BACKGROUND
Cementless cups are routinely employed in resurfacing and total hip arthroplasty. The acetabular component fixation is by interference fit, which can have the option of screw fixation. The use of screws can potentially compromise neurovascular structures around the pelvis.1,2 The use of the pelvic quadrant system1,3,4 provides the surgeon with the safe areas for placement of screws. The postero-superior and the postero-inferior quadrants have been shown to be safe and also provide the maximum screw purchase.1,3,4 Most instrumentation sets employ a fixed angle drill guide for the placement of the acetabular screws. This can make screw placement technically difficult in sockets with reduced access due to small incisions, depth of acetabulum or a relatively closed cup position. If the screw is inserted at an oblique angle, the head of the screw remains prominent and can obstruct the insertion of the liner, damage the polyethylene liner, break the ceramic liner and cause subluxation of the ceramic or metal liner.
TECHNIQUE
We describe a simple variable angled drill guide (Fig. 1), which allows the screw to be placed in a wide range of angles from 120° to 160° (Figs 2 and 3). It consists of a handle with a drill guide. The attachment of the drill guide allows for variable angles to be set by the use of a ratchet (Fig. 1). Thus, the angle of the drill guide can be varied to allow safe and accurate screw insertion.
Figure 1.
Variable angled guide.
Figure 2.
Variable angled guide at 120°.
Figure 3.
Variable angled guide at 160°.
DISCUSSION
This novel and simple device allows ease of placement of screws and enables the surgeon to utilise the safe quadrants with the maximum bony purchase and accurate seating of the liner within the cup.
References
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