Unconstrained shoulder arthroplasty.

Shoulder arthroplasty is in a stage of development that is ahead of replacement of other joints, if one considers not only movement and function but also durability. It is a difficult and demanding procedure requiring a meticulous cement and rotator cuff technique. Stability of a nonconstrained implant depends on its height and the length of the head version. Active motion depends on the rotator cuff and deltoid. Neither loss of bone nor tears of the rotator cuff contraindicate a nonconstrained replacement; however, massive defects of the muscles or bone are treated with a "limited goals rehabilitation" program to achieve stability with less motion. Shoulder replacement seems to enjoy unique durability; however, glenoid component follow-up is limited to 11 years. Up to now the incidence of reoperation for loosening of a glenoid component in 455 patients reported in four recent series combined was under 1%, and most radiolucent lines at the glenoid are believed to be attributable to errors in technique rather than loosening. Because of recent breakage of two polyethylene glenoid components, a standard-sized metal-backed glenoid component has been made available for general use and is preferred especially in active patients and those with sloping glenoids. The 600% glenoid component is no longer used; however, it is expected that the 200% component will be made available for general use after adequate clinical trial of the new holding device.(ABSTRACT TRUNCATED AT 250 WORDS)