DePuy Synthes
9
Preoperative screw-length selection using an AP
radiograph
To select the proper screw length for the condyle, it is possi-
ble to perform a preoperative x-ray with the 50 mm wide
calibrator and to use the table below.
1. Place the x-ray calibrator medially or laterally at the height
of the condyle.
2. Take an AP radiograph of the distal femur.
3. Measure the width of the x-ray calibrator (XRC) on the
radiograph.
4. Measure the maximum condyle width (MCW) on the
radiograph.
5. Determine the real condyle width (RCW).
6. Determine the screw lengths for the screw holes A to G
using the table below. The positions A to G are indicated
on the x-ray template and on the LISS DF insertion guide.
Length of locking screws (mm)
RCW =
50
XRC
⫻
MCW
Real condyle
width (RCW)
60 – 80 mm
81 – 87 mm
88 – 95 mm
96 –110 mm
Hole
A
65
75
75
85
Hole
B
40
40
55
65
Hole
C
40
55
65
75
Hole
D
55
65
65
75
Hole
E
65
75
75
75
Hole
F
65
75
75
85
Hole
G
55
65
75
85
