Download techniques of absolute and relative stability including

TECHNIQUES OF ABSOLUTE AND
RELATIVE STABILITY INCLUDING
EXTERNAL FIXATION
PRESENTER:DR.MUNENE
FACILITATOR:DR.MUTISO
-Stability : degree of displacement at fracture site
induced by load
-Stable fracture : fracture that does not visibly displace
under physiological load
-Aim of fracture stabilization
a) Maintain achieved reduction
b) Restore stiffness at fracture site(thus allowing
function)
c) Minimize pain related to instability at fracture site
-Fracture fixation with absolute stability-there’s no
micro-motion at the fracture site under physiological
load
-This reduces
formation
mechanical
stimulus
for
callus
-Fixation with relative stability-aims to maintain
reduction and still keep mechanical stimulation for
callus formation
-Displacement
occurring
elastic(reversible)
under
load
is
ABSOLUTE FIXATION
-It aims to provide a mechanically
environment for fracture healing
neutral
-Lack of micromotion results in primary bone healing
mechanical stimulus for repair by callus formation
-This also reduces mechanical stimulus for repair by
callus formation
-Hence implant must provide and maintain absolute
stability for prolonged periods of time
-Without tmt, mobile fragments are stabilized by
pain induced contraction of surrounding muscles→
malunion and shortening
-Implants include lag screws and plates
-Skeletal traction: pin inserted along long axis of
bone. It helps to align bone fragments by
ligamentotaxis and reduced motion.
-External splinting: wood, plastic ,plaster
Skeletal Traction
-Traction on a bone structure by means of a pin or wire
surgically inserted into the bone.
- continuous traction is desired to immobilize, position,
and align a fractured bone properly during the
healing process
Aim of Skeletal Traction
• regain normal length and alignment of involved bone
• lessen or eliminate muscle spasms
• relieve pressure on nerves, especially spinal and
• prevent or reduce skeletal deformities or muscle
contractures
Proximal Tibial Pins:
- contraindications:
- ligament injury to ipsilateral knee;
- should never be used in children;
- may cause recurvatum injury due to
damage of tibial physis;
- pins are inserted from lateral side to avoid
damaging peroneal nerve;
- pin insertion: proper insertion site: 2.5 cm
posterior to & 2.5 cm distal to tibial tubercle;
- landmark is to place pin one to two finger
breaths below tibial tuberosity in the midportion of
the tibia;
- proximal pin placement, places it thru too much
cancellous bone, which is weaker;
- distal femoral pin placement, while in
stronger cortical bone, risks damage to peroneal
nerve as it passes anterior after it passes
around fibular neck;
- make a transverse skin incision about 1 cm in
length, placed about 3 cm below lesser tuberosity;
Lag Screws
-Stabilizes fracture by compression alone
- Oblique, non comminuted fractures in bones which
are not osteoporotic
- Involves placement of one or more screws across an
osteotomy site to achieve inter-fragmentary
compression
-lag screw is best positioned at right angles to the
fractures plane;
Advantages
-Allow for a smaller incision
-Don’t have to be removed
-Don’t interfere with sydesmotic screws if needed
Disadvantages
-lever arm is too small to resist functional
loading(bending/ shearing). Therefore combined
with a plate to protect them from these forces
-Lack of tolerance to single overload
PLATES
• Combined with screws, they act as splints to protect the screw
by reducing shear or bending forces( hence term protection
plate/neutralization plate)
• 5 functional uses of a plate:
i. Protection-of the lag screws
ii.
Compression-drives ends of fracture together
iii. Tension band-plate placed on tension side of bone
iv. Bridging –used in multifragmentary fractures
v.
Buttress:-used in metaphyseal areas(resists axial load by
applying force at 90˚ to axis of potential deformity)
•LC-DCP has limited plate-bone contact(plate
footprint), hence less impairment of capillary
network of the periosteum->relative improvement of
cortical perfusion
•Locking compression plates(LCP)-designed in such a
way that screws effectively bolt into plate and bone,
hence as screw is tightened, bone maintains its
position and is not drawn to plate
Implications
-Contouring of plates
-Screw angulation and numbers
-Screw diameter and strength
-Minimally Invasive Plate Osteosynthesis (MIPO)periosteum,angular rigidity,osteoporosis
disadv of plates
-prominent lateral screws may cause symptoms or
wound necrosis
- possibility of distal intra-articular screw insertion
-inadequate fixation if distal screws are too short
-may not allow adequate fixation in osteoporotic bone
- may interfere w/ syndesmotic screw insertion
(especially when two syndesmoic
screws are to be used);
RELATIVE FIXATION
-Bone fragments displace in relation to each other
when physiological load is applied across fracture.
-Implants: internal fixators,ext. fixators,IM nails
-All allow inter fragmentary movement which can
stimulate callus formation
-Incorrect application leads to excess movement and
inhibit bone union
Ext. fixators
- External fixation is a method of immobilizing bones to
allow a fracture to heal.
-External fixation is accomplished by placing pins or
screws into the bone on both sides of the fracture
-The pins are then secured together outside the skin
with clamps and rods. The clamps and rods are
known as the "external frame."
Factors influencing stability of fixation:
-stiffness of connecting rods
-distance between rods and bone axis
-no, spacing and diameter of schanz screws
Advantages
-rigid fixation
-compression, neutralization, or fixed distraction of the
fracture fragments
-direct surveillance of the limb and wound status
- associated treatment e.g dressing changes, skin
grafting, bone grafting, and irrigation, is possible
without disturbing the fracture alignment or fixation
-immediate motion of the proximal and distal joints is
allowed
-extremity is elevated without pressure on the
posterior soft tissues
-early patient mobilization
-can de done under L.A
- used in infected, acute fractures or non union
Disadvantages
-pin tract infection
-expensive equipment
-cumbersome frame(aesthetic)
-fracture through pin tracts
- re fracture after ex-fix removal
-joint stiffness: over a joint e.g pilon fracture
-pin and fixator frame may be difficult to assemble
Complications
-pin tract infection
-neurovascular impairment
-muscle/tendon impairment
-compartment syndrome
-delayed union
IM NAILS
-Classical kuntscher nail- stable against bending and
shear forces perpendicular to its long axis. Its
confined to simple transverse/oblique fractures
-IM nails are:
-unstable against torsional forces
-confined for simple transverse or short oblique
fractures which cannot shorten and will inter-digitate
to prevent rotation
-Locked IM Nails-withstand torsional forces and axial
loading
-Holes are larger than screws
-Stability dependent on diameter of the nail,
geometry, number of interlocking screws, spatial
arrangement
Internal fixators and bridging plates
-Plating with relative stability should only be used in
multi-fragmentary fractures
-Use in simple fractures causes high incidence of
delayed or nonunion
-Bridge plating uses the plate as an extramedullary
splint, fixed to the two main fragments, while the
intermediate fracture zone is left untouched.
-anatomical reduction of the shaft fragments is not
necessary.
-direct manipulation risks disturbing their blood supply
• Stiffness of an internal fixation method depends on:
-dimensions of the implant
-number and position of screws
-quality of coupling btn screw and plate and btn
screw and bone