Supracondylar Femoral Fractures In Adult Animals

Vol. 22, No. 11 November 2000

CE

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Refereed Peer Review

FOCAL POINT ★Choosing appropriate orthopedic implants and surgical techniques is critical to the successful management of supracondylar femoral (SCF) fractures in adult animals.

Supracondylar Femoral Fractures in Adult Animals University of Tennessee

David A. Lidbetter, BVSc, MVS, CertSAS, MACVSc, MRCVS University College Dublin

KEY FACTS ■ SCF fractures may be more challenging surgically in adult dogs than in immature animals in which the fracture tends to be through the growth plate. ■ After the fracture is thoroughly assessed, implants and surgical techniques should be tailored to individual fracture configurations. ■ Traditional repair methods such as intramedullary pinning and standard bone plating may not provide ideal stability for SCF fractures. ■ Alternative devices should be considered to stabilize SCF fractures in adult animals.

Mark R. Glyde, BVSc, MVS, MACVSc, MRCVS ABSTRACT: Supracondylar femoral (SCF) fractures in adult animals present significantly greater challenges to veterinary orthopedists than do fractures in immature animals in which the bone breaks are usually type I or II Salter-Harris physeal fractures. In adult animals, SCF fractures are often unstable because of their distal position and propensity to be comminuted. Because of the composition of the distal femur, minimal bone stock is usually available for implant placement. As a result, traditional implants such as intramedullary pins and dynamic compression plates may not be adequate to stabilize fracture forces. A range of available implants offers additional approaches to the management of this relatively uncommon fracture.

F

emoral fractures are commonly repaired in small animals. Midshaft diaphyseal fractures are the most common femoral fractures, followed by fractures of the distal epiphyseum. Supracondylar femoral (SCF) fractures occur infrequently in adult animals.1 The major texts and veterinary scientific literature cover the management of growth plate injuries in immature animals and midshaft femoral fractures in adults in some detail; however, far less information is available on the management of the often more challenging distal fractures.2–8 In humans, SCF fractures are a common fracture in which two distinct patient populations exist: Younger people sustain these fractures as a result of high-velocity trauma, and elderly people with osteoporosis often sustain them after minimal trauma.9–20 Various orthopedic implants and techniques, including intramedullary (IM) pinning, blade plating, buttress condylar plating, dynamic compression plating, interlocking nailing, Zickel supracondylar nailing, and double plating, are employed in humans to repair the fractures.9–20 Management of distal femoral fractures in young animals is typically straightforward because of the simple nature of the fracture and the innate potential of young animals to heal rapidly. The fractures normally occur through the weak zone of hypertrophy in the physis; the surface of the fracture often interdigitates in a W shape, giving the repair some inherent stability.21

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In adult dogs, SCF fractures implants to stabilize the fracture. can present substantial challenges The bone tends to have poorer because of the unique composiholding potential because of its tion of the distal femur and the material properties; however, it fact that the fractures are often does have a greater surface area more comminuted and unstable for fracture healing to occur. Im(Figure 1). These fractures are plant placement must also avoid difficult to manage because of key structures (e.g., articular carthe presence of large moments tilage, collateral and cruciate ligand forces acting on them with aments). short segments of bone distally. CLINICAL FINDINGS SCF fractures are located near an AND DIAGNOSIS area of high motion due to the Animals with SCF fractures presence of the knee joint and commonly present in an unstahave a small distal target for imble condition and may have sufplant placement that is eccentrifered concurrent injuries. They cally placed to the bone column. are usually non–weight-bearing In adult animals in which bioin the affected leg and will have buttress formation is slow, maxiconsiderable femoral swelling. mum stability (which is difficult Thorough physical, orthopedic, to achieve because of the small eccentric distal target) must be Figure 1—Lateral radiograph of a comminuted su- and neurologic examinations are necessary. Assessment of the cruobtained from the implant used pracondylar femoral fracture. ciate and collateral ligaments is to repair the fracture. Recently, especially important. Instability veterinary orthopedists have seen from the fracture and local swelling can make assessan influx of new repair devices that can be used to ment difficult. The cruciate ligaments in these animals manage these more difficult fractures (Table I). should be assessed directly by inspection via arthrotoANATOMY my during fracture repair. Initial diagnostics should inThe shaft of the distal femur is composed of hard clude a complete blood count, chemistry panel, urinalcortical bone, typical of the diaphysis of long bones. ysis, and chest and abdominal radiography. Continuous The femur begins to flare in its central midshaft region electrocardiography for 24 to 48 hours is advised. and is widest in the supracondylar/epicondylar area. FRACTURE CONFIGURATION The condylar bone is spongy, being primarily cancelAND NOMENCLATURE lous with a thinner cortical rim. Cranially, the condylar Fracture classification systems, which are based on region of the femur is bordered by the medial and laterthe patterns of large numbers of fractures, have been al condylar ridges and trochlear sulcus, which are covcreated for humans. These systems aid in rationalizing ered by hyaline cartilage.22 Distally, the condyles curve caudally with the intercondylar notch, separating the the use of a particular treatment, evaluating outcome, medial and lateral condyles. The intercondylar notch is and prognosticating. Although such systems have been the origin of the cranial and caudal cruciate ligaments. devised in veterinary orthopedics, they have not gained The stifle joint is a hinge joint with limited ability to widespread recognition and are not used universally.23,24 For reasons of simplicity, SCF fractures can be classified rotate and is primarily stabilized by the cruciate ligaas supracondylar, condylar, and supracondylar/interments. Primary mediolateral stability is from the collatcondylar. Commonly used descriptive terms include eral ligaments. The lateral collateral ligament attaches simple, multiple, comminuted, and open or closed. the caudal distal femoral condylar region to the head of the fibula, and the medial collateral ligament attaches SURGICAL APPROACH the medial epicondyle to the proximal medial tibia.22 More cranially on the lateral side of the stifle, the long Occasionally, SCF fractures that are incomplete or mindigital extensor tendon attaches onto the distal femoral imally displaced may be treated closed without any surgicondyle. cal approach. With the introduction of image intensifiers The relevance of the local anatomy is that SCF fracin veterinary surgery, closed reduction may be increasingly tures result in minimal bone stock in which to place used with implants placed percutaneously. Most often, DISTAL FEMUR ■ IMPLANT PLACEMENT ■ CRUCIATE LIGAMENTS

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TABLE I Devices Used to Repair Supracondylar Fractures in Adult Animals Repair Devices

Indications

Relative Contraindications

Important Points

Intramedullary pins

Use as adjunct fixation

Most SCF fractures

Poor rotational stability

Crossed K-wires

Cats; small dogs; transverse, short oblique fractures

Comminuted, cortical defect fractures

Simple technique; requires limited equipment

Rush pins

Cats; small dogs; transverse, short oblique fractures

Comminuted, cortical defect fractures

More difficult technique; requires specialized equipment

Lag screws

Small chondrodystrophoid breeds of dogs; very distal transverse fractures

Nonchondrodystrophoid breeds of dogs; comminuted fractures

Avoid screw placement into intercondyloid fossa; careful case selection

DCP

Many SCF fractures, particularly more proximal fractures

Chondrodystrophoid breeds of dogs; very distal fractures

Avoid trochlear ridge and intraarticular screw placement; use care with capsule closure

Reconstruction plate

Cats; small- and medium-sized dogs; chondrodystrophoid breeds of dogs

Large dogs; comminuted or cortical deficit fractures

Requires load sharing with bone; contour to distal caudal femoral bow

Plate/rod

Most breeds and sizes of dogs and cats; comminuted and cortical defect fractures

Some cats and small dogs; very narrow medullary canals

Place bicortical screws in metaphysis; place monocortical screws in diaphysis

Modified type I ESF

All breeds and sizes of dogs and cats; comminuted, open SCF fractures

SCF fractures with an articular component

Use positive-profile pins; avoid quadriceps

Customized hook plate

Most breeds and sizes of dogs; most fracture configurations

Use extra care with cats and small dogs

Modification of existing DCP required

Interlocking nails

Most breeds and sizes of dogs and cats; more proximal SCF fractures

Chondrodystrophoid breeds of dogs; some cats with very distal fractures

Requires specialized equipment and training

Tibial head compression plate

Large-breed dogs; most fracture Animals weighing <25 kg configurations

Right-sided plates are used for left-sided fractures

Hybrid circular ESF

Most SCF fractures; most breeds and sizes of dogs and cats; very distal fractures

Technically difficult; requires specialized training and equipment

SCF fractures with an articular component

DCP = dynamic compression plate; ESF = external skeletal fixator; K = Kirschner; SCF = supracondylar femoral.

however, either a full-open approach, mini-approach, or open-but-do-not-touch approach is employed.25,26 Typically, because of the instability of these fractures and their distal location, an approach to the shaft of the femur is combined with a lateral approach to the stifle as described by Piermattei and Greeley.27 An alternative technique, which provides excellent

exposure with only a minor increase in morbidity, combines the approach to the lateral femur with a tibial crest osteotomy and proximal reflection of the straight patella ligament and quadriceps group.10,27 The firmly attached periosteum and joint capsule should be elevated from the distal lateral condylar region when a bone plate repair of the femur is applied.

REPAIR DEVICES ■ LATERAL APPROACH ■ QUADRICEPS

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not fit, K-wiring can be a simple, efficient means of successful fracture repair. In general, IM pinning is not recommended as a reliable means of fracture stabilization of SCF fractures in adult animals. In one study,33 159 primarily immature cats and dogs reported good results using IM pins normograded from the stifle. Single IM pinning appears to work best in young cats with distal femoral fractures because of their relatively straight femurs and small size. However, IM pinning alone is often less than satisfactory for treating SCF fractures in adults. The technique results in poor distal bone-holding purFigure 2—Craniocaudal postoperative Figure 3—Craniocaudal radiograph of a chase and strength, and the pins are ofradiograph of a supracondylar femoral supracondylar fracture repaired with ten driven into the proximal condylar fracture repaired with crossed Kirschner stacked intramedullary pins. Note the region, immediately adjacent to the poor purchase of distal metaphyseal wires. fracture line instead of more distally in cancellous bone predisposing to instadeeper condylar bone. Single IM pins bility. overcome rotational forces poorly, often resulting in inadequate stability.34 TREATMENT Pins that are stacked probably do not gain greater purThe goals of fracture repair are as follows: rigid anachase distally and do not achieve greater cortical contact. tomic reduction and fixation, when possible; anatomic Stacked pins are technically more difficult to place and reduction of the joint surface and rigid fixation (articuoften do not improve stability (Figure 3). Instead of being lar fractures); reduction and stabilization or buttressing used as a sole implant, IM pinning can be incorporated as of the metaphyseal region (comminuted fractures); a valuable adjunct to external fixation or bone plating berestoration of normal axial alignment and length; and cause it overcomes bending forces. early controlled motion. Rush pinning can be an excellent means of stabilizing these fractures in cats and small- to medium-sized dogs, Intramedullary Pinning, Kirschner particularly when the fracture line is transverse or short Wiring, or Rush Pinning oblique. Rush pinning allows for three points of fixaCrossed Kirschner wiring (K-wiring), which is the tion, providing greater tension and stability. Rush pins mainstay of distal femoral fracture repair in immature are introduced from either side of the distal fragment at animals, has limited applications in SCF fractures in an acute angle after the pins have been prestressed.34 mature dogs, although its use may be indicated in The points are beveled so as not to engage the cortex. small- or toy-breed dogs or cats. The availability of Awls to start the guide holes and driver extractor tools bone stock in these animals may be so small that it preare required for placement. Where comminution or cludes the use of other implants. Contact between the cortical deficits exist, the pins may not provide suffifracture fragments must be achievable. A lateral apcient stability and fracture collapse can occur. Rush proach can be made to the distal femur, and the caudalpinning requires specialized equipment and training. ly displaced fracture can be reduced and maintained IM cross-pinning has also been described.35 with reduction forceps. Care should be taken to avoid crushing the bone in young adult animals. Fine, plain Lag Screw K-wires should be placed in cross-fashion either from Some SCF fractures may be extremely distal because the medial and lateral sides or both from the lateral side of the marked bow of the femur in chondrodys(Figure 2).2-8,28–32 The pins may be placed distal to proxtrophoid breeds. Occasionally, there may be room on imal or proximal to distal, depending on personal prefthe distal fragment for only one implant (e.g., one bone erence. In small adult animals with transverse distal plate screw hole, one fixator pin) to be placed. Instead SCF fractures in which larger, stronger implants may of using crossed K-wires in some of these fractures, lag BONE STOCK ■ FRACTURE STABILIZATION ■ BONE PLATING

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Figure 4A

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Figure 4B

Figure 5—Lateral postoperative radio-

Figure 4—(A) Lateral radiograph of an extremely distal supracondylar fracture in a

chondrodystrophoid dog. (B) Lateral postoperative radiograph showing repair using two 2.7-mm cortical lag screws.

screws may be positioned in parallel fashion from the cranioproximal femur to the caudodistal condylar region of the femur (Figure 4). This technique is useful only in chondrodystrophoid breeds when other implants do not fit. Because the strength of this type of repair is limited, it should only be used in certain cases.

Dynamic Compression Plate In midshaft femoral fractures, conventional and limited-contact dynamic compression plating is often chosen because of the ease of approach, minimal contouring needed to apply the plate, and rigid stability of the plate. In proximal SCF fractures, dynamic compression plating is also used for all sizes and breeds of adult animals. With more distal SCF fractures, insufficient distal bone stock typically limits screw placement. Two screws in each fracture fragment are the minimum requirement for stability. Ideally, at least three screws should be placed, but it is often impossible to place even two screws.36 Because dynamic compression plates (DCPs) can only be bent in two planes, they cannot be contoured caudally with the natural bow of the femur. Apart from reducing the number of potential screw holes, plates often overrun the distal femur protruding past it, impinging on the lateral edge of the trochlear groove and patella fibrocartilage (Figure 5). DCPs may also interfere with closure of the joint capsule and surgical wound and perhaps, most importantly, may disturb the dynamics of the patella and quadriceps mechanism. The patella may be luxated laterally or displaced dorsally as a result of the position of the plate.

graph of a supracondylar fracture repaired with a 3.5-mm dynamic compression plate. Inadequate stability is achieved because only four cortices are engaged and the plate overruns the distal femur.

Reconstruction Plate Reconstruction plates are ideally suited to fractures of the distal femur because of their unique ability to be contoured in three planes. The plates are available in 2.7, 3.5, and 4.5 mm and have notches manufactured into them between screw holes to allow them to be bent. Reconstruction plates are not extensively cold worked and are left in the annealed or soft state, thus giving them the property of ductility.36 In humans, these plates were initially designed for maxillofacial fractures but also have been used extensively in pelvic fracture repair. These anatomic areas in humans are usually under minimal strain; therefore, the plate has some protection.10 These plates are not designed to withstand the forces of weight bearing and should not be used to buttress fractures with bone deficits and marked instability.36 These plates can easily undergo cycling and bend, or they can fatigue and break. Reconstruction plates can be bent caudally and flared outward to contour to the distal femur and have been used for SCF fractures in small animals (Figure 6). This can increase bone purchase by increasing the number of screws engaging the bone and preventing plates from extending distally, interfering with the stifle. Reconstruction plates ideally are used in smaller adult animals in which there can be reconstruction of the bone column and sharing of the load through the bone and plate when the animal bears weight on the limb. These plates are particularly useful in chon-

CORTICAL LAG SCREWS ■ SCREW PLACEMENT ■ PATELLA

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Figure 6—Lateral radiograph of supra-

Figure 7A

condylar fracture repair using a 2.7-mm reconstruction plate.

Figure 7—Craniocaudal radiographs of a highly comminuted midshaft supracondylar

Figure 7B

femoral fracture (A) and repair using a plate rod technique (B).

drodystrophoid breeds in which marked caudal bowing of the condylar region precludes using standard bone plates in more distal fractures.36 When only one or two screws are placed in the distal fragment, crossed Kwires should be used for additional stability.

Plate–Rod Combination The plate–rod technique attempts to synergize the actions of IM pins and bone plates.8,25,26,37–39 This technique is especially useful in highly comminuted fractures or when a significant cortical deficit that cannot be anatomically reconstructed is present (Figure 7). An open approach to the femur and stifle should be made, and an IM pin can be placed either retrograde or normograde in order to reduce the fracture and aid alignment. The trochlear sulcus and greater trochanter can be used as landmarks to avoid rotation of the stifle or anteversion of the femoral neck and head. The limb should be checked for varus deformation before a plate is applied to the lateral femur. The plate neutralizes rotational, bending, and axial forces while the pin, which is placed centrally in the bone, protects the plate and guards against bending.25,26,37–39 Although this technique involves a significant number of implants, no attempt should be made during repair to anatomically reconstruct multiple small fracture fragments. This biological approach to the repair tries to minimally disrupt the already fragile blood supply to the fracture.25,26,38 A bone graft should also be placed. A minimum of three monocortical screws and one bicortical screw should be used on either side of the frac-

ture.8 Guidelines for pin size and screw number have been published; a pin diameter of no greater than 50% of the medullary canal at its narrowest point is recommended. Because screw placement in the diaphysis is often extremely difficult, it may only be possible to place screws in the metaphyseal regions.

Modified Type I External Fixator The modified type I external skeletal fixator (ESF), which can be used in all cats and dogs, can be applied to most SCF fractures, including those that are transverse, comminuted, or very distal. No implants are placed at the fracture site and either a complete open approach, a limited approach, or closed reduction and frame application can be used. This type of implant has the potential for less soft tissue and associated vascular damage. Initially, in veterinary practice, the use of ESFs was primarily reserved for the distal limb with less use in proximal limbs owing to the larger mass of soft tissue and impingement of the body wall medially. The use of fixators in the femur and humerus in cats and dogs has increased because of the introduction of modified and more complicated strategies and frames. Simple type I ESFs can be used in SCF fractures; however, gaining adequate purchase in the distal fragment is not always feasible. Placing one or two centrally threaded positive-profile full pins in the distal condylar region from lateral to medial allows the use of a bent, additional connecting bar to be passed from the medial side of the distal femur to the lateral proximal femur (Figure 8).40,41 This increases the stiffness of the frame

COMMINUTED FRACTURES ■ OPEN APPROACH ■ PIN DIAMETER

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Figure 9—Customized hook plate from

a regular dynamic compression plate. Figure 8A

Figure 8B

Figure 8—(A) Supracondylar femoral (SCF) fracture treated with a modified type I

external skeletal fixator (ESF) with only a lateral connecting bar. (B) SCF fracture treated with a modified type I ESF with both lateral and medial connecting bars.

and minimizes fracture instability and pin loosening. It is advisable to use another one or two half-pins in the distal fragment, if possible, and four half-pins proximally. Positive-profile pins are used because of their added cortical bone contact, increased pin pull-out strength, and lower incidence of pin–bone interface problems.42–44 This frame is well tolerated by cats and dogs and results in minimal to no body wall contact with the frame.45 Alternatively, an acrylic frame can be used in the humerus to connect the lateral type I pins across the distal femur to the medial side, then continuing proximally over the thigh to the lateral proximal aspect.46 The bending strength of the frame is improved by placing an IM pin in the shaft of the femur and then connecting it to the main lateral frame in a “tied-in” configuration.47 In SCF fractures, fixators are often placed via an open approach because of the difficulty in reducing the fractures closed. If an open approach is made to a comminuted SCF fracture, it is usually an open-butdo-not-touch approach in which the proximal and distal bone columns are reduced, the hip and stifle joints are aligned, and no attempt is made to anatomically reconstruct the bone column.25,26 The presence of pins in the distal femur can cause irritation to the joint capsule, retinaculum, and soft tissue. The stifle, being a high motion area, can add to the irritation. The quadriceps muscle should be avoided, and soft tissue entrapment can be minimized by using retraction or drill guides. Morbidity associated with the pins can include pin tract discharge and infection,

pin loosening, and decreased stifle range of motion and leg usage.42–44 Although significant complications are uncommon, veterinarians and owners should monitor and clean the skin surrounding the pins, encourage controlled physical therapy, and monitor radiographs for evidence of pin loosening.

Customized Hook Plate A customized hook plate has been developed recently for use in metaphyseal fractures when minimal bone stock is a complicating consideration.48 The technique involves bending a standard DCP and fashioning sharp, pointed hooks with a hacksaw blade (Figure 9). This modified implant can be useful in SCF fractures with small distal targets and can have some advantages over conventional plates. The same number of screw holes can be used as in a DCP, with the addition of the fashioned hooks. Two parallel holes set the width of the plate apart should be drilled into a distal portion of the femoral fragment before gently hammering the hooks into the bone (Figure 10). Drill diameter should be slightly larger than that of the hooks. The fracture should be reduced and a screw hole in the proximal fracture fragment filled, securing reduction. The remainder of the screw holes in the distal and proximal fragments should be drilled and filled. In humans, a dynamic compression screw may be used to compress SCF/intercondylar femoral fractures, or an AO (Arbeitsgemeinschaft fur Osteosynthesefragen) blade plate can be used to provide increased surface area contact of the plate in distal bone.10,11,13,17

POSITIVE-PROFILE PINS ■ METAPHYSEAL FRACTURES ■ MODIFIED IMPLANT

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Figure 10—Customized hook plate placed using predrilled

Figure 11—Surgical application of an interlocking nail.

holes and a mallet.

These implants are generally too large to use in most animals; however, the customized hook plate follows similar principles to that of the blade plate. The tight security of the hooks is less important than is their contact in the bone.10 Screws can be placed through the hooked area, thus the number of screws in the distal fragment is not reduced yet the points of contact are increased.48 The drawback of this technique is that because an aiming jig is not available for screw placement, moderate force may be needed to hammer the hooks into the bone holes. This does not, however, detract significantly from the technique. Similar to the DCP, the modified hook plate may cause difficulty in closing the joint capsule and can affect the patella if the plate is positioned too close to the trochlea ridges. The technique is adaptable and has been used successfully in medium to large dogs. Care may be needed in small dogs and cats to ensure adequate width is present for the hooks to be placed distally.

Interlocking Nails Adapted from human medicine, the Dueland interlocking nail system is designed for veterinary patients.49 The nails are solid, surgical stainless steel with screw holes at either end. An open approach to the femur is usually made and limited muscle reflection is necessary. Screws should be inserted through the bone to engage the nail, thereby preventing rotation of the fracture and axial collapse (Figure 11).49–51 Interlocking nails (ILNs) offer the advantage of positioning the implant centrally in the bone, thereby providing excellent bending strength. Three nail models are available with lengths from 140 to 230 mm. Nail diameters range from 4.7 to

8 mm and accept 2.0-, 2.7-, 3.5-, and 4.5-mm screws.49 The largest nail that fits the medullary canal should be chosen. The nail should be long enough to place the screw holes 2 cm from the fracture site, and nails of similar length and contralateral limb radiographs should be used to ensure that the pin is seated in distal metaphyseal cancellous bone.49–51 The distal fragment in SCF fractures may need to be overreduced. The nails are usually placed in normograde fashion; however, an opening in the proximal cortex may be made using a separate pin in a retrograde fashion. Because the nails have been customized for animals, problems with aiming and executing the technique have been ameliorated. Nails are now made with more distal screw hole placement so that they can be applied to SCF fractures. An obstacle with this technique is the inability to lodge the pin distal enough to gain screw purchase below the fracture line; occasionally, a single screw hole below the fracture line is necessary. This should not significantly alter stability at the repair site.51 The ILN is an adaptable system requiring specialized equipment, which can be used for most sizes and breeds of adult animals. It can be used in transverse and comminuted fracture patterns. Complications with the technique include problems with screw aiming and placement, breakage of the nail at the screw hole, and sciatic nerve damage if the nail protrudes from the intertrochanteric fossa.49

Tibial Head Compression Plate The tibial head compression plate is primarily for use in dogs weighing more than 25 kg. The design of the

BLADE PLATE ■ AXIAL COLLAPSE ■ MEDULLARY CANAL

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conducive to bone healing.57 plate allows for more screws to be Hybrid circular fixators, which can placed in the distal fragment below the be used in all breeds and sizes of dogs SCF fracture line. The plate, which and cats, have an advantage over conhas been precontoured to fit the proxiventional external fixators in SCF fracmal lateral tibia in humans, was detures. Because the pins are so small, signed for complex fractures of the tibmore can be placed in a finite area; ial plateau.10,52 The plate has the same thus more cortices can be engaged in thickness as the 3.5-mm broad DCP, the case of very distal fractures.54,55 although it is 2 mm wider. The plate is Overall stability of the frame can be available with five, seven, or nine DCP increased by using the smallest-diamshaft holes, which accept 4.5-mm coreter ring, allowing for 1 to 2 cm betical screws, and is available in 118- to tween the ring and skin for swelling; 240-mm lengths. One end of the plate placing two parallel rings, if possible; is flared to a maximum width of 26 increasing the number of wires per mm and curves in a convex fashion ring; placing wires as close to 90° to about 13˚ (Figure 12).53 The flared each other as possible; using tear-drop head thickness gradually reduces censhaped wires; and using positive protrally to 1.57 mm and has three round file half-pins in the proximal fragholes in a triangular pattern.53 The ment.54–59 round holes are separated from regular Figure 12— Lateral tibial head plates. Hanging of the limb operatively DCP holes by an oval hole that can act helps aid reduction and preplanning; as a positioner when the first screw is partially constructing the frame preoperatively can help placed. The round head holes accept 4.5-mm cortical, reduce surgical time. As with the ESF, the hybrid circu6.5-mm cancellous, and cannulated screws. lar fixator can be placed after closed reduction or after a When the plate is placed in the opposite fashion to limited approach. The hybrid circular fixator is an its use on the tibia (i.e., a right-sided tibial plate is placed adaptable technique that requires specialized equipon the left femur upside down), it mimics the caudal ment and training. bow of the femur and its distal flaring.53 The advantage in SCF fractures in larger dogs is that more screws can SURGICAL PITFALLS be placed in the distal fragment when there is minimal When fracture fragments cannot be reduced anatombone stock because of the unique shape of the plates, ically, the femoral neck must be maintained at the corneck, and head (Figure 13). rect angle with respect to the stifle or a change in the angle of anteversion/retroversion at the coxofemoral Hybrid Circular External Skeletal Fixator joint will occur. This may lead to progressive degeneraOver the past 10 years, there has been increased attive joint disease, dysplasia, or predisposition to coxtention in veterinary medicine to the use of circular ofemoral luxation. ESFs for fracture repair, bone lengthening, and gradual Appreciation of the normal anatomy of the lateral correction of angular limb deformities.54–56 Most reports surface of the femoral shaft is essential. From slightly concentrate on the use of full rings for tibial and raproximal to the midshaft, the bone begins to flare and dius/ulna fractures.55 In the humerus and femur, full widen. If this contour is not accounted for in the plate, ring constructs cannot be used because of the presence the limb will be plated with a varus deviation and result of the body wall. in an incongruity in joint alignment, which may also Hybrid circular fixators combine one or two full result in lameness or degenerative joint disease. Radiogrings attached to the distal femoral fragment and are raphy of the contralateral leg can aid in avoiding this linked to a lateral connecting bar where half-pins simimistake when contouring the plate. lar to a type I external fixator are used.57 The full rings Distal femoral fractures usually require an approach allow two or more small-diameter wires or pins to be to the lateral stifle if internal implants are to be placed. placed percutaneously; these can be tensioned by a deAs a result, the lateral retinacular tissue of the patella vice that increases the bending stiffness of the wires. and soft tissue support is divided. If the implant exCircular fixators provide similar torsional bending and tends to the distal lateral limit of the femur or past the shear resistance as do type I external fixators.57 There is femur, the potential exists that the patella will not be less axial stiffness and increased continual micromotion stabilized correctly at closure, resulting in laxity. This at the fracture site when the animal is walking, which is TIBIAL PLATE ■ FULL RINGS ■ HALF-PINS ■ CORTICES

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Figure 13A

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Figure 13B

Figure 13C

Figure 13—Lateral postoperative (A) and craniocaudal (B) radiographs in an adult German shepherd of a supracondylar femoral

fracture repaired with a lateral tibial head plate. (C) The lateral tibial head plate in situ.

can lead to luxation or abnormal wear. In addition, it can be difficult to adequately close the joint capsule because of the presence of the implant. The common peroneal nerve, which lies caudal to the lateral fabella on the medial surface of the biceps, must be visualized before fracture repair to prevent iatrogenic damage.

POSTOPERATIVE REHABILITATION Supracondylar femoral fractures predispose the animal to soft tissue complications. Quadriceps contracture and tie-downs, which are seen more frequently in immature animals with fractures, can also occur in mature animals.60 Often, the quadriceps may be damaged by the trauma involved in creating the SCF fracture. After open surgical repair, the muscle is prone to undergo fibrosis and to scar to the underlying periosteum. Signs of quadriceps contracture begin subtly and include decreased limb usage, muscle atrophy, pain, stiffness, and a reduced range of stifle motion. This condition can rapidly progress to rigid hyperextension of the affected leg with reduced flexion of both the stifle and the hock. The quadriceps becomes firm and severely atrophied. After quadriceps contracture has begun, the process can be difficult to reverse; therefore, prevention is often better than cure.61 A physical therapy program must be instituted soon after surgery. Rigid surgical stabilization and adequate analgesia are required. Following surgery, the limb should be iced, the circumference measured, and range of motion assessed with a goniometer.62 If available, force plate analysis can be used to document weight-bearing status. This base-

line data can be used throughout the recovery period to quantify progress. Early use of the limb is of paramount importance; therefore, range-of-motion exercises should be performed daily. The limb should be iced before each session and massaged before beginning vigorous physical therapy. Exercises can include sit-stand, short leash walks, treadmill walking, or walking up inclines. Supervised hydrotherapy in a bath or underwater treadmill can begin after suture removal. At discharge, owners must be thoroughly educated regarding care and procedures, and regular follow-up visits should be encouraged. To avoid soft tissue disease, active physical therapy must be continued until fracture healing is completed. Further therapy after this time will help reverse muscle atrophy and improve long-term limb function.

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About the Authors Dr. Lidbetter is affiliated with the Department of Small Animal Clinical Sciences, University of Tennessee, Knoxville. Dr. Glyde is affiliated with the Department of Veterinary Surgery, University College Dublin.