Fluoroscopy-Based Surgical Navigation versus Fluoroscopic Guidance to Control Guide Wire Insertion for Osteosynthesis of Femoral Neck Fractures

AbstractBackground and Purpose: Long fluoroscopic times and related radiation exposure are a universal concern when C-arm fluoroscopy is used to guide percutaneous procedures. Fluoroscopy-based surgical navigation has been proposed as an alternative guidance method requiring limited fluoroscopic times to achieve precision. The purpose of this experimental study was to compare fluoroscopy-based surgical navigation with C-arm fluoroscopy for guidance with respect to the precision achieved, the fluoroscopic time, and the resources needed.Material and Methods: 114 guide wires were placed in 38 synthetic bone models using either C-arm fluoroscopy (group A) or fluoroscopy-based surgical navigation (group B) for guidance. Precision of guide wire placement was rated on the basis of an individual CT scan on all fracture models of both groups. The fluoroscopic time, the procedure time, and the number of attempts required to place the guide wires were documented as well.Results: An average fluoroscopic time of 26 s was needed with C-arm fluoroscopy to place three guide wires compared with an average fluoroscopic time of 2 s that was needed when fluoroscopy-based surgical navigation was used for guidance (p < 0.0001). Precision of guide wire placement and procedure times required to place the guide wires did not differ significantly between both groups. The number of attempts required for correct placement was found significantly reduced with fluoroscopy-based surgical navigation when compared with fluoroscopic guidance (p = 0.04).Conclusion: Fluoroscopic times to achieve precision are reduced with fluoroscopy-based surgical navigation compared with C-arm fluoroscopy. The impact of this new technique on minimally invasive, percutaneous procedures has to be evaluated in controlled prospective clinical studies.     

Does Less Invasive Spine Surgery Result in Increased Radiation Exposure? A Systematic Review

Background

Radiation exposure to patients and spine surgeons during spine surgery is expected. The risks of radiation exposure include thyroid cancer, cataracts, and lymphoma. Although imaging techniques facilitate less invasive approaches and improve intraoperative accuracy, they may increase radiation exposure.

Questions/purposes

We performed a systematic review to determine whether (1) radiation exposure differs in open spine procedures compared with less invasive spine procedures; (2) radiation exposure differs in where the surgeon is positioned in relation to the C-arm; and (3) if radiation exposure differs using standard C-arm fluoroscopy or fluoroscopy with computer-assisted navigation.

Methods

A PubMed search was performed from January 1980 to July 2013 for English language articles relating to radiation exposure in spine surgery. Twenty-two relevant articles met inclusion criteria. Level of evidence was assigned on clinical studies. Traditional study quality evaluation of nonclinical studies was not applicable.

Results

There are important risks of radiation exposure in spine surgery to both the surgeon and patient. There is increased radiation exposure in less invasive spine procedures, but the use of protective barriers decreases radiation exposure. Where the surgeon stands in relation to the image source is important. Increasing the distance between the location of the C-arm radiation source and the surgeon, and standing contralateral from the C-arm radiation source, decreases radiation exposure. The use of advanced imaging modalities such as CT or three-dimensional computer-assisted navigation can potentially decrease radiation exposure.

Conclusions

There is increased radiation exposure during less invasive spine surgery, which affects the surgeon, patient, and operating room personnel. Being cognizant of radiation exposure risks, the spine surgeon can potentially minimize radiation risks by optimizing variables such as the use of barriers, knowledge of position, distance from the radiation source, and use of advanced image guidance navigation-assisted technology to minimize radiation exposure. Continued research is important to study the long-term risk of radiation exposure and its relationship to cancer, which remains a major concern and needs further study as the popularity of less invasive spine surgery increases.     

骨科机器人辅助微创精准手术治疗胸腰段骨折的初步经验

目的 比较骨科机器人辅助经皮椎弓根螺钉内固定术治疗胸腰段骨折与传统后路椎弓根螺钉内固定术、C形臂X线机透视导航经皮椎弓根螺钉内固定术的临床疗效,探讨机器人辅助手术治疗胸腰段骨折的微创化与精准化价值。方法 2018年2月—2019年6月,收治无神经症状胸腰段骨折患者52例,18例接受机器人辅助经皮椎弓根螺钉内固定术治疗（机器人组）,15例接受C形臂X线机透视导航经皮椎弓根螺钉内固定术治疗（透视组）,19例接受传统后路椎弓根螺钉内固定术治疗（传统组）。记录并比较3组的手术时间、透视时间、辐射剂量、术中出血量、置钉准确率、卧床时间、住院天数,术前、术后6个月伤椎前缘相对高度及Cobb角,以及术前、术后3 d、术后6个月的疼痛视觉模拟量表（VAS）评分和日本骨科学会（JOA）评分。结果 所有手术顺利完成,未出现手术相关并发症。所有患者随访6~12个月,平均8个月。机器人组和透视组的手术时间、术中出血量、卧床时间、住院天数均少于传统组,差异有统计学意义（P<0.05）;透视组透视时间最长、辐射剂量最大,机器人组透视时间最短、辐射剂量最少,差异有统计学意义（P<0.05）;机器人组置钉准确率高于透视组和传统组,差异有统计学意义（P<0.05）。3组患者术后6个月伤椎前缘相对高度、Cobb角、VAS评分和JOA评分均较术前改善,差异有统计学意义（P<0.05）。3组术前、术后3 d和术后6个月伤椎前缘相对高度、Cobb角及JOA评分差异无统计学意义（P>0.05）;机器人组与透视组术后3 d VAS评分优于传统组且差异有统计学意义（P<0.05）,术前及术后6个月3组VAS评分差异无统计学意义（P>0.05）。结论 机器人辅助经皮内固定术是治疗无神经症状胸腰段骨折的有效方法,具有手术时间短、精度高、创伤小、辐射少、患者术后恢复快等优势,满足适应证时可作为优先选择。     

Accuracy of upper thoracic pedicle screw placement using three-dimensional image guidance

Background contextPedicle screw malposition rates using conventional techniques have been reported to occur with a frequency of 6% to 41%. The upper thoracic spine (T1–T3) is a challenging area for pedicle screw placement secondary to the small size of the pedicles, the inability to visualize this area with lateral fluoroscopy, and significant consequences for malpositioned screws. We describe our experience placing 150 pedicle screws in the T1–T3 levels using three-dimensional (3D) image guidance.PurposeThe aim of this study was to assess the accuracy of 3D image guidance for placing pedicle screws in the first three thoracic vertebrae.Study designThe accuracy of pedicle screw placement in the first three thoracic vertebrae was evaluated using postoperative thin-section computed tomography (CT) scans of the cervicothoracic region.Patient sampleThirty-four patients who underwent cervicothoracic fusion were included.Outcome measuresRadiological investigation with CT scans was performed during the postoperative period.MethodsThirty-four consecutive patients underwent cervicothoracic instrumentation and fusion for a total of 150 pedicle screws placed in the first three thoracic vertebrae. All screws were placed using 3D image guidance. Medical records and postoperative imaging of the cervicothoracic junction for each patient were retrospectively reviewed. An independent radiologist reviewed the placement of the pedicle screws and assessed for pedicle breach. All cortical violations were reported as Grade 1, 0 to 2 mm; Grade 2, 2 to 4 mm; and Grade 3, greater than 4 mm.ResultsOverall, 140 (93.3%) out of 150 screws were contained solely in the desired pedicle. All 10 pedicle violations were Grade 1. The direction of pedicle violation included three medial, four inferior, two superior, and one minor anterolateral vertebral body. No complication occurred as a result of screw placement or the use of image guidance.ConclusionsUpper thoracic pedicle screw placement is technically demanding as a result of variable pedicle anatomy and difficulty with two-dimensional visualization. This study demonstrates the accuracy and reliability of 3D image guidance when placing pedicle screws in this region. Advantages of this technology in our practice include safe and accurate placement of spinal instrumentation with little to no radiation exposure to the surgeon and operating room staff.     

The use of computerized image guidance in lumbar disk arthroplasty

OBJECTIVES: Surgical navigation systems have been increasingly studied and applied in the application of spinal instrumentation. Successful disk arthroplasty requires accurate midline and rotational positioning for optimal function and longevity. A surgical simulation study in human cadaver specimens was done to evaluate and compare the accuracy of standard fluoroscopy, computer-assisted fluoroscopic image guidance, and Iso-C3D image guidance in the placement of lumbar intervertebral disk replacements. METHODS: Lumbar intervertebral disk prostheses were placed using three different image guidance techniques in three human cadaver spine specimens at multiple levels. Postinstrumentation accuracy was assessed with thin-cut computed tomography scans. RESULTS: Intervertebral disk replacements placed using the StealthStation with Iso-C3D were more accurately centered than those placed using the StealthStation with FluoroNav and standard fluoroscopy. Intervertebral disk replacements placed with Iso-C3D and FluoroNav had improved rotational divergence compared with standard fluoroscopy. Iso-C3D and FluoroNav had a smaller interprocedure variance than standard fluoroscopy. These results did not approach statistical significance. Relative to both virtual and standard fluoroscopy, use of the StealthStation with Iso-C3D resulted in improved accuracy in centering the lumbar disk prosthesis in the coronal midline. CONCLUSIONS: The StealthStation with FluoroNav appears to be at least equivalent to standard fluoroscopy and may offer improved accuracy with rotational alignment while minimizing radiation exposure to the surgeon. Surgical guidance systems may offer improved accuracy and less interprocedure variation in the placement of intervertebral disk replacements than standard fluoroscopy. Further study regarding surgical navigation systems for intervertebral disk replacement is warranted.     

Navigation Using Fluoro-CT Technology

Abstract Background: The mobile SIREMOBIL^® Iso-C^3D C-arm is a device that permits the intraoperative three-dimensional (3-D) representation of bony structures (multiplanar reconstructions). Linking to navigation makes it possible to transfer the generated 3-D data directly to the navigation system. The advantages of CT-based navigation with 3-D representation of bone structures are therefore combined with the advantages of inherent navigation with intraoperative imaging. The surgical instrument is immediately displayed in the image, i.e., without any complex manual registration procedure. Patients and Methods: Inherent navigation in 3-D images from the Iso-C^3D was successfully used for the first time in this study in a larger group of patients. 39 patients who intraoperatively underwent successful navigation in Iso-C^3D images were included in the study. Results: 143 drilling procedures were performed in the 39 patients. Pedicle instrumentations took place in 24 of the 39 patients. Eight patients underwent screw placements on the pelvic ring (sacroiliac joint screw placement, placement of anterior column screw, acetabulum osteosynthesis). Four patients underwent retrograde perforation of a talus cyst and filling with autologous cancellous bone, while one patient underwent screw osteosynthesis on the neck of the femur, and two patients underwent placement of an external fixator with a hinge at the elbow joint. One pedicle screw was found to be 2 mm out of position in the spinal group. All other screws/drillings were placed correctly. Additionally, in three patients intraoperative navigation had to be aborted due to hard- or software problems. In these cases, surgery was finished in conventional ways. Conclusion: The results herein for the extremities, spine, and pelvis are very encouraging and portend an advance in safety and quality in the operating room (OR). As compared to the conventional approach and other computer-assisted procedures (CT-based navigation, C-arm-based 2-D navigation), the lowest rate of incorrect placements and the lowest average fluoroscopy time were achieved during the placement of pedicle screws on the spine with Iso-C^3D navigation at a comparable average OR duration. Iso-C^3D navigation supports standardized work procedures in the OR.     

Abstracts Presented at Aps Forty-Fifth Annual Conference Paper Abstracts

Abstract

Background: Image guidance provides additional anatomic information to the surgeon, which may allowmore accurate insertion of spinal implants. Imprecise placement of anterior thoracic screws places the spinalcord and paraspinal structures at risk for injury. Image guidance may afford a safety benefit to patients whenanterior thoracic screws are required in the setting of spinal stabilization after trauma.

Objectives: To compare the accuracy of anterior thoracic screw placement using standard fluoroscopy,computer-assisted fluoroscopic image guidance, lso-C3D image guidance, and electromagnetic fluoroscopicimage guidance.

Study Design: A surgical simulation study in human cadaver spine specimens.

Methods: After an open thoracotomy approach, anterior thoracic screws were placed by experienced spinesurgeons using 4 different image-guided techniques in 4 human cadaver thoracic spines. Screws were placedin the 9th, 1Oth, and 11th thoracic vertebrae of each specimen. The specimens were then examined with thincutcomputed tomography (CT) scans, and with sagittal and coronal reconstructions. Measurements includedthe distance of the screw from the spinal canal, the angle of the screw path in relation to a perpendicular toa line that bisects the spinous process, and the angle of screw divergence from the superior endplate.

Results: There was no evidence of sp inal canal penetrance with any of the image-guided techniques usedto place anterior thoracic vertebral body screws. Screws inserted with standard fluoroscopy tended to aimanterolaterally by 18°. The image-guidance systems allowed more accurateplacement of anterior thoracicscrews in the transverse plane compared with standard fluoroscopy. There was no statistically significantdifference in coronal plane screw angulation (angle of divergence with the superior endplate) between anyof the imaging methods.

Conclusions: Spinal image-guidance systems may allow spine surgeons to place anteriorthoracic screws moreprecisely, particularly in the axial plane. The improved accuracy of spinal implant insertion could ultimately provide a benefit to patient safety, especially in the setting of malaligned vertebral bodies after trauma.     

Image guidance: fluoroscopic navigation

Computer-assisted orthopaedic surgery slowly is making its way into routine orthopaedic practice. Orthopaedic trauma has long been identified as a potential impact area of this new technology. Early experience with three-dimensional (3D) image-guided surgery was promising, but this particular technique was limited by the inability to update the 3D computer model in the operating room after fracture reduction maneuvers or implant placement. Virtual fluoroscopy, or fluoroscopic navigation, became available in 1999 and has proven to be a more versatile technology for fracture treatment. Fluoroscopic navigation systems allow the surgeon to store multiple intraoperative fluoroscopic images on a computer workstation; the position of special optically-tracked surgical instruments or implants then may be virtually overlaid onto the stored images in multiple planes during implant placement. The ability to update images after fracture manipulation now has expanded the application of computer-assisted surgery to any procedures that traditionally have relied on intraoperative C-arm use. In selected applications, this technology has been shown to decrease operative time and intraoperative radiation exposure. The advantages of the new technique of fluoroscopic navigation and its current use in trauma applications will be discussed.     

Intraoperative fluoroscopy,portable X-ray,and CT: patient and operating room personnel radiation exposure in spinal surgery

Background contextIntraoperative imaging is essential in spinal surgery to both determine the correct level and place implants safely. Surgeons have a variety of options: C-arm fluoroscopy (C-arm), portable X-ray (XR) radiography, and portable cone-beam computed tomography (O-arm). Although these modalities have their respective advantages and disadvantages, direct comparison of radiation exposure to either the patient or the operating room (OR) staff has not been made.PurposeTo determine the amount of radiation exposure to patients and OR staff during spine surgery with C-arm, XR, and O-arm.Study designAn experimental model to assess radiation exposure to OR staff and phantom patient during spine surgery.MethodsA plastic phantom was created to emulate patient volume and absorption scattering characteristics of a typical sized adult abdominal volume. Radiation exposure was measured with ion chamber dosimeters to determine entrance phantom and scatter exposures at common positions occupied by OR staff for C-arm, XR, and O-arm in typical image acquisition during spinal surgery.ResultsSingle lateral (LAT)/posterior-anterior entrance patient radiation exposure for C-arm was on average 116/102 mR, single-exposure XR for LAT/anterior-posterior (AP) was 3,435/2,160 mR, and single-exposure O-arm for LAT/AP was 4,360/5,220 mR. O-arm surface exposure LAT/AP was equivalent to 38/41 C-arm and 1.5/2.4 XR exposures. The surgeon and surgeon assistant had higher levels of scatter radiation for C-arm, followed by O-arm and XR. For the LAT C-arm acquisition, a 7.7-fold increase in radiation exposure was measured on the X-ray tube side compared with the detector side. The anesthesiologist scatter radiation level for a single acquisition was highest for O-arm, followed by XR and C-arm. The radiologic technologist scatter radiation level was highest for XR, followed by O-arm and fluoroscopy. Overall radiation exposure to OR staff was less than 4.4 mR for a single acquisition in all modalities.ConclusionsAssessment of radiation risk to the patient and OR staff should be part of the decision for utilization of any specific imaging modality during spinal surgery. This study provides the surgeon with information to better weigh the risks and benefits of each imaging modality.     

Virtual fluoroscopy: computer-assisted fluoroscopic navigation

STUDY DESIGN: In vitro accuracy assessment of a novel virtual fluoroscopy system. OBJECTIVES: To investigate a new technology combining image-guided surgery with C-arm fluoroscopy. SUMMARY OF BACKGROUND DATA: Fluoroscopy is a useful and familiar technology to all musculoskeletal surgeons. Its limitations include radiation exposure to the patient and operating team and the need to reposition the fluoroscope repeatedly to obtain surgical guidance in multiple planes. METHODS: Fluoroscopic images of the lumbar spine of an intact, unembalmed cadaver were obtained, calibrated, and saved to an ). A was used for the sequential insertion of a light-emitting diode-fitted probe into the pedicles of L1-S1 bilaterally. The trajectory of a "virtual tool" corresponding to the tracked tool was overlaid onto the saved fluoroscopic views in real time. Live fluoroscopic images of the inserted pedicle probe were then obtained. Distances between the tips of the virtual and fluoroscopically displayed probes were quantified using the image-guided computer's measurement tool. Trajectory angle differences were measured using a standard goniometer and printed copies of the workstation computer display. The surgeon's radiation exposure was measured using thermolucent dosimeter rings. RESULTS: Excellent correlation between the virtual fluoroscopic images and live fluoroscopy was observed. Mean probe tip error was 0.97 +/- 0.40 mm. Mean trajectory angle difference between the virtual and fluoroscopically displayed probes was 2.7 degrees +/- 0.6 degrees. The thermolucent dosimeter rings measured no detectable radiation exposure for the surgeon. CONCLUSIONS: Virtual fluoroscopy offers several advantages over conventional fluoroscopy while providing acceptable targeting accuracy. It enables a single C-arm to provide real-time, multiplanar procedural guidance. It also dramatically reduces radiation exposure to the patient and surgical team by eliminating the need for repetitive fluoroscopic imaging for tool placement.     

Radiation exposure to the spine surgeon during fluoroscopically assisted pedicle screw insertion

STUDY DESIGN: In vitro study to determine occupational radiation exposure during lumbar fluoroscopy. OBJECTIVES: To assess radiation exposure to the spine surgeon during fluoroscopically assisted thoracolumbar pedicle screw placement. SUMMARY OF BACKGROUND DATA: Occupational radiation exposure during a variety of fluoroscopically assisted musculoskeletal procedures has been previously evaluated. No prior study has assessed fluoroscopy-related radiation exposure to the spine surgeon. METHODS: Bilateral pedicle screw placement (T11-S1) was performed in six cadavers using lateral fluoroscopic imaging. Radiation dose rates to the surgeon's neck, torso, and dominant hand were measured with dosimeter badges and thermolucent dosimeter (TLD) rings. Radiation levels were also quantified at various distances from the dorsal lumbar surface using an ion chamber radiation survey meter. RESULTS: The mean dose rate to the neck was 8.3 mrem/min. The dose rate to the torso was greatest when the surgeon was positioned ipsilateral to the beam source (53.3 mrem/min, compared with 2.2 mrem/min on the contralateral side). The average hand dose rate was 58.2 mrem/min. A significant increase in hand dose rate was associated with placement of screws ipsilateral to the beam source (P = 0.0005) and larger specimens (P = 0.0007). Radiation levels significantly decreased as distance from the beam source and dorsal body surface increased. The greatest levels of radiation were noted on the side where the primary radiograph beam entered the cadaver. CONCLUSION: Fluoroscopically assisted thoracolumbar pedicle screw placement exposes the spine surgeon to significantly greater radiation levels than other, nonspinal musculoskeletal procedures that involve the use of a fluoroscope. In fact, dose rates are up to 10-12 times greater. Spine surgeons performing fluoroscopically assisted thoracolumbar procedures should monitor their annual radiation exposure. Measures to reduce radiation exposure and surgeon awareness of high-exposure body and hand positions are certainly called for.     

Accuracy of fluoroscopic navigation of pedicle screws. CT-based evaluation of bone screw placement

While the advantages of C-arm navigation in computer-assisted spine surgery are obvious, the accuracy of pedicle screw placement with virtual fluoroscopy still needs to be verified. The C-arm-based ION system (Medtronic Sofamor Danek) was used to navigate pedicle screw insertion in patients undergoing spinal surgery for various conditions. In a prospective study, a total of 160 screws were inserted in the first 30 consecutive patients since introduction of the system at our institution: 54 at the thoracic spine (highest level: TH4) and 106 at the lumbar spine. Computed tomography (CT) scans were performed postoperatively by two independent radiologists to control the accuracy of screw placement at the level of the pedicles after reconstruction of axial images according to Laine et al. The comparison of the calculated accuracy rate of pedicle screw placement using virtual fluoroscopy with reported results achieved with CT-based navigation shows similar results for virtual fluoroscopy and a remarkable increase of accuracy in comparison to reports on conventional pedicle screw placement.     

CT、C臂机联合导引下椎体成形术治疗椎体压缩性骨折

目的探讨CT、C臂机联合导引下椎体成形术（PVP）治疗压缩性骨折的效果及穿刺方法。方法接受PVP治疗的181例压缩性骨折患者的207个椎体进入研究。治疗在CT、C臂机联合导引下进行,经单侧椎弓根斜向进入椎体中央前1/3,注入骨水泥。结果全部椎体完成PVP,患者无严重并发症发生。术后随访有效率95.58%。结论CT、C臂机联合导引下PVP安全、有效。     

Minimally invasive percutaneous transpedicular screw fixation: increased accuracy and reduced radiation exposure by means of a novel electromagnetic navigation system

Background  

Minimally invasive percutaneous pedicle screw instrumentation methods may increase the need for intraoperative fluoroscopy, resulting in excessive radiation exposure for the patient, surgeon, and support staff. Electromagnetic field (EMF)-based navigation may aid more accurate placement of percutaneous pedicle screws while reducing fluoroscopic exposure. We compared the accuracy, time of insertion, and radiation exposure of EMF with traditional fluoroscopic percutaneous pedicle screw placement.     

Fluoroscopy-based percutaneous posterior screw placement in the lateral position using the tunnel view technique: technical note

Purpose

Lumbar fusion using lateral single position surgery (LSPS) gained popularity during the last few years. While prone percutaneous pedicle screw placement is well described, placing percutaneous pedicle screws with the patient in the lateral position is considered the most complicated part of LSPS. In this article we describe the fluoroscopy navigated technique for lateral percutaneous screw placement using the tunnel view technique.

Methods

The radiologic background and principles of the tunnel view technique are described. In addition, the special positioning of the patient, the C-arm and the surgical technique is discussed in detail.

Results

This technique is used as the standard for percutaneous screw placement in the prone or lateral positions in our department since 2017. Since the introduction of this technique we have had 0% reoperation rate for symptomatic malpositioned pedicle screws.

Conclusion

The tunnel view technique simplifies pedicle screw placement while allowing for permanent observation of pedicle walls and the superior joint surface during placement of the Jamshidi needle. It also allows for confirmation of intrapedicular position of the screw after its implantation. This technique is safe and feasible in our clinical experience.

     

Utility of computerized isocentric fluoroscopy for minimally invasive spinal surgical techniques

OBJECTIVE: The purpose of this study was to prospectively evaluate the clinical utility and accuracy of intraoperative three-dimensional fluoroscopy as an adjunct for the placement of a complex spinal instrumentation. METHODS: The Siemens Iso-C three-dimensional fluoroscopy unit in the combination with the Stealth Treon computer volumetric navigational system was used. A total of 279 spinal instrumentation screws or transpedicular cannulations were performed in 69 patients. Accuracy, operative time, and amount of fluoroscopy utilization time were assessed for transforaminal lumbar interbody fusion (TLIF) and kyphoplasty cases. RESULTS: Only 4 percutaneous transpedicular lumbar screws out of 265 total (1.5%) were malpositioned. Average operative time for TLIF cases was 185 minutes (range 114-311 minutes) for one-level and 292.6 minutes (range 173-390 minutes) for two-level procedures. Biplanar fluoroscopy utilization time was 93 seconds (range 27-280 seconds) for one-level procedures and 216 seconds (range 80-388 seconds) for two-level procedures. Average surgery duration for kyphoplasty was 60 minutes (range 36-79 minutes) for one-level procedures and 68.5 minutes (range 65-75 minutes) for two-level cases. Biplanar fluoroscopy utilization time was 41.3 seconds per case (range 25-62 seconds). CONCLUSIONS: Use of intraoperative three-dimensional fluoroscopy for image guidance in minimally invasive complex spinal instrumentation procedures is feasible and safe. This technique provides excellent visualization of three-dimensional relationships. This potentially results in improved accuracy of screw positioning and the ability to detect misplaced screws prior to wound closure. This technique also potentially results in a significant reduction in radiation exposure for both the patient and the staff.     

Radiographic criteria for placement of translaminar facet screws

Background contextScrew fixation of the facet joint has been reported to stabilize the lumbar spine and facilitate spinal fusion. Accurate placement of translaminar facet screws (TLFSs) requires identification of the posterior spinal elements, and the facet joints in particular, which may be facilitated by intra-operative fluoroscopy.PurposeThe purpose of this study was to define the radiographic parameters that will allow for successful placement of TLFSs.Study designEighteen TLFSs were placed in three human cadaver spines using fluoroscopic guidance, with screws placed from L3–L4 to L5–S1 bilaterally. After screw placement, the spines were dissected and examined for the accuracy of screw placement.MethodsIn the first cadaver spine, TLFSs were placed with direct visualization of the posterior lumbar spine, during which a fluoroscopic image intensifier was used to define the appropriate radiographic parameters for safe placement of the screws. Bilateral TLFSs were then placed percutaneously using the radiographic parameters developed, after which the spines were dissected to examine the positions of the screws.ResultsThe radiographic views identified to achieve proper TLFS placement were a true lateral, anteroposterior (AP), a 45-degree oblique and an AP view with the X-ray beam at a 30- to 45-degree cephalad angle (“spinal outlet” view). Using these views and the defined radiographic criteria, proper positioning of percutaneously placed TLFSs was achieved, with no spinal canal breaches found.ConclusionsThis study defines intra-operative radiographic criteria that will assist in placement of TLFSs. The use of this technique may allow for screw placement with less extensive exposure of the posterior spine.     

The utility of mini C-arm in the fixation of unstable paediatric supracondylar humeral fractures

BackgroundPediatric supracondylar humerus fractures have traditionally been reduced and fixed with conventional C-arm (CCA) fluoroscopy guidance. With the increase in popularity of the newer mini C-arm (MCA) system within other fields of surgery due to its ease of use and lower radiation emission, the same adoption should be explored in pediatric orthopedic surgeries. The purpose of this study is to compare the MCA and CCA primarily in reduction and fixation outcomes and secondarily in other perioperative parameters.MethodsRetrospective analysis of 193 patients who underwent surgical fixation for displaced supracondylar humerus fractures. 44 and 149 cases were performed with the MCA and CCA respectively. Baumann’s angle and the intersection of anterior humeral line (AHL) were assessed on postoperative anterior posterior and lateral radiographs and adequate reduction was defined by an angle between 64 and 81˚, and AHL intersecting middle third of the capitellum. Surgical time, fluoroscopy duration, number of images and radiation exposure were obtained from the surgical notes.ResultsAmongst the CCA cases, there were greater satisfactory coronal plane reduction (p < 0.05), while no difference in sagittal plane accuracy (p > 0.05) was seen. In MCA group, longer surgical (p < 0.05) and fluoroscopy times (p < 0.05), and greater number of shots (p < 0.05) was noted. However overall radiation exposure in the MCA group was still lower (p < 0.05).ConclusionThe MCA system is potentially less accurate in coronal plane reduction and more challenging to use. However, pitfalls can easily be avoided. Usage should be advocated as overall radiation exposure can be reduced.Level of evidenceLevel III retrospective comparative study.     

Accuracy of patient-specific template-guided vs. free-hand fluoroscopically controlled pedicle screw placement in the thoracic and lumbar spine: a randomized cadaveric study

Purpose

Dorsal spinal instrumentation with pedicle screw constructs is considered the gold standard for numerous spinal pathologies. Screw misplacement is biomechanically disadvantageous and may create severe complications. The aim of this study was to assess the accuracy of patient-specific template-guided pedicle screw placement in the thoracic and lumbar spine compared to the free-hand technique with fluoroscopy.

Methods

Patient-specific targeting guides were used for pedicle screw placement from Th2–L5 in three cadaveric specimens by three surgeons with different experience levels. Instrumentation for each side and level was randomized (template-guided vs. free-hand). Accuracy was assessed by computed tomography (CT), considering perforations of <2 mm as acceptable (safe zone). Time efficiency, radiation exposure and dependencies on surgical experience were compared between the two techniques.

Results

96 screws were inserted with an equal distribution of 48 screws (50 %) in each group. 58 % (n = 28) of template-guided (without fluoroscopy) vs. 44 % (n = 21) of free-hand screws (with fluoroscopy) were fully contained within the pedicle (p = 0.153). 97.9 % (n = 47) of template-guided vs. 81.3 % (n = 39) of free-hand screws were within the 2 mm safe zone (p = 0.008). The mean time for instrumentation per level was 01:14 ± 00:37 for the template-guided vs. 01:40 ± 00:59 min for the free-hand technique (p = 0.013), respectively. Increased radiation exposure was highly associated with lesser experience of the surgeon with the free-hand technique.

Conclusions

In a cadaver model, template-guided pedicle screw placement is faster considering intraoperative instrumentation time, has a higher accuracy particularly in the thoracic spine and creates less intraoperative radiation exposure compared to the free-hand technique.