Repeated trauma to the radial head may be one of the causative factors in the genesis of osteochondritis dissecans of the capitellum. We measured the force, contact area and pressure across the radiocapitellar articulation of the elbow before and after radial shortening osteotomy in five fresh-frozen cadaver upper limbs with loads of 45, 90 and 135 N, respectively. Measurements were made on pressure-sensitive film placed in the radiocapitellar articulation with the forearm in the supinated, neutral and pronated positions before and after radial shortening. Radial shortening significantly reduced the mean force and contact area across the radiocapitellar articulation in all positions of the forearm

The anatomy of the first metatarsophalangeal (MTP) joint and, in particular, the metatarsosesamoid articulation remains poorly understood. Its effect on sesamoid function and the pathomechanics of this joint have not been described. Fresh frozen cadaveric specimens without evidence of forefoot deformity were dissected to assess the articulating surfaces throughout a normal range of motion. The dissections were digitally reconstructed in various positions of dorsiflexion and plantarflexion using a MicroScribe, enabling quantitative analyses in a virtual 3D environment. In 75% of specimens, there was some degree of chondral loss within the metatarsosesamoid articulation. The metatarsal surface was more commonly affected. These changes most frequently involved the tibial metatarsosesamoid joint. The tibial sesamoid had an average excursion of 14.2 mm in the sagittal plane when the 1st MTP joint was moved from 10 degrees of plantarflexion to 60 degrees of dorsiflexion; the average excursion of the fibular sesamoid was 8.7 mm. The sesamoids also move in a medial to lateral fashion when the joint was dorsiflexed. The excursion of the tibial sesamoid was 2.8 mm when the joint was maximally dorsiflexed while that of the fibular sesamoid was 3.2 mm. There appears to be differential tracking of the hallucal sesamoids. The tibial sesamoid has comparatively increased longitudinal excursion whilst the fibular sesamoid has comparatively greater lateral excursion. This greater excursion of the tibial sesamoid could explain the higher incidence of sesamoiditis in this bone. The differential excursion of the 2 metatarsosesamoid articulations is also a factor that should be considered in the design and mechanics of an effective hallux MTP joint arthroplasty

Introduction. The purpose of this study was to evaluate the functional and radiographical results in patients who underwent a modified minimally invasive two-incision total hip arthroplasty using large-diameter ceramic-on-ceramic articulations for osteonecrosis of the femoral head. Methods. One hundred and one patients (135 hips) who underwent unilateral minimally invasive two-incision total hip arthroplasties using large diameter ceramic-on-ceramic bearings for osteonecrosis of the femoral head with a minimum 12-months follow-up were included in this study. There were 22 women and 79 men who had a mean age of 46 years (range, 22 to 82 years). The mean follow-up was 25 months (range, 12 to 36 months). All surgeries were done by a single hip surgeon. The authors modified the original minimally invasive two-incision total hip arthroplasty technique and used large-diameter (32mm, 36mm) ceramic-on-ceramic articulations. In the lateral position, an anterolateral approach between the gluteus medius and tensor fascia lata muscles and a posterior approach between the piriformis and gluteus medius muscles was used. Functional results were measured by Harris hip (HHS) and WOMAC scores. Radiographic evaluation was assessed for positioning of the components and complications were assessed. Results. The mean Harris hip score improved from 43 points (range, 13 to 58 points) pre-operatively to 96 points (range, 73 to 100 points) post-operatively and the mean WOMAC score improved from 67 points (range, 50 to 98 points) to 28 points (range, 26 to 39 points). On radiological evaluation, the mean lateral opening angle of the acetabular component was 35.9 degrees (range, 27.1 degrees to 47.4 degrees) and the mean stem position was valgus 2.4 degrees (range, varus 2.7 degrees to valgus 5.3 degrees). One patient suffered an intra-operative femur fracture and another underwent revision surgery due to stem subsidence. There were no complications such as immediate post-operative deep infection, delayed infection, or recurrent dislocation. Conclusion. A modified minimally invasive two-incision total hip arthroplasty using large-diameter ceramic-on-ceramic articulation for osteonecrosis of the femoral head is safe and reproducible in terms of achieving proper implant positioning and early functional recovery. In particular, the complication rates encountered, especially dislocation, were low

Dislocation post THA confers a higher risk of re-dislocation (Kotwal et al, 2009). The dual mobility (DM) cup design (1974) was aimed at improving the stability by increasing the femoral head to neck ratio (Cuthbert et al., 2019) combining the ideas of low friction arthroplasty with increased jump distance associated with a big head arthroplasty.

Understand the dislocation rates, rates of aseptic loosening, infection rate and revision rates between the 2 types of constructs to provide current and up-to date evidence.

Medline, pubmed, embase and Cochrane databases were used based on PRISMA guidelines. RevMan software was used for the meta-analysis. Studies (English literature) which used DM construct with atleast 6 months follow-up used as intervention and non DM construct as control were included. 2 independent reviewers conducted the review with a third reviewer in case of difference in opinion regarding eligibility. Primary outcome was dislocation rate and secondary outcome was rate of revision.

564 articles identified out of which 44 articles were screened for full texts and eventually 4 systematic review articles found eligible for the study. Thus, study became a review of systematic reviews. From the 4 systematic reviews, another 35 studies were identified for data extraction and 13 papers were used for meta-analysis. Systematic reviews evaluated, projected an average follow up of 6-8 years with significantly lower dislocation rates for DM cups. The total number of patients undergoing DM cup primary THA were 30,559 with an average age 71 years while the control group consisted of 218,834 patients with an average age of 69 years. DM group had lower rate of dislocation (p < 0.00001), total lower rate of cup revision (p < 0.00001, higher incidence of fracture (p>0.05).

DM THA is a viable alternative for conventional THA. The long-term results of DM cups in primary THA need to be further evaluated using high quality prospective studies and RCTs.

Abstract

We revised seven alumina-blasted cementless hip prostheses (Ti-alloy stems, cp Ti threaded sockets) with low- or high-carbon Co-alloy bearings at a mean of 20.1 months after implantation because of pain and loosening. Histological examination of the retrieved periprosthetic tissues from two cases in which the implant was stable and three in which the socket was loose showed macrophages with basophilic granules containing metal and alumina wear particles and lymph-cell infiltrates. In one of the two cases of stem loosening the thickened neocapsule also contained definite lymphatic follicles and gross lymphocyte/plasma-cell infiltrates. Spectrometric determination of the concentration of elements in periprosthetic tissues from six cases was compared with that of joint capsules from five control patients undergoing primary hip surgery. In the revisions the mean concentration of implant-relevant elements was 693.85 μg/g dry tissue. In addition to Cr (15.2%), Co (4.3%), and Ti (10.3%), Al was predominant (68.1%) and all concentrations were significantly higher (p < 0.001) than those in the control tissues. The annual rates of linear wear were calculated for six implants. The mean value was 11.1 μm (heads 6.25 μm, inserts 4.82 μm). SEM/EDXA showed numerous fine scratches and deep furrows containing alumina particles in loosened sockets, and stems showed contamination with adhering or impacted alumina particles of between 2 and 50 μm in size.

Aims. Second-generation metal-on-metal (MoM) articulations in total hip arthroplasty (THA) were introduced in order to reduce wear-related complications. The current study reports on the serum cobalt levels and the clinical outcome at a minimum of 20 years following THA with a MoM (Metasul) or a ceramic-on-polyethylene (CoP) bearing. Methods. The present study provides an update of a previously published prospective randomized controlled study, evaluating the serum cobalt levels of a consecutive cohort of 100 patients following THA with a MoM or a CoP articulation. A total of 31 patients were available for clinical and radiological follow-up examination. After exclusion of 11 patients because of other cobalt-containing implants, 20 patients (MoM (n = 11); CoP (n = 9)) with a mean age of 69 years (42 to 97) were analyzed. Serum cobalt levels were compared to serum cobalt levels five years out of surgery. Results. The median cobalt concentration in the MoM group was 1.04 μg/l (interquartile range (IQR) 0.64 to 1.70) at a mean of 21 years (20 to 24) postoperatively and these values were similar (p = 0.799) to cobalt levels at five years. In the CoP control group, the median cobalt levels were below the detection limit (< 0.3 μg/l; median 0.15 μg/l, IQR 0.15 to 0.75) at 20 years. The mean Harris Hip Score was 91.4 points (61 to 100) in the MoM group and 92.8 points (63 to 100) in the CoP group. Conclusion. This study represents the longest follow-up series evaluating the serum cobalt levels after 28 mm head MoM bearing THA and shows that serum cobalt concentrations remain at low levels at a mean of 21 years (20 to 24) after implantation. Cite this article:Bone Joint Res. 2020;9(3):145–150

Articulating cartilage experiences a multitude of biophysical cues. Due to its primary function in distributing load with near frictionless articulation, it is clear that a major stimulus for cartilage homeostasis and regeneration is the mechanical load it experiences on a daily basis. While these effects are considered when performing in vivo studies, in vitro studies are still largely performed under static conditions. Therefore, an increasing complexity of in vitro culture models is required, with the ultimate aim to recreate the articulating joint as accurately as possible. We have for many years utilized a complex multiaxial load bioreactor capable of applying tightly regulated compression and shear loading protocols. Using this bioreactor, we have been able to demonstrate the mechanical induction of human bone marrow stromal cell (BMSC) chondrogenesis in the absence of exogenous growth factors. Building on previous bioreactor studies that demonstrated the mechanical activation of endogenous TGFβ, and subsequent chondrogenesis of human bone marrow derived MSCs, we have been further increasing the complexity of in vitro models. For example, the addition of high molecular weight hyaluronic acid, a component of synovial fluid, culture medium leads to reduced hypertrophy and increased glycosaminoglycan deposition. The ultimate aim of all of these endeavors is to identify promising materials and therapies during in vitro/ ex vivo studies, therefore reducing the numbers or candidates that are finally tested using in vivo studies. This 3R approach can improve the opportunities for success while leading to more ethically acceptable product development pathways

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

Dual mobility hip arthroplasty utilizes a freely rotating polyethylene liner to protect against dislocation. As liner motion has not been confirmed in vivo, we investigated the liner kinematics in vivo using dynamic radiostereometry. 16 patients with Anatomical Dual Mobility acetabular components were included. Markers were implanted in the liners using a drill guide. Static RSA recordings and patient reported outcome measures were obtained at post-op and 1-year follow-up. Dynamic RSA recordings were obtained at 1-year follow-up during a passive hip movement: abduction/external rotation, adduction/internal rotation (modified FABER-FADIR), to end-range and at 45° hip flexion. Liner- and neck movements were described as anteversion, inclination and rotation. Liner movement during modified FABER-FADIR was detected in 12 of 16 patients. Median (range) absolute liner movements were: anteversion 10° (5–20), inclination 6° (2–12), and rotation 11° (5–48) relative to the cup. Median absolute changes in the resulting liner/neck angle (small articulation) was 28° (12–46) and liner/cup angle (larger articulation) was 6° (4–21). Static RSA showed changes in median (range) liner anteversion from 7° (-12–23) postoperatively to 10° (-3–16) at 1-year follow-up and inclination from 42 (35–66) postoperatively to 59 (46–80) at 1-year follow-up. Liner/neck contact was associated with high initial liner anteversion (p=0.01). The polyethylene liner moves over time. One year after surgery the liner can move with or without liner/neck contact. The majority of movement is in the smaller articulation between head and liner

Introduction and Objective. The patients with a total hip arthroplasty is growing in world manly in Europe and USA, and this solution present a high success at 10years in several orthopaedic registers. The application of total press-fit hip fixation presents the most used solution, but presents some failures associated to the acetabular component fixation, associated to the load transfer and bone loss at long term. The aim of this work is to investigate the influence of different acetabular bone loss in the strain distribution in iliac bone. To evaluate implant fixation, an experimental study was performed using acetabular press-fit component simulating different acetabular bone loss and measuring the strain distribution. Materials and Methods. The experimental samples developed was based in an iliac bone model of Sawbones supplier and a acetabular component Titanium (Stryker) in a condition press-fit fixation and was implanted according surgical procedure with 45º inclination angle and 20º in the anteversion angle. Were developed five models with same initial bone, one with intact condition simulating the cartilage between bones and four with different bone loss around the acetabular component. These four models representing the evolution of bone support of acetabular components presented in the literature. The evolution of bone loss was imposed with a CAD CAM process in same iliac bone model. The models were instrumented with 5 rosettes in critical region at the cortical bone to measure the strain evolution along the process. Results. The results of strain gauges present the influence of acetabular component implantation, reducing the bone strains and presented the effect of the strain shielding. The acetabular component works as a shield in the load transfer. The critical region is the posterior region with highest principal strains and the strain effect was observed with different bone loss around acetabular component. The maximum value of principal strain was observed in the intact condition in the anterior region, with 950μ∊. In the posterior superior region, the effect of bone loss is more important presenting a reduction of 500% in the strains. The effect of bone loss is presented in the strains induced with acetabular implantation, in the first step of implantation the maximum strain was 950μ∊ and in the last model the value was 50μ∊, indicating lower press-fit fixation. Conclusions. The models developed allows study the effect of bone loss and acetabular implant fixation in the load transfer at the hip articulation. The results presented a critical region as the anterior-superior and the effect of strain shielding was observed in comparison with intact articulation. The results of press-fit fixation present a reduction of implant stability along bone loss. The process of bone fixation developed present some limitation associated to the bone adhesion in the interface, not considered. Acknowledgement. This work was supported by POCI-01-0145-FEDER-032486,– FCT, by the FEDER, with COMPETE2020 - (POCI), FCT/M

Abstract. Objectives. Total hip replacement (THR) is one of the most successful and cost-effective interventions in orthopaedic surgery. Dislocation is a debilitating complication of THR and managing an unstable THR constitutes a significant clinical challenge. Stability in THR is multifactorial and is influenced by surgical, patient and implant related factors. It is established that larger diameter femoral heads have a wider impingement-free range of movement and an increase in jump distance, both of which are relevant in reducing the risk of dislocation. However, they can generate higher frictional torque which has led to concerns related to increased wear and loosening. Furthermore, the potential for taper corrosion or trunnionosis is also a potential concern with larger femoral heads, particularly those made from cobalt-chrome. These concerns have meant there is hesitancy among surgeons to use larger sized heads. This study presents the comparison of clinical outcomes for different head sizes (28mm, 32mm and 36mm) in primary THR for 10,104 hips in a single centre. Methods. A retrospective study of all consecutive patients who underwent primary THR at our institution between 1st April 2003 and 31st Dec 2019 was undertaken. Institutional approval for this study was obtained. Demographic and surgical data were collected. The primary outcome measures were all-cause revision, revision for dislocation, and all-cause revision excluding dislocation. Continuous descriptive statistics used means, median values, ranges, and 95% confidence intervals where appropriate. Kaplan-Meier survival curves were used to estimate time to revision. Cox proportional hazard regression analysis was used to compare revision rates between the femoral head size groups. Adjustments were made for age at surgery, gender, primary diagnosis, ASA score, articulation type, and fixation method. Results. 10,104 primary THRs were included; median age 68.6 years with 61.5% females. A posterior approach was performed in 71.6%. There were 3,295 hips with 28 mm heads (32.6%), 4,858 (48.1%) with 32 mm heads and 1,951 (19.3%) with 36 mm heads. Overall rate of revision was 1.7% with the lowest rate recorded for the 36mm group (2.7% vs. 1.3% vs. 1.1%). Cox regression analysis showed a decreased risk of all-cause revision for 32mm & 36mm head sizes as compared to 28mm; this was statistically significant for the 32mm group (p = 0.01). Risk of revision for dislocation was significantly reduced in both 32mm (p = 0.03) and 36mm (p = 0.03) head sizes. Analysis of all cause revision excluding dislocation showed no significant differences between head sizes. Conclusion. There was a significantly reduced risk of revision for all causes, but particularly revision for dislocation with larger head sizes (36mm & 32mm vs. 28mm). Concerns regarding increased risk of early revision for aseptic loosening, polyethylene wear or taper corrosion with larger heads appear to be unfounded in this cohort of 10,104 patients with a mean of 6.0-year follow-up. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. Hip instability following total hip arthroplasty in treatment of intracapsular neck of femur fractures is reported at 8–11%. Utilising the principle of a small articulation to minimize the problems of wear coupled with a large articulation, dual-mobility total hip arthroplasty prostheses stabilise the hip further than conventional fixed-bearing designs. The aim of this study is to compare the rate of dislocation and complication between standard fixed-bearing and dual-mobility prostheses for the treatment of intracapsular neck of femur fractures. Methods. A four-year retrospective review in a large district general hospital was completed. All cases of intracapsular neck of femur fractures treated with total hip arthroplasty were identified through the theatre logbooks. Patient's operative and clinical notes were retrospectively reviewed to collect data. Results. A total of 91 patients underwent total hip arthroplasty for intracapsular neck of femur fracture in the four-year period. 61.5% were dual-mobility design versus 28.5% had fixed-bearing implants. There were no statistical differences between patient group characteristics. Choice of implant was dependent on surgeon preference. There was a 0.0% dislocation rate in the dual-mobility group versus 8.6% in the fixed-bearing prosthesis group. All dislocations occurred in patients who underwent total hip arthroplasty with 36.0mm fixed-bearing prosthesis via posterior surgical approach. There was no statistical difference in mortality between both groups. Conclusion. There was an increasing trend of towards the use of dual-mobility prosthesis for fractured neck of femur within this department with excellent outcomes. Dual-mobility designs provide reduced dislocation rates in total hip arthroplasty in intracapsular neck of femur fractures compared to standard fixed-bearing designs at this institution. The authors recommend that all orthopaedic staff consider the use of dual-mobility prostheses in suitable patients and ensure trainees are suitably trained in use of dual-mobility designs. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Introduction. Bipolar hemiarthroplasty(BPHA) for displaced intracapsular neck of femur fractures(DICNOF) is a controversial topic as conflicting evidence exists. The most common reason for revision to total hip arthroplasty(THA) from BPHA is acetabular erosion. In our study, we sought to quantify the direction of migration of the bipolar head within the first 3 years post-operatively. Methods. A proportional index in the horizontal and vertical planes of the pelvis were used to quantify migration. This method removed the need to account for magnification and rotation of the radiographs. Results. There were a total of 35 patients (8males, 27females) included, with an average followup of 2.3years (816days). 7 did not migrate, these were all female. For the remainder, per year of insertion, the average horizontal migration was 0.005769439 and the average vertical migration was 0.004543352, suggesting superomedial movement. Discussion. BPHA has been shown to provide results similar to those of THA in patients with DICNOF. The main cause of revision to THA is migration thought to be from loss of cartilage volume from mechanical wear, that causes pain. We have quantified this migration as minimal. None of our patients required revision to THA and none sustained dislocation or loosening in this followup period. This would fit with the meta-analyses looking at BPHA, which shows bipolar articulations reduce the amount of wear. We also identified a trend that in the female population migration is less likely to occur. This would add evidence to the theory that mechanical factors are significant in the volumetric wear caused by hemiarthoplasty. Conclusion. BPHA was found to be safe and effective in our cohort of patients with minimal migration and no need for revision at an average of 2.3years. Our data is concurrent with the literature in theorising that BPHA reduces wear at the prosthesis-cartilage interface

Abstract. OBJECTIVES. Dual mobility (DM) total hip replacements (THRs) were introduced to reduce the risk of hip dislocation in at-risk patients. DM THRs have shown good overall survivorship and low rates of dislocation, however, the mechanisms which describe how these bearings function in-vivo are not fully understood. This is partly due to a lack of suitable characterisation methodologies which are appropriate for the novel geometry and function of DM polyethylene liners, whereby both surfaces are subject to articulation. This study aimed to develop a novel semi-quantitative geometric characterisation methodology to assess the wear/deformation of DM liners. METHODS. Three-dimensional coordinate data of the internal and external surfaces of 14 in-vitro tested DM liners was collected using a Legex 322 coordinate measuring machine. Data was input into a custom Matlab script, whereby the unworn reference geometry was determined using a sphere fitting algorithm. The analysis method determined the geometric variance of each point from the reference surface and produced surface deviation heatmaps to visualise areas of wear/deformation. Repeatability of the method was also assessed. RESULTS. Semi-quantitative analysis of the surface deviation heatmaps revealed circumferential damage patterns similar to those reported in the literature. Additionally, the location of the damaged regions corresponded between the internal and external surfaces. Comparing five repeat measurements of the same liner, the maximum geometric variance of each surface varied by 1 µm (standard deviation) suggesting a high repeatability of the method. CONCLUSIONS. This study presents an effective and highly repeatable characterisation methodology to semi-quantitatively assess the wear/deformation of in-vitro tested DM liners. This method is suitable for the analysis of retrieved DM liners whereby no pre-service information is available, which may provide information about the complex in-vivo kinematics and mechanical failure mechanisms of these bearings

Abstract. Objectives. Current use of hard biomaterials such as cobalt-chrome alloys or ceramics to articulate against the relatively soft, compliant native cartilage surface reduces the joint contact area by up to two thirds. This gives rise to high and abnormal loading conditions which promotes degradation and erosion of the mating cartilage leading to pain, stiffness, and loss of function. Biomimetic soft lubrication strategies have been developed by grafting hydrophilic polymers onto substrates to form a gel-type surface. Surface grafted gels mimic the natural mechanisms of friction dissipation in synovial joints, showing a promising potential for use in hemiarthroplasty. This project aims to develop implant surfaces with properties tailored to match articular cartilage to retain and promote natural joint function ahead of total joint replacement. Methods. Four different types of monomers were grafted in a one-step photopolymerisation procedure onto polished PEEK substrates. The functionalised surfaces were investigated using surface wettability, FTIR, and simplified 2D-tribometry tests against glass and animal cartilage specimens to assess their lubricity and mechanical properties for hemiarthroplasty articulations. Results. Polymer functionalised surfaces under different grafting conditions were assessed for their wettability, graft density and quality. A reduction in water contact angle from 90° to < 20° was seen for functionalised highly hydrophilic PEEK surfaces. Similarly a reduction in the coefficient of friction (and subsequently shear stresses acting on cartilage) of 95% to ∼ 10. −2. was seen for functionalised PEEK surfaces slid against glass and cartilage in PBS. Conclusions. Development of this technology has the potential to vastly improve the performance of hemiarthroplasty. Providing earlier and targeted interventions for degenerative joint disease whilst preserving the function of the remaining healthy cartilage. Future work will concern using these promising hydrated functionalised surface architectures as focal cartilage deflects plugs along with long-term performance and suitability for implantation assessments using joint simulator testing

Background. When reversing the hard-soft articulation in inverse shoulder replacement, i.e. hard inlay and soft glenosphere, the tribological behaviour of such a pairing has to be tested thoroughly. Therefore, two hard materials for the inlay, CoCr alloy and alumina toughened zirconia ceramic (ATZ) articulating on two soft materials, conventional UHMWPE and vitamin E stabilised, highly cross-linked PE (E-XLPE) were tested. Methods. The simulator tests were performed analogue to standardised gravimetric wear tests for hip prosthesis (ISO 14242-1) with load and motion curves adapted to the shoulder. The test parameters differing from the standard were the maximum force (1.0 kN) and the range of motion. A servo-hydraulic six station joint simulator (EndoLab, Rosenheim) was used to run the tests up to 5 times 106 cycles with diluted calf serum at 37° C as lubricant. Results. The wear rates measured in the simulator when the CoCr alloy inlay articulated on UHMWPE and E-XLPE were respectively 32.50 +/− 3.48 mg/Mcycle and 10.65 +/− 2.36 mg/Mcycle. In comparison, when the ATZ inlay articulated on UHMWPE and E-XLPE the wear rates were 20.34 +/− 1.14 mg/Mcycle and 5.99 +/− 0.79 mg/Mcycle respectively. Conclusions. The simulator wear rate of the standard articulation CoCr – UHMWPE is similar to that found in the corresponding pairing for hip endoprosthesis. Replacing UHMWPE by E-XLPE, the wear rate is reduced to about 1/3 for both hard counterparts, CoCr and ZTA, respectively. Replacing the CoCr inlay by a part made from ZTA lowers wear by about 37 % in articulation against UHMWPE and about 44 % against E-XLPE. The lowest wear rate, with a reduction of about 80 % compared to the standard CoCr – UHMWPE, exhibits the pairing of both advanced materials, ZTA – E-XLPE. However, long-term clinical follow-up will confirm if this in-vitro wear reduction leads to longer in-vivo survival. Level of evidence. Laboratory test on sample implants. Study financed by Mathys Orthopaedie GmbH

Knee arthroplasty with a rotating hinge knee (RHK) prosthesis has become an important clinical treatment option for knee revisions and primary patients with severe varus or valgus deformities and instable ligaments. The rotational axle constraints the anterior-posterior shear and varus-valgus moments, but currently used polyethylene bushings may fail in the mid-term due to insufficient creep and wear resistance of the material. Due to that carbon-fibre-reinforced (CFR) PEEK as an alternativ bushing material with enhanced creep, wear and fatigue behaviour has been introduced in a RHK design [Grupp 2011, Giurea 2014]. The objective of our study was to compare results from the pre-clinical biotribological characterisation to ex vivo findings on a series of retrieved implants. In vitro wear simulation according to ISO 14243-1 was performed on rotating hinge knee devices (EnduRo® Aesculap, Germany) made out of cobalt-chromium and of a ZrN multi-layer ceramic coating for 5 million cycles. The mobile gliding surfaces were made out of polyethylene (GUR 1020, β-irradiated 30 ± 2 kGy). For the bushings of the rotational and flexion axles and the flanges a new bearing material based on CFR-PEEK with 30% PAN fiber content was used. Analysis of 12 retrieved EnduRo. ®. RHK systems in cobalt-chromium and ZrN multi-layer in regard to. -. loosening torques in comparison with initial fastening torques. -. Optical, DSLR camera and stereo light microscope analysis. -. distinction between different wear modes and classification with a modified HOOD-score. -. SEM & EDX of representative samples. -. surface roughness and depth profilometry. with a focus on the four CFR-PEEK components integrated in the EnduRo. ®. RHK design. For the rotating hinge knee design with flexion bushing and flanges out of CFR-PEEK the volumetric wear rates were 2.3 ± 0.48 mm. 3. /million cycles (cobalt-chromium) and 0.21 ± 0.02 mm. 3. /million cycles (ZrN multi-layer), a 10.9-fold reduction (p = 0.0016). The UHMWPE and CFR-PEEK particles were comparable in size and morphology and predominantly in submicron size [5]. The biological response to representative sub-micron sized CFR-PEEK particles has been demonstrated in vivo based on the leucoyte-endothelian-cell interactions in the synovia of a murine intra-articular knee model by Utzschneider 2010. Schwiesau 2013 extracted the frequency of daily activities in hip and knee replacement patients from literature and estimated an average of 1.76 million gait cycles per year. Thus, the 5 million cycles of in vitro wear testing reflect a mean in vivo service life of 2.9 years, which fits to the time in vivo of 12–60 months of the retrieved RHK devices. The in vitro surface articulation pattern of the wear simulation tests are comparable to findings on retrieved CFR-PEEK components for both types of articulations – cobalt-chromium and ZrN multi-layer coating. For the rotating hinge knee design the findings on retrieved implants demonstrate the high suitability of CFR-PEEK as a biomaterial for highly loaded bearings, such as RHK bushings and flanges in articulation to cobalt-chromium and to a ZrN multi-layer coating

No therapeutic strategy, administered in the early stage of osteoarthritis (OA), is fully able to block the degenerative and inflammatory progress of the pathology, whose only solution remains surgery. Aiming to identify minimally invasive therapies able to act on both degenerative and inflammatory processes, infiltrative treatments based on mesenchymal stem cells represent a promising solution due to their proliferative, immunomodulatory, anti-inflammatory, and paracrine ability. Accordingly, the aim of the present study was to investigate the performance of different cell therapies (stem cells from adipose tissue, ADSCs, stromal vascular fraction, SVF, and culture expanded, AECs vs negative control NaCl) in the treatment of OA. An in vivo model of early OA was developed in sheep knee (research protocol N.62/2018-PR date 29/01/2018 approved by the local Ethical Committee). Three and six months after the treatments injections, gross evaluation of articular surfaces (damage score, DS), histological (cartilage thickness, Th; fibrillation index, FI; collagen II content, C2) and mechanical assessment (elastic modulus, E; stress-relaxation time, τ) of cartilage were carried out. Due to the importance of the relationship between structure/composition (histology) and function (mechanics), this study investigated which of the revealed parameters were involved in such relation and how they were influenced by the level of degeneration and by the specific cell treatment, thus to better understand cell-tissue interaction. A statistically significant multi-variable linear regression model was found between τ and Th, FI, C2 (R2 0.7, p-value 8.39E-5). The relation was particularly strong between τ and C2 (p-value 7E-4), with a positive coefficient of 0.92. This is in agreement with literature, where a higher cartilage viscosity was related to a major content of collagen. By dividing the samples in two groups depending on cartilage damage, the more degenerated group (DS > 5) showed statistically significant lower C2 (p-value 0.0124) and τ (p-value 0.05), confirming that collagen content and viscosity decrease with OA grade increasing. Averaging the entire group of samples, the OA degeneration progressed between 3 and 6 months after, and despite, the treatment. But focusing on specific treatments, SVF and AECs differed from the general trend, inducing a higher amount of collagen at 6 months respect to 3 months. Moreover, articular cartilage treated by AECs and, overall, SVF showed a higher content of collagen and a major viscosity respect to the other treatments. We conclude that an injection of mesenchymal stem cells from stromal vascular fraction in early OA articulations could hinder the degenerative process, preserving or even restoring collagen content and viscosity of the articular cartilage

An increase in metal ion levels is seen after implantation of all MoM hip prosthesis due to release from the surface directly, more so during articulation and corrosion of the bearing surfaces. The bearing surfaces in MoM prosthesis consist of cobalt, chromium and molybdenum. Several case-reports of cobalt toxicity due to a MoM prosthesis have been published in the last decade. Cobalt intoxication may lead to a variety of symptoms: neuro-ocular toxicity (tinnitus, vertigo, deafness, blindness, convulsions, headaches and peripheral neuropathy), cardiotoxicity and thyroid toxicity. Nausea, anorexia and unexplained weight loss have been described. Systemic effects from metal ions even with well functioning implants or with ion concentrations lower than those associated with known adverse effects may exist and warrant investigation. The aim of this study is to investigate self-reported systemic complaints in association with cobalt ion concentrations in patients with any type of MoM hip prosthesis. A cohort study was conducted. Patients with both unilateral and bilateral, resurfacing and large head metal on metal total hip arthroplasties were included for the current study. Blood metal ion concentrations (cobalt and chromium) were measured by inductively coupled plasma mass spectrometry (ICP-MS). Based on the known cobalt toxicity symptoms of case-reports and toxicology reports a new non-validated questionnaire was developed. questions were subdivided in general questions/symptoms, vestibular symptoms, neurological symptoms, emotional health and cardio- and thyroid toxicity symptoms. Independent samples T test, Fishers Exact Test and Pearsons (R) correlation were used. Analysis was performed on two groups; a low cobalt ion concentration group and a high cobalt ion concentration group A total of 62 patients, 36 (58%) men and 26 (42%) women, were included with a mean age at surgery of 60.8 ± 9.3 years (41.6 – 78.1) and a mean follow up of 6.3 ± 1.4years (3.7 – 9.6). In these patients a total of 71 prosthesis were implanted: 53 unilateral and 9 bilateral. Of these, 44 were resurfacing and 27 large head metal on metal (LHMoM) total hip arthroplasties. Mean cobalt and chromium ion concentrations were 104 ± 141 nmol/L (9 – 833) and 95 ± 130nmol/L (6 – 592), respectively. Based on the different thresholds (120 – 170 or 220 nmol/L) the low cobalt ion concentration group consisted of 44 (71%), 51 (82%) or 55 (89%) subjects respectively. No differences were found in general characteristics, independently of the threshold. The composite score of vestibular symptoms (vision, hearing, tinnitus, dizziness) was significantly higher (p < .050) in all high cobalt ion concentrations groups, independent of the threshold value This study aimed to detect a trend in self-reported systemic complaints in patients with metal-on-metal hip arthroplasty due to raised cobalt ion concentrations. Vestibular symptoms were more common in high cobalt ion concentration groups independent of the three threshold levels tested. The upper limit of acceptable cobalt ion concentrations remains uncertain. With regards to proactively inquired, self-reported symptoms the threshold where effects may be present could be lower than values currently applied in clinical follow-up. It is unknown what exposure to elevated metal ion concentrations for a longer period of time causes with aging subjects. Further research with a larger cohort and a more standardized questionnaire is necessary to detect previously undiscovered or under-reported effects