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Dr Rajesh PurushothamanAssociate ProfessorGovernment Medical College, KozhikodeGraft Fixation Options in
ACL Reconstruction
GoalFunctional and anatomicalrestoration of ACL insymptomatic ACL deficiency
Most Important FactorsUnder Surgeons Control• Graft selection• Graft positioning• Graft fixation• Rehabilitation
Graft HealingBTB graft heal by bone to bonehealing by 6 weeksSoft tissue grafts incorporate bySharpey fibers by 12weeksAll...
Current RehabAccelerated rehab protocol•Early weight bearing•Early return to full ROM•Neuromuscular coordination•Strengthe...
Biomechanics of Rehab• Reconstructed ACL subjected to150-500N forces by activities ofdaily living and rehab• Within the fi...
Biomechanics•Ultimate load to failure is about 3000N for BPTBand 4000N for QSTGG•This far exceeds the usual forces of 150-...
3 Types of Graft Motion• Longitudinal motion calledBungee Cord Effect• Horizontal motion called Wind-wiper effect• Creep o...
What Does Graft TunnelMotion Do?• >3mm motion interferes with graftincorporation• May cause tunnel widening
Tunnel Widening• Due to biological and mechanical causes• More with non-aperture fixation
Biomechanics of Fixation• Strength - Ultimate load to failure• Stiffness- Resistance to displacement underload• Slippage o...
Ideal Fixation• Strong enough to avoidfailure• Stiff enough to restoreknee stability• Secure enough to avoidslippage
Ideal Graft Fixation• Anatomic• Biocompatible• Safe and reproducible• MRI compatible• Allow easy revision
Types of FixationAperture FixationAt the joint level-Interference screwsSuspensory Fixation• Cortical- Endobutton,staples,...
Interference ScrewsInterference is definedas the amount by whichdiameter of the screwexceeds the gapbetween graft and thet...
Advantages ofAperture Fixation• Minimises Graft-Tunnel motion• Less femoral canalwidening• Creep is less
Factors Influencing
Interference Screw FixationLengthSize and geometry ofscrewDivergence of screw• Torque of screwinsertio...
Length• Longer screw providebetter fixation• In BPTB engage onlythe bone plugStadelmaier DM, Lowe WR, Elah OA, Noble PC, K...
SizeScrew diameter should be 1mm more than tunneldiameter for soft tissue grafts and same for boneplug graftKohn D, Rose C...
Geometry• Use soft threads screw for softtissue fixation• Use reverse threaded screw for leftsideWeiler A, Hoffmann RF, Si...
Insertion Torque• More the resistance better thefixation• More with metal screws• Torque higher if screw diameter ismore• ...
Tunnel Dilatation• Under ream by 2mm• Next 2mm increase doneusing dilators• Compacts the bone thanremoving it
Divergence• Difference between theangle of tunnel andscrew direction• More with transtibialtechnique of femoraltunnel prep...
BMD• <0.6 gm2 associatedwith less pull outstrength• Use hybrid techniqueBrand JC Jr, Pienkowski D, Steenlage E, et al. Int...
Bioabsorbable screws• Polyglycolide-absorbs early, henceloses fixation early• Crystallinepolylactides takeyears to be abso...
Attractions• No need for implantremoval• Does not interfere withMRI• Revision easier
But…….• May break during insertion. Usewith special screw driver only• Tissue reaction in some• Fixation lost after partia...
And…•By 6 weeks, 80% loss of strength and60% loss of stiffness•Incidence of effusion is more•Tunnel widening more
Titanium Or Steel•Titanium gets covered by bone•Steel gets enveloped by fibroustissue
Suspensory Fixation- CorticalEndobuttonTightropeGraft tunnelmotion moreMay lead to tunnelwideningClinical outcomestudies s...
Endobutton• First generation suspensoryfixation• Femoral tunnel has 2 parts-Insertion & Connection parts• Insertion part d...
Maths of EndobuttonFemoral tunnel length –Desired graft insertionlength = Loop lengthInsertion tunnel lengthshould be 10mm...
If the tunnel length is 60mm, desiredinsertion length is 40mm then the looplength should be 20mm and the insertiontunnel s...
TightropeSecond generationsuspensory fixationLoop length reducedafter flipping bytightening the ropeAllows full length fil...
Tightrope
Fixation Options•Femoral• Bone plug fixation• Soft tissue fixation•Tibial• Bone plug fixation• Soft tissue fixation
Bone Plug Fixation-Femur• Interference screws-Gold standard• Suspension type-Endobutton BTB,• Transfixation type-Transfix
Bone Plug FixationTibia• Staples with or withoutsutures• Screws as screwposts• Interference screws
Soft Tissue FixationFemur• Interference screws• Suspension type likeEndobutton, Tightrope• Transfixation typeInterference ...
Soft Tissue FixationTibia• Staples singly or with two staplesusing belt buckle technique• Screws as posts or with spikedwa...
Tibial Vs FemoralFixation• Tibial fixation is lesssecure• Reduced bone density• Angle of forces in linewith the graft• Bon...
Conclusions• In the early postoperative period fixation is theweakest link• Tibial fixation is at greater risk of failure•...
Conclusions• Aperture fixation theoretically better• Interference screws are the gold standard• Tunnel dilation improves f...
Thank YouDr Rajesh PurushothamanAssociate Professor of OrthopaedicsGovernment Medical College,Kozhikode, Kerala, Indiadrra...
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Acl graft fixation options

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Presentation on various graft fixation options in ACL Reconstruction

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Acl graft fixation options

  1. 1. Dr Rajesh PurushothamanAssociate ProfessorGovernment Medical College, KozhikodeGraft Fixation Options in
ACL Reconstruction
  2. 2. GoalFunctional and anatomicalrestoration of ACL insymptomatic ACL deficiency
  3. 3. Most Important FactorsUnder Surgeons Control• Graft selection• Graft positioning• Graft fixation• Rehabilitation
  4. 4. Graft HealingBTB graft heal by bone to bonehealing by 6 weeksSoft tissue grafts incorporate bySharpey fibers by 12weeksAllografts take longerTill that time, fixation device shouldsecure the graft
  5. 5. Current RehabAccelerated rehab protocol•Early weight bearing•Early return to full ROM•Neuromuscular coordination•Strengthening
  6. 6. Biomechanics of Rehab• Reconstructed ACL subjected to150-500N forces by activities ofdaily living and rehab• Within the first 6 weeks, the graftis subjected to 2,20,000 suchloading cyclesNoyes FR, Butler DL, Grood ES, Zernicke RF, Hefzy MS. Biomechanical analysis of human ligamentgrafts used in knee-ligament repairs and reconstructions. J Bone Joint Surg (Am) 1984;66:344–352.
  7. 7. Biomechanics•Ultimate load to failure is about 3000N for BPTBand 4000N for QSTGG•This far exceeds the usual forces of 150-500N•Fixation has load to failure of about 500NFixation is the weakest link in the earlypostoperative period
  8. 8. 3 Types of Graft Motion• Longitudinal motion calledBungee Cord Effect• Horizontal motion called Wind-wiper effect• Creep of graft tissue leading toelongation
  9. 9. What Does Graft TunnelMotion Do?• >3mm motion interferes with graftincorporation• May cause tunnel widening
  10. 10. Tunnel Widening• Due to biological and mechanical causes• More with non-aperture fixation
  11. 11. Biomechanics of Fixation• Strength - Ultimate load to failure• Stiffness- Resistance to displacement underload• Slippage of graft- Change in initial positionunder specific number of submaximal cycles
  12. 12. Ideal Fixation• Strong enough to avoidfailure• Stiff enough to restoreknee stability• Secure enough to avoidslippage
  13. 13. Ideal Graft Fixation• Anatomic• Biocompatible• Safe and reproducible• MRI compatible• Allow easy revision
  14. 14. Types of FixationAperture FixationAt the joint level-Interference screwsSuspensory Fixation• Cortical- Endobutton,staples, screw posts• Cancellous- Transfixionpins
  15. 15. Interference ScrewsInterference is definedas the amount by whichdiameter of the screwexceeds the gapbetween graft and thetunnel
  16. 16. Advantages ofAperture Fixation• Minimises Graft-Tunnel motion• Less femoral canalwidening• Creep is less
  17. 17. Factors Influencing
Interference Screw FixationLengthSize and geometry ofscrewDivergence of screw• Torque of screwinsertion• BMD• Screw Material
  18. 18. Length• Longer screw providebetter fixation• In BPTB engage onlythe bone plugStadelmaier DM, Lowe WR, Elah OA, Noble PC, Kohl HW 3rd. Cyclic pull-out strengthof hamstring tendon graft fixation with soft tissue interference screws: influence ofscrew length. Am J Sports Med 1999;27:778-83.
  19. 19. SizeScrew diameter should be 1mm more than tunneldiameter for soft tissue grafts and same for boneplug graftKohn D, Rose C. Primary stability of interference screw fixation:influence of screw diameter and insertion torque. Am J SportsMed 1994;22:334-8.
  20. 20. Geometry• Use soft threads screw for softtissue fixation• Use reverse threaded screw for leftsideWeiler A, Hoffmann RF, Siepe CJ, Kolbeck SF, Sudkamp NP. Theinfluence of screw geometry on hamstring tendon interference fitfixation. Am J Sports Med 2000; 28:356-9.
  21. 21. Insertion Torque• More the resistance better thefixation• More with metal screws• Torque higher if screw diameter ismore• Torque better if tunnel is preparedby dilatation method than byextraction drillingKohn D, Rose C. Primary stability of interference screw fixation: influence of screwdiameter and insertion torque. Am J Sports Med 1994;22:334-8.
  22. 22. Tunnel Dilatation• Under ream by 2mm• Next 2mm increase doneusing dilators• Compacts the bone thanremoving it
  23. 23. Divergence• Difference between theangle of tunnel andscrew direction• More with transtibialtechnique of femoraltunnel preparation• >20 degreecompromises stabilitySchroeder FJ. Reduction of femoral interference screw divergence during endoscopic anteriorcruciate ligament reconstruction. Arthroscopy 1999;15:41-8.
  24. 24. BMD• <0.6 gm2 associatedwith less pull outstrength• Use hybrid techniqueBrand JC Jr, Pienkowski D, Steenlage E, et al. Interference screw fixation strength of a quadrupledhamstring tendon graft is directly related to bone mineral density and insertion torque. Am J Sports Med2000;28:705-10.
  25. 25. Bioabsorbable screws• Polyglycolide-absorbs early, henceloses fixation early• Crystallinepolylactides takeyears to be absorbed
  26. 26. Attractions• No need for implantremoval• Does not interfere withMRI• Revision easier
  27. 27. But…….• May break during insertion. Usewith special screw driver only• Tissue reaction in some• Fixation lost after partialdegradation
  28. 28. And…•By 6 weeks, 80% loss of strength and60% loss of stiffness•Incidence of effusion is more•Tunnel widening more
  29. 29. Titanium Or Steel•Titanium gets covered by bone•Steel gets enveloped by fibroustissue
  30. 30. Suspensory Fixation- CorticalEndobuttonTightropeGraft tunnelmotion moreMay lead to tunnelwideningClinical outcomestudies show nodifference
  31. 31. Endobutton• First generation suspensoryfixation• Femoral tunnel has 2 parts-Insertion & Connection parts• Insertion part drilled to thediameter of graft• Connection part is of 4.5mmdiameter
  32. 32. Maths of EndobuttonFemoral tunnel length –Desired graft insertionlength = Loop lengthInsertion tunnel lengthshould be 10mm morethan desired graftinsertion length
  33. 33. If the tunnel length is 60mm, desiredinsertion length is 40mm then the looplength should be 20mm and the insertiontunnel should be 50mm long
  34. 34. TightropeSecond generationsuspensory fixationLoop length reducedafter flipping bytightening the ropeAllows full length fillingof graft part of thefemoral tunnel
  35. 35. Tightrope
  36. 36. Fixation Options•Femoral• Bone plug fixation• Soft tissue fixation•Tibial• Bone plug fixation• Soft tissue fixation
  37. 37. Bone Plug Fixation-Femur• Interference screws-Gold standard• Suspension type-Endobutton BTB,• Transfixation type-Transfix
  38. 38. Bone Plug FixationTibia• Staples with or withoutsutures• Screws as screwposts• Interference screws
  39. 39. Soft Tissue FixationFemur• Interference screws• Suspension type likeEndobutton, Tightrope• Transfixation typeInterference screw fixationespecially with bioscrewsneeds slower rehabilitation
  40. 40. Soft Tissue FixationTibia• Staples singly or with two staplesusing belt buckle technique• Screws as posts or with spikedwashers• Interference screwsInterference screw fixation especially withbioscrews needs slower rehabilitation.Hybrid fixation preferrable
  41. 41. Tibial Vs FemoralFixation• Tibial fixation is lesssecure• Reduced bone density• Angle of forces in linewith the graft• Bone strength fallsrapidly away from thejoint line
  42. 42. Conclusions• In the early postoperative period fixation is theweakest link• Tibial fixation is at greater risk of failure• Clinical results of various methods arecomparable• Tunnel widening is a growing concern
  43. 43. Conclusions• Aperture fixation theoretically better• Interference screws are the gold standard• Tunnel dilation improves fixation• Hybrid fixation is becoming more popular
  44. 44. Thank YouDr Rajesh PurushothamanAssociate Professor of OrthopaedicsGovernment Medical College,Kozhikode, Kerala, Indiadrrajp@gmail.com

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