Rheumatoid Neck

Conditions

 

Atlanto-axial subluxation (AAS) - ADI > 3 mm

Vertical subluxation (VS) / Basilar Invagination - Ranawat < 13 mm

Subaxial subluxation (SAS) - irreducible translation > 2 mm

 

AADI greater than 5 mmSuperior Migration Ondontoid Lateral Xray Close UpRheumatoid Arthritis Subaxial Instability Extension View

Atlanto-axial subluxation                      Vertical subluxation                                         Subaxial subluxation

 

Epidemiology

 

AAS 65%

VS 15 - 20%

SAS 20 - 25%

 

Symptoms

 

Neck pain

Occipital headaches - compression of occipital nerves

Neck / mastoid / ear / facial pain - compression of C2 nerve root

Instability symptoms

Brainstem compression symptoms - tinnitus, vertigo, visual disturbance, diplopia

Myelopathy

Acute spinal cord injury

 

Associations

 

Seropositive disease

Severe long standing disease

 

Natural History

 

Yarube et al Spine 2012

- 140 patients with RA initially without cervical spine involvement

- followed for 5 years

- 44% developed cervical instability

- severe instability in 13%

- AAS in 32.1%

- VS in 11.4%

- SAS in 16.4%

 

Natural History with Biologics

 

Neo-RACo study

- 10 year study using infliximab in early RA

- cervical spine involvement only 4.7%

 

Lebouille-Veldman et al J Neurosurg Spine 2023

- 10 year follow up of 272 patients in BeST trial (optimal treatment including biologics)

- AAS 24%, VS 0%, SAS 22%

- 40% of patients develop at least mild cervical spine deformity

 

Screening

 

Cervical spine flexion / extension xray mandatory in all patients pre-operatively

 

Atlanto - Axial subluxation (AAI / AAS)

 

Aetiology

 

A. Attrition of transverse ligament

B. Erosion of peg

 

Epidemiology

 

Most common of RA cervical deformities - occurs in up to 50% of patients

May cause myelopathy symptoms - www.boneschool.com/myelopathy

 

Xray

 

Atlanto-dens interval (ADI)

Space available for Cord (SAC) / posterior atlanto-dens interval (PADI)

 

Downs ADI SAC

 

Diagnosis

 

1.  AADI (anterior atlantodental interval) > 3 mm

 

Cervical Flexion Instability Increased AADIAADI greater than 5 mm

 

2.  Instabilty

A.  Instability : > 3 mm difference in flexion / extension views

B.  Severe instability: > 7 mm difference

 

RA neck Flexion View AADA > 3 mmRA Neck Extension View AADI 1 mm

Instability 3 mm

 

RA instability 1RA instability 2

Severe instability

 

3.  PADI (posterior atlantodental interval / SAC (space available for cord))

- > 14 mm 94% predictive no neural deficit

- < 14 mm 97% predictive neural compression

 

Management

 

Nonoperative management

 

Matsunaga et al Spine 2003

- 40 patients with RA, myelopathy, and atlantoaxial fixed instability

- 19 treated with occipito-cervical fusion, 21 treated nonoperatively

- operative group: 68% neurological improvement, 37% 10 year survival

- nonoperative group: 100% bedridden in 3 years, 0% 8 year survival

 

Algorithm

1. PADI >14mm -> observe

2. PADI < 14mm MRI

3. Cervicomedullary angle <135° / SAC < 13 - fusion

 

Options

 

1.  C1/2 fusion

- instability reducible

- no neurology / no decompression needed

 

2.  Occipito-cervical fusion

- instability irreducible

- neurological symptoms

- decompression of lamina C1 required

 

C1/C2 fusion

 

AO Surgery Reference C1/C2 fusion

 

Options

1.  Transarticular screws (Magerl)

2.  C1 lateral mass / C2 pedicle screws (Goel-Harms)

+/- Brooks interlaminar wire with posterior bone graft

 

C1 C2 Posterior Spinous Process WiringC1 C2 Posterior Spinous Process Wiring

Gallie-Brooks fusion

 

Dens Nonunion C12 fusionC1 C2 fusion

C1 lateral mass / C2 pedicle screws (Goel Harms)

 

Transarticular screws

Transarticular / Magerl screws from: Koepke et al Nature Reports

 

Results

 

Ryu et al World Neurosurg 2017

- 58 patients with RA and AAS

- treated with either transarticular screws or C1/C2 screws

- no difference in fusion rates / clinical outcomes / complications

 

Occipito-cervical fusion

 

C0 C3 fusion AAI Rheumatoid

 

Basilar invagination / Vertical subluxation

 

Superior Migration Ondontoid Lateral Xray

 

Definition

 

Superior migration of the odontoid into foramen magnum

 

Pathology

 

Due to erosion of lateral masses of atlas and occipital condyles

- can lead to compression of brain stem

- risk of myelopathy / sudden death

- associated with severe peripheral disease

 

Diagnosis

 

Ranawat measurement < 13 mm

- line between anterior and posterior arch C1

- centre of pedicle of C2

 

Superior Migration Ondontoid Lateral Xray Close UpSMO Ranawat Measurement

 

McCrae

- line of foramen magnum

- tip of odontoid should not protrude above this line

 

SMO McCrae LineSMO McCrae Line CT

 

McGregor line > 4.5 mm

- line hard palate to posterior occiput

- if tip of dens > 4.5 mm above this line = vertical settling

- severe > 8 men or > 10 women

 

SMO McGregor Line

 

Redlund-Johnell measurement

- assesses entire occiput to C2 complex

- base of dens to McGregor line

- men < 34mm / women <29 mm = abnormal

 

SMO Redlund-Johnell

 

CT

 

Superior Migration Ondontoid CT CoronalSuperior Migration Ondontoid CT Sagittal

Coronal and sagittal CT of basilar invagination

 

MRI

 

Cervico-medullary angle < 135 degrees

- the line parallel to ventral side of medulla oblongata

- the line parallel to the ventral side of the upper cervical cord

- normal angle is 135-175°

- <135° consistent with vertical settling and correlated with myelopathy

 

Cervicomedullary angle

From: Guo et al Sci Rep 2019http://creativecommons.org/licenses/by/4.0/.

 

Management

 

Algorithm

1. No symptoms & no cord compression on MRI -  observe

 

2. Cord compression

- occiput to C2 fusion

- +/- C1 laminectomy

- +/- odontoidectomy

 

Occipital Cervical Fusion LateralOccipito Cervical Fusion AP

 

Results

 

Dasenbrock et al Neurosurgery 2012

- 15 patients with RA and basilar invagination

- posterior stabilization and endoscopic odontoidectomy

- myelopathy improved in all patients

 

McDowall et al J Craniovert Junction Spine 2021

- Swedish registry

- review of 176 patients with RA undergoing cervical stabilizaton

- 48 (27%) with basilar invagination

- improvement in pain

- early improvement in neurology, returning to baseline at 5 years

 

Subaxial Subluxation (SAS)

 

Definition

 

Anterior subluxation of one vertebral body on another

Results in spinal stenosis

 

Diagnosis

 

A.  Instability on Flexion / Extension views

- > 3mm

- > 11o

 

Rheumatoid Arthritis Subaxial InstabilityRheumatoid Arthritis Subaxial Instability Extension View

Anterior subluxation of C3 on C4

 

B.  Space available for cord / SAC

- subaxial canal diameter on lateral

- < 13 mm high incidence neurology

 

RA Subaxial Subluxaton SAC

 

Pathology

 

Facet erosions / ligament incompetence

 

May see at multiple levels with stepladder type deformity & kyphosis

Can occur beneath previous cervical fusions including C1/C2

 

MRI

 

Cervical Spine MRI Subaxial Subluxation

 

Management

 

Indications for surgery

- SAC < 13 mm

- stenosis symptoms

- instability

 

Options

 

ACDF

Posterior laminectomy and fusion

 

Anterior decompression and fusion

 

Subaxial Stabilisation

 

Posterior laminectomy and fusion

 

May need long fusion to prevent SAS above and below

 

Cervical Spine Posterior Fusion for SASCervical Spine Posterior Fusion for SAS

 

Results

 

McDowall et al J Craniovert Junction Spine 2021

- Swedish registry

- review of 176 patients with RA undergoing cervical stabilizaton

- 19 (11%) with SAS

- improvement in pain

- highest risk of death within 5 years after surgery (11/19, 58%).