3.5 mm Intrapelvic Acetabular System
Michael D Stover, Jorge D Barla, Robin E Peter, Ramesh K Sen, David Stephen
Fig 1: Acetabular plate in the small, extended version shown on a bone model with fracture pattern (black) and screw trajectories (gray). Due to demographics and an increasingly aging population, pelvic fractures are becoming highly relevant for society and the healthcare system. Moreover, with a shift from nonoperative to operative treatment, the number of surgical procedures worldwide is expected to grow by more than 30% [1, 2]. Nowadays, sustained physical or even sports activity is an inherent factor of the quality of life in this population. Consequently, medium- to low-energy fractures, such as pelvic ring or acetabulum fractures, are more frequent.
Similarly, there are trends within acetabulum fractures of the elderly to include specific fracture patterns and their variants. These include associated both column fractures, anterior column posterior hemitransverse, and anterior column variants. These fracture patterns will have fracture components that include the quadrilateral surface and a portion of the adjacent joint. Screw fixation alone may not be sufficient in some of these patterns because of bone quality. A plate applied to the quadrilateral surface may be required.
These trends define a need for new intrapelvic acetabular devices to be used for stabilization of these acetabular fractures. The possibility to deploy such new devices while using less invasive surgical approaches is of significant benefit to more fragile patients. The solution is to provide a biomechanically sound implant set that can be adjusted intraoperatively to match the patient's anatomy. Further, a new complete set of instruments including plate trials and plateholders, retractors, reduction forceps, benders, and tools for screw insertion will provide superior ease of use compared with other available solutions.
The system was designed taking into consideration the increasing popularity of the anterior intrapelvic approach and techniques for plate fixation of these fracture types. Emphasis was put on reducing surgical complexity.
The 3.5 mm intrapelvic acetabular plating system offers four anatomically precontoured plates per side to address fracture and patient variation. For each side these include a small and large sized plate in standard and extended version. Implants are provided in sterile packaging and are manufactured exclusively from stainless steel.
The plate offers superior anatomical fit. An extended version includes an additional posterior screw hole, with the posterior tail of the plate extending lateral to the sacroiliac joint. The plate provides contourable quadrilateral surface extension with improved screw anchorage options in the sciatic buttress, ischium, and posterior column.
Angulated screw holes allow for an engagement with the protection sleeve used for placing screws. Recesses on the outer contour of the plate allow for flexibility when placing additional screws outside the plate.
Fig 2: The acetabular plate in large size and extended version with an additional posterior screw hole. References
- Rinne PP, Laitinen MK, Huttenen T, et al. The incidence and trauma mechanisms of acetabular fractures: a nationwide study in Finland between 1997 and 2014. Injury. 2017 Oct;48(10):2157–2161.
- United Nations, Department of Economic and Social Affairs, Population Division. In: World Population Prospects: The 2017 Revision, Key Findings and Advance Tables. Working Paper No. ESA/P/WP/248. New York: United Nations; 2017.
Reduction of the system's complexity has also been addressed with new and updated instruments and retractors, designed to ease exposure, plate, and screw insertion.
Specific radiolucent retractors were designed for superior pubic ramus, iliac fossa, and quadrilateral surface. Each offers a method to help maintain retractor position without interfering with the placement of the acetabular plate. The QS retractor includes a channel for the attachment of an optional light strip.
Fig 3: Acetabular plate together with retractors. Maintaining the QS retractor's position is facilitated by its notched tip, whereas the other retractors are held in place using K-wires. New reduction instruments provide a longer working length compared with standard low-profile pelvic sets. Pointed reduction forceps are offered in right, left, and straight versions. Ball-spiked reduction forceps and ball-spiked pushers can be used with optional spiked discs, if necessary.
Fig 4: New set of reduction instruments with ball-spiked tips and optional spiked plate extensions in circular and rectangular shapes. A plateholder provides a stable connection to the plate or sizing trials, which are included in small and standard size and for the left and right sides. They ensure that the most suitable plate size is identified to fit the patient anatomy and the fracture pattern. For additional adjustments, ex-situ and in-situ bending instruments allow the surgeon fine-tuning implants to optimize bone-plate contact.
Fig 5: Plate holder with locking mechanism, providing a stable connection while maintaining the required flexibility for plate positioning. Screw insertion is facilitated by an innovative through-plate screw insertion concept to reduce the potential of soft-tissue exposure to the drill and the risk of losing a screw or its trajectory. Drilling, measuring, and screw insertion is done through one single sleeve. A dedicated measuring device, drill bits, drill guides, and 2.5 hex/T15 screwdrivers support the process of screw insertion.
Fig 6: Screw insertion using the multi-purpose sleeve and an innovative through-plate insertion concept to prevent soft-tissue damage. 
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