title: Comparison of patients undergoing primary shoulder arthroplasty before and after the age of fifty.
abstract: BACKGROUND
  The reported outcomes of shoulder arthroplasty in patients under the age of fifty years are worse than those in patients over fifty. While there are several possible explanations for this finding, we explored the possibility that patients who had a primary shoulder arthroplasty when they were under fifty years of age differed from those who had the procedure when they were over fifty with respect to their pre-arthroplasty self-assessed comfort and function, sex distribution, and specific type of arthritis.
  
  
  METHODS
  The study group consisted of patients with glenohumeral arthritis who were treated with a primary shoulder arthroplasty by the same surgeon between 1990 and 2008. For each decade of age, the sex distribution, the pre-arthroplasty self-assessed shoulder comfort and function, and the prevalence of twelve different diagnoses were documented. We reviewed the series for three potential causes of worse outcomes in patients under fifty years of age as compared with those over fifty years of age: (1) a higher percentage of women, (2) a lower score for pre-arthroplasty self-assessed comfort and function, and (3) more complex pathological conditions.
  
  
  RESULTS
  Patients under the age of fifty years were not more likely than those over fifty to be female or to have a lower pre-arthroplasty self-assessed comfort and function score, but they did have more complex pathological conditions, such as capsulorrhaphy arthropathy, rheumatoid arthritis, and posttraumatic arthritis. Only 21% of the younger patients had primary degenerative joint disease, whereas 66% of the older patients had that diagnosis. This difference was significant (p < 0.000000001).
  
  
  CONCLUSIONS
  Surgeons performing shoulder arthroplasty in individuals under the age of fifty should be prepared to encounter pathological conditions such as capsulorrhaphy arthropathy, rheumatoid arthritis, and posttraumatic arthritis rather than primary osteoarthritis, which is more common in individuals older than fifty. The pathoanatomy in these younger patients may complicate the surgery, the rehabilitation, and the outcome of the shoulder arthroplasty.
authors.affiliation: Department of Orthopedics and Sports Medicine, University of Washington Medical Center, Seattle, Washington, USA. mdsaltzman@gmail.com
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Saltzman
authors.forename: Deana M
authors.initials: DM
authors.lastname: Mercer
authors.forename: Winston J
authors.initials: WJ
authors.lastname: Warme
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Bertelsen
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Matsen
mesh_terms: D000367:Age Factors; D001168:Arthritis / Q000601:surgery*; D001178:Arthroplasty; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012785:Shoulder Joint / Q000601:surgery*; D016896:Treatment Outcome