Table of Contents  
Year : 2016  |  Volume : 1  |  Issue : 4  |  Page : 145-151

3D-printed module-assisted minimally invasive lumbar pedicle screw placement: study protocol for a self-controlled, open-label clinical trial with 2-year follow-up

Department of Orthopedics, Affiliated Hospital of Putian University, Teaching Hospital of Fujian Medical University; Affiliated Putian Hospital of Southern Medical University; Affiliated Hospital of Putian University, Putian, Fujian Province, China

Date of Web Publication30-Nov-2016

Correspondence Address:
Xuan-huang Chen
Department of Orthopedics, Affiliated Hospital of Putian University, Teaching Hospital of Fujian Medical University; Affiliated Putian Hospital of Southern Medical University; Affiliated Hospital of Putian University, Putian, Fujian Province
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Source of Support: This study was supported by the Scientific Research Fund of Putian University, China (No. 2016055); and a grant for the Medical Innovation Project of Fujian Provincial Health and Family Planning Commission in China (No. 2012-CX-34)., Conflict of Interest: None

DOI: 10.4103/2542-4157.194810

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Background: Minimally invasive pedicle screw fixation is an effective treatment for thoracolumbar diseases, but skilled operations are required during the internal fixation. If inaccurate implantation occurs, adverse reactions will appear postoperatively; for example, the implanted screw will fall off. 3D printing can manufacture a suitable implant for a patient, accurately simulate the repair process, and reduce the difficulty and complexity of the operation, aiming to produce an implant that is most suitable for repair surgery. Here, we describe our protocol for testing the hypothesis that precise localization during minimally invasive lumbar pedicle screw placement can be achieved with the assistance of a 3D-printed module.
Methods/Design: A single-center, self-controlled, open-label study with 2-year follow-up was carried out at the Affiliated Hospital of Putian University, Putian, Fujian Province, China. Preoperative thin-layer CT data from 36 cases of lumbar spine fixation were collected and digitally reconstructed using Mimics software. An ideal channel for screw insertion via the vertebral pedicle was preset, and a 3D-printed navigation module with a screw channel was designed and printed based on the anatomical structures of the bone surface that could be stripped around the screw channel. Minimally invasive pedicle screw fixation was then navigated by the 3D-printed module using the Quadrant system. A thin-layer CT scan was used for postoperative three-dimensional reconstruction. The primary outcome measure was accurate rate of screw placement, which was used to assess whether the screw placement under navigation by the 3D-printed module achieved the desired results. Secondary outcome measures included lumbar CT results preoperatively, 6 and 24 months postoperatively, operation time, intraoperative blood loss, duration of radiation exposure, and incidence of adverse events at 6 and 24 months postoperatively. Some results from the completed surgery are given below: the time of operation, amount of bleeding and duration of radiation exposure were 120.58 ± 56.46 minutes, 136.83 ± 40.62 mL, and 50 ± 11 seconds, respectively. A total of 186 screws were inserted in the patients, with a 98% accuracy rate.
Discussion: The study aims to test our hypothesis that a 3D-printed module is a valuable aid for screw localization in minimally invasive lumbar pedicle screw placement, providing clinical data for 3D-printed module-assisted minimally invasive lumbar surgery using the Quadrant system.
Trial registration: identifier: NCT02970578.
Ethics: The study protocol was approved by the Ethics Committee of the Affiliated Hospital of Putian University, Fujian Province, China, and performed in accordance with the guidelines of the Declaration of Helsinki, formulated by the World Medical Association.
Informed consent: Written informed consent was obtained from all participants prior to the trial.

Keywords: clinical trial; 3D printing; lumbar pedicle screw; Quadrant system; minimally invasive; precision; CT scan; adverse reactions; self-controlled trial

How to cite this article:
Yu Zx, Chen Xh, Zhang Gd, Chen X, Wu Cf, Zheng Zg, Gao Xq, Lin Hb. 3D-printed module-assisted minimally invasive lumbar pedicle screw placement: study protocol for a self-controlled, open-label clinical trial with 2-year follow-up. Clin Trials Orthop Disord 2016;1:145-51

How to cite this URL:
Yu Zx, Chen Xh, Zhang Gd, Chen X, Wu Cf, Zheng Zg, Gao Xq, Lin Hb. 3D-printed module-assisted minimally invasive lumbar pedicle screw placement: study protocol for a self-controlled, open-label clinical trial with 2-year follow-up. Clin Trials Orthop Disord [serial online] 2016 [cited 2021 Jul 29];1:145-51. Available from:

  Introduction Top

History and current related studies

Pedicle screw fixation has been widely used in spinal surgery, in procedures dealing with spinal fractures, lumbar spondylolisthesis, scoliosis, and lumbar spinal stenosis (Schwender et al., 2005; Fan et al., 2015; Shinohara et al., 2016; Toquart et al., 2016; Yang et al., 2016a, b). However, difficulties in pedicle screw placement are unavoidable because of anatomical variations in the spinal structure, as well as spinal degeneration. Consequently, the precise localization for screw placement is essential. If not, errors in screw placement will result in reduced strength or even failure of the internal fixation, which may lead to a series of injuries, including nerve root injury, dural sac tear, vascular injury and even spinal cord injury (Isaacs et al., 2005; Scheufler et al., 2007; Yang et al., 2016a, b). To conclude, improving the accuracy of screw placement and reducing the complications of screw placement during pedicle screw fixation is urgently required.

With the rapid adoption of digital medicine and 3D printing technology in orthopedic practice (Tarafder et al., 2013; Ventola, 2014), 3D techniques, based on preoperative high-resolution CT scan data, can theoretically restore the three-dimensional structure of the bone. That is to say, we can present a detailed description of the complex anatomical structure of the bone, to accurately produce a preoperative plan and an intraoperative simulation (Laine et al., 2000; Kosmopoulos et al., 2007; Tian and Xu, 2009). Wide-ranging evidence that digital three-dimensional reconstruction and 3D techniques can assist the posterior pedicle screw fixation in the treatment of spine lesions has been collected (Lu et al., 2009; Merc et al., 2013; Rόcker et al., 2016).

Main objectives

The main purpose of the study is to explore the accuracy of 3D-printed module-assisted minimally invasive lumbar pedicle screw placement using the Quadrant system, and to verify the feasibility of the module in reducing the error rate of screw placement, as well as postoperative complications.

Distinguishing features from related studies

This study is designed to complete a minimally invasive posterior lumbar pedicle screw placement with the help of 3D printing technology, to achieve the accurate localization of the screw.

  Methods/Design Top

Study design

A single-center, self-controlled, open-label clinical trial with 2-year follow-up.

Study setting

The Affiliated Hospital of Putian University, Putian, Fujian Province, China.

Study procedures

Thirty-six patients with lumbar degenerative lesions admitted to the Affiliated Hospital of Putian University, China from 2012 to 2015 were enrolled. These patients underwent 3D-printed module-assisted lumbar pedicle screw placement using the Quadrant system, aiming to restore the stability of the spine. Anatomically, imaging results of the spine were used preoperatively to provide a precise localization of the screw placement, and to help achieve a minimally invasive procedure. All the patients were followed up for 6 and 24 months. Three-dimensional reconstruction of the spine was performed based on preoperative and postoperative imaging data. The accuracy rate of screw placement, operation time, intraoperative blood loss and duration of radiation exposure were recorded, and postoperative complications were monitored. These findings were used to assess whether the screw placement achieved the desired results ([Figure 1]).
Figure 1: Flow chart of the trial protocol.

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Inclusion criteria

Patients of both genders were required to meet all of the following conditions to be included in this trial:

  • Lumbar degenerative diseases as diagnosed by the criteria for diagnosis of lumbar degenerative diseases (Guigui et al., 1999)
  • Indications for internal fixation in the degenerative lumbar spine
  • Lumbar single segment or multi-segment lesions
  • Average age 63 years
  • Provision of informed consent

Exclusion criteria

Patients presenting with any one or more of the following conditions were excluded from this trial:

  • Lumbar spine tumors, lumbar tuberculosis, trauma fractures or joint disorders
  • Lumbar infection or acute inflammation in other parts of the body
  • Unable to undergo lumbar surgery because of surgical contraindications (coagulation disorders) and poor cardiopulmonary function

Baseline analysis

Baseline data, including demographic data and general disease history, were collected from the participants prior to randomization ([Table 1]).
Table 1: Baseline analysis

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Sample size

Based on our previous experience, we assumed that the accurate rate of screw placement navigated by 3D printed module in 36 patients would be 98%, and totally 216 screws (6 screws per patient) would be used. Considering α = 0.05 (two-sided), β = 0.1, and power = 90%, the final number of screws was calculated to be 322 using PASS 11.0 software (NCSS, MD, USA). With a predicted dropout rate of 20%, the required sample size would be 72 patients with 387 screws. In accordance with the inclusion and exclusion criteria, we finally included 36 patients in this trial.


Potential patients hospitalized in our hospital were informed about the trial through a recruitment advertisement on the hospital bulletin board. Those interested in participating were asked to contact the project investigator via telephone. After providing written informed consent, potential participants who met the requirements of the inclusion and exclusion criteria were enrolled in this study. Patient recruitment began at November 2012, and follow-up data collection will be accomplished until March 2017.


This is an open-label study. All participants, surgeons and assessors were informed of therapeutic schedules.


Three-dimensional reconstruction: The DICOM data of the lumbar CT scan were input to Mimics 15.0 software and segmented using thresholding and region growing methods.

The three-dimensional reconstruction was completed based on Edit Mask in 3D and Calculate 3D.

Design of the screw channel: The pedicle was longitudinally cut based on Simulation/Cut orthogonal to the Screen , and then the ideal channel for screw insertion was designed. The channel was copied and enlarged to 10 mm with a distance of approximately 70 mm from the talus surface as the support column ([Figure 2]).
Figure 2: Design sketch of the channel for screw insertion and the support column.
Note: (A) Rear view; (B) right lateral view

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Design and printing of the 3D-printed module: To determine the strippable bone surface, the three-dimensional cutting range (the bone surface around the screw channel exposed by the Quadrant minimally invasive system) included the superior articular process, the mastoid process, the sub-processes and the spine recess. The cut model was enlarged (Simulation/Rescale) 1.2 times to obtain a block module prototype with a thickness of about 4 mm. Module design with the screw channel: the navigation module was obtained using a Boolean operation support column, a block module and the vertebra. The navigation module was exported in STL format and printed by 3D printing technology ([Figure 3]).
Figure 3: The navigation module with the channel for screw insertion.
Note: (A) Range for the strippable bone surface. (B) Transparent view of the effect of the module. (C) Navigation module with the screw channel. (D) 3D-printed navigation module.

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3D-printed module-assisted screw placement: All the implants were made of titanium alloys with high strength, good corrosion resistance and high bone compatibility, and were provided by qualified manufacturers. An incision was made based on the surgical requirements. The general positioning rule is: posterior lumbar interbody fusion, 2.0-2.5 cm from the posterior midline; Pedicle Screws, 3.0-3.5 cm from the posterior midline; transforaminal lumbar interbody fusion, 4.0-4.5 cm from the posterior midline.

A guide pin was inserted towards the correct marking point. The first dilator tube was inserted along the guide pin, which was then pulled out. Successively, other dilator tubes were inserted until the desired diameter was achieved. Afterwards, the Quadrant system was inserted into the bone and fixed. Dilator tubes were removed, and the surgical access was made successfully. We then confirmed again that there were enough skin incisions and deep fascia. Radiance X dual light sources were attached to the left and right channel walls, respectively, aiming to provide ideal lighting conditions for surgery. The Quadrant system was distended, and the support stent was rotated counterclockwise, which could be stretched by 30 mm, allowing the left and right blades of the channel to be stretched up to 55 mm in parallel. According to surgical need, the left and right blades of the channel could be tilted 12 mm to the left and right, to provide sufficient space for minimally invasive spinal surgery. The channel tube was designed to be connected with the fixation system at the top, so that the bottom of the channel tube could be easily tilted to different angles during the operation, depending on the actual needs of the operation.

Following exposure of the surgical field and removal of the surrounding soft tissue, the navigation module was used for surgical localization, the Kirschner wire was inserted and hollow taps were used followed by pedicle screw placement to gradually complete the following procedures: intraoperative decompression, intervertebral fusion, locking the fixation device, fluoroscopy confirmation, and incision suturing. The time of operation, the amount of intraoperative bleeding, and the duration of intraoperative radiation exposure were recorded. Postoperatively, all the patients underwent a lumbar CT scan and three-dimensional reconstruction.

Outcome measures

Primary outcome

  • The accuracy rate of screw placement, which was used to assess whether the screw placement by 3D-printed module navigation achieved the desired results, was calculated with the following formula: the number of screws placed in the correct direction during the operation/the number of screws predicted by preoperative 3D-printed module design ×100%. A higher value indicates a higher accuracy.

Secondary outcomes

  • Preoperative and postoperative lumbar CT imaging: To observe the conditions of lumbar fixation.
  • Time of operation: To evaluate the speed of surgery. A shorter operation time indicates that this method was easier to operate.
  • Amount of intraoperative bleeding: To evaluate the conditions of intraoperative blood loss. Less blood loss indicates a higher improvement in the surgical quality by the method being studied.
  • Duration of intraoperative radiation exposure: To evaluate the safety of intraoperative radiation. A shorter duration of intraoperative radiation exposure indicates that this method is conducive to reducing the time of radiation exposure.
  • Incidence of adverse reactions: To evaluate the incidence of postoperative complications.

The schedule of outcome measurement assessment is shown in [Table 2].
Table 2: Timing of outcome assessment

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Adverse events

  • Postoperative adverse events were recorded and reported to the Affiliated Hospital of Putian Hospital within 24 hours.
  • Proper therapeutic measures could be performed if the following adverse events occurred, including incision infection, back muscle pain, dural sac tear, vascular injury, nerve root injury, spinal cord injury, screw falling off and loosening.

Data collection, management, analysis, and open access

  • Baseline data were collected at the day when the participants were enrolled in the study. Other data were collected preoperatively, intraoperatively, postoperatively and during the follow-up. All data were input using Epidata and saved electronically.
  • All data regarding this clinical study were preserved by the Affiliated Hospital of Putian University, China.
  • All data were statistically analyzed by professional statisticians who were responsible for completing an outcome analysis report that was submitted to the project manager who was responsible for completing a research report. An independent data monitoring committee was responsible for data monitoring and management throughout the entire trial.
  • Published data will be released at

Statistical analysis

All data were statistically analyzed by statisticians using SPSS 19.0 software (IBM Corporation, Armonk, NY, USA) in accordance with the intention-to-treat principle.

Normally distributed measurement data were expressed as means, standard deviations, minimums, and maximums; non-normally distributed data were expressed as lower quartiles, medians, and upper quartiles.


Trial progress was reported to the ethics committee of the China Institute of Sport Science every 3 months and was updated in the registration database after each report.


Valuable trial data were transcribed, dated, and uploaded to a dedicated computer by two staff members. These data were scheduled, checked, locked by an investigator. The locked data could not be altered. Unauthorized persons were unable to access the database. Data reported regarding this trial protocol were preserved by the Affiliated Hospital of Putian Hospital, China.

  Trial Status Top

Surgery was completed in all the 36 patients with lumbar degenerative lesions who had been admitted at the Affiliated Hospital of Putian University from 2012 to 2015 ([Figure 4]). The time of operation, amount of bleeding and duration of radiation exposure were 120.58 ± 56.46 minutes, 136.83 ± 40.62 mL, and 50 ± 11 seconds, respectively.In total, 186 screws were inserted in the patients, 183 of which achieved the desired results in accordance with the preoperative digital design. The accuracy rate of screw placement was calculated to be 98%. Collection of 2-year follow-up data is still ongoing.
Figure 4: Intraoperative procedures and postoperative CT findings of inpatients with lumbar degenerative lesions admitted at the Affiliated Hospital of Putian University from 2012 to 2015.
Note: (A) Surgical operation. (B) Postoperative CT imaging of the implanted screws (cross-section). (C) Postoperative CT imaging of the implanted screws (coronal plane). (D) Postoperative CT imaging of the implanted screws (sagittal plane). (E) Postoperative CT reconstruction (rear view). (F) Postoperative CT reconstruction (right lateral view).

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  Discussion Top

Significance of the study

The 3D-printed module-assisted minimally invasive lumbar pedicle screw placement used in this study could provide an important basis for guiding the direction of surgery and reducing surgical errors. Its therapeutic efficacy could be confirmed by comparing preoperative and postoperative CT reconstruction images, determining time of operation, intraoperative blood loss, and duration of intraoperative radiation exposure, as well as recording postoperative adverse events.


  • Under the Quadrant system, surgical anatomical landmarks available for identification are limited to a small surgical field of view. Screw placement might only depend on the surgeon's experience, with a certain degree of difficulty. Once a little drift occurs in the screw placement in a narrow channel, it is more likely to cause spinal cord or nerve injury.
  • The small sample size could affect the accuracy of outcome evaluation.
  • In this study, no control group was set up, and there was poor credibility because of a lack of a statistically significant comparison.

Contribution to future studies

This study has shown that a 3D-printed module-assisted minimally invasive lumbar pedicle screw placement can improve the accuracy of screw placement, and reduce radiation injury in patients and surgeons, as there is no need for repeated fluoroscopy or even any radiation during the operation.[18]

  References Top

Fan G, Guan X, Zhang H, Wu X, Gu X, Gu G, Fan Y, He S (2015) Significant improvement of puncture accuracy and fluoroscopy reduction in percutaneous transforaminal endoscopic discectomy with novel lumbar location system: preliminary report of prospective hello study. Medicine 94:e2189.  Back to cited text no. 1
Guigui P, Barre E, Benoist M, Deburge A (1999) Radiologic and computed tomography image evaluation of bone regrowth after wide surgical decompression for lumbar stenosis. Spine 24:281-289.  Back to cited text no. 2
Isaacs RE, Podichetty VK, Santiago P (2005) Minimally invasive mieroendoseopy-assisted transforaminal lumbar interbody fusion with instrumentation. J Neurosurg Spine 3:98-105.  Back to cited text no. 3
Kosmopoulos V, Schizas C (2007) Pedicle screw placement accuracy: a meta-analysis. Spine 32:E111-120.  Back to cited text no. 4
Laine T, Lund T, Ylikoski M (2000) Accuracy of pedicle screw insertion with and without computer assistance: a randomized controlled clinical study in 100 consecutive patients. Eur Spine J 9:235-240.   Back to cited text no. 5
Lu S, Xu YQ, Zhang YZ (2009) A novel computer-assisted drill guide template for lumbar pedicle sc rew placement: a cadaveric and clinical study.Int J Med Robot 5:184-191.  Back to cited text no. 6
Merc M, Drstvensek I, Vogrin M (2013) A multi-level rapid prototyping drill guide template reduces the perforation risk of pedicle screw placement in the lumbar and sacral spine. Arch Onhop Trauma Surg 133:893-899.  Back to cited text no. 7
Rücker C, Kirch H, Pullig O, Walles H (2016) Strategies and first advances in the development of prevascularized bone implants. Curr Mol Biol Rep 2:149-157.   Back to cited text no. 8
Scheufler KM, Dohmen H, Vougioukas VI (2007) Percutaneous trans-foraminal lumbar interbody fusion for the treatment of degen-erative lumbar instability. Neurosurgery 60:203-212.  Back to cited text no. 9
Schwender JD, Holly LT, Rouben DP (2005) Minimally invasive transforaminal lumbar interbody fusion): technical feasibility and initial results. J Spinal Disord Tech 18:S1-6.  Back to cited text no. 10
Shinohara A, Sairyo K, Mishiro T, Chikawa T, Soshi S (2016) Insertional torque in cervical vertebrae lateral mass screw fixation: magerl technique versus roy-camille technique. Clin Spine Surg.  Back to cited text no. 11
Tarafder S, Balla VK, Davies NM (2013) 3D printed tricaleium phosphate scaffolds for bone tissue engineering. Zuzhi Gongcheng He Zaisheng Yixue 7:631-641.  Back to cited text no. 12
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Toquart A, Graillon T, Mansouri N, Adetchessi T, Blondel B, Fuentes S (2016) Management of spinal metastasis by minimal invasive surgery technique: surgical principles, indications: a literature review. Neurochirurgie 62:157-164.  Back to cited text no. 14
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Yang SH, Zhang X, Yu YF, Yao QQ, Liu S, Zhou J, Hu J (2016b) Clinical application of 3d printing rapid prototyping assisted posterior reduction and pedicle screw-rod fixafion in the treatment of thoracolumbar vertebral fracture with ankylosing spondylitis. Zhongguo Shuzi Yixue 11:77-80.  Back to cited text no. 17
Zhuang Y, Yang L, Li HJ, Ren YJ, Cao XJ (2016) A novel technique of unilateral percutaneous kyphoplasty achieves effective biomechanical strength and reduces radiation exposure. Am J Transl Res 8:1172-1179.  Back to cited text no. 18

Declaration of patient consent
The authors certified that they obtained all appropriate patient consent forms. In the form the patient(s) gave his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understood that their names and initials would not be published and due efforts would be made to conceal their identity, but anonymity could not be guaranteed.
Conflicts of interest
None declared.
Author contributions
All authors conceived and designed the study protocol. ZXY, XHC, GDZ and XC wrote the paper and XHC approved the final version of this paper.
Plagiarism check
This paper was screened twice using CrossCheck to verify originality before publication.
Peer review
This paper was double-blinded and stringently reviewed by international expert reviewers.


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2]


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