Pitfalls during Sacroiliac Joint Arthrodesis for Patients with Severe Sacroiliac Joint Pain: Report of Three Cases with Sacral Dysmorphism Induced by Lumbosacral Transitional Vertebrae

INTRODUCTION: Lumbosacral transitional vertebrae (LSTV) can cause sacral dysmorphism. Sacroiliac joint (SIJ) arthrodesis has been widely performed as the last resort for severe SIJ pain. We report three kinds of technical pitfalls identified in the surgical records of SIJ arthrodesis for the patients with sacral dysmorphism induced by LSTV. CASE REPORT: For the cases of a 34-year-old man with LSTV Castellvi’s Type IV, anterior SIJ arthrodesis using a plate and screws was performed. The most cranial sacral foramen was larger and irregularly round, and the nerve root ran to the lateral side from the deformed foramen more than usual. A firm medial traction of the nerve root together with the psoas major muscle for the purpose of attaching a plate and inserting screws on the sacrum side could cause the temporary radiculopathy. For a 26-year-old woman with a thin sacral alar due to IIIb, SIJ arthrodesis using multi screws with the posterolateral approach was performed. The most cranial screw penetrated the anterior margin of the sacrum and caused nerve root injury. For a 35-year-old man with Ib, posterior SIJ arthrodesis was attempted using screws and cylinder cages. The insertion of the implants using the posterior approach was technically challenging due to the small size of the sacrum. CONCLUSIONS: Pre-surgical planning for SIJ arthrodesis, including a surgical approach, is particularly important when we see patients with sacral dysmorphism induced by each type of LSTV. The presented surgical pitfalls will be valuable when surgeons perform SIJ arthrodesis for patients with LSTV.