Does the Additional Articulation in Retrieved Bipolar Hemiarthroplasty Implants Decrease Trunnionosis Compared to Total Hip Arthroplasty?

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.

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.

Gross Trunnion Failure in the Bipolar Hemiarthroplasty; Raising Concern about Short Trunnion: A Case Report

There have been some reports of gross trunnion failure (GTF) in total hip arthroplasty. Here, we report a case of GTF 19 years after bipolar hemiarthroplasty using a 28-mm head with a 14/16 taper bore. Compared to other GTF reports, the current case had some unusual aspects: bipolar hemiarthroplasty, 28-mm head, relatively late-onset, and no apparent findings of metallosis though a severe one was evident. A Computed tomography scout view provided valuable information in evaluating polyethylene, metal head, and neck inside the bipolar cup. The current report suggests a need for concerned regarding short trunnion length which may be associated with GTF.

Taper corrosion: a complication of total hip arthroplasty

The focus on taper corrosion in modular hip arthroplasty increased around 2007 as a result of clinical problems with large-head metal-on-metal (MoM) bearings on standard stems. Corrosion problems with bi-modular primary hip stems focused attention on this issue even more.

Factors increasing the risk of taper corrosion were identified in laboratory and retrieval studies: stiffness of the stem neck, taper diameter and design, head diameter, offset, assembly force, head and stem material and loading.

The high variability of the occurrence of corrosion in the clinical application highlights its multi-factorial nature, identifying the implantation procedure and patient-related factors as important additional factors for taper corrosion.

Discontinuing the use of MoM has reduced the revisions due to metal-related pathologies dramatically from 49.7% (MoM > 32 mm), over 9.2% (MoM ⩽ 32 mm) to 0.8% (excluding all MoM).

Further reduction can be achieved by omitting less stiff Ti-alloys and large metal heads (36 mm and above) against polyethylene (PE).

Standardized taper assembly of smaller and ceramic heads will reduce the clinical occurrence of taper corrosion even further. If 36 mm heads are clinically indicated, only ceramic heads should be used.

Taper-related problems will not comprise a major clinical problem anymore if the mentioned factors are respected.

Cite this article: EFORT Open Rev 2020;5:776-784. DOI: 10.1302/2058-5241.5.200013

A Case Report and Literature Review to Aid in the Management of Trunnion Failure in Hip Arthroplasty Patients: Can Trunnionosis and Prosthetic Joint Infection Co-Exist?

Trunnionosis is a type of corrosion and wear at the head-neck taper junction of the femoral implant, and it can be a slow and silent catastrophe. Simultaneous prosthetic joint infection (PJI) is occasionally possible based on the fulfillment of a few of the minor criteria from the Musculoskeletal Infection Society (MSIS), but the existing literature lacks adequate evidence to support that the infection actually exists. We are presenting a case of an 82-year-old man with right total hip arthroplasty performed over a decade prior to presenting to the emergency room with a sudden-onset pop followed by groin pain and difficulty in walking. Radiographs showed a dissociated femoral implant at the level of trunnion with malalignment and heterotopic ossification. Metal Artifact Reduction Sequence MRI of the right hip showed mixed type-two and type-three pseudotumors, and atrophy of surrounding abductor muscles. The erythrocyte sedimentation rate was within normal limits, C-reactive protein was borderline raised, and serum cobalt-chromium levels were elevated without any signs of systemic metal toxicity. Hip joint aspirate revealed blood-stained fluid flooded with red blood cells, leukocytes and neutrophils, and a positive alpha-defensin assay. These findings were interpreted as positive for prosthetic joint infection. Intraoperatively, there was severe wear of the inferomedial aspect of the femoral head-neck junction and extensive metallosis throughout the right hip. Tissue and fluid specimens were sent for cultures, sensitivities, and histopathology for pseudotumor and infection evaluation. An articulating antibiotic spacer was then placed with the intent to perform a staged reconstruction of the femur and right acetabulum. Final synovial, bone, and soft tissue cultures, as well as histopathological photomicrograph of the tissue slides, were negative for infection. This case demonstrates the striking features of metallosis associated with trunnion failure of a metal-on-polyethylene total hip joint prosthesis that was simultaneously showing signs of prosthetic infection by satisfying the minor criteria according to the latest guidelines by the MSIS with a strikingly high cell count of red blood cells in the synovial fluid exam, indicating inflamed hyper-vascular pseudotumors vs. hemarthrosis vs. bloody tap. Diagnostic dilemma led by positive synovial fluid alpha defensin, high synovial neutrophil and white cell count results with negative final cultures or infection on histological slides raises concern that infection was not present and two-stage revision arthroplasty with six weeks of antibiotics was not necessary along with increased risk of morbidity, mortality as well as cost of care.

Fretting and Corrosion Damage of Retrieved Dual-Mobility Total Hip Arthroplasty Systems

BACKGROUND

Dual-mobility (DM) total hip arthroplasty (THA) systems are designed to increase stability while potentially avoiding problems associated with large femoral heads. Complications of these systems are not yet fully understood. This study aims at characterizing in vivo performance of DM hip systems and assessing modes of clinical failure.

METHODS

Under an institutional review board-approved implant retrieval protocol, 18 DM THA systems from 17 patients were included. Implants were graded at the head-neck junction for fretting and corrosion based on the system of Goldberg et al. Components were also macroscopically examined for different damage modes. Demographics and surgical data were collected from medical records, and radiographs were assessed for component positioning. Data were analyzed through Spearman rank-order correlation and Mann-Whitney U-tests, with α = 0.05.

RESULTS

The average length of implantation was 13.4 months with mild to moderate fretting corrosion damage. Polyethylene (PE) liners exhibited edge deformation, scratching, and pitting damage. Metallic components exhibited burnishing and scratching damage. Summed fretting and corrosion scores were strongly correlated (ρ = 0.967, P < .0001). Summed corrosion score was moderately correlated with presence of embedding on the PE liner (ρ = 0.690, P = .017). PE liner abrasion and edge deformation of the femoral stem taper were moderately positively correlated (ρ = 0.690, P = .017). Fretting and corrosion damage were not significantly correlated with patient demographics or radiographic positioning of implants. There were no differences in scores between modular and monoblock designs.

CONCLUSION

These findings demonstrate that dual-mobility THA systems may be susceptible to the same fretting and corrosion damage observed in traditional modular THA systems. Future studies are needed to confirm these results and clinical significance.