Preliminary study of ethylene oxide sterilization of full-thickness cortical allografts used in segmental femoral fracture repair

Full-thickness canine cortical allografts were cleanly harvested, sterilized with ethylene oxide, and stored at room temperature. The allografts were incorporated into canine segmental femoral fracture repairs and compared clinically, radiographically, and morphologically with control femoral cortical autografts for function of the limb, graft acceptance, and bone union. Sterility was maintained and the cortical allografts were well accepted by the host animals, resulting in full use of the limb which was subjected to surgical operation. The allografts showed healing patterns similar to those of the autografts, as determined by radiographic, gross, and histologic evaluation of the proximal and distal host-graft interfaces. Evaluations were made monthly. The host-graft interfaces of the allografts and autograft were filled with woven bone with adjacent vascular invasion and remodeling of the graft at the final 4th-month evaluation.     

Healing of Cortical Bone Grafts in the Dog The Role of Azathioprine

Sixteen unrelated beagles, randomly divided into groups of four, were used in evaluating the role of therapeutic immunosuppression in the healing of fresh cortical bone allografts over a 16-week period. The four groups included: nontreated allograft, treated allograft, nontreated autograft, and treated autograft. A 2.7-cm tibial cortical graft was fixed orthotopically using a dynamic compression plate. Healing was evaluated by radiography and by gross and histologic studies at 2, 4, 8, and 16 weeks after surgery. The treated dogs were immunosuppressed with azathioprine for eight weeks postsurgery. The conclusions were that: temporary immunosuppression did not significantly alter healing of fresh cortical bone autografts; healing of fresh cortical bone allografts in immunosuppressed dogs was similar to healing of fresh cortical bone autografts; slight differences were observed in the healing of bone grafts in all groups after eight weeks; and cellular reaction typical of graft rejection was found in nontreated allografts, but healing still occurred.     

Effects of tissue antigen matching on the healing of fresh cancellous bone allografts in dogs

The radiographic and histologic healing patterns of fresh cancellous bone allografts were compared with those of fresh cancellous autografts in dogs. Two groups of allografts were studied: 1 group of littermate pairs with minor histocompatibility mismatches, and 1 group of unrelated pairs with major histocompatibility mismatches. Pairs were chosen on the basis of preoperative serologic typing and mixed lymphocyte cultural assay of lymphocyte-defined compatibility. Generally, grafts with minor mismatches and autografts achieved bony union in 6 weeks with grafted bone serving as a scaffold for new bone formation. Grafts with major mismatches were resorbed and replaced by fibrocartilage. Healing of osteotomy sites grafted with mismatched bone occurred by ingrowth of host periosteal and endosteal new bone.     

Feline model for the study of frozen osteoarticular hemijoint transplantation: qualitative and quantitative assessment of bone healing

Twenty-four outbred cats underwent massive osteoarticular allograft and control autograft transplantation, using the right distal femur with its articular cartilage, capsule, and medial collateral ligament intact. The cats were monitored clinically and radiographically for 1 year. Groups of cats (4 allografts and 2 control autografts) were euthanatized at 3-, 6-, 9-, and 12-month intervals. At necropsy, the grafts were photographed and assessed for bone healing and replacement by standard radiography, quantitative 99mTc bone scans, microradiography, and histologic examination of decalcified and nondecalcified specimens. The osteosynthesis site of the allografts usually healed by 5 months, compared with the autografts that healed by 3 months. As illustrated by quantitative bone scans, creeping appositional new bone slowly invaded and replaced the allograft bone. Seemingly, the cat can be used as an acceptable and clinically comparable model for the massive osteoarticular allografts currently being used for the reconstruction of joints damaged or destroyed by neoplasm surgery in limb-sparing procedures in human beings. This model may also be used to assess the rate and method of bone healing.     

Biomechanical properties of canine cortical bone allografts: effects of preparation and storage

The effects of various preparation and storage procedures and of different storage times on structural properties of canine cortical bone allografts were determined by evaluation of the compressive load to failure of a whole diaphyseal segment, the ability of a screw to resist being pulled from a cortical segment, and the torque required to strip the threads of a screw hole in a cortical segment. Preparation and storage procedures evaluated were sterile collection and storage at -20 C; ethylene oxide sterilization and storage at room temperature (22 C); chemical sterilization (methanol and chloroform, then iodoacetic acid) and storage at -20 C; and chemical sterilization, partial decalcification, and storage at -20 C. Storage times were 1, 16, and 32 weeks for each procedure. After 1 week of storage, aseptically collected frozen bone and ethylene oxide-sterilized bone had an increase, compared with matched controls, in load to failure in compression, but pullout load or screw-stripping torque did not change. Chemically sterilized bone had not changed after 1 week of storage, whereas chemically sterilized and partially decalcified bone had a 40% to 60% decrease in compressive load to failure, pullout load, and screw-stripping torque. Chemically sterilized and partially decalcified bone remained weak after 16 and 32 weeks of storage. Significant structural alterations were not detected in aseptically collected bone after 16 or 32 weeks of storage. Ethylene oxide-sterilized bone had a reduced pullout load after 32 weeks of storage. Chemically sterilized bone had significantly reduced compressive load to failure and pullout load after 16 and 32 weeks of storage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Femoral bone adaptation to stable long-term cemented total hip arthroplasty in dogs

OBJECTIVE: To quantify long-term bone adaptation after stable cemented total hip arthroplasty (cTHA) in dogs. STUDY DESIGN: Clinical study. ANIMALS: Fourteen dogs. METHODS: Femoral specimens were collected from client-owned dogs that were donated after death because of causes unrelated to their cTHA. Mean (+/-SEM) dog age was 11.4+/-0.7 years and implant duration was 5.3+/-0.7 years. Implant stability was established from radiographic signs and gross mechanical stability. Femurs were evaluated at 3 levels based on implant length: proximal stem (PS), mid-stem (MS), and distal to stem (DS). Cortical area, medullary area, and porosity were measured at each level. Implanted femurs were compared to contralateral nonimplanted femurs. RESULTS: Cortical area and cortical porosity were significantly increased in implanted femurs compared to nonimplanted femurs. Cortical area was increased at the MS and DS levels, and porosity was increased at the PS and MS levels in implanted femurs. Porosity was greatest in the endosteal region at the PS and MS levels in implanted femurs. CONCLUSIONS: Significant differences in femoral geometry and cortical porosity were detected after long-term stable cTHA. Net bone loss proximally and increased bone mass distally support stress shielding as a important mechanical factor associated with bone adaptation. Distribution of porosity shifts to endosteal regions after long-term cTHA. CLINICAL RELEVANCE: Significant site-specific femoral adaptation occurs in response to stable cTHA and may precede implant loosening.     

Effect of Ethylene Oxide Sterilization and Storage Conditions on Canine Cortical Bone Harvested for Banking

Two hundred seventeen cortical bones were harvested cleanly and prepared for banking for 2 months by using one of three types of packing materials, two ethylene oxide (EO) concentrations and procedures, and two storage temperatures. Bone subjected to the various treatments was compared to freshly harvested cortical bone and bone tested immediately after sterilization. Parameters evaluated were handling characteristics during preparation for and placement of a 3.5 mm cortex screw, and the percentage of weight lost as water when the bones were dried in an oven at 100 degrees C for 72 hours. Methods of sterilization, packaging material, and temperature of storage affected the handling characteristics and dehydration of the bone specimens. Twelve per cent EO at an elevated temperature and pressure, paper packaging, and room temperature storage appeared to cause the most significant changes. The use of 84% EO at room temperature and pressure, polyethylene wrapping material, and storage at -20 degrees C appeared to protect bone from dehydration. There was an increase in cracking and splitting of the bones as the percent of water loss decreased (indicating dehydration at the time of testing). Dehydration due to sterilization and storage processes may lead to difficulty in preparing bone for insertion of a bone screw and subsequently jeopardizing the stability of a repair in which such alloimplants are used.     

Ethylene Oxide Sterilization of Cortical Bone for Bone Banking Technique and Results in Three Dogs and One Cat

A protocol for clean harvesting, ethylene oxide sterilization, and room temperature storage of canine and feline cortical bone for use as allografts in fracture repair is described. Three dogs and one cat received cortical allografts prepared in this manner for reconstruction of severely comminuted mid-diaphyseal femoral fractures. Function of the affected limb returned to normal, and radiographic evaluations of the allografted femurs showed union at the host-graft interface and incorporation of the allograft.     

Evaluation of full cortical allografts in 25 dogs

Twenty-five dogs received 26 cortical allografts from Apr 9, 1976 through Jan 31, 1982. Cortical allografts were used to reconstruct fractures of the femur, humerus, tibia, radius, and ulna. These grafts were used to replace comminuted fragments; to lengthen bones; to correct malunions, delayed unions, and nonunions; and in one case, to replace bone lost to sequestrum formation in an infected fracture site. All fractures were stabilized by use of standard ASIF techniques and dynamic compression plates. Frozen bone allografts were used in all cases. These were harvested aseptically and stored in a household freezer for 3 days to one year before use. Clinically normal function was achieved in 96% of the dogs.     

Alterations in bone remodeling in the femur after medullary reaming and cemented hip arthroplasty in dogs.

OBJECTIVE: To determine whether medullary reaming alone, or followed by cemented hemiarthroplasty, influenced porosity, vascularity, and new bone formation in the proximal portion of the femur in dogs. ANIMALS: 12 adult mixed-breed dogs. PROCEDURE: Unilateral femoral head and neck excisions were performed, followed by femoral medullary reaming in 6 dogs and femoral medullary reaming and cemented hemiarthroplasty in 6 dogs; the contralateral femur was used as a control. All dogs were euthanatized 28 days after surgery, and femurs were harvested. Vascularity, porosity, and new bone formation were quantified for all femurs of dogs from both groups at 3 proximal-to-distal levels, 3 regions (periosteal, midcortical, and endosteal), and 4 quadrants (cranial, caudal, medial, and lateral) of the femur. RESULTS: Medullary reamed and cemented hemiarthroplasty femurs had significant increases in vascularity and porosity at all levels and in new bone formation at levels 2 and 3. Porosity was increased significantly in the periosteal region of the cemented hemiarthroplasty (9.7+/-0.7%), compared with control (2.3+/-0.2%) and medullary reamed (8.4+/-0.7%) femurs. Porosity was increased in the caudal and medial quadrants in the medullary reamed and cemented hemiarthroplasty femurs; vascularity results were similar. CONCLUSION: Increased porosity, vascularity, and new bone formation in reamed and cemented hemiarthroplasty-treated femurs supports the theory that surgical trauma associated with medullary reaming is an important factor in early cortical bone loss after hip arthroplasty. CLINICAL RELEVANCE: Femoral remodeling associated with reaming and broaching is appreciable but may be only a temporary response, whereas other factors may be responsible for chronic cortical bone loss.     

Post-implantation histology of composite autografts used as conduits in the systemic circulation

Aortic allografts, which are often used as conduits in reconstructive surgery for congenital cardiac malformations, usually become continuously calcified and so lose their ability to increase in diameter in response to the needs of the growing child. We examined the growth potential of an alternative conduit composed of a longitudinal strip of autologous aortic wall incorporated into an autologous pericardial tube. Ten such composite autografts were implanted in the descending thoracic aortas of lambs for 12 months. Sequential radiological examinations demonstrated appropriate growth, with an increase of more than 200% in the area of the aortic strip. Histological examination of the explanted grafts showed proliferation of a deep band of aortic intima over the surface of the adjacent pericardium, invasion of the intimallpericardial tissue by aortic smooth muscle cells, and the formation of new elastic fibres where smooth muscle replication was most advanced. Thus, the model demonstrated true growth potential. Such composite autografts may well be superior to other types of conduit for clinical reconstructive procedures in young, growing patients.     

Screw fixation of accessory carpal bone fractures in racing Greyhounds: 12 cases (1981-1986)

Fractures of the accessory carpal bone in 12 racing Greyhounds were repaired by use of internal fixation with screws. All dogs had a sprain-avulsion fracture of the distal margin of the articular surface of the accessory carpal bone, where the accessorioulnar ligament inserts (type I). Two dogs had a second avulsion fracture at the proximal margin of the articular surface, where the palmar ulnocarpal ligament inserts (type II), and 2 dogs had a second fracture at the caudal end of the bone at the insertion of the accessoriometacarpal ligaments (type III). Fractures were exposed surgically, using a palmarolateral approach between the fourth and fifth accessoriometacarpal ligaments, and were repaired using 1.5-mm or 2-mm cortical screws. Eight dogs were evaluated radiographically to monitor fracture healing. Union of fractures, with bridging of the fracture gap, usually developed by 5 to 8 weeks after surgery. Follow-up evaluation after surgical repair was possible in 11 dogs; 10 (91%) returned to training or racing, and 5 (45%) of those won 1 or more races.     

Cortical Bone Allografting in the Horse

Half and full cylindrical frozen cortical bone allografts were transplanted into groups of horses. All horses accepted, resorbed, and began replacement of their grafts to varying degrees, according to frequent radiographic and monthly histologic evaluation. Clinically, all the recipients appeared to return to varying degrees of function. This method of bone allografting is suggested as an adjunct to current methods of fracture fixation in the horse.     

Treatment of severely comminuted diaphyseal fractures in the dog, using standard bone plates and autogenous cancellous bone graft to span fracture gaps: 11 cases (1979-1983)

Severely comminuted diaphyseal fractures in 11 dogs were repaired with standard bone plates that spanned a fracture gap filled with autogenous cancellous bone graft. Five dogs had closed injuries, 4 dogs had open fractures, and 2 dogs had infected nonunion fractures for which previous attempts at internal pin fixation had failed. A second autogenous cancellous bone graft was performed in 3 of the dogs during the healing period. The technique was successful in all dogs. The technique was considered a versatile and relatively simple alternative, compared with meticulous small fragment reconstruction and cortical bone allografts.     

Antigenicity of cortical bone allografts in dogs and effect of ethylene oxide-sterilization.

The aims of the present study were to determine the antigenicity of cortical bone allografts and the effect of ethylene oxide-sterilization (EO-sterilization). Cortical bone allografts from one donor dog were implanted in a muscle pouch in four groups of four dogs each. The grafts were either fresh, EO-sterilized, demineralized or demineralized and EO-sterilized. The immune response against the grafts was determined by measuring the antibody response against surface antigens of donor cells and by the mixed lymphocyte reaction. Dogs receiving EO-sterilized grafts or bone matrix did not demonstrate an immune response. Only two of the four dogs with fresh cortical bone grafts showed a very weak immune response. This suggests a priming of the host by the fresh bone grafts. However, implanting skin grafts from the donor dog subdermally, in one dog of each of the groups, four months after implanting the bone grafts did not induce a secondary immune response. Macroscopic and histologic examination of the bone grafts five months after their implantation consistently revealed graft resorption (activity of osteoclasts) and vascularization of the fresh bone grafts, but not of EO-sterilized fresh grafts. For most EO-sterilized grafts, a strong inflammatory reaction was present in the tissues surrounding the graft and this was not apparent around the non-sterilized grafts. The absence of resorption and the presence of the inflammation seemed to be unwanted effects of the EO-sterilization. The EO-sterilisation did not affect osteoinduction since osteocytes were observed in the EO-sterilized demineralized grafts. Results indicate that cortical bone allografts used in the present study are very weak antigens and that the EO-sterilization procedure used has no effect on osteoinduction, but decreases bone resorption.     

Effects of treadmill exercise on cortical bone in the third metacarpus of young horses.

The effects of exercise and relative inactivity on cortical bone were compared in young horses. Two groups were used; one was given a 14-week programme of exercise (n = 6) and the other kept as unexercised controls (n = 6). The first nine weeks of exercise involved trotting and cantering (2 to 4 km d-1 at speeds up to 12 m s-1) on a treadmill set at an incline of 3 degrees. Over the next five weeks the horses were trained at near maximal speeds (that is, up to 14.5 m s-1) with no incline of the treadmill. At the end of the programme marked differences in cortical porosity and distribution of subperiosteal osteogenesis at the mid-shaft of the third metacarpal bone were found between the groups. Histomorphometrical examination of the dorsal cortex showed minimal bone remodelling in the exercised horses, but extensive modelling as evidenced by the large amount of subperiosteal bone formation. In contrast, the unexercised horses had significantly more bone remodelling and less formation of subperiosteal bone. The histomorphometric and microradiographic findings provided an explanation for changes in the non-invasive bone measurements that occurred during training. Bone mineral content of the mid-metacarpus was found to increase more in the exercised than the unexercised horses despite a lower overall growth in bodyweight. In those horses that completed the full training programme, ultrasound speed increased significantly by the end of the training programme. It remained unchanged in the horse that did not complete the full exercise programme and decreased slightly in the unexercised horses. The difference in ultrasound speed between the groups was considered to reflect differences in intracortical bone porosity, endosteal bone formation and alterations in skin thickness. The stiffness of cortical bone increased significantly in the exercised horses but remained unaltered in the unexercised horses.     

Femoral bone adaptation to unstable long-term cemented total hip arthroplasty in dogs

OBJECTIVE: To evaluate femoral adaptation after unstable long-term cemented total hip arthroplasty (cTHA) in dogs. STUDY DESIGN: Clinical study. ANIMALS: Four dogs. METHODS: Paired femurs were examined from client-owned dogs that were donated to a retrieval program after death from causes unrelated to their cTHA. Mean (+/-SEM) dog age was 10.0+/-1.5 years and implant duration was 6.0+/-1.4 years. Implanted femurs had radiographic changes associated with implant loosening and gross mechanical instability at femur retrieval. Femurs were evaluated at 3 levels relative to implant length. Cortical area and medullary area were measured at each level, and cortical porosity was assessed at each level in 4 quadrants and in 3 regions. Implanted femurs were compared with the contralateral non-implanted femurs. RESULTS: Cortical area and cortical porosity were increased at all levels in femurs with unstable implants. Implanted femurs had increased porosity in all quadrants and regions at the proximal 2 levels, and increased porosity in only the cranial quadrant and mid-cortical area at the distal level, when compared with contralateral non-implanted femurs. Corresponding medullary areas were not different. CONCLUSIONS: Significant histomorphometric changes occur in femurs after unstable cTHA. The patterns of periosteal bone formation and endosteal bone resorption support mechanisms of stress shielding and wear debris-mediated osteolysis as factors that may contribute to femoral adaptation and implant loosening. CLINICAL RELEVANCE: Despite popularity and excellent return to function with cTHA, aseptic loosening remains a serious long-term complication. Substantial net bone loss and unfavorable environment with unstable cTHA may make revision surgery less successful.     

Epiglottic Augmentation in the Horse

Epiglottic augmentation with injectable bovine collagen or an autogenous or allogenous auricular cartilage graft was performed in 12 horses with endoscopically and radiographically normal epiglottises. The grafting procedures were easy to perform and did not cause apparent discomfort. Cartilage graft extrusion or resorption may have occurred, but was not seen by endoscopy and lateral laryngeal radiography. Only collagen implants remained evident endoscopically, as smooth round submucosal bulges ventral to the epiglottic cartilage. Two horses with collagen implants, and all horses with cartilage autografts and allografts, were euthanatized at week 16. One horse with a collagen implant was euthanatized at week 4 and one at week 6. The epiglottis appeared thickened in three horses with collagen implants, two horses with autogenous grafts, and three horses with allogenous grafts. Pharyngeal lymphoid tissue was hyperplastic in two horses with autografts and three horses with allografts, but not in horses with collagen implants. Collagen grafts persisted as one or two smooth bulges 8 mm in diameter. Collagen incited a brisk foreign body reaction that was surrounded by a fibrous connective tissue capsule. Epiglottises of the horses with collagen implants were significantly thicker 20 mm from the tip than those of normal horses and horses with allografts. Cartilage graft incorporation was not evident grossly and was seen on microscopic examination in only one autograft. Thickening was caused by submucosal fibrosis.     

Comparable bone healing capacity of different bone graft matrices in a rabbit segmental defect model

We compared the bone healing capacity of three different demineralized bone matrix (DBM) products applied using different carrier molecules (hyaluronic acid [HA] vs. carboxymethylcellulose [CMC]) or bone compositions (cortical bone vs. cortical bone and cancellous bone) in a rabbit segmental defect model. Overall, 15-mm segmental defects in the left and right radiuses were created in 36 New Zealand White rabbits and filled with HA-based demineralized cortical bone matrix (DBX), CMC-based demineralized cortical bone matrix (DB) or CMC-based demineralized cortical bone with cancellous bone (NDDB), and the wound area was evaluated at 4, 8, and 12 weeks post-implantation. DBX showed significantly lower radiopacity, bone volume fraction, and bone mineral density than DB and NDDB before implantation. However, bone healing score, bone volume fraction, bone mineral density, and residual bone area at 4, 8, and 12 weeks post-implantation revealed no significant differences in bone healing capacity. Overall, three DBM products with different carrier molecules or bone compositions showed similar bone healing capacity.     

Application of osteochondral autografts and allografts in the treatment of articular cartilage lesions in animals

The paper describes current views on the use of osteochondral autografts and allografts in the treatment of articular cartilage lesions in animals. It presents surgical techniques of grafting and the biological features of osteochondral auto- and allografts, and their effect on the recipient's cartilage.