Rheumatoid arthritis(RA) of the cervical spine

RA (Rheumatoid arthritis) of the cervical spine is the commonly affected part of the spine affected by rheumatoid arthritis(RA) among vertebrae.

Initial inflammatory synovitis will later lead to the destruction of ligaments and bone which will lead to cervical instability.

3 types of cervical instability in RA

AAS	SMO	SAS
Atlanto-axial subluxation (65%)	Superior Migration of Odontoid or Basilar Invagination (20%)	Sub- Axial Subluxation
Most common Due to the destruction of the alar and apical ligaments around the anterior C1-C2 articulation	2nd common type Bony destruction around cranio-cervical junction which leads to cranial setting This is associated with AAS   Destruction of lateral mass of atlas (Unilateral destruction :- torticollis	Bony + Ligamentous destruction Sub-axial joints are involved  A Step-ladder pattern is seen

Clinical Features of RA of the cervical spine

Following are the clinical features in the cervical spine

• Asymptomatic mostly
• Axial neck pain
• Occipital headache
• Restricted neck movements and rotations
• Neurological symptoms

Radiological findings in the cervical spine

AP / Lateral (Flexion-extension)

Atlanto-axial subluxation (AAS)

Diagnosis in X ray by AADI (anterior atlanto dens interval) and PADI (posterior atlanto dens interval)

PADI:- Better predictor for neuro deficit

Superior Migration of Odontoid (SMO)

Diagnosed in lateral radiographs (position of tip of odontoid to skull base)

McRae’s Line:- Preferred radiological references

Connects anterior and posterior margin of foramen magnum

Normally the tip of the odontoid lies 1 cm below McRae’s line however if it lies with in 1cm / reaches McRae’s line then it indicates SMO.

Chamberlin’s Line:

The line that passes from the posterior margin of the hard palate to the posterior margin of foramen magnum

Normally odontoid tip should not project beyond 3 mm above this line. If it projects beyond 3 mm it indicates SMO.

McGreagor’s Line:

This line connects the posterior margin of hard palate to most caudal point on occiput

Odontoid should not project beyond 5 mm of this line and if it projects beyond 5 mm it indicates SMO

In some patients with osteopenia/ destruction of odontoid process then alternate criteria are used: REDLUND-JOHNELL CRITERIAS

Redlund – Johnell criterias:

Here the perpendicular distance from the middle of lower end plate of axis to McGreagor’s line is traced.

Normal upper limit is 34 mm (men) and 29 mm (female)

Sub- Axial Instability (SAS)

Staircase or step ladder pattern in this instability in lateral radiograph

Management Options for RA of the cervical spine

Early management should begin via medication (DMARDS)

Surgical Indications:

Clinical Indication:

• Intractable pain and neurological deficiet

Radiological Indications:

• SAC <13 mm
• Spinal cord diameter < 6mm
• SAS exceeding 4mm in plain Xray with SAC < 13mm at level of SAS
• Any demonstrable SMO in radiograph
• Presence of dymanic instability

Surgical Options for RA of cervical spine.

Before comments for surgery, pre-operative traction ( Cervical) with Halo or Gardner Well tongs is used

( ↓ pain, subluxation, arrest neurological deterioration, correct fixed deformity)

During intubation, fiberoptic intubation with/out neck extension is indicated to avoid worsening of neurological deficit is considered

Atlanto-axial subluxation (AAS)

• Treated by postero-altantoaxial fusion
  •  C1-C2 fusion by Magerl’s transarticular technique, when subluxation is small / reducible
  • C1 lateral mass and C2 pars screw, Goel- Harm’s technique when subluxation is irreducible  (technically more difficult)

Superior Migration of Odontoid (SMO)

• Instrumented posterior occipito cervical fusion
• In the presence of cord compression, decompression by sub-occipital decompression and laminectomy is indicated

Sub-Axial Instability (SAS)

• In the presence of significant cord compression/ or an worsening neurological deficiet is indicated for surgery
• Standard surgery is posterior cervical fusion with lateral mass instrumentation
• When irreducible subluxation >50% is present then anterior decompression with corpectomy and reconstruction with graft and plate may be indicated.

Complications following surgery in RA cervical spine.

• Death
• Infection
• Wound dehiscence
• Implant breakdown
• Loss of reduction
• Pseudoarthosis
• Adjacent segment degeneration