Experimental study on vascularized bone allografts for reconstruction of massive bone defects

To study the healing mechanism of vascularized bone allografts under short-term as well as long-term immunosuppression with cyclosporin A, experimental vascularized intercalary bone allograft transplantation was carried out between inbred rats using the tibiofibula graft model. Bone scintigram and radiographs were used as an indicator for early detection of rejection after transplantation and bone union. In vascularized bone allografts under long-term immunosuppression with cyclosporin A, early bone union and continuous incorporation were similar to that observed in vascularized bone autograft transplantation. When administration of cyclosporin A was discontinued before completion of bone union, the graft was rejected and bone union was delayed. Apparent swelling on the operated limb associated with a decrease in bone scintigram uptake suggested the occurrence of rejection of the allograft. Vascularized bone allograft transplantation is useful for reconstruction of massive bone defects only if immunosuppressants are used and maintained at least until bone union is obtained. © 1994 Wiley-Liss, Inc.     

肢体大块骨缺损的大段同种异种骨关节移植

作者为３５例四肢恶性肿瘤切除后的骨缺损患者进行了大段同种异体骨移植重建，其中男性２３例，女性１２例。股骨下端和胫骨上端占６８．５％。骨肉瘤占４０％。所有病例均经术前、术后化疗。植骨材料来源于该院综合骨库。作者强调充分的术前准备，仔细选择匹配移植骨段，手术中注意设计骨膜油套和软组织袖套以利于骨愈合。本组病例随访５个月￣１０年，平均３年，其中无病存活者２５例，死亡６例，带病存活４例。部分患者于术后２年     

Consolidation of massive bone allografts in limb-preserving operations for bone tumours

Summary This study analysed the influence of several factors affecting the consolidation time of 83 massive bone allografts in 79 patients with malignant bone tumours: osteosarcoma 57; Ewing's sarcoma 8; malignant fibrous histiocytoma 3; chondrosarcoma 4; fibrosarcoma 5; and giant cell tumours 2. The mean age of the patients was 19 years and the mean length of the allografts was 18 cm. The minimum follow up was for 12 months. The mean consolidation time for metaphyseal and diaphyseal osteotomies was 6.5 and 16 months respectively. Fifteen diaphyseal osteotomies required autologous cancellous grafting. There were 8 allograft fractures after consolidation. The following factors which might influence consolidation were analysed: age of the host and donor; allograft length and site; type of osteotomy and osteosynthesis; intra-arterial and systemic chemotherapy; intraoperative and external radiotherapy. In diaphyseal osteotomies there were statistically significant differences in consolidation time with the use of systemic chemotherapy, external radiotherapy and the recipient's age.

---

Résumé Dans le present travail, est analysé le temps de consolidation et les facteurs qui ont pu l'influencer de 83 allogreffes corticospongieuses placées chez 79 patients affectés de tumeurs osseuses primitives malignes (57 ostéosarcomes, 8 sarcomes d'Ewing, 3 HFM, 4 chondrosarcomes, 5 fibrosarcomes et 2 TCG), traités par chirurgie conservatrice, avec un age compris entre 4 et 69 ans (m=19). La durée moyenne de consolidation fut 6.5 mois pour les ostéotomies métaphysaires, 16 pour les diaphysaires, avec 1 pseudarthrose métaphysaire et 7 diaphysaires. Quinze allogreffes ont eu besoin d'un apport de greffe autologue pour consolider et 8 eurent une fracture une fois consolidé. On a analysé les différents facteurs qui ont pu influencer la consolidation; âge du donneur et du receveur, longueur et localisation de l'allogreffe, type d'ostéotomie et d'ostéosynthèse, chimiothérapie (intra-art`erielle ou systémique) et radiothérapie (intraopératoire ou externe). Dans les ostéotomies diaphysaires, la chimiothérapie systémique (p<0.05), la radiothérapie externe (p<0.01) et l'age du receveur (p<0.01) retardent la consolidation.

     

Tissue-typing in human massive allografts of frozen bone

The cases of twenty-six patients who received a massive allotransplant of frozen bone, with a known degree of histocompatibility between the donor and the recipient, were studied. Twenty-two patients were followed for more than two years (range, twenty-four to ninety-two months). Twenty-three biopsies were performed in sixteen patients from nine to seventy-eight months after transplantation. No clear relationship could be established between the degree of histocompatibility of the donor and the recipient and the incorporation of the graft, probably in part due to the number of variables involved and the polymorphism of the HLA system. However, no early massive resorption of the transplant was seen in this series, in which, by the design of the protocol, no recipients had pre-existing circulating antibodies to the antigens of the donor. Two allografts showed infiltration by round cells and vascular lesions in the absence of infection, which is suggestive of an immune response against antigens from the donor. Both matched poorly with the donor for HLA antigens. The individual who had the strongest reaction was the only recipient in the series who had a massive failure of the transplant.     

Radiological and histological analysis of cortical allografts: an experimental study in sheep femora

Introduction We developed an experimental model in sheep femora to evaluate the process of cortical allograft incorporation.Materials and methods Twenty-four sheep were divided into four groups according to the various treatments of cortical allografts as follows: fresh, frozen, autoclaved, and frozen with perforation. Periodical radiographic and histological evaluations were performed for each group.Results Perforated frozen allograft proved to be superior radiographically in the first stage to fresh, frozen, and autoclaved forms. Revascularization was demonstrated by both Spalteholzs technique and histological examination. Histological analysis also showed creeping substitution, from the host bone to the allograft, which increased the reabsorption to facilitate new bone penetration, including endochondral ossification at the host-graft interface.Conclusion We believe that endochondral ossification is probably a biological event occurring routinely during the bone healing process and that the processes of incorporation of variously treated cortical allografts differ only at the early phase of implantation.     

Fracture resistance of gamma radiation sterilized cortical bone allografts.

Gamma radiation is widely used for sterilization of human cortical bone allografts. Previous studies have reported that cortical bone becomes brittle due to gamma radiation sterilization. This embrittlement raises concern about the performance of a radiation sterilized allograft in the presence of a stress concentration that might be surgically introduced or biologically induced. The purpose of this study was to investigate the effect of gamma radiation sterilization on the fracture resistance of human femoral cortical bone in the presence of a stress concentration. Fracture toughness tests of specimens sterilized at a dose of 27.5 kGy and control specimens were conducted transverse and longitudinal to the osteonal orientation of the bone tissue. The formation of damage was monitored with acoustic emission (AE) during testing and was histologically observed following testing. There was a significant decrease in fracture toughness due to irradiation in both crack growth directions. The work-to-fracture was also significantly reduced. It was observed that the ability of bone tissue to undergo damage in the form of microcracks and diffuse damage was significantly impaired due to radiation sterilization as evidenced by decreased AE activity and histological observations. The results of this study suggest that, for cortical bone irradiated at 27.5 kGy, it is easier to initiate and propagate a macrocrack from a stress concentration due to the inhibition of damage formation at and near the crack tip.     

Experimental study of the ossification of decalcified cortical bone

Authors examined in animal experiments the ossification of decalcinated cortical bone. A more rapid rebuilding of the demineralised bone than that of the not decalcinated one, seems to them as proven. An acceleration of the process is tried by dosing anabolic steroids and calcium.     

Survival of massive allografts in segmental oncological bone defect reconstructions

Reconstructions of large segmental bone defects after resection of bone tumours with massive structural allografts have a high number of reported complications including fracture, infection and non-union. Our goal is to report the survival and complications of massive allografts in our patients. A total of 32 patients were evaluated for fracture, infection, non-union rate and survival of their massive allograft reconstructions. The average follow-up for this group was five years and three months. The total fracture rate was 13% with a total infection rate of 16%. We found a low union rate of 25%. The total survival of the allografts was 80.8% (± 18.7%) after five years. We found a five-year allograft survival of 80.8% which is comparable with other studies.

---

Résumé  La reconstruction des larges pertes de substances osseuses après la résection des tumeurs osseuses par des allogreffes structurales est pourvoyeuse d’un pourcentage élevé de complications, telles que fractures, infections et pseudarthroses. Le but de notre étude est de rapporter la courbe de survie et les complications de ces allogreffes massives. 32 patients ont été évalués en terme de fractures, d’infections et de pseudarthroses, après mise en place d’allogreffes massives, le suivi moyen du groupe a été de 5 ans et 3 mois. le taux de fractures est de 13%, le taux d’infections de 16%. Nous avons trouvé un taux relativement bas de consolidation 25%. La survie de ces allogreffes, globalement est de 80,8% (± 18,7%) après 5 ans. le taux de survie de ces allogreffes à plus de 5 ans est de 80,8%, il est comparable aux autres études.

     

Effect of nimodipine on vasospasm of cortical arteries. Experimental study]

The efficacy of the calcium channel blocker Nimodipine (N) in prevention and treatment of chronic cerebral vasospasm (V.S.) after subarachnoid haemorrhage (S.A.H.) was tested in a blind randomized experimental study. Twenty seven dogs (French Grande Venerie) weighing between 40 to 50 kg, were randomly assigned in three groups. Under general anesthesia, each animal underwent baseline angiography, followed by right frontotemporal craniectomy. A retractor was placed under the temporal lobe and the arachnoid membrane over the internal carotid artery was dissected. 10 ml of autologous arterial blood was placed around the internal carotid artery, and 5 ml of arterial blood was injected into the cisterna magna. Group I was placebo group: ten randomly pre selected animals received a placebo. Group II was preventive group: seven animals received N (5 mg/kg) per os each day, from D0. Group III was curative group: ten animals received N (5 mg/kg) per os each day, from D2. At Day 2 and Day 5, all animals underwent a control angiography. The basilar artery, the internal carotid artery were measured. The craniectomy was reopened and the cortical arteries were measured with a calibrated optical micrometer. Intergroup comparisons at Day 0, Day 2 and Day 5, were made by analysis of variance. The level of significance was n < 0.05. V.S. was defined as a reduction in vessel caliber of 10% or greater, compared to baseline value. In the placebo group (Group 1), V.S. of the basilar and cortical arteries was present in all cases, from D2 to D5.(ABSTRACT TRUNCATED AT 250 WORDS)     

Initial stability of circumferential meshes with impacted bone allografts for massive femoral defects

When the proximal femur is absent due to a failed femoral stem in total hip arthroplasty, impacted bone grafts contained within circumferential meshes could be an alternative reconstructive method. The purpose of this study was to analyse the initial resistance to axial and rotational forces in a fresh frozen bovine model with complete loss of the proximal femur reconstructed with a circumferential metal mesh, impacted bone allografts and a long cemented stem. Four bovine femurs with a complete proximal bone defect were reconstructed with a circumferential mesh, impacted bone grafts and a cemented stem. The results were compared with four intact femurs using the same implant. Under axial load, subsidence was observed at an average of 617 kg in the experimental group, and a cortical fracture occured at 1335 kg in the control group. Under rotational load, experimental femurs failed at an average of 79 kg and the control femurs fractured at 260 kg. This model provided 50% of the resistance to axial load and 30% of the resistance to rotational load compared to an intact femur, which is enough to resist physiological load. This stability encourages the use of circumferential meshes, impacted bone allografts and cemented stems in revision hip surgery with massive bone loss.     

The versatility of massive allografts in the treatment of bone tumours of the proximal humerus

Endoprosthetic replacement (EPR) of the proximal humerus following tumour resection has resulted in proximal subluxation, pain, instability and poor function. Alternative reconstructive options to EPR include leaving the shoulder flail, insertion of a passive spacer and arthrodesis. Five patients were treated using massive cadaveric allografts as the method of reconstruction following tumour resection. The pathology was three osteosarcoma, one chondrosarcoma and one metastasis from a renal primary. The patients were evaluated clinically using the Musculoskeletal Tumour Society (MSTS) and Constant shoulder assessments. All four patients with primary tumours were alive and disease free at review after a median follow-up of 23 months (range 14–112). No patients suffered immediate complications. Three of the four patients were pain free. Function was limited, causing at least partial occupational restriction in three of four patients. Allograft remains a viable alternative to EPR in reconstruction following tumour resection. Costs are favourable, and patients gain good analgesia. Function is sacrificed (as it is in EPR), especially if tumour resection necessitates nerve sacrifice. In our patients, the allograft was used either as a passive spacer, arthrodesis or arthroplasty, demonstrating its versatility.     

The resurfacing of adult rabbit articular cartilage by multiple perforations through the subchondral bone.

The repair of articular cartilage removed from the femora of adult rabbits at the knee was studied. When multiple perforations were made through the subchondral bone a cartilaginous material, staining heavily with safranin O, first filled the holes. This material resembled hyaline cartilage, and by twelve months there was complete resurfacing of the joint, although the material lost its hyaline appearance after eight months and at one year it resembled dense collagenous tissue.     

Long-term results of anti-protrusion cage and massive allografts for the management of periprosthetic acetabular bone loss

From 1992 to 1995, 71 total hip arthroplasties with extensive acetabular bone loss underwent revision using bulk allografts and Burch-Schneider anti-protrusio cages. Twelve patients died of unrelated causes and 3 were lost to follow-up. Fifty-six hips were available for clinical and radiographic follow-up examination at an average of 11.7 years after surgery. The average final Harris hip score was 75. X-ray signs of incorporation of massive bone graft were observed in 49 hips. Two cases developed deep infection that required resection arthroplasty. Aseptic loosening of the acetabular cage occurred in 5 patients, and 2 of them underwent re-revision. With a total survival rate of 87.5%, anti-protrusio cages and structural allografts compare favorably with other techniques in the long-term reconstructive treatment of extensive loss of acetabular bone stock.     

The mechanical and biological properties of demineralised cortical bone allografts in animals

We studied the calcium content and mechanical strength of cortical bone from rats and dogs after different periods of demineralisation, showing that the rate of demineralisation differed considerably between the species. Specimens from the rat were further treated by chemical extraction and autolysis and tested for osteoinductive properties. We showed that partially demineralised cortical bone retained adequate mechanical strength, while retaining the biological effects of completely demineralised bone. This shows that it is possible to prepare allografts which have adequate mechanical strength and still retain osteo-inductive properties.     

Factors affecting outcome of massive intercalary bone allografts in the treatment of tumours of the femur

We retrospectively reviewed 101 consecutive patients with 114 femoral tumours treated by massive bone allograft at our institution between 1986 and 2005. There were 49 females and 52 males with a mean age of 20 years (4 to 74). At a median follow-up of 9.3 years (2 to 19.8), 36 reconstructions (31.5%) had failed. The allograft itself failed in 27 reconstructions (24%). Mechanical complications such as delayed union, fracture and failure of fixation were studied. The most adverse factor on the outcome was the use of intramedullary nails, followed by post-operative chemotherapy, resection length > 17 cm and age > 18 years at the time of intervention. The simultaneous use of a vascularised fibular graft to protect the allograft from mechanical complications improved the outcome, but the use of intramedullary cementing was not as successful. In order to improve the strength of the reconstruction and to advance the biology of host-graft integration, we suggest avoiding the use of intramedullary nails and titanium plates, but instead using stainless steel plates, as these gave better results. The use of a supplementary vascularised fibular graft should be strongly considered in adult patients with resection > 17 cm and in those who require post-operative chemotherapy.     

Improved osteoinduction of cortical bone allografts: A study of the effects of laser perforation and partial demineralization

Massive cortical bone allografts have been found to incorporate slowly into host bone and thus are subject to complications such as nonunion, fatigue fracture, and infection. To better understand and improve the process of osteoinduction in these types of bone grafts, a new experimental model was developed with use of diaphyseal cortical bone grafts from rat tibiae that were prepared by partial mineralization and drilling of 0.33 mm diameter holes with a pulsed, 2.94 μm wavelength, erbiunr:yttrium-aluminum-garnet laser. Six types of grafts were analyzed: untreated (Type I), demineralized 25 μm deep (Type II), demineralized 150 μm deep (Type III), laser perforated (Type V), laser perforated and then demineralized 25 μm deep (Type V), and laser perforated and then demineralized 150 μm deep (Type VI). The graft was orthotopically transplanted in the tibia of an adult Sprague-Dawley rat and followed for as long as 4 months. Histologic evaluation at 1 and 4 months postoperatively with use of hematoxylin and eosin staining confirmed that there was new bone growth in Types II, III, V, and VI grafts. The amount of growth was estimated by comparing bone mineral density before implantation with values obtained after retrieval of the graft. These measurements were correlated to histomorphometric analysis of graft incorporation. The results show that the processes of partial demineralization (p < 0.000001) and laser perforation with partial demineralization (p < 0.000001) were both significant in enhancing bone growth in this model. New bone growth was significantly increased when the grafts were prepared with extensive demineralization (p < 0.015). This study demonstrates that osteogenesis in cortical bone grafts can be fostered through the process of partial demineralization and laser perforation. To the extent that minimal partial demineralization and laser perforation allow maintenance of Structural integrity while altering the osteoinductive properties in such a way as to promote ingrowth of new bone, this experimental model represents an advance in understanding how osteogenesis in cortical bone grafts may be improved.     

Effect of periosteal stripping on cortical bone perfusion: A laser doppler study in sheep

The goals of internal fixation are an accurate reduction and stable fixation in the presence of adequate bony vascularity. This can be achieved by a variety of means including plate fixation. A certain amount of periosteal stripping is necessary for proper open reduction of a fracture and for proper plate application. With displaced diaphyseal fractures, cortical bone perfusion (CBP) is already compromised. Further damage, in terms of periosteal stripping for plate fixation, may not be acceptable. Little information is available as to what extent the periosteum contributes to cortical bone perfusion. The purpose of this study was to determine the acute effects of periosteal stripping on cortical bone perfusion in a sheep tibia model. Twenty-three sheep were operated on and had the medial aspect of their right tibia exposed. Cortical bone perfusion measurements were obtained using laser Doppler flowmetry prior to periosteal stripping and after periosteal stripping. The results of this study show that the cortical bone perfusion significantly decreased by 20% after periosteal stripping over the entire length of the tibia. We therefore conclude that the periosteum contributes to diaphyseal bone perfusion and that it is important to preserve this source with fractures where blood supply is already significantly compromised.