1. In the name of GOD

2. Patellofemoral joint in Total Knee Arthroplasty
M. Mardani Kivi
Guilan University of Medical Sciences

3. Poursina Hospital

4. Anatomy Patella is the largest sesamoid bone in the body.
Patella has the thickest articular cartilage of any of the joints:
Depth of articular cartilage  6-10 mm .
Overall thickness of patella  mm .

5. Anatomy
Thickness of less than 15 mm is relative contraindication for resurfacing patella and a thickness of 18 mm or more usually is considered safe.

6. Anatomy
Patella normally articulate with the distal femur at about 20 degrees of flexion undergoing 7 cm of excursion from extension of full flexion.

7. Anatomy
Patellofemoral contact zones changes with knee flexion

8. Biomechanics
The primary function of the patella is to increase the lever arm of the extensor mechanism around the knee, improving the efficiency of quadriceps contraction.

9. Biomechanics
Extensor lever arm is greatest at 20 degrees of flexion and the quadriceps force required for knee extension increases significantly in the last 20 degrees of extension.

10. Biomechanics Patellofemoral stability Articular surface geometry
Soft tissue remains

11. Biomechanics

12. Biomechanics
Patella provides 50% increase in knee extension strength compared with that after patellectomy.
Patellofemoral joint sustains some of the greatest contact pressures of all the joints of the body.
Normal walking generates 50% body weight joint reaction forces which increase to 8 times body weight for jumping from a small height.

13. Biomechanics Altered biomechanics at the patellofemoral joint
“Anterior Knee Pain”

14. Patellar resurfacing??? There are three approaches:
Relative indications for resurfacing and non-resurfacing
Selective resurfacing
Selective non-resurfacing

15. Relative indications for the patellar resurfacing:
Older age
Ant. Knee pain
Inflammatory arthritis
obesity
female
Hx. Of patellar subluxation
Intra-op. patellofemoral wear
Intra-op. patellar maltracking
Non-anatomic trochlea groove on femoral implant

16. Relative indications for the patellar NON resurfacing
Younger age
Non-Inflammatory arthritis
Thin patients
Thin/hypo-plastic patella
Intra-op. preserved patellar cartilage
Intra-op. congruent patellar tracking
Anatomic trochlea groove on femoral implant

17. Of all the indications for resurfacing, inflammatory arthritis has been the most widely accepted. Most authors have recommended routine resurfacing for all patients with R.A.
Lighter patients ending to do well with un- resurfacing patella.

18. Boyed et al.: retrospective study
Patellofemoral complications (Ant. Knee pain)
4% : Patella resurfacing
12% : patella un-resurfacing

19. Abraham et al.: Prospective study
Bilateral arthroplasty no difference in stair-climbing ability or incidence of anterior knee pain.

20. Barrack et al: randomized prospective study with 10-year follow up
No difference in Ant. Knee pain, functional score or revision rates between resurfaced and un-resurfaced groups.

21. Revisions in resurfaced group Revisions in Non-resurfaced group
Patello-femoral problems
All reasons
No. Knees
Min. F/Up (yr)
Knee implant used
Author 1 2 6
100
6.3
AMK
Bourne et al 40 3
PCA modular
Feller et al
Not specified
Schroeder et al 7 93 5
Miller Galante II
Barrack et al 9 15
198
wood et al 11
474
PFC
Waters
14 (1.5%)
17 (1.8%)
37 (3.9%)
41 (4.3%)
954 (100%)
3.4 (mean)
4 types
Totals
AMK: Anatomic Modular Knee; PFC: Press Fit Condylar; PCA: Porous Coated Anatomic

22. All-polyethylene component Metal-backed component
Implant designs
Inlay design
Onlay design
All-polyethylene component
Metal-backed component

23. Patellar cut
The prosthetic patella should be medialized to approximate the median eminance of the normal patella.

24. Patellar cut

25. Patellofemoral tracking
lateral mal-tracking of the patella
Internal rotation of tibial component
Q angle
Internal rotation of femoral component

26. “No thumb” test of patellar tracking should be used as a guide of patellar instability (before retinacular closure)
If the patella can be subluxated half of its diameter over the medial femoral condyle, the retinaculum is probably not too tight.
Resistance of one or two stitches on the medial side

27. If there is any abnormality in patellofemoral tracking deflate the torniquet and examine again 48% (Marson) or 31% (Husted) it will be normal.

28. Correction should be toward the reason
Correction should be toward the reason. if there is not any component mal-positioning lateral release should be done.

30. Patellofemoral complications
Patellofemoral instability
Patellar fractures
Patellar component loosening ( %)
Patellar clunk syndrome
Patellar tendon rupture (allo-graft Vs. auto-graft Repair)

31. Patellofemoral complications
Treatment  Arthroscopic debridement of nodule.

32. Patelloplasty First step Removal of osteophytes
Smoothing of fibrilated cartilage
Drilling of e burnated bone
First step

33. Patelloplasty Second step
Soft tissue release from lateral aspect of patella
Division of the patellofemoral ligament
Denervation of the patella with electrocautery of the patellar rim
Second step

34. Take home massage
Ant. Knee pain in TKA is usually due to tibial or femural component malrotation not because of patellofemoral joint DJD.

35. With Regards