Dynamic Posterior Instability Test: A New Test for Posterior Glenohumeral Instability

Area of Science:

• Orthopedics
• Sports Medicine
• Diagnostic Imaging

Background:

• Recurrent posterior shoulder instability is an increasingly recognized cause of shoulder disability, particularly in athletes.
• Diagnosis is often overlooked due to vague presentations and limited, difficult-to-perform diagnostic tests.
• Existing tests often lack specificity, failing to distinguish posterior labral tears from other shoulder pathologies.

Purpose of the Study:

• To describe the dynamic posterior instability test (DPIT) and a modified DPIT.
• To evaluate the accuracy of these tests in detecting posterior labral pathology.
• To hypothesize that the DPIT would improve diagnostic accuracy for posterior labral tears.

Main Methods:

• The DPIT and modified DPIT were performed on patients evaluated for posterior shoulder instability over 9 months.
• Records of patients undergoing posterior labral repair were reviewed, comparing test results to intra-operative findings.
• Anterior glenohumeral instability patients served as a control group.

Main Results:

• The DPIT demonstrated high accuracy with 94.4% sensitivity and 95% specificity.
• Fifty-one patients had a positive DPIT, and 3 had a negative result.
• The modified DPIT yielded identical results to the DPIT, with excellent predictive values.

Conclusions:

• The DPIT and modified DPIT are valuable new diagnostic tools for posterior shoulder instability.
• These tests, combined with clinical history and examination, enhance diagnostic accuracy.
• Improved diagnosis of posterior labral tears can lead to better patient outcomes.