Cortical bone development in black and white South African children: iliac crest histomorphometry

Fragility fracture rates in South Africa are lower in blacks (B) than in whites (W) both in adults and in children. In adults this difference may in part be explained by histomorphometric findings in iliac crest cortical bone of B of thicker, less porous cortices, greater endocortical (Ec) wall thickness, fewer canals and greater osteoid thickness accompanied by greater mineral apposition rate and bone formation rate compared to W. Since no comparative data for B and W children are available we examined iliac crest cortical bone of 57 B and 56 W aged 0-23 yrs by routine histomorphometry.

RESULTS

The effects of growth as expressed in differences between external and internal cortex were similar in B and W children. Cortical thickness increased with age similarly in B and W until about age 15 whereafter it continued to increase only in B. Ec wall thickness rose with age in B but did not change in W. After age 11 canal number was lower in B. Cortical porosity was highest between ages 6 and 15 with a tendency to lower values in the external cortex in B. Thus structural differences reported in adults were evident in children. Bone turnover as reflected in osteoid surface and eroded surface declined with age similarly in B and W but osteoid thickness did not change with age. Greater osteoid thickness in B children could reflect greater vigor of osteoblasts and greater osteoblast team performance as it did in B adults and may have contributed to the structural advantage in B children.

CONCLUSION

B children showed greater values for osteoid thickness, endocortical wall thickness and cortical thickness, and a tendency to lower porosity compared to W children. These features may contribute to lower fragility fracture rates in B children. Differing environmental influences and possibly genetic effects may play a role.

Cortical bone histomorphometry of the iliac crest in normal black and white South African adults

Fragility fracture rates in South African blacks (B) are lower than in whites (W). Since bone strength in many parts of the skeleton depends mainly on cortical bone, we examined iliac crest cortical bone from 97 B (49 male, 48 female) aged 22-80 and 111 W (60 male, 51 female) aged 21-84 histomorphometrically for differences between B and W and effects of age. B had thicker (P = 0.02) and less porous (P = 0.0007) cortices, fewer haversian (H) osteons (P < 0.0001), and greater endocortical (Ec) wall thickness (P < 0.0001). B also had thicker H (P = 0.0005) and Ec osteoid seams (P < 0.0001); greater Ec osteoid surface (P = 0.0005), Ec mineral apposition rate (P < 0.0001), and Ec bone formation rate (P = 0.038); and lower H (P = 0.0002) and Ec eroded surfaces (P = 0.029). Some of the differences were already present in subjects aged 21-30 years. Although cortical structure deteriorated with age in B and W, after age 40 Ec wall thickness declined only in W. Greater Ec mineral apposition and bone formation rates, i.e., greater osteoblast efficiency at the cellular and tissue levels, suggest better Ec bone preservation that may contribute to lower fragility fracture rates in B.

Ascorbic acid deficiency, iron overload and alcohol abuse underlie the severe osteoporosis in black African patients with hip fractures--a bone histomorphometric study

Osteoporosis and femoral neck fractures (FNF) are uncommon in black Africans although osteoporosis accompanying iron overload (from traditional beer brewed in iron containers) associated with ascorbic acid deficiency (oxidative catabolism by iron) has been described from sub-Saharan Africa. This study describes histomorphometric findings of iliac crest bone biopsies and serum biochemical markers of iron overload and of alcohol abuse and ascorbic acid levels in 50 black patients with FNFs (29 M, 21 F), age 62 years (40-95) years (median [min-max]), and in age- and gender-matched black controls. We found evidence of iron overload in 88% of patients and elevated markers of alcohol abuse in 72%. Significant correlations between markers of iron overload and of alcohol abuse reflect a close association between the two toxins. Patients had higher levels of iron markers, i.e., siderin deposits in bone marrow (P < 0.0001), chemical non-heme bone iron (P = 0.012), and serum ferritin (P = 0.017) than controls did. Leukocyte ascorbic acid levels were lower (P = 0.0008) than in controls. The alcohol marker mean red blood cell volume was elevated (P = 0.002) but not liver enzymes or uric acid. Bone volume, trabecular thickness, and trabecular number were lower, and trabecular separation was greater in patients than in controls, all at P < 0.0005; volume, surface, and thickness of osteoid were lower and eroded surface was greater, all at P < 0.0001. There was no osteomalacia. Ascorbic acid deficiency accounted significantly for decrease in bone volume and trabecular number, and increase in trabecular separation, osteoid surface, and eroded surface; iron overload accounted for a reduction in mineral apposition rate. Alcohol markers correlated negatively with osteoblast surface and positively with eroded surface. Relative to reported data in white FNF patients, the osteoporosis was more severe, showed lower osteoid variables and greater eroded surface; FNFs occurred 12 years earlier and were more common among men. We conclude that the osteoporosis underlying FNFs in black Africans is severe, with marked uncoupling of resorption and formation in favor of resorption. All three factors--ascorbic acid deficiency, iron overload, and alcohol abuse--contributed to the osteoporosis, in that order.

Hepatic osteodystrophy in rats results mainly from portasystemic shunting

BACKGROUND AND AIMS

In chronic liver disease, bone disease frequently develops. The contributions of the different features of liver disease such as parenchymal inflammation, portal hypertension, and portasystemic shunting on bone metabolism have not been systematically studied. The aim of this study was to identify the features of liver disease contributing to bone disease using rat models.

METHODS

Parenchymal liver disease was induced by carbon tetrachloride administration, portal hypertension by partial portal vein ligation, and portasystemic shunting by end to side anastomosis of the portal vein to the inferior vena cava. Normal and sham operated surgical animals served as controls. Serum calcium, 25-hydroxy vitamin D (25-OH vit D), and osteocalcin levels, and urinary deoxypyridinoline excretion were analysed. Testosterone and oestradiol levels were determined in male and female rats, respectively. Interleukin 1, interleukin 6, and tumour necrosis factor alpha (TNF-alpha) were determined in serum. Bone density was measured in all groups and in addition, in the surgical groups, histomorphometry was performed on undecalcified specimens of the proximal tibia. The calcium content of the femurs, removed at termination and ashed, was determined.

RESULTS

Early parenchymal disease and portal hypertension did not affect bone metabolism or body mass. Portasystemic shunting increased bone resorption, decreased bone formation, bone density, and trabecular bone volume which were commensurate with a reduction in body mass. TNF-alpha levels were elevated and testosterone levels were low in male portasystemic shunted rats.

CONCLUSIONS

Portasystemic shunting in the rat adversely affects bone metabolism as part of a generalised catabolic state where high TNF-alpha and low testosterone and 25-OH vit D levels may play a role.

Bone disease in African children with slipped capital femoral epiphysis: histomorphometry of iliac crest biopsies

African teenagers with slipped capital femoral epiphysis (SCFE) not infrequently also have genu valgum (knock-knee). Because we had previously demonstrated metabolic bone disease attributable to dietary calcium deficiency in black teenagers with genu valgum, we examined 29 black teenagers (15 male, 14 female) with SCFE for metabolic bone disease. Each patient had an iliac crest bone biopsy taken (after double tetracycline labeling) for routine histomorphometry, and blood and urine samples for bone biochemistry. Spinal bone mineral density was measured in 13 patients. Compared to reported data, we found our patients to be sexually more immature, older, at least as obese, and to have more severe and more frequently bilateral hip disease. Eighty percent of the children took dairy products only once or twice a week or less frequently, and 37.9% had genu valgum. Compared with race- and age-matched South Africans, bone biopsies in our patients showed lower bone volume (BV/TV, p = 0.0003), wall thickness (p = 0.0002), and trabecular thickness (Tb.Th, p = 0.0002), and a tendency to greater trabecular spacing (Tb.Sp, p = 0.053). Lower osteoid volume (OV/BV, p = 0.0001), osteoid surface (OS/BS, p = 0.0001), osteoid thickness (O.Th, p = 0.0002), double labeled surface (dLS/BS, p = 0.029), and bone formation rate (BFR/BS, p = 0.037) suggested poorer bone forming capacity in our patients. No evidence of hyperparathyroid bone disease or osteomalacia was found. BV/TV was below the reference range (14.2%) in 65.5% of cases; these patients had lower values for Tb.Th (p = 0.037) and Tb.N (p = 0.0003), greater Tb.Sp (p = 0.0002), a tendency to lower adjusted apposition rate (Aj.AR, p = 0.057), and had had less frequent intake of dairy products than those with normal BV/TV (p = 0.024). Furthermore, months since menarche correlated with histomorphometric variables BV/TV (r = 0.667, p = 0.009), Tb.Th (r = 0.745, p = 0.002), Tb.Sp (r = -0.549, p = 0.042), O.Th (r = 0.784, p = 0.0009), and Aj.AR (r = 0.549, p = 0.042). The correlation between Tb.Th and spinal bone mineral content (r = 0.656, p = 0.015) suggests that the reduced trabecular thickness reflected a generalized bone condition. A greater than normal proportion of patients had spinal bone mineral density values below -1 standard deviation (SD) of the mean (osteopenia) (p = 0.001). Patients tested for parathyroid hormone and 25-hydroxyvitamin D levels were found to have normal values. Parathyroid hormone correlated with Aj.AR (r = 0.661, p = 0.038) and serum phosphorus (r = -0.764, p = 0.010). We conclude that sexual immaturity and possibly past dietary calcium deficiency contributed to osteopenia, and that this, together with obesity, led to the development of more severe and more frequently bilateral SCFE in our patients than in reported series of black and white children.

Fewer bone histomorphometric abnormalities with intermittent than with continuous slow-release sodium fluoride therapy

To help resolve the uncertainty whether sodium fluoride (NaF) therapy should be given intermittently or continuously, we examined iliac crest bone biopsies (before and after treatment) and fragility fracture rates in 35 intermittently treated (group I) and 69 continuously treated (group C) patients; all received calcium. The following statistically significant results were obtained. Reduction in vertebral fracture rate was similar in the two groups. Trabecular thickness and the structurally more important mineralized thickness increased only in group I. Group I also accumulated less excess osteoid (surface, volume). Mean osteoid thickness did not change in either group because of a bimodal distribution of wide seams with osteoblasts and double tetracycline labels, and thin seams without osteoblasts or labels. Osteoid was lamellar. Osteoid in abnormal sites (within bone marrow or bone, or around osteocytes) was found less frequently in group I. Adjusted apposition rate declined and mineralization lag time increased in both groups because of extended unlabelled osteoid seams. Erosion surface increased only in group C. Hook and/or tunnel erosion was seen less frequently in group I; it was closely associated with osteoid in abnormal sites and correlated with osteoid surface. Extended osteoid surface may have forced osteoclasts to hollow out trabeculae, leaving the empty osteoid shell in marrow. Excess osteoid volume and eroded surface and osteoid and erosion in abnormal sites correlated with bone fragility in group C. We conclude that intermittent therapy is to be preferred because it (1) increased mineralized trabecular thickness, (2) did not cause excessive osteoid accumulation and erosion, (3) showed less osteoid and erosion in abnormal sites and (4) led to a similar reduction in the vertebral fracture rate as did continuous treatment. The question of whether intermittency of therapy has some other effect independent of the cumulative dose of fluoride administered cannot be answered by this study.

Bone structure and turnover in the distal radius and iliac crest: a histomorphometric study

In bone grafting procedures of the wrist, the distal radius would be a more convenient graft donor site than the conventionally used iliac crest. We compared tetracycline-labeled bone biopsies from these two sites in 18 white patients (12 males, 6 females, aged 26-66 years) undergoing bone grafting procedures of the wrist. Fourteen had had previous trauma, 1 osteonecrosis of the lunate, 2 mild rheumatoid arthritis, and 1 a brachial plexus palsy. The specimens were processed undecalcified and examined by routine histomorphometry for bone structure, static and dynamic bone turnover variables, and marrow cellularity. We found that bone from the distal radius had thinner cortices (p = 0.0001), lower bone volume (p = 0.01), thinner trabeculae (p = 0.029), greater trabecular separation (p = 0.015), and lower wall thickness (p = 0.0001), marrow cellularity (p = 0.0001), osteoid volume (p = 0.01), osteoid surface (p = 0.02), osteoid thickness (p = 0.0002), osteoblast surface (p = 0.001), eroded surface (p = 0.01), osteoclast surface (p = 0.012), mineral apposition rate (p = 0.0002), double-labeled surface (p = 0.0005), single-labeled surface (p = 0.006), bone formation rate (p = 0.0005), adjusted apposition rate (p = 0.0001), longer mineralization lag time (p = 0.012), and greater activation frequency (p = 0.003). Prolonged mineralization lag time in the radius was associated with thin osteoid seams and low adjusted apposition rates and was therefore attributable to a low level of osteoblast activity rather than to osteomalacia. We conclude that bone from the distal radius was structurally inferior to and had lower turnover than the iliac crest bone. We suggest that where a graft has to provide immediate structural integrity, the iliac crest is the preferred donor site. However, where bone graft is to be compacted into a small cavitary defect, distal radial bone may be an adequate alternative. A clinical study is needed to confirm this assumption.

Osteoporosis in African hemosiderosis: role of alcohol and iron

This paper aims to examine the relative contributions made by alcohol and iron overload and hypovitaminosis C to the osteoporosis associated with African hemosiderosis. To characterize this bone disorder, we examined double-tetracycline-labeled iliac crest bone biopsies and serum biochemistry in 53 black male drinkers, 38 with (Fe+) and 15 without (Fe-) iron overload, and in controls. We reasoned that abnormalities found in both patient groups were likely to be caused by alcohol abuse and those found only in the Fe+ group to be caused by iron overload and hypovitaminosis C (iron/C-). The patient groups differed only with respect to greater erosion depth (p < 0.05) and abnormal markers of iron overload in the Fe+ group. Ascorbic acid levels were lower in the Fe+ group than in controls (p < 0.001). Bone volume and trabecular thickness were significantly lower in both patient groups compared with controls and therefore likely caused by alcohol. There were no positive correlations between formation and erosion variables in either patient group, which suggests uncoupling of formation from erosion, possibly as a result of alcohol abuse. Prolonged mineralization lag time associated with thin osteoid seams was found in 32% of patients, affecting both groups. This rules out osteomalacia and suggests osteoblast dysfunction, probably caused by alcohol. The number of iron granules in the marrow correlated with erosion depth (r = 0.373, p < 0.01), trabecular number (r = -0.295, p < 0.05), and trabecular separation (r = 0.347, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic bone disease in black teenagers with genu valgum or varum without radiologic rickets: a bone histomorphometric study

Calcium deficiency in black (African) children can cause rickets and osteomalacia with severe limb deformities. It is not known whether black teenagers with genu valgum or varum but without radiologic rickets suffer from a related disorder. To examine this question we studied 26 such patients by iliac crest bone biopsy and serum and urine biochemistry: 12 patients (46%) had osteopenia with normal or low bone turnover, 5 (19%) mildly increased bone turnover, 4 (15%) histologic hyperparathyroidism, 2 (8%) preosteomalacia, and 3 (12%) osteomalacia (with features of hyperparathyroidism). Radiographs did not reflect the severity of the bone disease. Serum calcium levels correlated inversely with eroded mineralized surface (p < 0.001), osteoid surface (p < 0.01), osteoid thickness (p < 0.001), mineralization lag time (p < 0.001), and 1,25-(OH)2 vitamin D (p < 0.005), and 1,25-(OH)2 vitamin D correlated positively with osteoid surface (p < 0.05), osteoid thickness (p < 0.05), osteoid volume (p < 0.01), eroded surface (p < 0.05), and eroded mineralized surface (p < 0.0005). Tubular reabsorption of phosphate and 25-OH vitamin D levels were normal, and 1,25-(OH)2 vitamin D levels were normal to high. This suggests that calcium deficiency may have caused the increase in bone turnover and the mineralization defects. The most severe osteomalacia was found in males aged 16-19 years. We cannot explain the cause of the osteopenia. We conclude that all patients had bone disease.

Histomorphometry of iliac crest trabecular bone in adult male baboons in captivity

Data in the literature on bone histomorphometry in the baboon are scant. This study provides data from analysis of trabecular bone of the iliac crest of 16 adult male chacma baboons (Papio ursinus) in captivity. Five animals were young adults judging by the presence of growth cartilage in the iliac crest biopsy. Bone volume resembled that in humans, but trabeculae were thinner and more closely spaced. Bone turnover appeared somewhat lower than in humans. Coupling of resorption and formation was excellent as judged by cellular and kinetic variables; erosion surface was an unreliable indicator of ongoing coupling. The similarities between human and baboon trabecular bone make the baboon suited for the study of microstructure and bone turnover of trabecular bone with relevance to humans.

Bone histomorphometry of the iliac crest, and spinal fracture prevalence in atrophic and hypertrophic osteoarthritis of the hip

While some authors report high bone density in osteoarthritis (OA), surgical experience with total hip arthroplasty (THA) for primary OA suggests the existence of osteoporotic subsets of patients. To identify these we analysed 107 iliac crest bone biopsies, taken at THA, by routine histomorphometry for trabecular structural and bone turnover features, and examined radiographs of the spine for vertebral fractures. Patients were grouped by hip osteophyte size (none, atrophic; small, hypotrophic; moderate, supertrophic; large, hypertrophic OA), and by major architectural disorganization of the hip (hip joint destruction, protrusio). We found hip joint destruction to be 3 times more common in atrophic than in supertrophic and hypertrophic OA (p less than 0.05). Overall, the OA patients had lower bone volume (p less than 0.05) and thinner trabeculae (p less than 0.05) than controls. Worst affected were patients with hip joint destruction and with protrusio: they also had fewer and more widely spaced trabeculae than controls (p less than 0.05). The spinal fracture prevalence was highest in patients with hip joint destruction (higher than in the general population), intermediate in those with protrusio or atrophic OA, and lowest in patients with supertrophic or hypertrophic OA. We conclude that OA hip patients with joint destruction or protrusio have a high prevalence of generalized osteoporosis, and that the larger the hip osteophytes, the lower is the prevalence of generalized osteoporosis. Our findings suggest that the generalized bone status may influence the outcome of OA of the hip.

Skeletal manifestations of primary oxalosis

We describe the clinical, radiographic and histological features of skeletal involvement in four patients with end-stage renal failure due to primary oxalosis. The clinical features were unrelenting bone pain, and in two patients multiple fractures. Radiographic features were, in chronological order: (1) radiodense metaphyses and other red marrow bone; (2) cortical defects in metaphyses; (3) spontaneous fracture-separations of epiphyses of long limb bones which healed poorly. The fractures occurred through crystal deposits, and fracture displacement was associated with extrusion of crystalline material from bone. On histological examination crystals were found to replace metaphyseal bone. Pericrystalline giant cell granulomata replaced bone marrow. Erosion surfaces near granulomas were increased. Subperiosteal and intra-osseous tophi of calcium oxalate were seen. Calcium oxalate appears to precipitate with greater facility than does physiological mineral. Bone showed the features of mixed uraemic osteodystrophy in all four patients. We conclude that: (1) the fractures occurred through heavy crystal deposits; (2) ununited fractures and intra-osseous and subperiosteal tophi contributed to the pain; (3) spontaneous fractures are of poor prognostic significance. We recommend that unstable fractures be internally fixed.

Histomorphometry of iliac crest bone in 346 normal black and white South African adults

We examined undecalcified transiliac bone samples from 346 normal black and white South African adults (age range 21-83 years) by routine histomorphometry. The results were analysed for race-, age- and sex-dependent characteristics of trabecular microstructure (bone volume, trabecular thickness, trabecular number, trabecular separation) and static bone turnover variables (osteoid surface, osteoid volume, osteoid thickness, erosion surface). Trabecular thickness was greater in blacks than in whites, and bone volume was greater in black males, but not in black females, than in their white counterparts. Values for osteoid surface, volume and thickness, and for erosion surface were greater in blacks than in whites. Age-related changes were: a decline in bone volume in all race/sex groups; a decline in trabecular thickness in all groups except black males; a decline in trabecular number in all groups except black females; and a rise in trabecular separation in all groups except black females. There was an increase with age in osteoid surface in all groups except white males, in osteoid volume in all groups, and in erosion surface in blacks only. When correcting for age there were no sex-dependent differences in microstructure but values of some osteoid variables were greater in males than in females. If the greater osteoid and erosion values in blacks reflect greater bone turnover, then trabecular bone in blacks would be renewed more frequently, be subjected to fewer loading cycles and be less prone to fatigue failure. Blacks may thus have trabecular bone of better quality and sturdier microarchitecture. These features could contribute to the lower spontaneous fracture rate in blacks.

Risk factors for the development of stress fractures during fluoride therapy for osteoporosis

We attempted to identify risk factors for the development of lower limb stress fractures during fluoride therapy for osteoporosis (OP). We compared 18 patients who developed 41 such fractures (26 periarticular, 6 femoral neck, 5 long bone shaft, 1 greater trochanter and 3 pubic rami fractures) during fluoride therapy, with 24 similarly treated patients who did not develop stress fractures. Treatment consisted of sodium fluoride 0.99 mg/kg per day, elemental calcium 1 g/day, and vitamin D. We obtained a previous fracture history, annual radiographs of the spine (fractures), hands (metacarpal cortical index, MCI) and pelvis (Singh index, femoral cortical index), three-monthly serum fluoride and alkaline phosphatase levels, and pretreatment transiliac bone biopsies (routine histomorphometry). The stress fracture group was found to have, before treatment: lower MCI (p less than 0.05), lower trabecular bone volume (p less than 0.05), a lower number of trabeculae (p less than 0.05), greater trabecular separation (p less than 0.05), less extensive eroded surfaces (p less than 0.05), a lower double/single tetracycline label ratio (p less than 0.05); and during treatment: more new spinal fractures (p less than 0.05) and higher serum alkaline phosphatase levels (p less than 0.01). We conclude that stress fracture patients had more severe trabecular and cortical OP and possibly a poorer bone-forming capacity before therapy than patients without stress fractures. We suspect that fluoride therapy may temporarily further weaken bone and so lead to stress fractures in severely osteoporotic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Iliac bone biopsies at the time of periarticular stress fractures during fluoride therapy: comparison with pretreatment biopsies

We attempted to establish whether systemic changes in trabecular bone explain the development of stress fractures in the lower limbs during fluoride therapy for osteoporosis. To this end we compared transiliac bone biopsies obtained before treatment with those taken around the time of stress fractures after 14.3 +/- 10.9 (SD) months of therapy in six patients (group A). Biopsies from a comparable group of six patients without stress fractures at the time of the second biopsy (after 11.9 +/- 2.7 months of treatment) served for comparison (group B). The biopsies were processed undecalcified and examined by routine histomorphometry. The second biopsies did not show any significant improvement in mean bone volume or trabecular architecture. Although the second biopsies in group A had increased erosion surfaces (p less than 0.05) and greater osteoid volume (p less than 0.05), group B biopsies showed no difference in erosion surfaces but an increase in all osteoid parameters: osteoid volume (p less than 0.05), osteoid surface (p less than 0.05), and osteoid seam thickness (p less than 0.01). We reached the following conclusions: (1) the combination of increased erosion and replacement of removed bone by as yet unmineralized osteoid in the stress fracture group must have weakened bone and allowed the development of stress fractures. (2) Stress fracture patients may have mounted a less vigorous osteoblast response to fluoride than non-stress fracture patients. Under these conditions microfractures are likely to heal poorly and propagate to develop into full stress fractures. (3) Renal failure is a contraindication to fluoride therapy.

Histomorphometric analysis of osteopenia associated with endemic osteoarthritis (Mseleni joint disease)

Mseleni Joint Disease (MJD), a polyarticular osteoarthritis of uncertain etiology is endemic among the Tonga-Zulu tribe. The traditional diet is deficient in calcium, and palm wine (2-4% alcohol) is drunk widely. Patients with MJD are reported to be more osteopenic than those without. Iliac bone biopsies of 19 arthritic patients were examined by routine histomorphometry and revealed decreased trabecular bone volume (p less than 0.0005), increased resorption surfaces (p less than 0.01), decreased bone formation rate at the BMU (p less than 0.01) level and increased mineralization lag time (p less than 0.01). Six of the 19 patients (31.6%) had features of osteomalacia and six (31.6%) signs of osteoblast failure. The most likely cause of the bone disorder is calcium deficiency, but inanition, inactivity and alcohol abuse may have contributed. Although the joint disorder may have contributed to the bone disorder, the converse is unlikely the case.