Evaluation of Glenoid Dysplasia and its Association with Posterior Labral Tears on Magnetic Resonance Imaging of Shoulder: A Retrospective Study

Abstract

Introduction: Glenoid Dysplasia (GD) also known as posterior glenoid rim deficiency is generally known to be asymptomatic with its incidence being greatly underestimated. Atraumatic pain is the predominant symptom in 21% of subjects with GD. GD has been associated with posterior labral tear and is generally thought to predispose to shoulder instability and consequentially to accelerate degenerative joint disease. Aim: To determine the incidence of GD, the type and extent of GD and to study its association with posterior labral tears on Magnetic Resonance Imaging (MRI). Materials and Methods: A retrospective observational study was done on 98 consecutive MRI shoulder studies obtained over a period of six months from January 2020 to June 2020 in the Department of Radiodiagnosis of Mysore Medical College and Research Institute. Those subjects with fractures, arthritic changes or mass lesions involving the glenoid process were excluded. The postero-inferior glenoid was evaluated for dysplasia on axial T1-Weighted, T2-Weighted and Proton Density with Fat Saturation (PDFS) images (slice thickness, 3-4 mm). Subjects were divided into four categories: Normal, Mild, Moderate, and Severe GD. Once the acquired images were reviewed and assigned in to the above mentioned four categories based on severity of dysplasia, they were further assigned into three categories defining the type of glenoid into three categories: normal curved lazy J and triangular bony deficiency or the Delta type. The caudal most axial scan image which depicted the articular cartilage of the glenoid was taken as the reference image. The Statistical software SPSS version 22.0, and (Robert and Ross) environment ver. 3.2.2 were used for the analysis of the data. Results: In present study of 98 consecutive MRI shoulders, six were rejected due to factor such as poor image quality, infective arthritis and trauma. Of the remaining 92 subjects (75 males and 17 females, mean age 36.73±12.50 years), 54 (58.69%) had a normal glenoid fossa, 25 (27.17%) had mild dysplasia and 13 (14.13%) had moderate dysplasia. We did not have any subjects with severe dysplasia. Of the total 38 cases of GD, 21 (55.26%) cases were of the lazy J variant while 17 (44.73%) cases were of the delta type variant. Among the 38 cases of total dysplasias, 25 cases were of mild GD of which 17 (68%) were of the lazy J variant, while 8 (32%) belonged to the delta variant. Out of the remaining 13 cases of moderate GD, 4 (30.76%) belonged to the lazy J category while the remaining 9 (69.23%) belonged to the delta variant. The difference in incidence of posterior labral tears between the normal (0) and combined mild and moderate dysplasia groups (41.3%) was statistically significant (p<0.001). Conclusion: In the study, it was found that the incidence of posterior labral tears was significantly increased in subjects with moderate GD versus healthy subjects even when cases of mild dysplasia were included.