The sacrum, a small triangle-shaped bone between the iliums, links the pelvis to the spine via the sacroiliac joints. Sacroiliac luxation or fracture (SIL/F) is often seen in pets after road traffic accidents. Most commonly, SIL/F repair surgery involves gluteal dissection and displacement of the ilium so the surgeon can see the sacrum and drill a hole through it. The joint is then put back into place and a screw is used to reattach the ilium to the sacrum. This approach, known as open reduction and internal fixation (ORIF), while regularly successful, is complicated and often results in poor screw placement that could lead to complications.

“A lot of dogs with SIL/F are not operated on because of the surgical complexity and fear of complications. Many dogs are simply ‘cage rested,’ which needlessly prolongs recovery and discomfort,” explains Dr. Loïc Déjardin, professor and head of orthopedic surgery for the Department of Small Animal Clinical Sciences.
Fifteen years ago, a minimally invasive procedure was proposed to improve screw placement accuracy and reduce complications. Here, the joint is reduced from the outside under fluoroscopic guidance, then kept in place by an assistant or with a temporary pin through the ilium and into the sacrum. A small gluteal incision allows the surgeon to insert an iliosacral screw to secure the joint in place. While this technique is somewhat more reliable than ORIF, maintaining accurate screw orientation is challenging. Also, the surgery must be done using intraoperative radiography, which exposes the surgical team to ionizing radiation.

To overcome these shortcomings, Déjardin has invented a new surgical technology to repair SIL/F in small animals. The sacroiliac luxation instrument system (SILIS) allows accurate and reliable screw placement while eliminating radiation hazard to the surgical team.

“This novel instrumentation and surgical technique has allowed our team to be more precise, more consistent, and faster in treating SIL/F than ever before. The procedure is easier and safer for the surgical team who is not exposed to dangerous radiation,” Déjardin says.
 
The SILIS consists of three components: 1) six-axis arms that can be deployed in any direction, then locked in place, 2) reduction handles to manipulate bones, and 3) a minimally invasive lucent aiming device (MILAD) attached to another arm for accurate screw positioning. The surgeon couples the reduction handle(s) and MILAD to their respective arms, reduces the SIL/F, moves the MILAD over the sacrum, and then locks the arm(s). With everything secured, the surgical team moves away, avoiding exposure to deleterious radiation, while radiographs are taken to check reduction and MILAD location and orientation.
 
“The MILAD acts like a scope on a rifle,” Déjardin says. “It allows the surgeon to accurately orient the screw very quickly. Because everything is locked into place, confirmation radiographs can be taken without the surgeons in the OR.”

Traditional surgery takes about one to two hours. Déjardin’s invention has cut that time to 10 to 20 minutes at most while improving accuracy, reducing patient morbidity, and eliminating exposure to radiation.