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Surgical Repair of Distal Femoral Physeal Fractures in the Dog and Cat

Fractures involving the distal femoral physis are relatively common in immature dogs and cats with the greatest incidence occurring between the ages of 5 and 8 months.

Physel fractures have been classified by Salter and Harris into 5 categories: Type 1 traverse the physeal plate through the zone of hypertrophying cartilage; Type 2 involves the physis and continues through the mtaphysis; Type 3 involves the physis and continues through the epiphysis to involve the articular surface; Type 4 involves the articular surface, crosses the physis and continues into the metaphysis; and Type 5 a compression injury to the zone of resting cartilage of the physis.

Distal femoral physeal fractures are commonly Types 1 and 2; most physeal fractures in the dog are Type 2 while those in the cat are Type 1. This is due in part to the fact that the distal femoral metaphysis has four projections that correspond to four similar deep depressions in the epiphysis in the dog while in the cat, the projections are flatter and do not interdigitate as deeply with the corresponding epiphyseal depressions. Physeal fractures usually occur through the zone of hypertrophying cartilage, because this zone is characterized by large, vacuolated cells with minimal intercellular matrix.  Therefore, this zone is the weakest.

A variety of treatment methods have been described for repair of distal femoral physeal fractures including closed reduction and external fixation, normograde or retrograde placement of a single intramedullary pin with or without an anti-rotational Kirshner wire, multiple intramedullary pins, paired Rush pins, Steinman pins, or Kirshner wires employed in Rush pin technique, cross pins, bone plates, and lag screws. The ultimate goal of treatment should be accurate reduction and rigid stabilization of these fractures with as little iatrogenic damage to the germinal cells of the physis and their blood supply as possible.

While closed reduction and external fixation may be successful in selected cases, every attempt should be made to satisfactorily stabilize the fracture internally so that early return to function is achieved and restricted joint movement is avoided. When closed reduction and external fixation is used, a good result is the most that one can expect.

Surgical exposure for open reduction and internal fixation is achieved via a lateral parapatella approach with reflection of the patella medially. Interference with growth is a consideration in the selection of the method of repair; however, recent studies have suggested that premature closure of the physis occurs more commonly as a result of the initial trauma than the method of treatment employed. Distal femoral physeal closure normally occurs between six and eight months of age; as the majority of physeal fractures occur in dogs and cats greater than five months of age, over 90 percent of their skeletal growth has already been achieved by the time of injury. Therefore, in animals over five months of age, while some degree of femoral shortening may occur, the overwhelming majority of animals clinically accommodate shortening by a change in stifle or hock angulation. In dogs and cats under five months of age with substantial growth potential, the method of fixation chosen should provide adequate stabilization but should not mechanically bridge the physis. Early implant removal may minimize premature physeal closure. Any implant, which traverses the growth plate, will result in some degree of permanent damage to the growth plate. The least damage occurs when round, smooth, non-threaded implants are placed perpendicularly to the long axis of the growth plate.

Single intramedullary pin fixation, Rush pinning and modified Rush pin technique, and cross pinning are the most commonly employed techniques used to treat Salter Type 1 and 2 fractures. A single intramedullary pin should provide excellent alignment and stability if the opposing surfaces of the fracture interlock following anatomic reduction. However, in large dogs, single pin fixation may be inadequate to allow early use of the limb. In addition, femoral intramedullary pins existing the trochanteric fossa have been associated with sciatic nerve injury. Normograde pinning of distal femoral physeal fractures is less likely to induce sciatic nerve injury then retrograde pinning. Implant migration may also result in damage to the intra-articular surface of the stifle joint.

Although cross pin fixation works well, it is associated with more complications than other techniques including caudal malalignment and/or displacement of the distal fragment and quadriceps tie-down. In very immature animals, cross pin fixation may interfere with physeal growth because of the excessive pin angulation necessary for adequate stabilization.

Rush pins provide excellent fixation for distal femoral physeal fractures. Their disadvantage is the need for special instrumentation and the cost of the implants. Rush pins provide three point fixation, thereby increasing stabilization and making their application especially indicated in large dogs. If Rush pins are used in very immature animals, great care must be taken when driving the pins to prevent excessive compression of the germinal cell layer, which may result in growth arrest.

Steinman pins or Kirshner wires may be used in exactly the same way as Rush pins. Once the fracture is reduced, the pins are inserted laterally just cranial to the tendon of origin of the long digital extensor muscle, and medially on the distal medial bondyle symmetric to the later pin placement. The pins are alternately advanced in the medullary cavity. I prefer that the pins do not exit the trochanteric fossa so as to minimize the potential complication of sciatic nerve injury. Pre-bending the pins accentuates a three point fixation and results in rigid internal fixation and rotational stability. This technique can be used in very immature animals when fear of Rush pin compression of the germinal layer may be a factor. Such pins may be placed with relative minor trauma to the physis, and most animals continue to lengthen their femurs despite the pins through the growth plate. With proper alignment and internal fixation, an excellent result should be expected.

Surgical Repair of Distal Femoral Physeal Fractures in the Dog and Cat

Surgical Repair of Distal Femoral Physeal Fractures in the Dog and Cat

Surgical Repair of Distal Femoral Physeal Fractures in the Dog and Cat

Surgical Repair of Distal Femoral Physeal Fractures in the Dog and Cat

Surgical Repair of Distal Femoral Physeal Fractures in the Dog and Cat


Surgical Management of Lateral Humeral Condylar Fractures

Fractures of the humerus are relatively common in the dog and cat with approximately half of all humeral fractures occurring in the distal portion of the bone.

The overwhelming majority of distal humeral fractures involve the elbow joint and are classified according to their anatomic location. Lateral condylar fractures are common and may occur from either minor or severe trauma in dogs and cats of all ages. Because of the close proximity of the thoracic cavity, additional injuries such as pneumothorax, hemothorax, pulmonary contusion, traumatic myocarditis, diaphragmatic hernia, and thoracic wall trauma can occur concurrently with humeral fractures. These potential injuries should be identified and treated appropriately prior to repair of the humeral fracture.

The severity of the trauma sustained has been shown to influence the resulting fracture type. While severe trauma has been shown to result in simple lateral condylar fractures and the associated injuries previously mentioned, the majority of lateral condylar fractures result from minor trauma. The high incidence of condylar fractures resulting from minor trauma in immature animals may be explained by the relative weakness of the fusion zones of the principal centers of ossification of the developing distal humerus. A substantial number of condylar fractures, however, occur in adult animals. One study found an increased risk for male Cocker Spaniels over two years of age fracturing their humeral condyle with only minor loading forces. The findings of this study suggest that certain breeds of dogs may be predisposed to distal humeral condylar fractures after sustaining minor trauma equal to or only slightly greater than the loading forces generated by the normal activity. Distal humeral condylar fractures are far more common in dogs than in cats. The rarity of condylar fractures in cats may be partially explained by their straighter condyles and relatively wider and thicker epicondylar crests.

Fractures of the lateral humeral condyle (capitulum) occur as abnormal compressive forces are directed upward through the radius. The condyle shears off the intercondylar area through the supratrochlear foramen and the lateral supracondylar ridge. Several factors are associated with the higher incidence of lateral versus medial condylar fractures. The capitulum is the major weight-bearing surface because of its articulation with the radial head. As forces are directed through the radius, they are transmitted directly to the capitulum. Fractures of the medial condyle (trochela) are less common because of its less frequent weight bearing position. In addition, the shape of the distal humerus is such that the capitulum sits off the midline of the central axis of the body, predisposing itself in injury. Finally, the lateral supracondylar ridge is smaller and biomechanically weaker than its medial counterpart.

Treatment of lateral condylar fractures should be directed at complete restoration of joint anatomy and function. Because these fractures are intraarticular, perfect reduction with interfragmentary compression is required for optimal postoperative function. Closed methods of reduction and external fixation cannot usually reduce the fracture fragments perfectly and prolonged immobilization of the joint, which is necessary for fracture healing may lead to joint stiffness. Closed reduction and stabilization using a condyle clamp to place a transcondylar screw through a stab incision is possible. The results obtained with this technique depend on the length of time since the injury occurred, the expertise and experience of the surgeon, the amount of swelling and edema present, and the amount of soft tissue interposed at the fracture site.

Open reduction and internal fixation are indicated for optimal alignment and stabilization of lateral condylar fractures and an early return to function. An early return to function will help alleviate elbow stiffness and degenerative joint disease. While several surgical approaches may be used to expose lateral condylar fractures, excellent exposure with minimal soft tissue dissection is achieved via a lateral or craniolateral approach to the elbow. The most common method employed for repair of lateral condylar fractures is a transcondylar lag screw with or without an additional crosspin for increased rotational stability.

Once the fracture site is adequately exposed, fibrin, clots, blood, and interposed soft tissue should be removed to allow perfect anatomic reduction of the articular surface. With the fracture reduced, a transcondylar hole is drilled beginning at a point just cranial and ventral to the palpable lateral epicondylar crest. The drill hole is tapped, the later condylar fragment is over-drilled to create a gliding hole, and transcondylar lag screw is placed. In order to ensure central placement of the lag screw through the condyle, an alternate technique may be employed. The lateral condylar fragment is outwardly rotated and the gliding hole is drilled from the intercondylar fracture surface out through the lateral side of the condyle. The fracture is then reduced, the medial condyle is appropriately drilled, and tapped and a lag screw is placed. An anti-rotational Kirshner wire or Steinman pin is then driven from the lateral condyle and seated into the medial cortex of the distal humeral shaft. The elbow joint should be put through a full range of motion to assess stability and to check for crepitus.

I prefer to place the limb in a modified Bobby Jones dressing to help control swelling during the immediate post-operative healing period. The owners are advised to restrict the animal’s exercise for the first 6-8 weeks after surgery while employing gentle, passive physiotherapy to help prevent elbow stiffness. When early surgical intervention, accurate anatomic reduction, and rigid internal fixation are employed a good to excellent result should be expected.

Surgical Management of Lateral Humeral Condylar Fractures

 

Surgical Management of Lateral Humeral Condylar Fractures

Surgical Management of Lateral Humeral Condylar Fractures


Management of Sacroiliac Fracture/Luxation in the Dog and Cat

Injury to the sacroiliac joint in the dog and cat commonly occurs in association with fractures of the pelvis and pelvic limb.

Substantial soft tissue injury and neurologic dysfunction may also be present. A patient with a sacroiliac fracture/luxation has in all probability sustained a significant external blow to the pelvis, and because of the probability of multiple fractures and soft tissue injuries, a thorough physical and neurologic examination must be performed.

The sacroiliac joint is a combined synovial and cartilaginous joint which functions as a supportive bridge between the appendicular and axial skeletons. Because the pelvis and sacrum form a rigid rectangular or boxlike unit, unilateral displacement of the sacroiliac joint cannot occur without associated pelvic fractures or a pelvic symphyseal separation. Unilateral separation of the sacroiliac joint occurring in conjunction with other severe orthopedic injuries is much more common than bilateral sacroiliac joint injury. Few unilateral sacroiliac injuries are associated with ischial and/or pelvic fractures alone.

Clinical signs exhibited by the patient obviously depend on the severity of the trauma as well as the extent of the associated injuries. Caudal abdominal herniation, urethral laceration, intestinal perforation, urinary bladder rupture, diaphragmatic hernias, and pulmonary contusions have all been associated with fractures of the pelvis. It is imperative that associated soft tissue injuries be diagnosed, as they affect treatment and prognosis. The patient may be ambulatory or nonambulatory, depending on the nature of the associated orthopedic and/or neurologic injuries.

In fracture/luxation of the sacroiliac joint in dogs and cats, treatment is either conservative or surgical. Current recommendations indicate conservative treatment in subluxations or in complete luxations when the patient is ambulatory and exhibits minimal discomfort. Before a course on conservative therapy is chosen, a neurologic examination should indicate that there are no functional deficits of the lumbosacral trunk and/or sciatic nerve. Complications of conservative management include increased cranial or medial displacement of the hemipelvis and obstruction of the pelvic outlet. Conservative treatment may also prolong the period of instability and lameness and prolong the period of patient discomfort and client concern. In addition, if marked displacement is present, asymmetry of the acetabulae may result in an abnormal gait posttrauma.

Open reduction and internal fixation is indicated for fracture/luxations when one or more of the following clinical or radiographic signs are present: 1) marked instability and displacement of the hemipelvis, 2) neurologic deficits attributable to the luxation or 3) obstruction of the pelvic outlet is observed. Surgical intervention is of particular value when associated orthopedic injuries are present, as surgical stabilization allows the patient to become ambulatory earlier and provides a better prognosis for the return to a normal gait.

In light of the fact that the overwhelming majority of sacroiliac fracture/luxations are associated with additional orthopedic injuries, my personal preference is to opt for early surgical repair. Even in cases of unilateral fracture/luxations with minimal associated orthopedic injuries, in my experience surgical intervention returns these animals to a normal gait more quickly and with a shorter convalescent period than if conservative therapy was chosen.

Sacroiliac fracture/luxations may be surgically repaired by either a dorsolateral or ventrolateral approach. The approach chosen may be dictated by the presence of additional pelvic injuries requiring open reduction and internal fixation, or surgeon preference. Both approaches provide adequate exposure for visualization of the sacroiliac joint.

Stabilization of sacroiliac fracture/luxations is most commonly accomplished with lag screw fixation. The two most important variables in the technique of lag screw fixation affecting sacroiliac stability are screw location and depth of screw placement. Screws placed within the sacral body have the lowest rate of loosened fixation compared to other areas of the sacrum. Proper positioning within the sacral body is also essential to prevent injury to the nerve roots within the spinal canal, and the lumbosacral trunk or sciatic nerve ventral to the sacral body. With regard to depth of screw placement, a cumulative screw depth/sacral width of 60% or more significantly reduces the likelihood of loosening of the fixation. While some authors have suggested that 2 screws be used routinely for sacroiliac stabilization, in all feline and most canine sacrums there is room for only one properly placed screw within the sacral body. In the giant breeds of dogs, a second screw or an intramedullary pin may be placed, but the placement of this additional screw or pin within the sacral body is dependent upon the accuracy of placement of the first screw. In addition, a recent study did not demonstrate a difference in the number of loosened fixations when one or two screws were used.

When a sacroiliac fracture/luxation occurs, most if not all of the fibrocartilage remains attached to the lateral surface of the sacral wing. When placing lag screws for fixation, the location of the sacral body must be determined by palpation as well as by the anatomical landmarks of the sacral wing. Screw placement should always be just caudal to the sacral wing notch.

Postoperative care should include restriction of exercise for a period of 6-8 weeks. A mild laxative may be administered if bowel movements appear to be painful during the immediate postoperative healing period. A significant number of sacroiliac fracture/luxations repaired with lag screw fixation may loosen and result in loss of reduction and sacroiliac instability. The guidelines for the location of screw placement mentioned here should improve the results of fixation and allow for a better prognosis for return to a normal gait and conformation.

Sacroiliac Fracture/Luxation

Sacroiliac Fracture/Luxation


Principles of External Skeletal Fixation

Numerous methods of fracture fixation are available to the veterinary surgeon.

External skeletal fixation is an effective method of fracture repair, which has experienced a resurgence in popularity in the last few years. Several types of external skeletal fixation devices are commonly utilized, including the Kirshner-Ehmer apparatus and the Synthes and Hoffman external fixators. Many configurations and various modifications have been described for the application of external fixators. A review of apparatus design has resulted in a classification of external skeletal fixators into three types, each possessing separate attributes and indications for use. Type 1 for unilateral splints uses fixation pins, which are inserted through both bone cortices but penetrate only on the skin surface. Type 2 or bilateral splints use fixation pins, which are inserted through both cortices and both skin surfaces. Type 3 or biplanar splints are a combination of unilateral and bilateral splintage employed in a three-dimensional configuration.

An external skeletal fixator (ESF) can be used as the primary method of fracture fixation or can be used to enhance the stability provided by another primary fixation modality. External fixators may be used in a variety of clinical situations including simple fractures, open or compound fractures, delayed and non-unions, highly comminuted fractures, fractures in which there is extensive soft tissue damage, and infected fractures. They are also frequently recommended in cases requiring transarticular stabilization and for stabilization of corrective osteotomies. When used properly, application of an ESF results in a number of advantages over other techniques of fracture repair, including minimal disruption of soft tissues attachments to bone and minimal disturbance of the blood supply to the bone. When used in difficult fracture situations involving open or compound wounds, osteomylitis and/or extensive soft tissue injury, the contaminated fracture sites are not disturbed by the presence of the fixation device and dissemination of the contamination is minimized.

As with any surgical technique, the use of an ESF is not without some disadvantages or potential complications. Disadvantages of an ESF include delayed healing under certain condition, ideal reduction is not always possible, the fixation may fail in cases of osteoporosis, and the ESF may catch on an object thereby ruining the fixation. Complications associated with the use of an ESF include pin tract drainage and infection, pin loosening, pin breakage, iatrogenic fractures, damage to vessels and nerves, and disturbed muscle function due to pin placement. The disadvantages and complications must be taken into consideration when deciding whether to use external fixation. The majority of the disadvantages and complications associated with an ESF can be alleviated if the important principles of application are followed carefully.

Historically, the major limitation for the use of external skeletal fixation has been its ability to adequately stabilize fracture fragments until healing has occurred. It is absolutely essential to maintain the holding power of the pins the bone and the stiffness of the fixation pins if rigid immobilization is to be maintained. Maximum stress of the fixation pins occurs at the pin-bone interface. Stress transfer from bone to metal and, over time, stress concentration at these sites can eventually lead to pin loosening, drainage, infection, or breakage. Information gathered from numerous studies and clinical experience indicates that stiffness, bone holding power, and clinical performance of an ESF is dependent upon numerous factors including configuration, diameter and number of connecting bars, pin diameter, number of pins, type of pin, angle and location of pins in cortical bone, length of pins from the connecting bars to the bone, method of pin insertion, and inherent stability at the fracture site. Each of these factors must be critically assessed by the surgeon to decrease the likelihood of pin loosening and loss of fixator stiffness and associated morbidity.

The method of fixation pin insertion used should avoid generating mechanical damage and bone necrosis. High speed power insertion of pins results in thermal necrosis of bone, while insertion by a hang drill results in excessive mechanical damage. Both techniques are associated with a decreased force required for axial extraction of the fixation pins. Current recommendations include predrilling with a smaller drill bit and either low speed power or hand chuck insertion of fixation pins to decrease the incidence of mechanical or thermal necrosis and subsequent premature pin loosening.

The type of pin used influences greatly the stability of the pin-bone interface, as well as fixators stiffness. While nonthreaded pins exhibit decreased bone holding power, they are stiffer, stronger, and more resistant to bending and breaking than threaded pins. A recent study indicated that single cortex partially threaded pins compare favorable to pins with threads engaging both cortices with regard to holding power. In addition, these pins provided more resistance to bending at the pin-bone interface than fully threaded pins. Essentially, the single cortex partially threaded pin combines the increased holding power of threaded pins with the stiffness of the nonthreaded pins. The use of partially threaded pins, either exclusively or in combination with nonthreaded pins, should be considered in clinical cases where prolonged external skeletal fixation is required. Other studies have indicated that morbidity decreased significantly with the exclusive use of threaded pins or a combination of threaded and smooth pins as compared to the exclusive use of the smooth pins. Prolonged stability of the pin-bone interface was considered to be the reason.

Numerous recommendations have been made with regard to the angle and location of fixation pin placement in cortical bone. Information gathered from many studies indicates that an angle of approximately 70 degrees to the long axis of the bone and inward (central) angling of the pins improves fixation stiffness. It may also reduce pin loosening, because nonparallel pins will tend to restrict the motion of their neighbor. The appropriate number of pins per fragment has not been objectively determined; however, a minimum of 2 and perhaps 3 or 4 pins per fragment should be used as increasing the number of fixation pins per fragment reduces the incidence of premature loosening. Each pin should be inserted through a separate stab incision in intact skin and avoid penetration of large muscles masses. This practice will help alleviate problems with incision or wound management, decrease the incidence of pin tract infection and make incision closure easier.

Bone-connecting bar distance should be minimized while avoiding interference with the skin. Doubling the bone-clamp distance reduces the fixator stiffness by 25%. Increasing the diameter of the fixation pins or the diameter and number of the connecting bars will increase fixator stiffness. The configuration of the fixators will also affect fixator stiffness, with Type 3, or biplanar splints, being the strongest configuration.

In conclusion, since fractures vary widely in type, stability, the condition of the soft tissues, and activity and size of the patient, it is obvious that no one configuration is best suited for all fractures. Providing that the proper principles of application are followed, external skeletal fixation can provide the stable fixation necessary for fracture healing and good to excellent post-operative limb function. The information presented should hopefully enable the surgeon in choosing the best ESF design for the fracture type under consideration.