Introduction. Modern acetabular shells have many liner options from which the surgeon can choose to most appropriately reconstruct the arthritic hip. Lateralised liners are one option that is available to the surgeon and these liners have potential benefits over “standard” polyethylene liners. Benefits include decreased Von Mises stresses which may lead to decreased polyethylene wear, lateralisation of the femur away from the pelvis which can decrease impingement / increase ROM and having the ability to use larger femoral heads in a smaller shell improving stability of the THA. Despite these benefits, lateralised liners are not routinely used by surgeons as there is concern over lateralisation of the centre of rotation of the hip with increased joint reaction forces, unsupported polyethylene that could lead to liner failure, and a slightly increased torque moment to the shell which could lead to micromotion and failure of the shell to obtain bony ingrowth. This study reports on 5-year minimum clinical and radiographic F/U of a prospective series of lateralised, moderately crosslinked polyethylene liners. Methods. 102 consecutive patients who were to have a THA with a polyethylene liner were enrolled prospectively in an acetabular shell study. Two patients that had standard thickness liners were excluded from this analysis. The remaining 100 patients all had +4 lateralised liners of the same construct (Marathon polyethylene / Pinnacle Cup, DePuy, Warsaw, Indiana). All surgeries were performed by the same surgeon via a posterior approach. A neutral or 10 degree face changing liner was chosen based on shell position and stability of the THA construct. Patient data including the Harris Hip Score (HHS), WOMAC and ROM was collected at 3, 6 and 12 months and yearly thereafter. Radiographs were obtained at each visit. Results. 87 patients with minimum 5-year clinical and radiographic F/U were evaluated. Average age was 68.7 years with an average BMI of 27.3. Average F/U was 7.5 years (5–10.1). Sixty-one liners were neutral and 26 were 10° face changing. HHS improved from 44 pre-op (18–71) to 95 at latest F/U (68–100). Kaplan-Meier survivorship was 97% at an average of 7.5 yr. Three liners were revised – one during revision of a femoral stem, one for sepsis, and one for instability. There were no mechanical failures or liner dissociations. Radiographic F/U revealed no obvious polyethylene wear or osteolysis. All cups were radiographically ingrown. Conclusions. Lateralised liners can provide advantages with respect to wear, ROM and stability of the THA construct when compared to standard thickness liners. Concerns of increased polyethylene wear, failure of the cup to ingrow and potential liner dissociation or failure were not seen. At midterm F/U this particular lateralised liner/shell construct appears to be performing well clinically and radiographically with excellent survivorship. Although further F/U is required to evaluate long-term performance, these results should allow surgeons to use this construct on a routine basis without fear of early or mid-term complication

Introduction. Durable bone fixation of uncemented porous-coated acetabular cups can be observed at a long-term, however, polyethylene (PE) wear and osteolysis may affect survivorship. Accurate wear measurements correlated with clinical data may offer unique research information of clinical interest about this highly debated issue. Objetive. We assessed the clinical and radiological outcome of a single uncemented total hip replacement (THR) after twenty years analysing polyethylene wear and the appearance of osteolysis. Materials and Methods. 82 hips implanted between 1992 and 1995 were prospectively evaluated with a mean follow-up of 20.6 years (range, 18 to 23). A hemispherical porous-coated acetabular cup matched to a proximally hydroxyapatite-coated anatomic stem and a 28 mm standard PE liner, sterilised by gamma irradiation in air, was used in all hips. Radiological position and the possible appearance of loosening and osteolysis were recorded over time. Penetration of the prosthetic head into the liner was measured by the Roentgen Monographic Analysis (ROMAN) Tool at 6 weeks, 6 months, one year and yearly thereafter. Results. Six cups were revised due to wear and four due to late dislocation. All cups were radiographically well-fixed and all stems showed radiographic ingrowth. Six un-revised hips showed osteolysis on the acetabular side and two on the proximal femoral side. Creep at one year was 0.30 (±0.23) mm. Mean total femoral head penetration was 1.23 mm at 10 years, 1.52 mm at 15 years and 1.92 mm at 23 years. Overall mean wear was 0.12 (± 0.1) mm/year and 0.09 (±0.06) mm/year after the creep period. Mean wear was 0.08 (± 0.06) mm/year in hips without osteolysis and 0.14 (±0.03) mm/year in revised hips or with osteolysis (p<0.001). Conclusions. Although continued durable fixation can be observed with a porous-coated cups and a proximally hydroxyapatite-coated anatomic stem, true wear continues to increase at a constant level over time. PE wear remains as the main reason for revision surgery and osteolysis in uncemented THR after twenty years

Introduction. In total hip arthroplasty (THA), polyethylene (PE) liner oxidation leads to material degradation and increased wear, with many strategies targeting its delay or prevention. However, the effect of femoral head material composition on PE degradation for ceramic-PE articulation is yet unknown. Therefore, using two different ceramic materials, we compared PE surface alterations occurring during a series of standard ceramic-PE articulation tests. Materials and Method. Ceramic-PE THA bearings were tested in a simulator, using ASTM F2003-02, ASTM F1714-96 (2013) and ISO 14242:1–3 standards. Acetabular liners (Apex-Link PolyTM, OMNI Life Science, East Taunton, MA, USA) were articulated against Ø28 mm Si3N4 femoral heads (Amedica Corp., Salt Lake City, UT, USA). For comparison, ArCom® PE liners (Biomet Inc. Warsaw, IN, USA) were also tested against Ø28 mm zirconia-toughened alumina (ZTA) femoral heads (BIOLOX®delta, CeramTec GmbH, Plochingen, Germany), under the same conditions. After 5 million cycles of wear, all specimens were examined using nano-spectroscopy tools. Evaluations were performed on six couples per group, plus 3 untested control couples; n= 6 (+3). Spectrographic examinations generated 8 maps of 400 points each randomly selected on the wear zones of each liner, with each map area being 20 µm2 at an in-plane spatial resolution of 1 µm. Results. Volumetric wear loss for the ArCom®-BIOLOX®delta bearing was twofold greater than for Apex-Link PETM-Amedica Si3N4 (i.e., ∼220 mm3 vs. ∼100 mm3). Crystallization is a consequence of the PE chain-scission induced by oxidation. When compared to new Si3N4 heads, the crystallinity increase in the worn area of the PE tested against Si3N4 was consistently 3%, with negligible oxidation (i.e., oxidation index; OI < 0.25). In comparison, the amount of PE crystallization in ArCom®-PE worn against ZTA was ∼21% higher when compared to new liners of the same type (Fig. 1). Also, higher oxidation was consistently detected in PE liners articulated against ZTA (average OI increase = 0.42 at a sub-surface depth of 5 µm in the wear zone with hot spots up to OI = 2.1). Surface inspection of the worn ZTA and Si3N4 heads unequivocally revealed the occurrence of oxygen-release and oxygen-trapping mechanisms, respectively (i.e., formation of oxygen vacancies in ZTA vs. amorphous silica on the surface of Si3N4 (Fig. 2)). Discussion. Despite different brands of PE liners in this study, their underlying chemistry was identical. Our data showed that, when compared to Al2O3, non-oxide ceramics like Si3N4 may discourage PE oxidation in ceramic-PE articulations. One explanation for these observations is that Al2O3 is known to release dehydroxylated and ionized oxygen under wear conditions due to a frictional triboplasma within the contact region, and this phenomenon contributes to oxidative degradation. In contrast, Si3N4 (a non-oxide ceramic) scavenges oxygen under identical conditions, thus “protecting” the polyethylene from oxidation. These observations may have relevance to the anticipated longevity of PE liners in ceramic-PE THA. Conclusions. Consistent with the unique surface characteristics of these bioceramics at the molecular level, Al2O3 and Si3N4 exert different effects on the oxidation, and therefore the projected lifespan of PE in vivo