Abstract: The metal lock ring of the invention has an oblong exterior periphery which allows the ring to have a small "width" and a larger "height." The small "width" provides a strong locking mechanism on the poly liner and the larger "height" allows the ring to remain secure within the groove of the metal shell prior to and during assembly of the polyethylene liner. The ring has a chamfer on its inside leading edges defining its width to facilitate assembly of the liner. This optimizes the ease of assembly and is simpler and more economically to produce than a chamfer all the way around the oblong ring. In the preferred embodiment, the lock ring has a constant thickness such that the inner periphery and the outer periphery are oval.In an alternative embodiment, the metal lock ring has a round inner diameter and a round outer diameter that are not concentric, thereby creating a thickening of the ring at one end.

Abstract: The acetabular cup assembly of this invention includes a bearing component having an elevated rim and a metal cup. A groove is formed about the component for engagement with a locking ring carried by the metal cup. The bearing component may be inserted into the cup and tilted or tipped so that the elevated rim is pressed downwardly against the rim of the metal cup. In this position, the elevated portion of the rim is out of the way of the surgeon permitting the head to be more easily inserted into the bearing component. Once the head is seated the surgeon presses against the raised lip of the bearing component to shift the bearing component such that the elevated lip is properly positioned. A snap ring locks into a groove of the bearing component when positioned for use.Accordingly, it is an obejct of the invention to provide a novel acetabular hip cup assembly.

Abstract: A set of provisional prosthesis instrumentation including an outer shell component, a first inner component, and a second inner component different from the first inner component. The first inner component comprises a substantially hemispherical interior surface therein, while the second inner component comprises a nonhemispherical, truncated cone or a nonhemispherical, substantially cylindrical surface therein. Either the first inner component style or the second inner component style may be selectively inserted into the shell component. The first and second inner components (inserts) are releasably connectable with the shell. The first style inner component may typically be used as a provisional for a bipolar prosthesis for a hemiarthroplasty procedure, while the second style of inner component may typically be used as a unipolar endoprosthesis provisional for a hemiarthroplasty procedure. The same style of shell component is utilized for both styles of inner components.