title: The effect of deltoid lengthening on functional outcome for reverse shoulder arthroplasty.
abstract: OBJECTIVE
  Reverse shoulder arthroplasty (RSA) is based on the biomechanical advantages of lengthening the deltoid while medializing its center of rotation (COR). Little evidence exists describing the clinical benefits of these biomechanical advantages. The purpose of this study is to assess the relationship between deltoid lengthening and medialization of the COR with functional outcomes for RSA patients.
  
  
  METHODS
  We retrospectively reviewed patients treated with primary RSA. Radiographic measurements of deltoid length and COR, assessment of forward elevation (FE) and external rotation (ER), and functional outcome scores were obtained pre- and postoperatively. Linear regression analyses were performed to assess the relationship between these radiographic measurements and changes in shoulder functionality.
  
  
  RESULTS
  On average, patients improved significantly in function and functional outcome scores. Postoperative COR correlated weakly with postoperative FE. There were weakly negative correlations between increase in acromion to greater tuberosity distance and postoperative FE, and between deltoid lengthening and FE improvement.
  
  
  CONCLUSIONS
  Our results suggest that deltoid lengthening does not correlate with improvements in active FE or ER. These findings could indicate that change in deltoid length is less important than previously thought. Furthermore, the negative correlations seen could indicate that there is over-tensioning of the deltoid in specific cases. Further studies are needed to better assess the role of deltoid length and other factors that may impact RSA outcomes.
authors.affiliation: Department of Orthopaedic Surgery, Wayne State University School of Medicine, 18100 Oakwood Blvd. Suite 305, Dearborn, MI, 48124, USA. sabes001@gmail.com.
authors.forename: V J
authors.initials: VJ
authors.lastname: Sabesan
authors.affiliation: Department of Orthopaedic Surgery, Wayne State University School of Medicine, 18100 Oakwood Blvd. Suite 305, Dearborn, MI, 48124, USA.
authors.forename: D
authors.initials: D
authors.lastname: Lombardo
authors.affiliation: Department of Orthopedic Surgery, Botsford Hospital, Michigan State University, Farmington Hills, MI, USA.
authors.forename: D
authors.initials: D
authors.lastname: Josserand
authors.affiliation: Department of Orthopaedic Surgery, Wayne State University School of Medicine, 18100 Oakwood Blvd. Suite 305, Dearborn, MI, 48124, USA.
authors.forename: D
authors.initials: D
authors.lastname: Buzas
authors.affiliation: Department of Orthopaedic Surgery, Wayne State University School of Medicine, 18100 Oakwood Blvd. Suite 305, Dearborn, MI, 48124, USA.
authors.forename: T
authors.initials: T
authors.lastname: Jelsema
authors.affiliation: Department of Orthopaedic Surgery, Wayne State University School of Medicine, 18100 Oakwood Blvd. Suite 305, Dearborn, MI, 48124, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Petersen-Fitts
authors.affiliation: Department of Orthopaedic Surgery, Oakland University William Beaumont School of Medicine, Royal Oak, MI, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Wiater
mesh_terms: D000368:Aged; D000072228:Arthroplasty, Replacement, Shoulder; D057645:Deltoid Muscle / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012189:Retrospective Studies; D012399:Rotation; D012720:Severity of Illness Index; D012785:Shoulder Joint / Q000000981:diagnostic imaging; D000072227:Shoulder Prosthesis; D016896:Treatment Outcome
keywords: Center of rotation; Deltoid length; Prosthesis design; Reverse shoulder arthroplasty; Surgical outcomes