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Cervical Vertebral Fractures in 56 Dogs: A Retrospective Study
Julia C. Hawthorne, DVM; William E. Blevins, DVM, MS, Diplomate ACVR; Larry J. Wallace, DVM, Diplomate ACVS; Nita Glickman, MPH, MS; David J. Waters, DVM, PhD, Diplomate ACVS
Journal of the American Animal Hospital Association
March 1, 1999
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The clinicopathological features of cervical fractures in 56 dogs were reviewed. “Hit by car” (HBC) was the most common inciting cause, and the axis and atlas were the vertebrae most frequently affected. Surgical treatment was associated with high (36%) perioperative mortality. However, all dogs that survived the perioperative period achieved functional recovery. Functional recovery was achieved in 25 (89%) of 28 nonsurgically treated dogs with adequate follow-up. Overall, severity of neurological deficits (nonambulatory status) and prolonged interval (five days or longer) from trauma to referral were associated with poorer outcome. Nonsurgical treatment is a viable therapeutic approach for many dogs with cervical fractures. Early neck immobilization and prompt referral are recommended, because delay in referral decreases the likelihood of functional recovery.
J Am Anim Hosp Assoc 1999;35:135–46.
Introduction
In dogs, cervical vertebral fractures occur less frequently than fractures of
the thoracolumbar spine. Thoracolumbar fractures are well characterized with
respect to epidemiology, anatomic distribution, and prognosis after surgical or
nonsurgical treatment.1–3 In contrast, cervical vertebral
fractures of dogs are poorly characterized. The largest reported case
series,4 published nearly 20 years ago, provided
information on 12 dogs and reviewed 15 previously reported cases.5–10 Since then, seven reports have contributed data on an
additional 21 cases.11–17 The paucity of published
information on cervical fractures in dogs, in particular the factors that
influence functional outcome after nonsurgical treatment, prompted the authors
to conduct this retrospective study.
The specific aims of this study
were: 1) to characterize the clinicopathological features of 56 dogs with
cervical vertebral fractures, and 2) to identify factors that were predictive of
successful outcome in 46 dogs with adequate follow-up, including the subset of
28 dogs that underwent nonsurgical treatment. The results indicate that
functional recovery often can be achieved with nonsurgical treatment. Surgical
management of cervical vertebral fractures is associated with high perioperative
mortality. Nonambulatory status and delayed referral are associated with
decreased likelihood for a functional recovery.
Materials and
Methods
Case Selection
Dogs with cervical vertebral fractures admitted to the Veterinary Teaching
Hospitals of Purdue University and the University of Minnesota (1969 through
1992) were studied. Medical records were reviewed, and cases were selected for
study if cervical radiographs, neurological examination findings, and treatment
information were available. Fifty-six dogs satisfied these inclusion criteria.
In all cases, diagnosis of cervical vertebral fracture was based upon
radiographs, necropsy findings, or both. The following data was obtained from
the medical record: signalment, inciting cause of fracture, onset and severity
of neurological signs, concurrent injuries, and radiographic interpretation. The
time interval from trauma to presentation to the referral institution was
recorded. Specific location of each fracture, treatment (surgical versus
nonsurgical), and follow-up information also were recorded. Follow-up data was
obtained from medical records or telephone questionnaires from the pet owner or
referring veterinarian.
Analysis of Possible Prognostic Factors
Data from 46 dogs with adequate follow-up was analyzed to determine if
particular factors were associated with functional recovery. Ten dogs that were
lost to follow-up after nonsurgical treatment were excluded from this analysis.
A separate analysis was performed to identify factors predictive of outcome in
the subset of 28 dogs that underwent nonsurgical treatment. Functional recovery
was defined as pain-free ambulation with urinary and fecal continence. The
following potential prognostic factors were evaluated: inciting cause (HBC
versus other); level of affected vertebra (first cervical [C1] and second
cervical [C2] versus other); multiplicity (single versus multiple vertebrae);
time interval from trauma to presentation to referral institution (less than
five days versus five or more days); severity of neurological deficits on
presentation (nonambulatory versus ambulatory); concurrent head trauma; and
surgical versus nonsurgical treatment. Two by two tables were constructed, and
chi-square (c2) or Fisher’s exact tests were used to determine the association
between these factors and functional recovery. Whenever possible, odds ratio
(OR) and 95% confidence intervals were calculated.18 Odds
ratio provides an estimate of the relative risk that a patient with a particular
characteristic will have a certain outcome (e.g., functional recovery in this
study). Odds ratios were considered statistically significant if the 95%
confidence interval did not include 1.0.
Results
Signalment and Inciting Cause
The clinicopathological features of 56 dogs with cervical fractures are
summarized in Table 1. Median age was two years (range, 4 mos to 14 yrs), and
there was an equal sex distribution. Median body weight was 18 kg (range, 1 to
50 kg). Twenty-six (46%) of 56 dogs with cervical fractures were HBC. Other
inciting causes included a big dog/little dog fight (n=8); collision/rough play
(n=6); a door slam (n=4); a gunshot injury (n=2); a fall into a hole or down
stairs (n=3); blunt trauma (n=1); a leash injury (n=1); and a tumor-associated
pathological fracture (n=1). In four cases, there was no history of
trauma.
Concurrent Injuries
Concurrent injuries were noted in 27 (48%) of 56 dogs. Hit by car was the
inciting cause of vertebral fracture in 17 (63%) of 27 dogs that had concurrent
injuries. These included fractures of long bones (n=3), mandible (n=2), scapula
(n=2), rib (n=1), occiput (n=2), and thoracolumbar vertebrae (n=2). Soft-tissue
wounds, usually associated with gunshot injuries or animal bites, were found in
eight dogs. Three dogs had thoracic trauma (e.g., pneumothorax, lung
contusions). Clinical signs of head trauma (e.g., hemorrhage from the nose or
mouth, seizures, loss of consciousness) were reported in nine
dogs.
Severity and Progression of Neurological Deficits
Severity of neurological deficits upon presentation to the referral
institution was variable [Table 1]. Thirty-two (57%) of 56 dogs were
nonambulatory. However, loss of voluntary motor function (i.e., tetraplegia) was
noted in only four dogs, and none of these dogs had complete sensorimotor loss.
Eight (14%) of 56 dogs had cervical pain as the only abnormality on neurological
examination.
In many cases, diagnosis of cervical vertebral fracture was
not made immediately, and a decline in neurological status noted days to weeks
after the traumatic event prompted reevaluation. Median interval from trauma to
presentation at the referral institution was five days (range, 2 hrs to 2 mos).
Deterioration in neurological status was documented in 13 (48%) of 27 dogs for
which detailed histories were available.
Anatomic Distribution
The axis (C2) was the most commonly affected vertebra [Figure 1]. Twenty-nine
(52%) of 56 dogs had C2 fractures, which accounted for 29 (36%) of 81 fractures.
Twenty-five percent of dogs had C1 fractures. Nineteen (34%) of 56 dogs had
multiple cervical vertebrae affected. When the third cervical, fourth cervical,
or fifth cervical vertebra was fractured, a single vertebra was affected in only
15% of the cases. A big dog/little dog fight and unknown trauma were the only
subgroups in which fractures of the third through the seventh cervical vertebrae
outnumbered fractures of C1 and C2
Treatment and Outcome
Fifty-six dogs with cervical fractures were subdivided into three groups
based upon treatment/outcome: 1) dogs that died or were euthanized within 24
hours of referral; 2) dogs that received surgical treatment; and 3) dogs that
received nonsurgical treatment [Figure 2].
The present study was
performed using dogs that were part of another study investigating various
methods of attachment of Seven dogs died or were euthanized within 24 hours of
referral. Two of these seven dogs suffered cardiopulmonary arrest, and two dogs
were euthanized within hours after presentation due to the severity of systemic
injuries. Three dogs were euthanized after myelography due to the severity of
injuries or anesthetic complications.
Eleven dogs received surgical treatment for their cervical vertebral
fractures. Nine of 11 dogs had C1 or C2 lesions. Preoperative neurological
status in nine of 11 dogs was nonambulatory tetraparesis. Surgical management
consisted of dorsal suturing/wiring with or without dorsal laminectomy (n=5),
dorsal laminectomy alone (n=2), screw fixation/stabilization using
methylmeth-acrylate via a ventral approach (n=2), or hemilaminectomy with
plastic dorsal spinous process plating (n=1). Surgical treatment was associated
with high perioperative mortality; four (36%) of 11 surgically treated dogs
died. Cardiopulmonary arrest occurred in three dogs within 24 hours after
surgery, while the fourth dog had cardiopulmonary arrest on the fourth
postoperative day. All dogs that survived the perioperative period achieved
functional recovery.
Thirty-eight dogs received nonsurgical treatment
consisting of a neck brace/splint with activity restriction (n=26) or activity
restriction alone (n=12). Follow-up data was available for 28 dogs that
underwent nonsurgical treatment. Twenty (71%) of these 28 dogs had C1 or C2
lesions, and 14 were nonambulatory at the time of referral. In contrast to
surgically treated patients, only three (11%) of 28 dogs died or were
euthanized. One dog was euthanized after respiratory arrest and resuscitation
two days after neck cast application. Two dogs that were treated with activity
restriction were euthanized because of residual deficits at two weeks and three
months, respectively. Twenty-five (89%) of the 28 nonsurgically treated dogs
achieved functional recovery. Four of 25 dogs that achieved functional recovery
had mild residual neurological deficits (median follow-up, 3.5
wks).
Predictors of Functional Recovery
Follow-up (median, 1.5 mos; range, 0.5 to 77 mos) outcome data was available
from the medical records or telephone questionnaires for 46 dogs [Table 1].
Functional recovery (i.e., pain-free ambulation, urinary and fecal continence)
was achieved in 32 (70%) of 46 dogs. Overall, severe neurological deficits (OR,
13.00; 95% confidence interval, 1.52 to 111.47) and delayed interval from trauma
to referral (OR, 5.50; 95% confidence interval, 1.38 to 21.85) were associated
with a decreased likelihood for functional recovery [Table 2]. Thus, dogs with
nonambulatory tetraparesis were 13 times less likely to have functional recovery
compared to ambulatory dogs, whereas dogs with a trauma to referral interval of
five days or longer were 5.5 times less likely to recover than dogs with a
trauma to referral interval of less than five days. Analysis of prognostic
factors for 28 non-surgically treated dogs showed that delayed presentation to
the referral institution (i.e., five days or longer) was significantly
associated with a decreased likelihood for functional recovery when compared to
dogs with a trauma to referral interval of less than five days (p=0.04) [Table
3]. No other factors were significantly associated with
outcome.
Discussion
In contrast to thoracolumbar fractures, the clinicopathological features of
cervical fractures in dogs have been poorly characterized. Previously reported
data on functional outcome after surgical or nonsurgical treatment is limited to
33 and 12 dogs, respectively.4–17 Importantly, no previous
reports have evaluated prognostic factors that might predict functional outcome.
The lack of information regarding patient outcome, in particular for those dogs
that underwent nonsurgical treatment, prompted this study. The authors’ results
indicate that nonsurgical treatment (i.e., neck immobilization and activity
restriction) can be used successfully in many dogs with cervical fractures.
Furthermore, this study provides the first information that certain factors may
predict the likelihood of functional recovery in dogs with cervical
fractures.
Surgical treatment of cervical fractures was associated with high
perioperative mortality. The 36% perioperative mortality rate is consistent with
a previous report4 in which 37% of surgically treated dogs with cervical
fractures did not survive the perioperative period [Table 4]. However, the
prognosis for functional recovery in perioperative survivors is excellent; 100%
of dogs in the authors’ series that survived the perioperative period had
functional recovery. Collectively, 36 (97%) of 37 dogs in the authors’ series
and the literature that survived the perioperative period achieved functional
recovery.4–17 An explanation for the high perioperative
mortality in dogs with cervical fractures is not apparent, but this observation
is consistent with previous reports of complications associated with cervical
spinal surgery.19–21
Nonsurgical treatment resulted
in functional recovery in 89% of dogs in the authors’ series [Table 5]. The
three dogs that did not achieve functional recovery died or were euthanized
because of neurological deficits six days to three months after referral.
Collectively, in the authors’ series and the literature, functional recovery
after nonsurgical treatment was seen in 37 (93%) of 40 cases.4–10 The authors conclude that many cervical fractures are
amenable to nonsurgical treatment because this approach offers a high likelihood
of success. dogs that did not achieve functional recovery died or were
euthanized because of neurological deficits six days to three months after
referral. Collectively, in the authors’ series and the literature, functional
recovery after nonsurgical treatment was seen in 37 (93%) of 40 cases.4–10 The authors conclude that many cervical fractures are
amenable to nonsurgical treatment because this approach offers a high likelihood
of success.
Definitive criteria for selection of dogs with cervical
fractures that would benefit from surgical treatment (instead of nonsurgical
treatment) have not been established. General indications for surgical treatment
have been proposed, including vertebral displacement or comminution,
deteriorating neurological status amidst conservative management, or persistent
pain.4,13 A retrospective case review cannot provide
definitive conclusions regarding the superiority (or inferiority) of surgical
treatment compared to nonsurgical treatment of cervical fractures. Instead, the
authors sought to identify a subset of cervical fractures that was associated
with a poor outcome after nonsurgical treatment. If identified, these cases
would have provided valuable insight into fracture characteristics that might
render cases unsuitable for nonsurgical management. However, almost 90% of
nonsurgically treated cases had functional recovery. As a result, particular
types of cervical fractures that would mandate surgical treatment were not
identified.
Several possible predictors (i.e., inciting cause, level of
affected vertebra, multiplicity, time interval from trauma to referral, severity
of neurological deficits on presentation, concurrent head trauma) of functional
outcome were evaluated. Overall, nonambulatory dogs were l3 times less likely to
have functional recovery than ambulatory dogs. However, severity of neurological
deficits was not predictive of functional recovery in nonsurgically treated
dogs. This may reflect that nonambulatory dogs in this series were more likely
to be euthanized prior to treatment (perhaps due to concurrent non-neurological
injury). Nonambulatory dogs may also have been more likely to undergo surgical
treatment which was associated with high perioperative mortality. Importantly,
the results indicate that nonambulatory dogs with cervical fractures do not have
a grave prognosis. In fact, once the decision was made to pursue nonsurgical
treatment, there was no difference in prognosis for nonambulatory and ambulatory
dogs.
A prolonged interval from trauma to referral was a consistent
negative predictor of functional recovery. Overall, dogs with a trauma to
referral interval of five days or more were 5.5 times less likely to achieve
functional recovery than dogs referred less than five days after trauma. The
strong negative association between trauma to referral interval and functional
recovery also was seen in the 28 nonsurgically treated dogs. One possible
explanation is that dogs with delayed referral may have an unstable vertebral
fracture which results in progressive spinal cord damage. This instability may
be related to the nature of the fracture or may reflect inadequate spinal
stabilization during the post-traumatic period. Alternatively, it may reflect
diminished owner enthusiasm to pursue treatment; lack of owner commitment
ultimately leads to a less favorable outcome.
Conclusion
Dogs that undergo nonsurgical treatment of their cervical fractures have a
high likelihood of functional recovery. Due to the high perioperative mortality
associated with cervical spinal surgery, it is imperative that specific criteria
be defined that justify surgical intervention. Delay in presentation to the
referral institution decreases the likelihood of functional recovery.
Accordingly, early neck immobilization, prompt referral, or both are recommended
to increase the likelihood of successful outcome in dogs with cervical
fractures.
References
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