Is C2-3 fusion an evidence of atlantoaxial instability? An analysis based on surgical treatment of seven patients

Abstract

Objective: The authors analyze the rationale of atlantoaxial fixation in patients presenting with symptoms related to cervical myelopathy and wherein the radiological images depicted C2-3 fusion and presence of single or multiple level neural compression of the subaxial cervical spinal cord attributed to "degenerative" spine.

Materials and methods: Seven adult males were analyzed who presented with long-standing symptoms of progressive cervical myelopathy and where imaging showed presence of C2-3 fusion, no cord compression related to odontoid process, and evidence of single or multiple level lower cervical cord compression conventionally attributed to spinal degeneration. There was no other bone or soft tissue abnormality at the craniovertebral junction. There was no evidence of atlantoaxial instability when assessed by conventional radiological diagnostic parameters. Atlantoaxial instability was diagnosed on the basis of clinical understanding, atlantoaxial facetal malalignment, and manual assessment of instability by bone handling during surgery. All the seven patients underwent atlantoaxial fixation and no surgical manipulation at lower cervical spinal levels.

Results: At an average follow-up of 34 months, all patients have recovered satisfactorily in their neurological function.

Conclusion: The presence of C2-3 fusion is an indication of atlantoaxial instability and suggests the need for atlantoaxial stabilization. Effects on the subaxial spine and spinal cord are secondary events and may not be surgically addressed.

Keywords: Atlantoaxial instability; C2–3 fusion; spinal degeneration.

Figure 1

Images of a 31-year-old male patient. (a) T2-weighted magnetic resonance imaging showing C2–3 fusion and signal alteration of cord opposite C3–4 disk space. (b) Computed tomography scan showing C2–3 fusion. (c) Computed tomography scan showing the facets of atlas and axis in alignment and C2–3 facetal fusion. (d) Postoperative computed tomography scan showing atlantoaxial fixation. (e) Postoperative computed tomography scan with the cuts passing through the facets showing the implant

Figure 2

Images of a 56-year-old male patient. (a) T2-weighted magnetic resonance imaging showing C2–3 fusion. Evidences of cord compression are seen opposite C3–4, C4–5, C5–6 and C6–7 levels. (b) Computed tomography scan showing C2–3 fusion and degenerative cervical spinal changes. (c) Computed tomography scan showing facets of atlas and axis in alignment. (d) Postoperative magnetic resonance imaging. (e) Postoperative computed tomography scan after atlantoaxial fixation. (f) Postoperative computed tomography scan with the cuts passing through the facets showing the fixation construct