Eur Spine J DOI 10.1007/s00586-014-3310-2
ORIGINAL ARTICLE
Prospective comparative study between straight and curved probe for pedicle screw insertion Yogesh K. Pithwa • Kumar Venkatesh
Received: 5 January 2014 / Accepted: 9 April 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose To evaluate difference in accuracy of pedicle screw insertion in thoracic and lumbosacral spine using a straight pedicle probe vis-a`-vis a curved one. Methods Prospective, comparative, non-randomized, singleblind study. Straight and curved pedicle probes used on opposite sides of same vertebra in patients undergoing thoracolumbar pedicle screw fixation for various indications. Postoperative blinded evaluation for pedicle breaches done with a CT scan. Pedicle breaches graded as grade 0: no breach, grade 1:\2 mm, grade 2: 2–4 mm and grade 3:[4 mm breach. Results After appropriate statistical power analysis, 300 screws inserted in 59 patients from T4–L5 levels. No significant differences noted between the two probes in terms of screw length [two-tailed p = 0.16]; grade 0 screws [two-tailed p = 0.49] or screws with grade 2/3 breaches [two-tailed p = 0.68]. With the right-hand-dominant operating-surgeon standing to left of patient during surgery, no difference noted between the two probes for either the right or left-side pedicle screw insertion [two-tailed p = 1]. Repeating these tests in the subset of thoracic pedicle screws too, revealed no significant difference. Conclusions No significant difference in outcome of pedicle screw insertion with either a straight or a curved pedicle probe. Keywords
Pedicle screw Pedicle probe Pedicle starter
Y. K. Pithwa K. Venkatesh Spine Surgery, HOSMAT Hospital, Bangalore, India Y. K. Pithwa (&) Flat No. D-209, USHAS Apartments, Site No. 26, 16th Main, Jayanagar 4th Block, Bangalore 560011, India e-mail: [email protected]; [email protected]
Introduction Various pedicle probes exist with varying shapes and sizes that spine surgeons use to create a trajectory for insertion of screws into the spine. Though it is difficult to define each variety due to lack of standardization, one can broadly categorize these pedicle probes into two types (Fig. 1): a straight one and a curved one [1]. Kim et al. [1] described free-hand insertion of thoracic pedicle screws with a curved probe (Fig. 2) inserted initially with the curvature facing laterally up to a depth of about 20 mm, thereafter removing and reinserting the same with the curvature facing medially up to the anteromedial aspect of the vertebral body. This curved trajectory created thereby is ‘straightened’ by the use of a straight tap following which the pedicle screw is inserted [1]. On the other hand, the straight probe is generally inserted ‘straight’ along the actual intended final trajectory of the screw. Based on the above-mentioned method of insertion of a curved pedicle probe, the present study hypothesized that lateral direction of curvature of the curved pedicle probe during the initial depth of 20 mm would lead to a lesser incidence of medial pedicle breach. Though the study by Kim et al. was specific to thoracic pedicles, the present study aimed at extrapolating these logical principles over to the lumbar spine as well. Anatomical studies have also revealed that the medial wall of pedicle is thicker than the lateral wall [2–4]. In view of this, one may be inclined to hypothetically presume that the curved trajectory created by the curved probe may get ‘straightened’ by the straight tap by getting lateralized on its dorsal aspect in view of the relatively weak lateral pedicle wall. This kind of dorsal ‘lateralization’ may thereby lead to a longer screw length. This was the second hypothesis for the present study which
123
Eur Spine J
was a prospective, comparative, single-blind study carried out at a tertiary referral center.
Materials and methods After appropriate institutional review board approval, the patients were included in the study after informed consent for the same.
Fig. 1 Different kinds of pedicle probes: a straight pedicle probe, and b curved pedicle probe
Fig. 2 Free-hand insertion of pedicle screws with a curved probe inserted initially with the curvature facing laterally up to a depth of about 20 mm (a), thereafter removing and reinserting the same with the curvature facing medially up to the anteromedial aspect of the vertebral body (b)
123
Inclusion criterion was patients undergoing pedicle screw stabilization surgeries in the thoracolumbar spine for varied indications. Patients with scoliosis were excluded in view of relative asymmetry between the concave and convex side pedicle [5]. Vertebral levels with unilateral fixation too were excluded. Accordingly, 59 patients, including 28 males and 31 females were included in the study. Indications for surgery included spondylolisthesis (n = 26), degenerative instability (n = 16), spinal infections (n = 4) and unstable spinal trauma (n = 13). Pedicle screws were inserted using straight and curved probe (Fig. 1) into opposite pedicles of the same vertebra, in an alternating manner. All screws were inserted by a single surgeon, fellowship trained in spine surgery, well past the learning curve, having inserted more than 300 screws into the thoracolumbar spine using both, the straight and curved pedicle probe [6]. Following creation of the screw tract with either probe, integrity of the tract was checked using a ball-tipped pedicle sound [1]. The screw was inserted thereafter and its position was verified with intra-operative C-arm images in anteroposterior and lateral planes. Pedicle breach was evaluated in the postoperative period using spiral CT scans with 2-mm slice thickness and 2-mm interval with retro reconstruction of 1-mm slice thickness and 1-mm interval [7]. This was a blinded evaluation done by a radiologist. Pedicle screw positions were graded as grade 0: no breach, grade 1: up to 2 mm breach, grade 2: 2–4 mm breach, grade 3: [4 mm breach [8]. With a significance level (alpha) of 0.05 (two-tailed), power analysis was done to detect a 5 % difference between the two probes in being able to accurately insert (grade 0) screws. Accordingly, 150 screws had to be inserted with either probe to give a power of 80 %. With a significance level (alpha) of 0.05 (two-tailed), this sample
Eur Spine J Table 1 Distribution of screws as per vertebral levels
Vertebral level
Number of screws
T4
2
T5
4
T6
2
T7
2
T8
4
T9
6
T10
2
T11
14
T12
14
L1
8
L2 L3
26 34
L4
92
L5
90
Fig. 3 CT scan showing a grade 2 lateral breach on the right side. Being lateral, it was asymptomatic
Table 2 CT grading of pedicle screw breaches Grade of breach
Straight
Curved
Grade 0
142 of 150
138 of 150
Grade 1
4 of 150
10 of 150
Grade 2
4 of 150
1 of 150
Grade 3
0
1 of 150
size also had a 80 % power of detecting 0.11 mm difference in the screw length using either probe. Statistical analysis was done using GraphPad Instat version 3.10, while power analysis was done using GraphPad StatMate version 2.00.
Results Age of the included patients was 42.3 ? 12.3 years. Three hundred pedicle screws were inserted. The distribution of screws in terms of vertebral level was as per Table 1. CT analysis for pedicle breaches revealed numbers as shown in Table 2. There was no statistically significant difference (two-tailed, p = 0.49 using Fisher’s exact test) in the placement of accurate (grade 0) screws with either probe (142 of 150 with straight probe and 138 of 150 with curved probe). Repeating the analysis for thoracic levels exclusively too, did not reveal any difference (21 of 25 with each, straight and curved probe). Up to 2 mm breach of the pedicle has been considered to be within the safe zone for neural structures [9]. Hence, analysis was repeated considering grades 2 and 3, i.e. [2 mm breach as unsafe. Using this criterion, 146 of 150 (97.33 %) with straight probe and 148 of 150 (98.67 %)
Fig. 4 CT scan showing a grade 3 lateral breach on the right side. Being lateral, it was asymptomatic
with curved probe were within the safe zone. This difference too, was found to be statistically insignificant (twotailed, p = 0.68 using Fisher’s exact test). Similar analysis for thoracic screws exclusively too, did not reveal any statistically significant difference (23 of 25 with straight probe and 24 of 25 with curved probe were in the safe zone; two-tailed, p = 1 using Fisher’s exact test). Six screws (four with straight probe and two with curved prove) of the total 300 screws studied had grade 2 (Fig. 3) or 3 (Fig. 4) breaches. However, these screws were asymptomatic in view of the breaches being lateral and hence, warranted no revision. Contrary to the first hypothesis of the present study, use of a curved pedicle probe did not cause any statistically significant reduction in medial breach (one medial breach
123
Eur Spine J Table 3 Distribution of absolutely accurate (grade 0) screws Absolutely accurate (grade 0) screws
Straight probe
Curved probe
Left side
95.78 % (68 of 71)
92.41 % (73 of 79)
Right side
93.67 % (74 of 79)
91.55 % (65 of 71)
with straight probe while two medial breaches with curved probe: two-tailed p = 1 using Fisher’s exact test). With the right-hand dominant operating-surgeon standing to the left of patient at the time of surgery, assessment for absolutely accurate [grade 0] screws using either probe for insertion of pedicle screw on the left or right-side was done. This data is presented in Table 3. Statistical analysis did not reveal any significant difference in this data between the use of the two probes for either the right or left-side pedicle (two-tailed p = 1, Fisher’s exact test). One hundred and fifty screws were inserted using each probe. Screw length was 44.27 ± 3.49 mm for straight probe while it was 44.47 ± 3.58 mm for curved probe. Paired ‘t’ test analysis did not reveal any statistically significant difference (two-tailed, p = 0.16) between the two outcomes. Exclusively testing for thoracic levels, the screw length was 42 ± 3.23 mm for straight probe while it was 42 ± 3.53 mm for curved probe. Paired ‘t’ test analysis did not reveal any statistically significant difference (twotailed, p = 0.99) between the two outcomes at thoracic level either. This contradicted the second hypothesis of the current study.
Discussion Ever since Roy-Camille [10] introduced pedicle screw fixation of the spine, it has presently become the most popular mode of securing an anchor in the thoracolumbar spine. Though there was initial reservation related to the use of pedicle screws in the thoracic spine, this reservation too has been successfully addressed in recent times [1]. In a study of 640 freehand pedicle screws in the thoracolumbar spine of 98 patients, Karapinar et al. [11] reported 94.2 % accuracy rate. In another study of 1,009 freehand pedicle screws (689 thoracic and 320 lumbosacral) into patients with neuromuscular scoliosis, Modi et al. [9] considered up to 2 mm medial and up to 4 mm lateral breach as within-safe zone. As per this criterion, the authors reported 93.3 % (942/1,009, 92.4 % in thoracic and 95.3 % in lumbar spine) screws within the safe zone. The present study considered up to 2 mm medial and up to 2 mm lateral breach as within-safe zone. Considering this, 97.33 % (146 of 150) screws with straight probe and 98.67 % screws (148 of 150) with curved probe were within the safe zone.
123
To the best of authors’ knowledge, the present study is the first one to analyze the efficacy of straight versus curved pedicle probe for screw insertion into the thoracolumbar spine. There was no statistically significant difference between the two pedicle probes in terms of the overall accuracy of screw placement or the ultimate length of screw inserted into the spine. Thus, the hypothesis of the study could not be supported by the findings. To the best of authors’ knowledge, the present study is also the first one to analyze any difference in outcome of pedicle screw insertion based on the side on which the operating surgeon is standing while doing the surgery. With the right-hand dominant operating surgeon standing to the left of patient, there was no statistically significant difference in the accuracy of insertion of pedicle screw on either side with either probe. So the present study does not allude to any scientific advantage for the operating surgeon to change sides from right to left or vice versa while inserting pedicle screws on the corresponding sides. In view of using the two probes on opposite sides of the same vertebra, matching of the two groups was inherently incorporated in the study. The power of this prospective single blind study for cumulative assessment of all the screws is also within acceptable limits. However, single surgeon involvement, relative paucity of thoracic levels, lack of pediatric cases and lack of standardized ‘‘straight’’ and ‘‘curved’’ pedicle probes remain the obvious limitations of this study. These limitations can, however, become points for further research on this topic. In conclusion, there was no definite evidence to support the fact that accuracy of pedicle screw insertion into the thoracolumbar spine varies as per the type of pedicle probe used. Conflict of interest
None.
References 1. Kim YJ, Lenke LG, Bridwell KH et al (2004) Freehand pedicle screw placement in the thoracic spine: is it safe? Spine 29(3):333–342 2. Mughir AM, Yusof MI, Abdullah S, Ahmad S (2010) Morphological comparison between adolescent and adult lumbar pedicles using computerised tomography scanning. Surg Radiol Anat 32(6):587–592 3. Liau KM, Yusof MI, Abdullah MS, Abdullah S, Yusof AH (2006) Computed tomographic morphometry of thoracic pedicles: safety margin of transpedicular screw fixation in malaysian malay population. Spine (Phila Pa 1976) 31(16):E545–E550 4. Datir SP, Mitra SR (2004) Morphometric study of the thoracic vertebral pedicle in an Indian population. Spine (Phila Pa 1976) 29(11):1174–1181 5. Liljenqvist UR, Allkemper T, Hackenberg L et al (2002) Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction. J Bone Joint Surg Am 84-A(3):359–368
Eur Spine J 6. Gonzalvo A, Fitt G, Liew S et al (2009) The learning curve of pedicle screw placement: how many screws are enough? Spine (Phila Pa 1976) 34(21):E761–E765 7. Rydberg J, Buckwalter KA, Caldemeyer KS et al (2000) Multisection CT: scanning techniques and clinical applications. Radiographics 20(6):1787–1806 8. Neo M, Sakamoto T, Fujibayashi S et al (2005) The Clinical risk of vertebral artery injury from cervical pedicle screws instead in degenerative vertebrae. Spine 30:2800–2805 9. Modi HN, Suh SW, Fernandez H et al (2008) Accuracy and safety of pedicle screw placement in neuromuscular scoliosis
with free-hand technique. Eur Spine J 17(12):1686–1696 (epub 2008 Oct 1) 10. Roy-Camille R, Saillant G, Mazel C (1986) Plating of thoracic, thoracolumbar, and lumbar injuries with pedicle screw plates. Orthop Clin North Am 17(1):147–159 11. Karapinar L, Erel N, Ozturk H et al (2008) Pedicle screw placement with a free hand technique in thoracolumbar spine: is it safe? J Spinal Disord Tech 21(1):63–67
123
ORIGINAL ARTICLE
Prospective comparative study between straight and curved probe for pedicle screw insertion Yogesh K. Pithwa • Kumar Venkatesh
Received: 5 January 2014 / Accepted: 9 April 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose To evaluate difference in accuracy of pedicle screw insertion in thoracic and lumbosacral spine using a straight pedicle probe vis-a`-vis a curved one. Methods Prospective, comparative, non-randomized, singleblind study. Straight and curved pedicle probes used on opposite sides of same vertebra in patients undergoing thoracolumbar pedicle screw fixation for various indications. Postoperative blinded evaluation for pedicle breaches done with a CT scan. Pedicle breaches graded as grade 0: no breach, grade 1:\2 mm, grade 2: 2–4 mm and grade 3:[4 mm breach. Results After appropriate statistical power analysis, 300 screws inserted in 59 patients from T4–L5 levels. No significant differences noted between the two probes in terms of screw length [two-tailed p = 0.16]; grade 0 screws [two-tailed p = 0.49] or screws with grade 2/3 breaches [two-tailed p = 0.68]. With the right-hand-dominant operating-surgeon standing to left of patient during surgery, no difference noted between the two probes for either the right or left-side pedicle screw insertion [two-tailed p = 1]. Repeating these tests in the subset of thoracic pedicle screws too, revealed no significant difference. Conclusions No significant difference in outcome of pedicle screw insertion with either a straight or a curved pedicle probe. Keywords
Pedicle screw Pedicle probe Pedicle starter
Y. K. Pithwa K. Venkatesh Spine Surgery, HOSMAT Hospital, Bangalore, India Y. K. Pithwa (&) Flat No. D-209, USHAS Apartments, Site No. 26, 16th Main, Jayanagar 4th Block, Bangalore 560011, India e-mail: [email protected]; [email protected]
Introduction Various pedicle probes exist with varying shapes and sizes that spine surgeons use to create a trajectory for insertion of screws into the spine. Though it is difficult to define each variety due to lack of standardization, one can broadly categorize these pedicle probes into two types (Fig. 1): a straight one and a curved one [1]. Kim et al. [1] described free-hand insertion of thoracic pedicle screws with a curved probe (Fig. 2) inserted initially with the curvature facing laterally up to a depth of about 20 mm, thereafter removing and reinserting the same with the curvature facing medially up to the anteromedial aspect of the vertebral body. This curved trajectory created thereby is ‘straightened’ by the use of a straight tap following which the pedicle screw is inserted [1]. On the other hand, the straight probe is generally inserted ‘straight’ along the actual intended final trajectory of the screw. Based on the above-mentioned method of insertion of a curved pedicle probe, the present study hypothesized that lateral direction of curvature of the curved pedicle probe during the initial depth of 20 mm would lead to a lesser incidence of medial pedicle breach. Though the study by Kim et al. was specific to thoracic pedicles, the present study aimed at extrapolating these logical principles over to the lumbar spine as well. Anatomical studies have also revealed that the medial wall of pedicle is thicker than the lateral wall [2–4]. In view of this, one may be inclined to hypothetically presume that the curved trajectory created by the curved probe may get ‘straightened’ by the straight tap by getting lateralized on its dorsal aspect in view of the relatively weak lateral pedicle wall. This kind of dorsal ‘lateralization’ may thereby lead to a longer screw length. This was the second hypothesis for the present study which
123
Eur Spine J
was a prospective, comparative, single-blind study carried out at a tertiary referral center.
Materials and methods After appropriate institutional review board approval, the patients were included in the study after informed consent for the same.
Fig. 1 Different kinds of pedicle probes: a straight pedicle probe, and b curved pedicle probe
Fig. 2 Free-hand insertion of pedicle screws with a curved probe inserted initially with the curvature facing laterally up to a depth of about 20 mm (a), thereafter removing and reinserting the same with the curvature facing medially up to the anteromedial aspect of the vertebral body (b)
123
Inclusion criterion was patients undergoing pedicle screw stabilization surgeries in the thoracolumbar spine for varied indications. Patients with scoliosis were excluded in view of relative asymmetry between the concave and convex side pedicle [5]. Vertebral levels with unilateral fixation too were excluded. Accordingly, 59 patients, including 28 males and 31 females were included in the study. Indications for surgery included spondylolisthesis (n = 26), degenerative instability (n = 16), spinal infections (n = 4) and unstable spinal trauma (n = 13). Pedicle screws were inserted using straight and curved probe (Fig. 1) into opposite pedicles of the same vertebra, in an alternating manner. All screws were inserted by a single surgeon, fellowship trained in spine surgery, well past the learning curve, having inserted more than 300 screws into the thoracolumbar spine using both, the straight and curved pedicle probe [6]. Following creation of the screw tract with either probe, integrity of the tract was checked using a ball-tipped pedicle sound [1]. The screw was inserted thereafter and its position was verified with intra-operative C-arm images in anteroposterior and lateral planes. Pedicle breach was evaluated in the postoperative period using spiral CT scans with 2-mm slice thickness and 2-mm interval with retro reconstruction of 1-mm slice thickness and 1-mm interval [7]. This was a blinded evaluation done by a radiologist. Pedicle screw positions were graded as grade 0: no breach, grade 1: up to 2 mm breach, grade 2: 2–4 mm breach, grade 3: [4 mm breach [8]. With a significance level (alpha) of 0.05 (two-tailed), power analysis was done to detect a 5 % difference between the two probes in being able to accurately insert (grade 0) screws. Accordingly, 150 screws had to be inserted with either probe to give a power of 80 %. With a significance level (alpha) of 0.05 (two-tailed), this sample
Eur Spine J Table 1 Distribution of screws as per vertebral levels
Vertebral level
Number of screws
T4
2
T5
4
T6
2
T7
2
T8
4
T9
6
T10
2
T11
14
T12
14
L1
8
L2 L3
26 34
L4
92
L5
90
Fig. 3 CT scan showing a grade 2 lateral breach on the right side. Being lateral, it was asymptomatic
Table 2 CT grading of pedicle screw breaches Grade of breach
Straight
Curved
Grade 0
142 of 150
138 of 150
Grade 1
4 of 150
10 of 150
Grade 2
4 of 150
1 of 150
Grade 3
0
1 of 150
size also had a 80 % power of detecting 0.11 mm difference in the screw length using either probe. Statistical analysis was done using GraphPad Instat version 3.10, while power analysis was done using GraphPad StatMate version 2.00.
Results Age of the included patients was 42.3 ? 12.3 years. Three hundred pedicle screws were inserted. The distribution of screws in terms of vertebral level was as per Table 1. CT analysis for pedicle breaches revealed numbers as shown in Table 2. There was no statistically significant difference (two-tailed, p = 0.49 using Fisher’s exact test) in the placement of accurate (grade 0) screws with either probe (142 of 150 with straight probe and 138 of 150 with curved probe). Repeating the analysis for thoracic levels exclusively too, did not reveal any difference (21 of 25 with each, straight and curved probe). Up to 2 mm breach of the pedicle has been considered to be within the safe zone for neural structures [9]. Hence, analysis was repeated considering grades 2 and 3, i.e. [2 mm breach as unsafe. Using this criterion, 146 of 150 (97.33 %) with straight probe and 148 of 150 (98.67 %)
Fig. 4 CT scan showing a grade 3 lateral breach on the right side. Being lateral, it was asymptomatic
with curved probe were within the safe zone. This difference too, was found to be statistically insignificant (twotailed, p = 0.68 using Fisher’s exact test). Similar analysis for thoracic screws exclusively too, did not reveal any statistically significant difference (23 of 25 with straight probe and 24 of 25 with curved probe were in the safe zone; two-tailed, p = 1 using Fisher’s exact test). Six screws (four with straight probe and two with curved prove) of the total 300 screws studied had grade 2 (Fig. 3) or 3 (Fig. 4) breaches. However, these screws were asymptomatic in view of the breaches being lateral and hence, warranted no revision. Contrary to the first hypothesis of the present study, use of a curved pedicle probe did not cause any statistically significant reduction in medial breach (one medial breach
123
Eur Spine J Table 3 Distribution of absolutely accurate (grade 0) screws Absolutely accurate (grade 0) screws
Straight probe
Curved probe
Left side
95.78 % (68 of 71)
92.41 % (73 of 79)
Right side
93.67 % (74 of 79)
91.55 % (65 of 71)
with straight probe while two medial breaches with curved probe: two-tailed p = 1 using Fisher’s exact test). With the right-hand dominant operating-surgeon standing to the left of patient at the time of surgery, assessment for absolutely accurate [grade 0] screws using either probe for insertion of pedicle screw on the left or right-side was done. This data is presented in Table 3. Statistical analysis did not reveal any significant difference in this data between the use of the two probes for either the right or left-side pedicle (two-tailed p = 1, Fisher’s exact test). One hundred and fifty screws were inserted using each probe. Screw length was 44.27 ± 3.49 mm for straight probe while it was 44.47 ± 3.58 mm for curved probe. Paired ‘t’ test analysis did not reveal any statistically significant difference (two-tailed, p = 0.16) between the two outcomes. Exclusively testing for thoracic levels, the screw length was 42 ± 3.23 mm for straight probe while it was 42 ± 3.53 mm for curved probe. Paired ‘t’ test analysis did not reveal any statistically significant difference (twotailed, p = 0.99) between the two outcomes at thoracic level either. This contradicted the second hypothesis of the current study.
Discussion Ever since Roy-Camille [10] introduced pedicle screw fixation of the spine, it has presently become the most popular mode of securing an anchor in the thoracolumbar spine. Though there was initial reservation related to the use of pedicle screws in the thoracic spine, this reservation too has been successfully addressed in recent times [1]. In a study of 640 freehand pedicle screws in the thoracolumbar spine of 98 patients, Karapinar et al. [11] reported 94.2 % accuracy rate. In another study of 1,009 freehand pedicle screws (689 thoracic and 320 lumbosacral) into patients with neuromuscular scoliosis, Modi et al. [9] considered up to 2 mm medial and up to 4 mm lateral breach as within-safe zone. As per this criterion, the authors reported 93.3 % (942/1,009, 92.4 % in thoracic and 95.3 % in lumbar spine) screws within the safe zone. The present study considered up to 2 mm medial and up to 2 mm lateral breach as within-safe zone. Considering this, 97.33 % (146 of 150) screws with straight probe and 98.67 % screws (148 of 150) with curved probe were within the safe zone.
123
To the best of authors’ knowledge, the present study is the first one to analyze the efficacy of straight versus curved pedicle probe for screw insertion into the thoracolumbar spine. There was no statistically significant difference between the two pedicle probes in terms of the overall accuracy of screw placement or the ultimate length of screw inserted into the spine. Thus, the hypothesis of the study could not be supported by the findings. To the best of authors’ knowledge, the present study is also the first one to analyze any difference in outcome of pedicle screw insertion based on the side on which the operating surgeon is standing while doing the surgery. With the right-hand dominant operating surgeon standing to the left of patient, there was no statistically significant difference in the accuracy of insertion of pedicle screw on either side with either probe. So the present study does not allude to any scientific advantage for the operating surgeon to change sides from right to left or vice versa while inserting pedicle screws on the corresponding sides. In view of using the two probes on opposite sides of the same vertebra, matching of the two groups was inherently incorporated in the study. The power of this prospective single blind study for cumulative assessment of all the screws is also within acceptable limits. However, single surgeon involvement, relative paucity of thoracic levels, lack of pediatric cases and lack of standardized ‘‘straight’’ and ‘‘curved’’ pedicle probes remain the obvious limitations of this study. These limitations can, however, become points for further research on this topic. In conclusion, there was no definite evidence to support the fact that accuracy of pedicle screw insertion into the thoracolumbar spine varies as per the type of pedicle probe used. Conflict of interest
None.
References 1. Kim YJ, Lenke LG, Bridwell KH et al (2004) Freehand pedicle screw placement in the thoracic spine: is it safe? Spine 29(3):333–342 2. Mughir AM, Yusof MI, Abdullah S, Ahmad S (2010) Morphological comparison between adolescent and adult lumbar pedicles using computerised tomography scanning. Surg Radiol Anat 32(6):587–592 3. Liau KM, Yusof MI, Abdullah MS, Abdullah S, Yusof AH (2006) Computed tomographic morphometry of thoracic pedicles: safety margin of transpedicular screw fixation in malaysian malay population. Spine (Phila Pa 1976) 31(16):E545–E550 4. Datir SP, Mitra SR (2004) Morphometric study of the thoracic vertebral pedicle in an Indian population. Spine (Phila Pa 1976) 29(11):1174–1181 5. Liljenqvist UR, Allkemper T, Hackenberg L et al (2002) Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction. J Bone Joint Surg Am 84-A(3):359–368
Eur Spine J 6. Gonzalvo A, Fitt G, Liew S et al (2009) The learning curve of pedicle screw placement: how many screws are enough? Spine (Phila Pa 1976) 34(21):E761–E765 7. Rydberg J, Buckwalter KA, Caldemeyer KS et al (2000) Multisection CT: scanning techniques and clinical applications. Radiographics 20(6):1787–1806 8. Neo M, Sakamoto T, Fujibayashi S et al (2005) The Clinical risk of vertebral artery injury from cervical pedicle screws instead in degenerative vertebrae. Spine 30:2800–2805 9. Modi HN, Suh SW, Fernandez H et al (2008) Accuracy and safety of pedicle screw placement in neuromuscular scoliosis
with free-hand technique. Eur Spine J 17(12):1686–1696 (epub 2008 Oct 1) 10. Roy-Camille R, Saillant G, Mazel C (1986) Plating of thoracic, thoracolumbar, and lumbar injuries with pedicle screw plates. Orthop Clin North Am 17(1):147–159 11. Karapinar L, Erel N, Ozturk H et al (2008) Pedicle screw placement with a free hand technique in thoracolumbar spine: is it safe? J Spinal Disord Tech 21(1):63–67
123
