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INTRODUCTION

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The atlanto-occipital (AO) and atlanto-axial (AA) joints are unique joints in the spine, connecting the cervical region to the base of the skull. The AA and AO joints are an often under-appreciated cause of pain and should be part of the differential diagnosis of cervical spine pain and occipital headaches.

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INDICATIONS

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AA joint injections are indicated for:

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  • The diagnosis and treatment of AA joint pathology, which presents as deep pain in the suboccipital region, often unilateral.

    • Especially after flexion/extension injuries

    • Particularly when movement in rotation causes pain

    • Cervicogenic headaches that are impairing functional life indices (poor restorative sleep capacity, endurance, and quality of life).

    • Persistent upper cervical pain that is leading to escalating opioids to control symptoms.

    • Persistent occipital neuralgia poorly responsive to occipital nerve blocks.

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The lateral AA joint is a common cause of cervicogenic headache and may account for up to 16% of patients with occipital headache.1 The AA joint primarily refers to the occipito-cervical region, radiating to the posterior auricular region.2 There may be decreased range of motion, crepitance, and abnormal head position. When pain is increased at far cervical rotation, either during protraction or retraction, the AA joint is likely to be responsible. Unfortunately, the radiologic diagnosis of AA joint pathology has a high false-negative result, since onset of pain precedes any observable structural abnormalities. Characteristic referred pain patterns from AA and AO joint pathology overlap those patterns from the greater and lesser occipital nerves as well as the pain from the C2/C3 facet joint,2 making clinical diagnosis difficult.

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CONTRAINDICATIONS

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  • Infection at the injection site

  • Coagulopathy

  • Cervical spine instability

  • Previous cervical fusion at that level

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RELEVANT ANATOMY

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  • The first two bones of the cervical spine are unique in their shape and function. The C1, or atlas, vertebra is unique in that it does not have a ventral vertebral body, but rather functions as a relay between the occiput and C2 (Figure 15-1).

  • The AA joint articulates the atlas (C1) with the axis (C2) and constitutes the C1-C2 joint.

  • The AA joint slopes caudally and laterally (Figures 15-2 and 15-3).

  • Unlike the lower cervical segments, the AO and AA joints lack intervertebral discs and uncinate processes.

  • The C1 and C2 nerves, which are primarily sensory, travel through the suboccipital muscles to the occipital area as the greater occipital nerve and the lesser occipital nerve (Figure 15-4).

  • The dorsal root ganglion of C2 lies at the medial portion of the AA joint.

  • The posterior arch of C2 is very deep to the skin and difficult to palpate.

  • The transverse processes are long and perforated by a foramen, which protects the vertebral artery, and the anterior and posterior arches form a triangular conduit for the brainstem.

  • There are grooves in the C1 posterior surface that ...

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