Minimally invasive lag screw fixation of sacroiliac luxation/fracture using a dedicated novel instrument system: Apparatus and technique description

Abstract

Objective: To describe a novel Sacroiliac Luxation Instrument System (SILIS TM ) and its application in minimally invasive osteosynthesis (MIO) of sacroiliac luxations/fractures (SIL/F). The SILIS was designed to provide stable SIL/F reduction and accurate sacral screw placement while reducing personnel exposure to ionizing radiation during intraoperative fluoroscopy.Study design: Descriptive, proof of concept cadaveric study. Methods:A right SIL and a left SIL/F were created on a Labrador Retriever that had died of natural causes. Bilateral sacroiliac lag screw fixation was performed under fluoroscopic guidance with the SILIS, which consists of dedicated reduction and fixation instruments rigidly linked to table-bound 6-axis arms.Results: Throughout surgery, the SILIS facilitated and maintained stable reduction and allowed accurate placement of a custom designed drill guide over the sacral body without the surgeon's manual holding of any reduction or fixation instruments. The surgical team was therefore able to step away from the C-arm when acquiring fluoroscopic images, thus reducing exposure to radiation. Dorsoventral and craniocaudal screw deviation from an ideal trajectory ranged from 0.98 to 3.88. Both screws were fully located within the sacral body. Conclusion:The SILIS addresses limitations associated with MIO of SIL/F, including maintenance of reduction throughout surgery along with reliable and accurate sacral screw placement. Distance from the X-ray source is the most effective protection against radiation. Use of the SILIS allows the surgical team to move away from the C-arm during fluoroscopy, thereby reducing personnel exposure to dangerous direct and back-scattered ionizing radiation.

Radiation exposure associated with percutaneous fluoroscopically guided lag screw fixation for sacroiliac luxation in dogs

“…The dorsoventral screw angle (DVA) and craniocaudal screw angle (CCA) were measured in the transverse and dorsal planes, respectively. The DVA has previously been defined as the angle between the long axis of the screw and the dorsal plane 12,18 . The CCA has been defined as the angle between the long axis of the screw and the transverse plane 12,18 .…”

“…The DVA has previously been defined as the angle between the long axis of the screw and the dorsal plane 12,18 . The CCA has been defined as the angle between the long axis of the screw and the transverse plane 12,18 . Screws with dorsal angulation for DVA and cranial angulation for CCA were assigned positive screw angles, while ventral and caudal angulation were assigned negative screw angles.…”

“…The pilot hole length to sacral width ratio (PL/SW‐R) was calculated as a surrogate measurement for potential sacral screw purchase 12,18 . The mean sacral width was determined by averaging measurements through the center of the sacral body in both the transverse and dorsal planes.…”

“…Original descriptions of the MIO technique in dogs required that the surgeon hold a drill guide while using fluoroscopy to guide drilling of the pilot hole, exposing surgical personnel to ionizing radiation 7,8 . Methods to mitigate this include using elongated handheld aiming guides or table‐mounted holding arms and aiming devices 18 . In man, surgeons who specialize in trauma and or deformity surgery are exposed to relatively high doses of radiation from intraoperative fluoroscopy, and junior surgeons received higher doses of radiation than senior surgeons 19,20 .…”

Defining a safe corridor for trans‐iliac pin placement in cats

“…SI lag screw placement can be technically challenging and potentially high risk, leading to many specialists preferring intraoperative imaging and novel instruments to improve their accuracy. 19,21,22 Trans-iliac pin placement, however, requires a less extensive surgical approach and fewer orthopaedic tools and has a lower risk of damaging the caudal sacral plexus or penetrating the intervertebral canal due to the smaller diameter of the pin. A trans-iliac pin may be an alternative to SI lag screws; however, a safe corridor for this type of implant has not been defined before.…”