Background. Stress fracture of the acromium and scapular spine is a common complication following reverse total shoulder arthroplasty (RSA), with a reported incidence of 3.1%–11%. There is some evidence associating osteoporosis with increased risk of acromial stress fractures, but little else is known about the causes of acromial stress fractures after RSA. This study aims to define better preoperative factors, including demographics, comorbidities, and diagnoses, which predispose patients to postoperative acromial stress fractures. Methods. We retrospectively identified patients who underwent primary or revision RSA for any indication between January 2013 and December 2018 by two surgeons at two separate hospitals. Stress fractures of the acromion were identified on plain radiographs or computed tomography, when necessary. Patient demographics, comorbidities, and surgical indications were compared between patients with and without acromial stress fractures. Results. A total of 1,488 arthroplasties were identified and met the inclusion criteria. Of the study sample, 54 patients were diagnosed with a postoperative acromial stress fracture, an incidence of 3.6%. Patients in the stress fracture cohort were significantly more likely to have preoperative rotator cuff pathology (p<0.001), be of female gender (p<0.001), older (p=0.002), and osteoporotic (p<0.001; Table I). Thyroid disease (p=0.045) and inflammatory or rheumatoid arthritis (p=0.02) were also more frequent among patients with acromial stress fractures (Table I). No other comorbidities, including obesity (p=0.21) and diabetes (p=0.58), correlated significantly with postoperative acromial stress fracture (Table I). Conclusions. Old age, female gender, diagnosed osteoporosis, inflammatory arthritis, thyroid disease, and preoperative rotator cuff deficiency may all be risk factors for postoperative acromial stress fractures. Given that rotator cuff pathology is among the predominant indications for RSA, further research is required to determine the etiology and biomechanical basis for acromial stress fractures. For any figures or tables, please contact the authors directly

Displaced proximal humerus fractures remain a difficult clinical problem, and techniques as diverse as percutaneous pinning, locked plating, intramedullary nailing, and shoulder arthroplasty have been proposed. In recent years, reverse total shoulder arthroplasty (RTSA) has become a very popular option to fix just about any fracture. However, RTSA is not without risk, with complications ranging from infection, instability, acromial stress fractures, aseptic loosening, notching and more. In a 2017 study on 39 patients, Tokish et al. compared non-operative treatment to reverse shoulder arthroplasty for displaced 3- and 4-part fractures. There was no difference in pain, range of motion or outcome scores between the two groups. Among the patients who underwent RTSA, there was no difference between early (<30 days) and late (>30 days) surgery suggesting that it could be safe to attempt a non-operative trial in most patients and see how they do. This is also supported by a 2016 study by Sanchez-Sotelo et al. in which they compared 18 patients with primary RTSA to 26 patients with failed ORIF who underwent salvage RTSA. There was no difference in ASES score, ROM and overall satisfaction between both groups suggesting that an ORIF can be attempted in many patients without the fear of compromising a revision RTSA. And although RTSA may provide more predictable results, in a properly selected patient, a well-executed hemiarthroplasty can outperform an RTSA. In a study from Molé et al., 38 patients were randomised to either RTSA or to a hemiarthroplasty. In the hemiarthroplasty group, half of the patients had <90 degrees of forward elevation and half the patients had >120 degrees of forward elevation showing a bi-modal distribution dependent on tuberosity healing. In the RTSA group, however, while having an average of 115 degrees of forward elevation, 68% of patients had less than 120 degrees of forward elevation. While RTSA is a great tool to treat complex displaced comminuted fractures in elderly patients with poor bone quality, it should not be blindly applied to all fractures types and all patients

Introduction. Reverse total shoulder arthroplasty (RTSA) is a commonly performed operation for a variety of pathologies. Despite excellent short-term outcomes, complications are commonly encountered. Recurrent instability occurs in up to 31% of cases, often due to components placed with too little tension. Acromial stress fractures can occur in up to 7% of cases, often due to components placed in too much tension. Despite these concerns, there is little evidence evaluating the intraoperative tension and glenohumeral contact forces (GHCF) during RTSA. The purpose of this study was to measure the intraoperative GHCF during RTSA. Methods. 26 patients were enrolled after obtaining IRB approval. Inclusion criteria were patients undergoing primary RTSA. An instrumented strain gauge implant was designed to attach to an Exactech Equinoxe (Gainesville, FL) baseplate during RTSA. A specially designed trial glenosphere was then attached to the instrumented baseplate. Wires from the strain gauges were connected to a 24-bit analog input and placed outside the operative field to a computer that measure the forces. After joint reduction, GHCF were measured in neutral, passive flexion, passive abduction, passive scaption and passive external rotation (ER). Five patients were excluded due to wire calibration issues. Results. 21 patients were enrolled. The average age was 70 (range 54–84). The average height was 169.5cm (range 154.9–182.9), and average weight was 82.7 kg (range 45.4–129.3) There were 11 females and 10 males. There were thirteen 42mm glenospheres and eight 38mm glenospheres used. The mean GHCF values were 135N at neutral, 123N at ER, 165N in flexion, 110N in scaption, and 205N in abduction. The mean force values were significantly affected by joint position (p=0.002). The mean force at terminal abduction is significantly greater than the mean force at terminal ER and terminal scaption (p<0.05). Conclusion. This study demonstrates that an intraoperative measurement of GHCF can be successfully performed during RTSA using strain gauges. GHCF during RTSA are at their lowest in scaption and ER. They are at their maximum in abduction. Surgeons should keep these findings in mind during trialing to potentially reduce complications associated with inappropriate intraoperative tensioning

Massive uncontained glenoid defects are a difficult surgical problem requiring reconstruction in the setting of either primary or revision total shoulder arthroplasty. Our aim is to present a new one-stage technique that has been developed in our institution for glenoid reconstruction in the setting of massive uncontained glenoid bone loss. We utilise a modified delto-pectoral approach to perform our dual biology allograft autograft glenoid reconstruction. The native glenoid and proximal femoral allograft are prepared and shaped to create a precisely matched contact surface, which permits axial compression to secure fixation. The surface of the glenoid is lateralised to at least the level of the coracoid. The central cancellous femoral allograft is removed and impaction autografting is performed prior to implantation of a glenoid base plate with 25-mm long centre peg. Two screws are inserted into the best quality native scapular bone available to ensure compression. A reverse shoulder arthroplasty is implanted. We have performed our dual-biology reconstruction of the glenoid in combination with reverse total shoulder arthroplasty in 8 patients to date. The technique has been performed in the setting of massive uncontained glenoid defects without prostheses as well as in revisions from failed hemiarthroplasties and total shoulder arthroplasties. Our post-operative follow-up is now up to 32 months. CT scanning as early as 6 months demonstrates incorporation of the graft. There has been no evidence of loosening. None of our cases have been complicated by infection or peri-prosthetic fracture and there have been no dislocations. One patient sustained an acromial stress fracture at 9 months post-operatively after lifting a 100-pound gas cylinder. This was diagnosed on bone scan, had no impact on the construct and was managed in a sling for comfort. Another patient has developed Nerot grade I notching which substantially in all patients, with an average improvement of 6.6 on a 10-point scale. Our dual biology allograft-autograft reconstruction is a useful and elegant technique in the setting of massive uncontained defects of the glenoid, which permits the implantation of a reverse total shoulder arthroplasty. We believe this technique to be reproducible and uses materials that are both readily available and familiar