Biomechanical Stability of a Stand-Alone Interbody Spacer in Two-Level and Hybrid Cervical Fusion Constructs.

Study Design: In vitro human cadaveric biomechanical analysis.

Objective: To evaluate the segmental stability of a stand-alone spacer (SAS) device compared with the traditional anterior cervical plate (ACP) construct in the setting of a 2-level cervical fusion construct or as a hybrid construct adjacent to a previous 1-level ACP construct.

Methods: Twelve human cadaveric cervical spines (C2-T1) were nondestructively tested with a custom 6-degree-of-freedom spine simulator under axial rotation (AR), flexion-extension (FE), and lateral bending (LB) at 1.

Effects of rod reduction on pedicle screw fixation strength in the setting of Ponte osteotomies.

Background Context: The use of a rod reduction device can have deleterious consequences on pedicle screw pullout strength (POS) in the thoracic spine. However, posterior-only osteotomies in the thoracic spine are often performed to improve flexibility of the spine and offset forces of deformity correction maneuvers.

Purpose: To investigate the effect on pedicle screw POS caused by the rod reduction technique in the presence of facet osteotomies in the thoracic spine.

Pedicle screw reinsertion using previous pilot hole and trajectory does not reduce fixation strength.

Study Design: Fresh-frozen human cadaveric biomechanical study.

Objective: To evaluate the biomechanical consequence of pedicle screw reinsertion in the thoracic spine.

Summary Of Background Data: During pedicle screw instrumentation, abnormal appearance on fluoroscopic imaging or low current reading with intraoperatively evoked electromyographic stimulation of a pedicle screw warrants complete removal to reassess for pedicle wall violation or screw malposition.

Pedicle screw "hubbing" in the immature thoracic spine: a biomechanical and micro-computed tomography evaluation.

Background: A previous biomechanical study using adult thoracic vertebrae (both normal and osteoporotic bone density) demonstrated the deleterious effect of the pedicle screw hubbing technique. Pedicle screw "hubbing" involves seating and engaging the ventral aspect of the screw head onto the dorsal lamina cortex. This technique is postulated to provide a load-sharing effect by improving pullout resistance, as well as decreasing cephalocaudad toggling and implant loosening.

Do stand-alone interbody spacers with integrated screws provide adequate segmental stability for multilevel cervical arthrodesis?

Background Context: Some postoperative complications after anterior cervical fusions have been attributed to anterior cervical plate (ACP) profiles and the necessary wide operative exposure for their insertion. Consequently, low-profile stand-alone interbody spacers with integrated screws (SIS) have been developed. Although SIS constructs have demonstrated similar biomechanical stability to the ACP in single-level fusions, their role as a stand-alone device in multilevel reconstructions has not been thoroughly evaluated.

The ventral lamina and superior facet rule: a morphometric analysis for an ideal thoracic pedicle screw starting point.

Background Context: With the increasing popularity of thoracic pedicle screws, the freehand technique has been espoused to be safe and effective. However, there is currently no objective, definable landmark to assist with freehand insertion of pedicle screws in the thoracic spine. With our own increasing surgical experience, we have noted a reproducible and unique anatomic structure known as the ventral lamina.

The biomechanical consequences of rod reduction on pedicle screws: should it be avoided?

Background Context: Rod contouring is frequently required to allow for appropriate alignment of pedicle screw-rod constructs. When residual mismatch is still present, a rod persuasion device is often used to achieve further rod reduction. Despite its popularity and widespread use, the biomechanical consequences of this technique have not been evaluated.

The biomechanical effect of pedicle screw hubbing on pullout resistance in the thoracic spine.

Background Context: The biomechanical fixation strength afforded by pedicle screws has been strongly correlated with bone mineral density. It has been postulated that "hubbing" the head of the pedicle screw against the dorsal laminar cortex provides a load-sharing effect, thereby limiting cephalocaudad toggling and improving the pullout resistance of the pedicle screw.

Purpose: To evaluate the pullout strength (POS) of monoaxial hubbed pedicle screws versus standard fixation in the thoracic spine.