Comparison of bone healing by demineralized bone matrix and autogenous cancellous bone in horses

OBJECTIVE: The purpose of this study was to compare bone healing induced by equine demineralized bone matrix (DBM) to autogenous cancellous bone graft (ACB) or no graft (control) in a rib-defect model in horses. STUDY DESIGN: The osteogenic properties of ACB and DBM were evaluated in bilateral 19-mm circular defects created in the outer cortex of the 6th and 8th ribs of each horse. ANIMALS OR SAMPLE POPULATION: Eight mature horses. METHODS: Three rib defects in each horse were randomly treated with each of the 3 treatment groups, and the fourth rib defect received a random treatment. Rib sections, including the defects, were harvested 56 days after implantation and examined for bone mineral density, percent ash and calcium and graded for signs of radiographic and histological healing. RESULTS: All ribs were fractured at the defect site and were classified as nonunion fractures 56 days after implantation. There were no significant differences among groups in bone mineral density and signs of radiographic or histological healing. There was an increased volume of bone in control and ACB-treated sites compared with DBM-treated sites. Rib defects treated with ACB were significantly higher in percent ash and calcium than those treated with DBM. DBM elicited no inflammatory reaction, and remodeling occurred around the periphery and within vascular channels of the decalcified particles. CONCLUSION: DBM particles remodel from the periphery, which may explain the significantly lower percent ash, calcium, and bone when compared with ACB, because 2- to 4-microL pieces of DBM may act as space-occupying masses until completely mineralized. There was no evidence of enhanced healing associated with the use of DBM in this model. CLINICAL RELEVANCE: Particles of 2 to 4 mm DBM should not be used as an aid to fracture repair because particles of this size interfere with normal mineralization. However, our model of nonunion fracture healing may be useful in future studies.     

Effects of a fixed compression load on the osteogenic effect of autogenous cancellous bone grafts in dogs.

A standardized cortical defect was created on the caudal cortex of the proximal portion of each ulna in 5 adult mixed-breed dogs. One gram of autogenous cancellous bone graft (ACBG) was obtained from the greater tubercle of the ipsilateral humerus. The cortical defect in the ulna of 1 limb was filled with 1 g of ACBG that had been compressed with 2-MPa pressure for 30 seconds. One gram of noncompressed ACBG was placed into the contralateral ulnar cortical defect. The compressed and noncompressed ACBG recipient sites were radiographed at weekly intervals. Dogs were euthanatized 8 weeks after surgery, and the ACBG recipient sites were harvested for histomorphometric analysis. Optical densitometry was performed on all radiographs. There was no significant difference between compressed and noncompressed ACBG with optical densitometry or histomorphometric analysis for total bone area. We concluded that there was no difference in osteogenic capability between compressed and noncompressed ACBG of equal mass.     

Comparison of bone healing,as assessed by computed tomography,following tibial tuberosity advancement in dogs with and without autogenous cancellous bone grafts

Abstract

AIMS: To objectively compare measures of bone healing, using computed tomography (CT) in dogs following bilateral tibial tuberosity advancement (TTA), between tibiae treated with and without autogenous cancellous bone grafts.

METHODS: Ten dogs with bilateral cranial cruciate ligament disease requiring surgical stabilisation were prospectively recruited to undergo single-session bilateral TTA, with only one, randomly assigned, tibia receiving bone graft in the osteotomy deficit. Bone healing at the osteotomy site was assessed using CT performed 38–70 days post-operatively. CT images were evaluated using both objective measurements of osseous bridging and subjective evaluation by six radiologists. Repeated measures ANOVA was used to compare the objective outcomes between the grafted and non-grafted tibiae.

RESULTS: The mean percentage of the osteotomy deficit bridged at the lateral cortex was greater in grafted (77.6, SD 35.2%) compared to non-grafted (63.0, SD 36.5%) tibiae (p=0.001), but did not differ at the medial cortex (p=0.1). The mean minimum callus width was greater in grafted (7.2, SD 3.3 mm) compared to non-grafted (3.6, SD 2.9 mm) tibiae (p<0.001). There was no difference in mean attenuation (measured in Hounsfield units) of the callus between grafted and non-grafted tibiae (p=0.5). The grafted tibia was deemed to have superior bone healing in 50/60 subjective assessments made by radiologists.

CONCLUSIONS: Superior osseous bridging was detected by CT analysis following TTA using autogenous cancellous bone grafts compared with no graft. This was shown by greater bridging percentage at the lateral cortex and formation of a broader callus. Qualitative assessments made by six radiologists also supported the conclusion that bone healing was improved by use of autogenous cancellous bone graft. CT was a useful method for assessing evidence of bone healing following TTA.

CLINICAL RELEVANCE: These findings justify the application of autogenous cancellous bone graft to augment healing following TTA in dogs.     

Vascularization of cancellous chip bone grafts

Fresh autogenous, frozen allogeneic, and commercially prepared xenogeneic cancellous chip bone grafts were placed into plug holes in the tibia and into surgically simulated nonunion defects in the ulna of dogs. The microvascular and correlated histologic reactions were studied at given times up to 12 weeks after the graft implantation. Marked and characteristic differences were noted among the 3 graft materials. Fresh autogenous chips were extensively vascularized by 1 week, and subsequent microscopic healing was rapid. Allogeneic chips were incorporated into all defects, but vascularization and histologic healing rates were slower than those with the fresh autogenous graft material. The xenogeneic graft was poorly incorporated. A foreign body reaction was seen histologically, and corresponding vascularization of the graft was slow and incomplete.     

Comparison of autogenous cancellous bone grafts obtained from the sternum and proximal portion of the tibia of llamas.

OBJECTIVE: To describe the anatomy of the sternum in llamas, define the surgical approach to the sternum for collection of cancellous bone graft tissue, and compare the histologic appearance of graft tissue obtained from the sternum with that obtained from the proximal portion of the tibia. DESIGN: Prospective study. ANIMALS: 12 llamas, 3 to 19 years old, that had been submitted for necropsy. PROCEDURE: Radiographs were taken of the sternum and left tibia of the llamas. Measurements of the sternum were determined from the radiographs and adjusted for magnification. Sternebrae volumes were estimated from these measurements. Anatomic dissections to the center of the fourth sternebra and the proximal portion of the tibia were made, and a surgical approach to the sternum was developed. Cancellous graft tissue was obtained from each site and submitted for histologic evaluation. RESULTS: Sternebrae 3, 4, and 5 were significantly larger in volume than the other sternebrae. The ventral aspect of the fourth sternebra was readily accessed for removal of graft tissue by making a 6-cm-long ventral midline incision centered 17 cm craniad to the xipnoid. Mean soft tissue thickness overlying the ventral aspect of the fourth sternebra was 3.1 cm. More tissue was obtained from the sternal (mean, 9.11 g) than from the tibial (mean, 5.16 g) sites. Sternal graft tissue consisted of trabecular bone spicules with predominantly hematopoietic marrow, whereas tibial tissue consisted of trabecular bone spicules with only fatty marrow. CONCLUSIONS AND CLINICAL RELEVANCE: The fourth sternebra in llamas is readily accessible for obtaining autogenous cancellous bone graft tissue that consists of predominantly hematopoietic marrow.     

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.     

Qualitative aspects of the incorporation of equine cancellous bone grafts

The incorporation of autogenous cancellous bone graft was studied in eight yearling ponies. The site for the defect to be grafted was chosen so that the effect on the graft, of both the host cortical and trabecular bone, could be assessed. To obtain information concerning the vitality of the graft and the dynamic aspects of the modelling and remodelling processes of graft incorporation, a double and treble tetracycline intravital labelling technique was used. Radiographs of the graft and host tissues of all ponies were obtained regularly, but were of little assistance in assessing graft incorporation. The ponies were destroyed humanely at regular intervals between nine and 241 days after installation of the graft, followed by histological examination of undecalcified sections. The study revealed that all installed graft trabeculae showed signs of non-vitality at nine days after installation and gradually disintegrated. Two processes of new bone formation were observed. First, finger-like projections of immature new trabeculae were found to originate from the graft/host interfaces. Second, a gradual process of accretion of osteoid and woven bone upon disintegrating graft trabeculae occurred uniformly throughout the graft. The graft adapted to the structure of opposing host bone by corticalisation and trabecularisation. The present study confirmed clinical observations relating to convalescence time following grafting of large osseous defects in horses and indicated that equine bone reacts to autogenous bone grafts in a similar manner to other mammals.     

Comparison of healing of the osteotomy gap after tibial tuberosity advancement with and without use of an autogenous cancellous bone graft

Objective: To evaluate and compare healing, with and without the use of bone graft, of the gap created during tibial tuberosity advancement (TTA). Study Design: Prospective study and case series. Animals: Dogs treated with TTA (n=67). Methods: Prospective study: Mediolateral radiographic projections (6 weeks and 4 months) after TTA without use of bone graft (group I, n=14) were compared with radiographs of consecutive TTA in which the gap was filled with autologous cancellous bone graft (group II, n=14). Two scoring techniques (A, B) were used. Score A was used to grade the overall osteotomy healing (0=no healing, 4=healed osteotomy). Score B evaluated, independently of each other, healing in 3 sites: proximal to the cage (B1), between cage and plate (B2), and distal to the plate (B3). Case series: nongrafted TTA (4–25 weeks, n=39) were evaluated for healing (Score A). Data was analyzed using t‐tests and ANOVA. Significance was set at P≤.05. Results: Prospective study: Score A, B2, and B3 showed no difference in healing between groups at 6.8 weeks and 4.2 months. Score B1 revealed, in both rechecks, a significantly higher density in group II. Case series: Radiographs at 11.59±5.99 weeks scored 3.3 (2–4). No healing related complications were observed. Conclusion: The osteotomy gap created during TTA healed within expected time regardless of bone graft use.     

Results of treatment of subchondral bone cysts in the medial condyle of the equine femur with an autogenous cancellous bone graft

The results of surgical treatment of 10 subchondral bone cysts, all located in the medial femoral condyle, are presented. A cancellous bone graft was used in nine cases and a two component acrylic bone cement was used in the case of an extremely large cyst. Eight out of the 10 cases made a satisfactory clinical recovery.     

Effects of isobutyl-2-cyanoacrylate on bone healing

An in vivo evaluation of isobutyl-2-cyanoacrylate as an osseous adhesive was performed to determine its effect on bone healing. Oblique cortical fractures were induced at the tibial-fibular junctions of adult rabbits. Forty-eight fractures were repaired by the use of isobutyl-2-cyanoacrylate and a full cerclage wire. The opposite control fracture was repaired with a full cerclage wire only. One hundred percent of the glued fractures were not united through the glue interface, although normal periosteal new bone formation (secondary bone healing) took place around the glue. One hundred percent of the nonglued fractures healed by secondary bone union. Reactions were not seen in the bone or soft tissue adjacent to the adhesive material.     

Open drainage and delayed autogenous cancellous bone grafting for treatment of chronic osteomyelitis in dogs and cats

Ten dogs and 1 cat with 12 chronically infected bones were treated surgically by means of saucerization, primary internal or external rigid fixation, and open irrigation drainage. After formation of a healthy granulation bed, autogenous cancellous bone grafting and skin closure were performed. Eleven of 12 bones healed 4 to 7 weeks (mean, 4.8 weeks) after treatment, without recurrence of infection. Eight of 12 chronically infected bones had a polymicrobial infection, with 2 to 6 bacterial species isolated. Gram-negative bacteria were isolated from 7 of the 12 bones, and anaerobic bacteria were isolated twice.     

The effect of compacted cancellous bone grafting on the healing of subchondral bone defects of the medial femoral condyle in horses

Objective— To compare the quality of second-intention healing and that of compacting sternally harvested cancellous bone into subchondral bone defects of the medial femoral condyle in horses.
Study Design— A controlled experiment using a surgical technique that minimizes soft tissue trauma, customized for consistency among horses.
Animals or Sample Population— Ten horses, aged 2 to 5 years, free of hindlimb lameness and with radiographically normal stifles.
Methods— After a 12.7-mm-diameter × 19-mm-deep defect was created into randomly selected medial femoral condyles, bone and cartilage healing was evaluated over a 6-month period in control horses (  n = 5  ) and horses receiving a compacted cancellous bone graft (  n = 5  ). Healing was evaluated using lameness assessment, radiographic and microradiographic interpretation, arthroscopic appearance, percent bone fill, proteoglycan content, and histology.
Results— Six months after surgery, there was no significant difference between grafted and ungrafted defects with respect to lameness, radiographic score, or percent bone fill. Histologically, grafted defects were characterized by the presence of dead graft and secondary cyst formation in four defects. Ungrafted defects filled with fibrous tissue and no cyst formation were identified.
Conclusions— Grafted defects do not heal better than ungrafted defects, and lameness was not affected by surgical technique.
Clinical Significance— Cartilage healing is similar in grafted and ungrafted defects in the equine medial femoral condyle at 6 months, suggesting that surgical debridement alone of cystic structures remains the treatment of choice.     

Use of autogenous cancellous bone graft for treatment of osteolytic defects in the phalanges of three cattle.

Osteolytic defects were detected radiographically in the distal sesamoid bone of a 16-month-old Bralers heifer, in the middle phalanx of a 14-month-old American Gray Brahman bull, and in the distal phalanx of a 3-year-old American Gray Brahman bull. The articular cartilage was damaged in each animal because of osteolysis or pathologic fracture. After each animal was anesthetized and positioned in lateral recumbency, the lesions were curetted and packed with cancellous bone harvested from the same animal's tuber coxae. Basic postoperative management involved stall rest and immobilization of the graft site with a fiberglass cast (42 to 79 days), after which a support bandage was used for approximately 2 weeks. Recurrence of lameness has not been observed in these animals for 60 months, 58 months, and 21 months, respectively. These cases exemplify the benefit of using an autogenous cancellous bone graft for treatment of severe osteolysis of a digit in cattle.     

Use of an autogenous cancellous bone graft in the treatment of subchondral bone cysts in the medial femoral condyle of the horse

The clinical features, diagnosis and radiological findings of eight cases of a subchondral bone cyst involving the medial condyle of the femur are described. Surgical treatment, which comprised performing an arthrotomy of the femorotibial joint, curetting and packing the cystic cavity with an autogenous cancellous bone graft, is described.     

Evaluation of the proximal portion of the femur as an autogenous cancellous bone donor site in dogs.

The proximal portion of the femur was evaluated as a source of autogenous cancellous bone in dogs. Bilateral oval cortical defects were created in the lateral subtrochanteric area of the femur in 16 dogs. Cancellous bone was removed and the weight recorded. Cancellous bone was similarly harvested from the proximal portion of the humerus in 7 of these dogs. Subtrochanteric femoral defects in 11 dogs were randomly assigned to receive cancellous bone graft obtained from the femur (n = 4) or the humerus (n = 7). Subtrochanteric defects in 5 dogs were not grafted. Radiographic assessment of subtrochanteric defects was performed at 4-week intervals, and histologic assessment at 4, 8, 16, and 24 weeks after surgery. Nongrafted donor sites healed by ingrowth of trabecular bone during the first 12 weeks after surgery. By week 24, the lateral cortical wall had reformed, but remodeling was incomplete. Donor sites grafted with cancellous bone healed similarly, but with more rapid healing and more complete remodeling evident by week 24. Although the mean weight of cancellous bone harvested from the proximal portion of the femur (0.82 +/- 0.22 g) was significantly (P less than 0.05) less than that harvested from the proximal portion of the humerus (1.38 +/- 0.29 g), there was no qualitative histologic or radiographic difference in bony healing of grafted defects. We determined that the proximal portion of the femur can be safely used to provide moderate amounts of cancellous bone, and that a second bone graft can be collected from the same subtrochanteric donor site after 12 weeks.     

Effect of hyperbaric oxygen treatment on incorporation of an autogenous cancellous bone graft in a nonunion diaphyseal ulnar defect in cats

OBJECTIVE: To determine whether hyperbaric oxygen treatment (HBOT) would affect incorporation of an autogenous cancellous bone graft in diaphyseal ulnar defects in cats. ANIMALS: 12 mature cats. PROCEDURE: Bilateral nonunion diaphyseal ulnar defects were created in each cat. An autogenous cancellous bone graft was implanted in 1 ulnar defect in each cat, with the contralateral ulnar defect serving as a nongrafted specimen. Six cats were treated by use of hyperbaric oxygen at 2 atmospheres absolute for 90 minutes once daily for 14 days, and 6 cats were not treated (control group). Bone labeling was performed, using fluorochrome markers. Cats were euthanatized 5 weeks after implanting, and barium sulfate was infused to evaluate vascularization of grafts. Ulnas were evaluated by use of radiography, microangiography, histologic examination, and histomorphometric examination. RESULTS: Radiographic scores did not differ between treatment groups. Microangiographic appearance of grafted defects was similar between groups, with all having adequate vascularization. Differences were not observed between treated and nontreated groups in the overall histologic appearance of decalcified samples of tissue in grafted defects. Mean distance between fluorescent labels was significantly greater in cats given HBOT than in nontreated cats. Median percentage of bone formation in grafted defects was significantly greater in cats given HBOT. CONCLUSIONS: Hyperbaric oxygen treatment increased the distance between fluorescent labels and percentage of bone formation when incorporating autogenous cancellous bone grafts in induced nonunion diaphyseal ulnar defects in cats, but HBOT did not affect revascularization, radiographic appearance, or qualitative histologic appearance of the grafts.     

Effects of gelatin sponge implantation in cancellous bone defects in dogs

Reports from oral surgeons suggested that packing bone defects with cellulose or collagen stimulated cancellous bone replacement. The study reported here was designed to evaluate a similar method for augmenting the remodeling of cancellous bone defects and graft donor sites. Gelatin sponge was implanted into bony defects created in the proximal humeral metaphysis of 5 adult Beagles after collection of cancellous bone. A similar defect created in the contralateral humerus was left unpacked. Four months after creation of the defect, the dogs were euthanatized, and the surgical sites were evaluated by use of correlated microradiographic and histologic examination. Unpacked sites had filled completely with loosely woven trabecular bone. Remodeling had not taken place in sites packed with gelatin sponge. Gelatin sponge did not elicit any reaction in the surrounding bone, but remained in situ and obstructed new bone formation. Gelatin sponge blocked rather than augmented cancellous bone replacement.     

Preliminary study of quantitative aspects and the effect of pulsed electromagnetic field treatment on the incorporation of equine cancellous bone grafts

The quantitative aspects of equine cancellous bone graft incorporation and the possibility of influencing graft incorporation by daily exposure to a pulsed electromagnetic field (PEMF) was studied in eight yearling ponies. In order to be able to quantify formative aspects of graft remodelling, a double and treble tetracycline intravital labelling technique was used. Intravital radiographs were obtained at regular intervals throughout the trial, but were found to be of little assistance in assessing any differences between stimulated and non-stimulated grafts. The ponies were humanely destroyed at regular intervals between nine and 241 days after installation of the graft. Light microscopy and fluorescent light microscopy were used to evaluate quantitative aspects of graft incorporation and to compare PEMF-stimulated grafts with control grafts. There was a small but statistically significant effect of PEMF-stimulation on cancellous bone graft incorporation. In view of this, these observations can only be considered as indicative of a possible trend, but should encourage further studies using different signal modalities.