Mechanical complications after spinal instrumentation and fusion, namely pedicle screw loosening, rod or construct fracture, interbody cage subsidence, implant failure secondary to pseudarthrosis, and proximal junctional kyphosis/failure (PJK/PJF) have emerged as a major cause of reoperation in contemporary spine neurosurgery. These failures are multifactorial: they result from an unfavourable bone–implant interface (osteoporosis, steroid use), suboptimal construct design (overly rigid, long thoracolumbar fusions without sacropelvic anchorage, lack of interbody support at L5–S1), and inadequate biology (delayed or absent fusion). Recent guideline-driven approaches from NASS (2024), AO Spine (2025), and EuroSpine (2025) advocate a proactive strategy that starts before the index operation: routine preoperative bone mineral density assessment, short-course anabolic therapy in osteoporotic patients, load-sharing construct design using sacropelvic fixation and multi-rod systems in long fusions, interbody support at the lumbosacral junction, and early radiological surveillance to detect halo or subsidence at a reversible stage.