Biomechanical evaluation of the impact of various facet joint lesions on the primary stability of anterior plate fixation in cervical dislocation injuries: a cadaver study

Secondary Dislocations in Type B and C Injuries of the Subaxial Cervical Spine: Risk Factors and Treatment

INTRODUCTION

This study analyzed the incidence of secondary dislocations (sDLs) after surgical stabilization of AO Spine type B and C injuries of the subaxial cervical spine (sCS).

MATERIALS AND METHODS

Patients treated for injuries of the sCS from 2010 to 2020 were retrospectively analyzed for the incidence of sDL within 60 days after first surgery. A univariate analysis of variables potentially influencing the risk of sDL was performed. Patients with solitary anterior stabilization underwent subgroup analysis. The treatment of sDLs was described.

RESULTS

A total of 275 patients were included. sDLs occurred in 4.0% of patients (n = 11) in the total sample, most frequently after solitary anterior stabilization with 8.0% (n = 10, p = 0.010). Only one sDL occurred after combined stabilization and no sDLs after posterior stabilization. In the total sample and the anterior subgroup, variables significantly associated with sDL were older age (p = 0.001) and concomitant unstable facet joint injury (p = 0.020). No neurological deterioration occurred due to sDL and most patients were treated with added posterior stabilization. sDL is frequent after solitary anterior stabilization and rare after posterior or combined stabilization.

DISCUSSION

Patients of higher age and with unstable facet joint injuries should be followed up diligently to detect sDLs in time. Neurological deterioration does not regularly occur due to sDL, and most patients can be treated with added posterior stabilization.

The Effect of Anterior-Only, Posterior-Only, and Combined Anterior Posterior Fixation for Cervical Spine Injury with Soft Tissue Injury: A Finite Element Analysis

OBJECTIVE

This finite element analysis aimed to investigate the effects of surgical procedures for cervical spine injury.

METHODS

A three-dimensional finite element model of the cervical spine (C2-C7) was created from computed tomography. This model contained vertebrae, intervertebral discs, anterior longitudinal ligament, and posterior ligament complex. To create the cervical spine injury model, posterior ligament complex and anterior longitudinal ligament at C3-C4 were resected and the center of the intervertebral disc was resected. We created posterior-only fixation (PF), anterior-only fixation (AF), and combined anterior-posterior fixation (APF) models. A pure moment with a compressive follower load was applied, and range of motion, annular/nucleus stress, instrument stress, and facet forces were analyzed.

RESULTS

In all motion except for flexion, range of motion of PF, AF, and APF models decreased by 80%-95%, 85%-93%, and 97%-99% compared with the intact model. C3-C4 annulus stress of PF, AF, and APF models decreased by 28%-72%, 96%-100%, and 99%-100% compared with the intact model. Facet contact forces of PF, AF, and APF models decreased by 77%-79%, 97%-99%, and 77%-86% at C3-C4 compared with the intact model. Screw stress in the PF model was higher than in the APF model, and plate stress in the AF model was lower than in the APF model, but bone graft stress in the AF model was higher than in the APF model.

CONCLUSIONS

Cervical stabilization was preserved by the APF model. Regarding range of motion, the PF model had an advantage compared with the AF model except for flexion. An understanding of biomechanics provides useful information for the clinician.

Post-operative Use of Cervical Orthoses for Subaxial Cervical Spine Injuries - a Survey-based Analysis at German Spine Care Centres

INTRODUCTION

There are no evidence-based recommendations for the post-operative treatment and application of soft or rigid cervical collars after operative treatment of injuries of the subaxial cervical spine. Cervical collars can restrict peak range of motion and serve as a reminder to the patient. However, they can also cause pressure ulcers. The aim of this online-based survey among German spine centres was to gain an overview of post-operative treatment and the application of soft or rigid cervical collars after surgical treatment of injuries of the subaxial cervical spine.

MATERIALS AND METHODS

An online-based survey was conducted among 59 spine centres certified by the German Spine Society. It comprised seven items and the option of adding remarks in the form of open-ended responses.

RESULTS

The return rate was 63% (37 out of 59). Of the 37 analysed spine centres, 51% routinely apply a cervical collar post-operatively, 27% apply a soft and 16% a rigid cervical collar, 8% sequentially apply first a rigid and later a soft cervical collar. Less than half of the spine centres (43%) routinely use no cervical collar. Rigid collars are applied for more than 6 weeks and soft collars up to 6 weeks at some spine centres. Standardised post-operative treatment plans are common. The selection of the post-operative treatment plan depends primarily on the type of injury and method of operation and partly on patient age and bone quality. The satisfaction of German spine centres with the current handling of post-operative treatment of subaxial cervical spine injuries is high.

DISCUSSION

The post-operative treatment of injuries of the subaxial cervical spine at German spine centres is heterogeneous, and the evidence on advantages and disadvantages of the post-operative application of cervical collars is insufficient. Planning and implementation of randomised controlled clinical trials in subaxial cervical spine injuries is challenging.

Impact of 2 different posterior screw fixation techniques on primary stability in a cervical translational injury model: A biomechanical evaluation

BACKGROUND

In case of injuries to the subaxial cervical spine, especially in osteoporotic bone, the question of the most stable operative technique arises. There are several techniques of screw fixation available regarding dorsal stabilization. This study investigates 2 techniques (lateral mass screws (LMS) vs cervical pedicle screws (CPS)) in the subaxial cervical spine regarding primary stability in a biomechanical testing using a translational injury model.

METHODS

A total of 10 human formalin fixed and 10 human fresh-frozen specimens (C 4 - T 1) were investigated. Specimens were randomized in 2 groups. Fracture generation of a luxation injury between C 5 and C 6 was created by a transection of all ligamentous structures as well as the intervertebral disc and a resection of the facet joints.Dorsal stabilization of C 4/C 5 to C 6/C 7 was performed in group A by lateral mass screws, in group B by pedicle screws. In the biomechanical testing, the specimens were loaded at 2 N/s in translation direction until implant failure.

RESULTS

Formalin fixed specimen: Mean load failure was 513.8 (±86.74) Newton (N) for group A (LMS) and 570.4 (±156.5) N for group B (CPS). There was no significant difference (P = .6905).Fresh frozen specimen: Mean load failure was 402.3 (±96.4) N for group A (LMS) and 500.7 (±190.3) N for group B (CPS). There was no significant difference (P = .4206).

CONCLUSION

In our loading model respecting the translational injury pattern and a flexion movement we could not verify statistically significant differences between lateral mass screws and cervical pedicle screws. Mean loading failure was slightly higher in the CPS group though.

A biomechanical analysis of anterior cervical discectomy and fusion alone or combined cervical fixations in treating compression-extension injury with unilateral facet joint fracture: a finite element study

Background

Compression-extension injury with unilateral facet joint fracture is one of the most devastating injuries of subaxial cervical spine. However, it is not yet clear which fixation technique represents the optimal choice in surgical management. This study aims to assess the construct stability at the operative level (C4/C5 cervical spine) following anterior cervical discectomy and fusion (ACDF) alone and combined fixation techniques (posterior-anterior fixations).

Methods

A previously validated three-dimensional C2-T1 finite element model were modified to simulate surgical procedures via the anterior-only approach (ACDF) and combined cervical approach [(transarticular screw, lateral mass screw, unilateral pedicle screw, bilateral pedicle screw) + ACDF, respectively] for treating compression-extension injury with unilateral facet joint fracture at C4/C5 level. Construct stability (range of rotation, axial compression displacement and anterior shear displacement) at the operative level was comparatively analyzed.

Results

In comparison with combined fixation techniques, a wider range of motion and a higher maximum von Mises stress was found in single ACDF. There was no obvious difference in range of motion among transarticular screw and other posterior fixations in the presence of anterior fixation. In addition, the screws inserted by transarticular screw technique had high stress concentration at the middle part of the screw but much less than 500 MPa under different conditions. Furthermore, the variability of von Mises stress in the transarticular screw fixation device was significantly lower than ACDF but no obvious difference compared with other posterior fixations.

Conclusions

Of the five fixation techniques, ACDF has proven poor stability and high structural stress. Compared with lateral and pedicle screw, transarticular screw technique was not worse biomechanically and less technically demanding to acquire in clinical practice. Therefore, our study suggested that combined fixation technique (transarticular screw + ACDF) would be a reasonable treatment option to acquire an immediate stabilization in the management of compression-extension injury with unilateral facet joint fracture. However, clinical aspects must also be regarded when choosing a reconstruction method for a specific patient.

Posterior Ligament-Bone Injury Classification and Severity Score: A Novel Approach to Predict the Failure of Anterior-only Surgery for Subaxial Cervical Facet Dislocations

STUDY DESIGN

Clinical case series.

OBJECTIVE

The aim of this study was to propose a novel posterior ligament-bone injury classification and severity (PLICS) score system that can be used to reflect the severity of subaxial cervical fracture dislocations (SCFDs) and predict the failure of anterior-only surgery; and to measure the intraobserver and interobserver reliability of this system.

SUMMARY OF BACKGROUND DATA

The approach selection for SCFDs is controversial. Although the anterior approach is familiar for most surgeons, postoperative hardware failure and/or delayed cervical deformity is a nonnegligible complication.

METHODS

Ten patients were randomly selected for intraobserver reliability evaluation on two separate occasions, one month apart. Another 30 patients were randomly selected, and the interobserver reliability was measured by comparing results of each case between each reviewer and averaging. To analyze the difference in the PLICS score, 354 patients fulfilled the follow-up were divided into stable and unstable groups according to whether radiologically stable was observed during follow-up.

RESULTS

For the intraobserver reliability, the mean intraclass correlation coefficient for the 10 reviewers was 0.931. For the interobserver reliability, the mean interobserver correlation coefficient for the three elements was 0.863. Among 16 patients with PLICS score ≥7, two patients in the stable group manifested with severe injury of the posterior ligamentous complex (PLC); extremely unstable lateral mass fractures with or without severe injury of PLC were detected in the 14 patients of the unstable group.

CONCLUSION

The proposed PLICS score system showed excellent intraobserver and interobserver reliability. When a PLICS score is >7 or 7 accompanied by extremely unstable lateral mass fractures, the risk of postoperative failure after an anterior-only reconstruction is high and supplemental posterior strengthening can be considered.Level of Evidence: 4.

Circumferential Reconstruction of Subaxial Cervical and Cervicothoracic Spine by Simultaneously Combined Anterior-posterior Approaches in the Sitting Position

OBJECTIVE

To introduce and analyze the feasibility of a new surgical strategy for circumferential reconstruction of subaxial cervical and cervicothoracic spine by simultaneously combined anterior-posterior approach in the sitting position.

METHODS

A retrospective review was performed for seven patients who underwent the above surgical procedure between July 2011 and January 2015. Among the seven patients, there were six men and one woman, with an average age of 52 years (range, 36-79 years). Six patients were confirmed to have a lower subaxial cervical fracture and dislocation with a locked facet joint, and the other patient had an invasive tumor involving both anterior and posterior parts of vertebrae and lamina, detected by radiological examination. The levels involved for all patients were from C₄ to T₂ . According to American Spinal Injury Association (ASIA) classification, one case was class A, four were class B, and two were class D. The patients were restricted in the sitting position with traction and a halo in extension to immobilize the head during the operation. The simultaneously combined anterior-posterior operation for reduction, decompression or tumor resection and circumferential reconstruction was carried out.

RESULTS

Both anterior and posterior procedures were successfully completed simultaneously in the sitting position in all cases. There were no perioperative complications. The average operative time was 175 ± 32 min (range, 120-240 min), and the mean blood loss was 430 ± 85 mL (range, 200-1100 mL). The patients were followed up for 35.8 months (range, 18-60 months). The symptom of neck pain improved distinctly and no evidence of implant failure was noted in any patients. Neurological status improvement was confirmed in six patients, who had suffered incomplete paralysis. The ASIA grade improved in five patients, and two cases had no change in grade.

CONCLUSIONS

The "sitting position" simultaneously combined anterior-posterior approach is safe and is superior to the traditional prone position and supine position, and the surgical results are satisfactory.

Simultaneously Combined Anterior-Posterior Approaches for Subaxial Cervical Circumferential Reconstruction in a Sitting Position

The purpose of this article is to introduce and analyze the feasibility of simultaneously combined anterior-posterior approaches for subaxial cervical circumferential reconstruction in sitting position. A retrospective case review was performed for above surgery procedure. A 79-year-old man was confirmed subaxial cervical fracture and dislocation with facet locked by radiological examination, and the involved levels were C5-6. According to American Spinal Injury Association (ASIA) classification, the impairment scale was grade B. And the Subaxial Cervical Spine Injury and Severity Score (SLIC) were 9. The patient was restricted in sitting position with traction on a halo in extension to immobilize the head during the operation. A posterior laminectomy and pedicle screws insertion to the involved cervical spine was performed firstly. And then the anterior discectomy and strut graft were accomplished through an anterior cervical approach. The final fixation was finished by clamping the strut graft with pedicle screw system. Total blood loss was 600 ml and the total operating time was 150 min. The patient was followed up for 6 months. The symptom of neck pain improved distinctly and no evidence about implant failure was noted. Neurological status improvement was confirmed and the ASIA scale was improved to grade C. We believed that the simultaneously combined anterior-posterior approach in sitting position was safe and more advantageous for appropriate cases.