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PATHOLOGY
Division of Surgery, Indian Veterinary Research Institute, Izatnagar, UP, India
Occurrence and Pattern of Long Bone Fractures in Growing Dogs with Normal and
Osteopenic Bones
K. Kumar1, I. V. Mogha
1, H. P. Aithal1,3, P. Kinjavdekar
1, Amarpal1, G. R. Singh
2, A. M. Pawde1 and
R. B. Kushwaha
Addresses of authors: 1Division of Surgery, Indian Veterinary Research Institute, Izatnagar 243�122, UP, India; 2College ofVeterinary Sciences, Aizawl 796�001, Mizoram, India; 3Corresponding author: Tel.: +91 581 2302870; fax: +91 581 2303284;E-mail: [email protected] or [email protected]
With 10 figures Received for publication December 15, 2006
Summary
A retrospective study was undertaken to record the occurrenceand pattern of long bone fractures, and the efficacy of Intra-
medullary (IM) Steinmann pin fixing in growing dogs. All therecords of growing dogs during a 10-year-period were screenedto record the cause of trauma, the age and sex of the animal,
the bone involved, the type and location of the fracture, thestatus of fixation, alignment, maintenance of fixation andfracture healing. The results were analysed and comparisonswere made between growing dogs with normal and osteopenic
bones. Among the 310 cases of fractures recorded, the boneswere osteopenic in 91 cases (29%). Minor trauma was theprincipal cause of fracture in dogs with osteopenia (25%), and
indigenous breeds were most commonly affected (38%).Fractures in dogs with osteopenic bones were most commonlyrecorded in the age group of 2–4 months (53%), whereas
fractures in normal dogs were almost equally distributed be-tween 2 and 8 months of age. Male dogs were affected signi-ficantly more often in both groups. In osteopenic bones, most
fractures were recorded in the femur (56%), and they weredistributed equally along the length of the bone. Whereas innormal bones, fractures were almost equally distributed inradius/ulna, femur and tibia, and were more often recorded at
the middle and distal third of long bones. Oblique fractureswere most common in both groups; however, comminutedfractures were more frequent in normal bones, whereas
incomplete fractures were more common in osteopenic bones.Ninety-nine fracture cases treated with IM pinning (66 normal,33 osteopenic) were evaluated for the status of fracture
reduction and healing. In a majority of the cases (61%) withosteopenic bones, the diameter of the pin was relatively smallerthan the diameter of the medullary cavity (<70–75%),whereas in 68% of the cases in normal bones the pin diameter
was optimum. The status of fracture fixing was satisfactory togood in significantly more osteonormal (59%) than osteopenicdogs (42%). Fracture healing, however, was satisfactory in
significantly more cases with osteopenic than normal bones.The appearance of callus was relatively early and the amount
of bridging callus was relatively large in greater number of
osteopenic bone fractures. Mal-union and non-union wererecorded more often in osteopenic cases than in normal cases.However, the incidence of bone shortening and osteomyelitiswas significantly higher in normal bones than in osteopenic
bones.
Introduction
Fracture of long bones is a common orthopaedic conditionnoticed in dogs. Femur is the most frequently fractured longbone in dogs, comprising almost half of all long bone fractures
(Piermattei and Flo, 1997; Harasen, 2003a; Beale, 2004).Oblique fractures, though, were most commonly recorded indifferent long bones; comminuted fractures were often encoun-
tered, especially in tibia and femur (Harasen, 2003b).Several researchers have reported a high occurrence of long
bone fractures in growing dogs (Phillips, 1979; Schwarz, 1991;Harasen, 2001). The most common direct cause of fracture in
growing dogs is a road traffic accident or a fall from height(Aithal and Singh, 1999; Harasen, 2003b; Beale, 2004).Nevertheless, growing dogs suffer from a variety of metabolic
and nutritional disorders, which may lead to osteopenia, inturn weakness in the bone due to material property differenceoften leading to fractures (Rosol and Capen, 1997).
There are several studies on the occurrence and pattern offractures in osteoporotic bones in human patients, especially inpost-menopausal women. The application of conventional
implants for fracture fixing to osteoporotic bone is limited, andfixing failure occurs as a consequence of the weak bonestructure (Cornell, 2003; Stromsoe, 2004). Major researchefforts are being made to improve the currently available
treatment options and to develop new techniques for thesurgical treatment of osteoporotic fractures (Egermann et al.,2005). The studies on spontaneously occurring osteoporosis/
osteopenia are limited in dogs. Further, the pathogenesis ofosteopenia in growing dogs is different from that of geriatrichuman patients. To the best of our knowledge, there is no
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J. Vet. Med. A 54, 484–490 (2007)
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study regarding the occurrence and pattern of fractures in dogswith osteopenic bones.
Different fixing methods including bone plates, interlocking
nails, plate-rod constructs, lag screws and external fixatorswere used for the management of different long bone fracturesin dogs (Dvorak et al., 2000; Harasen, 2003a,b; Beale, 2004),
but intramedullary pins and wires were used most frequently.Management of fractures in growing dogs is difficult, especiallyin osteopenic bones. Complications such as pin migration and
failure of plate fixing due to inadequate purchase of screws arecommon (Schwarz, 1991). A detailed study on the occurrenceand pattern of fractures would help to understand the fractureprocess in osteopenic bones better and thus may help in their
management. To the best of our knowledge, there is noretrospective study regarding the evaluation of the mostcommonly used internal fixation technique, i.e. IM pin fixation
in cases of osteopenic bone fractures. Hence, the presentinvestigation was planned to study the occurrence and patternof long bone fractures, and to evaluate IM pin fixing in the
management of long bone fractures in growing dogs withnormal and osteopenic bones.
Materials and Methods
All the radiographs of growing dogs with suspected fracturedbones (aged up to 1 year) made during a 10-year period (April1993 to March 2003) were screened. The bones were categor-
ized as osteopenic or normal, based on the clinical history,radiographic bone density and mass. All the dogs whichshowed any of the clinical signs of fractures like lameness,
swelling, shortening of limb or crepitation on palpation of thesuspected site of fracture were subjected to radiographicexamination. Radiographically, the cortical thickness (cortical
index) and the density of long bones were measured and theywere compared with those of normal animals of the samebreed and age group (Kumar et al., 2003). The animals which
showed reduced radiographic bone density and thickness alongwith other clinical signs of osteopenia/bone weakness likehind-quarter weakness, bending of limbs, enlargement ofmetaphyses of long bones, pain on palpation of bones, and/
or laxity of carpal and tarsal joints were categorized asosteopenic. Those animals which showed normal radiographicbone density and did not show any clinical signs of bone
weakness were categorized as normal.Among a total of 474 radiographs of fracture cases recorded
during the 10-year period, 164 cases (35%) were of dogs aged
>1 year and 310 cases (65%) were of growing dogs aged up to1 year. Among the growing dogs, in 91 cases of fractures(29%), clinical and radiographic signs of osteopenia werepresent, while in the remaining 219 cases (71%) the bones were
normal.Information was collected regarding the primary cause of
trauma, the age, sex and the breed of the animal, the bone
involved, and the type and location of the fracture. Age-wise,the dogs were grouped as 0–2, 2–4, 4–6, 6–8, 8–10 and10–12 months. Fractures recorded in different long bones were
classified as femoral, tibial/fibular, humeral, radial/ulnar andmetacarpal/metatarsal fractures. Based on the type of frac-tures, they were classified as either incomplete or complete;
and, based on the fracture line, they were classified astransverse, comminuted/multiple, spiral/oblique and folding/greenstick fractures. Location-wise fractures were classified as
diaphyseal (proximal, middle and distal), metaphyseal (prox-imal or distal) and epiphyseal (proximal or distal) fractures.These data were collected, analysed and compared between
normal and osteopenic bones.Various fracture fixing techniques were used to treat long
bone fractures in different animals. All the cases of fractures
were treated by the same group of surgeons. Complete follow-up radiographs of different cases treated with external fixingwere not available for review. Further, among the internal
fixing techniques, a majority of the fractures was treated by IMSteinmann pinning, mostly in the femur, tibia or humerus.Only closed fractures were treated by IM pinning. In commi-nuted fractures, full cerclage wiring was also done along with
IM pinning. Ninety-nine such fracture cases (66 normal, 33osteopenic) with complete follow-up radiographs were consid-ered for evaluation of the IM pinning technique and fracture
healing. Fracture type was not considered while grouping theanimals and only the status of the bone cortex was considered.The IM pinning technique used for the management of long
bone fractures was studied and analysed for the status offracture fixation, reduction, alignment and healing. Theoccurrence and possible causes of complications like fixing
failure, delayed union, non-union, malunion, shortening ofbone, and osteomyelitis were analysed.The data were tabulated and differences amongst the breeds,
sexes and age groups of dogs, the location and type of
fractures, and different parameters of fixation and manage-ment as well as differences between osteopenic and normalbones were analysed by the chi-squared test using the
programme spss (SPSS Inc., Michigan Avenue, Chicago, IL,USA). The differences were considered significant at P < 0.05.
Results
Occurrence of fractures
The hospital incidence of fractures in dogs has shown anincreasing trend every year. Among the total of 310 fracture
cases in growing dogs, in 108 (35%) cases of fracture wascaused by a fall/jump from a height, and in 46 (15%) cases, atraffic accident was the cause of the fracture. Significantly(P < 0.05), more fractures were caused by fall in normal than
in osteopenic bones (40% and 22% respectively), whereas inosteopenic bones, significantly more fractures were caused byminor trauma than in normal bones (25% and 13% respect-
ively; Fig. 1).Among the different breeds of growing dogs affected with
fractures, 106 (34%) were Spitz and 87 (28%) were indigenous
dogs. Looking at dogs with and without osteopenia revealed adifferent breed distribution of fracture cases: Among theanimals with osteopenic bones, indigenous dogs were affected
significantly more often (38%), whereas in normal bonessignificantly more fractures (41%) were recorded in Spitz(Fig. 2). When the incidence of osteopenia was calculatedamong the total number of fracture cases of a particular breed
presented, significantly less animals of the breeds Spitz andGreat Dane (16% and 14% respectively) were found to haveosteopenic bones. In the other breeds, osteopenia was present
in 33–40% of the fracture cases (Fig. 3).In 218 (70%) growing dogs, fractures were recorded in the
age group of 0–6 months. In osteopenic bones, most of
fractures were recorded during the first 6 months of life, in
Occurrence and Pattern of Long Bone Fractures 485
particular, in the age group of 2–4 months (54%); whereas innormal bones, fractures were almost equally distributedbetween 2 and 8 months (Fig. 4). Further, significantly morefractures in osteopenic bones were recorded during the first
4 months and significantly more fractures in normal bones atthe age of 6–12 months.
Fractures were significantly (P < 0.05) more frequent inmales than in females, but no significant difference was
recorded for the sex distribution between osteopenic andnormal dogs (Fig. 5).
Altogether, fractures involving pelvic limbs (63%) were
presented more often than those involving pectoral limbs(37%) in growing dogs. In cases with osteopenic bones,fractures were recorded most frequently in femur (56%),
followed by tibia/fibula (21%). In contrast, fractures weredistributed almost equally among radius/ulna (32%), femur(31%) and tibia/fibula (26%) in normal bones (Fig. 6). The
frequency of femoral fractures recorded in osteopenic boneswas significantly higher than in normal bones, whereas inradius/ulna significantly more fractures were recorded innormal bones. Fractures were equally distributed between
the left and right sides in different long bones. The onlyexception was fractures in radius/ulna which were morecommon in the left limb in osteopenic bones, and in the right
limb in normal bones.Regarding the location of fractures within the bones,
fractures were distributed almost evenly along the length of
22
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1015202530354045
GSD Dob Spitz GD ND OthersBreeds
Fre
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case
s (%
) **
d
a
b
ab
c bc
ADAC
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C C
D
Osteopenic Normal
Fig. 2. Breed wise distribution of fracture cases in growing dogs withosteopenic (n = 91) and normal (n = 219) bones. [Different smallletters show significant (P < 0.05) differences between the breeds inosteopenic bones; different capital letters show significant (P < 0.05)differences between the breeds in normal bones; asterisk (*) showssignificant (P < 0.05) differences between osteopenic and normalbones for a particular breed]. GSD, German shepherd; Dob, Dober-man; GD, Great Dane; ND, Indigenous.
35 34
16 14
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1015202530354045
GSD Dob Spitz GD ND OthersBreeds
Ost
eop
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nes
in %
of
tota
l fra
ctu
re c
ases
a a
b b
a
a
Fig. 3. Incidence of osteopenia in fracture cases among differentbreeds of growing dogs (n = 310). [Different small letters showsignificant (P < 0.05) differences between the breeds]. GSD, Germanshepherd; Dob, Doberman; GD, Great Dane; ND, Indigenous.
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0–2 2–4 4–6 6–8 8–10 10–12Age (month)
Fre
qu
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of
case
s (%
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*
*
*
* *
a
A
b
B
aB
c
B
c
cA A
Osteopenic Normal
Fig. 4. Distribution of fractures among different age groups ofgrowing dogs with osteopenic (n = 91) and normal (n = 219) bones.[Different small letters show significant (P < 0.05) differences betweenthe age groups in osteopenic bones; different capital letters showsignificant (P < 0.05) differences between the age groups in normalbones; asterisk (*) shows significant (P < 0.05) differences betweenosteopenic and normal bones for a particular age group].
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42
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0
10
20
30
40
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60
70
Male FemaleSex
Fre
qu
ency
of
case
s (%
)
a
b
A
B
Osteopenic Normal
Fig. 5. Distribution of fractures among male (n = 189) and female(n = 121) growing dogs with osteopenic (n = 91) and normal(n = 219) bones. [Different small letters show significant (P < 0.05)differences between males and females in osteopenic bones; differentcapital letters show significant (P < 0.05) differences between malesand females in normal bones].
Osteopenic Normal
22
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11
28
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1015202530354045
Fall Auto.accident
Minortrauma
Hit injury Unknown
Cause of fracture
Fre
qu
ency
of
case
s (%
)
*
*
aa
a
A
b B BB
C
b
Fig. 1. Different causes of fractures in growing dogs with osteopenic(n = 91) and normal (n = 219) bones. [Different small letters showsignificant (P < 0.05) differences between the causes of fracture inosteopenic bones; different capital letters show significant (P < 0.05)differences between the causes of fracture in normal bones; asterisk (*)shows significant (P < 0.05) difference between osteopenic andnormal bones for a particular cause of fracture].
486 K. Kumar et al.
the bone in osteopenic animals, while in normal bones,
fractures were located mainly at the middle/distal diaphysisand distal metaphysis/epiphysis (Fig. 7). Further, in theproximal diaphysis significantly more fractures were recorded
in osteopenic bones than in normal bones, and significantlymore fractures were recorded in the distal diaphysis in normalbones than in osteopenic bones.
Both in cases of osteopenic and normal bones, oblique/spiral
fractures were most common (Fig. 8). However, in osteopenicbones, incomplete and multiple fractures were significantlymore frequent than in normal bones, but transverse and
comminuted fractures were encountered significantly moreoften in normal bones than in osteopenic bones.
Management of fractures
Ninety-nine fracture cases (66 normal, 33 osteopenic) withcomplete follow-up radiographs were considered for the study.
In a majority of the cases (61%) with osteopenic bones, thediameter of the pin was relatively smaller than the diameter of
the medullary cavity (<70–75% of the medullary cavity),
whereas in 68% of the cases in normal bones, the pin diameterwas optimum (>70–75% of the medullary cavity). Pinplacement was satisfactory in 67% of the normal fracture
cases and 52% of the cases with osteopenia. Penetration ofbone cortex and improper seating of the pin in distalmetaphysis were seen more often in cases with osteopenicbones (24% each) than normal bones (15% and 18%
respectively).The status of fracture fixing was satisfactory to good in
significantly more osteonormal (59%) than osteopenic dogs
(42%). The fixing was fair in 52% and 37% of fractures inosteopenic and normal animals respectively (Fig. 9). The IMpin was maintained in a majority of the cases in both
osteopenic (52%) and normal (56%) bones. Proximal pinmigration was seen with a similar frequency in osteopenic andnormal bones (about 30% cases), however, distal pin migra-tion was observed more often (not significantly more) in cases
with osteopenia (18%) than in normal bones (14%).
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P M/E P D M D D D D M/ELocation within bone
Fre
qu
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of
frac
ture
lo
cati
on
(%
)
**
A AD
B
C
BDa
a
a a
a
Osteopenic Normal
Fig. 7. Location of fractures in different bones of growing dogs withosteopenic (n = 91) and normal (n = 219) bones. [Different smallletters show significant (P < 0.05) differences between the locations inosteopenic bones; different capital letters show significant (P < 0.05)differences between the locations in normal bones; asterisk (*) showssignificant (P < 0.05) difference between osteopenic and normal bonesfor a particular location]. P M/E, proximal metaphysis/epiphysis; PD,proximal third of diaphysis; MD, middle third of diaphysis; DD, distalthird of diaphysis; D M/E, distal metaphysis/epiphysis.
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Tr Ob/Sp Com In MulType of fracture
Fre
qu
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of
case
s (%
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*
* **a
b
a
aa
A
B
CCD
D
Osteopenic Normal
Fig. 8. Different types of fractures in growing dogs with osteopenic(n = 91) and normal (n = 219) bones. [Different small letters showsignificant (P < 0.05) difference between the types of fracture inosteopenic bones; different capital letters show significant (P < 0.05)differences between the types of fracture in normal bones; asterisk (*)shows significant (P < 0.05) difference between osteopenic andnormal bones for a particular type of fracture]. Tr, transverse; Ob/Sp, oblique/spiral; Com, comminuted; In, incomplete; Mul, multiple.
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Satisfactory/Good Fair PoorStatus of fracture fixation
Fre
qu
ency
of
case
s (%
)
a
a
b
A
B
C
**
Osteopenic Normal
Fig. 9. Status of fracture fixing in growing dogs with osteopenic(n = 33) and normal (n = 66) bones. [Different small letters showsignificant (P < 0.05) differences between the status of fixing inosteopenic bones; different capital letters show significant (P < 0.05)differences between the status of fixing in normal bones; asterisk (*)shows significant (P < 0.05) difference between osteopenic andnormal bones for a particular status of fracture fixation].
56
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Femur T/F MT Hum R/U MCBones
Fre
qu
ency
of
frac
ture
lo
cati
on
(%
)*
*
a
A
bA
c Bcd B
bd
A
cd B
Osteopenic Normal
Fig. 6. Distribution of fractures in different bones of growing dogswith osteopenic (n = 91) and normal (n = 219) bones. [Differentsmall letters show significant (P < 0.05) differences between differentlong bones with osteopenia; different capital letters show significant(P < 0.05) differences between different normal long bones; asterisk(*) shows significant (P < 0.05) difference between a particular bonewith osteopenia and normal cortex]. T/F, tibia/fibula; MT, metatarsus;Hum, humerus; R/U, radius/ulna; MC, metacarpus.
Occurrence and Pattern of Long Bone Fractures 487
Fracture healing was satisfactory in significantly more caseswith osteopenic than normal bones (Fig. 10). The appearanceof callus was relatively early and the amount of bridging callus
was relatively large in a greater number of osteopenic bonefractures. Mal-union and non-union were recorded in 12% ofthe cases each in osteopenic bones, which were slightly, but not
significantly, more often than in normal cases (8% and 5%respectively). The incidence of mal-union was not related tothe percentage of the medullary cavity filled by the IM pin.
However, most of the fracture cases that suffered non-unionhad a lesser reduction or fixation, both in cases of osteopenicand normal bones. The incidence of bone shortening, however,was significantly higher in normal bones (18%) than in
osteopenic bones (3%). Bone shortening was seen mostly incases of comminuted fractures both in normal and osteopenicbones. Similarly osteomyelitis occurred also more frequently in
normal bones (15%) than in osteopenic bones (3%), and it wasmostly seen in cases with unstable comminuted fractures.
Discussion
Occurrence of fractures
The occurrence of fractures in dogs increased at our clinic inrecent years, probably due to an increased population of dogs,
increased vehicular traffic and greater awareness among dogowners of the veterinary services available (Aithal et al.,1999b). In the present study, about 65% of the fracture caseswere recorded in dogs aged up to 1 year, a finding similar to
our earlier study (Aithal et al., 1999b) and indicating thatyoung growing dogs are more prone to fractures. In this study,osteopenia was diagnosed in 29% of the fracture cases. As it
may not be possible to diagnose osteopenia radiographicallyuntil a demineralisation of 30–60% has occurred (Krook andLowe, 1964), the incidence of osteopenia and associated
fractures may be even higher among growing dogs.Several workers have reported road traffic accidents as the
major cause of fractures in dogs (Kolata et al., 1974; Phillips,
1979; Braden et al., 1995; Harasen, 2003a). However, in thepresent study, a fall/jump from height was the most commonfracture cause in growing dogs with normal bone density,which may be attributed to the more agile nature of young
dogs. In dogs with osteopenia, minor trauma (25%) and
unknown causes (28%) were the major causes, suggesting thatan inherent weakness of bone was the predisposing cause offracture. Growing dogs are susceptible to different skeletal
diseases of nutritional/metabolic origin (like nutritional sec-ondary hyperparathyroidism and rickets), which lead toosteopenia (Grubb and Talmage, 1983; Kushwaha et al.,
2003). Mineral imbalance and vitamin-D3 deficiency stimulatethe release of parathyroid hormone, leading to demineraliza-tion of long bones (Rosol and Capen, 1997), and thus
predisposing them to fractures (Sato et al., 1999).Among all the growing dogs, the highest incidence of
fractures was recorded in Spitz and indigenous dogs. For theSpitz, this may be attributed to its large population. The
normal bone mass and density is good in Spitz (Kumar et al.,2003), which was also reflected in this study, since the incidenceof osteopenia in this breed was significantly lower than in other
breeds. In indigenous dogs, a high occurrence of fractures wasonly partially due to their large population in this locality.Also the incidence of osteopenia was quite high in these dogs.
As indigenous dogs are generally reared by the poorer sectionof the society, they might have less access to a balanced diet.
In dogs with osteopenic bones, most of the fractures (95%)
were recorded during the first 6 months of life, in particularbetween 2 and 4 months of age. As most of the bone growthoccurs during this period (Braden, 1993), the dogs might bemost vulnerable to a variety of developmental/metabolic bone
diseases. In normal bones the fractures were distributed almostequally in all age groups between 2 and 8 months. Very youngdogs (<2 months) are relatively less prone to get injured, as
they are normally protected in early age of life and their bonesare less brittle and more flexible.
The male dogs were significantly more affected than the
females (Kolata et al., 1974; Aithal et al., 1999b; Dvoraket al., 2000), probably because males are metabolically moreactive than their female counterparts.
Fractures involving pelvic limbs were more frequently recor-
ded than those involving pectoral limbs. In contrast to thescapula, the pelvis is fixed rather rigidly and hencemore likely tosustain injury during a fall or an automobile accident (Aithal
and Singh, 1999). Singh et al. (1983) were of the opinion thatmore fractures occur in the hind limbs because animals areslower to react at their hind limbs. It is possible that the animals
may see the impending trauma coming, and in their effort to fleemay expose their hind limbs to the major force of the impact.Further, a trauma to the caudal half of the animal would be less
likely to produce life-threatening injury, and such animals maybe presented for treatment more frequently (Harasen, 2003a).Considering all fracture cases, femur was the most commonlyaffected bone, as also reported by several earlier researchers
(Singh et al., 1983; Braden et al., 1995; Piermattei and Flo,1997; Aithal et al., 1999b; Harasen, 2003a; Beale, 2004).However, Dvorak et al. (2000) reported almost equal distribu-
tion of fractures in different long bones like radius/ulna, tibia/fibula and femur. Looking at dogs with and without osteopeniaseparately, revealed differences regarding the fracture pattern.
In cases with osteopenic bones, a majority of the fractures wasrecorded in femur, whereas in normal bones the fractures werealmost equally distributed in radius/ulna, femur and tibia/fibula. Markel and Sielman (1993) opined that in most of the
skeletal diseases in growing dogs, femur is the mostly affectedbone, because of its normal anatomical position and itsgeometric variation in bone length. Femur is subjected to
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Status of fracture healing
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s (%
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*
* *
Osteopenic Normal
Fig. 10. Status of fracture healing in growing dogs with osteopenic(n = 33) and normal (n = 66) bones. [Asterisk (*) shows significant(P < 0.05) difference between osteopenic and normal bones for aparticular status of fracture healing].
488 K. Kumar et al.
greater stress during the weight bearing or otherwise due toincreased forces andmoments (Markel et al., 1994), and, hence,femur is most likely to get fractured in osteopenic cases.
Fractures in normal growing dogs were more frequent inthe distal and mid diaphysis as also reported by otherworkers (Phillips, 1979; Singh et al., 1983; Dvorak et al.,
2000; Harasen, 2003a). The metaphysis/epiphysis of longbones is weaker in growing animals and the distal diaphysisof long bones (especially femur and radius/ulna) is subjected
to greater stress during a fall or an injury (Aithal and Singh,1999; Harasen, 2003b). In cases with osteopenic bones,fractures were recorded almost with equal frequency alongthe whole length of the long bones, suggesting that the stress
is distributed equally along the length of the osteopenic bone,possibly due to material property difference (Aithal et al.,1999a).
Oblique fractures are the most common type of fracturereported by several researchers in different long bones ofdogs, followed by comminuted fractures (Phillips, 1979;
Singh et al., 1983; Harasen, 2003a,b; Beale, 2004). Dvoraket al. (2000) reported more comminuted and transversefractures in different long bones of dogs. In the present
study, oblique fractures accounted for about 50% in bothosteopenic and normal animals, indicating a low energytrauma (predominance of bending or compression stress)causing fractures (Smith, 1985). However, incomplete/folding
and multiple fractures were significantly more frequent inosteopenic than in normal bones. Such fractures werecommonly reported in immature/diseased bones (Rosol and
Capen, 1997), and may also be attributed to materialproperty difference in the bone.
Management of fractures
Management of fractures in growing dogs is a challenge,especially in dogs with osteopenia. Ideally for a stable
fixation of fractures, the Steinmann pin should occupyalmost the diameter whole of the medullary cavity. However,as the long bone is curved and the medullary cavity is not of
uniform diameter throughout its length, it is impossible foran IM pin to completely fill the entire length of the medullarycavity (Howard, 1991). Several investigators have recommen-
ded that the IM pin, if used as a sole device, should occupyat least 70–75% of the medullary cavity (De Young andProbst, 1985). The use of pins with a smaller diameter
generally reduces the fixation rigidity, and shearing forcesmay lead to fracture displacement (Smith, 1985; Howard,1991). Some investigators advocate complete filling of thenarrowest part of the medullary cavity to prevent shear
displacement (Rudy, 1975). In the present study, in mostcases (61%) with osteopenic bones, the diameter of the pinwas relatively smaller than the medullary cavity diameter
(<70–75% of the medullary cavity). This was mainly due toa widened medullary cavity subsequent to decreased miner-alization of the cortex. Mostly it was not possible to use pins
with a diameter that equals the diameter of the medullarycavity in osteopenic bones, as it would lead to re-fracture dueto a mismatch in the material properties of the pin and thebone. Even though the loss of mechanical strength of a long
bone due to the loss of bone mass in the diaphyseal area canbe compensated by an increasing diameter of the bone,expansion of the medullary area does not help much to
improve the holding strength of the implants (Seebeck et al.,2004; Stromsoe, 2004). In addition, pin placement was moreoften unsatisfactory in osteopenic dogs, and this was owing
to penetration of the bone cortex. Further, due to lessresistance during the pin introduction, it could be difficult tojudge when the proper seating of the pin was achieved in the
distal metaphysis/epiphysis.Potential complications with the use of IM pin fixation are
rotational instability and fracture shortening (Smith, 1985).
The resultant motion at the fracture site may predispose topin migration and ultimately lead to non-union/malunion.Dvorak et al. (2000) reported that 44% of the long bonefractures treated in dogs by different techniques were
accompanied by various radiographically apparent compli-cations, which were, however, functionally tolerated. In thisstudy, the fracture fixation with IM pinning was maintained
till healing in about 50% of the osteopenic bones, almostsimilar to normal bones. This may be due to the fact that IMpin, being close to the central axis of the bone, is more
resistant against one of the most common stresses inosteopenic bones bending (Howard, 1991). Further, theoccurrence of pin migration was almost equal in osteopenic
and normal bones (except for distal pin migration, which wasseen slightly more often in osteopenic bones). Nevertheless,the relatively high frequency of malunion and non-unionrecorded in osteopenic bones may indicate that fracture fixing
was relatively less stable (Prieur and Sumner-Smith, 1984).Further, non-union was mostly observed in cases wherefracture reduction or fixation was inadequate both in animals
with normal and osteopenic bones. Inadequate fixation maycontribute to delayed union or non-union due to constantmotion at the fracture site leading to disruption of ingrowing
capillaries and in turn delayed revascularization (Aron, 1990).For osteoporotic human patients, failure rates of up to 50%have been reported, mostly due to a pull-out or cut-throughphenomenon when plate and/or screws were used for fixing
(Cornell, 2003). An early occurrence of implant failure inosteoporotic bones has been reported to be due to theinferior properties of the bone and the early full load bearing
after surgery (Egermann et al., 2005). On the other hand, theincidence of bone shortening and osteomyelitis was signifi-cantly higher in normal bones, which could probably be
attributed to a larger number of comminuted fractures causedby severe trauma.Several experimental studies in animals have indicated
reduced healing capacity of bone fractures in osteoporoticbones (Namkung-Matthai et al., 2001; Egermann et al.,2005). Osteoporosis has been shown to affect callus formationin the early stages of bone healing and callus mineralization
in the later stages of healing (Egermann et al., 2005).However, in the present study, fracture healing was satisfac-tory in significantly more cases of osteopenic bones than in
normal bones. In spite of a relatively less stable fracturefixing, better healing observed in osteopenic bones could bedue to a higher number of simple fractures (oblique/folding),
while in normal bones, more comminuted fractures wereobserved. Fractures in osteopenic bones were recorded morefrequently in younger animals, probably attributing to betterfracture healing. The appearance of the callus was relatively
early and the bridging callus was relatively larger in osteop-enic bones. The size of callus is directly proportional to theamount of fragment motion (Prieur and Sumner-Smith,
Occurrence and Pattern of Long Bone Fractures 489
1984); the greater the fragment motion, the larger the callus.Nevertheless, the results indicate that the use of IM pin issatisfactory to maintain fracture fixing in osteopenic bones.
Further, the results suggested that fractures in osteopenicbones can heal normally, provided the fixing is maintaineduntil healing.
From the results of this study, it can be concluded that theoccurrence of pathological fractures due to osteopenic bonediseases is very high (about 30%) in growing dogs. Therefore,
young dogs up to 6 months of age need special attention in themanagement, especially feeding of balanced diet. The patternof long bone fractures differs between growing dogs withnormal and osteopenic bones. Fracture management in grow-
ing dogs needs special attention, especially in osteopenicbones, though IM Steinmann pin seems to provide satisfactoryfixing in simple long bone fractures.
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