anti-inflammatory agents, such as acetyl salicylate or phenylbutazone. They were all relatively mobile patients.
BMC was determined by direct photon absorptiometry on both forearms (Fig. I ) . Antebrachium is fixed in a plexiglass container filled with distilled water. Water is used, since it has nearly the same coefficient of absorption as plexiglass and soft tissue. The source of radiation (25 mCi and the detector are fixed in holders on either side of the bones to be examined. A mechanical scanner displaces the detector and the source perpendicular to the longitudinal axis of the bones. The transmission of photons through the bones depends on the BMC. Cameron et al. (2) showed a direct relation between the absorption of photons from 1251 and BMC. In our modified version of the method (3), the BMC is expressed in arbitrary units as a mean value of six scans from each forearm. The coefficient of variation of duplicate measurements in the same patient on different days is of the order 3 4 %. BMC of the forearm is fairly well correlated to the body’s total calcium content (3, 4, 5, 6). The BMC value in each patient was compared with the values in a group of 127 normal subjects matched for age and sex (4), in such a way that the patient’s value was classified using the mean and S.D. in the corresponding age- and sexdependent subgroup. Furthermore, the patient’s BMC value was expressed as a percentage of the corresponding normal mean,
RESULTS The percental value of BMC in the patients did not correlate significantly to the duration of illness, and the patients were accordingly considered as a sample of the population of “relatively mobile rheumatoid arthritis patients without corticosteroid treatment”. The BMC values in the patients scattered around the corresponding normal mean, and n o patient had a BMC value lower than the normal range (mean + 2 S.D.). The group mean for the 15 patients amounted to 94% (S.D. 18%) of the corresponding normal mean. This is not significantly different from the normal mean (100%. S.D. 16%), according to either the t-test for differences between averages or Wilcoxon’s test. Acra med. scand. 198
454 C. Christansen and P R ~ d h r o plexiglass qontainer
b
Fig. I . Principle for the measurement of bone mineral content by direct photon absorptiometry on t h e forearm. (a) Section through system showing plexiglass container, and U-shaped holder, with radioactive source and detector. ( h ) System seen from volar surface showing scanning movements of source and detector.
DISCUSSION The results indicate, in spite of the relatively few patients, that osteoporosis in rheumatoid arthritis is unusual in relatively mobile patients treated with “ordinary” anti-inflammatory drugs. Mueller and Jurist (7) found in six patients treated with corticosteroids that the BMC (investigated with almost the same technique, radius alone being studied with a non-scanning procedure) was significantly decreased to nearly 70% of the value in six matched controls without steroid treatment. Furthermore, they found that the mean BMC in 20 patients with rheumatoid arthritis without steroids did not differ significantly from the mean in 20 matched controls. The patients’ BMC amounted t o 95% of the corresponding normal mean. The present study confirms these findings, our mean value amounting to 94 % of normal.
Acta rned. scand. 198
From these two recent studies it is tempting to conclude that rheumatoid arthritis in ifself does not lead t o significant osteoporosis. However, further studies are clearly necessary to test whether and to what degree osteoporosis is found in this disease. A question of particular interest is the part played by immobilization in the development of osteoporosis in rheumatoid arthritis. AC K N OW L EDG EM EN T This study was supported by a grant from Carl J . Beckers Fond.
REFERENCES I . Bjelle, A. & Nilsson, B.: Osteoporosis in rheumatoid arthritis. Calcif. Tissue Res. 5: 327, 1970. 2. Cameron, J. R., Mazess, R. 9 . & Sorenson, J. A,: Precision and accuracy of bone mineral determination by direct photon absorptiometry. Invest. Radiol. 3: 141, 1968. 3. Christiansen, C. & Rsdbro, P.: Estimation of total body calcium from the bone mineral content of the forearm. To be published. 4 - Bone mineral content and estimated total body calcium in normal adults. To be published. 5. Cohn, S. H . , Ellis, K. J., Wallach, S.. Zanzi, I., Atkins, H . L. & Aloia, J . F.: Absolute and relative deficit in total-skeleton calcium and radial bone rninera1 in osteoporosis. J . nucl. Med. 15:428, 1974. 6 . Mazess, R . B.: Estimation of bone and skeletal weight by direct photon absorptiometry. Invest. Radiol. 6: 52, 1971. 7. Mueller. M. N. & Jurist, J . M.:Skeletal status in rheumatoid arthritis. Arthr. and Rheum. 16: 66,1973. 8. Saville, P. & Karmosh, 0.: Osteoporosis of rheumatoid arthritis. Influence of age, sex and corticosteroids. Arthr. and Rheum. 10:423, 1967. 9. Soila, P.: Roentgen manifestations of adult rheumatoid arthritis. Acta rheum. scand., Suppl. I , 1958.
