Influence of Arm Lengthening in Reverse Shoulder Arthroplasty

Abstract

Adequate deltoid tension obtained through restoration of humeral and arm length is one of the keys for postoperative function and prevention of instability following reverse shoulder arthroplasty (RSA). With a classic Grammont prosthesis, postoperative humeral lengthening is approximately 2 mm and arm lengthening is approximately 24 mm. Humeral and arm lengthening have been correlated with stability and improvement in active anterior elevation, whereas shortening of these variables leads to an increased risk of dislocation and poor active anterior elevation, respectively. Subclinical neurologic lesions are a frequent consequence of lengthening with a drastically increasing prevalence above 40 mm of arm lengthening. Therefore, arm lengthening should be controlled with 0–2 cm being a reasonable goal to avoid postoperative neurological impairment. Preoperative planning is mandatory in revision cases. However, current conventional radiographic preoperative planning techniques are limited.