Cannulated Screw System CSS+
Michael Swords, Tim Schepers, Matthew Tomlinson, Andrew Sands
Cannulated screws are commonly used by orthopedic surgeons for the fixation of multiple fracture patterns and bone reconstructions. The screw cannulation allows placement over a guidewire to facilitate better accuracy before drilling or screw insertion. The use of cannulated screws adopts the principles of interfragmentary screw fixation and aims to optimize screw position.
In December 2021 the AO Trauma Technical Commission approved the Next Generation Cannulated Screw System Plus (CSS+) which was designed and developed by the Foot and Ankle Expert Group in collaboration with the AO primary industrial partner, DePuy Synthes.
Ranging in diameter from 2.0–7.5 mm (with 0.5 mm diameter increments from 2.0– 4.5, and 1.0 mm increments from 5.5–7.5), the color-coded screws are available in titanium with short and long partial thread as well as fully threaded (Fig 1). All implants are available in sterile and non-sterile packaging. Color-coded washers are available for every screw size (Fig 2).
The Next Generation Cannulated Screw CSS+ is indicated for use in bone reconstruction, osteotomy, arthrodesis, joint fusion, fracture repair, and fracture fixation of bones appropriate for the size of the device. Color-coded instrumentation corresponding to its color-coded screw promotes ease of use and implantation (Fig 3).
In response to a clinical need for improved cutting performance the new and patented cannulated screw tip reduces the axial load needed to advance the screw; thereby achieving a more precise insertion with less, or no need for, pre-drilling and tapping (Fig 4).
The common problem of guidewire deflection was addressed with new cobalt chrome (CoCr) guidewires which provide a 29% higher bending stiffness compared with their stainless-steel counterparts. This ensures a straighter path and maintenance of the intended screw trajectory on insertion (Fig 5).
The system is neatly divided into preconfigured sets—small, medium, and large. These sets house separate screw racks and instrument trays according to size that is designed to provide efficiency in the operating room supply sourcing (Fig 6):
Small set: 2.0, 2.5, 3.0, 3.5, and 4.0 mm screws
Medium set: 4.5 and 5.5 mm screws
Large set: 6.5 and 7.5 mm screws
Large trauma set: 6.5 and 7.5 mm screws and long instruments specific for trauma use
Basic instruments in the sets are size appropriate and include guidewires, drill bits, drill guides, countersinks, measuring devices, screwdrivers with handles, and drive adaptor for power insertion. Additional instrumentation is provided for the medium set and large set trays which includes tissue protectors, guidewire sleeves, long drill bits, countersinks, screwdrivers, and guidewires. Three ergonomic screw handles are included in the set. Unique to the large trauma set (6.5 and 7.5 mm cannulated screws) is the inclusion of multiple and adjustable wire guides for accurate guide wire placement (Fig 7).
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