BackgroundLateral lumbar interbody fusion (LLIF) is a popular, minimally invasive technique that is used to address challenging multilevel degenerative spinal diseases. It remains controversial whether supplemental instrumentation should be added for multilevel LLIF. In this study, we compared the kinematic stability afforded by stand-alone lateral cages with those supplemented by bilateral pedicle screws and rods (PSR), unilateral PSR, or lateral plate (LP) fixation using a finite-element (FE) model of a multi-level LLIF construct with simulated osteoporosis. Additionally, to evaluate the prospect of cage subsidence, the stress change characteristics were surveyed at cage-endplate interfaces.MethodsA nonlinear 3-dimensional FE model of the lumbar spine (L2 to sacrum) was used. After validation, four patterns of instrumented 3-level LLIF (L2-L5) were constructed for this analysis: (a) 3 stand-alone lateral cages (SLC), (b) 3 lateral cages with lateral plate and two screws (parallel to endplate) fixated separately (LPC), (c) 3 lateral cages with bilateral pedicle screw and rod fixation (LC + BPSR), and (d) 3 lateral cages with unilateral pedicle and rod fixation (LC + UPSR). The segmental and overall range of motion (ROM) of each implanted condition were investigated and compared with the intact model. The peak von Mises stresses upon each (superior) endplate and the stress distribution were used for analysis.ResultsBPSR provided the maximum reduction of ROM among the configurations at every plane of motion (66.7–90.9% of intact spine). UPSR also provided significant segmental ROM reduction (45.0–88.3%). SLC provided a minimal restriction of ROM (10.0–75.1%), and LPC was found to be less stable than both posterior fixation (23.9–86.2%) constructs. The construct with stand-alone lateral cages generated greater endplate stresses than did any of the other multilevel LLIF models. For the L3, L4 and L5 endplates, peak endplate stresses caused by the SLC construct exceeded the BPSR group by 52.7, 63.8, and 54.2% in flexion, 22.3, 40.1, and 31.4% in extension, 170.2, 175.1, and 134.0% in lateral bending, and 90.7, 45.5, and 30.0% in axial rotation, respectively. The stresses tended to be more concentrated at the periphery of the endplates.ConclusionsSLC and LPC provided inadequate ROM restriction for the multilevel LLIF constructs, whereas lateral cages with BPSR or UPSR fixation provided favorable biomechanical stability. Moreover, SLC generated significantly higher endplate stress compared with supplemental instrumentation, which may have increased the risk of cage subsidence. Further biomechanical and clinical studies are required to validate our FEA findings.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-017-1387-6) contains supplementary material, which is available to authorized users.

A retrospective study evaluating complications in 2,233 consecutive patients of subaxial cervical disorders treated with an anterior cervical locking plate was performed, and recommendations for prevention and treatment were made. The average length of follow-up was 1.3 years. Any loosening or breaking of the plates and screws or malpositions that threatened tracheoesophageal or neurovascular structures were defined as the complications. There were 239 cases (10.7%) with different kinds of complications. The complications included oblique plating in 56 cases in which the screw could irritate the nerve root. Screws were driven into the disc space in four cases, which ultimately led to plate loosening. Screws penetrated the endplate or passed excessively close to it producing a triangle fracture in 19 cases. Loosening or breaking of the plate and the screw was found in 115 cases. These phenomena were always associated with non-union. Three oesophageal perforations occurred and conservative treatments proved effective. Finally, overlong plates impinged on the adjacent level in 14 cases and promoted disc degeneration ultimately leading to revision surgery. Good training and careful operation may help to decrease the complication rate. Most hardware complications are not symptomatic and can be treated conservatively. Only a few of them need immediate reoperation.Résumé Nous avons réalisé une étude rétrospective de 2,233 patients consécutifs, traités par plaques cervicales verrouillées pour divers problèmes cervicaux. Le suivi moyen a été de 1.3 ans. Nous n'avons observé aucun démontage ni aucune fracture de matériel. Les malpositions de la plaque avec des lésions trachéo oesophagiennes ou neurovasculaires ont été répertoriées comme complications. Celles-ci ont été au nombre de 239 (10.7%), notamment une malposition de plaque implantée obliquement avec une irritation des racines nerveuses. Les vis étaient dans l'espace inter discal dans 4 cas avec un démontage dans les suites. Les anomalies au niveau de la plaque ont été retrouvées dans 115 cas. Celles-ci sont toujours associées à une pseudarthrose. Nous avons observé trois perforations de l'oesophage qui ont été traitées de façon conservatoire. Un conflit avec la plaque ou une dégénération discale du disque adjacent est survenu 14 fois. Avec la courbe d'apprentissage, les résultats devraient s'améliorer et le taux de complication diminuer. La plupart des complications dues au matériel n'ont pas entraîné de symptômes et n'ont pas été traitées.

We believe that the need for single stage 360° fusion of hangman's fractures can be somewhat predicted by a combination of high resolution imaging. For hangman's fractures with significant deformity and gapping, it is our experience that immediate single-stage anterior-posterior reduction, instrumentation, and arthrodesis achieve superior postoperative reduction and long-term functional outcomes.

The biomechanical study indicated that, contrary to expectation, addition of a cage did not increase the stability compared with C1-C2 pedicle screw alone. However, the C1 + C2 + Cage technique may be a viable alternative for atlantoaxial stabilization when the posterior arch of the atlas is absent or removed for decompression and a Gallie fixation is impossible.

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