Stemless Shoulder Arthroplasty: Review of Early Clinical and Radiographic Results
Humeral stem design in shoulder arthroplasty has evolved tremendously over the past 60 years. Neer first introduced modern shoulder arthroplasty in 1955 with his series of 12 patients treated with a hemiarthroplasty for fracture dislocations or fracture sequelae 1 . The humeral component was uncemented, was 15 cm in length, had 3 flanges at the neck for rotational control, and was constructed of Vitallium. It came in 3 different sizes: small, medium, and large. Appropriate implant sizing was determined preoperatively by taping the prosthesis to the lateral aspect of the arm and making an anteroposterior radiograph 1 . Following this, Neer reported his outcomes of 48 shoulders in 47 patients undergoing hemiarthroplasty for glenohumeral osteoarthritis with his first-generation stem, which included 5 different stem diameters, all of the same length, and a 44.5-mm head. He also reported on a revised design that was modified for implantation with cement 2 . Neer’s clinical results were considered excellent; in the 46 shoulders of the 45 patients who were evaluated at follow-up, 40 patients (89%) had excellent or satisfactory physician-rated results, and 42 patients (93%) were enthusiastic or satisfied with their results. There was no radiographic evidence of stem loosening, and there were also no postoperative infections or important complications 2 . However, surgeons began to understand the importance of re-creating patient-specific anatomy. This was first incorporated in the second-generation stem design with the concept of modularity, featuring separate heads and stems connected with a Morse taper. Further anatomic investigations of the proximal part of the humerus led to the design of the third-generation humeral implants, which allowed alteration of humeral head inclination and offset, in addition to stem and head sizes 3 . The majority of these designs still featured a standard-length humeral stem that engaged the diaphysis, and surgeons began to recognize the inherent difficulties with explantation in revision cases. Recently, this has led to the design of fourth-generation humeral components, which have evolved into short-stem or stemless designs that rely on fixation within the humeral metaphysis.