Minimally Invasive Therapy. 2014;23:173–178
TECHNICAL REPORT
Reduction in radiation during percutaneous lumbar pedicle screw placement using a new device
LEI ZHANG*, XU ZHOU*, XIAOBING CAI, HAILONG ZHANG, QINGSONG FU, SHISHENG HE Department of Orthopaedics, The Tenth People’s Hospital, Tongji University, Shanghai, China
Abstract Objective: To assess a new intradermal locator device for percutaneous placement of lumbar pedicle screws. Material and methods: Patients were alternately assigned to two groups. The locator group underwent lumbar pedicle screw placement using the intradermal locator. The control group was aided by traditional fluoroscopy. Baseline demographics, visual analog scale (VAS) pain scores, operation time, intraoperative fluoroscopy time and guidewire insertion time were recorded. All postoperative CT scans were reviewed by an independent spine surgeon to grade screw placement accuracy. Results: Thirty-six patients (180 screws) were assigned to the locator group and 30 patients (128 screws) to the control group. The locator device could significantly reduce the fluoroscopy time [3.9 sec (SD = 1.9) vs. 9.6 sec (SD = 5.8), p < 0.001] and guidewire insertion time [2.69 min (SD = 0.67) vs. 4.49 min (SD = 1.96), p < 0.001] compared with the conventional method for each pedicle screw. The whole operation time of the locator group was shorter than that of the control group [2-segment: 243.2 min (SD = 16.9) vs. 301.7 min (SD = 14.9), p < 0.001; 1-segment: 154.5 min (SD = 14.3) vs. 194.6 min (SD = 19.3), p < 0.001]. As for the rates of pedicle breaches, postoperative VAS scores, no significant difference was found between the two groups. Conclusion: The intradermal locator device could help reduce the radiation exposure in percutaneous pedicle screw placement while maintaining the accuracy.
Key words: Percutaneous pedicle screw, radiation reduction, safe placement, new device
Introduction Percutaneous pedicle screw implantation has become one of the most used techniques in the field of minimally invasive spinal surgery (MISS). Not only could it promote stability and fusion for numerous spinal pathologies – trauma, tumors, deformity and degenerative diseases – but it could significantly reduce the length of hospital stay, blood loss, postoperative analgesia and time to return to work (1,2). However, unlike with the traditional open method, there is no direct visualization of key anatomical structures and the sensory feedback is also limited. The reported rate of pedicle screw misplacement could range to 40% (3,4). The nerve root is particularly at risk as it passes around the pedicle and one study reported that almost 10% of the patients needed
revision surgery (5). Therefore, precise insertion of the pedicle screw could be a highly technically demanding procedure and an intraoperative imageguided system is necessary. Since Rontgen’s landmark discovery of X-ray in 1895 (6), fluoroscopic guidance has been widely used for many surgical operations. The real-time x-ray fluoroscopy imaging system could provide considerable temporal anatomical information to help surgeons improve their surgical performances. But the amount of radiation exposure has been a concern for many years (7,8). Reports have indicated an increased incidence of thyroid malignancies among orthopedic surgeons and surgeons’ hands are most at risk (9,10). And higher energy is usually required for spine surgery; dosimetry readings showed that it could be 10–12 times greater than for non-spine procedures
Correspondence: S. He, The Tenth People’s Hospital affiliated to Tongji University – Orthopaedics, No.301 Yan Chang Zhong Road, Shanghai 200072, China. E-mail: [email protected] *These authors contributed equally to this work. ISSN 1364-5706 print/ISSN 1365-2931 online 2014 Informa Healthcare DOI: 10.3109/13645706.2013.870914
174
L. Zhang et al. The main purpose of this prospective study was to assess the ability of an intradermal locator in percutaneous pedicle screw implantation to reduce radiation exposure and operation time while maintaining safe pedicle screw placement.
Material and methods
Figure 1. Product figure of the intradermal locator.
(11,12). During percutaneous pedicle screw implantation surgery, repeated fluoroscopies to adjust the puncture needle are a critical step before each pedicle screw is inserted. To avoid the artifact influence of the needles in the anterior-posterior image and to adjust the needles simultaneously, the senior surgeon usually stands close to the patient and holds the needles during each fluoroscopy. Thus, a method to reduce the radiation amount while maintaining accurate pedicle screw placement would be of great value.
The study was reviewed and approved by the Institutional Review Board for Human Participants. Ages of the patients were between 20 and 80 years. Patient enrollment was limited to those with a preoperative diagnosis requiring treatment with percutaneous pedicle screw fixation of the lumbar spine. Patients were excluded if they had previous instrumented surgery at the target level. After obtaining written informed consent, patients were assigned to alternating groups according to the order of enrollment. The locator group underwent the surgery aided by the intradermal locator. This is a bullet-shaped device with seven tubes, 12 cm in length and 1.5 cm in diameter. To avoid artifacts on radiograph, the main component material is plastics (Figure 1). Following induction of general anesthesia, the location of the target level and the pedicles, as well as the incision sites, are marked before sterilization (Figure 2a). After opening the skin and fascia, blunt separation with the surgeon’s finger is used to reach the junction of the facets and transverse process. Then the intradermal locator device is placed through the channel and put onto the target pedicle (Figure 2b). After K-wires are inserted through the tubes in the locator, fluoroscopy
Intradermal locator
Skin incision
Pedicle mark
a
b
Figure 2. (a) A diagram shows the preoperative location and skin marks of target vertebral level, pedicles and incisions before sterilization. (b) The intradermal locators are inserted through the channels which are bluntly separated with the surgeon’s finger and put onto the target pedicles.
Reduction in radiation during percutaneous lumbar pedicle screw placement
175
A
Pedicle
Skin incision
a
b
Pedicle
Figure 3. (a) A diagram describes the fluoroscopy image of the locators after the K-wires are inserted through the tubes. (b) At the upper outer quadrant of the pedicle area, the K-wire A represents the most ideal site for pedicle screw placement.
images are obtained by remote control of the C-arm fluoroscopy equipment (Figure 3a, Figure 4). At the upper outer quadrant of the pedicle site, the most ideal K-wire could be confirmed and used to insert the drill and guide wire (Figure 3b). The following steps are the same as in the conventional method. If the initial position of the locator is unsatisfactory, the K-wire closest to the pedicle site is chosen and the locator is revolved around it to obtain the most ideal K-wire position (Figure 5). Two locators could be used at the same time to locate the adjacent vertebral pedicles for one segment fixation. In the control group, the senior surgeon, wearing a lead apron, hat and thyroid gland shield, stands close to the patient and holds the guide wires during each time fluoroscopy is performed by the C-arm equipment. Demographic data collection included age, sex, height, weight and body mass index (BMI). Intraoperative data collection included treated levels, operative time, estimated blood loss, intraoperative complications, number and location of screws, screw diameters and lengths, and time of guidewire insertion in the pedicle. Total fluoroscopy time was
collected for each pedicle. Postoperative complications and duration of hospital stay were also noted. Patient-reported clinical outcomes were collected using the visual analog scale for leg (VAS leg) pain at baseline and within one week after surgery. Four surgeons were enrolled in this study. One surgeon had several years of experience inventing and using the device, two surgeons were inexperienced and were trained for the purpose of this study and the remaining surgeon had an intermediate experience level. Pedicle screw placement was assessed by a single, independent, blinded, board-certified spine surgeon with more than 20 years of experience and was based on a postoperative CT scan obtained within two weeks after surgery. The magnitude of pedicle perforation was categorized as A (no breach), B (breach 4 mm). The direction of the perforation was categorized as lateral, medial, inferior or superior. Clinical and radiographical data were analyzed using SPSS 16.0. An independent t test was used to compare mean results between treatment groups. The significant level was set at p value < 0.05. Results
a
b
Figure 4. (a) Image taken in kind shows the insertion of K-wires through the tubes in the locator device. (b) The locator device is transparent on the real fluoroscopy image, black arrows show the most adequate K-wires, which maybe need just a little adjustment. The white arrow shows the marker of the interbody.
Seventy patients were consented for study participation, ultimately 66 patients were included in the study; 36 patients were assigned to the locator group and 30 were assigned to the control group. The average age at surgery was 54 years(range 23–78) and the average body mass index was 33.5 kg/ m2(range 20.1–48.6). Indications for surgery included degenerative disc disease (86.7%), central or foraminal stenosis(45.4%), spondylolisthesis (29.7%), herniated nucleus pulposus(21.3%), degenerative scoliosis(10.4%), and postlaminectomy instability(3.9%). Baseline patient-reported pain scores
176
L. Zhang et al. B
Skin incision
Pedilce
b
a
Figure 5. A diagram shows the case of the intradermal locator malposition. (a) Removing all the K-wires except the one closest to the pedicle (K-wire A), revolving the locator around K-wire A to put the locator onto the right position. (b) Inserting the K-wires again and after fluoroscopy, the ideal K-wire B could be obtained.
were VAS left leg 37.5 mm (SD = 12.4), and VAS right leg 40.1 mm (SD = 15.4). Baseline variables including sex, sex-ratio, age, body mass index, and indications for surgery were well matched between the cohorts (p > 0.05) and are reported in Table I. A total of 308 screws were placed (180 locator, 128 control) from L2 to S1. Patients were treated with an average of 4.6 screws (range 2 to 10) and screw diameters ranged from 5.5 to 7.5 mm. The average screw diameter and number of screws placed per patient were not statistically different between treatment groups (p = 0.312 and p = 0.068, respectively). On average, the locator group used less fluoroscopy per pedicle [3.9 sec (SD = 1.9) vs. 9.6 sec (SD = 5.8), p < 0.001], and resulted in more expedient placement of guidewires per pedicle [2.69 min (SD = 0.67) vs. 4.49 min (SD = 1.96), p < 0.001]. The whole operation time of the locator group was shorter than that of the control group [2-segment: 243.2 min (SD = 16.9) vs. 301.7 min (SD = 14.9), p < 0.001; 1-segment: 154.5 min (SD = 14.3) vs. 194.6 min (SD = 19.3), p < 0.001](Table II). Preincision fluoroscopy included skin marking in both groups and was not significantly different between groups. Estimated blood loss was 300 cc in 6.7%. There was no difference
Table I. Patient demographics. Locator group Number of patients,n Sex-ratio(male:female)
Control group
p
36
30
NS
21:15
12:18
NS
Age(yrs):mean (range)
53.7(25–75)
54.2(23–78)
NS
BMI(kg/m2)(SD)
32.8(7.2)
34.1(6.9)
NS
NS: non-significant.
in blood loss between groups (p = 0.790). There were no intraoperative complications and all screws were placed percutaneously without transition to an open technique. Postoperative CT scans of 60 patients were available for review by an independent spine surgeon. CT data were available for 294 screws (168 locator, 126 control). There were 16 pedicle breaches, including nine (3.1%) in the locator group and seven (5.6%) in the control group (p = 0.079). All breaches in both groups were
TECHNICAL REPORT
Reduction in radiation during percutaneous lumbar pedicle screw placement using a new device
LEI ZHANG*, XU ZHOU*, XIAOBING CAI, HAILONG ZHANG, QINGSONG FU, SHISHENG HE Department of Orthopaedics, The Tenth People’s Hospital, Tongji University, Shanghai, China
Abstract Objective: To assess a new intradermal locator device for percutaneous placement of lumbar pedicle screws. Material and methods: Patients were alternately assigned to two groups. The locator group underwent lumbar pedicle screw placement using the intradermal locator. The control group was aided by traditional fluoroscopy. Baseline demographics, visual analog scale (VAS) pain scores, operation time, intraoperative fluoroscopy time and guidewire insertion time were recorded. All postoperative CT scans were reviewed by an independent spine surgeon to grade screw placement accuracy. Results: Thirty-six patients (180 screws) were assigned to the locator group and 30 patients (128 screws) to the control group. The locator device could significantly reduce the fluoroscopy time [3.9 sec (SD = 1.9) vs. 9.6 sec (SD = 5.8), p < 0.001] and guidewire insertion time [2.69 min (SD = 0.67) vs. 4.49 min (SD = 1.96), p < 0.001] compared with the conventional method for each pedicle screw. The whole operation time of the locator group was shorter than that of the control group [2-segment: 243.2 min (SD = 16.9) vs. 301.7 min (SD = 14.9), p < 0.001; 1-segment: 154.5 min (SD = 14.3) vs. 194.6 min (SD = 19.3), p < 0.001]. As for the rates of pedicle breaches, postoperative VAS scores, no significant difference was found between the two groups. Conclusion: The intradermal locator device could help reduce the radiation exposure in percutaneous pedicle screw placement while maintaining the accuracy.
Key words: Percutaneous pedicle screw, radiation reduction, safe placement, new device
Introduction Percutaneous pedicle screw implantation has become one of the most used techniques in the field of minimally invasive spinal surgery (MISS). Not only could it promote stability and fusion for numerous spinal pathologies – trauma, tumors, deformity and degenerative diseases – but it could significantly reduce the length of hospital stay, blood loss, postoperative analgesia and time to return to work (1,2). However, unlike with the traditional open method, there is no direct visualization of key anatomical structures and the sensory feedback is also limited. The reported rate of pedicle screw misplacement could range to 40% (3,4). The nerve root is particularly at risk as it passes around the pedicle and one study reported that almost 10% of the patients needed
revision surgery (5). Therefore, precise insertion of the pedicle screw could be a highly technically demanding procedure and an intraoperative imageguided system is necessary. Since Rontgen’s landmark discovery of X-ray in 1895 (6), fluoroscopic guidance has been widely used for many surgical operations. The real-time x-ray fluoroscopy imaging system could provide considerable temporal anatomical information to help surgeons improve their surgical performances. But the amount of radiation exposure has been a concern for many years (7,8). Reports have indicated an increased incidence of thyroid malignancies among orthopedic surgeons and surgeons’ hands are most at risk (9,10). And higher energy is usually required for spine surgery; dosimetry readings showed that it could be 10–12 times greater than for non-spine procedures
Correspondence: S. He, The Tenth People’s Hospital affiliated to Tongji University – Orthopaedics, No.301 Yan Chang Zhong Road, Shanghai 200072, China. E-mail: [email protected] *These authors contributed equally to this work. ISSN 1364-5706 print/ISSN 1365-2931 online 2014 Informa Healthcare DOI: 10.3109/13645706.2013.870914
174
L. Zhang et al. The main purpose of this prospective study was to assess the ability of an intradermal locator in percutaneous pedicle screw implantation to reduce radiation exposure and operation time while maintaining safe pedicle screw placement.
Material and methods
Figure 1. Product figure of the intradermal locator.
(11,12). During percutaneous pedicle screw implantation surgery, repeated fluoroscopies to adjust the puncture needle are a critical step before each pedicle screw is inserted. To avoid the artifact influence of the needles in the anterior-posterior image and to adjust the needles simultaneously, the senior surgeon usually stands close to the patient and holds the needles during each fluoroscopy. Thus, a method to reduce the radiation amount while maintaining accurate pedicle screw placement would be of great value.
The study was reviewed and approved by the Institutional Review Board for Human Participants. Ages of the patients were between 20 and 80 years. Patient enrollment was limited to those with a preoperative diagnosis requiring treatment with percutaneous pedicle screw fixation of the lumbar spine. Patients were excluded if they had previous instrumented surgery at the target level. After obtaining written informed consent, patients were assigned to alternating groups according to the order of enrollment. The locator group underwent the surgery aided by the intradermal locator. This is a bullet-shaped device with seven tubes, 12 cm in length and 1.5 cm in diameter. To avoid artifacts on radiograph, the main component material is plastics (Figure 1). Following induction of general anesthesia, the location of the target level and the pedicles, as well as the incision sites, are marked before sterilization (Figure 2a). After opening the skin and fascia, blunt separation with the surgeon’s finger is used to reach the junction of the facets and transverse process. Then the intradermal locator device is placed through the channel and put onto the target pedicle (Figure 2b). After K-wires are inserted through the tubes in the locator, fluoroscopy
Intradermal locator
Skin incision
Pedicle mark
a
b
Figure 2. (a) A diagram shows the preoperative location and skin marks of target vertebral level, pedicles and incisions before sterilization. (b) The intradermal locators are inserted through the channels which are bluntly separated with the surgeon’s finger and put onto the target pedicles.
Reduction in radiation during percutaneous lumbar pedicle screw placement
175
A
Pedicle
Skin incision
a
b
Pedicle
Figure 3. (a) A diagram describes the fluoroscopy image of the locators after the K-wires are inserted through the tubes. (b) At the upper outer quadrant of the pedicle area, the K-wire A represents the most ideal site for pedicle screw placement.
images are obtained by remote control of the C-arm fluoroscopy equipment (Figure 3a, Figure 4). At the upper outer quadrant of the pedicle site, the most ideal K-wire could be confirmed and used to insert the drill and guide wire (Figure 3b). The following steps are the same as in the conventional method. If the initial position of the locator is unsatisfactory, the K-wire closest to the pedicle site is chosen and the locator is revolved around it to obtain the most ideal K-wire position (Figure 5). Two locators could be used at the same time to locate the adjacent vertebral pedicles for one segment fixation. In the control group, the senior surgeon, wearing a lead apron, hat and thyroid gland shield, stands close to the patient and holds the guide wires during each time fluoroscopy is performed by the C-arm equipment. Demographic data collection included age, sex, height, weight and body mass index (BMI). Intraoperative data collection included treated levels, operative time, estimated blood loss, intraoperative complications, number and location of screws, screw diameters and lengths, and time of guidewire insertion in the pedicle. Total fluoroscopy time was
collected for each pedicle. Postoperative complications and duration of hospital stay were also noted. Patient-reported clinical outcomes were collected using the visual analog scale for leg (VAS leg) pain at baseline and within one week after surgery. Four surgeons were enrolled in this study. One surgeon had several years of experience inventing and using the device, two surgeons were inexperienced and were trained for the purpose of this study and the remaining surgeon had an intermediate experience level. Pedicle screw placement was assessed by a single, independent, blinded, board-certified spine surgeon with more than 20 years of experience and was based on a postoperative CT scan obtained within two weeks after surgery. The magnitude of pedicle perforation was categorized as A (no breach), B (breach 4 mm). The direction of the perforation was categorized as lateral, medial, inferior or superior. Clinical and radiographical data were analyzed using SPSS 16.0. An independent t test was used to compare mean results between treatment groups. The significant level was set at p value < 0.05. Results
a
b
Figure 4. (a) Image taken in kind shows the insertion of K-wires through the tubes in the locator device. (b) The locator device is transparent on the real fluoroscopy image, black arrows show the most adequate K-wires, which maybe need just a little adjustment. The white arrow shows the marker of the interbody.
Seventy patients were consented for study participation, ultimately 66 patients were included in the study; 36 patients were assigned to the locator group and 30 were assigned to the control group. The average age at surgery was 54 years(range 23–78) and the average body mass index was 33.5 kg/ m2(range 20.1–48.6). Indications for surgery included degenerative disc disease (86.7%), central or foraminal stenosis(45.4%), spondylolisthesis (29.7%), herniated nucleus pulposus(21.3%), degenerative scoliosis(10.4%), and postlaminectomy instability(3.9%). Baseline patient-reported pain scores
176
L. Zhang et al. B
Skin incision
Pedilce
b
a
Figure 5. A diagram shows the case of the intradermal locator malposition. (a) Removing all the K-wires except the one closest to the pedicle (K-wire A), revolving the locator around K-wire A to put the locator onto the right position. (b) Inserting the K-wires again and after fluoroscopy, the ideal K-wire B could be obtained.
were VAS left leg 37.5 mm (SD = 12.4), and VAS right leg 40.1 mm (SD = 15.4). Baseline variables including sex, sex-ratio, age, body mass index, and indications for surgery were well matched between the cohorts (p > 0.05) and are reported in Table I. A total of 308 screws were placed (180 locator, 128 control) from L2 to S1. Patients were treated with an average of 4.6 screws (range 2 to 10) and screw diameters ranged from 5.5 to 7.5 mm. The average screw diameter and number of screws placed per patient were not statistically different between treatment groups (p = 0.312 and p = 0.068, respectively). On average, the locator group used less fluoroscopy per pedicle [3.9 sec (SD = 1.9) vs. 9.6 sec (SD = 5.8), p < 0.001], and resulted in more expedient placement of guidewires per pedicle [2.69 min (SD = 0.67) vs. 4.49 min (SD = 1.96), p < 0.001]. The whole operation time of the locator group was shorter than that of the control group [2-segment: 243.2 min (SD = 16.9) vs. 301.7 min (SD = 14.9), p < 0.001; 1-segment: 154.5 min (SD = 14.3) vs. 194.6 min (SD = 19.3), p < 0.001](Table II). Preincision fluoroscopy included skin marking in both groups and was not significantly different between groups. Estimated blood loss was 300 cc in 6.7%. There was no difference
Table I. Patient demographics. Locator group Number of patients,n Sex-ratio(male:female)
Control group
p
36
30
NS
21:15
12:18
NS
Age(yrs):mean (range)
53.7(25–75)
54.2(23–78)
NS
BMI(kg/m2)(SD)
32.8(7.2)
34.1(6.9)
NS
NS: non-significant.
in blood loss between groups (p = 0.790). There were no intraoperative complications and all screws were placed percutaneously without transition to an open technique. Postoperative CT scans of 60 patients were available for review by an independent spine surgeon. CT data were available for 294 screws (168 locator, 126 control). There were 16 pedicle breaches, including nine (3.1%) in the locator group and seven (5.6%) in the control group (p = 0.079). All breaches in both groups were
