Fracture management Flashcards
What are the main goals of fracture fixation?
- Early return to function
- Achieve stability
How are fractures classified?
- Bone affected
- Position within bone affected
- Fracture pattern
- Open or closed
- Additional features e.g. articular
- Over-riding
- Displacement of segments
- Degree of malalignment
- Soft tissue swelling
What is a simple fracture described as?
One with only 1 fracture line i.e. bone split into 2 pieces
What is required in order to classify a fracture?
Good radiographs, 2 orthogonal views minimum - need to be able to clearly see the bone and make a detailed examination
What is the classification for a fracture where the fracture line is less than 30˚ to the long axis of the bone?
Oblique fracture
What is meant by an interdigitating fracture?
One where the fracture surface is irregular with spikes and depressions on both ends of fractured bone that interlock/interdigitate with each other
What forces are transverse fractures stable and unstable to?
Stable to compression, unstable to rotation
What forces are interdigitating fractures stable to?
Compression and rotation
What classification is given to a fracture where the fracture line is >30˚ to the perpendicular to the long axis of the bone?
Oblique fracture
What is meant by a spiral fracture?
An oblique fracture that curves/spirals around the bone
When do spiral fractures most commonly occur and what is the importance of this?
- Usually low energy fractures i.e. little/no trauma
- Osteons debond
- Often pathologic fractures so need to look for underlying cause
What are comminuted fractures?
- More than one fracture line that connects
- May me multiple joining fractures
- Produce 3 or more pieces of bone
What are segmental fractures?
- Rare, specific types of comminuted
- 2 or more fracture lines that do not connect
- Each bone has a complete piece of cortex
- Produces 3 or more pieces of intact bone
- Wedge/butterfly
How do forces at a fracture site occur?
- Fragments form lever arms
- Coupled with normal loading generate shear, compression/tension and rotation at the fracure site
Explain how avulsion fractures occur
- Apophyseal bone avulses at pointof tendon or ligament insertion
- Usually puppies/kittens due to open growth plates being weaker than bone
- Often landing injury from jumping
- Tendon pulls apophysis away from bone when lands
When do physeal fractures occur?
In skeletally immature animals
What are the classifications for physeal fractures?
- Salter Harris classification type 1 to 5
- TI: complete across the physis
- TII: spur through metaphysis
- TIII: articularte fracture
- TIV: articular and chip in metaphysis
- TV: compression/crush injury of the growth plate
What are the 5 primary forces acting on normal bone?
- Axial compression
- bending
- Shear
- Torsion
- Tension (avulsion, only at insertion points of ligaments)
How do avulsive/tension forces occur on bones?
Tendons or ligaments apply a distractive force e.g. patellar tendon on tibial tuberosity
Give examples of common sites of avulsive fractures
- Patellar tendon on tibial tuberosity
- Gluteal insertion on geater trochanter of femur
- Triceps on olecranon
- Common calcaneal tendon on the calcaneus of the foot
Compare the effect of axial compression on transverse and oblique fractures
- Transverse: compression is stable,
- Oblique: produces shear force leading to over-riding and collapse of fracture
How do bending forces on bones occur?
- Caused by compression
- Bones not straight and not loaded centrally so compressive forces become bending
- Leads to bending on one side and tension on another
Where should plates be placed on a transverse fracture and why?
Should be placed on the tension side to minimise the bending of the bone due to compression
Which aspects of the following bones are the tension surfaces?
a: humerus
b: radius
c: femur
d: tibia
Humerus: lateral and cranial
Radius: cranial and medial
Femur: lateral
Tibia: medial and cranial
What is meant by shearing forces?
Forces that displace the bone perpendicularly
What are the fracture fixation options dependent on?
- Fracture type
- Patient factors
- equipment available
- Surgeon experience/confidence with fixation method
Against which forces are fracture plates stable?
- Compression
- Torsion
- Shear
- Tension
Against which forces are External Skeletal Fixators stable?
All forces
Against which forces are IM pins stable?
Bending and shear
Against which forces are interlocking nails stable?
Best against bending, moderate for compression and ok for torsion and shear forces
Against which forces are pins + tension band stable?
Only tension (moderate stability)
What is strain theory?
Measurement of the strain (% movement) at a fracture site
How is strain applied to a fracture calculated?
- % movement of a fracture
- Amount of movement divided by the original fracture length i.e. fracture 10mm that moves mm = 10% strain
Explain the application of strain theory to fracture repair
- Different healing tissue types can cope with different degrees of deformation
- Can reduce strain to increase chance of healing
- Increase distance between fracture ends and/or reduce fracture movement
List the tissues in bone healing from first to last
- Fracture haematoma
- Granulation tissue
- Fibrous tissue
- Cartilage
- Bone
Compare the strain limits of the healing tissue of bone
- Haematoma and granulation tolerate 100% strain
- Fibrous: 20% strain
- Fibrocartilage: 10% strain
- Woven/lamellar bone: 2% strain
Explain why having a large fracture gap minimises strain and when this method of reducing strain is used
- For comminuted fractures
- Large gap means movement creates low strain e.g. 50mm gap, 5mm movement is only 10% strain - tolerated all bone healing tissues
What are the most common causes of high strain on a fracture repair?
- Movement
- Small fracture gap
- Incomplete reduction leaving small gap (healing tissue ruptures)
What is meant by primary healing of bone?
Bone apposition and reduction used to create stability, ideally compression (contact or gap healing)
What is meant by secondary healing of bone?
Bone not apposed or reconstructed, relative movement instability, bone heals by callus formation
What is required in order for a fracture to be describe as reconstructable?
- Must be able to have a perfect reconstruction - all pieces must be able to be put back together
- Need orthogonal radiographic views
Which types of fractures are good candidates for fracture reconstruction?
Simple fractures: transverse, oblique and spiral
What factors would contraindicate attempts at fracture reconstruction?
- If procedure will be time consuming
- Large amounts of implants required
- Risks for further bone fracture
- Complex (segmental/comminuted) fracture
What methods are commonly used for primary bone healing?
- Open Reduction internal Fixation approach (ORIF)
- Compression plate
- Lag screw
- Positional screw
- K-wires (for physeal fracture)
What methods are commonly used for secondary bone healing?
- ESF
- Bridging plate
What are tje advantages of an ORIF approach to fracture fixation?
- Precise anatomical reduction of bone fragments
- Rigid fixation creating stability at the fracture site
- Bone takes load reducing stress on implants
- More likely to achieve primary bone healing
What are the disadvantages of an ORIF approach to fracture fixation?
- Extensive surgical approach
- Greater soft tissue disruption and compromises bone blood supply
Why is a larger fracture gap with small fragments of bone preferable in fracture repair?
Provides blood supply which contributes to the healing of a callus
What are the risks associated with fracture implants that are too stiff?
- Implants take too much load and reduce load to bone
- Leads to disuse and slow/inadeqaute healing (Wolff’s law) with delayed union, risk of refracture (esp. if plate requires removal)
What are the risks associated with no reconstruction approach to a fracture?
- Less/no loading shared between bone and implants leading to increased stress on fixation, increased risk of failure
- May require more frequent checks and second operation to remove implants for ESF
- Rigid stability leads to decreased callus formation
What are the 4 surgical approaches for fracture fixation?
- Open
- Open “look-but-do-not-touch” approach
- Minimally invasive (MIPO)
- Closed approach
Described advantages the closed approach to fracture reduction
- Most biological
- No surgical incision
- No surgical dissection
- No bone devascularisation
- Fracture haematoma and growth fractures undisturbed
Outline the MIPO approach to fracture reduction
- Limited surgical incisions for implant placement only
- Prevents massive dissection and preserves biology better
- More dissection than closed but not much more
- Fluoroscopy/intraoperative x-ray guidance common
Outline the “look-but-do-not-touch” approach to fracture reduction
- Big incisions
- More dissection and trauma but minimise dissection to that required to place implants
- Leave fracture haematoma alone
- Allows for lag screws/compression palte
- Prevents devascularisation
Outline the reconstruction (open) approach to fracture reduction
- Big incisions, more dissection and trauma (but aim for minimal)
- If possible leave haematoma alone
- Allows for lag screws/compression paltes
- Massive trauma, often remove haematoma
Why should removal of the fracture haematoma during fracture repair be avoided?
Contains a lot of growth factors beneficial to new bone growth
What is the fracture healing score?
- How likely/unlikely a fracture is to heal based on fracture features, patient factors, owner factors, surgeon factors
- 10 = high chance of healing with low risk of complication
- 1 = high risk of complication and unlikely to heal without a problem
Compare the healing in cancellous and cortical bone
Cancellous heals better and faster than cortical
What are the indications for use of intramedullary pins in fracture repair?
- Non-reconstructable comminuted fractures (main indication)
- Intraoperative fracture alignment
- Long oblique fractures e.g. cat femur
Describe the use of intramedullary pins for intraoperative fracture alignment
- Restores fracture length and stabilises bone
- Combine with ESF or plate application
Describe the use of intramedullar pins for long oblique fractures
- Usually combine wide IM pin with multiple cerclage wires
- Rarely the best option as more stable methods are available
What are the methods for the insertion of IM pins? Briefly describe these
- Normograde: from end of bone towards fracture
- Retrograde: from fracture towards bone ends
Compare the advantages and disadvantages of the methods for the insertion of IM pins
- Normo: generally best method, but more difficult to achieve
- Retro: easier but can enter joints or cause nerve damage
What bones can IM pins be inserted into?
- Only femur, tibia, humerus and ulna
- Never the radius as will inevitably encroach on joints
Discuss the use of IM pins in the repair of oblique or comminuted fractures
- IM pins cannot resist compression
- Oblique or comminuted have no inherent stability to compression
- IM pin must be combined with pate or ESF in these types of fractures
Name the different ways in which orthopaedic wire can be used
- Cerclage wire
- Tension band
- Hemicerclage wire
- K-wire figure of 8
Discuss the use of cerclage wires in fracture fixation
- Loop around bone
- Usually placed inappropriately
- Require more dissection to place
- Loosen quickly and easily
- Cause injury to bone and vessels when loosen
- Usually better options available (unavoidable in hip replacement)
What are the indications for the use of cerclage wire?
- Hip replacement
- Only in reconstructable fractures, oblique/spiral fractures
- Only bones with even shape
Outline the principles for cerclage wire use
- Encircle bone and twist ends around each other evenly
- Length of fracture minimum 2x bone diameter
- Minimum for 2 wires
- Place 1cm apart, at least 5mm from fracture end
- Must be tight
- Cut ends short (1.5 twists) or leave longer (3-4 twists) and bend ends over
- Check tension after bending
- Remove even if slightly loose
Compare single loop cerclage wire and double loop cerclage wire (advantages, dequipment required)
- Single: more robust, easier to place well, need single eyed cerclage wire and single wire tightener
- Double: more robust, more difficult to place, need normal oerthopaedic wire and double wire tightener
Explain the theory underlying use of pin and tension band for avulsion fractures
- Converts avulsion into compression forces
- Based on Newton’s 2nd law
- 2 opposing forces = resultant vector force that compresses the fracture
- Summation of forces in x axis compressing the fragment against the bone
Outline the principles of tension band wires in fracture repair
- Wire resists major forces so must be thick
- Pins maintain alignment and prevent shear forces
- Cortex that forms the bending point must be intact
- Most effective when animal is weight bearing (dynamic)
What are the main considerations when treating physeal fractures?
- Cartilage weaker than bone
- Physis usually interdigitating so stable following reduction
- TI and II have good contact and ability to load share when fracture reduced
- Less bending forces as are at ends of bone
- Use smaller less rigid implants in most cases
- Most growth stops due to original injury
- Avoid implants that will cause compression across physis during other repairs
- Limbs may be shorter if 4-5mo old
- Limbs may deviate during growth
In physeal fractures, what would lead to limbs deviating during growth?
- If damage to growth plate is asymmetrical
- If one of a “paired” bone set is damaged
What are the specific considerations regarding articular fracture repair?
- Will develop traumatic/secondary OA
- Any incongruency in articular surface will make OA worse
- Articular surfaces are subject to compressive loads
- Require perfect reduction
- Must have primary bone healing, no callus
- Repair must facilitate early limb use
Why is it important that repair of articular fractures facilitates early limb use?
If cannot use limb will develop joint stiffness and eventual fibrosis with poor range of motion
What are the most important factors in articular fracture repair?
- Accurate (perfect) anatomic alignment
- Rigid internal fixation (compression to give primary bone union and no callus)
- As rapidly as possible, max 1-5 days
Outline the use of arthrotomy in articular fracture repair
- Usually required
- Need good surgical approach to ensure adequate visualisation, perfect reduction, optimal implant placement
- Protect cartilage using dab or lavage
- Flush joint thoroughly before closure
Explain the methods are required in articular fracture repair
- Rigid stabilisation e.g. use of positional screw (alone not good, no compression, relatively unstable)
- Compression with lag screw or dynamic compression plate (possible, but usually not possible in joint) required
Explain how compression of an articular fracture can be achieved using a lag screw
- Gap closed using reduction forceps then place lag screw
- Then place anti-rotational K-wire or screw
What methods can be used for articular fracture repair where perfect reconstruction/compression is not possible?
- Arthroplasty (e.g. hip replacement)
- Arthrodesis (e.g. pancarpal arthrodesis)
- Amputation as a final resort
What repair methods are typically used for Type I or II physeal fractures? What forces are these types of fractures stable to?
Cross K wires or parallel K wires, are relatively stable when reduced, resistant to compression, moderately resistant to bending and rotation
What repair methods are typically used for Type III and IV physeal fractures?
Need to compress so use lag screws, must have anatomic reduction and alignment, and rigid stabilisation
What is a possible consequences of a Type V physeal fracture?
Premature closure of the growth plate and angular limb deformities, can prevent progression of deformity but not stop it happening
Which site is prone to type V physeal fracture?
Distal ulnar growth plate (conical shape)
Compare self-tapping and non-self tapping screws
- Self tapping have thread on screw and cutting flutes at end, cut own thread so are faster to place, risk of bone fracture with placement
- Non-self tapping have no cutting flutes so must use tap
- No difference in effictiveness
What does screw size relate to?
Diameter of the thread
Name the different types of bone screw
- Lag
- Positional
Name the different types of plate screw
- Non-locking: axial compression or neutral
- Locking (neutral screw)
Describe the function of positional bone screws
- Hold 2 pieces of bone in position
- Not to be used where there is a gap
Describe the function of lag screws in bone
- Compresses/squeezes 2 pieces of bone together as far (trans) cortex is pulled towards near (cis) cortex
- Not to be used where there is a gap
Describe the placement of a positional bone screw
- Drill both cortices
- Measure depth of hole, add 2mm
- Use appropriate tap for screw in guide and tap both cortices
- Place screw of appropriate length
- Tighten but not overtightened
Describe the placement of a lag screw
- Drill glide hole in near cortex (same diameter as screw)
- Insert sleeve into glide hole
- Drill far cortex as for normal preparation
- Countersink hole
- Measure depth of hole, add 2mm
- Use tap to tap trans cortex
- Choose and place screw of appropriate length until tight
When should lag screws be used?
- For oblique fractures only
- Fracture held reduced with bone holding forceps
- Lag screw placed 90˚ to fracture line
Compare the use of fully threaded or partially threaded screws
- Fully threaded can be used as lag or positional screws
- Partially threaded can only be used as lag screws
Explain the use of non-locking plate screws
- Screwplaced inbone through plate, head of screw engages plate
- Tighten screw, pulls bone up towards plate and squeezes plate onto bone
- leads to high friction at interface between bone and plate
- Screws placed as for positional
Describe the use of plate screws as lag screws
- Fracture reduced
- Plate applied,
- Lag screw applied at 90˚ to fracture line
- Place lag screw first to compress fracture, then place others
- Becomes neutralisation plate
Name the different types of fracture repair plate based on function
- Compression
- neutralisation
- Bridging
- Locking (can neutralisation or bridging)
What is the size of plate determined by?
The size of screws the place works with i.e. 3.5mm plate is for use with 3.5mm screws
How can plates be named other than based on mechanical function?
Size, manufacturer and features e.g. dynamic compression plate, 3.5mm Synthes locking TPLO plate
