Primary total knee arthroplasty

1. Primary Total Knee Arthroplasty Jatinder S. Luthra MS DNB MRCS

2. Historic Evolution 19 th century – Soft tissue interposition 1950 Walldius Hinged knee replacement 1960 MacIntosh & McKeever Acrylic tibial plateau 1973 – Total condylar prosthesis

3. Prosthetic Design Femoral rollback Posterior translation femur with flexion Controlled by PCL Improves Quad function and knee flexion

4. Prosthetic Design Modularity Augmentation of 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 Cruciate retaining 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 Avoid post cam impingement/ dislocation More closely resembles knee kinematics Bone preserving Improved proprioception Disadvantage Tight PCL – Increased poly wear 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 Hinged design 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 Bearing Design Poly Rotates over tibial base plate Reduced poly wear Bearing spin out

13. Fixed Bearing or mobile bearing - Evidence No advantage of mobile bearing over fixed bearing Increased wear in undersurface of mobile bearing

14. Prosthetic Design Hi flex design 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 and tibial 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 Spares VMO insertion Advantages Accelerated rehab. Improved patellar tracking Disadvantages Less extensile Difficult in obese & flex contracture

21. Subvastus approach Vastus medialis lifted off Lateral intermuscular septum Advantages Intact quad Preserved vascularity of patella Disadvantage Least extensile Denervation of VMO possible

22. Extensile Exposure Quad snip VY turndown Tibial Tubercle osteotomy

23. Technical Goals Restore mechanical alignment Restore joint line Balanced ligaments Normal Q angle

24. Femoral Cut Valgus cut angle AAF – MAF Between 5 – 7 deg Intramedullary guide

25. Tibial Cut Angle between 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 P atella Baja Lowering joint line Lack of full extension

27. Knee Balancing Balance in 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

29. Grade 1 release

30. Grade 2 release Grade 2A

31. Grade 2 release Grade 2B release Posterior part tight in extension Anterior part tight in flexion

32. Grade 3 release Grade 2A + 2B

33. Grade 4 release

34. Valgus deformity Osteophytes Lateral capsule Iliotibial band - Tight in extension Popliteus – Tight in flexion LCL

35. Pie crusting

36. Flexion contracture Osteophytes Posterior capsule Gastrocnemius ( Medial and lateral head) Inreased distal femoral cut

37. Sagital plane balancing Mc Pherson’s rule Symmetric gap – address tibia Asymmetric gap – address femur

38. Tight in Extension Tight in flexion Symmetric gap Cut more tibia Loose in Extension Loose in Flexion Symmetric gap Thicker poly Tibial Metal augmentation

39. Extension good Loose in flexion Asymmetric gap Increase size femoral component Translate femoral component posterior Use thicker poly and readdress as tight extension gap

40. Extension Tight Flexion Good Asymmetric Gap Cut more distal femur Release posterior capsule

41. Extension Good Flexion Tight Asymmetric gap Decrease femoral component size Recess PCL Check slope of tibia

42. Extension Loose Flexion Good Asymmetric gap Distal femoral augmentation Decrease femoral component size and thicker poly

43. Patellofemoral alignment Most common complication Maintain Q angle Proper component rotation Maintain normal patellofemoral tension

44. Maintain Q angle Avoid Int rotn fem component Medial fem component Int rotn tibia Patella prosthesis lateral

45. Femoral component rotation Ap Axis ( whiteside line) Transepicondylar axis Post condylar axis Tibial alignment axis Gap balance

46. Tibial component Int rotn tibia – increased Q angle

47. Patellar component Centre or medialized Avoid lateralizing Increases Q angle and cause patella maltracking

48. Patella Baja Patellar component superior Lower joint line Transfer tibial tubercle cephalad Patellectomy

49. Patella resurfacing vs non resurfacing Resurfacing Component loosening Clunk Fracture AVN Non resurfacing Anterior knee pain May require second resurfacing

50. Patellar resurfacing Vs non resurfacing - Evidence Metal backed patella higher complications Patellar replacement does not gurantee painless Patellofemoral joint No significant benefit of patellar replacement

51. Complication Femoral notch Saw cuts into anterior femoral cortex Increases chance of periprosthetic fracture Femoral stem extension

52. Complication Peroneal Nerve palsy ( .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

53. Complication Vascular complication ( <.17% - .2%) Risk factor Sharp dissection Posterior retractor placement Pre existing vascular disease Immediate vascular repair

54. Complications Extensor mechanism rupture ( .17% - 2.5% ) Direct repair with suture - < 30 % avulsion Primary repair and augment with graft Allograft repair

55. Complications Stiffness Flexion contracture 10 – 15 % deg Flexion < 90 deg Treatment Manipulation under Anaesthesia Arthroscopic lysis of adhesion Revision TKR

56. Complications Hypersensitivity Rare ( nickel) Patch testing Lymphocyte transformation test Revise to non allergic metal prosthesis

57. Summary Choose correct pt 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 !!

58. THANK YOU