Cervical Instabilities Spine Clinical Trial
Official title:
Occipito-Cervical Stabilization Using Occipital Condyle as a Cranial Anchor
The Occipito-Cervical (OC) junction is the most cephalad portion of the spinal axis, with
anatomical osseous complex that allows significant mobility while maintaining biomechanical
stability. OC instability is a rare disorder with potentially life-threatening consequences.
Instability may manifest as disabling pain, cranial nerve dysfunction, paralysis, or even
sudden death. The most common acute presentation is secondary to major trauma. Other
pathologic processes that may lead to chronic instability include rheumatoid arthritis,
infections, tumors, and even congenital malformations; OC fusion in aforementioned cases each
according is then indicated.
Stabilization of the OC junction remains a challenge, owing to the regional anatomy and poor
occipital bone purchase. OC stabilization techniques have undergone continuous refinement.
Early techniques involving simple posterior only bone grafts demonstrated a high rate of
failure and have largely been replaced by rigid posterior fixation systems using rods/screws
or plates, providing superior biomechanical stability and higher rates of fusion. One of the
very modern modalities of fixation methods is the Occipital Condyle Screw (OCS) as a sole
cranial anchor; believing that decreasing the length of lever arm of the construct,
increasing the length of the screw purchase, and decreasing stresses addressed on the rod
with no need to excessively bend it for the occipital slope may enhance the construct
rigidity, and leaving a greater clear metal-free area of the occiput for graft contact may
have a real potential benefits in fusion rates.
Clinical Evaluation: of patients with 1- Visual Analogue Scale (VAS), 2- Neck Disability
Index (NDI), 3- Modified Japanese Orthopaedic Association Cervical Myelopathy Score
(mJOA.CMS), 4- American Spinal Injury Association Score (ASIAs). Immediate preoperative
functional scoring, and 6 weeks, 3 months, 6 months, and 1 year postoperative.
Surgical Technique: The patient is handled in prone position after successful general
anaesthesia with supported head to ensure that the Occipito-Cervical junction maintains in
neutral position. The Occipito-Cervical junction is then exposed through a traditional
midline longitudinal posterior skin incision extends from the external occipital protuberance
to the C3-C4 level. The nuchal ligament is divided in the midline, and the occipital and
cervical musculature is dissected subperiosteally. The suboccipital and cervical paraspinous
muscles are retracted laterally to expose the underlying bony architecture. The posterior
arch of C1 is exposed and the dissection is continued laterally in a subperiosteal manner to
identify the horizontal segment of the vertebral arteries (VAs) which is enveloped in a dense
venous plexus. The atlanto-occipital joint capsule is to be approx. 3 mm. Cranial to the
superior margin of tht VA. Attention is then focused on the foramen magnum. Using curettes,
the atlanto-occipital membrane is gently dissected from the foramen magnum laterally until
the medial aspect of the occipital condyle is reached. At this point, the dissection
continues laterally, maintaining bone contact to prevent injury to the horizontal segment of
the VA along the condylar fossa, until the posterior condylar foramen and emissary vein are
identified. The condylar foramen and vein represent the lateral extent of the dissection. At
this stage, the operative field is prepared for instrumentation. Inserting the cervical
screws first provides useful information about the axial location of the occipital condyles.
The condylar entry point (CEP) is defined using a combination of radiographic and anatomic
landmarks. The CEP is located (4 to 5 mm) lateral to the posteromedial edge of the condyle,
and (2 mm) above the atlanto-occipital joint line. Pilot hole is then made at the entry point
using an awl with slight cranial angulation to avoid injury to the horizontal segment of the
VA. The pilot hole is then drilled under image-guidance in a convergent trajectory with (12
to 22 degrees) of medial angulation and (5 degrees) cranial angulation in the sagittal plane
with the tip of the drill directed toward the basion, advancing slowly until the anterior
cortical edge of the condyle is breached. The hole is tapped, and a (3.5 mm) polyaxial screw
of an appropriate length (30 to 34 mm) is inserted bicortically into the occipital condyle.
Approximately (12 mm) portion of the screw remains superficial to the posterior cortex of the
condyle, allowing the polyaxial portion of the screw to lie above the posterior arch of C1,
minimizing any chance of irritation of the VA by the rods.
Radiological Evaluation: 1- Preoperative: Plain X-ray (PXR) Antero-posterior (AP) and Lateral
(Lat.) views to study the upper cervical instability indices and measurements, Multi-Slice
Computed Tomography (MSCT) to study the boney Occipito-Cervical architecture for any
fractures or anomalies, CT Angiography (CTA) to study the vertebral artery for anomaly
especially in the horizontal segment of the VA, and Magnetic Resonance Imaging (MRI) to study
the spinal cord for any compression signs. 2- Postoperative: Immediate (PXR) AP. and Lat.
views for overall global assessment of the reduction and the construct installation. Then at
3 months, 6 months, and 1 year after surgery with flexion extension lateral view bending
stress films for assessment of stability. Immediate (MSCT) to study the crucial screws
placement estate for any breaches or successfulness, and after 1year for assessment of the
fusion rate achieved.
Serial Follow-Up: after 6 weeks for clinical evaluation and functional scoring. At 3 and 6
months for radiological evaluation of stability, clinical evaluation and functional
re-scoring. At 1 year for evaluation of fusion rate, clinical evaluation and over all
resultant functional scores.
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| Status | Clinical Trial | Phase | |
|---|---|---|---|
| Enrolling by invitation |
NCT04770571 -
Posterior Cervical Fixation Study
|