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Objectives: The aim of this study was to report the clinical outcomes in a series of traumatic elbow luxations in cats treated with closed reduction and a temporary transarticular type II external skeletal fixator (ESF)., Methods: A retrospective review was conducted of traumatic elbow luxation cases in cats at two referral centres. Data collected included signalment, history, clinical assessment, radiographic findings, surgical procedures and complications. Short-term follow-up was based on clinical evaluations at 2 and 6 weeks postoperatively. Long-term follow-up was based either on a telephone interview with the owner or a clinical evaluation., Results: Eight cats were included. Five cats experienced lateral elbow luxation, while three cats had medial elbow luxation. All cats with medial elbow luxation exhibited radiographic signs of medial humeral epicondylitis. The median age was 9 years (range 3-15). The elbow luxation was treated by closed reduction and percutaneous placement of a temporary transarticular type II ESF, which was removed 2 weeks postoperatively. Two minor complications were recorded. Elbow reluxation and major complications were not encountered. The 6-week postoperative evaluation and long-term follow-up revealed a lameness of grade 1 in 1/8 cats and 0 in the remainder. Elbow range of motion was normal in all cats., Conclusions and Relevance: None of the cases treated with this protocol experienced recurrence of elbow luxation. All cats demonstrated an excellent outcome based on the lameness score, the low complication rate and the follow-up telephone interview. The technique is minimally invasive and carries a low incidence of complications. Concurrent orthopaedic disease, such as medial humeral epicondylitis, may predispose to medial elbow luxation., Competing Interests: Conflict of interestThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Aims: To provide veterinarians with confidence when using a commercially available epoxy resin in external skeletal fixators (ESF), testing was conducted to determine exothermia during curing of the epoxy resin compared to polymethylmethacrylate (PMMA), the hardness of the epoxy resin as a bar over 16 weeks, and the strength of the epoxy resin bar compared with metal clamps in similarly constructed Type 1a ESF constructs simulating the repair of feline long bone fractures., Methods: Exothermia of the epoxy resin during curing was tested against PMMA with surface temperatures recorded over the first 15 minutes of curing, using four samples of each product. The hardness of 90 identical epoxy resin bars was tested by subjecting them to cyclic loads (1,000 cycles of 20.5 N, every 7 days) over a 16-week period and impact testing 10 bars every 2 weeks. Ten bars that were not subjected to cyclic loads were impact tested at 0 weeks and another 10 at 16 weeks. Strength of the epoxy resin product, as a bar and clamp composite, was tested against metal SK and Kirschner-Ehmer (KE) clamps and bars in Type 1a, tied-in intramedullary pin, ESF constructs with either 90° or 75° pin placement, subjected to compressive and bending loads to 75 N., Results: The maximum temperature during curing of the epoxy resin (min 39.8, max 43.0)°C was less than the PMMA (min 85.2, max 98.5)°C (p<0.001). There was no change in hardness of the epoxy resin bars over the 16 weeks of cyclic loading (p=0.58). There were no differences between the median strength of the epoxy resin, SK or KE ESF constructs in compression or bending when tested to 75 N (p>0.05). Stiffness of constructs with 75° pin placement was greater for SK than epoxy resin constructs in compression (p=0.046), and was greater for KE than epoxy resin constructs in bending (p=0.033)., Conclusions: The epoxy resin tested was found to be less exothermic than PMMA; bars made from the epoxy resin showed durability over an expected fracture healing timeframe and had mechanical strength characteristics comparable to metal bar and clamp ESF constructs., Clinical Relevance: The epoxy resin ESF construct tested in this study can be considered a suitable replacement for SK or KE ESF constructs in the treatment of feline long-bone fractures, in terms of mechanical strength.

Objectives: The objective of this study was to quantify complications associated with external skeletal fixators (ESFs) in cats and to identify potential risk factors., Methods: A retrospective review of medical records and radiographs following ESF placement was performed., Results: Case records of 140 cats were reviewed; fixator-associated complications (FACs) occurred in 19% of cats. The region of ESF placement was significantly associated with complication development. Complications developed most frequently in the femur (50%), tarsus (35%) and radius/ulna (33%). Superficial pin tract infection (SPTI) and implant failure accounted for 45% and 41% of all FACs, respectively. SPTI occurred more frequently in the femur, humerus and tibia, with implant failure more frequent in the tarsus. No association between breed, age, sex, weight, fracture type (open vs closed), ESF classification, number of pins per bone segment, degree of fracture load sharing, and the incidence or type of FAC was identified. No association between region of placement, breed, age, sex, weight, fracture type (open vs closed), ESF classification, number of pins per bone segment, fracture load sharing and the time to complication development was identified., Conclusions and Relevance: Complication development is not uncommon in cats following ESF placement. The higher complication rate in the femur, tarsus and radius/ulna should be considered when reviewing options for fracture management. However, cats appear to have a lower rate of pin tract infections than dogs.

Objective: To report our experience with the use of contoured mini circular transarticular external skeletal fixators for the management of traumatic tarsal luxations in 15 cats., Materials and Methods: Fifteen cats with traumatic tarsal joint luxation treated by using mini circular transarticular external fixators with available clinical records and complete clinical and radiographic follow-up of at least 30 weeks duration were included in the study. Data collected were the signalment, history, type of injury, concomitant injury, frame configuration, stabilization technique, duration of the surgery, time to first use of the operated limb, fixator removal time, complications, final outcome and follow-up., Results: The surgical procedure chosen was based on the type of luxation; partial tarsal arthrodesis was performed in 10 cases, tarso-crural stabilization in four cases, and pantarsal arthrodesis in three cases. Five cats started to use the operated limb immediately after recovering from anaesthesia. In the other 10 cats, time to first use ranged from one to four days (mean 2 days). In one case, early pin loosening due to half pin fixation bolt failure was observed as a postoperative complication. Fixator removal time ranged from 24 to 60 days (mean 45 days). Functional outcome was excellent in 15 cats and good in two., Clinical Relevance: This is a preliminary report about the treatment of tarsal luxations with a mini circular transarticular external fixation system in which early postoperative and long-term results seem to be favourable.

Objectives: To compare the outcome of three different fixation methods and to determine prognostic factors in cats with diaphyseal femoral fractures., Methods: Retrospective analysis of case records of cats with diaphyseal femoral fractures surgically corrected using external fixators, bone plate or plate-rod construct. Outcome was evaluated by estimating the time to bone healing and by calculating the complication rate., Results: In total, an external fixator was used in 30 cases, a bone plate in 20 cases and a plate-rod construct in 56 cases. All methods were successful in achieving bone healing without significant differences. There was a significant difference between the categorized complication rates between the treatment groups. The external fixation group had the most complications overall. When only the major and catastrophic complications were taken into account, it had the fewest complications. The plate-rod construct had the fewest complications overall, with most being major complications. The bone plate group had a complication rate between that of the external fixation and plate-rod construct groups. It had the most catastrophic complications in relative terms., Clinical Significance: There was no statistically significant difference in the time to achieve bone healing but there was a significant difference in categorized complication rates between the groups., (© 2013 British Small Animal Veterinary Association.)

Objectives: To report on a series of dogs and cats with long bone fractures that occurred as a direct consequence of linear external skeletal fixation (ESF) application., Methods: Retrospective study. Data from the medical records and radiographs of canine (n = 4) and feline (n = 7) cases were collected from three referral and three first opinion practices in the UK (1999 to 2011)., Results: Long bone fractures occurred following the application of linear ESF either while the ESF was in situ or after removal. All fractures occurred through either a pin tract or an empty drill hole. Pins associated with ESF-related fracture tended to be in the higher end of the recommended size range. The majority of cases had additional complicating factors such as multiple injuries, revision surgery, poor owner compliance with postoperative exercise restriction and the presence of empty drill holes., Clinical Significance: In cases with features that could complicate outcome, careful attention should be paid to recommendations for ESF application. Leaving empty drill holes is suboptimal. The retrospective nature of the study, low numbers of, and diversity amongst, cases should be taken into consideration when interpreting the results from this study., (© 2012 British Small Animal Veterinary Association.)

Objectives: Intra-condylar humeral fracture with supracondylar comminution in cats is rare, and the stabilisation for such fractures is challenging. The purpose of our study was to describe the use of a hybrid external skeletal fixator, and to report the complications and outcomes of this surgical technique., Methods: A retrospective review was performed of clinical, radiographic and surgical records of all cats with intra-condylar humeral fractures and non-reconstructable supracondylar comminution stabilized by linear- circular external skeletal fixator in two institutions between January 2005 and March 2010., Results: Four cats met the inclusion criteria of the study. All cases achieved fracture union and clinical outcome was considered excellent at the time of the final assessment (11 - 24 weeks)., Clinical Significance: This study demonstrates that a linear-circular fixator system can be used successfully in the management of intra-con dylar humeral fractures with non-reconstructable supracondylar comminution in cats.

Objectives: To report the surgical technique and short-term radiographic and functional outcome data for a series of client owned, small breed dogs and cats treated for traumatic craniodorsal coxofemoral luxation using open reduction and internal fixation with the Arthrex Mini TightRope (mTR) and TightRope (TR) systems., Methods: Data were collected retrospectively from the clinical case records, including the initial clinical and radiographic findings, surgical technique, and postoperative short-term clinical and radiographic data. Functional data collected after the six weeks reassessment were obtained via owner questionnaire., Results: Four cats (mTR = 4) and five small breed dogs (mean weight 15 kg; TR = 4, mTR = 1) were included. Median time to postoperative weight bearing was one day. Median lameness score at six weeks postoperatively was 0 out of 5. Coxofemoral joint congruity was radiographically confirmed at the six weeks postoperative visit. Telephone follow-up (at a median of 16 weeks) revealed all animals had returned to their previous level of activity. Complications were minor, and limited to postoperative swelling (n = 1)., Clinical Significance: Clinical use of the Arthrex Mini TightRope and TightRope systems can be recommended for traumatic craniodorsal coxofemoral luxation in this novel application as short-term results are at least comparable to existing surgical techniques. Long-term follow-up studies are needed.

Objective: To report the successful use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in the treatment of an antebrachial non-union, secondary to gunshot fracture, stabilized with circular external fixation in a cat., Procedure: Following a diagnosis of a highly comminuted gunshot fracture of the distal right radius and ulna, the fracture was stabilized with a circular external fixation. A two-ring frame was placed in closed fashion., Results: The skin wound healed uneventfully by second intention in 21 days. Twenty-eight weeks after external fixation, bone healing was absent. 0.8mL of 0.2mg/mL of rhBMP-2 in two collagen sponges was placed in the bone defect. Eight weeks after rhBMP-2 implantation, an early bone healing response was noted on radiographic evaluation. Sixteen weeks after rhBMP-2 implantation, fracture union was achieved., Discussion: To the authors' knowledge, 160 μg is the lowest reported dose of rhBMP-2 that leads to bony union in a cat. However as an individual case study, this report can not be used as evidence that rhBMP-2 at this lower dose is appropriate for use in all cats. Further studies are needed to establish the minimum efficient dose of rhBMP-2 in cats.

The objective of this retrospective study was to report the clinical use, advantages, disadvantages, complications and outcome of an epoxy putty external skeletal fixator (EPESF) used for the repair of fractures of all four main metatarsal or metacarpal bones in a single limb in 11 dogs and 11 cats. The aim of this technique was to achieve satisfactory alignment of the proximal and distal joints and the digits, rather than anatomical reconstruction of the metacarpal/metatarsal bones themselves. All of the cases achieved fracture union and they all recovered fully without any residual lameness.

Case History and Clinical Findings: Eight feline patients with fractures of the femur, tibia or humerus were presented non-weight-bearing, with varying degrees of soft tissue and concurrent injury. Five fractures were comminuted, two were open fractures and there was one malunion., Treatment: Fracture repair was performed in each case using a low-cost resin-acrylic external skeletal fixator (ESF). An open, limited open, or 'open but do not touch' (OBDNT) approach allowed intra-medullary (IM) pinning of the major fragments, establishing axial alignment and countering bending stress. Application of a unilateral, uniplanar (Type IA) ESF using small diameter half-pins provided stabilisation against rotational and compressive forces. The half-pins and IM pin (tied-in) were incorporated into a composite bar with the resin-acrylic. The single humeral construct incorporated a transcondylar pin into a Type I-II design., Results: Seven cats, including all five comminuted fractures, had uncomplicated fracture healing. Median time to complete removal of the construct was 7 (range 5-12) weeks. In the eighth cat, an open fracture developed into a non-union, which required revision with a plate and bone graft. This cat and six others available for follow-up (median 6 months) were reported by their owners to enjoy normal activity. Two had a mild, intermittent lameness, one had a mild but persistent lameness, and four were sound. Six out of seven owners rated the appearance of their pet's limb as normal., Clinical Relevance: The resin-acrylic ESF/tied-in IM pin construct was versatile and lightweight and allowed even highly comminuted non-load-sharing fracture configurations to be stabilised successfully using a biological strategy. Failure of the pin/acrylic interface did not occur and the frames provided sufficient strength as evidenced by healing without failure of the bar in these cases. A resin-acrylic ESF construct is inexpensive and affords the occasional orthopaedist the means to provide rotational stability when IM pinning has been used as the primary mode of fracture repair for short-oblique and transverse fractures. An extensive and costly clamp/bar inventory is not required, and there is greater flexibility for the orientation and placement of fixation pins than allowed by traditional linear bar systems.

Objectives: To describe placement of hinged transarticular external fixation (HTEF) frames and evaluate their ability to protect the primary repair of unstable joints while allowing joint mobility in dogs and cats., Design: Retrospective study., Animals: 8 cats and 6 dogs., Procedure: HTEF frames were composed of metal or epoxy connecting rods and a hinge. Measurements of range of motion of affected and contralateral joints and radiographs were made after fixator application and removal., Results: 9 animals (4 cats and 5 dogs) had tarsal and 5 (4 cats and 1 dog) had stifle joint injuries. Treatment duration ranged from 45 to 100 days (median, 57 days). Ranges of motion in affected stifle and tarsal joints were 57% and 72% of control while HTEF was in place and 79% and 84% of control after frame removal. Complications were encountered in 3 cats and 2 dogs and included breakage of pins and connecting rods, hinge loosening, and failure at the hinge-epoxy interface., Conclusions and Clinical Relevance: HTEF in animals with traumatic joint instability provided adjunctive joint stabilization during healing and protection of the primary repair and maintained joint motion during healing, resulting in early weight bearing of the affected limb.

The humeri of eleven feline cadavers were dissected and safe anatomical areas for placing external skeletal fixator pins were determined. Relevant measurements taken of the humeral condyle enabled a determination of a safe pin diameter range of 1.5 to 2.2 mm for transcondylar pins. Further anatomical measurements allowed recommendations to be made to angle pins in the distal humerus in a distolateral proximomedial direction so that the ESF pin penetrates the for cortex at least 20 mm proximal to the medial epicondyle in order to avoid pin penetration of the supracondylar foramen. Cross sections taken of the distal humerus revealed that passage of an IM pin into the medial aspect of the humeral condyle was possible in less than half the cases.

The healing of 62 cases of radial and tibial fractures treated with low-stiffness Kirschner-Ehmer external skeletal fixation frames (frame types 1a, 1a plus intramedullary pin [1aIMP], 1b and 2b) was evaluated. The mean time to clinical union was 65 days. All cases treated with 1b, 2b or 1aIMP frames healed. Four of 25 cases treated with 1a frames failed to heal due to premature pin loosening; these failures were in heavier patients than 1a cases which healed (P=0.041). Complications occurred in 40 of 62 cases, and were more common in cases treated with type 2b frames. Pin loosening was the most frequent complication (35 cases) and most commonly involved the most proximal pin (P<0.001). In type 2b frames, full pins loosened more frequently than half pins (P<0.001). This study indicates that canine and feline fractures can heal readily when treated with these frames, suggesting that more rigid type 2a or type 3 frames are unnecessary in the majority of cases. Increased morbidity compared with the use of more rigid frames need not be expected, but 1a frames should be avoided in heavier patients.

Complex long-bone fractures with short juxta-articular fracture segments can be difficult to manage. Recently, IMEX Veterinary, Inc., began producing titanium hybrid rods that can be secured to ring components of the IMEX circular external skeletal fixation system to create SK-circular hybrids. In this case series, SK-circular hybrids were used to stabilize long-bone fractures (two femoral, one humeral, and three tibial fractures) with short distal bone segments in three dogs and three cats with body weights ranging from 1.9 to 15 kg (mean, 6.7 kg; median, 5.4 kg). Although three cases required surgical revision, animals ambulated well and all fractures obtained union. Time to radiographic union ranged from 62 to 137 days (mean, 90 days; median, 84 days). The functional outcome was considered excellent in all six cases.

Objective: Evaluate the effects of varying ring diameter, wire tension, and wire-divergence angle on the axial stiffness characteristics of circular external skeletal fixator single-ring constructs. Study Design-Biomechanical evaluation using circular fixator components and a Delrin cylinder bone model., Methods: Single ring constructs using two 1.6 mm diameter Kirschner wires to secure a 19 mm Delrin cylinder centered within the ring were examined. Component variables evaluated were ring diameter (50 mm, 66 mm, 84 mm, and 118 mm), wire-divergence angle (30 degrees, 60 degrees, and 90 degrees ), and wire tension (0 kg, 30 kg, 60 kg, and 90 kg). A total of 48 constructs were examined. Rings were rigidly mounted on a universal testing system and the cylinder loaded in axial compression (7.4 N/s) to 220 N. Load/displacement curves were analyzed to determine the following: the displacement (mm) that occurred before the slope of each load/displacement curve became linear, the stiffness (N/mm) of the linear portion of each load/deformation curve, and the total displacement (mm) produced at maximal load. Least-squares linear regression was used to model response variables as linear functions of ring diameter, wire divergence angle, and wire tension. Three-way interactions and 2-way interactions among independent component variables were evaluated first in the modeling process and included in a best model if response variables were found to have statistically significant regression coefficients. The regression coefficients and corresponding standard errors and covariances were used to estimate the maximal effect and standard error attributable to wire divergency angle (change from 30 degrees to 90 degrees ) and wire tension (change from 0 to 90 kg) for each ring diameter., Results: All load/deformation curves had an initial exponential increase in stiffness, with the slope becoming linear at higher loads. The exponential phase was more pronounced in larger-diameter ring constructs and was mitigated by tensioning the wires. Ring diameter had the greatest influence on displacement that occurred before the curve became linear (semipartial r(2) [sp-r2] = .89), stiffness (sp-r2 = .94), and total displacement (sp-r2 = .93). Wire tension exerted a smaller influence on displacement that occurred before the curve became linear (sp-r2 =.06), stiffness (sp-r2 = .03), and total displacement (sp-r2 = .05). Wire divergence angle had a nominal effect on displacement that occurred before the curve became linear (sp-r2 = .0001), on stiffness (sp-r2 = .004), and on total displacement (sp-r2 =.003)., Conclusions: Ring diameter had a profound effect on the axial stiffness characteristic of single ring constructs. Tensioning of the fixation wires can improve the axial stiffness characteristics of these constructs, particularly in larger diameter ring constructs, by mitigating the initial exponential phase of the load/deformation curve. Wire divergence angle had only a nominal differential effect on axial stability., Clinical Relevance: Understanding how individual component variables and their interactions influence bone segment stability should help surgeons to optimize interfragmentary strain. Tensioning fixation wires is probably unnecessary in 50 mm diameter ring constructs, but assumes greater importance as ring diameter increases., (Copyright 2001 by The American College of Veterinary Surgeons)

While the use of external skeletal fixation was once associated with substantial postoperative morbidity, clinical and experimental studies have led to technological advances and modifications in application techniques that have greatly improved the results obtained with this treatment modality. The past decade saw numerous advances in external skeletal fixator implants, components and instrumentation, including improvements in fixation pin design, and the development of new linear external skeletal fixation systems and economical circular external skeletal fixation systems specifically engineered for use in dogs and cats. In addition, a greater understanding of fixator biomechanics and the pathobiology of the bone-fixation pin interface have improved fixator application practices. This article reviews many of the more significant recent advances in external skeletal fixation.

Seventeen cats with injuries involving the distal tibia, talocrural joints, tarsus and metatarsus were treated with contoured connecting bar transhock external fixators as either primary or secondary fixation. The assemblies stabilised all the injuries successfully. Fracture union was achieved in 11 out of 12 cases. Excellent results were achieved in eight cats and the outcome was satisfactory in a further five. Those cats with injuries involving talocrural joint luxation with displacement and significant periarticular soft tissue disruption had poorer long-term results. Complications occurred in seven cases.

Five cats with fracture of the talar neck were treated using external skeletal fixation (ESF). In four of the cases, ESF was the only fixation technique used and this was applied in a closed manner coupled with traction. In the remaining cat, ESF was used in combination with a lag screw. All the fractures eventually healed, demonstrating that ESF provided a simple and effective method of treatment for these cases.

Extra-articular suturing techniques and transarticular external skeletal fixators were used to repair traumatic luxation of the stifle joint in four cats. Rupture of the cranial cruciate, caudal cruciate and medial collateral ligaments, together with injury to one or both menisci, were the most common injuries observed. The method of stifle repair was successful in all cases, but serious complications occurred when cats with transarticular external fixators were not kept confined indoors. Complications consisted of pin loosening and disruption of the fixator, or fractures through proximal or distal pins. Transarticular external skeletal fixation was considered to be a simple and effective method of maintaining short-term joint stability to allow healing of injured soft tissue structures. The apparatus facilitated early weightbearing and, on removal, allowed for the return of near-normal stifle function. Careful pin insertion and owner compliance in enforcing confinement are essential in minimising complications associated with immobilising the stifle joint using transarticular external skeletal fixation.

Circular external skeletal fixation (CEF) has been used in recent years to treat acute and chronic fractures and bone deformities, to stabilize joints while maintaining range of motion, and to perform arthrodeses and limb-sparing in dogs. Dr. Ilizarov defined the general principles and methods of CEF. This article reviews these principles. It also describes the indications, preoperative planning, surgical placement, postoperative management, clinical results, and complications of CEF used to treat fractures in dogs.

Linear external skeletal fixators offer some unique advantages over other fixation systems; they are biomechanically versatile, minimize surgical trauma to the fracture environment, and allow for simple staged disassembly to help promote bone healing. Historically, the use of linear external skeletal fixators has been reported to result in numerous complications, primarily related to the pin-bone interface. External skeletal fixators have experienced a resurgence in the past two decades. Increased knowledge of proper pin insertion techniques and advancements in pin design have greatly enhanced the longevity of the pin-bone interface, resulting in fewer complications. This article reviews some of the potential advantages of linear external skeletal fixators and principles of application to help strengthen the pin-bone interface and minimize complications.

We report here a review of 33 cases of isolated tibial fractures (i.e., with the fibula intact) in 10 cats and 23 dogs, presented to four orthopaedic referral clinics. The purpose of this study was to identify factors to be considered when selecting the therapy for an isolated tibial fracture in cats and dogs. The animal species, the size of the dog breed, the age of the patient, the type of tibial fracture, the presence of an additional fracture, the treating clinic, the therapy applied, and the results after treatment were taken into account. A step-backward logistic regression analysis was applied to the series of cases to examine possible relations among the covariates. Treatment outcome was found by logistic regression analysis to depend significantly (P < or = 0.05) on age, the presence of an additional fracture, and the therapy applied. No other relations were present between the covariates. In the immature cat or dog with an isolated tibial fracture, treatment by external splinting has a good prognosis. In the mature cat or dog with an isolated tibial fracture, rigid fixation by external fixator or internal fixation is the method of choice.

Thirteen feline humeral fractures were stabilized using external skeletal fixation alone or in combination with supplementary devices. Eleven of the 13 fractures healed. Pins placed in the distal humerus should be angled to avoid the supracondylar foramen and radial nerve. An intramedullary pin in combination with external skeletal fixation is indicated for mildly comminuted reconstructable fractures. For severely comminuted humeral fractures, closed application of an external skeletal fixator may be preferable to open reduction and internal fixation to provide healing and is recommended as an alternative to amputation.

An alternative method for external coaptation of fractures in young animals utilizes tongue depressors incorporated in a bandage consisting of a thick layer of cotton padding, gauze bandaging, and adhesive tape. This method was used in 13 cases with fractures of the tibia or the radius and ulna, some of which were open. Five cases (four dogs and a cat) had displaced fractures, and eight cases had either nondisplaced or only mildly displaced fractures. Size of the animal was not considered a limiting factor. Bandages were examined periodically. All fractures healed uneventfully, and the splints were removed 21-to-44 days after application. This method of external coaptation proved to be easy to apply and modify during the healing process and was applicable to a wide variety of fractures with good results.

This paper reports the results of fixation of 35 femoral fractures in cats using an external skeletal fixator alone or in combination with supplementary devices. All the fractures healed. The average time to fixator removal was eight weeks and two days. The external skeletal fixator offers a method of repairing many types of femoral fractures in cats allowing sound orthopaedic principles to be maintained and producing a successful outcome.

Results and experience of 38 applications of the small AO/ASIF external fixator in cats are reported. Problems, limits with this fixation system and possible further indications are discussed. In this study the external fixator proved to be a helpful supplement of stabilisation methods for treatment of fractures and luxations in cats. The external fixator was well tolerated by the cats in this study.

In the first part general principles and indications for external fixator use in cats for treatment of fractures and luxations are described. This study considers only one of many external fixator systems. The results of the clinical use of this system in cats are described in the second part of this investigation. Technical aspects, post operative care, implants removal, possible complications and their therapy are discussed.

Fractures of the radius and ulna are common in the dog and cat. If treated inappropriately, complications may result. These include delayed union, nonunion, malunion, and growth deformities. ESF is a versatile method of fixation for fractures of the radius and ulna. Types that are applicable range from the simple type I to the complex type III fixator. In general, the more unstable the fracture, the more rigid the assembly must be to counteract fracture forces. There are three basic phases to consider when using ESF: (1) preoperative planning, (2) application of the ESF, and (3) long-term management. A deficiency in any one of these phases can lead to complications and an unsatisfactory clinical outcome. Although ESF can be used on many types of fractures, the technique is especially well suited for open or highly comminuted fractures when internal fixation is not applicable. In these cases, close attention must be paid to the integrity of the soft tissues. In addition, cancellous bone grafts should be placed either at the time of initial repair or in a delayed fashion after adequate vascularity has been established. Staged or complete removal of the ESF should be individualized to each fracture case. In general, staged disassembly or "dynamization" can begin when the bone and fixator begin to function as a composite as determined by radiographs. Complete fixator removal should be considered when the fracture exhibits clinical and radiographic evidences of union.

ESF is an ideal fixation for most tibial fractures. Many ESF configurations have been used in repair of tibial fractures including ESF supplementation of intramedullary pin or interfragmentary screw fixation. Tibial fractures are often comminuted or open, and the tibia is prone to postoperative infections after open reduction and internal fixation. ESF is ideal for stabilization of open tibial fractures and management of associated soft tissue injury.

External fixation is an effective method for stabilization of many mandibular fractures. Thorough physical examination and patient stabilization should be instituted before attending to the fractures and associated soft tissue trauma. Normal occlusion rather than perfect reduction is the goal of oral fracture repair. Loose teeth or teeth in the fracture should be removed, as should any avascular bone fragments. Soft tissue wounds should be treated as for any contaminated wound. Mucosal wounds are allowed to heal by second intention. Although prophylactic perioperative antibiotics are indicated, they are usually not needed postoperatively. The three basic types of external fixators described include the Kirschner-Ehmer splint, pins or screws and acrylic, and the biphase splint. All three types are relatively easy to apply, and the principles of their application are similar. A minimum of two pins or screws are placed percutaneously in each fragment, avoiding the mandibular canal. The Kirschner-Ehmer splint is more easily adjustable than the biphase splint or the pin-acrylic splint, which use acrylic connecting bars. The advantages of fixators that use acrylic bars are that the pins or screws need not all be in the same plane and that they are more lightweight than the Kirschner-Ehmer splint. The disadvantages of the biphase splint are its increased expense and its use being limited to larger dogs. External fixators are well tolerated by the animals, and postoperative care is minimal. Mandibular fractures are usually healed in 3 to 5 weeks, and the fixators can be removed with the animal under sedation.

The most common indications for the use of ESF in femoral fractures are closed transverse, short oblique, and minimally comminuted fractures in the central one third of the bone. External skeletal fixation is usually used in combination with IM pins and wiring techniques. During the process of open reduction and internal fixation, the surgeon should strive for accurate anatomic alignment and stability at the fracture site. The fixator is applied after the internal fixation is in place and the surgical wound is closed. The number of fixation pins placed in each fracture fragment depends on the type of fracture and the stability gained by internal fixation. Partially threaded fixation pins are recommended. They are inserted through skin stab incisions with low-speed power equipment. Recent modifications of the Type Ia fixator may increase fixator rigidity. Important postoperative concerns include exercise restriction, pin tract care, and protection of the fixator from the environment. Complications associated with ESF can be minimized by realizing its indications and limitations.

ESF is useful in treatment of open fractures and delayed union and nonunion fractures. The fixation pins can be placed away from the fracture site to avoid disruption of blood supply. The appliance is well tolerated and inexpensive, and many of the parts can be reused. Adjustment of the splint is possible to permit correction of stabilization for optimal results. Gradual reduction of frame rigidity improves the quality of healing by increasing the stress on the bone. As stiffness of the healing fracture increases, return of limb function occurs. Early fixator removal reduces patient morbidity and permits a return to normal activity.

External fixation is an effective method of stabilizing many fractures in veterinary orthopedics, however, it is not foolproof. Although careful attention to the principles of fixator selection and application is the optimal way to minimize complications, they do still occur. Prompt recognition of these complications and appropriate treatment, however, will minimize their effects and result in the successful outcome of fracture healing and normal limb function.