Aims. The liner design is a key determinant of the constraint of a reverse total shoulder arthroplasty (rTSA). The aim of this study was to compare the degree of constraint of rTSA liners between different implant systems. Methods. An implant company’s independent 3D shoulder arthroplasty planning software (mediCAD 3D shoulder v. 7.0, module v. 2.1.84.173.43) was used to determine the jump height of standard and constrained liners of different sizes (radius of curvature) of all available companies. The obtained parameters were used to calculate the stability ratio (degree of constraint) and angle of coverage (degree of glenosphere coverage by liner) of the different systems. Measurements were independently performed by two raters, and intraclass correlation coefficients were calculated to perform a reliability analysis. Additionally, measurements were compared with parameters provided by the companies themselves, when available, to ensure validity of the software-derived measurements. Results. There were variations in jump height between rTSA systems at a given size, resulting in large differences in stability ratio between systems. Standard liners exhibited a stability ratio range from 126% to 214% (mean 158% (SD 23%)) and constrained liners a range from 151% to 479% (mean 245% (SD 76%)). The angle of coverage showed a range from 103° to 130° (mean 115° (SD 7°)) for standard and a range from 113° to 156° (mean 133° (SD 11°)) for constrained liners. Four arthroplasty systems kept the stability ratio of standard liners constant (within 5%) across different sizes, while one system showed slight inconsistencies (within 10%), and ten arthroplasty systems showed large inconsistencies (range 11% to 28%). The stability ratio of constrained liners was consistent across different sizes in two arthroplasty systems and inconsistent in seven systems (range 18% to 106%). Conclusion. Large differences in jump height and resulting degree of constraint of rTSA liners were observed between different implant systems, and in many cases even within the same implant systems. While the immediate clinical effect remains unclear, in theory the degree of constraint of the liner plays an important role for the dislocation and notching risk of a rTSA system. Cite this article: Bone Jt Open 2024;5(10):818–824

Special acetabular polyethylene (PE) liners are intended to increase the stability of the artificial hip joint, yet registry studies on them are limited. The pupose of this study was to investigate differences in revision rates for mechanical complications in primary cementless total hip arthroplasty (THA) with standard and special PE acetabular liners in patients with ostheoarthritis. Data from the German Arthroplasty Registry (EPRD) between 2012 until 2020 were analysed. Patients with diagnosed ostheoarthritis of the hip without relevant prior surgeries, who received a primary cementless THA with a ceramic/PE bearing articulation were included. Cumulative incidences of revision for mechanical complications for Standard and 4 special PE liners (Lipped, Increased Offset, Angulated, Angulated|Increased Offset) were determined using the Kaplan-Meier Estimator. Confounding factors were investigated with a Cox proportional-hazards model. In total 151.104 cases were included. 7-year unadjusted revision-free survival for mechanical complications compared to Standard liners (97.7%) was lower for Angulated (97.4%), Lipped (97.2%) and Angulated|Increased Offset liners (94.7%), but higher for Increased Offset liners (98.1%). Risk of revision for mechanical complications was not significantly different between Standard, Lipped and Angulated liners. Increased Offset liners (HR=0.68; 95% CI=0.5–0.92) reduced, while Angulated|Increased Offset liners (HR= 1.81; 95% CI=1.38–2.36) increased the risk. Higher age at admission and an Elixhauser comorbidity index greater zero increased the risk, whereas a larger liner share slightly reduced the risk. Only the use of Increased Offset liners reduced the risk of revision for mechanical complications compared to Standard liners — other special liners did not

Aims. The most frequent indication for revision surgery in total hip arthroplasty (THA) is aseptic loosening. Aseptic loosening is associated with polyethylene liner wear, and wear may be reduced by using vitamin E-doped liners. The primary objective of this study was to compare proximal femoral head penetration into the liner between a) two cross-linked polyethylene (XLPE) liners (vitamin E-doped (vE-PE)) versus standard XLPE liners, and b) two modular femoral head diameters (32 mm and 36 mm). Methods. Patients scheduled for a THA were randomized to receive a vE-PE or XLPE liner with a 32 mm or 36 mm metal head (four intervention groups in a 2 × 2 factorial design). Head penetration and acetabular component migration were measured using radiostereometric analysis at baseline, three, 12, 24, and 60 months postoperatively. The Harris Hip Score, University of California, Los Angeles (UCLA) Activity Score, EuroQol five-dimension questionnaire (EQ-5D), and 36-Item Short-Form Health Survey questionnaire (SF-36) were assessed at baseline, three, 12, 36, and 60 months. Results. Of 220 screened patients, 127 were included in this study. In all, 116 received the allocated intervention, and 94 had their results analyzed at five years. Head penetration was similar between liner materials and head sizes at five years, vE-PE versus XLPE was -0.084 mm (95% confidence interval (CI) -0.173 to 0.005; p = 0.064), and 32 mm versus 36 mm was -0.020 mm (95% CI -0.110 to 0.071; p = 0.671), respectively. No differences were found in acetabular component migration or in the patient-reported outcome measures. Conclusion. No significant difference in head penetration was found at five years between vE-PE and XLPE liners, nor between 32 mm and 36 mm heads. Cite this article: Bone Joint J 2020;102-B(10):1303–1310

Aims

Pelvic discontinuity is a rare but increasingly common complication of total hip arthroplasty (THA). This single-centre study evaluated the performance of custom-made triflange acetabular components in acetabular reconstruction with pelvic discontinuity by determining: 1) revision and overall implant survival rates; 2) discontinuity healing rate; and 3) Harris Hip Score (HHS).

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. 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) system after twenty years analysing polyethylene wear and the appearance of osteolysis. Materials and Methods. 82 hips implanted between 1992 and 1995 were prospectively evaluated. The mean follow-up was 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 rate over time. PE wear remains as the main reason for revision surgery and osteolysis in uncemented THR and does not stop 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

The prevalent cause of implant failure after total joint replacement is aseptic loosening caused by wear debris. Improvement of the wear behaviour of the articulating bearing between the cup and femoral head is essential for increased survival rate of artificial hip joints. Cross-linking of the polyethylene (PE) material is one attempt to reduce wear particle release at the articulating surface. Various cross-linked polyethylenes (X-PE) are used in orthopaedics since several years. In total hip arthroplasty (THA) the use of larger femoral head sizes has specific reasons. Larger heads lead to a decreased risk of total hip dislocation and impingement as well as an improved range of motion in comparison to smaller head sizes like 28mm or less. However, the increasing diameter of femoral head can be associated with lower thickness of the PE liner and increased wear rate. Cross-linking of PE can improve the wear rate of the liner and hence supports the use of larger femoral heads. The aim of this experimental study was to evaluate the wear of standard vs. sequential X-PE (X3-PE) liner in combination with different ceramic femoral head sizes. Wear testing was performed for 5 million load cycles using standard UHMW-PE liners (N2Vac) and X3-PE liners (each Stryker GmbH & Co. KG, Duisburg, Germany) combined with 28mm ceramic ball heads and the Trident PSL acetabular cup (Stryker). Furthermore, X3-PE liners with an internal diameter of 36mm and 44mm and decreased wall thickness (5.9mm and 3.8mm) were combined with corresponding ceramic heads. An eight station hip wear simulator according to ISO 14242 (EndoLab GmbH, Rosenheim, Germany) was used to carry out the standard wear tests. The tests were realised in temperature-controlled chambers at 37°C containing calf serum (protein content 20g/l). The average gravimetrical wear rates of the standard UHMW-PE (N2Vac) liners combined with 28mm ceramic heads amounted to 12.6 ± 0.8mg/million cycles. Wear of X3-PE liners in combination with 28 mm ceramic heads was not detectable. The average gravimetrical wear rates of the X3-PE liners in combination with 36mm and 44mm ceramic heads amounted to 2.0 ± 0.5mg and 3.1 ± 0.3mg/million cycles, respectively. The purpose of this study was to evaluate the effect of femoral head size at THA on standard and sequential X-PE liner. The wear simulator tests showed that the wear rate of PE liners with small heads (28mm) decreased by cross-linking of the PE significantly. The amount of wear at X-PE increased slightly with larger head size (36mm and 44mm). However, by sequential cross-linking, the wear rate using thinner liners and larger femoral heads is reduced to a fractional amount of wear at conventional UHMW-PE. Hence, the above-mentioned advantages of larger femoral head diameters can be realised by improved wear behaviour of sequential X-PE

Introduction Polyethylene wear debris is an important cause of failure in cemented total hip arthroplasty. As a result of the biological response to debris at the bone-cement interface, osteolysis and subsequent failure occurs in both femoral and acetabular components. Most acetabular components and liners are made of ultra high molecular weight polyethylene (UHMWPE). Cross-linking UHMWPE has been shown to significantly reduce abrasive wear in hip simulator studies. The wear rates measured in vitro do not always correlate with the wear rates measured in clinical studies[. 1. ]. Some new polyethylenes have shown catastrophic wear in clinical studies despite encouraging hip simulator study results[. 2. ]. The aim of this study was to compare the wear of standard UHMWPE to that of cross-linked UHMWPE (Longevity, Zimmer, Warsaw, USA). Patients and Methods This was a prospective, double blind, randomised control trial. 50 subjects were recruited, all of whom received the cemented CPT stem and uncemented Trilogy liner (Zimmer, UK). Subjects were randomised to receive either a standard Trilogy liner or a Longevity liner at the time of operation. Both liners are identical in appearance. All liners were of a neutral configuration. RSA was used to measure linear wear. This was calculated by measuring the distance between the centre of the femoral head and the centre of the acetabular liner. The preliminary results of the study are presented. Results Both groups underwent significant wear over two years. The two year linear wear of the cross-linked UHMWPE was 0.3mm (+/− 0.06mm, p< 0.001). The two year linear wear of the standard UHMWPE was 0.39mm (+/− 0.04mm, p< 0.001). No significant difference existed between the two groups (p=0.24). Both cohorts had around 0.15 to 0.2 mm of measured wear per year. Cross-linked UHMWPE therefore underwent less wear than standard UHMWPE at two years, however this difference was not statistically significant. Discussion This study suggests that Longevity UHMWPE has similar wear properties to standard UHMWPE in the first two years following implantation. This does not correlate with in vitro hip simulator studies of Longevity polyethylene, which show a significantly lower wear rate than standard UHMWPE. It suggests that hip simulator studies may be of little value in predicting in vivo wear rates and that all new types of polyethylene should be evaluated clinically and radiologically prior to general release. Whether both cohorts continue to wear at similar rates will only be revealed through continued observation

A polyethylene liner can be cemented into a well-fixed and well-oriented acetabular component with success. This technique has been used by us for over 5 years. In the last year, we have used this technique in patients that are considered to be unlimited community ambulators and who participate in vigorous exercises as well as sports such as golf and skiing. These cemented inserts have therefore functioned in patients who have activity levels, which vary from a household ambulator to an unlimited community ambulator. We have reviewed 17 patients with 18 hips that have follow-up beyond 2 years. Ten of these patients had the cemented insert performed because of dislocation and a constrained liner was inserted into the shell. Seven of these patients had a liner cemented at the time of revision because either the locking mechanism of the cup was not good enough to replace the liner or a new bearing surface was desired by the patient. Twelve of the liners that were cemented into the shells were constrained and five were standard polyethylene articulation surfaces (without constraint). Two of these were crosslinked polyethylene liners. At the time of revision eight hips also had stem revision and in nine hips only the modular femoral head and insert were exchanged. There have been three revisions of these 18 hips. In the second hip replacement performed, the size of polyethylene used was too large and the ledge of the polyethylene rim was not abutted against the metal rim of the shell (the poly stood proud). This polyethylene disassembled within three months and a revision of this cup was done to a constrained cup and liner. The second revision was in a patient who had a cup changed with a standard polyethylene liner for dislocation. The dislocation persisted so that this patient was reoperated five months later and a constrained liner was cemented into the acetabular shell, which successfully stopped the dislocation. The third was a patient who had a constrained liner cemented into a cup, but continued to dislocate even with the constrained liner. There was no loosening of the cemented constrained insert. This patient had the entire cup revised to a ring support with a new constrained liner. In all three of these patients there was profound gluteus medius muscle absence of function. Radiographic review of these acetabular reconstructions show that in those patients who had screw holes in the acetabulum there are no radiolucent lines apparent around the cement “puffs” which are visible in the acetabular bone. In those cups that did not have screw holes, the inner aspect of the acetabular cup was roughened with a Midas-Rex and there is no visible cement outside these cups. All of the acetabular plastic liners had the backside roughened with the Midas-Rex prior to being cemented into the metal shell. Lever-out strengths of cemented polys into metal shells have shown that this is stronger than that provided by a regular locking mechanism