Stress shielding: short-term radiological results of the reverse shoulder arthroplasty with an anatomic proximal coated stem in proximal humeral fractures.

PURPOSE: This study aims to determine the stress shielding and other radiological outcomes of patients who underwent an uncemented reverse shoulder arthroplasty (RSA) with an anatomic proximal coated stem for complex proximal humeral fractures (PHF) with 3 or 4 parts at 2 years postoperatively. METHODS: 37 shoulders underwent an uncemented RSA for PHF from November 2015 to February 2019 and were followed up for 2 years. A radiographic assessment of stress shielding, filling ratio, stem stability (radiolucent lines/subsidence/alignment), tuberosity healing and notch was performed. RESULTS: The mean age at the time of surgery was 72 years (range, 61-85). Stress shielding was appreciated in 31 shoulders (83.8%). The most important characteristic of stress shielding is cortical resorption: Grade 3 resorption occurred in 3 shoulders (8.1%) and grade 4 in 23 (62.2%) as per the grading system defined by Inoue et al. (Inoue et al. in J Shoulder Elbow Surg 26:1984-1989, 2017). A high occurrence of bone resorption was observed in Gruen zones 2 (Lateral Stress shielding) and 7 (Medial Stress shielding). The mean distal filling ratio in patients without stress shielding was 78,48(SD 14,9), whereas in patients with stress shielding, it was slightly higher with a mean of 81,68% (SD 4,89). Tuberosity healing was found in 94.6% (35/37) of the shoulders. No patient had any radiolucent line. No notch was observed. CONCLUSION: At short-term follow-up, a high rate of tuberosity healing was achieved (94.6%) even though stress shielding was found in 83.8% (31/37) of the shoulders. Bone resorption was most frequently observed externally at zone 2 (Lateral stress shielding) and internally at zone 7 (Medial stress shielding). A higher filling ratio was associated with an increased occurrence of stress shielding. The uncemented anatomic humeral component did not result in early loosening. LEVEL OF EVIDENCE: IV; Case Series; Treatment study.

Reverse total shoulder arthroplasty with latissimus dorsi and teres major transfer: biomechanical and electromyographical outcomes.

PURPOSE: There is controversy regarding the optimal treatment for patients with rotator cuff arthropathy with external rotation deficit (CLEER group). This study analyzes the biomechanical and electromyographical outcomes of reverse total shoulder arthroplasty (RTSA) with latissimus dorsi and teres major transfer. The primary objective of this study is to compare the biomechanical and electromyographical outcomes between the treated and contralateral shoulder. Secondary objective is to define clinical and functional outcomes, and to report the radiological findings. Our hypothesis is that with this technique patients regain at least 50% of the strength in external rotation of the contralateral shoulder, and that the transferred muscles remain EMG active over time. MATERIALS AND METHODS: All patients who underwent RTSA with latissimus dorsi and teres major transfer in our hospital between 2007 and 2015 were included. From 16 eligible patients, 10 were finally reviewed. Biomechanical assessment of rotation strength was performed postoperatively in both shoulders, and fine needle EMG of latissimus dorsi and teres major muscles was recorded at the same time in both shoulders. Constant test and clinical evaluation (Lag sign and Hornblower test) were obtained preoperative and at final follow up. Radiological (X-ray, US) assessment was also obtained for both shoulders at final follow up. RESULTS: External rotation strength of the operated shoulder was higher than 50% the strength of the contralateral shoulder, and the differences were statistically significant (p < 0.05). No statistically differences were found regarding to internal rotation. The electromyographic assessment found no significant differences (p > 0.05) between the treated and contralateral shoulders. The mean Constant-Murley score significantly increased (30.9 points) after surgery (p < 0.01). Lag sign and Hornblower test were negative in all patients. CONCLUSIONS: Performing RTSA with latissimus dorsi and teres major transfer is an effective procedure improve function and to restore ER strength in patients in CLEER group. The EMG records shows that transposed latissimus dorsi and teres major adapt to their new function and remain functional over time, even in elderly patients.