Rheumatoid Neck

Epidemiology

 

Neck involved in 86%

- second most common site after hands and feet

- closely associated with MCPJ subluxation

 

Associations

 

Males / Steroid use / Seropositivity Nodules / Severe long standing disease

 

Conditions

 

Atlanto-axial subluxation

Subaxial subluxation

Superior migration ondontoid

 

1.  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

 

Diagnosis

 

1.  Lateral view AADI

- anterior atlantodental interval

- AADI > 3 mm

 

Cervical Flexion Instability Increased AADI

 

2.  AADI

 

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

 

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

 

B.  Severe instability: > 7 mm difference

 

AADI greater than 5 mm

 

3.  PADI

- posterior atlantodental interval / SAC (space available for cord)

- > 14 mm 94% predictive no neural deficit

- < 14 mm 97% predictive neural compression

 

2.  Superior Migration of Odontoid / Pseudobasilar Invagination / Atlantoaxial vertical subluxation

 

Superior Migration Ondontoid CT CoronalSuperior Migration Ondontoid CT Sagittal

 

Definition

- vertical translocation of Dens into foramen magnum

- compresses medulla

 

Pathology

- due to erosion of lateral masses of atlas and occipital condyles

- can lead to compression of brain stem

- risk of myelopathy / sudden death

 

Epidemiology

- seen in 40% of RA patients

 

Symptoms

- C1/C2 compression gives occipitocervical pain

- ventral pressure can compress respiratory centre and cause sudden death

 

Diagnosis

 

Superior Migration Ondontoid Lateral XraySuperior Migration Ondontoid Lateral Xray Close Up

 

Ranawat measurement < 13 mm

- line between anterior and posterior arch atlas

- centre of pedicle of C2

 

SMO Ranawat Measurement

 

McCrae

- line of foramen magnum

- tip of dens 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 <29mm = abnormal

- if abnormal -> highly correlated with severe disease & neurology

 

SMO Redlund-Johnell

 

3.  Subaxial Subluxation (SAS)

 

Definition

- anterior subluxation of one vertebral body on another

 

Rheumatoid Arthritis Subaxial InstabilityRheumatoid Arthritis Subaxial Instability Extension View

 

Diagnosis

 

A.  Instability on Flexion / Extension views

- > 3mm

- > 11o

 

B.  Space available for cord / SAC

- subaxial canal diameter on lateral

- < 13 mm high incidence neurology

 

RA Subaxial Subluxaton SAC

 

Aetiology

- facet erosions / ligament incompetence

 

Epidemiology

- 10-20% of RA patients

 

Pathology

- may see at multiple levels with stepladder type deformity & kyphosis

- occurs beneath previous cervical fusions

- anterior subluxation / destructive changes of facet joints / destruction of disc

- can result in 2° canal stenosis

 

Cervical Spine MRI Subaxial Subluxation

 

Neurological Classification Ranawat

 

I        No neurological deficit

II      Subjectively weak / hyperreflexia & dysesthesia

IIIA   Objectively weak / ambulatory

IIIB   Objectively weak / non ambulatory

 

Clinical Features

 

Pain

- neck radiating to shoulders / occipital headaches

- occipital neuralgia / greater occipital nerve compression

- ear pain / greater auricular nerve compression

- facial pain / trigeminal

 

Stiffness

 

Parasthesiae

- most common & earliest symptom 

- pain & temp / spinothalamic tract compression

 

Weakness

 

Frequency or retention / constipation

 

NHx

 

Incidence of cervical involvement increases with duration of disease

- after 10 years 60% will have AAS

 

Postmortem study of 104 patients with RA

- 10% died 2° medullary compression

- impossible to predict which patients will progress

 

MRI

 

Supplanted CT

- site of compression

- accurate SAC / account for soft tissue

 

Dimensions

1.  Foramen magnum SAC < 14 mm = neurological compression

2.  C1-2 SAC < 13mm

3.  Subaxial spine SAC < 12mm

 

Rheumatoid Arthritis Limited Space Available for Cord

 

Cervicomedullary angle (MRI)

- long axis brainstem to long axis cord

- normal angle is 135-175°

- <135° = vertical settling & is correlated with myelopathy

 

Management

 

Goals of Treatment

 

1. Prevent development of neurologic deficit

2. Prevent sudden death due unrecognised neurological compromise
- 10% of deaths in RA occur suddenly due neurological complications

 

Screening

 

Cervical spine flexion / extension xray

- mandatory in all patients pre-operatively

 

Management

 

2 Groups 

1.  Intractable pain or neurologic compromise -> fuse

2.  No pain & no neurology – controversial

 

AAS

 

Algorithm

1. PADI >14mm -> observe

2. PADI < 14mm MRI

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

 

Options

 

1.  C1/2 fusion

- if instability reducible / no decompression needed

 

2.  Occipito-cervical fusion

- instability irreducible

- must decompress / remove lamina C1

 

C1/2 fusion

- fusion in situ if reducible and no neurology

- laminectomy C1 + fusion if fixed deformity with neurology

 

A. Gallie / Brooks fusion

- contra-indicated if any displacement or neurology

- unable to perform decompression / laminectomy

 

C1 C2 Posterior Spinous Process WiringC1 C2 Posterior Spinous Process Wiring

 

B.  Transarticular / Mageryl screws

- 95% fusion rates

- +/- laminectomy of C1 if displaced or with neurology

- pannus resorbed in 19 of 22 patients with fusion

 

Occipitocervical fusion

 

C0 C3 fusion AAI Rheumatoid

 

Results

 

90% of pts improve 1 Ranawat grade if have neurology pre-op

- PADI < 10mm predicts patinet unlikely to improve

 

Problem

- due to bone erosion may be insuffiency bone quality for C1/2 fusion

- may need C0 - C3

 

SMO

 

More serious & should be treated more aggressively

- xray screening

- MRI in flexion to evaluate cord compression

 

Algorithm

1. No symptoms & no cord compression on MRI

-  observe

2. Cord compression

- occipitocervical fusion

- +/- C1 laminectomy +/- anterior dens excision if fixed deformity & neurology

 

Results

- 75% improve

 

Occipital Cervical Fusion LateralOccipito Cervical Fusion AP

 

SAS

 

Algorithm

- SAS >14mm & no symptoms -> observe

- SAS < 14, MRI for true SAC

- SAC < 13 or instability - surgery

 

Surgery

1.  Anterior decompression and fusion

 

Subaxial Stabilisation

 

2.  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