Indications for Reverse Shoulder Arthroplasty (RSA) have been extended over the last 25 years, and RSA has become the most frequently implanted shoulder arthroplasty worldwide. The initial Grammont design with medialization of the joint center of rotation (JCOR), placement of the JCOR at the bone–implant interface, distalization and semi-constrained configuration has been associated with drawbacks such as reduced rotation and range of motion (ROM), notching, instability and loss of shoulder contour. This review summarizes new strategies to overcome these drawbacks and analyzes the use of glenoid-sided, humeral-sided or global bipolar lateralization, which are applied differently by surgeons and current implant manufacturers. Advantages and drawbacks are discussed. There is evidence that lateralization addresses the initial drawbacks of the Grammont design, improving stability, rates of notching, ROM and shoulder contour, but the ideal extent of lateralization of the glenoid and humerus remains unclear, as well as the maximal acceptable joint reaction force after reduction. Overstuffing and spine of scapula fractures are potential risks. CT-based 3D planning as well as artificial intelligence will help surgeons with planning and execution of appropriate lateralization in RSA. Long-term follow-up of lateralization with new implant designs and implantation strategies is needed.

In part II of this comprehensive review on the optimization of reverse shoulder arthroplasty (RSA), we focus on three other challenges: 1. “Conservation of sufficient subacromial and coracohumeral space”; 2. “Scapular posture”; and 3. “Moment arms and muscle tensioning”. This paper follows a detailed review of the basic science and clinical literature of the challenges in part I: 1. “External rotation and extension” and 2. “Internal rotation”. “Conservation of sufficient subacromial and coracohumeral space” and “Scapular posture” may have a significant impact on the passive and active function of RSA. Understanding the implications of “Moment arms and muscle tensioning” is essential to optimize active force generation and RSA performance. An awareness and understanding of the challenges of the optimization of RSA help surgeons prevent complications and improve RSA function and raise further research questions for ongoing study.

A detailed overview of the basic science and clinical literature reporting on the challenges for the optimization of reverse shoulder arthroplasty (RSA) is presented in two review articles. Part I looks at (I) external rotation and extension, (II) internal rotation and the analysis and discussion of the interplay of different factors influencing these challenges. In part II, we focus on (III) the conservation of sufficient subacromial and coracohumeral space, (IV) scapular posture and (V) moment arms and muscle tensioning. There is a need to define the criteria and algorithms for planning and execution of optimized, balanced RSA to improve the range of motion, function and longevity whilst minimizing complications. For an optimized RSA with the highest function, it is important not to overlook any of these challenges. This summary may be used as an aide memoire for RSA planning.

Background: The comma sign is a useful marker for combined retracted supraspinatus and subscapularis tears. It was first described by the group of Burkhart as a “composite ligamentous structure” of the rotator interval attached to the retracted subscapularis. However, Neyton and coworkers suggested that the ruptured superior part of subscapularis is pulled upward by supraspinatus retraction. This video illustrates the value of “comma” recognition for reduction and repair stability. We feel that the comma tissue can be a composition of rotator interval ligaments with or without superior subscapularis contribution depending on an associated cleavage tear. Indications: Patients with retracted anterosuperior tears, unless muscle quality is poor (Goutallier classification ≥3). Understanding of the comma tissue is difficult but of crucial importance to assess complex anterosuperior cuff tears for reduction and repair with stability by maintaining and integrating this comma link into the repair construct. Technique Description: Arthroscopic setup includes beach chair position, armholder, cerebral saturation monitoring (target mean arterial blood pressure of about 70 mm Hg). Previously described circumferential portals were used for a repair with a double row construct (4 medial anchors: 2.5 for subscapularis; 1.5 for supraspinatus) and 2 lateral anchors. The superior boarder of subscapularis as well as the retracted capsular layer of supraspinatus was reduced and fixed using a lasso loop technique. Key stages are (1) tendon manipulation with 2 traction sutures; (2) tendon release; (3) comma reduction; (4) footprint preparation (burr, microfracture); (5) retrograde suture passing; (6) knot tying, knotless lateral row; and (7) a close surgeon to physiotherapist rehabilitation link (6 weeks passive to 90°, no resistance training for 3-6 months). Results: Senior author’s (S.B.) series: 32 anterosuperior tears over 4 years (mean age: 62 years, 48-73 years), minimum follow-up 1 year showed good results (mean SSV: 85% [preop. 35%], range: 40%-95%; mean Constant: 82 [preop. 30], range: 40-90). One major complication (cutibacterium infection; brick layer; workers compensation; invalidity demand; Constant/Subjective Shoulder Value both 40) and minor temporary stiffness at 3 months (8 patients; 22%). Conclusion: Adequate reduction and comma integration into a solid repair construct, as well as responsible rehabilitation surveillance, deliver successful results after technically intricate anterosuperior repairs.

Objective: Radial head arthroplasty (RHA) is the principal treatment option for comminuted radial head (RH) fractures. Here, we present six cases of failed RHA using a modular monopolar press-fit RHA that was subsequently withdrawn from the market because it was associated with a high incidence of loosening. Methods: We retrospectively collected data from six patients who had received Radial Head Prothesis System^TM at our centre between July 2015 and June 2016. The average follow-up was 40 months. Results: Aseptic loosening of the stem affected five (83%) of the six RHA. Four of these were symptomatic and RHA removal was performed. For these patients, the pain subsided and their elbow range of motion (ROM) improved. Conclusion: While the ideal design for an RHA is still debatable, RHA is an efficient treatment option that restores elbow stability and function after a comminuted RH fracture. Importantly, removal of the prosthesis is an effective remedy following RHA associated elbow pain and decreased ROM.