Basic mammalian bone anatomy and healing.

The goal of any method of fracture repair should be the early return to function of the patient with minimum postoperative morbidity. This is accomplished most optimally by having a basic understanding of the biology of bone healing and by being familiar with the musculoskeletal system of the species before attempting fracture repair. Applying the fundamental principles of mammalian bone anatomy and physiology to the bird ensures the best prognosis possible and minimizes postoperative complications in the avian patient.     

A Fresh Look at the Process of Arriving at a Clinical Prognosis Part 4: Fractures

Equine bone and biomechanics research continues to provide us with sound and practical concepts for preventing fractures in equine athletes, accelerating a safe return to training and competition, and avoiding recurrence. Bone is a living, dynamic tissue that is constantly in a state of turnover as part of its ongoing maintenance, and is constantly responding to the various forces it experiences, from within and without. Even the seemingly inert, acellular components of bone are in a perpetual state of flux under both biomechanical and metabolic/nutritional influences. Homeostasis in bone involves both modeling and remodeling; modeling is bone's adaptive response to increases or decreases in load that are of insufficient magnitude to damage the bone. It involves the addition or removal of existing bone, changing the shape and loading capacity of the bone as needed. Remodeling is bone's reparative response to injury; it involves the removal and replacement of bone in the area of damage. Fractured bone needs the following conditions for best repair: protection—remove the primary cause of bone injury and prevention of further such injury; stability—depends on the type and site of fracture; blood flow—bone is dependent on good blood supply for repair; competent immune response—a robust white cell response is necessary both for tissue repair and for prevention/resolution of bacterial infection at the site; nutrients—all living tissues need adequate calories, and protein, minerals (including trace minerals), and vitamin D are of primary importance for optimal bone repair; and load—after fracture healing, increasing the loading capacity of the bone directs further bone repair and modeling. The prognosis may be adversely affected when any of these conditions are not met adequately. Generally, fractures in horses are not fatal injuries by themselves but most often prompted by a poor prognosis for return to soundness because of the fracture type, the development of serious complications, and the economic investment required for adequate repair. Factors that determine the prognosis for survival are degree of structural failure, ease of fixation and potential for complications, adequacy of stabilization, concurrent and complicating conditions, owner's wishes, and prognosis for return to athletic performance. Fractures of the metacarpus and metatarsus are used to illustrate the aforementioned principles.     

Basic avian bone growth and healing.

There have been few studies on the process of fracture repair in avian species. Most of the information shows similarities between avian and mammalian bone growth and fracture repair, but there are differences. The main finding confirms that fractures must be reduced properly, stabilized, and immobilized with an adequate blood supply to the bone fragments for optimal healing. The return to function of extremities, particularly the legs and wings, is an important consideration when internal fixation methods are used. Causing little or no collateral damage to soft tissue and joint when implanting internal hardware is ideal and reduces the likelihood of impaired function. Whether internal or external fixation methods are used for fracture reduction, the knowledge of avian bone growth and fracture repair is essential for veterinarian understanding and when discussing the healing process with clients.     

T-plate repair of fracture of the nasal bones in a horse.

A 5-hole T-plate was used to repair an unstable compound depression fracture of the nasal bones in a horse. Substantial bone loss was evident as a result of severe trauma. Satisfactory bone healing, facial contour, and airway function were achieved. The use of a T-plate can be an alternative means of repair of a nasal bone fracture in a situation in which instability and/or bone loss exists.     

Fracture healing after stabilization with intramedullary xenograft cortical bone pins: a study in pigeons

OBJECTIVE: To investigate the effectiveness of intramedullary xenograft cortical bone pins compared with stainless steel Kirschner wire for the repair of a standardized avian humeral fracture. STUDY DESIGN: Prospective randomized study. SAMPLE POPULATION: Thirty mature pigeons (Columba livia). METHODS: Birds were randomly assigned to 3 groups. Transverse mid-diaphyseal humeral fractures were created in 1 humerus in each bird. Fractures were stabilized with intramedullary ostrich or canine xenograft cortical bone pins or Kirschner wire. Radiographic, histological, and biomechanical assessments were used to compare fracture healing 6 weeks after fracture stabilization. The contralateral humerus of each bird was used as a control. RESULTS: All fractures healed regardless of intramedullary pin type. There were no statistically significant biomechanical differences among groups or within groups. Xenograft cortical bone pins induced a mononuclear inflammatory reaction that did not impair bone healing. Bones stabilized with intramedullary cortical bone pins had more periosteal callus and inflammation at the fracture site than bones stabilized with stainless steel Kirschner wires. CONCLUSIONS: Intramedullary xenograft cortical bone pins, derived from mammalian or avian sources, appear to represent an alternative for the repair of avian humeral fractures. CLINICAL RELEVANCE: Intramedullary xenograft cortical bone pins are biodegradable and may reduce the need for additional surgery to remove implants after fracture healing.     

Bone grafts.

Bone grafting provides a method of enhancing bone healing in veterinary orthopedic patients. Specifically, autogenous cancellous bone graft provides the cellular components and matrix proteins that can accelerate bone healing, dramatically. Allografts provide immediate mechanical support for fracture repair and patient function, but these grafts do not create the osteogenic environment seen with the use of autogenous cancellous bone graft. Xenograft bone implants may also hold a place for use in fracture management. With the advent of recombinant bone-derived tissue growth factor technology, bone grafting may some day become a practiced technique of the past. For now, however, bone grafting still holds a strong place in orthopedic surgery when dealing with bone defects in animals.     

Closed reduction and blind cross-pinning for repair of a proximal tibial fracture in a foal

A 4-day-old foal underwent repair of a proximal metaphyseal fracture of the tibia. After closed reduction, fixation was achieved by use of blind cross-pinning. Thirty-five days after surgery, radiography demonstrated complete healing. The foal was mildly lame 4 months after repair of the fracture. Blind cross-pinning may be considered as a method of repair for certain long bone fractures in small foals.     

Composite fixation of comminuted ilial wing fractures in cats: three cases

CLINICAL SUMMARY: The surgical repair of comminuted ilial wing fractures (comprising a long oblique fracture with ventral multiple fragmentation) in three cats using composite internal fixation is reported. The technique comprised the use of pins, screws, wire and polymethylmethacrylate. All cases had an excellent outcome with uneventful bone healing. One case had a very mild reduction in pelvic canal diameter postoperatively. There was no evidence of implant loosening or migration in any cat on follow-up radiographs. PRACTICAL RELEVANCE: This technique provided a quick and highly adaptable means of stabilising this fracture configuration, as well as restoring pelvic symmetry, when limited buttressing support and bone stock were available cranial and ventral to the acetabulum. This method of fixation may have biomechanical advantages over lateral or dorsal plating techniques for this particular type of fracture configuration.     

Principles of long bone fracture management.

The fixation of fractures in which one of the following primary devices is used: IM pins, bone plates, external skeletal fixators, can benefit from the additional application of any number of secondary devices. The secondary devices include cerclage, hemicerclage, or interfragmentary wires, skewer-pins, screws, and external skeletal fixators. These are indicated to facilitate the repair and eliminate the forces acting on the fracture site. A complete understanding of all the methods of fixation facilitates the selection of the proper implant or combination of implants. This information must be combined with the knowledge of how each device is most appropriately used depending on both the fracture type and fracture location. Taking into consideration all of these factors helps ensure that fracture healing occurs in the shortest possible time with the fewest complications. The ultimate goal of obtaining a full return to function may thereby be achieved.     

Standing repair of a proximal,incomplete, articular fracture of the third metatarsal bone

A 5-year-old National Hunt Thoroughbred mare presented with sudden onset left hindlimb lameness after race training on the gallops. Clinical examination revealed a marked painful reaction over the proximal metatarsal region but no other obvious abnormalities were detected. Survey radiographs at the yard did not reveal any abnormalities. Nuclear scintigraphic examination 3 days after injury revealed focal marked increased radiopharmaceutical uptake in the proximal metatarsal region. Subsequent radiography revealed an incomplete, articular fracture of the proximal left third metatarsal bone. Repair of the fracture using 3 × 4.5 mm cortical screws placed in lag fashion was performed under standing sedation following perineural analgesia. Follow-up radiographs demonstrated progressive healing of the fracture. The mare returned to race training 8 months after the fracture was repaired and raced successfully 12 months post injury.     

The effect of intralesional injection of bone marrow derived mesenchymal stem cells and bone marrow supernatant on collagen fibril size in a surgical model of equine superficial digital flexor tendonitis

Reasons for performing study: Collagen fibril size is decreased in repair tissue following tendon injury compared to normal tendon matrix in horses. Mesenchymal stem cells have been suggested to promote regeneration of tendon matrix rather than fibrotic repair following injury, although this concept remains unproven. Objectives: To explore the hypothesis that implantation of autologous mesenchymal stem cells derived from bone marrow into a surgically created central core defect in the superficial digital flexor tendon (SDFT) of horses would induce the formation of a matrix with greater ultrastructural similarities to tendon matrix than the fibrotic scar tissue formed in control defects. Methods: Tissue was collected 16 weeks after induction of injury and 12 weeks after treatment from normal and injured regions of control and treated limbs of 6 horses and examined using transmission electron microscopy. Collagen fibril diameters were measured manually with image analysis software and surface areas calculated. Three parameters assessed for normal and injured tissue were mass average diameter (MAD), collagen fibril index (CFI) and the area dependent diameter (ADD). Results: Normal regions from both treated and control limbs displayed higher MAD and CFI values, as well as a characteristic bimodal distribution in fibril size. Injured regions from both treated and control limbs displayed significantly lower MAD and CFI values, as well as a unimodal distribution in fibril size. There were no significant differences between treated and control limbs for any of the parameters assessed. Conclusions: Intralesional injection of autologous bone marrow derived mesenchymal stem cells had no measurable effect on the fibril diameter of collagen in healing tissue in the SDFT of this experimental model 16 weeks after injury. Potential relevance: Favouring matrix regeneration over fibrotic repair may not be the mechanism by which autologous mesenchymal stem cells assist healing of tendon injury.     

Plate fixation of iliac shaft fractures in the dog.

In a series of 20 dogs, 23 fractured ilia were reduced and stabilized with a variety of bone plates. The results indicated that fixation was rigid enough for fracture healing and for the patient to be ambulatory soon after surgery. Plate fixation can therefore be recommended as a reliable method of repair in selected fractures of the canine ilium.     

纤维蛋白胶复合物促进犬骨折愈合的临床学观察

为了探索纤维蛋白胶(FG)联合人骨形态发生蛋白(rhBMP-2)、碱性成纤维细胞生长因子(bFGF)和妥布霉素的复合物对犬骨折愈合的影响,建立了犬胫骨骨折模型,将FG复合物应用于实验组和空白对照组的胫骨骨折处,在术后2、4、8、12、16周,测定骨折处周围软组织充血水肿消除时间、利用X射线影像学评价骨折愈合程度、测定骨折愈合部位的骨密度(BMD)及骨密度比率、骨痂体积,测定胫骨生物力学强度并进行统计和分析。实验组和对照组比较:术部红、肿、热消失时间显著缩短,术后各时间点的X射线影像学评分更高,术后各时间点骨痂更大,术后16周术部骨骼能承受的最大载荷和最大位移显著增大。结果表明FG联合rhBMP-2、bFGF与妥布霉素应用于骨折部位,可促进骨折愈合过程中软组织的生成,缩短骨折愈合的时间,提高骨生物力学强度。     

Biological osteosynthesis versus traditional anatomic reconstruction of 20 long-bone fractures using an interlocking nail: 1994-2001

ObJECTIVE: To observe differences in surgical and healing times as well as complication rates in dogs with a comminuted long-bone fracture stabilized with an interlocking nail (IN) using either anatomic or biologic repair. STUDY DESIGN: Retrospective study. ANIMALS: Twenty client-owned dogs with comminuted long-bone fractures. METHODS: Medical records for dogs with fractures repaired during a 7-year period were reviewed; 20 dogs had repair with an IN nail and radiographic evidence of healing. These 20 dogs where divided into 2 groups, anatomic (11 dogs) and biological (9) repair, for statistical evaluation. Surgical and healing time and complication rates were compared between groups. RESULTS: Median surgical times were: anatomic (95 minutes) and biologic (110 minutes; P=.06). Median healing times were anatomic (8 weeks) and biologic (6 weeks; P=.04). No statistical differences were observed in complication rates (the likelihood that a case required a second surgery [P=.58], the likelihood of a complication that was managed non-surgically [P=.27]). Use of a bone graft did not shorten healing times (P=.55). CONCLUSIONS: Biological osteosynthesis provides clinical advantages over anatomic reconstruction with respect to a reduction in surgical and healing time without increasing complication rates. CLINICAL RELEVANCE: Highly comminuted long-bone fractures can be successfully repaired using an IN without reconstructing the fracture fragments in dogs.     

A preliminary investigation of the effect of selected electromagnetic field devices on healing of cannon bone osteotomies in horses

The effect of electrical stimulation by means of selected electromagnetic field devices on healing of cannon bone osteotomies in horses was examined. The defects were created as 3 cm x 1 mm longitudinal osteotomies through the dorsal cortices of the mid-metacarpi/metatarsi of adult horses. This type of defect would asses bone healing in a situation similar to an acute, stable fracture of the cortex. Three electromagnetic devices of different design were tested in three different groups of horses. Healing was evaluated radiographically and histologically. Results showed that osteotomies treated with the electromagnetic devices healed similarly to untreated controls. Our conclusion is that the electromagnetic devices studied did not have a local effect on the repair process of an acute, stable, osseous defect.     

Management of fractures in small animals.

Fracture repair in small animals has arrived at a crossroads because of advances in fracture repair and client demands. Research into bone healing and repair techniques, collective professional experience,economics, and client demands are obligating veterinarians to greater expertise in the actual act of repairing fractures. The influx of surgery specialists into burgeoning private practices has improved access to specialty service beyond what the limited number of academic practices could previously provide and has raised the local standard of practice for orthopedic surgery at the same time. The necessity to deal with the preoperative and postoperative management of traumatized small animals by the general practitioner has not changed, however.Treatment of the small animal patient with a fractured bone does involve accurate definition of the fracture, selection of an appropriate method of fracture fixation from the variety of devices available, and correct application of the fixation. Far more than these, however, it involves assessment and treatment of the traumatized patient as a whole,including preanesthetic evaluation of critical body systems, preoperative preparation of the patient and client, and postoperative management of the repaired fracture and patient.     

Arthroscopic guided repair of a slab fracture of the fourth carpal bone in an 8-month-old thoroughbred horse

An 8-month-old thoroughbred colt presented with sudden onset right forelimb lameness. A radiographic series of the right carpus was performed, and it revealed a slab fracture of the fourth carpal bone and fracture of the proximal part of the third metacarpal bone. Arthroscopically guided repair of the slab fracture of the fourth carpal bone with a 3.5 mm cortex screw and lag screw fixation of the fracture of the proximal part of the third metacarpal bone were performed. The horse started to race at 32 months old and started in 65 races over three years without any trouble associated with the right carpus.     

Can bone marrow aspirate improve mandibular fracture repair in camels (Camelus dromedarius)? A preliminary study

BackgroundMandibular fractures are common in camels, leading to considerable economic losses. This study explored methods of improving mandibular fractures repair, adjuvant with interdental wire, or bone plate fixation. Autologous bone marrow (BM) injection enhances osteogenesis and rapid healing.ObjectivesTo investigate the effect of autologous BM aspirate as an adjuvant treatment for repairing mandibular fractures in camels with interdental wire, or bone plate fixation.MethodsThirty dromedary camels aged 5–8 years and of both sexes were randomly divided into 4 treatment groups: group 1 (n = 10) treated with stainless steel wire fixation and BM injection at the fracture line, group 2 (n = 10) treated with plate fixation and BM injection at the fracture line, group 3 (n = 5) treated with stainless steel bone wire fixation and placebo saline injection at the fracture line, and group 4 (n = 5) treated with plate fixation and placebo injection at the fracture line. The mandibular fractures were followed weekly for 12 weeks postoperatively to assess improvement and healing based on clinical evaluation, radiographic union scale, and bone turnover markers (i.e., bone alkaline phosphatase, osteocalcin, pyridinoline, and deoxypyridinoline).ResultsCompared to other groups, elevated bone turnover markers in group 1 were demonstrated (p < 0.05) on the seventh postoperative day. Likewise, compared to other groups, both clinical findings and radiographic union scale significantly improved (p < 0.05) in group 1 on the 56th postoperative day.ConclusionsBM aspirate has a promising beneficial osteogenic effect on mandibular fracture repair in camels, most notably when combined with interdental wire fixation.     

Results of treatment of 145 fractures of the third metacarpal/metatarsal condyles in 135 horses (1986-1994).

The objectives of this study were to correlate condylar fracture characteristics and type of treatment with subsequent capacity for athletic ability, and to determine the characteristics of healing that affect prognosis after fracture fixation. Medical records, post operative radiographic studies and race records were examined for 135 horses sustaining 145 fractures. Sixty-five percent of horses overall started in a race post injury (SPI) in a mean time of 9.7 months with a mean of 13.7 races post injury. Having raced pre-injury did not confer an advantage to starting post injury, though nonstarters pre-injury tended to take longer to return. For horses starting pre- and post injury, 66% improved or maintained their race class level after injury, whereas 64.2% decreased their race earnings post injury. Eighty-five percent of the fractures received internal fixation, of which 70% were complete fractures. Eighty-seven percent of horses with incomplete-nondisplaced fractures treated conservatively raced post injury. The percent SPI for incomplete-nondisplaced, complete-nondisplaced and complete-displaced fractures treated with internal fixation were 74%, 58%, and 60%, respectively. Males (72%) raced post injury more frequently than fillies (53%), and may represent a truer probability of SPI. Spiral fractures tended to take longer until their first start (mean 13.3 months). Fifty-two percent of horses with articular fragments were able to race post injury. Horses were more likely to start if 2-4 month radiographic healing revealed no evidence of the fracture except the presence of lag screws. Based on this series of cases, the majority of horses, with proper treatment, were able to return to racing regardless of fracture characteristic. Prognosis appeared to be affected by the severity of the injury to the joint, the presence of articular comminution and the quality of surgical repair.     

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.