Assessing Taper Geometry, Head Size, Head Material, and Their Interactions in Taper Fretting Corrosion of Retrieved Total Hip Arthroplasty Implants

Evaluating trunnionosis in modular anatomic shoulder arthroplasties: a retrieval study

BACKGROUND

Shoulder arthroplasty procedures are widely indicated, and the number of shoulder arthroplasty procedures has drastically increased over the years. Rapid expansion of the utilization of reverse total shoulder arthroplasty has outpaced the more modest growth of anatomic total shoulder arthroplasty (aTSA) while shoulder hemiarthroplasty (HA) has trended down. Recently, shoulder prostheses have transitioned to increasingly modular systems offering more individualized options with the potential for decreased pain and increased range of motion. However, increased primary procedures has resulted in increased revision surgeries, with one potential cause being fretting and corrosion damage within these modular systems.

METHODS

Following institutional review board approval, 130 retrieved aTSA and 135 HA explants were identified through database query. Humeral stem and head components were included in all 265 explants, whereas 108 included polyethylene glenoid liner components. All explanted components were macroscopically evaluated for standard damage modes, and taper junctions were microscopically examined for fretting/corrosion using a modified Goldberg-Cusick classification system that was 4-quadrant graded for both the male and female component. Medical records were reviewed for patient demographics and surgical information.

RESULTS

In this series, 158 of explants were from female patients (male = 107), and 162 explants were from the right shoulder. Average age at implantation was 61 years (range: 24-83), average age at explanation was 66 years (range, 32-90), and average duration of implantation was 61.4 months (range, 0.5-240). Scratching, edge deformation, and burnishing were the most commonly observed standard damage modes. Of the 265 explants, 146 had a male stem component vs. 118 with a female stem component. Average summed fretting grades on male and female stem components were 8.3 and 5.9, respectively (P < .001). Average summed corrosion grades for male and female stem components were 8.2 and 6.2, respectively (P < .001). Wider male tapers (>11 mm) showed significantly less fretting and corrosion (P < .001). Lastly, mismatched metal compositions between the head and stem components showed greater fretting and corrosion damage (P = .002).

CONCLUSION

In this series of 265 aTSA and HA explants, there was substantial damage present on the explanted components. All components demonstrated macroscopic damage. In this retrieval study, small-tapered male stems with small, thin female heads and mismatched metal composition between components were risk factors for increased implant wear. As shoulder arthroplasty volume increases, optimizing design is paramount for long-term success. Additional work could determine the clinical significance of these findings.

A convolutional neural network for high throughput screening of femoral stem taper corrosion

Corrosion at the modular head-neck taper interface of total and hemiarthroplasty hip implants (trunnionosis) is a cause of implant failure and clinical concern. The Goldberg corrosion scoring method is considered the gold standard for observing trunnionosis, but it is labor-intensive to perform. This limits the quantity of implants retrieval studies typically analyze. Machine learning, particularly convolutional neural networks, have been used in various medical imaging applications and corrosion detection applications to help reduce repetitive and tedious image identification tasks. 725 retrieved modular femoral stem arthroplasty devices had their trunnion imaged in four positions and scored by an observer. A convolutional neural network was designed and trained from scratch using the images. There were four classes, each representing one of the established Goldberg corrosion classes. The composition of the classes were as follows: class 1 (n = 1228), class 2 (n = 1225), class 3 (n = 335), and class 4 (n = 102). The convolutional neural network utilized a single convolutional layer and RGB coloring. The convolutional neural network was able to distinguish no and mild corrosion (classes 1 and 2) from moderate and severe corrosion (classes 3 and 4) with an accuracy of 98.32%, a class 1 and 2 sensitivity of 0.9881, a class 3 and 4 sensitivity of 0.9556 and an area under the curve of 0.9740. This convolutional neural network may be used as a screening tool to identify retrieved modular hip arthroplasty device trunnions for further study and the presence of moderate and severe corrosion with high reliability, reducing the burden on skilled observers.

Fretting corrosion behavior of Ti6Al4V alloy against zirconia-toughened alumina ceramic in simulated body fluid

The fretting corrosion at the head-neck interface of artificial hip joints is an important reason for the failure of prostheses. The Ti6Al4V alloy-zirconia-toughened alumina (ZTA) ceramic combination has been widely used to make the head and neck of artificial hip joints. In this study, its fretting corrosion behavior in simulated body fluid was studied by electrochemical monitoring, surface morphology characterization, and chemical composition analysis. A running condition fretting map (RCFM) of load and displacement was established, including three regimes, namely partial slip regime (PSR), mixed fretting regime (MFR), and gross slip regime (GSR). The friction dissipation energy increased gradually from the PSR to MFR and GSR. In the PSR, the damage mechanisms were slight abrasive wear and tribocorrosion at the edge of contact area, as well as extremely slight adhesive wear at the center. In the MFR, the damage mechanisms were mainly adhesive wear, abrasive wear, and corrosive wear. In the GSR, the damage mechanism was serious abrasive wear, fatigue wear, and corrosive wear combined with slight adhesive wear. Finally, an ion-concentration map was created, displaying the material-loss transition of different displacements and loads. The material loss increased with the increased displacement, and increased first and then decreased with the increased load.

What Patient and Implant Factors Affect Trunnionosis Severity? An Implant Retrieval Analysis of 664 Femoral Stems

BACKGROUND

Corrosion at the modular head-neck taper interface of total and hemiarthroplasty hip implants (trunnionosis) is a cause of implant failure and thus a clinical concern. Patient and device factors contributing to the occurrence of trunnionosis have been investigated in prior implant retrieval studies but generally with limited sample sizes and a narrow range of models. The purpose of the present investigation was to determine which patient and device factors were associated with corrosion damage on the femoral stem taper across a large collection of different implant models retrieved following revision hip arthroplasty.

METHODS

A retrieval study of 664 hip arthroplasty modular stem components was performed. Patient and device information was collected. Trunnions were imaged under digital microscopy and scored for corrosion damage using a scaling system. Damage was related to patient and device factors using regression analyses.

RESULTS

Greater duration of implantation (P = .005) and larger head size (P < .001) were associated with an elevated corrosion class. Older age at index surgery (P = .035), stainless steel stem material (P = .022), indication for revision as bone or periprosthetic fracture (P = .017), and infection (P = .018) and certain larger taper geometries were associated with a decreased corrosion class.

CONCLUSION

Factors identified as contributing to a higher or lower risk of more severe corrosion are consistent with most prior smaller retrieval studies. Surgeons should be aware of these risk factors when selecting implants for their patients and when diagnosing trunnionosis in symptomatic hip arthroplasty patients.