Prevalence of Isolated Idiopathic Teres Minor Atrophy: A Retrospective Study

Introduction. Isolated idiopathic teres minor atrophy is a relatively understudied condition characterized by selective atrophy of the teres minor muscle without any identifiable underlying pathology. This study aimed to determine the prevalence of isolated idiopathic teres minor atrophy. Methods. Data were collected retrospectively by examining magnetic resonance imaging scans of the right and left shoulders of individuals aged 18 years or older performed at the Medical Centre of Majmaah University, Al Majma’ah, Saudi Arabia, between February 2019 and October 2022. Teres minor atrophy was classified using the original Goutallier classification system to assess fatty infiltration. In addition, demographics, including age, gender, and nationality, were collected. Associated imaging-based factors, such as teres minor and deltoid muscle edema, rotator cuff muscle tears, and injuries to the labrum and quadrilateral space, were also documented. Results. Among the 2, 194 patients studied, 59 (2.7%) were diagnosed with isolated idiopathic teres minor atrophy, aged 27 to 75 years. Females comprised 59.3% of the affected individuals, and the majority of cases were Saudi nationals (81.4%). The right side was affected in 61% of cases. Nearly half of the affected individuals (50.9%) were classified as grade 2, while 25.4% were classified as grade 4. Patients with grade 3 and grade 4 isolated idiopathic teres minor atrophy were significantly older than those with grade 2 (58.29 ± 7.12 and 57.93 ± 12.34 versus 49.96 ± 11.72, respectively (p=0.029). No statistically significant associations were found between the demographic characteristics of individuals (age and gender) and the pattern of teres minor fatty involvement. Conclusions. The incidence of isolated idiopathic teres minor atrophy was found to be 2.7%. Age was the main statistically significant factor associated with isolated idiopathic teres minor atrophy and the grade of teres minor atrophy. Other evaluated factors, including gender and the pattern of involvement, did not demonstrate any statistically significant associations.