The Allen Test for Blood Flow: Difference between revisions

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== Purpose&nbsp;<ref>J.G. Seiler et al. Essentials of hand surgery, American society for surgery of the hand, lippincot Williams and Wilkins, 2002</ref><ref>Andrew Ronald et al. Is the Allen's test adequate to safely confirm that a radial artery may be harvested. CardioVasc Thorac Surg 2005;4:332-340</ref><ref>Christine B. Novak. Outcome Following Conservative Management of Thoracic Outlet Syndrome. J Hand Surg 1995;20A:542-548.)</ref><ref>Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007</ref>  ==
== Purpose&nbsp;<ref>J.G. Seiler et al. Essentials of hand surgery, American society for surgery of the hand, lippincot Williams and Wilkins, 2002</ref><ref>Andrew Ronald et al. Is the Allen's test adequate to safely confirm that a radial artery may be harvested. CardioVasc Thorac Surg 2005;4:332-340</ref><ref>Christine B. Novak. Outcome Following Conservative Management of Thoracic Outlet Syndrome. J Hand Surg 1995;20A:542-548.)</ref><ref>Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007</ref>  ==
Allen's test was first described in 1929 by Edgar V. Allen <ref name=":2">ALLEN E. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. The American Journal of the Medical Sciences. 1929;178(2):237-243. </ref> and is a first line standard test used to assess the arterial blood supply of the hand.  It is a valuable clinical test for patency of arteries and arterial arches in the hand <ref name=":0">Oettlé A, van Niekerk A, Boon J, Meiring J. Evaluation of Allen’s test in both arms and arteries of left and right-handed people. Surgical and Radiologic Anatomy. 2006;28(1):3-6. </ref>. This test is performed whenever intravascular access to the radial artery is planned or for selecting patients for radial artery harvesting, such as for coronary artery bypass grafting or for forearm flap elevation <ref name=":0" />. Allen's test is also part of the diagnostic work up for vascular abnormalities of the upper limb such as Raynaud’s phenomenon as can be found in Raynaud’s disease, thromboangiitis obliterans and thoracic outlet syndrome <ref name=":0" />
Allen's test was first described in 1929 by Edgar V. Allen <ref name=":2">Allen E. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. The American Journal of the Medical Sciences. 1929;178(2):237-243. </ref> and is a first line standard test used to assess the arterial blood supply of the hand.  It is a valuable clinical test for patency of arteries and arterial arches in the hand <ref name=":0">Oettlé A, van Niekerk A, Boon J, Meiring J. Evaluation of Allen’s test in both arms and arteries of left and right-handed people. Surgical and Radiologic Anatomy. 2006;28(1):3-6. </ref>. This test is performed whenever intravascular access to the radial artery is planned or for selecting patients for radial artery harvesting, such as for coronary artery bypass grafting or for forearm flap elevation <ref name=":0" />. Allen's test is also part of the diagnostic work up for vascular abnormalities of the upper limb such as Raynaud’s phenomenon as can be found in Raynaud’s disease, thromboangiitis obliterans and thoracic outlet syndrome <ref name=":0" />


The test is an inexpensive, non-invasive procedure, which can be done almost anywhere.  
The test is an inexpensive, non-invasive procedure, which can be done almost anywhere.  

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Purpose [1][2][3][4][edit | edit source]

Allen's test was first described in 1929 by Edgar V. Allen [5] and is a first line standard test used to assess the arterial blood supply of the hand. It is a valuable clinical test for patency of arteries and arterial arches in the hand [6]. This test is performed whenever intravascular access to the radial artery is planned or for selecting patients for radial artery harvesting, such as for coronary artery bypass grafting or for forearm flap elevation [6]. Allen's test is also part of the diagnostic work up for vascular abnormalities of the upper limb such as Raynaud’s phenomenon as can be found in Raynaud’s disease, thromboangiitis obliterans and thoracic outlet syndrome [6]

The test is an inexpensive, non-invasive procedure, which can be done almost anywhere.

A positive Allen's Test shows that the patient does not have a dual blood supply to the hand, which is a negative indication for catheterisation or removal of the radial arteries.

Clinically Relevant Anatomy[7][8][edit | edit source]

The supply in the arm starts in the neck between the scalenus muscles. It is the subclavian artery who supply the arm from above. The subclavian artery becomes the arteria axillaris, who becomes after 3 inches an arteria brachialis. In the region af the elbow (fossa cubita) divides the arteria in two pieces: the ulnar artery and the radial artery.

The hand has a complex and rich vascular network, which is mostly supplied by the radial and ulnar arteries.

The radial artery runs between the brachioradialis and flexor carpi radialis muscles. At the wrist, it splits into a superficial branch to contribute to the superficial palmar arch. The other branch crosses dorsally deep to the tendons of the anatomic snuffbox to form the deep palmar arch.

The ulnar artery lies under flexor carpi ulnaris. At the wrist it enters the Guyons canal, where it splits into a deep palmar branch and a superficial palmar branch. The superficial palmar branch forms the superficial palmar arch, while the deep branch contributes to the deep palmar arch.

Since the radial as well as the ulnar arteries both form anastomosis (the deep and superficial palmar arch) the blood supply of the hand is ensured even if one of the arteries is occluded,

Differential Diagnosis[edit | edit source]

Allen's test can be used as a diagnostic tool for a number of disorders, such as any diseases with reduced vascularisation in the arm, i.e. thoracic outlet syndrome or compartment syndrome. It is also commonly used after operations to the hand to determine whether the blood supply is normalised.

Technique[edit | edit source]

During Allen’s test digital compression of both ulnar and radial arteries at the level of the proximal wrist crease is applied, which causes palmar blanching followed by release of compression on either artery, which causes hyperaemia in the non-diseased state.[6]

The radial artery is located by palpation at the proximal skin crease of the wrist and then compressed with three digits. The ulnar artery is similarly located and then compressed with three digits. With both arteries compressed, the subject is asked to clench and unclench the hand 10 times. The hand is then held open, ensuring that the wrist and fingers are not hyperextended and splayed out. The palm is observed to be blanched. The ulnar artery is released and the time taken for the palm and especially the thumb and thenar eminence to become flush is noted. If the capillary refill time is greater than 6 seconds the test is considered positive. The test is then completed with the radial artery tested in a similar fashion [9]. Both hands should be tested for comparison. 

When performing the Allen’s test, hyperextension of the hand and wide separation of the fingers can lead to a false positive result [9]. This is due to occlusion of the transpalmar arch, and parts of the fingers and palm will continue to remain blanched after release of the ulnar artery [10]. To prevent this from occurring the test should be performed with the hand partially open as originally described by Allen’s [5] original description

[11]

[12]

Evidence [13][edit | edit source]

Martin et al (2000) reported a sensitivity of 73.2% and a specificity of 97.1%. Based on these findings the Allen test is a good and valid screening test for blood supply of the hand.

References[edit | edit source]

  1. ↑ J.G. Seiler et al. Essentials of hand surgery, American society for surgery of the hand, lippincot Williams and Wilkins, 2002
  2. ↑ Andrew Ronald et al. Is the Allen's test adequate to safely confirm that a radial artery may be harvested. CardioVasc Thorac Surg 2005;4:332-340
  3. ↑ Christine B. Novak. Outcome Following Conservative Management of Thoracic Outlet Syndrome. J Hand Surg 1995;20A:542-548.)
  4. ↑ Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007
  5. ↑ 5.0 5.1 Allen E. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. The American Journal of the Medical Sciences. 1929;178(2):237-243.
  6. ↑ 6.0 6.1 6.2 6.3 Oettlé A, van Niekerk A, Boon J, Meiring J. Evaluation of Allen’s test in both arms and arteries of left and right-handed people. Surgical and Radiologic Anatomy. 2006;28(1):3-6.
  7. ↑ Joints and associated structures of the hand, University of Michigan medical school, 1995
  8. ↑ S. Moses, Cardiovascular medicine book, family practise notebook, 20/02/2011
  9. ↑ 9.0 9.1 Asif M, Sarkar P. Three-Digit Allen’s Test. The Annals of Thoracic Surgery. 2007;84(2):686-687.
  10. ↑ Greenhow D. Incorrect Performance of Allenʼs Test—Ulnar-artery Flow Erroneously Presumed Inadequate. Anesthesiology. 1972;37(3):356-357.
  11. ↑ Physiotutors. Allen Test⎟Hand Vascularisation. Available from: https://www.youtube.com/watch?v=D1tJO0RW9UM
  12. ↑ The Student Physical Therapist. Allen's Test [Internet]. 2017 [cited 12 July 2018]. Available from: https://www.youtube.com/watch?time_continue=66&v=6M9MzzzpCek
  13. ↑ A. Martin et al. Reliability of Allen’s test in selection of patients for radial artery harvest, The society of thoracic surgeons. Ann Thorac Surg 2000;70:1362-1365
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