EXTERNAL SKELETAL FIXATION
0195-5616/92 $0.00 + .20
FRACTURES AND LUXATIONS OF THE VERTEBRAL COLUMN Andy Shores, DVM, MS, PhD
Use of external skeletal fixation, in combination with dorsal fixation devices, has been described for treatment of caudal lumbar fractures in dogs. 5, 6 Applications of this technique require careful attention to the anatomic landmarks and placement of skin as pins are inserted. Without careful planning and adequate dissection to identify necessary landmarks, vital structures may be violated, and poor surgical wound closure can result. The technique, however, is relatively simple and does provide rigid fixation of caudal lumbar fractures. This article reviews the technique for use of external fixation in caudal lumbar fractures, discusses advantages of the fixation in two of the three vertebral compartments, and briefly describes the use of external fixation of vertebral fracture/luxations in other regions of the vertebral column.
TECHNIQUE FOR COMBINED EXTERNAL AND DORSAL FIXATION OF CAUDAL LUMBAR FRACTURES
The animal is positioned in sternal recumbency with the area prepared for surgery extending cranial to caudal from the thoracolumbar junction to a point beyond the sacrocaudal junction and laterally to include the entire flank. A dorsal approach is made with the site of the From the Department of Small Animal Clinical Sciences, Michigan State University College of Veterinary Medicine, East Lansing, Michigan VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 22 • NUMBER 1 • JANUARY 1992
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fracture as the approximate center of the incision.6 It is advisable to extend the incision cranially by four vertebral segments and caudally to the sacrocaudal junction. If deemed necessary, a dorsal laminectomy is performed. 6 Indications for decompression include bone or soft tissue structure (e.g., intervertebral disc), which would cause continued compression of neuropil following reduction of the fracture/luxation. 2, 3, 7 The dorsal fixation device is positioned over the vertebrae after reduction of the fracture (Fig. 1). Plastic and metal dorsal spinal plates can be used,6 and the last hole of the plate is positioned caudal to the spinous process of the seventh lumbar vertebra. Dorsal spinal plates are placed on both sides of the fracture and extend from a point caudal to the seventh lumbar vertebra to at least two spinous processes cranial to the fracture/ luxation site. The muscle and skin on the surgeon's side are pulled to the center of the incision, using penetrating towel clamps that grasp the skin and muscle fascia (Fig. 2). A 0.125" diameter Steinmann pin, attached to a Jacob's chuck, is inserted percutaneously through epaxial muscles, the ipsilateral wing of the ilium, and a hole in each plate just caudal to the seventh lumbar vertebra (Fig. 3). The pin is best positioned when it contacts the dorsal surface of the lumbosacral joint and is perpendicular to the axis of the spine. Next, the towel clamp on the
Figure 1. After fracture reduction, dorsal spinal plates are positioned over the vertebrae. (From Shores A, Nichols C, Rochat M, et al: Combined Kirschner-Ehmer device and dorsal spinal plate fixation for caudal lumbar vertebral functions in dogs. J Am Vet Med Assoc 195:335, 1989; with permission.)
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Figure 2. Backhaus towel forceps are used to pull skin and muscle fascia to the midline before insertion of the Steinmann pin.
i
/
Figure 3. Insertion of Steinmann pins for the external fixation device. The first pin traverses the ipsilateral wing of the ilium, a hole of each dorsal spinal plate caudal to the L7 spinous process, and the contralateral wing of the ililJm. The second pin is placed perpendicular to the vertebral column and just caudal to the junction of the transverse process and the vertebral body. (From Shores A, Nichols C, Rochat M, et al: Combined Kirschner-Ehmer device and dorsal spinal plate fixation of caudal lumbar vertebral fractures in dogs. J Am Vet Med Assoc 195:335, 1989; with permission.)
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surgeon's side is released, and muscle fascia and skin on the opposite side are pulled to the center of the incision in the same manner. The Steinmann pin is advanced through the opposite iliac wing, muscle, and skin. When the pin has exited the skin on the opposite side, the skin and fascia are released. The surgeon should check the pin position through the wings of the ilium to ensure sufficient bone purchase since the pin can easily be placed too far dorsally.6 A second 0.125" Steinmann pin is placed into the vertebral body cranial and adjacent to the fracture/luxation (see Fig. 3). This pin should enter the vertebral body perpendicular to the axis of the spine, just caudal to the caudal junction of the transverse process and the vertebral body. Placement of the pin at this location allows good bone purchase, avoids injury to the lumbar spinal nerve, and is below the level of the spinal canal. The surgeon again positions the skin and muscle to the midline before the pin is inserted. The pin is carefully inserted through the skin and muscle and visualized lateral to the vertebral bodytransverse process junction (Fig. 4). Before inserting the pin into the vertebral body, its position is carefully evaluated to ensure that the pin is perpendicular to the spine and parallel to the operating table. As the pin exits the opposite side of the vertebral body, its position is again inspected, and the skin and muscle are pulled to the midline before the pin is advanced through these structures. 6 The DFD is secured with stainless steel bolts and nuts following reduction of the fracture. Connecting bars are attached to the external fixation pins, and clamps are placed V2 to 1 cm away from the skin.
Figure 4. Position of the Steinmann pin (arrow) is visualized lateral to the vertebral body before insertion.
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Muscle fascia, subcutaneous tissue, and skin are closed in routine fashion. Walking sutures are occasionally needed to obtain skin closure without tension. The fracture repair is evaluated by radiography. Dorsoventral and across-the-table views are necessary to appraise position of the vertebrae adequately (Fig. 5). Occasionally minor adjustments can be made in the position of the bone fragments by adjusting the external fixation device. External portions of the fixation device' are wrapped with tape, gauze, and elastic bandaging material (Fig. 6). The animal is limited to cage confinement for the first 3 to 4 postoperative days, and analgesics are administered as needed. Drainage from the pins is cleaned daily, and additional routine care is performed (e.g., bladder evacuation for incontinent patients).6 Following the initial postoperative period, activity is restricted to a small area (approximately 4 x 6 feet) for 2 weeks. If reevaluation by the surgeon reveals evidence of fracture healing and stability, exercise can be gradually increased to preinjury levels as the animal's neurologic function allows. If there is radiographic evidence of a healed fracture 1 to 2 months after surgery, the animal can be sedated and the external fixation device removed. In the author's experience, the presence of the external fixation device has not caused problems with catching the device on the cage door or other objects. Animals seem to adapt well to the device and do not exhibit undue discomfort. This fixation method has also been used on cats with caudal lumbar fractures, and results are similar to those reported for the dog. FRACTURE BIOMECHANICS
Most fracture/luxations occur at the junction of mobile and immobile spinal segments such as the lumbosacral region. 2, 6 The forces responsible for creating vertebral fracture/luxations are extension, flexion, rotation, shearing, and axial loading (compression).!" Most fracture classification schemes used in the veterinary literature are based on the forces responsible for the fracture, stability of the vertebral segments, or both factors.' The three-compartment (three-column) scheme for classification of spinal fracture/luxations (Fig. 7), a method recently introduced in human orthopedic literature,! appears to be adaptable to small animals for classification of vertebral fracture/luxations and their mechanical stability.4 The dorsal compartment consists of articular facets, pedicle, laminae, spinous processes, and ligamentum flava (yellow ligament) . The middle compartment contains the dorsal annulus, dorsal vertebral body (floor of the spinal canal), and the dorsal longitudinal ligament. The remainder of the vertebral body, lateral and ventral annulus, and the ventral longitudinal ligament constitute the ventral compartment. Evaluation of fracture images (radiographs, com-
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Figure 5. A, Postoperative dorsoventral, and e, postoperative across-the-table lateral radiographs of a fractured caudal lumbar spine repaired using an external fixation device and a dorsal spinal plate.
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Figure 6. Postoperative photograph of a dog with the external fixation device wrapped with gauze, elastic bandaging material, and tape.
puted tomographic scan) is based on determining which levels are involved in the fracture. 4 Most fractures that include only one compartment are stable (fractured spinous processes, articular process fractures without luxation), whereas those involving multiple (two or three) compartments are unstable. I, 4 Application of this method of evaluation should influence fixation techniques. In published biomechanical studies of canine vertebral fixation,s, 8 methods that incorporate more than one compartment are the most stable and rigid. The combined external fixation device/dorsal fixation device incorporates the dorsal and ventral compartments. This should perhaps be a consideration in designing new methods of
Figure 7. Divisions of the three compartment vertebral classification. A, Dorsal compartment (articular facets, pedicle, lamina, spinous process); B, middle (dorsal longitudinalligament, dorsal anulus, dorsal vertebral body); C, ventral (lateral and ventral portions of the anulus, remainder of the vertebral body, and ventral longitudinal ligament).
~~--~~~--~~-A ~~~~~~--~~--B
A=-+--C
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vertebral fracture/luxation fixation. Combining an external fixation device with other methods of fixation would seem to accomplish this goal. ADDITIONAL APPLICATIONS FOR EXTERNAL SPINAL FIXATION
The author has used external fixation for fracturelluxations of the vertebral column in regions other than caudal vertebral segments and with other configurations for caudal vertebral fractures. A thoracolumbar fracture was temporarily stabilized using an external fixation device in a IO-year-old female Poodle with accompanying thoracic and abdominal injuries resulting from an attack by a larger dog. The temporary stability allowed emergency thoracoabdominal surgery without further displacement of the vertebrae. A 6-year-old male Chow Chow with a fracture luxation in the thoracolumbar region had reduced motor function in the pelvic limbs. Nociception was reduced in the pelvic limbs and tail. The fracture/ luxation was repaired with a vertebral body plate and dorsal spinal plate. The dog's neurologic status improved until the fifth day after
Figure 8. Infection resulted in failure of a vertebral body plate internal fixation of a thoracolumbar fracture. The internal fixation device was removed, the fracture was again reduced, and this external fixation device applied for stabilization. A combination of the external fixation device, external splinting, cage confinement, and wound management resulted in recovery to an acceptable level of neurologic function (ambulatory, slight paresis, urinary and fecal continence).
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surgery when the surgical incision began to separate and a purulent exudate was evident. The neurologic status of the dog deteriorated to paraplegia and absent nociception as loosening of the internal fixation devices allowed displacement of the fracture. Radiography revealed vertebral osteomyelitis, and surgery was performed to remove the vertebral body plate, realign the fracture, and apply an external fixation device (Fig. 8). Internal fixation devices could not be used because of infection. The postoperative neurologic status was improved. Appropriate antibiotic therapy was instituted following culture and sensitivity results. After 10 days of antibiotic therapy and cage confinement, the incision healed and the dog was discharged. At the time of release from the hospital, the dog was ambulatory and had urinary continence. The external fixation device was removed after 4 weeks and, although the dog remained slightly paraparetic, the dog's quality of life was considered acceptable to the owner. Caudal lumbar fractures may also be repaired using only a fourpin, full-pin external fixation device. Two pins are placed through the
Figure 9. A model of a four-pin external fixation device for stabilizing the caudal lumbar
spine.
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iliac wings caudal to the fracture. Cranial to the fracture, one pin is placed in each of the next two vertebral bodies (Fig. 9). Double clamps are sometimes needed to facilitate placement of the connecting rods. This method provides four points of fixation and should result in adequate stability without additional internal fixation devices. SUMMARY
External fixation of the vertebral column is indicated to treat fractures of the caudal lumbar spine, open fractures where vertebral osteomyelitis is present or likely to occur, and vertebral fractures not easily stabilized by internal fixation alone (e.g., compression fractures, fractures including spinous processes, and articular facets). Advantages of external fixation of caudal lumbar fractures, especially in combination with dorsal fixation devices, include the following: Fracture fixation does not preclude dorsal decompression; fixation devices need not be applied directly to the fractured vertebrae; and the combined technique provides dorsal and ventral vertebral fixation, which is more stable than dorsal fixation alone. Although external fixation is not applicable to all vertebral fracture/ luxations in small animals, it provides additional points of fixation for rigid stability. Animals with vertebral fracture/luxations treated with an external fixation device have tolerated the external portion well. Development of additional applications for this method of vertebral fracture repair seems warranted. References 1. Bradford DS: Techniques of surgery. In Bradford DS (eds): Moe's Textbook of Scoliosis
and Other Spinal Deformities. Philadelphia, WB Saunders, 1987, p 135 2. Hoerlein BF: Spinal fractures, luxations, and fusions. In Hoerlein BF (ed): Canine Neurology, ed 3. Philadelphia, WB Saunders, 1978, p 561 3. Shores A: Intervertebral disk disease. In Newton CD, Nunamaker DM (eds): Textbook of Small Animal Orthopaedics. Philadelphia, JB Lippincott, 1985, p 739 4. Shores A, Braund KG, Brawner WR: Management of acute spinal cord trauma. Vet Med 85:724, 1990 5. Shores A, Nichols C, Koelling HA, Fox WR: Combined Kirschner-Ehmer apparatus and dorsal spinal plate fixation of caudal lumbar fractures in dogs: Biomechanical properties. Am J Vet Res 49:1979, 1988 6. Shores A, Nichols C, Rochat M, et al: Combined Kirschner-Ehmer device and dorsal spinal plate fixation technique for caudal lumbar vertebral fractures in dogs. J Am Vet Med Assoc 195:335, 1989 7. Walker TL, Tomlinson J, Sorjonen DC, Kornegay IN: Diseases of the spinal column. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia, WB Saunders, 1985, p 1367 8. Walter MC, Smith GK, Newton CD: Canine lumbar spinal internal fixation techniques: A comparative biomechanical study. Vet Surg 15:191, 1986
Address reprint requests to Andy Shores, DVM, MS, PhD Department of Small Animal Clinical Sciences Michigan State University East Lansing, MI 48824
0195-5616/92 $0.00 + .20
FRACTURES AND LUXATIONS OF THE VERTEBRAL COLUMN Andy Shores, DVM, MS, PhD
Use of external skeletal fixation, in combination with dorsal fixation devices, has been described for treatment of caudal lumbar fractures in dogs. 5, 6 Applications of this technique require careful attention to the anatomic landmarks and placement of skin as pins are inserted. Without careful planning and adequate dissection to identify necessary landmarks, vital structures may be violated, and poor surgical wound closure can result. The technique, however, is relatively simple and does provide rigid fixation of caudal lumbar fractures. This article reviews the technique for use of external fixation in caudal lumbar fractures, discusses advantages of the fixation in two of the three vertebral compartments, and briefly describes the use of external fixation of vertebral fracture/luxations in other regions of the vertebral column.
TECHNIQUE FOR COMBINED EXTERNAL AND DORSAL FIXATION OF CAUDAL LUMBAR FRACTURES
The animal is positioned in sternal recumbency with the area prepared for surgery extending cranial to caudal from the thoracolumbar junction to a point beyond the sacrocaudal junction and laterally to include the entire flank. A dorsal approach is made with the site of the From the Department of Small Animal Clinical Sciences, Michigan State University College of Veterinary Medicine, East Lansing, Michigan VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 22 • NUMBER 1 • JANUARY 1992
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fracture as the approximate center of the incision.6 It is advisable to extend the incision cranially by four vertebral segments and caudally to the sacrocaudal junction. If deemed necessary, a dorsal laminectomy is performed. 6 Indications for decompression include bone or soft tissue structure (e.g., intervertebral disc), which would cause continued compression of neuropil following reduction of the fracture/luxation. 2, 3, 7 The dorsal fixation device is positioned over the vertebrae after reduction of the fracture (Fig. 1). Plastic and metal dorsal spinal plates can be used,6 and the last hole of the plate is positioned caudal to the spinous process of the seventh lumbar vertebra. Dorsal spinal plates are placed on both sides of the fracture and extend from a point caudal to the seventh lumbar vertebra to at least two spinous processes cranial to the fracture/ luxation site. The muscle and skin on the surgeon's side are pulled to the center of the incision, using penetrating towel clamps that grasp the skin and muscle fascia (Fig. 2). A 0.125" diameter Steinmann pin, attached to a Jacob's chuck, is inserted percutaneously through epaxial muscles, the ipsilateral wing of the ilium, and a hole in each plate just caudal to the seventh lumbar vertebra (Fig. 3). The pin is best positioned when it contacts the dorsal surface of the lumbosacral joint and is perpendicular to the axis of the spine. Next, the towel clamp on the
Figure 1. After fracture reduction, dorsal spinal plates are positioned over the vertebrae. (From Shores A, Nichols C, Rochat M, et al: Combined Kirschner-Ehmer device and dorsal spinal plate fixation for caudal lumbar vertebral functions in dogs. J Am Vet Med Assoc 195:335, 1989; with permission.)
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Figure 2. Backhaus towel forceps are used to pull skin and muscle fascia to the midline before insertion of the Steinmann pin.
i
/
Figure 3. Insertion of Steinmann pins for the external fixation device. The first pin traverses the ipsilateral wing of the ilium, a hole of each dorsal spinal plate caudal to the L7 spinous process, and the contralateral wing of the ililJm. The second pin is placed perpendicular to the vertebral column and just caudal to the junction of the transverse process and the vertebral body. (From Shores A, Nichols C, Rochat M, et al: Combined Kirschner-Ehmer device and dorsal spinal plate fixation of caudal lumbar vertebral fractures in dogs. J Am Vet Med Assoc 195:335, 1989; with permission.)
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surgeon's side is released, and muscle fascia and skin on the opposite side are pulled to the center of the incision in the same manner. The Steinmann pin is advanced through the opposite iliac wing, muscle, and skin. When the pin has exited the skin on the opposite side, the skin and fascia are released. The surgeon should check the pin position through the wings of the ilium to ensure sufficient bone purchase since the pin can easily be placed too far dorsally.6 A second 0.125" Steinmann pin is placed into the vertebral body cranial and adjacent to the fracture/luxation (see Fig. 3). This pin should enter the vertebral body perpendicular to the axis of the spine, just caudal to the caudal junction of the transverse process and the vertebral body. Placement of the pin at this location allows good bone purchase, avoids injury to the lumbar spinal nerve, and is below the level of the spinal canal. The surgeon again positions the skin and muscle to the midline before the pin is inserted. The pin is carefully inserted through the skin and muscle and visualized lateral to the vertebral bodytransverse process junction (Fig. 4). Before inserting the pin into the vertebral body, its position is carefully evaluated to ensure that the pin is perpendicular to the spine and parallel to the operating table. As the pin exits the opposite side of the vertebral body, its position is again inspected, and the skin and muscle are pulled to the midline before the pin is advanced through these structures. 6 The DFD is secured with stainless steel bolts and nuts following reduction of the fracture. Connecting bars are attached to the external fixation pins, and clamps are placed V2 to 1 cm away from the skin.
Figure 4. Position of the Steinmann pin (arrow) is visualized lateral to the vertebral body before insertion.
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Muscle fascia, subcutaneous tissue, and skin are closed in routine fashion. Walking sutures are occasionally needed to obtain skin closure without tension. The fracture repair is evaluated by radiography. Dorsoventral and across-the-table views are necessary to appraise position of the vertebrae adequately (Fig. 5). Occasionally minor adjustments can be made in the position of the bone fragments by adjusting the external fixation device. External portions of the fixation device' are wrapped with tape, gauze, and elastic bandaging material (Fig. 6). The animal is limited to cage confinement for the first 3 to 4 postoperative days, and analgesics are administered as needed. Drainage from the pins is cleaned daily, and additional routine care is performed (e.g., bladder evacuation for incontinent patients).6 Following the initial postoperative period, activity is restricted to a small area (approximately 4 x 6 feet) for 2 weeks. If reevaluation by the surgeon reveals evidence of fracture healing and stability, exercise can be gradually increased to preinjury levels as the animal's neurologic function allows. If there is radiographic evidence of a healed fracture 1 to 2 months after surgery, the animal can be sedated and the external fixation device removed. In the author's experience, the presence of the external fixation device has not caused problems with catching the device on the cage door or other objects. Animals seem to adapt well to the device and do not exhibit undue discomfort. This fixation method has also been used on cats with caudal lumbar fractures, and results are similar to those reported for the dog. FRACTURE BIOMECHANICS
Most fracture/luxations occur at the junction of mobile and immobile spinal segments such as the lumbosacral region. 2, 6 The forces responsible for creating vertebral fracture/luxations are extension, flexion, rotation, shearing, and axial loading (compression).!" Most fracture classification schemes used in the veterinary literature are based on the forces responsible for the fracture, stability of the vertebral segments, or both factors.' The three-compartment (three-column) scheme for classification of spinal fracture/luxations (Fig. 7), a method recently introduced in human orthopedic literature,! appears to be adaptable to small animals for classification of vertebral fracture/luxations and their mechanical stability.4 The dorsal compartment consists of articular facets, pedicle, laminae, spinous processes, and ligamentum flava (yellow ligament) . The middle compartment contains the dorsal annulus, dorsal vertebral body (floor of the spinal canal), and the dorsal longitudinal ligament. The remainder of the vertebral body, lateral and ventral annulus, and the ventral longitudinal ligament constitute the ventral compartment. Evaluation of fracture images (radiographs, com-
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Figure 5. A, Postoperative dorsoventral, and e, postoperative across-the-table lateral radiographs of a fractured caudal lumbar spine repaired using an external fixation device and a dorsal spinal plate.
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Figure 6. Postoperative photograph of a dog with the external fixation device wrapped with gauze, elastic bandaging material, and tape.
puted tomographic scan) is based on determining which levels are involved in the fracture. 4 Most fractures that include only one compartment are stable (fractured spinous processes, articular process fractures without luxation), whereas those involving multiple (two or three) compartments are unstable. I, 4 Application of this method of evaluation should influence fixation techniques. In published biomechanical studies of canine vertebral fixation,s, 8 methods that incorporate more than one compartment are the most stable and rigid. The combined external fixation device/dorsal fixation device incorporates the dorsal and ventral compartments. This should perhaps be a consideration in designing new methods of
Figure 7. Divisions of the three compartment vertebral classification. A, Dorsal compartment (articular facets, pedicle, lamina, spinous process); B, middle (dorsal longitudinalligament, dorsal anulus, dorsal vertebral body); C, ventral (lateral and ventral portions of the anulus, remainder of the vertebral body, and ventral longitudinal ligament).
~~--~~~--~~-A ~~~~~~--~~--B
A=-+--C
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vertebral fracture/luxation fixation. Combining an external fixation device with other methods of fixation would seem to accomplish this goal. ADDITIONAL APPLICATIONS FOR EXTERNAL SPINAL FIXATION
The author has used external fixation for fracturelluxations of the vertebral column in regions other than caudal vertebral segments and with other configurations for caudal vertebral fractures. A thoracolumbar fracture was temporarily stabilized using an external fixation device in a IO-year-old female Poodle with accompanying thoracic and abdominal injuries resulting from an attack by a larger dog. The temporary stability allowed emergency thoracoabdominal surgery without further displacement of the vertebrae. A 6-year-old male Chow Chow with a fracture luxation in the thoracolumbar region had reduced motor function in the pelvic limbs. Nociception was reduced in the pelvic limbs and tail. The fracture/ luxation was repaired with a vertebral body plate and dorsal spinal plate. The dog's neurologic status improved until the fifth day after
Figure 8. Infection resulted in failure of a vertebral body plate internal fixation of a thoracolumbar fracture. The internal fixation device was removed, the fracture was again reduced, and this external fixation device applied for stabilization. A combination of the external fixation device, external splinting, cage confinement, and wound management resulted in recovery to an acceptable level of neurologic function (ambulatory, slight paresis, urinary and fecal continence).
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surgery when the surgical incision began to separate and a purulent exudate was evident. The neurologic status of the dog deteriorated to paraplegia and absent nociception as loosening of the internal fixation devices allowed displacement of the fracture. Radiography revealed vertebral osteomyelitis, and surgery was performed to remove the vertebral body plate, realign the fracture, and apply an external fixation device (Fig. 8). Internal fixation devices could not be used because of infection. The postoperative neurologic status was improved. Appropriate antibiotic therapy was instituted following culture and sensitivity results. After 10 days of antibiotic therapy and cage confinement, the incision healed and the dog was discharged. At the time of release from the hospital, the dog was ambulatory and had urinary continence. The external fixation device was removed after 4 weeks and, although the dog remained slightly paraparetic, the dog's quality of life was considered acceptable to the owner. Caudal lumbar fractures may also be repaired using only a fourpin, full-pin external fixation device. Two pins are placed through the
Figure 9. A model of a four-pin external fixation device for stabilizing the caudal lumbar
spine.
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SHORES
iliac wings caudal to the fracture. Cranial to the fracture, one pin is placed in each of the next two vertebral bodies (Fig. 9). Double clamps are sometimes needed to facilitate placement of the connecting rods. This method provides four points of fixation and should result in adequate stability without additional internal fixation devices. SUMMARY
External fixation of the vertebral column is indicated to treat fractures of the caudal lumbar spine, open fractures where vertebral osteomyelitis is present or likely to occur, and vertebral fractures not easily stabilized by internal fixation alone (e.g., compression fractures, fractures including spinous processes, and articular facets). Advantages of external fixation of caudal lumbar fractures, especially in combination with dorsal fixation devices, include the following: Fracture fixation does not preclude dorsal decompression; fixation devices need not be applied directly to the fractured vertebrae; and the combined technique provides dorsal and ventral vertebral fixation, which is more stable than dorsal fixation alone. Although external fixation is not applicable to all vertebral fracture/ luxations in small animals, it provides additional points of fixation for rigid stability. Animals with vertebral fracture/luxations treated with an external fixation device have tolerated the external portion well. Development of additional applications for this method of vertebral fracture repair seems warranted. References 1. Bradford DS: Techniques of surgery. In Bradford DS (eds): Moe's Textbook of Scoliosis
and Other Spinal Deformities. Philadelphia, WB Saunders, 1987, p 135 2. Hoerlein BF: Spinal fractures, luxations, and fusions. In Hoerlein BF (ed): Canine Neurology, ed 3. Philadelphia, WB Saunders, 1978, p 561 3. Shores A: Intervertebral disk disease. In Newton CD, Nunamaker DM (eds): Textbook of Small Animal Orthopaedics. Philadelphia, JB Lippincott, 1985, p 739 4. Shores A, Braund KG, Brawner WR: Management of acute spinal cord trauma. Vet Med 85:724, 1990 5. Shores A, Nichols C, Koelling HA, Fox WR: Combined Kirschner-Ehmer apparatus and dorsal spinal plate fixation of caudal lumbar fractures in dogs: Biomechanical properties. Am J Vet Res 49:1979, 1988 6. Shores A, Nichols C, Rochat M, et al: Combined Kirschner-Ehmer device and dorsal spinal plate fixation technique for caudal lumbar vertebral fractures in dogs. J Am Vet Med Assoc 195:335, 1989 7. Walker TL, Tomlinson J, Sorjonen DC, Kornegay IN: Diseases of the spinal column. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia, WB Saunders, 1985, p 1367 8. Walter MC, Smith GK, Newton CD: Canine lumbar spinal internal fixation techniques: A comparative biomechanical study. Vet Surg 15:191, 1986
Address reprint requests to Andy Shores, DVM, MS, PhD Department of Small Animal Clinical Sciences Michigan State University East Lansing, MI 48824
