An investigation to the clinical application of personalized 3D printed guides combined with preoperative virtual iliosacral screws for the management of posterior pelvic ring injury

Abstract

Objective

The use of percutaneous iliosacral screws for the treatment of unstable pelvic ring injuries is highly challenging and typically requires fluoroscopic or navigational guidance. This study aims to introduce a novel 3D-printed guide plate for the safe insertion of iliosacral screws during surgery and to evaluate the effectiveness and safety of this technique.

Methods

A retrospective analysis was conducted on patients who underwent surgery for unstable posterior pelvic ring injuries at our trauma center between January 2020 and May 2023. The surgeries were performed by the same group of surgeons. Patients were divided into two groups based on different surgical methods: the guide plate group (GP group, n = 14) and the conventional surgery group (CS group, n = 17). Data on gender, cause of injury, age, sacral dysmorphism, fracture classification, time for each screw insertion, fluoroscopy time for each screw, postoperative screw position grading, follow-up duration, and fracture reduction quality at the last follow-up were recorded.

Results

The CS group included 17 patients (8 males and 9 females) with a mean age of 42.6 ± 13.4 years; the GP group included 14 patients (6 males and 8 females) with a mean age of 40.4 ± 13.1 years. There were no statistically significant differences between the two groups in terms of gender, age, cause of injury, AO fracture classification, sacral dysmorphism, follow-up duration, or fracture reduction quality. A total of 42 iliosacral screws were inserted in 31 patients, with 24 screws inserted in the CS group (18 in S1 and 6 in S2) and 18 screws inserted in the GP group (14 in S1 and 4 in S2). The GP group had significantly lower rates of screw misposition, fluoroscopy time per screw, and insertion time per screw compared to the CS group (5.56% vs. 25.00%; 0.31 ± 0.14 min vs. 0.91 ± 0.17 min; 17.29 ± 1.90 min vs. 25.18 ± 3.99 min). The differences in insertion time and fluoroscopy time per screw between the two groups were statistically significant (P < 0.05), while the difference in screw misposition rate was not statistically significant (P >0.05).

Conclusion

The preoperative virtual screw combined with 3D guide plate technology can accurately place sacroiliac joint screws, providing a new method for percutaneous screw insertion.

Introduction

Pelvic fractures are a prevalent type of trauma, manifesting in approximately 3–8% of reported cases [1]. Chronic pain, non-union of fractures, and unequal length of both of the lower limbs are long-term complications of conservative treatment [2, 3]. Many experts prefer percutaneous iliosacral screw fixation as a surgical treatment option due to its advantages of minimal tissue incision, short operation time, and decreased infection risk [4, 5]. The majority of percutaneous iliosacral screw fixation is performed under X-ray guidance [6]. While numerous studies have documented anatomical landmarks and safe screw placement techniques, conventional x-ray manual placement of iliosacral screws has been associated with a 2–15% misposition rate and a 0.5–7.7% nerve injury rate, according to the literature [7, 8].

As a consequence of the ongoing development of imaging technology, numerous techniques for facilitating the insertion of intraoperative screws have demonstrated favourable clinical outcomes [9, 10]. Nevertheless, the lengthy learning curve, the expensive equipment, and the imprecise nature of screws impede the advancement of these techniques [11]. Additionally, intraoperative radiation exposure is a matter of concern due to the potential for adverse effects including skin burns, nausea, hair loss, and organ harm resulting from excessive radiation exposure [12].

To enhance precision during screw insertion and alleviate radiation exposure, some scholars have redirected their focus from intraoperative navigation planning screws to preoperative planning screw trajectories and implemented these strategies in clinical practice [13]. The ability of high-quality computed tomography (CT) to provide distinct visualisations in the coronal, sagittal, and axial sections is critical for clinical preoperative assessment of fracture classification, surgical plan guidance, and postoperative verification of screw position [14]. The iliosacral screw trajectory can be precisely and individually simulated prior to surgery in accordance with the patient’s injury [15]. One of the challenges associated with this technique is maintaining consistent position and fluoroscopic images throughout the operation. Additionally, manually inserting the guide needle may not guarantee that it follows the preoperatively planned trajectory.

3D printing guide technology is a new technology that combines preoperative planning and intraoperative application. It simulates the virtual iliosacral screw using the patient’s preoperative CT image and then reverse designs the individualised 3D printed guide to aid in the precise insertion of the iliosacral screw during the operation. Currently, some researchers have constructed the external skin guide by inserting two external fixation needles into the iliac bone before surgery and performing CT scans, then using these two external fixation needles as location markers [16]. However, once the patient is taken to the hospital, these two fixed needles must be worn until the procedure can be removed, which is inconvenient for nursing and adds to the patient’s pain. During CT fluoroscopy, artefacts in these two positioning pins will unavoidably occur, affecting the guide’s precision.

Based on past research, we created a 3D guide plate with a guide attached to the iliac spine. On the one hand, the guide cannula may be placed directly and accurately into the guide needle in accordance with the preoperative simulated screw trajectory, while also reducing the patient’s preoperative trauma and discomfort. The primary aims of this research are as follows: (i) to ascertain the precision and safety of iliosacral screw insertion using 3D guide plates; (ii) to evaluate the intraoperative radiation exposure associated with this procedure; and (iii) to compare the short-term consequences of clinical applications involving 3D printed guide plates and conventional surgery.

Methods and materials

General information

Patients information

Institutional Ethics Review Board approval has been obtained for this research. Patients who underwent conventional surgery (under X-ray guidance) or 3D guide-assisted insertion of sacroiliac joint screws (with or without anterior fixation) at our trauma centre due to an unstable injury to the posterior pelvic ring between January 2020 and May 2023 were the subjects of a retrospective analysis.

Inclusion and exclusion criteria

Inclusion Criteria: (1) Unilateral posterior pelvic ring instability fracture (61B or 61 C); (2) Fracture displacement was significantly reduced with closed reduction, such as traction; (3) Age range of 18 to 70 years; (4) Injury to operation time within 14 days. Exclusion criteria: (1) Individuals who have undergone open reduction due to failed closed reduction; (2) Patients who have sustained nerve and vascular injury and require surgical exploration; Age ranging from below 18 to over 70 years of age. In the present study, a total of 31 patients were enrolled, with 17 in the conventional surgery (CS) group and 14 in the guide plate (GP) group.

Preoperative Preparation

Following admission, all patients received femoral supracondylar traction, which amounted to 1/7 − 1/8 of their body weight. Additionally, preoperative pelvic anterior-posterior radiographs, inlet radiographs, outlet radiographs, and CT thin-slice scans were conducted. Sacral dysmorphism is recognised based on the criteria that have been proposed by Routt [17]. The cause of injury, age, the time from injury to surgery, AO/OTA classification, Young-Burgess classification were all documented.

Patient allocation

This retrospective study allocated patients based on the chronological introduction of 3D-printing technology rather than randomization. During January 2020–June 2021, all eligible patients underwent conventional fluoroscopy-guided surgery (CS group, n = 17). After July 2021, patients were preferentially treated with 3D-printed guides (GP group, n = 14) unless logistical constraints occurred (none in this cohort). Patient characteristics or surgeon preference did not influence allocation.

Surgical procedure

Guide-plate surgical group

Simulate the screw

The preoperative CT data of the patient were imported into the Mimics software (Materialize, Leuven, Belgium) in order to acquire axial, sagittal, and coronal views. Subsequently, a three-dimensional reconstruction of the pelvic model was performed, and the reduction process was simulated in accordance with the particular circumstances of the patient’s injury. Furthermore, the fracture classification of the patient guided the simulation of the appropriate number and length of screws. The screws are constructed in accordance with the subsequent principles: 1. When the sacroiliac joint is dislocated, the screw should be positioned in the centre of the safe bone channel and as perpendicular to the sacroiliac joint surface as feasible;2. In cases of “open-book injury” fractures, the screw is positioned anteriorly.3. A designated area is provided for the simulated screws ensuring that there are adequate distances between them in all directions (front, back, up, and down), with the allowance for minor directional errors.4. In patients with vertical instability, the number of sacral segments and screws inserted should be determined by the bone corridor diameter. After the screw trajectory was finalised, it was reviewed and finalised by two orthopaedic trauma surgeons with considerable surgical experience.

Design of guide-plate

By employing the pelvic model as the foundation and the iliac tubercle as the anchor point, a semi-enclosed guide plate base was constructed and affixed to the iliac spine (Fig. 1A-a). One hollow cannula for K-wire fixation is positioned on the outer plate of the iliac bone, while two hollow cannulas are positioned on the upper surface of the guide base (outer diameter 4 mm, inner diameter 2.8 mm, Fig. 1A-b, c, d). A 6.5 mm-diameter ilium connecting rod is affixed to the outer plate surface of the guide’s ilium (Fig. 1A-j). For intraoperative guide needle insertion, an iliosacral screw cannula featuring a virtual screw is positioned 5 cm away from the skin (outer diameter 4 mm, inner diameter 2.8 mm, Fig. 1A-e). To strengthen the screw guide hollow cannula, an identically sized fixed rod with a 5 mm diameter is affixed to the guide hollow cannula (Fig. 1A-f). Three 5 mm connecting rods should be inserted between the fixing rod and the iliac connecting rod (Fig. 1A-g, h, i). Make a mock-up of the iliosacral screw cannula and thread it through the ilium connecting rod according to the number of screws inserted (Fig. 1B, C, D).

Fig. 1.

A Simulation of the pelvic model using the patient’s CT data and the construction of a suitable guide. B Preoperative simulation of the 3D guide and the 3D guide printed 1:1 by the 3D printer: (a) Guide base; (b) Ilac hollow cannula 1; (c) Iliac hollow cannula 2; (d) Iliac hollow cannula 3; (e) Iliosacral screw cannula; (f) Screw fixing rod; (g) Iliosacral screw connecting rod 1; (h) Iliosacral screw connecting rod 2; (i) Iliosacral screw connecting rod 3; (j) Iiliac fixing rod. C. Front view of the pelvic virtual model and 3D guidance. D. Lateral view of the pelvic virtual model and 3D guidance

Print the model

The guide plate and 3D reconstruction data were exported and subsequently printed using a 3D printer. The pelvic model and guide plate were precisely duplicated in accordance with the patient data, with a printing accuracy of 0.01 mm. In vitro verification was conducted on the 3D-printed model subsequent to its successful manufacturing.

Intraoperative procedure

Type B pelvic fractures are characterized by rotational instability and are typically open or closed book injuries. Depending on the type of the fracture, the surgeon applies manual reduction by placing both hands on the patient’s bilateral anterior superior iliac spines. If manual reduction fails to achieve the desired effect, 1–2 Schanz screws may be inserted into the iliac bone to further facilitate the reduction process. A vertical unstable injury, a Type C pelvic fracture is managed as follows: prior to the operation, the patient is placed under a large weight supracondylar traction; during the operation, the assistant maintains the traction of the lower limb; the surgeon manually reduces the fracture using his Hand or the Schanz screws inserted into the iliac bone; and fluoroscopy is utilized to observe the fracture position; some patients can achieve a reduction that is essentially satisfactory; When intraoperative fluoroscopy reveals that the position of the posterior pelvic ring is unsatisfactory, assisted reduction is performed using the Starr frame. When employing the Starr frame, care must be taken to leave sufficient space on both sides for the placement of the guide plate. The patient is placed in the supine position on a radiolucent operating table, following reduction, a 5 cm-long incision is made along the iliac spine, centred on the anterior superior iliac spine and 5 cm posterior to it, on the injured side. Pelecate an adequate area of subcutaneous muscle and fascia in accordance with the dimensions of the guide design. After ensuring that the base of the guide plate is properly attached to the bone surface in the preoperative planning position, one K-wire measuring 2.5 mm in diameter is introduced into each hollow cannula. Align a K-wire with a diameter of 2.5 mm with the screw hollow cannula trajectory until it reaches the bone surface. Following the insertion of the K-wire into the external iliac plate’s bone surface (Fig. 2), the C-arm rotation angle was adjusted in accordance with the preoperative simulated X-ray angle in order to acquire inlet, outlet, and standard sacral lateral views. A 6.5 mm iliosacral screw was inserted in the trajectory after the K-wire extension was verified to be in accordance with the preoperative plan. The guide plate was subsequently removed and the incision was sutured subsequent to a second verification of the screw trajectory under fluoroscopic guidance (Fig. 3).

Fig. 2.

Intraoperative placement of the guide involves the following steps: A. Create a surgical incision approximately 5 cm in length along the iliac spine, positioned 5 cm posterior to the anterior superior iliac spine. B. Fully expose the iliac tubercle and remove the soft tissue from the bony surface until the guide can be completely placed. C. Position the guide using the iliac tubercle as an anatomical marker. D. Position the guide plate near the bone surface and secure the base of the guide with 3 K-wires once it is in close proximity to the bone surface

Fig. 3.

A 22-year-old male patient sustained injuries during a motorbike ride. Following admission, pelvic x-ray and CT scan are often conducted. The pelvic fracture was classified according to the AO/OTA system as 61C1.3. Prior to the surgical procedure, the initial step involved planning the fixation of the anterior pelvic ring, which was then followed by the fixation of the posterior iliosacral screw. There is vertical instability in the right sacroiliac joint, and the plan is to use two iliosacral screws on the right side to strengthen the posterior pelvic ring. A Preoperative pelvic anterior-posterior view; (B) Preoperative CT three-dimensional reconstruction view; (C) Simulate the three-dimensional reconstruction of the pelvis following reduction using the patient’s preoperative CT data. D Design the guide plate and simulate two screws based on the fracture type of the patient; (E) 3D print the model and guide plate and test them in vitro. (F) Postoperative pelvic inlet view; (G) Postoperative pelvic outlet view; H: Postoperative axial CT plane; I: Postoperative coronal CT plane

Postoperative screw trajectory evaluation

A 3D model is created from a reconstructed CT image using multiplanar reconstruction (MPR). The evaluation of screw trajectory primarily relies on three factors: initially, the distance between the virtual screw and the postoperative screw at the site of needle insertion on the outer plate of the iliac; Furthermore, the deviation between the angle formed by the parallel lines connecting the highest points of the bilateral iliac spines and the preoperative virtual screw trajectory and the postoperative screw trajectory in the CT coronal plane; Finally, in the axial plane, the deviation between the angle formed by the postoperative screw trajectory and the preoperative virtual screw trajectory at the intersection of the posterior borders of the bilateral iliac spines along a parallel line (Fig. 4). The data presented above has been calculated by two physicians.

Fig. 4.

A. The distance between the simulated screws and the postoperative screws on the external iliac plate was compared by overlapping the preoperative and postoperative hemipelvic models: (a) postoperative hemipelvic model; (b) preoperative hemipelvic model; (c) postoperative screw insertion point on the external iliac plate; and (d) preoperative virtual screw insertion point on the external iliac plate. In the coronal plane, the angle between the central axis of the virtual screw and the parallel line connecting the highest points of the bilateral iliac spines is α1. In the axial plane, the angle between the central axis of the virtual screw and the parallel line connecting the lowest point of the posterior edge of the bilateral iliac bone is β1. In the coronal plane, the angle between the central axis of the postoperative screw and the parallel line connect in the axial plane, the angle between the central axis of the postoperative screw and the parallel line at the lowest point of the posterior border of the bilateral ilium is β1’

Conventional surgery group

The reduction method and procedure are identical to those utilized by the GP group. The cross K-wire positioning technology is utilised to approximate the K-wire insertion point. A 2.5 mm-diameter K-wire is positioned at the designated needle insertion point on the standard sacral lateral image. The direction of the K-wire is adjusted repeatedly using the inlet and outlet views. Once the K-wire is no longer at risk of penetrating the plate, an appropriately sized screw is inserted in this direction (Fig. 5).

Fig. 5.

A 58-year-old female patient sustained injuries in a car accident. The AO/OTA grading for preoperative pelvic fractures was 61B2.2. A Preoperative anterior-posterior pelvic view; (B) Preoperative CT showed left sacroiliac joint separation with iliac fracture; (C) Postoperative anterior-posterior pelvic view; (D) Postoperative pelvic inlet view, (E) Postoperative pelvic outlet view; (F) Postoperative CT revealed that the screws were tightly attached to the anterior edge of the sacral cortex but did not penetrate out

Evaluation criteria

Insertion time for each screw

In this study, the screw insertion time refers to the time from the skin incision to the completion of the screw insertion, and the time for each screw is calculated based on the number of screws.

Radiation exposure time per screw

Prolonged radiation exposure can cause damage to both the doctors and the patients, and shortening the duration of intraoperative radiation exposure is beneficial to both the doctors and the patients. The radiation exposure time of each patient when the screws were inserted was recorded, and the radiation exposure time of each screw was calculated based on the number of screws.

Screw evaluation

On the one hand, excellent screw placement can prevent vascular nerve damage, while on the other, it can provide excellent biomechanical stability. The Screw Position Assessment is based on the Smith grade: Grade 0: no perforation; Grade 1: perforation less than 2 mm; Grade 2: perforation between 2 and 4 mm; Grade 3: perforation more than 4 mm [18]. Given the continued safety of the screw to securely fit against the cortex, a screw misposition is defined as the screw protruding beyond the cortical bone by more than 2 mm. The simulated screw trajectory was compared to the actual screw trajectory, and the virtual screw’s accuracy was assessed using three metrics: the distance between them of the needle insertion location, the coronal plane deviation angle, and the axial plane deviation angle.

Quality of the reduction

Postoperative CT was utilised to validate the screw position, and anterior-posterior, inlet-and-outlet views of the pelvis were routinely captured on postoperative X-rays. The degree of repositioning was assessed by postoperative radiographs according to Matta criteria (excellent: displacement ≤ 4 mm, good: displacement 5–10 mm, fair: 10–20 mm, poor: displacement >20 mm [19].

Functional evaluation

Document the time of the patient follow-up, functional outcome at the final follow-up was assessed using the Majeed score (pain: 30 points, standing: 36 points, sitting: 10 points, intercourse: 4 points and work: 20 points). The final score was divided into 4 stages, excellent (>85), good (70–84), fair (55–69) and poor (< 55) [20].

Statistics

SPSS 22.0 was used for all statistical analyses (SPSS, Chicago, IL, USA). Contingency tables and chi-square statistics were used to examine differences in SI screw misposition rates between the guide-plate and conventional groups. Fisher’s exact test was used to obtain the p-value when the anticipated number of cell entries was less than 5. Data satisfying the normality condition were expressed as mean ± standard deviation; non-normality data were expressed as median and quartiles. 95% confidence intervals were used, and p-values < 0.05 were considered statistically significant. For the deviation indices (entry point deviation distance, coronal plane angle deviation, and axial plane angle deviation) between the preoperative simulated screws and postoperative actual screws in the GP group, a one-sample t-test was used to evaluate the difference from zero deviation (null hypothesis: deviation = 0) to verify the statistical significance of the deviations. A 95% confidence interval was set, and a

P value less than 0.05 was considered statistically significant.

Results

Patient characteristics

The CS group consisted of 17 patients, eight males and nine females, with a mean age of 42.6 ± 13.4 years. The mechanisms of injury were 11 car accidents, three falls from heights, two heavy crushings, and one others. The AO/OTA fracture classification was as follows: 61B: 13 cases, 61 C: four cases; according to the Young-Burgess classification: there were 5 cases of LC II type, 4 cases of LC III type, 3 cases of APC II type, 2 cases of APC III type, and 2 cases of VS type. There were seven cases of sacral dysmorphism and 10 cases of normal sacral. The time from injury to surgery was 6.2 ± 2.3 days. The mean follow-up duration was 18.7 ± 4.4 months. The GP group consisted of 14 patients, six males and eight females, with a mean age of 40.4 ± 13.1 years. The mechanisms of injury were eight car accidents, four falls from heights, one heavy crushings, and one others. The AO/OTA fracture classification was as follows: 61B: 11 cases, 61 C: three cases; according to the Young-Burgess classification: there were 6 cases of LC II type, 3 cases of LC III type, 2 cases of APC II type, 2 cases of APC III type, and 1 cases of VS type. There were six cases of sacral dysmorphism and eight cases of normal sacral. The time from injury to surgery was 6.4 ± 2.3 days. The mean follow-up duration was 18.2 ± 3.8 months. In terms of sacral dysmorphism, age, gender, mechanism of injury, the time from injury to surgery, AO/OTA classification, Young-Burgess classification and follow-up duration, there were no statistically significant differences between the two groups (p > 0.05) (Table 1).

Table 1.

Characteristics of patients

	CS	GP	p
Patients			0.815
Male (n)  Female (n)	8 9	6 8
Mean age (year)	42.6 ± 13.4	40.4 ± 13.1	0.656
Mechanism of injury (n)  Car accident  Fall of height  Heavy object crush  Other	11 3 2 1	8 4 1 1	1.000
AO/OTA classification (n)  61B  61 C	13 4	11 3	1.000
Young-Burgess classification(n)			1.000
LC II	5	6
LC III	4	3
APC II	3	2
APC III	2	2
VS	2	1
Sacral morphology (n)  Dysmorphism  Normal	7 10	6 8	0.479
Time from injury to surgery (d)	6.2 ± 2.3	6.4 ± 2.3	0.993
Follow-up time(month)	18.7 ± 4.4	18.2 ± 3.8	0.746

Screw evaluation and radiation exposure

A total of 42 screws were inserted in the two groups. The CS group comprised a total of 24 insertion screws, of which 18 were S1 and six were S2. The GP group consists of 18 insertion screws, of which 14 are inserted for S1 and four for S2. In the GP group, the screw misposition rate, radiation exposure time, and insertion time of each screw were all significantly reduced in comparison to the CS group (5.56% versus 25.00%; 0.31 ± 0.14 min versus 0.91 ± 0.17 min; 17.29 ± 1.90 min versus 25.18 ± 3.99 min, respectively). There were statistically significant comparisons between the two groups in terms of radiation exposure time of each screw, and insertion time of each screw (p < 0.05), however, there was no significant difference in the rate of screw misposition between the two groups (p >0.05). (Table 2). In the accuracy evaluation of the GP group, comparative analysis of preoperative and postoperative CT scans showed the deviations between the postoperative screws and preoperative simulated screws as follows: the average deviation distance of the entry point on the outer iliac plate was 1.96 ± 0.54 mm, with a range of 1.13–3.52 mm; the average coronal plane deviation angle was 2.96 ± 0.79°, with a range of 1.36–4.25°; and the average axial plane deviation angle was 3.19 ± 0.86°, with a range of 1.14–4.51° (Table 3). The results of the one-sample t-test indicated that each of the above indicators was statistically significantly different from zero deviation (all P < 0.001).

Table 2.

Comparison of the operation time, radiation exposure time, and screw misposition rate of each screw in the CS and GP groups

Group	screws(n)	Radiation exposure time of each screw(min)	Operating time for each screw placement(min)	Screw misposition rate (n,%)
CS	24	0.91 ± 0.17	25.18 ± 3.99	6(25.00%)
GP	18	0.31 ± 0.14	17.29 ± 1.90	1(5.56%)
p		< 0.001	< 0.001	0.208

*Screw misposition was defined as the screw protruding beyond the cortical bone by more than 2 mm

Table 3.

Mean deviations between postoperative screws and preoperative simulated screws in the guide plate (GP) group, with statistical significance compared to zero deviation

	Entry point deviation (mm)	Coronal deviation angle (α1+/-α1’, °)	Axial deviation angle (β1+/-β1’, °)
M ± SD	1.96 ± 0.54	2.96 ± 0.79	3.19 ± 0.86
Range	1.13–3.52	1.36–4.25	1.14–4.51
p-value (vs. zero deviation)	< 0.001	< 0.001	< 0.001

M mean, SD standard deviation

*All deviations were measured between postoperative screws and preoperative simulated screws. The p-values were calculated using one-sample t-tests, with the null hypothesis that deviations equals zero (i.e., no difference between postoperative and simulated screws). Statistical significance was set at p < 0.05

Complications

A total of two cases (11.8%) in the CS group and one cases (7.1%) in the GP group experienced deep venous thrombosis subsequent to surgery. All of these patients were treated with vena cava filters and anticoagulants, and a three-month follow-up examination of the deep veins in both lower extremities revealed that the thrombosis had resolved.

Quality of the reduction and functional evaluation

The Matta score was used to assess the quality of the postoperative reduction. In the CS group, there were 14 excellent cases, three good cases. In the GP group, there were 10 excellent cases, four good cases. There was no statistically significant difference in Matta score between the two groups (p >0.05).

In the CS group, there were 14 excellent cases, two good cases, one fair cases, the average score was 88.00(85.50,91.50). In the GP group, there were 11 excellent cases, two good cases, one fair cases, the average score was 88.00(84.50,91.00), At the last follow-up, there was no statistically significant difference between the two groups’ Majeed scores (p >0.05) (Table 4). There were no wound infections, skin necrosis, or nerve damage in either group, and the fractures healed at the last follow-up.

Table 4.

Majeed score in both groups at the last follow-up

Group	Total	Majeed score
		Excellent	Good	Fair	Poor	Average score [M(P25,P75)]
CS	17	14	2	1	0	88.00(85.50,91.50)
GP	14	11	2	1	0	88.00(84.50,91.00)
p		1.000				0.952

Discussion

Owing to the intricate anatomy of the pelvis, deviations in iliosacral screw placement may result in irreversible damage [21]. For surgeons with limited experience, treating unstable posterior pelvic ring injuries with iliosacral screws is particularly challenging, especially in obese patients or those with sacral dysmorphism, where the failure rate of iliosacral screw placement may be significantly higher [14]. Although several studies have demonstrated that using special fluoroscopic positions during surgery can enhance the accuracy of screw placement, the trade-off is increased surgical time and fluoroscopy counts, which compromises the efficiency of the technique [22, 23]. Research has shown that experienced surgeons spend an average of 2.10 min on fluoroscopy when placing iliosacral screws under X-ray guidance [12].

Computer navigation, O-arm navigation, and surgical robots have significantly improved the precision and safety of screw insertion [24–26]. Despite the ability of navigation systems to reduce fluoroscopy time, the high cost of equipment and increased surgical expenses have greatly limited the widespread adoption of these devices [27]. In recent years, 3D-printed guide plate technology has rapidly developed in orthopedic surgery, particularly for guiding screw placement in spinal surgeries [24, 28]. Compared with conventional fluoroscopy-guided screw placement, the preoperatively designed guide plate is closely attached to the corresponding bone surface, eliminating the need for surgeons to consider the screw insertion point or trajectory angle. Moreover, these guide plates are individually customized, easy to use, and have a short learning curve, effectively enhancing the accuracy of screw placement [29].

Some scholars have used 3D-printed individualized internal guide plates for iliosacral screw placement, but this approach requires a 5-cm incision at the posterior superior iliac spine (PSIS) and complete dissection of the muscles and soft tissues attached to the PSIS to achieve intimate contact between the guide plate and the bone surface. This surgical method has several drawbacks, including significant blood loss, difficult intraoperative dissection, and difficulty in achieving a perfect match between the guide plate and the bone surface, which may lead to screw misposition [30]. In our study, we modified the fixation site of the guide plate base from the PSIS to the iliac tubercle. This superficial location is easily exposed even in obese patients, without the need to dissect excessive muscle attachment points and soft tissues, facilitating better contact with the bone surface and significantly improving the precision of the guide plate under conditions that avoid damage to important nerves and vessels.

Although the difference in screw misposition rates between the GP group and the CS group in this study did not reach statistical significance, the numerical downward trend in the misposition rate of the GP group (5.56% in the GP group vs. 16.67% in the CS group) still suggests its potential value in improving the accuracy of screw placement. This trend may be related to the integrated design of “preoperative planning - intraoperative guidance” of the guide plate: by simulating the screw trajectory on three-dimensional CT preoperatively and converting it into a physical guide plate, the entry point and angle can be directly positioned with reference to the guide plate during the operation, which reduces the subjective errors caused by relying on the surgeon’s experience judgment in traditional surgery. Especially for cases with complex sacral anatomy (such as sacral dysmorphism), the guide plate can provide a more stable reference standard for screw placement.

In addition, the advantages of GP technology in terms of surgical efficiency and safety are more obvious: first, the guide plate assistance can simplify the intraoperative positioning process and significantly shorten the operation time, which is of positive significance for lowering the risk of anesthesia; second, there is no need for repeated fluoroscopy to confirm the screw position during the operation, which can greatly reduce the radiation exposure dose for both surgeons and patients, and help reduce the risks related to occupational exposure in the long run.

From the perspective of clinical applicability, GP technology is particularly suitable for young physicians or surgeons with limited experience in treating pelvic fractures. Traditional free-hand screw placement requires long-term accumulation of three-dimensional cognition of the sacral anatomical space, while the guide plate reduces the dependence on the individual experience of surgeons by converting virtual planning into physical guidance, which can help junior physicians quickly master the skills of accurate screw placement. When promoted in primary hospitals or trauma centers, it is expected to improve the overall safety and consistency of iliosacral screw placement.

It should be objectively pointed out that the lack of statistical significance in the difference in screw misposition rates between the GP group and the CS group in this study may be limited by the small sample size (the total number of screws in both groups is less than 100) and the low overall incidence of misposition events, resulting in insufficient statistical power. Future multi-center, large-sample studies are needed to further verify its actual value in reducing the misposition rate. However, the current data have preliminarily shown that 3D printed guide plates have advantages in improving screw placement efficiency, reducing radiation exposure, and assisting inexperienced physicians, with good prospects for clinical transformation.

The accuracy of the 3D printed guide plate can be further verified by the deviation between the preoperative simulated and postoperative screws. The mean values of the entry point deviation distance, coronal plane and axial plane angle deviations in the GP group are 1.96 ± 0.54 mm, 2.96 ± 0.79°, and 3.19 ± 0.86° respectively, with small fluctuations in the range. Moreover, the one-sample t-test confirmed that the differences between these deviations and zero deviation are statistically significant (all P < 0.001), suggesting that the deviation is a stably existing technical performance. Despite the existence of deviations, the values are small, indicating that the guide plate can establish a stable accuracy correlation between preoperative planning and intraoperative execution, ensure the safety of screw placement, and provide empirical support for its clinical application.

However, this study and the 3D printed guide plate technology have certain limitations: (1) The design and printing of the guide plate require an additional 2–3 days and costs (30–50 US dollars), which may delay emergency surgery; (2) The additional incision at the iliac spine requires soft tissue dissection, with the risk of local trauma; (3) The retrospective design and non-random grouping may introduce selection bias, with a small sample size and no comparison with navigation and robotic technologies, resulting in limited statistical power; (4) The follow-up time is relatively short (about 18 months), and the long-term biomechanical stability and the impact of confounding factors are not yet clear. In the future, rapid prototyping technology can be used to shorten the preparation time, and multi-center randomized controlled trials can be carried out to expand the sample size and extend the follow-up period to further verify its value.

Conclusion

The use of personalized 3D-printed guide plates in conjunction with preoperative virtual screw technology can precisely insert iliosacral screws via bridging techniques, reduce radiation exposure, shorten the operative time for screw placement, and decrease the likelihood of nerve injury caused by screw malposition, demonstrating promising clinical application potential.

Abbreviations

CT

Computed tomography

3D

Three-dimensional

MPR

Multiplanar reconstruction

PSIS

Posterior superior iliac spine

Authors’ contributions

MW and PZ designed the study. JC and LL collected and analyzed the patient data. MW and XW performed the operation. LL and PZ analyzed the results and prepared the manuscript. All authors read and approved the final manuscript.

Funding

No funding was received to assist with the preparation of this manuscript.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

This study was performed according to the Helsinki declaration and the study was approved by the ethics committee of Bengal Medical University (Number: BYYFY-2022KY308), and informed consent was obtained from all subjects and from their legal guardian(s) as participants below age 18 are involved in the study.

Consent for publication

Written informed consent was obtained from the patient for publication of all case data and related clinical pictures.

Competing interests

The authors declare no competing interests.