Dual mobility (DM) total hip replacements (THRs) were introduced to reduce dislocation risk, which is the most common cause of early revision. Although DM THRs have shown good overall survivorship and low dislocation rates, the mechanisms which describe how these bearings function in-vivo are not fully understood. Therefore, the study aim was to comprehensively assess retrieved DM polyethylene liners for signs of damage using visual inspection and semi-quantitative geometric assessment methods.

Retrieved DM liners (n=18) were visually inspected for the presence of surface damage, whereby the internal and external surfaces were independently assigned a score of one (present) or zero (not present) for seven damage modes. The severity of damage was not assessed. The material composition of embedded debris was characterised using energy-dispersive x-ray analysis (EDX). Additionally, each liner was geometrically assessed for signs of wear/deformation [1].

Scratching and pitting were the most common damage modes on either surface. Additionally, burnishing was observed on 50% of the internal surfaces and embedded debris was identified on 67% of the external surfaces. EDX analysis of the debris identified several materials including titanium, cobalt-chrome, iron, and tantalum. Geometric analysis demonstrated highly variable damage patterns across the liners.

The incidence of burnishing was three times greater for the internal surfaces, suggesting that this acts as the primary articulation site. The external surfaces sustained more observable damage as evidenced by a higher incidence of embedded debris, abrasion, delamination, and deformation. In conjunction with the highly variable damage patterns observed, these results suggest that DM kinematics are complex and may be influenced by several factors (e.g., soft tissue fibrosis, patient activities) and thus further investigation is warranted.

Background. Skeletal stem cells can be combined with human allograft, and impacted to produce a mechanically stable living bone composite. This strategy has been used for the treatment of femoral head avascular necrosis, and has been translated to four patients, of which three remain asymptomatic at up to three year follow-up. In one patient collapse occurred in both hips due to widely distributed and advanced AVN disease, necessitating bilateral hip arthroplasty. However this has provided the opportunity to retrieve the femoral heads and analyse human tissue engineered bone. Aims. Analysis of retrieved human tissue-engineered bone in conjunction with clinical follow-up of this translational case series. Methods. A parallel in vitro culture of the implanted cell-graft constructs was set up at the time of surgery, with serial cell viability stains performed up to six weeks. Patient follow-up was by serial clinical and radiological examination. Tissue engineered bone from the two retrieved femoral heads was analysed histologically by Alcian blue & Sirius red stain and bi-refringence, by micro computed tomography (microCT) for both bone density and morphology, and by compression testing for mechanical strength. Normal trabecular and cortical bone from the femoral heads was used as controls. Results. Parallel in vitro analysis demonstrated sustained cell growth and viability on the allograft. Histologically, the retrieved tissue engineered specimens demonstrated a mature trabecular micro-architecture and organization identical to normal trabecular bone. MicroCT revealed trabecular morphology within the tissue-engineered bone, with bone density of 1400 Grey scale units (compared to 1200 for natural trabecular bone and 1800 for cortical bone). Axial compression testing showed no difference in strength between engineered and trabecular bone. Conclusions. Widespread residual necrosis in the femoral heads of one patient resulted in collapse requiring hip arthroplasty, but analysis of the tissue engineered bone sections has demonstrated the translational potential of a living bone composite to restore both the biological and mechanical characteristics of bone defects. Clinical follow-up shows this to be an effective new treatment for focal early stage avascular necrosis of the femoral head, and this unique retrieval analysis data confirms the potential of cell-based strategies for clinical treatment of bone defects

This study reports the mid-term results of a large bearing hybrid metal on metal total hip replacement (MOMHTHR) in 199 hips (185 patients) with mean follow up of 62 months. Clinical, radiological outcome, metal ion levels and retrieval analysis were performed. Seventeen patients (8.6%) had undergone revision, and a further fourteen are awaiting surgery (defined in combination as failures). Twenty one (68%) failures were females. All revisions and ten (71%) of those awaiting revision were symptomatic. Twenty four failures (86%) showed progressive radiological changes. Fourteen revision cases showed evidence of adverse reactions to metal debris (ARMD). The failure cohort had significantly higher whole blood cobalt ion levels (p=0.001), but no significant difference in cup size (p=0.77), inclination (p=0.38) or cup version (p=0.12) in comparison to the non revised cohort. Female gender was associated with an increased risk of failure (chi squared p=0.04). Multifactorial analysis demonstrated isolated raised Co levels in the absence of either symptoms or XR changes was not predictive of failure (p=0.675). However both the presence of pain (p<0.001) and XR changes (p<0.001) in isolation were both significant predictors of failure. Wear analysis (n=5) demonstrated increased wear at the trunnion/head interface (mean out of roundness measurements of 34.5 microns +/−13.3 (+/−2SD, normal range 8-10 microns) with normal levels of wear at the articulating surfaces. There was evidence of corrosion at the proximal and distal stem surfaces. The cumulative survival rate, with revision for any reason was 92.4% (95%CI: 87.4-95.4) at 5 years. Including those awaiting surgery, the revision rate would be 15.1% with cumulative survival at 5 years of 89.6% (95% CI: 83.9-93.4). This MOMHTHR series has demonstrated unacceptable high failure rates with evidence of high wear at the head/trunnion interface and passive corrosion to the stem surface. This raises concern with the use of large heads on conventional 12/14 tapers. Female gender was an independent risk factor of failure. Metal ion levels remain a useful aspect of the investigation work up but in isolation are not predictive of failure

Summary Statement

This study assesses oxidation, mechanical behavior and revision reasons of 2^nd generation HXLPE used in total hip and knee arthroplasty. While oxidation was low for both X3 and E1 HXLPEs, oxidative regional variations were detected in the sequentially annealed cohort.

Objectives. The Attune total knee arthroplasty (TKA) has been used in over 600 000 patients worldwide. Registry data show good clinical outcome; however, concerns over the cement-tibial interface have been reported. We used retrieval analysis to give further insight into this controversial topic. Methods. We examined 12 titanium (Ti) PFC Sigma implants, eight cobalt-chromium (CoCr) PFC Sigma implants, eight cobalt-chromium PFC Sigma rotating platform (RP) implants, and 11 Attune implants. We used a peer-reviewed digital imaging method to quantify the amount of cement attached to the backside of each tibial tray. We then measured: 1) the size of tibial tray thickness, tray projections, peripheral lips, and undercuts; and 2) surface roughness (Ra) on the backside and keel of the trays. Statistical analyses were performed to investigate differences between the two designs. Results. There was no evidence of cement attachment on any of the 11 Attune trays examined. There were significant differences between Ti and CoCr PFC Sigma implants and Attune designs (p < 0.05); however, there was no significant difference between CoCr PFC Sigma RP and Attune designs (p > 0.05). There were significant differences in the design features between the investigated designs (p < 0.05). Conclusion. The majority of the earliest PFC Sigma designs showed evidence of cement, while all of the retrieved Attune trays and the majority of the RP PFC trays in this study had no cement attached. This may be attributable to the design differences of these implants, in particular in relation to the cement pockets. Our results may help explain a controversial aspect related to cement attachment in a recently introduced TKA design. Cite this article: A. Cerquiglini, J. Henckel, H. Hothi, P. Allen, J. Lewis, A. Eskelinen, J. Skinner, M. T. Hirschmann, A. J. Hart. Analysis of the Attune tibial tray backside: A comparative retrieval study. Bone Joint Res 2019;8:136–145. DOI: 10.1302/2046-3758.83.BJJ-2018-0102.R2

Femoral neck fractures remain the leading cause of early failure after metal-on-metal hip resurfacing. Although its' exact pathomechanism has yet to be fully elucidated, current retrieval analysis has shown that either an osteonecrotic event and/or significant surgical trauma to the femoral head neck junction are the leading causes. It is most likely that no single factor like patient selection and/or femoral component orientation can fully avoid their occurrence. As in osteonecrosis of the native hip joint, a certain cell injury threshold may have to be reached in order for femoral neck fracture to occur. These insults are not limited to the surgical approach, but also include femoral head preparation, neck notching, and cement penetration. Although some have argued that the posterior approach does not represent an increased risk fracture for ON after hip resurfacing because of the so-called intraosseous blood supply to the femoral head, to date, the current body of literature on femoral head blood flow in the presence of arthritis has confirmed the critical role of the extraosseous blood supply from the ascending branch of the medial circumflex, as well as the lack of any substantial intraosseous blood supply. Conversely, anterior hip dislocation of both the native hip joint as well as the arthritic hip preserves femoral head vascularity. The blood supply can be compromised by either sacrificing the main branch of the ascending medial femoral circumflex artery or damaging the retinacular vessels at the femoral head-neck junction. Thus an approach which preserves head vascularity, while minimizing soft tissue disruption would certainly be favorable for hip resurfacing. This presentation will review the current state of knowledge on vascularity of the femoral head as well as surgical techniques enhancing its preservation

Objectives

Mechanical wear and corrosion at the head-stem junction of total hip arthroplasties (THAs) (trunnionosis) have been implicated in their early revision, most commonly in metal-on-metal (MOM) hips. We can isolate the role of the head-stem junction as the predominant source of metal release by investigating non-MOM hips; this can help to identify clinically significant volumes of material loss and corrosion from these surfaces.