Humeral FracturesHumeral Fractures

Brian Daubs DVMBrian Daubs DVMDACVS-SADACVS-SA

Animal Specialty & Emergency HospitalAnimal Specialty & Emergency HospitalRockledge, FLRockledge, FL

Causes of humeral fracturesCauses of humeral fractures

Minor trauma:Minor trauma: Walking, running down Walking, running down

stairs, playing, and falling stairs, playing, and falling from less than one meter.from less than one meter.

Major trauma:Major trauma: HBC, falling from more that HBC, falling from more that

one meter, and jumping out one meter, and jumping out of a moving vehicle.of a moving vehicle.

Minor vs Major TraumaMinor vs Major Trauma

Most (87%) minor trauma Most (87%) minor trauma incidents involve the distal incidents involve the distal humerus and the articular humerus and the articular surface.surface.

Most (68 %) major trauma Most (68 %) major trauma involve the humeral shaft involve the humeral shaft and not the articular surfaceand not the articular surface

Distal humeral fracturesDistal humeral fractures

Distal humeral condylar fractures account for about ½ Distal humeral condylar fractures account for about ½ of all humeral fracturesof all humeral fractures

Most distal humeral fractures involve the articular Most 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 Y Dicondylar fractures can be further classified as T, or Y fractures. fractures.

Distal humeral condylar fracturesDistal humeral condylar fractures

About 60 % involve the lateral About 60 % involve the lateral condyle.condyle.

About 30 % are dicondylar About 30 % are dicondylar (Y, and T).(Y, and T).

About 10% involve the medial About 10% involve the medial condyle.condyle.

Left HumerusLeft Humerus

Right Humeral FractureRight Humeral Fracture

Right Humeral fractureRight Humeral fracture

Distal Humeral Condylar FracturesDistal Humeral Condylar Fractures

Usually occur in animals less than one year of Usually occur in animals less than one year of ageage

Often associated with incomplete ossification of Often associated with incomplete ossification of the humeral condylethe humeral condyle

Spaniel breed are over represented (especially Spaniel breed are over represented (especially Cocker spaniels and Springer spaniels)Cocker spaniels and Springer spaniels)

Why is the lateral condyle most Why is the lateral condyle most commonly involved ?commonly involved ?

Large surface area of the Large surface area of the radial head articulates with radial head articulates with the lateral portion of the the lateral portion of the humeral condyle.humeral condyle.

Weight-bearing force directed Weight-bearing force directed along radius to lateral aspect along radius to lateral aspect of condyle.of condyle.

Fixation Methods for lateral humeral Fixation 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 < 5 rotational k wire (only used in animals < 5 kg.)kg.)

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 the Reduced 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.

Orthofix self compressing bone pinOrthofix self compressing bone pin

Compression across the fragment can be Compression across the fragment can be generated with no over drilling of the near generated with no over drilling of the near cortex. cortex.

Orthofix self compressing bone pin Orthofix self compressing bone pin ProcedureProcedure

Lateral approachLateral approach Reduce fracture and hold in place with bone Reduce fracture and hold in place with bone

forceps.forceps. Insert the orthofix pin from the lateral aspect of Insert 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

Is the lag screw method better than the Is the lag screw method better than the self compressing orthofix pins?self compressing orthofix pins?

Studies to this point indicate both are clinically Studies to this point indicate both are clinically acceptable.acceptable.

One study indicates that at physiologic loads the One study indicates that at physiologic loads the orthofix pin provides fracture stability equal to orthofix pin provides fracture stability equal to the lag screw method.the lag screw method. However, at loads greater than what is expected in However, at loads greater than what is expected in

an animal post operatively the lag screw provided an animal post operatively the lag screw provided greater fracture stabilization.greater fracture stabilization.

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between the lag screw method and the self

compression orthofix pin.compression orthofix pin. Materials and Methods:Materials and Methods:

Humeri Humeri 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

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between 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 placed Pressure film was placed across the fracture lineacross the fracture line

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between 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)

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between 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)

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between 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).).

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between 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

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between 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 cm2 2 ** Lag screws:Lag screws: 2.39 ± 1.29 cm2.39 ± 1.29 cm2 2 **

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

Comparison of compression generated Comparison of compression generated between the lag screw method and the self between the lag screw method and the self

compression orthofix pin.compression orthofix pin.

Discussion:Discussion: Pressure sensitive film was a cost effective measure of compression Pressure 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

Questions?Questions?