BACKGROUND: Ankylosing spondylitis (AS) is a rheumatoid disease leading to progressive ossification of the spinal column. Patients suffering from AS are highly susceptible to unstable vertebral fractures and often require surgical stabilisation due to long lever arms. Medical treatment of these patients improved during the last decades, but until now it is unknown whether the annual number of spinal fractures changed during the last years. Since the annual count of fracture is an effective measure for efficacy of injury prevention and patient safety in AS patients, the current recommendations of activity have to be revised accordingly.

METHODS: Data for all patients with AS treated as inpatients between 01/01/1987 and 31/12/2008 were extracted from the Swedish National Hospital Discharge Registry (SNHDR). The data in the registry are collected prospectively, recording all inpatient admissions throughout Sweden. The SNHDR uses the codes for diagnoses at discharge according to the Swedish versions of the International Classification of Diseases (ICD-9 and ICD-10).

RESULTS: During the years from 1987 to 2008 17,764 patients with AS were treated as inpatients; of these 724 patients were treated due to spinal fractures. The annual number of cervical, thoracic and lumbar fractures in the registry increased until 2008 (r = 0.94).

CONCLUSIONS: Despite the improved treatment of AS the annual number of vertebral fractures requiring inpatient care increased during the last two decades. Possible explanations are population growth, greater awareness of fractures, improved diagnostics, improved emergency care reducing fatalities, and a higher activity level of patients receiving modern medical therapy. Obviously the improvement of medical treatment did not reduce the susceptibility of these patients to unstable fractures. Thus the restrictive injury prevention recommendations for patients with AS cannot be defused, but must be critically revised to improve patient safety.

STUDY DESIGN: 

Prospective cohort study.

OBJECTIVE: 

This study investigates the results of long posterior instrumentation with regard to complications and survival.

SUMMARY OF BACKGROUND DATA: 

Fractures of the cervical spine and the cervicothoracic junction related to ankylosing spinal disease (ASD) endanger both sagittal profile and spinal cord. Both anterior and posterior stabilization methods are well established, and clear treatment guidelines are missing.

METHODS: 

Forty-one consecutive patients with fractures of the cervicothoracic junction related to ASD were treated by posterior instrumentation. All patients were followed prospectively for 2 years using a standardized protocol.

RESULTS: 

Five patients experienced postoperative infections, 3 patients experienced postoperative pneumonia, 2 patients required postoperative tracheostomy, and 1 patient had postoperative cerebrospinal fluid leakage due to accidental durotomy. No patient required reoperation due to implant failure or nonunion. Mean survival was 52 months (95% confidence interval: 42-62 mo). Survival was affected by patient age, sex, smoking, and spinal cord injury.

CONCLUSION: 

Patients with ASD experiencing a fracture of the cervicothoracic region are at high risk of developing complications. The posterior instrumentation of cervical spinal fractures related to ASD is recommended due to biomechanical superiority. Level of Evidence: 4.

STUDY DESIGN: National registry cohort studyObjective. To investigate the effect of surgical stabilisation on survival of spinal fractures related to ankylosing spondylitis (AS).

SUMMARY OF BACKGROUND DATA: Spinal fractures related to AS are associated with considerable morbidity and mortality. Multiple studies suggest a beneficial effect of surgical stabilisation in these patients.

METHODS: In the Swedish patient registry all patients treated in an inpatient facility are registered with diagnosis and treatment codes. The Swedish mortality registry collects date and cause of death for all fatalities. Registry extracts of all patients with AS and spinal fractures including date of death and treatment were prepared and analysed for epidemiological purposes.

RESULTS: 17297 individual patients with AS were admitted to treatment facilities in Sweden between 1987 and 2011. 990 patients with AS (age 66±14 years) had 1131 spinal fractures, of which 534 affected cervical, 352 thoracic, and 245 lumbar vertebrae. 13% had multiple levels of injuries during the observed period. Surgically treated patients had a greater survival than those treated non-surgically (HR = 0.79, p = 0.029). Spinal cord injury was the major factor contributing to mortality in this cohort (HR = 1.55, p<0.001). The proportion of surgically treated spinal fractures increased linearly during the last decades (r = 0.92, p<0.001) and was 64% throughout the observed years.

CONCLUSIONS: Spinal cord injury threatened the survival of patients with spinal fractures related to AS. Even though surgical treatment is associated with a considerable complication rate, it improved the survival of spinal fractures related to AS.

Objective

Ankylosing spondylitis (AS) is associated with increased spinal fracture risk due to loss of elasticity in spinal motion segments. With the introduction of biological disease modifying anti-rheumatic drugs (bDMARD) treatment for AS patients the individual course of the disease has been decelerated.  This study aims to clarify whether the improved medical therapy reduced the spinal fracture incidence.

Methods

Included were all patients with the diagnosis of AS 1987 to 2014 from the Swedish Patient Registry. From the Swedish Prescribed Drug Registry the Anatomical Therapeutic Chemical codes for bDMARD, non-steroidal anti-inflammatory drugs (NSAID), methotrexate (MTX) and sulfasalazine were extracted and numbers of prescriptions and years of treatment counted since 2005.

Results                

12297 patients with ankylosing spondylitis were included between 1987 and 2014 (age 67±19, 67% male). Of these 291 had spinal fractures between 2011 and 2014. The number of prescriptions of bDMARD increased during the last decade, but not of MTX, sulfasalazine and NSAID. 64% of all AS patients used NSAID, 13% used bDMARD, 13% used MTX, and 10% used sulfasalazine. A multivariate analysis of patients with spinal fractures 2011-2014 found bDMARD delaying spinal fracture debut by 1.24 years per year of bDMARD treatment (p=0.028). The use of bDMARD had no significant effect on spinal fracture risk (OR=0.93, 95%-C.I.=0.85-1.01, p=0.09).

Conclusion

This study failed to demonstrate a beneficial effect on spinal fracture risk for AS patients treated with bDMARD during the last decade. Still bDMARD treatment delayed spinal fracture occurrence, which is promising with regard to results from future studies.

Trial registration

ClinicalTrials.gov, Identifier NCT02840695.

Background: Spinal fractures related to AS are often treated by long posterior stabilisation. The biomechanical rationale behind is the neutralisation of long lever arms in the ankylosed spine to avoid non-union or neurological deterioration. Despite the widespread application of long posterior instrumentation it has never been investigated in a biomechanical model. The objective of this study is to develop a finite element model for spinal fractures related to AS and to establish a biomechanical foundation for long posterior stabilisation of cervicothoracic fractures related to ankylosing spondylitis (AS).

Methods: An existing finite element-model (consisting of two separately developed models) including the cervical and thoracic spine were adapted to the conditions of AS (all discs fused, C0-C1 and C1-C2 mobile) and a fracture at the level C6-C7 was simulated. Besides a normal spine (no AS, no fracture) and the uninstrumented fractured spine four different posterior transpedicular instrumentations were tested: 1. Fracture uninstrumented, 2. Short instrumentation C6-C7, 3. Medium instrumentation C5-T1, 4. Long instrumentation C3-T3, 5. Skipped level long instrumentation C3-C6-C7-T3.

Three loads (1.5g, 3.0g, 4.5g) were applied according to a specific load curve. Kinematic data such as the gap distance in the fracture site were obtained. Furthermore the stresses in the ossified parts of the discs were evaluated.

Findings: All posterior stabilisation methods could normalise the axial stability at the fracture site as measured with gap distance. With larger accelerations than 1.5g ,  it was seen that the longer instrumentations resulted in lesser maximal gap distance than the Short instrumentation. The maximum stress at the cranial instrumentation end (C3-C4) was slightly greater if every level was instrumented, than in the skipped level model. The skipped level instrumentation achieved similar rotatory stability as the long multilevel instrumentation.

Interpretation: The FE model developed simulated a spinal fracture at C6-C7 level. Skipping instrumentation levels without giving up instrumentation length also reduces the stresses in the ossified tissue within the range of the instrumentation and does not decrease the stability in a finite element model of a cervicothoracic fracture related to AS. Considering the risks associated with every additional screw placed, the skipped level instrumentation has advantages with regard to patient safety. The effects of the degree of osteoporosis, screw placement and pre-existing kyphosis on the construct stability were not investigated in this study and should be a matter of further research.