Periosteal Resorption Research Articles

Bone remodelling in the mouse tibia is spatio-temporally modulated by oestrogen deficiency and external mechanical loading: A combined in vivo/in silico study

Osteoporosis disrupts the healthy remodelling process in bone and affects its mechanical properties. Mechanical loading has been shown to be effective in stimulating bone formation to mitigate initial bone loss. However, no study has investigated the effects of repeated mechanical loading, with a pause of one week in between, in the mouse tibia with oestrogen deficiency. This study uses a combined experimental and computational approach, through longitudinal monitoring with micro-computed tomography, to evaluate the effects of loading on bone adaptation in the tibiae of ovariectomised (OVX) C57BL/6 mice from 14 to 22 weeks of age. Micro-FE models coupled with bone adaptation algorithms were used to estimate changes in local tissue strains due to OVX and mechanical loading, and to quantify the relationship between local strain and remodelling. The first in vivo mechanical loading increased apposition, by 50–150%, while resorption decreased by 50–60%. Both endosteal and periosteal resorption increased despite the second mechanical loading, and periosteal resorption was up to 70% higher than that after the first loading. This was found to correlate with an initial decrease in average strain energy density after the first loading, which was lower and more localised after the second loading. Predictions of bone adaptation showed that between 50 and 90% of the load-induced bone apposition is linearly strain driven at the organ-level, but resorption is more biologically driven at the local level. The results imply that a systematic increase in peak load or loading rate may be required to achieve a similar bone adaptation rate in specific regions of interests.

AGE-RELATED CHANGES IN THE CROSS-SECTIONAL AREA OF THE I AND II PHALANGES, THEIR BONE MARROW CAVITIES AND COMPACTS IN THE POSTNATAL ONTOGENESIS OF ROMANOV SHEEP

The article presents the results of morphological studies of cross-sectional area growth in the first and second phalanges, their bone-marrow cavities and compacted tissue in the postnatal ontogenesis of Ro-manov sheep. As the material for this work we used the I and II phalanges, taken from the left thoracic limb of opposite gender twins at birth, as well as at 3,6,9,12 months of age and in adults 3–4 years of age. To identify phalanges development patterns we used classical morphological methods of research: we determined the growth rate (“K”), age-related changes in the cross-sectional area of the first and second fingers, their bone-marrow cavities and compacts in the studied age periods (M ± m) and in relation to the same indicator in adult sheep in %.. The received digital material was subjected to static processing. It was established that, due to the periosteal growth of bone tissue, cross-sectional area of the I and II phalanges increases all the time, reaching the definitive value by 12 months at the I phalanx, and in the II phalanx it occurs somewhat later. More accelerated periosteal growth is observed in both phalanges in the first three months of lambs’ life. Due to the processes of bone resorption on the side of endosteum, the same thing happens with the cross section of bone marrow cavities, they only reach the definitive state a little earlier, that was noted in the cross section of the bones. In general, the intensity of periosteal growth and resorption processes occur more quickly in I phalanges compared with II.

Assessment Strategies to Improve the Diagnosis of Osteomyelitis in Diabetic Foot Using Radiography

Background: Diabetes mellitus is a multi-system disease that affects people of both genders and any age or ethnic group. Foot wounds are common and can lead to loss of limb in cases of therapeutic failure. Aim: The aim of this study was to correlate initial diagnoses of osteomyelitis by radiography with bacterial cultures and identify ways to improve the diagnosis using this method. Method: In a prospective random clinical trial, the correlation between radiographs and bacterial cultures were evaluated in diabetic patients undergoing amputation of toes or part of the foot in Hospital de Base in the period from October 2010 to January 2012. Radiographs were considered suggestive of osteomyelitis if they identified an irregular bone surface, obliteration, bone resorption or periosteal resorption. The diagnostic impression from imaging was compared to the results of a bacterial growth culture prepared using bone removed during surgery. Results: An analysis of the radiographs identified 29 patients with results that were suggestive of osteomyelitis. Of these, the results of 27 bacterial cultures were positive. Eight of the 22 radiographs that were not suggestive of osteomyelitis were negative and 14 were positive. Conclusion: The diagnosis of osteomyelitis in diabetic foot can be improved by stratifying the results, taking the positive results and creating a diagnostic window with another diagnostic evaluation in cases that are initially negative.

Effectiveness of various isometric exercises at improving bone strength in cortical regions prone to distal tibial stress fractures.

A computational model was used to compare the local bone strengthening effectiveness of various isometric exercises that may reduce the likelihood of distal tibial stress fractures. The developed model predicts local endosteal and periosteal cortical accretion and resorption based on relative local and global measures of the tibial stress state and its surface variation. Using a multisegment 3-dimensional leg model, tibia shape adaptations due to 33 combinations of hip, knee, and ankle joint angles and the direction of a single or sequential series of generated isometric resultant forces were predicted. The maximum stress at a common fracture-prone region in each optimized geometry was compared under likely stress fracture-inducing midstance jogging conditions. No direct correlations were found between stress reductions over an initially uniform circular hollow cylindrical geometry under these critical design conditions and the exercise-based sets of active muscles, joint angles, or individual muscle force and local stress magnitudes. Additionally, typically favorable increases in cross-sectional geometric measures did not guarantee stress decreases at these locations. Instead, tibial stress distributions under the exercise conditions best predicted strengthening ability. Exercises producing larger anterior distal stresses created optimized tibia shapes that better resisted the high midstance jogging bending stresses. Bent leg configurations generating anteriorly directed or inferiorly directed resultant forces created favorable adaptations. None of the studied loads produced by a straight leg was significantly advantageous. These predictions and the insight gained can provide preliminary guidance in the screening and development of targeted bone strengthening techniques for those susceptible to distal tibial stress fractures.

Long-Term High-Dose Resveratrol Supplementation Reduces Bone Mass and Fracture Strength in Rats.

Resveratrol (RSV) is a natural polyphenolic compound. A recent study suggests a positive effect on BMD in men; however, the underlying changes in microstructure and strength remain unknown. We aimed to investigate the effects of RSV on the skeleton in hindlimb-immobilized and non-immobilized rats. Seventy-two female Wistar rats were divided into six groups. Two baseline (BSL) groups underwent short-term diet intervention for 4weeks before sacrifice [phytoestrogen-deficient diet (PD) (BSL+PD) or RSV diet (600mg/kg body weight/day) (BSL+RSV)]. Four groups were injected in the right hindlimb with botulinum toxin (BTX) (immobilized) or saline (non-immobilized), and fed either PD diet or RSV diet 4 weeks pre-injection and 6weeks post-injection before sacrifice (BTX+PD, BTX+RSV, PD, and RSV, respectively). DXA, µCT, dynamic histomorphometry, and mechanical tests were performed. Short-term RSV treatment did not affect bone parameters, whereas long-term RSV exposure had a consistent negative impact on non-immobilized rats (RSV vs. PD); whole femoral aBMD (p=0.01) and distal femoral metaphyseal Tb.N (p=0.01), Tb.Sp (p=0.02), and BV/TV (p=0.07). At the femoral mid-diaphysis, RSV increased periosteal resorption (p=0.01) and increased endosteal formation (p=0.02), while mineralization was unaffected. In addition, RSV reduced femoral mid-diaphyseal three-point bending strength (p=0.03) and stiffness (p=0.04). BTX-induced immobilization resulted in significant bone loss and reduced bone strength; however, RSV supplementation was unable to prevent this. In conclusion, long-term high-dose RSV reduced bone mass and fracture strength and did not prevent immobilization-induced bone loss in rats.

Bone SPECT/CT Localizes Increased Bone Metabolism and Subsequent Bone Resorption in Reflex Sympathetic Dystrophy

A 64-year-old man with lung cancer with a history of revascularization of the occluded right femoral artery underwent bone scintigraphy, which showed intense uptake in the distal side of the right leg. The additional SPECT/CT clarified that the uptake was predominantly increased in the epiphyses of the right ankle and foot with possible osteopenia. One month later, follow-up SPECT/CT showed the manifestation of periosteal resorption in the hypermetabolic sites with slight decrease in bone metabolism. Radiological correlation between bone metabolism and subsequent bone resorption in addition to clinical symptoms in this patient suggested the diagnosis of reflex sympathetic dystrophy.

One-month spaceflight compromises the bone microstructure, tissue-level mechanical properties, osteocyte survival and lacunae volume in mature mice skeletons

The weightless environment during spaceflight induces site-specific bone loss. The 30-day Bion-M1 mission offered a unique opportunity to characterize the skeletal changes after spaceflight and an 8-day recovery period in mature male C57/BL6 mice. In the femur metaphysis, spaceflight decreased the trabecular bone volume (−64% vs. Habitat Control), dramatically increased the bone resorption (+140% vs. Habitat Control) and induced marrow adiposity invasion. At the diaphysis, cortical thinning associated with periosteal resorption was observed. In the Flight animal group, the osteocyte lacunae displayed a reduced volume and a more spherical shape (synchrotron radiation analyses), and empty lacunae were highly increased (+344% vs. Habitat Control). Tissue-level mechanical cortical properties (i.e., hardness and modulus) were locally decreased by spaceflight, whereas the mineral characteristics and collagen maturity were unaffected. In the vertebrae, spaceflight decreased the overall bone volume and altered the modulus in the periphery of the trabecular struts. Despite normalized osteoclastic activity and an increased osteoblast number, bone recovery was not observed 8 days after landing. In conclusion, spaceflight induces osteocyte death, which may trigger bone resorption and result in bone mass and microstructural deterioration. Moreover, osteocyte cell death, lacunae mineralization and fatty marrow, which are hallmarks of ageing, may impede tissue maintenance and repair.

The Periosteal Bone Surface is Less Mechano-Responsive than the Endocortical.

Dynamic processes modify bone micro-structure to adapt to external loading and avoid mechanical failure. Age-related cortical bone loss is thought to occur because of increased endocortical resorption and reduced periosteal formation. Differences in the (re)modeling response to loading on both surfaces, however, are poorly understood. Combining in-vivo tibial loading, in-vivo micro-tomography and finite element analysis, remodeling in C57Bl/6J mice of three ages (10, 26, 78 week old) was analyzed to identify differences in mechano-responsiveness and its age-related change on the two cortical surfaces. Mechanical stimulation enhanced endocortical and periosteal formation and reduced endocortical resorption; a reduction in periosteal resorption was hardly possible since it was low, even without additional loading. Endocortically a greater mechano-responsiveness was identified, evident by a larger bone-forming surface and enhanced thickness of formed bone packets, which was not detected periosteally. Endocortical mechano-responsiveness was better conserved with age, since here adaptive response declined continuously with aging, whereas periosteally the main decay in formation response occurred already before adulthood. Higher endocortical mechano-responsiveness is not due to higher endocortical strains. Although it is clear structural adaptation varies between different bones in the skeleton, this study demonstrates that adaptation varies even at different sites within the same bone.

Microarchitectural Changes in the Aging Skeleton

The age-related reduction in bone mass is disproportionally related to skeletal weakening, suggesting that microarchitectural changes are also important determinants of bone quality. The study of cortical and trabecular microstructure, which for many years was mainly based on two-dimensional histologic and scanning electron microscopy imaging, gained a tremendous momentum in the last decade and a half, due to the introduction of microcomputed tomography (μCT). This technology provides highly accurate qualitative and quantitative analyses based on three-dimensional images at micrometer resolution, which combined with finite elemental analysis predicts the biomechanical implications of microstructural changes. Global μCT analyses of trabecular bone have repeatedly suggested that the main age-related change in this compartment is a decrease in trabecular number with unaltered, or even increased, trabecular thickness. However, we show here that this may result from a bias whereby thick trabeculae near the cortex and the early clearance of thin struts mask authentic trabecular thinning. The main cortical age-related change is increased porosity due to negatively balanced osteonal remodeling and expansion of Haversian canals, which occasionally merge with endosteal and periosteal resorption bays, thus leading to rapid cortical thinning and cortical weakening. The recent emergence of CT systems with submicrometer resolution provides novel information on the age-related decrease in osteocyte lacunar density and related micropetrosis, the result of lacunar hypermineralization. Last but not least, the use of the submicrometer CT systems confirmed the occurrence of microcracks in the skeletal mineralized matrix and vastly advanced their morphologic characterization and mode of initiation and propagation.

The mechanism for consolidation of bone mass in young men and women: A high resolution quantitative computed tomography study

The period between the end of linear growth and peak bone mass has been referred to as ‘consolidation’. We have found that in men and women peak bone mass at the radius and lumbar spine occurs in the middle of the third decade. The aim of this study was to better understand the changes in the bone compartments of the radius using high resolution peripheral quantitative computed tomography (HR-pQCT) and to relate these changes to bone turnover markers. We studied 113 healthy male and female volunteers ages 16–18 and 30–32.Wemeasured spine and hip BMD with DXA, and examined the distal radius with HR-pQCT (Xtreme CT, Scanco Medical). We analysed the HR-pQCT images with the standard software and also with extended cortical bone measures software. We also measured serum βCTX and PINP. Spine BMDwas higher at ages 30–32 than at ages 16–18 inmen andwomen. Hip BMDwas similar in both age groups. Radius cortical BMDwas higher at ages 30–32 than at ages 16–18 in men and women, due to lower porosity and higher tissue mineral density. Trabecular bone volume, BMD, number, thickness and separation did not differ between age groups. Cortical perimeter, endosteal perimeter and trabecular area were greater at ages 30–32 than at ages 16–18 inmen, but not inwomen. Serum βCTX and PINPwere lower at ages 30–32 than at ages 16–18 in men and women. These analyses demonstrate that cortical consolidation is due to an increase in mineralisation of bone tissue and a decrease in porosity. This consolidation is probably due to the decrease in bone turnover between the end of growth and peak bone mass. Also, there is evidence for periosteal apposition and endosteal resorption with increase in bone size in men. The trabecular compartment does not contribute to consolidation, and seems to have reached its mature state by the end of growth.

Stimulation of mouse calvarial periosteal resorption and inhibition of osteoclast formation in human peripheral CD14+ cells by vitamin A

Stimulation of mouse calvarial periosteal resorption and inhibition of osteoclast formation in human peripheral CD14+ cells by vitamin A

Tibial Bone Geometry in Chronic Stroke Patients: Influence of Sex, Cardiovascular Health, and Muscle Mass

This study aimed to examine the geometry of the tibia in chronic stroke survivors. Fifty-five ambulatory individuals with chronic stroke were included in the study. pQCT was used to obtain a cross-sectional scan of the tibia at the 30% site on both the paretic and nonparetic sides. Leg lean mass was derived from a total body scan using DXA. Each subject was also evaluated for peak oxygen consumption rate, spasticity, and functional mobility. Paired t-tests were used to compare the pQCT parameters between the two sides. Multiple linear regression analysis was used to identify the significant determinants of tibial bone strength index (BSI). In men, marrow cavity area on the paretic side was significantly greater than the nonparetic side (p = 0.011), whereas the total bone area showed no significant side-to-side difference (p = 0.252). In women, total bone area on the paretic side was significantly smaller than the nonparetic side (p = 0.003), whereas the marrow cavity area had no side-to-side difference (p = 0.367). Peak oxygen consumption (r(2) = 0.739, F(5,49) = 22.693, p < 0.001) and paretic leg lean mass (r(2) = 0.802, F(6,48) = 32.475, p < 0.001) remained independently associated with tibial BSI, after controlling for age, sex, body mass index, years since stroke onset, and physical activity level. The geometry of the tibia in stroke patients showed sex-specific side-to-side differences. The results suggested that, whereas endosteal resorption was apparent in men, periosteal resorption was more predominant in women. The results also highlight the potential importance of promoting cardiovascular health and leg muscle mass in enhancing bone geometry in chronic stroke survivors.

Cyclical Intravenous Pamidronate Treatment Affects Metaphyseal Modeling in Growing Patients With Osteogenesis Imperfecta

This analysis of 50 growing patients with osteogenesis imperfecta revealed that 2-4 years of pamidronate treatment lead to abnormalities in the shape of the distal femoral metaphyses. Cyclical intravenous pamidronate therapy is of clinical benefit in children and adolescents with moderate to severe osteogenesis imperfecta (OI) but might interfere with the shaping of long bone metaphyses during growth. We evaluated the distal femur in 50 growing children with moderate to severe OI (mean age, 6.7 +/- 3.4 years; 26 girls) who had received 2-4 years of pamidronate therapy (annual dose, 9 mg/kg body weight). The mediolateral width of the distal femoral growth plate and of the metaphysis, as well as the ratio between these two measures (called metaphyseal index), were determined on lower limb radiographs. Compared with untreated OI patients who were matched for OI type and age, pamidronate-treated patients had similar growth plate width but wider metaphyses, resulting in a 26% higher metaphyseal index (p < 0.001). Apart from the effect on bone shape, each pamidronate cycle induces a transverse line in metaphyses that are adjacent to active growth plates. Analyses of these transverse lines revealed that they persist for an average time of approximately 4 years, with a range from 2 to 8 years. Pamidronate interferes with the process of periosteal resorption that is normally responsible for shaping the distal femoral metaphysis. Pamidronate-induced transverse lines disappear with time, supporting the view that these lines represent horizontal trabeculae that undergo remodeling. There is no evidence at present that these treatment induced morphological changes have any clinical implications.

Bone growth patterns in two cordylid lizards, Cordylus cataphractus and Pseudocordylus capensis

Cross-sections through the midshaft of the femora from an ontogenetic range of individuals were examined for Cordylus cataphractus, a heavily armoured, group-living lizard found in the western parts of South Africa, and Pseudocordylus capensis, an agile, montane lizard, occurring in the Cape Fold Mountains of South Africa. Relative bone thickness was found to be high in C. cataphractus and low in P. capensis. Both species displayed a high incidence of double lines of arrested growth. Endosteal resorption and deposition were extensive in C. cataphractus, occurring around the entire medullary cavity margin, and, except in the smallest juveniles, embryonic bone and the birthline had been completely resorbed. In P. capensis, on the other hand, endosteal resorption and deposition were limited and highly localized. Remnants of embryonic bone and a birthline were present in juveniles of varying size, as well as in several adults. These remnants always occurred in the dorsal half of the femoral midshaft and coincided with endosteal deposits, when present. In both species, maximum endosteal deposition and minimum periosteal deposition characterized the dorsal half of the femoral midshaft, while the ventral half was characterized by maximum periosteal deposition and most intensive endosteal resorption. In C. cataphractus, the correlation between medullary cavity area and total bone area differed significantly between the sexes, but not so in P. capensis. The remodelling process in each species can be explained in terms of the respective lifestyles of the species.

Changes in the bucco‐lingual thickness of the mandibular alveolar process and skeletal bone mineral density in dentate women: a 5‐yr prospective study

After tooth extraction there is a great interindividual variation in the remodelling pattern of the alveolar process in edentulous areas, with some individuals losing little bone and others undergoing extensive resorption. However, little is known about possible longitudinal changes in the dentate region of the alveolar process of adults and if these are related to alterations in the skeletal bone mineral density (BMD). In a prospective study, on two occasions, 5-yr apart, the BMD of 117 women was determined in the distal forearm by using dual-energy X-ray absorptiometry, and the bucco-lingual thickness of the mandibular alveolar process was measured on dental casts by using a dial calliper. A decrease in the mean alveolar thickness, exceeding a cut-off value of 0.1 mm, was found in 60% of the women and an increase was found in 3% of the individuals. This decrease was 0.22 +/- 0.20 mm in the posterior region and 0.16 +/- 0.19 mm in the anterior region. The changes in alveolar thickness in the posterior region were significantly correlated to the BMD changes both on the mid-crestal level site and on the cervical level site. We conclude that the bucco-lingual thickness decreases with age in the dentate alveolar process, possibly owing to periosteal resorption related to skeletal bone loss.

Long-Term Disuse Osteoporosis Seems Less Sensitive to Bisphosphonate Treatment Than Other Osteoporosis

We sought to determine whether risedronate can preserve cortical bone mass and mechanical properties during long-term disuse in dogs, assessed by histomorphometry and biomechanics on metacarpal diaphyses. Risedronate slowed cortical thinning and partially preserved mechanical properties, but it was unable to suppress bone loss to the degree seen in other osteoporoses. Disuse induces dramatic bone loss resulting from greatly elevated osteoclastic resorption. Targeting osteoclasts with antiresorptive agents, such as bisphosphonates, should be an effective countermeasure for preventing disuse osteoporosis. Single forelimbs from beagles (5-7 years old, n = 28) were immobilized (IM) for 12 months. Age-matched, non-IM dogs served as controls. One-half the animals received either risedronate (RIS, 1 mg/kg) or vehicle daily. Histomorphometry was performed on second metacarpal mid-diaphyses. Cortical mechanical properties were determined by testing third metacarpal diaphyses in four-point bending. IM caused marked reduction in cortical area (-42%) and cortical thinning (-40%) through endocortical resorption, extensive intracortical tunneling, and periosteal resorption; both bone resorption and formation were significantly elevated over control levels on all envelopes. IM also decreased maximum load and stiffness by approximately 80% compared with controls. RIS reduced both periosteal bone loss and marrow cavity expansion; however, cortical area remained significantly lower in RIS-treated IM animals than in untreated non-IM controls (-16%). RIS also increased resorption indices in all envelopes compared with nontreated IM, indicating that RIS suppressed osteoclast activity but not osteoclast recruitment. RIS did not affect bone formation. RIS treatment conserved some whole bone mechanical properties, but they were still significantly lower than in controls. There were no significant differences in tissue level material properties among the groups. RIS treatment reduces cortical bone loss at periosteal and endocortical surfaces caused by long-term immobilization, thus partially conserving tissue mechanical properties. This modest effect contrasts with more dramatic actions of the bisphosphonate in other osteoporoses. Our results suggest that risedronate impairs osteoclastic function but cannot completely overcome the intense stimulus for osteoclast recruitment during prolonged disuse.

Toward an expanded understanding of the role of the periosteum in skeletal health.

Toward an expanded understanding of the role of the periosteum in skeletal health.

The development of metaphyseal cortex--implications for distal radius fractures during growth.

Fractures of the distal radial metaphysis are very common in otherwise healthy children. The reasons for this high fracture incidence are not entirely clear. To address this problem, we undertook a detailed analysis of distal radius development using peripheral quantitative computed tomography (pQCT) at a site 4% proximal to the radial articular surface. The study population comprised 337 healthy children and adolescents (aged 6-18 years; 171 girls) and 107 adults (aged 29-40 years; 88 women). Total volumetric bone mineral density (vBMD) remained stable at about 70% of the adult value between the ages of 6-7 years and 14-15 years in both genders. Cortical thickness increased little between 6-7 years and 12-13 years in girls and 14-15 years in boys. Strength-Strain Index (SSI; a parameter combining geometry and density) was still at only 20% of the adult value in girls aged 10-11 years and at 21% of the adult level in boys aged 12-13 years. At these ages, factors that contribute to the mechanical challenge to the distal radius in case of a fall (forearm length and body weight) had already reached 49% and 36% of the adult value in girls and boys, respectively. The shaping of the distal radius cortex (metaphyseal inwaisting) was assessed by analyzing the decrease in cross-sectional bone size between adjacent bone slices in a separate population of 44 children (aged 8-19 years; 26 girls). The rates of periosteal resorption and endocortical apposition were estimated to average 8 microm/day and 10 microm/day, respectively, during the growth period. In conclusion, during growth the increase in distal radius strength lags behind the increase in mechanical challenges caused by a fall, because metaphyseal cortical thickness does not increase sufficiently. The endocortical apposition rate is already very high at that site and apparently cannot be further increased to levels that would be necessary to keep bone strength adapted to the mechanical requirements.

Proximal femoral allografts for reconstruction of bone stock in revision arthroplasty of the hip. A nine to fifteen-year follow-up.

Revision of a femoral component in a patient who has severe bone loss is a complex problem that is likely to increase with the increasing numbers of patients who have multiple revision hip arthroplasties. A valuable option in such a situation is use of a long-stem prosthesis that is cemented to a proximal femoral allograft but not to the host bone. Between April 1984 and December 1989, sixty-three total hip arthroplasties in sixty consecutive patients were revised with a proximal femoral allograft-prosthesis construct. The average length of the allograft was 15 cm. The average age of the patients at the time of the revision was 62.5 years. All patients had undergone at least one previous total hip arthroplasty, and an average of 3.8 previous total hip arthroplasties had been performed in the series. Each patient was assigned a modified Harris hip score. Radiographs were examined for trochanteric union, allograft-host union, endosteal and periosteal resorption, component loosening, and fracture. At an average of eleven years (range, nine years and four months to fifteen years) after the revision, forty-five patients were alive, fourteen patients had died, and one patient had been lost to follow-up. The patients who had died or had been lost to follow-up had had a total of fifteen allografts (24%) and had been followed for an average of five years and seven months (range, two years and four months to eight years). The average preoperative Harris hip score for the sixty-three hips was 30 points (range, 6 to 65 points). At the latest follow-up evaluation, the average score for the hips with the original graft in situ was 71 points (range, 47 to 95 points). Five hips failed because of infection, and four of them were successfully revised. Three hips failed because of aseptic loosening, at an average of ten years and three months; two were successfully revised, and the third was awaiting revision at the time of writing. An additional operation was performed in three hips with allograft-host nonunion and in two with dislocation. Success was defined as a postoperative increase in the Harris hip score of greater than 20 points, a stable implant, and no need for additional surgery related to the allograft at the time of the review. The success rate for all hips was 78% (forty-nine of sixty-three) after an average of nine years of follow-up. The success rate for the patients who were alive at the time of follow-up was 77% (thirty-seven of forty-eight hips) after an average of eleven years of follow-up. The clinical and radiographic results at an average of eleven years after revision hip arthroplasty with a proximal femoral allograft are encouraging. This report represents our early experience; improvements in the technique have been made. We believe that this technique provides a viable option for treatment of the difficult problem of severe femoral bone loss.

Structural and cellular changes during bone growth in healthy children

Normal postnatal bone growth is essential for the health of adults as well as children but has never been studied histologically in human subjects. Accordingly, we analyzed iliac bone histomorphometric data from 58 healthy white subjects, aged 1.5–23 years, 33 females and 25 males, of whom 48 had undergone double tetracycline labeling. The results were compared with similar data from 109 healthy white women, aged 20–76 years, including both young adult reference ranges and regressions on age. There was a significant increase with age in core width, with corresponding increases in both cortical width and cancellous width. In cancellous bone there were increases in bone volume and trabecular thickness, but not trabecular number, wall thickness, interstitial thickness, and inferred erosion depth. Mineral apposition rates declined on the periosteal envelope and on all subdivisions of the endosteal envelope. Because of the concomitant increase in wall thickness, active osteoblast lifespan increased substantially. Bone formation rate was almost eight times higher on the outer than on the inner periosteum, and more than four times higher on the inner than on the outer endocortical surface. On the cancellous surface, bone formation rate and activation frequency declined in accordance with a fifth order polynomial that matched previously published biochemical indices of bone turnover. The analysis suggested the following conclusions: (1) Between 2 and 20 years the ilium grows in width by periosteal apposition (3.8 mm) and endocortical resorption (3.2 mm) on the outer cortex, and net periosteal resorption (0.4 mm) and net endocortical formation (1.0 mm) on the inner cortex. (2) Cortical width increases from 0.52 mm at age 2 years to 1.14 mm by age 20 years. To attain adult values there must be further endocortical apposition of 0.25 mm by age 30 years, at a time when cancellous bone mass is declining. (3) Lateral modeling drift of the outer cortex enlarges the marrow cavity; the new trabeculae filling this space arise from unresorbed cortical bone and represent cortical cancelization; (4) Lateral modeling drift of the inner cortex encroaches on the marrow cavity; some trabeculae are incorporated into the expanding cortex by compaction. (5) The net addition of 37 μm of new bone on each side of a trabecular plate results from a <5% difference between wall thickness and erosion depth and between bone formation and bone resorption rates; these small differences on the same surface are characteristic of bone remodeling. (6) Because the amount of bone added by each cycle of remodeling is so small, the rate of bone remodeling during growth must be high to accomplish the necessary trabecular hypertrophy.