Whole Bone Mechanics and Bone Quality

Background  

The skeleton plays a critical structural role in bearing functional loads, and failure to do so results in fracture. As we evaluate new therapeutics and consider treatments to prevent skeletal fractures, understanding the basic mechanics underlying whole bone testing and the key principles and characteristics contributing to the structural strength of a bone is critical.     

Bone Transport for Reconstruction in Benign Bone Tumors

Background

The aim of this study was to assess the results of using the Ilizarov apparatus to transport bones in the treatment of benign bone tumors.

Methods

Seven patients (six males and one female) with benign bone tumors were treated by bone transport with an Ilizarov apparatus at our institution. Their mean age at surgery was 14.4 years (range, 4.8 to 36.9 years). The histological diagnoses were osteofibrous dysplasia (4), giant-cell tumor (1), intraosseous cavernous hemangioma (1), and aneurysmal bone cyst (1). Three radiological indices were used for evaluating the results: an external fixation index, a distraction index, and a maturation index. The bone and functional results were evaluated according to the Association for the Study and Application of the Method of Ilizarov classification.

Results

Five patients had bone union at the reconstructed site, one patient had a local recurrence, and the other had a nonunion at the docking site. The mean length of distraction was 7.3 cm (range, 5.1 to 12.1 cm). The mean external fixation index was 26.0 day/cm (range, 19.8 to 32.5 day/cm), the distraction index was 9.6 day/cm (range, 6.8 to 12.0 day/cm), and the maturation index was 14.9 day/cm (range, 8.0 to 22.5 day/cm). Ultimately, the bone and the functional results were rated excellent in six cases and good in one case.

Conclusions

Bone transport using the Ilizarov apparatus is a good treatment option in patients with bone defects after the resection of an active or aggressive benign bone tumor.     

Penetration of Acrylic Bone Cements into Cancellous Bone

The depth of penetration of five commercial acrylic bone cements into cancellous bone was measured in vitro. Under standard, idealized conditions, cement penetration was found to vary significantly with different cements. Penetration was critically influenced by the coarseness of the cancellous bone and increased directly with the effective volume of the “cells” within the osseous matrix. An inverse correlation was determined between the mean cement viscosity during flow into the bone and final penetration depth. The dough time, set time and working time of each acrylic formulation was found to have no significant effect upon the depth of cement penetration.

It is suggested that in addition to the techniques adopted for introduction of cement to the bone, the selection of the bone cement itself may critically influence the incidence of late loosening following total joint replacement.     

Penetration of Acrylic Bone Cements into Cancellous Bone

The depth of penetration of five commercial acrylic bone cements into cancellous bone was measured in vitro. Under standard, idealized conditions, cement penetration was found to vary significantly with different cements. Penetration was critically influenced by the coarseness of the cancellous bone and increased directly with the effective volume of the “cells” within the osseous matrix. An inverse correlation was determined between the mean cement viscosity during flow into the bone and final penetration depth. The dough time, set time and working time of each acrylic formulation was found to have no significant effect upon the depth of cement penetration.

It is suggested that in addition to the techniques adopted for introduction of cement to the bone, the selection of the bone cement itself may critically influence the incidence of late loosening following total joint replacement.     

Repair of Bone Defects by Bone Inductive Material

Experimental fibular defects in 16 rats were filled with an acid decalcified homogenous bone matrix (bone inductive material). Autogenous bone grafts in corresponding defects in the other legs of the same rats served as controls. After 3 months, 11 of the 16 defects filled with bone inductive material healed with bony union, but only 4 of the 16 defects treated with autogenous bone grafts had healed. The results suggest that bone inductive material can repair bone defects which are too large to be healed by autogenous bone grafts.     

A Bone Replaceable Artificial Bone Substitute: Osteoinduction by Combining with Bone Inducing Agent

Bone inducing agent (BIA) isolated from Saos-2 human osteosarcoma cells was added to an artificial bone substitute composed of 980 degrees C-heated carbonate apatite (CAp) and Type I atelocollagen (AtCol) extracted from bovine tail skins (88/12 in wt/wt %), and a CAp-AtCol-BIA substitute was prepared as an osteoinductive bone substitute. Rat calvaria osteoblasts treated by the isolated BIA demonstrated significantly increased alkaline phosphatase (ALP) activity after 3 days (p < 0.05). In vitro cell attachment and proliferation and ALP activity were investigated for the bone substitute combined with BIA. Osteoblasts cultured onto the surface of the CAp-AtCol-BIA substitute demonstrated remarkable morphological changes such as radial spreading, flattening, and projecting filopodia after 5 days. In comparison with the substitute without BIA, osteoblasts grown in the BIA-combined CAp-AtCol substitute expressed significantly increased proliferation and ALP activity, respectively (p < 0.05). Both the substitutes combined with and without BIA were implanted into artificial defects created in rabbit radii. After 4 weeks, the CAp-AtCol-BIA substitute implanted lesion was completely replaced by regenerated host bone in radiological observation whereas the substitute without BIA was partially resorbed. No histologic abnormalities appeared in the substitute either with or without BIA.     

Bone cement

The knowledge about the bone cement is of paramount importance to all Orthopaedic surgeons. Although the bone cement had been the gold standard in the field of joint replacement surgery, its use has somewhat decreased because of the advent of press-fit implants which encourages bone in growth. The shortcomings, side effects and toxicity of the bone cement are being addressed recently. More research is needed and continues in the field of nanoparticle additives, enhanced bone–cement interface etc.     

骨形态发生蛋白复合同种松质骨载体修复节段性骨缺损的实验研究

目的　本实验将探讨同种松质骨作为 BMP的载体修复节段性骨缺损。方法　将 rh BMP- 2复合同种松质骨载体 (其中含 rh BMP- 2 0 .4 mg)植入兔桡骨 15 m m人工缺损处 ,以新鲜自体松质骨植入 ,单纯同种松质骨植入作为对照 ,通过放射学骨缺损修复 L ane评分 ,Nilsson骨愈合组织学评分 ,扫描电镜观察 ,比较术后 4、8、12周各组修复骨缺损的效果。结果　 rh BMP- 2复合同种骨载体组术后 4、8、12周各项评分与同期自体骨组之间无显著性差异 (P>0 .0 5 ) ,明显优于单纯同种骨组 (P<0 .0 5 )。结论　 rh BMP- 2具有高效的骨诱导能力。同种骨是一种较理想的 BMP载体 ,rh BMP- 2复合同种松质骨载体的骨修复效果与自体骨基本一致     

Bone substitutes

Summary Biocompatible calcium phosphate ceramics has been used for several years in orthopeadic surgery. We have been using two new synthetic biphasic calcium phosphate ceramics (BCP) since September 1996 for bone defect filling in any orthopaedic or trauma operation where autograft use was not possible or even wanted. The first, Eurocer 400® has 300 to 500 micron wide macropores with a totally interconnected porosity. This salt seed like product can be used in bone defect filling, when solidity is not a major concern. The second, Eurocer 200® has not totally interconnected 200 micron large pores. Its main characteristic is a mechanical resistance up to 30 Mpa. We use it in any case of weight-bearing surgery. Different sizes and presentation forms are available and will be chosen according to the recipient site shape. We report one hundred and fifty cases with a six to thirty month follow-up. In one third of the patients hip revision surgery was addressed. Another third concerned recent trauma or sequelae cases,.whereas the last third involved cold orthopaedic procedures. General principles are the need of a living and non-infected site after thorough debridement if necessary. Osteocompatibility of calcium phosphate ceramic is confirmed by our results. We report no mechanical failure. In all cases X-rays show a progressive integration, with new bone formation. Our substitutes have been histologically studied in nine cases, four to fifteen months after implantation. New bone formation around and in the substitute is impressive. Indeed, their good mechanical properties without loss of biological quality is the most relevant feature of these BCPs, leading to a wider indication field; therefore we have now abandoned the use of any bony auto, allo or xenograft.Paper presented at the 1998 meeting of GECO (Arc 1800, Bourg-Saint-Maurice, France)     

Bone water

Summary A short review is given of the water in bone. Various analyses of bone water content are discussed, and its possible location is considered in relation to the behaviour of water in isolated components of bone. Some of the difficulties encountered in examining such microscopic phenomena as water structure in a heterogeneous system such as bone are also discussed.     

Bone transplantations

From personal observations on 652 autogenous bone transplantations, the excellent properties of autogenous cancellous bone as graft material are discussed. Under conditions of mechanical stability it can be successfully used even in infected and poorly vascularized areas. The wide range of indications is discussed, and some clinical examples are presented.     

Solid Aneurysmal Bone Cyst of the Metacarpal Bone

Background: A solid aneurysmal bone cyst is a rare tumor-like lesion of bone. As conventional aneurysmal bone cyst it is a benign, although locally destructive lesion. While the aneurysmal bone cyst is characterized by cyst-like walls of predominantly fibrous tissue filled with free-floating blood, the solid variant shows essential findings identical to those seen in the walls of conventional aneurysmal bone cysts, except that the lesion almost completely lacks the blood-filled spaces and the cyst walls. Differential Diagnosis: Aneurysmal bone cysts and solid aneurysmal bone cysts may easily be mistaken for a malignant tumor, both radiologically and histologically, due to their great rate of growth, tremendous destruction of bone, and marked cellular exuberance in the early to mid phase of development. Case Study: A case of solid aneurysmal bone cyst of the fourth metacarpal is presented. In spite of the relatively unusual location it allows to clearly demonstrate both, the task of correct differential diagnosis and the surgical spectrum of therapy including local recurrence.     

Bone transplantation

Summary According to one principle of surgery, the transplantation of vital tissue is the best method of reconstructing a defect. Because of absent immunologic reactions, high osteogenic potency, and preserved stability, transplantation of autogenous bone shows the best results. Necrosis of transplanted bone, leading inevitibly to absorption and remodeling of the graft, can be avoided if microsurgically vascularized autogenous bone segments are transferred. Disadvantages are the low availability and the necessity of additional operations. As an alternative, deep-frozen allogeneic bone is used. However, this kind of bone shows delayed incorporation based on cellular and humoral immune reactions, and it is also installed into the host bed after overcoming the immune barrier. The risk of microbiological contamination or transmission of unrecognized germs such as HIV is a cause of great expense in bone banking techniques. If one succeeds in reducing (a) the immunologic defense reaction and (b) the risk of infection by sterilization or disinfection without damaging the osteoinductive proteins of bone matrix, the rate of complications can be lowered. Demineralized bone matrix can be used if biomechanical stability is not required. Its ability to induce osteogenesis without a major immune reaction or the risk of transmitting diseases justifies its clinical application. Further intensive research in these areas is unavoidable.

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Zusammenfassung Ein Grundprinzip der Chirurgie lautet, daß die Übertragung von vitalem Gewebe die beste Methode zur Rekonstruktion eines Defekts darstellt. Aufgrund fehlender Immunreaktionen, hoher osteogenetischer Potenz und erhaltener Stabilität können daher mit der Transplantation autogenen Knochens die besten Ergehnisse erzielt werden. Die Nekrose des transplantierten Knochens, die unweigerlich zu Resorption und Umbau führen, kann umgangen werden, wenn mikrochirurgisch-vasklarisierte, autogene Knochensegmente Anwendung finden. Nachteile autogener Transplantate bestehen in ihrer geringen Verfügbarkeit und der Notwendigkeit zusätzlicher Operationen. Alternativ wird daher tiefgefrorener allogener Knochen verwendet. Nach Überwindung der Immunschranke, basierend auf zellu lären und humoralen Immunreaktionen, wird dieser wenn auch verzögert in das Wirtslager eingebaut. Die Gefahr der mikrobiologischen Kontamination und das Risiko einer Übertragung nicht erkannter Keime, insbesondere HIV, bedingen einen hohen Aufwand der Knochenbanktechnik. Gelingt es, durch geeignete Verfahren (a) die immunologische Abwehr und (b) durch Desinfektion oder Sterilisation die Infektionsgefahr zu reduzieren, ohne die osteoinduktiven Proteine der Knochenmatrix zu zerstören, kann die heute noch hohe Komplikationsrate gesenkt werden. Demineralisierte Knochenmatrix stellt deshalb eine Alternative als Knochenersatz dar. Ihre osteogenetischen Eigenschaften bei fast vollständigem Fehlen einer Immunreaktion oder der Gefahr, eine Infektionskrankheit zu übertragen, rechtfertigen ihren Einsatz in der Klinik. Weitere intensive Forschung auf diesen Gebieten bleibt jedoch unverzichtbar.