Pedicle versus laminar screws: what provides more suitable C2 fixation in congenital C2–3 fusion patients?

Abstract

Patients with Klippel-Feil syndrome (KFS) have congenital fusions of at least 1 cervical motion segment, and often present with compensatory hypermobility or symptomatic stenosis of the cranio-vertebral junction which requires occipitocervical reconstruction and fusion. One subgroup of KFS patients in which this is particularly common is those with isolated C2-3 congenital fusion (C2-3 CF). The anatomic suitability for C2 pedicle and laminar screw placement had been analyzed in the general adult population, and guidelines for their techniques had been established. However, the feasibility and safety of the two techniques in KFS patients with congenital C2-3 fusion has not been reported. This radiographic study was performed to evaluate the feasibility of these two widely used methods in such patients. We recruited 108 patients with atlantoaxial dislocation and reconstructed CTs were performed. Among them, 53 had C2-C3 congenital fusion diagnosed as KFS and 55 had normal cervical segmentation (NCS). The maximum possible diameters and length were measured along the ideal screw trajectories. Both of mean diameters and lengths of the C2 laminar screw trajectory in the C2-3 CF group were significantly larger than that in NCS. Mean diameters of the C2 pedicle screw trajectory in this group were significantly smaller than that in NCS group, however, C2-3 CF patients had longer pedicle paths than NCS. In the C2-3 CF group, all 53 cases had suitable trajectory for C2 laminar screw, while 21 (39.6%) had a pedicle diameter less than 4.5 mm. In the NCS group, 5 cases (9.1%) had a pedicle diameter less than 4.5 mm. All 108 cases had sufficient diameters for C2 laminar screw placement. Klippel-Feil patients with C2-3 CF are good candidates for the technique of C2 laminar screw. Preoperative radiography should be carefully evaluated and the option of C2 fixation be determined with a thorough consideration in these patients.

A retrospective study of congenital osseous anomalies at the craniocervical junction treated by occipitocervical plate-rod systems

“…Various congenital osseous anomalies at the craniocervical junction have been reported [11][12][13][14][15][16][17][18][19][20][21]. In the current study, the congenital lesions include os odontoideum, occipitalization of the atlas, congenital C2-3 fusion, congenital atlantoaxial subluxation, congenital basilar invagination and combined anomalies.…”

“…In the present study, occipitalization of the atlas was associated with congenital C2-3 fusion in three patients and os odontoideum in one. Occipitalization of the atlas, in association with congenital C2-3 fusion, exerts more strain on the atlantoaxial articulation during flexion and extension [15,16]. Repeated excessive strain at this joint more likely predisposes a patient to atlantoaxial instability.…”

The options of C2 fixation for os odontoideum: a radiographic study for the C2 pedicle and lamina anatomy

“…Fin [10] reported several drawbacks of the C2 laminar screw including associated reduced the surface of fusion bed and biomechanically weaker than the C2 pedicle screws. It was also indicated by Wang et al [34] that the C2 laminar screw had less force when act as a posterior anchor in comparison with the pedicle screw. In the present study, 20 C2 pedicles from 14 patients were found to have a diameter less than 5.5 mm.…”

“…For an average adult, the mean diameter and length of C2 pedicle are 5.8-8 and 24-31 mm, respectively [25,27,34,37], and those of C2 lamina are 5.75-6.3 and 24.6-31.6 mm [4,7,32]. These parameters should allow the use of both pedicle and laminar screws for C2 fixation.…”

“…The slice with the thickest isthmus and laminar of C2 were selected for the measurement. The method recommended by Neo et al [24] and Wang et al [34] was used to determine the diameters and length for the ideal screw trajectory from the CT images, i.e. along the ideal screw trajectory in the sagittal and axial planes, the maximum possible diameters and length of lamina and pedicle screws were measured (Fig.…”