Mechanically assisted crevice corrosion of the head-neck taper in a large head metal-on-metal total hip arthroplasty

Metallosis and Corrosion Associated With Revision Total Knee Arthroplasties With Metaphyseal Sleeves

Metallosis and corrosion have been associated with metal-on-metal and modular total hip arthroplasty but are rarely described in the setting of primary or revision total knee arthroplasty (TKA). In this series, we report on cases of metallosis due to mechanically assisted crevice corrosion at modular junctions of machined trunnion-bore tapers in a revision TKA system with metaphyseal sleeves. The unique design of metal modular junctions used in sleeve-based revision TKA, along with potential patient and surgical factors, may predispose these designs to fretting, corrosion, and adverse reaction to metal debris. We now consider metallosis and corrosion in the workup of painful or failed revision TKAs with sleeves. Future studies that investigate the incidence of this phenomenon may be warranted.

Surface Analysis of Ti-Alloy Micro-Grooved 12/14 Tapers Assembled to Non-Sleeved and Sleeved Ceramic Heads: A Comparative Study of Retrieved Hip Prostheses

Ti6Al4V titanium alloy (Ti-alloy) sleeved ceramic heads have become widely used in revision surgery when the hip stem is left in situ. This solution guarantees a new junction between the bore of the ceramic head and the Ti-alloy sleeve, regardless of any possible, slight surface damage to the Ti-alloy taper of the stem. However, this solution introduces an additional Ti-alloy/Ti-alloy interface pairing, which is potentially susceptible to mechanically assisted crevice corrosion. This study evaluated both qualitatively and quantitatively the damage that occurred in vivo on Ti-alloy micro-grooved 12/14 tapers of (i) primary implants with non-sleeved ceramic heads (Group 1), (ii) secondary implants with non-sleeved ceramic heads (Group 2), and (iii) secondary implants with sleeved ceramic heads (Group 3). A total of 45 explants-15 for each group, including short-, medium- and long-neck heads-underwent optical evaluation for surface damage (Goldberg scoring), surface roughness analysis, and SEM/EDX analysis. The Goldberg scores did not reveal different patterns in the tapers' surface damage; surface damage was classified as absent or mild (surface damage score ≤2) in 94%, another 94%, and 92% of the analysed regions for Group 1, Group 2, and Group 3, respectively. Small but significant differences in morphological changes occurred in the tapers of the three groups: reductions no greater than a few percentage points in median values of roughness parameters were found in Group 1 and Group 2, while negligible changes were found in Group 3. SEM/EDX analysis revealed little (i.e., a slight increase in the oxygen content) to undetectable changes in the chemical composition on the Ti-alloy surface independently of the group. These results suggest that the Ti-alloy/Ti-alloy sleeve/taper junction is only mildly susceptible to mechanically assisted crevice corrosion. Assembling a sleeved ceramic head, with variable neck lengths up to a "long-neck", to a Ti-alloy micro-grooved 12/14 taper of a stem left in situ does not seem to increase the risk of revision due to trunnionosis, as long as junction stability (i.e., the proper seating of the sleeved ceramic head on the 12/14 taper) is achieved intraoperatively.

Impending Trunnion Failure: An Uncommon Radiographic Presentation of Total Hip Arthroplasty Failure

Trunnionosis is emerging as an early mode of failure in conventional metal-on-polyethylene total hip arthroplasty. It is defined as wear or corrosion at the trunnion, the taper at the femoral head-neck interface. Trunnion wear can result in a variety of negative sequelae and, in severe cases, necessitate revision arthroplasty. We describe a 64-year-old man with a metal-on-polyethylene total hip arthroplasty who presented with a sensation of clunking in the hip. Initial imaging and laboratory studies were inconclusive, and the decision was made to monitor. Two years later, trunnion wear was detected on radiographs, presenting as an abnormal alignment of the femoral neck relative to the femoral head. Several case reports and series describe catastrophic total hip arthroplasty failure due to trunnionosis. However, few describe the radiographic signs of wear at the trunnion before gross failure. This early presentation is important to recognize to minimize patient morbidity and aid surgical planning.

Comparison of Pre-Revision Magnetic Resonance Imaging and Operative Findings in Mechanically Assisted Crevice Corrosion in Symptomatic Metal-on-Polyethylene Total Hip Arthroplasties

BACKGROUND

Failed total hip arthroplasty (THA) caused by mechanically assisted crevice corrosion (MACC) has serious consequences-notably, adverse local tissue reactions. Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been used to evaluate failed THA for other reasons but has not been assessed for the analysis of cases of MACC in the setting of metal-on-polyethylene arthroplasties.

METHODS

We examined the correlation between preoperative MARS MRI and surgical findings in a cohort of 20 consecutive patients undergoing revision THA for symptomatic MACC without other associated orthopedic diagnoses. Surgical findings included soft tissue and bone evaluation, presence and location of fluid, abductor disruption, composite tissue damage grade, and prosthesis trunnion damage at the time of revision.

RESULTS

MARS MRI complex synovitis, thickened pseudocapsule, and extra-articular fluid extension each strongly correlated with both the soft-tissue damage grade and trunnion damage noted at surgery. Bone marrow edema was also found to strongly correlate with bone necrosis intraoperatively.

CONCLUSION

MARS MRI is an excellent diagnostic tool for evaluation of patients with elevated serum Co after metal-on-polyethylene THA. Patients with complex synovitis, a thick pseudocapsule, bone marrow edema, and extra-articular fluid should strongly consider revision surgery.