Evaluation of thoracic pedicle screw placement in adolescent idiopathic scoliosis

Şarlak, Ahmet Yılmaz; Tosun, Bilgehan; Atmaca, Halil; Sarisoy, Hasan Tahsin; Buluç, Levent

doi:10.1007/s00586-009-1065-y

Cited by 95 publications

(65 citation statements)

References 19 publications

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“…Considering the complexity of pedicle anatomy, pedicle screw insertion could be mentally and technically demanding [26,27]. The priority is to make sure that each screw is contained solely in the desired pedicle and its alignment with its neighbors often comes after this priority [27][28][29]. Even with computer-assisted image-guided techniques, there is considerable variation in the placement of each pedicle screw with respect to its neighbors.…”

Section: Discussionmentioning

confidence: 99%

“…Variation in screw insertion orientation is also significant, sometimes with pedicle violation (medial, inferior, superior, and anterolateral vertebral body) [27]. Variation of coronal plane screw position greater than 2 mm was reported (distance between medial pedicle wall and medial margin of the pedicle screw and between lateral margin of the pedicle screw and lateral vertebral corpus) [29]. The final positions of all screw head slots are therefore unlikely to be perfectly smoothly aligned.…”

Section: Discussionmentioning

confidence: 99%

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Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

2011

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Purpose The objective of this computational study was to compare the biomechanical effects of different implant densities in terms of curve reduction and the force levels at the implant-vertebra interface and on the intervertebral elements. Methods Eight cases were randomly picked among patients who have undergone a posterior spinal instrumentation for adolescent idiopathic scoliosis (AIS). For each case, two computer simulations were performed, one with the actual surgery implant pattern and another with the same fusion levels but an alternative implant pattern proposed by an experienced surgeon. The two implant patterns for each case were respectively put into higher and lower implant density group. The spinal correction and the force levels at bone-implant interface and on the intervertebral elements were analyzed and compared between the two groups. Results There were on average 13% more pedicle screws and 30% more bilaterally placed pedicle screws in the higher versus lower density group. The difference in the density of screws (92% vs. 79%) did not lead to significant difference in terms of the resulting main thoracic (MT) Cobb angle, and the MT apical axial vertebral rotation. The average and maximum implant-vertebra force levels were about 50 and 65%, respectively higher in the higher versus lower density group, but without consistent distribution patterns. The average intervertebral forces did not significantly differ between the two groups. Conclusions With the same fusion levels, lower density screws allowed achieving similar deformity correction and it was more likely to have lower screw-vertebra loads.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

2011

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“…The overall rate of misplacement reported in this study was 17%. Five of the studies dealing with assessment of pedicular screw placement in scoliosis showed a misplacement rate of 5.7, 50.7, 25, 29.1, and 18.5% [1,3,9,20,22].…”

Section: Discussionmentioning

confidence: 99%

Radiological and clinical outcome of screw placement in adolescent idiopathic scoliosis: evaluation with low-dose computed tomography

et al. 2009

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Posterior corrective surgery using ''all pedicle screw construct'' carries risk of neurovascular complications. The study aims were to assess the screw placement in patients with adolescent idiopathic scoliosis using CT with low-radiation dose, and to evaluate the clinical outcome in patients with misplaced pedicle screws. CTs of 49 consecutive patients (873 screws, 79% thoracic) were retrospectively evaluated by two independent radiologists. A new grading system was developed to distinguish between lateral, medial and anterior cortical perforations, endplate perforation and foraminal perforation. The grading system is based on whether the cortical violation is partial or total rather than on mm-basis. The overall rate of screw misplacement was 17% (n = 149): 8% were laterally placed and 6.1% were medially placed. The rates of anterior cortical, endplate and foraminal perforation were 1.5, 0.9, and 0.5%, respectively. Lateral cortical perforation was more frequent in the thoracic spine (P = 0.005), whereas other types of misplacement including medial cortical perforation were more frequent on the left and the concave side of scoliotic curves (P = 0.002 and 0.003). No neurovascular complications were reported. The association between the occurrence of screw misplacement and the Cobb angle was statistically significant (P = 0.037). Misplacements exceeding half screw diameter should be classified as unacceptable. Low-dose CT implies exposing these young individuals to a significantly lower radiation dose than do other protocols used in daily clinical practice. We recommend using low-dose CT and the grading system proposed here in the postoperative assessment of screw placement.

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“…21,25,32 Pedicle screw placement, however, can be challenging, particularly in the thoracic spine. 17,19,21,37 In this region, the pedicles are typically smaller and have more complex morphologies, thus increasing the risk of malpositioned screws.…”

Section: Discussionmentioning

confidence: 99%

Freehand thoracic pedicle screw technique using a uniform entry point and sagittal trajectory for all levels: preliminary clinical experience

Fennell¹,

Palejwala²,

Skoch³

et al. 2014

SPI

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Object Experience with freehand thoracic pedicle screw placement is well described in the literature. Published techniques rely on various starting points and trajectories for each level or segment of the thoracic spine. Furthermore, few studies provide specific guidance on sagittal and axial trajectories. The goal of this study was to propose a uniform entry point and sagittal trajectory for all thoracic levels during freehand pedicle screw placement and determine the accuracy of this technique. Methods The authors retrospectively reviewed postoperative CT scans of 33 consecutive patients who underwent open, freehand thoracic pedicle-screw fixation using a uniform entry point and sagittal trajectory for all levels. The same entry point for each level was defined as a point 3 mm caudal to the junction of the transverse process and the lateral margin of the superior articulating process, and the sagittal trajectory was always orthogonal to the dorsal curvature of the spine at that level. The medial angulation (axial trajectory) was approximately 30° at T-1 and T-2, and 20° from T-3 to T-12. Breach was defined as greater than 25% of the screw diameter residing outside of the pedicle or vertebral body. Results A total of 219 thoracic pedicle screws were placed with a 96% accuracy rate. There were no medial breaches and 9 minor lateral breaches (4.1%). None of the screws had to be repositioned postoperatively, and there were no neurovascular complications associated with the breaches. Conclusions It is feasible to place freehand thoracic pedicle screws using a uniform entry point and sagittal trajectory for all levels. The entry point does not have to be adjusted for each level as reported in existing studies, although this technique was not tested in severe scoliotic spines. While other techniques are effective and widely used, this particular method provides more specific parameters and may be easier to learn, teach, and adopt.

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Evaluation of thoracic pedicle screw placement in adolescent idiopathic scoliosis

Cited by 95 publications

References 19 publications

Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

Radiological and clinical outcome of screw placement in adolescent idiopathic scoliosis: evaluation with low-dose computed tomography

Freehand thoracic pedicle screw technique using a uniform entry point and sagittal trajectory for all levels: preliminary clinical experience

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