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Distal Radial Ulnar Joint (DRUJ) Stability Test

Exams and Signs

Historical Overview

  • The Piano key test, also called the “stress test” or the ballottement maneuver by some authors,1 follows from the anatomy of distal radial ulnar joint (DRUJ) instability. It is not known when it was first introduced into clinical practice.

Description

  • The examiner pushes the ulna up and down like a piano key.2 The test is positive if the patient finds this painful, or if there is ulnar laxity.1

Pathophysiology

  • Instability of the DRUJ can be traumatic acute and chronic, atraumatic constitutional, or a combination.3
  • Distal DRUJ stability depends on osseous anatomy, soft-tissue stabilizers, and muscle activity. Injuries to any of those structures may lead to instability of the DRUJ.3

Instructions2

  1. Stabilize the radius with on hand, and grip the ulna with the other.
  2. Push up and down on the ulna.

Variations

  • To our knowledge, there are no published descriptions of variations in the Piano Key test.

Related Signs and Tests

  • Radius pull test1
  • Clunk test1
  • ECU synergy test3
  • Press test1
  • Scaphoid shift test3
  • Ulnomeniscotriquetral dorsal glide test3
  • Distal ulna ballotment test3
  • Transverse loaded pronosupination test3
  • Radioulnar compression test3

Diagnostic Performance Characteristics

Citation

Sensitivity*

Specificity†

PPV‡

NPV§

Wijffels et al, 20121

66%

68%

—

—

La Stayo and Howell, 19954

64%

44%

24%

81%

NOTE: sensitivity and specificity reported by Wijffels are from a review article that did not reference an original source; thus, the reliability of the values provided is uncertain.
*Sensitivity: true positive rate; proportion of actual positives that are correctly identified as such
†Specificity: true negative rate; proportion of actual negatives that are correctly identified as such
‡Positive predictive value (PPV): measure of precision; true positives / total number of positives (depends on prevalence)
§Negative predictive value (NPV): true negatives / total number of negatives (depends on prevalence)
ǁAccuracy: proportion of true results (positive and negative) in the population
Definition of Positive Result
  • The test is positive if the patient experiences pain when the ulna is depressed, or if there is DRUJ laxity.1
Definition of Negative Result
  • The test is negative if the patient does not experience pain when the ulna is depressed, and if there is no DRUJ laxity.
Comments and Pearls
  • There is no consensus on the definition and objective measurement of DRUJ instability.2
  • The key to performing the test is compare its results from the injured with the uninjured wrist.2,5
  • In the presence of a chronic instability, there is a likelihood of concomitant injury to multiple stuctures.3
  • The diagnostic value of this test in controversial.3
Diagnoses Associated with Exams and Signs
Videos
Distal Radioulnar Joint Stability Testing
Hyperligamentous Laxity and DRUJ Stability Testing
References
  1. Wijffels M, Brink P and Schipper I. Clinical and Non-Clinical Aspects of Distal Radioulnar Joint Instability. The Open Orthopaedics Journal 2012;6:204-210. PMID: 22675411*
  2. Culp R and Jacoby S. Musculoskeletal Examination of the Elbow, Wrist, and Hand: Making the Complex Simple. Thorofare: Slack Inc., 2012.
  3. Badur N, Garcia-Elias M. Functional evaluation of the distal radioulnar joint Available at: http://www.handclinic.ch/htm/pdf/functional-evaluation-of-distal-radioulnar-joint.pdf
  4. LaStayo P and Howell J. Clinical provocative tests used in evaluating wrist pain: a descriptive study. J Hand Ther 1995;8(1):10-17. PMID: 7742888
  5. Fornalski S, Lee TQ and Gupta R. Chronic instability of the distal radioulnar joint: A review. Univ Penn Orthopaed J 2000;13:43-52.* 
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