Standard multiplanar fluoroscopy versus a fluoroscopically based navigation system for the percutaneous insertion of iliosacral screws: a cadaver model

Accuracy in navigated percutaneous sacroiliac screw fixation: a systematic review and meta-analysis

INTRODUCTION

Percutaneous sacroiliac screw fixation of pelvic fragility fractures is increasingly being used to maintain mobility and reduce pain in the elderly patient population. Traditionally, this is performed using 2D fluoroscopy. Several newer, navigated techniques have emerged that may further facilitate this procedure. It, however, remains unclear whether there is a benefit regarding accuracy, radiation exposure and complications of these new navigation techniques when compared to the traditional 2D fluoroscopy.

METHODS

A systematic review and meta-analysis were performed. PubMed, CENTRAL and Embase were searched for both randomized controlled trials and observational studies comparing new navigation techniques to 2D fluoroscopy for percutaneous sacroiliac screw fixation. Effect estimates were pooled (random effects) and presented as odds ratio, mean difference and standardized mean difference with a 95% confidence interval.

RESULTS

19 studies were included. The 2D fluoroscopy group had 642 patients and the new navigation group 663 patients. Accuracy was significantly higher in the new navigation group (OR 2.44, 95% CI 1.53-3.90), especially O-Arm, 3D CT and Robotic navigation. On average, accuracy was 82% in the 2D group and 92% in the new navigation group, which was significant. Also, fluoroscopy time (MD 71.89 s, 95% CI 51.37-92.41) and frequency (MD 17.22 images in total, 95% CI 7.73-26.70) were significantly reduced in the new navigation group. Complications are acceptably low, however, poorly reported in both groups.

CONCLUSION

This meta-analysis demonstrated a higher accuracy, lower fluoroscopic frequency and time for new navigation techniques compared to 2D fluoroscopy. More advanced navigation techniques, such as 3D CT and robotic navigation, appeared to be even better.

Intelligent robot-assisted fracture reduction system for the treatment of unstable pelvic fractures

BACKGROUND

Precise and minimally invasive closed reduction is the premise of minimally invasive internal fixation. This paper aims to explore the safety and efficacy of a robot-assisted fracture reduction system (RAFR) in the treatment of pelvic fractures and to analyze its clinical advantages and existing problems.

METHODS

The RAFR system intelligently designed the optimal reduction path and target position based on a preoperative three-dimensional(3D) CT scan of the patient. The reduction robotic arm automatically reduced the affected hemipelvis according to the pre-planned reduction path.

RESULTS

The average residual displacement was the 6.65 ± 3.59 mm. According to Matta's criteria, there were 7 excellent, 10 good, and 3 fair, and the excellent and good rate was 85%. No postoperative complications occurred.

CONCLUSION

In our study, the RAFR system could complete accurate and minimally invasive closed reduction for most patients with unstable pelvic fractures, which could achieve good fracture reduction quality and short-term efficacy.

3D-navigation for SI screw fixation - How does it affect radiation exposure for patients and medical personnel?

BACKGROUND

3D-navigation for percutaneous sacroiliac (SI) screw fixation is becoming increasingly common and several studies report great advantages of this technology. However, there is still limited clinical evidence on the efficacy regarding radiation exposure for patient and personnel.

METHODS

This is a retrospective, single-center cohort study. All patients who underwent percutaneous sacroiliac screw fixation for an injury of the posterior pelvic ring from 2014 to 2021 were screened. Inclusion criteria were: conclusive radiation dosage reports, signed informed consent, a twelve month follow up and a complete data set. Patients were stratified in two groups (3D-navigation (Group 3D-N) vs. control (Group F)) based on the imaging modality used. Primary outcomes were radiation exposure for patient and personnel. Secondary outcomes were reoperations, complications, and intraoperative precision.

RESULTS

Of 392 patients screened, 174 patients (3D-N: n = 50, F: n = 124) could be included for final analysis. We noted a significant reduction of the dose corresponding to potential radiation exposure for medical personnel (-15.3 mGy, 95 %CI: -2.1 to -28.5, p = 0.0232), but also a significant increase of the dose quantifying radiation exposure for patients (+77.0 mGy, 95 %CI: +53.3 to +100.6, p < 0.0001), when using navigation. In addition, the rate of radiographic malplacement was significantly reduced (F: 11.3% vs. 3D-N: 0 %, p = 0.0113) despite a substantial increase in transsacral screw placement (F: 19.4% vs. 3D-N: 76 %).

CONCLUSION

Our data clearly suggests that the use of 3D-navigation for percutaneous SI screw fixation decreases radiation exposure for medical personnel, while increasing radiation exposure for patients. Furthermore, intraoperative precision is improved, even in more challenging operations.

Percutaneous iliosacral screw insertion with only outlet and inlet fluoroscopic view for unstable pelvic ring injuries: Clinical and radiological outcomes

Background:

Percutaneous iliosacral screw fixation in posterior pelvic ring fractures is challenging and commonly performed under fluoroscopy or navigation techniques. This study aimed to assess the safety and efficacy of percutaneous iliosacral screw implantation under fluoroscopy guidance with only inlet and outlet views.

Methods:

This retrospective study included 58 consecutive unstable posterior pelvic injury patients (36 sacral fractures and 22 sacroiliac joint disruptions) treated with percutaneous iliosacral screws between January 2015 and November 2019. Acceptable inlet radiographs show the anterior cortex of the S1 body superimposed on the S2 body. Acceptable outlet radiographs show the superior pubic symphysis at the level of the S2 foramen and visualize the S1 and S2 sacral foramina. In our technique, the screw was inserted at the inferior half of the outlet view and the posterior half of the inlet view. The time needed for screw insertion and the radiation exposure time was recorded. Intra and postoperative complications were documented. Postoperative computed tomography (CT) scans assessed screw position.

Results:

In total, 69 iliosacral screws were inserted in 58 patients. In postoperative CT scans, the screw position was assessed, 89.8% were in a secure position, and 10.2% had malposition. The mean operation time per screw was 21.18 min and the mean fluoroscopy time per screw was 112 s. There was no evidence of wound infection or iatrogenic neurovascular injury. No reoperation was performed.

Conclusion:

Percutaneous iliosacral screws can be placed using the only outlet and inlet fluoroscopic views with comparable radiological and clinical outcomes to the conventional method.

Do three-dimensional modeling and printing technologies have an impact on the surgical success of percutaneous transsacral screw fixation?

Objectives

This study aims to determine the role of computed tomography (CT)-derived templates, produced by three- dimensional (3D) modeling, image processing and printing technology, in percutaneous transsacral screw fixation and evaluate the effects of their use on surgical success.

Materials and methods

This prospective study conducted between June 2018 and December 2019 utilized 15 composite pelvis models for transsacral-transiliac screw fixation. For the procedure, modeled templates were utilized for wiring on the left side of the pelvis models, while the conventional method was performed on the right side of the pelvis models. In the computed tomography images acquired after wiring, appropriate wire position was evaluated.

Results

The placed wires held the S1 body appropriately in all of the procedures with or without template use. With the template use, the wires were placed appropriately in the surgical bone corridor suitable for the transsacral-transiliac screw fixation in all of the models. However, with the conventional methods, the wires were not placed in the safe surgical bone corridor in four models. The wire deviation angle in the axial plane was significantly lower in the template group (p=0.001), whereas it was not different between the template group and the conventional method group in the coronal plane (p=0.054). The amount of deviation from the ideal wire entry site was significantly reduced in the template group compared to the conventional method group (p=0.001).

Conclusion

With the use of 3D modeling and printing technology, CT-derived templates can be produced and utilized for transsacral screw fixation procedures and their use increases surgical success by reducing the surgical margin of error.

Robotic assisted fixation of sacral fractures: A pilot study

Objectives:

Sacral fractures that require fixation are a challenge for the orthopaedic surgeon. Due to anatomical consideration, implant insertion is not risk free, and requires a steep learning curve. A robotic system has been successfully used in pedicle screws insertion and can be also used for iliosacral screws. The aim of the study was to demonstrate the use of the robot in the treatment of unstable sacral fractures.

Design:

Retrospective case series.

Setting:

An academic level I trauma center.

Patients:

Fourteen patients with sacral fractures were eligible for robotic assisted treatment. These included 9 high-energy fractures, 4 osteoporotic fractures, and 1 pathological fracture.

Intervention:

Fixation constructs included iliosacral screws, transiliac screws, lumbopelvic fixation, sacroplasty, or a combination of the above techniques. A Renaissance robot was mounted on a multidirectional bridge that was attached to the patients spine and implant trajectories were planned either on preoperative or intraoperative 3D scans. Guide wires were inserted percutaneously and screws were placed subsequently.

Main outcome measurements:

Accuracy of implant placement, operating room and fluoroscopy time.

Results:

Mean patient age was 36 (17–84), and number of screws, including iliosacral and pedicular ranged 1–14 per patient (average 4.25). Mean operative time was 150 minutes (range 90–300). Average fluoroscopic time was 18 seconds (7–42) for 2D and 40 seconds (12–72) for 3D imaging. All fractures healed, no hardware failure was observed. All hardware was always within bony confines, and no procedure-related neurological deficits were observed.

Conclusion:

Robotic assisted fixation of sacral fracture is a safe and reproduceable method, allowing precise and accurate implant placement.

Sacroiliac screw versus a minimally invasive adjustable plate for Zone II sacral fractures: a retrospective study

OBJECTIVE

Fracture line of the sacrum always involves the Zone II region because sacral foramina are anatomically and physiologically weak regions of the sacrum. The purpose of this study is to compare the therapeutic effects of a sacroiliac screw and a minimally invasive adjustable plate (MIAP) for Zone II sacral fractures.

METHODS

Patients with unilateral Zone II sacral fractures fixed with a unilateral sacroiliac screw or MIAP from August 2009 to January 2016 were recruited into this study and were divided into two groups: group A (sacroiliac screw) and group B (MIAP). Surgical time, blood loss, frequency of intraoperative fluoroscopy, and relative complications were reviewed. Radiographs and CT scans were routinely acquired to evaluate the fracture displacement and reduction quality. Fracture healing was evaluated in the radiographs at each follow-up. Functional outcome was assessed based upon the Majeed scoring system at the final follow-up.

RESULTS

Thirty-one patients in group A and thirty-nine patients in group B were included in this study. No significant differences in average surgical time (P = 0.221) or blood loss (P = 0.234) were noted between group A and group B. The mean frequency of intraoperative fluoroscopy was 15.74±2.98 in group A and 6.08±1.94 in group B (P = 0.000). All fractures healed well within four months in all patients, and the healing time exhibited no significant difference between the two groups (P = 0.579). Satisfactory rates of reduction quality and functional outcome were not statistically different between the two groups (P > 0.05). The complication rate was 16.13% (5/31) in group A and 5.13% (2/39) in group B (P = 0.222).

CONCLUSION

MIAP has a fixation effect and exhibits reduction potential for Zone II sacral fractures. Favourable radiographic and functional results could be obtained through the MIAP technique, which is easy to conduct without pre-contouring. Compared with the unilateral S1 sacroiliac screw technique, repeated projections and iatrogenic sacral injury can be avoided.

Effects of minimally invasive plate-screw internal fixation in the treatment of posterior pelvic ring fracture

Effects of minimally invasive plate-screw internal fixation and sacroiliac joint screw fixation in the treatment of posterior pelvic ring fracture were compared. Continuous selection of 20 cases of unstable pelvic posterior ring fractures, according to indications of operation, were divided into a group of 13 cases of plate-screw internal fixation and a group of 7 cases of sacroiliac joint screw fixation, and the operation effect and complications were compared. The comparisons of operation time, amount of radiation exposure, intraoperative blood loss, length of incision, partial load and full load time, and complications between two groups were carried out, and there were no statistically significant differences (P>0.05). The evaluation of clinical effects (based on the Majeed pelvic functional scoring criteria) and the evaluation of anatomic effects (based on Matta and Tornetta scoring criteria) between the two groups were compared, there was no statistically significant difference (P>0.05). Minimally invasive plate-screw internal fixation and sacroiliac joint screw fixation in the treatment of the posterior pelvic instability fracture both have indications and their therapeutic effects are equally matched.

Accuracy of sacroiliac screw placement with and without intraoperative navigation and clinical application of the sacral dysmorphism score

INTRODUCTION

Percutaneously-placed sacroiliac (SI) screws are currently the gold-standard fixation technique for fixation of the posterior pelvic ring. The relatively high prevalence of sacral dysmorphism in the general population introduces a high risk of cortical breach with resultant neurovascular damage. This study was performed to compare the accuracy of SI screw placement with and without the use of intraoperative navigation, as well as to externally validate the sacral dysmorphism score in a trauma patient cohort.

PATIENTS AND METHODS

All trauma patients who underwent sacroiliac screw fixation for pelvic fractures at a level 1 trauma centre over a 6 year period were identified. True axial and coronal sacral reconstructions were obtained from their pre-operative CT scans and assessed qualitatively and quantitatively for sacral dysmorphism - a sacral dysmorphism score was calculated by two independent assessors. Post-operative CT scans were then analysed for breaches and correlated with the hospital medical records to check for any clinical sequelae.

RESULTS

68 screws were inserted in 36 patients, most sustaining injuries from road traffic accidents (50%) or falls from height (36.1%). There was a male preponderance (83.3%) with the majority of the screws inserted percutaneously (86.1%). Intraoperative navigation was used in 47.2% of the patient cohort. 30.6% of the cohort were found to have dysmorphic sacra. The mean sacral dysmorphism scores were not significantly different between navigated and non-navigated groups. Three cortical breaches occurred, two in patients with sacral dysmorphism scores >70 and occurring despite the use of intraoperative navigation. There was no significant difference in the rates of breach between navigated and non-navigated groups. None of the breaches resulted in any clinically observable neurovascular deficit.

CONCLUSION

The sacral dysmorphism score can be clinically applied to a cohort of trauma patients with pelvic fractures. In patients with highly dysmorphic sacra, reflected by high sacral dysmorphism scores, intraoperative navigation is not in itself sufficient to prevent cortical breaches. In such patients it would be prudent to consider instrumentation of the lower sacral corridors instead.

Safe Zone Quantification of the Third Sacral Segment in Normal and Dysmorphic Sacra

OBJECTIVE

To quantify the osseous anatomy of the dysmorphic third sacral segment and assess its ability to accommodate internal fixation.

DESIGN

Retrospective chart review of a trauma database.

SETTING

University Level 1 Trauma Center.

PATIENTS

Fifty-nine patients over the age of 18 with computed tomography scans of the pelvis separated into 2 groups: a group with normal pelvic anatomy and a group with sacral dysmorphism.

MAIN OUTCOME MEASUREMENTS

The sacral osseous area was measured on computed tomography scans in the axial, coronal, and sagittal planes in normal and dysmorphic pelves. These measurements were used to determine the possibility of accommodating a transiliac transsacral screw in the third sacral segment.

RESULTS

In the normal group, the S3 coronal transverse width averaged 7.71 mm and the S3 axial transverse width averaged 7.12 mm. The mean S3 cross-sectional area of the normal group was 55.8 mm. The dysmorphic group was found to have a mean S3 coronal transverse width of 9.49 mm, an average S3 axial transverse width of 9.14 mm, and an S3 cross-sectional area of 77.9 mm.

CONCLUSIONS

The third sacral segment of dysmorphic sacra has a larger osseous pathway available to safely accommodate a transiliac transsacral screw when compared with normal sacra. The S3 segment of dysmorphic sacra can serve as an additional site for screw placement when treating unstable posterior pelvic ring fractures.

Fluoroscopic iliosacral screw placement made safe

AIM

Unstable posterior pelvic ring injuries should be stabilised successfully by percutaneous iliosacral screwing. The intervention takes place under intraoperative fluoroscopic guidance. The inlet and outlet views are crucial and are performed by tilting the image intensifier. Safely interpreting fluoroscopic views can be challenging in certain clinical scenarios. We demonstrated on a series of patients howpreoperative CT scans can be used to anticipate the appropriate intraoperative inlet and outlet fluoroscopic views and positioning of the patient on the operating table, thereby avoiding possible operating table obstacles.

MATERIALS AND METHODS

We analysed at random 30 pelvic CT scans from patients of different ages and both sexes, utilising the sagittal reconstructions. Inlet and outlet angle measurements were calculated on the scans to determine the appropriate intraoperative inlet and outlet views.

RESULTS

The analysed CT scans showed an average inlet view of 22.3° (range 10.4°-39.8°) and an average outlet view of 42.3° (range 31.5°-53.1°). Sex and age had no influence on results. The calculated required free space under the operating table for unobstructed tilting of the C-arm was a minimum of 145cm.

CONCLUSION

The significant anatomic variations of the posterior pelvic ring have been well documented in the literature. The angles required to obtain appropriate intraoperative inlet and outlet views are not perpendicular and differ greatly from traditional settings, which directed the beam 45° caudally and 45° cranially. The fluoroscopic beam would need to be angled differently in each patient to obtain ideal cardinal views that ultimately assist in safe iliosacral screw placement. To avoid collision of the C-arm with the operating table, it is essential to provide secure free space under the operating table of at least 145cm.

Percutaneous Placement of Iliosacral Screws Under the Guidance of Axial View Projection of the S1 Pedicle: a Case Series

The aim of this study was to evaluate the safety and efficacy of percutaneous placement of iliosacral screws under the guidance of axial view projection of the S1 pedicle clinically. This case series includes 58 consecutive unstable pelvic injury patients, which were treated with iliosacral screws between July 2011 and July 2016. Patients were divided into two groups: normal sacrum (n = 31) and dysmorphic sacrum (n = 27). A single orthopedic surgeon operated on all patients, with percutaneous placement of iliosacral screws under the guidance of axial view projection of the S1 pedicle. The time needed for screw insertion and the radiation exposure time were recorded. Chi-squared test and Student t-test were used to analyze the differences between the two groups. Sacral dysmorphism was present in 47% of patients. The median time for screw insertion and radiation exposure time in these two groups showed no statistical difference (P > 0.05). No clinical complications or malpositioned screws occurred in any case. Preoperative pelvic CT is necessary to determine the sacral osseous anatomy. In patients with either a normal or dysmorphic sacrum, iliosacral screws can be placed by this method with less radiation exposure and complications than in the conventional method.

Placement of iliosacral screws using 3D image-guided (O-Arm) technology and Stealth Navigation: comparison with traditional fluoroscopy

AIMS

We compared the accuracy, operating time and radiation exposure of the introduction of iliosacral screws using O-arm/Stealth Navigation and standard fluoroscopy.

MATERIALS AND METHODS

Iliosacral screws were introduced percutaneously into the first sacral body (S1) of ten human cadavers, four men and six women. The mean age was 77 years (58 to 85). Screws were introduced using a standard technique into the left side of S1 using C-Arm fluoroscopy and then into the right side using O-Arm/Stealth Navigation. The radiation was measured on the surgeon by dosimeters placed under a lead thyroid shield and apron, on a finger, a hat and on the cadavers.

RESULTS

There were no neuroforaminal breaches in either group. The set-up time for the O-Arm was significantly longer than for the C-Arm, while total time for placement of the screws was significantly shorter for the O-Arm than for the C-Arm (p = 0.001). The mean absorbed radiation dose during fluoroscopy was 1063 mRad (432.5 mRad to 4150 mRad). No radiation was detected on the surgeon during fluoroscopy, or when he left the room during the use of the O-Arm. The mean radiation detected on the cadavers was significantly higher in the O-Arm group (2710 mRem standard deviation (sd) 1922) than during fluoroscopy (11.9 mRem sd 14.8) (p < 0.01).

CONCLUSION

O-Arm/Stealth Navigation allows for faster percutaneous placement of iliosacral screws in a radiation-free environment for surgeons, albeit with the same accuracy and significantly more radiation exposure to cadavers, when compared with standard fluoroscopy.

TAKE HOME MESSAGE

Placement of iliosacral screws with O-Arm/Stealth Navigation can be performed safely and effectively. Cite this article: Bone Joint J 2016;98-B:696-702.

Laparoscopic Acetabular Fracture Fixation after Three-dimensional Modelling and Printing

Current surgical treatment of acetabular fractures is open reduction and internal fixation and requires a large incision resulting in considerable blood loss and a potentially long duration of recovery. We report a case of an acetabular fracture that received laparoscopic internal fixation after three-dimensional (3D) modelling and printing of the acetabulum. A 43 year old male fell from a height of 3 m resulting in a right acetabulum anterior column fracture. Thin section computed tomography scanning with 0.6 mm increments and subsequent 3D reconstruction was performed, and a 3D model of the acetabulum and fracture was printed. The steel reconstruction plate was prebent in vivo and placed into the optimized position based on the 3D modelling and the optimized insert orientation and measured screw length were determined. The fracture was reduced and the plate placed laparoscopically without complications, and the patient had excellent functional recovery. Acetabular fractures are complex injuries, and while minimally invasive surgical techniques are used in many fields, they are not common for the treatment of acetabular fractures. 3D modelling is commonly used in medicine, and although 3D printing is used in some fields, it has not found widespread use in orthopedics.

2D versus 3D fluoroscopy-based navigation in posterior pelvic fixation: review of the literature on current technology

PURPOSE

Percutaneous sacroiliac (SI) fixation of unstable posterior pelvic ring injuries is a widely accepted procedure. The complex sacral anatomy with narrow osseous corridors for SI screw placement makes this procedure technically challenging. Techniques are constantly evolving as a result of better understanding of the posterior pelvic anatomy. Recently developed tools include fluoroscopy-based computer-assisted navigation, which can be two-dimensional (2D) or three-dimensional (3D). Our goal is to determine the relevant technical considerations and clinical outcomes associated with these modalities by reviewing the published research. We hypothesize that 3D fluoroscopy-based navigation is safer and superior to its 2D predecessor with respect to lower radiation dose and more accurate SI screw placement.

METHODS

We searched four medical databases to identify English-language studies of 2D and 3D fluoroscopy-based navigation from January 1990 through August 2015. We included articles reporting imaging techniques and outcomes of closed posterior pelvic ring fixation with percutaneous SI screw fixation. Injuries included in the study were sacral fractures (52 patients), sacroiliac fractures (88 patients), lateral compression fractures (20 patients), and anteroposterior compression type pelvic fractures (8 patients). We excluded articles on open reduction of posterior pelvic ring injuries and solely anatomic studies. We then reviewed these studies for technical considerations and outcomes associated with these technologies.

RESULTS

Six studies were included in our analysis. Results of these studies indicate that 3D fluoroscopy-based navigation is associated with a lower radiation dose and lower rate of screw malpositioning compared with 2D fluoroscopy-based systems.

CONCLUSIONS

It may be advantageous to combine modern imaging modalities such as 3D fluoroscopy with computer-assisted navigation for percutaneous screw fixation in the posterior pelvis.

Correct Positioning of Percutaneous Iliosacral Screws With Computer-Navigated Versus Fluoroscopically Guided Surgery in Traumatic Pelvic Ring Fractures

OBJECTIVES

To assess the correct positioning of iliosacral screw in patients with unstable traumatic pelvic ring injury by comparing fluoroscopically guided computer-navigated surgery (CNS) with conventional fluoroscopy (CF) through reviewing postoperative computed tomography (CT) and clinical indicators.

DESIGN

A comparative multicenter cohort study.

SETTING

Two level I Trauma Centers in the Netherlands.

PATIENTS

The computer-navigated group (n = 56) and the CF group (n = 24) were comparable regarding age (mean, 43 years), sex (58%, male), body mass index (25 kg/m), injury severity score (27), injury-to-surgery interval (7 days), and Orthopaedic Trauma Association classification (40% 61-B, 60% 61-C).

MAIN OUTCOME MEASUREMENTS

The position of the iliosacral screws was evaluated on postoperative CT. In addition, clinical morbidity and reoperation were assessed.

RESULTS

In the CNS group, a total of 111 screws were placed (2.0 per patient), of which 83% were placed correctly. In the CF group, 39 screws (1.6 per patient) were placed, 82% of them correctly.Inadequate fixation included neural foramina hit [12 screws (11%) in the CNS group versus 3 screws (8%) in the CF group, P = 0.76] and extraosseous dislocation [7 screws (6%) vs. 4 screws (10%), respectively, P = 0.47]. Five patients required reoperation, all in the CNS group, P = 0.32. We observed more adequate positioning with increased surgical experience, P = 0.12.

CONCLUSIONS

In contrast to what has been suggested by previous studies, we found no benefit from computer-navigated iliosacral screw fixation compared with fluoroscopically guided surgery regarding the correct positioning of iliosacral screw on postoperative CT and related morbidity.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Biomechanical Comparison of Two Kinds of Internal Fixation in a Type C Zone II Pelvic Fracture Model

BACKGROUND

Unstable pelvic fractures are complex and serious injuries. Selection of a fixation method for these fractures remains a challenging problem for orthopedic surgeons. This study aimed to compare the stability of Tile C pelvic fractures fixed with two iliosacral (IS) screws and minimally invasive adjustable plate (MIAP) combined with one IS screw.

METHODS

This study was a biomechanical experiment. Six embalmed specimens of the adult pelvis were used. The soft tissue was removed from the specimens, and the spines from the fourth lumbar vertebra to the proximal one-third of both femurs were retained. The pubic symphysis, bilateral sacroiliac joints and ligaments, bilateral hip joints, bilateral sacrotuberous ligaments, and bilateral sacrospinous ligaments were intact. Tile C pelvic fractures were made on the specimens. The symphysis pubis was fixed with a plate, and the fracture on the posterior pelvic ring was fixed with two kinds of internal fixation in turn. The specimens were placed in a biomechanical machine at a standing neutral posture. A cyclic vertical load of up to 500 N was applied, and displacement was recorded. Shifts in the fracture gap were measured by a grating displacement sensor.

STATISTICAL ANALYSIS USED

Paired-samples t-test.

RESULTS

Under the vertical load of 100, 200, 300, 400, and 500 N, the average displacement of the specimens fixed with MIAP combined with one IS screw was 0.46, 0.735, 1.377, 1.823, and 2.215 mm, respectively, which was significantly lower than that of specimens fixed with two IS screws under corresponding load (P < 0.05). Under the vertical load of 500 N, the shift in the fracture gap of specimens fixed with MIAP combined with one IS screw was 0.261 ± 0.095 mm, and that of specimens fixed with two IS screws was 0.809 ± 0.170 mm. The difference was significant (P < 0.05).

CONCLUSION

The stability of Tile C pelvic fractures fixed with MIAP combined with one IS screw was better than that fixed with two IS screws.

Assessment of pelvic injuries treated with ilio-sacral screws: injury severity and accuracy of screw positioning

PURPOSE

The aim of this study was to analyse possible indicative parameters for percutaneous ilio-sacral stabilisation and to identify parameters associated with screw misplacement.

METHODS

Cohort study, level I trauma centre.

INCLUSION CRITERIA

(1) unstable pelvic injury, (2) percutaneous ilio-sacral screws placement.

EXCLUSION CRITERIA

(1) sacral dysmorphy, (2) failed closed reduction, (3) navigated techniques. Indicative parameters were age, gender, body mass index, number of screws, screw angulation, fracture type and injury severity. End points were ilio-sacral screw position and associated complications. Screw placement accuracy was graded as follows: grade 0, no perforation; grade 1, perforation <2 mm; grade 2, perforation from 2 to 4 mm; grade 3, ≥4 mm perforation.

RESULTS

Between March 2008 and March 2013, 102 (53 women) patients were included (mean age, 48.5 ± 21.4 years). The Injury Severity Score (ISS) and New Injury Severity Score (NISS) were 18.9 ± 9.9 and 22.3 ± 22.3, respectively. The positions of 137 ilio-sacral screws were analysed. Of all screws, 87.6 % (120) were placed satisfactory (<2 mm perforation). The incidence of screw misplacement was significantly higher in the case of two unilateral S1 screws compared with a single screw (failure rate: two unilateral screws 23.1 % vs single screw 7.0 %; p < 0.05). Screw perforation anterior to the lateral mass (in-out-in) represented the most frequent malposition. Revision was necessary in three cases due to malpositioning. Furthermore, no major complication occurred.

CONCLUSIONS

We conclude, that twofold ilio-sacral screw positioning from one side increases the risk for screw misplacement. In this case, alternative techniques like navigation should be considered. Anterior screw perforation represents a common problem with a high incidence and warrants particular attention.

Correlating preoperative imaging with intraoperative fluoroscopy in iliosacral screw placement

Background

Percutaneous iliosacral screw placement can successfully stabilize unstable posterior pelvic ring injuries. Intraoperative fluoroscopic imaging is a vital component needed in safely placing iliosacral screws. Obtaining and appropriately interpreting fluoroscopic views can be challenging in certain clinical scenarios. We report on a series of patients to demonstrate how preoperative computed tomography (CT) imaging can be used to anticipate the appropriate intraoperative inlet and outlet fluoroscopic views.

Materials and methods

24 patients were retrospectively identified with unstable pelvic ring injuries requiring operative fixation using percutaneous iliosacral screws. Utilizing the sagittal reconstructions of the preoperative CT scans, anticipated inlet and outlet angle measurements were calculated. The operative reports were reviewed to determine the angles used intraoperatively. Postoperative CT scans were reviewed for repeat measurements and to determine the location and safety of each screw.

Results

Preoperative CT scans showed an average inlet of 20.5° (7°–37°) and an average outlet of 42.8° (30°–59°). Intraoperative views showed an average inlet of 24.9° (12°–38°) and an average outlet of 42.4° (29°–52°). Postoperative CT scans showed an average inlet of 19.4° (8°–31°) and an average outlet of 43.2° (31°–56°). The average difference from preoperative to intraoperative was 4.4° (−21° to 5°) for the inlet and 0.45° (−9° to 7°) for the outlet. The average difference between the preoperative and postoperative CT was 2.04° (0°–6°) for the inlet and 2.54° (0°–7°) for the outlet.

Conclusion

There is significant anatomic variation of the posterior pelvic ring. The preoperative CT sagittal reconstruction images allow for appropriate preoperative planning for anticipated intraoperative fluoroscopic inlet and outlet views within 5°. Having knowledge of the desired intraoperative views preoperatively prepares the surgeon, aids in efficiently obtaining correct intraoperative views, and ultimately assists in safe iliosacral screw placement.

Level of evidence

IV, Retrospective case series.

Iliosacral screw insertion using CT-3D-fluoroscopy matching navigation

BACKGROUND

Percutaneous iliosacral screw insertion requires substantial experience and detailed anatomical knowledge to find the proper entry point and trajectory even with the use of a navigation system. Our hypothesis was that three-dimensional (3D) fluoroscopic navigation combined with a preoperative computed tomography (CT)-based plan could enable surgeons to perform safe and reliable iliosacral screw insertion. The purpose of the current study is two-fold: (1) to demonstrate the navigation accuracy for sacral fractures and sacroiliac dislocations on widely displaced cadaveric pelves; and (2) to report the technical and clinical aspects of percutaneous iliosacral screw insertion using the CT-3D-fluoroscopy matching navigation system.

METHODS

We simulated three types of posterior pelvic ring disruptions with vertical displacements of 0, 1, 2 and 3cm using cadaveric pelvic rings. A total of six fiducial markers were fixed to the anterior surface of the sacrum. Target registration error over the sacrum was assessed with the fluoroscopic imaging centre on the second sacral vertebral body. Six patients with pelvic ring fractures underwent percutaneous iliosacral screw placement using the CT-3D-fluoroscopy matching navigation. Three pelvic ring fractures were classified as type B2 and three were classified as type C1 according to the AO-OTA classification. Iliosacral screws for the S1 and S2 vertebra were inserted.

RESULTS

The mean target registration error over the sacrum was 1.2mm (0.5-1.9mm) in the experimental study. Fracture type and amount of vertical displacement did not affect the target registration error. All 12 screws were positioned correctly in the clinical series. There were no postoperative complications including nerve palsy. The mean deviation between the planned and the inserted screw position was 2.5mm at the screw entry point, 1.8mm at the area around the nerve root tunnels and 2.2mm at the tip of the screw.

CONCLUSION

The CT-3D-fluoroscopy matching navigation system was accurate and robust regardless of pelvic ring fracture type and fragment displacement. Percutaneous iliosacral screw insertion with the navigation system is clinically feasible.

A low-cost tracked C-arm (TC-arm) upgrade system for versatile quantitative intraoperative imaging

PURPOSE

C-arm fluoroscopy is frequently used in clinical applications as a low-cost and mobile real-time qualitative assessment tool. C-arms, however, are not widely accepted for applications involving quantitative assessments, mainly due to the lack of reliable and low-cost position tracking methods, as well as adequate calibration and registration techniques. The solution suggested in this work is a tracked C-arm (TC-arm) which employs a low-cost sensor tracking module that can be retrofitted to any conventional C-arm for tracking the individual joints of the device.

METHODS

Registration and offline calibration methods were developed that allow accurate tracking of the gantry and determination of the exact intrinsic and extrinsic parameters of the imaging system for any acquired fluoroscopic image. The performance of the system was evaluated in comparison to an Optotrak[Formula: see text] motion tracking system and by a series of experiments on accurately built ball-bearing phantoms. Accuracies of the system were determined for 2D-3D registration, three-dimensional landmark localization, and for generating panoramic stitched views in simulated intraoperative applications.

RESULTS

The system was able to track the center point of the gantry with an accuracy of [Formula: see text] mm or better. Accuracies of 2D-3D registrations were [Formula: see text] mm and [Formula: see text]. Three-dimensional landmark localization had an accuracy of [Formula: see text] of the length (or [Formula: see text] mm) on average, depending on whether the landmarks were located along, above, or across the table. The overall accuracies of the two-dimensional measurements conducted on stitched panoramic images of the femur and lumbar spine were 2.5 [Formula: see text] 2.0 % [Formula: see text] and [Formula: see text], respectively.

CONCLUSION

The TC-arm system has the potential to achieve sophisticated quantitative fluoroscopy assessment capabilities using an existing C-arm imaging system. This technology may be useful to improve the quality of orthopedic surgery and interventional radiology.

Malposition and revision rates of different imaging modalities for percutaneous iliosacral screw fixation following pelvic fractures: a systematic review and meta-analysis

INTRODUCTION

Percutaneous iliosacral screw placement following pelvic trauma is associated with high rates of revisions, screw malpositioning, the risk of neurological damage and inefficient stability. The correct entry point and the small target corridor may be difficult to visualize using only an image intensifier. Therefore, 2D and 3D image-based navigation and reconstruction techniques could be helpful tools. The aim of this systematic review and meta-analysis was to evaluate the best available evidence regarding the rate of malpositioning and revisions using different techniques for screw implantation, i.e., conventional, 2D and 3D image-based navigation and reconstruction techniques, CT navigation.

METHODS

A systematic review and meta-analysis were performed using the data available on Ovid Medline. 430 studies published between 1/1948 and 2/2011 were identified by two independent investigators. Inclusion criteria were percutaneous iliosacral screw fixation after traumatic pelvic fractures with included revision rate or positioning of the screw, language of the article English or German. Exclusion criteria were osteoporotic fracture, tumor, reviews, epidemiological studies, biomechanical/cadaveric studies, studies about operative technique. For statistical analysis the random effect model was used.

RESULTS

A total of 51 studies fulfilled the inclusion requirements describing 2,353 percutaneous screw implantations following pelvic trauma in 1,731 patients. The estimated rate of malposition was 0.1 % for 262 screws using CT navigation. This rate was significantly lower (p < 0.0001) than for the conventional technique with malposition rate of 2.6 % (total 1,832 screws). Using 2D and 3D image-based navigation and reconstruction techniques, the malposition rate was 1.3 % (total 445 screws). No significance was observed between the conventional and the 2D and 3D image-based navigation and reconstruction techniques. The rates of revision were not statistically significant with 2.7 % (1,832 implantations) in the conventional group, 1.3 % (445 implantations) in the group of 2D and 3D image-based navigation and reconstruction techniques and 0.8 % (262 implantations) using the CT navigation.

CONCLUSIONS

CT navigation has the lowest rate of screw malposition, but on the other hand it could not be used for all type of fractures where surgical procedures (reduction maneuvers, additional osteosynthetic procedures) are necessary. The 2D and 3D image-based navigation and reconstruction techniques provide encouraging results with slightly lower rate of complications compared to the conventional technique and are additional tools to enhance the precision and decrease the rate of revision.

Treatment of posterior pelvic ring disruptions using a minimally invasive adjustable plate

OBJECTIVE

Iliosacral (IS) screw fixation and posterior tension band plate (TBP) technique are two treatment alternatives for posterior pelvic ring injuries. However, IS screw fixation requires continuous fluoroscopic guidance for appropriate screw insertion and carries a risk of neurovascular injuries. TBP technique also has some disadvantages, including limited reduction potential, difficulty in precontouring the plate and a higher rate of symptomatic implants. To address these limitations, we introduced a minimally invasive adjustable plate (MIAP). This study aims to present the preliminary radiological and clinical results of posterior pelvic ring disruptions treated with MIAP.

METHODS

The MIAP conforms to the irregular shape of posterior pelvic ring and can be used without prebending. This plate has a role in reducing compressed or separated fractures/dislocations. Sixteen patients, including seven males and nine females, were treated with MIAP through a minimally invasive approach. The fracture patterns consisted of six Type B and ten Type C fractures according to OTA classification of fracture. Preoperative and postoperative radiography was taken to assess the fracture displacement and reduction quality. Postoperative rehabilitation programme was individualised and early exercise was encouraged. Patients were followed up and the functional outcome was evaluated based upon the scoring system proposed by Lindahl and associates.

RESULTS

All posterior pelvic ring disruptions were reduced and fixed with MIAP. The average duration of surgery was 49 min, the average radiation exposure was 6s, and the average blood loss was 80 mL for the treatment of posterior pelvic ring injuries. Overall radiological results of the reduction were excellent in eleven patients and good in five. The patients were followed up for 30 months on average. All fractures healed. The functional outcome was excellent in ten patients, good in four and fair in two. There were no iatrogenic neurovascular injuries, implant failures, irritative symptoms or pressure sores due to subcutaneous implantation.

CONCLUSION

Favourable clinical and radiological outcomes can be achieved in treating posterior pelvic disruptions with MIAP. This plate is effective in view of its simplicity, less radiation exposure, safety, minimal invasion and stable fixation.

Percutaneous iliosacral screwing in pelvic ring injury using three-dimensional fluoroscopy

BACKGROUND

Iliosacral screw fixation is a popular technique for treatment of unstable pelvic injuries involving the posterior ring. However, screw malposition may result in dangerous complications involving injury to adjacent neurovascular structures. This study was conducted in order to evaluate the results and efficacy of using three-dimensional fluoroscopy in the performance of iliosacral screw fixation.

METHODS

Twenty-nine patients (31 cases, two bilateral) who suffered injury to the pelvic ring requiring surgical treatment were included in this study. According to the Association for Osteosynthesis-Orthopaedic Trauma Association (AO-OTA) classification, there were 14 patients with type B, 13 patients with type C, and 2 patients with a bilateral sacral fracture. The mean age of patients was 39 years. Once the guide pin had been inserted, its safety was confirmed using three-dimensional fluoroscopy; screw fixation was then performed. Eighteen patients underwent percutaneous iliosacral screw fixation and anterior fixation, while 11 patents underwent screw fixation only. Postoperative computed tomography (CT) was performed for evaluation of the screw position, including any invasion into the sacral foramen or canal and neurovascular injury. The perforation of the screw was divided according to the location (sacral zones I, II, and III) and the degree (grade 0, no perforation; grade 1, perforation <2 mm; grade 2, perforation between 2 and 4 mm; grade 3, perforation >4 mm).

RESULTS

The mean operation time was 35.6 min, and the mean radiation exposure time was 85.9 s. For accurate location of the guide pin, one patient underwent three-dimensional reconstruction twice. None of the patients required reoperation or suffered any neurovascular injury. Although seven cases involved perforation, all were less than 2 mm (grade 0: 24 cases, grade 1: 7 cases).

CONCLUSIONS

When performing percutaneous iliosacral screw fixation in a patient with an unstable pelvic ring injury, use of three-dimensional fluoroscopy may allow for accurate location of the screw and result in fewer complications.

Accuracy study of new computer-assisted orthopedic surgery software

PURPOSE

The new computerized system is based on image analysis and designed to aid in orthopedic surgeries by virtual trajectory of the guide wire, intra-operative planning and various measurements. Validation of the accuracy and safety of any computer-aided surgery system is essential before implementing it clinically. We examined the accuracy of guide-wire length and angle measurements and fusion of multiple adjacent images (panoramic view image, PVI(®)) of the new software.

METHODS

This is a 2-part study. Part I: twenty guide wires were drilled to various depths in a synthetic femur model and the results obtained by the software measurements were compared with manual measurements by a caliper and a depth gauge. Part II: a sawbone femur shaft was osteotomized and various inclinations of > 10° to the varus or valgus angles were tested. The manually obtained measurements of angles and lengths were compared to the new computerized system software PVI.

RESULTS

There was a significant positive linear correlation between all groups of the computerized length and the control measurements (r>0.983, p<0.01). There was no significant difference among different distances, angles or positions from the image intensifier. There was a significant positive linear correlation between the angle and length measurement on the PVI and the control measurement (r>0.993, p<0.01).

CONCLUSIONS

The new computerized software has high reliability in performing measurements of length using an aiming, positioning and referring device intra-operatively.

Minimally invasive fluoro-navigation screw fixation for the treatment of pelvic ring injuries

Intensive use of intraoperative fluoroscopy is mandatory to achieve good accuracy and avoid neural or vascular injury and may prolong surgical time and increase exposure-related hazards. New methods of percutaneous treatment in conjunction with innovative fluoroscopy-based computerized navigation have evolved in an attempt to overcome the existing difficulties. This report described our experience in applying fluoroscopic surgical navigation technique and evaluated its clinical application to pelvic ring injuries, including its feasibility, merits and limitations. Twenty-two patients with pelvic ring injuries were treated with percutaneous pubic ramus screw and sacroiliac screw techniques under the guidance of a fluoroscopy-based navigation system. A total of forty-four screws were inserted, including twenty-seven pubic ramus screws and seventeen sacroiliac screws. The average operation time and the average fluoroscopy time per screw were 23.6 minutes and 22.2 seconds respectively. Compared to the final position of the screw, the average deviated distance of wire tip was 2.8 mm and the average trajectory difference was 2.6°. A ventral cortex perforation of the sacrum was found in one sacroiliac screw without any clinical symptoms. No superficial or deep infection occurred. No patient sustained recognized neurologic, vascular, or urologic injury as a result of percutaneous screw fixation of pubic ramus fractures, sacroiliac disruptions, or sacral fractures. Our results showed that fluoroscopy-based navigation technique for the pelvic ring injuries could become a safe and effective alterative method for the treatment of pelvic ring injuries in some selected patients.

Percutaneous iliosacral screw insertion: malpositioning and revision rate of screws with regards to application technique (navigated vs. Conventional)

BACKGROUND

Conventional percutaneous iliosacral screw placement in pelvic surgery is considered to be a highly demanding operative technique with a high rate of screw malpositions, which may be associated with the risk of neurologic damage or inefficient stability. In the conventional technique, the correct entry point for the screw and the small target corridor for the iliosacral screw may be difficult to visualize using an image intensifier. We tried to find out in this study whether the positioning of percutaneous screw implantations could be optimized by evaluating the rate and grade of malpositions and whether the needed revisions could be reduced by using computer navigation and three-dimensional (3D) image intensifier.

METHODS

A group of 54 patients with 63 screws implanted using computer navigation was compared with 87 patients with 131 screws implanted using the conventional fluoroscopic technique. The exact screw position was controlled in a postoperative computed tomography scan, and the grade of malposition of every screw was investigated and compared.

RESULTS

A complete intraosseous screw position was found in 42% of cases using the conventional technique and was significantly less compared with 81% using a 3D image intensifier in combination with a navigation system. Moreover, the revision rate of 1.6% was significantly less in the navigated group compared with 19% in the conventional group.

CONCLUSIONS

The results indicate that 3D-computer navigation of the percutaneous iliosacral screw insertion can facilitate surgical performance in respect to reducing screw malposition and revision rates.

Intraoperative three-dimensional fluoroscopy assessment of iliosacral screws and lumbopelvic implants stabilizing fractures of the os sacrum

INTRODUCTION

Percutaneous iliosacral screw fixation of unstable sacrum fractures has gained popularity since its introduction in the 1990s. The combination with lumbopelvic implants allows the application even in situations of higher instability. Both manual and navigated screw insertion in the sacrum and vertebra bodies shows unchanged relevant malpositions. The current standard to control the screw position is postoperative computed tomography. The study presents the results of assessment of these implants by intraoperative three-dimensional fluoroscopy.

METHODS

From January 2008 through March 2009, 14 patients had stabilization of the dorsal pelvic ring with iliosacral screws alone or in combination with lumbopelvic implants. Intraoperative 3D fluoroscopy was performed to evaluate the position of the implants stabilizing the posterior pelvic ring.

RESULTS

Fourteen iliosacral screws and eight pedicle screws were depicted. In all patients, we were able to adequately evaluate the placement of iliosacral screws, lumbar pedicle screws and iliacal screws. As a consequence of intraoperative 3D scan a lumbar pedicle screw was corrected. The entire scanning procedure required 5 min. The time for analyzing the 3D scan took 3 min.

CONCLUSIONS

Intraoperative 3D fluoroscopy is a valuable tool for intraoperative assessment of iliosacral screws and lumbopelvic implants. The technique should help us to detect intraoperative malplacement of the screws more reliably than conventional fluoroscopy and allows an immediate correction of malplaced implants. Therefore, a postoperative computed tomography to control the position of implants is dispensable.

Quantification of the upper and second sacral segment safe zones in normal and dysmorphic sacra

OBJECTIVES

To quantify the obliquity and dimensions of the upper and second sacral segment iliosacral screw safe zones and to determine the differences between normal and dysmorphic sacral morphology.

DESIGN

Retrospective cohort.

SETTING

University Level I trauma center.

PATIENTS/PARTICIPANTS

Fifty patients with pelvic computed tomography scans.

INTERVENTION

All sacra were characterized as normal or dysmorphic based on plain pelvic radiographs and previously described criteria. Multiple computed tomography scan reconstructions were viewed and manipulated simultaneously with 6 degrees of freedom to allow for custom visualization in any plane.

MAIN OUTCOME MEASUREMENTS

In each patient, a unique reconstruction plane was created perpendicular to the safe zone axis. The narrowest safe zone cross-sectional area was measured. Next, on simulated pelvic outlet and inlet views, safe zone obliquity and width were measured. Finally, the space available for a transverse screw was assessed. Measurements were performed for both upper and second sacral segment. Values for normal and dysmorphic safe zones were compared.

RESULTS

Sacral dysmorphism was identified in 22 patients. In these sacra, the upper sacral segment safe zone cross-section was 36% smaller than in normal sacra (P < 0.001). No transverse screws could be placed, but accommodating for the caudal to cranial obliquity (30° versus 21° in normals, P < 0.001) and posterior to anterior obliquity (15% versus 4% in normals, P < 0.001) of the safe zone, an iliosacral screw at least 75 mm in length could be placed safely in 91% of patients. A transverse screw could be placed in 75% of normal sacra. In the second segment safe zone, the cross-sectional area was more than twice as large in dysmorphic sacra compared to normals (220 mm versus 109 mm, P < 0.001). The obliquity was not different on either the inlet or outlet views between groups. A transverse screw could be placed at this level in 95% of those with dysmorphic sacra and in only 50% of normal sacra.

CONCLUSIONS

Sacral dysmorphism occurred in 44% of patients in this consecutive series. Many anatomic differences were consistently found between the two morphologies with clinical relevance to iliosacral screw placement. Specifically, the dysmorphic upper sacral segment safe zone is significantly smaller and more obliquely oriented but is still large enough to accommodate an iliosacral screw in nearly all patients. The second sacral segment safe zone is approximately transversely oriented in both sacral types but is more than twice as large in dysmorphic sacra. This segment may be a primary fixation opportunity in patients with sacral dysmorphism.

2D-fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries--a case series

BACKGROUND

Screw fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system.

METHODS

Between August 2004 and December 2007, 44 of 442 patients with pelvic injuries were included for closed reduction and percutaneous screw fixation of disrupted pelvic ring lesions using an optoelectronic 2D-fluoroscopic based navigation system. Operating and fluoroscopy time were measured, as well as peri- and postoperative complications documented. Screw position was assessed by postoperative CT scans. Quality of live was evaluated by SF 36-questionnaire in 40 of 44 patients at mean follow up 15.5 +/- 1.2 month.

RESULTS

56 iliosacral- and 29 ramus pubic-screws were inserted (mean operation time per screw 62 +/- 4 minutes, mean fluoroscopy time per screw 123 +/- 12 seconds). In post-operative CT-scans the screw position was assessed and graded as follows: I. secure positioning, completely in the cancellous bone (80%); II. secure positioning, but contacting cortical bone structures (14%); III. malplaced positioning, penetrating the cortical bone (6%). The malplacements predominantly occurred in bilateral overlapping screw fixation. No wound infection or iatrogenic neurovascular damage were observed. Four re-operations were performed, two of them due to implant-misplacement and two of them due to implant-failure.

CONCLUSION

2D-fluoroscopic navigation is a safe tool providing high accuracy of percutaneous screw placement for pelvic ring fractures, but in cases of a bilateral iliosacral screw fixation an increased risk for screw misplacement was observed. If additional ramus pubic screw fixations are performed, the retrograde inserted screws have to pass the iliopubic eminence to prevent an axial screw loosening.

The application of the axial view projection of the S1 pedicel for sacroiliac screw

BACKGROUND

The objective of this study was to position the iliosacral screws speedily, easily, and safely, we sought to delineate readily reproducible radiographic anatomic clues of the pedicel of S1 for the iliosacral screw placement.

METHODS

We used eight normal adult pelvic specimens lying on the operation table in the prone position. First, the C-arm fluoroscope unit is positioned for the lateral view of the body of S1. We gradually changed the angle of the C-arm to ventral and cephalad. When a clear oval track image appears, we fix the angle of the C-arm. With the assistance of the C-arm projection, the starting point for the guide pin is centered on the oval track, and the orientation is adjusted. When the projection of the guide pin became a point inside of the oval track, the guide pin is inserted using battery-powered equipment. The accuracy and angle of pin placement is assessed using computed tomography scans in all cases.

RESULTS

In all the pelves, the oval track has been successfully found, and the guide pins are accurately inserted using the sacral pedicel axial view. In the angular orientations by the computed tomography scan, the transverse plane inclination to the ventral of the guide pin is approximately 38.3 degrees +/- 1.9 degrees, and the frontal plane inclination to the cephalad is approximately 29.6 degrees +/- 2.0 degrees.

CONCLUSION

The sacral pedicel axial view projection is a optimal radiographic technique for percutaneous placement of iliosacral screws in clinical practice. We can get the limpid axial view of pedicel of S1 to applicate this project method, which provides a speedier method with less radiation exposure for percutaneous placement of iliosacral screws.

Computer-navigated iliosacral screw insertion reduces malposition rate and radiation exposure

Insertion of percutaneous iliosacral screws with fluoroscopic guidance is associated with a relatively high screw malposition rate and long radiation exposure. We asked whether radiation exposure was reduced and screw position improved in patients having percutaneous iliosacral screw insertion using computer-assisted navigation compared with patients having conventional fluoroscopic screw placement. We inserted 26 screws in 24 patients using the navigation system and 35 screws in 32 patients using the conventional fluoroscopic technique. Two subgroups were analyzed, one in which only one iliosacral screw was placed and another with additional use of an external fixator. We determined screw positions by computed tomography and compared operation time, radiation exposure, and screw position. We observed no difference in operative times. Radiation exposure was reduced for the patients and operating room personnel with computer assistance. The postoperative computed tomography scan showed better screw position and fewer malpositioned screws in the three-dimensional navigated groups. Computer navigation reduced malposition rate and radiation exposure.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Is the lateral sacral fluoroscopic view essential for accurate percutaneous sacroiliac screw insertion? An experimental study

The aim of this study was to evaluate the role of the lateral fluoroscopic view in optimising percutaneous sacroiliac screw insertion. Plastic pelvic models (n=26) were used for the introduction of 104 cannulated screws into the first and second sacral (S1 and S2) vertebral bodies, controlled with an image intensifier using either two views (inlet/outlet) for the right side (group A, n=52) or three views (inlet/outlet/lateral) for the left side (group B, n=52). The mean radiation exposure times for S1 were 18.6s and 14s, in groups A and B, respectively, and for S2 were 16.1s and 12.2s, respectively; 13 cortex perforations were noted in group A and 20 in group B. After insertion into S1, in both groups there were three cases of foraminal and none of central canal perforation, but after S2 insertion in both groups there were ten foraminal and five canal perforations. A higher incidence of misplacement of S1 screws was found in group A in comparison with group B (p=0.001), with sufficient data to support percutaneous screw fixation using inlet, outlet and lateral views rather than only inlet and outlet acquisition images.

Computer assisted percutaneous placement of augmented iliosacral screws: a reasonable alternative to sacroplasty

STUDY DESIGN

A technical report of fluoroscopy guided placement of augmented iliosacral screws in osteoporotic insufficiency fractures of the sacrum.

OBJECTIVE

To describe a combined approach of navigated iliosacral screw placement and screw augmentation as an option for osteosynthesis of sacral insufficiency fractures in the elderly.

SUMMARY OF BACKGROUND DATA

The incidence of sacral insufficiency fractures is increasing. Outcome of conservative treatment is inconsistent. Recently sacroplasty is propagated as an interventional therapy but the long-term outcome is still unknown. Evidence from finite element models suggests that stabilization of the sacrum achieved by sacroplasty is insufficient to restore the weight bearing capacity of the sacrum permanently.

METHODS

We suggest a minimally invasive fluoroscopically navigated iliosacral screw osteosynthesis with cement augmentation of the screws for treatment of insufficiency fractures of the sacrum.

RESULTS

The procedure, especially fluoroscopic visualization and navigation of the osteoporotic sacrum is technically feasible. A total radiograph time of 7,4 minutes, including image acquisition for navigation and fluoroscopic control of cement injection, is acceptable and can be expected to be significantly reduced with repeated applications of the procedure. The patient presented in the report was discharged to rehabilitation soon after the operation. An assistive device (delta wheel) is only needed for longer walking distances. Pain was reduced drastically immediately after surgery.

CONCLUSION

In general, fractures are treated by reduction and fixation to restore the biomechanical function of the injured bone. These principles should be applied to elderly patients with osteoporotic fractures as well. The technique reported here is adapted to the special demands of the elderly patient, i.e., minimally invasive, support of the weakened bone by cement augmentation, bone protective screw positioning and safety due to navigation support.

Anterior plating and percutaneous iliosacral screwing in an unstable pelvic ring injury

BACKGROUND

This study was carried out to evaluate the effectiveness of anterior plating with subsequent percutaneous iliosacral screwing for the management of unstable pelvic ring injuries.

METHODS

Nineteen patients with unstable pelvic ring injuries were included in this retrospective study. All patients were followed up for at least 1 year, and their mean age was 43 years. According to the Association for Osteosynthesis-Orthopaedic Trauma Association (AO-OTA) classification, there were 5 B2 injuries, 11 C1 injuries, and 3 C2 injuries. After anterior fixation by means of plating, an iliosacral screw fixation was carried out percutaneously using a C-arm fluoroscope.

RESULTS

All fractures healed, except for 1 case of nonunion at the pubic ramus. Radiological results showed that there were 9 anatomic, 7 nearly anatomic, 2 moderate, and 1 poor reduction. Sixteen of the 19 patients had good or excellent results for function, and all these had satisfactory (anatomic or nearly anatomic) reductions. The two moderate and 1 poor result were from an unsatisfactory reduction in a type-C injury with residual neurological signs. A screw misplacement with a neurological compromise occurred in 1 patient, but there were no adverse sequelae after its removal. The complications encountered were 2 cases of screw loosening, 2 cases of anterior metal failure, and 1 deep infection.

CONCLUSIONS

Anterior plating with subsequent percutaneous iliosacral screwing may be a useful method of treatment for unstable pelvic ring injuries, and the reduction quality and residual neurological signs were important in its functional outcome.

A comparison of optical and electromagnetic computer-assisted navigation systems for fluoroscopic targeting

OBJECTIVES

Freehand targeting using fluoroscopic guidance is routine for placement of interlocking screws associated with intramedullary nailing and for insertion of screws for reconstruction of pelvic and acetabular injuries. New technologies that use fluoroscopy with the assistance of computer guidance have the potential to improve accuracy and reduce radiation exposure to patient and surgeon. We sought to compare 2 fluoroscopic navigation tracking technologies, optical and electromagnetic versus standard freehand fluoroscopic targeting in a standardized model.

INTERVENTION

Three experienced orthopaedic trauma surgeons placed 3.2-mm guide pins through test foam blocks that simulate cancellous bone. The entry site for each pin was within a circular (18-mm) entry zone. On the opposite surface of the test block (130-mm across), the target was a 1-mm-diameter radioopaque spherical ball marker. Each surgeon placed 10 pins using freehand targeting (control group) navigation using Medtronic iON StealthStation (Optical A), navigation using BrainLAB VectorVision (Optical B), or navigation using GE Medical Systems InstaTrak 3500 system (EM).

OUTCOME MEASUREMENTS

Data were collected for accuracy (the distance from the exit site of the guidewire to the target spherical ball marker), fluoroscopy time (seconds), and total number of individual fluoroscopy images taken.

RESULTS

The 2 optical systems and the electromagnetic system provided significantly improved accuracy compared to freehand technique. The average distance from the target was significantly (3.5 times) greater for controls (7.1 mm) than for each of the navigated systems (Optical A = 2.1 mm, Optical B = 1.9 mm EM = 2.4 mm; P < .05). Accuracy was similar for the 3 navigated systems, (P > 0.05). The ability to place guidewires in a 5-mm safe zone surrounding the target sphere was also significantly improved with the optical systems and the EM system (99% of wires in the safe zone) compared to controls (47% in the safe zone) (P < 0.002). Safe zone placement was similar among the 3 navigated systems (P > 0.05). Fluoroscopy time (seconds) and number of fluoroscopy images were similar among the three navigated groups (P > 0.05). Each of these parameters was significantly less when using the computer-guided systems than for freehand-unguided insertion (P < 0.01).

CONCLUSIONS

Both optical and electromagnetic computer-assisted guidance systems have the potential to improve accuracy and reduce radiation use for freehand fluoroscopic targeting in orthopaedic surgery.

[Percutaneous, 2D-fluoroscopic navigated iliosacral screw placement in the supine position: technique, possibilities, and limits]

OBJECTIVE

In pelvic surgery, computer-assisted procedures are currently used predominantly for percutaneous iliosacral screw placement. The aim of this study was to evaluate the possibilities and limits of a 2D-fluoroscopic navigated procedure used for this indication.

METHODS

A consecutive series of patients with non or slightly displaced injuries of the posterior pelvic ring were prospectively investigated. Cannulated cancellous screws of 7.3 mm were percutaneously implanted in the supine position. The navigated procedure was performed using an active optoelectronical system and a 2D C-arm. Target parameters were practicability, precision and intraoperative radiation exposure time compared to patients treated using a non-navigated technique.

RESULTS

In a 15 month period, 35 screws were implanted in 20 patients. The average procedure took 36.2+/-12.5 min (range 18-62 min), with a fluoroscopic time of 0.9+/-0.3 min (range 0.6-1.8 min) per screw. The displacement rate was 8% (n=3/35, CI 1.8-23.0). Compared to retrospectively selected patients treated using a non-navigated technique (n=13), a significant increase in procedure time (P=0.01), a significant decrease of radiation exposure time (P<0.001) and a decreased displacement rate (P>0.05) were observed in the navigated group.

CONCLUSION

The 2D-fluoroscopic navigated procedure used in this study can be recommended for percutaneous stabilisation of non or minor displaced injuries of the posterior pelvis. This procedure reduces intraoperative radiation exposure and improves intraoperative orientation but does not crucially enhance the precision of screw placement compared to the non-navigated technique. Finally, it is limited by its poor image resolution and lack of three-dimensionality.

[A new parallel drill guide for navigating femoral neck screw placement. Development and evaluation]

BACKGROUND

Trauma navigation applications employ conventional mechanical surgical instruments for the simulation of drilling trajectories. Few complex mechanical targeting instruments, such as guides with fixed angles or with multiple parallel cannulas, have been adapted into trauma navigation systems. We have integrated a complex mechanical tool, the parallel drill guide (PDG) for the minimally invasive treatment of femoral neck fractures, into a trauma navigation module. The combined advantage of a complex yet commonly used mechanical tool with the benefits of fluoroscopic navigation was evaluated.

MATERIAL AND METHODS

To adapt the conventional PDG to a fluoroscopic navigation system, the instrument was fitted with a non-detachable reflective marker array. Navigation engineers developed custom software to enable visualization of the navigated PDG. A comparison of conventional versus navigated PDG techniques was performed on plastic bone models and cadavers. No software or mechanical failures occurred with the navigated PDG procedures.

RESULTS

While the total operative time was 30% more with navigation compared with conventional techniques, the total radiation time for the navigated group was reduced by more than 60%. This study demonstrates the successful integration of a cannulated parallel drill guide with a fluoroscopic navigation system.

CONCLUSION

The continuous display of the complex PDG mechanical instrument, with multiple parallel virtual trajectories, enables safe and accurate parallel screw placement. The integration of complex mechanical instrumentation with navigation for the accurate placement of hardware represents an attractive direction in multiple trauma applications.

Image guidance in pelvic and acetabular surgery--expectations, success and limitations

During the last decade navigation techniques in pelvic and acetabular surgery have been described. Nowadays, available techniques include CT-based navigation, 2D C-arm navigation and 3D C-arm navigation. The main indication is the navigated percutaneous SI screw fixation, but acetabular screw fixations are also reported. In this article, based upon a literature review and our own clinical experiences, the indications for and limitations of navigated techniques in pelvic and acetabular surgery are described.

Fracture-table-mounted versus bone-mounted dynamic reference frame tracking accuracy using computer-assisted orthopaedic surgery--a comparative study

OBJECTIVE

Fluoroscopy-based computerized navigation systems enable accurate implant placement while reducing radiation exposure. The navigation process normally requires the attachment of a dynamic reference frame (DRF) to a bone, causing additional surgical trauma. The aim of this study was to compare the accuracy of navigation with the DRF either attached to the bone or mounted on the fracture table.

METHODS

We conducted a prospective study on 10 consecutive patients who underwent operative fixation of femoral neck fractures with cannulated screws using computerized navigation. After insertion of the three guide wires, the DRF was moved from the patient's bone to the fracture table. For each screw, angular and translational deviations of the navigated images as compared to the conventional fluoroscopic images were analyzed.

RESULTS

The accuracy of navigated Kirschner wire placement was similar with both techniques, resulting in an average translational error of less than 2 mm in both groups and around 1 degrees in angulation error--both of these accuracy measurements are acceptable and sufficient for the insertion of cannulated screws into the femoral head.

CONCLUSION

Our study suggests that attaching the DRF to a fracture table during navigated femoral neck fixation allows for acceptable accuracy with the possible added benefit of reducing patient morbidity.

Computerized navigation for treatment of slipped femoral capital epiphysis

In situ pinning with a single screw is the treatment of choice for symptomatic slipped capital femoral epiphysis (SCFE). Some technical features are critical and include proper screw entry point, screw direction in relation to the epiphysis, and the length of screw. These are complicated by the deformity created as a result of the posterior slip of the epiphysis. Fluoroscopic based computerized navigation system can increase precision in screw placement while performing the surgical task, and markedly reduce radiation. By using real fluoroscopy-based navigation, the screw can be placed with only two fluoroscopic images. Entry point, length, and precise direction can all be easily determined through this technique.

Computerized navigation for the internal fixation of femoral neck fractures

BACKGROUND

Accurate placement of cannulated screws is essential to ensure secure fixation of femoral neck fractures. We compared computerized navigation and conventional fluoroscopy with regard to the accuracy of screw placement for the fixation of femoral neck fractures.

METHODS

We retrospectively compared two groups of twenty consecutive patients with a femoral neck fracture who underwent internal fixation with three cannulated screws. Computer-based navigation was used to guide screw placement in one group, and conventional fluoroscopy was used in the other group. Radiographic evaluation included the measurement of screw parallelism and spread, the calibrated distance from the lesser trochanter, and joint penetration. The follow-up period was two years. The rates of complications in both groups were evaluated.

RESULTS

The navigation-assisted group had better screw parallelism and greater spread of the screws. There was a tendency for fewer reoperations and significantly fewer overall complications in the patients in whom computerized navigation was used (p < 0.018).

CONCLUSIONS

Computerized navigation improves the accuracy of cannulated screw placement in the internal fixation of femoral neck fractures. It may provide better mechanical stability and improved fracture outcome.