THE OCCIPITOCERVICAL FIXATION Bernucci Claudio M D Head

THE OCCIPITOCERVICAL FIXATION Bernucci Claudio, M. D. Head of Neurosurgery Unit Department of Neuroscience and Surgery of the Nervous System ASST Papa Giovanni XXIII– Bergamo

The Cranio-Cervical Junction (CCJ) More than 50% of the rotation and flexion-extension of the head and neck occurs in CCJ. It permits movements in eight axes of rotation. These include flexion, extension, bilateral bending; and bilateral rotation, distraction, and axial loading. The motion of the AO junction is dictated by osseous constraints, whereas stability of the AA articulation is provided primarily by ligament restraints Intrinsic ligaments (tectorial membrane, cruciate & alar ligaments) & joint capsules provide most of the stability of the CCJ: the rest is provided by extrinsic ligaments

Indications for OC fixation Occipitocervical arthrodesis is indicated to treat instability of the CCJ The causes of occipitocervical and atlantoaxial pathology include: • CCJ Trauma (more common in the paediatric population) • Rheumatological diseases (Rheumatoid arthritis) • Tumor • Infection • Congenital malformation (Chiari malformation, Os odontoideum, osteogenesis imperfecta) • Degenerative disease processes OC fusion blocks all the movement of the CCJ: it is best to prefer more conservative treatment as a first option

Signs of CCJ Instability

OC Fixation - Techniques Fusion success rates as high as 100% using plate and screw fixation have been reported by Smith et al and Sasso et al. Occipital wire and rod constructs are less stable especially under axial loads The methods noted to be the most stable were screw fixation techniques that include C 2.

Surgical planning: what do you need to know? Angio-CT: vertebral artery CT: C 1 lateral mass lenght and orientation, C 2 pedicle lenght and diameter, isthmic point , occipital bone thickness

Positioning

Positioning Shoulders raised and pulled caudally • Spine parallel to the floor • Head flexed • Check the caudo-cranial trajectory for C 2 screwing with a kirschner pin and X-rays

Head positioning The OC fusion does not allow all the movements of the upper cervical spine. Therefore it is mandatory to place the head in order to allow for horizontal gaze Place the patient in the prone position with the head fixed in a 3 -pin head-clamp. First, it is best to put the head slightly flexed in order to open the space between vertebrae. Once the screws are inserted it is better to slightly extend the head in order to avoid kyphotizing the spine.

Procedure Intraoperative X-rays useful, but not reliable helps in antero-posterior lenght and caudo-cranial direction for C 1 screws helps in caudo-cranial direction for C 2 screws (parallel and tangent to the upper margin of the C 2 pedicle) it is an anatomical procedure based on surgical landmark …. unless O-ARM

The Occipital Bone • The occipital squama bone thickness is the greatest at the external occipital protuberance (EOP) and decreases in a radial distribution • Bone thickness in the EOP is 15 mm in males and 12 mm in females on an average. The other “safe area” is relatively thin strips of bone that extends caudally from the EOP and is a reflection of the internal occipital crest. Suchomel P, Choutka O : Reconstruction of Upper Cervical Spine and Craniocervical Junction

Case 1 A 6 -year-old female with no prior medical history was brought to the emergency room after a high energy car accident, complaining: • Paraplegia • Weakness (0/5) of the right upper limb • Severe neck pain • Respiratory distress The imaging showed an Atlanto-Occipital Dissociation

C 1, C 2 fixation with Goel. Harms technique and C 4 transarticular screw insertion