Reference values for volume, fat content and shape of the hip abductor muscles in healthy individuals from Dixon MRI.

Healthy hip abductor muscles are a good indicator of a healthy hip and an active lifestyle, as they are greatly involved in human daily activities. Fatty infiltration and muscle atrophy are associated with loss of strength, loss of mobility and hip disease. However, these variables have not been widely studied in this muscle group. We aimed to characterize the hip abductor muscles in a group of healthy individuals to establish reference values for volume, intramuscular fat content and shape of this muscle group. To achieve this, we executed a cross-sectional study using Dixon MRI scans of 51 healthy subjects. We used an automated segmentation method to label GMAX, GMED, GMIN and TFL muscles, measured normalized volume (NV) using lean body mass, fat fraction (FF) and lean muscle volume for each subject and computed non-parametric statistics for each variable grouped by sex and age. We measured these variables for each axial slice and created cross-sectional area and FF axial profiles for each muscle. Finally, we generated sex-specific atlases with FF statistical images. We measured median (IQR) NV values of 12.6 (10.8-13.8), 6.3 (5.6-6.7), 1.6 (1.4-1.7) and 0.8 (0.6-1.0) cm3 /kg for GMAX, GMED, GMIN and TFL, and median (IQR) FF values of 12.3 (10.1-15.9)%, 9.8 (8.6-11.2)%, 10.0 (9.0-12.0)% and 10.2 (7.8-13.5)% respectively. FF values were significantly higher for females for the four muscles (p < 0.01), but there were no significant differences between the two age groups. When comparing individual muscles, we observed a significantly higher FF in GMAX than in the other muscles. The reported novel reference values and axial profiles for volume and FF of the hip abductors, together with male and female atlases, are tools that could potentially help to quantify and detect early the deteriorating effects of hip disease or sarcopenia.

What happens to the lower lumbar spine after marathon running: a 3.0 T MRI study of 21 first-time marathoners.

OBJECTIVE: To better understand the impact of long-distance running on runners' lumbar spines by assessing changes before and after their first marathon run. MATERIALS AND METHODS: The lumbar spines of 28 asymptomatic adults (14 males, 14 females, mean age: 30 years old), who registered for their first marathon, the 2019 London Richmond Marathon, were examined 16 weeks before (time point 1) and 2 weeks after (time point 2) the marathon. Participants undertook a pre-race 16-week training programme. Magnetic resonance imaging (MRI) of high-resolution 3.0 Tesla was used at each time point. Senior musculoskeletal radiologists assessed the lower lumbar spine condition. RESULTS: Out of 28 participants, 21 completed both the training and the race and 7 neither completed the training nor started the marathon but not due to spine-related issues. At time point 1, disc degeneration was detected in 17/28 (61%), most predominantly at spinal segments L4-L5 and L5-S1. No back pain/other symptoms were reported. When compared to time point 2, there was no progression in the extent of disc degeneration, including intervertebral disc (IVD) height (p = 0.234), width (p = 0.359), and intervertebral distance (p = 0.641). There was a regression in 2 out of 8 (25%) participants who had pre-marathon sacroiliac joint bone marrow oedema, and a small increase in the size of a pre-marathon subchondral cyst in one participant, all asymptomatic. CONCLUSION: Running 500 miles over 4 months plus a marathon for the first time had no adverse effects on the lumbar spine, even when early degenerative changes were present. Additionally, there was evidence of regression of sacroiliac joint abnormalities.

Reconstruction of acetabular defects greater than Paprosky type 3B: the importance of functional imaging.

BACKGROUND: 3D Surgical planning has become a key tool in complex hip revision surgery. The restoration of centre of rotation (CoR) of the hips and leg length (LL) are key factors in achieving good clinical outcome. Pelvic imaging is the gold standard for planning and assessment of LL. We aimed to better understand if 3D planning is effective at equalising LL when large acetabular defects are present. MATERIALS AND METHODS: This was a prospective case study of 25 patients. We report the analysis of pre-operative LL status and planned LL restoration measured on CT, in relation to the achieved LL measured post-operatively in functional, weight bearing position. Our primary objective was the assessment of restoration of CoR as well as the anatomical and functional LL using biplanar full-length standing low-dose radiographs; our secondary objective was to evaluate the clinical outcome. RESULTS: Pre-operative intra-pelvic discrepancy between right and left leg was a mean of 28 mm (SD 17.99, min = 3, max = 60 mm). Post-operatively, the difference between right and left vertical femoral offset (VFO), or CoR discrepancy, was of 7.4 mm on average, significantly different from the functional LL discrepancy (median = 15 mm), p = 0.0024. Anatomical LLD was a median of 15 mm. In one case there was transient foot drop, one dislocation occurred 6 months post-operatively and was treated by closed reduction, none of the patients had had revision surgery at the time of writing. Mean oxford hip score at latest follow up was 32.1/48. DISCUSSION: This is the first study to investigate limb length discrepancy in functional position after reconstruction of large acetabular defects. We observed that VFO is not an optimal surrogate for LL when there is significant bone loss leading to length inequality, fixed flexion of the knee and abduction deformity. CONCLUSIONS: Although challenging, LLD and gait abnormalities can be greatly improved with the aid of an accurate surgical planning. Surgeons and engineers should consider the integration of EOS imaging in surgical planning of reconstruction of large acetabular defects.

Mechanical wear analysis helps understand a mechanism of failure in retrieved magnetically controlled growing rods: a retrieval study.

BACKGROUND: To assess the relationship between mechanical wear and the failure of the internal lengthening mechanism in retrieved MAGnetic Expansion Control (MAGEC) growing rods. METHODS: This study included 34 MAGEC rods retrieved from 20 patients. The state of the internal mechanism and mechanical wear were assessed in all the rods using plain radiographs and visual inspection. Metrology was then performed to assess the topography and mechanical wear of the telescopic bars, using a Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine. RESULTS: Plain radiographs showed evidence of a broken internal mechanism in 29% of retrieved rods. Single-side wear marks were found in 97% of retrieved rods. Material loss was found to significantly increase in rods with a damaged internal mechanism (p < 0.05) and rods with longer time in situ (r = 0.692, p < 0.05). CONCLUSIONS: We found an association between damage to the internal mechanism of the rods and (1) patterns of single-side longitudinal wear marks and (2) increased material loss. As the material loss was also found to increase over time of rod in situ, we emphasise the importance of early detection and revision of failed MAGEC rods in clinical practice.

Prevalence of abnormal findings in 230 knees of asymptomatic adults using 3.0 T MRI.

OBJECTIVE: To identify abnormalities in asymptomatic sedentary individuals using 3.0 Tesla high-resolution MRI. MATERIALS AND METHODS: The cohort comprised of 230 knees of 115 uninjured sedentary adults (51 males, 64 females; median age: 44 years). All participants had bilateral knee 3.0 T MRIs. Two senior musculoskeletal radiologists graded all intraarticular knee structures using validated scoring systems. Participants completed Knee Injury and Osteoarthritis Outcome Score questionnaires at the time of the MRI scan. RESULTS: MRI showed abnormalities in the majority (97%) of knees. Thirty percent knees had meniscal tears: horizontal (23%), complex (3%), vertical (2%), radial (2%) and bucket handle (1%). Cartilage and bone marrow abnormalities were prevalent at the patellofemoral joint (57% knees and 48% knees, respectively). Moderate and severe cartilage lesions were common, in 19% and 31% knees, respectively, while moderate and severe bone marrow oedema in 19% and 31% knees, respectively. Moderate-intensity lesion in tendons was found in 21% knees and high-grade tendonitis in 6% knees-the patellar (11% and 2%, respectively) and quadriceps (7% and 2%, respectively) tendons being most affected. Three percent partial ligamentous ruptures were found, especially of the anterior cruciate ligament (2%). CONCLUSION: Nearly all knees of asymptomatic adults showed abnormalities in at least one knee structure on MRI. Meniscal tears, cartilage and bone marrow lesions of the patellofemoral joint were the most common pathological findings. Bucket handle and complex meniscal tears were reported for the first time in asymptomatic knees.

Is the immediate effect of marathon running on novice runners' knee joints sustained within 6 months after the run? A follow-up 3.0 T MRI study.

OBJECTIVE: To evaluate changes in the knee joints of asymptomatic first-time marathon runners, using 3.0 T MRI, 6 months after finishing marathon training and run. MATERIALS AND METHODS: Six months after their participation in a baseline study regarding their knee joints, 44 asymptomatic novice marathoners (17 males, 27 females, mean age 46 years old) agreed to participate in a repeat MRI investigation: 37 completed both a standardized 4-month-long training programme and the marathon (marathon runners); and 7 dropped out during training (pre-race dropouts). The participants already underwent bilateral 3.0 T MRIs: 6 months before and 2 weeks after their first marathon, the London Marathon 2017. This study was a follow-up assessment of their knee joints. Each knee structure was assessed using validated scoring/grading systems at all time points. RESULTS: Two weeks after the marathon, 3 pre-marathon bone marrow lesions and 2 cartilage lesions showed decrease in radiological score on MRI, and the improvement was sustained at the 6-month follow-up. New improvements were observed on MRI at follow-up: 5 pre-existing bone marrow lesions and 3 cartilage lesions that remained unchanged immediately after the marathon reduced in their extent 6 months later. No further lesions appeared at follow-up, and the 2-week post-marathon lesions showed signs of reversibility: 10 of 18 bone marrow oedema-like signals and 3 of 21 cartilage lesions decreased on MRI. CONCLUSION: The knees of novice runners achieved sustained improvement, for at least 6 months post-marathon, in the condition of their bone marrow and articular cartilage.

Retrieval analysis of contemporary antioxidant polyethylene: multiple material and design changes may decrease implant performance.

PURPOSE: With the introduction of the Attune Knee System (DePuy) in March 2013, a new polyethylene formulation incorporating anti-oxidants was used. Although several in vitro studies have demonstrated the positive effects of antioxidants on UHMWPE, no retrieval study has looked at polyethylene damage of this system yet. It was the aim of this study to investigate the in vivo performance of this new design, by comparing it with its predecessors in retrieval analysis. METHODS: 24 PFC (18 fixed bearing and 6 rotating platform designs) and 17 Attune (8 fixed bearing and 9 rotating platform designs) implants were retrieved. For retrieval analysis, a macroscopic analysis of polyethylene components, using a peer-reviewed damage grading method was used. Medio-lateral polyethylene thickness difference was measured with a peer-reviewed micro-CT based method. The roughness of metal components was measured. All findings were compared between the two designs. RESULTS: Attune tibial inserts with fixed bearings showed significantly higher hood scores on the backside surface when compared with their PFC counterparts (p = 0.01), no other significant differences were found in the polyethylene damage of all the other surfaces analysed, in the surface roughness of metal components and in medio-lateral linear deformations. CONCLUSION: A significant difference between PFC and Attune fixed bearing designs was found in terms of backside surface damage: multiple changes in material and design features could lead to a potential decrease of implant performance. Results from the present study may help to understand how the new Attune Knee System performs in vivo, impacting over 600,000 patients.

3D patient imaging and retrieval analysis help understand the clinical importance of rotation in knee replacements.

PURPOSE: The purpose of the present study was to correlate highly accurate CT measurements of pre-revision total knee arthroplasty (TKA) implant position with findings of retrieval analysis post-revision, to understand the clinical relevance of TKA orientation. METHODS: This study involved 53 retrieved TKA implants with pre-revision 3D-CT scans used to determine coronal (varus-valgus), sagittal (tibial slope) and rotational (internal rotation-external rotation) TKA orientation as well as tibiofemoral leg axis. Differences between femoral and tibial angles to describe the "relative rotational mismatch" were also calculated. All tibial inserts were forensically analyzed using the Hood score. Statistical analysis was performed to investigate correlations between TKA component orientation and surface damage (p < 0.05). RESULTS: Femoral components were found to have axial rotations mainly within ± 3° (68%), whilst 45% of the tibial components and 66% of the relative rotational mismatches were > 3° and < - 3°, respectively. The majority of femoral and tibial components (87% in both cases), as well as the femorotibial angle (70%), showed coronal orientations within ± 3°. The 64% of the tibial components showed posterior tibial slopes out of both the 0°-3° and 5°-7° ranges. There was a significant correlation between tibial slope and damage score on polyethylene tibial inserts (r = 0.2856; p = 0.0382) as well as a significant correlation between implants' position in the axial plane and damage score on polyethylene tibial inserts (r = 0.6537, p = 0.0240). CONCLUSIONS: This is the first study to use accurate measurements from pre-revision 3DCT to compare tibial and femoral orientation in all three planes with retrieval findings in total knee replacements. A significant correlation between implant position and polyethylene surface damage was found. These results showed the importance of optimizing component position to minimize polyethylene damage. Further analysis involving more accurate polyethylene wear measurements are fundamental to fully understand the role of components' orientation in TKAs.

Effect of Bearing Type on Taper Material Loss in Hips From 1 Manufacturer.

BACKGROUND: Numerous studies have reported on clinical significant volumes of material loss and corrosion at the head-stem junction of metal-on-metal (MOM) hips; less is understood about metal-on-polyethylene (MOP) hips. We compared the effect of bearing type (MOM vs MOP) on taper material loss for a hip system of a single design. METHODS: In this cohort study, we recruited retrieved MOM (n = 30) and MOP (n = 22) bearing hips that were consecutively received at our center. We prospectively collected associated clinical and imaging data. We measured the severity of corrosion and volumes of material loss at each head taper surface and used multivariate statistical analysis to investigate differences between the 2 bearing types. RESULTS: The median rate of material loss for the MOM and MOP groups was 0.81 mm3/y (0.01-3.45) and 0.03 mm3/y (0-1.07), respectively (P < .001). Twenty-nine of 30 MOM hips were revised for adverse metal reactions, compared with 1 of 22 MOP hips. CONCLUSION: MOP hips lost significantly less material from their taper junctions than MOM hips. Our results can reassure patients with MOP Pinnacle hips that they are unlikely to experience clinically significant problems related to material loss from the taper junction.

Computed Tomography Techniques Help Understand Wear Patterns in Retrieved Total Knee Arthroplasty.

BACKGROUND: Suboptimal total knee arthroplasty (TKA) position of both femoral and tibial components is thought to be linked with poor clinical outcomes, polyethylene wear and the "unexplained" painful knee arthroplasty. The aim of this study was to better understand the effect of implant orientation on knee implant performance. METHODS: We analyzed 30 retrieved contemporary TKA implants. Implant positioning measurements in the coronal plane were made prior to revision using a diagnostic algorithm, based on 3D computed tomography (CT) images. Each retrieved polyethylene component was imaged using a micro-CT scanner and a high resolution computational 3D model of each component was digitally reconstructed. The difference in thickness between medial and lateral components was calculated. Statistical analysis was performed to investigate the association between component positioning and damage patterns. RESULTS: We found a significant correlation between both the tibiofemoral and femoral angles and difference in thickness between polyethylene compartments: varus angulations were strongly associated with thinner medial compartments, whilst valgus angulations were associated with thinner lateral compartments. Moreover, suboptimal tibiofemoral orientations and tibial component angulations were associated to greater differences in thickness between polyethylene compartments. CONCLUSION: Our study is the first to compare accurate 3D CT measurements of prerevision TKA positioning in the coronal plane with postrevision retrieval analysis from innovative, accurate and highly reliable micro-CT-based method. Our results demonstrate the impact of component positioning on polyethylene damage and helps understanding of the in vivo performance of these implants. LEVEL OF EVIDENCE: III.

Analysing a mechanism of failure in retrieved magnetically controlled spinal rods.

PURPOSE: We aim to describe a mechanism of failure in magnetically controlled growth rods which are used for the correction of the early onset scoliosis. METHODS: This retrieval study involved nine magnetically controlled growth rods, of a single design, revised from five patients for metal staining, progression of scoliosis, swelling, fractured actuator pin, and final fusion. All the retrieved rods were radiographed and assessed macroscopically and microscopically for material loss. Two implants were further analysed using micro-CT scanning and then sectioned to allow examination of the internal mechanism. No funding was obtained to analyse these implants. There were no potential conflicts interests. RESULTS: Plain radiographs revealed that three out of nine retrieved rods had a fractured pin. All had evidence of surface degradation on the extendable telescopic rod. There was considerable corrosion along the internal mechanism. CONCLUSIONS: We found that a third of the retrieved magnetically controlled growth rods had failed due to pin fracture secondary to corrosion of the internal mechanism. We recommend that surgeons consider that any inability of magnetically controlled growth rods to distract may be due to corrosive debris building up inside the mechanism, thereby preventing normal function.

Registry Data-Valuable Lessons But Beware the Confounders.

A mature national joint registry with widespread adoption and audit can successfully demonstrate trends and influence future orthopedic practice. Correlations can be identified; however, this should not be misinterpreted as causality. It is essential to consider confounding when analyzing observational datasets.

Fretting and Corrosion Between a Metal Shell and Metal Liner May Explain the High Rate of Failure of R3 Modular Metal-on-Metal Hips.

BACKGROUND: The R3 acetabular system used with its metal liner has higher revision rates when compared to its ceramic and polyethylene liner. In June 2012, the medical and healthcare products regulatory agency issued an alert regarding the metal liner of the R3 acetabular system. METHODS: Six retrieved R3 acetabular systems with metal liners underwent detailed visual analysis using macroscopic and microscopic techniques. RESULTS: Visual analysis discovered corrosion on the backside of the metal liners. There was a distinct border to the areas of corrosion that conformed to antirotation tab insertions on the inner surface of the acetabular shell, which are for the polyethylene liner. Scanning electron microscopy indicated evidence of crevice corrosion, and energy-dispersive X-ray analysis confirmed corrosion debris rich in titanium. CONCLUSION: The high failure rate of the metal liner option of the R3 acetabular system may be attributed to corrosion on the backside of the liner which appear to result from geometry and design characteristics of the acetabular shell.

Clinical Cold Welding of the Modular Total Hip Arthroplasty Prosthesis.

BACKGROUND: A head that is "clinically cold welded" to a stem is one of the commonest reasons for unplanned removal of the stem. It is not clear which hip designs are at greatest risk of clinical cold welding. METHODS: This was a case-control study of consecutively received hip implant retrievals; we chose the design of hip that had the greatest number of truly cold-welded heads (n = 11). For our controls, we chose retrieved hips of the same design but without cold welding of the head (n = 35). We compared the clinical variables between these 2 groups using nonparametric Mann-Whitney tests to investigate the significance of differences between the cold-welded and non-cold-welded groups. RESULTS: The design that most commonly caused cold welding was a combination of a Ti stem and Ti taper: 11 out of 48 (23%) were truly cold welded. Comparison of the clinical data showed that no individual factor could be used to predict this preoperatively with none of the 4 predictors tested showing any significance: (1) time to revision (P = .687), (2) head size (P = .067), (3) patient age at primary (P = .380), and (4) gender (P = .054). CONCLUSION: We have shown that clinical cold welding is most prevalent in Ti-Ti combinations of the stem and taper; approximately 25% of cases received at our center were cold welded. Analysis of clinical variables showed that it is not possible to predict which will be cold welded preoperatively. Surgeons should be aware of this potential complication when revising a Ti-Ti stem/head junction.

Factors Associated With Trunnionosis in the Metal-on-Metal Pinnacle Hip.

BACKGROUND: Trunnionosis of the tapered head-stem junction of total hip arthroplasties, either through corrosion or mechanical wear, has been implicated in early implant failure. Retrieval analysis of large numbers of failed implants can help us better understand the factors that influence damage at this interface. METHODS: In this study, we examined 120 retrieved total hip arthroplasties of one bearing design, the 36-mm diameter metal-on-metal, DePuy Pinnacle, that had been paired with 3 different stems. We measured material loss of the bearing and head-trunnion taper surfaces and collected clinical and component data for each case. We then used multiple linear regression analysis to determine which factors influenced the rate of taper material loss. RESULTS: We found 4 significant variables: (1) longer time to revision (P = .004), (2) the use of a 12/14 taper for the head-trunnion junction (P < .001), (3) decreased bearing surface wear (P = .003), and (4) vertical femoral offset (P = .05). These together explained 29% of the variability in taper material loss. CONCLUSION: Our most important finding is the effect of trunnion design. Of the 3 types studied, we found that S-ROM design was the most successful at minimizing trunnionosis.

Damage Patterns at the Head-Stem Taper Junction Helps Understand the Mechanisms of Material Loss.

BACKGROUND: Material loss at the taper junction of metal-on-metal total hip arthroplasties has been implicated in their early failure. The mechanisms of material loss are not fully understood; analysis of the patterns of damage at the taper can help us better understand why material loss occurs at this junction. METHODS: We mapped the patterns of material loss in a series of 155 metal-on-metal total hip arthroplasties received at our center by scanning the taper surface using a roundness-measuring machine. We examined these material loss maps to develop a 5-tier classification system based on visual differences between different patterns. We correlated these patterns to surgical, implant, and patient factors known to be important for head-stem taper damage. RESULTS: We found that 63 implants had "minimal damage" at the taper (material loss <1 mm3), and the remaining 92 implants could be categorized by 4 distinct patterns of taper material loss. We found that (1) head diameter and (2) time to revision were key significant variables separating the groups. CONCLUSION: These material loss maps allow us to suggest different mechanisms that dominate the cause of the material loss in each pattern: (1) corrosion, (2) mechanically assisted corrosion, or (3) intraoperative damage or poor size tolerances leading to toggling of trunnion in taper.

Retrieval evidence of impingement at the third articulation in contemporary dual mobility cups for total hip arthroplasty.

PURPOSE: We aimed to assess polyethylene liners of retrieved hips of one design of a dual mobility (DM) cup liner and two designs of femoral stems to better understand the role of femoral stem design on polyethylene impingement. METHODS: This was a case-control study involving 70 retrieved highly cross-linked polyethylene (X3) liners used with ABGII (n = 35) and Rejuvenate (n = 35) stems (Stryker). All polyethylene liners were assessed for evidence of rim deformation and the damage quantified using metrology methods. RESULTS: A total of 80% of polyethylene liners paired with ABGII necks had macroscopic evidence of neck impingement resulting in a raised lip whilst 23% of liners paired with Rejuvenate necks had evidence of a raised lip (p < 0.0001). The height of the raised rims of the DM cups paired with ABGII necks had a median (range) of 139 µm (72-255). The height of the raised rims of the DM cups paired with Rejuvenate necks had a median (range) of 52 µm (45-90) (p < 0.0001). CONCLUSION: Our new findings from retrieved dual mobility bearings showed that polyethylene liner rim deformation resulting from impingement with the femoral neck occurs in early in-human function, is circumferential in distribution, and is affected by the stem neck design. We recommend the use of highly polished and non-edged neck designs when used in conjunction with DM cups.

Detection of metallic cobalt and chromium liver deposition following failed hip replacement using T2* and R2 magnetic resonance.

BACKGROUND: Failed hip prostheses can cause elevated circulating cobalt and chromium levels, with rare reports of fatal systemic organ deposition, including cobalt cardiomyopathy. Although blood cobalt and chromium levels are easily measured, organ deposition is difficult to detect without invasive biopsy. The T2* magnetic resonance (MR) method is used to quantify tissue iron deposition, and plays an important role in the management of iron-loading conditions. Cobalt and chromium, like iron, also affect magnetism and are proposed MR contrast agents. CASE PRESENTATION: We describe a case of a 44-year-old male with a failed hip implant and very elevated blood cobalt and chromium levels. Despite normal cardiac MR findings, liver T2* and R2 values were abnormal, triggering tissue biopsy. Liver tissue analysis, including X-ray fluorescence, demonstrated heavy elemental cobalt and chromium deposition in macrophages, and no detectable iron. CONCLUSIONS: Our case demonstrates T2* and R2 quantification of liver metal deposition in a patient with a failed hip implant. Further work is needed to investigate the role of T2* and R2 MR in the detection of metal deposition from metal on metal hip prostheses.

The Relationship Between Cobalt/Chromium Ratios and the High Prevalence of Head-Stem Junction Corrosion in Metal-on-Metal Total Hip Arthroplasty.

BACKGROUND: The size of the clinical impact of corrosion of the taper junction of metal-on-metal total hip arthroplasties (MOM-THAs) is unclear. Examination of a large number of retrieved MOM resurfacings and total hip arthroplasties can help us understand the role of taper corrosion in metal ion release. METHODS: We graded the severity of corrosion at the taper junction of 395 MOM-THAs and compared the prerevision whole blood metal ion levels of these hips with 529 failed MOM hip resurfacings. RESULTS: Virtually all MOM-THA hips (n = 388) had evidence of corrosion of the head-stem taper junction and graded as severe in 31% (n = 124). The median cobalt/chromium (Co/Cr) ratio was 1.58 (0.01-13.82) and 1.08 (0-4.86) for MOM-THA and MOM hip resurfacing, respectively; this difference was significant (P < .001). THA hips with severely corroded tapers had the highest median Co/Cr ratio of 1.86 (0.01-10). CONCLUSIONS: This study demonstrates the high prevalence of severe taper corrosion, which may be related to an elevated Co/Cr ratio before revision.