Pedicle Morphometric Analysis in Adolescent Idiopathic Scoliosis: Importance of Surgeon Familiarity with Patient Specific Variables

Abstract

Introduction A morphometric analysis of convex and concave pedicles in scoliotic spines depends on the three-dimensional reconstructions of the spine. As the standard of care relies on two-dimensional X-rays, there have been few reports on this topic and an underestimation of the morphological irregularities. We present our data of AIS patients who underwent HRCT as part of the preoperative planning for robotic-guided corrective surgery. Material and Methods A retrospective study of adolescent idiopathic scoliosis patients indicated for corrective surgery at our center. All patients underwent a CT scan with 1-mm slice thickness as part of their preoperative planning. The morphometric parameters documented were: transverse pedicle width, pedicle angle and maximum chord length in both convex and concave sides of the curve and were analyzed in the software (Renaissance) used for robotic guidance. Results We reviewed charts of 23 patients with an average age of 14.9 years. Average Cobb angles of the major curve measured 48.4° (Range 27.7° to 82.8°). There were 7 type 5 Lenke curves, 6 type 3 and type 1, and 4 cases of type 6. On the concave side 247 pedicles were measured, of which 104 (42%) were hypoplastic (i.e., transverse pedicle width <4 mm). Of the 249 convex pedicles measured, 74 (30%) were hypoplastic (p < 0.005). Mean concave pedicle angle was 15.6 ± 3.8° and maximum chord length was 40.9 ± 7.1 mm, while the convex pedicle angle was 16.1 ± 3.9° (p = 0.22) and maximum chord length was 40.8 ± 6.4 mm (p = 0.82). Conclusion Knowledge of patient-specific anatomical variances is critical when instrumenting scoliotic vertebrae. Based on our findings, despite the patient's added exposure to radiation, we advocate the use of CT-based preoperative planning to maximize safety of the instrumentation and emphasize the importance of Surgeon familiarity with patient specific anatomic variances in instrumentation of scoliotic vertebrae.

Comparison of the Accuracy of Pedicle Screw Placement Using a Fluoroscopy-Assisted Free-Hand Technique with Robotic-Assisted Navigation Using an O-Arm or 3D C-Arm in Scoliosis Surgery

“…Of the 249 convex pedicles measured, 74 (30%) were hypoplastic ( P < .005). 36 Pedicles on the concave side in scoliosis patients tend to be thinner, dysplastic, and more sclerotic, and the spinal cord is in direct contact with the medial wall of the pedicles, compared with non-scoliotic patients, making pedicle screw insertion challenging. 9 , 37 Therefore, we can cautiously conclude that 1 of the main reasons for screw misplacement under robotic-assisted navigation using an O-arm or 3D C-arm is hypoplastic pedicles in patients with scoliosis, especially on the concave side.…”