Tricortical screw spinal fixation: a scoping review and introduction of technique, biomechanical advantages, and clinical outcomes in high-risk vertebral fractures

Abstract

Background/objective

Tricortical pedicle screw (TCPS) fixation has emerged as a biomechanically superior alternative to conventional unicortical/bicortical methods for spinal stabilization in high-risk populations, particularly elderly patients with osteoporotic or diffuse idiopathic skeletal hyperostosis (DISH)-related vertebral fractures. This review evaluates TCPS fixation’s biomechanical advantages, clinical outcomes, and surgical considerations to address these challenges.

Methods

A scoping review was conducted using the PRISMA scoping review checklist. PubMed was searched through March 1, 2025. Inclusion criteria were studies reporting treatment parameters and follow-up results of TCPS spinal fixation. Data was analyzed to synthesize clinical outcomes, with a focus on hardware failure rates.

Results

5 studies satisfied the final inclusion criteria, consisting of 3 case series and 2 cohorts. These 5 studies included 85 patient cases. The included patients had a weighted mean age of 78.97 years, with a sex distribution consisting of 54.8% (n = 40) males and 45.2% (n = 33) females. 62.4% (n = 53) patients were positive for DISH. Affected vertebrae were mostly located in the thoracolumbar region (64.1%), followed by the thoracic (21.8%) and lumbar regions (14.1%). 76.5% (n = 65) of patients were treated with TCPS fixation, and 23.5% (n = 20) were treated conventionally. A total of 636 screws were inserted, consisting of 46.2% (n = 294) tricortical and 53.8% (n = 342) conventional pedicle screws. Of the tricortical screws, 1.36% (n = 4) loosened, while 20.5% (n = 70) of conventional screws loosened. 3 patients treated with TCPS fixation experienced implant failure, while 6 patients treated with conventional pedicle screw fixation experienced implant failure.

Conclusion

TCPS fixation enhances spinal stabilization in high-risk fractures through tri-cortical load distribution, minimizing screw loosening and invasiveness. While requiring precise trajectory planning to avoid perforation risks, it offers shorter operative times, reduced blood loss, and improved biomechanical stability, particularly in osteoporotic/DISH patients. Further prospective studies are needed to optimize patient selection and refine navigation-assisted techniques for broader applicability.

Introduction

Pedicle screw fixation is a widely used surgical technique for stabilizing spinal fractures, particularly in cases involving diffuse idiopathic skeletal hyperostosis (DISH) or unstable osteoporotic vertebral fractures [1, 2]. This population subset is generally comprised of older adults with multiple comorbidities, such as diabetes, obesity, and cardiovascular disease, which increase their risk of perioperative complications and implant failure [2, 3]. The complexity of this patient population poses two primary challenges for successful spinal fixation. The first is the need for rigid and secure fixation while minimizing complications and perioperative mortality—a concern particularly relevant given the advanced age and comorbidities of these patients [2, 3]. The second challenge is the high incidence of implant failure, often caused by pedicle screw loosening due to biological (osteoporotic bone density loss) and mechanical factors (stress distribution and toggling at the screw-bone interface) [1].

Tricortical pedicle screw (TCPS) fixation is a novel fixation technique that can address these challenges. TCPS fixation offers a mechanically superior alternative to conventional unicortical and bicortical fixation methods by engaging three distinct cortical layers [4]. By distributing mechanical loads across these three layers, tricortical screws significantly enhance pullout strength, reduce micromotion at the screw-bone interface, and lower the risk of screw backout, which is particularly problematic in osteoporotic bone [1–3].

In this review we aim to present an overview of existing clinical data and computational analyses regarding the use of tricortical pedicle screws for spinal fixation to highlight its potential as an effective, safe, and biomechanically secure option for high-risk spinal stabilization.

Methods

Literature review

A literature search was completed to identify all publications reporting tricortical pedicle screw fixation in accordance with the PRISMA scoping review checklist [5]. PubMed was searched to March 1 st, 2025 operating the Boolean full-text search (tricortical OR tri-cortical OR “penetrating endplate”) AND (screw OR fixation) AND (spine OR vertebra* OR thoracic OR lumbar OR sacral). All search results were exported to Rayyan, and duplicates were manually deleted.

Study selection

Articles were included if they (1) included patients who underwent spinal fixation using tricortical pedicle screws, (2) reported patient treatment and outcome data, and (3) were written in English. Studies were excluded if they (1) were autopsy reports, animal studies, or cadaver studies, (2) were conference abstracts, literature reviews, meta-analyses, systematic reviews, perspectives, or editorials, and/or (3) were from non-English or non-peer reviewed sources.

Two independent reviewers (H.Q. and D.O.) screened all titles and abstracts and then assessed the full texts of articles that met the inclusion criteria. A third reviewer (K.B.) settled disagreements. Eligible papers were included, and references were also screened to identify additional pertinent studies.

Data extraction

One reviewer (H.Q.) extracted data from each article, then confirmed independently by two additional reviewers (A.Y. and G.M.). The primary variables of interest were patient characteristics and treatment outcomes, particularly in relation to screw loosening rate and implant failure. Continuous variables are summarized as weighted means with ranges, and categorical variables as frequencies with percentages.

Data synthesis and quality assessment

The primary outcome of interest was the percentage of hardware failure comparing conventional fixation to TCPS fixation. For each study, two independent authors (K.B. and G.M.) assessed the level of evidence using the 2011 Oxford Centre For Evidence-Based Medicine guidelines and the risk of bias by applying the Joanna Briggs Institute checklists for case reports and case series (Fig. 1).

Table 1.

Summary of included studies

Study Author	Year	Study type	Study Location	Treatment Group	Number of Patients	Mean Age (Range)	Sex	Use Case	DISH	Affected Vertebrae	Mean Number of Fixed Vertebrae	Screw Technique	Number of Patients with Follow-Up	Mean Follow-Up (months)	Number of TCPS Inserted	Number of TCPS loosened	Number of Conventional Screws Inserted	Number of Conventional Screws Loosened	Number of Patients with Implant Failure (Failure %)
Fujii et al.	2	Case Series	Japan	Treatment	20	83 (68–94)	M: 11 F: 9	Unstable OVF	No	Thoracolumbar: 13 Lumbar: 7	3	Combined dPES, uPES	11	11.26	80	4	40	2	1 (9%)
Shiraishi et al.	13	Case Series	Japan	Treatment	3	80 (70–88)	M: 3	Unstable OVF	Yes	Thoracolumbar: 3	5.3	Combined dPES, uPES	3	28.66	28	0	4	0	0 (0%)
Hishiya et al.	3	Cohort	Japan	Treatment	18	79.1	M: 10 F: 8	Thoracolumbar Fracture	Yes	Thoracic: 5 Thoracolumbar: 14	5	Combined uPES, PS	14	16	95	0	38	4	0 (0%)
				Control	8	82.8	M: 4 F: 4	Thoracolumbar Fracture	Yes	Thoracic: 2 Thoracolumbar: 3 Lumbar: 3	5.5	PS	8	11	0	N/A	88	49	2 (25%)
Takeuchi et al.	15	Cohort	Japan	Treatment	12	83.8 (61–94)	M: 4 F: 8	Unstable OVF	Yes	Thoracic: 2 Thoracolumbar: 10	5.1	Combined uPES, PS	12	22.3	50	0	56	3	2 (17%)
				Control	12	78 (65–92)	M: 8 F: 4	Unstable OVF	Yes	Thoracic: 8 Thoracolumbar: 7 Lumbar: 1	4.7	PS	12	27.8	0	N/A	116	12	4 (33%)
Nottmeier et al.	19	Case Series	United States	Treatment	12	65.92 (42–79)	N/A	Posterior Spinal Fusion, Pedicle Subtraction Osteotomy	No	N/A	2.33	Combined uPES, PS	12	7	41	0	N/A	N/A	0 (0%)

Abbreviations: M male, F female, OVF osteoperotic vertebral fracture, DISH diffuse idiopathic skeletal hyperostosis, DPES downward penetrating end plate screw, UPES upward penetrating endplate screw, PS conventional pedicle screw, TCPS tricortical pedicle screw, N/A not available 

Fig. 1.

illustrates the flow diagram of the literature search. The search strategy yielded 150 studies, of which 4 were included upon the pre-specified study inclusion criteria. 1 additional study was included after further search of the literature (Table 1). 3 case series and 2 cohorts were included. Critical appraisal returned low risk of bias for all included studies

Results

Patient characteristics

85 patients were included in this review, with a weighted mean age of 78.97 years. Of these, 40 patients were male (54.8%) and 33 were female (45.2%). Most affected vertebrae were in the thoracolumbar region (n = 50, 64.1%), followed by thoracic (n = 17, 21.8%) and lumbar vertebrae (n = 11, 14.1%). DISH was present in 62.4% of patients. (Table 2)

Table 2.

Summary of patient demographics

Characteristic (no. of patients for whom information is available)	Value (among patients with available data)
Cohort size (no.)	85
Patient Age (n=85)
Mean age (yrs)*, (range)	78.97, (42-94)
Patient Sex (n=73)	No. (%)
Male	40 (54.8)
Female	33 (45.2%)
Affected Vertebrae (n=78)	No. (%)
Thoracic	17 (21.8)
Thoracolumbar	50 (64.1)
Lumbar	11 (14.1)
DISH Status (n=85)	No. (%)
Positive	53 (62.4)
Negative	32 (37.6)

 *Represents weighted mean across included studies

Treatment and outcomes

65 patients (76.5%) were treated with tricortical pedicle screws (TCPS). A further 20 patients (23.5%) were treated with only conventional pedicle screws. The weighted mean number of fixed vertebrae for patients treated with TCPS was 3.92. The weighted mean number of fixed vertebrae for patients treated with conventional pedicle screws was 5.02. 72 patient cases reported follow-up data, with a weighted mean follow-up of 16.76 months and a range of 6–72 months. Of the patients with reported follow-up, 52 (72.2%) were treated with TCPS and 20 were treated with only conventional pedicle screws. In total, 636 screws were inserted, consisting of 294 tricortical pedicle screws and 342 conventional pedicle screws. 4 tricortical screws experienced loosening, representing 1.36% of the inserted tricortical screws. 70 conventional pedicle screws loosened, representing 20.5% of conventional screws. Implant failure was seen in 3 patients that underwent treatment with TCPS, representing 5.8% of TCPS patients. 6 patients treated with only conventional pedicle screws experienced implant failure, which represents 30% conventional pedicle screw patients (Table 3).

Table 3.

Summary of treatments and outcomes

Treatment Characteristic (no. of patients for whom information is available)	Value (among patients with available data)
Procedure Range (n = 85)	T5-S1
Patient Treatment Technique (n = 85)	No. (%)
Treated with TCPS	65 (76.5)
Treated without TCPS	20 (23.5)
Mean Number of Fixed Vertebrae*(n = 85)
Treated with TCPS	3.92
Treated without TCPS	5.02
Mean Length of Follow-up*; Range (n = 72)	16.76 Months; 6–72 Months
Screws Inserted (n = 636)	No. (%)
Tricortical Pedicle Screw	294 (46.2)
Loosened	4 (1.36)
Conventional Pedicle Screw	342 (53.8)
Loosened	70 (20.5)
Implant Outcome (n = 72)	No. (%)
Treated with TCPS	52 (72.2)
Success	49 (94.2)
Failure	3 (5.8)
Treated without TCPS	20 (27.8)
Success	14 (70.0)
Failure	6 (30.0)

*Represents weighted mean across included studies/cohorts

Discussion

The role of screw insertion technique on pedicle screw stability

The biomechanical stability of pedicle screw fixation is influenced by insertion trajectory, cortical engagement, and augmentation strategies. The three most common insertion methods—Roy-Camille, Magerl, and Krag techniques—demonstrate varying stress distribution patterns across the screw-rod system (Fig. 2) [6]. For instance, the Caudad trajectory, which directs screws inferomedially toward the vertebral body, provides superior stability compared to the Krag trajectory (lateral-to-medial angulation) in osteoporotic bone. Additionally, augmentation with polymethylmethacrylate (PMMA) can further reinforce the screw-bone interface, particularly in sub-endplate regions where cement interdigitation with trabecular bone mitigates subsidence under cyclic loads [7].

Fig. 2.

The methods of three pedicle screw insertion techniques. From top to bottom, they are Roy-Camille, Magerl, and Krag, respectively. From Smith, J. (2022. Retrieved from Song M, Sun K, Li Z, et al. “Stress distribution of different lumbar posterior pedicle screw insertion techniques: a combination study of finite element analysis and biomechanical test.” Sci Rep. Jun 21 2021;11(1):12968. 10.1038/s41598-021-90686-6

Screw reinsertion along the same trajectory, often necessitated by intraoperative repositioning in patients with poor bone quality, is another consideration. Biomechanical testing in synthetic models revealed that reinserted screws retained pullout strength and stiffness compared to primary insertions, even in osteoporotic analogs [8]. This suggests that the residual bone-cement interface or preserved trabecular architecture maintains structural integrity. However, surgeons must balance the perceived loss of haptic feedback during reinsertion with objective biomechanical data, as over-tightening risks pedicle fracture [8, 9]. Advancements in robotic navigation have further refined trajectory accuracy, reducing misplacement rates to < 5% compared to 20–30% with freehand techniques, thereby optimizing cortical engagement and minimizing loosening risks [9]. 

Complexities of spinal fixation in DISH and osteoporotic vertebral fractures

Spinal fixation in cases of DISH and osteoporotic fractures presents unique challenges due to altered biomechanics and poor bone quality. DISH-related fractures, often occurring at the caudal end of ankylosed segments, are inherently unstable due to three-column involvement, necessitating extended posterior instrumentation [10, 11]. Traditional fixation spanning three vertebrae above and below the fracture risks complications, especially in elderly patients with comorbidities. Innovative strategies, such as vertebroplasty via double-endplate penetrating screw (DEPS) trajectories, allow shorter constructs, thereby reducing stress concentration [10]. Concurrent use of cement-augmented fenestrated pedicle screws at the caudal end improves load distribution, balancing cranial fixation strength from triangulated DEPS techniques [10, 11].

In osteoporotic fractures, PMMA augmentation remains pivotal, but its application must address both anterior vertebral body support and posterior screw stability. Sub-endplate cement placement in DEPS trajectories enhances screw anchorage by leveraging the higher bone mineral density of the superior endplate, while fenestrated screws with cement interdigitation resist pullout forces [11]. However, cement leakage and thermal necrosis risks necessitate precision, particularly in DISH patients with aberrant anatomy [10, 11]. Combined anterior-posterior approaches, though effective, are often precluded by patient frailty, underscoring the importance of minimally invasive techniques such as vertebral body stenting and percutaneous cement-augmented screws [11]. These methods prioritize rapid stabilization while mitigating surgical morbidity, though long-term outcomes require further validation in high-risk cohorts [10, 11].

Description and definition of tricortical screw spinal fixation

Tricortical screw fixation has emerged as a biomechanically advantageous alternative for DISH and osteoporotic vertebral fractures. TCSP offered greater stability by engaging the posterior cortex, anterior superior endplate, and anterior cortex of the vertebral body. This approach increases pullout strength by leveraging denser subchondral bone near the endplates, which retains higher mineral density even in osteoporosis [1]. In DISH, tricortical trajectories may reduce cantilever forces on screws by enabling triangulation within the fused vertebral segment, potentially mitigating stress concentration at the screw-bone interface [3]. Comparative studies demonstrate significantly lower subsidence displacement in tricortical screws compared to bicortical configurations [1]. Additionally, tricortical fixation minimizes reliance on osteoporotic bone, offering an advantage in maintaining long-term stability [12]. These biomechanical benefits position tricortical fixation as a viable strategy for addressing the dual challenges of poor bone quality and altered spinal mechanics in DISH and osteoporotic fractures [1, 3].

The entry point of the tricortical screw starts from the inferior lateral corner of pedicle with trajectory toward the superior medial corner of pedicle then piercing through lower-level vertebral body superior endplate into the disc then pass through the higher-level vertebral body inferior endplate (Fig. 3). The tip of the tricortical screw stays in the vertebral body of the upper-level vertebrae.

Fig. 3.

Lateral view of the spine depicting the three insertion methods of pedicle screw fixations; unicortical (USPS), bicortical (BCPS) and tricortical (TCPS). BCPS penetrates the pedicle and endplate of the fractured vertebrae. TCPS penetrates the endplate of the fractured vertebrae in addition to the endplate of the adjacent vertebrae

The tricortical technique, which engages the posterior cortex, anterior superior sacral endplate, and anterior cortex, offers several biomechanical advantages:

1. It allows for placement of longer screws compared to unicortical or bicortical techniques.

2. It permits greater angulation with the sagittal plane, forming a triangulation fixation in both sagittal and coronal planes.

3. It reduces the lumbosacral interscrew angle in the sagittal plane, facilitating screw-rod connection.

Biomechanical rationale for tricortical screw effectiveness

TCPS fixation derives superior mechanical stability from its engagement of three distinct cortical bone layers. Due to the distribution of mechanical loads across three cortical bone layers, stress concentration at the screw-bone junction can be reduced, and loads are dispersed across a broader osseous interface [1]. Finite element analysis (FEA) conducted by Zhang et al. was able to quantify the benefits using a simulation of spinal motion using computer modeling and computed tomography (CT) data (Fig. 4).

Fig. 4.

FEA values of mean range of motion, maximum motion displacement and maximum stress experienced by screws with UCPS, BCPS and TCPS insertion. Tested motion states include flexion, extension, left lateral bending, right lateral bending, left rotation, and right rotation. Data from Zhang et al. 2020

Von Mises stress is a critical predictor of material yield or fracture and reflects localized stress intensity; lower values indicate a reduced likelihood of screw deformation or breakage under physiological loads [1]. Von Mises stress testing of the implant under six vertebral motion states, including flexion, extension, left and right lateral bending, and left and right rotation, showed that TCPS displayed the lowest average stress values when compared to bicortical (BCPS) and unicortical (UCPS) fixation [1]. Notably, TCPS demonstrated the lowest stress levels in four motion states: extension, right lateral bending, left rotation, and right rotation [1]. The TCPS implant additionally demonstrated superior biomechanical stability with vertebral movement, showing a 26% reduction in maximum displacement and a 56% decrease in range of motion compared to BCPS [1]. Reduced range of motion and displacement under conditions of vertebral stress suggests increased resistance to loosening and pull-out under conditions of movement and activity, a factor that is particularly relevant as patients return to activities of daily living post-operatively [1].

These FEA findings underscore TCPS’s enhanced ability to stabilize spinal segments while improving implant longevity. Although silico models provide robust theoretical validation for the potential benefits of TCPS spinal fixation, translational studies are needed to refine clinical applicability. Nevertheless, the silico biomechanical superiority of TCPS positions it as a promising solution to the challenges faced by conventional spinal fixation methods, particularly in high-risk vertebral fractures.

A cadaver study conducted by Rodriguez-Martinez et al. provides further evidence for the clinical utility of TCPS in high-risk spinal fixation [18]. Range of motion was examined during flexion-extension, lateral bending, and axial rotation [18]. Although the authors did not find a statistically significant reduction in range of motion compared with conventional pedicle screw fixation, the comparable results suggest that, at a minimum, TCPS offers stability and rigidity on-par with the current standard of care [18]. In this context, the increased mechanical resistance to loosening of tricortical screws, through engaging additional cortical layers, offers additional utility in cases of poor bone quality where screw loosening is a concern [18].

Clinical findings: reduced screw loosening/implant failure

A serious complication in spinal fixation surgery is implant failure resulting from screw loosening and pull-out. This concern is particularly relevant in cases involving patients with DISH, with osteoporosis also being an important risk factor [1, 2, 13, 14]. These patients often exhibit compromised bone quality, increasing susceptibility to screw migration, implant failure, and subsequent bone non-union [14]. It is critical to ensure that the implanted screws will not dislodge to achieve successful healing and to avoid revision surgeries [2]. Tricortical screw fixation addresses this challenge by incorporating screw purchase in additional bone cortices, enhancing overall anchorage strength.

A retrospective study by Hishiya et al. evaluated 26 patients treated for DISH-related thoracolumbar fractures using either exclusively conventional pedicle screw (PS) fixation (N = 8) or combined fixation utilizing both tricortical penetrating endplate screws (PES) and conventional PS methods (N = 18). Upon follow up assessment at 6 months post-op, the combined group was found to have a screw loosening rate of 3% (4/133 screws) while the group utilizing only conventional PS fixation had a loosening rate of 49% (43/88 screws) [3]. Of the screws that loosened in the combined group, all of them were screws inserted with a conventional PS method [3]. Two patients in the PS only group experienced implant failure within the 6 month follow-up time frame, and required revision surgery to either extend the fixation level or to replace PS screws with tricortical pedicle screws [3]. No cases of implant failure requiring revision were seen in the combined treatment group [3]. The stark disparity seen in screw migration highlights the potential of tricortical pedicle screws in mitigating loosening and implant failure.

Comparable results are seen in a study by Takeuchi et al. involving 24 DISH patients with osteoporotic vertebral body fractures [15]. A treatment group consisting of 12 patients was treated with either exclusively PES screws or a combined treatment with both PES and conventional pedicle screws. The remaining 12 patients in the control group were treated with only conventional pedicle screws [15]. None of the screws (0/70) inserted using a PES method experienced loosening, while 10.3% (12/116) of the conventional PS screws loosened [15]. 2 patients in the PES/combined treatment group (17%) and 4 patients in the control group (33%) experienced implant failure and screw loosening [15]. Similar to the study by Hishiya et al., all cases of screw loosening seen in the combined PES treatment group were conventional pedicle screws [15].

Further evidence comes from a case series from Fujii et al. involving 20 patients who were treated with both upward and downward-angled PES fixation. 11 patients completed a 6 month follow-up, with 10 of those patients exhibiting successful bone union and 1 case showing bone nonunion with screw loosening [2]. While this suggests that tricortical screw fixation can still exhibit screw loosening despite the improved screw purchase and load distribution, combined results across these studies suggest that the loosening rate of TCPS fixation is likely significantly lower when compared with conventional pedicle screw spinal fixation techniques.

Clinical findings: reduced invasiveness and risk of operative complications

For elderly patients with osteoporosis or DISH—a population frequently burdened by comorbidities such as diabetes, cardiovascular disease, and obesity—minimizing perioperative risks is critical to avoiding catastrophic postoperative decline [2]. Simultaneously, sufficient implant strength must be achieved to address weakened bone strength in these patients which typically necessitates the fixation of additional vertebral segments, or the consideration of more invasive surgical techniques [2]. TCPS fixation offers a solution that is less invasive than more involved spinal fixation techniques such as lateral lumbar interbody fusion or anterior cage insertion while also reducing invasiveness by allowing less vertebral segments to be fixed when compared to conventional pedicle screw fixation due to the enhanced inherent stability of tricortical fixation [2]. The surgical procedure may be completed using percutaneous techniques, with no requirement for special facilities or equipment beyond a radiolucent operating table and fluoroscopic apparatus—equipment already used for the insertion of conventional pedicle screws—is needed for the insertion of TCPS [2, 3].

The study by Hishiya et al. reported a shorter mean fixation range for the patient group treated with TCPS (5) compared with the conventional PS group (5.5) [3]. Additionally, lower mean operative blood loss of 63 mL in the TCPS group versus 173 mL in conventional pedicle screw (PS) cohorts was also noted [3]. Similarly, Fujii et al. demonstrated the utility potential of reduced fixation ranges in a 20-patient cohort utilizing a fixation range of only one vertebral level above and one below using PES fixation, with mean blood loss of 6.1 mL and surgical time of 57 min, minimizing anesthesia exposure in this vulnerable demographic. Postoperatively, 19 of 20 patients regained ambulatory ability by discharge, with four able to walk independently without support.

Despite these benefits, two operative complications occurred in Fujii et al.’s cohort: one nerve root injury from screw malposition and one deep surgical site infection [2]. Additionally, one case of early postoperative adjacent vertebral fracture was noted, however bone union was nonetheless achieved at 111 days post-op [2]. However, the absence of mortality and low overall complication rates align with Hishiya et al.’s findings of no significant difference in morbidity or mortality between TCPS and PS groups, despite the latter’s higher loosening rates. Notably, even the single adjacent vertebral fracture observed achieved union by postoperative day 111, suggesting TCPS’s stability may mitigate effects of secondary complications [2].

Surgical and patient considerations

Accurate screw placement is critical for TCPS fixation. Achieving successful tricortical penetration often requires a greater cephalad angle than what is used for bicortical or unicortical screws. In particular, this increases risks of pedicle edge perforation in regions of the spine where anatomy dictates a significantly higher cephalad angle [16]. Simultaneously, utilizing an angle that is too small can lead to anterior cortical perforation [16]. This delicate balance underscores the importance of preoperative planning and the potential utility of intraoperative navigation to maximize the biomechanical benefits of TCPS while minimizing complications [1, 13, 17].

A report by Gamada et al. identified screw cephalad angles for 50 patient cases involving tricortical screw spinal fixation. Vertebral levels from T7 through L5 were included, and screw cephalad angles ranged from 23.4°–37.6° in the thoracic spine and 34.8°–40.8° in the lumbar spine [16]. Total perforation rate was 10%, or 108 of the 1078 pedicles included in the study [16]. No perforations occurred between vertebral levels T10 and T12, while 90 of the 108 perforated pedicles occurred at vertebral levels T7, L4, and L5, representing 83% of the total perforated pedicles [16]. The remainder of the vertebral levels showed low rates of perforation, ranging from 1 to 8% of screws inserted at the respective vertebral level perforating the pedicle edge [16].

Anatomical limitations complicating the utilization of an appropriate cephalad angle can be seen in the regions of the middle thoracic and lower lumbar vertebrae when compared to the lower thoracic and upper lumbar vertebrae [16]. The increased height of the lower lumbar vertebral disks and the lordotic alignment of the vertebrae increases the necessary cephalad angle required to achieve tricortical purchase which carries the associated increase of pedicle edge perforation [16]. Likewise, anatomic characteristics including pedicles located more proximally and kyphotic vertebrae alignment seen in the mid-thoracic region make utilizing an optimal tricortical screw trajectory challenging [16]. Despite these limitations, TCPS spinal fixation has demonstrated very good results when used in a suitable patient population, with low rates of perforation within the lower thoracic and upper lumbar regions while offering improved screw loosening and implant stability characteristics [16]. Patient selection remains a key element of surgical planning for TCPS fixation. Surgeons must weigh the increased stability afforded by TCPS against the vertebral-level–specific risk of pedicle perforation. Spinal alignment abnormalities such as kyphosis or lordosis may further affect the safe trajectory angles, making a tailored approach vital [16].

Advanced imaging and navigation represent promising solutions to many of these challenges. O-arm navigation provides real-time 3D visualization during surgery, allowing surgeons to dynamically adjust trajectories and significantly reducing the chance of screw misplacement [13]. This is particularly beneficial in DISH patients, where ossified ligaments and bridged vertebral segments may obscure bony landmarks [13]. In addition, advancements in 3D modeling now enable precise evaluation of critical parameters and facilitate the accessibility of individualized operative solutions [17]. Preoperative 3D reconstruction can also help map pedicle morphology, identify fracture geometry, and plan screw insertion angles [17]. This may help minimize intraoperative reliance on fluoroscopy—and thus reduce radiation exposure—while aiding in the accuracy of screw placement [17]. Moving forward, continued refinements in navigation technology and preoperative planning should further mitigate risks, expand the indications for TCPS, and potentially improve clinical outcomes.

Patient selection and pre-operative considerations

Patient selection for TCPS fixation primarily focuses on individuals with DISH and osteoporotic vertebral fractures, populations consisting of elderly patients often with multiple comorbidities. These underlying conditions significantly increase the risk of perioperative complications and implant failure, necessitating careful preoperative assessment and planning. Ideal candidates for TCPS fixation have documented instability of spinal segments with adequate bone quality to support tricortical purchase, though the technique specifically addresses concerns in osteoporotic bone. Contraindications include severe osteoporosis that might compromise tricortical purchase, active infections at the operative site, and patients with compromised vascularity that would impede healing. The patient’s overall health status must be thoroughly evaluated, as those with multiple comorbidities face elevated risks during spinal procedures but may particularly benefit from the minimally invasive nature of TCPS fixation.

Comprehensive preoperative imaging represents a critical component of surgical planning for TCPS implementation, typically including plain radiographs with flexion-extension views to assess instability patterns, MRI evaluation of soft tissues, and thin-slice CT with multiplanar reconstructions to analyze bony architecture. Three-dimensional reconstructive imaging is particularly valuable for TCPS planning, allowing surgeons to precisely evaluate pedicle morphology, fracture patterns, and potential screw trajectories. Advanced preoperative planning software enables virtual simulation of screw placement and determination of optimal screw dimensions, significantly enhancing surgical precision and reducing complication risks. Specialized imaging protocols with 0.5 mm slice thickness facilitate optimal three-dimensional reconstruction and preoperative trajectory planning.

Technical planning for TCPS fixation must address anatomical challenges unique to this technique, particularly regarding screw trajectory and pedicle perforation risk. Preoperative analysis should determine appropriate screw cephalad, with special consideration for anatomically challenging areas such as the middle thoracic and lower lumbar regions where perforation rates are highest. By contrast, vertebral levels T10-T12 demonstrate the lowest perforation rates, making them potentially ideal regions for TCPS application. Patient-specific anatomical variations, including spinal alignment abnormalities, significantly impact safe trajectory angles and must be identified preoperatively. Advanced intraoperative navigation systems such as O-arm technology provide real-time visualization during surgery, potentially reducing screw misplacement rates and improving outcomes in anatomically complex cases.

Limitations

Despite its advantages, current evidence for TCPS is limited to elderly cohorts, restricting its applicability to younger populations. Future studies are needed to explore the effectiveness of TCPS fixation across broader age groups, define preoperative criteria to optimize patient selection, and refine the surgical protocol to optimize screw trajectory, particularly in challenging regions of the spine, such as the lower lumbar spine, where risks of pedicle perforation remain elevated. Prospective studies are especially needed to establish evidence-based guidelines for determining patient candidacy, ensuring TCPS is used in patients most likely to benefit while avoiding unnecessary interventions. Addressing these limitations could expand the clinical utility of TCPS fixation as a universally adaptable solution that balances biomechanical durability with surgical efficiency to benefit a wider population of patients.

Conclusion

TCPS fixation represents a significant advancement in spinal fixation, particularly in patients with osteoporotic or DISH related vertebral fractures. Biomechanically, TCPS demonstrates superior load distribution and stability across three cortical layers, reducing stress concentrations and enhancing pullout resistance compared to traditional pedicle screws utilizing unicortical or bicortical insertion methods. By balancing improved stability with reduced invasiveness, TCPS spinal fixation provides a surgical option with shorter operative times and lower blood loss while enabling good postoperative recovery and functional independence. Existing clinical evidence universally exhibits good rates of bone healing and good patient outcomes with low rates of implant failure and perioperative complications—critical for elderly patients with comorbidities. Despite these advantages, precise screw placement is crucial to avoid complications such as pedicle edge perforation, particularly in vertebral regions requiring a high cephalad angle. Although thorough preoperative planning and precise intraoperative techniques are essential for risk mitigation, tricortical screw spinal fixation nonetheless provides a promising solution for the treatment of high-risk vertebral fractures when used in appropriate patient cohorts.

Source: Page MJ, et al. BMJ 2021;372:n71. doi: 10.1136/bmj.n71.

This work is licensed under CC BY 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

Author contributions

CRediT: HQ: Conceptualization, Data curation, Formal Analysis, Methodology, Project administration, Writing – original draft, Writing – review & editing; KB: Conceptualization, Data curation, Investigation, Supervision, Writing – original draft, Writing – review & editing; DO: Data curation, Formal Analysis, Writing – original draft, Writing – review & editing; AY: Investigation, Supervision, Validation, Writing – original draft, Writing – review & editing; GM: Investigation, Supervision, Validation, Writing – original draft, Writing – review & editing; CL: Project administration, Supervision, Validation, Visualization, Writing – review & editing.

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No datasets were generated or analysed during the current study.

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Competing interests

The authors declare no competing interests.

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