Computer-assisted periacetabular screw placement: Comparison of different fluoroscopy-based navigation procedures with conventional technique

Tripod Fixation of Periacetabular Metastatic Lesions Using the IlluminOss Device

Background

Percutaneous tripod fixation of periacetabular lesions is performed at our institution for patients with metastatic bone disease and a need for quick return to systemic therapy. We have begun to use the IlluminOss Photodynamic Bone Stabilization System instead of the metal implants previously described in the literature because of the success of the IlluminOss implant in fixing fragility fractures about the pelvis.

Description

At our institution, the procedure is performed in the interventional radiology suite in order to allow for the use of 3D radiographic imaging and vector guidance systems. The patient is positioned prone for the transcolumnar PSIS-to-AIIS implant and posterior column/ischial tuberosity implant or supine for the anterior column/superior pubic ramus implant. Following a small incision, a Jamshidi needle with a trocar is utilized to enter the bone at the chosen start point. A hand drill is utilized to advance the Jamshidi needle according to the planned vector; alternatively, a curved or straight awl can be utilized. The 1.2-mm guidewire is placed and reamed. We place both the transcolumnar and posterior column wires at the same time to ensure that there is no interference. The balloon catheter for the IlluminOss is assembled on the back table and inserted according to the implant technique guide. The balloon is inflated and observed on radiographs in order to ensure that the cavity is filled. Monomer is then cured, and the patient is flipped for the subsequent implant. Following placement of the 3 IlluminOss devices, adjunct treatments such as cement acetabuloplasty or cryoablation can be performed.

Alternatives

Alternative treatments include traditional open fixation of impending or nondisplaced acetabular fractures in the operating room, or percutaneous implant placement in the operating room. Implant placement may be performed with the patient in the supine, lateral, or prone position, depending on surgeon preference. Alternative implants include standard metal implants such as plates and screws, or cement augmentation either alone or with percutaneous screws. Finally, ablation alone may be an alternative option, depending on tumor histology.

Rationale

Open treatment of acetabular fractures is a more morbid procedure, given the larger incision, increased blood loss, longer time under anesthesia, and increased length of recovery. Percutaneous fixation may be performed in either the operating room or interventional radiology suite, depending on the specific equipment setup at an individual institution. At our institution, we prefer utilizing the interventional radiology suite as it allows for more precise implant placement through the use of an image-based vector guidance system and 3D fluoroscopy to accurately identify safe corridors. The use of percutaneous fixation allows for faster recovery and earlier return to systemic therapy. Because the IlluminOss implant is radiolucent, it allows for better evaluation of disease progression and can better accommodate nonlinear corridors or fill a lytic lesion to provide stability.

Expected Outcomes

Postoperatively, we expect the patient to be weight-bearing as tolerated with use of an assistive device. We expect the small incisions to fully heal within 2 weeks. Patients should be able to return to systemic therapy as indicated earlier than with an open procedure.

Important Tips

The use of a hand drill with the Jamshidi needle and trocar can help adjust a drilled pathway and allow for close adherence to a planned vector.Vector guidance systems can be useful to fully capture the area at risk for fracture and to provide maximal stability with the expandable implant, but they are not necessary to perform the procedure.Placing both posterior implants at the same time can be helpful to avoid interference. This is accomplished by drilling and placing the guidewire for both implants prior to reaming and placing the balloon implant.

Acronyms and Abbreviations

CT = Computed tomographyPSIS = posterior superior iliac spineAIIS = anterior inferior iliac spine.

Optimizing percutaneous reduction and fixation with guidewire modification in pelvic and acetabular fractures: surgical technique and case series

BACKGROUND

Minimally invasive percutaneous screw fixation for pelvic ring and acetabular fractures has become increasingly popular due to its numerous benefits. However, the precise placement of the screw remains a critical challenge, necessitating a modification of the current techniques. This paper introduces a refined technique employing a modified guidewire to enhance the precision and efficiency of percutaneous fixation in pelvic and acetabular fractures.

METHODS

This study details the surgical techniques implemented for correcting guidewire misdirection in percutaneous screw fixation and includes a retrospective analysis of patients treated with this modified approach over a three-year period.

RESULTS

In this study, 25 patients with pelvic ring and acetabular fractures underwent percutaneous screw fixation. The cohort, predominantly male (23 out of 25), had an average age of 38 years. The majority of injuries were due to traffic accidents (18 out of 25). Types of injuries included pelvic ring (6 cases), acetabular fractures (8 cases), and combined injuries (11 cases). Various screw types, including antegrade and retrograde anterior column screws, retrograde posterior column screws, and lateral compression screws, were used, tailored to each case. Over an average follow-up of 18 months, there were no additional procedures or complications, such as neurovascular injury or hardware failure, indicating successful outcomes in all cases.

CONCLUSIONS

This study introduces a simple yet effective method to address guidewire misdirection during percutaneous fixation for pelvic and acetabular fractures, offering enhanced precision and potentially better patient outcomes. Further research with a larger patient cohort is required for a more comprehensive understanding of its efficacy compared to traditional methods.

LEVEL OF EVIDENCE

IV. Therapeutic Study (Surgical technique and Cases-series).

Extra-articular screw placement strategy in Stoppa approach based on three-dimensional reconstruction model

The study aimed to explore an extra-articular screw placement strategy in Stoppa approach. Radiographic data of patients who underwent pelvic computed tomography from January 2016 to June 2017 were imported into Materiaise's interactive medical image control system software for three-dimensional reconstruction. Superior and lower margins of acetabulum and ipsilateral pelvic brim could be observed simultaneously through inlet-obturator view. A horizontal line from superior acetabular margin intersected pelvic brim at point "A" and another vertical line from lower margin intersected pelvic brim at point "B" were drawn, respectively. Lengths form sacroiliac joint to "A" (a), "A" to "B" (b), and "B" to pubic symphysis (c) were measured. Patients were divided into four groups depending on gender and side difference of measured hemi-pelvis: male left, male right, female left, and female right. Lengths of adjacent holes (d) and spanning different holes (e) of different plates were also measured. Mean lengths of a, b, c in four groups were 40.94 ± 1.85 mm, 40.09 ± 1.93 mm, 41.78 ± 3.62 mm, and 39.77 ± 2.23 mm (P = 0.078); 40.65 ± 1.58 mm, 41.48 ± 1.64 mm, 40.40 ± 1.96 mm, and 40.66 ± 1.70 mm (P = 0.265); 57.03 ± 3.41 mm, 57.51 ± 3.71 mm, 57.84 ± 4.40 mm, and 59.84 ± 4.35 mm (P = 0.165), respectively. Mean d length of different plates was 12.23 mm. Average lengths spanning 1, 2, 3 and 4 holes were 19.33 mm, 31.58 mm, 43.80 mm, and 55.93 mm. Our data showed that zones a and c could be safely inserted three and four screws. Penetration into hip joint could be avoided when vacant 3-hole drilling was conducted in zone b. Fracture line in zone b could serve as a landmark for screw placement.

Outcomes of spring-locking plate fixation method using locking mesh plate/box plate for posterior wall fractures of the acetabulum: a retrospective single-centre study

INTRODUCTION

This retrospective study evaluated the outcomes of variable-angle locking compression plate, mesh plate, or footplate box fixation for posterior acetabular wall fractures.

PATIENTS AND METHODS

The study included nine patients with unstable posterior acetabular wall fractures who underwent internal fixation with the "spring-locking plate fixation method" between January 2015 and December 2019. Patient demographics, fracture classifications, surgical details, radiological and clinical evaluations, and complications were collected from electronic medical records. Statistical analyses were performed to assess the relationship between preoperative and postoperative dislocations.

RESULTS

The mean age of the patients was 46 years, and the majority were men (88.9%). Fracture types included posterior wall fractures and posterior column plus posterior wall fractures. The mean operative time was 246 min and the mean blood loss was 663 mL. The surgical approaches included the Kocher-Langenbeck, Ganz trochanteric flip, and transtrochanteric approaches. Variable-angle locking compression plate mesh plates and footplate box type implants were used for fixation. The mean preoperative dislocation was 23 mm, which was significantly reduced to 1 mm immediately post-operation and at the final observation. The bone fusion rate was 100% and radiological and clinical evaluations revealed favourable outcomes. Complications were minimal, with mild heterotopic ossification observed in four patients.

CONCLUSION

The spring-locking plate fixation method demonstrated satisfactory outcomes for the treatment of posterior acetabular wall fractures. This technique provides rigid fixation. Furthermore, the use of variable-angle locking screws minimizes the risk of intra-articular perforations. Despite limitations such as a small sample size and the absence of a control group, the results suggest that the spring-locking plate fixation method may be valuable in managing these fractures.

Augmented reality-based surgical navigation of pelvic screw placement: an ex-vivo experimental feasibility study

BACKGROUND

Minimally invasive surgical treatment of pelvic trauma requires a significant level of surgical training and technical expertise. Novel imaging and navigation technologies have always driven surgical technique, and with head-mounted displays being commercially available nowadays, the assessment of such Augmented Reality (AR) devices in a specific surgical setting is appropriate.

METHODS

In this ex-vivo feasibility study, an AR-based surgical navigation system was assessed in a specific clinical scenario with standard pelvic and acetabular screw pathways. The system has the following components: an optical-see-through Head Mounted Display, a specifically designed modular AR software, and surgical tool tracking using pose estimation with synthetic square markers.

RESULTS

The success rate for entry point navigation was 93.8%, the overall translational deviation of drill pathways was 3.99 ± 1.77 mm, and the overall rotational deviation of drill pathways was 4.3 ± 1.8°. There was no relevant theoretic screw perforation, as shown by 88.7% Grade 0-1 and 100% Grade 0-2 rating in our pelvic screw perforation score. Regarding screw length, 103 ± 8% of the planned pathway length could be realized successfully.

CONCLUSION

The novel innovative system assessed in this experimental study provided proof-of-concept for the feasibility of percutaneous screw placement in the pelvis and, thus, could easily be adapted to a specific clinical scenario. The system showed comparable performance with other computer-aided solutions while providing specific advantages such as true 3D vision without intraoperative radiation; however, it needs further improvement and must still undergo regulatory body approval. Future endeavors include intraoperative registration and optimized tool tracking.

The Anatomic Position of the Sciatic Nerve During Percutaneous Retrograde Posterior Column Fixation Is Determined by Hip Position

OBJECTIVES

There are multiple established patient positions for placement of a percutaneous retrograde posterior column screw for fixation of acetabulum fractures. The sciatic nerve is at risk of injury during this procedure because it lies adjacent to the start point at the ischial tuberosity. The purpose of this study was to define how the position of the sciatic nerve, relative to the ischial tuberosity, changes regarding the patient's hip position.

METHODS

In a cohort of 11 healthy volunteers, ultrasound was used to measure the absolute distance between the ischial tuberosity and the sciatic nerve. Measurements were made with the hip and knee flexed to 90 degrees to simulate supine and lateral positioning and with the hip extended to simulate prone positioning. In both positions, the hip was kept in neutral abduction and neutral rotation.

RESULTS

The distance from the lateral border of the ischial tuberosity to the medial border of the sciatic nerve was greater in all subjects in the hip-flexed position versus the extended position. The mean distance was 17 mm (range, 14-27 mm) in the hip-extended position and 39 mm (range, 26-56 mm) in the hip-flexed position ( P < 0.001).

CONCLUSIONS

The sciatic nerve demonstrates marked excursion away from the ischial tuberosity when the hip is flexed compared with when it is extended. The safest patient position for percutaneous placement of a retrograde posterior column screw is lateral or supine with the hip flexed to 90 degrees.

Antegrade Posterior Column Acetabulum Fracture Screw Fixation via Posterior Approach: A Biomechanical Comparative Study

Background and Objectives: Minimally invasive surgeries for acetabulum fracture fixation are gaining popularity due to their known advantages versus open reduction and internal fixation. Antegrade or retrograde screw fixation along the long axis of the posterior column of the acetabulum is increasingly applied in surgical practice. While there is sufficient justification in the literature for the application of the anterior approach, there is a deficit of reports related to the posterior approach. The aim of this study was to evaluate the biomechanical competence of posterior column acetabulum fracture fixation through antegrade screw placement using either a standard cannulated screw or a cannulated compression headless screw (CCHS) via posterior approach. Materials and Methods: Eight composite pelvises were used, and a posterior column acetabulum fracture according to the Letournel Classification was simulated on both their left and right sides via an osteotomy. The sixteen hemi-pelvic specimens were assigned to two groups (n = 8) for either posterior column standard screw (group PCSS) or posterior column CCHS (group PCCH) fixation. Biomechanical testing was performed by applying steadily increased cyclic load until failure. Interfragmentary movements were investigated by means of motion tracking. Results: Initial stiffness demonstrated significantly higher values in PCCH (163.1 ± 14.9 N/mm) versus PCSS (133.1 ± 27.5 N/mm), p = 0.024. Similarly, cycles and load at failure were significantly higher in PCCH (7176.7 ± 2057.0 and 917.7 ± 205.7 N) versus PCSS (3661.8 ± 1664.5 and 566.2 ± 166.5 N), p = 0.002. Conclusion: From a biomechanical perspective, CCHS fixation demonstrates superior stability and could be a valuable alternative option to the standard cannulated screw fixation of posterior column acetabulum fractures, thus increasing the confidence in postoperative full weight bearing for both the patient and treating surgeon. Whether uneventful immediate postoperative full weight bearing can be achieved with CCHS fixation should primarily be investigated in further human cadaveric studies with a larger sample size.

Next step trauma and orthopaedic surgery: integration of augmented reality for reduction and nail implantation of tibial fractures

INTRODUCTION

There is a tremendous scope of hardware and software development going on in augmented reality (AR), also in trauma and orthopaedic surgery. However, there are only a few systems available for intra-operative 3D imaging and guidance, most of them rely on peri- and intra-operative X-ray imaging. Especially in complex situations such as pelvic surgery or multifragmentary multilevel fractures, intra-operative 3D imaging and implant tracking systems have proven to be of great advantage for the outcome of the surgery and can help reduce X-ray exposure, at least for the surgical team (Ochs et al. in Injury 41:1297 1305, 2010). Yet, the current systems do not provide the ability to have a dynamic live view from the perspective of the surgeon. Our study describes a prototype AR-based system for live tracking which does not rely on X-rays.

MATERIALS AND METHODS

A protype live-view intra-operative guidance system using an AR head-mounted device (HMD) was developed and tested on the implantation of a medullary nail in a tibia fracture model. Software algorithms that allow live view and tracking of the implant, fracture fragments and soft tissue without the intra-operative use of X-rays were derived.

RESULTS

The implantation of a medullar tibia nail is possible while only relying on AR-guidance and live view without the intra-operative use of X-rays.

CONCLUSIONS

The current paper describes a feasibility study with a prototype of an intra-operative dynamic live tracking and imaging system that does not require intra-operative use of X-rays and dynamically adjust to the perspective of the surgeons due to an AR HMD. To our knowledge, the current literature does not describe any similar systems. This could be the next step in surgical imaging and education and a promising way to improve patient care.

Entry Point Variation in the Osseous Fixation Pathway of the Anterior Column of the Pelvis—A Three-Dimensional Analysis

Fractures of the superior pubic ramus can be treated with screw insertion into the osseous fixation pathway (OFP) of the anterior column (AC). The entry point determines whether the screw exits the OFP prematurely. This can be harmful when it enters the hip joint or damages soft tissues inside the lesser pelvis. The exact entry point varies between patients and can be difficult to ascertain on fluoroscopy during surgery. The aim of this study was to determine variation in the location of the entry point. A retrospective single center study was performed at a level 1 trauma center in the Netherlands. Nineteen adult patients were included with an undisplaced fracture of the superior pubic ramus on computer tomography (CT)-scan. Virtual three-dimensional (3D) models of the pelvises were created. Multiple screws were placed per AC and the models were superimposed. A total of 157 screws were placed, of which 109 did not exit the OFP prematurely. A universally reproducible entry point could not be identified. A typical crescent shaped region of entry points did exist and was located more laterally in females when compared to males. Three-dimensional virtual surgery planning can be helpful to identify the ideal entry points in each case.

Clinical outcomes of percutaneous screw fixation of acetabular fracture: A minimally invasive procedure

Objective

Open reduction with internal fixation is the surgical intervention of choice for acetabular fractures (AFs). Percutaneous screw fixation for AFs is a new procedure that is desirable because of the complex anatomy of the pelvis. In this study, we aimed to assess the functional outcomes, mobility, healing, and distal neurovascular abnormalities in patients who underwent percutaneous retrograde screw fixation.

Methods

Our study included 36 patients with AFs treated with percutaneous screw fixation between January 2016 and June 2021. There were 18 cases with anterior column AF, 7 cases with transverse AF, and 11 cases with associated AF, 6 of which had a T-shaped AF. Frequencies and percentages were used to describe characteristics and clinical outcomes. Mean and standard deviation were used for continuous variables. SPSS version 23 (IBM Corporation, Armonk, NY, USA) was used for statistical analysis.

Results

The average time to regain full mobility with full weight bearing was 12.9 ± 5.4 weeks, and approximately 11.1 ± 2.8 weeks was required for patients to be pain-free with satisfactory fracture healing. Only a minority (8.3%) of patients had abnormalities affecting the distal neurovascular system, and 11.1% experienced sexual dysfunction. Pain severity was assessed with a visual analogue scale. The average pain severity on the first and third post-operative days was 4 ± 2.4 and 3.8 ± 2.6, respectively. However, the average pain intensity before discharge was 1.7 ± 2.6.

Conclusion

Percutaneous screw fixation is the most efficient surgical choice for most pelvic/AFs.

Preclinical evaluation of a prototype freehand drill video guidance system for orthopedic surgery

Purpose: Internal fixation of pelvic fractures is a challenging task requiring the placement of instrumentation within complex three-dimensional bone corridors, typically guided by fluoroscopy. We report a system for two- and three-dimensional guidance using a drill-mounted video camera and fiducial markers with evaluation in first preclinical studies. Approach: The system uses a camera affixed to a surgical drill and multimodality (optical and radio-opaque) markers for real-time trajectory visualization in fluoroscopy and/or CT. Improvements to a previously reported prototype include hardware components (mount, camera, and fiducials) and software (including a system for detecting marker perturbation) to address practical requirements necessary for translation to clinical studies. Phantom and cadaver experiments were performed to quantify the accuracy of video-fluoroscopy and video-CT registration, the ability to detect marker perturbation, and the conformance in placing guidewires along realistic pelvic trajectories. The performance was evaluated in terms of geometric accuracy and conformance within bone corridors. Results: The studies demonstrated successful guidewire delivery in a cadaver, with a median entry point error of 1.00 mm (1.56 mm IQR) and median angular error of 1.94 deg (1.23 deg IQR). Such accuracy was sufficient to guide K-wire placement through five of the six trajectories investigated with a strong level of conformance within bone corridors. The sixth case demonstrated a cortical breach due to extrema in the registration error. The system was able to detect marker perturbations and alert the user to potential registration issues. Feasible workflows were identified for orthopedic-trauma scenarios involving emergent cases (with no preoperative imaging) or cases with preoperative CT. Conclusions: A prototype system for guidewire placement was developed providing guidance that is potentially compatible with orthopedic-trauma workflow. First preclinical (cadaver) studies demonstrated accurate guidance of K-wire placement in pelvic bone corridors and the ability to automatically detect perturbations that degrade registration accuracy. The preclinical prototype demonstrated performance and utility supporting translation to clinical studies.

Utility of 3-Dimensional Intraoperative Imaging in Pelvic and Acetabular Fractures: A Network Meta-Analysis

BACKGROUND

Successful surgical management of pelvic ring and acetabular fractures requires technical expertise to achieve an accurate reduction and stable fixation. The use of 3-dimensional (3D) intraoperative imaging (3DIOI) as an assessment tool has led to improved reduction and placement of implants. The purpose of this study was to assess the utility of using 3DIOI in the management of acetabular and pelvic fractures on the basis of outcomes reported in the literature.

METHODS

A literature search was performed using PubMed, the Cochrane Database of Systematic Reviews (CDSR), and Google Scholar using key terms. A network meta-analysis conducted using the frequentist approach allowed for statistical analysis of reported outcomes regarding screw position (in mm), fracture reduction (in mm), and complications.

RESULTS

A total of 9 studies were included in this analysis. When compared with conventional radiography, the mean radiation dose (in cGy·cm2) was significantly higher in 3DIOI (mean difference, 82.72; 95% confidence interval [CI], 21.83 to 143.61; p = 0.007). Use of 3DIOI yielded a 93% lower risk of developing medical complications (odds ratio [OR], 0.07; 95% CI, 0.02 to 0.35; p = 0.014). Use of 3DIOI yielded higher odds of achieving accurate screw placement (OR, 4.21; 95% CI, 1.44 to 12.32; p = 0.008) and perfect reduction (OR, 2.60; 95% CI, 1.19 to 5.68; p = 0.016). In ranking the imaging modalities, 12 of the 13 parameters analyzed were in favor of 3DIOI over conventional fluoroscopy and 2D navigation imaging.

CONCLUSIONS

Current literature supports the use of 3DIOI because of the decreased rates of misplaced implants, malreduced fractures, complications, and subsequent revision operations. The use of 3DIOI allows for improved visualization of pelvic anatomy when repairing pelvic and acetabular fractures, and helps surgeons to achieve favorable surgical outcomes.

LEVEL OF EVIDENCE

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

Fracture reduction and screw position after 3D-navigated and conventional fluoroscopy-assisted percutaneous management of acetabular fractures: a retrospective comparative study

BACKGROUND

Navigational techniques in orthopaedic trauma surgery have developed over the last years leaving the question of really improving quality of treatment. Especially in marginal surgical indications, their benefit has to be evident. The aim of this study was to compare reduction and screw position following 3D-navigated and conventional percutaneous screw fixation of acetabular fractures. The study hypothesis postulated that better fracture reduction and better screw position are obtained with 3D navigation.

MATERIALS AND METHODS

Preoperative and postoperative CT scans of 37 acetabular fractures treated by percutaneous screw fixation (24 3D-navigated, 13 conventional) were evaluated. Differences in pre- and postoperative fracture gaps and steps were compared in all reconstructions as well as the screw position relative to the joint and the fracture.

RESULTS

The differences in fracture gaps and fracture steps with and without 3D navigation were not significantly different. Distance of the screw from the joint line, angle difference between screw and ideal angle relative to the fracture line, length of the possible corridor used and position of the screw thread did not show any significant differences.

CONCLUSION

Comparison of 3D-navigated and conventional percutaneous surgery of acetabular fractures on the basis of pre- and postoperative CTs revealed no significant differences in terms of fracture reduction and screw position.

Computer-Assisted Orthopedic and Trauma Surgery

BACKGROUND

There are many ways in which computer-assisted orthopedic and trauma surgery (CAOS) procedures can help surgeons to plan and execute an intervention.

METHODS

This study is based on data derived from a selective search of the literature in the PubMed database, supported by a Google Scholar search.

RESULTS

For most applications the evidence is weak. In no sector did the use of computer-assisted surgery yield any relevant clinical or functional improvement. In trauma surgery, 3D-navigated sacroiliac screw fixation has become clinically established for the treatment of pelvic fractures. One randomized controlled trial showed a reduction in the rate of screw misplacement: 0% with 3D navigation versus 20.4% with the conventional procedure und 16.6% with 2D navigation. Moreover, navigation-assisted pedicle screw stabilization lowers the misplacement rate. In joint replacements, the long-term results showed no difference in respect of clinical/functional scores, the time for which the implant remained in place, or aseptic loosening.

CONCLUSION

Computer-assisted procedures can improve the precision of certain surgical interventions. Particularly in joint replacement and spinal surgery, the research is moving away from navigation in the direction of robotic procedures. Future studies should place greater emphasis on clinical and functional results.

Multidimensional Pelvic Fluoroscopy: A New and Novel Technique for Assessing Safety and Accuracy of Percutaneous Iliosacral Screw Fixation

OBJECTIVES

Multidimensional fluoroscopy is new imaging technology that generates intraoperative cross sectional imaging. Can this technology be used to assess accuracy and safety of percutaneously placed iliosacral screws intraoperatively?

DESIGN

Retrospective study.

SETTING

Level 1 academic trauma center.

PATIENTS/PARTICIPANTS

Fifty-two consecutive patients during a 7-month period with unstable posterior pelvic ring disruptions.

INTERVENTION

All patients were treated with percutaneous iliosacral and/or transsacral screw fixation by a single experienced surgeon. Traditional triplanar fluoroscopy was performed during guidepin insertion. Intraoperative multidimensional fluoroscopy was used for all patients after iliosacral screw fixation.

MAIN OUTCOME MEASUREMENTS

Intraoperative multidimensional fluoroscopy and postoperative computed tomography (CT) scans for each patient were retrospectively reviewed by the treating surgeon and another trauma surgeon. Screw position in relation to the sacral neuroforamen was assessed using multidimensional fluoroscopy and compared to postoperative CT scan. Screws were classified as extraforaminal, juxtaforaminal, or intraforaminal.

RESULTS

No screws were intraforaminally seen on intraoperative multidimensional fluoroscopy or postoperative CT scan. All iliosacral and transsacral screws were considered safe. Intraobserver and interobserver variability existed between reviewers when grading screws as extraforaminal versus juxtaforaminal. This was not clinically significant because both agreed that extraforaminal and juxtaforaminal screw positions are safe. Multidimensional fluoroscopy was used in 3 patients to assess guidepin placement before definitive screw fixation. Two patients underwent a change of fixation after reviewing multidimensional fluoroscopy. No postoperative neurological examination changes occurred.

CONCLUSIONS

Multidimensional fluoroscopy is a novel imaging technology that can safely be used intraoperatively to accurately determine iliosacral and transsacral screw placement.

LEVELS OF EVIDENCE

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

An efficient end-to-end CNN for segmentation of bone surfaces from ultrasound

The application of ultrasound (US) imaging in orthopedic surgery has always been a research direction. However, the various problems of US imaging hinder the development of computer assisted orthopedic surgery guided by US. US bone segmentation has been an important yet challenging task for many clinical applications. We propose a new end-to-end fully convolution network called BoneNet for real-time and accurate segmentation of bone surface from US image. The BoneNet employs the squeeze-and-excitation residual to realize a robust feature learning. In order to speed up the segmentation, we reduce the convolution kernel and used depth-wise separable convolution to reduce network parameters. In addition, we assessed the impact of different normalization operations and loss functions on network performance. Finally, we realize the comparison of the segmentation performance and generalization ability of the existing real-time US bone surface segmentation network under the unified dataset. We achieved an average Dice coefficient of 93.03 % on segmentation performance test, and 91.25 % on the generalization ability test. The results show that our proposed method ensures the real-time performance and achieves significant improvements in accuracy, which substantially outperformed the state-of-the-art.

Computer navigation-assisted minimally invasive percutaneous screw placement for pelvic fractures

Pelvic fractures are often caused by high-energy injuries and accompanied by hemodynamic instability. Traditional open surgery has a large amount of bleeding, which is not suitable for patients with acute pelvic fracture. Navigation-guided, percutaneous puncture-screw implantation has gradually become a preferred procedure due to its advantages, which include less trauma, faster recovery times, and less bleeding. However, due to the complexity of pelvic anatomy, doctors often encounter some problems when using navigation to treat pelvic fractures. This article reviews the indications, contraindications, surgical procedures, and related complications of this procedure for the treatment of sacral fractures, sacroiliac joint injuries, pelvic ring injuries, and acetabular fractures. We also analyze the causes of inaccurate screw placement. Percutaneous screw placement under navigational guidance has the advantages of high accuracy, low incidence of complications and small soft-tissue damage, minimal blood loss, short hospital stays, and quick recovery. There is no difference in the incidence of complications between surgeries performed by new doctors and experienced ones. However, computer navigation technology requires extensive training, and attention should be given to avoid complications such as screw misplacement, intestinal injury, and serious blood vessel and nerve injuries caused by navigational drift.

Three-dimensional-guided navigation percutaneous screw fixation of fragility fractures of the pelvis

BACKGROUND

Three-dimensional (3D)-guided navigation percutaneous screw fixation of pelvi-acetabular fractures has been reported in patients with high-energy trauma. Its use in fragility fractures of the pelvis is expanding and its results are promising.

METHODS

We report a series of 17 consecutive patients with fragility fractures of the pelvis treated with 3D-guided navigation percutaneous screw fixation from 2016 to 2017. Percutaneous screw trajectories were planned preoperatively for the majority of patients. Closed reduction was performed prior to fixation in grossly displaced fractures.

RESULTS

The mean time to surgery was 8.6 ± 2.4 days, and the mean intraoperative blood loss was 94.1 ± 26.6 mL. One early surgical complication occurred involving an infected pelvic external fixator iliac pin track site, and there were no cases of neurological deficits after fixation. In total, 7 of the 14 patients had screw backout, and the mean backout distance was 8.3 ± 4.4 mm. Cortical perforation was seen in one patient involving an anterior column screw by 5.7 mm; 14 patients were followed up for a mean of 18.7 ± 2.8 months; 13 patients achieved complete fracture union, and 1 patient had a fracture non-union. Premorbid ambulatory function was restored in 8 of the 14 patients. The mean visual analogue scale for pain severity at follow-up was 0.36 ± 0.50. There were no cases of 30-day and 1-year mortality.

CONCLUSION

3D-guided navigation percutaneous screw fixation is a safe, precise, and effective surgical technique for managing fragility fractures of the pelvis.

Minimally invasive surgical treatment of minimally displaced acetabular fractures does not improve pain, mobility or quality of life compared to conservative treatment: a matched-pair analysis of 50 patients

Background

Currently available procedures for the treatment of minimally displaced acetabular fractures include conservative treatment and minimally invasive percutaneous screw fixation. Screw fixation of acetabular fractures allows patients’ early full-weight bearing due to improved biomechanic stability. Can the range of motion, pain and mobility and quality of life in patients with acetabular fractures be improved by minimally invasive screw fixation, compared to conservative treatment in the long term?

Methods

Patients treated for a minimally displaced acetabular fracture, either conservatively or by closed reduction percutaneous screw fixation, in the period from 2001 to 2013 were included in this retrospective study. Minimal displacement was considered to be less than 5 mm. As well as the collection and analysis of baseline data, Harris Hip Score, Merle d’Aubigné score and Short Form 12 (SF-12) questionnaire data were recorded in the context of a clinical study. To better account for confounding factors, patients of each group were matched. The matched-pair criteria included age, BMI, Letournel fracture classification and the presence of associated injuries.

Results

Twenty-five patients from each group were matched. On the Harris Hip Score, conservatively treated patients obtained 96 points (52–100, SD 17) vs. 89 points (45–100, SD 17, p = 0.624). On the Merle d’Aubigné score, conservatively treated patients obtained 17 points (10–18, SD 2) vs. 17 points (11–18, SD 2, p = 0.342).

Patients with acetabular fractures treated by minimally invasive screw fixation did not result in improved quality of life, measured by SF-12 questionnaire, compared to conservatively treated patients (PCS 47, SD 9 vs. 44, SD 10; p = 0.294 and MCS 51, SD 7 vs. 53, SD 7; p = 0.795).

Conclusions

The clinical results of the two groups revealed no statistically significant differences. From the data, it cannot be deduced that minimally invasive surgical therapy is superior to conservative treatment of minimally displaced acetabular fractures. Prospective randomised studies are recommended to allow reliable evaluation of both treatment options.

Trial registration

Retrospectively registered

Technical Considerations and Fluoroscopy in Percutaneous Fixation of the Pelvis and Acetabulum

Surgical treatment of the pelvic ring and acetabulum continues to evolve. Improved imaging technology and means for closed reduction have meant that percutaneous techniques have gained popularity in the treatment of the pelvic ring and, more recently, in the acetabulum. Potential benefits include decreased soft-tissue dissection, blood loss, and surgical time. However, these are technically demanding procedures that require substantial expertise from both the surgeon and the radiographer. This article details the necessary fluoroscopic views and general methods used in percutaneous techniques around the pelvis and acetabulum. Despite most studies reporting good-to-excellent clinical and radiographic results, further work is needed to facilitate standardization and optimization of these outcomes.

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.

Ultrasound imaging and segmentation of bone surfaces: A review

Due to its real-time, non-radiation based three-dimensional (3D) imaging capabilities, ultrasound (US) has been incorporated into various orthopedic procedures. However, imaging artifacts, low signal-to-noise ratio (SNR) and bone boundaries appearing several mm in thickness make the analysis of US data difficult. This paper provides a review about the state-of-the-art bone segmentation and enhancement methods developed for two-dimensional (2D) and 3D US data. First, an overview for the appearance of bone surface response in B-mode data is presented. Then, classification of the proposed techniques in terms of the image information being used is provided. Specifically, the focus is given on segmentation and enhancement of B-mode US data. The review is concluded by discussing future directions of research and additional challenges which need to be overcome in order to make this imaging modality more successful in orthopedics.

Accurate fixation of plates and screws for the treatment of acetabular fractures using 3D-printed guiding templates: An experimental study

OBJECTIVE

To investigate the feasibility of the use of 3D-printed guiding templates for accurate placement of plates and screws for internal fixation of acetabular fractures.

METHODS

3D models of the pelvises of 14 adult cadavers were reconstructed using computed tomography (CT). Twenty-eight acetabular fractures were simulated and placement positions for plates and screw trajectories were designed. Bending module was obtained by 3D cutting; guiding template was manufactured using 3D printing, and the plate was pre-bent according to the bending module. Plates and screws were placed in cadaveric pelvises using the guiding template, and 3D model was reconstructed using CT. The designed and real trajectories were matched using 3D registration including the coordinates (entry and exit points) of designed trajectory. The number of qualified points with different accuracy levels was compared using Chi-squared test.

RESULTS

Sixty-four plates and 339 screws were placed with no cortical breach. The absolute difference of the X, Y, and Z coordinates between the designed and real entry points were 0.52±0.45, 0.43±0.36, and 0.53±0.44mm, respectively. The corresponding values for the exit points were 0.83±0.67, 1.22±0.87, and 1.26±0.83mm, respectively. With an accuracy degree ≥1.9mm for the entry points and ≥3.8mm for the exit points, there was no significant difference between the designed and the real trajectories.

CONCLUSION

The 3D-printed guiding template helped achieve accurate placement of plates and screws in the pelvis of adult cadavers.

[Percutaneous internal fixation of pelvic fractures. German version]

BACKGROUND

Percutaneous internal fixation of pelvic fractures is increasing in popularity with multiple new techniques reported.

OBJECTIVES

The purpose of this article is to outline the imaging, indication, planning, equipment, surgical technique and complications of these methods.

METHODS

A review of the literature is provided and the techniques for anterior and posterior pelvic stabilization are discussed.

RESULTS

High-quality preoperative CT scans are essential in planning for this technique. The anterior internal fixator ("InFix") is an effective method for stabilizing the anterior ring and should be usually used in conjunction with posterior fixation. Good technique avoids neurovascular injury, which can be a devastating complication. The retrograde anterior column screw (RACS) is a technique that can be used in most patients, although in smaller patients smaller screw diameters may be needed. The entry point for the screw is more lateral in women than men. Iliosacral screws (ISS) are an effective method of posterior stabilization and can be placed using 2D or 3D fluoroscopy, computer navigation or CT navigation.

CONCLUSION

Percutaneous fixation of pelvic fractures requires high-quality imaging and can be aided by computer navigation. Safe techniques are reproducible; however, not all patients and fracture patterns can be treated using these techniques.

Insertion of psoas minor tendon at pelvic brim, a novel anatomic landmark for extra-articular, screw placement through Stoppa approach

BACKGROUND

The psoas minor partially inserted to the superior pelvic brim. And the plate used to fix the acetabular fracture has always been positioned at the pelvic brim after reduction through the Stoppa approach. However, there are few studies depicting the clinical significance of the psoas minor. The purpose of this paper was to explore the relationship between the insertion of the psoas minor tendon at the pelvic brim (IPMTPB) and screw placement through the Stoppa approach.

MATERIALS AND METHODS

Fifteen cadavers were dissected for adequate exposure to IPMTPB in our study. However, not all specimens had a psoas minor. For the specimens with IPMTPB, the posterior and anterior edges were used as the first and second entry points, dividing the area from the sacroiliac joint to the pubic symphysis into three zones (d1, d2 and d3). The average proportion of each zone was obtained after measurement the three zones, to locate the two entry points for the specimens without a psoas minor. From the longitudinal Stoppa incision, the first wire was inserted horizontally, and the second wire was placed vertical to the bone surface. Fluoroscopy and computed tomography (CT) were conducted to examine the relationship between the wires and the acetabulum.

RESULTS

There was a psoas minor in sixteen hemipelvises (53.33%). After measurement and calculation, we determined that the average proportions of zones d1, d2, and d3 were 28.03%, 29.14%, and 42.83%, respectively. For all specimens, the wires were successfully inserted, and the trajectories of the wires were outside the hip joint cavity.

CONCLUSIONS

IPMTPB could be used as an anatomic landmark of safe zones for screw placement through the Stoppa approach. For cases without a psoas minor, the zones for extra-articular screw placement could be determined through the measurements in this paper.

How to obtain and identify the acetabular anterior column axial view projection in patients?

PURPOSE

This study aims at sharing our experience as how to obtain and identify axial view image of the acetabular anterior column in patients.

METHODS

Pelvic computed tomography data of six normal adults were used to reconstruct three-dimensional (3D) models. The transparency of each 3D model was downgraded at the view perpendicular to the cross section of the anterior column axis to simulate the anterior column axial view image. Fluoroscopy was performed in all patients to obtain the anterior column axial view image in the operating room. Each fluoroscopic image was compared with the corresponding simulation image to analyze potential anatomic landmarks that were helpful to identify the translucent area (projection of the screw path) in the patients.

RESULTS AND CONCLUSIONS

To obtain ideal anterior column axial fluoroscopic image, the patient should be positioned supine with the leg of "abnormal side" straight and contralateral side flexion, abduction, and external rotation; the C-arm machine should be placed at the caudal end of the operation table with the C-arm fluoroscopic intensifier first positioned at the pelvic lateral view and then tilted approximately 30° toward the "abnormal side" and rotated approximately 45° toward the caudal end of the operation table. To identify the translucent area on the anterior column axial view fluoroscopic image obtained from the patient, the greater sciatic notch, the true pelvis edge, and the acetabulum should be identified first and the translucent area is located in the area surrounded by these three anatomic landmarks.

Gun barrel view of the anterior pelvic ring for percutaneous anterior column or superior pubic ramus screw placement

BACKGROUND

Traditionally, operative fixation of pelvic and acetabular injuries involves complex approaches and significant complications. Accelerated rehabilitation, decreased soft tissue stripping and decreased wound complications are several benefits driving a recent interest in percutaneous fixation. We describe a new fluoroscopic view to guide the placement of screws within the anterior pelvic ring.

METHODS

Twenty retrograde anterior pelvic ring screws were percutaneously placed in ten cadaveric specimens. Arranging a standard C-arm in a position similar to obtaining a lateral hip image, with angles of 54° ± 2° beam to body, 75° ± 5° of reverse cantilever and 14° ± 6° of outlet, a gun barrel view of the anterior pelvic ring is identified. Fluoroscopic images were taken, and the hemipelvi were harvested to examine the dimensions of the anterior pelvic ring and inspected for any cortical or articular perforation.

RESULTS

The minimum cranial-to-caudal distance in the anterior pelvic ring was 9 mm (range 6.5-12 mm), and the minimum anterior-to-posterior dimension was 9 mm (range 5-15 mm). All but 2 screws were completely confined within the osseous corridors. Identifiable on final fluoroscopic evaluation, one screw perforated the psoas groove and a second perforated the acetabular dome. Overall, 90 % of our screws were accurately and safely placed, upon the first attempt, within the anterior pelvic ring using the described gun barrel view.

CONCLUSION

Employing either open reduction, or following a closed or percutaneous reduction, the anterior pelvic ring gun barrel view can reproducibly guide safe placement of anterior pelvic ring screw fixation.

LEVEL OF EVIDENCE

IV.

A radiographic simulation study of fixed superior pubic ramus fractures with retrograde screw insertion

OBJECTIVES

The study's aim is to calculate the parameters for retrograde insertion points for fixed superior pubic ramus fractures.

METHODS

From the pubic symphysis, diameter and length of the screw were measured, as well as the angle between the screw axis and the 3 planes.

RESULTS

When the diameter was fixed at 4.5 mm, the maximum lengths were 125 mm and 119 mm.

CONCLUSIONS

When the fracture occurs in Zone I, the penetration point could be selected in the pubic symphysis pubis angle to ensure that medial fracture fragments have sufficient screw channel length.

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.

An Effective and Feasible Method, "Hammering Technique," for Percutaneous Fixation of Anterior Column Acetabular Fracture

Objective. The objective of this study was to evaluate the effectiveness and advantages of percutaneous fixation of anterior column acetabular fracture with “hammering technique.” Materials and Methods. We retrospectively reviewed 16 patients with percutaneous fixation of anterior column acetabular fracture with “hammering technique.” There were 11 males and 5 females with an average age of 38.88 years (range: 24–54 years) in our study. Our study included 7 nondisplaced fractures, 6 mild displaced fractures (<2 mm), and 5 displaced fractures (>2 mm). The mean time from injury to surgery was 4.5 days (range: 2–7 days). Results. The average of operation time was 27.56 minutes (range: 15–45 minutes), and the mean blood loss was 55.28 mL (range: 15–100 mL). The mean fluoroscopic time was 54.78 seconds (range: 40–77 seconds). The first pass of the guide wire was acceptable without cortical perforation or intra-articular perforation in 88.89% (16/18) of the procedures, and the second attempt was in 11.11% (2/18). Conclusion. Our study suggested that percutaneous fixation of anterior column acetabular fracture with “hammering technique” acquired satisfying surgical and clinical outcomes. It may be an alternative satisfying treatment for percutaneous fixation of anterior column acetabular fracture by 2D fluoroscopy using a C-arm with less fluoroscopic time.

Prospective Assessment of the Oncogenic Risk to Patients From Fluoroscopy During Trauma Surgery

OBJECTIVE

Concern about radiation exposure during surgery has focused on surgeon exposure. However, the patient receives exposure that is more direct and, in surgery about the pelvis and hip, internal pelvic nonskeletal organs often cannot be shielded without obscuring the region of surgical interest. The purpose of this study was to prospectively evaluate patients' radiation exposure during fracture surgery of the acetabulum, pelvic ring, and femur to calculate future cancer incidence (CI).

DESIGN

Prospective descriptive cohort.

SETTING

Level-1 trauma center.

PATIENTS/PARTICIPANTS

One hundred eight patients with acetabulum, pelvic, or femur fractures requiring operative repair were prospectively enrolled.

INTERVENTION

Dosimeters were placed in locations determined for each surgery type by a medical physicist.

MAIN OUTCOME MEASUREMENTS

Demographics, operative records, and average x-ray emission energy were recorded. Effective dose, specific organ doses, and lifetime CI for a 30-year-old patient were calculated.

RESULTS

Diagnoses included 27 acetabular fractures, 30 intertrochanteric femur fractures, 26 femoral shafts, and 25 pelvic ring injuries. Patients with pelvic ring injuries received the highest effective dose at 0.91 ± 0.74 mSv. The average lifetime increase in CI, for any cancer type, after pelvic ring fixation is 0.0097% for females and 0.0062% for males. The greatest mean single-organ dose to the ovaries (3.82 ± 3.34 mGy) occurred during pelvic ring surgery, correlating to an increased ovarian cancer risk of 0.0013%. The greatest mean single-organ dose to the prostate (6.81 ± 5.91 mSv) also occurred during pelvic surgery, correlating to increased prostate cancer risk of 0.0024%.

CONCLUSIONS

Fracture surgery to the pelvis and femur is exceptionally fluoroscopy-dependent; however, the radiation exposure incurred represents a relatively small increased risk of future cancer development in patients.

LEVEL OF EVIDENCE

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

Electromagnetic Real Time Navigation in the Region of the Posterior Pelvic Ring: An Experimental In-Vitro Feasibility Study and Comparison of Image Guided Techniques

Background

Electromagnetic tracking is a relatively new technique that allows real time navigation in the absence of radiation. The aim of this study was to prove the feasibility of this technique for the treatment of posterior pelvic ring fractures and to compare the results with established image guided procedures.

Methods

Tests were performed in pelvic specimens (Sawbones^®) with standardized sacral fractures (Type Denis I or II). A gel matrix simulated the operative approach and a cover was used to disable visual control. The electromagnetic setup was performed by using a custom made carbon reference plate and a prototype stainless steel K-wire with an integrated sensor coil. Four different test series were performed: Group OCT: Optical navigation using preoperative CT-scans; group O3D: Optical navigation using intraoperative 3-D-fluoroscopy; group Fluoro: Conventional 2-D-fluoroscopy; group EMT: Electromagnetic navigation combined with a preoperative Dyna-CT. Accuracy of screw placement was analyzed by standardized postoperative CT-scan for each specimen. Operation time and intraoperative radiation exposure for the surgeon was documented. All data was analyzed using SPSS (Version 20, 76 Chicago, IL, USA). Statistical significance was defined as p< 0.05.

Results

160 iliosacral screws were placed (40 per group). EMT resulted in a significantly higher incidence of optimal screw placement (EMT: 36/40) compared to the groups Fluoro (30/40; p< 0.05) and OCT (31/40; p< 0.05). Results between EMT and O3D were comparable (O3D: 37/40; n.s.). Also, the operation time was comparable between groups EMT and O3D (EMT 7.62 min vs. O3D 7.98 min; n.s.), while the surgical time was significantly shorter compared to the Fluoro group (10.69 min; p< 0.001) and the OCT group (13.3 min; p< 0.001).

Conclusion

Electromagnetic guided iliosacral screw placement is a feasible procedure. In our experimental setup, this method was associated with improved accuracy of screw placement and shorter operation time when compared with the conventional fluoroscopy guided technique and compared to the optical navigation using preoperative CT-scans. Further studies are necessary to rule out drawbacks of this technique regarding ferromagnetic objects.

Comparison of Isocentric C-Arm 3-Dimensional Navigation and Conventional Fluoroscopy for Percutaneous Retrograde Screwing for Anterior Column Fracture of Acetabulum: An Observational Study

Percutaneous screw insertion for minimally displaced or reducible acetabular fracture using x-ray fluoroscopy and computer-assisted navigation system has been advocated by some authors. The purpose of this study was to compare intraoperative conditions and clinical results between isocentric C-arm 3-dimensional (Iso-C 3D) fluoroscopy and conventional fluoroscopy for percutaneous retrograde screwing of acetabular anterior column fracture.A prospective cohort study was conducted. A total of 22 patients were assigned to 2 different groups: 10 patients in the Iso-C 3D navigation group and 12 patients in the conventional group. The operative time, fluoroscopic time, time of screw insertion, blood loss, and accuracy were analyzed between the 2 groups.There were significant differences in operative time, screw insertion time, fluoroscopy time, and mean blood loss between the 2 groups. Totally 2 of 12 (16.7%) screws were misplaced in the conventional fluoroscopy group, and all 10 screws were in safe zones in the navigation group. Percutaneous screw fixation using the Iso-C 3D computer-assisted navigation system significantly reduced the intraoperative fluoroscopy time and blood loss in percutaneous screwing for acetabular anterior column fracture.The Iso-C 3D computer-assisted navigation system provided a reliable and effective method for percutaneous screw insertion in acetabular anterior column fractures compared to conventional fluoroscopy.

Minimally invasive surgery under fluoro-navigation for anterior pelvic ring fractures

BACKGROUND

The incidence of pelvic fractures in trauma patients is reported to be 3-8.2%, with roughly half of these fractures being caused by high energy injuries with a potential for catastrophic hemorrhage and death. Indications for internal fixation of anterior pelvic ring are controversial. Because of fears of disturbing the pelvic hematoma and causing additional hemorrhage, open reduction and internal fixation of pelvic ring disruption is routinely delayed. In contrast to conventional surgery, percutaneous screw fixation is gaining popularity in the treatment of pelvic and acetabular fractures mainly because of minimal soft tissue damage, less operative blood loss, early surgical intervention and comfortable mobilization of the patient. Fluoro-navigation is a new surgical technique in orthopedic trauma surgery. This study is to investigate clinical results of fluoro-navigation surgery in anterior pelvic ring fractures.

MATERIALS AND METHODS

From January 2006 to October 2011, 23 patients with anterior pelvic ring fractures were treated with percutaneous cannulated screw under fluoro-navigation. There were 14 men and 9 women, with a mean age of 40.1 years (range 25-55). According to the AO and Orthopedic Trauma Association classification, there were seven A 2.1, two A 2.2, one A 2.3, six B 1.2, one B 2.1: 1, one B 2.2, one C 1.2, two C 1.3 and two C 2.3 types of fractures. Amongst these patients, 13 had posterior pelvic ring injuries, 8 had other injuries including urethral, lumbar vertebrae fractures and femoral fractures. All patients were operated when their general condition stabilized after emergency management. The mean time from injury to percutaneous screw fixation of the anterior pelvic ring fracture was 12 days (3-15 days). All the anterior ring fractures were fixed with cannulated screws by two senior surgeons. They were familiar with the navigation system and had gained much experience in the computer-assisted percutaneous placement of screws.

RESULTS

A total of 32 screws were inserted, including 19 in the pubic ramis and 13 in the anterior acetabular columns. The average surgical time was 23.3 min/screw. The average time of X-ray exposure was 19.1 ± 2.5 s/screw. The virtual images of fluoro-navigation were compared with real-time X-rays during and after the surgery. Compared to the final position of the screw, the average deviated distance was 3.11 mm and the average trajectory difference was 2.81°. Blood loss during the operation was minimal (22.3 ml/screw). One screw (3.1%) deviated out of the fracture site during the operation. No superficial or deep infection occurred. No patient sustained recognized neurologic, vascular, or urologic injury as a result of the percutaneous screw fixation. All fractures united at the last followup.

CONCLUSIONS

Fluoro-navigation technique could become a safe, accurate, and fairly quick method for the treatment of anterior pelvic ring fractures. Standardization of the operative procedure and training are mandatory for the success of this procedure.

Monitoring reduced scattering coefficient in pedicle screw insertion trajectory using near-infrared spectroscopy

Pedicle screw (PS) implantation is an ideal treatment for severe multilevel vertebra instabilities. The accuracy of fixating PS is a key factor of spinal surgery. We developed a near-infrared spectroscopy device with a needlelike optical fiber probe to monitor optical parameters (reduced scattering coefficient) of vertebra models in real time. The fresh-frozen cadaver, cats and porcine vertebras were first studied in the experiments. Moreover, the reduced scattering coefficient (μ' s) along the different trajectories of PS insertion was obtained. In the fresh-frozen cadavera experiment, μ' s values could be used to distinguish the different compositions of the thoracic vertebra. In cat vertebra experiment, μ' s values of vertebrae bones, including cortical bone (15.30 ± 0.18 cm(-1)), cancellous bone (7.84 ± 1.11 cm(-1)) and spinal cord (19.46 ± 0.21 cm(-1)), were different in vivo. In the pig vertebrae experiment, there were obvious differences between the normal and abnormal PS puncture curves based on μ' s values. Thus, μ' s values measured by using the proposed device could be used as the pattern factor in spinal fusion surgery. Our studies demonstrate that near-infrared spectroscopy method may be potentially used for assisting the PS insertion.

A novel electromagnetic navigation tool for acetabular surgery

BACKGROUND

Acetabular fracture surgery is demanding and screw placement along narrow bony corridors remains challenging. It necessitates x-ray radiation for fluoroscopically assisted screw insertion. The purpose of this cadaver study was to evaluate the feasibility, accuracy and operation time of a novel electromagnetic navigation system for screw insertion along predefined acetabular corridors.

METHODS

A controlled laboratory study with a total of 24 electromagnetically navigated screw insertions was performed on 8 cadaveric acetabula. 3 peri-acetabular bony corridors (QSS, Quadrilateral Surface Screw; IAS, Infra-Acetabular Screw; PCS, Posterior Column Screw) were defined and screws were placed in a defined order without fluoroscopy. Operation time was documented. Postoperative CT scans were performed to analyse accuracy of screw placement.

RESULTS

Mean cadaver age was 70.4 ± 11.7. Successful screw placement was accomplished in 22 out of 24 (91.7%) cases. The overall mean time for all 3 acetabular screws was 576.6 ± 75.9s. All 3 complications occurred during the placement of the IAS due to an impassable narrow bony corridor. QSS mean length was 50 ± 5mm, IAS mean length was 85 ± 10mm and PCS mean length was 120 ± 5mm.

CONCLUSION

In this cadaver study the novel electromagnetic navigation system was feasible to allow accurate screw placement without fluoroscopy in defined narrow peri-acetabular bony corridors.

Virtual mapping of 260 three-dimensional hemipelvises to analyse gender-specific differences in minimally invasive retrograde lag screw placement in the posterior acetabular column using the anterior pelvic and midsagittal plane as reference

BACKGROUND

Due to complex pelvic geometry, percutaneous screw placement in the posterior acetabular column can pose a major challenge even for experienced surgeons.

METHODS

The present study examined the preformed bone stock of the posterior acetabular column in 260 hemipelvises. Retrograde posterior column screws were virtually implanted using iPlan CMF (BrainLAB AG, Feldkirchen, Germany); maximal implant length, maximal implant diameter and angles between the screw trajectories and the reference planes anterior pelvic plane as well as the midsagittal plane were assessed for gender-specific differences.

RESULTS

The virtual analysis of the preformed bone stock column showed two constrictions of crucial clinical importance. These were located 49.6 ± 3.4 (41.0-60.2) mm (inferior margin of acetabulum) and 77.0 ± 5.6 (66.5-95.3) mm (centre of acetabulum) from the entry point of the implant in men and respectively 43.7 ± 2.3 (38.3-49.3) mm as well as 71.2 ± 3.5 (63.5-79.99) mm in women (men vs. women: p < 0.001). The entry point of the retrograde posterior column screw was located dorsal from the transition of the lower margin of the ischial tuberosity to ramus inferior pointing to the medial margin of the ischial tuberosity. In female patients, the entry point was located significantly closer to the medial margin of the ischial tuberosity. However, 7.3 mm screws can generally be used in men and women. The angle between the screw trajectory and the anterior pelvic plane in sagittal section was 14.0 ± 4.9 (2.5-28.6) °, the angle between the screw trajectory and the midsagittal plane in axial section was 31.1 ± 12.8 (1.5-77.9) ° and the angle between the screw trajectory and the midsagittal plane in coronal section was 8.4 ± 3.8 (1.5-20.0) °. For all angles, significant gender-specific differences were found (p < 0.001).

CONCLUSION

Therefore, the anterior pelvic plane as well as the midsagittal plane can facilitate intraoperative orientation for retrograde posterior column screw placement considering gender-specific differences in preformed bone corridor, implant length as well as angles formed between screw trajectory and these reference planes.

The "Down the PC" view - A new tool to assess screw positioning in the posterior column of the acetabulum

INTRODUCTION

Minimal-invasive placement of screws into the posterior column of the acetabulum (PC) is challenging. Due to the saddle-shaped curvature of the medial cortical border of the PC, the standard fluoroscopic views of the pelvis cannot provide the desired safety during screw insertion. The aim of this study was to define a view tangentially to the medial cortex of the PC and to evaluate its accuracy and inter-observer reproducibility.

METHODS

Radio-dense markers on the medial cortex of the PC along the axis of a PC screw were brought in line and landmarks of the new "Down the PC" view were determined. Kirschner wires were placed into the PC of a pelvis composite model and five pelvic cadaver specimens in a total of 34 different correct and incorrect positions. Based on either only the "Down the PC" view, only the standard views, or a combination of both, three fellowship-trained orthopaedic surgeons had to decide if the inserted wires were in bone in the posterior column or had exited cortex, and if they penetrated the acetabulum. Sensitivity, specificity, and the intra-class correlation coefficient were calculated.

RESULTS

A view using three radiographic landmarks (pelvic brim, medial cortical wall of the body of the ischium, ischial spine) was found. Sensitivity and specificity to detect perforation out of the bone were 1.00 and 0.97 for the "Down the PC" view, 0.46 and 0.97 if only the standard views were used, and 1.00 and 0.95 for a combination of both. Sensitivity and specificity to detect intra-articular wire placement were 1.00 and 0.96 for the "Down the PC" view, 0.72 and 0.95 if only the standard views were used, and 0.94 and 0.99 for a combination of both. Inter-observer agreement using only the "Down the PC" view was excellent with an ICC of 0.92 for perforation and ICC of 0.82 for intra-articular wire placement.

CONCLUSIONS

The "Down the PC" view is a useful addendum in the orthopaedic trauma surgeon's tool box. Using simple landmarks, it is easily to reproduce and thereby shows excellent accuracy and inter-observer agreement in order to detect medial perforation or intra-articular implant position.

A novel navigation template for fixation of acetabular posterior column fractures with antegrade lag screws: design and application

PURPOSE

To test whether a novel guide template we designed can facilitate accurate insertion of antegrade lag screws in the fixation of acetabular posterior column fractures.

METHODS

We created virtual three-dimensional reconstruction models of the pelvis from CT scan data obtained from 96 adult patients without any bony problems. A virtual cylindrical implant was placed along the longitudinal axis of the acetabular posterior column passing through the ischial tuberosity. The diameter of cylindrical implant was augmented to 6.5 mm, and the direction was adjusted until the optimal screw path was found using the reverse engineering technique. The orifice of this cylinder from the iliac fossa was determined as the entry point for the antegrade lag screw. The anatomical parameters of the screw entry path were measured and saved in .stl format. The guide template was designed according to the acetabular morphology and the measured anatomical parameters before it was put into manufacture of a solid template with the rapid prototyping technique. The feasibility and accuracy of the guide template were tested in cadaveric pelvises. Finally, the guide template was used in real surgery for five patients. Furthermore, the time required for surgery was recorded.

RESULTS

Under the guide of this navigation template, antegrade lag screws were successfully placed in the posterior column of the acetabulum in the cadaveric test. And five lag screws were successfully placed in five patients. The mean time of antegrade lag screw insertion required 5.8 (3-10) min.

CONCLUSIONS

Antegrade lag screws can be more accurately put into the posterior column of the acetabulum with the help of this navigation template.

Axial view of acetabular anterior column: a new X-ray projection of percutaneous screw placement

INTRODUCTION

To search for a new radiographic view/projection of the acetabular anterior column to provide a safe guide for percutaneous screw placement for acetabular fractures.

MATERIALS AND METHODS

Eight pelvic specimens taken from normal adult cadavers were positioned in a supine position on the operating table. First, the ipsilateral ilium-oblique view of the observed side was obtained on C-arm fluoroscopy by tilting the C-arm approximately 35° toward the contralateral hip joint. Then, the tilting angle of the C-arm was changed gradually until an oval track image (acetabular anterior column axial view) appeared. The oval shadow was clear only in one position as the angle of the C-arm was changed toward the caudal side of the operating table. A guide pin was put on the skin of the cadaver, and the location and tilting direction of the guide pin were adjusted under C-arm fluoroscopy until the pin's shadow became a point in the center of the oval track. Then, the guide pin was inserted into the bone using a battery-powered drill. The degree of inclination of the guide pin in the cadaver in the frontal and sagittal planes was measured using computed tomography (CT).

RESULTS

Axial views of the anterior column were found successfully in all of the pelvic specimens, and the guide pins were inserted accurately into the acetabular anterior column under C-arm fluoroscopic guidance. On the CT-reconstructed image, the average degree of angle between the guide pin and the sagittal plane was 33.6° (range 29.6°-36.5°). The average angle between the guide pin and the transverse plane was 59.1° (range 56.4°-63.2°).

CONCLUSION

This axial view of the acetabular anterior column is a novel X-ray projection which provides an optimal method for guiding percutaneous insertion of anterior column screws for acetabular fractures.

Three-dimensional fluoroscopy-navigated percutaneous screw fixation of acetabular fractures

OBJECTIVE

Anatomic reduction and articular restoration after acetabular fractures occur (Ac-Fxs) are accepted predictors for good function and slow progression of posttraumatic osteoarthritis of the hip. The aim of this study was to retrospectively analyze Ac-Fxs, which were treated with closed reduction and percutaneous (three-dimensional) fluoroscopy-based navigated screw fixation.

DESIGN

Level 4, retrospective clinical and radiographic assessment.

SETTING

Level 1 trauma center.

PATIENTS

Twelve patients (male/female: 9/3; mean age: 60 years; range: 16-80 years) with moderately displaced Ac-Fxs were included.

INTERVENTION

In enrolled patients, the treatment involved percutaneous three-dimensional fluoroscopy-based navigated lag screw positioning. Closed reduction was achieved by lag screws, or reduction was aided by the insertion of percutaneous Schanz pins.

MAIN OUTCOME MEASUREMENTS

The quality of the reduction and screw positions were assessed using intraoperative and postoperative computed tomography scans. Functional outcome was assessed using the Harris hip score, the visual analog scale for pain, and the Tegener activity scale.

RESULTS

A total of 22 periacetabular screws were placed (mean: 1.8 ± 1.1 screws/patient, range: 1-5). The mean follow-up was done for 30 (16-72) months. The postoperative reduction was anatomical in all patients, and the mean fracture displacement was significantly reduced (gap: 4.1 ± 1.8 mm to 0.4 ± 0.7 mm/step: 1.4 ± 0.6 mm to 0.2 ± 0.4 mm). No secondary dislocations or malunions/nonunions were found. All screws correctly addressed the fracture morphology and corresponded to preoperative planning. The Harris hip score, the visual analog scale (motion), and Tegener activity scale showed excellent to very good results (92.4 ± 6.8, 1.9 ± 1.3, and 3.8 ± 1.6, respectively).

CONCLUSIONS

The navigated, percutaneous screw fixation of selected Ac-Fxs is a promising method that allows for closed reduction and fixation while obtaining a very good radiographic and functional outcome.

LEVEL OF EVIDENCE

Therapeutic level 4.

Determination of detection depth of optical probe in pedicle screw measurement device

BACKGROUND

There is a high probability of accidental perforation of the vertebral pedicle wall in pedicle screw insertion surgery. A pedicle screw (PS) measurement device with an optical probe has been reported to send out a warning signal before the PS tip breaking the vertebral pedicle wall.

METHODS

In this study, we explored the detection depth of optical probe in this measurement device, which was closely related to the effective alarm distance. In the boundary, the vertebrae tissues could be treated as 2-layer models including spongy bones and compact bones. The Monte Carlo simulation and phantom models were performed to analyse and define the detection depth. Then the porcine vertebrae models were performed to obtain optical spectrum and reduced scattering coefficient, based on which the detection depths were deduced. Moreover, a comparison was made to explore the most significant pattern factor from the experiment results.

RESULTS

According to the pattern factor, an alarm threshold was successfully deduced to define the alarm distance during pedicle screw monitoring.

CONCLUSIONS

Thus, the proposed alarm standard based on detection depth provides a potential for guiding pedicle screw in surgery.

Retrograde lag screw placement in anterior acetabular column with regard to the anterior pelvic plane and midsagittal plane -- virtual mapping of 260 three-dimensional hemipelvises for quantitative anatomic analysis

Percutaneous screw placement can be used for minimally invasive treatment of none or minimally displaced fractures of the anterior column. The complex pelvic geometry can pose a major challenge even for experienced surgeons. The present study examined the preformed bone stock of the anterior column in 260 hemipelvises (130 male and 130 female). Screws were virtually implanted using iPlan(®) CMF (BrainLAB AG, Feldkirchen, Germany); the maximal implant length and the maximal implant diameter were assessed. The study showed, that 6.5mm can generally be used in men; in women however individual planning is essential in regard to the maximal implant diameter since we found that in 15.4% of women, screws with a diameter less than 6.5mm were necessary. The virtual analysis of the preformed bone stock corridor of the anterior column showed two constrictions of crucial clinical importance. These can be found after 18% and 55% (men) respectively 16% and 55% (women) measured from the entry point along the axis of the implant. The entry point of the retrograde anterior column screw in our collective was located lateral of tuberculum pubicum at the level of the superior-medial margin of foramen obturatum. In female patients, the entry point was located significantly more lateral of symphysis and closer to the cranial margin of ramus superior ossis pubis. The mean angle between the screw trajectory and the anterior pelvic plane in sagittal section was 31.6 ± 5.5°, the mean angle between the screw trajectory and the midsagittal plane in axial section was 55.9 ± 4.6° and the mean angle between the screw trajectory and the midsagittal plane in coronal section was 42.1 ± 3.9° with no significant deviation between both sexes. The individual angles formed by the screw trajectory and the anterior pelvic and midsagittal plane are independent from anthropometric parameters sex, age, body length and weight. Therefore, they can be used for orientation in lag screw placement keeping in mind that the entry point differs in both sexes.

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.

Percutaneous screw placement in acetabular posterior column surgery: gender differences in implant positioning

Percutaneous reduction and periarticular screw implantation techniques have been successfully introduced in acetabular surgery. Image guided navigation techniques might be beneficial in increasing accuracy. However, a thorough understanding of standard values is needed to oversee pitfalls. This cadaver study was designed to identify reliable angulation values for screw implantation in the posterior acetabular column and to provide knowledge of the bony thickness for the periarticular corridor. Gender differences were specifically addressed. 27 embalmed cadaveric hemipelvic specimens (13 male, 14 female) were used. After soft-tissue removal posterior column acetabular screw placement was conducted by one experienced orthopaedic trauma surgeon under visibility. Radiographic verification of ideal screw placement was followed by radiographic assessment in three standard views and angulation values were assessed. Through bony dissection the maximal periarticular canal width was assessed. Various angulation values with regard to anatomical landmarks could be determined in the anteroposterior radiograph, as well as in the iliac oblique and the obturator oblique view. Gender differences were significant for all reference points with the pubic rami involved. The minimal canal width was 1.1cm in female and 1.6 cm in male specimen. The findings provide standard values for safe passages in percutaneous posterior column acetabular surgery. Gender differences have to be taken in consideration when planning the drill corridor. By adherence to standard values, screw placement can be performed safely.

Percutaneous retrograde posterior column acetabular fixation: is the sciatic nerve safe? A cadaveric study

OBJECTIVES

The purpose of this cadaveric study was to determine the proximity of the neurologic structures to the path of the screw inserted percutaneously into the ischial tuberosity.

DESIGN

Cadaver study.

INTERVENTION

Ten screws were inserted in 10 limbs (5 cadavers) under fluoroscopic guidance. Dissection was then performed to expose the head of the screw and was extended laterally to expose the sciatic nerve, the posterior cutaneous nerve of the thigh, and its inferior cluneal branches.

MAIN OUTCOME MEASURE

The distance from the screw head to the sciatic nerve, posterior cutaneous nerve of the thigh, and the inferior cluneal nerves.

RESULTS

The distance from the center of the screw head to the sciatic nerve averaged 58 mm (range, 40-70 mm). The average distance between the screw head and the posterior cutaneous nerve of the thigh was 42 mm (range, 30-60 mm). The inferior cluneal branches were the closest to the path of the screw with an average distance of 3.5 mm in 6 specimens (range, 1-6 mm) and were injured by the screw in 3 and could not be located in another specimen.

CONCLUSIONS

The sciatic nerve and the posterior cutaneous nerve of the thigh appear to be safe during retrograde percutaneous screw fixation of a posterior column acetabular fracture through a central entry point in the ischial tuberosity. However, the inferior cluneal nerves that are responsible for the cutaneous sensitivity of the lower half of the gluteal region are at risk of injury.