Optimization of PS fixation to improve the bone-screw interface is a key strategy for mitigating implant-related complications in osteoporotic spine surgery. Previous studies have shown that the screw pullout strength is affected not only by BMD but also by screw trajectory, diameter, and length [12,20,21]. The optimal PS trajectory involves positioning the screw within the upper third of the vertebral body in the sagittal plane, aligned parallel to or directed toward the superior endplate, while achieving the highest feasible degree of convergence permitted by the anatomy to enhance pullout strength and resistance to screw loosening [21–23]. PS diameter directly influences its proximity to the cortical bone and the screw-pedicle fill ratio, both of which are critical determinants of pullout strength and resistance to flexion-extension loading [24]. Increasing the screw diameter can substantially improve the mechanical stability of the screw-bone interface, particularly in osteoporotic spines [25]. PS is characterized by distinct inner and outer diameters. A larger outer diameter combined with a smaller core diameter may enhance fixation strength and decrease the risk of screw loosening [26]. Previous studies have also demonstrated that PS length influences resistance to lateral bending and axial rotational loads, as well as the distribution of mechanical stress at the bone-screw interface [24]. The ratio of screw length to vertebral body height is a critical determinant of fixation strength and intravertebral stress distribution, consistent with the principles of lever mechanics [27]. Greater screw depth augments anchorage within the vertebral body, whereas incomplete thread purchase may result in localized stress concentration, thereby increasing the risk of screw breakage and loosening [28]. Consequently, when anatomical conditions permit, selecting the longest and widest PS that can be safely accommodated within the pedicle is recommended to improve the fixation of osteoporotic vertebrae (Fig. 2).

Instrumentation at the lumbosacral junction is particularly challenging because this region is highly susceptible to screw loosening due to high mechanical stress, wide diameter, short sacral pedicle length, and relatively poor sacral bone quality [29,30]. Therefore, bicortical or tricortical S1 PS fixation techniques have been employed to enhance screw purchase by allowing screw tips to engage additional sacral cortical bone. Previous studies have demonstrated that these approaches provide greater fixation strength than conventional unicortical fixation; however, screw loosening may still occur in osteoporotic patients, especially following long-segment fusion [8,31]. However, bicortical and tricortical PS fixation may increase the risk of injury to the major neurovascular structures anterior to the sacrum because of their close anatomical proximity [32]. Accordingly, careful selection of appropriate sacral fixation techniques is essential when performing lumbosacral fusion in osteoporosis patients.

In osteoporotic bone, undertapping may both enhance insertional torque and pullout strength. In a biomechanical analysis of thoracic PS fixation, Kuklo and Lehman [33] demonstrated that 1 mm undertapping, compared to 0.5 mm undertapping, was linked to a 47% increase in maximal insertion torque, thereby supporting undertapping as a strategy to boost fixation strength. However, its effectiveness depends on meticulous hole preparation, including matching the thread pitch between the tap and PS, as mismatches can impair fixation strength [34,35].

Cortical bone trajectory (CBT) is an alternative fixation approach with specific advantages in osteoporosis patients. By following a medial-to-lateral path in the transverse plane and a caudal-to-cephalad path in the sagittal plane, CBT maximizes cortical bone engagement while reducing reliance on compromised trabecular bone [27,36,37]. Finite element analyses and biomechanical studies have shown that CBT provides increased pullout strength and lowers stress on interbody cages and screws compared to traditional trajectories in healthy and osteoporotic bone [27,36–38]. In a clinical study of patients with osteoporosis, Liu et al. [39] demonstrated that CBT achieved superior outcomes compared to conventional trajectories, with significantly decreased screw loosening rates (6.5% vs. 28.13%) and reduced cage subsidence.

In addition, a meta-analysis revealed that CBT is a less invasive technique that minimizes soft tissue dissection, resulting in reduced postoperative complications, shorter surgical duration, and lower blood loss while achieving fusion rates comparable to those of traditional trajectories [40]. However, CBT has a technical learning curve, and the relatively shorter screw length and limited anterior column purchase may compromise construct rigidity in long-segment fusion or deformity correction procedures [41]. Biomechanical studies have suggested that the optimal screw dimensions for CBT are a diameter ≥5.5 mm and a length ≥35 mm [27].

Cement augmentation of PS has been widely utilized to effectively improve screw fixation in patients with osteoporosis, particularly when conventional PS fixation is inadequate due to severely reduced bone strength. Augmentation with polymethylmethacrylate augments the bone-screw interface strength, mitigates the risk of screw loosening, improves fusion rates, preserves intervertebral height, and is linked to superior long-term clinical outcomes compared to conventional PS fixation in the osteoporotic spines [5,6]. Recently, fenestrated PSs with one or two distal fenestrations have been increasingly adopted to facilitate cement augmentation (Fig. 3) [5,8].

High-risk criteria warranting consideration for cement augmentation include age >65 years, osteoporosis, chronic kidney disease, and autoimmune diseases. The presence of two or more risk factors is a strong indication for cement augmentation [42]. Son et al. [5] reported that cement-augmented screws reduce radiological implant-related complications, including screw loosening and loss of correction, compared with conventional PS fixation in patients with osteoporosis, despite the cement-augmented group being comprised of participants who were significantly older and had lower T-scores. Comparative studies by Gu et al. [8] revealed that sacral fixation with cement augmentation provided superior outcomes in osteoporotic spines compared to bicortical or tricortical fixation alone. These findings suggest that cement augmentation effectively minimizes screw loosening while avoiding the increased risk of major neurovascular injury associated with anterior cortical penetration. Furthermore, cement augmentation of the PS at the upper instrumented vertebra has been shown to significantly lower PJF incidence in adult spinal deformity surgery among patients with low BMD or osteoporosis, primarily through enhancement of PS pullout strength [43].

However, cement augmentation is associated with several potential complications, including cement leakage, pulmonary embolism, neurovascular complications, and increased technical difficulty during revision surgery. Among these, cement leakage is the most commonly reported, with incidence rates ranging from 38.3% to 93.6%. Although frequently observed on imaging, it is usually clinically asymptomatic. Technical modifications, such as restricting cement volume (approximately 1.5–2.5 mL per lumbar screw and 1 mL per thoracic screw), injecting during the dough phase, using slow controlled injection, and maintaining continuous fluoroscopic monitoring, have been shown to substantially reduce the incidence of cement leakage. In addition, cement delivery through fenestrated screws via a specialized tube, rather than pre-injecting cement prior to conventional screw insertion, may reduce the risk of cement leakage [5,6,8,44,45].

Cage subsidence is a frequent implant-related complication following interbody fusion procedures, particularly in patients with osteoporosis, in whom reduced vertebral bone strength predisposes to endplate collapse. Several studies have shown that a lower BMD is linked to an increased risk of cage subsidence after lumbar interbody fusion. However, cage subsidence does not always result in clinical deterioration [4,46–48].

In addition to osteoporosis, excessive disc height restoration during surgery is an independent risk factor for cage subsidence. Overdistraction of the disc space increases loading on compromised endplates, promoting cage subsidence and potential loss of restored disc height. These findings highlight the importance of achieving disc height restoration in a controlled manner while avoiding excessive distraction [48,49].

Preservation of bony endplates during intervertebral disc preparation is crucial in preventing cage subsidence. Excessive endplate removal may damage the bony endplate and weaken structural support for interbody cages, thereby predisposing to subsidence. Accordingly, in patients with osteoporosis, meticulous endplate handling aimed at preserving the bony endplate and facilitating even load distribution across the endplate surface can help minimize subsidence risk [4,48,49].

In addition to surgical optimization, perioperative pharmacological treatment of osteoporosis may further reduce implant-related complications and enhance fusion outcomes. Anabolic agents have demonstrated beneficial effects in patients with osteoporosis undergoing spinal fusion [2]. Teriparatide, a recombinant form of the human parathyroid hormone, stimulates osteoblastic activity and promotes new bone formation when administered intermittently, leading to increased bone mass and improved bone microarchitecture. By promoting bone formation at the bone-implant interface and accelerating fusion, perioperative teriparatide treatment has been shown to be associated with reduced screw loosening, prevention of cage subsidence, and higher fusion rates following spinal instrumentation, supported by high-grade evidence (grade B) [7,47,50]. More recently, romosozumab, an antisclerostin antibody with dual anabolic and antiresorptive effects, has been shown to rapidly increase vertebral body BMD and BMD around the PS [51]. Sawada et al. [52] reported that perioperative administration of romosozumab effectively increased BMD and reduced PJK risk, particularly fracture-related PJK, as well as other osteoporosis-related complications in patients undergoing adult spinal deformity surgery. Emerging evidence suggests that romosozumab treatment may provide early reinforcement of vertebral structural integrity, making it a potential anabolic option for bone optimization in patients with osteoporosis requiring spinal surgery. Although the optimal duration of perioperative anabolic agent therapy remains uncertain, an expert consensus by Sardar et al. [11] recommends initiating anabolic agents at least 2 months and up to 6 months before elective multilevel spinal reconstructive surgery, with continuation for a minimum of 8 months postoperatively to optimize surgical outcomes.

Antiresorptive agents, including bisphosphonates and denosumab, are widely employed for managing osteoporosis and are recommended as second-line options before spinal instrumentation when anabolic therapy is contraindicated or unavailable [11]. Although concerns have been raised regarding potential delays in fusion due to inhibition of bone turnover, available clinical evidence indicates that bisphosphonates do not significantly impair fusion rates [53]. While perioperative bisphosphonate use has been linked to lower incidence of screw loosening and adjacent-level vertebral fracture, the supporting evidence is limited, corresponding to grade C recommendations [14,53]. Denosumab, a human monoclonal antibody targeting RANKL, is supported by high-level evidence exhibiting enhanced fusion rates and increased screw pullout strength, making it an effective treatment option for patients with osteoporosis. Accordingly, denosumab may be recommended as a grade B alternative when anabolic therapy is contraindicated or not feasible due to cost [53,54]. Following the completion of anabolic therapy, transition to antiresorptive therapy is recommended to preserve therapeutic benefits and sustain gains in BMD [11].

Adequate calcium and vitamin D3 supplementation prior to spinal instrumentation is recommended to optimize surgical outcomes. Unless contraindicated, all patients should be administered a total daily calcium intake of 1,000–1,200 mg through diet and/or supplementation. In addition, vitamin D3 supplementation of 1,000–2,000 IU per day is recommended for patients with osteoporosis or documented vitamin D insufficiency or deficiency [11].