Incidence of Early Development of Radiolucent Lines in Keeled Polyethylene Glenoid Components After Total Shoulder Arthroplasty
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Loosening of the glenoid component remains a major concern, as it is one of the most common reasons for revision shoulder arthroplasty. Estimated incidence of radiolucent lines (RLLs) varies widely from series to series, with reported rates ranging from 28.4% to more than 90%. Studies with long-term serial radiographs have found RLL progression as early as 1 to 3 years after recognition. Although the incidence of RLLs and glenoid component loosening has been reported in numerous series, the significance of RLLs around the glenoid is still unclear, because the number of patients who required revision surgery for a radiographically loose glenoid component is relatively small.
Most articles in the RLL literature describe early surgical techniques and first-generation cement application. The initial keeled-back glenoid components were prepared with an unguided hand-held motorized burr and digitally packed cement. These initial case series raised concern about the presence of RLLs identified with radiographs as early as the immediate postoperative period. As a result, glenoid component implantation changed dramatically. More recent studies, evaluating the rate of early RLLs, have suggested that RLL incidence has improved with meticulous glenoid bone preparation assisted with guides that provide the ability to accurately machine the glenoid to match the glenoid component, cement pressurization, and glenoid component design.
Pegged-back glenoids appeared to have a lower incidence of early RLLs and gained favor over keeled-back glenoids. The improvement with pegged-back components was attributed to the design of the component as well as to improved initial fixation, with the press-fit technique requiring less cement, which is thought to be a possible cause of thermal necrosis. Modern keeled-back glenoid components, however, are now implanted with a similar surgical technique, including bone compaction with identical keel geometry as the prosthetic component, and cement pressurization.
The purpose of the present study was to determine the incidence of early development of RLLs after total shoulder arthroplasty (TSA) performed with modern glenoid bone preparation and cement techniques for contemporary keeled-back glenoid components. Our hypothesis was that, with improvements in glenoid bone preparation and cement techniques, the RLL rate for keeled-back glenoid components would be less than previously reported in clinical series and would be similar to recently reported rates for pegged-back components.