The method of arthroplasty described is based on a new principle,—that of interposition of a mold by which nature can do its repair work; this mold is removed at a secondary operation, leaving congruous joint surfaces, which are capable of function because their covering approximates normal cartilage. Even though this two-stage mold arthroplasty has been proved practical, present indications are that the "mold principle" should be abandoned; if this be true, the mold becomes a permanent insurmountable barrier to recurring ankylosis.
No end results can be reported, since the twenty-nine patients in whom the vitallium mold has been used have all been operated upon since June 1938. The very fact that we have felt justified in doing as large a series as this in a relatively short period of time points to the success of the method during the first few months. Furthermore, the experience gained from the use of the glass molds has given us confidence in the soundness of the method.