Sharp Purser Test

Sharp Purser Test is used to assess the atlanto-axial joint instability specially in patients with rheumatoid arthritis (RA). It was first described by Dr. Sharp and Dr. Purser.

The aim of the test was to determine whether the instability was significant enough to provoke central nervous system’s signs or symptoms.

See Also: Spurling Test

How do you perform the Sharp Purser Test?

The Sharp Purser Test should be performed with extreme caution.

• With the patient in sitting position, and the neck is semi flexed to 20º-30, the examiner assesses for numbness and/or tingling in the arms or legs (If the transverse ligament is injuried, the dens of C2 vertebra may compress the tracts of the spinal cord with upper cervical flexion, producing myelopathic symptoms in the arms and/or legs).
• The examiner places palm of one hand on patient’s forehead and index finger of the other hand on the spinous process of the axis (C2) to stabilize it.
• The patient is asked to slowly flex the head; while this is occurring, an anterior to posterior force is applied through the forehead of the patient with the clinician’s other hand (the examiner presses backward with the palm).

What is the positive Sharp Purser Test?

Sharp Purser Test is positive if the myelopathic symptoms, that were produced, resolve with upper cervical flexion, or a sliding motion of the head occurs posteriorly in relation to axis (sometime this results in an audible clunk with the approximation of the dens on the posterior aspect of the anterior ring of the atlas).

Reliability

A Comparative Study by G Uitvlugt & Indenbaum assessed the validity of the Sharp-Purser test in 123 outpatients with rheumatoid arthritis and found:

• Sensitivity: 88% (when subluxation was greater than 4 mm).
• Specificity: 96%.

The authors concluded that the Sharp Purser test is a useful clinical examination to diagnose A-A instability in the RA population.

Another Systematic review by Cody J Mansfield found that the Sharp Purser Test may be inappropriate to use due to inconsistent validity, poor inter-rater reliability, and potential to cause harm.

Notes

The Sharp Purser Test was designed originally to test the sagittal stability of the atlanto-axial ligament in patients with RA, because a number of pathologic conditions can affect the stability of the osseoligamentous ring of the median joints of this segment in this patient population. These changes result in degeneration and thinning of the articular cartilage between the odontoid process and the anterior arch of the atlas, or, occasionally, in a softening of the dens.

The clinician should assesses for any numbness and/or tingling in the arms or legs before performing the test, because if the transverse ligament is injured, the dens of C2 may compress the tracts of the spinal cord with upper cervical flexion, thereby producing myelopathic symptoms such as numbness and/or tingling in the arms and/or legs. 

In the presence of a positive Sharp Purser Test, a provisional assumption is made that the symptoms are caused by excessive translation of the atlas, compromising one or more of the sensitive structures listed previously, and the physical examination is terminated. No intervention should be attempted other than the issuing of a cervical collar to prevent craniovertebral flexion and an immediate referral to the patient’s physician.

Atlantoaxial instability is diagnosed with full flexion and extension lateral radiographs, where atlantodens interval greater than 3 mm was considered abnormal.

References

1. SHARP J, PURSER DW, LAWRENCE JS. Rheumatoid arthritis of the cervical spine in the adult. Ann Rheum Dis. 1958 Sep;17(3):303-13. doi: 10.1136/ard.17.3.303. PMID: 13583915; PMCID: PMC1007053.
2. Sharp J, Purser DW. Spontaneous Atlanto-Axial Dislocation in Ankylosing Spondylitis and Rheumatoid Arthritis. Ann Rheum Dis. 1961 Mar;20(1):47-77. doi: 10.1136/ard.20.1.47. PMID: 18623858; PMCID: PMC1007181.
3. Uitvlugt G, Indenbaum S. Clinical assessment of atlantoaxial instability using the Sharp-Purser test. Arthritis Rheum. 1988 Jul;31(7):918-22. doi: 10.1002/art.1780310715. PMID: 3395385.
4. Mansfield CJ, Domnisch C, Iglar L, Boucher L, Onate J, Briggs M. Systematic review of the diagnostic accuracy, reliability, and safety of the sharp-purser test. J Man Manip Ther. 2020 May;28(2):72-81. doi: 10.1080/10669817.2019.1667045. Epub 2019 Sep 17. PMID: 31526113; PMCID: PMC7170372.
5. Netter’s Orthopaedic Clinical Examination An Evidence-Based Approach 3rd Edition Book.