PRESENTER:DR.MUNENE FACILITATOR:DR.MUTISO 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 Maintain achieved reduction Restore stiffness at fracture site(thus allowing function) 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 mechanical stimulus for callus formation -Fixation with relative stability-aims to maintain reduction and still keep mechanical stimulation for callus formation -Displacement occurring under load is elastic(reversible)

ABSOLUTE FIXATION -It aims to provide a mechanically neutral environment for fracture healing -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;                  

-Stabilizes fracture by compression alone 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: Protection-of the lag screws Compression-drives ends of fracture together Tension band-plate placed on tension side of bone Bridging –used in multifragmentary fractures 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

-pin tract infection Complications -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