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A 60-year-old woman with rheumatoid arthritis has long term neck pain and new onset of difficulty holding cards in her weekly poker tournament. She does not complain of weakness, but states she has become "clumsy" in her old age, fumbling with buttons and dropping her change. On exam she has hyperreflexia, but no weakness. Radiographs show atlantoaxial subluxation. She is considering decompressive surgery, but wants to know if she will recover function. Which radiographic marker may predict neural recovery after decompression?
Posterior atlanto-dens interval of >13mm
Atlanto-dens interval of <5mm
Subaxial subluxation of <3.5mm
Basilar invagination <0.5cm
Rotary subluxation of <10 degrees
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The clinical presentation is consistent for cervical myelopathy due to atlantoaxial subluxation in a patient with rheumatoid arthritits.
Boden et al found "The most important predictor of the potential for neurological recovery after the operation was the preoperative posterior atlanto-odontoid interval (PADI). In patients who had paralysis due to atlanto-axial subluxation, no recovery occurred if the PADI was less than 10mm, whereas recovery of at least one neurological class always occurred when the PADI was at least 10mm. All patients who had paralysis and a PADI or diameter of the subaxial canal of 14mm had complete motor recovery after the operation." They found no correlation with the anterior atlanto-odontoid interval (ADI) with the severity of paralysis or the potential for recovery.
Monsey et al report that the most helpful radiographic measurements to evaluate atlantoaxial subluxation are the anterior atlantodens interval (ADI) and the posterior atlantodens interval (PADI). Atlantoaxial subluxation greater than 9 mm and a posterior atlantodens interval less than 14 mm correlate with neurologic deficit. They argue nonoperative management does not change the natural history of cervical disease, and recommend posterior arthrodesis in patient's with neurologic deficits.
Boden SD, Dodge LD, Bohlman HH, Rechtine GR
J Bone Joint Surg Am. 1993 Sep;75(9):1282-97. PMID: 8408150 (Link to Abstract)
Boden, JBJS 1993
J Am Acad Orthop Surg. 1997 Oct;5(5):240-248. PMID: 10795060 (Link to Abstract)
Monsey, JAAOS 1997
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A 63-year-old woman with rheumatoid arthritis has long standing neck pain and new onset of difficulty with manual dexterity, such as buttoning her shirt and holding small objects. She reports difficulty walking up the stairs, and reports she feels increasingly unsteady on her feet. On exam she has 4+ patellar reflexes. Flexion and extension radiographs are shown in Figure A and B. What is the most appropriate treatment at this time?
Immobilization in a soft cervical collar for 6 weeks
Halo immobilization for six weeks
Transoral odontoid resection
Occipitocervical fusion with instrumentation
Posterior C1-C2 fusion with instrumentation
The radiographs show atlantoaxial subluxation in a patient with rheumatoid arthritis and symptoms of cervical myelopathy. Her symptoms are severe and progressive, and therefore a posterior C1-C2 fusion is indicated.
Boden et al. found that the posterior atlanto-dens interval (PADI) is predictive of neurologic injury in patients with atlantoaxial subluxation and for neurologic recovery after surgery. They found that all patients with pre-op PADI of >14mm had complete neurologic recovery after decompression, while patients with pre-op PADI <10mm had no neurologic improvement after decompression.
Monsey et al. report that the most helpful radiographic measurements to evaluate atlantoaxial subluxation are the anterior atlantodens interval (ADI) and the posterior atlantodens interval (PADI). Atlantoaxial subluxation greater than 9 mm and a posterior atlantodens interval less than 14 mm correlate with neurologic deficit. They argue nonoperative management does not change the natural history of cervical disease, and recommend posterior arthrodesis in patient's with neurologic deficits.
Figure A shows atlantoaxial instability on flexion/extension films with a dynamic increase in the ADI. Illustration A shows hows to measure the atlanto-dens-interval and PADI (also know as SAC). Illustration B shows how to measure the Ranawat C1-2 Index in this patient. Illustration C and D are flexion and extension radiographs that show severe atlantoaxial subluxation in a patient with RA.
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This is a quick and dirty video describing the ADI, SAC, and how those radiograp...