There were 2 important findings in the current study. The first was that both corticosteroid hydrodilatation with and without arthroscopic release enhance passive ROM, relieve pain, and effectively improve function in treatment of freezing-phase frozen shoulder. The second was that arthroscopic release with corticosteroid hydrodilatation yield better improvement in passive ROM and function, with similar pain relieve.
Frozen shoulder is marked by acute synovitis and progressive capsular contracture [3, 17]. It is generally acknowledged that inflammation is manifested in early stages of this disease, with collagen and matrix production later culminating in fibrosis . During the early period, synovial hyperplasia and increased vascularity develop, promoting fibrosis of capsular synovium and subsynovial tissue, so-called freezing stage . Compared with control subjects, multiple inflammatory factors are expressed at substantially high levels within joint capsules and subacromial bursae of patients with frozen shoulders [2, 17]. The main aims of the treatment are pain relief and improvement of ROM and function.
Corticosteroid injection is a standard treatment for frozen shoulder proven effective in reducing pain and inflammation by disrrupting inflammatory mediators and synovitis [5, 19]. Unfortunately, this approach is less successful at thawing capsular and rotator interval contractures . In the present study, in group B, pAB, pFL, and pIR did not improve at 1 week, and passive ROM in group A regularly surpassing group B at the former 24 weeks. Single-dose corticosteroid injections are inadequate for long-standing frozen shoulders. A series of three injections at least, and possibly four to six injections, may subsequently be advantageous [1, 21]. In the present study, three injections were performed in both groups. According to Cho and Sun [5, 22], intra-articular space and rotator interval are preferable to subacromial space in this regard, although some authors have achieved similar functional improvement by injecting between intra-articular and subacromial spaces . The inflammation in glenohumeral joint is fundamental for frozen shoulder, subacromial space is also involved . Combined subacromial/intra-articular space injection seems to additively increase the angle of internal rotation . Recent evidence highly recommends hydrodilatation as a choice for treatment of frozen shoulder, contributing greatly to pain relief and functional improvement . Combining hydrodilatation with corticosteroid injection provides superior pain relief in the short term and improvement in ROM across all time frames for frozen shoulder when compared to corticosteroid injection alone . We prefer corticosteroid hydrodilatation, because the high-pressure delivery enhances spread throughout articular cavities, especially along biceps tendon sheath, for broader anti-inflammatory effects.
Arthroscopic capsular release could improve ROM remarkablely, even at Week 1 in group A, the passive ROM significantly improved compared with baseline. PAB, pFL and pER reached 144.0, 150.8, 35.0 in group A at Week 4, and near-normal by postoperative Week 12. Studies have shown that arthroscopic capsular release provides complete and long-lasting improvement in shoulder pain and function, faster than any other therapeutic modality [1, 11,12,13]. Nevertheless, the extent of capsular release remains in question. Anterior release (including superior glenohumeral ligament and rotator interval) is essential, with some advocating 360° circumferential release [24, 25] and others claiming no demonstrable ROM gains through vaster posterior release [26, 27]. Timing of arthroscopic capsular release is another issue [14, 19, 28]. It is generally agreed that such treatment is indicated for refractory adhesive capsulitis and is appropriate for frozen phase. More recently, however, there is mounting evidence that the timing of intervention does not impact outcomes. Rizvi et al. discovered that unlike patients with protracted symptoms of frozen shoulder, those whose symptoms lasted < 10 months made greater strides in internal rotation after arthroscopic capsular release, with similar outcomes in flexion, abduction, and external rotation, so there was no reason to delay surgery . In another study of 127 patients with frozen shoulders, grouped by symptom duration (onset to surgical intervention), arthroscopic release brought effective and rapid improvement in shoulder motion and function, unrelated to surgical timing . The duration of frozen shoulder was apparently shortened by arthroscopic capsular release [29, 30], reducing the natural disease course by > 12 months . In the present study, passive ROM in group A improved enough to finished most of the daily work at Week 4, and enabling near-normal ROM and shoulder function by postoperative Week 12, the course of frozen shoulder was shortened as a result. That was why we did not continue the follow-up to more than 1 year.
The suitability of arthroscopic capsular release in treating freezing-phase frozen shoulder is still unsettled. Arthroscopic flushing may mitigate inflammatory factors, but cellular infiltrates and hypervascularity are not fully constrained . Consequently, the risk of recurrence is high. This also explains why we had no comparator group expressly for arthroscopic capsular release only. In the present study, arthroscopic release and corticosteroid hydrodilatation complement one another, reaping enhanced effects. Arthroscopic capsular release readily improved ROM, whereas corticosteroid hydrodilatation dampened inflammation in patients of group A, the rapid improvement of ROM was kept. Remarkably, arthroscopic release combined with sequential corticosteroid hydrodilatation had yet to be reported until now.
Although multiple studies have shown that corticosteroid injection in close proximity to arthroscopic surgery raises the risk of infection [32, 33], still other authors using corticosteroid injection in shoulder arthroscopic surgery . In the current study, corticosteroid was mixed with ropivacaine and saline to a relative low concentration. On the other hand, no implants were used in the surgery. Furthermore, arthroscopic shoulder capsule release was not difficult and the surgical time was short. There was no infection in all patients. Anesthesia was imposed on the patient in group A, which may have side effects for them. In the current study, general anesthesia was performed and no side effects was found. Maybe it was because the short time of the surgeries.
There were certain limitations of the present trial, one being the lack of separate comparator groups, one for arthroscopic release only and one for untreated patients. Frozen shoulder is also a progressive disease of spontaneous onset and overlapping phases, so the durations cited by patients may not have been accurate, undermining our results. Then, frozen shoulder developed from injury and diabetes was excluded from the study, which could be a substantial proportion of the frozen shoulder population. And there was potential baseline imbalance in participants with different social engagement, occupation, etc. Likewise, when injecting, leakage of fluid from joint cavities was not totally preventable. Then, the sample size was small, the complications such as infection and cartilage damage were not definite. Then, the follow-up was 1 year, while the natural history of frozen shoulder was longer. Finally, the physician who performed these injections and patients were not blinded to specific protocols, given the obvious group differences in therapeutics.