Step 14a - The Patella.

The soft tissue attachments at the periphery of the patella are incised to expose the insertions of the quadriceps and patella tendons. The lateral patello-femoral synovial fold is incised and released close to the femur avoiding the geniculate arteries. An important release of the lateral retinaculum is performed on the lateral margin of the patella from the proximal quadriceps tendon down to the distal patella tendon. Sufficient release should be performed so that the patella moves freely both medially and laterally. (A sub-periosteal Peri-patella release).

Step 14b

The height of the patella is measured with the callipers. (Measurement A). Allowance is made for the patella wear.The patella cutting guide is positioned so that after allowing for the worn bone and cartilage, between 6mm and 11mm is removed.This is equivalent to the thickness of the prosthesis and should correctly restore the patella hight.

Step 15a

An oscillating saw is used to make the cut and the residual bone thickness checked with the Callipers . A minimum of 12mm of patella bone should always be left after the resection, and it should be no thicker than 15mm to prevent overstuffing. (Measurement B, step 14b). In very small patients the patella bone can be reduced to 10 mm with use of the extra small patella which has shorter pegs.

Step 15b

Apply and centralise the Patella Drill Template and drill the three peg holes. The appropriate patella trial is inserted (extra small, small, medium, large) and the restored height is checked (Measurement C, Step 14b). The thickness of the patella prostheses are: Extra Small 8.5mm, Small 9mm, Medium 9.5mm and Large 10mm.