eO
RIGINAL
ARTICLE
Radiation Exposure to Surgeon in Minimally Invasive Transforaminal Lumbar Interbody Fusion With Novel Spinal Locators Guoxin Fan, MD,* Qingsong Fu, MD,w Guangfei Gu, MD,* Hailong Zhang, MD,* Xiaofei Guan, MD,* Lei Zhang, MD,* Xin Gu, MD,* and Shisheng He, MD*
Study Design: A prospective study.
36.42% for the gonad gland (unprotected), 59.42% for the eye (protected), and 59.70% for the eye (unprotected).
Objective: To further investigate the implication of our surface locator and intradermal locator to reduce the radiation exposure to surgeons in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery.
Conclusion: The study indicated that radiation exposure to the surgeon would be effectively reduced in MIS-TLIF using our surface locator and intradermal locator, and it could be another practical choice for radiation-minimizing strategy.
Summary of Background Data: Our previous studies published in the journal have introduced our novel spinal locators effectively minimizing fluoroscopic time during minimally invasive spinal surgery.
Key Words: radiation exposure, transforaminal lumbar interbody fusion, minimally invasive, G-arm fluoroscopy, spinal locators
Methods: Twenty patients underwent MIS-TLIF surgery with G-arm fluoroscopy from January 2013 to June 2013. There were 10 patients in group A who underwent standard MIS-TLIF using our spinal locators, and the other 10 in group B underwent conventional MIS-TLIF without spinal locators. The radiation dosages to the arm, the finger, the whole body, thyroid gland, gonad gland, and the eye of the surgeon were measured by thermoluminescence badges for both groups. Results: All 20 patients (9 male, 11 female), aged from 48 to 77 years old, successfully underwent the surgery. The operation time was 171.20 ± 10.28 minutes for group A and 189.80 ± 11.99 minutes for group B. The fluoroscopy time was 49.60 ± 7.32 seconds for group A and 68.40 ± 7.62 seconds for group B, hence a reduction of 27.49% was observed. There was no correlation between operation time and exposure time for group A or group B. The radiation reduction was 35.28% for the arm, 17.95% for the finger, 45.23% for the whole body, 53.62% for the thyroid gland (protected), 52.44% for the thyroid gland (unprotected), 44% for gonad gland (protected),
Received for publication February 15, 2014; accepted October 16, 2014. From the *Department of Orthopaedics, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, Shanghai; and wDepartment of Orthopaedics, Ningbo No. 2 Hospital, Ningbo, China. G.F. and Q.F. contributed equally. G.F. and Q.F. designed the study and wrote the manuscript. G.G., H.Z., and X. Gu were involved in the experiment. X. Guang and L.Z. gave critical points. S.H. approved the final version. The authors declare no conflict of interest. Reprints: Shisheng He, MD, Department of Orthopaedics, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Yanchang Road, Shanghai 200072, China (e-mail: hss7418@ aliyun.com). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 3, April 2015
(J Spinal Disord Tech 2015;28:E173–E180)
L
umbar fusion is a common surgical procedure for treating degenerative spinal disease in clinical practice.1 For the past 3 decades, open transforaminal lumbar interbody fusion (TLIF) has been used for a variety of degenerative lumbar disorders.2 Nevertheless, like other open posterior procedures, one of the drawbacks of open TLIF is the iatrogenic lumbar soft-tissue injury, which is supposed to relate with postoperative pain, long recovery time, and impaired spinal function.3 For the past decades, spine surgery has witnessed a trend toward increasing numbers of minimally invasive procedures.4 Compared with the traditional lumbar spine surgery, minimally invasive TLIF (MIS-TLIF) has merits of small incision, little lumbosacral muscle dissection scope, less bleeding, rapid recovery, etc.5 It has been considered to be a practical method of treating lumbar degenerative disease with confirmed curative effect.6,7 However, minimally invasive surgery requires imaging equipment to position the operation section under intraoperative fluoroscopy, which inevitably leads to high risk of radiation damage, such as the local tissue injury, cataracts, leukemia, skin soft-tissue tumor, etc.8–11 In recent years, the popularity of MIS-TLIF has increased around the world.1–3 However, the radiation exposure to the operation personnel was not fully investigated. The purpose of this study is to investigate the advantages of our surface locator and intradermal locator in reducing the radiation exposure to surgeons in the MIS-TILF surgery. To the best of our knowledge, this is the first study to quantify the radiation exposure to specific sensitive organs of the surgeon with the advantages www.jspinaldisorders.com |
E173
J Spinal Disord Tech
Fan et al
of surface locator and intradermal locator in the MISTILF surgery in reducing radiation exposure. We also reviewed the published literatures to optimize the strategy of reducing radiation exposure to surgeons.
MATERIALS AND METHODS General Information This prospective cohort study was approved by local Committee of Medical Ethics and the institutional review boards of the authors’ institutions. A total of 20 patients, 9 males and 11 females, were admitted for MISTILF from January 2013 to June 2013. Patients admitted on odd-numbered days were assigned to group A with the use of surface locator and intradermal locator, and those admitted on even-numbered days were assigned to the group B without the use of surface locator or intradermal locator. Of all the 20 patients, 10 patients were assigned to group A and the other 10 patients were assigned to group B. The inclusion criterion was the single segment disk herniation combined with lumbar instability. All the 20 patients were operated by the only 1 experienced surgeon using the standard technique of percutaneous pedicle screw reduction and fixation, spinal canal decompression and intervertebral disk excision, and intervertebral bone graft fusion. Every operation required the surgeon to be dressed in the leaded clothing, collar, and lead masks, and 3 thermoluminescence badges (Panasonic, Japan) were attached to the right hand, right forearm, orbit, thyroid region, left chest, and gonad region. In the same position outside the lead protection, another 3 thermoluminescence badges were also attached and the mean radiation dosage was calculated from each of the 3 badges. Estimated whole-body effective dose equivalent (HE) was approximated by the formula: HEE1.5 H1+0.04 H2, where H1 is the dose equivalent recorded by the dosimeter under the lead apron and H2 is the exposure measured by the collar dosimeter unprotected by lead.12 Dosimeters were transported from and to the operating theater in a leaded box.
Surface Locator and Intradermal Locator The surface locator is made up of radiopaque material (such as stainless steel or titanium alloy) and consists of 19 horizontal and 4 longitudinal rods (Fig. 1A). Each horizontal rod is about 9 cm, whereas each longitudinal rod is about 18 cm. Different marks are made on the rods with a 1 cm space between each horizontal rod. Stamping die and 1-step forming technology are applied to manufacture the locator. The surface locator was also well discussed in our previous studies.13,14 The intradermal locator is a bullet-shaped device with 7 tubes, 12 cm in length and 1.5 cm in diameter. To avoid artifacts on radiograph, the main component material is plastics (Fig. 1B). The device is also allowed for repeated use after sterilization with plasma. The intradermal locator was also documented in details in our previous publication.15
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Volume 28, Number 3, April 2015
Surgical Methods Preoperative Preparation All the patients underwent general anesthesia before MIS-TLIF surgery. G-arm x-ray machine (Biplanar 500e; Swemac Medical Appliances AB, Sweden) was prepared. METRx Quadrant System, percutaneous pedicle screw (Sextant; Medtronic, Minneapotics, MN), surface locator, and intradermal locator were prepared before the surgery.
Surgery Under general anesthesia, the patient was evenly placed in a prone position on a radiolucent operating table. The waist bowed a bit, making the intervertebral space open and expanding Kambin triangle. The iliac crests were preoperatively palpated, and lines connecting to the uppermost margin of both iliac crests were marked. For group A, our self-made surface locator was then placed on the patient’s back with the central part in the midline over the approximate spinal levels of interest and was fixed with an adhesive plaster (Fig. 2A). Under Garm fluoroscopy, the targeted levels were confirmed according to the different markers on the locator. On the basis of the spatial relationship, the intervertebral spaces and the pedicle positions were marked on the body surface (Fig. 2B). An incision was planned by connecting a line between the outer portions of the both ends pedicles (approximately 3.0 cm off midline). Then a skin incision about 3.0 to 4.0 cm was made on the more symptomatic side or more severe pathology side according to the imaging. The paravertebral muscles were split and retracted laterally to the outer edge of the facet joint, and the zygopophysis was confirmed. Expansion tube was then inserted and Quadrant System was placed step by step. X-ray examination was repeated to confirm the target segments and the placement of Quadrant System. The procedures of decompression and pedicle screw placement with intradermal locator are well described in our recent published study (Fig. 3A).13,15 Briefly, the intradermal locator device was placed through the channel and put onto the target pedicle. After K-wires were inserted through the tubes in the locator, fluoroscopy images were obtained by remote control of the C-arm fluoroscopy equipment. At the upper outer quadrant of the pedicle site, the most ideal K-wire could be confirmed and used to insert the drill and guidewire. If the initial position of the locator was unsatisfactory, the K-wire closest to the pedicle site was chosen and the locator was revolved around it to obtain the most ideal K-wire position. The remaining procedures were followed exactly as in the conventional methods mentioned above (Fig. 3B). For group B, patients underwent the conventional method which was well described in our previous study.13 Briefly, a 1 to 2 cm lateral skin incision was made to insert the Jamshidi needle at an appropriate angle into the pedicle depending on the depth of the tissue between the skin and pedicle. Using the Jamshidi needle, docked against the bone at the junction of the base of the transverse process and facet joint, the anteroposterior and Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 3, April 2015
Radiation Exposure in MIS-TLIF
FIGURE 1. Picture of real products of our spinal locators. A, The surface locator consists of 19 horizontal rods and 4 longitudinal rods. Each horizontal rod is about 9 cm, whereas each longitudinal rod is about 18 cm. B, The intradermal locator was a cylindershaped device. The diameter and length of the device were 1.5 and 12 cm, respectively.
lateral images were obtained to localize the needle tip. The needle was then gently tapped with a mallet to engage the tip in the bone. Fluoroscopy was intermittently used to confirm the direction and the depth to make sure that the needle remained lateral to the medial pedicle wall. As the needle advanced to cross the pedicle center, a guidewire was inserted through the cannula into the pedicle. The cannula was then carefully removed, leaving the guidewire in place. The fascia and muscle were dilated to allow screw placement. After preparation of the pedicle with a tap using cannulated taps, the percutaneous cannulated pedicle screw-rod system (Sextant; Medtronic Sofamor Danek, Memphis, TN) was placed.
Data Collection Intraoperatively, we recorded the tube voltage and tube current of G-arm x-ray machine, exposure time of Garm x-ray machine, and the duration of each operation. The thermoluminescence badges were measured by semiautomatic type thermoluminescent dosimeter (RADOS Company, Mirion Group San Francisco Bay area, CA) to assess the radiation exposure. Readings from dosimeters Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
representing the arm, finger, whole body, thyroid gland, gonad gland, and eye exposure were put in perspective of guidelines for occupational radiation exposure limits to report the annual number of MIS-TLIF cases a surgeon might perform before exceeding recommended dose limits for planned exposure situations as defined by the International Commission on Radiological Protection (ICRP).
Data Analysis Statistical analysis was performed with SPSS version 17.0. Descriptive statistics were calculated in terms of means and SDs for continuous variables and frequencies and percentages for categorical variables. The difference of radiation dosage from group A and group B were compared by the Student t test (with P < 0.05 as statistical significance) and the correlation between operation time and exposure time was also analyzed.
RESULTS Demographic data and clinical characteristics are summarized in Table 1. All 20 patients (9 male, 11 female), aged from 48 to 77 years old, successfully underwent www.jspinaldisorders.com |
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Volume 28, Number 3, April 2015
FIGURE 2. The use of surface locator in minimally invasive transforaminal lumbar interbody fusion. A, Surface locator was placed on the patient’s back with the central part in the midline over the approximate spinal levels of interest and was fixed with an adhesive plaster. B, On the basis of spatial relationship, the intervertebral spaces and the pedicle positions were marked on the body surface.
MIS-TLIF. The average age was 61.9 years old for group A, whereas it was 66 years old for group B, and the difference was with statistical significance. The weight was 63.8 ± 11.24 kg for group A and 59.5 ± 9.07 kg for group B, and the body mass index was 21.95 ± 2.39 kg/m2 for group A and 21.7 ± 1.56 kg/m2 for group B. The voltage of G-arm x-ray machine for anteroposterior imaging was 74.4 ± 3.60 V for group A and 74.8 ± 3.33 V for group B, and the voltage for lateral imaging was 104.1 ± 4.28 V for group A and 103.4 ± 4.77 V for group B. The difference of voltage for anteroposterior imaging between group A and group B was with statistical significance. The current of Garm x-ray machine for anteroposterior imaging was 2.6 ± 0.24 mA for group A and 2.61 ± 0.28 mA for group B, and the current for lateral imaging was 3.48 ± 0.33 mA for group A and 3.49 ± 0.20 mA for group B. For surgery segment, there were 1 case for L3/L4, 5 cases for L4/L5, and 4 cases for L5/S1 in group A and 1 case for L3/L4, 5 cases for L4/L5, and 4 cases for L5/S1 in group B. The operation time was 171.20 ± 10.28 minutes for group A and 189.80 ± 11.99 minutes for group B. The fluoroscopy time was 49.60 ± 7.32 seconds for group A and 68.40 ± 7.62 seconds for group B, hence a reduction of 27.49% was observed. There was no correlation between operation time and exposure time for group A or group B (Fig. 4). The radiation dosage for different parts of the surgeon is listed in Table 2. The radiation exposure to the arm of the surgeon was 0.0587 ± 0.0175 mSv for group A and 0.0907 ± 0.0291 mSv for group B, and for the finger the
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radiation dosage was 0.0946 ± 0.0438 mSv for group A and 0.1153 ± 0.0282 mSv for group B. For group A, the radiation dosage to the left chest was 0.0042 ± 0.0015 mSv under lead apron (protected) and 0.0356 ± 0.0154 mSv above the lead apron (unprotected); for group B, the radiation dosage to the left chest was 0.0077 ± 0.0032 mSv with lead apron protected and 0.0638 ± 0.0195 mSv without lead apron protected. With thyroid shield protected, the radiation dosage to the thyroid gland was 0.0032 ± 0.0012 mSv for group A and 0.0069 ± 0.0031 mSv for group B, whereas it was 0.0273 ± 0.0100 mSv for group A and 0.0574 ± 0.0178 mSv for group B without protection. For the gonad gland, the radiation dosages were 0.0042 ± 0.0014 mSv (protected) and 0.0391 ± 0.0144 mSv (unprotected) for group A, 0.0075 ± 0.0021 mSv (protected) and 0.0615 ± 0.0227 mSv (unprotected) for group B. Under lead mask, the radiation exposure to the eye was 0.0028 ± 0.0017 mSv for group A and 0.0069 ± 0.0027 mSv for group B; above the lead mask, the radiation exposure to the eye was 0.0216 ± 0.0107 mSv for group A and 0.0536 ± 0.0164 mSv for group B. The differences of radiation exposure to all detective organs or tissues between group A and group B were with statistical significance, respectively. The radiation reduction observed was 35.28% for the arm, 17.95% for the finger, 45.23% for the whole body, 53.62% for the thyroid gland (protected), 52.44% for the thyroid gland (unprotected), 44% for gonad gland (protected), 36.42% for the gonad gland (unprotected), 59.42% for the eye (protected), and 59.70% for the eye (unprotected). Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 3, April 2015
Radiation Exposure in MIS-TLIF
FIGURE 3. The use of intradermal locator in minimally invasive transforaminal lumbar interbody fusion. A, Insertion and fixation of intradermal locator in the pedicle area after the dissection of the skin and thoracolumbar fascia followed by separation of the soft tissue. B, The proper channel in intradermal locator was chosen based on fluoroscopic images.
DISCUSSION For the past few years, MIS-TLIF has been adopted by more and more surgeons due to its numerous advantages. However, the minimally invasive process requires the fluoroscopy equipment for navigation (eg, G-arm x-ray machine), hence the amount of radiation exposure to surgeons and staff should be quantified.16 In this prospective study, we found the use of surface and intradermal locators to significantly reduce radiation exposure to the surgeon. The radiation reduction observed was 35.28% for the arm, 17.95% for the finger, 45.23% for the whole body, 53.62% for the thyroid gland (protected), 52.44% for the thyroid
gland (unprotected), 44% for gonad gland (protected), 36.42% for the gonad gland (unprotected), 59.42% for the eye (protected), and 59.70% for the eye (unprotected). The operation time was 171.20 ± 10.28 minutes for group A and 189.80 ± 11.99 minutes for group B. The fluoroscopy time was 49.60 ± 7.32 seconds for group A and 68.40 ± 7.62 seconds for group B. There was no correlation between operation time and exposure time for group A or group B, which was consistent with the previous study.16 Radiation exposure has often been associated with cardiovascular disease, tumor, cataract, etc.,11,17–19 which was classified as deterministic (ie, hair loss, skin burns,
TABLE 1. Demographic Data and Clinical Characteristics Demographic Data Sex (male:female) Age (y) Weight (kg) Body mass index (kg/m2) Voltage for anteroposterior imaging (V) Voltage for lateral imaging (V) Current for anteroposterior imaging (mA) Current for lateral imaging (mA) Surgery segment (L3/L4:L4/L5:L5/S1)
Copyright
r
Group A (n = 10)
Group B (n = 10)
P
5:5 61.9 ± 7.36 63.8 ± 11.24 21.95 ± 2.39 74.4 ± 3.60 104.1 ± 4.28 2.6 ± 0.24 3.48 ± 0.33 1:5:4
4:6 66 ± 10.76 59.5 ± 9.07 21.7 ± 1.56 74.8 ± 3.33 103.4 ± 4.77 2.61 ± 0.28 3.49 ± 0.20 1:5:4
— < 0.05 > 0.05 > 0.05 < 0.05 > 0.05 > 0.05 > 0.05 —
2014 Wolters Kluwer Health, Inc. All rights reserved.
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Volume 28, Number 3, April 2015
TABLE 3. Yearly Occupational Exposure Limit Recommended by the International Commission on Radiation Protection Yearly Occupational Exposure Limit (mSv)
Organs Extremities Skin Thyroid gland Eye Whole body Other tissues or organs
500.0000 500.0000 300.0000 150 (20)* 50.0000 500.0000
*Means the most recently updated yearly occupational exposure limit recommended by ICRP was 20mSv for the eye.
FIGURE 4. The correlation between operation time and exposure time. A, There was no correlation between operation time and exposure time for group A. B, There was no correlation between operation time and exposure time for group B.
nausea, and cataract) and stochastic effects (ie, carcinogenesis and teratogenesis).20,21 The organs sensitive to radiation include the gonads, bone marrow, breast, cornea, gastrointestinal tract, lung, and thyroid and concern has been expressed regarding the difference of the susceptibilities of organs in human body.21 In an attempt to minimize sequelae of occupational exposure to ionizing radiation, the ICRP has published the maximum, yearly, occupational exposure limit for all sensitive organs or tissues (Table 3).12,20 For medical personnel, it has been recommended that the exposure should not exceed 20 mSv per year for the whole body. The maximum duration for which this level of exposure is allowed is 5 years, hence a maximal total body exposure over 5 years
should not exceed 100 mSv. The maximum permissible exposure recommended is 150 mSv for the eye and 500 mSv for the skin as well as the extremities. According to the updated recommendation, the radiation exposure to the eye should not exceed 20 mSv per year.22–24 These values can be used for the subset of population whose specific organs are exposed to radiation rather than the whole body. Previous studies have identified fluoroscopy as a safe procedure which maintains exposure within the ICRP-recommended annual limits.25–27 With the radiation dose of specific sensitive organs and updated occupational exposure limit values from ICRP, we could calculate the maximum number of MIS-TLIF surgeries one surgeon could perform per year without exceeding the recommended exposure. Using our spinal locators, the maximum number of MIS-TLIF surgery for 1 surgeon per year was 8517 for the arm, 5285 for the finger, 6473 for the whole body, 7142 for the eye (protected), and 952 for the eye (unprotected). That was to say, one surgeon could only operate no more than 952 MIS-TLIF surgeries without wearing lead mask but using our spinal locators per year. If the surgeon wear lead mask to protect the eyes, he could only operate no more than 5285 MIS-TLIF surgeries using our spinal locators. Without using our spinal locators, the maximum number of MISTLIF surgery for 1 surgeon per year was 5512 for the arm, 4336 for the finger, 3545 for the whole body, 2898 for the eye (protected), and 373 for the eye (unprotected). That was to say, one surgeon could only operate
RIGINAL
ARTICLE
Radiation Exposure to Surgeon in Minimally Invasive Transforaminal Lumbar Interbody Fusion With Novel Spinal Locators Guoxin Fan, MD,* Qingsong Fu, MD,w Guangfei Gu, MD,* Hailong Zhang, MD,* Xiaofei Guan, MD,* Lei Zhang, MD,* Xin Gu, MD,* and Shisheng He, MD*
Study Design: A prospective study.
36.42% for the gonad gland (unprotected), 59.42% for the eye (protected), and 59.70% for the eye (unprotected).
Objective: To further investigate the implication of our surface locator and intradermal locator to reduce the radiation exposure to surgeons in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery.
Conclusion: The study indicated that radiation exposure to the surgeon would be effectively reduced in MIS-TLIF using our surface locator and intradermal locator, and it could be another practical choice for radiation-minimizing strategy.
Summary of Background Data: Our previous studies published in the journal have introduced our novel spinal locators effectively minimizing fluoroscopic time during minimally invasive spinal surgery.
Key Words: radiation exposure, transforaminal lumbar interbody fusion, minimally invasive, G-arm fluoroscopy, spinal locators
Methods: Twenty patients underwent MIS-TLIF surgery with G-arm fluoroscopy from January 2013 to June 2013. There were 10 patients in group A who underwent standard MIS-TLIF using our spinal locators, and the other 10 in group B underwent conventional MIS-TLIF without spinal locators. The radiation dosages to the arm, the finger, the whole body, thyroid gland, gonad gland, and the eye of the surgeon were measured by thermoluminescence badges for both groups. Results: All 20 patients (9 male, 11 female), aged from 48 to 77 years old, successfully underwent the surgery. The operation time was 171.20 ± 10.28 minutes for group A and 189.80 ± 11.99 minutes for group B. The fluoroscopy time was 49.60 ± 7.32 seconds for group A and 68.40 ± 7.62 seconds for group B, hence a reduction of 27.49% was observed. There was no correlation between operation time and exposure time for group A or group B. The radiation reduction was 35.28% for the arm, 17.95% for the finger, 45.23% for the whole body, 53.62% for the thyroid gland (protected), 52.44% for the thyroid gland (unprotected), 44% for gonad gland (protected),
Received for publication February 15, 2014; accepted October 16, 2014. From the *Department of Orthopaedics, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, Shanghai; and wDepartment of Orthopaedics, Ningbo No. 2 Hospital, Ningbo, China. G.F. and Q.F. contributed equally. G.F. and Q.F. designed the study and wrote the manuscript. G.G., H.Z., and X. Gu were involved in the experiment. X. Guang and L.Z. gave critical points. S.H. approved the final version. The authors declare no conflict of interest. Reprints: Shisheng He, MD, Department of Orthopaedics, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Yanchang Road, Shanghai 200072, China (e-mail: hss7418@ aliyun.com). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 3, April 2015
(J Spinal Disord Tech 2015;28:E173–E180)
L
umbar fusion is a common surgical procedure for treating degenerative spinal disease in clinical practice.1 For the past 3 decades, open transforaminal lumbar interbody fusion (TLIF) has been used for a variety of degenerative lumbar disorders.2 Nevertheless, like other open posterior procedures, one of the drawbacks of open TLIF is the iatrogenic lumbar soft-tissue injury, which is supposed to relate with postoperative pain, long recovery time, and impaired spinal function.3 For the past decades, spine surgery has witnessed a trend toward increasing numbers of minimally invasive procedures.4 Compared with the traditional lumbar spine surgery, minimally invasive TLIF (MIS-TLIF) has merits of small incision, little lumbosacral muscle dissection scope, less bleeding, rapid recovery, etc.5 It has been considered to be a practical method of treating lumbar degenerative disease with confirmed curative effect.6,7 However, minimally invasive surgery requires imaging equipment to position the operation section under intraoperative fluoroscopy, which inevitably leads to high risk of radiation damage, such as the local tissue injury, cataracts, leukemia, skin soft-tissue tumor, etc.8–11 In recent years, the popularity of MIS-TLIF has increased around the world.1–3 However, the radiation exposure to the operation personnel was not fully investigated. The purpose of this study is to investigate the advantages of our surface locator and intradermal locator in reducing the radiation exposure to surgeons in the MIS-TILF surgery. To the best of our knowledge, this is the first study to quantify the radiation exposure to specific sensitive organs of the surgeon with the advantages www.jspinaldisorders.com |
E173
J Spinal Disord Tech
Fan et al
of surface locator and intradermal locator in the MISTILF surgery in reducing radiation exposure. We also reviewed the published literatures to optimize the strategy of reducing radiation exposure to surgeons.
MATERIALS AND METHODS General Information This prospective cohort study was approved by local Committee of Medical Ethics and the institutional review boards of the authors’ institutions. A total of 20 patients, 9 males and 11 females, were admitted for MISTILF from January 2013 to June 2013. Patients admitted on odd-numbered days were assigned to group A with the use of surface locator and intradermal locator, and those admitted on even-numbered days were assigned to the group B without the use of surface locator or intradermal locator. Of all the 20 patients, 10 patients were assigned to group A and the other 10 patients were assigned to group B. The inclusion criterion was the single segment disk herniation combined with lumbar instability. All the 20 patients were operated by the only 1 experienced surgeon using the standard technique of percutaneous pedicle screw reduction and fixation, spinal canal decompression and intervertebral disk excision, and intervertebral bone graft fusion. Every operation required the surgeon to be dressed in the leaded clothing, collar, and lead masks, and 3 thermoluminescence badges (Panasonic, Japan) were attached to the right hand, right forearm, orbit, thyroid region, left chest, and gonad region. In the same position outside the lead protection, another 3 thermoluminescence badges were also attached and the mean radiation dosage was calculated from each of the 3 badges. Estimated whole-body effective dose equivalent (HE) was approximated by the formula: HEE1.5 H1+0.04 H2, where H1 is the dose equivalent recorded by the dosimeter under the lead apron and H2 is the exposure measured by the collar dosimeter unprotected by lead.12 Dosimeters were transported from and to the operating theater in a leaded box.
Surface Locator and Intradermal Locator The surface locator is made up of radiopaque material (such as stainless steel or titanium alloy) and consists of 19 horizontal and 4 longitudinal rods (Fig. 1A). Each horizontal rod is about 9 cm, whereas each longitudinal rod is about 18 cm. Different marks are made on the rods with a 1 cm space between each horizontal rod. Stamping die and 1-step forming technology are applied to manufacture the locator. The surface locator was also well discussed in our previous studies.13,14 The intradermal locator is a bullet-shaped device with 7 tubes, 12 cm in length and 1.5 cm in diameter. To avoid artifacts on radiograph, the main component material is plastics (Fig. 1B). The device is also allowed for repeated use after sterilization with plasma. The intradermal locator was also documented in details in our previous publication.15
E174 | www.jspinaldisorders.com
Volume 28, Number 3, April 2015
Surgical Methods Preoperative Preparation All the patients underwent general anesthesia before MIS-TLIF surgery. G-arm x-ray machine (Biplanar 500e; Swemac Medical Appliances AB, Sweden) was prepared. METRx Quadrant System, percutaneous pedicle screw (Sextant; Medtronic, Minneapotics, MN), surface locator, and intradermal locator were prepared before the surgery.
Surgery Under general anesthesia, the patient was evenly placed in a prone position on a radiolucent operating table. The waist bowed a bit, making the intervertebral space open and expanding Kambin triangle. The iliac crests were preoperatively palpated, and lines connecting to the uppermost margin of both iliac crests were marked. For group A, our self-made surface locator was then placed on the patient’s back with the central part in the midline over the approximate spinal levels of interest and was fixed with an adhesive plaster (Fig. 2A). Under Garm fluoroscopy, the targeted levels were confirmed according to the different markers on the locator. On the basis of the spatial relationship, the intervertebral spaces and the pedicle positions were marked on the body surface (Fig. 2B). An incision was planned by connecting a line between the outer portions of the both ends pedicles (approximately 3.0 cm off midline). Then a skin incision about 3.0 to 4.0 cm was made on the more symptomatic side or more severe pathology side according to the imaging. The paravertebral muscles were split and retracted laterally to the outer edge of the facet joint, and the zygopophysis was confirmed. Expansion tube was then inserted and Quadrant System was placed step by step. X-ray examination was repeated to confirm the target segments and the placement of Quadrant System. The procedures of decompression and pedicle screw placement with intradermal locator are well described in our recent published study (Fig. 3A).13,15 Briefly, the intradermal locator device was placed through the channel and put onto the target pedicle. After K-wires were inserted through the tubes in the locator, fluoroscopy images were obtained by remote control of the C-arm fluoroscopy equipment. At the upper outer quadrant of the pedicle site, the most ideal K-wire could be confirmed and used to insert the drill and guidewire. If the initial position of the locator was unsatisfactory, the K-wire closest to the pedicle site was chosen and the locator was revolved around it to obtain the most ideal K-wire position. The remaining procedures were followed exactly as in the conventional methods mentioned above (Fig. 3B). For group B, patients underwent the conventional method which was well described in our previous study.13 Briefly, a 1 to 2 cm lateral skin incision was made to insert the Jamshidi needle at an appropriate angle into the pedicle depending on the depth of the tissue between the skin and pedicle. Using the Jamshidi needle, docked against the bone at the junction of the base of the transverse process and facet joint, the anteroposterior and Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 3, April 2015
Radiation Exposure in MIS-TLIF
FIGURE 1. Picture of real products of our spinal locators. A, The surface locator consists of 19 horizontal rods and 4 longitudinal rods. Each horizontal rod is about 9 cm, whereas each longitudinal rod is about 18 cm. B, The intradermal locator was a cylindershaped device. The diameter and length of the device were 1.5 and 12 cm, respectively.
lateral images were obtained to localize the needle tip. The needle was then gently tapped with a mallet to engage the tip in the bone. Fluoroscopy was intermittently used to confirm the direction and the depth to make sure that the needle remained lateral to the medial pedicle wall. As the needle advanced to cross the pedicle center, a guidewire was inserted through the cannula into the pedicle. The cannula was then carefully removed, leaving the guidewire in place. The fascia and muscle were dilated to allow screw placement. After preparation of the pedicle with a tap using cannulated taps, the percutaneous cannulated pedicle screw-rod system (Sextant; Medtronic Sofamor Danek, Memphis, TN) was placed.
Data Collection Intraoperatively, we recorded the tube voltage and tube current of G-arm x-ray machine, exposure time of Garm x-ray machine, and the duration of each operation. The thermoluminescence badges were measured by semiautomatic type thermoluminescent dosimeter (RADOS Company, Mirion Group San Francisco Bay area, CA) to assess the radiation exposure. Readings from dosimeters Copyright
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representing the arm, finger, whole body, thyroid gland, gonad gland, and eye exposure were put in perspective of guidelines for occupational radiation exposure limits to report the annual number of MIS-TLIF cases a surgeon might perform before exceeding recommended dose limits for planned exposure situations as defined by the International Commission on Radiological Protection (ICRP).
Data Analysis Statistical analysis was performed with SPSS version 17.0. Descriptive statistics were calculated in terms of means and SDs for continuous variables and frequencies and percentages for categorical variables. The difference of radiation dosage from group A and group B were compared by the Student t test (with P < 0.05 as statistical significance) and the correlation between operation time and exposure time was also analyzed.
RESULTS Demographic data and clinical characteristics are summarized in Table 1. All 20 patients (9 male, 11 female), aged from 48 to 77 years old, successfully underwent www.jspinaldisorders.com |
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FIGURE 2. The use of surface locator in minimally invasive transforaminal lumbar interbody fusion. A, Surface locator was placed on the patient’s back with the central part in the midline over the approximate spinal levels of interest and was fixed with an adhesive plaster. B, On the basis of spatial relationship, the intervertebral spaces and the pedicle positions were marked on the body surface.
MIS-TLIF. The average age was 61.9 years old for group A, whereas it was 66 years old for group B, and the difference was with statistical significance. The weight was 63.8 ± 11.24 kg for group A and 59.5 ± 9.07 kg for group B, and the body mass index was 21.95 ± 2.39 kg/m2 for group A and 21.7 ± 1.56 kg/m2 for group B. The voltage of G-arm x-ray machine for anteroposterior imaging was 74.4 ± 3.60 V for group A and 74.8 ± 3.33 V for group B, and the voltage for lateral imaging was 104.1 ± 4.28 V for group A and 103.4 ± 4.77 V for group B. The difference of voltage for anteroposterior imaging between group A and group B was with statistical significance. The current of Garm x-ray machine for anteroposterior imaging was 2.6 ± 0.24 mA for group A and 2.61 ± 0.28 mA for group B, and the current for lateral imaging was 3.48 ± 0.33 mA for group A and 3.49 ± 0.20 mA for group B. For surgery segment, there were 1 case for L3/L4, 5 cases for L4/L5, and 4 cases for L5/S1 in group A and 1 case for L3/L4, 5 cases for L4/L5, and 4 cases for L5/S1 in group B. The operation time was 171.20 ± 10.28 minutes for group A and 189.80 ± 11.99 minutes for group B. The fluoroscopy time was 49.60 ± 7.32 seconds for group A and 68.40 ± 7.62 seconds for group B, hence a reduction of 27.49% was observed. There was no correlation between operation time and exposure time for group A or group B (Fig. 4). The radiation dosage for different parts of the surgeon is listed in Table 2. The radiation exposure to the arm of the surgeon was 0.0587 ± 0.0175 mSv for group A and 0.0907 ± 0.0291 mSv for group B, and for the finger the
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radiation dosage was 0.0946 ± 0.0438 mSv for group A and 0.1153 ± 0.0282 mSv for group B. For group A, the radiation dosage to the left chest was 0.0042 ± 0.0015 mSv under lead apron (protected) and 0.0356 ± 0.0154 mSv above the lead apron (unprotected); for group B, the radiation dosage to the left chest was 0.0077 ± 0.0032 mSv with lead apron protected and 0.0638 ± 0.0195 mSv without lead apron protected. With thyroid shield protected, the radiation dosage to the thyroid gland was 0.0032 ± 0.0012 mSv for group A and 0.0069 ± 0.0031 mSv for group B, whereas it was 0.0273 ± 0.0100 mSv for group A and 0.0574 ± 0.0178 mSv for group B without protection. For the gonad gland, the radiation dosages were 0.0042 ± 0.0014 mSv (protected) and 0.0391 ± 0.0144 mSv (unprotected) for group A, 0.0075 ± 0.0021 mSv (protected) and 0.0615 ± 0.0227 mSv (unprotected) for group B. Under lead mask, the radiation exposure to the eye was 0.0028 ± 0.0017 mSv for group A and 0.0069 ± 0.0027 mSv for group B; above the lead mask, the radiation exposure to the eye was 0.0216 ± 0.0107 mSv for group A and 0.0536 ± 0.0164 mSv for group B. The differences of radiation exposure to all detective organs or tissues between group A and group B were with statistical significance, respectively. The radiation reduction observed was 35.28% for the arm, 17.95% for the finger, 45.23% for the whole body, 53.62% for the thyroid gland (protected), 52.44% for the thyroid gland (unprotected), 44% for gonad gland (protected), 36.42% for the gonad gland (unprotected), 59.42% for the eye (protected), and 59.70% for the eye (unprotected). Copyright
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J Spinal Disord Tech
Volume 28, Number 3, April 2015
Radiation Exposure in MIS-TLIF
FIGURE 3. The use of intradermal locator in minimally invasive transforaminal lumbar interbody fusion. A, Insertion and fixation of intradermal locator in the pedicle area after the dissection of the skin and thoracolumbar fascia followed by separation of the soft tissue. B, The proper channel in intradermal locator was chosen based on fluoroscopic images.
DISCUSSION For the past few years, MIS-TLIF has been adopted by more and more surgeons due to its numerous advantages. However, the minimally invasive process requires the fluoroscopy equipment for navigation (eg, G-arm x-ray machine), hence the amount of radiation exposure to surgeons and staff should be quantified.16 In this prospective study, we found the use of surface and intradermal locators to significantly reduce radiation exposure to the surgeon. The radiation reduction observed was 35.28% for the arm, 17.95% for the finger, 45.23% for the whole body, 53.62% for the thyroid gland (protected), 52.44% for the thyroid
gland (unprotected), 44% for gonad gland (protected), 36.42% for the gonad gland (unprotected), 59.42% for the eye (protected), and 59.70% for the eye (unprotected). The operation time was 171.20 ± 10.28 minutes for group A and 189.80 ± 11.99 minutes for group B. The fluoroscopy time was 49.60 ± 7.32 seconds for group A and 68.40 ± 7.62 seconds for group B. There was no correlation between operation time and exposure time for group A or group B, which was consistent with the previous study.16 Radiation exposure has often been associated with cardiovascular disease, tumor, cataract, etc.,11,17–19 which was classified as deterministic (ie, hair loss, skin burns,
TABLE 1. Demographic Data and Clinical Characteristics Demographic Data Sex (male:female) Age (y) Weight (kg) Body mass index (kg/m2) Voltage for anteroposterior imaging (V) Voltage for lateral imaging (V) Current for anteroposterior imaging (mA) Current for lateral imaging (mA) Surgery segment (L3/L4:L4/L5:L5/S1)
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Group A (n = 10)
Group B (n = 10)
P
5:5 61.9 ± 7.36 63.8 ± 11.24 21.95 ± 2.39 74.4 ± 3.60 104.1 ± 4.28 2.6 ± 0.24 3.48 ± 0.33 1:5:4
4:6 66 ± 10.76 59.5 ± 9.07 21.7 ± 1.56 74.8 ± 3.33 103.4 ± 4.77 2.61 ± 0.28 3.49 ± 0.20 1:5:4
— < 0.05 > 0.05 > 0.05 < 0.05 > 0.05 > 0.05 > 0.05 —
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TABLE 3. Yearly Occupational Exposure Limit Recommended by the International Commission on Radiation Protection Yearly Occupational Exposure Limit (mSv)
Organs Extremities Skin Thyroid gland Eye Whole body Other tissues or organs
500.0000 500.0000 300.0000 150 (20)* 50.0000 500.0000
*Means the most recently updated yearly occupational exposure limit recommended by ICRP was 20mSv for the eye.
FIGURE 4. The correlation between operation time and exposure time. A, There was no correlation between operation time and exposure time for group A. B, There was no correlation between operation time and exposure time for group B.
nausea, and cataract) and stochastic effects (ie, carcinogenesis and teratogenesis).20,21 The organs sensitive to radiation include the gonads, bone marrow, breast, cornea, gastrointestinal tract, lung, and thyroid and concern has been expressed regarding the difference of the susceptibilities of organs in human body.21 In an attempt to minimize sequelae of occupational exposure to ionizing radiation, the ICRP has published the maximum, yearly, occupational exposure limit for all sensitive organs or tissues (Table 3).12,20 For medical personnel, it has been recommended that the exposure should not exceed 20 mSv per year for the whole body. The maximum duration for which this level of exposure is allowed is 5 years, hence a maximal total body exposure over 5 years
should not exceed 100 mSv. The maximum permissible exposure recommended is 150 mSv for the eye and 500 mSv for the skin as well as the extremities. According to the updated recommendation, the radiation exposure to the eye should not exceed 20 mSv per year.22–24 These values can be used for the subset of population whose specific organs are exposed to radiation rather than the whole body. Previous studies have identified fluoroscopy as a safe procedure which maintains exposure within the ICRP-recommended annual limits.25–27 With the radiation dose of specific sensitive organs and updated occupational exposure limit values from ICRP, we could calculate the maximum number of MIS-TLIF surgeries one surgeon could perform per year without exceeding the recommended exposure. Using our spinal locators, the maximum number of MIS-TLIF surgery for 1 surgeon per year was 8517 for the arm, 5285 for the finger, 6473 for the whole body, 7142 for the eye (protected), and 952 for the eye (unprotected). That was to say, one surgeon could only operate no more than 952 MIS-TLIF surgeries without wearing lead mask but using our spinal locators per year. If the surgeon wear lead mask to protect the eyes, he could only operate no more than 5285 MIS-TLIF surgeries using our spinal locators. Without using our spinal locators, the maximum number of MISTLIF surgery for 1 surgeon per year was 5512 for the arm, 4336 for the finger, 3545 for the whole body, 2898 for the eye (protected), and 373 for the eye (unprotected). That was to say, one surgeon could only operate
