The Effects of Cerclage Wiring on the Immature Canine Diaphysis A Biomechanical Analysis

When cerclage wiring is used in skeletally immature dogs, the wires become imbedded in the cortical bone due to radial appositional bone growth.
Six groups of five dogs each received one or two extraperiosteal cerclage wires at the mid-diaphysis of the left femur at the age of five months. Ten dogs were killed immediately, ten dogs were killed at eight weeks postoperatively, and ten at twelve weeks. Both femora from each animal were collected and subjected to torsional loading to failure within.5 seconds. The maximum torque, shear stress, energy absorption, angular deformation, and torsional stiffness were determined and subjected to í test analysis.
Application of the wires predictably caused an increase in weight and cortical bone thickening at the implant site, which was primarily due to endosteal bone deposition in the 8-and 12-week groups. The 8-and 12-week wired bones were stiffer and failed at a lower angular deformation than did their corresponding control femurs, but the zero-time bones did not show this tendency. Significantly less shear stress accumulation and energy absorption at failure were present In the 8-and 12-week implants, but no difference was seen in the zero-time femora. The 8-week groups showed a greater difference between the wired and control femurs than did the 12-week groups. No significant difference was found between one-and two-wire implants in the study.
The results indicate that confinement of dogs with clinically wired fractures of immature canine femurs should extend past eight weeks.     

The Radiographic and Histologic Appearance of Controlled Surgical Manipulation of the Equine Periosteum

This study documented the normal histologic features of the equine metacarpal and metatarsal periosteum and characterized its osteogenic response to surgical manipulation. Two periosteal flaps were elevated from the dorsomedial matacarpal and metatarsal diaphysis in each of three limbs of four yearling and four adult lightbreed horses. The superficial metacarpal cortex under the flap was resected with a bone chisel in one-half of the horses and was undisturbed in the remainder. One periosteal flap in each limb was excised and the other flap was replaced and secured by sutures. All limbs in the horses were radiographed at regular intervals postoperatively. Horses were killed either 30 or 120 days after surgery. Periosteal bone production occurred only at treatment sites of young horses treated by periosteal flap replacement and was limited to approximately 50% of these sites, as determined by radiography and microradiography. Cortical abrasion resulted in an increased incidence of bone production in the periosteum adjacent to the flap perimeter. The histologic features of the periosteum were similar to those reported in other species; young horses had active osteogenesis referable to appositional growth and adults had an inactive periosteum. Histologically, osteogenesis induced by surgery resembled accentuated appositional growth in both yearlings and adults. In the horse, the cambial (osteogenic) layer is included in sharply elevated periosteal flaps. It should be removed in surgical procedures where bone production is to be avoided, and preserved where osteogenesis is desired.     

An avian model of limb deviation induced by periosteal surgery

A model of limb deviation induced by hemi-circumferential periosteal stripping of the distal tibiotarsus of domestic chicks is described. This model has been developed to study the effects of periosteal stripping on the cellular, mechanical, vascular, and biochemical status of the immature bone and growth plate. It is hoped that such studies may further elucidate the mechanisms involved in altered bone growth following periosteal stripping techniques which are used in human and equine orthopaedics for the management of leg length discrepancies and angular limb deformities respectively (Auer and Martens 1980, Warrell and Baker 1987). Hemi-circumferential periosteal stripping of the left distal tibiotarsus of 28-day-old chicks resulted in significant change in metaphyseal-diaphyseal angle with time, compared to both the controls and the untreated right legs (P<0.0001). This model of limb deviation developed rapidly and consistently, and the procedures were well tolerated by the birds over the short survival time (maximum 28 days).     

Open reduction and internal fixation with a locking plate for the treatment of a femoral fracture in a ferret (Mustela putorius furo)

Long bone fractures in ferrets (Mustela putorius furo) are usually traumatic in etiology, and the femur is commonly affected [1]. A 4-year-old, castrated male ferret was examined for acute, non-weight-bearing lameness of the left pelvic limb after presumably falling from its elevated enclosure. Clinical and radiographic evaluation showed a complete, comminuted fracture of the proximal diaphyseal third of the left femur. Open reduction and internal fixation (ORIF) of the left femoral fracture was performed with cerclage wires and a 1.5 mm locking compression plate with associated locking screws. Anatomic reconstruction was achieved, and postoperative radiographs confirmed appropriate fracture fragment apposition, limb alignment, and implant placement. At 9 weeks postoperatively, the ferret was ambulatory with no evidence of lameness, and complete radiographic union was noted. This is the first published report of the use of a bone plate for femoral fracture stabilization in a ferret. Bone plates, including locking plates, could be considered for long bone fracture stabilization in ferrets as an alternative to other methods.     

Use of a hybrid external skeletal fixator for repair of a periarticular tibial fracture in a Patagonian cavy

An 8-week-old female Patagonian cavy was examined because of acute right hind limb lameness; radiography revealed a moderately displaced, comminuted fracture of the proximal third of the tibia. The fracture was stabilized with a hybrid external skeletal fixator. Two Kirschner wires were placed in the main proximal fragment, parallel to the tibial plateau and at right angles to each other. These wires were connected to a partial circular external fixator ring. Three half pins were placed in the distal fragment, and a straight connecting rod positioned on the medial side of the limb was connected to these pins and the fixator ring. A second connecting rod was positioned on the craniomedial side of the limb and was connected to the fixator ring and a fourth half pin in the distal fragment. The fracture healed without complications, and the fixator was removed 3 weeks after surgery. Hybrid external skeletal fixators combine the benefits of circular and linear external skeletal fixation methods, enabling rigid fixation of periarticular long bone fractures without adversely affecting mobility of the adjacent joint.     

Large segmental radius and ulna defect treated by bone transportation with the Ilizarov technique

An 8-year-old male Boxer with a severely contaminated open fracture of the left radius and ulna fracture, produced by a helicopter propeller, was treated using bone transport by the Ilizarov method. Extensive diaphyseal bone loss and soft-tissue vascular damage were present. The radius and ulna were stabilised with an Ilizarov ring external fixator. The bone defect was partially shortened and restored by gradual transport of a bone segment created from proximal segments of the radius and ulna. The external fixator was removed 4 fi months after the beginning of the latency period, due to instability caused by osteolysis around the wires. A cast was placed for 3 weeks. Although the bone transport had resulted in formation of approximately 4 cm of bone, the antebrachium showed approximately 50% shortening when compared to the contralateral limb. The infection was eradicated, and the dog was able to bear weight on the operated limb when walking.     

Evaluation of biocompatible osteoconductive polymer as an orthopedic implant in dogs.

The biocompatibility and osteoconductive properties of biocompatible osteoconductive polymer (BOP), a synthetic implant, were evaluated. Bilateral oval cortical defects (1 x 2 cm) were made in the lateral subtrochanteric area of the proximal portion of the femur in 16 dogs that later were treated with BOP fiber (n = 16) or autogenous cancellous bone (n = 11), or were not treated (n = 5). The BOP block was attached extraperiosteally to the proximal portion of the humerus in 6 dogs. Radiographic assessment of surgery sites was performed at 4-week intervals, and histologic evaluation was performed at 4, 8, 16, and 24 weeks after surgery. Radiographic signs of bone healing were not observed in defects treated with BOP fiber. Defects treated with cancellous bone or not treated had radiographic signs of progressive bone ingrowth. Radiographic evidence of periosteal new bone formation near control and BOP-treated defects was observed 4 weeks after surgery; increased periosteal reaction was associated with BOP fiber. This new bone had resorbed by week 24, except bone adjacent to BOP fiber, where continued periosteal reaction was apparent. Histologic evidence of bone formation was observed extending to, but not incorporating, BOP fibers. The BOP fibers became surrounded by a fibrous capsule, and fibrovascular connective tissue infiltrated between and into BOP fibers, but minimal bone formation incorporated the BOP material during the follow-up period. During that time, active periosteal new bone formation was evident adjacent to the BOP fibers. Defects treated with cancellous bone or not treated healed by ingrowth of cancellous bone during the first 12 weeks after surgery and by reformation of the lateral cortical wall by week 24. The BOP blocks became surrounded by a fibrous capsule, but connective tissue or bone ingrowth into BOP blocks was not observed. Results indicate that BOP is not osteoconductive within a 6-month time frame when used in subtrochanteric femoral defects or when placed extraperiosteally on the proximal portion of the humerus of clinically normal dogs.     

Tibial segmental bone defect treated with bone plate and cage filled with either xenogeneic composite or autologous cortical bone graft. An experimental study in sheep.

Tibia segmental defect healing in sheep were clinically, radiographically and histologically evaluated. Twelve young sheep aged four to five months were divided into two groups, G1 and G2. A 3.5 cm long segmental defect was created in the right tibial diaphysis with maintenance of the periosteum. The bone defects in both groups were stabilized with a bone plate combined with a titanium cage. In G1 the cage was filled with pieces of autologous cortical bone graft. In G2 it was filled with a composite biomaterial which consisted of inorganic bovine bone, demineralized bovine bone, a pool of bovine bone morphogenetic proteins bound to absorbable ultra-thin powdered hydroxyapatiteand bone-derived denaturized collagen. Except for one G1 animal, all of them showed normal limb function 60 days after surgery. Radiographic examination showed initial formation of periosteal callus in both groups at osteo-tomy sites, over the plate or cage 15 days postoperatively. At 60 and 90 days callus remodeling occurred. Histological and morphometric analysis at 90 days after surgery showed that the quantity of implanted materials in G1 and G2 were similar, and the quantity of new bone formation was less (p = 0.0048) and more immature in G1 than G2, occupying 51 +/- 3.46% and 62 +/- 6.26% of the cage space, respectively. These results suggest that the composite biomaterial tested was a good alternative to autologous cortical bone graft in this experimental ovine tibial defect. However, additional evaluation is warranted prior to its clinical usage.     

Unusual Bone Healing in a White-tailed Deer

Two sequential fractures in the left hind leg of a deer and their treatments are described. The first, a tibial fracture was treated using an intramedullary pin with full cerclage wires supported by a plaster cast. This fracture healed uneventfully. A subsequent second fracture involving the distal metatarsus was stabilized by external fixation. This fracture healed with the formation of a periosteal involucrumlike structure which encased the full length of the metatarsal bone. This involucrum was thought to be due to a sub-periosteal hematoma.     

Evaluation of tension obtained by use of three knots for tying cerclage wires by surgeons of various abilities and experience

OBJECTIVE: To compare tension of 3 cerclage wire knots tied by surgeons of various abilities and experience. DESIGN: Cross-sectional study. SAMPLE POPULATION: Participants and faculty at a postgraduate course in veterinary orthopedics. PROCEDURE: Subjects tied a cerclage of their choice on an instrumented tying stand that displayed the tension on a computer. Mean tensions in cerclage wires tied with twist, single loop, or double loop knots were compared. The relationship between level of surgeon experience and tension achieved was examined. RESULTS: 29 twist, 30 single loop, and 16 double loop wires were analyzed. Mean +/- SD tension for twist knots was significantly less than for single loop knots (82.3+/-46.1 vs 166.6+/-42.2 N, respectively). Double loop knots achieved significantly greater tension (392.0+/-116.6 N) than twist and single loop knots did, even though few participants had ever tied this knot previously. There was no correlation with experience of the participant. For twist knots, wiggling the wire during cutting and pushing the twist over to flatten it to the bone further reduced tension. CONCLUSIONS AND CLINICAL RELEVANCE: Cerclage applied with a twist knot does not compress fracture fragments as effectively as cerclage applied with single loop or double loop techniques. Because greater compression of fragments will improve the stability of a fracture, a surgeon should strive to maximize the tension in the cerclage that they use. Experience and abilities of the surgeon are not associated with ability to tie cerclage wires tightly.     

Dual-Energy X-Ray Absorptiometry and Force-Plate Analysis of Gait in Dogs With Healed Femora After Leg-Lengthening Plate Fixation

Dual-energy x-ray absorptiometry was used to measure bone mineral density of four regions in healed femora of nine dogs after fracture fixation with a leg-lengthening plate. Six to 85 months (mean, 46 months) after surgery, the bone mineral density of healed femora was not significantly different from the contralateral uninjured femora ( P >.05; power = 0.8 at Δ= 15%). Radio-lucencies around the proximal screws, apparently associated with screw loosening, were seen on radiographic views of the healed femora of three dogs. In one of these dogs, one screw in the proximal metaphysis had broken. Force-plate analysis of gait was also performed on dogs at the time of bone mineral density measurement. Peak vertical force was decreased in the pelvic limb with the healed fracture compared with the contralateral unoperated limb ( P < 0.05). Clinically apparent lameness in three dogs did not appear to be associated with altered bone mineral density and may have been caused by hip osteoarthritis, a nondisplaced hairline diaphyseal fracture, and screw loosening in conjunction with extensive post-traumatic soft tissue injury.     

Use of intraosseous blood for repeated hematologic and biochemical analyses in healthy pigs

OBJECTIVE: To evaluate the clinical and histologic effects of repeated intraosseous (IO) needle placement in domestic pigs and determine whether blood and serum obtained intraosseously could be used for CBC and biochemical analyses. ANIMALS: 5 healthy 10-week-old pigs. PROCEDURE: An IO needle was placed in the proximomedial region of the tibia of anesthetized pigs every other week for 2 months, and IO blood was obtained for CBC and serum biochemical analyses. Results were compared with those obtained for blood collected at the same time from the auricular vein. Two weeks after the final samples were obtained, pigs were euthanatized and tibias were processed for histologic examination. RESULTS: Clinical abnormalities, including lameness, were not detected following IO needle placement. Histologic examination revealed only mild multifocal periosteal fibrosis and slight thickening of the periosteum without evidence of osteomyelitis. Chloride, creatinine, glucose, total protein, sodium, and BUN concentrations, alanine transaminase and gamma glutamyl transpeptidase activities, RBC count, mean corpuscular volume, and Hct did not significantly differ between IO and venous samples. However, aspartate transaminase activity, potassium, hemoglobin, and mean corpuscular hemoglobin concentrations, mean corpuscular hemoglobin, and platelet and WBC counts were significantly different. CONCLUSION AND CLINICAL RELEVANCE: Repeated placement of 10 needles may be a safe and clinically useful method to obtain serial blood samples from domestic pigs, particularly when other vascular sites are not accessible. Intraosseous blood can be used for many of the tests comprising CBC and serum biochemical analyses.     

Repair of a proximal diaphyseal femoral fracture in a calf, using intramedullary pinning, cerclage wiring, and external fixation.

Repair of a comminuted, spiral oblique, proximal diaphyseal femoral fracture in a 7-day-old calf was achieved by use of an intramedullary pin, cerclage wires, and external fixator. Six stainless steel wires were used for full cerclage to secure a long butterfly fragment and multiple incomplete and complete nondisplaced fragments to the femur in order to create 2 principal fragments. Axial alignment and resistance to bending was provided by a round, double-pointed, end-threaded intramedullary pin (6.35 mm in diameter), which was inserted in a retrograde fashion. A type-1, double-connecting-bar external fixator, using 4 round pins (4.8 mm in diameter), was used to provide supplemental stabilization against shear and torsional forces. At 45 days after surgery, healing at the fracture site was seen on radiography of the limb, and the external fixator was removed. Eight months after surgery, the calf had a normal gait.     

Direct current stimulation of bone production in the horse: preliminary study with a "gap healing" model

The effect of a 20-microA direct-current implantable bone growth stimulator (BGS) on bone production with a "gap healing" model in the horse was evaluated. The right and left 4th metatarsal bones (Mt-4) were used in 7 adult horses to create the "gap healing" model. A 4-mm section of the Mt-4 bone was resected bilaterally in each horse. The BGS was surgically placed into the 7 left Mt-4 defects. The 7 right Mt-4 defects served as controls. Six horses survived the 16-week experimental period. Signs of pain, decreased range of limb motion, or lameness was not observed in any animal during the 16 weeks. None of the animals showed complete healing radiographically. Four stimulated sites showed less periosteal reaction and 2 showed greater reaction than the 6 controls. The greatest amount of periosteal reaction or bone resorption was seen around the screws and plates in both groups. Uptakes of 99mTc-MDP in counts/pixel for control sites and stimulated sites were 7.90 and 8.25 in the "gap defect" and 5.19 and 5.06 in the areas adjacent to the gap defect. The ratio of uptake between the gap defect and adjacent area was 1.5 and 1.58 respectively. Biocompatability of the BGS was excellent; however, 1 horse had a broken cathode wire 5 cm from the generator capsule at 6 weeks. All polyethylene cathode sheaths were fluid filled at 16 weeks. The average mineralization rates were 1.57 +/- 0.34, 1.71 +/- 0.28 mm/day and bone formation activity was 0.0182 +/- 0.171, and 0.0168 +/- 0.0149 mm2/day for control limbs and stimulated limbs, respectively. There was no significant difference between groups in any of the histomorphometric values measured. Direct current (20 microA) did not increase bone production in this experiment. Methods to objectively evaluate electrically induced osteogenesis and a "gap defect" model for BGS research on the horse are discussed. The results provide a basis for additional research on electrical stimulation of fractures in the horse and for dose-response studies.     

Mechanical Characteristics and Comparisons of Cerclage Wires: Introduction of the Double-Wrap and Loop/Twist Tying Methods

Objective — Evaluate the mechanical properties of twist, loop, double loop, double-wrap and loop/twist cerclage.
Methods — The initial tension generated by 18 cerclage of each type was determined using a materials testing machine after tying around a testing jig. Six wires from each type were distracted and the initial stiffness and yield load were determined. Yield behavior was further investigated in six wires of each type by determining the load required to reduce cerclage tension below 30 Newton (N) following an incremental (50 N) stepwise load and unload regimen. The amount of collapse of the simulated bone fragments that resulted in the reduction of initial tension to 30 N was measured for the final six wires of each group. Data were analyzed by analysis of variance and a multiple comparison test.
Results — Twist type cerclage generated less tension than loop-type cerclage. The yield load of these two types was similar. Double-loop and double-wrap cerclage generated superior tension and resisted a greater load before loosening. Loop/twist cerclage had an intermediate initial tension but had the greatest resistance to loading. In the collapse test, the greater the initial tension, the more collapse could occur before the wire was loose. For all types of cerclage wire fixation, a reduction of diameter of the testing jig of more than 1% caused loosening.
Clinical Relevance — Double-loop and double-wrap cerclage provide greater compression of fragments and resist loads associated with weight-bearing better than the twist and loop methods. Loop/twist cerclage may have advantages because of their superior resistance to loading. All cerclage will loosen if fracture fragments collapse.     

Correction of angular limb deformity in two subspecies of flamingo (Phoenicopterus ruber) utilizing a transphyseal bridging technique.

Three hand-raised American flamingo (Phoenicopterus ruber ruber) chicks and one hand-raised Chilean flamingo (Phoenicopterus ruber chilensis) developed valgus angular limb deformities of the proximal tarsometatarsal bone. All flamingos underwent surgical correction to unequally retard the growth plate using transphyseal bridging. Positive profile pins were placed in the proximal epiphysis and distal to the growth plate in the metaphysis on the convex side of the affected tarsometatarsus. Various banding techniques were used in each flamingo to create tension. Three of the four flamingos responded in 7-14 days with correction or slight overcorrection of the valgus limb deformity. The fourth flamingo's leg deformity did not improve for reasons thought to be related to improper implant placement. Growth plate retardation by transphyseal bridging proved successful in correcting valgus limb deformity of the proximal tarsometatarsus. This technique may be considered as an option for correction of angular limb deformities of the proximal tarsometatarsus in flamingos less than 90-120 days of age.     

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.     

Unusual Polydactylism in a Foal: A Case Report

A 2 month old quarter horse colt had multiple skeletal abnormalities of the left fore limb, including two supernumerary metacarpal bones, two supernumerary carpal bones, abnormal carpal bone development, and a valgus deformity originating at the carpal joint. The largest supernumerary metacarpal bone was removed completely, a portion of the smaller supernumerary metacarpal bone was removed, and the leg was placed in a tube cast. Surgical treatment improved the clinical appearance and prevented further injury to the limb. The carpal joint width remained increased but the carpal valgus deformity partially responded to hemicircumferential periosteal transection. The foal was sound 2 1/2 years after surgery.     

Influence of short-term confinement and exercise on tibia development in growing pigs

The influence of short-term confinement and moderate exercise on tibia development was investigated in growing pigs (36-41 kg, 10 weeks at the beginning of the study). Animals were kept for 2 weeks either in individual crates of 0.8 m(2) ('confinement', n = 4) or kept in groups of four animals in large crates of 5.6 m(2) without ('control') or with additional exercise (30 min walking at 5 days/week; 'exercise'). Bone density and morphological parameters were evaluated by computer tomography (CT). Periosteal apposition and longitudinal growth were determined after polychrome sequential labelling in weekly intervals. Cortical areas of the cross sections at the mid-shaft and at 75% of the length of the bone measured distal to the carpus by CT were significantly correlated to each other (r = 0.70) and revealed a significant reduction in confined animals. This difference was explained by lower periosteal apposition rates in these animals compared with exercised and group-housed pigs. Similarly longitudinal growth and the formation and calcification of spongiosa of the tibiae were inhibited by confinement. Thus, 2 weeks of confinement led to significant differences in bone growth and metabolism in young growing piglets when compared with animals with moderate activity.     

Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum

Canine hepatozoonosis, caused by Hepatozoon americanum, is an emerging tick-borne disease of dogs in North America. In addition to the skeletal and cardiac myositis that are prominent features of the disease, there is disseminated periosteal bone proliferation in most dogs that manifest clinical disease. Each of six experimentally infected animals (four dogs and two coyotes) and seven of eight naturally infected dogs had gross or histopathologic osteoproliferative lesions. Experimental animals were 6-9 months of age when exposed. Naturally infected dogs were 8 months to 11 years old when subjected to necropsy. Lesions occurred primarily on the diaphysis of the more proximal long bones of the limbs; however, flat and irregular bones were frequently involved. Lesions involving metacarpals, metatarsals, and digits were infrequent. The earliest observed periosteal lesions were in an experimentally infected dog 32 days after exposure to sporulated oocysts of H. americanum. There were hypertrophy and hyperplasia of osteoprogenitor cells, and osteoblasts appeared in the cellular zone of the periosteum. Spicules of woven bone oriented perpendicularly to bone cortex followed. Later yet, periosteal new bone was remodeled and tended to become oriented parallel to the cortical bone. Horizontally oriented zones of remodeled, condensed bone sometimes occurred in multiple layers on the original cortex, forming "pseudocortices." The osseous lesions of American canine hepatozoonosis, with few variations, are remarkably similar to those of hypertrophic osteopathy in domestic dogs and other mammalian species, including humans.