Im nailing


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Im nailing

  1. 1. Interlocking Nail
  2. 2. IntroductionThese implants are introduced into the boneremote to the fracture site and sharecompressive, bending, and torsional loads withthe surrounding osseous structuresIM nails act as internal splintswith load-sharing characteristics.
  3. 3. HISTORYStimson in 1883 described the insertion of an ivory peg inmedullary canal.Rush brothers described their IM pinning system in 1927.
  4. 4. Gerhard KuntschnerFemoral Nail-1939Stable OsteosynthesisPrinciple of fixation was based on compression between boneand implant
  5. 5. Flexible NailsRush pinsEnder nailsMorote NailsNancy Nails
  6. 6. MechanicsAct by stabilizing fractures with three or four pointcompressionEquilibrium between the tensioned pin and the bonewith its soft attached tissues will hold the alignment.Bending movements are neutralized but telescopiningand rotational torsion are not prevented.
  7. 7. ApplicationsChildren- Mainly for forearm fracturesfemur fracture.Adults-Clavicle fractureProximal humerus fractureHumeral shaft fractureForearm fracture
  8. 8. DisadvantagesAdditional immobilization is often required.Secondary loss of reductionShortening with loading
  9. 9. Intramedullary NailingUnlocked NailInterlocking NailUnreamed NailReamed Nail
  10. 10. Unlocked Nail
  11. 11. MechanicsElastic Deformation is principle of nail stabilityNail insertion causes radially oriented forceForce is proportional to the contact area between the bone andnailProduced friction stops the nail from pulling out“Elastic Locking”
  12. 12. Elastic LockingBending of the nail (curvature)Cross-sectional shape (particularly the geometry of thesurface of the implant), and its diameterThe corresponding properties of the canal (eg, size, shape,bone quality)
  13. 13. Interlocking NailingThese nails have proximal and distal lockingscrews.The resistance to axial and torsional forcesis mainly dependant on screw boneinterphase.
  14. 14. Interlocking screws placed proximal anddistal to the fracture site restrict translationand rotation at the fracture site; however,minor movements occur between the nailand screws, allowing toggling of the bone.
  15. 15. Nail Bio-MechanicsIntrinsicExtrinsic
  16. 16. Intrinsic FactorsMaterial propertiesCross-sectional shapeAnterior bowDiameter
  17. 17. Extrinsic FactorsReaming of the medullary canalFracture stability (comminution)The use and location of locking bolts
  18. 18. StabilityNail sizeNumber of locking screws or bolts, andDistance of the locking screw or bolt from thefracture site.
  19. 19. Nail DiameterBending rigidity is proportional to the nail diameter to thethird power,The torsional rigidity is proportional to the fourth power
  20. 20. Working LengthIt is the distance between proximal and distal locking screwsThe working length influences nail stiffness in bending andtorsion.
  21. 21. Physiological loading of the Nail
  22. 22. Screw BreakageWith cortical bone contactweight is transmitted throughbone also.However in its absence fourpoint bending can occur
  23. 23. Implant FailuresUnlocked nails typically fail either at the fracture site orthrough a screw hole or slot.Locked nails fail by screw breakage or fracturing of the nailat locking hole sites, most commonly at the proximal hole ofthe distal interlocks
  24. 24. PATHOPHYSIOLOGY OF NAILINGLocal effectsSystemic effects.These effects are described with reamed nailing.
  25. 25. Local effectsDamage to endosteal blood supplyHeat necrosisWith intact soft tissue envelop reaming increases thecirculation in the surrounding musclesRate of non union is less with reamed nail as compared tounreamed nail.
  26. 26. SystemicReaming causes transient raise of the pulmonary arterial pressureIM instrumentation causes liberation of bone marrow contents toblood streamThey undergo an increase in size due to platelet adhesions
  27. 27. Leads to a transient decrease in perfusionSubsequent cascade reaction follows.
  28. 28. Unreamed nailsIt is said that unreamed nailing is advantageous in treatmentof Gustilo IIIB open fractures.It has got less amount of superficial infection and malunion ascompared to external fixation.
  29. 29. DisadvantagesNonunionDistal Screw breakage
  30. 30. Special DesignsProximal Femoral NailsRetrograde NailsDistraction NailsKnee Arthrodesis
  31. 31. Proximal Femoral NailSub trochanteric fractureFracture NOFIntertrochanteric Fractures
  32. 32. Retrograde NailsDistal femur fracturesHumeral fracturesPeriprosthetic fractures
  34. 34. PrinciplesA motor with sub-cutaneous receiver for gradual lengtheningA mechanical function with one way cluches
  35. 35. Advantages over externalfixatorsLimb lengthening by external fixators is associated withproblems such as Pain at the pin tracts Pin tract infections Reduced joint motion and Prolonged fixation time.
  36. 36. Coated ImplantsHydroxyapatiteGrowth FactorsAntibiotics
  37. 37. Hydroxyapatite coated implantsThe extraction torque of HAP coatedimplants found to be higher.Coating of the dynamic screw reducedsignificantly rate of cutout
  38. 38. Growth FactorsLocal application of the growth factors significantlyaccelerates the fracture healing in early phaseThe sustained release of growth factors doesn’t induce HO.
  39. 39. AntibioticsGentamycin coated implants have shownreduced rate of infection in animal studies.