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Supplemental Material, sj-pdf-1-ojs-10.1177_23259671211010405 for Magnetic Resonance Imaging of the Hips of Runners Before and After Their First Marathon Run: Effect of Training for and Completing a Marathon by Laura M. Horga, Johann Henckel, Anastasia Fotiadou, Anna Di Laura, Anna C. Hirschmann and Alister J. Hart in Orthopaedic Journal of Sports Medicine

The mechanisms of metal release from the articulation at the head cup bearing and the tapered junctions of orthopaedic hip implants are known to differ and the debris generated varies in size, shape and volume. Significantly less metal is lost from the taper junction between Cobalt-Chromium-Molybdenum (CoCrMo) and Titanium (Ti) components (fretting-corrosion dominant mechanism), when compared to the CoCrMo bearing surfaces (wear-corrosion dominant mechanism). Corrosion particles from the taper junction can lead to Adverse Reactions to Metal Debris (ARMD) similar to those seen with CoCrMo bearings. We used synchrotron methods to understand the modes underlying clinically significant tissue reactions to Co, Cr and Ti by analysing viable peri-prosthetic tissue. Cr was present as Cr2O3 in the corroded group in addition to CrPO4 found in the metal-on-metal (MoM) group. Interestingly, Ti was present as TiO2 in an amorphous rather than rutile or anatase physical form. The metal species were co-localized in the same micron-scale particles as result of corrosion processes and in one cell type, the phagocytes. This work gives new insights into the degradation products from metal devices as well as guidance for toxicological studies in humans.

Background and purpose 2D analysis of metal-on-metal (MoM) hip arthroplasty (HA) has been conducted in several large series on conventional radiographs with the use of Ein Bild Roentegen Analyse (EBRA) software, but there have been no comparisons with 3D analysis in the literature. The main aim of this study was to quantify the agreement in measurements of cup version of large-diameter MoM hips obtained by EBRA and by 3D computed tomography (3D-CT). The secondary aim was to quantify the agreement for cup inclination. Lastly, we wanted to determine the inter- and intra-observer reliability of both methods. Patients and methods 87 MoM hips in 81 patients were analyzed for cup inclination and version in 2D on conventional radiographs using EBRA software. The results were compared with 3D measurements using CT. Results Cup version was underestimated by EBRA when compared to 3D-CT, by 6° on average with the pelvis supine and by 8° on average with the pelvis orientated to the anterior pelvic plane (APP). For inclination, the mean difference was no more than 1°. 53% of hips were within a 10° safe zone of 45° inclination and 20° version when measured by 3D-CT with the pelvis supine (and 54% with the pelvis in the APP). The proportion was only 24% when measured by EBRA. Inter- and intra-observer reliability of cup version is poorer using 2D analysis than when using 3D-CT. Interpretation Errors in version in 2D were due to the difficulty in delineating the cup rim, which was obscured by a large-diameter metal head of the same radio-opacity. This can be overcome with 3D analysis. The present study demonstrates that measurements using EBRA have poor agreement and are less reliable than those with 3D-CT when measuring cup version and inclination in MoM hips.

Material loss from the head-stem taper junction of total hip arthroplasty (THA) is implicated in adverse reactions to metal debris (ARMD); the mechanisms for this are multi-factorial. We investigated the relationship between the roughness of the "as manufactured" taper surface and the wear rate from this junction. Fifty retrieved Pinnacle metal-on-metal (MOM) bearings paired with a Corail stem were included in the study. Multivariable statistical analysis was performed to determine the influence of taper roughness on material loss rate after controlling for other confounding surgical, implant, and patient factors. The surface roughness of the "as manufactured" head taper surface was associated with the rate of material loss from this surface. Four of eighteen roughness variables taken from ISO 4,287 and ISO 13,565-2 were significant: The Reduced Peak Height (Rpk, the protruding peaks above the core) (p = 0.004), Material Ratio 1 (Mr1, the ratio of the protruding peaks above the core) (p = 0.002), Area of the Peak Region (A1, the area of the Abbott-Curve that contains the peaks from the profile) (p = 0.003) and the Skewness (Rsk, the asymmetry of the height distribution corresponding to the height or depth of surface features) (p = 0.03). We found a large variability in the measured values with a median (range) of 0.50 (0.05-2.98), 11.98 (0.46-39.98), 30.89 (0.15-581.00), and 0.04 (-0.73-0.84), respectively. A 1-unit increase in Rpk was associated with a 73% increase in the taper wear rate. The variability of "as manufactured" surface roughness has a significant effect on taper material loss.

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.

It has been speculated that material loss, either as corrosion or wear, at the head–stem taper junction is implicated in the\ud high revision rates reported for metal-on-metal total hip replacements. We measured the volume of material loss from the taper and\ud bearing surfaces of retrieved devices, and investigated the associations with blood metal ion levels and the diagnosis of a cystic or solid\ud pseudotumor. The median volumes of material lost from the female and male taper surfaces were 2.0 and 0.29 mm3, respectively, while\ud the median volumes of wear from the cup and head bearing surfaces were 1.94 and 3.44 mm3, respectively. Material loss from the female\ud taper was similar to that from the acetabular bearing surface (p ¼ 0.55), but significantly less than that from the femoral bearing surface\ud (p < 0.001). Material loss from the male taper was less than that from both bearing surfaces (p < 0.001). Multivariable analysis\ud demonstrated no significant correlations between the volume of material lost from the taper surfaces and either blood cobalt or chromium\ud ions, or the presence of pseudotumor. While a substantial volume of material is lost at the taper junction, the clinical significance of this\ud debris remains unclear.

Metal-on-metal (MOM) total hip arthroplasty using large diameter femoral heads offer clinical advantages however the failure rates of these hips is unacceptably high. Retrieved hips have undergone a wide range of changes at their bearing and taper surfaces and there is no agreement regarding the cause of failure.\ud Detailed visual inspection is the first step in the forensic examination of failed hip components in order to report on the changes that have occurred at the bearing surface and may help explain the mechanisms of failure.