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Primary total knee arthroplasty
- 1. Primary Total KneeArthroplasty Jatinder S. Luthra MS DNB MRCS
- 2. Historic Evolution • 19thcentury – Soft tissue interposition • 1950 Walldius Hinged knee replacement • 1960 MacIntosh & McKeever Acrylic tibial plateau • 1973 – Total condylar prosthesis
- 3. Prosthetic Design • Femoralrollback – Posterior translation femur with flexion – Controlled by PCL – Improves Quad function and knee flexion
- 4. Prosthetic Design Modularity • Augmentationof standard prosthesis Metal base plate + Poly Metal augment - bone loss Femoral/ tibial stem
- 5. Prosthetic Design • Constraint –Ability of prosthesis to provide varus – valgus and flexion –extension stability in presence of ligamentous laxity / bone loss
- 6. Prosthetic Design • Cruciateretaining prosthesis (CR) • Cruciate sacrificing prosthesis (CS) • Varus – valgus constrained • Hinged prosthesis • Total condylar Prosthesis
- 7. Prosthetic Design Cruciate retaining •Intact PCL Varus def. < 10 Valgus def. < 15 • Advantage 1. Avoid post cam impingement/ dislocation 2. More closely resembles knee kinematics 3. Bone preserving 4. Improved proprioception • Disadvantage 1. Tight PCL – Increased poly wear 2. Rupture PCL – flexion instability
- 8. Prosthetic Design Cruciate stabilized •Cam and post mechanism • Insert more congruent / dished Advantages Easier to balance knee More range of motion Disadvantages Cam jump Post wear Patellar clunk syndrome Additional cut from distal femur ABSOLUTE INDICATION •Previous patellectomy •Inflammatory arthritis •Deficient PCL
- 9. Cruciate sacrifice /retain - Evidence • PS increased ROM – No functional improvement • No difference in ROM between PS and CR • PCL does not work in CR knees • Increased wear Ps knee – cam & post Cochrane review – No difference in function whether cruciate retained or sacrificed
- 10. Prosthetic Design Semiconstrained design •No axle connecting tibia and femur • Large tibial post and deep femoral box • Varus / valgus stability • Rotational stability More femoral resection Early loosening – increased constrained INDICATIONS MCL/ LCL attenuation Flexion gap instability
- 11. Prosthetic Design Constrained Hingeddesign • Linked femoral and tibial components • Tibial bearing rotates around yoke Aseptic loosening Large amount bone resection INDICATION Global ligamentous deficiency Hyperextension instability
- 12. Prosthetic Design Mobile BearingDesign • Poly Rotates over tibial base plate • Reduced poly wear • Bearing spin out
- 13. Fixed Bearing ormobile bearing - Evidence • No advantage of mobile bearing over fixed bearing • Increased wear in undersurface of mobile bearing
- 14. Prosthetic Design Hi flexdesign • Cultural / pt expectation • Cut more posterior condyle Preop flexion - most significant - Gatha etal 2008 No difference in ROM - Mehin JBJS 2010 No difference in ROM Sumino Int Ortho 2010
- 15. Radiographs • Standing Ap& Lateral • Sunrise – Merchant view • Hip to ankle x- rays – Bony deformity – Short stature ( < 150 cm) – Very tall ( > 190 cm)
- 16. Radiographs • Femoral andtibial cut • Position of femoral canal entry • Bone defects • Joint subluxation • Ligament stretch out – Varus Thrust • Ligament release • Constraint needed
- 17. Approaches • Multiple incision– choose lateral incision • Previous transverse incision – cross at right angles
- 18. Approaches Medial parapatellar approach •Most common • Surgeon are familiar
- 19. Lateral parapatellar approach •Valgus knee • Allows access to lateral side • Technically demanding • Medial patellar eversion difficult
- 20. Midvastus approach • SparesVMO insertion • Advantages Accelerated rehab. Improved patellar tracking • Disadvantages Less extensile Difficult in obese & flex contracture
- 21. Subvastus approach • Vastusmedialis lifted off Lateral intermuscular septum • Advantages Intact quad Preserved vascularity of patella • Disadvantage Least extensile Denervation of VMO possible
- 22. Extensile Exposure • Quadsnip • VY turndown • Tibial Tubercle osteotomy
- 23. Technical Goals • Restoremechanical alignment • Restore joint line • Balanced ligaments • Normal Q angle
- 24. Femoral Cut • Valguscut angle • AAF – MAF • Between 5 – 7 deg • Intramedullary guide
- 25. Tibial Cut • Anglebetween AAT – MAT • Tibial cut angle- Zero • Tibial deformity – cut perpendicular to MAT • Intra or extramedullary guide
- 26. Joint line preservation •Inserting prosthesis prosthesis same size as removed bone and cartilage • Elevate joint line – mid flexion instability Abnormal patellofemoral tracking Equivalent to Patella Baja • Lowering joint line Lack of full extension
- 27. Knee Balancing • Balancein Coronal and saggital plane • Concave side – ligaments contracted – release • Convex side – ligaments stretched – Fill gap
- 28. Varus Knees HenriK Schroeder– Boesch – Ligament balancing in TKR
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- 31. Grade 2 release •Grade 2B release Posterior part tight in extension Anterior part tight in flexion
- 32. Grade 3 release •Grade 2A + 2B
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- 34. Valgus deformity • Osteophytes •Lateral capsule • Iliotibial band - Tight in extension • Popliteus – Tight in flexion • LCL
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- 37. Flexion contracture • Osteophytes •Posterior capsule • Gastrocnemius ( Medial and lateral head) • Inreased distal femoral cut
- 38. Sagital plane balancing •Mc Pherson’s rule Symmetric gap – address tibia Asymmetric gap – address femur
- 39. Tight in Extension Tightin flexion Symmetric gap Cut more tibia Loose in Extension Loose in Flexion Symmetric gap •Thicker poly •Tibial Metal augmentation
- 40. Extension good Loose inflexion Asymmetric gap 1. Increase size femoral component 2. Translate femoral component posterior 3. Use thicker poly and readdress as tight extension gap
- 41. Extension Tight Flexion Good AsymmetricGap 1. Cut more distal femur 2. Release posterior capsule
- 42. Extension Good Flexion Tight Asymmetricgap 1. Decrease femoral component size 2. Recess PCL 3. Check slope of tibia
- 43. Extension Loose Flexion Good Asymmetricgap 1. Distal femoral augmentation 2. Decrease femoral component size and thicker poly
- 44. Patellofemoral alignment • Mostcommon complication • Maintain Q angle • Proper component rotation • Maintain normal patellofemoral tension
- 45. • Maintain Qangle Avoid 1. Int rotn fem component 2. Medial fem component 3. Int rotn tibia 4. Patella prosthesis lateral
- 46. Femoral component rotation •Ap Axis ( whiteside line) • Transepicondylar axis • Post condylar axis • Tibial alignment axis • Gap balance
- 47. Tibial component • Introtn tibia – increased Q angle
- 48. Patellar component • Centreor medialized • Avoid lateralizing • Increases Q angle and cause patella maltracking
- 49. Patella Baja • Patellarcomponent superior • Lower joint line • Transfer tibial tubercle cephalad • Patellectomy
- 50. Patella resurfacing vsnon resurfacing • Resurfacing – Component loosening – Clunk – Fracture – AVN • Non resurfacing – Anterior knee pain – May require second resurfacing
- 51. Patellar resurfacing Vsnon resurfacing - Evidence • Metal backed patella higher complications • Patellar replacement does not gurantee painless Patellofemoral joint • No significant benefit of patellar replacement
- 52. Complication • Femoral notch Sawcuts into anterior femoral cortex Increases chance of periprosthetic fracture Femoral stem extension
- 53. Complication • Peroneal Nervepalsy ( .3 to 2 %) Pre op Flexion and Valgus def Tourniquete time > 120 min. Epidural anaesthesia post op Aberrant retractor placement EMG & NCV at 3 months Nerve decompression at 3 months
- 54. Complication • Vascular complication( <.17% - .2%) • Risk factor – Sharp dissection – Posterior retractor placement – Pre existing vascular disease – Immediate vascular repair
- 55. Complications • Extensor mechanismrupture ( .17% - 2.5% ) – Direct repair with suture - < 30 % avulsion – Primary repair and augment with graft – Allograft repair
- 56. Complications • Stiffness – Flexioncontracture 10 – 15 % deg – Flexion < 90 deg • Treatment – Manipulation under Anaesthesia – Arthroscopic lysis of adhesion – Revision TKR
- 57. Complications • Hypersensitivity Rare (nickel) • Patch testing • Lymphocyte transformation test • Revise to non allergic metal prosthesis
- 58. Summary • Choose correctpt • Plan properly • Adequate exposure • Follow principles to align and balance knee • Meticulous closure Hope for the best because 20 % of pt. with well performed TKR are not happy !!
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