Complications of the lumbosacral junction in adult deformity surgery. Indications and technique for posterior and anterior revision surgery

Surgical correction of ASD can be challenging. The indication for surgery is individual and after specification of the therapeutic goals, detailed planning of the surgery is essential to achieve a good postoperative result. The reasons for the comparatively high complication rate are well investigated and are often located at the lumbosacral junction. In addition to negative general factors like osteoporosis, especially undercorrection of the sagittal profile and insufficient lumbo-pelvic stabilization are causative. The main indications for revision surgery are a loss of lordosis due to progressive degeneration of the unfused segment L5/S1 or implant loosening and pseudarthrosis of a failed lumbosacral fusion. The goals of revision surgery are restoration of the spinal balance as well as stable fixation and fusion in consideration of the general condition of the patient. Besides osteotomies in a previously fused region, especially reinstrumentation of the lumbosacral region can be challenging, although ala-ilium and ilium screws give the greatest stability. Additional anterior intersomatic cages allow for a better fusion rate, and, moreover they provide better lordozation. Each PLIF, TLIF, and ALIF cage has its own specific advantages. This article summarizes the reasons for complications of the lumbosacral junction after ASD correction and describes surgical principles for revision surgery.