Institutional Review Board approval was obtained for this study. Our first series of LA included 20 patients (12 men, 8 women) with an average age of 62 ± 4.2 years. All patients underwent arthroscopic RC repair of an isolated supraspinatus tendon tear (mid-size) and an additional LA. The mean preoperative CSA measured 39.7 ± 1.0°, which was reduced to an average value of 32.1 ± 1.2°. Short-term follow-up after an average of 16 ± 2.4 months showed no re-tear at ultrasound evaluation and an average Constant score of 88.4 ± 5.5 points. No local complications were observed at the lateral acromion edge with no evident impairment of the acromial mid-third portion of the deltoid origin.
The importance of the present study lies in the introduction of a new all-arthroscopic technique for normalization of a CSA, which we call „lateral acromioplasty“ (LA).
In 1972, Neer  published his work on anterior acromioplasty for chronic subacromial impingement syndrome. In 1986, Bigliani et al.  classified the shape of the anterior acromion in supraspinatus outlet view into three types. For many years, shoulder surgeons have „corrected“ the acromion shape in patients with subacromial impingement or as additional procedure in patients undergoing RC repair in order to remove the cause of subacromial mechanical conflict or to avoid postoperative stress to the repaired RC. In the past few decades, arthroscopic acromioplasty ranged among the most widely performed procedures in shoulder surgery .
However, several recent studies have questioned the true benefit of a normalization of the anterior acromial slope. The effectiveness of surgical management of stage II impingement has been investigated in high-quality controlled randomized trials and no significant difference was found compared with the nonsurgical treatment with supervised exercises [6, 8, 12]. Furthermore, ithas beenshown that outcomes after RCT repair were similar with and without acromioplasty [15, 16]. Probably due to this research, the number of conventional acromioplasties performed has been declining .
Recently, new parameters were introduced describing a specific scapula morphology, which might represent pathogenetic factors for RC disease. These parameters, the acromion index (AI) and the CSA, are a matter of current debate among shoulder surgeons.
In 2006 Nyffeler et al.  proposed the AI as the lateral extension of the acromion in relation to the humeral head. Since then, some authors have found significant correlations between high AI values and RCT [13, 19, 25]. Other studies could not support this possible association [2, 10].
More recently, Moor et al.  introduced the CSA, defined as the angle between the plane of the glenoid and the line to the most lateral aspect of the acromion on a true AP view. Large angles have been found to correlate with degenerative RCT, while small angles correlate with osteoarthritis [17, 23] and, as recently published, with SLAP (superior labrum anteriorposterior) lesions . A biomechanical study by Gerber et al.  supported the hypothesis that high CSAs can induce supraspinatus overload especially at low degrees of active abduction.
If deemed a pathogenetic factor in the development of degenerative RCTs, a normalization of the CSA might help to avoid future tears or re-tears in patients with pathologically large angles.
So far, no clinical study has been published in the literature describing the technique and the preliminary outcomes for normalization of the CSA via an LA. The technique is capable of normalizing the CSA based on preoperative planning. It was shown to be easy, reproducible, and led to a reliable correction of the CSA in the first case series.
The study is limited by the lack of longterm follow-up data. The sample size is quite small, and larger, prospective controlled trials are necessary in order to evaluate the role of LA compared with conventional acromioplasty according to Neer. There was discussion on whether the technique itself might be limited by a potential weakening of the deltoid muscle due to violation of the insertion site or alteration of the pretension. However, the deltoid muscle arises from the superior surface and the anterior surface of the acromion, with prominent tendinous origins from the superior surface . These insertion sites are preserved during the LA procedure. A recent laboratory study by Katthagen et al.  reported that the deltoid origin was not damaged when performing an LA. In a second study, the same group showed that LA did not weaken the structural or mechanical integrity of the lateral deltoid origin . In the present study, no clinically evident impairment of the deltoid function was detected. In all patients, a normal CSA was achieved with LA and all patients regained good shoulder function.
To date, only one study exists in cadaveric shoulder specimens proving the feasibility of a technique for LA . However, no other clinical pilot study exists reporting on the feasibility and preliminary outcomes using an arthroscopic technique fornormalizationofthe CSA in a real operating room setting, where surgical complications, e.g., bleeding, may occur.
Future research will reveal whether this new technique will lead to better clinical results or will end up being declined according to Scott’s parabola .