Diagnostic Needle Arthroscopy of the Shoulder: A Validation Study.

Background: Diagnostic needle arthroscopy offers an alternative imaging modality to magnetic resonance imaging (MRI) for the diagnosis of intra-articular pathology. Purpose: To compare the accuracy of a needle arthroscopy device (Mi-eye2) versus MRI in identifying intra-articular anatomic abnormalities in the glenohumeral joint, with formal arthroscopy as the gold standard. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 22 patients underwent diagnostic needle arthroscopy of the shoulder, of whom 20 had preoperative MRI scans. A standardized 12-point noninstrumented diagnostic arthroscopy was performed on each patient using the 0° needle arthroscope, followed by a 30°, 4 mm-diameter conventional arthroscope. Intraoperative images were randomized and reviewed by 2 independent blinded fellowship-trained shoulder surgeons for identification of key pathology and anatomic structures. The MRI scans were reviewed by a single musculoskeletal radiologist to identify pathology in the same key areas. Results: For the identification of rotator cuff pathology, needle arthroscopy (sensitivity, 0.75; specificity, 1.00) was superior to MRI (sensitivity, 0.75; specificity, 0.75) with an interobserver reliability (κ) of 0.703. For long head of the biceps pathology, needle arthroscopy (sensitivity, 0.67; specificity, 0.95) was superior to MRI (sensitivity, 0.00; specificity, 0.83). It was less accurate for labral (sensitivity, 0.33; specificity, 0.50; κ = 0.522) and articular cartilage pathology (sensitivity, 0.00; specificity, 0.94; κ = 0.353). The number of anatomic structures that could be clearly identified was 8.35 of 12 (69.58%) for needle arthroscopy versus 10.35 of 12 (86.25%) for standard arthroscopy. Conclusion: Diagnostic needle arthroscopy was found to be more accurate than MRI for the diagnosis of rotator cuff and long head of the biceps pathology but was less accurate for diagnosing labral and cartilage pathology. Although the field of view of a 0° needle arthroscope is not equivalent to a 30° conventional arthroscope, it presents an alternative with potential for use in an outpatient setting.