The evolution of elbow arthroplasty: innovative solutions to complex clinical problems.

Introduction Total elbow design has evolved dramatically over the last century. Prior to 1947, resection and interposition arthroplasty were the primary surgical procedures for the treatment of severe posttraumatic deformity, trauma, and rheumatoid arthritis. In 1947, surgeons began performing partial elbow replacements of the distal part of the humerus and proximal part of the ulna as well as using custom hinged metal devices to treat these problems. The results were unpredictable pain relief and predictable loosening and/or instability. Beginning in the 1970s, the first simple hinged prosthesis was inserted with use of methylmethacrylate fixation. This improved the stability of the construct, but three to five-year loosening rates were as high as 50%. As a result of these and other failures, three design concepts have emerged: linked, unlinked, and convertible prostheses. Linked, or ‘‘semi-constrained,’’ prostheses (e.g., GSB III [Zimmer, Warsaw, Indiana], Coonrad-Morrey [Zimmer], Discovery [Biomet, Warsaw, Indiana]) are the most commonly used implants in North America and allow some out-of-plane motion. Varus, valgus, and rotational motion of around 6 to 8 is permitted by the ‘‘sloppy’’ hinge. The advantage of this design is that instability and dislocation are rare. However, as a result of the inherent constraint, increased stress is transferred to the bonecement interface, and higher loosening rates have been reported. The second major design is an unlinked prosthesis (e.g., Souter-Strathclyde [Stryker Howmedica Osteonics, Limerick, Ireland], Kudo [Biomet], Instrumented Bone Preserving [Biomet]), in which there is no mechanical linkage between the humeral and ulnar components. Advantages include maintenance of bone stock and decreased polyethylene wear. However, because there is no linkage, the stability of the implant requires exacting surgical technique and an intact softtissue envelope. Well-balanced soft-tissue attachments reduce stress at the bone-cement interface, lowering loosening rates with this design. However, unlinked devices are associated with higher rates of instability and dislocation when compared with linked prostheses. The need for intact soft tissues prevents the