Bone stiffness predicts strength similarly for human vertebral cancellous bone in compression and for cortical bone in tension

The yield strength and ultimate strength of cortical and cancellous bone tissue are very highly correlated to bone stiffness. For samples of human vertebral cancellous bone in compression and for bovine cortical bone in tension, the coefficient of determination (r2) for regression between ultimate strength and stiffness was 0.89 and 0.92, and between yield strength and stiffness it was 0.94 and 0.93, respectively. The slope of the regression for human vertebral cancellous bone ultimate strength predicted by stiffness was not statistically different from similar regressions for cortical bone in tension in either a bovine sample or in published data from multiple species. We believe that the observed correlation results from the evolutionary need to build sufficiently strong bones using cells that are sensitive to deformation and that directly control bone stiffness, but not strength. The practical significance of this work is that an in vivo estimate of bone stiffness (e.g., from ultrasound measurement) may be a surrogate for bone strength.     

张力侧与压力侧不同程度皮质缺损对骨干生物力学性能的影响

目的 探讨皮质缺损程度和位置对骨干生物力学性能的影响. 方法山羊股骨标本72个,分别按照骨干冠状面直径的10%、20%、30%、40%和50%制作张力侧和压力侧的皮质环形缺损.正常羊骨作为健康对照.对标本进行三点弯曲测试,力学指标包括最大负倚、最大功耗和弹性模量.记录每个标本的冠状面和矢状面直径,张力侧和压力侧皮质厚度. 结果各组标本的外径和皮质厚度差异均无统计学意义(P>0.05).张力侧皮质缺损在50%亚组的最大负荷较健康对照组显著降低(P<0.05),压力侧皮质缺损在50%、40%和30%亚组的最大负荷较健康对照组显著降低(P<0.05);张力侧皮质缺损在50%、40%和30%亚组的最大功耗较健康对照组有显著降低(P分别为0.000,0.000,0.015),压力侧皮质缺损在各个缺损组的最大功耗均较健康对照组显著降低(P均为0.000).张力侧、压力侧皮质缺损的冠状径、矢状径、压力侧皮质厚度、弹性模量及张力侧皮质缺损的张力侧皮质厚度与健康对照组比较差异均无统计学意义(P>0.05),压力侧皮质缺损的张力侧皮质厚度与健康对照组比较,差异有统计学意义(P<0.05). 结论皮质缺损对骨干力学性能有影响,张力侧和压力侧皮质缺损对骨干力学性能的影响不同.     

Caveolin-1 knockout mice have increased bone size and stiffness.

The skeletal phenotype of the cav-1(-/-) mouse, which lacks caveolae, was examined. muCT and histology showed increased trabecular and cortical bone caused by the gene deletion. Structural changes were accompanied by increased mechanical properties. Cell studies showed that cav-1 deficiency leads to increased osteoblast differentiation. These results suggest that cav-1 helps to maintain osteoblast progenitors in a less differentiated state. INTRODUCTION: The absence of caveolin-1 in cellular membranes causes dysregulated signaling. To understand the role of the caveolar microdomain in bone homeostasis, we examined the skeletal phenotype of 5- and 8-wk-old cav-1(-/-) mice. MATERIALS AND METHODS: High-resolution microCT imaging showed a region-specific effect of cav-1 deficiency on the skeleton. At 5 wk, cav-1(-/-) mice had increased epiphyseal bone volume (+58.4%, p = 0.05); at 8 wk, metaphyseal bone volume was increased by 77.4% (p = 0.008). Cortical bone at the femoral mid-diaphysis showed that the periosteal area of cav-1(-/-) mice significantly exceeded that of cav-1(+/+) mice by 23.9% and 16.3% at 5 and 8 wk, respectively, resulting in increased mechanical properties (I(max): +38.2%, p = 0.003 and I(mi): +23.7%, p = 0.03). RESULTS: Histomorphometry complemented microCT results showing increased bone formation rate (BFR) at trabecular and cortical sites at 5 wk, which supported findings of increased bone at 8 wk in cav-1(-/-) mice. Formal mechanical testing of the femoral diaphysis confirmed increased bone structure: stiffness increased 33% and postyield deflection decreased 33%. Stromal cells from cav-1(-/-) marrow showed a 23% increase in von Kossa-positive nodules; osteoclastogenesis was also modestly increased in cav-1-deficient marrow. Knockdown of cav-1 with siRNA in wildtype stromal cells increased alkaline phosphatase protein and expression of osterix and Runx2, consistent with osteoblast differentiation. CONCLUSIONS: These data suggest that cav-1 helps to maintain a less differentiated state of osteoblast progenitor cells, and the absence of cav-1 causes bone to mature more rapidly. Caveolin-1 may thus be a target for altering skeletal homeostasis.     

Nonmineralized and mineralized bone collagen in bone of immobilized monkeys

Summary Monkey bones from different time periods of immobilization and reambulation of the monkeys were assessed histologically. The bone was also assessed biochemically for nonmineralized collagen in bone. Results indicate that more non-mineralized bone is present in monkeys that have been immobilized, and upon reambulation, these values tend to be normalized to control bone.     

Abnormal microarchitecture and reduced stiffness at the radius and tibia in postmenopausal women with fractures

Measurement of areal bone mineral density (aBMD) by dual‐energy x‐ray absorptiometry (DXA) has been shown to predict fracture risk. High‐resolution peripheral quantitative computed tomography (HR‐pQCT) yields additional information about volumetric BMD (vBMD), microarchitecture, and strength that may increase understanding of fracture susceptibility. Women with (n = 68) and without (n = 101) a history of postmenopausal fragility fracture had aBMD measured by DXA and trabecular and cortical vBMD and trabecular microarchitecture of the radius and tibia measured by HR‐pQCT. Finite‐element analysis (FEA) of HR‐pQCT scans was performed to estimate bone stiffness. DXA T‐scores were similar in women with and without fracture at the spine, hip, and one‐third radius but lower in patients with fracture at the ultradistal radius (p < .01). At the radius fracture, patients had lower total density, cortical thickness, trabecular density, number, thickness, higher trabecular separation and network heterogeneity (p < .0001 to .04). At the tibia, total, cortical, and trabecular density and cortical and trabecular thickness were lower in fracture patients (p < .0001 to .03). The differences between groups were greater at the radius than at the tibia for inner trabecular density, number, trabecular separation, and network heterogeneity (p < .01 to .05). Stiffness was reduced in fracture patients, more markedly at the radius (41% to 44%) than at the tibia (15% to 20%). Women with fractures had reduced vBMD, microarchitectural deterioration, and decreased strength. These differences were more prominent at the radius than at the tibia. HR‐pQCT and FEA measurements of peripheral sites are associated with fracture prevalence and may increase understanding of the role of microarchitectural deterioration in fracture susceptibility. © 2010 American Society for Bone and Mineral Research.     

Deterioration of trabecular plate-rod and cortical microarchitecture and reduced bone stiffness at distal radius and tibia in postmenopausal women with vertebral fractures

Postmenopausal women with vertebral fractures have abnormal bone microarchitecture at the distal radius and tibia by HR-pQCT, independent of areal BMD. However, whether trabecular plate and rod microarchitecture is altered in women with vertebral fractures is unknown. This study aims to characterize the abnormalities of trabecular plate and rod microarchitecture, cortex, and bone stiffness in postmenopausal women with vertebral fractures. HR-pQCT images of distal radius and tibia were acquired from 45 women with vertebral fractures and 45 control subjects without fractures. Trabecular and cortical compartments were separated by an automatic segmentation algorithm and subjected to individual trabecula segmentation (ITS) analysis for measuring trabecular plate and rod morphology and cortical bone evaluation for measuring cortical thickness and porosity, respectively. Whole bone and trabecular bone stiffness were estimated by finite element analysis. Fracture and control subjects did not differ according to age, race, body mass index, osteoporosis risk factors, or medication use. Women with vertebral fractures had thinner cortices, and larger trabecular area compared to the control group. By ITS analysis, fracture subjects had fewer trabecular plates, less axially aligned trabeculae and less trabecular connectivity at both the radius and the tibia. Fewer trabecular rods were observed at the radius. Whole bone stiffness and trabecular bone stiffness were 18% and 22% lower in women with vertebral fractures at the radius, and 19% and 16% lower at the tibia, compared with controls. The estimated failure load of the radius and tibia were also reduced in the fracture subjects by 13% and 14%, respectively. In summary, postmenopausal women with vertebral fractures had both trabecular and cortical microstructural deterioration at the peripheral skeleton, with a preferential loss of trabecular plates and cortical thinning. These microstructural deficits translated into lower whole bone and trabecular bone stiffness at the radius and tibia. Our results suggest that abnormalities in trabecular plate and rod microstructure may be important mechanisms of vertebral fracture in postmenopausal women.     

Trabecular bone failure at the microstructural level

Although biomedical imaging technology is now readily available, few attempts have been made to expand the capabilities of these systems by adding not only quantitative but also functional analysis tools combining microimaging with time-lapsed mechanical testing. An area of special interest is multiscale functional imaging of trabecular bone to assess the relative importance of bone “quality” in the assessment of the mechanical competence of bone. First, relevant studies dealing with hierarchical imaging of trabecular bone and classic analyses such as quantitative morphometry and finiteelement analysis to predict bone strength are reviewed. Second, studies are presented investigating failure mechanisms of three-dimensional trabecular bone through dynamic, time-lapsed microimaging, including image-guided techniques developed for this purpose and utilizing microcompression. For the first time, these allow the direct three-dimensional visualization and quantification of failure initiation and progression at the microstructural level.     

Primary hyperparathyroidism is associated with abnormal cortical and trabecular microstructure and reduced bone stiffness in postmenopausal women

Typically, in the milder form of primary hyperparathyroidism (PHPT), now seen in most countries, bone density by dual‐energy X‐ray absorptiometry (DXA) and detailed analyses of iliac crest bone biopsies by histomorphometry and micro–computed tomography (µCT) show detrimental effects in cortical bone, whereas the trabecular site (lumbar spine by DXA) and the trabecular compartment (by bone biopsy) appear to be relatively well preserved. Despite these findings, fracture risk at both vertebral and nonvertebral sites is increased in PHPT. Emerging technologies, such as high‐resolution peripheral quantitative computed tomography (HRpQCT), may provide additional insight into microstructural features at sites such as the forearm and tibia that have heretofore not been easily accessible. Using HRpQCT, we determined cortical and trabecular microstructure at the radius and tibia in 51 postmenopausal women with PHPT and 120 controls. Individual trabecula segmentation (ITS) and micro–finite element (µFE) analyses of the HRpQCT images were also performed to further understand how the abnormalities seen by HRpQCT might translate into effects on bone strength. Women with PHPT showed, at both sites, decreased volumetric densities at trabecular and cortical compartments, thinner cortices, and more widely spaced and heterogeneously distributed trabeculae. At the radius, trabeculae were thinner and fewer in PHPT. The radius was affected to a greater extent in the trabecular compartment than the tibia. ITS analyses revealed, at both sites, that plate‐like trabeculae were depleted, with a resultant reduction in the plate/rod ratio. Microarchitectural abnormalities were evident by decreased plate‐rod and plate‐plate junctions at the radius and tibia, and rod‐rod junctions at the radius. These trabecular and cortical abnormalities resulted in decreased whole‐bone stiffness and trabecular stiffness. These results provide evidence that in PHPT, microstructural abnormalities are pervasive and not limited to the cortical compartment, which may help to account for increased global fracture risk in PHPT. © 2013 American Society for Bone and Mineral Research.     

Analysis of bone composition at the microscopic level

A study of the composition of bone tissue at the level of microscopic structures, previously limited to the Haversian systems, has been extended to interstitial periosteal lamellar bone and to the Mittellinien. Phosphorus, calcium, total nitrogen, mucopolysaccharides (as hexosamines) and collagen (as hydroxyproline) were determined in these materials on both weight and volume basis. Calcium was also been determined in osteones at the initial and final stage of calcification. In spite of virtually identical Ca/P ratios, interstitial periosteal lamellar bone and Mittellinien differ in their organic composition. Interstitial bone has a higher total nitrogen content (both absolute and relative to phosphorus) as well as higher hydroxyproline and non-collagenous nitrogen than the Mittellinien. A compilation of data on the composition of osteoid tissue, osteones at different degrees of calcification and the above structures, shows how variable is the composition of bone tissue even from one microscopic structure to the one adjacent. Tentative indications of a general rule governing the process of calcification were obtained from the analytical data; namely that wherever calcification is taking place rapidly, non-collagenous proteins (possibly proteoglycans) are present.This investigation was supported by grants from the Italian National Research Council.     

Delayed bone healing following high tibial osteotomy related to increased implant stiffness in locked plating

Introduction

Asymmetrical callus formation and incomplete bone formation underneath stiff locking plates have been reported recently in clinical and experimental fracture healing studies. After similar effects were observed in the outcome of high tibial osteotomy (HTO) patients, a retrospective study was performed to quantify the frequency and level of such incomplete healing cases.

Material and methods

Twenty-three patients treated with medial open wedge HTO and locking plate (Tomofix™) for posttraumatic or congenital genu varum were investigated. No bone grafts were applied to fill the osteotomy gap. The median correction angle was 8° (5–18°). Elective hardware removal was performed after a median of 19.5 months (12–58 months) following an uneventful clinical course. The most recent postoperative X-ray available (median 21 months; 13–56 months) was evaluated for consolidation of the osteotomy. We performed an in vitro biomechanical experiment using the same HTO on a loaded cadaver knee joint to compare interfragmentary movements (IFMs) when using regular locking screws with the Tomofix™ plate and screws that enabled dynamic stabilisation of this plate.

Results

Fifteen patients (65%) displayed incomplete consolidation of the osteotomy underneath the locking plate (10.9% of the osteotomy length) and cortical deficiency. The time to implant removal for these patients of 27 months was longer than the 21 months for the patients with a complete osteotomy gap healing. The biomechanical experiment demonstrated that very low IFMs and corresponding interfragmentary strain occur underneath the plate when using regular locking screws. Replacement with dynamic screws resulted in an increased IFM.

Discussion and conclusions

These results support the hypothesis that low bone formation underneath locking plates is induced by increased stiffness. This high stiffness situation could be altered by replacing the standard screws with dynamic screws which allow for a movement of 0.35 mm perpendicular to the screw axis. This resulted in an approximately threefold increase in the IFM and may be a potential concept to avoid incomplete bone healing under stiff plate fixations.     

Differentiation of osteoblasts and formation of mineralized bone in vitro

Summary Periostea consisting of the osteogenic layer and the fibrous layer of the periosteum were dissected from 17-day-old embryonic chick calvariae, leaving the osteoblasts behind on bone. The dissected periostea were folded with the osteogenic cells in apposition. The explants were cultured on plasma clots for up to 6 days, during which time osteodifferentiation was observed followed by osteoid formation in between the two layers. These cultures consistently mineralized in the presence of 5 or 10 mMβ-glycerophosphate. The mineralization and osteoid formation displayed many characteristics identical with those seen in vivo. Specifically, the osteoid formed was birefringent under polarized light, the central zone of osteoid became mineralized within 24 h of formation in vitro, and a clear border between mineralized and non-mineralized osteoid suggestive of a mineralization front was present. The unmineralized osteoid at the periphery was surrounded by osteoblasts. These data suggest that physiologic mineralization of osteoid produced in vitro did occur in this system by the addition of the alkaline phosphatase substrateβ-glycerophosphate.     

Effect of stem stiffness and bone stiffness on bone remodeling in cemented total hip replacement

The hypothesis in this study is that the stem stiffness-to-bone stiffness ratio influences the incidence and type of bone remodeling and fixation with cemented total hip arthroplasty. Ninety-one patients with 99 hips had cemented stems using 3 different anatomic porous replacement designs. The APR I and APR II titanium stems with proximal porous coating on the proximal one fourth of the stem were cemented into 49 and 35 patients. The APR II-C stem, which is a cobalt-chrome stem only for cemented fixation, was cemented into 15 patients. These 3 different stem designs were used to study different metals as well as different stem shapes. The average follow-up was 4.3 years (range, 2-10 years) with all hips having 2 years' follow-up and 42 hips at least 5 years' follow-up. Bone remodeling was measured as stress shielding, calcar resorption, and distal hypertrophy on anteroposterior and lateral radiographs of the hip. Stress shielding was measured by the 4 grades described by Engh. A stem stiffness-to-femoral bone stiffness ratio was calculated from the plain radiographs with the stem stiffness known from the manufacturer and the bone stiffness calculated using measurements of the outer and inner diameters of the femur. There was no statistical difference for bone remodeling and fixation between the 3 stem shapes or 2 metal types used in these hips. No stem was loose, and only 10 had radiolucent lines. Stress shielding was statistically related to stem stiffness but was more strongly related to the axial stiffness ratio, mediolateral bending stiffness ratio, anteroposterior stiffness ratio, and torsional stiffness ratio. Stress shielding grade 3 and 4 was present in 20% of hips with a torsional stiffness ratio < 0.33, in 38% of hips with a torsional stiffness ratio of 0.34 to 0.5, and in 70% of hips with a torsional stiffness ratio > 0.5. Five-year results showed no statistical change in stress shielding, calcar resorption, and distal hypertrophy from the 2-year observations. The stem stiffness-to-bone stiffness ratio influenced bone remodeling but not fixation of these cemented stems.     

Size and habit of mineral particles in bone and mineralized callus during bone healing in sheep

Bone healing is known to occur through the successive formation and resorption of various tissues with different structural and mechanical properties. To get a better insight into this sequence of events, we used environmental scanning electron microscopy (ESEM) together with scanning small‐angle X‐ray scattering (sSAXS) to reveal the size and orientation of bone mineral particles within the regenerating callus tissues at different healing stages (2, 3, 6, and 9 weeks). Sections of 200 µm were cut from embedded blocks of midshaft tibial samples in a sheep osteotomy model with an external fixator. Regions of interest on the medial side of the proximal fragment were chosen to be the periosteal callus, middle callus, intercortical callus, and cortex. Mean thickness (T parameter), degree of alignment (ρ parameter), and predominant orientation (ψ parameter) of mineral particles were deduced from resulting sSAXS patterns with a spatial resolution of 200 µm. 2D maps of T and ρ overlapping with ESEM images revealed that the callus formation occurred in two waves of bone formation, whereby a highly disordered mineralized tissue was deposited first, followed by a bony tissue with more lamellar appearance in the ESEM and where the mineral particles were more aligned, as revealed by sSAXS. As a consequence, degree of alignment and mineral particle size within the callus increased with healing time, whereas at any given moment there were structural gradients, for example, from periosteal toward the middle callus. © 2010 American Society for Bone and Mineral Research.     

Evaluation of tension and compression forces in the canine femur in vivo

Summary In order to verify the existence of tension and compression forces from the cortical surface of canine femora, rosette strain gauges and a radio telemetry system were used to observe the animals during normal locomotion. Surface strain measured from the lateral cortical surface was consistently in tension whereas surface strain measured from the medical cortical surface was in compression. This data supported in vitro work which showed that eccentric loading of bone results in the convex side of bone being in tension and the concave side of bone being in compression.

---

Zusammenfassung Spannungs- und Druckkräfte auf der kortikalen Oberfläche des Femurs beim Hund wurden geprüft. Um die Verhältnisse beim freien Bewegungsablauf beobachten zu können, wurden Rosetten-Belastungsmeßgeräte und ein drahtloses Telemetriesystem verwendet. Die abgeleiteten Belastungsmessungen ergaben, daß die laterale Kortexoberfläche regelmdßig unter Spannung stand, während die mediale Kortexoberfläche unter Druck stand. Dieses Ergebnis bestätigt das in vitro Resultat, welches zeigte, daß exzentrisches Belasten von Knochen zu Spannung in der konvexen Seite und Druck in der konkaven Seite des Knochens führt.

---

---

Supported by the J. P. Bickell Foundation, University of Toronto, Toronto, Ontario, Canada     

Genetic perturbations that impair functional trait interactions lead to reduced bone strength and increased fragility in mice

Functional adaptation may complicate the choice of phenotype used in genetic studies that seek to identify genes contributing to fracture susceptibility. Often, genetic variants affecting one trait are compensated by coordinated changes in other traits. Bone fracture is a prototypic example because mechanical function of long bones (stiffness and strength) depends on how the system coordinately adjusts the amount (cortical area) and quality (tissue-mineral density, TMD) of bone tissue to mechanically offset the natural variation in bone robustness (total area/length). We propose that efforts aimed at identifying genes regulating fracture resistance will benefit from better understanding how functional adaptation contributes to the genotype–phenotype relationship. We analyzed the femurs of C57BL/6J–Chr^A/J/NaJ Chromosome Substitution Strains (CSSs) to systemically interrogate the mouse genome for chromosomes harboring genes that regulate mechanical function. These CSSs (CSS-i, i = the substituted chromosome) showed changes in mechanical function on the order of −26.6 to +11.5% relative to the B6 reference strain after adjusting for body size. Seven substitutions showed altered robustness, cortical area, or TMD, but no effect on mechanical function (CSS-4, 5, 8, 9, 17, 18, 19); six substitutions showed altered robustness, cortical area, or TMD, and reduced mechanical function (CSS-1, 2, 6, 10, 12, 15); and one substitution also showed reduced mechanical function but exhibited no significant changes in the three physical traits analyzed in this study (CSS-3). A key feature that distinguished CSSs that maintained function from those with reduced function was whether the system adjusted cortical area and TMD to the levels needed to compensate for the natural variation in bone robustness. These results provide a novel biomechanical mechanism linking genotype with phenotype, indicating that genes control function not only by regulating individual traits, but also by regulating how the system coordinately adjusts multiple traits to establish function.     

Zonal analysis of phospholipids in the epiphyseal cartilage and bone of normal and rachitic chickens and pigs

The effect of various degrees of simple, vitamin D-deficient rickets on the levels, composition and extractability of phospholipids from calcifying and soft tissues was studied in chickens and pigs. A variety of effects of rickets on the phospholipid composition of the calcifying tissues were detected; there was little change in the soft tissues. The quantitative effects on the lipid concentration of rachitic hard tissues were variable from zone to zone and appeared to reflect variations in other tissue constituents. However, the qualitative differences indicated a direct effect on specific phospholipids. Acidic phospholipids displayed the greatest percentage change, although numerous statistically-significant changes were also seen in the neutral phospholipids. Tissue zones displaying the greatest change in phospholipid composition in rickets were proliferating and hypertrophic cartilage, and cancellous bone, with calcified cartilage showing the least effect. Rickets also reduced the extractability of certain acidic and neutral phospholipids from zones of early mineralization. These findings are interpreted as indicating the presence of elevated levels of phospholipid complexed with calcium phosphate in rachitic tissue, presumably due to the blockage of normal mineralization.

---

Zusammenfassung Die Auswirkung von verschiedenen Graden von Rachitis (verursacht durch Vitamin D-Mangel) auf die Mengen, die Zusammensetzung und auf die Extrahierbarkeit der Phospholipide von verkalkenden und weichen Geweben wurde an Hühnern und Schweinen untersucht. Es wurden verschiedene Wirkungen von Rachitis auf die Phospholipid-Zusammensetzung der verkalkenden Gewebe gefunden, in den weichen Geweben jedoch nur wenige. Der Grad dieser Wirkung auf die Lipid-Konzentration der rachitisch verknöchernden Gewebe änderte sich von Schicht zu Schicht und schien die Änderungen in anderen Gewebebestandteilen wiederzugeben. Die qualitativen Unterschiede zeigten jedoch eine direkte Wirkung auf spezifische Phospholipide an. Saure Phospholipide zeigten den größten prozentualen Unterschied, obgleich zahlreiche statistisch signifikante Unterschiede auch in den neutralen Phospholipiden gefunden wurden. Die Gewebeschichten, welche bei Rachitis die größte Änderung in der Phospholipidzusammensetzung zeigten, waren proliferierender und hypertrophischer Knorpel und spongiöser Knochen, während verkalkter Knorpel die geringste Änderung zeigte. Rachitis verminderte auch die Extrahierbarkeit von gewissen sauren und neutralen Phospholipiden aus den Schichten der frühen Mineralisierung. Diese Ergebnisse weisen auf das Vorhandensein von erhöhten Phospholipidmengen im rachitischen Gewebe hin, welche Calciumphosphat binden; dies wird wahrscheinlich durch die Blockierung der normalen Mineralisierung verursacht.

---

Résumé Les effets de divers degrés de rachitisme non compliqué, provoqué par avitaminose D, sur les concentrations, la composition, et l'extractibilité de phospholipides de tissus moux et en voie de calcification ont été étudiés chez le poulet et le porc. Le contenu en phospholipides des tissus en voie de calcification est modifié au cours du rachitisme; cependant, on n'a constaté que peu de changements dans les tissus moux. Les effets quantitatifs sur la concentration en lipides des tissus rachitiques calcifiés varient de zone en zone et semblent indiquer desvariations dans d'autres constituants tissulaires. Cependant les différences qualitatives indiquent un effet direct sur des phospholipides spécifiques. Les phospholipides acides présentent les changements de pourcentage les plus élevés bien que de nombreuses modifications statisstiquement significatives dans les phospholipides neutres ont pu être observés. Les zones stisulaires présentant le plus grand changement de composition phospholipidique au cours du rachitisme, sont constituées par le cartilage hypertrophique et en voie de prolifération et par l'os spongieux, alors que le cartilage calcifié est le moins affecté. Le rachitisme diminue aussi l'extractibilité de certains phospholipides neutres et acides des zones de minéralisation précoce. Ces résultats semblent indiquer la présence, dans le tissu rachitique, de concentrations élevées de phospholipide complexé avec le phosphate de calcium, probablement causé par l'inhibition de la minéralisation normale.

     

Bilateral median nerve compression at the level of Struthers' ligament. Case report

Struthers' ligament syndrome is a rare cause of median nerve entrapment. Bilateral compression of the median nerve is even more rare. It presents with pain, sensory disturbance, and/or motor function loss at the median nerve's dermatomal area. The authors present the case of a 21-year-old woman with bilateral median nerve compression caused by Struthers' ligament. She underwent surgical decompression of the nerve on both sides. To the authors' knowledge, this case is the first reported bilateral compression of the median nerve caused by Struthers' ligament. The presentation and symptomatology of Struthers' ligament syndrome must be differentiated from median nerve compression arising from other causes.     

Zonal analysis of electrolytes in epiphyseal cartilage and bone of normal and rachitic chickens and pigs

Electrolytes were analyzed in serum, and in mineralizing tissues at varying stages of calcification, in normal and vitamin D-deficient chickens and pigs. Moisture, ash, and organic matter were also measured.Results revealed that in addition to Ca, other serum electrolytes were altered in rickets. Mg and inorganic P were diversely affected by the vitamin deficiency. Larger changes in mineral level were seen in the tissues in the early stages of calcification than were seen at corresponding times in the serum, suggesting a direct effect of the vitamin deficiency on the calcifying tissue itself. Relative to the serum level, Ca was deposited in the tissues of rachitic animals to a greater extent than in normal animals. This was not true for Mg or inorganic P, indicating a preferential affinity for Ca in the rachitic tissue. Gravimetric analyses of organic and dry matter in epiphyseal zones revealed that the amounts of proliferating and hypertrophic cartilage were increased, and calcified cartilage decreased, in rickets, in accord with previous histological observations. Unexpectedly, the proportion of resting cartilage was also increased.

---

Zusammenfassung Die Elektrolyte im Serum und in mineralisierenden Geweben wurden zu verschiedenen Zeitpunkten der Verkalkung bei normalen Hühnern und Schweinen und bei solchen mit Vitamin D-Mangel analysiert. Wassergehalt, Asche, trockene und organische Substanz wurden ebenfalls gemessen.Die Ergebnisse zeigten, daß außer Ca auch andere Elektrolyte bei Rachitis verändert wurden. Mg und anorganischer P wurden durch den Vitaminmangel bei den beiden Gattungen verschiedenartig beeinflußt. In den Geweben wurde in den frühen Phasen der Verkalkung eine größere Änderung des Mineral-Spiegels gefunden, als dies zu übereinstimmenden Zeiten im Serum der Fall war, was auf eine direkte Wirkung des Vitaminmangels auf das verkalkende Gewebe schließen läßt. Im Verhältnis zum Serumspiegel wurde Ca in den Geweben der rachitischen Tiere zu einem größeren Grade als normal abgeschieden. Dies war nicht der Fall bei Mg oder anorganischem P, was einen Vorzug für Ca in den rachitischen Geweben anzeigt.Gravimetrische Analysen von organischer und trockener Substanz in epiphysischen Schichten zeigten, daß die Menge des proliferierenden und hypertrophischen Knorpels zunahm und daß verkalkter Knorpel bei Rachitis abnahm, gemäß klassischen histologischen Beobachtungen. achtungen. Ganz unerwartet war bei Rachitis eine verhältnismäßige Zunahme des ruhenden Knorpels festzustellen.

---

Résumé Les électrolytes ont été analysés dans le sérum et dans les tissues en voie de minéralisation, à des stades variables de calcification, chez des poulets et des pores normaux et rachitiques. L'humidité, les cendres et les matières organiques et déssèchées ont été analysées.Il apparait que d'autres électrolytes sériques, en plus du Ca, sont modifiés au cours du rachitisme. Le Mg et le P inorganique sont modifiés de façon variable au cours de l'avitaminose D. Des changements plus importants en contenu minéral des tissus sont observés dans les stades précoces de calcification que ceux que l'on a pu constater dans le sérum à des stades similaires, ce qui suggère un effet direct de l'avitaminose sur le tissu en voie de calcification. Quant au contenu du sérum, le dépôt de Ca est plus élevé dans les tissus d'animaux rachitiques par rapport aux témoins. Ceci n'est pourtant pas le cas du Mg ou du P inorganique, indiquant une affinité préférentielle du Ca pour le tissue rachitique.L'analyse gravimétrique de matières organiques et déssèchées des zones épiphysaires montre que les quantités de cartilage hypertrophique et en voie de dévelopment augmentent dans le cas de rachitisme, alors que le cartilage calcifié diminue, confirmant les observations histologiques antérieures. De manière inattendue, la proportion de cartilage au repos augmente au cours du rachitisme.