Pedicle morphometry in patients with adolescent idiopathic scoliosis

Abstract

Background:The key to the safe and effective use of thoracic pedicle screws in the deformed spine is to thoroughly understand pedicle anatomy. There are a few studies related to pedicle anatomy in the Indian population and no pedicle morphometric studies in scoliosis patients. The present study aims to highlight the differential features of pedicle morphometry, including pedicle width, transverse pedicle angle and the depth to anterior cortex on the concave and convex side, in a group of Indian patients with adolescent idiopathic scoliosis and compare this to that of a western population.Materials and Methods:This is a prospective study of 24 patients with adolescent idiopathic scoliosis. The average age is 14.6 years (12.3-18.3 years) of which 14 were females and 10 were males. All the patients underwent CT scan using Siemens 4th generation scanner. The scans were analyzed by measuring the transverse pedicle width, transverse pedicle angle and the chord length; all the measurements being made both on the convex as well as the concave pedicle. Statistical analysis was performed with unpaired ‘t’ test.Results:A total of 1295 measurements were performed from 24 patients and an average of 215 pedicles were assessed for each set of the measurements made. The transverse pedicle width was consistently found to be smaller on concave side in comparison with the convex side at all levels except at T1. The transverse pedicle angle was greater on the concave side at all levels as compared to the convex side, though there was wide individual variation. The depth to anterior cortex was lesser on convex side in comparison to the concave side except at T1.Conclusions:The concave pedicle is much thinner and directed more medially than the convex side, especially at the apical region of the scoliotic curve. The pedicle anatomy in scoliosis patients shows very high individual variations and a careful study of pre-operative CT scans is essential for planning proper pedicle screw placement. Slightly longer screws can be accommodated on the concave side as compared to the convex side, though the difference in the chord length is not statistically significant at most levels.

Patients with adolescent idiopathic scoliosis of Lenke type-1 curve exhibit specific pedicle width pattern

“…Pedicle width measurements reported by Liljenqvist et al [17] were almost similar to the results of our study whereas Upendra et al [19] surprisingly showed wider pedicles almost throughout the curve. In several levels, data on pedicle width reported by Liljenqvist et al [17] showed smaller pedicles than our data.…”

“…Small pedicles at the concave side of the scoliotic apex have also been shown by two previous studies [17,19]. Pedicle width measurements reported by Liljenqvist et al [17] were almost similar to the results of our study whereas Upendra et al [19] surprisingly showed wider pedicles almost throughout the curve.…”

“…Low-dose spine CT with at least 20-fold reduction of the radiation doses has recently been introduced as a reliable method in the perioperative work-up of scoliosis [12]. Numerous reports on the pedicle morphometry in normal individuals as well as in cadavers and in patients with AIS have been published [13][14][15][16][17][18][19][20]. Many of these studies have pointed out a significant reduction of pedicle width at the concavity of the curve.…”

“…Liljenqvist et al [17,18] were among the first who presented data on pedicle morphometry based on patients data using CT and MRI17, 18, but their assessments were focused only on the morphological changes at the level of scoliotic apex. Upendra et al [19] has recently published a report on pedicle morphometry of the whole spine in patients with scoliosis of King curve type II, III and IV.…”

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

“…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]. The majority of these studies have identified clear size asymmetry in the pedicle widths between the concave and convex sides of the curve.…”