Use of a four pin and methylmethacrylate fixation in L7 and the iliac body to stabilize lumbosacral fracture-luxations: a clinical and anatomic study

Objectives— To describe the clinical outcome of a 4 pin lumbosacral fixation technique for lumbosacral fracture–luxations, and to refine placement technique for iliac pins based on canine cadaver studies.
Study Design— Retrospective and anatomic study.
Sample Population— Dogs (n=5) with lumbosacral fracture-luxations and 8 cadaveric canine pelvi.
Methods— Lumbosacral fracture–luxations were stabilized with a 4 pin (positive-profile threaded) and bone cement fixation. Caudal pins were inserted in the iliac body and cranial pins were inserted into the L7 or L6 pedicle and body. Follow-up examinations and radiographs were performed to assess patient outcome. Intramedullary pins were inserted into the iliac bodies of 8 cadaver pelvi. Radiographs were taken to measure pin insertion angles and define ideal insertion angles that would maximize pin purchase in the ilium.
Results— Follow-up neurologic examination was normal in 4 dogs. Radiographic healing of the fracture was evident in 5 dogs. One implant failure occurred but did not require re-operation. For cadaver iliac pins, mean craniocaudal insertion angle was 29° and mean lateromedial insertion angle was 20°.
Conclusions— Four pin and bone cement fixation effectively stabilizes lumbosacral fracture luxations. The iliac body provides ample bone stock, which can be maximized using an average craniocaudal pin trajectory of 29° and an average lateromedial pin trajectory of 20°.
Clinical Relevance— Lumbosacral fracture–luxations can be stabilized with 4 pin and bone cement fixation in the lumbar vertebrae and iliac body, using 29 and 20° as guidelines for the craniocaudal and lateromedial pin insertion angles in the ilium.