Evaluating 3D-Printed Guide Plates in Elbow Fixation: A Comparative Study

Introduction

Complex elbow fractures and dislocations often result in significant damage to the joint capsule and ligaments, as well as fractures of 1 or more major stable structures, including the radial head, coronoid process, and olecranon [1–3]. Such injuries frequently lead to elbow instability, which requires surgical reconstruction to restore elbow anatomical relationships and stability [4,5]. However, even after surgery, complications such as osteoarthritis, elbow stiffness, loss of motion, and elbow instability are common, which can impact long-term function [6]. It is widely believed that early postoperative functional exercises are critical for preventing these complications and improving long-term outcomes [7].

Early postoperative functional exercises place higher demands on elbow stability [8]. Early mobilization with unstable elbow structures can lead to pain and failure of ligament reconstruction and internal fixation, increasing the need for a second operation [9]. Therefore, precise intraoperative reconstruction of the elbow’s anatomical relationships and stability is crucial to surgery success [10,11]. Plate internal fixation systems are commonly used to reconstruct the bone structures of the elbow, while rivets and wires are applied to repair non-bony structures such as ligaments and tendons to restore the elbow’s stability. Once these procedures are completed, elbow stability is routinely assessed through fluoroscopy. If instability persists or there is a risk of re-dislocation, external fixation is often necessary [12,13].

Hinged external fixators are particular effective in maintaining the flexion-extension axis activities of the elbow, protecting repaired osseous and soft-tissue structures, and allowing early postoperative functional exercises, which can safely and effectively prevent elbow stiffness and reduce the need for secondary surgeries [14–16]. The insertion of guide pins in flexion-extension movement axis of the elbow joint is a key step in installation of the hinged external fixator, which determines the success of the operation [17–19]. However, positioning the guide pin is technically demanding and typically requires repeated use of C-arm X-ray fluoroscopy, which increases both the operation time and radiation exposure for surgeons and patients [20].

To address these challenges, three-dimensional (3D)-printed guide plates have been proposed as an innovative solution [21]. Using patient-specific imaging data, 3D printing technology can produce highly accurate and custom-designed guide plates to assist in precise positioning of the rotation axis of the elbow joint during surgery. This method significantly reduces reliance on fluoroscopy, minimizes the risk of radiation exposure, and improves the efficiency of the surgical procedure. Furthermore, 3D printing offers a personalized, cost-effective, and precise method for planning complex surgeries [21,22].

Therefore, this study aimed to compare outcomes in 20 patients with complex elbow fracture dislocation with and without 3D-printed guide plate-assisted rotation axis positioning of a hinged external elbow fixator.

Material and Methods

ETHICS STATEMENT:

This study was approved by the Human Ethics Committee of Nanjing First Hospital. Written informed consent was obtained from all participants before inclusion in the study. All procedures were conducted in accordance with the principles outlined in the Declaration of Helsinki.

INCLUSION AND EXCLUSION CRITERIA:

Inclusion criteria were patients requiring hinged external fixators during elbow surgery, with complex elbow fracture dislocation or post-traumatic elbow stiffness (PTES). Exclusion criteria were malunion and pathological fracture around the elbow joint.

STUDY DESIGN AND PATIENTS DATA:

From December 2018 to December 2022, 20 patients with complex elbow fracture dislocation or PTES were retrospectively enrolled in this study. The patients were divided into 2 groups:

the free-hand group (n=10) and the guide template group (n=10) (Table 1). Types of fractures included varus posteromedial rotatory instability (VPMRI), terrible triad injury (TTI), and PTES. In the free-hand group, 6 males and 4 females were enrolled with left side (5 cases) and right side (5 cases). The mean age of those patients was 40.5 years (range, 19–58). The mechanism of injury included fall (8 cases) and traffic accident (2 cases). The type of injury included VPMRI (2 cases), TTI (2 cases), and PTES (6 cases). In the guide template group, 6 males and 4 females were enrolled with injury to the left side (3 cases) and right side (7 cases). The mean age of those patients was 40.5 years (range, 19–58). The mechanisms of injury were fall (7 cases) and traffic accident (3 cases). The types of injury were VPMRI (1 cases), TTI (4 cases), and PTES (5 cases).

PREOPERATIVE IMAGING AND PLANNING:

Prior to surgery, all patients underwent anteroposterior and lateral X-ray imaging and CT scans of the elbow joint. The CT scans were used for creating 3D models of the humeral portion of the elbow joint using Mimics Medical 16.0 (Materialise, Belgium) software. The 3D models were then used to design the pin guide templates. MRI scans were performed if clinically required.

DESIGN AND MANUFACTURE OF PIN GUIDE TEMPLATE:

First, CT scans (slice thickness 1 mm, reconstruction interval 1 mm) of elbow the joint for each patient were stored in DICOM (Digital Imaging and Communications in Medicine) format (Figure 1A–1C). Then, 3D models of the humeral portion were reconstructed based on those data by using Mimics Medical 16.0 (Materialise, Belgium) software (Figure 1D). After that, the pin guide plate was designed by 3-matic 12.0 (Materialise, Belgium) for the flexion-extension movement axis (Figure 2A, 2B). Lastly, the physical model of the distal humerus and the pin guide plate were rapidly prototyped using polymer photosensitive resin via a 3D printer (Dreamer, Flsaforge, Zhejiang, China) (Figure 2C, 2D).

OPERATION PROCEDURES:

Free-hand group: The patients underwent open reduction and internal fixation for elbow fracture and dislocation, repair of damaged ligaments, or release of post-traumatic elbow stiffness. After this procedure, to assess whether there was instability in elbow joint, flexion activities were checked in the neutral, supination, and pronation positions. If the instability still existed, a hinged external fixator was further required. Installation of the hinged external fixator (DJDII™, Stryker, Kalamazoo, MI, USA) was performed in accordance with standard procedures [23]. Intraoperative C-arm fluoroscopy was repeatedly used to confirm that the pin hole of the external fixation bracket passed through the rotation center of the elbow joint, that is, in the standard lateral position of the elbow joint, the guide pin accurately passed through the “concentric circle” center of the elbow joint, and the guide pin overlapped with the rotation center axis of the elbow joint (Figure 3A, 3B).

In the guide template group, the procedure before pin placement was the same as in the free-hand group. The installation of hinged external fixators also followed standard procedures. Before the insertion of the guide pin in the rotation axis of the elbow joint, the lateral condyle of the humerus was properly detached, and the guide template was correctly placed, then the guide wire was inserted along the pin channel of the guide template. C-arm fluoroscopy confirmed that the guide pin was accurately located in the rotation center of the elbow joint, and the needle tail overlapped with the “concentric circle” center of the elbow joint (Figure 3C, 3D).

MEASUREMENT PARAMETERS:

Pin placement time was the time taken to accurately place the guide pin during surgery measured in minutes. This was recorded from the moment the surgeon began inserting the pin until it was confirmed to be in the correct position, as assessed by C-arm fluoroscopy. The time was compared between the guide template group and the free-hand group to evaluate any time-saving benefits of the guide template.

The total fluoroscopic exposure time was recorded for each patient during the pin placement procedure. Fluoroscopy was used to guide the positioning of the pin in both groups. The exposure time was monitored to assess the potential reduction in radiation exposure associated with the use of the 3D-printed guide template.

Range of motion (ROM) of the elbow joint was measured postoperatively using a goniometer. The measurement focused on elbow flexion and extension, as these are critical for assessing functional recovery of the elbow joint. ROM was measured during follow-up visits, and the data were compared between the 2 groups to determine if use of the guide template affected the functional outcome.

STATISTICS ANALYSIS:

All statistical analyses were performed using SPSS 19.0 software (IBM, Armonk, NY, USA). We collected and analyzed data from continuous variables such as pin placement time, fluoroscopic exposure time, and ROM, presented as mean±standard deviation (SD) for each group. This allowed for data summarization in terms of central tendency and variability. To compare the outcomes between the 2 groups (the guide template group and the free-hand group), an independent sample t-test was used. This test is appropriate for comparing the means of 2 independent groups when the data are normally distributed. A P value of less than 0.05 was considered statistically significant for all tests. This threshold indicates that there is a less than 5% chance that the observed difference between the groups is due to random variation.

Results

PREOPERATIVE AND SURGICAL PROCEDURES:

All operational procedures were performed according to pre-surgery planning for each group. In the guide template group, the guide templates were precisely fitted to the surface of the lateral condyle of the humerus, and guide pins were drilled though the designated channel accordingly.

PIN PLACEMENT TIME:

The pin placement time for each patient was recorded and compared between the 2 groups (Table 2). The results showed that the guide template group had a significantly shorter pin placement time compared to the free-hand group (6.80±1.32 min vs 26.00±9.44 min, P<0.0001). These results demonstrate the efficiency of using a guide template in reducing the time required for pin placement.

FLUOROSCOPIC EXPOSURE TIME:

Similarly, the fluoroscopic exposure times using the C-arm machine were measured for both groups. The guide template group had significantly fewer fluoroscopic exposures compared to the free-hand group (3.60±1.27 vs 41.90±14.80, P<0.0001). These findings indicate that the use of the guide template resulted in a substantial reduction in the number of fluoroscopic images taken during surgery, thereby reducing radiation exposure.

ACCURACY AND STABILITY:

The scatter diagram and bar graph further illustrated the reduction in pin placement time and fluoroscopic exposure times, with greater accuracy and stability in guide template group (Figure 4A, 4B). The data support the hypothesis that the guide template enhances the precision and reliability of the surgical procedure.

RANGE OF MOTION (ROM):

To assess the functional outcomes, ROM of elbow joint was measured postoperatively. The ROMs in both groups were over 130°, indicating that both groups achieved good elbow mobility. However, there were no significant differences in ROM between the 2 groups (P=0.069), suggesting that the use of the guide template did not negatively impact functional recovery of the elbow joint (Table 2, Figure 4C).

Discussion

This study aimed to evaluate the effectiveness of a three-dimensional (3D)-printed guide template in assisting the installation of a hinged external elbow fixator. Our findings demonstrate that the use of the guide template significantly reduced pin placement time and fluoroscopic exposure time compared to the free-hand technique. Specifically, the guide template group had a mean pin placement time of 6.80±1.32 minutes, compared to 26.00±9.44 minutes in the free-hand group, with a statistically significant difference (P<0.0001). Similarly, fluoroscopic exposure time was markedly lower in the guide template group (3.60±1.27 minutes) versus the free-hand group (41.90±14.80 minutes), again with a significant difference (P<0.0001). However, there was no significant difference in the range of motion (ROM) between the 2 groups, with both groups achieving functional ROM postoperatively (guide template group: 137.40±4.40°, free-hand group: 132.60±6.48°, P=0.069).

Several studies have explored the use of 3D printing and guide templates in orthopedic surgery, specifically in the context of complex elbow injuries. A recent study by Ma et al [24] also investigated the use of 3D-printed guide plates for positioning the rotation axis of the elbow when using hinged external fixators. They found that the use of 3D-printed guide plates significantly reduced pin placement time and radiation exposure, similar to our findings. Specifically, their study reported a mean pin placement time of 329.32±42.38 seconds and a mean fluoroscopy count of 2.32±0.48 times, which were notably lower than traditional methods that require frequent fluoroscopy, and they also reported similar functional outcomes in terms of ROM, which aligns with our study. Both studies found no significant difference in ROM between the groups, indicating that 3D-printed guide plates do not hinder elbow joint mobility. These findings are consistent with our study, suggesting that 3D-printed guide plates provide a substantial advantage in reducing operation time and radiation exposure, and the use of 3D-printed guides does not adversely affect postoperative recovery.

3D printing is a new revolutionary technology, which has been widely applied in orthopedic surgery, such as spinal pedicle screw placement, joint replacement, internal fixation of fracture, and bone tumor surgery [25,26]. 3D printed guide screw placement technology is also widely used in spinal surgery to achieve accurate pedicle screw placement [27]. In elbow fracture surgery, 3D-printed models were used to accurately depict the fracture characteristics, which could help surgeons make pre-surgical plans and improve physician–patient communication [28]. Additionally, a cadaver study has reported on the application of 3D printed guide technology in assisting the installation of elbow external fixator screws [29]. However, few studies have assessed use of 3D-printed guide nail technology to assist the clinical installation of hinged elbow external fixators. In this study, we designed and manufactured a guide template for assisting pin placement in surgery of hinged external fixator installation. The guide template was made of polymer photosensitive resin, which is easy to disinfect and operate.

Hinged elbow external fixators are often applied for unstable elbow joints after fracture and ligament repaired during complex elbow fracture and dislocation surgery, and post-traumatic elbow stiffness (PTES) release surgery [14,15,30]. The use of hinged elbow external fixator can maintain the “concentric center” stability to achieve early postoperative functional exercise, improve the range of motion, and reduce adhesion and contracture of the surrounding soft tissue, which can improve elbow joint and forearm functional recovery. Accurate pin placement of elbow rotational axis is the key to successful installation of hinged external fixator. Failure of pin placement often leads to elbow instability and dislocation, and even failure of internal fixation systems. Therefore, to ensure the accuracy of pin placement, the traditional operation needs to repeatedly adjust the position of elbow joint and C-arm, in pursuit of a complete lateral “concentric circle” sign, and then the Kirschner-wire needs to be drilled into the center of the circle with as little deviation as possible [23,31]. Such procedures often take much time and require many fluoroscopies, which increases the surgical time and radiation exposure. The results of our study showed that use of the guide template could significantly reduce pin placement time and fluoroscopic exposure times, with more accuracy and stability. An argument for static external fixation was similar outcomes; however, our device decreases the operative time of the hinged fixator and the fluoroscopic exposure times; therefore, it may be more useful [31].

To further evaluate the accuracy of the pin placement and the effect of surgery, the ROM was measured after the installation of hinged external fixator. Most daily elbow activities can be performed within the range of 30°–130° flexion and extension [32]. Elbow stiffness is diagnosed when the ROM is less than this normal range. In this study, ROM in guide template group and free-hand group were 137.40±4.40°and 132.60±6.48°, which were both more than 130°. These results predicted good surgical outcomes in both groups. Meanwhile, no significant differences of ROM between 2 groups were observed, which indicated that “concentric circle” perspective technique is feasible in the operation of hinged external fixator installation.

During the operation, the affected limb was often placed on a table and in the position of elbow flexion and humerus internal rotation (Figure 3B). In this position, it was easy to tear the repaired lateral collateral ligament during surgery. To avoid the tear of the lateral collateral ligament, 2 Kirschner-wires were usually used to fix the ulnar-humeral joint, and it was easy to artificially cause the articular surface injury. This problem could be easily avoided by using our guide template. The affected limb was placed on a table in the extended position, which was convenient for intraoperative operation and avoided tearing the lateral collateral ligament (Figure 3D).

This study also has some limitations. Firstly, the sample size was relatively small, with only 20 patients, which may limit the generalizability of the results. A larger sample size would provide more robust data and allow for better detection of any small differences between groups. Secondly, the study was conducted in a single-center setting, which could introduce bias related to institutional practices, surgical expertise, and equipment used. A multi-center trial would improve the external validity of the results and ensure a more diverse patient population. Thirdly, the retrospective nature of the study may have led to selection bias, as the patients were not randomly assigned to groups. Additionally, the assessment of ROM was based on clinical measurements, which are subject to observer variability. More objective and consistent methods of assessing functional outcomes, such as 3D motion analysis or patient-reported outcomes, could have provided a more comprehensive evaluation of the impact of the guide template on elbow function. Finally, although fluoroscopic exposure was reduced with the use of the guide template, the study did not assess the long-term effects of radiation exposure, which could be important for determining the safety of prolonged use of fluoroscopy during complex surgeries.

Conclusions

The use of the 3D-printed guide template significantly reduced pin placement time and fluoroscopic exposure, demonstrating its potential to enhance surgical efficiency and safety in complex elbow fracture surgeries. The guide template provided precise positioning of the rotation axis without compromising ROM, yielding satisfactory functional outcomes. These findings support the use of 3D-printed guide plates as an effective tool for improving precision in hinged external fixator implantation, reducing operation time and radiation exposure, and improving postoperative recovery.