title: Early dislocation after reverse total shoulder arthroplasty.
abstract: BACKGROUND
  Although instability can occur after reverse total shoulder arthroplasty (RTSA), the risk factors, the treatment, and ultimate fate of the implant in these patients remains poorly understood.
  
  
  METHODS
  Demographics, acute treatment, and the need for revision were evaluated in all patients with RTSAs who sustained a subsequent dislocation within the first 3 months. Standardized outcome scores were collected preoperatively and at the final follow-up.
  
  
  RESULTS
  Atraumatic instability occurred in 11 patients (incidence, 2.9%) treated with RTSA early (before 3 months postsurgery). The mean time to dislocation was 3.4 weeks. These patients tended to be previously operated-on (64%), male (82%), overweight (mean body mass index (BMI) of 32.2 kg/m(2), with 82% having a BMI ≥30 kg/m(2)), and without a satisfactory subscapularis repair at initial RTSA (64%). Initial treatment included closed reduction in 9 patients, open reduction in 1, and open reduction with a thicker polyethylene insert in 1. Four experienced recurrent instability requiring a thicker polyethylene insert. Two additional patients were converted to hemiarthroplasty due to persistent instability. Visual analog pain scores (P = .014) and American Shoulder and Elbow Surgeons scores (P = .018) were significantly improved. Simple Shoulder Test scores trended towards improvement (P = .073).
  
  
  CONCLUSIONS
  Early dislocations of the RTSA prosthesis were uncommon. The most common associated factors were a BMI >30 kg/m(2), male gender, subscapularis deficiency, and previous surgery; in these patients, we now use an abduction orthosis. Closed reduction alone was successful in 4 of the 9 closed reductions (44%). Five of 11 RTSAs (45%) required polyethylene exchange. The RTSA was retained in 82%, 36% with the original implant.
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA. Electronic address: p.n.chalmers@gmail.com.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Chalmers
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Zain
authors.initials: Z
authors.lastname: Rahman
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Romeo
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Nicholson
mesh_terms: D000368:Aged; D019643:Arthroplasty, Replacement / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000601:surgery; D004204:Joint Dislocations / Q000209:etiology* / Q000628:therapy; D007593:Joint Instability / Q000209:etiology* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016059:Range of Motion, Articular; D012086:Reoperation; D012189:Retrospective Studies; D012785:Shoulder Joint / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome
keywords: Reverse total shoulder arthroplasty; complication; dislocation; revision; shoulder instability