what are the main advantages to internal fixation?
allows for rigid fixation of fracture fragments until they are healed while also allowing patient to move limbs unencumbered and to bear weight as soon as they are comfortable
what is the main disadvantage to internal fixation?
these methods are invasive and require surgical approach to the bone
any damage from surgical approach or manipulation of fragments can potentially compromise vascular supply (and negatively impact healing)
fill in the blank: absolute stability is especially important for fractures invading the _____ surface
articular
what is a neutralization implant?
= this implant neutralizes all forces being borne by the bone
- this is an implant that calls for anatomic reconstruction = both perfect alignment AND perfect reduction
- the bone supports fixation while at the same time fixation supports the bone
anatomic reconstruction is necessary for WHAT TYPE of fractures?
articular fractures – a smooth articular surface is essential in order to minimize future cartilage injury
what is a bridging implant?
= this implant bridges the fracture gap – carries all the weight, and resists all the forces applied to the bone
- this implant is for when anatomic reconstruction is not possible (complex fracture)
- this implant must be rigidly fixed to major proximal and distal segments that can bear the entire load of the patient onto the bone
- priority is preserving blood supply
what is a buttress implant?
like a bridging implant (supports fracture), but this term describes implants that are near the joints
- short up cortical defects within metaphyseal region
- negates compression & shearing forces
- relatively uncommon fractures in vet setting
if the fracture can be reconstructed, and anatomic reconstruction is desired, what are the AO principles of fixation to achieve primary bone healing?
- fracture reduction to restore anatomic relationships
- fracture fixation provides absolute/relative stability depending on the ‘personality’ of the fracture, patient, and injury needs
- preserve blood supply to bone & soft tissues
- early and safe mobilization of injury and patient as whole
what are 6 types of fractures that are suitable for open anatomic reconstruction?
transverse
short oblique
long oblique
segmental
minimally comminuted
articular fractures
what’s important to keep in mind when it comes to open anatomic reconstruction and soft tissue?
open anatomic reconstruction needs some degree of soft tissue dissection to manipulate, reduce, and rigidly stabilize fracture segments – there will be iatrogenic damage (to soft tissue, periosteum, fracture hematoma) that can impede healing
what are 4 principles of biological osteosynthesis?
- indirect fracture reduction via limited surgical approaches with minimal to no disturbance of fracture hematoma
- stabilize fracture using bridging implants over anatomic reconstruction or rigid fixation
- little reliance on secondary implants
- limited to no use of bone grafts
what is the foundation of biological osteosynthesis?
Reducing iatrogenic trauma to the fracture site using less precise reconstruction and less rigid fixation will encourage the formation of callus with rapid secondary bone healing.
what types of implants for fracture repair exist?
primary implants = bone plates, interlocking nails, intramedullary pins, external skeletal fixators
secondary / supplemental implants = Kirschner wires (K wires), cerclage wires, interfragmentary screws
orthopedic wire: what is a tension band? what does it do, how is it used and how does it work?
this wire apposes the pull of muscle or ligament on the bone fragment
- often used in tandem with pins that align the fragment and prevent rotation
- tension converted into compression by the band, which may also facilitate healing
orthopedic wire: what is cerclage wire? what does it do, how is it used and how does it work?
this wire fully encircles a bone to hold fragments apposed
- Supplementary implant for long oblique fractures of the diaphysis
- Minimum of 2 wires should be used
- Anatomic reconstruction of the ENTIRE bone column is essential – any loose wire and movement will impede healing
orthopedic wire: what is hemicerclage wire? what does it do, how is it used and how does it work?
this is used in fractures of diaphysis when it is not possible to place a full cerclage
- this may improve alignment but does NOT add stability
- primary role is to keep alignment while a definitive fixation is applied, absolutely CANNOT be relied on as primary fixation
orthopedic wire: what is interfragmentary wire? what does it do, how is it used and how does it work?
this wire is placed between two fragments of bone
- used in long bone fractures but is most often used between fragments of mandible or maxilla
- fracture fragments should make good contact and ideally should interdigitate!
what are two main types of pins used as internal fixation and how are they applied?
- kirschner wires (K wires)
- steinmann pins
often used within the medullary cavity of long bones to counter any bending forces or skewer fragments to hold location and prevent rotation
normograde vs retrograde pin placement: what’s the difference?
normograde = pin started outside bone and advanced INTO medullary canal– necessary for closed placement
retrograde = advancing pin from fracture site out of the bone; fracture is reduced, and pin is advanced into opposing fragment
crossed pin vs. rush pin
crossed-pin = using small diameter pins starting from sides of joint, pins penetrate cortex opposite
rush pin = do not penetrate cortex opposite and generate a “spring effect”; they are driven at angle that they glance off the opposite cortex and continue up medullary canal
what are interlocking nails? what forces do they resist? when are they used?
what? IM rod that locks prox & dist to fix cortical bone to major bone segment
forces? resist bending, rotation, compression, tension
used? for treatment of closed, communited diaphyseal fractures (except radius); also for angular deformity and some metaphyseal fractures
what are the advantages of using a nail compared to a plate?
+ nails are placed near neutral bone axis while plates are placed eccentrically on surface – plates fatigue at lower loads especially with unstable fractures
+ interlocking nail has more resistance to bending compared to similar sized bone plate
+ because nail is placed in intramedullary location, this eliminates the risk of screw pull-out failure, unlike plates
what are the disadvantages of interlocking nails?
mostly biomechanical disadvantages:
- the breaking of screw, bolt or nail at the level of the hole is possible – must select your device carefully
- there is some rotational instability compared to plate-rod constructs
- limitation of what fracture types you can repair
what are the two types of screws based on their shaft threads?
cortical screws – small pitch, less depth
cancellous screws – large pitch, more depth
- pitch = longitudinal distance between threads
