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Total Knee Replacement

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Total Knee Replacement

  1. 1. Arthroplasty of the Knee
  2. 2. Arthroplasty of
  3. 3. ∗ Insall and others, its introduction in 1973 marked the beginning of the modern era of total knee arthroplasty  The Total Condylar prostesis ∗ The duopatellar prosthesis evolved into the kinematic prosthesis, which was widely used in the 1980s Implant Evolution
  4. 4. ∗ To correct these problems, the Insall-Burstein posterior cruciate–substituting or posterior-stabilized design was developed in 1978 by adding a central cam mechanism to the articular surface geometry of the total condylar prosthesis ∗ The cam on the femoral component engaged a central post on the tibial articular surface at approximately 70 degrees of fl exion and caused the contact point of the femoral-tibial articulation to be posteriorly displaced, effecting femoral rollback and allowing further flexion
  5. 5. ∗ 1980s and 1990s, patellofemoral complications became the primary cause for reoperation in TKA. Consequently, improved reconstruction of the patellofemoral joint has received attention in more recent designs ∗ Some total knee systems have incorporated a deep-dish design as one of their available modular tibial polyethylene options. This design is similar to the original total condylar design that uses sagittal plane concavity or dishing alone to control anteroposterior stability
  6. 6. ∗ The CCK design has been used extensively for revision arthroplasty when instability is present and for difficult primary arthroplasties in patients with extreme valgus deformity and medial collateral ligament insuffi ciency. ∗ Enlarging the central post of the tibial polyethylene insert, constraining it against the medial and lateral walls of a deepened central box of the femoral component . Varus- valgus stability is controlled by this mechanism
  7. 7. ∗ Many current prosthesis designs attempt to reproduce normal knee kinematics closely ∗ Knee motion during gait occurs in flexion and extension, abduction and adduction, and rotation around the long axis of the limb ∗ Average of 2 mm of posterior translation of the medial femoral condyle on the tibia during flexion compared with 21 mm of translation of the lateral femoral condyle  medially based pivoting of the knee explains the observed external rotation of the tibia on the femur during extension, known as the “screw- home mechanism’ and internal rotation of the tibia during knee fl exion Biomechanic of Knee Artroplasty Kinematics…..
  8. 8. ∗ Transverse axis of fl exion and extension of knee constantly changes and describes J-shaped curve around femoral condyles.
  9. 9. ∗ Triaxial motion of normal knee during walking, as measured by electrogoniometer. Flexion and extension are about 70 degrees during swing phase and 20 degrees during stance phase. About 10 degrees of abduction and adduction and 10 to 15 degrees of internal and external rotation occur during each gait cycle. FF, fl atfoot; HO, heel-off; HS, heelstrike; TO, toe-off.
  10. 10. ∗ relative merits of each design have been debated, PCL-retaining and PCL-substituting prostheses ∗ PCL retention achieves an increased potential range of motion by effective femoral rollback and a relatively fl at tibial articular surface. ∗ PCL substitution achieves femoral rollback by a tibial post and femoral cam mechanism Role of the Posterior Cruciate Ligament in Total Knee Arthroplasty
  11. 11. ∗ In PCL-substituting designs, posterior displacement in fl exion is produced by the tibial post contacting the femoral cam, with the resultant stress borne by the prosthetic construct and ultimately transferred to the bone-cement interface  PCL-substituting designs would have higher failure rates than PCL-retaining devices because of loosening??? The loosening rates of these two designs are similar at 10-year follow-up PCL-retaining VS PCL-substituting prostheses
  12. 12. ∗ The relationship of the patella to the joint line is potentially altered more with PCL-substituting prostheses than with PCL-retaining designs. Figgie et al. suggested that joint line elevation may alter patellofemoral mechanics and result in postoperative pain and subluxation ∗ PCL-substituting femoral components have a cutout for a cam mechanism. The patella and hypertrophic synovium on the undersurface of the quadriceps tendon can bind in this mechanism. This clinical entity, termed patellar clunk syndrome PCL-retaining VS PCL-substituting prostheses
  13. 13. ∗ Another argument in favor of PCL substitution is that significant deformity can be more reliably corrected with its use. ∗ Scott and Volatile stated that extensive collateral ligament release on the concave side of a fixed knee deformity may not be effective without release of the contracted PCL
  14. 14. ∗ This less conforming geometry in the sagittal plane is responsible for higher tibial polyethylene contact stresses in PCL-retaining prostheses Retaining
  19. 19. GOAL
  20. 20. To achieve the goals, TKR should: 1. Restore knee alignment and stability. 2. Restore patellofemoral tracking. 3. Be done with good fixation technique.
  21. 21. Alignment ∗ Vertical axis ∗ Perpendicular to transverse knee axis ∗ Mechanical axis ∗ Line from center of hip to center of ankle ∗ Anatomical axis ∗ Line from tip of greater trochanter to center of ankle (5-7 degrees from mechanical axis)
  22. 22. Alignment ∗ Articular surface of tibia ∗ 3 degrees of varus ∗ Articular surface of femur ∗ 9 degrees of valgus ∗ Femoro-tibial axis ∗ 6 degrees of valgus
  23. 23. Prosthetic alignment ∗ Tibial component ∗ Placed at 90 degrees to longitudinal axis of tibial shaft ∗ Femoral component ∗ Placed in 6 degrees of valgus
  25. 25. Surgical plan ∗ Assessment of intraoperative difficulty ∗ Range of motion ∗ Sufficient flexion involve adequate exposure ∗ Inability to flex knee prevent removal of residual posterior bone ∗ Deformity ∗ MCL deficient indicate for constrained condylar prosthesis ∗ Ligamentous balance
  26. 26. Pre-operative x-ray analysis  Standing AP, lateral, skyline view of patella  Show distal femur and proximal tibia  Anatomical axis in neutral rotation  Long leg film  Determine bowing of tibia  For IM tibia alignment guide  Full length film  Determine mechanical axis  Template for component size
  27. 27. Tibia and Femur film  Degree of bone loss at femur and tibia  Typical greater on concave side of deformity  Appearance of attenuated ligament at convex side of deformity  Subluxation  Typical lateral subluxation of tibia  Osteophyte  Diaphysis  Hardware  Extra articular bony  Deformity  Unusual canal size  Lateral film  Loose body, osteophyte
  28. 28. Surgical approach ∗ Principles : ∗ Good visualization ∗ Gentle atraumatic technique ∗ Avoidance of neurovascular structure ∗ Absolute hemostasis
  29. 29. Surgical approach ∗ Vascular supply ∗ Subfascial flap
  30. 30. Surgical exposure ∗ Standard medial parapatellar approach (classical approach) ∗ Subvastus approach ∗ Midvastus approach ∗ Lateral approach
  31. 31. Surgical exposure ∗ Standard approach (anterior midline skin incision with medial parapatellar arthrotomy) ∗ Gold standard ∗ Dissect directly to extensor mechanism ∗ Medial retinaculum incision can curve or straight ∗ Weakening quad & possible quad lag
  32. 32. Surgical exposure Subvastus approach Save the entire quadriceps insertion on the patella Minimal disruption of quad’s mechanism Preservation of patellar blood supply Improve PF stability May injury to femoral a. in adductor hiatus
  33. 33. Preservation of Quad’s mechanism  Advantage  Lead to decrease post-op. pain  Earlier to return of quadriceps function and strength  Improve patellar tracking and stability  Decrease lateral release  Disadvantage  Limited operative exposure  May damage to neurovascular structures
  34. 34. Surgical exposure Midvastus approach Vastus medialis muscle fiber divided in midsubstance along the line and direction of muscle fibers (muscle splitting approach) Begin at superior medial border of patella Quad sparing, preserve supreme geniculate a.
  35. 35. Surgical exposure ∗ Lateral approach ∗ SevereValgus knee ∗ Plan lateral arthrotomy ∗ Increase visualization of ligamentous balancing
  36. 36. Theories of surgical technique ∗ The gap technique ∗ Develop in conjuction with the design of cruciate-substituting prostheses ∗ The measured resection technique ∗ Develop by surgeon and designer who favored cruciate retention, measure femoral and tibial resection
  37. 37. Bone work  Soft tissue release (in extension) to achieve alignment  Perpendicular tibial resection  Entry hole femoral IM guide  Distal femoral resection  Size the femur  Set rotational alignment of femur to achieve rectangular flexion gap  External rotation of femoral component in flexion  Lateralize of femoral component  Chamfer cut and housing cut (PS)  Posterior clearance  Balance flexion and extension gap
  39. 39. Tibia cut ∗ Tibia alignment in TKA ∗ Classic alignment ∗ Distal femur 5-6 degrees valgus ∗ Proximal tibia perpendicular to anatomical axis ∗ Anatomic alignment (joint line technique) ∗ Distal femur 9-10 degrees valgus ∗ Proximal tibia 2-3 degrees varus
  40. 40. Step of bone cut ∗ Distal femur first ∗ Does not effect alignment of tibia cut ∗ May effect level of tibia resection ∗ Tibia first (tibial shaft axis technique) ∗ May effect both femoral rotation and resection level if use “Gap technique” ∗ No effect if use “Measure resection”
  41. 41. Cutting guide ∗ Extramedullary guide ∗ Intramedullary guide ∗ Navigation
  42. 42. Extramedullary guide ∗ Align the guide with center of tibial plateau, medial 1/3 of tubercle, crest and center of ankle ∗ Usually need to shift the guide medially about 5-10 mm at the ankle ∗ Difficult to obese patient
  43. 43. Intramedullary guide ∗ Entry point is critical to alignment ∗ Must have pre-op template ∗ Limitation in bowed tibia
  44. 44. Tibial component alignment ∗ Coronal plane ∗ Perpendicular to anatomical axis and mechanical axis ∗ Varus cut > 3 degrees has resulted in early failure
  45. 45. Tibial component alignment ∗ Sagittal plane ∗ PS TKA ∗ 3-7 degrees posterior tilt depending on each design ∗ CR TKA ∗ Follow each patient’s own posterior tilt for optimal PCL tension
  46. 46. Tibial component alignment ∗ Rotational alignment ∗ Center at medial 1/3 of tibial tubercle ∗ Slight posterolateral overhang usually occurred when using symmetrical tibial tray ∗ Self align ∗ Insert trial implant without broaching then put knee through range of motion and tray will rotate to rest at certain position ∗ Recheck and landmark
  47. 47. Level of bone cut ∗ Two method for resection level ∗ 10 mm resection from less damaged compartment ∗ Lower limit of recommended PE thickness ∗ 2 mm resection below most eroded articular surface ∗ Bone preserving ∗ Gap may be to tight if only mild or moderately eroded
  48. 48. Effect of tibial cut on F-E gap ∗ Tibia cut effect both flexion and extension gap ∗ Increase posterior slope can loosen flexion gap but only slightly
  49. 49. Effect of tibial cut on F-E gap ∗ Resection too high ∗ Tight both flexion and extension ∗ Sclerotic bone not ideal for cement interdigitation ∗ Solution ∗ Recut tibia
  50. 50. Effect of tibial cut on F-E gap ∗ Resection too low ∗ Loose both flexion and extension ∗ Weaker bony support for implant ∗ Risk of peroneal nerve injury ∗ Solution ∗ Use thicker PE insert
  51. 51. FEMORAL PREPARATION 1. Remove all osteophyt . 2. Determine the entry point of femoral rod. The entry point of femoral rod: . 7-10 mm anterior to the origin of the PCL. . 3-5 mm medial to intercondylar notch. Error in determining the point will alter the degree of valgus cutting.
  52. 52. Femoral Rod Entry Point. . It is usually 3-5 mm medial to intercondylar notch. Varus knee Valgus knee Varus deformity (more medial) (far lateral)
  54. 54. Distal femoral bone cut ∗ Remove bone that replace by the femoral prosthesis
  55. 55. Rotation alignment Epicondylar axis Posterior condylar reference AP axis Parallel tibial cut
  56. 56. Posterior condylar axis ∗ Advantage ∗ Simple instrumentation ∗ Usually accurate ∗ Neutral/Varus knees ∗ Minimal deformity ∗ No bone erosion ∗ Disadvantage ∗ Less reliable in valgus knee ∗ Severe deformity ∗ Femoral condyle hypoplasia ∗ Revision case
  57. 57. AP axis ∗ Advantage ∗ Easy to locate ∗ Primary TKA ∗ Enhance PF tracking ∗ Useful if condylar hypoplasia or mark osteophyte ∗ Disadvantage ∗ Less reliable ∗ Trochlear dysplasia ∗ Advance PF arthritis ∗ High variability ∗ Error in presentation of osteophtye at intercondyar notch
  58. 58. Epicondylar axis ∗ Advantage ∗ Numerous study show it most accurate axis ∗ Available in revision TKA ∗ Accurate in knees with condylar hypoplasia/erosion ∗ Decrease femoral condylar lift-off ∗ Disadvantage ∗ Difficult to palpate medial epicondyle ∗ Can not seen in small incision
  59. 59. Flexion gap method ∗ Advantage ∗ Better flexion stability ∗ More reproducible ∗ Disadvantage ∗ Unreliable if ∗ Ligamentous imbalance/insufficiency ∗ Inaccurate tibial resection
  60. 60. External rotation of femoral component in flexion
  61. 61. Lateralize of femoral component
  62. 62. Complete femoral cut ∗ Lateralize femur ∗ Chamfer cut ∗ Housing cut ∗ Posterior clearance
  63. 63. Complete femoral cut
  64. 64. Patellar resurface  Surgical technique  Prepare the patella  Measure thickness  Patellar osteotomy  Inset or onset  Patellar position  PF tracking  +- Lateral release
  65. 65. Patellar resurface  Prepare patella  Remove osteophyte and synovial tissue  Measure thickness  Not less than 12 mm after resection  Patellar osteotomy surgical method  Inset (inlay) technique  Onset (onlay) technique
  66. 66. Patellar resurface  Patellar position  Medial to midline  Decrease Q angle  Better tracking  Lateral wear decrease  Lateral contact stress decrease  Tracking evaluation  No thumb technique  Tower clip  Lateral release  Good exposure  Avoid cut superior lateral geniculate artery
  67. 67. Cementing technique ∗ Cementing of both baseplate and stem are still recommended ∗ Both manual packing and cement gun work well ∗ Pulsatile larvage can reduced incidence of radiolucent line ∗ 3 mm cement mantle is ideal
  68. 68. Correct deformity ∗ Correct balancing and handling of the soft tissues ∗ Ligaments ∗ Tendons ∗ Joint capsule
  69. 69. THANK YOU