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1 From the Medical Department, Roskilde University Hospital Koge, Koge, Denmark (MFH and PCE), and the Calcium- and Bone-Metabolic Unit, Endocrine Department, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark (J-EBJ)
2 Supported by the East Danish Research Fund Region III, the Research Council for Health and Disease, and The Eli Lilly Osteoporosis Research Fund. Materials were donated by Pharma Vinci A/S, Frederiksvaerk, Denmark. 3 Address reprint requests to M Friberg Hitz, Calcium- and Bone-Metabolic Unit, Endocrine Department, Copenhagen University Hospital Hvidovre, Kettegaards Allé 30, Hvidovre 2650, Denmark. E-mail: mettehitz{at}hotmail.com.
ABSTRACT
Background: Low-energy fractures of the hip, forearm, shoulder, and spine are known consequences of osteoporosis.
Objective: We evaluated the effect of 1 y of treatment with calcium and vitamin D on bone mineral density (BMD) and bone markers in patients with a recent low-energy fracture.
Design: In a double-blinded design, patients with fracture of the hip (lower-extremity fracture, or LEF) or upper extremity (UEF) were randomly assigned to receive 3000 mg calcium carbonate + 1400 IU cholecalciferol or placebo (200 IU cholecalciferol). BMD of the hip (HBMD) and lumbar spine (LBMD) were evaluated by dual-energy X-ray absorptiometry, and physical performance was assessed by the timed Up & Go test. Serum concentrations of 25-hydroxycholecalciferol, parathyroid hormone (PTH), telepeptide of type I collagen (ICTP), osteocalcin, and N-terminal propeptide of collagen type I were measured.
Results: A total of 122 patients were included (84% women;
Key Words: Bone markers • bone mineral density • calcium • immobility • low-energy fracture • hip fracture • shoulder fracture • forearm fracture • vitamin D
INTRODUCTION
Low-energy fractures of the hip, forearm, shoulder, and spine are known consequences of osteoporosis (1-3). Hip fractures occur mainly in older individuals at risk of being deficient in calcium and vitamin D (4). Calcium and vitamin D deficiencies result in the elevation of parathyroid hormone (PTH), increased bone remodeling, and skeletal loss of calcium (5). Bone turnover and serum concentrations of biochemical bone markers increase in women after menopause. A disequilibrium arises when the amount of bone resorption is higher than the amount of bone formed, and net loss of bone is seen (6).
Correction of calcium and vitamin D deficiencies has been investigated in clinical trials, and positive effects on bone remodeling, bone mineral density (BMD), rate of falling, and fracture incidences have been shown, but studies evaluating the effects of intervention in patients with a recent low-energy fracture are sparse (7-10). A fracture episode, the subsequent surgical trauma, and immobilization all affect the serum concentration of bone markers and the formation of new bone (11). To be able to use the measurement of biochemical markers of bone remodeling in the evaluation of bone turnover in patients with recent fractures, more studies investigating the concentration of bone turnover markers in the post-fracture period and the effect of intervention with calcium and vitamin D are needed. Bone turnover increases as soon as 24 h after a patient is immobilized, with a subsequent release of calcium and suppression of PTH. Immobilization after a fracture also influences bone turnover, but whether supplementation with calcium and vitamin D can reduce this turnover is unknown.
The aim of the present study was to investigate the effect of treatment with 3000 mg calcium carbonate plus 1400 IU cholecalciferol in a group of patients with a recent low-energy fracture of the hip, distal forearm, or proximal humerus. The effect of treatment was evaluated by the measurement of BMD at the hip and lumbar spine region and by the measurement of biochemical markers of bone remodeling.
SUBJECTS AND METHODS
Patients
Women and men admitted to Roskilde Amt University Hospital in Koge with a relevant low-energy fracture and aged>50 y were included in the study. All women were postmenopausal (>2 y since last menstruation).
Patients with dementia or in such a state that their ability to sign an informed consent form was affected were excluded from the study. Patients with a history of cancer except superficial skin cancers or with excessive alcohol abuse were also excluded. Excessive alcohol abuse was identified by history of abuse and by hospital records and was defined as a use of alcohol exceeding the recommendations of the Danish Health Board of no more than 21 units of alcohol per week for men and no more than 14 units of alcohol per week for women.
Patients using hormone replacement therapy, taking medication for the treatment of osteoporosis, having an intake of cholecalciferol >800 IU, or using 1,25-dihydroxycholecalciferol were excluded, as were patients with serum creatinine concentrations >130 µm/L or serum alanine aminotransferase >2.5 times the upper limit.
During the inclusion period (18 mo), 277 patients with a low-energy hip fracture were screened for participation, and 117 hip fracture patients were eligible according to the inclusion criteria. Of these, 23% did not wish to participate; the most frequently stated reasons for not wanting to participate in the trial were feeling too old, sensation of poor health, and a wish to commence treatment with anti-osteoporotic medication.
A total of 141 patients with a fracture of the distal forearm and 46 patients with a fracture of the proximal humerus were invited to participate in the study; 34% and 41% of these were included in the study. The number of included individuals was 122 patients: 55 hip-fracture patients, 48 forearm fracture patients, and 19 proximal humerus fracture patients. The group consisted of 101 women and 21 men.
Design and methods
The hip-fracture patients were included consecutively over a period of 18 mo and were informed about the study while admitted to the hospital. Differences in the health status of the fracture patients postoperatively resulted in variation in the time after fracture to inclusion into the study. Variation in time to inclusion had to be accepted, even though time since fracture has an important influence on the concentrations of bone markers.
The patients with fracture of the upper extremity were informed about the study through the mail and were subsequently invited to a meeting if they met the inclusion criteria. The upper-extremity fracture patients were recruited over a period of 12 mo.
The study was prospective and double-blinded, and patients were randomly assigned in blocks to one of the following treatment regimens (total daily dose): 1) 3000 mg calcium carbonate (corresponding to a dose of 1200 mg elementary calcium) + 1200 IU cholecalciferol and 200 IU cholecalciferol given as a multivitamin tablet (a total of 1400 IU corresponding to 35 µg cholecalciferol), or 2) placebo tablets + 200 IU cholecalciferol given as a multivitamin tablet (5 µg cholecalciferol). The tablets looked identical and had the same flavor. The regimens were taken as one tablet with a meal 3 times daily plus a multivitamin tablet. Pharma Vinci A/S, Frederiksvaerk, Denmark, performed the blinding and coding. Compliance was recorded by counting the tablets at all visits.
History of self-reported use of vitamin tablets and vitamin D supplements (<800 IU) was recorded, as were smoking habits and alcohol use. Smoking habits were recorded by using a frequency questionnaire, recording the number of pack-years (20 cigarettes per day) ever smoked. Alcohol use was recorded as a mean of consumed units of alcohol per week. Calcium intake was recorded by using a food-frequency questionnaire and was calculated from the intake of dairy products with the addition of 300 mg daily for all other food products. Body mass index (BMI) and age at menopause were recorded as well.
Bone mineral density
BMD was measured at the hip region of the nonfractured hip for the hip fracture patients and of the left hip if possible for patients with upper-extremity fractures. Of the hip fracture patients, 8 did not undergo a dual-energy X-ray absorptiometry scan of the hip because of the presence of osteosynthetic material from a previous fracture episode or total hip replacement caused by osteoarthritis.
As a result of recent surgical repair, many of the patients with a fracture of the hip were unable to elevate their legs during the lumbar spine scanning procedure; as a result, all hip fracture patients were scanned without their legs elevated. Double scans were obtained in a group of 23 healthy women both with and without leg elevation. Investigation for any systematic difference was evaluated from a Bland-Altman plot; the mean difference between the 2 scanning procedures was 1% (SD: 1.78), which resulted in an overestimation of the BMD value for the procedure in which the patients' legs were not elevated.
For the patients with upper-extremity fractures, the lumbar scan was performed with the patients' legs elevated. For all patients, no effort was made to scan the side of dominance, because side of dominance has been shown to affect only BMD of the upper extremities (12).
Dual-energy X-ray absorptiometry with a Hologic QDR-2000 (Hologic Inc, Waltham, MA) was used to measure BMD at the hip and lumbar spine. Hologic System Software version 7.10 was used for subsequent analyses. The software-provided reference database was used. This reference is used as a standard in Denmark (13). Variation between identical double scans (CV for scanner) was 1.3% for the lumbar spine region and 1.5% for the hip region on the basis of 20 duplicate measurements.
Physical performance was evaluated at inclusion and after 12 mo. The timed Up & Go test was used to evaluate physical performance (14).
Ethical approval
The study was designed according to the Helsinki II Declaration and was approved by the local scientific ethical committee. Informed consent was obtained from all participants before inclusion.
Sample collection and analysis
Control visits were performed 1, 3, and 12 mo after inclusion. Automated chemical analysis was used for analysis of sodium, potassium, creatinine, alkaline phosphatase, alanine aminotransferase, calcium, phosphate, and thyrotropin in serum (T3; reference value: 0.82-5 nmol/L) and free thyroxine (FT4; reference value: 7.0–22.0 pmol/L). To minimize the effect of circadian rhythm on markers of bone remodeling, blood tests were obtained before noon with a time window of 3 h duration. All sample analyses were performed blinded.
Serum concentrations of intact N-terminal propeptide of type I collagen (PINP) were measured by using the UniQ PINP radioimmunoassay (Orion Diagnostica, Espoo, Finland). The intraassay CVs were 4.8% (for a concentration of 39 µg/L) and 8.0% (for a concentration of 90 µg/L). The interassay CVs were 3.1% (for a concentration of 27 µg/L) and 4.6% (for a concentration of 78 µg/L).
Serum osteocalcin concentrations were measured with the N-MID Osteocalcin One Step ELISA Kit (Nordic Bioscience Diagnostics A/S, Herlev, Denmark). The intraassay CVs were 3.4% (for a concentration of 7.0 ng/mL) and 2.4% (for a concentration of 43.2 ng/mL). The interassay CVs were 3.6% (for a concentration of 6.8 ng/mL) and 6.4% (for a concentration of 50.5 ng/mL).
Serum concentrations of C-terminal telopeptide of type I collagen (ICTP) were measured with the UniQ ICTP radioimmunoassay (Orion Diagnostica, Finland). The intraassay CVs were 3.5% (for a concentration of 3.7 ng/mL) and 9.4% (for a concentration of 24.5 ng/mL). The interassay CVs were 5.6% (for a concentration of 5.5 ng/mL) and 9.0% (for a concentration of 21.3 ng/mL).
Vitamin D status [25-hydroxyvitamin D2 [25(OH)D2] and 25(OH)D3] was measured in serum by using the Gamma-B-Hydroxy Vitamin D radioimmunoassay from Immunodiagnostic System, Boldon, UK. The intraassay precision was 5.0% for a mean of 58.4 nmol/L and the interaassay precision was 8.1% for a mean of 56.7 nmol/L (for vitamin D, concentrations > 50 nmol/L are considered normal).
Serum intact PTH was measured by using an immunometric assay with CVs of 15% (for a concentration of 2.4 pmol), 10% (for a concentration of 6.3 pmol), and 12% (for a concentration of 22.8 pmol) (Immulite 2000; Diagnostic Products Corporation, Los Angeles, CA). All samples were stored at –80 °C during the study, and samples from each patient were analyzed by using the same assay to minimize interassay variations.
Safety
Serum ionized calcium concentrations were measured at baseline and after 1, 3, and 12 mo of intervention. Furthermore, additional serum calcium measurements were performed if hypercalcemia was suspected or if a rise in serum calcium was observed. No cases of hypercalcemia were recorded during the study.
Statistics
The normally distributed data were analyzed by using parametric statistics. For the skewed data, a normal distribution was obtained by logarithmic transformation, and statistical analysis was performed on the log-transformed data. Independent-sample t tests were used to compare means with the use of SPSS 11.5 for WINDOWS (SPSS Inc, Chicago, IL). To analyze the longitudinal data (biochemical parameters), a mixed general linear model was used to account for the stronger association between variables in the same individual over time using SAS 9.1 (SAS Institute Inc, Cary, NC). Only data from patients completing the study were included in this analysis.
To evaluate the effect of treatment for 1 y with calcium and vitamin D on BMD, we included both an intention-to-treat analysis and an evaluation of the treatment effect for the group of participants who completed the study to investigate the biological effect when receiving the intervention in a per protocol analysis. Pearson's correlation coefficients or general linear model was used to analyze relations between variables.
Power calculations
Prestudy power calculations
The intervention was expected to result in an increase in BMD for the active intervention group of 8%. The level of significance was set to 5% (SD = 0.08) and the power of the study to 80%. Significant results were expected after the inclusion of 60 patients.
For biochemical markers of bone turnover, the intervention was expected to result in a change in biochemical markers of 1 SD. The power of the study was again set to 80% and the level of significance to 5%. With this design, significant results would be obtained after the inclusion of 16 patients in each group.
Poststudy power calculations
These were performed for those variables for which a significant effect of treatment could not be shown. This was done to evaluate whether a type II error was present.
The actual power of the study in an intention-to-treat analysis was calculated to be 57.7% for the BMD of the hip. In the per-protocol analysis, the actual power of the study was 73.2% for BMD of the lumbar spine and 29.9% for BMD of the hip.
RESULTS
Of the 122 included patients, 79 (68%) completed the study: 53% of the patients with a hip fracture, 74% of the patients with a fracture of the proximal humerus, and 75% of the patients with a fracture of the distal forearm. The reasons for dropping out were as follows: 27% of the patients wanted to be excluded, 1% were excluded because of compliance problems, and 4% of the patients died.
Compliance in adherence to the treatment regimens in taking the tablets every day was 95% for the patients who completed the study (95 of 100 tablets were consumed). We compared the baseline values of those who completed the study with those who did not and found no significant differences except in age at menopause (P < 0.001), for which those who did not complete the study were significantly younger at menopause.
Baseline data
The baseline characteristics of all fracture patients are shown in Table 1. No significant differences were found between patients randomly assigned to the active treatment group and those assigned to the placebo group except in menopausal age, which was significantly lower in the placebo group (P < 0.05). In a regression analysis, however, menopausal age had no significant effect on BMD. There was a strong tendency toward a higher BMD at the spine region for patients randomly assigned to the active treatment, though the difference was not significant (P = 0.06).
View this table:
TABLE 1. Baseline data for all patients completing the study by fracture group1
Compared with the upper-extremity fracture patients, the hip fracture patients were older (P < 0.001), had lower BMIs (P < 0.001), tended toward a lower calcium intake (P < 0.09), had a lower intake of alcohol (P < 0.001), and had a lower hip BMD (P < 0.001). The hip fracture group was also characterized as having low vitamin D concentrations without elevation of PTH. The hip fracture patients took longer to perform the timed Up & Go test than did the upper-extremity fracture group, demonstrating poorer physical performance, but the hip fracture patients were evaluated in the early post-fracture period, 1–2 wk after hip-fracture surgery, which makes it inappropriate to compare the 2 groups.
Effect of treatment
The hip fracture group was included 13.6 ± 11.0 d after fracture, and the upper-extremity fracture group was included 26.8 ± 15.5 d after fracture; the difference was significant (P < 0.01). Because serum concentrations of osteocalcin were positively related with time since fracture episode and time since surgical trauma (r = 0.242, P < 0.05), we chose to evaluate the effect of treatment with calcium and vitamin D on bone markers for the 2 fracture groups separately.
Vitamin D
For the hip fracture group, the intervention increased the vitamin D concentration from 33 ± 17 to 82 ± 19 nmol/L, whereas the placebo group increased only from 40 ± 17 to 53 ± 16 nmol/L. The changes in serum 25(OH)D were significant for both intervention groups after 1 mo. Serum concentrations of 25(OH)D were significantly higher in the active intervention groups after 1, 3, and 12 mo (P < 0.001). Changes in serum 25(OH)D are shown in Figure 1A and Figure 2A.
FIGURE 1.. Biochemical changes during the study in the hip fracture patients in the active intervention () and placebo (•) groups. Significant differences between groups are identified by asterisks as follows: *P < 0.05, **P < 0.01, ***P < 0.001. Changes relative to baseline are not indicated by a symbol. A) Changes in serum concentrations of 25-hydroxyvitamin D [25(OH)D]. The interaction between treatment and time was significant (P < 0.001) and, compared with baseline, serum 25(OH)D was significantly different after 1, 3, and 12 mo (P < 0.001) in both intervention groups (not indicated on the figure). B) Changes in serum concentrations of parathyroid hormone (PTH). The interaction between time and treatment was significant (P < 0.05). Serum PTH was significantly higher after 12 mo in the placebo group compared with baseline but did not change significantly from baseline for the active intervention group (not indicated on the figure). C) Changes in serum concentrations of N-terminal propeptide of type I collagen (PINP). An interaction between time and treatment was found after control for baseline values (P < 0.05). No significant difference was found between the groups at 0 mo (baseline), but significant differences between groups were found at 1, 3, and 12 mo. Serum PINP was significantly lower than baseline after 12 mo in both intervention groups (P < 0.001, not indicated on the figure). D) Changes in serum concentrations of osteocalcin (OC). An interaction between time and treatment was found after control for baseline values (P < 0.05). No significant difference was found between intervention groups at 0 mo (baseline), but a significant difference between groups was shown at 1, 3, and 12 mo. E) Changes in serum concentrations of C-terminal telopeptide of type I collagen (ICTP). No interaction between treatment and time was found. No effect of treatment was found. Serum ICTP was significantly different from baseline after 12 mo (P < 0.05) in both intervention groups (not indicated on the figure).
FIGURE 2.. Biochemical changes during the study in the upper-extremity fracture patients in the active intervention () and placebo (•) groups. Significant differences between intervention groups are identified by asterisks as follows: *P < 0.05, **P < 0.01, ***P < 0.001. Changes relative to baseline are not indicated by a symbol. A) Changes in serum concentrations of 25-hydroxyvitamin D [25(OH)D]. The interaction between time and treatment was significant (P < 0.001). Compared with baseline, serum 25(OH)D was significantly higher at 1, 3, and 12 mo in the active intervention group (P < 0.001) but only after 12 mo in the placebo group (not indicated on the figure). B) Changes in serum concentrations of parathyroid hormone (PTH). The interaction between time and treatment was significant (P < 0.05). The reduction in serum PTH compared with baseline was significant after 1, 3, and 12 mo in the active intervention group but was not significant in the placebo group (not indicated on the figure). C) Changes in serum concentrations of N-terminal propeptide of type I collagen (PINP). An interaction between time and treatment was found after control for baseline values (P < 0.05). No significant difference was found between intervention groups at 0 mo (baseline), but a significant difference was shown at 1, 3, and 12 mo. Compared with baseline, serum PINP declined throughout the study, and the decline was significant after 12 mo in both intervention groups (P < 0.001, not indicated on the figure). D) Changes in serum concentrations of osteocalcin (OC). The interaction between time and treatment was significant (P < 0.001). Serum osteocalcin after 3 and 12 mo was significantly lower than baseline in the active intervention group (P < 0.05) but not the placebo group. E) Changes in serum concentrations of C-terminal telopeptide of type I collagen (ICTP). No interaction between treatment and time was found. No difference was found between intervention groups at any visit.
For the upper-extremity fracture group, the intervention increased the vitamin D concentration increased from 63 ± 18 to 90 ± 24 nmol/L (P < 0.001) for the intervention group and from 69 ± 34 to 77 ± 31 nmol/L (P < 0.01) for the placebo group. The increase was significantly higher in the active intervention group than in the placebo group (Figure 2).
Parathyroid hormone
Hip fracture group.
Serum PTH was significantly lower in the active intervention group at 1, 3, and 12 mo than in the placebo group, but the change compared with baseline was not significant for the active intervention group. PTH increased in the placebo group, and the difference between intervention groups was significant after 12 mo (P < 0.001; Figure 1B).
Upper-extremity fracture group.
PTH was significantly lower in the active intervention group at 1 and 3 mo than in the placebo group, and the change compared with baseline was significant after 1, 3, and 12 mo (P < 0.001) for the active intervention group but not for the placebo group (Figure 2B).
Bone markers
Hip fracture group.
To account for differences present already at baseline, we included baseline as a covariate in a repeated-measures analysis of variance (mixed model) and found the difference between treatments to remain significant (P < 0.05).
PINP increased significantly in both groups after 1 mo (P < 0.01) and declined at 3 and 12 mo. PINP was lower in the intervention group at all visits than in the placebo group (P < 0.05) and had reached a lower level after 12 mo for both intervention groups compared with baseline (P < 0.001; Figure 1C).
Osteocalcin increased from baseline to 12 mo in both groups. Osteocalcin concentrations were significantly higher in the placebo group than in the active intervention group after 1, 3, and 12 mo (P < 0.05; Figure 1D).
ICTP increased for both intervention groups after 1 mo but not significantly. Then ICTP declined and after 12 mo was below the baseline concentration for both intervention groups (P < 0.05). No significant difference was found between the intervention groups after at any visit (Figure 1E).
Upper-extremity fracture group.
To account for differences present already at baseline, we included baseline as a covariate in a repeated-measures analysis of variance (mixed model) and found the difference between treatments to remain significant (P < 0.05).
PINP declined throughout the study and was significantly lower than at baseline after 12 mo in both groups (P < 0.05). Concentrations of PINP were significantly lower in the active intervention group than in the placebo group after 1, 3, and 12 mo (P < 0.01; Figure 2C).
Serum osteocalcin was significantly lower at 1, 3, and 12 mo in the intervention group than in the placebo group (P < 0.01), and the change compared with baseline was significant for in active intervention group (P < 0.001) but not in the placebo group (Figure 2D).
ICTP declined in both intervention groups and was significantly different from baseline after 12 mo in both groups (P < 0.05). No significant difference between intervention groups was found (Figure 2E). For all patients, bone resorption evaluated by ICTP correlated with the level of physical mobility evaluated by the timed Up & Go test. Patients who took longer to complete the test had a higher level of resorption (R2 = 0.423, P < 0.01, r = 0.651). Serum concentrations of 25(OH)D and PTH and age were not significantly correlated with the level of bone resorption.
Bone mineral density
BMD for the lumbar spine scanning procedures with and without the legs elevated showed that the BMD values with the legs elevated were 1 ± 1.78% lower than the values without the legs elevated. Both in a per-protocol analysis and an intention-to-treat analysis, intervention with calcium and vitamin D resulted in a significant increase in BMD of the lumbar spine after 12 mo compared with baseline values for the intervention group, whereas BMD of the lumbar spine after 12 mo had decreased compared with baseline in the placebo group. No significant changes were shown for BMD of the hip. The results are shown in Table 2.
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TABLE 2. Changes () in bone mineral density (BMD) after 12 mo of intervention in both hip and upper-extremity fracture patients1
In a regression analysis, age had an effect on change in BMD for both scanning regions (age x hip BMD, P < 0.01, and age x lumbar spine BMD, P < 0.05). Stratification according to age showed a more pronounced effect of treatment (lumbar spine BMD) in the patients aged 70 y than in those aged >70 y (0.993 ± 0.131 compared with 0.868 ± 0.216; P < 0.05). Lumbar spine BMD increased in the group aged 70 y and decreased in the age group aged >70 y. BMD values stratified by age and intervention group are shown in Figure 3. No significant differences were found between subgroups for the hip region.
FIGURE 3.. Changes in bone mineral density (BMD) of the total hip region and lumbar spine after 1 y stratified by age group: 70 y or >70 y old. A significant age-by-treatment interaction was found for both variables. The results of the statistical comparison between the intervention group and the placebo group within age subgroups are denoted by an asterisk. *P < 0.05.
DISCUSSION
In old age, the amount of bone resorption exceeds the amount of bone formation, which results in a decline in bone quality and bone strength with a subsequently increased risk of fracture (15, 16). Deficiency in vitamin D worsens the condition by reducing active intestinal calcium absorption and increasing bone resorption to mobilize calcium to the circulation (17).
In the present study, patients with a fracture of the hip had higher bone turnover, lower BMD, and lower vitamin D concentrations and demonstrated poorer physical performance than did patients with upper-extremity fractures. The dropout rate was also significantly higher for the hip fracture patients, which indicates that these patients are generally frailer and have poorer bone status than do patients with fracture of the upper extremity (18).
Intervention with both 1400 IU cholecalciferol and 200 IU cholecalciferol resulted in a significant increase in serum 25(OH)D; the larger dose resulted in the greatest increase in 25(OH)D. Patients with a hip fracture showed the greatest benefit from treatment: 25(OH)D increased from an insufficient concentration of 33 nmol/L to 85 nmol/L. Intervention with calcium and vitamin D also increased the daily intake of elementary calcium to 1550 mg, which may be responsible for the concomitant decline in PTH. Baseline concentrations of PTH were lower than expected in a vitamin D–deficient population. Physical activity has been shown to correlate with bone resorption and level of PTH. The sudden immobilization of these patients may release calcium from bone and be the cause of the relative low PTH concentration at baseline (19, 20).
In animal studies, a resistance to IGF-I at the cellular level has been proposed as a possible mechanism causing bone loss during immobilization (21). Other theories consider an altered communication between bone cells or altered gene expression (22, 23). The strong effect of immobility on bone remodeling has also been described in clinical studies. Calcium is released from bone when patients are immobilized and prevents secondary hyperparathyroidism, even though the patients are vitamin D deficient (24, 25). The osteonecrosis in relation to the fracture episode and the subsequent immobilization causes an initial increase in bone resorption. This is succeeded by an increase in bone formation as the result of both fracture healing and incipient mobilization (11). The higher level of bone resorption found in the hip fracture patients correlated with a lower physical mobility status independently of serum concentrations of 25(OH)D and PTH. Intervention with calcium and vitamin D for 12 mo sig-nificantly reduced the level of bone formation markers in both fracture groups, whereas concentrations of bone resorption markers were reduced significantly only in the upper-extremity fracture group.
PINP and osteocalcin are both markers of bone formation, but whereas PINP decreased after the fracture episode, osteocalcin increased. An increase in osteocalcin after a fracture episode was reported in previous studies (26). Osteocalcin is cleaved from the procollagen molecule during formation and is incorporated into bone during mineralization. Osteocalcin is also released from bone during resorption. It has been argued that the molecule is partly metabolized during this process and that, therefore, osteocalcin cannot be considered a bone turnover marker, because these metabolized products are expected to be cleared by the kidneys and not evaluated in the assays (27). Differences in osteoid volume could result in corresponding differences inserum concentrations of osteocalcin. Biopsy studies have shown a correlation between osteoid volume and serum osteocalcin concentration (28). A more optimal supply of calcium and vitamin D and a consequently better environment for mineralization of bone in the intervention group may reduce osteoid volume and explain the lower osteocalcin concentration in the intervention group.
In the present study, lumbar spine BMD was evaluated without leg elevation, and this method resulted in a 1% overestimation of BMD, which may result in an underestimation of the effect of treatment. Lumbar BMD increased significantly for patients in the active treatment group aged 70 y. The changes in BMD correlated with the level of physical activity, ICTP, and age. Because frail patients older than 70 y of age are immobile, they are not able to decrease bone resorption and increase bone mass when treated with calcium and vitamin D. The importance of sufficient mechanical loading has been shown in clinical trials; the effect of intervention with calcium and vitamin D is reduced if patients are immobile (29, 30).
Because of higher precision and higher metabolic activity, a treatment effect is detected earlier in the lumbar spine region than in the hip region. In our study, however, no significant effect of treatment was detected in the hip region (31). This could be explained by a lack of power. Recent, large randomized clinical trials failed to show an effect of calcium and vitamin D supplementation on BMD and fracture rates (32, 33). The studies were large and well designed with an intention-to-treat approach in their analysis. The lack of a significant effect of intervention may have been due to poor compliance in the study populations and participant dropout. The use of an intention-to-treat approach may under these circumstances mask the effect of intervention, but gives a more correct picture of what we can expect when a population is treated.
If lack of compliance and drop out is a great problem in these elderly populations, a different strategy may be necessary in which more attention is given to obtaining better compliance. We showed that in a population of women and men with a recent low-energy fracture, it is possible to obtain an increase in serum 25(OH)D of 200% to a concentration of 85 nmol/L when a great deal of attention is paid to compliance.
In conclusion, the hip fracture patients had poorer bone status, vitamin D deficiency, and lower physical performance than did the upper-extremity fracture patients. Both in a per-protocol analysis and in an intention-to-treat analysis, calcium and vitamin D supplementation for 1 y increased vitamin D status and BMD in the lumbar spine region, especially for those younger than 70 y of age. The biochemical markers of bone remodeling increased around 1 mo after fracture and declined thereafter. Supplementation with calcium and vitamin D is important for patients with low-energy fractures because it decreases bone loss. The effect of intervention was positively related to physical performance, which emphasizes the importance of mobilization.
ACKNOWLEDGMENTS
Blinding, coding, and donation of tablets by Pharma Vinci A/S, Frederiksvaerk, Denmark is acknowledged with appreciation. We are grateful for Lise Martinussen's excellent work in the unit with the care of the patients and with sample analysis. Special acknowledgment also goes to associate professor Lene T Skovgaard for her statistical assistance.
All authors contributed to all aspects of the production of this manuscript. None of the authors had any conflicts of interest with the funding agencies.
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