Hidden and missed shoulder pathology can be one reason for failed shoulder surgery. The supraspinatus is the most commonly torn portion of the rotator cuff so other parts of the rotator cuff may not receive the required scrutiny. A recent study found subscapularis tears to be present in 37% of rotator cuff tear cases. The subscapularis is the most powerful portion of the rotator cuff responsible for over 50% of total rotator cuff strength. It is the only portion of the rotator cuff located at the front (anterior) of the shoulder and is also the only portion of the rotator cuff that rotates the shoulder inwards (internally).
It plays a vital role in helping maintain a stable center of rotation for the shoulder, providing a balancing role, which allows the shoulder girdle to work efficiently. Muscles need two relatively fixed points to work effectively, and if the shoulder cannot maintain a stable center of rotation, the muscles that are attached to the shoulder can’t work at maximum efficiency, resulting in muscular inhibition and weakness.
Unfortunately, this can start a cascade of events that with repetitive activity results in further injury and tearing in the shoulder. This is of particular importance in throwing, overhead, repetitive and high-speed sports. Swimming, tennis, volleyball, gymnastics, baseball, and football are just a few of the many sports that require optimal shoulder balance and function. Aside from sports, any activities that require heavy lifting, pulling, acceleration, deceleration, and twisting bring the subscapularis’ role as a stabilizer into play and missed subscapularis tears can mean persistent instability and weakness that can ultimately result in failure of an otherwise well performed repair in another part of the shoulder.
The subscapularis also plays a leading role in stability of the biceps tendon as the biceps tendon splits the posterior portion of the rotator cuff (supraspinatus, infraspinatus, and teres minor) from the anterior portion (subscapularis).
Clinical diagnosis of subscapularis tears first and foremost requires one to have a high index of suspicion and vigilance. As with many other areas of pathology in the shoulder, no one clinical test is 100% accurate. Because there can be quite a bit of variability in the region of the subscapularis tendon footprint, it can be difficult to diagnose partial tears via imaging modalities such as MRI, CT Scan, and ultrasound. This region is also very difficult to see during routine shoulder arthroscopy and unless the surgeon has significant experience evaluating this area reliably, these tears can be easily missed. Often, in the presence of a subscapularis tear, the tendon itself has migrated away from its insertion site, but a failed attempt at natural healing has resulted in significant development of scar and fibrous tissue that can also be mistaken for the subscapularis tendon.
Arthroscopic repair of the subscapularis is highly effective but can be very challenging and is typically the last type of rotator cuff repair to be mastered by surgeons who may otherwise routinely perform rotator cuff repairs. Our arthroscopic all suture technique for subscapularis repair is presented in the accompanying video. Given that subscapularis tears are present in more than a third of all rotator cuff tear cases and most orthopedic surgeons only rarely perform subscapularis rotator cuff repair, missed and hidden subscapularis tears may play a role in failed rotator cuff repair surgery.