Editorial Commentary: Snapping Scapula Syndrome: Predictors of Outcomes After Arthroscopic Treatment

In the article titled “Prognosis After Arthroscopic Superior Medial Scapuloplasty for Snapping Scapula Syndrome Improves Following a Transient Beneficial Response With an Ultrasound Guided Subscapular Cortisone Injection,” Tytherleigh-Strong, Al-Hadithy, Griffiths, and Gill retrospectively attempt to provide a quantitative perspective on the prognostic value of ultrasound-guided corticosteroid injections for patients who received surgical treatment of idiopathic snapping scapula syndrome (SSS) by use of patient-reported outcome measures. They used a systematic approach to their diagnostic workup, with patients first attempting 3 months of physiotherapy, prior to ultrasound-guided local or cortisone injections for those who did not improve with therapy alone. Patients were reassessed 3 months after the injection, and those who did not respond or had only a transient response were offered a repeated injection versus arthroscopic surgery.

Ultrasound-guided injections in the scapulothoracic joint have been described before in the radiology literature: Walter et al. performed ultrasound-guided injections in 27 shoulders and found that 63% of patients had immediate relief and 82% experienced some sort of relief. Thus, not all patients will experience pain relief, as was the case in the current study by Tytherleigh-Strong et al., in which 31 of 42 patients (71%) experienced a “good response” from injection preoperatively.

But why do about 20% to 30% of patients not experience relief with an injection? Perhaps not all of these patients had a true diagnosis of SSS. Tytherleigh-Strong et al. defined a diagnosis of SSS as “medial superior scapula pain, with or without associated palpable crepitus, with worsening symptoms when the scapula was compressed again the chest wall.” Gaskill and Millett suggested that SSS and scapulothoracic bursitis (STB) may exist independently or concomitantly and that painful crepitus or painful reproducible snapping is the hallmark of diagnosis. It would be interesting to see if there was a difference in response to injection or surgical outcomes between those patients who had painful crepitus and those who did not.

Tytherleigh-Strong et al. concluded that these patients experience a statistically significant difference in postoperative patient-reported outcomes as it pertains to QuickDASH (short version of Disabilities of the Arm, Shoulder and Hand questionnaire) and Constant scores (but not visual analog scale scores) when compared with patients who had “no to minimal response” to a preoperative injection. Notably, although these data may be statistically significant, when we look at the numbers more closely, we find that the differences may be small, and thus, we may need a larger study or longer follow-up to really determine whether a preoperative injection carries prognostic value in these patients.

Despite the limitations of their study, Tytherleigh-Strong et al. are commended for their efforts to optimize patient outcomes in patients with a rare, and challenging to treat, condition of the shoulder. They notably reported that although good outcomes can be achieved independently of an injection, only 22% of patients had complete resolution of their preoperative symptoms—reminding us that surgery may not be a cure for this condition. These findings have been mirrored in previous studies as well.^, For example, in 2018, Memon et al. performed a systematic review involving 203 shoulders with SSS or STB and reported an 89% rate of clinical improvement, with 68% of patients having persistent symptoms of some sort.

The findings in the study by Tytherleigh-Strong et al. raise the question as to whether other factors may help predict a more successful outcome from arthroscopic management of SSS and STB. They did not find any differences in age, sex, preoperative QuickDASH (short version of Disabilities of the Arm, Shoulder and Hand questionnaire) score, preoperative Constant score, and preoperative or postoperative visual analog scale score in their study. From an anatomic perspective, Spiegl et al. have analyzed the bony morphology of the scapula in idiopathic SSS patients and found that anterior angulation, concave-shaped scapulae, and a positive medial scapula corpus angle all were associated with, or increased the risk of, SSS. Perhaps more attention needs to be paid to these anatomic differences in our workups, particularly given that Millett et al. suggested that outcomes are better in patients who receive bursectomy in conjunction with partial scapulectomy versus bursectomy alone. In the largest cohort to date, Menge et al. in 2017 reported on 92 scapulae treated arthroscopically for SSS with a minimum 2-year follow-up. Similarly, all patients showed significant improvements in their patient-reported outcome measures. However, the authors were able to conclude that older age, a lower preoperative psychological score, and a longer duration of symptoms before surgery correlated with poorer outcomes. Thus, patient selection may go beyond a simple diagnostic injection and should also focus on specific demographic factors, as well as other factors in the patient’s history.

In essence, this study reminds us that optimizing the surgical indications in patients extends beyond just a single test. Patient selection involves a comprehensive history and examination, in addition to a thorough radiologic assessment and, perhaps most important, consideration of the patient’s physical and psychological well-being as a whole—not just the involved body part. Additionally, we must critically evaluate the data in any study because although the numbers may be statistically significant, their clinical relevance is of the utmost importance.