Lateral Mass Screws Fixation of Cervical Spine

Lateral Mass Screws Fixation of Cervical Spine

Lateral mass screw fixation of cervical spine was first introduced by Roy-Camille et al. in the 1980s.

* Surgical Indications

1) Trauma: – Unstable fractures

2) Reconstruction: Tumors / Osteomyelitis / Inflammation (Rheumatoid Arthritis )

3) Degenerative Conditions: Combined posterior decompression / adjacent multilevel fixation

4) Pediatric Spine: Congenital Malformation

Surgery Video:


* Important Questions should be considered when choosing the operative approach


Question (1) : What is the alignment of the c ervical spine? Lordotic, Straight or Kyphotic?

– Posterior decompression without fixation is primarily indicated for lordotic and possibly straight spinal configurations.

Question (2) : How rigid is the deformity?

– A single-stage posterior approach with stabilization remains an option even in the presence of kyphosis if postural reduction restores sagittal balance.

– Fixed kyphotic deformities are an absolute contraindication to the posterior approach.

Question (3) : What is the nature of the pathologic process? How many spinal levels are involved? Does the patient have congenital stenosis?

– Anterior interbody strut grafting beyond two levels is associated with an increased failure rate, in such cases supplemental posterior stabilization is required, or a single-stage posterior approach my be more appropriate.

Question (4) : Does a static or mobile subluxation exist?

– Severe subluxation or any increase seen on dynamic imaging would eliminate the possibility of a standalone laminectomy and require inclusion of a stabilization and fusion.

Question (5) : What is the patient’s baseline medical status?

– Older patients typically more prone to swallowing dysfunction with anterior approaches, severe osteoporosis will increase the chance of grafting subsidence.

– In order patients, a posterior approach may be more appropriate.

Question (6) : Does the patient complain of significant axial neck pain?

– The presence of axial neck pain, if attributed to motion across a spondylotic segment, may support the addition of an arthrodesis.

Lateral Mass Bony Structures:

Consists of superior and inferior facets.

It is the part: – Lateral to the lamina.

– Between the inferior margins of the adjacent inferior facets.

Mean diameters of lateral mass:

– Superoinferior from 11mm at C3 to 15mm C7.

– Mediolateral from 12mm to 13mm at C3 through C7.

– Anterioposterior the lateral mass is smaller at the C6-C7 levels than at the levels above.

– Width: 12mm to 13mm at C3 through C7.

– Height: 11mm at C3 – 15mm C7

– Thickness: smaller at C6-C7 than levels above.

Lateral Mass Width:

– Range: 8.0 mm – 16.1 mm

– Mean width greater in males at all levels and greatest at C6 for males (12.8mm) and females (11.1mm)

Anterior to the lateral mass:

– The Pedicle Anteromedially ),

– Transverse foramen,

– Posterior ridge of the transverse process ( Inferolaterally ) just above the inferior articular facet.

Transverse Foramen:

– Contains the vertebral artery, surrounded by:

   * anterior ridge of transverse process anteriorly,

   * the vertebral body medially,

   * the pedicle, anterior wall of the lateral mass, and the posterior ridge of the transverse process posteriorly.

– C3-C5 : anteromedial to the posterior center of the lateral mass.

– at C6 : courses laterally and lies in front of the posterior center of the lateral mass.

The vertebral artery:

– From the subclavian artery –> transverse foramen of C6 –> upward through the foramina above –> Deep in front of the lateral mass, separated by spinal nerve.

– Not at risk of injury as long as the screw is directed lateral in sagittal plane.

The interpedicular foramen:

– Formed by: * Adjacent pedicles,

    * Posterolateral wall of vertebral body,

    * Anteromedial aspect of the superior articular process.

The spinal nerve: Cervical Nerve Root

– Passes through the lower part of interpedicular foramen –> Laterally in the transverse foramen, it divides into a Larger anterior ramus and a smaller dorsal ramus.

– The ventral ramus courses on the transverse to form the cervical and brachial plexus.

The dorsal ramus:

– in the transverse foramen runs posteriorly against the corner of the base of the superior articular process

– Supplies –> the facet joint, ligaments, deep muscles, and the skin of the posterior aspect of neck.

– Diameter: * C3-C5: Larger (1.6mm – 2.2mm)   * C6-C7: smaller (1.2mm)

Lateral Mass Quadrants:

The superolateral quadrant is away from spinal nerve and vertebral artery.

Lateral Mass Screws: (C3-C7)

– Starting point –> near center of lateral mass –> Direct screw tip up and lateral ( Away from the nerve root, spinal cord, and vertebral artery )

Magrel Screw

– Length: 6.3 – 20.4 mm

– Greater in males at all subaxial levels, greatest at C6 for males (15.6mm) and females (14.0mm), shortest at C7 for males (11.4mm) and females (9.6mm)

– Directed as lateral as superior as possible, to avoid injury to the spinal nerve and its dorsal ramus.

Roy-Camille Screw

– Length: 6.3 – 16.7 mm

– Greater in males at all subaxial levels, greatest at C5 for males (12.9mm) and C4 for females (11.5mm), shortest at C7 for males (9.8mm) and females (8.5mm)

– The exit point seems safe because it lies inferior to the dorsal ramus, and it’s separated from the ventral ramus by the posterior ridge of the transverse process.

Roy-Camille VS Magrel Screw

– Magrel trajectory significantly longer than Roy-Camille trajectory.

– Average Magrel screw lengths: 2.6 mm longer at C3 – C6 levels, and 1.3 mm longer at C7 level.

Free hand technique of cervical lateral mass screw fixation:

Prof.Dr/Mohamed Mohi Eldin – Prof.Dr/Ahmed Salah Aldin Hassan

Read the full article here:

Lateral Mass screw efficiency

– High fusion success ( > 97%)

– Good maintenance of stability ( > 95%)

– Low complication rate: 10% increased kyphosis, rare hardware failure (except screws back out in plates )

Lateral Mass screw safety

– Nerve root injury ( 1.2%), Vertebral artery injury (small risk)


– Template lateral mass screw length on image scans for determination of safe scew lengths at each level.

Anatomic Studies pediatric cervical screws:

– Feasibility based on anatomic dimensions does not prove safety.

– Vertebral canal dimensions > 80% of the adult level by 5 years of age.

– Growth arrest 2^ to screw placement across neurocentral synchondrosis leading to canal stenosis is not a concern.


– Bleeding / Vascular injury.

– Neurologic injury.

– CSF Leak.

– Malposition.

– Implant loosening.

– Device breakage.

– Disassembly.

– Malfunction device.

– Bone Fractures.

– Graft settling / displacement.

– Loss of correction.

– Pseudoarthrosis.

– Wound infection.

– Skin irritation.

– Cardiac, Respiratory complications.

– Revision of surgery.