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

• Published in: Archives of orthopaedic and trauma surgery Vol. 144; no. 2; pp. 783 - 790
• Main Authors: Giol, F Goñalons, Parellada, C Ventura, Baños, F Gàmez, Guix, J M Mora
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2024; Springer Nature B.V
• Subjects: Aged; Aged, 80 and over; Arthroplasty, Replacement, Shoulder - adverse effects; Arthroplasty, Replacement, Shoulder - methods; Bone Resorption - surgery; Fractures; Humans; Humerus - surgery; Joint surgery; Medicine; Medicine & Public Health; Middle Aged; Orthopedics; Range of Motion, Articular; Retrospective Studies; Shoulder; Shoulder Fractures - diagnostic imaging; Shoulder Fractures - surgery; Shoulder Joint - surgery; Trauma Surgery; Treatment Outcome; Stress shielding; Radiological outcome; Proximal humeral fracture; Loosening; Uncemented; Reverse shoulder arthroplasty
• ISSN: 1434-3916; 0936-8051; 1434-3916
• DOI: 10.1007/s00402-023-05169-2

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.