In the context of reverse shoulder arthroplasty, some parameters of glenoid baseplate placement follow established golden rules, while other parameters still have no consensus. The assessment of glenoid wear in the future location of the glenoid baseplate varies among surgeons. The objective of this study was to analyze the inter-observer reproducibility of glenoid baseplate 3D positioning during virtual pre-operative planning.
Four shoulder surgeons planned the glenoid baseplate position of a reverse arthroplasty in the CT scans of 30 degenerative shoulders. The position of the glenoid guide pin entry point and the glenoid baseplate center was compared between surgeons. The baseplate\'s version and inclination were also analyzed.
The 3D positioning of the pin entry point was achieved within ± 4 mm for nearly 100% of the shoulders. The superoinferior, anteroposterior and mediolateral positions of the baseplate center were achieved within ± 2 mm for 77.2%, 67.8% and 39.4% of the plans, respectively. The 3D orientation of the glenoid baseplate within ± 10° was inconsistent between the four surgeons (weak agreement, K=0.31, p=0.17).
The placement of the glenoid guide pin was very consistent between surgeons. Conversely, there was little agreement on the lateralization, version and inclination criteria for positioning the glenoid baseplate between surgeons. These parameters need to be studied further in clinical practice to establish golden rules. Three-dimensional information from pre-operative planning is beneficial for assessing the glenoid deformity and for limiting its impact on the baseplate position achieved by different surgeons.
III. Case control study.

To demonstrate how reverse shoulder arthroplasty (RSA) planning software could be used to improve how the trainees position glenoid and humeral implants and obtain optimal simulated range of motion (ROM).
We selected four groups of five various level participants: medical student (MS), junior resident (JR), senior resident (SR), and shoulder expert (SE). Thereafter, the 20 participants planned five cases of arthritic shoulders for a RSA on a validated planning software following three phases: (1) no guidelines and no ROM feedback, (2) guidelines but no ROM feedback, and (3) guidelines and ROM feedback. We evaluated the final simulated impingement-free ROM, the choice of the implant (baseplate size, graft, glenosphere), and the glenoid implant positioning.
MS planning were significantly improved by the ROM feedback only. JR took the best advantage of both guidelines and ROM in final results. SR planning were less performant than SE into phase 1 regarding flexion, external rotation, and adduction (respectively - 10°, p = 0.03; - 11°, p = 0.003; and - 3°, p = 0,03), but reached similar results into phase 3 (respectively - 2°, p = 0.329; - 4°, p = 0.44; - 2°, p = 0.319). For MS, JR, and SR, we observed a systematic improvement in the agreement over the study course. The glenoid diameter remained highly variable even for SE. Comparing glenoid implant position to SE, the distance error decreased with advancing phases.
Planning software can be used as a simulation training tool to improve implant positioning in shoulder arthroplasty procedures.

BACKGROUND: Management of massive irreparable rotator cuff tears (MIRCTs) remains controversial owing to variability in patient features and outcomes contributing to a lack of unanimity in treatment recommendations. The purpose of this study was to implement the Delphi process using experts from the Neer Circle of the American Shoulder and Elbow Surgeons to determine areas of consensus regarding treatment options for a variety of MIRCTs.
METHODS: A panel of 120 shoulder surgeons were sent a survey regarding MIRCT treatments including arthroscopic débridement and partial cuff repair, graft augmentation, reverse shoulder arthroplasty (RSA), superior capsular reconstruction (SCR), and tendon transfer. An iterative Delphi process was then conducted with a first-round questionnaire consisting of 13 patient factors with the option for open-ended responses to identify important features influencing the treatment of MIRCTs. The second-round survey sought to determine the importance of patient factors related to the 6 included treatment options. A third-round survey asked participants to classify treatment options for 60 MIRCT patient scenarios as either preferred treatment, acceptable treatment, not acceptable/contraindicated, or unsure/no opinion. Patient scenarios were declared to achieve consensus for the preferred and not acceptable/contraindicated categories when at least 80% of the survey respondents agreed on a response, and a 90% threshold was required for the acceptable treatment category, defined by an acceptable treatment or preferred treatment response.
RESULTS: Seventy-two members agreed to participate and were deemed to have the requisite expertise to contribute based on their survey responses regarding clinical practice and patient volume. There were 20 clinical scenarios that reached 90% consensus as an acceptable treatment, with RSA selected for 18 scenarios and arthroscopic débridement and/or partial repair selected for 2. RSA was selected as the singular preferred treatment option in 8 scenarios. Not acceptable/contraindicated treatment options reached consensus in 8 scenarios, of which, 4 related to SCR, 3 related to RSA, and 1 related to partial repair with graft augmentation.
CONCLUSIONS: This Delphi process exhibited significant consensus regarding RSA as a preferred treatment strategy in older patients with pseudoparesis, an irreparable subscapularis, and dynamic instability. In addition, the process identified certain unacceptable treatments for MIRCTs such as SCR in older patients with pseudoparesis and an irreparable subscapularis or RSA in young patients with an intact or reparable subscapularis without pseudoparesis or dynamic instability. The publication of these scenarios and areas of consensus may serve as a useful guide for practitioners in the management of MIRCTs.