Thoracic and lumbar vertebrae morphology in Lenke type 1 female adolescent idiopathic scoliosis patients

Abstract

BackgroundPedicle screws are widely used in adolescent idiopathic scoliosis (AIS) surgeries. Pedicle screw malposition may lead to serious vascular and neurologic complications. Knowledge of the morphometric anatomy of the thoracic and lumbar vertebrae is essential for the surgeon while implanting pedicle screws. It has been reported that there is a reduction of pedicle width at the concavity of the curve in AIS patients. However, it is unclear if gender plays a role in this pedicle width pattern. The goal of this study is to assess the vertebrae morphology in a more homogeneous group of AIS patients - female patients with Lenke type 1 curve.MethodsThe thoracic and lumbar vertebra and pedicle morphometry of 17 consecutive Lenke type 1 female AIS patients was analyzed based on 1mm fine cut CT scans. Morphometric anatomy of 539 pedicles from T1 to L5 was studied. Measurements included pedicle length, chord length, transverse pedicle width, transverse pedicle angle and vertebral rotation angle.ResultsThe mean age of the patients was 14 years old (range 12-18). The mean Cobb angle was 56° (range 43° -88°) and the mean angle of vertebral rotation varied between 4-13.8°. The apical vertebra was between T7 and T11. The transverse pedicle width was significantly smaller (p < 0.05) on the concave side in the apical region of the thoracic spine (T7 and T8), measuring between 2.1-2.2 mm on the concave side and 2.7-3.1 mm on the convex side. Meanwhile, in some upper thoracic vertebrae (T3, T4, T5), the width was significantly bigger (p < 0.05) on the concave side than on the convex side, measuring between 2.8-4 mm on the concave side and 1.8-2.4 mm on the convex side. In the lumbar spine, the width varied between 4.1-9.9 mm without significant differences between the concave and convex sides (p > 0.05). The pedicle length varied between 15.4-28.7 mm and was significantly smaller (p < 0.05) on the concave side at T4, T5 and L2. The chord length was shortest at T1, measuring 32.4 mm and increased gradually to 54.3 mm at L3 but no statistical difference was found between the concave and convex sides. The transverse pedicle angle varied between 11.8° and 35° and was significantly bigger on the concave side at T7 and on the convex side at L1 (p < 0.05).ConclusionsThe vertebrae morphology in Lenke type 1 female AIS patients is substantially different from the vertebrae in normal spines especially at the apex and in the upper thoracic region. This is consistent with some previous reports which did not distinguish between male and female patients. Our findings suggest that gender does not play a major role in the vertebrae morphology pattern of AIS patients. Furthermore, recognizing this pattern is critical in order to optimize pedicle screw instrumentation and may allow for some leeway adjustments in the pedicle screw trajectory regardless of the methods of implantation.

Is There Asymmetry Between the Concave and Convex Pedicles in Adolescent Idiopathic Scoliosis? A CT Investigation

“…Our study showed clinically relevant smaller pedicle widths (inner and outer cortical) on the concave side periapically-a finding consistent with previous studies using CT, MRI, and cadavers [1,18,21,25,30,35]. Inner and outer cortical pedicle widths were measured to provide clarity over the inconsistencies or ambiguities that existed in the measurement definitions in previous studies [9,36]. With the chord length being longer on the concave side of the curve at T8-T10, but no difference seen in the pedicle lengths, it can be inferred that the length from the anterior cortex of the vertebral body to the anterior aspect of the pedicle along the pedicle axis is longer on the concave side.…”

“…In adolescent idiopathic scoliosis, where the anatomy is three-dimensionally asymmetrically distorted and the pedicles known to at times encroach closer to the spinal cord and aorta [16,32], it is vital to have an understanding of the morphologic features of the pedicle in all planes. While the pedicle width has been investigated in previous studies using various methods [8,9,16,18,30,33,36], there are clear knowledge gaps or inconsistencies when examining the remaining pedicle parameters. The current study identified clinically relevant asymmetry in the width, height, and angulation of the pedicle in multiple planes using a more clinically relevant and reliably reproducible measurement technique.…”

“…Although newly developed imaging navigation techniques can assist in improving pedicle screw placement, failure to select appropriate screw size, screw starting point, and screw trajectory can result in pedicle screw misplacement which potentially can cause serious neurologic, vascular, or visceral injury [9,10,12,29,32]. There have been numerous studies examining the morphologic features of the pedicle and placement of pedicle screws in normal and adolescent idiopathic scoliosis spines using various definitions and measuring modalities [18,25,30,31,35,36].…”

What is the Difference in Morphologic Features of the Thoracic Pedicle Between Patients With Adolescent Idiopathic Scoliosis and Healthy Subjects? A CT-based Case-control Study

“…Therefore, it is important that spinal surgeons have clear knowledge of the morphometric anatomy of pedicles, especially in deformed spines, to guarantee the safest pedicle screw placement. Using CT scans, we conducted a morphologic study of thoracic pedicles in 60 female patients with Lenke Type 1 adolescent idiopathic scoliosis and 60 sex-, age-, and height-matched controls, which provided a more-accurate assessment than previously published studies because of our large sample size and sample homogeneity [4,12].…”

Evaluation of robot-guided minimally invasive implantation of 2067 pedicle screws

“…5 The accuracy of guidance systems in screw insertion procedures is particularly notable in anatomically difficult cases, such as scoliosis correction surgeries, with a reported 6-fold reduction in perforation rates and mean insertion angle errors compared with conventional methods. 8,14 Similar to other navigation systems, miniature hexapod robots, such as Mazor's SpineAssist or Renaissance, provide intraoperative guidance and physically guide the surgeon along a preplanned trajectory. The Mazor system has been shown to improve surgical accuracy and, in combination with a minimally invasive approach, to minimize morbid sequelae and radiation doses for both patient and clinical staff in several studies.…”