NONGRAFTED AND GRAFTED OSTEOTOMIES OF PROXIMAL SESAMOID BONES OF THE HORSE

A radiographic study of healing patterns of nongrafted and grafted basilar osteotomies of proximal sesamoid bones in 14 horses was performed. Osteotomies were created in one proximal sesamoid bone of each fromt leg. One was treated by an autogenous rib graft, and the other was left nongrafted. Wedge-shaped cortical bone, corticocancellous bone with multiple drill holes, and chips of cancellous hbone were used as autogenous grafts. Presurgical, surgical, and postsurgical radiographic examinations were performed. The longest follow-up period was 40 weeks. High detail radiography of 3-mm bone sections and microangiography were also perofromed. Radiographic interpretation of lack of bone healing was erroneous in approximately one-half of the cases. Lack of an external bridging callus was incorrectly interpreted as lack of bony union. If noted, periosteal new bone formation failed to develop into a pattern of bridging callus. Radiographs did not permiit detection of the osteotomy line entering the articular surface or displacement of distal fragments. From angiography obtained ten weeks after surgery, the pattern of blood supply was similar in nontreated and grafted sesamoid bones. Microangiography showed rich vascularization of the cancellous graft and callus, reflecting good healing activity, whitle vascularization of the osteotomy site was absent in the nontreated osteotomies.     

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.     

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.     

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.     

Effects of autogenous cancellous bone on healing of homogenous cortical bone grafts

A comparative clinical and histological study was made of the effects of autogenous cancellous grafts on the rate of healing of homogenous cortical bone grafts in dogs: their right foreleg received homogenous bone grafts and their left foreleg received pre-drilled homogenous bone grafts filled with autogenous cancellous bone. Histologically, the use of homogenous cortical grafts with pre-drilled holes and autogenous cancellous bone appeared to accelerate reorganization and development of these grafts. This was seen particularly 1–2 months post-operatively and at nine months when the graft in the left leg was made up of spongy bone marrow; whereas the right leg graft still contained compact dead bone and the marrow was filled with fibrous tissue.     

The effect of cancellous autograft and novel plate design on radiographic healing and postoperative complications in tibial tuberosity advancement for cranial cruciate-deficient canine stifles

Objective: To assess the effect of autogenous cancellous bone graft (autograft) and novel plate use on radiographic healing and complications in tibial tuberosity advancement (TTA) for treatment of cranial cruciate ligament (CrCL)‐deficient stifles in dogs. Study Design: Prospective clinical study. Animals: Consecutive dogs (n=125) with unilateral CrCL‐deficient stifles. Methods: Four treatment groups: CPG, conventional plate with autograft; CPNG, conventional plate without autograft; NPG, novel plate with autograft; NPNG, novel plate without autograft were studied. Radiographs from 60 dogs were scored for healing at 6 and 10 weeks postoperatively; all 125 dogs were assessed for radiographic complications. Variables evaluated for relationship with healing scores and radiographic complications were age, weight, sex, cage and plate size, implant type, and graft use. Results: Dogs with autograft had overall higher healing scores at 6 and 10 weeks. Radiographic complications occurred in 13 dogs (12 minor, 1 major), and were not influenced by graft or novel plate use. Conclusion: Autograft increases healing scores, but was not found to have a significant impact on the rate of complications in TTA. The novel plate was not found to have healing scores or radiographic complication rates significantly different from the conventional plate design.     

Antebrachial deformities in the dog: Treatment with external fixation

The results of 12 dogs with antebrachial deformity treated by ulnar ostectomy, radial osteotomy and external skeletal fixation are presented. Postoperative complications were seen in only one dog; a delayed union requiring placement of autogenous cancellous bone graft at a second surgery to achieve healing. Postoperatively, owners reported limb function was good in almost all cases, although they were less pleased with the cosmetic appearance.     

Clinical Applications of Demineralized Bone Matrix: A Retrospective and Case‐Matched Study of Seventy‐Five Dogs

Objectives— To evaluate the outcome in dogs treated with demineralized bone matrix (DBM) as an adjunct to orthopedic procedures. Study Design— Retrospective and case‐match study. Animals— Dogs (n=75). Methods— Medical records (1999–2006) and radiographs of dogs that had orthopedic procedures (comminuted fractures, tibial plateau leveling osteotomy [TPLO] where correction for tibial rotation created an osteotomy gap, arthrodeses, open corrective osteotomies) where DBM was used were reviewed for signalment, quantity of DBM implanted, duration of exercise restriction, radiographic healing, and complications. Dogs that had TPLO and correction of tibial torsion (n=15), or arthrodesis (n=16) were compared with case‐matched controls. Data were analyzed using Kruskal–Wallis test, ANOVA, Tukey's HSD test, and logistic regression analysis. Results— Mean (±SD) healing time for orthopedic surgeries with DBM augmentation were 15±6.97 (weeks) and complication rate was 19% (14 dogs). Dogs with a TPLO gap filled with DBM were allowed to return to normal exercise 2 weeks earlier than dogs with a well‐apposed TPLO site. Radiographic healing, duration of exercise restriction, and timing of destabilization were similar in dogs undergoing carpal and tarsal arthrodesis whether they received DBM, autogenous graft, or both. Conclusions— DBM can be used to treat uncomplicated bone defects associated with comminuted fracture repairs, open osteotomies, and arthrodeses in dogs. Under these circumstances, clinicians might expect similar clinical outcomes without the possibility of side effects associated with the harvest of autogenous cancellous bone. Clinical Relevance— DBM is safe for use in dogs.     

Mesenchymal stem cells and bone regeneration

OBJECTIVE: To review the role of mesenchymal stem cells (MSC) in bone formation and regeneration, and outline the development of strategies that use MSC in bone healing and regeneration. STUDY DESIGN: Literature review. METHODS: Medline review, synopses of authors' published research. RESULTS: The MSC is the basic cellular unit of embryologic bone formation. Secondary bone healing mimics bone formation with proliferation of MSC then their differentiation into components of fracture callus. Bone regeneration, where large amounts of bone must form, mimics bone healing and can be achieved with MSC combined with strategies of osteogenesis, osteoinduction, osteoconduction, and osteopromotion. MSC based strategies first employed isolated and culture expanded stem cells in an osteoconductive carrier to successfully regenerate a critical segmental defect in the femur of dogs, which was as effective as autogenous cancellous bone. Because MSC appeared to be immunologically privileged, a study using mismatched allogeneic stem cells demonstrated that these cells would regenerate bone without inciting an immunologic response, documenting the possibility of banked allogeneic MSC for bone regeneration. A technique was developed for selectively retaining MSC from large bone marrow aspirates at surgery for bone regeneration. These techniques utilized osteoconductive and osteoinductive carriers and resulted in bone regeneration that was similar to autogenous cancellous bone. CONCLUSION: MSC can be manipulated and combined with carriers that will result in bone regeneration of critically sized bone defects. CLINICAL RELEVANCE: These techniques can be employed clinically to regenerate bone and serve as an alternative to autogenous cancellous bone.     

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.     

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.     

Evaluation of Collagen as a Retainer for Autogenous Cancellous Bone Used in Repair of Full Thickness Cortical Bone Defects

A commercially available collagen sponge acting as a cylindrical retainer containing autogenous cancellous bone graft was proposed for treatment of full thickness cortical defects in dogs. Three groups of three dogs each were subjected to removal of at least 1.5 cm of the tibial diaphyses. All tibias were stabilized with bilateral external fixators. Group 1 received collagen surrounding an autogenous cancellous bone graft. Group 2 received collagen and group 3 received no treatment of the ostectomy site. The collagen sponge appeared to allow vascularization of the bone graft as evidenced by new bone formation and was resorbed by 3 months after implantation. Radiographic, histomorphologic, and histomorphometric evaluation at 3 months after surgery showed a greater per cent of bone in the ostectomy site in group 1.     

Comparison of two doses of recombinant human bone morphogenetic protein in absorbable collagen sponges for bone healing in dogs

OBJECTIVE: To determine the effects of 2 doses of recombinant human bone morphogenetic protein-2 in an absorbable collagen sponge (rhBMP-2/ACS) on bone healing in dogs. ANIMALS: 27 adult dogs. PROCEDURES: Dogs underwent a mid-diaphyseal (1-mm) tibial osteotomy (stabilized with external skeletal fixation) and received an ACS containing 0.28 mg (0.2 mg/mL) or 0.56 mg (0.4 mg/mL) of rhBMP-2 or no treatment (control dogs). All dogs were examined daily; bone healing was assessed via radiography and subjective lameness evaluation every 2 weeks. After euthanasia at 8 weeks, tibiae were evaluated biomechanically and histologically. RESULTS: Control dogs required antimicrobial treatment for pin-site-related complications more frequently than did rhBMP-2/ACS-treated dogs. At 4 and 6 weeks, weight bearing was greater in dogs treated with rhBMP-2/ACS (0.2 mg/mL) than in control dogs, albeit not significantly. Compared with control treatment, both doses of rhBMP-2/ACS accelerated osteotomy healing at 4, 6, and 8 weeks, and the 0.2 mg/mL dose enhanced healing at 2 weeks; healing at 6 weeks was greater for the lower-dose treatment than for the higher-dose treatment. Histologically, healing at 8 weeks was significantly improved for both rhBMP-2/ACS treatments, compared with control treatment. Among groups, biomechanical variables did not differ, although less osteotomy-site failures occurred in rhBMP-2/ACS-treated groups. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs that underwent tibial osteotomy, rhBMP-2/ACS (0.2 mg/mL) appeared to accelerate bone healing and reduce lameness (compared with control treatment) and apparently augmented bone healing more than rhBMP-2/ACS (0.4 mg/mL). Compared with control dogs, rhBMP-2/ACS-treated dogs required antimicrobial treatments less frequently.     

Modified tibial tuberosity advancement procedure with tuberosity advancement in excess of 12 mm in four large breed dogs with cranial cruciate ligament-deficient joints

OBJECTIVE: To describe a modification of the tibial tuberosity advancement (TTA) procedure that required tuberosity advancement in excess of 12 mm for the stabilization of cranial cruciate ligament (CrCL) deficient stifle joints. METHODS: Four large breed dogs with CrCL deficient stifle joints (one bilateral) underwent a modified TTA of 15 or 16 mm in order to obtain a patellar tendon angle of 90 degrees to the tibial plateau slope or common tangent between femur and tibia in the extended limb position. The desired TTA was achieved by displacing a 12-mm cage distally; this displacement distance was calculated from two similar triangles formed within the planned osteotomy site. An allogenous cancellous bone block placed proximal to the cage provided buttress support; a corticocancellous allograft filled the remainder of the gap. Tibial tuberosity fixation was performed as previously described. RESULTS: Healing of the osteotomy defects with incorporation of the cancellous block was observed at a mean of 8.6 weeks postoperatively. Normal return of limb function was reported in all of the dogs except for one dog that underwent revision surgery four months postoperatively for a continued lameness. Technical errors at the time of the original surgical procedure in this dog resulted in insufficient tuberosity advancement; additional advancement was performed, which resolved the lameness. CLINICAL SIGNIFICANCE: Results in this series suggest that our modification of the TTA, in order to advance the tuberosity in excess of 12 mm, could be successfully obtained using the currently available implants.     

The Effects of Plaster of Paris and Autogenous Cancellous Bone on the Healing of Cortical Defects in the Femurs of Dogs

Four one quarter inch evenly spaced circular defects were created bilaterally in the lateral femoral diaphysis of 12 clinically normal adult dogs. The defects were left unfilled (control), or were filled with one of the following: (1) plaster of Paris, (2) an equal-volume mixture of plaster of Paris and autogenous cancellous bone, and (3) autogenous cancellous bone. The degree of bone healing was evaluated radiographically and histologically at 2, 4, 6, 8, 10, and 12 weeks. Radiographically, no objective conclusions could be drawn due to the small size of the defects and limited amount of plaster of Paris implanted. Histologically, there was no inflammatory reaction to the plaster of Paris. No differences were determined in the degree of bone healing between autogenous cancellous bone, plaster of Paris, and a mixture of plaster of Paris and autogenous cancellous bone. All implants were superior to the control defect in degree of bone healing.     

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.     

Comparison of Multistage Versus One-Stage Destabilization of a Type II External Fixator Used to Stabilize an Oblique Tibial Osteotomy in Dogs

OBJECTIVE: To compare the biomechanical effects of multistage versus one-stage destabilization of a type II external skeletal fixator (ESF) used to stabilize an oblique unstable tibial osteotomy in dogs. STUDY DESIGN: In vitro, in vivo, and ex vivo experimental study. ANIMAL POPULATION: Twelve healthy adult dogs. METHODS: The biomechanical characteristics of the type II ESF used in this study were determined. This fixator was applied to both tibiae of two groups of 6 dogs to stabilize a 2-mm-wide oblique osteotomy. One fixator on each dog remained unchanged throughout the 11-week study (control group). The fixator on the opposite limb was destabilized late and acutely in one group of dogs (single-stage) and early and progressively in the other (multistage). Clinical examination, radiographic examination, and force-plate analysis were used to evaluate the results. All dogs were euthanatized at 11 weeks. All tibiae were scanned to determine the cross-sectional area of the callus in the center of the osteotomy and subjected to biomechanical tests to determine mean pull-out strength of pins and callus strength and stiffness. RESULTS: Stiffness of the type II ESF used in this study was 578 N/mm in axial compression, 0.767 Nm/deg in torsion, 261 N/mm in medio-lateral bending, and 25 N/mm in cranio-caudal bending. Peak vertical forces of the hindlimbs were significantly lower at 2.5 and 5 weeks than before surgery. Peak vertical forces of the hindlimbs did not change before and after destabilization. No significant differences could be detected between the two destabilization sequences or between all control tibiae and pooled destabilized tibiae with regards to radiographic evaluation of the healing osteotomy, cross-sectional periosteal callus area, mean pull-out strength of transfixation pins, callus strength, and callus stiffness. CONCLUSIONS AND CLINICAL RELEVANCE: Bone healing of unstable osteotomies stabilized with a type II ESF is not significantly enhanced by staged destabilization of the fixation as performed in this study.     

Recombinant human bone morphogenetic protein-2 in absorbable collagen sponge enhances bone healing of tibial osteotomies in dogs

OBJECTIVE: To compare the efficacy of 2 doses of recombinant human bone morphogenetic protein-2 (rhBMP-2) on tibial osteotomy healing in dogs. STUDY DESIGN: Experimental, randomized complete block (n=7). ANIMALS: Adult female dogs (n=21). METHODS: Right midshaft tibial osteotomies were created and stabilized with a 1-mm gap using type I external fixators. Seven dogs were untreated controls and 14 with osteotomies were treated with either 0.05 or 0.2 mg/mL rhBMP-2 delivered in an absorbable collagen sponge (ACS). At 8 weeks, dogs were euthanatized and bones were mechanically tested and examined by microscopy. RESULTS: Bone healing based on radiographic scoring, was significantly improved in dogs treated with 0.2 mg/mL of rhBMP-2 compared with the other groups; these tibiae were also significantly stronger and stiffer than 0.05 mg/mL rhBMP-2 and control osteotomized tibiae. Histologic scores were significantly better for 0.2 mg/mL rhBMP-2 group than 0.05 mg/mL rhBMP-2 group, but neither was significantly different from control. CONCLUSIONS: rhBMP-2 in ACS at a concentration of 0.2 mg/mL improves healing of tibial osteotomies in dogs compared with untreated controls and 0.05 mg/mL rhBMP-2 based on force plate analysis and radiographic evaluation. This was not confirmed histologically but treated bones had improved mechanical properties at 8 weeks. CLINICAL RELEVANCE: After a long bone fracture, dogs may face a long recovery period before full return of limb function. rhBMP-2, in association with good fracture fixation principles, may enhance bone healing in dogs with diaphyseal fractures.     

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.     

Histologic features of the healing of bone graft donor sites in dogs

Healing of cancellous bone graft donor sites in the proximal tibial metaphysis of 12 healthy adult dogs was studied histologically. Cancellous bone was curetted from the metaphysis of the proximal end of the tibia, via a 1-cm diameter circular opening in the medial cortex. A hematoma and fibrovascular tissue filled the bone defect at 2 weeks. At 4 and 8 weeks, endosteal callus, composed initially of cartilage and woven bone and later of lamellar bone, filled the marrow cavity. At 12 weeks, the normal structural arrangement of lamellar bone and hematopoietic marrow was reestablished in the marrow cavity. The medial cortex defect was filled only with lamellar trabecular bone. It was concluded that, in adult dogs, a second cancellous bone graft could be collected from the proximal portion of the tibial metaphysis 12 weeks or more after an initial collection.