Irreparable massive rotator cuff tears cause pain, loss of function, and a decrease in range of motion, which cause serious disturbances in daily life [1,2]. In addition, since repairing irreparable massive rotator cuff tears have difficulty in complete footprint coverage and a high frequency of re-rupture, the postoperative clinical results often are unsatisfactory [3,4]. For this reason, in elderly patients with relatively few functional requirements, there are various surgical options for massive rotator cuff tears, such as debridement, biceps tenotomy/tenodesis, partial repair, tendon transfer, and reverse total shoulder arthroplasty (RTSA) [5-7]. However, since young patients are active and have relatively high functional requirements, these surgical options are limited to tendon transfer and patch augmentation [8,9]. In addition, although previous studies have reported that RTSA has good clinical result in elderly patients with massive rotator cuff tears, RTSA in active young patients under the age of 65 demonstrates relatively high complications and failure rates, and it is not an optimal surgical option in terms of longevity [10-12].

Mihata et al. [13,14] first proposed superior capsular reconstruction (SCR) using autologous tissue for irreparable massive rotator cuff tears, and they reported good clinical results in short-term follow up. Since then, SCR has been increasingly used for irreparable massive rotator cuff tears, and various studies have been published on clinical outcomes, biomechanical outcomes, surgical techniques, and graft types. A previous systematic review reported that SCR reduced acromial contact pressure, produced superior humeral translation, and improved short-term clinical outcomes [15,16]. However, biologic healing at the contact surface between graft and bone is the most important factor to improve mid- and long-term outcomes of SCR [16,17] . Therefore, for optimal biologic healing, selection of an optimal graft and appropriate surgical technique must be considered. For this reason, this article reviews the optimal graft and surgical options for improving clinical outcomes in SCR.

Mihata et al. [13] originally used a fascia lata autograft to reconstruct the superior capsule. Although their early results are promising, the fascia lata graft is thin, requiring doubling of the construct and a relatively large donor incision for harvesting. As an alternative, acellular dermal allografts were proposed for their theoretical advantages of reduced donor site morbidity, shorter associated operative times, ease of preparation, and strength of the graft [18,19]. Most of the previously reported studies described SCR using fascia lata graft or dermal allograft (Table 1) [20-29], Various biomechanical studies and clinical results report their use in SCR. Recently, however, various other autografts, allografts, xenografts, and synthetic grafts have been used in SCR, and the clinical results have been reported (Table 2) [30-34].

In a previous cadaveric study, the thickness of the superior capsule of the normal glenohumeral joint was reported from 4.1 mm to 9.1 mm [55]. Biomechanically, although both 4-mm- and 8-mm-thick fascia lata allografts reduced subacromial peak pressure after SCR, only the thicker 8-mm graft was able to decrease superior translation [56]. In an acellular dermal allograft, using a 6-mm-thick graft demonstrated similar maximum abduction angle, glenohumeral superior translation, subacromial peak contact pressure, and cumulative deltoid force compared with the intact state. When comparing the 3-mm- to the 6-mm-thick graft, significant differences were found in glenohumeral superior translation [36]. When comparing the 6-mm-thick acellular dermal allograft and the 8-mm-thick fascia lata allograft, SCR with a single, 6-mm-thick, acellular dermal allograft is non-inferior to a fascia lata tendon regarding subacromial space distance and peak subacromial contact pressures while restoring the superior stability of the glenohumeral joint compared to the intact state [38]. These results reveal that graft thickness determines the degrees of superior migration through compression of the humeral head. So, to visualize this effect adequately, graft thickness should be at least 6 mm in SCR.

For optimal fixation, graft tensioning has been implicated to play a major role in glenohumeral contact properties and forces [56]. In addition, previous literature suggests differences in ideal abduction angles during SCR graft fixation based on type of material used intraoperatively [20,56]. One method for tensioning the graft is through abduction of the glenohumeral joint during fixation. Mihata et al. [56] suggested that 8 mm graft thickness and an arm position between 15° and 45° of shoulder abduction are the major aspects for sufficient reconstruction of the superior capsule. Various abduction angles using dermal allografts have been described, ranging from 20° to 45° of clinical shoulder abduction [18,57]. However, the optimum graft tension for best results in SCR remains unclear. Adams et al. [58] reported that SCR with anterior and posterior margin convergence tensioned at 15° of glenohumeral abduction showed similar deltoid abduction force requirements to the native state in their biomechanical study. Dyrna et al. [59] reported in a biomechanical study of 10 fresh-frozen cadaveric shoulders that SCR using a graft fixed under tension (30 to 35 N) demonstrated a significant increase in maximum shoulder abduction compared with a nontensioned graft (65.0°±12.6° vs. 54.1°±16.1°, p=0.04). However, abduction remained significantly less than in the intact state (79.8°±5.8°, p=0.04). A tensioned SCR restored a maximum abduction of 81% of the native condition. Clinically, most surgeons have performed SCR graft fixation at 10° to 45° shoulder abduction per Mihata's recommendation [21-24]. But, there is a lack of clear clinical evidence for optimal abduction angle based on graft type in SCR.

Mihata et al. [13] recommended side-to-side suturing between the graft and infraspinatus tendon or subscapularis tendon when performing SCR in irreparable rotator cuff tears. In biomechanical studies, SCR without side-to-side suturing did not decrease glenohumeral superior translation, although subacromial peak contact pressure decreased [60]. Adding side-to-side suturing restored superior stability to the intact level by achieving capsular continuity in the transverse direction. Total ROM did not decrease significantly after SCR with or without side-to-side suturing when the graft size matched the defect size [60].

Although SCR can increase the AHD, friction can be induced on the undersurface of the graft and acromion through movement after surgery, and this can cause a tear in the graft. Mihata et al. [13] recommended acromioplasty during SCR for irreparable rotator cuff tears. They also investigated the effects of acromioplasty on shoulder biomechanics after superior capsule reconstruction for irreparable supraspinatus tendon tears [61]. Including acromioplasty decreased the subacromial contact area without increasing the subacromial contact pressure in SCR. Clinically, it is not necessary to perform acromioplasty in SCR, and acromioplasty was not necessarily performed in other studies. However, most surgeons performed acromioplasty if there was evidence of abrasion on the undersurface of the acromion [24,62,63].

Since Mihata et al. [13] introduced SCR for irreparable rotator cuff tear several years ago, various studies on SCR have been conducted, and considerable progress has been made. The long-term clinical results of SCR are insufficient, however, and further studies on the various factors necessary for the best results in irreparable rotator cuff tear are needed. Knowledge of these various factors that must be considered for a successful SCR will lead to a better life for patients with massive rotator cuff tears.