Step 16

The patella is reduced and the tracking checked to assess stability of the patella in the femoral groove while the knee is flexed through 120 degrees.The medial facet of the patella should be in contact with the femur throughout the range of movement.The ‘rule of no thumb’ is applied by ensuring that tracking is stable without pressure from the thumb. If tracking is not perfect further release of the retinaculum from the edge of the patella should be performed.The stitch test helps to judge the patella tracking. If there is persistent mal-alignment of the patella then it may be necessary to consider bony or soft tissue realignment using the Roux or Elmslie techniques. If this is felt to be inadvisable then the surgeon should proceed to a total joint replacement which will allow correction of tibial rotation.

Step 17

Once satisfactory tracking has been confirmed, bone cement is applied to the cut anterior femoral surface and the patella, using a cement gun (with an oblique cut to the nozzle) to pressurise the cement.
The Femoral Impactor and Patella Clamp are used to seat the femoral and patellar prosthesis. The inferior stud of the femoral component is inserted first. The prosthesis is punched into position in the line of the long axis of the femur. The angle is then increased to 30º, then to 70º and finally to 90º with the second flat surface of the punch. A final check of satisfactory patella tracking is made and the wound is closed in the usual way.
Ensure there is no edge impingement of the medial border of the patella on the femoral condyle at 120º flexion.The flat odd facet of the button should present a smooth surface at this point.

• Patients over   
• Patients
• Patients
• Patients under   
• Patients under   

5 ft 10"
5 ft 6" to 5 ft 10"   
5 ft 2" to 5 ft 6"   
5 ft 2"
4 ft8"

(1m78)
(1m68 - 1m78)   
(1m58 - 1m68)   
(1m58)
(1m48)

Large
Medium
Small
Extra Small
Custom made prothesis

This gives some guide to sizing. There will be overlaps between the different sizes.