Bone ingrowth into madreporic prostheses

Three madreporic prostheses in two patients were examined to evaluate resorption and formation of the surrounding bone tissue. All three prostheses were firmly fixed and had no clinical or radiographic signs of loosening. Transverse sections were examined by scanning electron microscopy at 40 days, 11 months and 2.5 years after implantation. The findings suggest that adaptive bone remodelling varies along the length of the stem; that bone resorption and formation are related to the time after implant; and that new bone formation (woven bone) can be found very close to the madreporic surface.     

Chronic osteomyelitis treated by cancellous homografts and fibrin adhesion

Twenty-nine bone defects caused by chronic osteomyelitis have been treated by radical excision of necrotic bone followed by packing the cavities with cancellous homografts held in position by a fibrin sealant. At follow-up three years after operation all except one had healed, though one case had needed a repeat operation. Good incorporation and remodelling of the grafts was observed even when the osseous bed was severely sclerosed.     

Remodelling and healing process of moderately heat-treated bone grafts after wide resection of bone and soft-tissue tumors

Introduction In the reconstruction of extensive bone defects after massive resection of malignant musculoskeletal tumors, the clinical results of moderately heat-treated autogenous bone graft have rarely been documented. We evaluated the remodelling and healing process of moderately heat-treated autogenous bone graft by means of imaging features.Materials and methods The subjects of this study were 19 patients with bone and soft-tissue tumors treated by heat-treated bone graft at our institution between 1992 and 2001, the mean follow-up period was 4.8±2.8 years (range 1–9 years). The remodelling and healing process of heat-treated bone graft was evaluated by means of radiography, bone scintigraphy, and MRI.Results The mean period to obtain bone union between host bone and grafted bone was 9.4 months. Infection was noted in 1 patient, and fracture was present in 2 patients. In 6 patients, pseudoarthrosis was found. Bone scintigraphy showed an increased uptake at the host-graft junction in the period between 3 and 36 months (median 10.7 months) postoperatively. A gradually increased diffuse uptake on the grafted side was evident at an average of 29.1 months (range 19–41 months) postoperatively. High signal intensity on T2-weighted images was observed in the early period after surgery, and iso-intense or low signal intensity became evident after an average of 28.3 months. A gradually increased diffuse uptake on scintigraphy and iso-intense or low signal intensity on T2-weighted images indicated remodelling of the grafted bone.Conclusion Bone union of a moderately heat-treated autogenous bone graft was noted at about 9 months, and its remodelling was proceeding at about 30 months. This method will be useful for bone defects after massive resection of soft-tissue and bone tumors.     

Familial expansile osteolysis: a morphological, histomorphometric and serological study.

Biopsies from the diseased bones of patients with familial expansile osteolysis (FEO) were examined by light and electron microscopy. Focal concentrations of multinuclear osteoclasts were present, and these contained viral-like microcylindrical inclusions which appeared exclusive to their nuclei. No consistent relationship was found between osteoclast size and the number of osteoclast nuclei containing microcylindrical inclusions. Quantitative histomorphometry showed evidence of increased bone remodelling with high bone cell densities and a decrease of the reversal period in bone remodelling. The lesions contained prominent woven bone and fibrovascular tissue, together with mononuclear cells and adipocytes. Little bone was found in the most radiolucent lesions, which were almost totally occupied by adipocytes and fibrovascular tissue. Serology did not reveal any significant differences between the viral antibody titres of patients and their age- and sex-matched controls. The present study suggests that intranuclear viral-like microcylindrical inclusions of osteoclasts are not a specific feature of Paget's disease, and are found in other disorders of osteoclast function, including pycnodysostosis, osteopetrosis, giant cell tumours, and familial expansile osteolysis.     

Early anchoring collagen fibers at the bone-tendon interface are conducted by woven bone formation: light microscope and scanning electron microscope observation using a canine model.

To clarify the early process of recovery at the bone-tendon interface, we used light microscopy and SEM to examine the process of anchoring of collagen fibers to bone in a canine model. At two weeks, tendon, scar tissue, woven bone and lamellar bone were present at the insertion site. SEM revealed anchoring of collagen fibril bundles of the scar to the woven bone. By 4 weeks, the number of anchoring fibers had increased and a parallel arrangement of fibers was observed. SEM demonstrated deep penetration of fibers into the woven bone layer. In addition, the fibers were observed to project into and intermingle with the scar tissue. By 6 weeks, the anchoring fibers had developed fully and were distributed densely over the interface. SEM also revealed that the collagen fibril bundles in the scar tissue had connected with the collagen fibrils of the woven bone by way of the anchoring bundles. The woven bone was identifiable throughout the early stages of recovery as the interface between soft tissue and hard tissue. Throughout all experimental periods, no staining was observed at the interface of the tendon and bone by Saffranin-O. The formation of woven bone was important during early recovery of the tendon-bone interface prior to the completion of fibrocartilage-mediated insertion.     

骨形态发生蛋白在异体骨段移植愈合中的表达及临床意义

目的：研究骨形态发生蛋白（BMP）在异体骨段移植愈中的表达及临床意义。方法：采用新西兰大白兔股骨中段切除1．5cm骨干和骨膜实验动物模型。方法：36只兔随机分实验组和对照组。实验组植入深低温保存的异体骨,对照组植入自体新鲜骨,均用髓内针固定,分别于术后第1、2、3个月用免疫组织化学染色法观察BMP在异体骨愈合过程的表达情况,结果：深低温保存的同种异体骨移植愈合BMP表达与体骨相似,移植骨段BMP表达阴性,新生骨及其周围类基质表达阳性。新生编织骨BMP表达活跃,成熟板层骨BMP表达减弱（P＜0．01）。结论：异体骨移植愈合中骨吸收和骨诱导是同时,骨诱导在异体骨愈合早期发挥了重要作用。     

Histological evaluation of allograft bone after acetabular revision arthroplasty: report of two cases

We recently had the opportunity to take histological sections from two patients who underwent acetabular reconstruction in which allograft and ME Müller acetabular roof reinforcement rings were used. In one patient (case 1), histological sections of the chipped allograft were taken on two separate occasions from the same area, at 7 months, and at 3 years and 11 months after the bone graft. The histology of the chipped allograft showed necrosis at 7 months, but almost normal morphology of trabecular bone formation at 3 years and 11 months after the bone graft. In the other patient (case 2) histological sections of the block allograft and chipped allograft were taken at 1 year and 8 months after the bone graft. The block allograft showed only a small amount of admixture of newly formed bone with the necrotic bone, while the chipped allograft showed a large amount of newly formed bone, with only a small amount of necrotic bone remaining. Therefore, we principally use chipped allograft for acetabular reconstruction, in order to achieve early and complete graft incorporation. If a block allograft is used in a weight-bearing area, it should be protected from excessive load by using an acetabular reinforcement device. Received: October 27, 1999 / Accepted: March 16, 2000     

Periprosthetic bone remodelling after total knee arthroplasty: early assessment by dual energy X-ray absorptiometry

The present investigation aims to evaluate periprosthetic bone remodelling after total knee arthroplasty by the use of dual-energy X-ray absorptiometry (DXA). Twelve patients affected by osteoarthrosis of the knee joint underwent primary total knee arthroplasty at an average age of 70.5 years. None of them had received a knee prosthesis before on the contralateral side. Anteroposterior and lateral DXA measurements of the femur, tibia and total knee (both sides) were taken 2 weeks, 3 and 9 months postoperatively. The 2-week measurement was used as an individual reference value to be compared with the 3- and 9-month findings. In addition, the contralateral knee was investigated also in order to estimate how far bone mineral loss was due to implantation or to an individual decline in bone mineral density (BMD). The comparison of BMD values after knee arthroplasty revealed a conspicuous decrease of bone density within 9 months. Bone mineral loss amounted to an average of 9.2% in anteroposterior and 17.8% in lateral DXA measurements. Lateral femur shots showed an average decrease of density of even 21.5%. In contrast, the BMD values of the contralateral knees remained almost unchanged. DXA, especially lateral shots of the femur, promises to be a suitable method for early assessment of periprosthetic bone remodelling after total knee arthroplasty. Received: 27 March 1998     

Pressure-induced periprosthetic osteolysis: a rat model.

Recent animal experiments have indicated that oscillating fluid pressure at the interface of bone and implant can lead to osteolysis. However, external nonphysiologic saline solutions were used to generate the pressure in these studies. In the present study on 15 Sprague-Dawley rats, hydrostatic pressure fluctuations were applied to bone through body fluids, by compressing a soft-tissue membrane adjacent to the proximal tibia. A titanium plate was fixed to the bone surface. After 28 days of osseointegration of the plate, a 1-mm-wide gap was created between it and the cortical bone and 5 days were given for fibrous tissue to form. Load was transmitted to this soft tissue by applying force on a piston mounted in the plate. In six rats, a cyclic pressure of 0.6 MPa was then applied to this tissue by 20 cycles twice a day with a frequency of 0.17 Hz for 5 days. The remaining rats served as controls, with the piston left untouched in its upper position. All of the rats were killed 10 days after creation of the gap. Histological sections were produced at a right angle to the loaded surface. In the pressurized specimens, osteoclastic bone resorption was dramatic. In all specimens, the original cortex was almost entirely resorbed but new woven bone had formed deeper in the marrow and walled off a cystic lesion. When necrotic remnants of the cortex were still in place, new woven bone was seen on the side away from the piston. This "lee effect" may indicate that bone formation was inhibited by fluid flow away from the pressurized tissue. The specimens with a nonloaded piston showed no signs of resorption. This new experimental model shows again that a moderate rise of hydrostatic pressure at the interface of bone and implant leads to considerable bone resorption. This could be a mechanism of prosthetic loosening.     

A dynamic classification of Paget's disease

A new dynamic classification of Paget's disease is proposed, incorporating both the radiographic phases of bone remodelling and the scintigraphic findings. Osteolytic, mixed and osteoblastic phases are associated with increased scintigraphic activity, while the osteosclerotic phase of remodelling is associated with normal or diminished activity and an osteoblastic radiographic appearance. Abnormal modelling of bone leading to deformity is produced by accelerated apposition or absorption at the periosteal and endosteal envelopes of the bone. In 112 patients with symptoms from Paget's disease, 527 lesions were classified. The most frequent remodelling phase was the mixed one and the most common modelling state was bone expansion with endosteal and periosteal apposition. Of 88 patients treated medically, 12 had lesions which progressed to increased bone formation without a change in modelling, and the active lesions in seven patients became inactive. Prolonged treatment with disodium etidronate led to progressive osteopenia in 11 patients.     

Atrophy of Cortical Bone Caused by Rigid Internal Fixation Plates: An Experimental Study in the Dog

The cortical atrophy induced by a rigid internal fixation plate on diaphyseal bone was studied on the femora of seven dogs. When the plate, which had been in position for 7 months without previous osteotomy, was removed, a pronounced reduction of the cortical hone was observed in the previously plated section of the diaphyseal bone. The atrophy took the form of loss of cortical bone mainly caused by endosteal resorption with enlargement of the medullary cavity. Neither periosteal resorption nor formation of woven hone under the site of the plate were observed. The process of adaption to the changed stress and strain conditions, caused by the mechanical joint, i.e., implants and bone, was studied by means of a histological technique, and was still in progress after a period of seven months.     

Repair of trabecular fatigue fractures. Cadaver studies of the upper femur

The healing process and the distribution of trabecular fatigue fractures were studied on upper femora obtained at autopsy. Macroscopically, two main types of trabecular fatigue fractures were found on the basis of callus formation that in histologic sections were composed of woven and lamellar bone. A third type characterized by its vestigial callus was found only in histologic sections. Fatigue fractures were more numerous in regions of the femoral head submitted mainly to compressive rather than tensile stress. Trabeculae submitted to compressive stress had a majority of the type of fatigue fractures with an exuberant thorny callus composed of woven bone (most of them located subjacent to the subchondral bone plate), whereas trabeculae submitted mainly to tension or to minimal stress, as in Ward's triangle, had a majority of fatigue fractures with a small, smooth-surfaced callus composed of lamellar bone.     

Repair of trabecular fatigue fractures Cadaver studies of the upper femur

The healing process and the distribution of trabecular fatigue fractures were studied on upper femora obtained at autopsy. Macroscopically, two main types of trabecular fatigue fractures were found on the basis of callus formation that in histologic sections were composed of woven and lamellar bone. A third type characterized by its vestigial callus was found only in histologic sections. Fatigue fractures were more numerous in regions of the femoral head submitted mainly to compressive rather than tensile stress. Trabeculae submitted to compressive stress had a majority of the type of fatigue fractures with an exuberant thorny callus composed of woven bone (most of them located subjacent to the subchondral bone plate), whereas trabeculae submitted mainly to tension or to minimal stress, as in Ward's triangle, had a majority of fatigue fractures with a small, smooth-surfaced callus composed of lamellar bone.     

自体颅骨粉末移植和膜引导再生技术修复兔颅骨缺损的组织学研究

目的应用自体颅骨粉末移植和膜引导再生技术修复兔颅骨缺损模型,观察其组织学演变过程。方法选取50只新西兰大白兔,建立直径1 cm的颅骨全层缺损模型。移植自体骨粉修复兔颅骨缺损,并在移植的骨粉上放置可吸收生物膜,以纤维蛋白胶固定。术后2、4、6、8、12周取材进行组织学观察。结果术后2周,可观察到颅骨缺损区大量骨粉,炎性细胞、毛细血管和成纤维细胞由周围向内浸润,骨粉被吞噬吸收,周边小部分是新生骨,两者之间界限明显。术后4周,观察到骨粉吸收和新骨形成活跃区域向缺损中央内移较多,新生编织骨有所增粗,编织骨之间连接更为紧密,观察到的组织和细胞成分与术后2周时无明显变化。术后6周,基本观察不到未被吸收的骨粉,新生的编织骨变粗,联系更紧密。术后8周,完全观察不到骨粉,缺损中央部已形成单层新生骨,周边部形成的编织骨较为粗大,与正常骨紧密连接,形成初级骨髓腔。术后12周,缺损中央部形成双层新生骨,可见新生骨的改建和较为成熟的骨髓腔,腔内容物形态和成分与正常骨无区别。结论应用自体颅骨粉末移植和膜引导再生技术可以修复颅骨缺损,其组织学演变过程实质是引导性和诱导性骨再生的过程。     

Histomorphometric study of ribs with Looser zones in Itai-itai disease

Twelve Looser zones and 17 healing bands of the ribs obtained from autopsy cases of Itai-itai disease were analyzed by bone histomorphometry. Furthermore, proper cancellous tissue of the ribs from 24 autopsy cases of Itai-itai disease with Looser zones or with the healing bands, 27 autopsy cases of Itai-itai disease without such lesions, and 29 control cases were studied by the same method to pursue the histogenesis of Looser zones. In translucent zones of Looser zones, 94% of the cancellous bone was occupied by thick woven bone in which 72% was woven osteoid and 22% was woven mineralized bone. In adjacent scleroses, 71% of the cancellous bone was occupied by woven bone in which 37% was woven mineralized bone, and 34% was woven osteoid; 53% of the cancellous bone consisted of mineralized bone. As compared with those in translucent zones, woven osteoid was decreased, and mineralized bone was increased significantly in the cancellous bone of adjacent scleroses. A significant increase of lamellar mineralized bone and a decrease of woven bone in healing bands were observed as compared with those in Looser zones. These findings suggest that the healing starts from the edge of the Looser zone, and slowly proceeds toward the center. In the cancellous bone of the ribs, the volume, thickness, and surface of osteoid and woven bone were significantly increased in patients with Ital-itai disease, with Looser zones as compared with those without Looser zones. It was concluded that Looser zones seem to occur in severe osteomalacic bones that contain abundant woven bone in the patients of Itai-itai disease.     

Bone induction in nonhuman primates. An experimental study on the baboon.

Development leading to local bone differentiation in response to intramuscular and subcutaneous implantation of demineralized bone matrix has been predominantly investigated in rodents. To investigate bone differentiation by induction in primates, diaphyseal bone was harvested from ten male baboons and chemosterilized to obtain autolyzed, antigen-extracted allogeneic (AAA) bone containing the bone morphogenetic protein essential for osteoinduction. A total of 96 AAA bone diaphyseal cylinders were implanted intramuscularly in 24 adult male baboons and harvested at three, six, and nine months. Histologic analysis showed that the matrix had undergone considerable resorption, particularly at six and nine months. Seventy-three implants showed variable amounts of newly formed bone at the internal and external surfaces of the chemosterilized matrix. Numerous specimens showed florid bone formation, and newly formed woven bone persisted in association with the matrix for as long as nine months. Coating the AAA bone matrix with an allogeneic fibrin-fibronectin protein concentrate prepared from fresh-frozen baboon plasma did not significantly increase the amount of induced bone. Bone formation was confirmed by intravital double tetracycline labeling of the mineralization fronts. The unequivocal demonstration of bone formation by induction in a large series of adult nonhuman primates provides evidence that long-lived higher vertebrates retain the bone-inductive proteins in the extracellular matrix of bone and the crucial set of responding mesenchymal cells capable of transformation and differentiation into osteoblastic cell lines.     

Solvent dehydrated bone transplants to bridge segmental bone defects: histomorphological and biomechanical investigations in an animal model

Cancellous bone is routinely used in human surgery to fill skeletal defects. The availabilty of autogenous and allogenous grafts is limited, however. The aim of this in vivo study was therefore to determine the in-growth behaviour and biomechanical properties of solvent dehydrated human bone as an alternative to the use of autografts. In a weight-bearing experimental model, solvent dehydrated bone transplants were implanted subchondrally in the medial proximal tibia of merino sheep. After 9 months, explants as well as controls from the contralateral leg were harvested and prepared for histomorphological, histomorphometrical and biomechanical examination. A smaller, but statistically insignificant difference was found for the yield strength after 9 months for harvested specimens in comparison with untreated controls. Regarding the histomorphological results, we found a homogenous ingrowth of new bone trabeculae throughout the transplants. The degradation of the solvent dehydrated bone was not complete within the study period as shown by persistent bone remodelling. The bone per tissue volume of remaining solvent dehydrated graft particles together with newly formed bone was significantly higher than for controls. Our observation period was not long enough to document complete remodelling, but good osteointegration and reasonable biomechanical properties in this weight-bearing large animal model support the application of solvent dehydrated bone in cancellous defects of clinical relevance.     

Histochemical examination of ectopic bone formation induced in rat bone marrow

We examined the rapid formation and subsequent resorption of woven bone induced by partial ablation of rat bone marrow. On the 1st day after ablation, masses of clots occupied the region from which marrow was eliminated. On the 3rd day, alkaline phosphatase-(ALPase-) positive osteoblastic cells appeared in the vicinity of the marrow-eliminated region, forming woven bone. Other ectopic woven bone extended from the endosteal surface toward the bone marrow. Therefore, the newly formed bone originated in two different sites, the endosteal bone surface and the marrow tissues near the marrow-eliminated region. On the 7th day, numerous tartrate-resistant acid phosphatase- (TRAPase-) positive osteoclasts and ALPase-positive osteoblasts expressing the osteonectin gene indicated high activity in both formation and resorption of ectopic woven bone. On the 10th day, the ectopic bone had been markedly resorbed and replaced by bone marrow tissue as the ectopically formed woven bone had not been dynamically maintained, probably because of reduced bone formation activity. Immunoreactivity for basic fibroblast growth factor (bFGF) was indistinctly observed on osteoblastic and preosteoblastic cells on the 1st day after ablation. The fibroblastic cells in the marrow-eliminated region on the 3rd day, and both osteoblasts and preosteoblasts in the woven bone on the 7th day, showed strong immunoreactivity for bFGF. Unlike fractured cortical bone, no chondrogenesis was observed. This model appears to provide convenient material and an important clue for investigation of imbalanced bone formation and subsequent resorption.     

Bone mineral density of the distal femur following uncemented total knee arthroplasty: a two-year follow-up of 11 knees using dual energy X-ray absorptiometry

Abstract In a prospective study, we evaluated the adaptive bone remodelling pattern of the distal femur using dual energy X-ray absorptiometry (DEXA) after total knee arthroplasty (TKA). Eleven patients underwent TKA with insertion of an Interax total knee system (Howmedica) because of primary osteoarthrosis of the knee. All patients received an uncemented femoral component with an uncoated cast-mesh ingrowth surface. The components had a 20-mm long central peg placed anteriorly just behind the anterior flange. DEXA scans were performed postoperatively at 2 weeks and at 3, 6, 12 and 24 months in the mediolateral plane of the distal femur and in the anteroposterior plane of the distal tibia and fibula. Compared to the immediate 2-week postoperative bone mineral density (BMD) value, we found no significant changes in BMD in 4 regions of interest (ROI) in the distal femur during the 2-year follow-up at 3 months. A temporary but significant decrease in BMD of 11.2% (95% CL, -17.3% to -5.0%) was observed in the most distal ROI just posterior to the fixation peg. Bone mineral content (BMC) of the distal tibia and fibula showed no significant changes in the operated and contralateral legs during the follow-up. The adaptive bone remodelling of the distal femur after TKA using an uncemented femoral component not previously examined by DEXA induced only a very limited and temporary loss of bone mineral.     

Magnetic resonance imaging and histology of repair in femoral head osteonecrosis

Different repair processes affect the clinical course of nontraumatic avascular femoral head osteonecrosis, not just necrotic lesion size and location. Fourteen femoral heads were retrieved at total hip arthroplasty after core decompression treatment, or after conservative treatment was done on 13 male patients diagnosed with different stages of femoral head osteonecrosis. To determine repair types, features of coronal magnetic resonance images were correlated with light microscopy findings on corresponding coronal undecalcified sections and microradiographs of the retrieved femoral heads. In five femoral heads, repair of necrotic bone and marrow remained restricted to the reactive interface for as many as 63 months, producing the diagnostic osteosclerotic rim with adjacent hypervascularity (limited repair). Nine femoral heads showed extension of the repair process into the necrosis. In five femoral heads, predominant resorption of necrotic bone led to femoral head breakdown within 2 to 50 months (destructive repair). In four femoral heads, reparative bone formation had started from subchondral fractures and/or the reactive interface, definitely reducing the size of the necrotic area (reconstructive repair). In the latter, the disease progressed slowly or stopped for as many as 45 months, irrespective of treatments, but elimination of risk factors seemed beneficial. Although core decompression did not always reach the necrotic area and improve repair, it reduced accompanying bone marrow edema and could delay the disease progress. Osteonecrosis with limited repair can be identified on magnetic resonance images obtained at followup, but the similar signal changes of destructive and reconstructive repair cannot be distinguished on magnetic resonance images alone. The evidence of reconstructive repair in nontraumatic osteonecrosis, however, gives hope for treatments that can improve repair to a sufficient creeping substitution of the affected femoral head.