29/03/2007
AO Technical Commission Approved

Headless Compression Screw (HCS) 3.0 mm

Intraarticular fractures (eg, scaphoid fractures) are best fixed with implants which can be countersunk under the bone surface for protection of the joint surface and adjacent soft tissues. Existing headless screws can be placed below the bone surface but offer only limited control of interfragmentary compression. The 3.0 mm cannulated screw with threaded washer can be used as a lag screw whilst being placed below the bone surface. It provides good interfragmentary compression, but has the disadvantage of a large head diameter which makes it difficult to use in small bones (eg, proximal pole fractures of the scaphoid). The new 3.0 mm Headless Compression Screw has a similar shaft size when compared to 3.0mm cannulated screws, but a smaller head diameter. Unlike other headless screws, the HCS is applied as a lag screw, which allows the surgeon to control closure and the degree of closure of the fracture gap.

The 3.0 mm HCS is indicated for fractures and nonunions, arthrodeses, bunionectomies, and osteotomies of small bones. The use of the Headless Compression Screw in heavily porotic bone is not recommended because of insufficient thread purchase and the likelihood of loss of stable fixation.

The main feature of the HCS system is the control of closure and compression of a fracture gap, which is achieved by means of the compression sleeve. Once the desired compression is achieved, the screw is advanced into the bone using the screwdriver, and the head is sunk.

The leading and trailing threads of the HCS both have the same pitch. This is to ensure that controlled compression can only be applied by means of the compression sleeve. The trailing thread has a double-start to ensure that the compression sleeve attaches to the trailing thread more readily. The cannulation of the screw allows minimally invasive insertion, as well as more accurate placement of the drill bit and, therefore, the screw. The leading thread tip is self-drilling as well as self-cutting. The trailing thread is also self-cutting. The screw is available in stainless steel and titanium. In addition, there are short and long thread screws to provide extra stability in larger bone fragments. The short threaded screws come in lengths from 1030 mm in 1 mm increments and from 3040 mm in 2 mm increments. The long thread screws come in lengths from 1630 mm in 1mm increments and from 3040 mm in 2 mm increments.

Acute scaphoid fracture treated percutaneously with the 3.0 mm HCS
a preop AP
b intraop AP
c 2 wks obl

Case provided by D Campbell, Leeds

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