Advancements in osteoporotic spine fixation

Abstract

With the global rise in the population of elderly along with other risk factors, spine surgeons have to encounter osteoporotic spine more often. Osteoporotic spine, however, causes problems in management, particularly where instrumentation is involved, resulting in screw loosening, pull out, pseudoarthroses or adjacent segment kyphosis. Osteoporosis alters the bio mechanics at the bone implant interface resulting in various degrees of fixation failure. Various advancements have been made in this field to deal with such issues in addition to modification of basic surgical techniques such as increasing the diameter and length of the screw, smaller pilot hole, under tapping, longer constructs, supplemental anterior fixation, sublaminar wires or laminar hooks, use of transverse connectors and triangulation techniques, among others. They include novel surgical techniques such as cortical bone trajectory, superior cortical trajectory, double screw technique, cross trajectory technique, bicortical screw technique or prophylactic vertebroplasty. Advances in the screw design include expandable screws, fenestrated screws, conical screws and coated screws. In addition to PMMA cement augmentation, other biodegradable cements have been introduced to mitigate the side effects of PMMA such as calcium phosphate, calcium apatite and hydroxyapatite. Pharmacotherapy with teriparatide can aid fusion and lower the rate of pedicle screw loosening. Many of these strategies have only bio mechanical evidence and require well designed clinical trials to establish their clinical efficacy. Though no single technique is fool proof, little modifications in the existing techniques or utilizing a combination of techniques without adding to the cost of the surgery may help to achieve a near-ideal result. Surgeons have to equip their armamentarium with all the recent advances, and should be open to novel thoughts and techniques.

Keywords: Evidence; Osteoporosis, surgery; Recent advances; Review literature; spine, surgery.

Fig. 1

AP (Antero-posterior) and lateral X-ray images of a patient showing the Cortical Bone Trajectory technique for pedicle screw fixation.

Fig. 2

CT image of the pedicles showing the position of a traditional pedicle screw (left) and a superior cortical screw (right).

Fig. 3

AP and lateral X-ray images of a patient operated by double screw technique of pedicle screw fixation.

Fig. 4

An illustration showing the cross trajectory technique of screw insertion.

Fig. 5

Image showing an expandable pedicle screw (Weigao Orthopedic Device Co. Ltd., Shandong, China).

Fig. 6

An image showing a fenestrated pedicle screw.

Fig. 7

An image showing a traditional pedicle screw (cylindrical) (a) and a conical pedicle screw(b).

Fig. 8

Image showing a HA coated screw and a traditional screw.

Fig. 9

An illustration showing the technique of bicortical screw fixation with cement augmentation.