Stifle joint luxation in the cat: treatment using transarticular external skeletal fixation

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.     

Instrumentation for external fixation.

External skeletal fixation is a very useful technique for managing many orthopedic problems in veterinary practice. The Kirschner apparatus has been the most widely used fixator for many years in veterinary orthopedics because of its versatility, simplicity, and economy in use. The medium-sized device has the widest indications and is easiest to begin with. The small size can be acquired later for use on cats and small dogs. The new "raised thread" fixation pin designs improve bone-pin integrity and can be used in combination with nonthreaded pins to decrease the incidence of postoperative complications and for economy. Acrylic-pin external fixators are particularly useful for treatment of mandibular fractures and transarticular application since they allow nonlinear placement of fixation pins in highly contoured bones. A commercial system, currently being developed, will have all the equipment and materials necessary for their application in a convenient kit. Circular fixators (Ilizarov design) use thin K wires placed under tension to replace rigid fixation pins. Their unique adjustability characteristics make them useful in the treatment of limb deformity and shortening. Many other human fixators can be used for veterinary application if the basic principles of fixators are followed. Instrumentation required for external fixator application include a pin driver, pin cutter, and wrenches. Although surgical versions of these materials are available, less expensive alternatives are available using gas sterilization instead of autoclaving. The use of selected orthopedic instrumentation such as a periosteal elevator, bone clamps, and curets will facilitate fracture management.     

Proximal interphalangeal joint instability in the dog

A prospective study into the use of transarticular external skeletal fixation in the treatment of proximal interphalangeal instability was undertaken. Only dogs with soft tissue injuries were included. All the dogs except one were greyhounds or related breeds. A hypothesis was proposed that if the articular surfaces were held in normal congruency for a period of time then the development of periarticular fibrosis would alone give sufficient joint support. Joint congruency was maintained by the application of a unilateral external skeletal fixator for approximately three weeks. Complications were common and were due to frame impingement on the neighbouring digit, pin tract infection and pin loosening, and all resolved following frame removal and antibiotic therapy. Careful pin placement and prophylactic antibiotic treatment prevented complications in subsequent cases. All dogs returned to normal function with no lameness, with the exception of one racing greyhound which had a recurrence of the instability.     

Use of hinged transarticular external fixation for adjunctive joint stabilization in dogs and cats: 14 cases (1999-2003)

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.     

Mechanical Evaluation of Half-Pin (Type 1) External Skeletal Fixation in Combination with a Single Intramedullary Pin

Half-pin (type 1) external skeletal fixators with four, three, and two fixation pins and an intramedullary pin, and four-pin external skeletal fixators without an intramedullary pin were applied to prepared canine femurs. Load to failure, load to yield, safe load, and stiffness under compressive and torsional loads were calculated. When tested in compression, all measurements for the four-pin fixators with an intramedullary pin were significantly higher than for the two-pin fixators with an intramedullary pin. The values for all parameters except load to yield were significantly higher for the four-pin fixators with an intramedullary pin than for the four-pin fixators without an intramedullary pin. When tested in torsion, all measurements for the four-pin fixators with an intramedullary pin were significantly higher than for the two or three-pin fixators with an intramedullary pin.     

Transfixation pinning and casting of radial-ulnar fractures in calves: A review of three cases

We reviewed the medical records of three calves with radial-ulnar fractures which were reduced and stabilized by transfixation pinning and casting. Multiple Steinmann pins were placed transversely through proximal and distal fracture fragments and the pin ends were incorporated in fiberglass cast material after fracture reduction. Cast material was placed from proximal to distal radius and served as an external frame to maintain pin position and fracture reduction.

At the time of injury, the calves ranged in age from one day to two months and weighed from 37-102 kg. Two fractures were comminuted and one was transverse. All fractures were closed. After surgery, all calves could walk within 24 hours. Radiographic and clinical evidence of fracture healing was present five to seven weeks (mean 6) after surgery. At that time, the pins and cast material were removed. Return to normal function was rapid and judged to be excellent at follow-up evaluation five to nine months later.

Advantages of transfixation pinning and casting in management of radial-ulnar fractures include flexibility in pin positioning, adequate maintenance of reduction, early return to weight-bearing status, preservation of joint mobility, and ease of ambulation. The inability to adjust fixation and alignment after cast application is a disadvantage of this technique compared with other external fixators. We concluded that transfixation pinning is a useful means of stabilizing radial-ulnar fractures in pediatric bovine patients.

     

A Novel Pin Distraction Device for Arthroscopic Assessment of the Medial Meniscus in Dogs

Objective— To describe an extra-articular joint distractor for meniscal examination and treatment during canine stifle arthroscopy.
Study Design— Case series.
Animals— Dogs ≥20 kg with suspected cranial cruciate ligament (CrCL) deficiency.
Methods— A custom designed linear side bar was constructed to allow invasive pin distraction of the stifle joint. Its design efficacy for distraction of the medial joint compartment, observation and probing of the medial meniscus, and value during meniscal surgery was evaluated by clinical use.
Results— Application of the stifle distractor medial to the stifle joint using 2 negative threaded pins was easily performed percutaneously without the need of power equipment; however, unintended intra-articular placement of 1 threaded pin occurred in 2 stifles, without appreciable consequence to joint function. Observation as well as thorough probing of the caudal horn of the medial meniscus, even in the presence of a prominent remnant of the CrCL or severe periarticular fibrosis, was possible. Partial meniscectomy was effectively performed as needed without apparent damage to the associated articular surfaces.
Conclusions— Distraction and translation of the medial compartment of the stifle joint using invasive pin distraction allowed observation and palpation of the caudal horn of the medial meniscus so that assessment and treatment were readily accomplished without apparent morbidity.
Clinical Relevance— With careful attention to accurate pin placement, invasive pin distraction of the medial compartment of the canine stifle joint may improve arthroscopic evaluation and treatment of meniscal pathology.     

Evolution of the treatment of canine radial and tibial fractures with external fixators

OBJECTIVES: To determine if indications for external fixator treatment of radial and tibial fractures, management of the fractures, or outcomes have changed over three decades. METHODS: Three groups of dogs were identified from discrete time spans within three decades and the medical records and radiographs were evaluated. The groups were compared in order to determine whether indications (signalment, etiology, fracture type and configuration), reduction method, equipment and implants, frame types and pin numbers, numbers of radiographic reevaluations, use of destabilization, frequency of pin track osteolysis, frame removal times and percentage of complications remained the same over the decades. RESULTS: The indications for external fixator treatment of radial and tibial fractures remained consistent over three decades. The equipment and implants changed over the decades. Frame construction changed from the predominately Type II frames constructed in the 1980's and 1990's to a variety of modified Type II, Type Ia, Type Ib and hybrid frames constructed in the 2000's. The frequency of pin track osteolysis decreased significantly over the decades. Frame removal times have not changed significantly over the past three decades. Complications (nonunion, delayed union, osteomyelitis, implant failure and premature frame loss) have decreased over this time. CLINICAL SIGNIFICANCE: Improvements in techniques and equipment have led to decreased complications with external fixators.     

Transfixation pinning and casting of tibial fractures in calves: five cases (1985-1989)

Medical records of 5 calves with tibial fractures that were reduced and stabilized by transfixation pinning and casting were reviewed. Multiple Steinmann pins were placed transversely through proximal and distal fracture fragments, and the pin ends were incorporated in fiberglass cast material after fracture reduction. Cast material serves as an external frame to maintain pin position and fracture reduction. Calves were between 2 weeks and 6 months old and weighed between 40 and 180 kg. Three fractures were spiral in configuration and 2 were comminuted. One tibial fracture was open. After surgery, all calves were ambulatory within 24 hours. To improve tarsal flexion and achieve normal stance in 3 calves, cast revision was required on the caudal aspect of the limb. Good radiographic and clinical evidence of stability was observed in 5 to 10 weeks (mean 8 weeks), at which time the pis and cast were removed. Return to normal function was rapid and judged to be excellent at follow-up evaluation 3 to 12 months later. Advantages of transfixation pinning and casting in management of tibial fractures include flexibility in pin positioning, adequate maintenance of reduction, early return to weight-bearing status, joint mobility, and ease of ambulation. The inability to adjust fixation and alignment after cast application is a disadvantage of this technique compared with other external fixators.     

Evaluation of strength at the acrylic-pin interface for variably treated external skeletal fixator pins

Objective: To report pullout force to failure at the acrylic–pin interface for variably treated 3.2 mm external skeletal fixator pins. Study Design: In vitro biomechanical evaluation. Sample Population: 3.2 mm external skeletal fixator pins in polymethylmethacrylate bars. Methods: 3.2 mm external skeletal fixator pins were used for each of 5 treatment groups: polished, unpolished, 3 notched, 5 notched, and machine knurled. Each pin was seated into a 2‐cm‐diameter acrylic connecting bar and tested in pullout force to failure. Each group consisted of 6 pins. The force required to remove the pins from the acrylic bar was measured and compared between groups. Results: Significant differences between treatment groups were determined (P<.05). Within a construct group failure mode was consistent. Fracture of the acrylic bar was only seen with knurled pin ends. Conclusions: When using 2 cm acrylic bars in external skeletal fixation (ESF), a knurled pin shaft or a pin surface with 5 notches should be considered to improve the overall stability of the ESF construct.     

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.     

Unilateral congenital elbow luxation in a Cavalier King Charles Spaniel

A 7-week-old, intact female, Cavalier King Charles Spaniel was evaluated for nonweight bearing lameness of the right forelimb. Type III unilateral congenital elbow luxation was diagnosed radiographically. After surgical reduction, temporary placement of a transarticular pin, and external splinting of the joint, full weight bearing was achieved. Radial head subluxation persisted.     

Management of a proximal pelvic limb skin laceration in a dog using a skin flap and an external fixator

A nine-year-old, spayed female crossbred dog sustained a traumatic skin lesion to the right proximal pelvic limb, extending to the extensor surface of the stifle. Surgical management of the wound included primary closure using a body skin flap fashioned from the right caudolateral abdominal wall. To achieve closure and prevent tension on the wound, the coxofemoral and stifle joints on the affected side needed to be immobilised in flexion. Flexion immobilisation of the stifle was achieved using the anatomical principle of muscle reciprocation. The ipsilateral tarsal joint was immobilised in flexion using a uniplanar-bilateral (type II) transarticular external skeletal fixator and this resulted in the automatic flexion of the stifle. The fixator was removed six weeks postoperatively when the wound had healed. There were no apparent complications associated with the fixator either during its use or in the longer term following its removal.     

The Effect of Trans-Stifle External Skeletal Fixation and Hyaluronic Acid Therapy on Articular Cartilage in the Dog

Transarticular external skeletal (TES) fixators were applied unilaterally to the stifle joints of 10 young adult dogs. After 4 weeks, the fixators were removed from all dogs. Two dogs were not allowed a remobilization period, whereas 8 dogs were provided with 4 additional weeks of weight-bearing activity in a kennel run. Four dogs were given high-molecular weight hyaluronic acid by intra-articular injection weekly during the remobilization period. Clinical gait evaluations and range of motion were determined during the remobilization period. Articular cartilage samples from both stifle joints of all dogs were evaluated histologically and histochemically. No significant differences in gait scores or range of motion were noted between treated and untreated dogs. Articular cartilage proteoglycan content was reduced after 4 weeks of trans-stifle external skeletal fixation as determined by loss of alcian blue (AB) histochemical staining. Improved homogeneity of histochemical staining was observed after remobilization. However, remobilization was associated with histological damage to the surface and tangential layers of articular cartilage. Remobilization combined with hyaluronic acid (HA) therapy improved histochemical staining and reduced structural damage to articular cartilage when compared with remobilization alone.     

Flexible External Fixation for Craniodorsal Coxofemoral Luxations in Dogs

An external fixator consisting of two Ellis pins connected by a flexible band was developed and evaluated as a treatment for craniodorsal coxofemoral luxations in dogs. The technique for closed application of the fixator without injury to the coxofemoral joint or sciatic nerve was developed in six dog cadavers. The coxofemoral joints were then surgically destabilized and the limbs were manipulated through a full range of motion to assess the efficacy of the fixator in maintaining joint reduction. The fixator maintained joint reduction and stability after a surgically created craniodorsal luxation except when the femur was externally rotated 90d?. A flexible external fixator was then applied unilaterally in four healthy dogs. The dogs tolerated the fixator well and were bearing weight on the limb within 2 days after surgery; the range of motion was not limited by the fixator. The efficacy of a flexible external fixator in maintaining joint reduction after craniodorsal coxofemoral luxation was then evaluated in eight large dogs. The right coxofemoral joint in each dog was luxated surgically by removal of the dorsal joint capsule and transection of the ligament of the head of the femur and deep gluteal muscle. The joint was reduced and the fixator pins were applied in a closed fashion. In four dogs, a flexible external band was applied to the pins. Luxation did not reccur in these four dogs. The bands were not applied initially in four control dogs. Luxation occurred in three of the four control dogs within 24 hours of surgery. The joints that luxated were reduced and the flexible bands applied. Luxation did not recur after the bands were in place. The dogs tolerated the external fixators well, were bearing weight within 2 days of surgery, and walking with only minimal lameness 5 days after surgery. Luxation of the coxofemoral joints did not occur during the 2-week period in which the fixators were in place. The joints remained stable 1 week after removal of the fixators, at which time the dogs were euthanatized. Necropsy evaluation identified inflammation surrounding the pins and fibrous thickening of the dorsal joint capsule. The flexible external fixators were applied closed, maintained reduction of the coxofemoral joint after replacement of a craniodorsal luxation, and allowed weight bearing and limb usage soon after surgery. The flexible external fixator has several advantages over other methods of treating craniodorsal coxofemoral luxations. Complications noted in this study included pin tract drainage, pin loosening, and disruption of the flexible bands.     

Influence of an interdental full pin on stability of an acrylic external fixator for rostral mandibular fractures in dogs

OBJECTIVE: To determine total stiffness and gap stiffness of an external fixation system in a canine mandibular fracture gap model incorporating a full interdental pin as the only point of rostral fixation in a bilateral type-I external fixator. SAMPLE POPULATION: 10 canine mandibles. PROCEDURE: Bilateral mandibular ostectomies were performed between premolars 3 and 4. A type-I external fixator incorporating a full interdental pin was placed to stabilize a 0.5-cm fracture gap. Four pin configurations (intact mandibular bodies with fixator; ostectomized mandibular bodies and complete fixator; ostectomized mandibular bodies with caudal pins of rostral fragment cut; ostectomized mandibular bodies with all pins of rostral fragment cut) were tested in dorsoventral bending 5 times on each mandible. The full interdental pin remained intact in all configurations. Total stiffness and gap stiffness were determined for each configuration on a materials testing machine. RESULTS: Total stiffness of intact mandibles was significantly greater than that of ostectomized mandibles, regardless of external fixator configuration. However, total stiffness and gap stiffness were not significantly different among different external fixator configurations applied to ostectomized mandibles. CONCLUSION AND CLINICAL RELEVANCE: External fixator configurations with only the full interdental pin engaging the rostral fragment were as stiff as configurations that had 2 or 4 additional pins in the rostral fragment for the applied loads. External fixators for rostral mandibular fractures may be rigidly secured with rostral fragment implants applied extracortically, avoiding iatrogenic trauma to teeth and tooth roots.     

Recent advances in external skeletal fixation

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.     

Comparison of normograde and retrograde intramedullary pinning of feline tibias

This study evaluated the effects of normograde and retrograde intramedullary pinning of mid-diaphyseal fractures of the feline tibia on the anatomical structures of the stifle joint. Using the paired pelvic limbs from five mature feline cadavers, a transverse, mid-diaphyseal osteotomy was performed, and each tibia was pinned in a normograde or retrograde fashion. The stifle joints were examined to determine the pin exit site and measure the distance from the exit site to pertinent anatomical structures of the stifle joint. Neither normograde nor retrograde intramedullary pinning resulted in damage to the cruciate ligaments, menisci, intermeniscal ligament, femoral condyles, or joint capsule. The patellar tendon was penetrated in all five tibias during retrograde pin insertion.     

Comminuted supracondylar humeral fractures repaired with a modified type I external skeletal fixator construct

Highly comminuted supracondylar humeral fractures were stabilised in six large-breed dogs with a modified type I external fixator using a craniomedial acrylic connecting column and an Intramedullary pin which was incorporated into the connecting frame. This construct provided sufficient stability to allow satisfactory bone healing in five of the six dogs, while premature removal of the intramedullary pin and external fixator resulted in subsequent refracture of the humerus in the remaining dog. Limb function at the time of final assessment was considered excellent in two dogs, good in three dogs and poor in one dog. The craniomedial acrylic connecting column simplified application of this modified type 1(a) configuration to the humerus by reducing the number of clamps required; the acrylic column also facilitated contouring of the cranlomedial connecting column to the brachium and was readily extended proxlmally to engage the intramedullary pin. In addition, the acrylic connecting column allowed placement of intramedullary pins of varying diameter.