CHARLES D. NEWTON AND DAVID M. NUNAMAKER
- Injuries of the Diaphysis
Injuries Involving the Epiphyseal Plate
Principles of Treatment
Specific Epiphyseal Plate Injuries
Injuries Involving the Epiphysis
INJURIES OF THE DIAPHYSIS
Diaphyseal Fractures in young growing animals may be of two types: complete or incomplete. Incomplete or greenstick fractures of the cortex are very common and are often overlooked. The animal may present with various histories of no or partial weight bearing. The limb exhibits no crepitus, but local pain is evident over the fracture site. Deformity may be present. Careful examination of radiographs of the limb in two views is necessary to complete the diagnosis. Treatment of incomplete fractures is carried out by some form of external immobilization. If no immobilization is used, deformities may result. If a severe deformity (>5¡) exists at the initial presentation, it may be necessary to create a complete fracture. Complete fractures in young animals can for the most part be treated as fractures in adults. Most complete fractures in young animals will heal rapidly if reduced and immobilized by external casts or splints. Open reduction and internal fixation should be reserved for older animals and should be used in the young only when absolutely necessary.
In a young animal there is always danger in damaging a growth plate by using some form of internal fixation that may cross it. Smooth round intramedullary pins are the least dangerous, while crossed pins, Rush pins, or screws or plates show increasing likelihood of causing major disturbances of the growth plate.
Other concerns exist when using internal fixation in very young animals. Often the cortex is very thin and soft, especially in large breed dogs; hence, the intramedullary cavity is very large, which may lead to problems when using single pinning techniques. Many small pins may represent a viable alternative in these cases. External skeletal fixation may not be stable because of the thin soft cortex that is penetrated by the transfixation pins. Thus, a dilemma exists when recommending a form of internal fixation in the young. It helps to emphasize the good results that are achieved through external casts and splints. When closed reduction is impossible, open reduction can often be achieved through a small incision, and immobilization can be carried out with a cast or splint. This is a common method of dealing with radial and ulnar fractures but may be used in other locations as well.
INJURIES INVOLVING THE EPIPHYSEAL PLATE
Diagnosis of epiphyseal plate fracture (fracture of the physis) is often difficult, since displacement may be minimal or nonexistent. Injuries resulting in deformity, pain, or swelling near the end of a long bone in an immature animal indicate a probable epiphyseal plate injury or fracture. The diagnosis is often difficult even with the aid of radiography.(7) Careful evaluation should include thickness of the growth plate, deviation of the epiphysis from the metaphysis, and any variation from the contralateral epiphysis. Soft tissue swelling may determine if trauma has occurred to the growth plate or epiphysis.
Crushing injuries are difficult to diagnose because the epiphysis is usually perfectly aligned, although its bony substance has been crushed. Lack of a radiographic diagnosis of epiphyseal injury does not exclude the diagnosis with all its sequelae.
Epiphyseal plate injury as described in the veterinary literatures.(10) is similar to that in the human orthopaedic literature. The following classification was published by Salter in 1963(14) and is used in classifying these injuries in animals.
Complete epiphyseal separation through the zone of hypertrophied cartilage cells is a type I injury. In this injury the growing cells of the epiphyseal plate remain with the epiphysis. The injury is usually the result of a shearing or avulsion force. Early reduction is likely to result in a good prognosis. Since the zone of proliferation is undamaged, normal growth is likely to proceed following reduction and healing (Fig. 34-1).
Type II is the most common epiphyseal injury seen in small animals, resulting from either a shearing injury or an avulsion force. The line of separation extends along the epiphyseal plate for a variable distance and exits through a portion of the metaphysis.
Early reduction of type II injuries usually results in a good prognosis. Premature closure of the growth plate is unlikely, since the zone of proliferation has not been damaged and normal longitudinal growth of the bone should occur (Fig. 34-2)
Type III is an intra-articular epiphyseal fracture. The fracture line extends from the joint surface to the hypertrophied cartilage zone of the epiphyseal plate and along the epiphyseal plate to the periphery. Early reduction is necessary to reconstruct the joint surface for a fully functional joint. The prognosis of a return to function following early accurate repair is good (Fig. 34-3).
FIG. 34-1 Type I epiphyseal plate injury: separation of the epiphysis. (Redrawn after Salter RB, Harris WR: Injuries involving the epiphyseal plate. J Bone Joint Surg 45A:587, 1963)
FIG. 34-2 Type II epiphyseal plate injury: fracture-separation of the epiphysis. (Redrawn after Salter HB, Harris WR: Injuries involving the epiphyseal plate. J Bone Joint Surg 45A:587, 1963)
FIG. 34-3 Type III epiphyseal plate injury: fracture of part of the epiphysis. (Redrawn after Salter RB, Harris WR: Injuries damaged and normal longitudinal growth of the bone involving the epiphyseal plate. J Bone Joint Surg 45A: 587,1963)
FIG. 34-4 Type IV epiphyseal plate injury: fracture of the epiphysis and epiphyseal plate. (Redrawn after Salter RB, Harris WR: Injuries involving the epiphyseal plate. J Bone Joint Surg 45A:588, 1963)
Type IV injuries involve an intra-articular fracture that traverses the entire epiphysis, epiphyseal plate, and metaphysis. This injury spans the growth cells of the epiphyseal plate.(12)
Early, accurate, stable fixation is necessary to reconstruct the joint surface because of the difficulty in obtaining perfect anatomical reduction, which is necessary to prevent a bony bridging of the physis at the line of the fracture (Fig. 34-4). The risk of partial closure of the injured growth plate is high; therefore, the prognosis for complete return to function is only fair.
Type V fracture is an uncommon injury resulting in epiphyseal and epiphyseal plate crushing. This injury destroys the growth cells of the epiphyseal plate, and closure of the plate is predicted.
Early diagnosis is usually difficult to determine even with the use of radiography. Early reduction is difficult because the bone has been crushed and repair is impossible. Premature closure will occur and bony deformity is likely; return of function is determined by the age and development of the animal. The older the animal at the time of injury, the greater the chance for a functional recovery (Fig. 34-5).
Rarely, the epiphyseal plate is injured peripherally and new bone heals and bridges the plate, resulting in growth deformity that is not easily preventable (Fig. 34-6).
FIG. 34-5 Type V epiphyseal plate injury: (A) crushing of the epiphyseal plate; (B) premature closure. (Redrawn after Salter RB, Harris WR: Injuries involving the epiphyseal plate. J Bone Joint Surg 45A:587, 1963)
FIG. 34-6 Type VI epiphyseal plate injury: peripheral injury to epiphyseal plate resulting in bony bridging and premature closure.
The prognosis for physeal injuries represents a real problem. Significant growth disturbance can follow epiphyseal plate injury. It is impossible to accurately predict significant problems among individual animals; however, some guidelines are available to assist the surgeon.
Most type I, II, and III injuries, if properly and rapidly treated, have a good prognosis, assuming the fragments have a normal blood supply. Type IV, V, and Vl injuries are likely to result in closure of the epiphyseal plate regardless of the rapidity or type of treatment.
Epiphyseal plate injury is significant in the young animal. Slight closure or slowing of growth will be magnified in an animal that must grow for an additional 6 to 8 months following the injury. Conversely, injuries in animals near skeletal maturity are unlikely to result in severe deformity regardless of type.
Care is necessary when reducing epiphyseal fractures. Regardless of method (closed or open), the bone is soft and must not be injured further during reduction. Use of sharp instruments or levers that tend to crush during realignment is contraindicated, since the crushing causes injury to the cellular line that is responsible for growth.
Certain epiphyseal plate injuries are likely to result in closure or deformity. When these injuries are encountered, a guarded prognosis is advised, regardless of the type of injury to the epiphyseal plate (i.e., type 1, 11, III, IV, V, or VI). In the dog, these injuries involve the distal radial epiphyseal plate, the distal ulnar epiphyseal plate, and the capital femoral epiphyseal plate.
PRINCIPLES OF TREATMENT
Epiphyseal plate injuries should be reduced by careful manipulation through the use of gentle hands and fingers. Instruments should be avoided for purchase or leverage. Any manipulation that will further traumatize the injured epiphyseal plate should be avoided.
Epiphyseal plate injuries are reduced more easily within 24 hours following injury. Type I and 11 injuries that have been present for 10 days or longer in very young animals may be treated best by corrective osteotomy, since forceful reduction will result in more severe injury rather than in correction.
Type 1, 11, or III injuries need not be reduced perfectly if manipulation results in further injury. Reduction may be less than perfect in flexion or extension without further ill effects; however, reduction must be perfect for varus or valgus to prevent further deformity.
METHOD OF FIXATION
Type I and 11 fractures can be successfully reduced and fixed using closed methods. Whether casts or coaptation splints are used, maintenance of the fracture in good alignment and maintenance of the joint in midrange position is necessary. If extreme joint positions are necessary to maintain reduction, open methods of fixation should be used.
Type 1, II, or III injuries involve all or part of the hypertrophied cell layer of the epiphyseal plate. These fractures heal in approximately half the time required for union of a fracture through the metaphysis of the same bone in the same aged animal. Type IV and V injuries unite in the same period as a metaphyseal fracture.
Epiphyseal injuries are amenable to internal fixation. In all instances care must be taken to prevent further injury to the growth plate. The ideal form of internal fixation is small, smooth Kirschner wires placed perpendicular to the epiphyseal plate.
When dealing with open epiphyseal plate injuries, threaded devices should not span the open growth plate. Therefore, threaded pins, screws, tension band wires, or plates that span the epiphyseal plate should not be used. If they must be used, they should be removed immediately following union. If such devices are used for a long period, they will close the epiphyseal plate and produce deformity.
Following epiphyseal plate injury, animals should be followed at biweekly intervals until union. Following union, the animal should be examined at least monthly for 2 to 3 months to ensure that deformity does not occur.
MANAGEMENT OF DEFORMITY DUE TO PREMATURE CESSATION OF GROWTH
Deformity will occur following premature closure of an epiphyseal plate. An individual bone may angulate or shorten. If the affected bone is one of a pair, such as the radius and ulna, bowing or rotation along the long axis may also occur. Considerable judgment is required in planning the most effective management of these progressive deformities.
Retardation or cessation of growth in one area of the epiphyseal plate with continuation of growth in the remainder produces gradually increasing angulation. In this circumstance, growth in the remainder of the plate eventually ceases prematurely. Thus, the problem of shortening is added to that of angulation. It is usually preferable to deal with progressive angulation by open wedge osteotomy in order to preserve the growing potential of the undamaged portion of the epiphyseal plate and to gain some length in the extremity. Unless the entire epiphyseal plate has ceased growing, the osteotomy should overcorrect the deformity so that its inevitable recurrence may be delayed. When progressive angulation exists in a young dog or cat, it may be necessary to perform osteotomy more than once since the epiphyseal plate is still growing. However, this method has the disadvantage of producing further shortening of the involved extremity.
If one of two paired bones (radius or ulna, tibia or fibula) is the site of premature cessation of growth, the resultant discrepancy in length between the two bones will produce a progressive deformity (varus or valgus) of the nearest joint. For example, premature cessation of growth at the distal lateral radial epiphyseal plate in the presence of continued growth at the distal ulnar epiphysis will produce an increasing valgus deformity or lateral deviation of the paw. Therefore, it may be necessary either to lengthen the shorter bone surgically or to shorten the longer bone and at the same time to arrest the growing epiphysis to prevent recurrence of deformity. When a single bone (femur or humerus) is the site of increasing shortening, the problem is one of discrepancy of limb length. Discussion of the various indications and methods for equalization of limb length is beyond the scope of this chapter.
SPECIFIC EPIPHYSEAL PLATE INJURIES
SUPRAGLENOID TUBERCLE EPIPHYSIS
The supraglenoid tubercle is a traction epiphysis and fractures as the result of trauma and the pull of the biceps brachii muscle. The fracture is most often a type I injury. Closed reduction and fixation is not possible, and open reduction and internal fixation is necessary for proper management. Deformities rarely occur following reduction and fixation.
PROXIMAL HUMERAL EPIPHYSIS
Most fractures result in type I injuries. Reduction can be difficult, since muscular contraction often results in fragment override. If reduced quickly and anatomically, deformity rarely occurs. Type V injuries involving the caudal epiphyseal plate have been reported. The injury results in premature closure of the caudal epiphyseal plate and caudal bowing of the humeral diaphysis.
DISTAL HUMERAL EPIPHYSIS
Usually a type I injury occurs with both condylar portions of the epiphysis remaining attached.(16) Reduction and fixation is uneventful and deformity rarely occurs.
Occasionally the lateral and medial condyles split, resulting in an intra-articular fracture as well. This complicates reduction, since it is difficult to reduce and fix the halves together. The potential for complications is greater, since manipulation of the fragment may result in crushing or further fragmentation.
PROXIMAL ULNAR EPIPHYSIS
The small, wedge-shaped proximal ulnar epiphysis rarely fractures; more commonly the entire olecranon fractures.
If the epiphysis does fracture, it is a type I injury. As a result of the traction of the triceps muscles, the fragment displaces proximally. Internal fixation is necessary for proper alignment and stability. Deformity rarely results owing to premature closure, since the epiphyseal plate is responsible for only 15% to 20% of ulnar growth.
PROXIMAL RADIAL EPIPHYSIS
The proximal radial epiphysis is rarely injured. When fractures do occur, they tend to be type I or type II injuries. Reduction can be very difficult owing to inaccessibility and small fragment size. This epiphysis is responsible for approximately 30% of radial growth. If growth slows or stops, the radial head may subluxate distally and result in an unstable elbow.(11) Bony deformities rarely occur.
DISTAL ULNAR EPIPHYSIS
The distal ulnar epiphysis is commonly injured. Type V and Vl injuries predominate. Occasionally a type I injury will occur, but regardless of fracture type, premature closure of the epiphyseal plate occurs.
Deformity results from premature closure, since the distal epiphyseal plate is responsible for 80% of ulnar lengthy The resulting deformity is a cranial bowing, a valgus deviation, and external rotation. The degree of deformity depends on the age of the animal at the time of the injury.(1)
DISTAL RADIAL EPIPHYSIS
Most fractures of the distal radial epiphyseal plate are type I injuries. Closed reduction and external fixation proves successful. The likelihood of limb deformity, however, is high, since a distal ulnar epiphyseal fracture probably occurred simultaneously. Should the distal radial epiphyseal plate close prematurely, a varus deformity of the forepaw will result. Radial shortening may also produce medial (internal) rotation of the paw and a medial bowing.
Type V injuries of the distal radial epiphyseal plate also occur commonly. They result in a valgus deformity below the site of the injury. Elbow subluxation may accompany this deformity if radial lengthening has been hampered appreciably.
Two epiphyses are prone to fracture in the pelvis: the epiphysis of the cranial dorsal iliac spine and the epiphysis of the ischiatic tuberosity. The epiphysis of the cranial dorsal iliac spine displaces only rarely. It remains in alignment owing to the heavy regional muscles. Treatment is seldom necessary, and bone deformities rarely result from the injury.
The epiphysis of the ischiatic tuberosity is a traction epiphysis. Most injuries are type I and displacement
distally is expected. Open reduction would be necessary for realignment; however, treatment is rarely instituted and deformity does not occur.
CAPITAL FEMORAL EPIPHYSIS
Most injuries are type I; however, type II injuries do occur. Owing to its position in a very active large joint, early reduction and fixation is necessary to prevent fragmentation, crushing, or grinding of the epiphysis. Internal fixation, regardless of method, results in closure of the growth plated Closure of the capital epiphyseal plate results in a varus deformity of the femoral neck.(2,9,13)
GREATER TROCHANTERIC EPIPHYSIS
Most injuries are type I and commonly displace, since the greater trochanteric epiphysis is a traction epiphysis. Open reduction and internal fixation is required.
Premature closure of the greater trochanteric epiphyseal plate may result in a valgus deformity of the femoral neck.(2,9,13) One researcher found no deformity following closured
DISTAL FEMORAL EPIPHYSIS
The distal femoral epiphysis is one of the most commonly fractured epiphyses in the young animal. Type I and type II injuries predominate. Early reduction makes alignment much easier. Fixation usually necessitates one or more small smooth Kirschner wires.(5) Premature closure of the epiphyseal plate may result in femoral shortening,(3) however, valgus or varus deformities are rare.
PROXIMAL TIBIAL EPIPHYSIS
Most commonly, lateral trauma results in type I, II or III injuries. Depending on the severity of the trauma, the tibial tuberosity epiphysis may also be involved. It is imperative to achieve perfect reduction prior to fixation, or a valgus deformity may result from malalignment. Deformities occur following reduction and fixation as a result of intraoperative trauma to the epiphyseal plate during reduction. The direction of the deformity depends on the specific area of the plate closure.
TIBIAL TUBEROSITY EPIPHYSIS
The tibial tuberosity epiphysis is a traction epiphysis usually resulting in type I injuries. The bony fragment displaces proximally. Open reduction and internal fixation is necessary for proper management. Closure of the epiphyseal plate rarely occurs. (Cranial bowing of the tibia can be expected if closure occurs.)
DISTAL TIBIAL EPIPHYSIS
Fracture of the distal tibial epiphysis is rare. Type I or II injuries predominate. Reduction is usually accomplished by closed manipulation; however, internal fixation may be needed to ensure that the reduction is maintained.
Premature closure of the epiphysis rarely results in deformity, since most tibial growth occurs at the proximal epiphyseal plate.
TUBER CALCIS EPIPHYSIS
The tuber calcis epiphysis is a traction epiphysis, prone to trauma, resulting in type I injuries. Open reduction and internal fixation is necessary to ensure proper alignment. Premature closure will not result in deformity.
INJURIES INVOLVING THE EPIPHYSIS
Injuries to the epiphysis, not involving the epiphyseal plate, are rare. They result from direct trauma of a penetrating object, shear, or avulsion. Most avulsions involve the origin or insertion of a collateral ligament.
Most epiphyseal fractures are intra-articular. Reduction and fixation requires an open approach, and either fixation or removal of bony fragments. Avulsion fractures require rigid internal fixation, usually a tension band wire or an interfragmentary screw. Other chip fractures should be realigned and fixed using one or more small diameter, smooth Kirschner wires.
If chips are removed from articular surfaces, the borders of the articular cartilage must be cut perpendicular to the subchondral bone surface. In this fashion, the defect can be filled with fibrocartilage or hyaline cartilage and will heal. (15)Any edges not cut perpendicular will heal incompletely and a cleft will result.
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