A 12-year-old obese (37 kg [81.4 lb]) spayed female American Staffordshire Terrier was admitted for evaluation of acute non–weight-bearing lameness of the right pelvic limb attributed to motor vehicle–related trauma that occurred 2 hours previously. The dog had a 6-month history of weight-bearing lameness of the right pelvic limb lameness caused by complete CrCL rupture, which had been diagnosed elsewhere. The owners had declined surgery to treat the ruptured CrCL at the time of diagnosis because of the dog's advanced age.
Physical examination revealed a 2-cm skin wound on the right pelvic limb over the craniomedial aspect of the midtibial region. Sterile nonadherent gauze was placed over the wound to prevent possible further contamination and secured with light bandaging. Orthopedic examination revealed non–weight-bearing lameness, muscle atrophy, and loss of typical morphology and alignment of the right pelvic limb as well as signs of pain on palpation of the right tibia. All other general, neurologic, hematologic, and thoracic radiographic findings were unremarkable.
To facilitate further evaluation, the dog was premedicated with methadone (0.2 mg/kg [0.09 mg/lb], SC) and acepromazine maleate (10 μg/kg [4.5 μg/lb], SC), and anesthesia was induced with propofol (3 mg/kg [1.4 mg/lb], IV) and maintained with isoflurane (1.5%) in oxygen. The bandage was removed. Mediolateral and caudocranial radiographic views of the right tibia were obtained. The wound was aseptically dressed, and a new sterile dressing was applied. Passive range of motion of the unaffected left stifle joint was then assessed, revealing an overall range of motion of 115° (flexion, 45°; extension, 160°). Results of a cranial drawer test performed while the dog was anesthetized were positive.1
Radiographic findings indicated tibial and fibular fractures of the right pelvic limb, which were classified as second-degree open,2 severely comminuted,3 complex nonreconstructible diaphyseal fractures4 (Figure 1). The features of these fractures suggested that rapid bone union and early return to function were unlikely.5,6 The right tibia appeared to be misaligned, with excessive proximal valgus deformity in the frontal plane and excessive procurvatum deformity in the sagittal plane (TPA, 37°; mMPTA, 104°; mMDTA, 104°).7 The mediolateral view of the right stifle joint revealed synovial effusion, with osteophytes on the trochlear ridges, proximal and distal aspects of the patella, distal aspect of the femur, proximal aspect of the tibia, tibial plateau, fabellae, and popliteal sesamoid bones. A Robert Jones bandage was applied over the region extending from the toe to midthigh to prevent swelling and further soft tissue damage from sharp bone fragments, and the dog was kept in the hospital overnight.
Mediolateral (A) and caudocranial (B) radiographic views of the right tibia and fibula of a 12-year-old obese spayed female American Staffordshire Terrier. The images show comminuted diaphyseal fractures of both bones, signs of osteoarthritis in the stifle joint, and malalignment with excessive proximal valgus deformity (mMPTA, 104°; mMDTA, 104°) and excessive procurvatum deformity (TPA, 37°). The red line represents the sagittal-plane proximal tibial joint orientation line (SPTJOL), the blue line the sagittal-plane mechanical axis (SMA), the yellow line the frontal-plane proximal tibial joint orientation line (FPTJO), the green line the frontal-plane mechanical axis (FMA), and the orange line the frontal-plane distal tibial joint orientation line (FDTJOL).
Citation: Journal of the American Veterinary Medical Association 254, 5; 10.2460/javma.254.5.613
The next day, the dog was anesthetized for surgery with the same protocol as used previously. Before surgery began, cefazolin (22 mg/kg [10 mg/lb], IV) was administered, the right pelvic limb was aseptically prepared, and the dog was positioned in dorsal recumbency.
Arthroscopy was performed, and use of a meniscal probea allowed identification of an incomplete vertical longitudinal tear of the caudal pole of the medial meniscus. Medial arthrotomy was performed to release the medial meniscus by complete transection of the body of the meniscus caudal to the medial collateral ligament.8
A MUESF device9,b was then applied to the medial side of the tibia with 1 threaded pin and 1 smooth half pin through the proximal clamp into the proximal tibial segment and with 2 threaded pins through the distal clamp into the distal tibial segment10 (Figure 2). Before each pin was inserted bicortically, a pilot hole was drilled at the site of insertion by use of a sleeved drill bit.11 The drill bit was then removed, and the selected pin was inserted with the aid of a low-speed power drill. The proximal cluster of pins was inserted first and oriented approximately perpendicular to both the patellar tendon and the proximal bone fragment. Pins were placed percutaneously in a mediolateral direction oriented perpendicular to the segment long axis.
Diagram of the MUESF system used for the dog in Figure 1. The clamps can be placed in many positions and orientations (A, B, and C). Each pin clamp (D) holds a cluster of 2 fixation pins. Two additional threaded half pins (E) were inserted on the same plane to increase implant rigidity. The first pin was connected through a Maynard clamp to a secondary 3.0-mm connecting rod bridging the proximal and distal clamps.
Citation: Journal of the American Veterinary Medical Association 254, 5; 10.2460/javma.254.5.613
With fluoroscopic guidance (with sterile technique applied), the 2 tibial bone segments were manipulated via the clamps to restore limb length and frontal plane alignment as well as correct the TPA in the sagittal plane until a TPA of approximately 6° was achieved, as assessed by another surgeon on fluoroscopic images transferred from the fluoroscope to a computer. The calcaneal-patellar axis was assessed by use of visible and palpable landmarks (calcaneus, lateral malleolus, medial malleolus, tibial tuberosity, patellar ligament, and patella) and fluoroscopically checked during rotation of the proximal segment in the sagittal plane. A carbon-fiber connecting rod (diameter, 15 mm; length, 200 mm) was placed approximately parallel to the axis of the tibial shaft, and the clamps were partially tightened. Gentle indirect manipulation was performed to reduce proximal and distal main bone fragments into planned alignment.
Clamp nuts were tightened. A distance of 1.5 cm was maintained between the skin and the pin clamps to allow for easier pin care and space for possible postoperative swelling. Two additional threaded half pins (1/main bone fragment) were inserted on the same plane to increase implant rigidity. The first pin was connected to the most proximal pin by use of a Maynard clamp and oriented in a mediolateral and proximodistal direction. The second additional pin was connected through a Maynard clamp to a secondary 3-mm connecting rod bridging the proximal and distal MUESF clamps and oriented in a mediolateral direction, as described elsewhere.10 All proximal fixation pins had a core diameter of 4 mm, whereas all distal pins had a diameter of 3.5 mm. Total duration of surgery was 90 minutes.
Results of a tibial compression test performed after surgery were negative.1 The open wound was left to granulate and heal by second intention. The MUESF device was wrapped with sterile foam sponges impregnated with 0.05% chlorhexidine solution, which were packed around the fixation pins between the skin and the device frame to limit postoperative swelling, protect pin insertion wounds, and prevent soft tissue movement relative to the fixation pins. Cotton padding and conforming outer wrap were placed around the MUESF device to pad contact between its frame and other objects.
Radiography was performed after surgery, revealing angular correction in the sagittal and frontal planes. The TPA of the right pelvic limb was 5°, resulting in recurvatum of the tibial and fibular diaphyses. The mMPTA was 92° (reference range, 90° to 97°), and the mMDTA was 96° (reference range, 91° to 101°).7 The fractured end of the proximal tibial main bone fragment appeared cranially displaced by approximately 4 mm (20% of the tibial diameter) in the sagittal plane with respect to the fractured end of the distal main fragment (Figure 3). The fractured ends of the proximal tibial and fibular main bone fragments appeared laterally displaced by approximately 4 mm in the frontal plane with respect to the fractured ends of the distal main fragments (25% of the tibial diameter and 100% of the fibular diameter at the fracture level).
Mediolateral (A) and caudocranial (B) radiographic views of the right tibia in the dog of Figure 1 obtained immediately after surgery, showing a TPA of 6° and apparently normal alignment in the frontal plane. See Figure 1 for remainder of key.
Citation: Journal of the American Veterinary Medical Association 254, 5; 10.2460/javma.254.5.613
The day after surgery, the dog was discharged from the hospital with a prescription for antimicrobials (amoxicillin–clavulanic acid at 20 mg/kg [9.1 mg/lb], PO, q 12 h until the skin wound had healed), an NSAID (carprofen at 2 mg/kg [0.9 mg/lb], PO, q 12 h for 3 weeks), and an analgesic (tramadol hydrochloride at 2 mg/kg, PO, q 12 h for 3 weeks). The owners were asked to clean the pin-skin interface twice daily with a gauze sponge and 0.05% chlorhexidine solution. The open wound was kept under sterile dressing, which was changed daily. The owners were taught to perform range-of-motion exercises twice a day for the right hip joint, stifle joint, and tarsal joint to minimize stiffiness, maintain range of motion, and promote muscle mass.
The dog was able to bear weight on the limb 2 days after surgery. Slow, controlled 20-minute walks on a leash were encouraged 4 times daily to promote limb use. Recheck physical and radiographic examinations were planned to occur at 2- and 4-week intervals, respectively; however, the owners returned the dog to the hospital only 2, 4, 8, 16, and 17 weeks after surgery, despite telephone reminders. At the 2-week recheck examination, the skin appeared to have completely closed. Mild drainage from the proximal pin tract was noted at the 4-week examination and managed by the owners with twice-a-day pin tract cleansing and bandaging. At the 8-week examination, radiography revealed mediolateral radiolucency at the level of the 3 proximal pins of the MUESF device, but no worsening of the lameness was noted. Bone remodeling of the fracture fragments but no bridging callus was identified. At the 16-week examination, radiolucency was observed in the mediolateral radiographic view at the level of the 3 proximal pins, together with bridging callus (Figure 4). The dog at this point had more severe lameness than at the previous examination, possibly due to the mobilization of the pin. Removal of all implants was scheduled and performed the following week (Figure 5). Passive range of motion of the unaffected left stifle joint at removal of the external fixator and at the 8-week recheck examination was unchanged from the preoperative measurements (flexion, 45°; extension, 160°; overall range of motion, 115°) and was considered unremarkable.12
Mediolateral-oblique (A) and caudocranial (B) radiographic views of the right tibia in the dog in Figure 1 that were obtained 16 weeks after surgery, showing callus bridging of the fracture.
Citation: Journal of the American Veterinary Medical Association 254, 5; 10.2460/javma.254.5.613
Mediolateral (A) and caudocranial (B) radiographic views of the tibia in the dog in Figure 1 after implant removal (17 weeks after the initial surgery). See Figure 1 for remainder of key.
Citation: Journal of the American Veterinary Medical Association 254, 5; 10.2460/javma.254.5.613
The fixator appeared stable on inspection and manipulation and appeared functional during the recovery period. Overall passive range of motion of the right stifle joint at this point (103°; flexion, 55°; extension, 158°) was reduced by 12° relative to that of the contralateral unaffected limb. No goniometric measurement of passive range of motion was performed at any point.
Throughout the recovery period, the dog remained lame but weight bearing. No implant failures or clinical neurovascular complications were noted. At recheck examinations performed 2 and 4 months after implant removal, the dog was walking unremarkably. No further radiographic examinations were performed. The dog died 8 months after surgery of unrelated causes.
Discussion
Cranial cruciate ligament rupture and tibial fracture are common in dogs.10,13–16 Reported risk factors for CrCL rupture include large-breed status, overweight body condition, and gonadectomy.1,16 The dog of the present report was an American Staffordshire Terrier, and this breed has one of the highest prevalences of CrCL rupture.16
The excessive tibial plateau slope in the dog of the present report was corrected in combination with fracture stabilization because the dog was likely to remain lame after fracture healing owing to persistent stifle joint instability caused by the previous CrCL rupture.17 If this approach had not been taken, it would have been necessary to first stabilize the fracture, and after the fracture had healed, the CrCL rupture could have been treated with a second surgery. This second option would not have been advisable because of the dog's advanced age and the owners’ prior refusal to have the CrCL surgically repaired 6 months before the fracture was sustained.
We opted for external fixation because the fracture was open and comminuted. Comminuted fractures, and particularly open fractures, benefit from techniques consistent with closed indirect reduction and external fixator application.5,10 The use of frame destabilization to promote fracture healing could have been a viable option. To destabilize the implant, 1 pin/fracture fragment could have been removed. However, we decided against this because at the 8-week recheck examination, radiographic signs of osteolysis were evident at the site of pin insertion in the proximal main bone fragment, and destabilization might have resulted in a structural collapse before the fracture had healed.
After the initial surgery and at 2 months after implant removal (4 months after surgery), the range of motion in the affected right stifle joint was 12° less than that in the unaffected left stifle joint. Because no preoperative range-of-motion measurement was performed for the right stifle joint, we could not ascertain whether the loss of range of motion preceded the fracture, possibly secondary to the chronic CrCL tear (eg, as a result of medial buttress scar tissue osteoarthritis), or it was secondary to the fracture itself, reduced activity during fracture healing, or any combination of these possibilities.
We chose to use a unilateral external skeletal fixator designed for human orthopedic application because this device allows for angular correction in case of limb deformity. The device was fairly easy to use because of its simple design, and it provided the fracture with sufficient stability to permit partial weight bearing from the very start of treatment. The MUESF device9 used for the dog of the present report consists of a carbon-fiber tube, carbon-fiber connecting rod, and pin clamps (available in 3 color-coded sizes); device size recommendations are made by the manufacturer on the basis of the location of the fracture, type of fracture or osteotomy, body weight of the patient, length of tube required, and possible dynamization requirements. We used the small (yellow) device for the 37-kg dog. A pin clamp in this size takes two 3- to 5-mm-diameter pins. The clamp can be placed in various positions and orientations on the connecting rod and allows for independent control of bone fragment alignment in 3 planes (360° of freedom in frontal [varus-valgus] and transverse [torsional] plane correction; 20° of freedom in sagittal plane [procurvatum-recurvatum] correction).
Correction of the fractured tibia in the sagittal plane resulted in recurvatum of the tibial anatomic axis and in craniolateral translation of the proximal bone fragment in the dog of the present report. The site at which the proximal and distal anatomic axis lines intersect is referred to as the CORA.18 In orthopedically normal dogs, the canine tibial anatomic axis has a proximal procurvatum in the sagittal plane. Therefore, the tibial CORA in the sagittal plane is at the level of its procurvatum. Correction of angular deformity consists of angling one bone segment relative to another around the ACA, which is an imaginary line in space around which the correction is performed.19 When the osteotomy (or fracture, as in the dog of the present report) is at a different level from that of the CORA but the ACA passes through the CORA, the correction produces angulation and translation at the level of the osteotomy site.19 Proximal bone fragment angulation and translation occurred because the fracture (osteotomy) was distal to the ACA-CORA intersection.
Times between surgery and complete fracture healing (16 weeks) and fixator removal (17 weeks) were longer for the dog of the present report than reported elsewhere. For example, mean time between surgical fracture repair and development of bridging callus was 11.4 weeks (range, 4 to 22 weeks) and mean time between surgery and fixator removal was 14.7 weeks (range, 4 to 27 weeks) in a previous study.3 However, because no recheck radiographic examinations were performed for the dog of the present report between 8 and 16 weeks after surgery, healing could have been achieved within that period, before 16 weeks. Overall, angular correction and fracture repair by use of a MUESF device were successful in treating combined tibial malalignment and fracture repair in the dog of the present report and may be helpful in similar cases.
Acknowledgments
The authors declare that there were no conflicts of interest.
ABBREVIATIONS
ACA | Angulation correction axis |
CORA | Center of rotation of angulation |
CrCL | Cranial cruciate ligament |
mMDTA | Mechanical medial distal tibial angle |
mMPTA | Mechanical medial proximal tibial angle |
MUESF | Monoplanar unilateral external skeletal fixator |
TPA | Tibial plateau angle |
References
1. Lampman TJ, Lund EM, Lipowitz AJ. Cranial cruciate disease: current status of diagnosis, surgery, and risk for disease. Vet Comp Orthop Traumatol 2003;16:122–126.
2. Grant GR, Olds RB. Treatment of open fractures. In: Slatter D, ed. Textbook of small animal surgery. Vol 2. Philadelphia: Saunders, 2003;1793–1798.
3. Johnson AL, Seitz SE, Smith CW, et al. Closed reduction and type-II external fixation of comminuted fractures of the radius and tibia in dogs: 23 cases (1990–1994). J Am Vet Med Assoc 1996;209:1445–1448.
4. Unger M, Montavon PM, Heim UF. A classification of fractures of long bones in the dog and cat: introduction and clinical application. Vet Comp Orthop Traumatol 1990;3:41–50.
5. Hulse DA, Johnson AL. Fundamentals of orthopedic surgery and fracture management. In: Fossum TW, ed. Small animal surgery. St Louis: Mosby, 1997;705–765.
6. Piermattei D, Flo L, DeCamp CE. Small animal orthopedics and fracture repair. 4th ed. Philadelphia: Saunders, 1997;633–660.
7. Dismukes DI, Tomlinson JL, Fox DB, et al. Radiographic measurement of the proximal and distal mechanical joint angles in the canine tibia. Vet Surg 2007;36:699–704.
8. Kowaleski PM, Boudrieau RJ, Pozzi A. Stifle joint. In: Tobias KM, Johnston SA, eds. Veterinary surgery: small animal. Vol 1. St Louis: Elsevier Saunders, 2012;906–998.
9. Striker Corp. Monotube Triax external fixation system. Available at: www.stryker.com.br/arquivos/Monotube%20Triax%20-%20Brochure.pdf.
10. Johnson AL, Schaeffer DJ. Evolution of the treatment of canine radial and tibial fractures with external fixators. Vet Comp Orthop Traumatol 2008;21:256–261.
11. Augustin G, Zigman T, Davila S, et al. Cortical bone drilling and thermal osteonecrosis. Clin Biomech (Bristol, Avon) 2012;27:313–325.
12. Jaegger G, Marcellin-Little DJ, Levine D. Reliability of goniometry in Labrador Retrievers. Am J Vet Res 2002;63:979–986.
13. Ness MG, Abercromby RH, May C. A survey of orthopaedic conditions in small animal veterinary practice in Britain. Vet Comp Orthop Traumatol 1996;9:6–16.
14. Johnson JA, Austin C, Breur GJ. Incidence of canine appendicular musculoskeletal disorders in 16 veterinary teaching hospitals from 1980 through 1989. Vet Comp Orthop Traumatol 1994;7:56–69.
15. Harasen G. Common long bone fracture in small animal practice—part 2. Can Vet J 2003;44:503–504.
16. Witsberger TH, Villamil JA, Schultz LG, et al. Prevalence of and risk factors for hip dysplasia and cranial cruciate ligament deficiency in dogs. J Am Vet Med Assoc 2008;232:1818–1824.
17. Reif U, Hulse DA, Hauptman JG. Effect of tibial plateau leveling on stability of the canine cranial cruciate–deficient stifle joint: an in vitro study. Vet Surg 2002;31:147–154.
18. Paley D. Frontal plane mechanical and anatomic axis planning. In: Paley D, ed. Principles of deformity correction. Berlin: Springer, 2002;61–98.
19. Paley D. Osteotomy concepts and frontal plane realignment. In: Paley D, ed. Principles of deformity correction. Berlin: Springer, 2002;99–154.