Outcome of limb fracture repair in rabbits: 139 cases (2007–2015)

Hiroshi Sasai Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Daisuke Fujita Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Eiko Seto Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Yuki Denda Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Yutaro Imai Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Kanako Okamoto Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Kensaku Okamura Kitasuma Animal Hospital, 9–5–8 Yokoo, Suma-ku, Kobe, Hyogo, 654–0131 Japan.

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Masaru Furuya Laboratory of Veterinary Internal Medicine, Division of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka 598–8531, Japan.

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Hiroyuki Tani Laboratory of Veterinary Internal Medicine, Division of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka 598–8531, Japan.

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Kazumi Sasai Laboratory of Veterinary Internal Medicine, Division of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka 598–8531, Japan.

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Abstract

OBJECTIVE To evaluate outcome of limb fracture repair in rabbits.

DESIGN Retrospective case series.

ANIMALS 139 client-owned rabbits with limb fractures treated between 2007 and 2015.

PROCEDURES Medical records were reviewed for information on fracture location, fracture treatment, and time to fracture healing.

RESULTS 25 rabbits had fractures involving the distal aspects of the limbs (ie, metacarpal or metatarsal bones, phalanges, and calcaneus or talus). Fractures were treated in 23 of these 25 rabbits (external coaptation, n = 17; external skeletal fixation, 4; and intramedullary pinning, 2) and healed in all 23, with a median healing time of 28 days (range, 20 to 45 days). One hundred ten rabbits had long bone fractures, and fractures were treated in 100 of the 110 (external skeletal fixation, n = 89; bone plating, 1; intramedullary pinning, 3; and external coaptation, 7). The percentage of fractures that healed was significantly lower for open (14/18) than for closed (26/26) tibial fractures and was significantly lower for femoral (19/26) and treated humeral (4/6) fractures than for radial (23/24) or closed tibial (26/26) fractures. Micro-CT was used to assess fracture realignment during external skeletal fixator application and to evaluate fracture healing.

CONCLUSIONS AND CLINICAL RELEVANCE The prognosis for rabbits with limb fractures was good, with fractures healing in most rabbits following fracture repair (109/123). Micro-CT was useful in assessing fracture realignment and evaluating fracture healing.

Abstract

OBJECTIVE To evaluate outcome of limb fracture repair in rabbits.

DESIGN Retrospective case series.

ANIMALS 139 client-owned rabbits with limb fractures treated between 2007 and 2015.

PROCEDURES Medical records were reviewed for information on fracture location, fracture treatment, and time to fracture healing.

RESULTS 25 rabbits had fractures involving the distal aspects of the limbs (ie, metacarpal or metatarsal bones, phalanges, and calcaneus or talus). Fractures were treated in 23 of these 25 rabbits (external coaptation, n = 17; external skeletal fixation, 4; and intramedullary pinning, 2) and healed in all 23, with a median healing time of 28 days (range, 20 to 45 days). One hundred ten rabbits had long bone fractures, and fractures were treated in 100 of the 110 (external skeletal fixation, n = 89; bone plating, 1; intramedullary pinning, 3; and external coaptation, 7). The percentage of fractures that healed was significantly lower for open (14/18) than for closed (26/26) tibial fractures and was significantly lower for femoral (19/26) and treated humeral (4/6) fractures than for radial (23/24) or closed tibial (26/26) fractures. Micro-CT was used to assess fracture realignment during external skeletal fixator application and to evaluate fracture healing.

CONCLUSIONS AND CLINICAL RELEVANCE The prognosis for rabbits with limb fractures was good, with fractures healing in most rabbits following fracture repair (109/123). Micro-CT was useful in assessing fracture realignment and evaluating fracture healing.

Bone fractures in rabbits can be serious; however, knowledge about the treatment of and prognosis for fractures in rabbits is extremely limited, compared with that available for dogs and cats.1,2 To our knowledge, no published scientific reports have described the treatment and outcome of fractures in rabbits, likely because rabbits have a relatively short history as companion animals. Recently, we reported the causes and characteristics of fractures in rabbits.3 In that report, limb fractures accounted for a large percentage of all fractures, and the tibia was the most common site for fractures. In addition, we found that segmental fractures were more common in the rabbits examined than in dogs.

The main purposes of limb fracture repair are to prevent loss of function and relieve pain. It has been reported that the surgical methods used for fracture repair in dogs and cats are not necessarily appropriate for rabbits.2,4,5 For example, bone fragility and the lack of suitable implants hamper fracture repair in rabbits. Therefore, methods customized to the characteristics of rabbits (high activity level, strong startle response, and high sensitivity to perceived threats) are essential.6

External skeletal fixation has been used to treat limb fractures of exotic companion animals, including rabbits.2 However, high-quality advanced diagnostic imaging is essential prior to treatment of limb fractures with ESF because plain radiographic images often are insufficient for fracture assessment. Although CT can provide more detailed imaging information about the fracture site,7,8 even CT may not detect minute lesions in smaller animal species. Furthermore, the risks presented by the required general anesthesia make CT less suitable for these species.

Newer imaging techniques such as m-CT allow assessment of bone disease with increased detail and a much shorter exposure time in small animals.9–11 Our previous study3 demonstrated that m-CT could be used to obtain high-definition images of fracture sites in rabbits. Therefore, the objective of the study reported here was to evaluate outcome of limb fractures in rabbits repaired by various methods, including use of m-CT for surgical planning.

Materials and Methods

Case selection criteria and medical records review

The medical records database of the Kitasuma Animal Hospital was reviewed to identify all rabbits with limb fractures treated between 2007 and 2015.

Diagnostic imaging

Diagnostic imaging of fractures was performed by means of conventional radiography,a digital radiography,b m-CT,c,d or a combination of these modalities. Two types of m-CT devices were used depending on body weight; device 1c was used for rabbits with a body weight < 2 kg (4.4 lb), and device 2d was used for larger rabbits. The protocol for m-CT scanning has been described previously.3

Anesthesia and analgesia

General anesthesia was induced with midazolam (0.2 mg/kg [0.09 mg/lb], IM), butorphanol (0.2 mg/kg, IM), and medetomidine (0.04 mg/kg [0.018 mg/lb], IM) and was maintained with delivery of isoflurane in oxygen. Analgesic agents were selected and administered according to the individual patient needs; these included meloxicam (0.2 mg/kg, IM, q 24 h), butorphanol (0.2 mg/kg, IM, q 12 h), buprenorphine (0.01 mg/kg [0.0045 mg/lb], IM, q 12 h), or a combination of these drugs. Enrofloxacin (5 to 10 mg/kg [2.3 to 4.5 mg/lb], IM or PO, q 24 h), marbofloxacin (2 to 5 mg/kg [0.9 to 2.3 mg/lb], PO, q 24 h), benzylpenicillin (20,000 U/kg [9,100 U/lb], IM, q 24 h), or cefovecin sodium (10 mg/kg, SC) was administered for antimicrobial prophylaxis.

Fracture repair

Fractures were repaired by means of noninvasive or invasive methods. If needed, osteotomy was used to treat malunions resulting from treatment delay or osteonecrosis secondary to open fracture.

Noninvasive fracture repair methods consisted of external coaptation (ie, a caste or splintf). Invasive repair methods consisted of ESF, intramedullary pinning, bone plating, cerclage wire application, or some combination of these methods, with the specific method selected on the basis of the fracture pattern. For ESF, Kirschner wires (0.6 to 1.4 mm in diameter)g and pins (1.6 to 2.0 mm in diameter)h or half-pinsi were inserted with a surgical drill,j and dental composite resink was used to connect and stabilize the external portions of the pins.

Most often, ESF was performed with the assistance of m-CT for surgical planning. For m-CT–assisted ESF, use of full pins or half-pins was selected on the basis of fracture site and configuration, with pin insertion sites chosen on the basis of results of m-CT imaging. Three or 4 pins were inserted into larger fragments, and 2 or 3 pins were inserted into smaller fragments. For each fragment, the external ends of the pins inserted into the fragment were connected and stabilized with dental resin, which allowed the fracture fragments to be easily manipulated by handling the external resin. The bone fragments were aligned and temporarily stabilized and then assessed with m-CT to determine 3-D alignment, including the distance between bone fragments. If necessary, as determined by means of m-CT, the temporary stabilization was removed, and the fragments were realigned. Following final fixation, the fracture site was again examined with m-CT to confirm proper fixation and alignment.

After 3 to 4 weeks and if fracture healing had progressed as expected, type II external skeletal fixators were converted to type I fixators. Beginning approximately 2 months after surgery, the external pins were sequentially cut, starting from the distal pins, to allow dynamization of the fracture fixation. However, if bone healing was not progressing as expected, the period of dynamization was extended.

Outcome

The extent of callus formation was evaluated with plain radiography or m-CT 3 to 4 weeks after surgery and then every 2 weeks thereafter. The external and internal calluses were assessed on MPR images acquired with m-CT. Surgery was performed a second time for patients in which reconstruction of the affected bone required osteotomy. Fractures that required a healing time of more than 12 weeks were defined as nonunions.

Statistical analysis

Data with nonnormal distributions were summarized as median and range. The Fisher exact test was used to compare outcome (healed vs nonunion) between fracture types. The Mann-Whitney U test was used to compare healing times between rabbits with closed versus open tibial fractures. The Kruskal-Wallis test was used to compare healing times between fracture types. Values of P < 0.05 were considered significant. All analyses were performed with statistical software.l

Results

Animals

Of 2,715 rabbits examined during the study period, 139 were evaluated because of limb fractures. For 126 of these 139 rabbits, the causes of injury were described previously.3 The remaining 13 rabbits were all treated in 2015.

Of the 139 rabbits included in the study, 25 (18.0%) had fractures involving the distal aspects of the limbs, including 8 (5.8%) with metacarpal bone fractures, 6 (4.3%) with metatarsal bone fractures, 5 (3.6%) with fractures of the talus or calcaneus, and 6 (4.3%) with fractures of the phalanges. Twenty-three of the 25 rabbits underwent fracture repair.

There were 110 (79.1%) rabbits with long bone fractures, including fractures of the humerus (n = 8 [5.8%]), radius (24 [17.3%]), femur (32 [23.0%]), and tibia (46 [33.1%]). Two of the rabbits had bilateral fractures. One hundred of the 110 rabbits with long bone fractures underwent fracture repair.

The remaining 4 rabbits had multiple fractures of all 4 limbs (n = 2), combined femoral and tibial fractures (1), or thoracic vertebral and femoral fractures (1). The 2 rabbits with multiple fractures of all 4 limbs were not treated, at the owners' request. The rabbit with femoral and tibial fractures underwent bone plating, but died 22 days after surgery. The rabbit with thoracic vertebral and femoral fractures underwent fracture repair by means of ESF, but died 3 days after surgery. These 4 rabbits were excluded from statistical analyses.

Outcome

Fractures of the distal aspects of the limbs—Transverse and oblique fractures of the metacarpal bones, metatarsal bones, and phalanges were generally treated by means of external coaptation (Table 1), except that 1 rabbit with metacarpal bone fractures and 1 rabbit with metatarsal bone fractures were treated with intramedullary pinning. Fractures of the talus or calcaneus were treated by means of external coaptation or m-CT–assisted ESF. Complete healing was achieved in all 23 (100%) rabbits that underwent fracture treatment, with a median healing time of 28 days (range, 20 to 45 days; Table 2). One of the 2 rabbits that did not undergo fracture repair and received only pain control had complete healing; the other developed a nonunion.

Table 1—

Fracture repair methods for 25 rabbits with fractures of the distal aspects of the limbs.

BoneNo. of rabbitsESFExternal coaptationIM pinningNone*
Metacarpal bone80512
Talus or calcaneus54100
Metatarsal bone60510
Phalanges60600
Total2541722

Rabbits that did not undergo fracture repair received only pain control (meloxicam, butorphanol, buprenorphine, or a combination of these drugs).

Rabbits with phalangeal fractures included 1 rabbit with forelimb phalangeal fractures and 5 rabbits with hind limb phalangeal fractures.

IM = Intramedullary.

Table 2—

Outcome of fracture repair for the 23 rabbits in Table 1 in which fractures were treated.

BoneNo. of rabbitsNo. (%) healedNo. (%) with nonunionHealing time (d)
Metacarpal bone66 (100)0 (0)22.5 (20–30)
Talus or calcaneus55 (100)0 (0)29 (28–45)
Metatarsal bone66 (100)0 (0)30 (21–32)
Phalanges66 (100)0 (0)26 (21–33)
Total2323 (100)0 (0)28 (20–45)

Data for healing time are given as median (range).

Long bone fractures—Forty-six of the 110 rabbits with long bone fractures had fractures of the tibia (including 2 rabbits with bilateral tibial fractures), and 39 of the 48 (81.3%) tibial fractures involved the tibial shaft. Fracture types included simple (n = 32 [34 fractures]), splintered (6), fragmentary (6), and segmental (2) fractures. Twenty-six rabbits had closed tibial fractures, and 20 had open fractures. An osteotomy was performed in 9 rabbits with open tibial fractures because of osteonecrosis.

Two rabbits with open tibial fractures died or were euthanized without undergoing fracture treatment. For the remaining 44 rabbits with tibial fractures, treatment consisted of application of a type II ESF alone (n = 42) or in combination with an IM pin (1) or cerclage wire (1; Table 3; Figures 1–3). Healing time did not differ significantly (P = 0.21) between rabbits with closed versus open tibial fractures (Table 4); however, the percentage of rabbits in which the fracture healed was significantly (P = 0.011) higher for rabbits with closed tibial fractures than for rabbits with open tibial fractures.

Table 3—

Fracture repair methods for 110 rabbits with fractures of the long bones.

BoneNo. of rabbitsESFBone platingIM pinningExternal coaptationAmputationNone*
Humerus8500102
Radius241800600
Femur322213015
Tibia (closed)262600000
Tibia (open)201800002
Total1108913719

Seven of the 9 rabbits that did not undergo fracture repair received only pain control; the remaining 2 died or were euthanized.

In 6 of the rabbits with femoral fractures and 2 of the rabbits with open tibial fractures, ESF was supplemented with an IM pin or cerclage wires.

IM = Intramedullary.

Table 4—

Outcome of fracture repair for the 100 rabbits in Table 3 in which fractures were treated.

BoneNo. of rabbitsNo. (%) healedNo. (%) with nonunionHealing time (d)
Humerus64 (67)*2 (33)44 (30–82)
Radius2423 (96)1 (4)52 (28–68)
Femur2619 (73)*7 (27)58 (28–91)
Tibia (closed)2626 (100)0 (0)53 (28–138)
Tibia (open)1814 (78)4 (22)73.5 (44–287)
Total10086 (86)14 (14)ND

Significantly (P < 0.05) lower than percentage for radial and closed tibial fractures.

Significantly (P < 0.05) higher than percentage for open tibial fractures.

ND = Not determined.

Data for healing time are given as median (range).

Figure 1—
Figure 1—

Postoperative radiographic images and photographs of 2 rabbits with a tibial (A) and a femoral (B and C) fracture repaired by means of an ESF, and a photograph of a rabbit obtained 1 week after repair of a femoral fracture with an ESF (D). Notice that rabbits were able to use the injured limb shortly after surgery.

Citation: Journal of the American Veterinary Medical Association 252, 4; 10.2460/javma.252.4.457

Figure 2—
Figure 2—

Three-dimensional MPR and m-CT images of a rabbit with a tibial fracture repaired by means of ESF (A through C) and of a second rabbit with a femoral fracture repaired by means of bone plating (D through F). Images obtained before reduction (A and D) illustrate the complex nature of the fractures, whereas images obtained after reduction (B and E) illustrate good alignment following fracture fixation. On m-CT images (C and E), the pins used for ESF (arrows; C) generated weaker signal artifacts, compared with the implants used for bone plating (arrowheads; F).

Citation: Journal of the American Veterinary Medical Association 252, 4; 10.2460/javma.252.4.457

Figure 3—
Figure 3—

Micro-CT images of a rabbit obtained 50 days after repair of a tibial fracture by means of ESF. Images acquired by means of m-CT provided valuable information about both internal (arrows; A and B) and external (arrowheads; C and D) callus formation at the fracture site. Pins used for ESF generated weak signal artifacts that generally did not interfere with assessment of fracture healing.

Citation: Journal of the American Veterinary Medical Association 252, 4; 10.2460/javma.252.4.457

Thirty-two rabbits had femoral fractures, which included simple (n = 17), splintered (5), segmental (4), complex (3), fragmentary (2), and epiphyseal (1) fractures. The percentage of rabbits in which femoral fractures healed was significantly lower than the percentages in which radial (P = 0.028) or closed tibial (P = 0.004) fractures healed (Table 4).

Twenty-four rabbits had fractures of the radius, including simple (n = 14), fragmentary (5), complex (3), splintered (1), and epiphyseal (1) fractures. All 24 rabbits with radial fractures underwent fracture treatment.

Eight rabbits had humeral fractures, which included simple (n = 5), splintered (2), or segmental (1) fractures. The percentage of rabbits in which humeral fractures healed was significantly lower than the percentages in which radial (P = 0.033) or closed tibial (P = 0.002) fractures healed.

There were no significant (P = 0.065) differences in healing times among humeral, radial, femoral, and tibial fractures (Table 4).

Discussion

In a previous study,3 we found that the incidence of fracture was significantly higher in rabbits < 3 years of age than in older rabbits. In addition, we found that fractures of the hind limbs occurred twice as frequently as fractures of the forelimbs and that more than half of all limb fractures resulted from idiopathic or spontaneous causes.3 These features must be considered when planning fracture treatment. Furthermore, it is quite difficult for rabbits to avoid putting weight on their hind limbs following fracture repair, unlike dogs and cats. For these reasons, fracture fixation in rabbits should be stable and rigid enough to resist high-energy forces, should allow mobility early in the treatment period, and should not affect daily behaviors such as coprophagia. However, studies of the occurrence or treatment of limb fractures in rabbits have been limited.4,5,12

Internal fixation or ESF is typically used to repair fractures of the distal aspects of the limbs in dogs and cats.13–15 In the present study, external coaptation was used for treatment of metacarpal bone, metatarsal bone, and phalangeal fractures in 16 rabbits and intramedullary pinning was used in 2. The fractures healed in all 18 rabbits, suggesting that a noninvasive fracture repair method may be appropriate for most fractures involving the metacarpal and metatarsal bones and phalanges in rabbits.

In rabbits, the bone fragments tend to separate in a dorsoplantar direction when the calcaneus or talus is fractured during trauma, and in such cases, invasive fracture treatment methods are generally needed to realign the fragments. In the present study, 4 of 5 rabbits with fractures of the calcaneus or talus were treated with m-CT–assisted ESF and 1 was treated with external coaptation. The fracture healed in all 5 rabbits, suggesting that m-CT–assisted ESF may be appropriate for most fractures of the calcaneus or talus in rabbits.

In contrast to fractures of the metacarpal and metatarsal bones and phalanges, noninvasive treatment was rarely chosen for treatment of long bone fractures in the present study. In rabbits, the femur tapers toward the distal end,1,16 making it difficult to achieve stable fixation with splinting or casting. Moreover, rabbits spend most of their time with their hind limbs bent, which would make a splint or cast a hindrance. In contrast, noninvasive fracture treatment methods may be useful for radial fractures when there is minimal displacement of bone fragments, but fractures of the humerus typically require realignment and rigid fixation.

Bone weight accounts for only 7% to 8% of total body mass in rabbits, which is lower than percentages for dogs and cats (12% to 13%).17 Therefore, use of bone screws in the cortical bone of rabbits cannot guarantee sufficient fixation, compared with use of screws in other species. On the other hand, the large medullary cavity offers an advantage for the use of intramedullary pinning or complex ESF. In the present study, ESF was used most often for the treatment of long bone fractures.

The tibia was the most common fracture site for rabbits in the present study (n = 46), and 20 of these 46 fractures were open, likely because continued movement of the injured limb caused additional damage to soft tissues and skin.4,5 Importantly, careful examination is needed in rabbits with tibial fractures, because their dense coat makes identification of open fractures difficult. In the present study, 100% (26/26) of closed and 78% (14/18) of open tibial fractures healed following fracture treatment. Although 4 rabbits with open tibial fractures developed a nonunion, there was no significant difference in healing time between closed and open fractures for those fractures that did go on to heal. Therefore, ESF was considered a satisfactory method for treatment of open tibial fractures.

The femur was the second most common site for long bone fractures in the present study (n = 32). Intramedullary pinning or ESF has been reported previously for repair of femoral fractures in rabbits.12 In the present study, 3 rabbits with femoral fractures were treated with intramedullary pinning, including rabbits with a simple fracture of the femoral shaft, a simple fracture of the distal end of the femur, and a fracture of the growth plate. External skeletal fixation was used to repair segmental or comminuted fractures in 22 rabbits, including 6 rabbits in which ESF was combined with an intramedullary pin or cerclage wires, and a bone plate was used in 1. Fractures were not repaired in the remaining 6 rabbits with femoral fractures, and treatment consisted of amputation (n = 1) or pain control alone. The finding that 7 of 26 (27%) rabbits in which femoral fracture repair was attempted developed a nonunion indicated the necessity for improved surgical methods and the challenges of postoperative management in this species, including surgical site infections and physical and psychological stress.18

Radial fractures occurred in 24 rabbits in the present study. Currently there is no suitable bone implant for internal fixation of radial fractures in rabbits because the bone is so thin and short.2 For this reason, ESF was selected for 18 of the 24 rabbits with radial fractures, with external coaptation used in the remaining 6. Overall, the fracture healed in 23 of the 24 rabbits with radial fractures, suggesting that, depending on fracture configuration and displacement, ESF and external coaptation may be effective methods for repair of radial fractures in rabbits.

Only 8 rabbits in the present study had fractures of the humerus. A type I ESF was used in 5 of these rabbits, and external coaptation was used in 1; however, the fracture healed in only 4 of these 6 rabbits. The remaining 2 rabbits with humeral fractures did not undergo fracture treatment and received only pain control, and the fracture did not heal in either of these rabbits. Because of the low number of rabbits with humeral fractures, it is hard to draw conclusions. However, methods for treatment of humeral fractures in rabbits warrant further investigation.

Overall, ESF (alone or combined with an intramedullary pin or cerclage wires) was used in 89 of the 100 rabbits in the present study with long bone fractures that underwent fracture treatment and generally resulted in a good outcome. Rabbits typically ambulated on the injured limb within a few days after treatment, and this early mobilization likely improved the blood supply in the region of the fracture, resulting in improved fracture healing.19 Our results indicated that ESF may be a suitable treatment for long bone fractures in rabbits, because the method was associated with a high rate of healing and appeared to have minimal effects on the behavior of the rabbits.

In general, ESF is recognized as a less invasive method than bone plating, although it is often difficult to optimally realign the bone fragments without unduly prolonging surgery time.1,20 Because the fracture is reduced without direct visualization, it is necessary to confirm alignment several times by means of diagnostic imaging. In the present study, we used m-CT to assist with ESF, which allowed us to confirm 3-D alignment and reduction of the fragments. The ESF pins that were used generated weaker signal artifacts than do other fracture implants and also facilitated manipulation of the bone fragments. Finally, it was possible to evaluate the postoperative callus on MPR images acquired by use of m-CT with minimal signal artifacts from the ESF pins.

Diagnostic imaging with m-CT is useful to detect small lesions that might not be seen on conventional radiographic images.3,9,10 In addition, compared with conventional multislice CT, m-CT requires shorter scanning times, which may reduce the risk posed by general anesthesia in these animals. In the present study, we found that m-CT could be used to obtain high-definition images of fractures in rabbits and provided detailed 3-D information to improve the precision of fragment reduction. During the postoperative period, m-CT provided information about the extent of fracture healing, as described previously.21,22 Thus, the routine use of m-CT may improve the outcome of limb fracture repair in rabbits. Future research is needed to improve surgical repair of fractures in rabbits, including development of novel osteogenic devices to aid repair of comminuted fractures and fractures resulting in large bone defects.

Acknowledgments

Supported by the Council for Science, Technology and Innovation, Cross-Ministerial Strategic Innovation Promotion Program, Innovative Design/Manufacturing Technologies (Establishment and Validation of the Base for 3D Design and Additive Manufacturing Standing on the Concepts of “Anisotropy” and “Customization”) from the New Energy and Industrial Technology Development Organization.

The authors thank Dr. Yasunori Arai, Dr. Yukihiro Hara, Kiyoshi Akiyama, and Isao Hamanaka for technical advice and assistance with the development of the micro-CT technique.

ABBREVIATIONS

ESF

External skeletal fixation

m-CT

Micro-CT

MPR

Multiplanar reconstruction

Footnotes

a.

Kodak MIN-R, Eastman Kodak Co, Rochester, NY.

b.

Canon CXDI-70C, Canon Inc, Tokyo, Japan.

c.

R_mCT2, Rigaku Co, Tokyo, Japan.

d.

R_mCTAX, Rigaku Co, Tokyo, Japan.

e.

Scotchcast 3J, 3M Healthcare Inc, Saint Paul, Minn.

f.

SAM Splint, Jorgensen Laboratories Inc, Loveland, Colo.

g.

Mizuho, Tokyo, Japan.

h.

Miltex Inc, York, Pa.

i.

Interface half-pin, IMEX, Longview, Tex.

j.

Stryker TPS & Core System, Stryker, Kalamazoo, Mich.

k.

Shofu Inc, Kyoto, Japan.

l.

Ekuseru-Toukei, Social Survey Research Information Co Ltd, Tokyo, Japan.

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    • Search Google Scholar
    • Export Citation
  • 16. Cruise LJ, Brewer NR. Anatomy. In: Manning PJ, Ringler DH, Newcomer CE, eds. The biology of the laboratory rabbit. 2nd ed. Orlando, Fla: Academic Press, 1994;4761.

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  • 17. Harkness JE, Wagner JE. Chapter 2. In: The biology and medicine of rabbits and rodents. 4th ed. Philadelphia: Lea & Febiger, 1995;1330.

    • Search Google Scholar
    • Export Citation
  • 18. Pollock C. Postoperative management of the exotic animal patient. Vet Clin North Am Exot Anim Pract 2002;5:183212.

  • 19. Peirone B, Rovesti GL, Baroncelli AB, et al. Minimally invasive plate osteosynthesis fracture reduction techniques in small animals. Vet Clin North Am Small Anim Pract 2012;42:873895.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. DeCamp CE, Johnston SA, Dejardin LM, et al. Fractures: classification, diagnosis, and treatment. In: Handbook of small animal orthopedics and fracture repair. 5th ed. St Louis: Saunders Elsevier, 2016;24152.

    • Search Google Scholar
    • Export Citation
  • 21. Lu M, Rabie AB. Microarchitecture of rabbit mandibular defects grafted with intramembranous or endochondral bone shown by micro-computed tomography. Br J Oral Maxillofac Surg 2003;41:385391.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22. Lu M, Rabie AB. Quantitative assessment of early healing of intramembranous and endochondral autogenous bone grafts using micro-computed tomography and Q-win image analyzer. Int J Oral Maxillofac Surg 2004;33:369376.

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    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Postoperative radiographic images and photographs of 2 rabbits with a tibial (A) and a femoral (B and C) fracture repaired by means of an ESF, and a photograph of a rabbit obtained 1 week after repair of a femoral fracture with an ESF (D). Notice that rabbits were able to use the injured limb shortly after surgery.

  • Figure 2—

    Three-dimensional MPR and m-CT images of a rabbit with a tibial fracture repaired by means of ESF (A through C) and of a second rabbit with a femoral fracture repaired by means of bone plating (D through F). Images obtained before reduction (A and D) illustrate the complex nature of the fractures, whereas images obtained after reduction (B and E) illustrate good alignment following fracture fixation. On m-CT images (C and E), the pins used for ESF (arrows; C) generated weaker signal artifacts, compared with the implants used for bone plating (arrowheads; F).

  • Figure 3—

    Micro-CT images of a rabbit obtained 50 days after repair of a tibial fracture by means of ESF. Images acquired by means of m-CT provided valuable information about both internal (arrows; A and B) and external (arrowheads; C and D) callus formation at the fracture site. Pins used for ESF generated weak signal artifacts that generally did not interfere with assessment of fracture healing.

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  • 14. Muir P, Norris JL. Metacarpal and metatarsal fractures in dogs. J Small Anim Pract 1997;38:344348.

  • 15. Risselada M, Verleyen P, van Bree H, et al. The use of an external skeletal traction device for distal fractures in the dog. A clinical case series of 11 patients. Vet Comp Orthop Traumatol 2007;20:131135.

    • Search Google Scholar
    • Export Citation
  • 16. Cruise LJ, Brewer NR. Anatomy. In: Manning PJ, Ringler DH, Newcomer CE, eds. The biology of the laboratory rabbit. 2nd ed. Orlando, Fla: Academic Press, 1994;4761.

    • Search Google Scholar
    • Export Citation
  • 17. Harkness JE, Wagner JE. Chapter 2. In: The biology and medicine of rabbits and rodents. 4th ed. Philadelphia: Lea & Febiger, 1995;1330.

    • Search Google Scholar
    • Export Citation
  • 18. Pollock C. Postoperative management of the exotic animal patient. Vet Clin North Am Exot Anim Pract 2002;5:183212.

  • 19. Peirone B, Rovesti GL, Baroncelli AB, et al. Minimally invasive plate osteosynthesis fracture reduction techniques in small animals. Vet Clin North Am Small Anim Pract 2012;42:873895.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. DeCamp CE, Johnston SA, Dejardin LM, et al. Fractures: classification, diagnosis, and treatment. In: Handbook of small animal orthopedics and fracture repair. 5th ed. St Louis: Saunders Elsevier, 2016;24152.

    • Search Google Scholar
    • Export Citation
  • 21. Lu M, Rabie AB. Microarchitecture of rabbit mandibular defects grafted with intramembranous or endochondral bone shown by micro-computed tomography. Br J Oral Maxillofac Surg 2003;41:385391.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22. Lu M, Rabie AB. Quantitative assessment of early healing of intramembranous and endochondral autogenous bone grafts using micro-computed tomography and Q-win image analyzer. Int J Oral Maxillofac Surg 2004;33:369376.

    • Crossref
    • Search Google Scholar
    • Export Citation

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