Abstract
Modern prosthetic stem construction strives to achieve the attractive goals of stress shielding prevention and optimal osteointegration. PhysioLogic stem is a new generation composite isoelastic femoral stem consisting of titanium core sheathed in implantable PEEK polymer and coated with titanium layer. This construction combines the benefits of both stress shielding prevention, due to its elasticity under bending load corresponding closely to that of natural bone, and rapid osteointegration, due to the stem's titanium coating.
The aim of this study is long-term clinical progress evaluation and retrospective analysis in patients undergoing primary PhysioLogic stem implantation at our institution.
From 1998 to 2003, we performed 51 primary total hip arthroplasty (THA) operations with implantation of PhysioLogic Stem at our institution. Indications for THA included osteoarthritis (21), hip dysplasia (14), rheumatoid arthritis (10), and femoral neck nonunion (6). In all patients we used totally uncemented system — PhysioLogic Stem and monoblock cup with different types of bearing surface articulation (40 metal/polyethylene, 3 ceramic/polyethylene, and 8 metal/metal). In all cases head size was 28mm. Two patients died in the early post-op period at day 1 and day 9 from disseminated intravascular coagulation and pulmonary embolism, respectively, and were excluded from subsequent analysis. Analyzed patients included 20 women and 29 men; median age 45, range 21–69. Post-operatively, the patients were evaluated at 3 and 6 months, 1 year, and yearly thereafter. Median follow-up period was 14 years, range 11 to 16 years. Clinical and functional outcomes were evaluated by Harris Hip Score. Bone density in Gruen's and Charnley's zones was measured by dual-energy x-ray absorptiometry.
Four patients died at 5–8 years postoperatively from cardiac causes. Two patients underwent revision surgery: one patient underwent “dry revision” due to hip dislocation with exchange for longer head while keeping the original PhysioLogic stem in place; second patient underwent stem removal after chronic periprosthetic infection. Among the 45 patients with surviving PhysioLogic Stem, 33 patients (75%) underwent subsequent contralateral total hip arthroplasty with standard uncemented stems types Spotorno or Zweymuller. These patients were surveyed at postoperative evaluation about subjective comparative performance of PhysioLogic Stem versus standard stem. Twenty seven patients (82%) reported the PhysioLogic stem to be equivalent or superior to the standard stem, with 15 patients (45%) rating the PhysioLogic stem as subjectively more comfortable than the standard stem.
The average Harris hip score improved from 40 points preoperatively (range 27 to 48) to 93 points (range 89 to 95) at the time of final follow-up. All stems continue to show adequate bone-ingrown fixation with no radiological signs of aseptic loosening to date. The PhysioLogic stem removed in the aforementioned case of chronic periprosthetic infection also showed clear signs of good osteointegration.
Our study showed that the PhysioLogic stem implantation resulted in favorable clinical and functional performance at long-term follow-up, making it an attractive alternative to standard stems.
