Use of the modified acrylic external fixator in 54 dogs and 28 cats

This paper describes the use of acrylic resin instead of a Kirschner clamp for treating bone fractures. The technique is cheaper than using Kirschner external skeletal fixator and allows greater flexibility for pin placement. It is also less prone to self mutilation by dogs than the entirely acrylic external fixator. The modified acrylic fixator gave results similar to those obtained with the Kirschner external fixator, when used in 54 dogs and 28 cats.     

Analysis of the external fixator pin-bone interface

External fixator pins were inserted into tibiae of dogs under four in vivo loading conditions to examine the mechanism of pin loosening. Pins were quantitatively measured for pin torque resistance, and the pin tracts were studied radiographically and histologically. The pins holding an unstable fracture had more gross pin loosening. Pins also may become loose under static loads. Radiographic lucency of 1 mm or more in the cortical bone around a pin was evidence of gross pin loosening. Histologic examination showed that tight pin tracts were characterized by a lack of bone remodeling. Loose pin tracts were characterized by extensive bone resorption and inflammatory infiltrates. Pin loosening can be detected radiographically. Pin insertion technique is important to improve the initial pin torque resistance to minimize pin loosening. Sixty-nine percent of pins with an initial torque resistance of less than 68 Ncm became grossly loose compared with only 9% of pins with an initial torque resistance greater than 68 Ncm, regardless of the experimental group. Unstable external fracture fixation is another important factor in producing pin loosening. Pins loaded under unstable fracture fixation had the highest incidence of gross loosening. When applying an external fixator, the fracture rigidity should be critically evaluated and, if necessary, protected weight bearing must be introduced initially to minimize pin loosening.     

Type-II external fixation, using new clamps and positive-profile threaded pins, for treatment of fractures of the radius and tibia in dogs

A new external fixation system for repair of fractures of the radius and tibia was developed that uses positive-profile threaded pins. This system allows for addition of a fixation clamp between 2 installed clamps, predrilling of pin holes through a drill sleeve, use of positive-profile threaded pins in all locations, and easier application of full pins. Type-II external fixators were applied, using this system, to fractures in 10 client-owned dogs, and outcome was evaluated. All fractures healed without complications. Duration of surgery, mean time until radiographic evidence of a bridging callus, and mean time until removal of the external fixator were shorter, and frequency of pin loosening were less than with other techniques. Pin loosening was uncommon. This system provides an important improvement in external skeletal fixation.     

Breaking strength retention and histologic effects around 1.3-mm. ORTHOSORB polydioxanone absorbable pins at various sites in the rabbit

Absorbable 1.3-mm polydioxanone (ORTHOSORB) pins were implanted in 75 New Zealand White rabbits in three sites: within the lateral subcutaneous tissue parallel to the femur, down the femoral intramedullary canal, and mediolaterally across the femoral condyles (transcondylar). Pins were harvested at periodic intervals up to 56 and 365 days for mechanical and histologic analyses, respectively. Mechanical analyses were performed by loading the pin in double shear. Histologic analyses were performed on the pin and surrounding tissue. Histologic observations revealed a typical nonspecific foreign-body reaction at all implant sites that resolved at 1 year after resorption of the pin. On histologic examination, there was complete resorption of the pin material in the subcutaneous site by day 182, and there was complete resolution of all response to the pin in six of nine rabbits by day 365. In the intramedullary site, pin material was completely resorbed, based on histologic examination, in five of six rabbits by day 182, and there was complete resolution of the response to the pin in eight of nine rabbits by day 365. The pin material was completely resorbed based on histologic examination of the transcondylar site by day 210, and there was complete resolution of the response to the pin in four of six rabbits by day 270 and in four of nine rabbits by day 365. No enlarged pin tracks or sinus formations were observed in or near the implants sites. The average initial shear strength as 171.4+/ 5.1 MPa, and the breaking strength retention decreased with increasing implantation time. Pins from the subcutaneous regions maintained above 97% of their initial strengths at 28 days, and those from the intramedullary canals maintained above 92%. At later times the strength of the pins implanted in the intramedullary canal decreased more rapidly than those from the subcutaneous region. Overall, the average breaking strength of the subcutaneous pins was significantly greater than that of the intramedullary pins at all time points beyond 14 days. These data indicate that the pins exhibited a strength retention profile sufficient to allow normal healing of bone without enlarged pin tracts, allergic reactions, or sinus formations.     

Use of the spiral pin for fracture of the humeral neck

Our new method of intramedullary fixation of humeral neck fracture is described. Spiral pin is made of stainless steel. The top is coiled, and the end is threaded. It is inserted from a small incision over the posterior surface of the supracondyle. It is passed across the fracture site into the head of the humerus, where it locks the head. The fracture surface is pressed together by tigtening nuts. The fracture fixation allows early movement of the shoulder joint. The method was used in eight patients. The average age was one-year-old.     

A simple technique for correction of complicated tibial deformity including rotational deformity

Although the simplest way to correct bone deformity is one-stage correction, the problem associated with that method is overstretching of the soft tissues, which limits the correction and leads to complications such as compartment syndrome or peripheral nerve palsy. If an adequate amount of tissue necessary for correction is formed in advance, the deformity can be corrected safely at one stage without overstretching of the tissues. A leg lengthening technique was employed to form the necessary tissues. After leg lengthening with an unilateral external fixator (Hifixator), deformities were corrected manually at one stage without anesthesia, and the corrected positions were again secured with the fixator. To correct rotational deformity, two sets of pins were inserted into the proximal bone fragment of the tibia at the time of the operation, and after lengthening the proximal pin clamp of the fixator was disconnected from one pin set and reconnected to the other set. We applied this method to four tibias of three patients without any complications. The tension of the tissues was monitored using a pressure sensor built into a Hifixator to prevent the tissues from overstretching. During and after the correction, the tension of the tissue was maintained at less than before the correction.     

Hinged Ilizarov external fixation for correction of antebrachial deformities

OBJECTIVE: To evaluate hinged circular external fixation for correction of antebrachial deformities in dogs. STUDY DESIGN: Uncontrolled clinical trial. ANIMAL POPULATION: Seven client-owned dogs. METHODS: Six dogs had one radius corrected and one dog had both radii corrected. Preoperative planning included measurement of the craniocaudal and mediolateral angular deformities, rotational deformity, length deficit, origin of deformity, graphical or mathematical determination of the amplitude and direction of the actual limb deformity, and frame assembly. RESULTS: Preoperatively, function and cosmesis were assessed to be fair to poor in all dogs. Deformity correction started 48 to 60 hours postoperatively and ranged from 0.46 mm to 1.36 mm twice daily. Hospitalization time ranged from 4 to 6 days. Corrections were mostly made by the owners, at home. Lengthening and angular correction ranged from 3 to 38 mm and 18 degrees to 48 degrees. Mean residual deformities were 2.7% of radial length and 2.7 degrees. The time duration with the circular external fixators in place ranged from 29 to 71 days. Two additional surgeries were necessary in one dog because of wire breakage. Mean follow-up was 40 months. Long-term function and cosmesis were good to excellent in all dogs. CONCLUSION: Although complications were present in six of seven dogs, the outcome of hinged Ilizarov external fixation was successful in all dogs treated for deformities of the antebrachium. CLINICAL RELEVANCE: Despite complex preoperative planning, the placement of hinged circular external fixators is straightforward, and allows precise correction of complex antebrachial deformities with minimal tissue trauma.     

Monitoring fracture site properties with external fixation

An in-vitro system has been devised to monitor the properties of an idealized fracture site immobilized with a Hoffman-Vidal external fixator. A dial gage was used to measure the relative pin displacements under controlled axial loading. The displacement measurements were then used in conjunction with a finite element model to predict the modulus of an idealized fracture site. Five fracture sites made of neoprene disks of different mechanical properties were monitored in order to simulate the increasing modulus of a healing fracture. Good agreement was observed between directly measured mechanical properties of the neoprene and those inferred from the combined finite element and pin displacement tests.     

Treatment of nonunion of the humerus using the Ilizarov external fixator

Ilizarov's method of monofocal compression was used in 30 humeri with a diaphyseal pseudarthrosis. Twenty-one patients had previous surgery but had loosening of the osteosynthesis material. Nine patients initially were treated with a hanging cast, resulting in interfragmentary distraction. Fourteen nonunions were hypertrophic, and 16 were atrophic, of which six were infected. A complete circular frame was used only in the first nine patients, whereas the remaining 21 patients were treated with the modified semicircular fixator. Union was obtained in all but two patients, with an average consolidation time of 4.5 months (range, 2.5-10 months). No patient required additional bone grafting. Apart from superficial pin tract infection seen in most of the patients, three had a minor temporary sensory neurologic problem. Four patients experienced a second fracture after removal of the fixator that required a second application of an Ilizarov frame. Although similar results with regard to union are reported after plate osteosynthesis, there was no radial nerve palsy or deep infection in this series, indicating that the treatment by the Ilizarov technique is associated with less complications. The authors' findings suggest that the Ilizarov method is a reliable treatment for humeral nonunions, even after multiple previous operations or in the event of infection.     

Mitochondrial DNA polymorphism in Jindo dogs

Mitochondrial DNA (mtDNA) polymorphism was studied in 21 Jindo dogs inhabiting Jin Island off the Korean peninsula. The polymorphism was analyzed with 10 restriction endonucleases that recognize six base pairs. The sizes of the mtDNA fragments produced by digestion using each endonucleases were separated by agarose gel electrophoresis, and the polymorphisms were detected with Japanese mongrel dog mtDNA as a probe. The mtDNA polymorphism in Jindo dogs was observed with four restriction endonucleases, Apa I, EcoR V, Hinc II, and Sty I. However, no polymorphism was detected with BamH I, Bgl II, EcoR I, Hind III, Pst I, or Xba I. The observed restriction endonuclease morphs were classified into 4 types of distinct cleavage patterns. The average number of nucleotide substitutions per nucleotide site in Jindodogs was estimated to be 0.0086. By UPG phylogenetic analysis, the 4 mtDNA types showed only one cluster. This suggests that Jindo dogs have not diverged from the other cluster up to the present and the species is considerably pure.     

Histomorphometric and angiographic analysis of the humerus in pigeons

OBJECTIVE: To identify the vascular supply and resorption/formation activity of the humerus of pigeons. DESIGN: Pigeons were injected with the fluorochrome label oxytetracycline and, 5 days later, with the label calcein. 5 days after administration of the second fluorochrome, a wing from each bird was infused with a microparticle barium solution immediately after euthanasia and the chosen humerus was prepared for angiography while the opposite was prepared for histomorphometry. ANIMALS: 17 nine-month-old pigeons, consisting of 9 male and 8 female birds. PROCEDURE: At euthanasia, 1 wing was chosen for infusion and the barium solution was injected through a catheter in the brachiocephalic artery. Both humeruses were harvested. The infused humerus was decalcified, radiographed, and sectioned for H&E staining. The opposite humerus was sectioned and measured by use of a morphometric analyzing system to determine cross-sectional area, endosteal and periosteal perimeters, and percentage of perimeter containing a single and/or double label. RESULTS: All pigeons had an intramedullary arterial supply. The bones had a quiescent appearance histologically, consisting principally of lamellar bone with few osteospecialized cells, resorption surfaces, or osteons. Less than 10% of either the periosteal or endosteal surface acquired a fluorochrome label. CONCLUSIONS: The intramedullary vascular supply of the humerus is similar in structure to the vascular supply to mammalian bones. The humerus is, however, a quiescent bone in the sexually mature pigeon, with little remodeling activity present. CLINICAL RELEVANCE: The intramedullary blood supply may have an important role in the healing of humeral fractures in avian species.     

Role of saphenous vein surgery in the treatment of venous ulceration

We present 19 ray lengthenings in 14 patients done with a small external fixator. In six cases the thumb was lengthened and in the other 13 cases, other digital rays. The most frequent reason for lengthening was an amputation sustained in a work accident. All the lengthenings were done by an osteotomy and subsequent gradual distraction with a small external fixator. The mean lengthening achieved was 20 mm (range, 0-32). An iliac-crest graft was needed in nine cases, corrective osteotomy in five cases and a deepening of the web in the six cases of thumb lengthening. In five cases an additional technique was needed to achieve bony consolidation. We have analysed the functional results and the ability to perform activities of daily living and resume employment. Although most of the patients had multiples injuries, the results have been very favourable, achieving a very high level of patient satisfaction.     

Production and cross-reactivity patterns of a panel of high affinity monoclonal antibodies to Vibrio cholerae O139 Bengal

Abnormal brain stem auditory-evoked responses (BAER) were recorded on 14 dogs with brain lesions confirmed by necropsy (n = 13) or magnetic resonance imaging and surgical biopsy (n = 1). Lesions included brain stem or cerebellar tumors (6 dogs), brain stem trauma (1 dog), forebrain tumors (3 dogs), hydrocephalus (2 dogs), granulomatous meningoencephalitis (1 dog), and meningoencephalitis (1 dog). Five affected dogs were comatose at the time of recording. BAER abnormalities could be classified as (1) absence of some or all of waves I to V, (2) increased latencies, with wave V being most frequently affected, or (3) a reduction in the amplitude ratio of waves V/I.     

External fixation for pelvic ring disruptions

The application of external fixation for acute treatment of unstable pelvic fractures can be a lifesaving procedure; however, it must be coordinated with other efforts of the trauma team. The patient with a pelvic fracture must be adequately resuscitated and carefully evaluated. This evaluation includes a careful physical examination and radiographic studies, which include plain films and computerized tomography. A proper evaluation enables classification of the pelvic injury and appropriate selection of patients that require acute pelvic external fixation. In this article, both open and percutaneous techniques for pin placement and fixator frame configurations are discussed.     

Clinical results of primary intramedullary osteosynthesis with the unreamed AO/ASIF tibial intramedullary nail of open tibial shaft fractures

From 04/91 to 06/96 sixty-nine open fractures of the tibia were primarily treated on the day of the accident with unreamed nailing (UTN, Synthese). The distributions of fracture type according to the AO classification and of soft tissue injury according to Gustilo were as follows: fracture type: A: 28%, B: 52%, C: 20%; soft tissue injury: I: 30%, II: 28%, IIIA: 12%, IIIB: 12%, IIIC: 6%. Of the 65 fractures assessed 46 (71%) healed within 18 weeks without secondary intervention. There was delayed healing in three fractures requiring secondary conversion to reamed nailing. Eight fractures (12%) developed pseudarthrosis of which five (8%) healed uneventfully. Deep infections was manifest in four fractures (6%). Three of these infections developed after secondary intervention to treat pseudarthrosis. Seven of the eight pseudarthroses and three of the four infections healed eventually. Revision procedures were necessary in 11 patients (17%) to deal with disturbed fracture healing or infection (10 reamed nailing procedures, three cancellous bone grafts, and one of each of the following: sequestrectomy, fibular osteotomy, plate fixation, external fixator, monorail procedure). The results show that the same good infection rates were achieved for the UTN as for the external fixator. The advantages of the UTN are, however, a lesser need for secondary intervention and greater patient comfort. Therefore, we find the UTN to be a good alternative to the external fixator in the treatment of open fractures with severe soft tissue damage.     

The effect of acute, unilateral transverse venous sinus occlusion on intracranial pressure in normal dogs

Lateral rostrotentorial and caudal suboccipital approaches to the brain were performed on six beagles. Intracranial pressure (ICP) was measured as the two craniectomies were connected by removing the bone of the nuchal crest and occluding the transverse venous sinus. Intracranial pressure remained constant after acute occlusion of the sinus with bone wax and there was no gross evidence of brain edema. All six dogs survived the surgery and five dogs survived for a minimum of 3 months. One dog died acutely during the postoperative period. The exact cause of the cerebellar hemorrhage and infarction found at necropsy in the latter dog was not evident. Anemia occurred in three of the six dogs as a result of intraoperative hemorrhage. All dogs surviving the perioperative period had mild, transient hypermetria and conscious proprioceptive deficits, but were neurologically normal 72 hours after surgery. Results of this study indicate that acute, unilateral transverse sinus occlusion is possible without an increase in ICP. The ability to do this allows access to the rostral aspect of the ipsilateral cerebellum and brain stem.     

Angiotensin II inhibits long-term potentiation within the lateral nucleus of the amygdala through AT1 receptors

We have treated 16 patients with recurrent complex elbow instability using a hinged external fixator. All patients had instability, dislocation or subluxation of the ulnohumeral joint. The injuries were open in eight patients and were associated with 20 other fractures and five peripheral nerve injuries. Two patients had received initial treatment from us; 14 had previously had a mean of 2.1 unsuccessful surgical procedures (1 to 6). The fixator was applied at a mean of 4.8 weeks (0 to 9) after the injury and remained on the elbow for a mean of 8.5 weeks (6 to 11). After treatment we found the mean range of flexion-extension to be 105 degrees (65 to 140). At a final follow-up of 23 months (14 to 40), the mean Morrey score was 84 (49 to 96): this translated into one poor, three fair, ten good and two excellent results. Complications included one fractured humeral pin, one temporary palsy of the radial nerve, one recurrent instability, one wound infection, one severe pin-track infection and one patient with reflex sympathetic dystrophy. Although technically demanding, the use of the fixator is an important advance in the management of recurrent complex elbow instability after failure of conventional treatment.     

Mechanical characterization of a totally intramedullary gradual elongation nail

An intramedullary gradual elongation nail (Albizzia) capable of fulfilling the function of traditional intramedullary nails while providing the gradual, controlled distraction of an external fixator was designed for progressive lengthening of lower limbs. In this study, the biomechanics of the gradual elongation nail were compared with several intramedullary nails: Grosse & Kempf, Russell-Taylor, AO, and Laffay. Bending stiffness, torsional stiffness, ultimate bending strength, and torsional strength were determined using the American Society for Testing and Materials standard F383-73 as a guide. The results show that in unextended and elongated conditions, the gradual elongation nail has torsional stiffness (1-5 Nm2) comparable with the AO nail (2 Nm2) and bending stiffness (41-89 Nm2), ultimate bending (246 Nm), and torsional (28-37 Nm) strengths within the ranges obtained for other intramedullary nails (27-105 Nm2, 167-298 Nm, and 2-100 Nm, respectively). Additionally, the low torque required to lengthen the device under a 500 N load (3 Nm) and the low longitudinal stiffness because of the active dynamization system with bimodal load deformation characteristics (80-120 N/mm initial, 600-800 N/mm secondary) produce a device with almost no torsional and longitudinal stress shielding. From a biomechanical point of view, this single, completely implantable device is a safe, viable, and efficacious alternative to external fixation for progressive lengthening of lower limbs.     

Dynamic external fixation for distal radius fractures

Thirty adult patients with closed comminuted and mostly intraarticular fractures of the distal radius were treated by closed reduction and immobilization with a dynamic external wrist fixator during a 2-year period. In 13 patients with severely comminuted and unstable fractures, additional Kirschner wires were used. After 10 to 14 days of rigid fixation in neutral position, the motion element was unlocked to allow up to 30 degrees flexion. Six weeks later, the fixator was removed. The patients then were observed for an average of 24 weeks. An excellent functional outcome was seen in 6 patients (20%), a good outcome in 20 patients (67%), and a fair outcome in 4 patients (13%). Anatomically, 15 patients (50%) had an excellent result, 14 (47%) a good outcome, and 1 (3%) a fair outcome. Only minimal loss of reduction averaging 1 degree palmar tilt was seen during mobilization. There were 2 major complications: 1 deep Kirschner wire tract infection and 1 index metacarpal fracture. Minor complications such as sensory disturbances and pin tenderness were present but recovered completely after removal of the fixator. This study provides promising data and offers an alternative method in the treatment of distal radius fractures with severe comminution. In cases with postreductive unstable fragments, additional Kirschner wires should be used to allow early mobilization of the wrist.     

Is the static external fixator a suitable method in the treatment of multi-fragmented fractures of the distal radius?

We present a retrospective study of 21 patients treated with an external fixator for comminuted fractures of the distal radius from May 1993 until May 1994. Mean follow-up was 14.5 months after operation. The 21 patients were on average 59 years old. The distal radius fractures were classified according to the AO: Type A2 (four times), Type A3 (two times), Type C1 (one time), C2 (nine times), C3 (five times). We mounted the external fixator generally in a static way. After two weeks it was dynamized. The fixator was removed after four to at least six weeks. An additional osteosynthesis with Kirschner wires was performed in twenty cases. Three times we added a primary cancellous bone graft, in one case an implantation of Endobone was used.