Inflammatory conditions of the spine

1. High-Yield Summary

• Spectrum of Pathology: Inflammatory conditions of the spine comprise a diverse group of non-infectious autoimmune and autoinflammatory disorders, predominantly axial spondyloarthritis (including ankylosing spondylitis and non-radiographic axial spondyloarthritis), rheumatoid arthritis of the cervical spine, psoriatic spondylitis, enteropathic arthropathy, and reactive arthritis.
• Axial Spondyloarthritis Hallmark: Characterized by enthesitis at the insertion of the annulus fibrosus and spinal ligaments, leading to progressive syndesmophyte formation, syndesmotic bridging, and a rigid “bamboo spine” prone to highly unstable hyperextension fractures from minor trauma.
• Rheumatoid Cervical Instability Triad: Cervical involvement occurs in up to 80% of patients with long-standing rheumatoid arthritis, manifesting as atlantoaxial subluxation (AAS), basilar invagination (cranial settling), and subaxial subluxation (SAS).
• Critical Neurologic Thresholds: In rheumatoid atlantoaxial subluxation, the posterior atlantodens interval (PADI) is the most reliable predictor of cord compression and postoperative recovery; a PADI of 14 mm or less represents an absolute threshold for surgical stabilization.
• Fractures in Ankylosed Spines: Any acute pain following trivial trauma in a patient with an ankylosed spine represents an unstable three-column fracture until proven otherwise by emergency thin-slice CT imaging; long-segment posterior instrumentation (at least three levels above and three levels below) is required to overcome the prolonged biomechanical lever arms.

2. Anatomy

The structural vulnerability of the spine across inflammatory arthropathies stems from the distinct anatomical affinity of each disease process: synovial joints and bursa in rheumatoid arthritis, and ligamentous entheses and fibrocartilaginous interfaces in the seronegative spondyloarthropathies.

Craniovertebral Junction and Upper Cervical Spine

The atlantoaxial articulation possesses substantial mobility, accounting for 50% of cervical rotation. Stability depends on ligamentous restraints rather than interlocking bony facets:

• Transverse Ligament: Originates from tubercles on the medial aspects of the C1 lateral masses and traverses posterior to the odontoid process. Synovial bursae exist between the anterior arch of C1 and the odontoid (atlantodental bursa) and between the odontoid and the transverse ligament (transversodental bursa). Inflammatory synovitis in rheumatoid arthritis attacks these bursae, attenuating the transverse ligament and precipitating anterior atlantoaxial subluxation.
• Alar Ligaments: Paired check ligaments originating from the superolateral odontoid and inserting on the medial condyles of the occiput. Once the transverse ligament attenuates, the alar and apical ligaments act as secondary stabilizers; their failure permits catastrophic subluxation exceeding 9 to 10 mm.
• Vertebral Artery Corridor: The vertebral artery ascends through the transverse foramina of C6 to C2, loops sharply behind the C1 lateral mass within the groove on the posterior arch, and penetrates the atlanto-occipital membrane. Cranial settling or rotatory subluxation risks tethering or compressing the vertebral arteries, predisposing to vertebrobasilar insufficiency.
• Steel Rule of Thirds: At the C1 level, the spinal canal space is equally partitioned into one-third odontoid process (approximately 10 mm), one-third spinal cord (approximately 10 mm), and one-third safe clearance space (approximately 10 mm). Subluxation exceeding 10 mm exhausts this functional buffer and compresses the cervicomedullary junction.

Subaxial Cervical, Thoracic, and Lumbar Spine

In axial spondyloarthritis, the primary target is the enthesis. Pathologic enthesitis targets:

• Discovertebral Junction (Sharpey Fibers): The insertion of the peripheral annulus fibrosus into the anterior and posterior vertebral margins undergoes chronic inflammatory osteitis (Romanus lesions), followed by reactive ossification (syndesmophyte development).
• Longitudinal and Interspinous Ligaments: Ossification of the anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), ligamentum flavum, and interspinous/supraspinous ligaments transforms the segmented column into a solid, brittle bone cylinder.
• Costovertebral and Costotransverse Joints: True synovial and syndesmotic articulations at each thoracic rib head undergo progressive ankylosis, eliminating thoracic expansion and chest cage compliance.
• Sacroiliac Articulation: The true synovial anterior-inferior compartment and the thick syndesmotic posterior-superior ligamentous compartment represent the primary index site of entheseal and subchondral inflammation.

3. Pathogenesis

The pathogenesis of spinal inflammatory disorders reflects two contrasting cellular and immunologic mechanisms: synovial pannus osteoclastogenesis (rheumatoid arthritis) and enthesitis-driven new bone formation (spondyloarthritis).

Rheumatoid Arthritis of the Spine

Rheumatoid arthritis is a systemic autoimmune syndrome mediated by pro-inflammatory cytokines, specifically tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6). Hyperplastic synovial pannus invades synovial articulations in the cervical spine. Macrophages and fibroblast-like synoviocytes secrete receptor activator of nuclear factor-kappa B ligand (RANKL) and matrix metalloproteinases (MMPs), stimulating aggressive osteoclastic bone resorption and enzymatic degradation of type I and type II collagen. This leads to:

• Ligamentous Incompetence: Softening and rupture of the transverse and alar ligaments.
• Facet and Lateral Mass Collapse: Symmetrical erosion of the atlanto-occipital and atlantoaxial facet joints causes telescoping of the cranium and atlas onto the axis, producing basilar invagination.
• Subaxial Instability: Infiltration of subaxial facet synovium and the discovertebral junction (joints of Luschka) produces multilevel subaxial anterior subluxations, creating a classic “stepladder” deformity.

Axial Spondyloarthritis and Ankylosing Spondylitis

Axial spondyloarthritis is an autoinflammatory disorder driven by strong genetic susceptibility, notably human leukocyte antigen B27 (HLA-B27), in combination with endoplasmic reticulum aminopeptidase (ERAP) variants and dysregulated gut microbiome interactions. Mechanical stress at entheseal sites triggers an innate immune cascade:

• The IL-23/IL-17 Inflammatory Axis: Tissue-resident gamma-delta T cells, mucosa-associated invariant T (MAIT) cells, and innate lymphoid cells (ILC3) respond to entheseal microdamage by secreting IL-17A, IL-17F, and IL-22 under the stimulation of myeloid-derived IL-23.
• Erosion to Ossification Transition: Early stages feature intense entheseal inflammation, osteitis, and subchondral marrow edema (Romanus lesion). In later stages, resolution of local inflammation stimulates bone morphogenetic protein (BMP) and Wnt/beta-catenin signaling pathways, downregulating endogenous inhibitors such as dickkopf-1 (DKK1) and sclerostin. This unleashes uncontrolled endochondral osteoblastogenesis, replacing elastic ligamentous tissue with bridging, vertical syndesmophytes.
• Andersson Lesions: Discovertebral destructive lesions occurring either as an aseptic inflammatory spondylodiscitis (early active phase) or as a nonunion/pseudoarthrosis secondary to localized stress fractures across a rigid ankylosed column.

4. Natural History

The clinical course of inflammatory spinal disease varies substantially depending on phenotypic presentation, timely biologic intervention, and mechanical risk management.

Epidemiology

• Axial Spondyloarthritis: Overall prevalence ranges between 0.3% and 1.4% in North American and European populations, closely mirroring the geographic prevalence of the HLA-B27 allele. Classic radiographic ankylosing spondylitis exhibits a male-to-female ratio of approximately 2:1 to 3:1, typically presenting with symptom onset between ages 18 and 35. Non-radiographic axial spondyloarthritis demonstrates near equal sex parity (1:1).
• Rheumatoid Cervical Disease: While modern early disease-modifying therapy has curtailed severe cervical progression, radiographic cervical instability develops in 30% to 50% of patients with seropositive, erosive disease within 10 years of initial diagnosis. Up to 10% develop symptomatic cervical myelopathy if left unmonitored.
• Diffuse Idiopathic Skeletal Hyperostosis (DISH): A non-inflammatory hyperostotic disorder often evaluated on the differential diagnosis of ankylosing spondylitis; DISH affects older individuals (predominantly males older than 65 years, prevalence up to 15% to 25%), strongly associated with metabolic syndrome and type 2 diabetes mellitus.

Disease Progression and Long-Term Prognosis

Without targeted systemic suppression, axial spondyloarthritis follows an insidious course over two to three decades, progressing from recurrent inflammatory sacroiliac pain to ascending spinal stiffening, loss of lumbar lordosis, fixed thoracic hyperkyphosis, and cervical flexion deformity (“chin-on-chest” deformity). Advanced fixed sagittal imbalance limits horizontal gaze, impedes swallowing and respiratory mechanics, and compromises ambulation. Concomitant trabecular osteopenia develops secondary to immobility and systemic cytokine release, creating a paradoxical structural vulnerability: an osteoporotic, rigid, brittle long bone prone to catastrophic fracture from minor low-energy mechanical falls.

5. Clinical Presentation

History and Symptom Profile

Differentiating inflammatory back pain from ubiquitous mechanical back pain is critical for avoiding prolonged diagnostic delay (historically averaging 7 to 9 years in axial spondyloarthritis):

• Inflammatory Back Pain Criteria (Calin and ASAS Criteria): Age of onset younger than 40 years, insidious onset, persistence for at least 3 months, marked morning stiffness exceeding 30 to 45 minutes, improvement of pain and stiffness with physical exercise, and lack of relief with passive rest. Frequent awakening during the second half of the night with deep gluteal ache (alternating buttock pain).
• Extra-Articular Manifestations: Recurrent acute anterior uveitis (seen in 25% to 40% of axial spondyloarthritis cases), psoriasis or nail dystrophies, inflammatory bowel disease (Crohn disease or ulcerative colitis), enthesitis (Achilles tendonitis, plantar fasciitis), dactylitis (“sausage digit”), and aortitis with aortic valve insufficiency.
• Rheumatoid Cervical Warning Signs: Severe suboccipital neck pain and headache radiating in a greater occipital nerve distribution (C2 neuralgia). Cranial settling produces brainstem or lower cranial nerve compression: dysphagia, dysarthria, sleep apnea, drop attacks, diplopia, and vertigo. Myelopathic symptoms include loss of fine motor hand dexterity (difficulty buttoning shirts), progressive spastic gait unsteadiness, and bladder urgency or incontinence.

Physical Examination and Diagnostic Accuracy

Standardized clinical measurements document axial mobility, chest wall expansion, and neurologic compromise:

6. Imaging and Diagnostic Studies

Modern imaging protocols utilize plain radiography, magnetic resonance imaging (MRI), and computed tomography (CT) in a complementary staged fashion.

Radiographic Criteria and Sacroiliac Grading

Pelvic anteroposterior (AP) and Ferguson views evaluate the sacroiliac joints, graded according to the Modified New York criteria:

• Grade 0: Normal joint margins, preserved joint space, absence of subchondral sclerosis.
• Grade 1: Suspicious changes; minimal blunting of subchondral joint margins.
• Grade 2: Minimal abnormality; localized small areas of erosions and sclerosis without joint space narrowing.
• Grade 3: Definite abnormality; moderate or advanced sacroiliitis with erosions, marked subchondral sclerosis, pseudowidening, or partial joint space loss.
• Grade 4: Complete ankylosis with total bony bridging across the joint.

Spinal radiographs demonstrate squarish vertebral bodies, shiny corner lesions (Romanus sign), fine, thin, vertically oriented syndesmophytes bridging disc spaces, dagger sign (ossification of supraspinous and interspinous ligaments on AP views), trolley-track sign (ossification of facet capsules and interspinous ligaments), and complete spinal autofusion (“bamboo spine”).

Cervical Spine Measurements in Rheumatoid Arthritis

Standard cervical evaluation requires upright neutral, flexion, and extension lateral plain radiographs. The essential diagnostic measurements include:

Advanced Imaging: MRI and CT

• Magnetic Resonance Imaging (MRI): Short tau inversion recovery (STIR) or T2-weighted fat-saturated sequences represent the gold standard for non-radiographic axial spondyloarthritis. Active inflammatory sacroiliitis requires subchondral bone marrow edema visible on at least two consecutive slices or in multiple locations on a single slice. In rheumatoid cervical disease, MRI assesses pannus volume, retro-odontoid retroflexion, cervicomedullary compression, cord myelomalacia (high cord signal on T2), and vertebral artery patency.
• Computed Tomography (CT): Helical thin-slice CT with multiplanar reconstructions is essential for delineating subtle bony erosions, facet autofusion, and nonunions (Andersson lesions). In the ankylosed spine, CT is the definitive emergency modality following any trauma, as plain radiographs miss up to 50% of occult extension fractures.

7. Classification

Modern management depends on validated diagnostic and staging systems that differentiate early non-radiographic inflammation from structural radiographic fusion, as well as grading neurologic compromise.

ASAS Criteria for Axial Spondyloarthritis

Applicable to patients with back pain lasting at least 3 months and age of onset younger than 45 years:

Ranawat Classification of Neurologic Deficit in Rheumatoid Cervical Disease

8. Treatment

Medical / Nonoperative Management

The contemporary management paradigm for inflammatory spinal disease prioritizes early multidisciplinary intervention, coordinated between rheumatologists and spine surgeons:

• First-Line Pharmacotherapy (Axial SpA): Nonsteroidal anti-inflammatory drugs (NSAIDs) taken continuously at full therapeutic doses are the proven first-line medical intervention. Sustained continuous NSAID therapy controls axial symptoms, improves spinal mobility, and reduces radiographic syndesmophyte progression in patients with elevated inflammatory markers.
• Biologic and Targeted Synthetic DMARDs (bDMARDs / tsDMARDs): Indicated for patients with active axial disease (BASDAI >= 4 or ASDAS >= 2.1) despite at least two distinct full-dose NSAID trials over 4 weeks. Tumor necrosis factor inhibitors (TNFi: infliximab, adalimumab, etanercept, certolizumab, golimumab) and interleukin-17A inhibitors (IL-17i: secukinumab, ixekizumab) demonstrate equivalent clinical efficacy in reducing spinal inflammation and controlling disease activity. Janus kinase inhibitors (JAKi: tofacitinib, upadacitinib) offer effective oral targeted synthetic options. In rheumatoid arthritis, conventional synthetic DMARDs (methotrexate) combined with TNF inhibitors, anti-IL-6 agents (tocilizumab), or T-cell costimulation modulators (abatacept) halt cervical erosion.
• Physical Therapy and Rehabilitation: Lifelong dedicated spinal extension exercises, deep diaphragmatic breathing training, postural ergonomics, and hydrotherapy preserve spinal compliance, thoracic vital capacity, and upright vertical alignment. High-impact contact activities, aggressive spinal manipulation, and passive immobilization in soft cervical collars are strictly contraindicated.

Operative Management

Surgical intervention in inflammatory spinal disease is complex and requires specialized reconstructive techniques addressing three primary clinical problems: acute traumatic fractures, fixed sagittal deformities, and rheumatoid cervical instability.

• Acute Traumatic Fractures in the Ankylosed Spine: Fractures through an ankylosed column act as long-bone fractures across a prolonged lever arm. Operative stabilization is indicated in virtually all patients, even minimally displaced fractures, due to extreme instability and high rates of secondary neurologic deterioration under nonoperative halo or brace treatment. Long-segment posterior pedicle screw instrumentation extending at least three segments above and three segments below the fracture level is mandatory. Anterior column reconstruction (corpectomy and mesh cage strut grafting) is added if severe anterior comminution or vertebral body deficiency precludes stable posterior load-sharing.
• Corrective Spinal Osteotomies for Fixed Sagittal Kyphosis: Patients with fixed chin-on-chest deformity or severe forward global imbalance benefit from corrective osteotomies to restore horizontal gaze, improve diaphragmatic breathing, and relieve abdominal visceral compression. Pedicle Subtraction Osteotomy (PSO) represents a closing-wedge three-column osteotomy through the posterior elements and vertebral body, capable of delivering 30 to 40 degrees of lordotic correction at a single lumbar level (typically L2 or L3) without lengthening the fragile anterior vascular structures. Polysegmental Smith-Petersen osteotomies (SPO) or Ponte osteotomies achieve 5 to 10 degrees per level when the anterior disc space remains open and mobile.
• Rheumatoid Cervical Stabilization: Posterior C1-C2 fusion using the Harms-Goel technique (C1 lateral mass screws paired with C2 pedicle or pars screws connected by rigid longitudinal rods and supplemented by autologous structural bone grafting) provides rigid internal fixation with fusion rates exceeding 95% for isolated reducible atlantoaxial subluxation. Basilar invagination (cranial settling) requires rigid occipitocervical fusion (occiput to C2, C3, or C4) with pre-operative skull traction to reduce vertical migration. Subaxial subluxation is managed with posterior cervical decompression and instrumented lateral mass fusion, supplemented with anterior cervical discectomy and fusion (ACDF) if severe kyphosis or ventral canal stenosis coexists.

Indications & Contraindications

• Absolute Surgical Indications: Acute traumatic fracture across an ankylosed spinal segment; progressive cervical myelopathy (Ranawat Class II, IIIa, or IIIb); posterior atlantodens interval (PADI) <= 14 mm; vertical basilar invagination with odontoid migration past the McGregor line > 4.5 mm or Ranawat metric < 13-15 mm; severe fixed sagittal chin-on-chest kyphosis precluding horizontal gaze.
• Relative Indications: Intractable mechanical pain refractory to full-dose systemic biologic and disease-modifying agents; asymptomatic atlantoaxial subluxation with AADI > 8 to 9 mm in an active patient; symptomatic Andersson pseudoarthrosis nonunion.
• Contraindications: Uncontrolled systemic sepsis; active bacteremia; untreated active tuberculosis; medically fragile patients with terminal cardiopulmonary decompensation; non-ambulatory Ranawat IIIb patients with profound chronic irreversible encephalopathy where perioperative mortality exceeds functional benefit.

9. Outcome

Modern clinical outcomes reflect substantial improvements in both pharmacologic preservation of function and surgical morbidity management:

• Biologic Therapy Response: Initiation of TNF or IL-17 inhibitors yields rapid, sustained clinical improvement, with 50% to 60% of patients achieving an ASAS40 response (40% improvement in validated Assessment of SpondyloArthritis international Society criteria) at 12 to 24 weeks. Early biologic intervention significantly halts the progression of structural spinal damage compared with conventional therapy.
• Surgical Fracture Outcomes: Rigid posterior multi-segment instrumentation for fractures in ankylosing spondylitis achieves bony union rates exceeding 90%, with significant reduction in secondary neurological deterioration compared with nonoperative immobilization (relative risk reduction exceeding 65%). However, overall 1-year mortality following spinal fractures in ankylosed patients remains substantial (15% to 30%), reflecting cardiopulmonary comorbidities and underlying frailty.
• Sagittal Realignment Outcomes: Pedicle subtraction osteotomy consistently restores 30 to 40 degrees of lumbar lordosis, corrects the sagittal vertical axis (SVA) by an average of 8 to 12 cm, restores unconstrained horizontal gaze, and improves validated quality-of-life scores (Oswestry Disability Index, SRS-22).
• Rheumatoid Cervical Stabilization: Posterior C1-C2 and occipitocervical fusions achieve solid bony arthrodesis in 92% to 98% of cases. Neurologic recovery correlates directly with pre-operative neurologic status: over 80% of Ranawat Class II and Class IIIa patients experience motor improvement, whereas fewer than 30% of Class IIIb patients regain ambulatory capacity.

10. Complications

Surgical intervention in patients with inflammatory spinal disorders carries elevated complication rates due to osteopenia, chronic systemic immunosuppression, altered biomechanical levers, and severe airway management challenges:

11. Pearls and Pitfalls

Diagnostic and Clinical Pearls

• The “Minor Trauma” Axiom: Any patient with an ankylosed spine (ankylosing spondylitis or DISH) presenting with new back or neck pain following a minor mechanical insult (such as a sudden jar, minor fall from standing height, or low-speed collision) has an unstable spinal fracture until definitively disproven by thin-slice multiplanar CT. Plain radiographs miss up to 50% of these injuries due to thoracic kyphosis, osteopenia, and shoulder artifact.
• PADI Over AADI: In rheumatoid cervical evaluation, do not rely solely on the anterior atlantodens interval (AADI). The posterior atlantodens interval (PADI) directly measures the remaining space for the cervical spinal cord. A PADI of 14 mm or less demands prompt surgical stabilization regardless of minimal subjective symptoms.
• Look for the Andersson Lesion: Focal, non-healing discovertebral erosion in an otherwise solidly ankylosed spine is frequently misdiagnosed as infectious discitis or tuberculous spondylitis. A true Andersson lesion represents an unstable stress nonunion requiring rigid posterior stabilization rather than prolonged antibiotic therapy.

Surgical Pitfalls

• Positioning Catastrophe: Forcing a patient with a fixed, hyperkyphotic ankylosed spine into a standard flat prone position on the operating table will cause fracture displacement, catastrophic spinal cord stretch, or complete cord transection. Position the patient with meticulous custom positioning pads and pillows matching their baseline deformity; pre-positioning neurological checks must confirm comfort before general anesthesia induction.
• Short-Segment Fixation Failure: Treating an ankylosing spondylitis fracture with standard one-above, one-below pedicle screw fixation invariably results in catastrophic screw pullout, construct cut-out, and progressive paralysis. The rigid, fused spine acts as an unyielding lever arm requiring at least three levels of rigid pedicle screw anchorage above and below the fracture.
• Ignoring Concomitant Cranial Settling: Stabilizing an atlantoaxial subluxation with an isolated C1-C2 fusion in a patient who has unrecognized concurrent vertical cranial settling will fail to decompress the brainstem and leads to postoperative neurologic decline. Always assess the Ranawat and Redlund-Johnell metrics before selecting an upper cervical fusion level.

12. Controversy

Several clinical and surgical management dilemmas in inflammatory spinal disorders remain actively debated among spine surgeons and rheumatologists:

• Radiographic Progression and Biologic Disease Modification: While TNF and IL-17 inhibitors dramatically control patient-reported symptoms, enthesitis, and bone marrow edema on MRI, debate persists regarding their long-term efficacy in preventing structural new syndesmophyte formation and spinal autofusion. Emerging long-term registry data suggest that very early, continuous biologic suppression for over 4 to 8 years may attenuate radiographic syndesmophyte growth, but late interventions after initial bridging has begun show minimal structural inhibition.
• Asymptomatic Rheumatoid Instability – Prophylactic Surgery vs Observation: Whether to perform prophylactic C1-C2 fusion in asymptomatic rheumatoid patients with severe radiographic atlantoaxial subluxation (AADI > 8 mm, PADI 14 mm) remains contentious. Proponents emphasize that neurologic deterioration may occur precipitously without warning trauma and that surgical morbidity is dramatically lower when performed prior to the onset of fixed myelopathic deficits. Opponents argue that modern biologic therapy stabilizes pannus proliferation and that serial dynamic radiographic surveillance is safe in carefully monitored compliant patients.
• Minimally Invasive Percutaneous vs Open Long-Segment Fixation for AS Fractures: In elderly or frail patients suffering traumatic fractures through an ankylosed spine, percutaneous long-segment pedicle screw fixation with cement augmentation is increasingly utilized to reduce massive blood loss, operative time, and soft-tissue morbidity. However, traditionalists contend that open surgical exposure is essential to achieve direct canal decompression when epidural hematomas are present and to facilitate robust decortication and structural autologous bone grafting to ensure permanent arthrodesis.

13. Evidence-Based Synthesis

Modern clinical decision-making is grounded in high-quality randomized controlled trials and prospective registry analyses, corroborated by seminal biomechanical and anatomical descriptions.

14. References

• van der Linden S, Valkenburg HA, Cats A. Evaluation of diagnostic criteria for ankylosing spondylitis. A proposal for modification of the New York criteria. Arthritis Rheum. 1984. doi:10.1002/art.1780270401 [Level II: Prospective Validation Cohort Study]
• Boden SD, Dodge LD, Bohlman HH, Rechtine GR. Rheumatoid arthritis of the cervical spine. A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am. 1993. doi:10.2106/00004623-199309000-00004 [Level II: Prospective Longitudinal Cohort]
• Ramiro S, Nikiphorou E, Sepriano A et al. ASAS-EULAR recommendations for the management of axial spondyloarthritis: 2022 update. Ann Rheum Dis. 2023. doi:10.1136/ard-2022-223296 [Level I: Systematic Review & Clinical Practice Guideline]
• Ward MM, Deodhar A, Gensler LS et al. 2019 Update of the American College of Rheumatology/Spondylitis Association of America/Spondyloarthritis Research and Treatment Network Recommendations for the Treatment of Ankylosing Spondylitis and Nonradiographic Axial Spondyloarthritis. Arthritis Rheumatol. 2019. doi:10.1002/art.41042 [Level I: Systematic Review & Clinical Practice Guideline]
• Westerveld LA, Verlaan JJ, Oner FC. Spinal fractures in patients with ankylosing spinal disorders: a systematic review of the literature on treatment, neurological status and complications. Eur Spine J. 2009. doi:10.1007/s00586-008-0764-0 [Level I: Systematic Review / Meta-Analysis]
• Lambert RG, Bakker PA, van der Heijde D et al. Defining active sacroiliitis on MRI for classification of axial spondyloarthritis: update by the ASAS MRI working group. Ann Rheum Dis. 2016. doi:10.1136/annrheumdis-2015-208642 [Level I: Diagnostic Consensus & Prospective Validation]
• Gossec L, Kerschbaumer A, Ferreira RJO et al. EULAR recommendations for the management of psoriatic arthritis with pharmacological therapies: 2023 update. Ann Rheum Dis. 2024. doi:10.1136/ard-2024-225531 [Level I: Systematic Review & Clinical Practice Guideline]
• Minozzi S, Bonovas S, Lytras T et al. Risk of infections using anti-TNF agents in rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis: a systematic review and meta-analysis. Expert Opin Drug Saf. 2016. doi:10.1080/14740338.2016.1240783 [Level I: Systematic Review / Meta-Analysis]

15. Master Class Pro-Tip

When evaluating a patient with advanced ankylosing spondylitis or DISH who reports even subtle neck or back pain after a trivial mechanical jar, never accept normal plain radiographs as reassurance. The combination of dense osteopenia, thoracic kyphosis, and scapular shadow obscures up to half of all unstable hyperextension fractures. Maintain high-level spinal precautions, immediately obtain an emergency multiplanar CT scan of the entire spine, and assess for trans-vertebral or trans-discal fracture lines. In the operating theater, never attempt to force the rigid cervical spine into anatomical extension during positioning; always support the patient’s pre-injury fixed alignment using specialized foam ramp contours, confirm position with intraoperative fluoroscopy before surgical incision, and use a minimum of three fixation points above and below the fracture line with dual-rod architecture to withstand the massive physiological lever arm of the ankylosed spine.

Master Class Surgical Pearl: Management of the Ankylosed and Inflammatory Spine