COMPARATIVE RESULTS OF A DISTAL MODULAR SLEEVE, CIRCUMFERENTIAL COATING, AND STIFFNESS RELIEF USING THE ANATOMIC POROUS REPLACEMENT-II

One hundred forty-eight primary Anatomic Porous Replacement II (APR-II , Intermedics Orthopaedics, Austin, TX) noncemented total hip arthropl asties were studied at follow-up periods of 2 to 5 years. Because the stem geometry has not changed since 1988, it was possible to study thr ee adjunctive criteria for porous-coated hip arthroplasties. The APR-I I stem geometry was used in three groups: APR-II stem in 56 hips, APR- IIS stem with distal sleeve in 44 hips, and APR-IIT stem with circumfe rential coating and hollow stem in 48 hips. The APR-IIT was followed 2 years; the APR-II and APR-IIS were followed an average of 3.4 years ( range, 2-5 years). For comparison of the results within these three gr oups 2-year results were compared. The results of the APR-II and APR-I IS at the last follow-up examination are also reported. There was no s tatistical difference within the three groups for any clinical compari son: 82% had excellent results, 14% good, 2% fair, and 2% poor. At the 2-year follow-up examination, radiographic fixation of the APR-TIS wa s worse than that of the APR-II and APR-IIT (P < .0005). The APR-IIS u ses a distal sleeve, which results in an adverse stiffness ratio betwe en bone and stem. Fixation of the APR-IIT was better than that of the APR-II (P < .0005), probably because the APR-IIT had an increased volu me and circumferential level of porous coating and was hollowed for st iffness relief. Al final followup examination, fixation of the APR-IIS was still worse than that of the APR-IT (P < .0005). There was no pro gressive loss of fixation for either the APR-II or APR-IIS between 2 a nd 5 years. Only 1 of 148 patients was revised for osteolysis. No othe r stem or acetabular component is loose. The adjunctive use of a modul ar sleeve seems to have little advantage, whereas stiffness relief of the stem seems to be beneficial. Circumferential porous coating seems the most important factor for durable fixation.