Twenty-year followup of an uncemented stem in primary THA

John B Meding, Merrill A Ritter, E Michael Keating, Michael E Berend
Clinical Orthopaedics and related Research 2015, 473 (2): 543-8

BACKGROUND: Uncemented stems have been used in THA for well over two decades, but there are relatively few studies reporting on the results after 20 years.

QUESTIONS/PURPOSES: The purpose of this study was to evaluate at a minimum followup of 20 years (1) hip scores; (2) radiographic findings, including stem fixation and osteolysis; (3) reoperations; and (4) survivorship free from aseptic loosening in a group of patients who underwent primary THA using a proximally porous-coated, plasma-sprayed, straight-stemmed, titanium-alloy femoral component.

METHODS: Between 1987 and 1993, we performed 1517 primary THAs, of which 447 were cementless, and 157 used the implant under study here (representing 10% of the THAs during the period in question). General indications for the use of the study stem included (1) younger age with relatively stronger bone (average age 55 years in this study); (2) patients not involved in another study protocol (as were the 278 other cementless hips implanted during this time); and (3) patients who, at the surgeon's discretion, would be compliant with protected weightbearing. Of those, 111 were available for followup at a minimum of 20 years (mean, 20 years), whereas 36 had died and nine (6%) were lost to followup or declined participation. The primary diagnosis was osteoarthritis in 77 hips (69%). The mean age at operation was 55 years. The clinical result was evaluated on the basis of the Harris hip score. Radiographic analysis was performed at each followup visit for distal cortical hypertrophy, spot welds, radiolucencies, stem subsidence, varus or valgus shift, osteolysis, and femoral component loosening. Kaplan-Meier analysis was performed to evaluate the survival of the femoral component.

RESULTS: The mean Harris hip score improved from 46 points to 87 points (of a possible 100 points) at the most recent followup. All hips had evidence of proximal femoral remodeling consistent with osseous ingrowth. Femoral osteolyis was seen in 22 hips (20%). One stem was revised as a result of a periprosthetic fracture. No femoral component had evidence of loosening, and none was revised. Thirty-three acetabular components (30%) were revised.

CONCLUSIONS: This femoral component provided durable long-term fixation for over two decades after THA. The porous stem geometry is still in use today and will continue to be studied into the third decade of use.

LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

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