Veterinary Healthcare - Distal limb injury: The hind-limb (Proceedings)
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Distal limb injury: The hind-limb (Proceedings)


CVC IN KANSAS CITY PROCEEDINGS

Orthopedic injuries to the distal limb may affect tendons, ligaments, bones, or articular structures. Common distal injuries of the hindlimb in small animals include calcanean tendon disruption, plantar ligament rupture, fractures of the calcaneus, malleolar fractures, collateral ligament rupture and shearing wounds. A less common injury is luxation of the superficial digital flexor tendon.

Injury to the Common Calcanean Tendon

Dysfunction of the common calcanean tendon can occur by rupture or avulsion of the gastrocnemius muscle proximally, laceration or rupture along the tendon, or avulsion of the tendinous insertion on the calcaneus. Avulsion of the distal insertion of the gastrocnemius is the most common presentation. The common calcanean tendon is composed of 3 major groups. The gastrocnemius muscle originates on the distal femur and is the most significant portion of the common calcanean tendon. The gastrocnemius tendon attaches laterally on the calcaneus. The combined tendon of the biceps, gracilis and semitendinosus muscles attaches medially on the calcaneus. The superficial digital flexor tendon caps the tuber calcanei, attaching on each side, and continues distally to insert on the plantar aspect of the second phalanges.

In animals with an intact calcanean tendon apparatus, there is a normal flexion angle of the tarsocrural joint while standing. This angle is approximately 140 degrees in the dog and 120 degrees in the cat. The standing angle will match the contralateral side. On physical examination, the animal is placed in lateral recumbency and the limb is held at a normal standing angle. In this position, flexing the tarsocrural joint to 90 degrees should produce tension in the calcanean tendon. Damage to the calcanean tendon creates varying degrees of a plantigrade stance, depending on the type of injury, and there may be laxity of the calcanean tendon when the joint is flexed to 90 degrees.

A classification scheme for common calcanean tendon lesions has been described. In this classification, there are 3 types. A Type 1 injury is complete rupture of all 3 components of the common calcanean tendon. Dogs with complete tendon rupture have a plantigrade stance. When the stifle joint is held at a normal standing angle, the tarsocrural joint can be completely flexed beyond 90 degrees. A gap between tendon ends may be palpable and there may be a visible laceration of the skin and underlying tissues. A Type 2 injury involves rupture of some but not all 3 major components of the common calcanean tendon. The most common presentation of a type 2 injury is avulsion of the gastrocnemius tendon from its insertion site on the calcaneus. A unique postural change occurs when the superficial digital flexor tendon remains functional but there has been disruption at some point along the calcanean tendon. Because of increased tension on the superficial digital flexor, there is flexion of the digits in a characteristic "claw" appearance. A type 3 injury is inflammation of the tendon. A type 3 injury causes lameness that becomes worse with exercise but the angle of the stance is normal. On palpation, a thickening is palpable just proximal to the calcaneus.

Radiographs are evaluated for soft tissue swelling along the common calcanean tendon and soft tissue calcification within the tendon. With distal avulsion injuries, the proximal calcaneus may be roughened and bony fragments may be present. There may also be a "beaklike" projection of bone on the plantar aspect of the tuber calcanei. This represents proliferative bone at the retinacular attachments of the superficial digital flexor tendon. Increased stress on this tendon presumably elicits this response.

Repair of Avulsion of the Gastrocnemius Tendon Insertion

For surgical stabilization, the distal end of the debrided tendon is affixed to the calcaneus by means of suture and a bone tunnel. In very chronic cases, resection of fibrous tissue at the distal end of the common calcanean tendon creates a gap that prohibits direct apposition of the tendon to the calcaneus. In these circumstances, surgical options include tendon transposition or pantarsal arthrodesis. A primary calcanean tendon repair can be supplemented with autogenous tissue or synthetic material. This would be indicated with a chronic injury, an injury that required a large resection of scar tissue, or an overweight animal. The repair is conducted in a standard fashion by using a tendon suture to secure the gastrocnemius and combined tendons to the calcaneus. The supplemental material is sutured over the primary repair. Fascia lata is an autogenous source and polypropylene mesh is a synthetic source of material. Synthetic mesh has been used successfully to strengthen calcanean tendon repair in human patients and in the dog. Mesh provides added tensile strength that is particularly beneficial early in the healing process to help prevent gap formation.

A lateral paramedian approach is made over the distal tendon and tuber calcanei. The tendon is debrided to create a smooth end for suturing. In chronic cases considerable debridement is necessary to resect fibrous tissue attachments from the calcaneus. Moving in a proximal direction, fibrous tissue is resected until normal appearing tendon is reached. The gastrocnemius tendon is reattached to the tuber calcanei by means of a bone tunnel and a modified triple loop pulley suture. A small stump of soft tissue is left attached to the calcaneal tuberosity if possible. Monofilament suture is used (nylon or polypropylene size 0 to 2). If both the gastrocnemius and the common tendons are both involved, they may be sutured as a single unit using a single lateral to medial drill hole in the calcaneus. The single drill hole is placed just distal to the site of tendon insertion on the calcaneus. When placing the modified triple loop pulley pattern in the tendon, the "far" bite is 1.5 cm, the "middle" bite is 1.0 cm and the "near" bite is 0.5 cm from the end of the tendon. There are 3 passes of suture and each pass is started approximately 60 degrees from the preceding one. The modified three-loop pulley pattern proceeds as follows: The first loop is passed from lateral-medial through the bone tunnel and then medial-lateral through the "far" position of the tendon. The second loop is passed in the same lateral-medial direction through the bone tunnel and then in a caudomedial-cranilateral direction through the "middle" portion of the tendon. The third is passed lateral-medial through the bone tunnel for a final time and then in a craniomedial-caudolateral direction through the tendon for the "near" bite. The lateral retinaculum of the superficial digital flexor tendon is sutured in an interrupted pattern during closure to prevent luxation.

The tarsocrural joint is stabilized with a transarticular external fixator for 4 to 5 weeks postoperatively. The modified transarticular fixator, with a pin in the distal tibia, calcaneus, and proximal metatarsals, is suitable for this application. The joint is placed in mild extension to relieve tension on the repair. The fixator is then removed and the joint is stabilized with a splint for 3 weeks followed by a soft padded bandage for 2 to 3 weeks for gradual transference of weightbearing.

Supplemented Repair

Autogenous or synthetic material can be used to supplement a calcanean tendon repair. To collect autogenous tissue, a craniolateral approach to the distal femur is performed. A strip of fascia lata, approximately 10 cm X 2 cm, is harvested. The graft is placed over the lateral aspect of the gastrocnemius tendon and longitudinally wrapped around the gastrocnemius tendon repair. The graft is secured proximally to the tendon with simple interrupted sutures. Distally the graft is secured to the calcaneus using a lateral to medial bone tunnel. Polypropylene mesh can be secured to the repair in a similar way. The mesh is divided lengthwise into 3 layers and is applied over the gastrocnemius tendon. The mesh is secured proximally to the tendon with simple interrupted sutures and distally to the calcaneus using a bone tunnel. A transarticular external fixator is placed as described for immobilization.

Plantar Ligament Rupture

Three distinct plantar ligaments have been described: the medial, middle, and lateral plantar ligaments. The middle is the most commonly injured plantar ligament. The middle plantar ligament originates on the body of the calcaneus and attaches to the fourth tarsal bone before inserting on the base of the fourth and fifth metatarsals. Rupture of the plantar ligaments destabilizes the proximal intertarsal joint. Subluxation of the proximal intertarsal joints is a common tarsal injury in small animals and often occurs with no history of known trauma. Middle-aged collies and Shetland Sheepdogs appear to be over-represented. Clinically, the affected hock is not especially painful despite local swelling, and a plantigrade stance occurs with weight bearing.

Luxation of the proximal intertarsal joint is associated with severe trauma and is more likely to be associated with fractures of the tarsal bones than subluxation injuries. There is no breed predisposition for this injury. On radiographs, the talus is displaced in a plantar direction and the distal aspect of the tarsus is displaced in a dorsal direction.

Surgical Repair

Arthrodesis of the calcaneoquartal joint is recommended and can be accomplished with a bone plate or intramedullary pin (IM pin) and tension band wire or a bone plate. The bone plate can be placed laterally or medially. There is more room for proximal screws with a lateral plate. A lateral approach to the calcaneus and metatarsus is made. The superficial digital flexor tendon is retracted medially and the abductor digiti quinti muscle is elevated to expose the calcaneus, fourth tarsal bone, and base of the fifth metatarsal bone. The paw is stressed medially and articular cartilage is removed from the calcaneoquartal joint. An appropriately sized dynamic compression plate (2.7 mm to 3.5 mm) is chosen. Three screws are placed in the calcaneus and 3 in the metatarsus. When drilling holes into the calcaneus, they should not be placed too close to the plantar cortex, as this may cause a stress riser and promote fracture of the calcaneus. After closure of the primary incision, multiple punctuate releasing incisions are placed on either side to limit postoperative swelling of the paw. This technique is helpful for most distal limb surgeries.

A lateral splint extending from the proximal tibia to the digits is placed for 3 to 4 weeks postoperatively weekly changes. This splint is replaced with a soft padded bandage for 2 weeks.

Malleolar Fractures

The medial and lateral malleolus serve as the origin for the respective collateral ligaments. Fracture of either malleolus results in significant tarsal joint instability and requires surgical repair.

Malleolar fractures are commonly repaired using a tension band fixation. This fixation consists of 2 small pins (K wires) that traverse the fracture line and anchor in the far cortex of the tibia. A cerclage wire is placed around the pins and through a hole in the distal tibia in a figure 8 fashion. Special care is taken not to penetrate the tarsocrural joint with the K wires. The malleoli extend distal to the articular surface, so the pins must be angled proximally enough to avoid the joint. Stability of the joint should be tested after fixation to verify the integrity of the collateral ligaments. An alternative to tension band fixation is lag screw fixation of the fractured malleolus.

Fractures of the Calcaneus

A calcaneal fracture disrupts the common calcanean tendon apparatus. The result is a plantigrade stance and marked displacement of the proximal bony fragment due to the tensile force of the calcanean tendon. The proximal half of the calcaneus is referred to as the tuber calcanei and the middle portion is the shaft. The distal portion is the base of the calcaneus. Fractures occur most commonly at the tuber or in the shaft and less commonly near the base. Fractures at the base of the calcaneus disrupt the origin of the plantar ligament and therefore cause subluxation and hyperextension of the calcaneoquartal joint.

Calcaneal fractures are common in racing greyhounds and, in this breed, often occur in conjunction with central tarsal bone fractures. Chronologically, the central tarsal bone fails, and next the head of the talus is displaced distally into the fracture gap of the central tarsal bone. Tension from the common calcaneal tendon and loss of dorsomedial support place abnormal stress on the calcaneus and plantar ligaments. Relief of the accumulated forces on the lateral and plantar aspect of the tarsus occurs by fracture of the calcaneus. If the calcaneus remains intact, as the central tarsal bone collapses, the brunt of the remaining fracture forces are conferred to the fourth tarsal bone and result in fracture of this bone.

Tension Band Fixation for Proximal Fractures of the Calcaneus

Tension band fixation is often used for proximal avulsion fragments. The skin incision begins on the lateral side of the common calcanean tendon just proximal to the tuber calcanei and extends to the level of the fourth tarsal bone. The skin and subcutaneous tissues are reflected to expose the deep fascia. The lateral border of the tendon of the superficial digital flexor muscle is located. An incision is made parallel to the lateral border of the tendon. If there is a small proximal avulsion fragment, the tension band fixation is placed in standard fashion: intramedullary pins are inserted down the shaft of the calcaneus and cerclage wire is anchored around the proximal pins and through a distal transverse hole in the bone. The proximal bone fragment is grasped with pointed reduction forceps and manually held in correct position for normograde pin insertion. It is not necessary to pre-drill for pin placement in the calcaneus of young dogs. In older animals a pre-drill is often necessary because the bone of the calcaneus is so dense. If a pre-drill is required, the drill size is slightly smaller than the intramedullary pin. The pins are placed in a slightly lateral and slightly medial orientation to minimize postoperative irritation of the overlying superficial digital flexor tendon. A transverse hole is drilled in the shaft of the calcaneus with a small drill bit (size 2.0 mm in a medium dog). The size of cerclage wire must be large enough to resist fatigue. The following sizes are recommended: up to 15 to 20 pounds, 22 gauge; 20 to 40 pounds, 20 gauge; and over 40 pounds, 18 gauge. The cerclage wire is placed in figure eight fashion and the proximal pins are bent over to the side and cut short. The cerclage wire is cut between the first and second twist.

If there is a larger fragment of proximal bone, the tension band is placed in a different manner. A single larger intramedullary pin is selected and placed in normograde fashion down the shaft of the calcaneus. Prior to placing the pin, a transverse hole is drilled through the proximal fragment and through the distal shaft of the bone. A pre-drill, slightly smaller than the pin, is used in mature animals to ease pin placement. The pin is cut as short as possible and then countersunk using a pin punch and mallet (Securos Veterinary Orthopedics, Charlton MA). The appropriate size wire is passed through the 2 transverse holes in a figure eight pattern and tightened. The cerclage wire is cut between the first and second twist. The superficial digital flexor tendon is sutured to the retinacular fascia using interrupted sutures.

Bone Plate Fixation of the Calcaneus

Bone plate fixation can be readily applied in many mid-shaft fractures of the calcaneus. The calcaneus must be large enough to permit the placement of 5 to 6 screws along the length of the bone. A size 2.7 mm bone plate will fit most medium sized dogs whereas a veterinary cuttable plate (Synthes, Paoli, PA) is useful for smaller animals. With comminuted fractures, a combination of a slightly undersized intramedullary pin with the bone plate strengthens the repair.

Surgical Repair for Collateral Ligament Rupture of the Tarsus

Complete rupture or avulsion of the collateral ligaments is categorized as a grade 3 sprain. This type of injury significantly destabilizes the tarsocrural joint. Medial injuries allow valgus (lateral) deviation of the foot, and lateral injuries allow varus (medial) angulation. For subluxations not visualized on standard lateral and craniocaudal radiographs, stress radiography is indicated for diagnosis. The examiner applies a valgus stress to show medial collateral ligament rupture and a varus stress to show lateral collateral ligament rupture. A widened joint space indicates collateral ligament instability. In some cases, it is helpful to do a stress view on the opposite side for comparison. At surgery, the ligament is typically too frayed to hold sutures and is instead supported using a prosthetic imbrication technique. Prosthetic imbrication supports the joint by anchoring suture material to the approximate origin and insertion sites of the ligament. The suture material provides initial stability and serves as a template for fibroplasia to provide long term stability.

Prosthetic Imbrication using Suture Anchors

There are several types of suture anchors designed for use in veterinary patients. (Suture Anchors, Imex Veterinary, Inc., Longview, TX; Bone Anchors, Securos Veterinary Orthopedics, Charlton, MA, FlexiTwist, Innovative Animal Products, Rochester, MN). Most suture anchor systems look similar to traditional bone screws in that they have a threaded shaft, but are equipped with a hole at the top for passage of suture material. Most products have specialized screw drivers that fit the suture anchors and are used to implant the device into bone. Traditional screws and washers can also be used as anchor points for suture instead of specialized suture anchors. Monofilament nylon suture or 60 to 80 pound test fishing line is suitable for this technique. A polyester blend suture can also be used in this application (Fiberwire, Arthrex, Inc., Naples, FL).

Prosthetic Imbrication Technique for Medial Collateral Ligament Rupture

A double prosthetic imbrication technique is used. This technique anchors suture from the origin of the collateral ligament to the distal insertions of both the long and the short portions of the collateral ligament. The origin of the medial collateral ligament is located just proximal to the medial malleolus. The surgeon must be aware that the malleolus extends 1 to 2 cm distal to the tarsocrural joint space. The anchor is placed as distally in the tibia as possible, without invading the joint space, and just cranial to midline. For the medial short ligament insertion site, the anchor is placed in the proximal plantar aspect of the medial talus. This screw should appear to be slightly distal and plantar to the origin screw. The anchor for the long ligament insertion is placed at the plantar base of the talus. Suture size is chosen according to the size of the animal. For a medium to large sized dog, size 60 to 80 pound test fishing line is used in proximal anchor and size 40 to 50 pound test fishing line is used in the distal anchors. One strand from the origin suture anchor is tied to both strands of the short insertion anchor with the joint held in 90 degrees of flexion. The remaining strand from the origin suture anchor is tied to both strands of the long insertion anchor with the joint held at the normal standing angle. Approximately 4 to 6 throws are placed in each knot to ensure security.

Prosthetic Imbrication Technique for Lateral Collateral Ligament Rupture

The tendon of the peroneus longus muscle is seen on the cranial aspect of the lateral malleolus and the lateral digital extensor and peroneus brevis tendons are caudal to the malleolus. The extensor retinaculum overlying the lateral malleolus is incised parallel to the peroneus longus tendon so the tendon can be retracted cranially. The origin of the lateral collateral ligament is located just proximal to the lateral malleolus. The surgeon must be aware that the malleolus extends 1 to 2 cm distal to the tarsocrural joint space. The origin anchor is placed through the distal fibula and into the tibia. The location is more caudal than that of the corresponding screw for medial collateral ligament imbrication. The insertion anchor for short portion of the ligament is placed in a position just proximal and plantar to the articular surface of the calcaneus. The insertion anchor for the long portion of the ligament is located at the base of the calcaneus. Suture size is chosen according to the size of the animal. For a medium to large sized dog, size 60 to 80 pound test fishing line is used in proximal anchor and size 40 to 50 pound test fishing line is used in the distal anchors. One strand from the origin suture anchor is tied to both strands of the short insertion anchor with the joint held in 90 degrees of flexion. The remaining strand from the origin suture anchor is tied to both strands of the long insertion anchor with the joint held at the normal standing angle. Approximately 4 to 6 throws are placed in each knot to ensure security.

Aftercare

The tarsocrural joint is immobilized with a transarticular external fixator for 4 weeks postoperatively. When the fixator is removed, a splint is applied for 3 weeks and then a soft padded bandage for 2 weeks. Alternatively, a mobile hinge external fixator may be employed (Slocum Enterprises, Eugene, OR; Imex Veterinary, Longview, TX). During initial healing phases, the hinge may be locked in position and then mobilized approximately 3 weeks later.

Polysulfated chondroitin (Adequan; Novartis Animal Health, Greensboro, NC) is recommended during and after joint immobilization. We use Adequan at a dose of 4.4 mg/kg subcutaneously 2 to 3 times weekly for the first month then taper to once every 2 to 4 weeks as needed.

Shearing Wounds

Minor to Moderate Shearing Wounds

Shearing injuries are commonly encountered in small animal practice. With minor to moderate shearing wounds, soft tissues of the distal limbs are avulsed or abraded following vehicular trauma. There is loss of skin, subcutaneous tissues, ligaments, and often bone. Shearing wounds tend to be heavily contaminated with foreign debris. The medial aspect of the distal portion of the limbs is affected most often, with tarsal injuries predominating over carpal injuries. The appearance of shear injuries suggests that many animals are oriented in a prone position with the hind limb abducted at the time of injury. This would expose the medial aspect of the tarsus to the ground if the limb was caught under the car at the moment of contact. The collateral ligament support of the tarsus often is lost, even in smaller wounds, due to the prominent position of the malleolus, resulting in medial or lateral instability of the tarsal joint. Approximately 72 % of tarsal shearing injuries result in joint instability.

The extent of ligamentous damage is estimated based on visual inspection of the wound, palpation under heavy sedation, and survey and stress radiographs. Mild shearing wounds have collateral ligament injury but no loss of bone. Moderate shearing wounds have ligament injury and bone loss, which can range from loss of the malleolus only to malleolar and talus involvement. Loss of bone from the articular surface of the tarsocrural joint is considered to be a severe shearing injury. The technique chosen for stabilization of collateral ligaments depends on the degree of damage to osseous structures in the tarsus and the expected activity level of the dog. Some animals with mild to moderate shearing injury do well treated conservatively, with splint fixation alone, for 6 to10 weeks. This technique relies on periarticular scar tissue to stabilize the joint. However, in our experience, early surgical stabilization provides the best opportunity for maximum joint function. Damage limited to malleoli and collateral ligaments can be repaired using prosthetic imbrication techniques as previously described for collateral ligament ruptures. Further stabilization is achieved by placing a transarticular external fixator. Surgical stabilization procedures can be initiated early in the healing process.

Conservative Management of Minor to Moderate Shearing Wounds

Conservative management of shearing wounds consists of wound lavage, debridement, application of topical medications, and immobilizing the tarsus with a soft padded bandage reinforced with fiberglass splint material. The bandage should extend from proximal tibia to the digits. Water-activated synthetic casting products such as fiberglass casting tapes are recommended to form the splint. The frequency of bandage changes depends on the size of the wound and degree of exudate. In one study of 98 cases of shearing wounds, the average time for second intention healing was 6.7 weeks.

Daily bandage changes are usually required for the first two weeks. Once a healthy bed of granulation tissue is established, the frequency of bandage changes can be gradually decreased. Exam or sterile gloves are worn for bandage changes. Bandage materials to be applied to the wound are placed on a clean impermeable surface. Disposable trays are useful for this purpose. The type of contact layer used changes with progression from an exudative open wound bed to a healthy bed of granulation tissue. Manipulation of the unstable tarsal joint and fragile wound bed causes patient discomfort. Appropriate analgesia and sedation are required to perform bandage changes. A combination of butorphanol (Torbugesic) and medetomidine (Domitor or Dexdomitor) provides satisfactory analgesia and sedation for most cases.

Surgical Stabilization of Shearing Wounds

A prosthetic imbrication technique is used to stabilize tarsal shearing wounds. The technique is identical to that described for treating collateral ligament ruptures. A significant difference is that the malleolus is absent in most shearing wounds, thus, it cannot be used as a landmark for placement of fixation devices.

A transarticular external fixator is placed using a type I or type II frame design is chosen. I prefer Type II frames for this. Hinges for transarticular external fixators are recommended as they permit limited movement in one plane to promote joint health while providing stability. Broad spectrum antibiotics, such as cephalosporins, can be administered during the initial phases of wound management when there is exposed bone that is not yet covered with a bed of granulation tissue. When bone is resurfaced with granulation tissue, antibiotics are generally discontinued. Sterile technique is maintained at all times during bandage changes.

If a hinged external connecting system is used, it is locked in place for the first 2 to 3 weeks. If a static external fixator is used (one without a hinge) it is removed in approximately 4 weeks and replaced with a splint. The splint is kept on for 3 weeks and is then replaced with a soft padded bandage for 2 to 3 weeks. If a hinged external fixator is used, it is kept in place for 6 to 8 weeks.

Severe Shearing Wounds Treated by Early Arthrodesis Using External Fixation

If damage extends to the articular surface of the tarsal joints, arthrodesis is indicated. Arthrodesis is accomplished by removing articular cartilage and applying rigid stabilization. The external fixator must remain in place until arthrodesis is completed so must be a rigid frame. A type II frame design is applied and is supplemented with connecting bars that span the joint in a cranial-caudal plane. Further stability can be attained by placing a normograde intramedullary pin from the tibia to the tarsocrural joint.

Arthrodesis may be performed relatively soon after the injury. Arthrodesis is performed once the exudative phase of wound healing is completed and the tissues appear healthy. There may still be exposed bone. It is not necessary to wait for granulation tissue to cover all bony surfaces prior to arthrodesing the joint.

A dorsal approach is made to extend from the distal tibia to the proximal metatarsals. Some shearing wounds are so extensive that a surgical skin incision is not required. All articular surfaces are exposed in order to remove articular cartilage. The cranial tibial tendon is incised as it crosses the tarsocrural joint to improve visualization. The long digital extensor tendon is left intact. The external fixation system is placed across the tarsocrural joint and positioned at a pre-determined angle. The standing angle of the tarsus varies from 130° to 150° in the average dog and 115 °to 125 ° in the cat. To tailor the angle to the individual, the angle of the opposite limb is measured preoperatively with a goniometer or with a conformable template. These devices can be autoclaved and used intraoperatively to ascertain the angle.

For added stability, a normograde intramedullary pin can be placed. A pin that is approximately 40 % of the medullary canal diameter of the tibia is chosen. Using a high speed drill and chuck, the pin is introduced in a normograde manner through the plantar aspect of the talus into the medullary cavity of the tibia. A paired pin is used to estimate the penetration depth of the intramedullary pin. The pin is cut short at the plantar aspect of the talus. A type II external fixation device is applied. The device must withstand significant bending forces for a long period of time. The pin width must not exceed 25 % of the diameter of the bone or there is a risk of iatrogenic fracture at the pin site. Metatarsal pins are placed in the proximal half of the bones. Pins placed more distally may interfere with postoperative weight bearing. The fixator extends to the proximal aspect of the tibia to disperse forces throughout a greater length of the bone.

Cancellous bone grafts are not typically placed in early shearing wounds because there are no soft tissues to close over the joint surface to help keep the graft in place. In selected cases, a delayed cancellous graft is harvested to accelerate arthrodesis. Grafts may be harvested from the patient (greater tubercle) or from a supplier (Veterinary Transplant Services; Kent, WA. www.vtsonline.com). The surgical site is bandaged as described for open wound. Arthrodesis is complete when joint spaces are replaced with healing bone. Without complications, the fixator should be able to be removed by 12 to 14 weeks.

References

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7. Beardsley SL, Schrader SC. Treatment of dogs with wounds of the limbs caused by shearing forces: 98 cases (1975-1993). J Am Vet Med Assoc 208(8):1071, 1995.

8. Diamond DW, Besso J, Boudrieau RJ. Evaluation of joint stabilization for treatment of shearing injuries of the tarsus in 20 dogs. J Am Anim Hosp Assoc 35:147, 1999.

9. Swaim SF. Management and bandaging of soft tissue injuries of dog and cat feet. J Am Anim Hosp Assoc 21:329-40, 1985

10. Benson JA, Boudrieau RJ. Severe carpal and tarsal shearing injuries treated with an immediate arthrodesis in seven dogs. J Am Anim Hosp Assoc 38:370, 2002.

11. Kirsch JA, Déjardin LM, DeCamp CD, et al. In vitro mechanical evaluation on the use of an intramedullary pin-plate combination for pantarsal arthrodesis in dogs. Amer J Vet Res 66:125-131, 2005.