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

An experimental study on the safe placement of sacroiliac screws using a 3D printing navigation module

Background

In this experimental study, we evaluated the use of digital 3D navigation printing in minimizing complications arising from sacroiliac screw misplacement.

Methods

A total of 13 adult pelvic specimens were studied using 3D navigation printing. Mimics software was used for preoperative planning and for obtaining sacrum median sagittal resection and long axis resection of the S1 pedicle center by 3D segmentation. The ideal screw path had its origin at the post-median part of the auricular surface of the sacroiliac joint, the midpoint at the mid-position of the lateral recess and outlet of the anterior sacral foramina; and the endpoint at the S1 sagittal resection. A sacroiliac screw fixed the pelvic specimens with the assistance of the navigation module. The distance between the start point (ilium surface) and endpoint (sacral median sagittal resection) of the screw path was measured after the pre- and postoperative 3D pelvis module was 3D-registered according to the standard precision range. The origin/endpoint qualified rates of the postoperative (n/26) and preoperative (26/26) screw paths were analyzed by the chi-square test.

Results

No screw misplacement occurred in the screw paths of any of the 13 pelvic specimens. The mean distance between the preoperative and postoperative origin of the screw path was 1.5415±0.6806 mm, and the mean distance between the preoperative and postoperative endpoint was 2.2809±0.4855 mm. The qualified rate of origin was 23/26 when the precision grade was 2.4 mm (P>0.05, χ²=1.41), while the qualified rate of endpoint was 21/26 when the precision grade was 2.7 mm (P>0.05, χ²=3.54).

Conclusions

In this experimental study, using a 3D printing navigation module helped attain an accurate and safe sacroiliac screw implantation.

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.

Minimally invasive posterior locked compression plate osteosynthesis shows excellent results in elderly patients with fragility fractures of the pelvis

Purpose

Fragility fractures of the pelvis (FFP) are common in older patients. We evaluated the clinical outcome of using a minimally invasive posterior locked compression plate (MIPLCP) as therapeutic alternative.

Methods

53 Patients with insufficiency fractures of the posterior pelvic ring were treated with MIPLCP when suffering from persistent pain and immobility under conservative treatment.

After initial X-ray, CT-scans of the pelvis were performed. In some cases an MRI was also performed to detect occult fractures. Postoperatively patients underwent conventional X-ray controls. Data were retrospectively analyzed for surgical and radiation time, complication rate, clinical outcome and compared to the literature.

Results

Patients (average age 79.1 years) underwent surgery with operation time of 52.3 min (SD 13.9), intra-operative X-ray time of 9.42 s (SD 9.6), mean dose length product of 70.1 mGycm (SD 57.9) and a mean hospital stay of 21.2 days (SD 7.7).

13% patients (n = 7) showed surgery-related complications, such as wound infection, prolonged wound secretion, irritation of the sacral root or clinically inapparent screw malpositioning. 17% (n = 9) showed postoperative complications (one patient died due to pneumonia 24 days after surgery, eight patients developed urinal tract infections).

42 patients managed to return to previous living situation. 34 were followed-up after a mean period of 31.5 (6–90) months and pain level at post-hospital examination of 2.4 (VAS) with an IOWA Pelvic Score of 85.6 (55–99).

Conclusion

We showed that MIPLCP osteosynthesis is a safe surgical alternative in patients with FFP 3 and FFP 4. This treatment is another way of maintaining a high level of stability in the osteoporotic pelvic ring with a relatively low complication rate, low radiation and moderate operation time and a good functional outcome.

[Minimally invasive stabilization of sacral fractures]

BACKGROUND

Sacral fractures can be of traumatic origin and can also occur as insufficiency fractures. While the therapeutic target of mechanically stable insufficiency fractures is mainly pain relief, mechanically unstable insufficiency fractures and traumatic sacral fractures following high-energy trauma require biomechanical stabilization. Various surgical strategies are available for this, whereby minimally invasive techniques are now preferred whenever possible.

OBJECTIVE

This article presents the clinical challenges and options for minimally invasive treatment of sacral fractures.

MATERIAL AND METHODS

Selected important study data are discussed and our own treatment approach is presented.

RESULTS

The most important minimally invasive techniques for operative treatment of sacral fractures are presented: sacroiliac screw osteosynthesis, lumbopelvic stabilization and sacroplasty. The selection of the surgical technique should be made on an individual basis. While sacroiliac screw osteosynthesis is the international gold standard, diverse authors have also published minimally invasive techniques for lumbopelvic stabilization. The latter enables a higher mechanical stability. In contrast, sacroplasty should only be used as an alternative treatment in insufficiency fractures. Comparative studies of the described techniques are still missing.

CONCLUSION

All surgical options have their indications. Nevertheless, the biomechanical stability which can be achieved differs widely. Therefore, an exact analysis should be carried out of what is necessary with respect to reduction and retention and what should be achieved when treating sacral fractures.

Iliosacral screwing under navigation control: Technical note

Percutaneous iliosacral screw fixation is an essential osteosynthesis technique for pelvic fractures and requires precise imaging tools to assist correct screw placement. 3D imaging coupled to navigation has significantly improved this technique. Several possibilities exist, depending on the instrument set used, with varying degrees of difficulty and very variable risk of error. The techniques traditionally described use a guide to navigate a drill bit, where a one-degree difference in trajectory can alter screw tip placement by several millimeters. The present article proposes a standardization of the procedure by using navigated pedicular screw instruments that have the advantage of navigating the instrument itself and not a projection. In a series of 90 screws implanted in 62 patients using this technique, only one path had to be repeated in the light of intraoperative control. No improperly positioned screws were found on postoperative control.

Anatomical conditions and patient-specific locked navigation templates for transverse sacroiliac screw placement: a retrospective study

Objective

To analyse the anatomical conditions of transverse sacroiliac screw (TSS) about the S1 and S2 segments in order to develop and validate a locked navigational template for TSS placement.

Methods

A total of 22 patients with sacral fractures were involved in this study from May 2018 to February 2019. Patients were divided into two groups according to the surgery procedure: locked template group and conventional group. The CT data of 90 normal sacra were analysed. The long axis, short axis and lengths of TSS, cancellous corridors were measured through 3D modelling. A patient-specific locked navigation template based on simulated screws was designed and 3D printed and then used to assist in TSS placement. The operative time and radiation times were recorded. The Matta criteria and grading score were evaluated. The entry point deviation of the actual screw placement relative to the simulated screw placement was measured, and whether the whole screw was in the cancellous corridor was ob`served.

Results

S1 screws with a diameter of 7.3 mm could be inserted into 69 pelvises, and S2 screws could be inserted in all pelvises. The S1 cancellous corridor had a long axis of 25.44 ± 3.32 mm in males and 22.91 ± 2.46 mm in females, a short axis of 14.21 ± 2.19 mm in males and 12.15 ± 3.22 mm in females, a corridor length of 153.07 ± 11.99 mm in males and 151.11 ± 8.73 mm in females, and a proportional position of the optimal entry point in the long axis of the cancellous corridor of 35.96 ± 10.31% in males and 33.28 ± 7.2% in females. There were significant differences in the corridor long axis and corridor short axis between sexes (p < 0.05), and there were no significant differences in corridor length and proportional position of the optimal entry point in the long axis of the cancellous corridor between sexes (p > 0.05). The S2 cancellous corridor had a long axis of 17.58 ± 2.36 mm in males and 16 ± 2.64 mm in females, a short axis of 14.21 ± 2.19 mm in males and 13.14 ± 2.2 mm in females, a corridor length of 129.95 ± 0.89 mm in males and 136.5 ± 7.96 mm in females, and a proportional position of the optimal entry point in the long axis of the cancellous corridor of 46.77 ± 9.02% in males and 42.25 ± 11.95% in females. There were significant differences in the long axis, short axis and corridor length (p < 0.05). There was no significant difference in the proportional position of the optimal entry point in the long axis of the cancellous corridor (p > 0.05). A total of 20 transversal sacroiliac screws were successfully implanted into 10 patients with the assistance of locked navigation templates, and a total of 24 transversal sacroiliac screws were successfully implanted into 12 patients under C-arm fluoroscopy. There was a significant difference in surgical time (88 ± 14.76 min vs 102.5 ± 17.12 min, p = 0.048), radiation times (11.5 ± 1.78 vs 54.83 ± 6.59, p < 0.05) and screw grading between two groups (nineteen screws in grade 0, one screw in grade 1 and 0 screws in grade 2 vs fourteen screws in grade 0, 8 screws in grade 1 and 2 screws in grade 2, p = 0.005). All screw entry point deviations were shorter than the short axis of the cancellous corridor, and all screws were located completely within the cancellous corridor.

Conclusion

Approximately 76% of males and females can accommodate screws with diameters of 7.3 mm in S1, and all persons can accommodate the same screw in S2. From the standard lateral perspective of the sacrum, the optimal entry point of the transverse screw is in the first 1/3 of the cancellous corridor for S1 and the centre of the cancellous corridor for S2. The patient-specific locked navigation template assisted in TSS placement with less operative time, less intraoperative fluoroscopy and higher safety of screw placement compared with traditional surgery.

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.

Comparing the Efficiency, Radiation Exposure, and Accuracy Using C-Arm versus O-Arm With 3D Navigation in Placement of Transiliac-Transsacral and Iliosacral Screws: A Cadaveric Study Evaluating an Early Career Surgeon

OBJECTIVES

To compare the efficiency, radiation exposure to surgeon and patient, and accuracy of C-arm versus O-arm with navigation in the placement of transiliac-transsacral and iliosacral screws by an orthopaedic trauma fellow, for a surgeon early in practice.

METHODS

Twelve fresh frozen cadavers were obtained. Preoperative computed tomography scans were reviewed to assess for safe corridors in the S1 and S2 segments. Iliosacral screws were assigned to the S1 segment in dysmorphic pelvises. Screws were randomized to modality and laterality. An orthopaedic trauma fellow placed all screws. Time of procedure and radiation exposure to the cadaver and surgeon were recorded. Three fellowship-trained orthopaedic trauma surgeons rated the safety of each screw on postoperative computed tomography scan.

RESULTS

Six normal and 6 dysmorphic pelvises were identified. Eighteen transiliac-transsacral screws and 6 iliosacral screws were distributed evenly between C-arm and O-arm. Average operative duration per screw was significantly shorter using C-arm compared with O-arm (15.7 minutes ± 6.1 vs. 23.7 ± 8.5, P = 0.014). Screw placement with C-arm exposed the surgeon to a significantly greater amount of radiation (3.87 × 10 rads vs. 0.32 × 10, P < 0.001) while O-arm exposed the cadaver to a significantly greater amount of radiation (0.03 vs. 2.76 rads, P < 0.001). Two S2 transiliac-transsacral screws (1 C-arm and 1 O-arm) were categorized as unsafe based on scoring. There was no difference in screw accuracy between modalities.

CONCLUSIONS

A difference in accuracy between modalities could not be elucidated, whereas efficiency was improved with utilization of C-arm, with statistical significance. A statistically significant increase in radiation exposure to the surgeon using C-arm was found, which may be clinically significant over a career. The results of this study can be extrapolated to a fellow or surgeon early in practice. The decision between use of these modalities will vary depending on surgeon preference and hospital resources.

Traumatic Sacral Fractures: Navigation Technique in Instrumented Stabilization

BACKGROUND

Sacral fractures are a challenge regarding treatment and classification. Surgical techniques using spinal navigation systems can improve treatment, especially if used in collaboration among different specialists.

METHODS

Between 2015 and 2017, we treated 25 consecutive cases of sacral fracture. Twelve patients (48%) underwent mechanical ventilation due to hypovolemic shock for severe thoracoabdominal trauma; bleeding was blocked with pelvic packing in 9 cases (36%) and transcatheter embolization in 2 cases (8%). External fixation was used in 7 cases (28%). In 20 cases (80%) spinal fractures were associated. All patients were operated on using spinal navigation by a team of neurosurgeons and orthopedic surgeons.

RESULTS

The mean time from first observation to surgery was 18 days (range 8-31). Surgical treatment consisted of iliosacral fixation in 19 cases (76%) and spinopelvic fixation in 6 cases (24%). The mean number of screws for spinopelvic fixation was 9.67 (range 6-17) with a mean operation time of 323.67 minutes (range 247-471); in iliosacral osteosynthesis the mean screw number was 1.37 (range 1-3) and mean surgical time was 78.93 minutes (range 61-130). Postoperative computed tomography showed the correct screw placement. Wound infection occurred in 2 cases (8%), managed with vacuum-assisted closure therapy; in 1 case (4%) a sacral screw was removed for decubitus.

CONCLUSIONS

Navigation systems in instrumented spinopelvic and sacropelvic reconstruction provide greater safety, reducing learning times and malpositioning. Multidisciplinary management allows us to achieve optimal results, especially when the sacral fracture is combined with spinal and pelvic lesions. The use of navigation systems could represent an important advancement.

Fragility fracture of pelvis caused by amenorrheic osteoporosis operated upon using computed-tomography-3D-fluoroscopy matching navigation system: a case report

INTRODUCTION

Low-energy trauma fractures of older people cause fragility fractures of the pelvis (FFPs), and secondary amenorrhea triggers osteoporosis that might lead to FFPs. Anorexia nervosa is a major causative factor in secondary amenorrhea, thus, FFPs might be a problem for young anorexia nervosa patients as well as older people. Here, we report a rare case of a young woman with anorexia nervosa who had an FFP, followed by gradual progression of severe sacral deformity.

CASE

A 49-year-old woman with hypothalamic amenorrhea (a subtype of secondary amenorrhea) caused by anorexia nervosa fell from a chair. She visited a nearby hospital and was diagnosed with an undisplaced sacral fracture; however, she chose to stay at home since the pain was slight and she could still walk. She fell to the floor several times while injured, and 3 months later, she had walking difficulty accompanied with severe pain, and was admitted to our facility. On radiological examination, she was diagnosed with FFP with severe sacral deformity, and was treated surgically. Because of the severe sacral deformity, a computed tomography (CT)-3D-fluoroscopy matching navigation system was used during surgery to support appropriate placement of percutaneous iliosacral (IS) and transiliac-trans-sacral (TITS) screws.

DISCUSSION

To our knowledge, this is the first report of FFP caused by amenorrheic osteoporosis, treated by matching navigation. This matching navigation could be a supportive tool in inserting IS and TITS screws during surgery for FFPs, especially in cases with severe deformity.

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.

The effect of robot-navigation-assisted core decompression on early stage osteonecrosis of the femoral head

BACKGROUND

The aim of the current paper is to evaluate the effects of robot-navigation-assisted core decompression compared with conventional core decompression surgery for early-stage osteonecrosis of the femoral head.

METHODS

Twenty patients with a total of 36 hips who were diagnosed with Association Research Circulation Osseous stage 2 avascular necrosis of the femoral head and who received core decompression with or without robotic assistance were reviewed. The Harris hip score and visual analog scale score were used to assess clinical function. Intraoperative radiation exposure and operation time were used to evaluate the effectiveness of the robot-assisted system.

RESULTS

At a mean follow-up of 26.4 months (24-36 months), the Harris hip score, visual analog scale score, and survival rate of the patients were similar between the conventional and robot-assisted groups. The guidewire insertion time, number of guidewire attempts, and radiation exposure during guidewire insertion were all significantly lower in the robot-assisted group than in the conventional group.

CONCLUSIONS

Robot-assisted core decompression of the femoral head is as safe and effective as a conventional core decompression surgery. It can reduce operation time and decrease intraoperative radiation exposure.

Minimally Invasive Screw Fixation of Unstable Pelvic Fractures Using the "Blunt End" Kirschner Wire Technique Assisted by 3D Printed External Template

Objective

This study aimed to determine the accuracy and safety of the “blunt end” Kirschner wire (KW) technique for the minimally invasive treatment of unstable pelvic fractures with the assistance of a 3D printed external template.

Methods

Clinical data of 28 patients with unstable pelvic fractures between January 2016 and January 2018 were retrospectively analyzed. There were 6 cases of B1, 10 of B2, 8 of C1, and 4 of C2 fractures, all of which received surgical treatment. The “blunt end” KW technique with a 3D template was adopted for the minimally invasive placement of the iliosacral (IS) or superior ramus screws. The number of intraoperative fluoroscopies, surgical time, and complications were recorded. Postoperative reduction was assessed using the Matta criteria, and the Majeed score system was used to evaluate postoperative functional recovery.

Results

The average number of fluoroscopies was 35 per patient, and the average surgical time was 85.2 min. A total of 19 S1 and 28 S2 IS screws were inserted. Eleven antegrade superior ramus screws and 4 retrograde screws were placed in 11 patients, and anterior subcutaneous internal fixation (INFIX) was used to fix the anterior pelvic ring in 17 patients. All patients were followed up for an average of 18 months. Postoperative reduction was evaluated by Matta's criteria: excellent in 16 cases, good in 9 cases, and fair in 3 cases. The Majeed score was used in the last follow-up to evaluate functional recovery: excellent in 13 cases, good in 10 cases, fair in 4 cases, and poor in 1 case. There were no cases of operative vascular injury.

Conclusion

The “blunt end” KW technique with a 3D printed external template is a safe and effective method for the placement of IS and superior ramus screws in unstable pelvic fractures with minimized surgical duration and radiation exposure.

CT-guided fixation of pelvic fractures after high-energy trauma, by interventional radiologists: technical and clinical outcome

OBJECTIVE

The aim of our study was to evaluate screw placement accuracy, safety, complications, and clinical outcomes including functional and pain score, in 32 patients treated with CT-guided pelvic ring fixation after high-energy trauma.

MATERIALS AND METHODS

Consecutive patients who were treated by CT-guided fixation of sacral or acetabular fractures after high-energy trauma were included. All procedures were performed under general anesthesia, with dual CT and fluoroscopic guidance, by interventional radiologists. Fractures were minimally displaced or reduced unstable posterior pelvic ring disruptions, with or without sacroiliac disjunction (Tile B or C) and minimally displaced acetabular fractures. The primary outcome evaluated was screw accuracy. Secondary outcomes included patient radiation exposure, duration of the procedure, complications, clinical functional score (Majeed score), and pain scale (VAS, visual analog scale) evaluation during a follow-up period from 4 to 30 months postoperatively.

RESULTS

Thirty-two patients were included (mean age 46) and 62 screws were inserted. Screw placement was correct in 90.3% of patients (95% of screws). Mean procedure duration was 67 min and mean patient radiation exposure was 965 mGy cm. Mean follow-up was 13 months and no complications were observed. The mean Majeed score at final follow-up was 84/100 and the mean VAS was 1.6/10.

CONCLUSION

This technique is an effective and safe procedure in specific cases of pelvic ring and acetabulum fractures. It allows accurate screw placement in a minimally invasive manner, leading to effective management of poly-traumatized patients.

KEY POINTS

• CT-guided pelvic ring fixation, including sacroiliac and acetabular fractures, is an effective and safe procedure. • It allows accurate and minimally invasive screw placement, leading to effective management of poly-traumatized patients. • Multidisciplinary cooperation is essential to ensure efficiency and safety.

Robot-assisted Percutaneous Cannulated Screw Fixation of Femoral Neck Fractures: Preliminary Clinical Results

OBJECTIVE

To assess the clinical efficacy of TiRobot-assisted percutaneous cannulated screw fixation in the treatment of femoral neck fractures.

METHODS

From September 2015 to July 2017, 26 patients with unilateral femoral neck fractures were treated with TiRobot-assisted percutaneous cannulated screw fixation. The femoral necks were fixed using three cannulated screws with robot assistance applying the following procedure: image acquisition, path planning, and needle and screw placement. The results of the treatment, including operation duration, frequency of fluoroscopy use, implant placement accuracy, intraoperative bleeding, total drilling, surgical complications, fracture healing time, fracture healing rate, and Harris scores at the last follow-up, were recorded and compared with 23 similar patients who underwent conventional manual positioning surgery.

RESULTS

A total of 147 cannulated screws were placed in all patients. The TiRobot group had shorter operation duration (62.6 ± 8.7 min vs 72.4 ± 10.3 min) and fracture healing time (5.1 ± 2.4 months vs 5.9 ± 2.8 months) than the conventional group (P > 0.05). The robot group had significantly less use of fluoroscopy (26.5 ± 7.4 times vs 51.3 ± 9.4 times), intraoperative bleeding (8.2 ± 5.3 mL vs 36.4 ± 12.5 mL), and total drilling (9.4 ± 4.2 times vs 18.3 ± 9.1 times) than the conventional group (all P < 0.05). The screw parallelism was significantly improved (24.0 ± 0.6 points vs 21.5 ± 1.2 points) and the neck-width coverage (72.0 ± 6.7 mm² vs 53.8 ± 10.4 mm² ) was significantly enlarged compared to the conventional group (P < 0.05). Only three guiding needles were used to penetrate the femoral head during manual insertion in the TiRobot group, which was significantly lower than that in the conventional group (3/78, 3.8% vs 9/69, 13.0%; P < 0.05). Other complications such as wound infection, vascular or nerve injury, screw loosening, and secondary screw displacement, did not occur in the two groups. There was no significant difference between the two groups in fracture healing rate (88.4% vs 82.6%) and Harris scores at the last follow up (88.2 ± 3.6 points vs 87.3 ± 4.7 points; P > 0.05).

CONCLUSION

TiRobot-assisted percutaneous cannulated screw fixation of femoral neck fractures is advantageous over conventional surgery with manual positioning due to easier manipulation, more accurate screw insertion, less invasion, and less radiation exposure, suggesting that it is a better method to stabilize femoral neck fractures.

Biomechanical comparison of three kinds of fixation in fracture-dislocation of the sacroiliac joint

BACKGROUND

Although there are several different kinds of fixation techniques for the sacroiliac fracture-dislocation, the treatment remains a challenge for orthopedic surgeons.

OBJECTIVE

The purpose of this study was to compare the stability of sacroiliac fracture-dislocation fixed with two iliosacral (IS) screws, tension band plate (TBP), and minimally invasive adjustable plate (MIAP).

METHODS

Five human cadavers (L4-pelvic-femora) were used to compare biomechanical stability. The pubic symphysis separation and left sacroiliac dislocation were created. The symphysis pubis was stabilized with a five-hole plate. The sacroiliac joint dislocation fracture was fixed with three kinds of internal fixation in a randomized design. The specimens were fastened in a biomechanical machine with a cycle vertical load. Displacements of the whole specimen and shifts in the fracture gap were recorded.

RESULTS

Under different vertical loads, the shifts in the fracture gap and the displacements of the pelvis fixed with MIAP were similar to those in fractures fixed with two IS screws. However, the shifts in the fracture gap and the displacements of the pelvis fixed with MIAP were significantly smaller than those fixed with TBP.

CONCLUSIONS

The stability of the sacroiliac joint dislocation fixed with MIAP was similar to that of dislocation fixed with two IS screws, and MIAP performed better than the TBP under vertical load.

The Surgical Approach Visualization and Navigation (SAVN) System reduces radiation dosage and surgical trauma due to accurate intraoperative guidance

OBJECT

The intraoperative fluoroscopy has been widely used in modern neuro-spinal surgery due to the overwhelming trend toward minimal-access surgery. However, both patients and surgical personnel were under ionizing-radiation exposure during fluoroscopy usage. Since the fluoroscopy constitutes the vast majority of radiation exposure for both surgeons and patients, the development and improvement of new interventional possibilities are of great importance and interests.

PATIENTS AND METHODS

A total of 20 patients were included in the current study, who received thoracic-spinal tumor resection via posterior midline approach. In comparison to the conventional C-Arm mobile fluoroscopy machine, the Surgical Approach Visualization and Navigation (SAVN) System was used to evaluate the effectiveness in reducing radiation.

RESULTS

The pain intensity and Japanese Orthopedic Association Score were equally ameliorated in patients of two groups. However, compared to C-arm group, the SAVN significantly reduced the screening time from 26.8 + 12.4 to 17.1 + 9.2 s (36.2% radiation reduction, P < 0.05), which was mainly due to the significant reduction of radiation attempts (from 12.8 + 4.9 to 7.1 + 5.5 times, P < 0.05). For patients, the direct and scatter radiation dose dropped 30.4% (P < 0.05) in the surgical region and 47.6% (P < 0.01) in the non-surgical region by using the SAVN System. Additionally, the tumor diameter/skin incision ratio increased from 0.39 + 0.4 to 0.47+ 0.28 after SAVN usage. Meanwhile, thedosimeter showed that the radiation dose to the primary surgeon was also lower in the SAVN group (72.1% reduction, P < 0.01).

CONCLUSION

Comparing the conventional C-arm, the SAVN System based thoracic-spinal surgery significantly lowered radiation duration and dosage application towards both surgeons and patients.

Intra- and interrater reliabilities and a method comparison of 2D and 3D techniques in cadavers to determine sacroiliac screw loosening

Sacroiliac (SI) screw loosening may indicate persistent instability, non-union and contribute to pain. Yet, there is no reliable objective measurement technique to detect and monitor SI screw loosening. In 9 cadaveric pelvises one of two SI screw was turned back approximately 20 mm and subsequently assessed by optical measurement, fluoroscopy and a 3D scan using an image intensifier. CTs were segmented and a contour-based registration of the 3D models and the fluoroscopies was performed to measure SI backing out (X-ray module). Three independent observers performed measurements with three repetitions. Deviation of the measurement techniques to the 3D scan, intra- and interrater reliabilities and method equivalence to the 3D scan were assessed. The X-ray module and two fluoroscopic measurement techniques yielded a difference less than 5 mm compared to the 3D scan and equivalence to the 3D scan. Intrarater reliability was for two observers and almost all techniques very good. Three fluoroscopic measurement techniques and optical measurements displayed a very good interrater reliability. The 3D scan and X-ray module yielded the most precise values for SI screw loosening but only the fluoroscopic measurement of the inlet lateral loosening displayed a good reliability and equivalence to the 3D scan.

Robot-assisted Minimally-invasive Internal Fixation of Pelvic Ring Injuries: A Single-center Experience

Objective

To investigate the indications, surgical strategy and techniques, safety, and efficacy of robot‐assisted minimally‐invasive internal fixation of pelvic ring injuries.

Methods

The clinical data of 86 patients with anterior and posterior pelvic ring injuries who underwent robot‐assisted minimally‐invasive internal fixation were retrospectively analyzed. The patients included 57 men and 29 women aged between 22 and 75 years, with an average age of (40.2 ± 13.6) years. According to the Tile classification, there were 5 (5.8%) type A2, 48 (55.8%) type B, and 33 (38.4%) type C fractures. The surgical plans were formulated based on the injury type of the pelvic ring, the effectiveness of the reduction, and the integrity of the osseous channel. Posterior pelvic ring injuries were treated with robot‐assisted percutaneous cannulated screw fixation of the sacroiliac joint. Anterior pelvic ring injuries were treated with robot‐assisted percutaneous cannulated screw fixation of the pubic ramus, INFIX fixation, or a “hybrid” fixation. The surgical complications and the efficacy of the surgical treatments were analyzed.

Results

A total of 274 screws were inserted with robotic assistance, of which 262 screws were successfully inserted to a satisfactory position on the first attempt. The number of screws placed per person was 3.2 on average, and the average operation time was 175 min (35–280 min). Fluoroscopies were performed an average of 29.1 times (range, 9–63 times), and it took 6.1 s to place each screw. There were 13 unsatisfactory guiding needle placements during the surgeries, among 7 of which cutting or penetration of the cortex was re‐planned until satisfactory insertions; 1 penetrated the pubic cortex, causing hemorrhage of the “crown of death,” and was changed to “hybrid surgery”. The robot‐assisted surgical wounds all healed by primary intention with satisfactory position and precision of screw insertions. All patients were followed up for 3–6 months, with an average of 4.2 months. There were two postoperative fixation failures, in which both patients had separated symphysis pubes after hybrid surgery. The average Majeed score at the last follow‐up was 92.4 points.

Conclusions

Robot‐assisted surgery is accurate and minimally invasive, with a high success rate for one‐time screw placement and satisfactory clinical results. The indications and surgical strategy should be rigorously selected, the level of surgical techniques mastered, and the operating procedures standardized, all of which may help to prevent surgical complications. Robot‐assisted surgery provides a novel modality for the minimally‐invasive treatment of pelvic ring injuries.

A novel computer navigation method for accurate percutaneous sacroiliac screw implantation: A technical note and literature review

The purpose of this study was to assess the accuracy of percutaneous sacroiliac screw (PSS) placement assisted by screw view model of navigation system for treatment of sacroiliac fractures.Data pertaining to 18 consecutive patients with posterior pelvic ring fracture who received sacroiliac screw fixation between January 2015 and July 2018 at the Second Hospital of Jilin University were retrospectively analyzed. Kirschner wires were placed under the guidance of navigation's screw view mode. The position of the screws was evaluated by computed tomography (CT) scan postoperatively. Fracture dislocation of sacroiliac joint was measured in axial, sagittal, and coronal views of 3 dimensional (3D) CT images preoperatively, postoperatively and at the last follow-up visit. The duration of trajectory planning, guide wire implantation time, screw placement time, intraoperative blood loss, and incidence of screw loosening and clinical complications were also assessed.A total of 27 screws were placed unilaterally or bilaterally into segments S1 or S2. Screw placement was rated as excellent for 88.9% of screws (n = 24), good for 7.4% (n = 2), and poor for 3.7% (n = 1). Preoperatively, the average fracture dislocation of sacroiliac joint on axial, sagittal, and coronal views was 14.3 mm, 9.6 mm, and 7.4 mm, respectively, and the corresponding postoperative figures were 5.6 mm, 3.2 mm, 4.1 mm, respectively. The corresponding correction rates were 60.8%, 66.7%, and 44.6%, respectively. The mean duration of trajectory planning was 6.5 min (2.7-8.9 min). Mean screw implantation time was 32 min (range, 20-53 min), and the mean guide wire implantation time was 3.7 min (range, 2.1-5.3 min). No clinical complications such as neurovascular injury, infection or screw loosening were observed on follow-up.The PSS placement under guidance of screw view model of navigation is a convenient, safe and reliable method.

Factors influencing the accuracy of iliosacral screw insertion using 3D fluoroscopic navigation

INTRODUCTION

The purpose of the present study was to determine which factors affect the positional accuracy of iliosacral screws inserted using 3D fluoroscopic navigation. Specifically, we asked: (1) does the screw insertion angle in the coronal and axial planes affect the positional accuracy of iliosacral screw insertion using 3D fluoroscopic navigation? (2) Is the positional accuracy of iliosacral screw insertion using 3D fluoroscopic navigation affected by the type of screw (transsacral versus standard iliosacral), site of screw insertion (S1 versus S2), patient position (supine versus prone), presence of a dysmorphic sacrum, or AO/OTA classification (type B versus C)?

MATERIALS AND METHODS

Twenty-seven patients with AO/OTA type B or C pelvic ring fracture were treated by percutaneous iliosacral screw fixation. A total of 55 screws were inserted into S1 or S2 using 3D fluoroscopic navigation combined with preoperative CT-based planning. The positional accuracy of screw placement was assessed by matching postoperative CT images with preoperative CT images. The distance between the central axis of the inserted screw and that of the planned screw placement was measured in the sagittal plane passing through the center of the vertebral body.

RESULTS

The mean deviation between the planned and the inserted screw position was 2.9 ± 1.7 mm (range 0-8.5 mm) at the vertebral body center. Multiple regression analysis showed that the screw insertion angle relative to the vertical line of the bone surface in the axial plane (β = 0.354, p = 0.013) and the use of a transsacral screw (β = 0.317, p = 0.017) were correlated with the positional accuracy of screw placement (adjusted R² = 0.276, p = 0.002).

CONCLUSIONS

A greater screw insertion angle relative to the vertical line on the bone surface and the use of transsacral screws increases the positional error of iliosacral screws inserted using 3D fluoroscopic navigation.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Effect of metallic tools on scattered radiation dose during the use of C-arm fluoroscopy in orthopaedic surgery

This study investigated the effect of metallic tools on the scattered radiation dose delivered to surgeons' radiosensitive organs while simulating hip surgery using C-arm fluoroscopy. Two phantoms, a pelvis and a Rando phantom, were used to simulate a patient and a surgeon in this study. Photoluminescence dosimeters were inserted into the Rando phantom in the positions of the eye, thyroid and gonad. A drill was positioned above the hip of the pelvis phantom or beside the pelvis phantom of the same height. For each drill location, the scattered radiation dose was measured when the angle to the operator phantom was 45°; this was repeated when the angle was 90°. The scattered radiation doses to the eye, thyroid and gonad when the drill was placed beside the pelvis phantom with 90° angulation to the operator phantom were significantly lower than the reference values and those when the drill was placed beside the pelvis phantom at a 45° angulation to the operator phantom. The scattered radiation doses to the eye and thyroid when the drill was placed above the hip were significantly lower than the references values. Of the four different scenarios, the scattered radiation doses to the eye, thyroid and gonad were lowest when the drill was placed beside the pelvis phantom with 90° angulation. This study showed that the scattered radiation doses to radiosensitive organs were affected by the location and angle of the metallic tools in relation to the operator. Therefore, orthopedic surgeons should consider the effect of metallic tools on the scattered radiation dose during intraoperative use of C-arm fluoroscopy.

[Treatment of unstable pelvic fractures by cannulated screw internal fixation with the assistance of three-dimensional printing insertion template]

Objective

To evaluate the effectiveness of unstable pelvic fractures treated by cannulated screw internal fixation with the assistance of three-dimensional (3D) printing insertion template.

Methods

The clinical data of 10 patients who underwent surgical treatment for unstable pelvic fractures by cannulated screw internal fixation with the assistance of 3D printing insertion template between May 2015 and June 2016 were retrospectively analysed. There were 7 males and 3 females with an average age of 37.5 years (range, 20-58 years). The causes of injury included falling from height in 5 cases, crushing from heavy load in 1 case, and traffic accidents in 4 cases. The interval from injury to admission was 1-5 hours (mean, 3.1 hours). The fracture situation included 6 cases of sacral fracture, 1 case of right sacroiliac joint dislocation, and 3 cases of iliac bone fracture. There were 10 cases of superior and inferior pubic rami fracture, including 3 cases on the left side (2 cases of suprapubic fracture adjacent to symphysis pubis), 2 cases on the right side, and 5 cases on the bilateral. All fractures were classified according to the Tile system, there were 4 cases of type B2, 1 of type B3, 4 of type C1, and 1 of type C2. The radiological outcome was evaluated by Matta scale, and the positions of the iliosacral screw and superior pubic ramus screw were evaluated according to 3D reconstruction of CT postoperatively. The functional outcome was evaluated by Majeed function scale.

Results

The average time of each screw implantation was 30 minutes, and the average blood loss per screw incision was 50 mL. The time of implantation of each sacroiliac screw was 24-96 seconds (mean, 62 seconds), and the time of implantation of each suprapubic screw was 42-80 seconds (mean, 63.2 seconds). The hospitalization duration was 17-90 days (mean, 43.7 days). All incisions healed by first intention. All patients were followed up 12-22 months (mean, 15.6 months). The radiological outcome was excellent in 8 cases and good in 2 cases according to Matta scale; and 3D reconstruction of CT demonstrated that all the 9 iliosacral screws were placed as type Ⅰ, and all the 13 suprapubic ramus screws were placed as grade 0 on the first postoperative day. No complication such as neurovascular injury, screw back out or rupture, or secondary fracture displacement was observed during the follow-up. At 6 months after operation, the X-ray films showed good fracture healing in all the 10 patients. The functional outcome was excellent in 9 cases and good in 1 case according to Majeed scale at 1 year after operation. One patient sustained Tile C2 pelvic disruption complicated with L ₅ nerve root injury achieved complete nervous functional recovery at last follow-up.

Conclusion

It has advantages of precise screw insertion and lower risk of neurovascular injury to treat unstable pelvic fractures by cannulated screw internal fixation with the assistance of 3D printing insertion template, which can be a good alternative for the treatment of unstable pelvic fractures.

Intra-operative imaging in trauma surgery

The reconstruction of anatomical joint surfaces, limb alignment and rotational orientation are crucial in the treatment of fractures in terms of preservation of function and range of motion. To assess reduction and implant position intra-operatively, mobile C-arms are mandatory to immediately and continuously control these parameters.Usually, these devices are operated by OR staff or radiology technicians and assessed by the surgeon who is performing the procedure. Moreover, due to special objectives in the intra-operative setting, the situation cannot be compared with standard radiological image acquisition. Thus, surgeons need to be trained and educated to ensure correct technical conduct and interpretation of radiographs.It is essential to know the standard views of the joints and long bones and how to position the patient and C-arm in order to acquire these views. Additionally, the operating field must remain sterile, and the radiation exposure of the patient and staff must be kept as low as possible.In some situations, especially when reconstructing complex joint fractures or spinal injuries, complete evaluation of critical aspects of the surgical results is limited in two-dimensional views and fluoroscopy. Intra-operative three-dimensional imaging using special C-arms offers a valuable opportunity to improve intra-operative assessment and thus patient outcome.In this article, common fracture situations in trauma surgery as well as special circumstances that the surgeon may encounter are addressed. Cite this article: EFORT Open Rev 2018;3:541-549. DOI: 10.1302/2058-5241.3.170074.

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.

Percutaneous Sacroiliac Screw Placement: A Prospective Randomized Comparison of Robot-assisted Navigation Procedures with a Conventional Technique

Background:

Sacroiliac (SI) screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot™ is an orthopedic surgery robot which can be used for SI screw fixation. This study aimed to evaluate the accuracy of robot-assisted placement of SI screws compared with a freehand technique.

Methods:

Thirty patients requiring posterior pelvic ring stabilization were randomized to receive freehand or robot-assisted SI screw fixation, between January 2016 and June 2016 at Beijing Jishuitan Hospital. Forty-five screws were placed at levels S1 and S2. In both methods, the primary end point screw position was assessed and classified using postoperative computed tomography. Fisher's exact probability test was used to analyze the screws’ positions. Secondary end points, such as duration of trajectory planning, surgical time after reduction of the pelvis, insertion time for guide wire, number of guide wire attempts, and radiation exposure without pelvic reduction, were also assessed.

Results:

Twenty-three screws were placed in the robot-assisted group and 22 screws in the freehand group; no postoperative complications or revisions were reported. The excellent and good rate of screw placement was 100% in the robot-assisted group and 95% in the freehand group. The P value (0.009) showed the same superiority in screw distribution. The fluoroscopy time after pelvic reduction in the robot-assisted group was significantly shorter than that in the freehand group (median [Q₁, Q₃]: 6.0 [6.0, 9.0] s vs. median [Q₁, Q₃]: 36.0 [21.5, 48.0] s; χ² = 13.590, respectively, P < 0.001); no difference in operation time after reduction of the pelvis was noted (χ² = 1.990, P = 0.158). Time for guide wire insertion was significantly shorter for the robot-assisted group than that for the freehand group (median [Q₁, Q₃]: 2.0 [2.0, 2.7] min vs. median [Q₁, Q₃]: 19.0 [15.5, 45.0] min; χ² = 20.952, respectively, P < 0.001). The number of guide wire attempts in the robot-assisted group was significantly less than that in the freehand group (median [Q₁, Q₃]: 1.0 [1.0,1.0] time vs. median [Q₁, Q₃]: 7.0 [1.0, 9.0] times; χ² = 15.771, respectively, P < 0.001). The instrumented SI levels did not differ between both groups (from S1 to S2, χ² = 4.760, P = 0.093).

Conclusions:

Accuracy of the robot-assisted technique was superior to that of the freehand technique. Robot-assisted navigation is safe for unstable posterior pelvic ring stabilization, especially in S1, but also in S2. SI screw insertion with robot-assisted navigation is clinically feasible.

Robot-assisted percutaneous screw placement combined with pelvic internal fixator for minimally invasive treatment of unstable pelvic ring fractures

Purpose

The purpose of this study was to investigate the safety and efficacy of the combination of robot‐assisted percutaneous screw placement and pelvic internal fixator (INFIX) for minimally invasive treatment of unstable anterior and posterior pelvic ring injuries.

Methods

From September 2016 to June 2017, twenty‐four patients with unstable anterior and posterior pelvic ring injuries were treated with TiRobot‐assisted percutaneous sacroiliac cannulated screw fixation on the posterior pelvic ring combined with robot‐assisted pedicle screw placement in the anterior inferior iliac spine along with INFIX on the anterior pelvic ring. The results of the treatment, including surgery duration, fluoroscopy frequency, total drilling, amount of blood loss, fracture healing time, and postoperative functional outcomes were recorded and compared with another 21 similar patients who underwent conventional manual positioning surgery.

Results

The TiRobot group incurred significantly shorter duration of surgery; less fluoroscopy frequency, intraoperative bleeding, and total drilling than in the conventional group (P < 0.05). Postoperative radiological follow‐up showed that all screws were in the safe area and no screw penetrated the cortex. All wounds healed by primary intention and no iatrogenic damage to the blood vessels, nerves, and organs occurred. Patients showed good tolerance to INFIX and reported no discomfort. The mean follow‐up duration was 5.4 months; the fractures were all healed, no loss of reduction occurred, and the mean Majeed score at the last follow‐up did not show any difference.

Conclusion

TiRobot‐assisted percutaneous screw placement combined with INFIX for the anterior and posterior pelvic ring injuries is accurate, safe, less invasive, and shows satisfactory efficacy, suggesting it is a better method for minimally invasive treatment of unstable pelvic ring fractures.

[The new treatment procedures of the DGUV from the perspective of an injury type procedure (VAV) clinic]

The new treatment procedures of the German Statutory Accident Insurance (DGUV) have ramifications for the injury type procedure clinics (VAV) from medical, economic and structural aspects. Whereas the latter can be assessed as positive, the medical and economical aspects are perceived as being negative. Problems arise from the partially unclear formulation of the injury type catalogue, which results in unpleasant negotiations with the occupational insurance associations with respect to financial remuneration for services rendered. Furthermore, the medical competence of the VAV clinics will be reduced by the preset specifications of the VAV catalogue, which opens up an additional field of tension between medical treatment, fulfillment of the obligatory training and acquisition of personnel as well as the continually increasing economic pressure. From the perspective of the author, the relinquence of medical competence imposed by the regulations of the new VAV catalogue is "throwing the baby out with the bathwater" because many VAV clinics nationwide also partially have competence in the severe injury type procedure (SAV). A concrete "competence-based approval" for the individual areas of the VAV procedure would be sensible and would maintain the comprehensive care of insured persons and also increase or strengthen the willingness of participating VAV hospitals for unconditional implementation of the new VAV procedure.

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.

Percutaneous iliosacral screw fixation in unstable pelvic fractures

Surgical treatment of unstable pelvic fractures Type C, has a vertical instability that is not controlled by traction and supine; therefore, orthopedic and functional treatments undertaken by default are sources of complications. The closed reduction with percutaneous sacroiliac fixation solves the problem of vertical instability; but at the cost of learning the method. Five patients with unstable pelvic fractures; were treated by percutaneous sacroiliac fixation. This reliable and useful method in the stabilization of unstable pelvic fractures. Good functional results are predictable based on the severity of pelvic fractures and associated injuries. The low rates of complications and the minimally invasive nature are the advantages of this method.

Percutaneous screw fixation of the iliosacral joint: A case-based preoperative planning approach reduces operating time and radiation exposure

INTRODUCTION

A preoperative planning approach for percutaneous screw fixation of the iliosacral joint provides specific entry points (EPs) and aiming points (APs) of intraosseous screw pathways (as defined by CT scans) for lateral fluoroscopic projections used intraoperatively. The potential to achieve the recommended EPs and APs, to obtain an ideal screw position (perpendicular to the iliosacral joint), to avoid occurrence of extraosseous screw misplacement, to reduce the operating time and the radiation exposure by utilizing this planning approach have not been described yet.

METHODS

On preoperative CT scans of eight human cadaveric specimen individual EPs and APs were identified and transferred to the lateral fluoroscopic projection using a coordinate system with the zero-point in the center of the posterior cortex of the S1 vertebral body (x-axis parallel to upper S1 endplate). Distances were expressed in relation to the anteroposterior distance of the S1 upper endplate (in%). In each specimen on one side a screw was placed with provided EP and AP (New Technique) whereas at the contralateral side a screw was placed without given EP and AP (Conventional Technique). Both techniques were compared using postoperative CT scans to assess distances between predefined EPs and APs and the actually obtained EPs and APs, screw angulations in relation to the iliosacral joint in coronal and axial planes and the occurrence of any extraosseous screw misplacement. The "operating time (OT)" and the "time under fluoroscopy (TUF)" were recorded. Statistical analysis was performed by the Wilcoxon signed-rank test.

RESULTS

EPs were realized significantly more accurate using the new technique in vertical direction. The screw positions in relation to the iliosacral joint showed no significant difference between both techniques. Both techniques had one aberrantly placed screw outside the safe corridor. The (mean±SD) "OT" and the (mean±SD) "TUF" were significantly decreased using the new technique compared to the conventional technique (OT: 7.6±2min versus 13.1±5.8min, p=0.012; TUF: 1.5±0.8min versus 2.2±1.1min).

CONCLUSION

The presented preoperative planning approach increases the accuracy in percutaneous screw fixation of the iliosacral joint, reduces operating time and minimizes radiation exposure to patient and staff.

Intra-operative multi-dimensional fluoroscopy of guidepin placement prior to iliosacral screw fixation for posterior pelvic ring injuries and sacroiliac dislocation: an early case series

PURPOSE

Traditional fluoroscopic techniques during percutaneous fixation of the posterior pelvic ring at times cannot adequately visualize errant or malpositioned iliosacral screws. Intra-operative fluoroscopic techniques have been advanced using multi-dimensional fluoroscopy to generate computed tomography-like images. This provides the surgeon not only the ability to assess iliosacral screw placement, but also the opportunity to assess reduction. We present a case series of four patients in which the Ziehm RFD multi-dimensional fluoroscopy was used to assess reduction and guidepin placement prior to definitive iliosacral screw fixation.

METHODS

Four patients at our university level 1 trauma center with posterior pelvic ring disruptions were treated with percutaneous iliosacral screw fixation. Traditional fluoroscopic techniques were used during guidepin placement. Multi-dimensional fluoroscopy was performed using the Ziehm RFD 3D to assess guidepin placement and reduction prior to definitive iliosacral screw fixation.

RESULTS

Our case series highlights two patients in which multi-dimensional fluoroscopy was utilized to ensure safe placement of iliosacral screws. In one of these two patients, a change was made after reviewing the imaging as a guidepin was found to be intruded into bilateral S2 neural tunnels. We also present two patient examples in which multidimensional fluoroscopy was used to assess reduction achieved by less invasive methods, precluding the need for direct visualization using more extensive open approaches.

CONCLUSIONS

This retrospective case series demonstrates the direct impact that the Ziehm RFD 3D technology provides in surgical management of patients with complex posterior pelvic ring injuries.

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.

Computer Navigation-aided Resection of Sacral Chordomas

BACKGROUND

Resection of sacral chordomas is challenging. The anatomy is complex, and there are often no bony landmarks to guide the resection. Achieving adequate surgical margins is, therefore, difficult, and the recurrence rate is high. Use of computer navigation may allow optimal preoperative planning and improve precision in tumor resection. The purpose of this study was to evaluate the safety and feasibility of computer navigation-aided resection of sacral chordomas.

METHODS

Between 2007 and 2013, a total of 26 patients with sacral chordoma underwent computer navigation-aided surgery were included and followed for a minimum of 18 months. There were 21 primary cases and 5 recurrent cases, with a mean age of 55.8 years old (range: 35-84 years old). Tumors were located above the level of the S3 neural foramen in 23 patients and below the level of the S3 neural foramen in 3 patients. Three-dimensional images were reconstructed with a computed tomography-based navigation system combined with the magnetic resonance images using the navigation software. Tumors were resected via a posterior approach assisted by the computer navigation. Mean follow-up was 38.6 months (range: 18-84 months).

RESULTS

Mean operative time was 307 min. Mean intraoperative blood loss was 3065 ml. For computer navigation, the mean registration deviation during surgery was 1.7 mm. There were 18 wide resections, 4 marginal resections, and 4 intralesional resections. All patients were alive at the final follow-up, with 2 (7.7%) exhibiting tumor recurrence. The other 24 patients were tumor-free. The mean Musculoskeletal Tumor Society Score was 27.3 (range: 19-30).

CONCLUSIONS

Computer-assisted navigation can be safely applied to the resection of the sacral chordomas, allowing execution of preoperative plans, and achieving good oncological outcomes. Nevertheless, this needs to be accomplished by surgeons with adequate experience and skill.

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.

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.

Fluoroscopic Views for a More Accurate Placement of Iliosacral Screws: An Experimental Study

OBJECTIVES

Misperception on the fluoroscopic image showing a well-placed iliosacral (IS) screw can occur, when the screw is in reality misplaced. The purpose of this study was to demonstrate and highlight examples of misperception and suggest alternative inlet and outlet views to confirm adequate IS screw placement.

METHODS

We used 9 different pelvic plastic models. In 8 of those models, IS screws were purposely misplaced: exiting anterior at the midportion of the S1 body, exiting at the lateral aspect of the anterior S1 body, abutting posterior to S1 body, exiting posterior to the S1 body, exiting superior to the far-side of the sacral ala, exiting superior to the S1 body, exiting partially in the S1 foramen, exiting completely in the S1 foramen. One model was used as control with correct screw placement. Different outlet and inlet views were tested to accurately detect important anatomic landmarks and avoid fake phenomenon (FP) using 3 different angles.

RESULTS

Misperception occurred in 3 models: (1) penetration at the midportion of the anterior border of S1, (2) penetration of the superior sacrum ala, and (3) partial penetration of S1 foramen. In the first situation, misperception could be avoided when the "anterior inlet view" was obtained. In the other 2 situations, misperception could be avoided using specific outlet views herein described.

CONCLUSIONS

Our findings highlight that misperception can occur using standard inlet and outlet views. We suggest using 2 variations of the inlet views and 3 variations of the outlet views to avoid misperception in clinical practice.

Precision insertion of percutaneous sacroiliac screws using a novel augmented reality-based navigation system: a pilot study

PURPOSE

Augmented reality (AR) enables superimposition of virtual images onto the real world. The aim of this study is to present a novel AR-based navigation system for sacroiliac screw insertion and to evaluate its feasibility and accuracy in cadaveric experiments.

METHODS

Six cadavers with intact pelvises were employed in our study. They were CT scanned and the pelvis and vessels were segmented into 3D models. The ideal trajectory of the sacroiliac screw was planned and represented visually as a cylinder. For the intervention, the head mounted display created a real-time AR environment by superimposing the virtual 3D models onto the surgeon's field of view. The screws were drilled into the pelvis as guided by the trajectory represented by the cylinder. Following the intervention, a repeat CT scan was performed to evaluate the accuracy of the system, by assessing the screw positions and the deviations between the planned trajectories and inserted screws.

RESULTS

Post-operative CT images showed that all 12 screws were correctly placed with no perforation. The mean deviation between the planned trajectories and the inserted screws was 2.7 ± 1.2 mm at the bony entry point, 3.7 ± 1.1 mm at the screw tip, and the mean angular deviation between the two trajectories was 2.9° ± 1.1°. The mean deviation at the nerve root tunnels region on the sagittal plane was 3.6 ± 1.0 mm.

CONCLUSIONS

This study suggests an intuitive approach for guiding screw placement by way of AR-based navigation. This approach was feasible and accurate. It may serve as a valuable tool for assisting percutaneous sacroiliac screw insertion in live surgery.

One year orthopaedic trauma experience using an advanced interdisciplinary hybrid operating room

Hybrid operating rooms have been used successfully in several surgical specialties, but no data have been published for orthopaedic trauma. We present our one-year orthopaedic trauma experience using a hybrid operating room, which incorporates 3D fluoroscopic imaging as well as navigation capabilities. Data were compiled for a series of 92 cases performed in an advanced hybrid operating room at the level one trauma center in Ulm, Germany. All patients who had surgery performed using this operating room during the first year were included. Setup time and surgical complications using hybrid operating room were recorded and analysed. The hybrid operating room resulted in no higher rate of complication than expected from the same cases in a conventional operating room. The hybrid room did however allow the surgeon to confidently place implants for orthopaedic trauma cases, and was most advantageous for spine and pelvis cases, both minimally invasive and conventional. Further, appropriate reduction and implant position was confirmed with 3D imaging prior to leaving the operating room and obviated the need for postoperative CT scan. Based on our one-year experience, the hybrid operating room is a useful and safe tool for orthopaedic trauma surgery.

Percutaneous iliosacral screw fixation after osteoporotic posterior ring fractures of the pelvis reduces pain significantly in elderly patients

INTRODUCTION

Osteoporotic posterior ring fractures of the pelvis are common injuries in the elderly, but the treatment of these fractures still remains controversial. Percutaneous iliosacral screw fixation is one surgical option if conservative treatment cannot provide sufficient pain reduction. The aim of this study is to provide short-term results of elderly patients with percutaneous screw fixation.

METHODS

30 patients with posterior ring fractures were treated between 12/2009 and 01/2014 with percutaneous iliosacral screw fixation. Patients' mean age was 78.4 years. Concerning short-term outcome, we focused on initial pain level and postoperative pain reduction together with intra- and postoperative complications.

RESULTS

The average hospital stay was 23.7 days, with surgical treatment performed after an average of 9.2 days. 90% of our patients were female. All 30 patients had a lower level of pain at discharge compared with admission or immediately prior to surgery. The difference in pain level at admission compared with the pain level upon discharge showed a mean reduction from 6.8 to 1.8 with a statistically significant change (P≤0.001). 24 of 30 patients had no registered complications, one screw malpositioning with postoperative nerve irritation occurred.

DISCUSSION

Conventional percutaneous iliosacral screw fixation is a successful operative treatment for elderly patients with persistent lower back pain after unstable posterior ring fractures of the pelvis. Intra- and postoperative complications are rare, so this treatment can be regarded as a safe procedure.

LEVEL OF EVIDENCE

IV (retrospective study).

Biomechanical comparison of three types of internal fixation in a type C zone II pelvic fracture model

OBJECTIVE

This study aimed to compare the stability of Tile C pelvic fractures fixed with two iliosacral (IS) screws, tension band plate (TBP), and minimally invasive adjustable plate (MIAP).

METHODS

Six embalmed specimens of adult pelvis were used. The soft tissue was removed from the specimens, but 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 created on the specimens. The symphysis pubis was fixed with a plate, and the fracture on the posterior pelvic ring was fixed with three types of internal fixation in a randomized block design. The specimens were placed in a biomechanical machine at a standing neutral posture. A cyclic vertical load of up to 500N was applied, and displacement was recorded. Shifts in the fracture gap were measured by a grating displacement sensor.

RESULTS

Under different vertical loads, the shift in the fracture gap and displacement of the pelvic fractures fixed with two IS screws were similar to those in fractures fixed with MIAP. However, the shift in the fracture gap and displacement of fractures fixed with MIAP was significantly smaller than those of fractures fixed with TBP.

CONCLUSION

The stability of the Tile C pelvic fractures fixed with MIAP was similar to that of fractures fixed with IS screws. MIAP performed better than TBP under vertical load.

CT-guided sacroiliac percutaneous screw placement in unstable posterior pelvic ring injuries: accuracy of screw position, injury reduction and complications in 71 patients with 136 screws

BACKGROUND

Sacroiliac-percutaneous-screw-placement (SPSP) for unstable-posterior-pelvic-ring-injuries (UPPRI) might be associated with severe neurovascular complications because of screw-mal-position. The aim of the present study was to analysis the effectivity of computer-tomography-guided (CTG)-SPSP including accuracy of screw-placement, quality of injury-reduction and documentation of perioperative-complications. Additionally, procedure-dependent radiation-dose and outcome should be analysed.

METHODS

A consecutive cohort of 71 patients with UPPRI was operated by CTG-SPSP at a single trauma level 1 hospital. 136 sacroiliac screws were inserted to S1 and S2. Postoperatively, by the use of a computerised-radiologic-work-station all screws were visualised three-dimensionally. Their distancesmin to the sacral-borders in anterior-posterior and cranio-caudal direction as well as to the neuroforamen S1/S2 were determined. After CTG-SPSP, injury-dislocation in anterior-posterior and cranio-caudal direction was quantified. Local and general complications were documented during the 30-day-period. In 55 patients (77.5%) a follow-up-investigation (29.1±19.1 months) was performed.

RESULTS

132 screws (97.1%) were placed completely intraosseous, 3 screws (2.2%) perforated up to 1.0 mm (n(S1)=one screw; n(S2)=two screws), and one screw (0.7%) extended 2.2 mm into the S2-neuroforamen without contact to neural structures. Postoperative dislocationanterior-posterior was 1.3±0.9 mm and dislocationcranio-caudal 1.5±0.9 mm. No procedure-associated-complication was observed. Operation time showed a significant "learning curve" during the six-year study period (initially: 88.6±60.3 min; finally: 44.3±24.6 min). Perioperative effective-radiation-dose for patientsmale was 5.9±3.1 mSv and for patientsfemale 8.7±4.5 mSv. All injuries healed and 33 patients (46.5%) had metal removal after 11.0 (±4.9) months. Only two (5.0%) out of 40 patients complained persistent UPPRI-related pain so they were not able to restart work.

CONCLUSIONS

The CTG-SPSP is a safe procedure for UPPRI-stabilisation especially in S1 but also in S2. Injury reduction was excellent and no procedure associated complications were observed.

Pedicle axis view combined by sacral mapping can decrease fluoroscopic shot count in percutaneous iliosacral screw placement

BACKGROUND

Percutaneous iliosacral screw fixation of the posterior pelvic ring is a demanding procedure with high exposure to radiation. The conventional technique includes the use of three classical projections with the C-arm: inlet, outlet, and true lateral views. A projection in the axis of the upper sacral alar pedicles with a 30° cephalad and 30° ventral oblique view would help in obtaining a more accurate visualization of the safe corridor. Two subcutaneously placed K-wires, one placed horizontally and one vertically, may facilitate the starting point and aim changes by offering the surgeon an option for exactly matching the position of the sacrum with the image. The purpose of this study was to detect if the radiation application could be decreased by our new methodology.

METHODS

Seventeen patients with pelvic posterior ring disruptions, in which percutaneous iliosacral screw placement was indicated, were included in the study. Group 1 comprised 7 patients in whom conventional projections and technique were used. Group 2 comprised 10 patients in whom 30°–30° projection and sacral mapping technique via two subcutaneous K-wires were applied. Radiation exposure time, total fluoroscopic shot count, fluoroscopic shot count needed for only guide wire and screw placement, radiation dose, and complications were compared between the two groups.

RESULTS

The median number of fluoroscopic images for guide and screw placement was 132 (56–220) and 29.5 (19–83) in Groups 1 and 2, respectively, and the difference was statistically significant (p < 0.001). The median total fluoroscopic radiation time was 138 (68–234) and 52 (28–77) s in Groups 1 and 2, respectively, and the difference was significant (p < 0.001). Group 1 had a significantly higher median radiation dose than Group 2 [3020 (1502–6032) vs. 1192 (426–2359); (p = 0.001)].

CONCLUSIONS

Iliosacral screw placement with the help of sacral mapping and a fourth view, “30°–30°”, helps the surgeon to markedly reduce the fluoroscopic shots, radiation time and dose during guide wire and screw placement.

LEVEL OF EVIDENCE

Therapeutic, Level II.

Three-dimensional navigation is more accurate than two-dimensional navigation or conventional fluoroscopy for percutaneous sacroiliac screw fixation in the dysmorphic sacrum: a randomized multicenter study

OBJECTIVES

To evaluate the accuracy of computer-assisted sacral screw fixation compared with conventional techniques in the dysmorphic versus normal sacrum.

DESIGN

Review of a previous study database.

SETTING

Database of a multinational study with 9 participating trauma centers.

PATIENTS

The reviewed group included 130 patients, 72 from the navigated group and 58 from the conventional group. Of these, 109 were in the nondysmorphic group and 21 in the dysmorphic group.

INTERVENTION

Placement of sacroiliac (SI) screws was performed using standard fluoroscopy for the conventional group and BrainLAB navigation software with either 2-dimensional or 3-dimensional (3D) navigation for the navigated group.

MAIN OUTCOME MEASUREMENTS

Accuracy of SI screw placement by 2-dimensional and 3D navigation versus conventional fluoroscopy in dysmorphic and nondysmorphic patients, as evaluated by 6 observers using postoperative computerized tomography imaging at least 1 year after initial surgery. Intraobserver agreement was also evaluated.

RESULTS

There were 11.9% (13/109) of patients with misplaced screws in the nondysmorphic group and 28.6% (6/21) of patients with misplaced screws in the dysmorphic group, none of which were in the 3D navigation group. Raw agreement between the 6 observers regarding misplaced screws was 32%. However, the percent overall agreement was 69.0% (kappa = 0.38, P < 0.05).

CONCLUSIONS

The use of 3D navigation to improve intraoperative imaging for accurate insertion of SI screws is magnified in the dysmorphic proximal sacral segment. We recommend the use of 3D navigation, where available, for insertion of SI screws in patients with normal and dysmorphic proximal sacral segments.

LEVEL OF EVIDENCE

Therapeutic level I.

Accuracy assessment of Tri-plane B-mode ultrasound for non-invasive 3D kinematic analysis of knee joints

Background

Currently the clinical standard for measuring the motion of the bones in knee joints with sufficient precision involves implanting tantalum beads into the bones. These beads appear as high intensity features in radiographs and can be used for precise kinematic measurements. This procedure imposes a strong coupling between accuracy and invasiveness. In this paper, a tri-plane B-mode ultrasound (US) based non-invasive approach is proposed for use in kinematic analysis of knee joints in 3D space.

Methods

The 3D analysis is performed using image processing procedures on the 2D US slices. The novelty of the proposed procedure and its applicability to the unconstrained 3D kinematic analysis of knee joints is outlined. An error analysis for establishing the method’s feasibility is included for different artificial compositions of a knee joint phantom. Some in-vivo and in-vitro scans are presented to demonstrate that US scans reveal enough anatomical details, which further supports the experimental setup used using knee bone phantoms.

Results

The error between the displacements measured by the registration of the US image slices and the true displacements of the respective slices measured using the precision mechanical stages on the experimental apparatus is evaluated for translation and rotation in two simulated environments. The mean and standard deviation of errors are shown in tabular form. This method provides an average measurement precision of less than 0.1 mm and 0.1 degrees, respectively.

Conclusion

In this paper, we have presented a novel non-invasive approach to measuring the motion of the bones in a knee using tri-plane B-mode ultrasound and image registration. In our study, the image registration method determines the position of bony landmarks relative to a B-mode ultrasound sensor array with sub-pixel accuracy. The advantages of our proposed system over previous techniques are that it is non-invasive, does not require the use of ionizing radiation and can be used conveniently if miniaturized.

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.