TECHNIQUES OF ABSOLUTE AND RELATIVE STABILITY INCLUDING EXTERNAL FIXATION

1. TECHNIQUES OF ABSOLUTE AND RELATIVE STABILITY INCLUDING EXTERNAL FIXATION PRESENTER:DR.MUNENE FACILITATOR:DR.MUTISO

2. -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

6. -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)

7. 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

8. -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

9. 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

10. 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

12.  Proximal Tibial Pins:    - contraindications:          - ligament injury to ipsilateral knee;          - should never be used in children;                - may cause recurvatum injury due to damage of tibialphysis;    - 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 tibialtuberosity in the midportion of the tibia;

13. - 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;

14. 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;

15. 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

18. 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)

20. 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

21. Implications -Contouring of plates -Screw angulation and numbers -Screw diameter and strength -Minimally Invasive Plate Osteosynthesis (MIPO)-periosteum,angular rigidity,osteoporosis

24. 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);

28. 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

29. 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."

30. Factors influencing stability of fixation: -stiffness of connecting rods -distance between rods and bone axis -no, spacing and diameter of schanz screws

31. Advantages -rigid fixation -compression, neutralization, or fixed distraction of the fracture fragments -direct surveillance of the limb and wound status -associated treatmente.g dressing changes, skin grafting, bone grafting, and irrigation, is possible without disturbing the fracture alignment or fixation

32. -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

33. Disadvantages -pin tract infection -expensive equipment -cumbersome frame(aesthetic) -fracture through pin tracts -re fracture after ex-fix removal

34. -joint stiffness: over a joint e.g pilon fracture -pin and fixator frame may be difficult to assemble

35. Complications -pin tract infection -neurovascular impairment -muscle/tendon impairment -compartment syndrome -delayed union

38. IM NAILS -Classical kuntschernail- 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

40. -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

43. 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. 

44. -anatomical reduction of the shaft fragments is not necessary. -direct manipulation risks disturbing their blood supply

45. 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