Introduction: Oxinium (OxZr) heads consist of zirconium with 2.5% niobium, and undergo heat-treatment to obtain a 5μm-thick zirconia (ZrO2) layer. Most available data are based on in vitro tests while data on the in vivo performance are limited. Thus, this study’s objective is to compare surgically retrieved Oxinium, ceramic and metal heads. Methods: 35 OxZr heads with a short time in situ were roughly time-matched with 23 ceramic and 26 CoCrMo heads, including all available stems and PE liners with little surgical damage. An optical coordinate-measuring machine was used to analyze the head bearing surfaces, liners and head and stem tapers. The liner damage was scored from 1-4 under a light-microscope based on the presence and severity of grooves/scratches, pit- ting/embedded debris, and polishing for a total possible score of 12. Selected OxZr heads’ areas and a cross-section of the layer were analyzed in a Scanning electron microscope (SEM). Capsule tissues of three patients with a damaged OxZr head were examined his- tologically and with SEM. Roughness measurements of heads and tapers were performed using a 3D Laser Confocal Scanning Microscope. Results: OxZr heads exhibited significantly higher shape deviation and bearing surface’s volume loss than ceramics and metals, despite extensive volume loss was not observed in most heads, tapers and liners. Loosening, instability and dislocation were highly detri- mental for OxZr heads. OxZr heads displayed pits, indents, and cracking of the layer. All tissues showed a benign response to OxZr debris. The liners’ total damage score was not significantly different among head materials. Also, OxZr heads had proximal engage- ment, with minimal head taper damage compared to CoCrMo. Finally, OxZr heads had a significantly higher surface area roughness and presented niobium-rich regions in the substrate, in the layer and at the interface. Conclusion: OxZr heads seem to outperform metal heads in corrosion resistance but appear to be less favorable with respect to bearing surface wear compared to both metals and ceramics. Thus, the justification for using OxZr over CoCrMo and, especially, ce- ramic heads remains unclear.
Introduzione: Le testine in Oxinium (OxZr) sono composte da zirconio con il 2,5% di niobio e sottoposte a trattamento termico per ottenere uno strato di zirconia (ZrO2) spesso 5μm. I dati disponibili sono principalmente in vitro, mentre i dati in vivo sono limitati. Perciò, copo di questo studio è confrontare teste in Oxinium, ceramica e metallo recuperate chirurgicamente. Metodi: 35 teste in OxZr, 23 in ceramica and 26 in CoCrMo con breve tempo in situ sono state confrontate insieme agli steli e agli inserti acetabolari in PE con poco danno chirurgico. Una macchina ottica di misura a coordinate ha analizzato le superfici di contatto di teste, inserti e tapers di testa e stelo. Il danno agli inserti è stato valutato da 1 a 4 con microscopio ottico per presenza e gravità di solchi/graffi, pitting/detriti incorporati e lucidatura, per un massimo possibile di 12. Aree selezionate delle teste in OxZr e una sezione dello ZrO2 sono state esaminate al microscopio elettronico a scansione (SEM). Tessuti capsulari di tre pazienti con teste in OxZr danneggiate sono stati esaminati istologicamente e con SEM. Misurazioni della rugosità di teste e tapers sono state eseguite utilizzando un Microscopio Confocale a Scansione Laser 3D. Risultati: Le teste in OxZr hanno mostrato deviazioni di forma e perdite di volume sulla superficie di contatto significativamente maggiori rispetto a quelle in ceramica e metallo, sebbene perdita di volume estesa non fosse osservata in maggior parte delle teste, tapers e inserti. Allentamento, instabilità e lussazione risultavano dannosi per le teste in OxZr. Le teste in OxZr hanno mostrato fossette, indentazioni e crepe nello strato. Tutti i tessuti hanno risposto benignamente ai detriti di OxZr. Il punteggio totale dei danni agli inserti non differiva significativamente tra materiali delle teste. Le teste in OxZr mostravano accoppiamento prossimale, con danni minimi al taper della testa rispetto a CoCrMo. Presentavano anche una rugosità superficiale significativamente maggiore e regioni ricche di niobio nello strato, nel substrato ed all’interfaccia. Conclusione: Le teste in OxZr resistono alla corrosione meglio delle metalliche ma mostrano maggiore usura superficiale rispetto alle metalliche e ceramiche. Pertanto, resta incerto l’uso di testine in OxZr rispetto alle metalliche e, soprattutto, alle ceramiche.
In vivo wear performance of total hip replacements with oxinium femoral heads: a retrieval perspective
CANOSSI, CARLO MARIA
2022/2023
Abstract
Introduction: Oxinium (OxZr) heads consist of zirconium with 2.5% niobium, and undergo heat-treatment to obtain a 5μm-thick zirconia (ZrO2) layer. Most available data are based on in vitro tests while data on the in vivo performance are limited. Thus, this study’s objective is to compare surgically retrieved Oxinium, ceramic and metal heads. Methods: 35 OxZr heads with a short time in situ were roughly time-matched with 23 ceramic and 26 CoCrMo heads, including all available stems and PE liners with little surgical damage. An optical coordinate-measuring machine was used to analyze the head bearing surfaces, liners and head and stem tapers. The liner damage was scored from 1-4 under a light-microscope based on the presence and severity of grooves/scratches, pit- ting/embedded debris, and polishing for a total possible score of 12. Selected OxZr heads’ areas and a cross-section of the layer were analyzed in a Scanning electron microscope (SEM). Capsule tissues of three patients with a damaged OxZr head were examined his- tologically and with SEM. Roughness measurements of heads and tapers were performed using a 3D Laser Confocal Scanning Microscope. Results: OxZr heads exhibited significantly higher shape deviation and bearing surface’s volume loss than ceramics and metals, despite extensive volume loss was not observed in most heads, tapers and liners. Loosening, instability and dislocation were highly detri- mental for OxZr heads. OxZr heads displayed pits, indents, and cracking of the layer. All tissues showed a benign response to OxZr debris. The liners’ total damage score was not significantly different among head materials. Also, OxZr heads had proximal engage- ment, with minimal head taper damage compared to CoCrMo. Finally, OxZr heads had a significantly higher surface area roughness and presented niobium-rich regions in the substrate, in the layer and at the interface. Conclusion: OxZr heads seem to outperform metal heads in corrosion resistance but appear to be less favorable with respect to bearing surface wear compared to both metals and ceramics. Thus, the justification for using OxZr over CoCrMo and, especially, ce- ramic heads remains unclear.| File | Dimensione | Formato | |
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2024_04_Canossi_Tesi_01.pdf
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2024_04_Canossi_Executive_Summary_02.pdf
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Descrizione: Executive summary
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https://hdl.handle.net/10589/218614