Injuries of the subscapularis: prevalence of partial lesions and their diagnostic difficulty

Abstract

Objective: to conduct a review of partial ruptures of the subscapularis muscle (SSC) and establish their prevalence and preoperative diagnostic difficulty, as well as their frequent association to injuries of the supraspinatus (SSP) and long portion of the biceps (LPB). Material and methods: a retrospective review was made of the data corresponding to 75 partial ruptures of the SSC out of 660 rotator cuff ruptures operated upon by the same team of surgeons between June 2008 and June 2018. With regard to the analysis of diagnostic reliability, the reference standard was taken to be the type of lesion diagnosed via arthroscopy, establishing comparisons against the results of the exploration tests and the magnetic resonance imaging (MRI) findings. The following surgical data were also recorded: type and size of the lesion, with definition of the types of lesion in relation to the association to those of SSP and LPB. Results: of the 660 cases, 280 (42.4%) presented SSC rupture, and of these, 75 (11.4% of the total and 26.8% of the SSC ruptures) presented ruptures considered to be partial. There were 33 women —including one operated upon in both shoulders (45.3%)— and 41 men (54.7%). The pain was located on the anterior surface of the shoulder, and in 66 cases (88.0%) it radiated to the anterior surface of the arm. The combination of exploration testing of the SSC only proved positive in 64.7% of the isolated injuries of the SSC and in 14.7% of the global sample, while the Neer test proved positive in 93.1% of the cases with associated injury of the SSP. Magnetic resonance imaging only identified 21.3% of the injuries of the SSC versus 70.7% of the associated injuries of the SSP. Conclusions: the prevalence of partial ruptures of the SSC corresponds to 11.4% of the total cuff injuries. Given their diagnostic difficulty due to the frequent association to injuries of the SSP and LPB, together with the limited validity of the exploration and imaging tests, a new subclassification is presented that contemplates this association with a view to improving surgical treatment.