Introduction. Previous studies of retrieved CoCr alloy femoral heads have identified imprinting of the stem taper surface features onto the interior head bore, leading researchers to hypothesize that stem taper microgrooves may influence taper corrosion. However, little is known about the role of stem taper surface morphology on the magnitude of in vivo corrosion damage. We designed a matched cohort retrieval study to examine this issue. Methods. From a multi-institutional retrieval collection of over 3,000 THAs, 120 femoral head-stem pairs were analyzed for evidence of fretting and corrosion using a visual scoring technique based on the severity and extent of fretting and corrosion damage observed at the taper. A matched cohort design was used in which 60 CoCr head-stem pairs with a smooth stem taper were matched with 60 CoCr head-stem pairs having a micro-grooved surface, based on implantation time, flexural rigidity, apparent length of taper engagement, and head size. This study was adequately powered to detect a difference of 0.5 in corrosion scores between the two cohorts, with a power of 82% and 95% confidence. Both cohorts included CoCr and Ti-6-4 alloy femoral stems. A high precision roundness machine (Talyrond 585, Taylor Hobson, UK) was used to measure surface morphology and categorize the stem tapers into smooth vs. micro-grooved categories. Fretting and corrosion damage at the head/neck junction was characterized using a modified semi-quantitative adapted from the Goldberg method by three independent observers. This method separated corrosion damage into four visually determined categories: minimal, mild, moderate and severe damage. Results. Mild to severe damage (Fretting Corrosion Score ≥ 2) was observed in 75% of the 120 CoCr femoral heads (78% of the heads mated with micro-grooved stems (47/60), Fig. 1A) and 72% of the heads mated with smooth stems (43/60, Fig 1B). Fretting and corrosion damage was not significantly different between the two cohorts when evaluated at the CoCr femoral head bore (p =0.105, Mann Whitney test, Fig. 2A) or the male stem tapers (p =0.428, Fig. 2B). No implant or patient factors were associated with fretting corrosion; corrosion scores were not significantly associated with stem alloy in the two cohorts (p=0.669, Mann-Whitney test). Discussion. The results of this matched cohort retrieval study do not support the hypothesis that taper surfaces with micro-grooved stems exhibit increased in vivo fretting corrosion. We accounted for implant, patient, and clinical factors that may influence in vivo taper corrosion with the matched cohort design and by post hoc statistical analyses. However, this study is limited by the semi-quantitative method used for evaluating damage in these components. Therefore, additional research will be necessary to quantify the volume of metal release from these two cohorts. To view tables/figures, please contact authors directly

Introduction. Three-dimensional (3D) printing of porous titanium implants marks a revolution in orthopaedics, promising enhanced bony fixation whilst maintaining design equivalence with conventionally manufactured components. No retrieval study has investigated differences between implants manufactured using these two methods. Our study was the first to compare these two groups using novel non-destructive methods. Materials and methods. We investigated 16 retrieved acetabular cups divided into ‘3D printed’ (n = 6; Delta TT) and ‘conventional’ (n = 10; Pinnacle Porocoat). The groups were matched for age, time to revision, size and gender (Table 1). Reasons for revision included unexplained pain, aseptic loosening, infection and ARMD. Visual inspection was performed to evaluate tissue attachment. Micro-CT was used to assess clinically relevant morphometric features of the porous structure, such as porosity, depth of the porous layer, pore size and strut thickness. Scanning electron microscopy (SEM) was applied to evaluate the surface morphology. Results. Significant differences (p = 0.0002) were found for all morphometric parameters (Table 2). Microscopic analysis revealed uniform beads over the backside of conventional implants, due to the manufacturing technique (Figure 1a). Conversely, beads of random size were found on 3D printed implants, representing a by-product of the manufacturing process, where some starting powder particles are not completely fused together (Figure 1b). The two groups showed similar tissue attachment (3D printed 76.9 ± 27.1%; conventional 73.8 ± 12.2%; p = 0.2635). Conclusion. This was the first study to analyse retrieved 3D printed orthopaedic implants. Differences were found between these and conventional implants, but both literature and registry data do not suggest a short-mid-term clinical issue with 3D printed components. Similar tissue on growth suggested a comparable behaviour with bone in situ. The key difference is the presence of the particles on 3D printed implants, whose clinical significance needs to be investigated. For any figures or tables, please contact the authors directly

Purpose: This study was designed to establish the poly-ethylene wear rates in the Oxford medial unicompert-mental knee replacement. Introduction: The Oxford meniscal bearing knee was introduced as a design to reduce polyethylene wear. There has been one previous retrieval study of the Oxford UKA, which reported very low wear rates in some specimens, but abnormal patterns of wear in others, including impingement. There has been no further investigation of these abnormal wear patterns. Methods: Forty-seven bearings were retrieved from patients who had received a medial Oxford UKA for anteromedial osteoarthritis of the knee, none of which had previously been studied. Mean time to revision was 8.4 years (SD 4.1) and 20 had been implanted for over 10 years. The macroscopic pattern of polyethylene wear and the linear penetration (dial gauge measurement) was recorded for each bearing. Results: The mean linear penetration rate (LPR) was 0.07mm/year. The patterns of wear fell into 4 categories, each with a different LPR; 1) No abnormal macroscopic appearance, n=16 (LPR = 0.01mm/year), 2) Abnormal macroscopic wear with extra-articular impingement, n=16 (LPR = 0.05mm/year), 3) Abnormal macroscopic wear with intra-articular impingement, n=6 (LPR = 0.10mm/year), 4) Abnormal macroscopic wear with impingement and signs of incongruous articulation, n=9 (LPR = 0.14mm/year). The differences in LPR were statistically significant (p< 0.05). Conclusion: The results show that very low polyethylene wear rates are possible if the device functions normally. However if the bearing displays abnormal function (extra-articular, intra-articular impingement or incongruous articulation) wear rates increase significantly

One of important issues of concern in total hip arthroplasty (THA) is osteolysis due to wear debris of ultra-high molecular weight polyethylene (PE), and it often leads to aseptic loosening. Reduction of PE wear debris is essential to prevent osteolysis, and different bearing interfaces as well as improvement of the bearing material itself have been attempted. Alumina ceramics as the bearing material for THA was introduced in Europe and Japan in the 1970s in aim to reduce the PE wear debris. The clinical results have proved the superiority of ceramic on PE couples to metal on PE couples in wear resistance. PE materials cross-liked by irradiation have also demonstrated a significant low wear by in vitro studies. Several types of highly cross-linked polyethylene (CLPE), with the irradiation dose of 50 to 105 kGy, have been developed and extensively used since 1998. In this study, the in vivo wear and oxidation of CLPE acetabular cup combined with ceramic femoral head were evaluated using retrieved cups. Eight retrieved CLPE acetabular cups (Aeonian; Kyocera Corp., Kyoto, Japan, currently Japan Medical Materials Corp., Osaka, Japan) with clinical use for 3–80 months (mean 34 months) were examined. All cups were used against alumina or zirconia ceramic femoral heads. The linear wear of the retrieved CLPE cups was measured using a three-dimensional coordinate measurement machine. The worn surfaces of retrieved CLPE cups were observed by a scanning electron microscope (SEM). Oxidative degradation of the retrieved CLPE cups was expressed in terms of an oxidation index which was calculated from microscopic Fourier transformed infrared spectroscopy analysis, according to ASTM F2102. The linear wear rate of retrieved CLPE cups was in 0.006–0.08 mm/year range, which was similar to the results reported by the previous radiographic study. In the worn surface of the CLPE cup retrieved after clinical use shorter than 39 months, machine marks were observed. In contrast, those retrieved after clinical use of 70 and 80 months were smooth. Oxidation indices of retrieved CLPE cups were: 0.12–0.37 in worn surface and 0.13–0.34 in unworn surface, respectively. There was no difference in the oxidation indices between the worn surface and unworn surface. The retrieved CLPE acetabular cups in this study showed low and stable wear rates. The results showed a notable reduction in wear of the CLPE cups compared to that of conventional PE cups in the previous studies. And also, the oxidation indices of the retrieved CLPE cups were the same level as conventional PE cups. These findings from this retrieval study showed that there is neither progressive wear in the clinical use for 3–80 months, material failures due to wear, delamination nor cracks. The lower wear rate and smooth surface of the CLPE acetabular cup suggest the possibility of reduced wear debris from those cups articulated against the ceramic femoral head. We expect that the CLPE acetabular cup has favorable wear properties in long-term clinical use

Hemi shoulder arthroplasty is an attractive treatment for shoulder arthritis in particular if the natural glenoid is still intact. However, comparing the clinical results of hemi and total shoulder arthroplasty clearly shows lower survival for the hemi arthroplasty. One of the most common reasons for revision surgery is gleniod erosion, where the cartilage or bone is worn of. Aim of the current study was to analyse if the metallic articular surface of retrieved hemi shoulder arthroplasty is different from new implants. We hypothesized that the surface roughness will increased due the articulation and that metallic wear is detectable on the implants. Twelve retrieved and three brand new hemi shoulder arthroplasty were included. The surface roughness (Ra, Rz, Rmax, Rsk) was measured on different sites of the surface (center of the head and at the edge). The implants were further measured using a coordinate measuring machine to gain information on volumetric wear and geometrical alterations.

Compared to new implants the surface roughness on the retrievals was significantly increased (Tab. 1), except for skewness.

Although the roughness parameters within the retrieval group were generally higher at the center of the head compared to the edge, this difference was not significant. Apart from form deviations no volumetric wear was detectable on the heads (Fig. 1).

The current results indicate that the metallic articular implant surface changes in vivo and that the material is hurt due to the articulation against the softer cartilage or bone. Although it can't be finally clarified by that study, to what extend the higher roughness is taking part in the process of the clinically observed erosion of the gleniod, it can be assumed that an increased roughness is disadvantageous. Possibly, the observed surface alterations won't occur clinically with harder materiel (e.g. ceramic), but this even needs to be validated.

Introduction

This study was performed to investigate the failure mechanism of one specific hip arthroplasty cup design that has shown a high clinical failure rate. The aim of this study was to identify general design problems of this polyethylene inlay.

Introduction

During revision surgery with a well-fixed stem, a titanium sleeve can be used in conjunction with a ceramic head to achieve better stress distribution across the taper surface. Previous studies have observed that the use of a ceramic head can mitigate the extent of corrosion damage at the taper. Moreover, in vitro testing suggests that corrosion is not a concern in sleeved ceramic heads [1]; however, little is known about the in vivo fretting corrosion of the sleeves. The purpose of this study was to investigate fretting corrosion in sleeved ceramic heads.

Introduction

Contemporary total knee systems accommodate for differential sizing between femoral and tibial components to allow surgeons to control soft tissue balancing and optimize rotation. One method some manufacturers use to allow differential sizing involves maintaining coronal articular congruency with a single radius of curvature throughout sizes while clipping the medial-lateral width, called a single coronal geometry system. Registry data show a 20% higher revision rate when the tibial component is smaller than the femur (downsizing) in the DePuy PFC system, a single coronal system, possibly from increased stresses from edge loading or varying articular congruency. We examined a different single coronal geometry knee system, Smith & Nephew Genesis II, to determine if edge loading is present in downsized tibial components by measuring area and location of deviation of the polyethylene articular surface damage.

Summary

Fifteen irradiated, vitamin E-diffused UHMWPE retrievals with up to three years in vivo service showed no appreciable oxidation, nor change in material properties from a never-implanted liner, and showed a 94% decrease in free radical content.

We have examined 26 retrieved, failed titanium-alloy femoral stems. The clinical details, radiological appearances and the histology of the surrounding soft tissues in each patient were also investigated.

The stems were predominantly of the flanged design and had a characteristic pattern of wear. A review of the radiographs showed a series of changes, progressive with time. The first was lateral debonding with subsidence of the stem. This was followed by calcar resorption and fragmentation or fracture of the cement. Finally, osteolysis was seen, starting with a radiolucency at the cement-bone interface and progressing to endosteal cavitation.

Three histological appearances were noted: granulomatous, necrobiotic and necrotic. We suggest that an unknown factor, possibly related to the design of the stem, caused it to move early. After this, micromovement at the cement-stem interface led to the generation of particulate debris and fracture of the cement. A soft-tissue reaction to the debris resulted in osteolysis and failure of fixation of the prostheses.

The causes of mechanical failure of five noncemented porous-coated components were studied. There were two cobalt-chromium alloy and three titanium alloy implants which fractured after 12 to 48 months. The implants included one acetabular component, and one femoral condylar, one patellar and two tibial components. Examination of the fractured surfaces revealed fatigue to be the mechanism of failure in all cases. The porous coating and the processes required for its fabrication had resulted in weakening and reduction of substrate thickness. Additional factors were stress concentration due to limited, localised bone ingrowth, and some features of the design of the implants.

Introduction

Coronal plane alignment is one of the contributing factors to polyethylene wear in total knee arthroplasty (TKA). The goal of this study was to evaluate the wear and damage patterns of retrieved tibial polyethylene inserts in relationship to the overall mechanical alignment and to the position of the tibial component.

Background:

Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads.

The PowerPoint (2007 Version; Microsoft, Redmond, Wash) method is reported to have improved repeatability and reproducibility and is better able to detect differences in radiographs than previously established manual wear measurement methods. In this study, the PowerPoint method and the Dorr and Wan method were used to calculate the polyethylene liner wear volume. The wear volumes of retrieved polyethylene liners calculated from the 3D laser scanning method were compared with each method. This study hypothesized that the wear volume calculated by the PowerPoint method would correlate well with the wear volume measured by 3D laser scanning method.

Between March 2004 and June 2009, 22 polyethylene liners from 20 patients were collected during revision Total hip arthroplasty(THA). Exclusion criteria included (1) missing an early primary postoperative radiograph or prerevision radiograph, (2) evidence of acetabular loosening or migration, (3) existence of significant mismatch between early primary postoperative radiograph and prerevision radiographs on vertical axis, and (4) liner wear-through. After applying these exclusion criteria, 17 retrieved polyethylene liners from 16 patients were included in this study. Wear volumes were calculated using the PowerPoint, the Dorr and Wan methods by 3 independent experienced observers who were unaware of the study design, and 3-dimensional (3D) laser scanning methods.

Spearman correlation coefficients for wear volume results indicated strong correlations between the PowerPoint and 3D laser scanning methods (range, 0.89–0.93). On the other hand, Spearman correlation analysis revealed only moderate correlations between the Dorr and Wan and 3D laser scanning methods (range, 0.67–0.77).

The PowerPoint method is an efficient tool for the sequential radiologic follow-up of patients after THA. The PowerPoint method can be used to monitor linear wear after THA and could serve as an alternative method when computerized methods are not available.

INTRODUCTION:

Clinical densitometry studies indicate that following TKR implantation there is loss of bone mineral density in regions around the implant. Bone density below the tibial tray has been reported to decrease 36% at eight years after TKR. This bone loss (∼5%/year) is substantially greater than osteoporosis patients in the same age group (∼1–2%/year) and could contribute the loss of mechanical support provided by the peri-implant leading to loosening of components in the long term. High patient mass and body mass index have also been implicated in increased loosening rates, and was thought to be due to high stress or strain on the tibial constructs. These findings suggest that peri-implant bone strain may be affected by time in service and patient factors such as body mass.

The goal of this project was to assess the proximal tibial bone strain with biomechanical loading using en bloc retrieved TKR tibial components. Note that the implants were not obtained from revision surgery for a loose implant, but rather after death; thus the implants can be considered to be successful for the lifetime of the patient. We asked two research questions, guided by the clinical and laboratory observations: (1) are the peri-implant bone strain magnitudes for cemented tibial components greater for implants with more time in service and from older donors?, (2) is tibial bone strain greater for constructs from donors with high body weight and lower peri-implant BMD?

The early failure and revision of bimodular primary total hip arthroplasty prostheses requires the identification of the risk factors for material loss and wear at the taper junctions through taper wear analysis. Deviations in taper geometries between revised and pristine modular neck tapers were determined using high resolution tactile measurements. A new algorithm was developed and validated to allow the quantitative analysis of material loss, complementing the standard visual inspection currently used.

The algorithm was applied to a sample of 27 retrievals (in situ from 2.9 to 38.1 months) of the withdrawn Rejuvenate modular prosthesis. The mean wear volumes on the flat distal neck piece taper was 3.35 mm³ (0.55 to 7.57), mainly occurring in a characteristic pattern in areas with high mechanical loading. Wear volume tended to increase with time to revision (r² = 0.423, p = 0.001). Implant and patient specific data (offset, stem size, patient’s mass, age and body mass index) did not correlate with the amount of material loss observed (p >  0.078). Bilaterally revised implants showed higher amounts of combined total material loss and similar wear patterns on both sides. The consistent wear pattern found in this study has not been reported previously, suggesting that the device design and materials are associated with the failure of this prosthesis.

Cite this article: Bone Joint J 2015;97-B:1350–7.

Introduction: Metal on metal hip resurfacing arthroplasty-induced pseudotumours are a serious complication, which occur in 1.8% of patients who undergo this procedure in our institution. The aim of this study was to measure the 3D in vivo wear on the surface of resurfacing components revised for pseudotumour, compared to a control group.

Method: Thirty-six hip resurfacing implants were divided into two groups; 18 patients with a clinical and histopathological diagnosis of pseudotumour and 18 controls (revised for femoral neck fracture and infection). Three dimensional contactless metrology (Redlux^™ Ltd) was used to scan the surface of the femoral and acetabular components, to a resolution of 20 nanometers. The location, depth and area of the wear scar were determined for each component. A separate blinded analysis to determine the presence of absence of impingement was performed by one of the authors.

Results: The volumetric wear rate for femoral component of the pseudotumour group was 3.29 mm3/yr (SD5.7) and 0.79 mm3/yr (SD1.2) for the control group (p=0.005). In the pseudotumour group, the volumetric wear rate of the acetabular component was 2.5 mm3/yr (SD6.9) compared to 0.36 mm3/yr (SD0.80) for the control group (p=0.008). Edge-wear was detected in 89% of acetabular components in the pseudotumour group and 21% of those in the control group (p=0.01). Anterior or posterior edge-wear, consistent with impingement was present on the femoral components of 73% of patients in the pseudotumour group and 22% in the control group (p=0.01).

Discussion: This work demonstrates that implants revised for pseudotumour have significantly higher volumetric wear rates than controls. They also have a significantly higher incidence of edge-wear than controls. We suggest that a significant proportion of pseudotumours are associated with high concentrations of metal wear debris; however a minority may result from a hypersensitivity reaction to metal ions.

Aims

We sought to establish whether an oxidised zirconium (OxZr) femoral component causes less loss of polyethylene volume than a cobalt alloy (CoCr) femoral component in total knee arthroplasty.

Four low-cost hip prostheses, explanted because of clinical failure within three years, were subjected to a retrieval analysis study to determine the cause of the early failure. The study aimed to determine whether the low-cost prosthesis was substandard and had consequently contributed to the need for early revision. The retrieval analysis included a photographic record, a fractographic examination, an analysis of the material composition of the components, and a mechanical property analysis. These investigations were done in accordance with the ASTM F561 standards. Results demonstrated substandard qualities in respect of all parameters analysed. We conclude that the inferior quality of these low-cost hip prostheses contributed appreciably to their early failure and revision

Introduction: Periprosthetic fractures have long been recognized as one of the major complications after hip resurfacing arthroplasty. Both biomechanical factors and pathological changes of bone tissue might hypothetically influence its occurrence. We analyzed retrieved femoral remnants to identify possibly different fracture modes.

Material and Methods: 83 hips revised for periprosthetic fracture (134.5 days in situ±159.2) were analyzed macroscopically, contact radiographically and histologically. Most cases (80.7%) were treated for advanced stages of osteoarthritis. Hips with preoperative femoral head necrosis were not included. 49 (59.0%) patients were men (57.8 years old±8.5) and 34 (41.0%) women (55.1 years old±10.0; p=.3445). Occurrence of reactive changes and of avascular necrosis in addition to amount of osteonecrosis were used as the major histological criteria for classification of the fracture as acute biomechanical, acute postnecrotic or chronic.

Statistical analyses were performed using statistical software. Probability of Type I error was set to 5% (alpha=0.05).

Results: 37 (44.6%) femoral neck fractures (83.9 days±87.7) occurred earlier than the remaining 46 (55.4%) head fractures (174.1 days±89.7; p=.0129). 50(60.2%) remnants revealed complete osteonecrosis and were thus classified as acute postnecrotic fractures, 29 (34.9%) chronic fractures were characterized by finding of pseudoarthrosis or preformed callus and the remaining 4 (4.8%) were classified as acute mechanic. Acute mechanic fractures (17.5 days±8.0) failed earlier than both acute postnecrotic (146.3 days±181.7; p=.0049) and chronic (130.8 days±120.6; p=.0017) fractures.

Osteonecrosis was found in 81 (97.6%) hips revised after fracture (p< .0001). The vertical size of avascular necrosis in hips after acute postnecrotic fracture (21.1mm±8.5) was bigger (p< .0001) than in both chronic (7.3mm±7.3) and acute mechanic (0.9 mm±1.2) fractures.

Even though 33 (66.0%) of 50 patients with acute postnecrotic fracture were men (p=.0237), no significant differences between males and females were found with respect to age of patients (p=.3445) or duration of prosthesis implantation (p=.1232).

Conclusion: We analyzed hips revised for periprosthetic fracture after the resurfacing arthroplasty. Three distinct fracture modes of this complication could have been identified morphologically. Osteonecrosis secondary to the hip resurfacing arthroplasty appeared to be causative for more than a half of all fractures in present cohort. Mechanical and biomechanical factors related to the procedure might have possibly influenced the occurrence of both postnecrotic fractures and cases with vital reactive changes of tissues neighbouring the fracture line.

The proposed classification may help to understand causes of periprosthetic fractures after hip resurfacing arthroplasty.