May 29, 2013

MatrixRIB - Minimally Invasive Plate Osteosynthesis

Paul Barbosa, Mark Lee

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Although some rib fractures are treated with pain management and bracing, as well as endotracheal intubation and mechanical ventilation, if necessary, some patients could further benefit from surgical stabilization (osteosynthesis). The potential benefits of surgical stabilization of fractures include reduced duration of mechanical ventilation support, shortened ICU stays and hospitalization, better secretion management through efficient coughing, and minimized chest wall deformities resulting from trauma.

Furthermore, studies have demonstrated increased morbidity in patients with rib fractures after blunt trauma, not only in elderly patients, but in those as young as 45-years-old presenting more than four rib fractures. These severe injuries increase the risk of adverse outcomes, including inhospital mortality.

Now, the Thorax Surgery Working Group, also within the AOTK System, has continued the development of the system, which focuses on implants and instruments to provide a minimally invasive plate osteosynthesis solution for rib fixation.

The Matrix Rib Fixation System (indicated for the fixation and stabilization of rib fractures, fusions, and osteotomies of normal and osteoporotic bone), was developed in 2009 under the guidance of cardiothoracic and plastic surgeons within the CMF branch of the AOTK System (Fig 1).

Minimally Invasive Plate Osteosynthesis instrumentation has been developed to support less invasive approaches for rib fracture stabilization by extending their reach without the need to extend incision size in challenging access areas (eg, higher rib levels and subscapula fractures).

Specifically devised for this procedure, large Plate Holding Forceps (Fig 2a) aid to initially secure the plate to the fractured rib. An upright version of the forceps improves visibility while its ball tip design, centered in the plate screw hole, helps to hold the plate-rib construct in place.

A trocar with universal handle and its related instruments such as a cannula (Fig 2a and b) and a 2.2 mm threaded drill guide for MatrixRIB locking plates, are intended to be used in combination with the appropriate size drill bit with stop for a safe drilling when reaching the rib's second cortex. The drill guide can be threaded to the locking plate through the cannula to ensure a perpendicular entry and precision in terms of concentric drilling in the plate hole. This benefits later screw insertion, especially for the second and third screws, where there is no longer a margin for plate mobility to adjust centering. The angled tissue reduction forceps (Fig 2b) can be clamped to the trocar cannula (Fig 3), allowing soft tissue manipulation and improved visibility.

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Fig 2 a-b: Minimally Invasive Plate Osteosynthesis with plate holding forceps, trocar with universal handle, and angled tissue retractor forceps (a) and upright forceps and trocar with universal handle (b)
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Fig 3: Angled tissue retractors clamped to the trocar cannula

Alternatively to reduction forceps, the new Threaded Reduction Tool (TRT) (Fig 4a) is a useful instrument to nicely reduce and hold the rib as well as distract fractures through a small incision. It can be attached to a power tool with AO coupling (Fig 4b). Introducing it through the trocar drill guide, which is itself threaded to the plate, it allows to engage the rib thanks to its self-drilling end with a maximum insertion stop of 15 mm (instructions reflected in the technique guide must be followed to limit the insertion to patient's rib thickness and to avoid injuries). Once the power tool has been removed, rib fracture reduction is achieved by tightening the TRT reduction nut (Fig 4c and d). Later, a 2.9 mm locking screw can be inserted in the same screw hole after TRT removal. A limitation for using this tool is the bone quality of the patient.

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Fig 4 a-d: Threaded Reduction Tool instrumentation (a), Threaded Reduction Tool attached to a powertool (b), and Threaded Reduction Tool through drill guide tightening reduction nut for fracture reduction (c-d)

Drill guides with multiple angle options and flat head (Fig 5a) were designed to allow engaging and holding the desired plate hole (Fig 5b), as well as to perform a controlled drilling. Dedicated drill bits to be used with the 90 screw driver handle (Fig 5c) have limited drilling depth to ensure a safe drilling (Fig 5d). This concept used with the 90 screw driver blades with self-retainer features (Fig 5e) aids reaching inaccessible fractured areas, including the end holes of the rib plates, thanks to the notches at both ends of the guiding groove.

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Fig 5 a-b: Drill guide with flat head and multiple angle options (a) and drill guide with flat head aligned to the plate (b)
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Fig 5 c: Drill guide and 90 screwdriver
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Fig 5 d-e: The 90 screw screwdriver/drill.

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