In our present study, we introduced a particular type of FS (FSASI) and a feasible method to treat the disease. FSASI was diagnosed in this study according to the symptoms of the patient, MRI, and arthroscopy examinations. We describe our experience with 169 patients with FSASI who required surgical management after conservative therapy alone failed. Over an average of 38 months after surgery, the patients improved significantly in key areas such as pain and functionality. Our results showed that arthroscopic coracoid decompression combined with manipulation is an alternative method for FSASI. The procedure had few complications, the rates of recurrence were low, and patient satisfaction was high. This study contributes to the limited literature on therapeutic interventions for FSASI.
Arthroscopic capsular release is a conventional, minimally invasive method for the treatment of FS. However, the optimal method for capsular release remains controversial [11]. Although the “360° total capsular release” allows for a complete release of the contracted capsule and provides immediate improvements in ROM, this technique may lead to axillary nerve injury [21–25]. Studies have shown that the rotator interval is the primary site of pathology in FS. The release of the rotator cuff space, combined with the inferior capsule release, provides a significant improvement in ROM [26]. Some other studies have indicated that the lower capsule release should be avoided to prevent axillary nerve injury. Many surgeons release only the rotator cuff interval and the contracted coracohumeral ligament; they report positive outcomes [27–29]. In our study, we performed a finite release of the rotator interval: we cleaned the pathological tissues covering the subscapularis and rotator interval as well as a part of the anterior articular capsule and the medial glenohumeral ligament, which was performed before the coracoid decompression. After the finite release, we found that it was insufficient for restoring full ROM; hence, we followed this procedure with MUA.
MUA is often used to treat FS when conservative treatments have failed. MUA can provide improvement of shoulder function [30, 31]. However, sometimes MUA is subject to great resistance because of joint adhesion, and aggressive manipulation may result in iatrogenic lesions, including hemarthrosis, superior labral anterior and posterior lesions, rotator cuff tears, and humeral or glenoid fractures. Arthroscopic release before MUA may decrease the incidence of these complications [32, 33]. We found a gentle manipulation could easily restore the patient’s ROM after arthroscopic coracoid decompression.
In summary, our treatment method is a combination and refinement of previously reported techniques [27–29, 31–33]. The axillary nerve injury resulting from a wide range of capsule release and iatrogenic injuries resulting from aggressive manipulation are avoided with our method. Meanwhile, coracoid decompression can increase the subcoracoid space, helping to relieve shoulder pain and promote the recovery of internal rotation function [19, 34].
In our study, we used ACMS and MUCLA scales to evaluate the patients. The ACMS scale excluded the strength subitem of the Constant-Murley score because the strength score was based on the weight of pull that a patient could resist in 90° of abduction, and this subitem does not apply to patients with FS [20, 35, 36]. As a supplement, we used the MUCLA scale to evaluate strength by testing forward flexion with manual muscle testing. In addition, the MUCLA scale evaluates pain and function according to different evaluation criteria and considers patient satisfaction. The MUCLA and ACMS scales complement each other and together reflect the symptoms and progress during recovery.
Limitations
The evaluation method we used has limitations. First, the full scores of forward flexion and abduction represent 151–180°; thus, a full score does not necessarily mean that patients recover completely. Moreover, the external rotation outcome in the ACMS reflects a functional movement that combines external rotation, forward flexion, and abduction. Pure external rotation was not assessed [37]. Although our results indicate that our surgical approach was effective and that most patients were satisfied with the rehabilitation process and the eventual outcome, the recovery of ROM was time-dependent, and a slight degree of loss in ROM may occur. As mentioned in the results, two patients were not satisfied with the operation. The lesson we learned from these two patients was that because we performed a finite release, postoperative rehabilitation exercise is essential, especially in the 1st month after surgery. Otherwise, ROM can be difficult to recover.
In addition, although the clinical manifestations of coracoid impingement and its association with FS are well established [1], the causal relationship between FS and subcoracoid impingement remains controversial [5, 38, 39]. Some authors propose that progressive osteoproliferation of the coracoid process caused by constant friction during the internal rotation leads to collagen fibers' thickening. They described coracoid impingement as a potential etiology of shoulder pain, limited ROM, and subscapularis tears [3–5]. Conversely, some authors argue that subcoracoid impingement is a consequence rather than a cause of FS, and they proposed that rotator interval lesions and the contracture of the capsule reduced the subcoracoid space, resulting in further impingement in patients with FS [40, 41]. This remains an important topic for future study.
Lastly, although we introduced a novel method to treat FSASI and found the procedure was effective, we did not use a randomized controlled trial to prove superiority over other methods. In future studies, randomized controlled trials are needed to compare our surgical approach with other treatment methods.