This document discusses humeral fractures in animals. It describes the causes, types, and treatment of humeral fractures. Most humeral fractures are caused by minor trauma from falls or playing. Distal humeral fractures, which involve the elbow joint, account for about half of all humeral fractures. The lateral humeral condyle is most commonly fractured due to the force from the radial head during weight bearing. Fixation methods for lateral condylar fractures include lag screws or self-compressing orthofix pins. A study found that while both methods provided adequate stability, lag screws generated greater compression over a larger area of the fracture site compared to pins.

1. Humeral FracturesHumeral Fractures
Brian Daubs DVMBrian Daubs DVM
DACVS-SADACVS-SA
Animal Specialty & Emergency HospitalAnimal Specialty & Emergency Hospital
Rockledge, FLRockledge, FL

2. Causes of humeral fracturesCauses of humeral fractures
 Minor trauma:Minor trauma:
 Walking, running downWalking, running down
stairs, playing, and fallingstairs, playing, and falling
from less than one meter.from less than one meter.
 Major trauma:Major trauma:
 HBC, falling from more thatHBC, falling from more that
one meter, and jumping outone meter, and jumping out
of a moving vehicle.of a moving vehicle.

3. Minor vs Major TraumaMinor vs Major Trauma
 Most (87%) minor traumaMost (87%) minor trauma
incidents involve the distalincidents involve the distal
humerus and the articularhumerus and the articular
surface.surface.
 Most (68 %) major traumaMost (68 %) major trauma
involve the humeral shaftinvolve the humeral shaft
and not the articular surfaceand not the articular surface

4. Distal humeral fracturesDistal humeral fractures
 Distal humeral condylar fractures account for about ½Distal humeral condylar fractures account for about ½
of all humeral fracturesof all humeral fractures
 Most distal humeral fractures involve the articularMost distal humeral fractures involve the articular
surface (63%)surface (63%)
 Can be classified by anatomical locationCan be classified by anatomical location
 Dicondylar fractures can be further classified as T, or YDicondylar fractures can be further classified as T, or Y
fractures.fractures.

5. Distal humeral condylar fracturesDistal humeral condylar fractures
 About 60 % involve the lateralAbout 60 % involve the lateral
condyle.condyle.
 About 30 % are dicondylarAbout 30 % are dicondylar
(Y, and T).(Y, and T).
 About 10% involve the medialAbout 10% involve the medial
condyle.condyle.

6. Left HumerusLeft Humerus

7. Right Humeral FractureRight Humeral Fracture

8. Right Humeral fractureRight Humeral fracture

9. Distal Humeral Condylar FracturesDistal Humeral Condylar Fractures
 Usually occur in animals less than one year ofUsually occur in animals less than one year of
ageage
 Often associated with incomplete ossification ofOften associated with incomplete ossification of
the humeral condylethe humeral condyle
 Spaniel breed are over represented (especiallySpaniel breed are over represented (especially
Cocker spaniels and Springer spaniels)Cocker spaniels and Springer spaniels)

10. Why is the lateral condyle mostWhy is the lateral condyle most
commonly involved ?commonly involved ?
 Large surface area of theLarge surface area of the
radial head articulates withradial head articulates with
the lateral portion of thethe lateral portion of the
humeral condyle.humeral condyle.
 Weight-bearing force directedWeight-bearing force directed
along radius to lateral aspectalong radius to lateral aspect
of condyle.of condyle.

11. Fixation Methods for lateral humeralFixation Methods for lateral humeral
condylar fracturecondylar fracture
 Traditional method:Traditional method:
 Screw placed in lag fashion across the condyleScrew placed in lag fashion across the condyle
 with or with out an anti-rotational k wire.with or with out an anti-rotational k wire.
 Orthofix self compressing bone pinsOrthofix self compressing bone pins
 (with an anti-rotational k-wire)(with an anti-rotational k-wire)
 Cross pinning on the condyle and an anti-Cross pinning on the condyle and an anti-
rotational k wire (only used in animals < 5rotational k wire (only used in animals < 5
kg.)kg.)

12. Lag screw procedureLag screw procedure
 Lateral approach to the elbow (can also be done closed)Lateral approach to the elbow (can also be done closed)
 Reduced the fracture and place bone clamp across theReduced the fracture and place bone clamp across the
condylescondyles
 Drill pilot holeDrill pilot hole
 Over drill near cortexOver drill near cortex
 Tap far cortexTap far cortex
 Place screw +/- washer in lag fashion.Place screw +/- washer in lag fashion.
 Place anti-rotational k wire as needed.Place anti-rotational k wire as needed.

13. Orthofix self compressing bone pinOrthofix self compressing bone pin
 Compression across the fragment can beCompression across the fragment can be
generated with no over drilling of the neargenerated with no over drilling of the near
cortex.cortex.

14. Orthofix self compressing bone pinOrthofix self compressing bone pin
ProcedureProcedure
 Lateral approachLateral approach
 Reduce fracture and hold in place with boneReduce fracture and hold in place with bone
forceps.forceps.
 Insert the orthofix pin from the lateral aspect ofInsert the orthofix pin from the lateral aspect of
the capitulum and seat it in the trochlea.the capitulum and seat it in the trochlea.
 Place an anti-rotational k-wirePlace an anti-rotational k-wire

15. Is the lag screw method better than theIs the lag screw method better than the
self compressing orthofix pins?self compressing orthofix pins?
 Studies to this point indicate both are clinicallyStudies to this point indicate both are clinically
acceptable.acceptable.
 One study indicates that at physiologic loads theOne study indicates that at physiologic loads the
orthofix pin provides fracture stability equal toorthofix pin provides fracture stability equal to
the lag screw method.the lag screw method.
 However, at loads greater than what is expected inHowever, at loads greater than what is expected in
an animal post operatively the lag screw providedan animal post operatively the lag screw provided
greater fracture stabilization.greater fracture stabilization.

16. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Materials and Methods:Materials and Methods:
 HumeriHumeri fromfrom 26 dogs (16 female, 10 male)26 dogs (16 female, 10 male)
 Mean weight = 13.53 kg ± 5.14Mean weight = 13.53 kg ± 5.14
 Mean age = 31.92 mo ± 33.59 moMean age = 31.92 mo ± 33.59 mo
 Right and left humeri randomly assignedRight and left humeri randomly assigned
 Group P (orthofix pin repair)Group P (orthofix pin repair)
 Group S (traditional screw repair)Group S (traditional screw repair)
 Simulated humeral condylar fractureSimulated humeral condylar fracture

17. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Materials and Methods:Materials and Methods:
 Anti-rotational k-wire placedAnti-rotational k-wire placed
 Pressure film was placedPressure film was placed
across the fracture lineacross the fracture line

18. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Materials and Methods:Materials and Methods:
 Fractures repairedFractures repaired
 2.0 mm lag screw2.0 mm lag screw
 Screw tightened until stripped (torque driver)Screw tightened until stripped (torque driver)

19. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Materials and Methods:Materials and Methods:
 Fractures repairedFractures repaired
 2.2 mm thread diameter Orthorfix pin2.2 mm thread diameter Orthorfix pin
 Pin tightened until stripped (torque driver)Pin tightened until stripped (torque driver)

20. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Materials and Methods:Materials and Methods:
 After fixationAfter fixation
 Film removed and digitally analyzedFilm removed and digitally analyzed
 Average compression (PSI)Average compression (PSI)
 Compressive force (Newtons)Compressive force (Newtons)
 Area of compression(cmArea of compression(cm22
).).

21. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Results:Results:
 Mean torque (NM at stripping)Mean torque (NM at stripping)
 Orthofix pins:Orthofix pins: 0.91 NM ± 0.18*0.91 NM ± 0.18*
 Lag screws:Lag screws: 0.49 NM ± 0.07*0.49 NM ± 0.07*
 Average compression (MPa)Average compression (MPa)
 Orthofix pins:Orthofix pins: 18.88 MPa ± 1.76* *18.88 MPa ± 1.76* *
 Lag screws:Lag screws: 20.36 MPa ± 1.51* *20.36 MPa ± 1.51* *
*p value <0.0001*p value <0.0001
* *p value < 0.003* *p value < 0.003

22. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Results:Results:
 Average area of compression (cmAverage area of compression (cm22
))
 Orthofix pins:Orthofix pins: 1.16 ± 0.84 cm1.16 ± 0.84 cm22
**
 Lag screws:Lag screws: 2.39 ± 1.29 cm2.39 ± 1.29 cm22
**
 Average compressive force (Newtons)Average compressive force (Newtons)
 Orthofix pins:Orthofix pins: 2.20 ± 1.65 KN *2.20 ± 1.65 KN *
 Lag screws:Lag screws: 4.96 ± 2.90 KN *4.96 ± 2.90 KN *
*p value <0.0001*p value <0.0001

23. Comparison of compression generatedComparison of compression generated
between the lag screw method and the selfbetween the lag screw method and the self
compression orthofix pin.compression orthofix pin.
 Discussion:Discussion:
 Pressure sensitive film was a cost effective measure of compressionPressure sensitive film was a cost effective measure of compression
generated across a simulated fracture.generated across a simulated fracture.
 Conventional lag screw repair:Conventional lag screw repair:
 Greater compression over a greater area.Greater compression over a greater area.
 Greater average pressure generated across the fracture siteGreater average pressure generated across the fracture site
 Orthofix pins:Orthofix pins:
 Subjectively took less time to insertSubjectively took less time to insert
 Generate compressionGenerate compression
 FailureFailure
 Screws stripped by failure at screw head and had less torque than pinsScrews stripped by failure at screw head and had less torque than pins
 Pins stripped at thread-bone interfacePins stripped at thread-bone interface

24. Questions?Questions?