A comparison between fixation methods of femoral
diaphyseal fractures in cats - A retrospective study on
106 cases (1997-2008)
T. Könning, R.J. Maarschalkerweerd, N. Endenburg, L.F.H. Theyse
Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht
University, Utrecht, The Netherlands
Summary
A retrospective study over the period 1997-2008 of femoral diaphyseal fractures in cats was
performed. Only patients with diaphyseal fractures were used in this study (n=106). Selected
cases had to have a complete medical record, with clinical and radiographic follow-up
examination. Of 106 fractures, 30 were treated with an external fixator, 20 with a bone plate, en
56 with a plate-rod construct. External fixators, bone plates and plate-rod constructs all were
successful in fracture healing. In the group treated with an external fixator and a plate-rod
construct, 93% of the fractures reached union. In the group treated with a bone plate 90%
reached union.
The fractures treated with a plate-rod construct had fewest complications (9%), followed by the
fractures treated with a bone plate (15%). The fractures treated with an external fixator had the
most complications (27%).
Although the differences between the groups in number of fractures that achieved union and
complication rates were not significant, we believe these differences could be clinically relevant.
Keywords
Femoral, fracture, cats, diaphyseal, fixation methods
1
and reduced healing time, low infection rates,
Introduction
decreased blood loss, reduction in surgical time and
Femoral fractures are common in cats, accounting
development of fewer complications, including
for 20% to 26% off all fractures. Most femur
decreased rate of non-union (8,12-15).
fractures are closed, because of the heavy overlying
When selecting a fixation method to repair a
muscles (1-3).
fracture, a thorough comprehension of both the
The repair process during fracture healing is
forces that created the fracture and the forces
dependent on an adequate blood supply. The major
neutralized by the fixation is necessary to optimize
blood supply of normal circulation to the diaphyseal
the repair (15). Compressive forces applied axially
region of the femur consists of an afferent supply
to the femur result in oblique fractures. Bending the
from the principal nutrient artery, entering the bone
femur results in transverse fractures. Compressive
at the nutrient foramen located at the caudal part
forces and bending at the same time result in
aspect of the proximal third of the diaphysis. The
butterfly fractures. Torsional forces applied to the
adductor muscle attachment to the caudal aspect of
femur result in a spiral fracture. High-energy
the diaphysis is also an important source of
fractures are typically very comminuted and highly
periosteal
unstable (16-18).
vessels.
This
becomes
especially
significant in the healing of diaphyseal fractures
Forces that implant systems must resist against, are
because medullary circulation is disrupted in most
bending
long bone fractures. Additional damage from the
(compression and tension) and torsional forces
application of an intramedullary (IM) pin (4,5).
(17,18).
Fractures may be repaired using anatomic reduction
Because of the anatomy of the femur, femoral
and rigid fixation or using the principles of biological
fractures
osteosynthesis. Biological osteosynthesis involves
treatment (1). Implant systems used, are external
minimally invasive surgical approaches, minimal
fixators, bone plates, plate-rod constructs and the
handling of the bone fragments and indirect
interlocking nail systems.
forces,
are
not
shear
forces,
amenable
to
axial
forces
conservative
reduction. Biological osteosynthesis is particularly
effective for highly comminuted and complex
The external fixator (figure 1) effectively resists axial
fractures because no attempt is made to reduce
loading, shear forces and torsional forces. The tie-in
fragments within the fracture zone. Because of this,
configuration with IM pin also resists bending loads
vascular supply and soft tissue attachments to bone
(19,20). External fixators are often used for
fragments are preserved, allowing faster fragment
management of fractures, because of the lower
incorporation into callus, resulting in a rapid healing
implant cost and relative ease of application (1).
(1,6,7-11).
provides
Appropriate fractures for repair with a external
clinical advantages over anatomic reconstruction. It
fixator include transverse, short oblique, long
has been associated with faster callus formation
oblique and mildly comminuted fractures (5). When
Biological
osteosynthesis
2
applied correctly, vascular supply of the fracture
stress due to repeated bending, resulting in implant
fragments can be preserved very effectively. Linear
fatigue failure (4,15). A bone plate can serve as a
external fixators are most commonly used with
compression plate, a neutralisation plate and a
fractures of the femur. The presence of muscle
bridging plate. Plates can be used as compression
bellies around the femoral diaphysis limits the use
plate in transverse or short oblique fractures, as
of external fixator pins to proximal and distal
neutralisation in long oblique fractures in which
insertion sites (5).
bone fragments can be reduced, and the use of a
The
disadvantage
plate as bridging in repairing comminuted fractures
of external fixators
in which bone fragments cannot be reduced or
is
when attempted reduction and stabilization of
the
demand
greater
in
fragments would cause excessive soft tissue
postoperative
trauma. (4,15,19,24). By the early rigid fixation that
period because of
is provided by plates, excellent stability can be
bandage
changes
obtained. Because of this, they resist all disruptive
pin
forces until callus is formed, which allows the early
and
Figure 1 – External Fixator
the
management.
use of joints and muscles. As such, in the
Possible
postoperative period the plate may be subject to
complications
are
plastic deformation, early breakage or fatigue
e.g. pin loosening and pintract infections (1,21,22).
failure. The bone can be infected or develop
The rigidity that is achieved by external fixation
osteoporosis
from
depends on the number and size of the pins, the
stress,
may
proximity of the fixator to the bone, and the stiffness
result
of the fixator (20,22). The optimum time for removal
(7,22).
of the fixator is six weeks, because this is giving the
The application of a
advantage of early stability and avoids the late
bone plate is, more
effects of stress protection (14). When the bone has
traumatic
not sufficiently healed in 6 weeks, dynamization can
application
be performed. Dynamization is the alternation of
external
axial forces across the fracture site without
because of the surgical
distraction of the fragments (23). The aim is to
stimulate
fracture-healing
through
which
in
a
fracture
than
the
of
the
fixator,
approach often needed
Figure 2 - Plate fixation
cyclical
for its application. A
intermittent compressive stress across the fracture
minimum of 2 screws (4 cortices), but preferably 3
site (22).
screws (6 cortices), should be engaged in both the
proximal and distal main bone segments. Bicortical
Bone plates (figure 2) effectively resist tension,
screws provide significantly stronger fixation than
compression,
monocortical
bending,
shearing
and
torsional
forces. Nevertheless, plates are susceptible to
screws
(14,15).
Plate
strength
depends on plate width, plate length, plate stiffness
3
and size and number of screw holes. The larger the
complication rates support the use of interlocking
number of screw holes on a given length of plate,
nails
the weaker the plate, but screws can be placed
interlocking nail treatment in not included in this
more precisely (15,24).
study.
A plate-rod construct is a combination of a bone
The purpose of this study was to compare external
plate with an IM pin (figure 3). The IM pin is equally
fixator, bone plate and plate-rod fixation by
resistant to bending loads applied from any
radiographical and clinical outcome. Because the
direction. The pin as has a poor resistance to axial
plate-rod construct is the most rigid of these three
and rotational loads (4).
fixation methods and is most effective in resisting
In a plate-rod construct
forces, we hypothesized that the use of a plate-rod
the bending support of
construct would result in faster healing times and
the IM pin and axial and
lower complication rates compared with the use of a
torsional support of the
bone plate alone or the use of an external fixator.
bone plate are combined.
In addition we investigated the influence of the size
The addition of the IM pin
of the fracture region on fracture healing.
to
the
bone
for
these
types
of
fractures(27).
plate
decreases strain on the
Materials and methods
plate
Medical
two-fold
subsequently
The
and
records
and
radiographs
of
femoral
increases
fractures in cats, treated at the DOCA, a referral
the fatigue life of the
orthopaedic clinic, in the period 1997-2008 were
plate-rod
10-
reviewed. Only patients with diaphyseal fractures
fold compared with that of
were used in this study. Selected cases had to have
the plate alone. The plate and the rod function as
a complete medical record, with clinical and
two beams acting in concert (1,7,15,25). Plate-rod
radiographic follow-up examination, and minimum of
constructs may be used for repair of a variety of
6 weeks of cage confinement postoperatively, we
fractures, ranging in severity from simple transverse
believed the owners on this matter.
Figure 3 –
Plate-rod construct
construct
to highly comminuted (25).
The information retrieved from medical records
Another fixation method of diaphyseal fractures is
included sex, age, weight, whether the femoral
the use of interlocking nail systems. The nail fixation
fracture was open or closed, fixation method, time
can be dynamic or static, depending on whether the
of existence of the fracture, presence of other
bolts are inserted in only the proximal or distal
fractures, date of surgery, follow-up data and the
fragment, or in both (26). Interlocking nails can be
presence of postoperative complications.
used to stabilize diaphyseal fractures of the femur,
tibia,
and
humerus.
The
high
healing
rate,
The fractures were classified according to Unger
associated with a functional outcome, and low
using mediolateral and craniocadal radiographs
4
(28). Three groups were determined with simple
fractures (A), with a wedge (B) and complex (C)
Surgical procedure
(Figure 4). The Unger system is based on the
The surgeries are done by a standard procedure.
complexity of the fracture. Error!
The cats were sedated with medetomidinea 0,100,15 mg/kg bodyweight. Propofolb 1-2 mg/kg
bodyweight
was
used
for
the
induction.
Maintenance of anesthesia was performed by
isofluranec 0,5-0,9 MAC with oxygen in combination
with continuous intravenous supplementation of
ketamined 2-5 µg/kg bodyweight. Cats received
buprenorfinee 20 µg/kg bodyweight or an epidural
Figuur 4 – Ungercode A, B, C
block with morfinef 0,1 mg/kg bodyweight for
additional analgesia.
In addition, the length of the proximal and distal
The femur is approached between the muscle
segment and the length of the reconstructed femur
bellies of the M. biceps femoris and the M.
were measured on the radiographs.
quadriceps femoris. The aim was to minimize the
The length of the proximal and distal segment of the
handling of fragments. Vascular supply and soft
femur
tissue
was
determined
from
preoperative
attachments
to
bone
fragments
were
mediolateral radiographic views, by measuring the
preserved wherever possible.
distance between the greater trochanter and the
The external fixator (mini SKEg) was applied in most
condyles to the nearest fracture site.
of the cases in a tie-in configuration.
The total length after reconstruction was determined
When smooth IM pins were used, they were placed
from postoperative mediolateral radiographic views,
diverging or converging. When pins were placed
by measuring the distance between the greater
parallel, positive threaded pinsg were used with a
trochanter and the condyles (figure 5).
variable diameter. When transcondylair pins are
placed central faced positive threaded pins were
used. When dynamization was desirable, it was
used 6 weeks postoperatively.
The procedure of the plate-rod construct starts with
the insertion of an IM Steinman pin with a diameter
ranging
from
1.4-3.5
mm,
to
recreate
axial
alignment. The IM pin was placed in a retrograde
manner from the fracture zone until it protruded
Figure 5 - Measering
from the proximal femur and than placed in a
normograde fashion. All used bone plates, in the
plate-rod construct and the bone plate alone, are
Veterinairy Cuttable Plates (VCPh1.5-2.0mm or 2.0-
5
2.7mm). Generally they are used as a single plate,
All follow-up radiographs were reviewed by one and
but in some cases as a sandwich plate. Where
the same investigator to determine healing time. For
possible bicortical screws are used, with a minimum
determination of union we looked at the presence of
of 2 proximal en 2 distal screws.
bridging callus and a narrowing fracture line on the
radiograph.
Post-operative care
Antibacterial treatment consisted of 7-14 days of
amoxicillin-clavulanic
2dd or
acidi
We classified union in 5 union classes. <50 days =
12,5 mg/kg bodyweight
1, 50<100 days = 2, 100<150 days = 3, 150<200
a single subcutaneously injection of
days = 4 and non-union / implant failure = 5. The
cefovecinj 8 mg/kg bodyweight.
last category includes fractures with an arrest in the
Non-steroidal-anti-inflammatory-drugs:
ketoprofenk
healing process and who needed a second surgery
1 mg/kg bodyweight 1dd, tolfenamine-acidl 1,5-3
before union was achieved.
mg/kg bodyweight 2dd, or meloxicam m 0,05 mg/kg
The first check up moment was generally at 6-8
bodyweight
weeks, where necessary the second check up
1dd,
were
given
5-14
days
postoperative. In the case of an open fracture,
moment was at 10-12 weeks.
amoxicillin-clavulanici acid was given for three
weeks with an additional 5 days of enrofloxacine n
Statistical analysis
5,0 mg/kg bodyweight 1dd
postoperatively. A
The data were pooled in a database and analyzed.
minimum
cage
confinement
Statistical analysis was performed using SPSS 15.0
postoperatively was prescribed for every patient.
Command Syntax Reference 2006, SPSS Inc.,
Based
weeks
Chicago Ill. for Windows. The Kruskal-Wallis H test
given
was used in order to compare the fixation methods
of
6
on
weeks
the
postoperatively,
of
consultation
recommendations
6-8
were
regarding allowed activity.
with
time
to
union
and
complication
rates.
Correlations between ordinal values were tested by
a. Domitor®
Pfizer Animal Health B.V.
Spearman’s rho, correlations between scale values
b. Propoflo®
Abbott Laboratories Ltd.
with normal distribution were tested by the Pearson
c. Isoflo®
Abbott Laboratories Ltd.
d. Ketamine®
AST B.V.
e. Temgesic®
Schering-Plough N.V.
f. Morfine®
Pharmachemie B.V.
g. Mini SKE®
Imex inc.
h. VCP®
Synthes B.V.
i. Synulox®
Pfizer Animal Health B.V.
j. Convenia®
Pfizer Animal Health B.V.
were treated at the DOCA.
k. Ketofen®
Merial B.V.
Of these fractures 122 were diaphyseal. Sixteen
l. Tolfedine®
Vetoquinol B.V.
were exceeded for this study because they did not
m. Metacam®
Boehringer Ingelheim B.V.
n. Baytril®
Bayer B.V.
test. A p value < 0.05 was considered significant.
Results
In the period 1997 – 2008, including 6 months
follow-up, 211 femoral fractures, from 202 cats,
meet the requirements. Eleven cats had no
sufficient follow-up information, 2 cats did not have
6 weeks of cage confinement postoperatively,
6
radiographs of 1 fracture were missing, 1 patient
In the group of fractures treated with a plate-rod
died during anaesthesia, 1 fracture was treated
construct 35 (63%) cats were male, amongst these
conservatively
One-hundred-six
30 (54%) had been castrated and 5 (9%) had not.
fractures did meet inclusion criteria. All calculations
Twenty-one cats (38%) were female, amongst these
were made with this number.
10 (18%) had been spayed and 11 (19%) had not.
with
a
brace.
The ratio Female: Male = 1: 1.7
Of 106 fractures, 30 (28%) were treated with an
Gender distributions between treatment groups did
external fixator, 20 (19%) with a bone plate, and 56
not differ significantly.
(53%) with a plate-rod construct.
The average age was 58 months (range, 2 to 266
Seventy (66%) cats were male. Amongst these 64
months, +/- SD 68). Thirty-eight cats (36%) were
(60%) had been castrated and 6 (6%) had not.
younger than 12 months, 33 cats (31%) were
Thirty-six (34%) were female, amongst these 14
between 12 and 60 months, 16 cats (15%) were
(13.) had been spayed and 22 (21%) had not. The
between 60 and 120 months and 19 cats (20%)
ratio Female : Male = 1 : 2 (figure 6).
were older than 120 months.
The average age of cats treated with an external
fixator was 75 months (range, 3 to 230 months, +/SD 76). Fifteen cats (50%) were younger than 12
months, 8 cats (27%) were between 12 and 60
months, 6 cats (20%) were between 60 and 120
months en 1 cat (3%) was older than 120 months.
The average age of cats treated with a bone plate
was 35 months (range, 2 to 208 months, +/- SD 45).
Five cats (25%) were younger than 12 months, 6
cats (30%) were between 12 and 60 months, 3 cats
Figure 6 – Gender distribution
(15) were between 60 and 120 months en 6 cats
In the group of fractures treated with an external
(30%) were older than 120 months.
fixator, 22 cats (74%) were male. All these males
The average age of cats treated with a plate-rod
had been castrated. Eight cats (27%) were female,
construct was 65 months (range, 4 to 266 months,
amongst these 1 cat (3%) had been spayed and 7
+/- SD 72). Eighteen cats (32%) were younger than
(24%) had not. The ratio Female: Male = 1: 2.8.
12 months, 19 cats (34%) were between 12 and 60
In the group of fractures treated with a bone plate
months, 7 cats (13%) were between 60 and 120
13 cats (65%) were male, amongst these 12 (60%)
months en 12 cats (21%) were older than 120
had been castrated and 1 (5%) had not. There were
months.
7 (35%) female cats, amongst these 3 (15%) had
Age distributions between treatment groups did not
been spayed and 3 (20.0%) had not. The ratio
differ significantly.
Female: Male = 1: 1.9.
7
The average weight was 3.9 kg (range, 0.9 to 7.1
Of the fractures treated with a bone plate 9 cats
kg, +/- SD 1.2). Four cats (4%) weighed less than 2
(45%) had a type A Unger code, 5 cats (25%) had a
kg, 19 cats (18%) weighed 2-3 kg, 31 cats (30%)
type B Unger code and 6 cats (30%) had a type C
weighed 3-4 kg, 32 cats (30%) weighed 4-5 kg and
Unger code.
20 cats (19%) weighed more than 5 kg.
Of the fractures treated with a plate-rod construct 19
The average weight of cats treated with an external
cats (34%) had a type A Unger code, 22 cats (40%)
fixator was 3.8 kg (range, 1.6 to 6.1 kg, +/- SD 1.0).
had a type B Unger code and 15 cats (27%) had a
Two cats (7%) weighed less than 2 kg, 4 cats (13%)
type C Unger code.
weighed 2-3 kg, 10 cats (33%) weighed 3-4 kg, 10
Unger code distributions between treatment groups
cats (33%) weighed 4-5 kg and 4 cats (13%)
did not differ significantly.
weighed more than 5 kg.
The average weight of cats treated with a bone
A few cats had next to a diaphyseal femoral fracture
plate was 3.7 kg (range, 0.9 to 5.2 kg, +/- SD 1.1).
also another fracture. This amounted to
One cat (5%) weighed less than 2 kg, 2 cats (10%)
2 cats (7%) in the group treated with an external
weighed 2-3 kg, 9 cats (45%) weighed 3-4 kg, 6
fixator, 2 cats (10.0%) in the group with a bone plate
cats (30%) weighed 4-5 kg and 2 cats (10%)
and 7 cats (13%) in the group with a plate-rod
weighed more than 5 kg.
construct.
The average weight of cats treated with a plate-rod
construct was 4.1 kg (range, 1.6 to 7.1 kg, +/- SD
Very few fractures were open fractures. None of the
1.3). One cat (2%) weighed less than 2 kg, 13 cats
fractures treated with an external fixator were open
(23%) weighed 2-3 kg, 12 cats (21%) weighed 3-4
fractures. 1 of the fractures treated with a bone
kg, 16 cats (29%) weighed 4-5 kg and 14 cats
plate was an open fracture. And 2 of the fractures
(25%) weighed more than 5 kg.
treated with a plate-rod construct were open
Weight distributions between treatment groups did
fractures.
not differ significantly.
The open fractures all healed well. 2 were in union
class 1, 1 were in union class 2.
Thirty-eight cats (36%) had a type A Unger code, 34
cats (32%) had a type B Unger code and 34 cats
Seven fractures were older than 7 days.
(32%) had a type C Unger code.
The older fractures all healed well. Six were in union
Of the fractures treated with an external fixator 10
class 1, 1 healed at were in union class 2.
cats (33%) had a type A Unger code, 7 cats (23%)
had a type B Unger code and 13 cats (43%) had a
type C Unger code.
8
patellar luxation (3x), irritation of pin-skin interface
(3x), pin loosening (1x) and fracturing a second time
(1x). 2 of these cats had a non-union. One of these
non-unions was a cat of 18 months old and a Unger
code B fracture. This cat had also a patellar
luxation. The other non-union was a cat of 48
months old and a Unger code C fracture. This cat
needed a second surgery because the femur had
broken again.
In the group of fractures treated with a bone plate 3
cats (15%) showed complications. Complications
that were met in this group were fracturing a second
Figure 7 – Fixation method - Uniontype
time
(1x),
implant
failure
(1x)
and
inactivity
Of the fractures repaired with an external fixator 13
osteoporosis. 2 of these cats had a non-union. One
cats (43%) were in union class 1, 11 cats (37%)
of these non-unions was a cat of 13 months old and
were in union class 2, 4 cats (13%) were in union
a Unger code A fracture. This cat needed a second
class 3, no cast were in union class 4 and 2 cats
surgery because the femur had broken again. The
(7%) were in union class 5. Ninety-three percent
other non-union was a cat of 7 months old and a
reached union.
Unger code B fracture. This cat needed a second
Of the fractures repaired with a bone plate 10 cats
surgery because of implant failure.
(50%) were in union class 1, 3 cats (15%) were in
In the group of fractures treated with a plate-rod
union class 2, 3 cats (15%) were in union class 3, 2
construct 5 cats (9%) showed complications.
cats were in union class 4 and 2 cats (10%) were in
Complications that were met in this group were
union class 5. Ninety percent reached union .
implant failure (4x) and a loose screw (1x). All cats
Of the fractures repaired with a plate-rod construct
with implant failure had a non-union. One of these
34 cats (61%) were in union class 1, 14 cats (25%)
non-unions was a cat of 228 months old, and had a
were in union class 2, 2 cats (4%) had were in union
non-regulated diabetes mellitus and a Unger code A
class 3, 2 cats (4%) had were in union class 4 and
fracture. Another non-union was a cat of 60 months
4 cats (7%) were in union class 5. Ninety-three
old and a Unger code B fracture. Another non-union
percent reached union. (Figure 7)
was a cat of 231 months old, was hyperthyroid and
a Unger code A fracture. The last non-union was a
Nevertheless, the difference between treatment
cat of 48 months old and a Unger code C fracture.
groups in time to achieve union was not significant.
In this study no osteomyelitis occurred.
The
8
cats
(27%)
showed
between
treatment
complication rates was not significant.
In the group of fractures treated with an external
fixator
difference
complications.
Complications that were met in this group were
9
groups
in
When we compared age with time to achieve union
Discussion
we found a positive correlation (rs= 0.38). This
The treatment groups were similar regarding to
parameter was not normal distributed.
signalment and types of fractures, so we can
When we compared weight with time to achieve
effectively compare the treatment groups with one
union we found a positive correlation as well (r=
another.
0.26). This parameter was normal distributed.
Assignment to a particular treatment group was not
Comparison of Unger code with time to achieve
random, but it reflected a change in treatment
union we likewise found a positive correlation (r s=
philosophy during the study period. Initially, most of
0.20).
the femoral diaphyseal fractures were repaired with
A comparison of the Unger code with weight
a bone plate or external fixator. At the start of this
showed a positive correlation (r= 0.31).
study, smooth pins were used for the external
Although all these correlations significant, it were all
fixator, they were placed diverging or converging.
small correlations. The Unger code did not have a
Later on only positive threaded pins were used,
significant effect on the presence of complications.
which were placed parallel.
A comparison of the Unger code with age showed
Toward the end of the study, most of the femoral
no significant correlation.
diaphyseal fractures were repaired with a plate-rod
For calculations
construct.
with the length of proximal
Selection of fixation method is was based on the
segment, distal segment and reconstructed femur
age, weight and fracture characteristics. With
we made ratios. Ratio 1 = length of proximal
difficult fractures the most stabile fixation method,
segment + length of distal segment / length of
the plate-rod construct, was used.
reconstructed femur. Ratio 2 = length of proximal
segment / length of reconstructed femur. Ratio 3 =
External
length of distal segment / length of reconstructed
fixators,
bone
plates
and
plate-rod
constructs all were successful in fracture healing.
femur. When we compared these ratios with time to
In the group treated with an external fixator, the
achieve union, it showed no significant correlation.
most fractures achieved union, this was 93%.
Followed by the group treated with a plate-rod
We compared the presence of other fractures with
construct, in this group 93% achieved union, in the
time to achieve union, this showed no significant
group treated with a bone plate fewest fractures
relation.
achieved union, this was 90%.
However, 2 of the 4 non-unions in the plate-rod
Comparison whether a fracture was open or closed
construct group, were questionable. Both cats were
with time to achieve union and comparison of time
old, above 19 years of age, and had a systemic
of existence of the fracture before treatment with
problem.
time to achieve union, both showed no significant
One
had
a
non-regulated
diabetes
mellitus, and one was hyperthyroid. This could have
relation.
affected the healing process in a negative way. It is
10
possible that this affected the outcome of the plate-
in literature that bones of young animals heal faster
rod construct in unfavourable.
than bones of older animals (18). Immature animals
We were aware of systemic problems in 4 other
have numerous arteries that perforate newly formed
cats. Two cats had kidney failure, both fractures
appositional bone running longitudinally over the
healed well. And 2 other cats were hyperthyroid,
periosteal surface (4). It is notable that a high
these fractures also healed well.
percentage of cats was <12 months old, which
means that young cats have more femoral fractures
The fractures treated with a plate-rod construct had
than average aged cats and older cats. This is
fewest complications (9%), followed by the fractures
possibly because young cats are more reckless in
treated with a bone plate (15%). The fractures
behaviour.
treated with an external fixator had the highest
number of complications (27%).
The positive correlation we found between weight
Although the differences between the groups in
and time to achieve union means that the heavier
number of fractures that achieved union and
the cat, the longer it takes till union is achieved. This
complication rates were not significant, we believe
can be due to the extra forces on the fracture in the
these differences could be clinically relevant.
postoperative period.
The male predominance,
especially of castrated males (60%), is remarkable.
In other studies the use of a bone plate gave more
This can be because males have more reckless
complications than the use of an external fixator.
behaviour than female cats.
However, this observation was based on major
The positive relation we found between Unger code
complications, including delayed union, implant
and time until achieve union is achieved means that
failure
the
the more complex the fracture, the longer it takes
breakdown between major and minor complications
until union is achieved. This is expected because
was not made. It is possible that there is no
more comminuted fractures are likely to have more
contradiction between these observations (10,14).
soft tissue disruption with subsequent damage done
In the study of Reems et al. (25) 2% of the fractures
to blood vessels, which both have strong negative
treated with a plate-rod construct did not achieve
influences on fracture healing (18,29).
and
osteomyelitis.
In
our
study
union. In our study this percentage was 7%. The
differences between these two studies are, that we
There were no significant correlations between the
used more bicortical screws where as Reems et al.
percentage of fractured femur and time to union.
used both monocortical and bicortical screws. Our
This is remarkable because we expected a longer
study is only about femoral fractures in cats,
time to union when a fracture is more comminuted.
whereas Reems et al. looked at all long bone
fractures in dogs and cats (25).
The presence of other fractures does not show a
significant relation to time to achieve union. This
The positive connection we found between age and
means healing time is not effected if another leg, or
time to achieve union corresponds with the findings
another bone in the same leg, is fractured.
11
However, the amount of patients with more than
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