The Biomaterials of Total Shoulder Arthroplasty: Their Features, Function, and Effect on Outcomes

Suture debris from high-tensile sutures contributes significantly to particle-induced tissue response in shoulder arthroplasty

HYPOTHESIS AND BACKGROUND

Polyethylene (PE) wear debris has long been known to be important for the development of osteolysis and aseptic loosening in total joint replacements. Evaluation of shoulder hemiarthroplasty (HA) specimens provided a unique opportunity to study the histopathologic response when a PE-bearing surface was absent. We hypothesized that HAs would exhibit no significant inflammatory periprosthetic tissue response due to the absence of significant numbers of wear particles from the articulation.

METHODS

We analyzed 13 shoulder HAs. The explants were examined for damage to the bearing surface and taper damage using a stereomicroscope. The periprosthetic tissues were examined histologically for wear debris and cellular biological response. Fourier Transform Infrared spectroscopy imaging and scanning electron microscopy with energy dispersive x-ray spectroscopy were used to characterize debris, if present, within tissue samples.

RESULTS

The average patient age at the time of implantation was 57.2 ± 7.3, and the average time in situ was 34.1 ± 29.4 months. The metal-bearing surface damage was primarily mild, with an average score of 1.5 ± 0.7. The same was true for taper damage on both humeral stem and head tapers, with average scores of 1.7 ± 0.5 and 1.7 ± 0.9, respectively. The histopathological analysis revealed the considerable presence of metal debris in 11 (91.7%), cement debris in 4 (33.3%), and suture debris in 11 (83.3%) cases. Scanning electron microscopy/energy dispersive x-ray spectroscopy revealed titanium alloy debris to be the most dominant type of metal particle present, while Fourier Transform Infrared spectroscopy imaging scans suggested polyester to be the most commonly occurring type of suture debris. Particles were mostly found within and around macrophages. The mean macrophage score was 3.1 ± 0.8, and the mean foreign-body giant cell score was 2.3 ± 1.1. There was, on average, no significant lymphocyte or neutrophil presence, except for a single septic case.

DISCUSSION AND CONCLUSION

This surgically retrieved shoulder HA cohort exhibited a considerable macrophage and foreign-body giant cell response within the periprosthetic environment. Interestingly, given the low amount of damage to metallic surfaces and the absence of a PE bearing, the tissue response does not appear to be driven by wear particles from the metal-bearing surface or taper junctions but rather from suture and, to a much lesser degree, cement and metal debris. Overall, these findings highlight the potential impact that high-tensile suture material, frequently used in high quantities around shoulder arthroplasty, may have on the periprosthetic environment and identify these materials as a potential driver of osteolysis.

Ceramic humeral heads in shoulder arthroplasty: a systematic review

HYPOTHESIS

Total shoulder arthroplasty has been used for over 50 years to treat glenohumeral arthritis. In recent years, one area of innovation has been the use of ceramic-bearing surfaces. The advantages of ceramic bearing surfaces include utility in stemless implants and hemiarthroplasty, where their use in hip arthroplasty has been shown to decrease wear rates compared to metal implants and potentially reduced revision rates. With interest in utilizing ceramics for other arthroplasty indications continuing to grow, the purpose of this systematic review is to consolidate recent clinical findings involving ceramic-bearing surfaces to determine their suitability for anatomic shoulder replacement.

METHODS

Medline, Embase, and Cochrane Library were searched up to April 2024 according to Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Metrics analyzed include patient-reported outcome measures, postoperative complications, and radiographic findings. Secondary outcomes included forward flexion, external rotation, and abduction.

RESULTS

Eight studies comparing 716 patients were included with an average follow-up of 57.3 months (range 24-70.7). The mean age for the study population was 67.7 year old. All 8 studies included cohorts that had undergone shoulder arthroplasty with an implant with a ceramic humeral head component. All studies showed significant improvement in range of motion and patient outcome scores both postoperatively and up to 2 years after the patient's initial operation. Patient satisfaction was similarly positive, with 97% of patients reporting satisfactory results. Radiographically, 6 studies reported Lazarus grades with 71.9% (213/296) were grade 0, 23.3% (69/296) were grade 1, 3.7% (11/296) were grade 2, and 0.67% (2/296) demonstrated a grade 3 Lazarus score. One study presented a patient with a grade 5 Lazarus, making up only 0.34% (1/296) of the observed population.

CONCLUSION

Anatomic shoulder replacements using ceramic-bearing surfaces show safety and efficacy at numerous follow-up intervals, with complication rates approaching those of historical controls with metal implants. Future randomized controlled trials should be performed to investigate potential advantages compared to titanium and cobalt-chromium alloy humeral heads.

Recent Advances in the Design and Application of Shoulder Arthroplasty Implant Systems and Their Impact on Clinical Outcomes: A Comprehensive Review

Purpose of Review

This narrative review comprehensively aims to analyze recent advancements in shoulder arthroplasty, focusing on implant systems and their impact on patient outcomes. The purpose is to provide a nuanced understanding of the evolving landscape in shoulder arthroplasty, incorporating scientific, regulatory, and ethical dimensions.

Recent Findings

The review synthesizes recent literature on stemless implants, augmented glenoid components, inlay vs onlay configurations, convertible stems, and associated complications. Notable findings include improved patient-reported outcomes with stemless implants, variations in outcomes between inlay and onlay configurations, and the potential advantages of convertible stems. Additionally, the regulatory landscape, particularly the FDA's 510(k) pathway, is explored alongside ethical considerations, emphasizing the need for standardized international regulations.

Summary

Recent innovations in shoulder arthroplasty showcase promising advancements, with stemless implants demonstrating improved patient outcomes. The review underscores the necessity for ongoing research to address unresolved aspects and highlights the importance of a standardized regulatory framework to ensure patient safety globally. The synthesis of recent findings contributes to a comprehensive understanding of the current state of shoulder arthroplasty, guiding future research and clinical practices.

Fabrication and Characterization of Biomedical Ti-Mg Composites via Spark Plasma Sintering

The fabrication of Ti-Mg composite biomaterials was investigated using spark plasma sintering (SPS) with varying Mg contents and sintering pressures. The effects of powder mixing, Mg addition, and sintering pressure on the microstructure and mechanical properties of the composite materials were systematically analyzed. Uniform dispersion of Mg within the Ti matrix was achieved, confirming the efficacy of ethanol-assisted ball milling for consistent mixing. The Young's modulus of the composite materials exhibited a linear decrease with increasing Mg content, with Ti-30vol%Mg and Ti-50vol%Mg demonstrating reduced modulus values compared to pure Ti. Based on density measurements, compression tests, and Young's modulus results, it was determined that the sinterability of Ti-30vol%Mg saturates at a sintering pressure of approximately 50 MPa. Moreover, our immersion tests in physiological saline underscore the profound significance of our findings. Ti-30vol%Mg maintained compressive strength above that of cortical bone for 6-to-10 days, with mechanical integrity improving under higher sintering pressures. These findings mark a significant leap towards the development of Ti-Mg composite biomaterials with tailored mechanical properties, thereby enhancing biocompatibility and osseointegration for a wide range of biomedical applications.

Common Factors in Shoulder and Hip Arthroplasty Implant Failures: A Historical Review

In this era of subspecialty care in orthopedics, iterations of implant design can occur in a silo which then precludes gaining knowledge from failures of implant design that may have occurred in different subspecialties. This literature review describes the history of failures in hip and shoulder arthroplasties with the purpose of identifying similar factors that led to previous implant failures. A review of the literature was performed by two reviewers assessing articles that described failed hip and shoulder arthroplasty systems over time. We identified and analyzed 53 implant failures-23 in hip arthroplasty and 30 in shoulder arthroplasty. These failures were categorized as material, mechanical, and technical. In hip arthroplasty, 48% were material, 39% mechanical, and 13% technical failures. In shoulder arthroplasty, the distribution was 10% material, 70% mechanical, and 20% technical failures. The distribution of these failures highlights similar and sometimes repeated failure mechanisms between subspecialties. This accentuates the importance of a collaborative approach to improve future arthroplasty designs.

Implant breakage after shoulder arthroplasty: a systematic review of data from worldwide arthroplasty registries and clinical trials

BACKGROUND

Implant breakage after shoulder arthroplasty is a rare complication after aseptic loosening, infection or persistent pain, resulting in malfunction of the components requiring revision surgery. This correlates with a high burden for the patient and increasing costs. Specific data of complication rates and implant breakage are available in detailed arthroplasty registries, but due to the rare occurrence and possibly underestimated value rarely described in published studies. The aim of this systematic review was to point out the frequency of implant breakage after shoulder arthroplasty. We hypothesized that worldwide arthroplasty registry datasets record higher rates of implant breakage than clinical trials.

METHODS

PubMed, MEDLINE, EMBASE, CINHAL, and the Cochrane Central Register of Controlled Trials database were utilized for this systematic review using the items "(implant fracture/complication/breakage) OR (glenoid/baseplate complication/breakage) AND (shoulder arthroplasty)" according to the PRISMA guidelines on July 3rd, 2023. Study selection, quality assessment, and data extraction were conducted according to the Cochrane standards. Case reports and experimental studies were excluded to reduce bias. The breakage rate per 100,000 observed component years was used to compare data from national arthroplasty registries and clinical trials, published in peer-reviewed journals. Relevant types of shoulder prosthetics were analyzed and differences in implant breakage were considered.

RESULTS

Data of 5 registries and 15 studies were included. Rates of implant breakage after shoulder arthroplasty were reported with 0.06-0.86% in registries versus 0.01-6.65% in clinical studies. The breakage rate per 100,000 observed component years was 10 in clinical studies and 9 in registries. There was a revision rate of 0.09% for registry data and 0.1% for clinical studies within a 10-year period. The most frequently affected component in connection with implant fracture was the glenoid insert.

CONCLUSION

Clinical studies revealed a similar incidence of implant failure compared to data of worldwide arthroplasty registries. These complications arise mainly due to breakage of screws and glenospheres and there seems to be a direct correlation to loosening. Periprosthetic joint infection might be associated with loosening of the prosthesis and subsequent material breakage. We believe that this analysis can help physicians to advise patients on potential risks after shoulder arthroplasty.

LEVEL OF EVIDENCE

III.

Metallosis-Induced Conversion Shoulder Arthroplasty: A Unique Experience and Literature Review

BACKGROUND

Total shoulder arthroplasty (TSA) can fail for several reasons, such as component loosening, periprosthetic fracture, instability, infection, soft tissue failure, or joint overstuffing. Severe metallosis without loose glenoid components after TSA may result in the need for revision to reverse TSA.

CASE PRESENTATION

Four years before the current presentation, an 86-year-old woman suffered from right shoulder pain and swelling. The initial diagnosis was osteoarthritis of the shoulder joint, for which she underwent TSA. Four years later, she complained of shoulder joint pain, swelling, and limited range of motion. On sonography, subscapularis and supraspinatus tendon tears were identified. Plain radiographs and computed tomography (CT) scans showed metallosis around the shoulder joint. Due to the rocking horse mechanism, wear of the upper portion of the glenoid component and bearing caused a foreign-body reaction and severe metallosis around the joint. Due to a massive rotator cuff tear combined with glenoid component wear, the patient eventually underwent reverse TSA (RTSA) and was satisfied with the final results.

CONCLUSIONS

Severe metallosis due to glenoid component wear combined with a massive rotator cuff tear in TSA may cause the need for revision to RTSA.

Innovations in Shoulder Arthroplasty

Innovations currently available with anatomic total shoulder arthroplasty include shorter stem designs and augmented/inset/inlay glenoid components. Regarding reverse shoulder arthroplasty (RSA), metal augmentation, including custom augments, on both the glenoid and humeral side have expanded indications in cases of bone loss. In the setting of revision arthroplasty, humeral options include convertible stems and newer tools to improve humeral implant removal. New strategies for treatment and surgical techniques have been developed for recalcitrant shoulder instability, acromial fractures, and infections after RSA. Finally, computer planning, navigation, PSI, and augmented reality are imaging options now available that have redefined preoperative planning and indications as well intraoperative component placement. This review covers many of the innovations in the realm of shoulder arthroplasty.

Tribocorrosion is Common, but Mild in Modular Humeral Components in Shoulder Arthroplasty: An Implant Retrieval Analysis

Background

Wear and corrosion at the junctions of modular implants are increasingly recognized issues in the design of hip and knee arthroplasty prostheses, yet less is known about their significance in shoulder arthroplasty.

Methods

A query of paired total shoulder implant specimens (eg, humeral head and stem components from the same patient) was performed using an institutional implant retrieval registry. Implants were examined under a stereomicroscope and evaluated for evidence of fretting and corrosion using the modified Goldberg scoring system. Available electronic medical records of included specimens were reviewed to report relevant clinical characteristics and identify potential associations with the presence of tribocorrosion.

Results

Eighty-three paired total shoulder implant specimens, explanted at a single institution between 2013 and 2020, were analyzed. Corrosion was identified in 52% (43/83) of humeral head components and 40% (33/83) of humeral stem components. Fretting was identified in 29% (24/83) of humeral head components and 28% (23/83) of humeral stem components. Of the 56 paired implants for which clinical data were available, the duration of implantation (DOI) was less than 2 years in 29% of paired implants and greater than 5 years in 36% of implants. The presence of corrosion or fretting was not associated with DOI, a male humeral head taper, or periprosthetic infection as the indication for revision.

Conclusion

Mild tribocorrosion was present in more than half of the retrieved humeral implant specimens. However, trunnionosis did not manifest as a clinical cause of revision surgery in our study.