SCR is a relatively new surgical method developed in Japan, which is performed as a joint-preserving surgery. The procedure has so far been associated with excellent biomechanical outcomes and has been used widely in many countries based on initial clinical results. In comparison, RSA was introduced in Japan after SCR, and there are only limited reports that clearly discuss the selection between these two surgical methods.
In 2011, a switch was made at our institution from arthroscopic patch surgery using fascia lata to SCR to treat massive and extensive rotator cuff tears for which primary repair is difficult. SCR is associated with numerous advantages such as low re-tear rates, optimal elevation angles, and indications [18, 19]. For those who underwent SCR at our institution, re-tears were observed in 5 (13%) out of 38 patients, which is almost equivalent to the reports from various authors [20, 21]. However, the Hamada classification of grade ≥ 4 is regarded as one of the high risk factors  and is considered to be inappropriate for SCR surgery. Therefore, in this study, we compared Hamada grade 1–3 cases with RSA.
RSA was introduced in Japan in 2014. In accordance with JOA guidelines, patients in whom primary repair is not feasible and in whom elevation restriction is severe (such as those with pseudoparalysis) are suitable candidates for RSA; however, the level of evidence for this method is grade B . Currently, many patients who would generally undergo SCR are now opting for RSA. Short-term results with RSA at our institution are similar to those reported by various authors in Japan [20, 24] in terms of improvements in JOA score and elevation angle.
Although improvements in active elevation angle with RSA were obtained in this study, no improvements in internal and external rotation before and after the surgery were noted, which is consistent with previous reports [18, 20]. Although this time we used 11 types of Grammont type as well as 13 types of lateralized type, neither internal nor external rotation was improved in our case. Various methods [25–27] for lateralization of RSA for which internal and external rotation are expected have been reported, and there have also been reports on latissimus dorsi and teres major transfers to improve the lag in preoperative external rotation . If adequate internal and external rotation cannot be obtained, it can substantially affect the activities of daily living, especially in older patients. Therefore the surgical method should be carefully selected.
In the R group, progressive fatty degeneration was observed in all preoperative SSP, ISP, and SSC (Table 1). Compared to the tendons that required primary repair, fatty degeneration of the remaining tendons was less predominant in both groups. It has been reported that grade 3 or 4 and higher progression in RSA affects external rotation and postoperative results . For internal and external rotation, the effect of fatty degeneration on rotator cuffs for each surgical method when SCR and RSA are compared and the condition of fatty degeneration prior to surgery must be standardized, and further examination, including that of the teres minor, is necessary.
There are no clear criteria for choosing SCR over RSA to treat massive and extensive rotator cuff tears for which primary repair is difficult. Ogimoto et al.  reported that SCR is chosen for patients with relatively mild arthropathic changes at Hamada grade ≤ 3, whereas RSA is generally chosen for arthropathic changes at Hamada grade ≥ 4. Furthermore, potential candidates for each group must meet the surgical indications specified in the JOA guidelines. At our institution, the risk of re-tears with SCR was significantly higher for patients ≥ 80 years of age, Hamada grade ≥ 4, and male patients according to the multiple regression analysis . Based on this finding, RSA was chosen first for the high-risk group. Long-term results for SCR have not yet been reported; however, SCR is known to be a joint preservation surgery in which anatomical reconstruction is performed with few complications. Improvements were also observed in one study in terms of postoperative internal and external rotation . Since capsular ligament is the most affected tissue in shoulder-joint ROM, the belief is that the anatomical reconstruction of the superior joint capsule helps improve the internal and external rotation in addition to active elevation. In this study, in patients with re-tears, the switch to RSA was performed in two out of five patients. The surrounding tissue of the shoulder was anatomically preserved, and none of the tissues were impaired in a few cases involving residual suture anchors from the SCR. However, since patients with re-tears did not have improved active elevation in addition to internal and external rotation, measures to prevent re-tearing were considered necessary in SCR. Therefore, a meticulous evaluation of surgery indications is required for this high-risk group.
According to the JOA guidelines of 2019 for RSA, patients ≥ 65years of age are indicated. At present, SCR is the joint preservation surgery that appears to be the first choice for patients who engage in immense physical work, sports enthusiasts, and those aged ≥ 65 years for maintaining a high quality of life. The complications are also minimal [6, 8, 9, 21]. Among the choices, SCR seemed to be associated with limitations in patients with arthropathic changes associated with Hamada grade ≥ 4, in elderly patients, and in those with shoulder pseudoparalysis. In these cases, RSA may be the procedure of choice. The postoperative complications of RSA included dislocation, infections, and loosening of the components. The 10-year overall survival was reported to be 89%; however, reports suggest that caution should be exercised in performing RSA in young patients . Additionally, there seems to be limitations associated with RSA in terms of optimal postoperative internal and external rotation and recovery. Based on the characteristics of both surgical procedures, SCR is advantageous for patients in whom extended rehabilitation is acceptable, and RSA is considered to be effective for elderly patients who have difficulty in coping with the extended rehabilitation.
Comparing the two surgical methods has been somewhat difficult since each procedure and the set of indications are completely different. As a treatment strategy for massive rotator cuff tears for which primary repair is difficult, the implementation of SCR and RSA in Japan is still quite novel; however, as more procedures are performed, a high level of evidence is accumulating, and it seems that further improvements and developments can be expected in the future.