The Window Test: A Simple Bedside Method to Detect Radial Deviation of the Wrist Commonly Seen in Posterior Interosseous Nerve Palsy

Abstract

Background: Posterior interosseous nerve palsy (PINP) is a disorder caused by damage to the posterior interosseous nerve, resulting in weak extension of the wrist and fingers as well as radial deviation of the wrist.

Methods: This study analyzed a new type of evaluation for PINP in hopes of increasing ease of diagnosis and earlier detection of the disorder. The window test is performed by the examiner laying hands on the ulnar aspect of the patient's pronated forearm while the patient tries to extend the wrist. A positive test is obtained when a gap (window) appears between the examiner's forearm and the patient's hand. Laypeople, medical students, residents, and practicing providers were assessed prospectively on their ability to correctly diagnose PINP by observing one hand, by observing both hands and by using the window test.

Results: The window test was consistently found to be the most effective method of evaluation, as it increased the accuracy of diagnosis in all groups surveyed. Additionally, case studies were performed using the window test on patients, further demonstrating the efficacy of the test by confirming wrist radial deviation.

Conclusions: The window test introduces a reference frame making it easier to assess wrist radial deviation and offering a simple evaluation that can be administered by virtually anyone. These findings indicate that the implementation of the window test will increase the accuracy and effectiveness of PINP diagnosis, thus allowing early diagnosis and better management.

Keywords: Brachial plexus; Neuropathy; Posterior interosseous nerve; Posterior interosseous nerve palsy; Radial deviation of the wrist; Window test.