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The tribological performance of internal joint prostheses is a fundamental influence on their longevity. The aim of this study is to characterise the tribological performance of the Porous Coated Anatomic total hip replacement by the analysis of 119 explanted prostheses. Investigations of the friction, wear, surface topography and wear debris were made and related to the joint's clinical performance. The friction of the joints at explant was similar to that of new prostheses. The median total wear volume (419mm(^3)) was found to agree with previous wear studies suggesting the existence of a threshold wear volume which promotes osteolysis. Clinical wear factor for the whole cohort matched that of alternative joint designs. The femoral head finish was shown to degrade but not in proportion to implant duration. The roughness of the UHMWPE liner was shown to fall but no relationship with any head roughness, or temporal, parameter could be distinguished. Simulator studies confirmed that the wear factor of a joint is likely to change over its lifespan. Wear models published previously describing the influence of femoral head roughness on wear could not predict the performance of explanted prostheses. An alternative relationship was observed indicating that head roughness is not as powerful a predictor of wear as previously held. A novel technique for the characterisation of the size distribution of ex vivo and in vitro wear debris was developed. A Low-Angle Laser Light Scattering Particle Analyser was used to size particles continuously over a range from 0.5 to 1000μm. This technique offers considerable unprovement over existing microscope-based methods in terms of the detail of the information and does so with less experimental effort. It was shown to be highly accurate and repeatable in preliminary investigations. Case studies of five tissue samples revealed the potential of this method.

Total knee arthroscopy is one of the most performed and most successful orthopedic surgeries, with nearly a million procedures performed in 2020 in the United States alone. Due to changing patient demographics, the use of cementless fixation for implant stability is becoming more prevalent amongst recipients. Cementless implants rely on the surface morphology of a porous coating to bond implant to bone; the quality of this bond is dependent on an interference fit and the roughness, or coefficient of friction, between implant and bone. Stress shielding is a comparison of the properties in implanted bone to natural bone; it is a commonly used measurable when using a finite element model to optimize implant design. The purpose of this study is to investigate how different coating types (coefficients of friction) and the location of their application affect the stress shielding response in the tibia. A finite element model was constructed to investigate the impact of these variables. The results concluded that the stress distribution in an implanted tibia is dependent on the coefficient of friction applied at the tip of the stem. Lower friction coefficients applied to the stem tip resulted in higher compressive stresses, and higher friction coefficients resulted in lower compressive stresses. Thus, lower friction coefficients provided more favorable stress shielding responses, however, at the expense of stress concentrations of greater magnitude.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Bacterial colonisation and biofilm formation onto total hip replacement femoral stems remain a serious complication detrimental to the success of total hip arthroplasty. Current treatment procedures are accompanied by a heavy financial burden and morbidity for the patient while failing to guarantee a successful outcome with no reinfection. In fact, infection rates after revision surgeries are typically higher than those for primary hip arthroplasties. This study investigates conceptual drug delivery channels to be incorporated within cementless femoral stems by applying additive manufacturing as enabler technology. Drug delivery from these features is aimed at both prophylaxis and treatment of infection, with the latter emphasising the concept of creating a reinforceable antimicrobial depot inside the implant. The novelty lies in facilitating the administration of multiple drug dosages from within the implant instead of the once-off implant-based release strategies currently employed. Samples containing internal channels were designed based on analogies to drug delivery studies reporting on the commercial antibiotic loaded bone cement, Palacos R+G loaded with gentamicin. These samples were manufactured by LaserCUSING® from Ti-6Al-4V ELI powder. For prophylactic proof of concept, testing the channels were filled with Palacos R+G and challenged with two clinical isolates of Staphylococcus aureus in a bacterial growth inhibition study. Gentamicin-susceptible S.aureus Xen 36 was prevented from colonising for a minimum of 72 hours, whereas gentamicin resistant S.aureus Xen 31 reached the material within 24 h, signifying the importance of drug selection according to pathogen. Hence, a solution of vancomycin in phosphate buffered saline pH 7.4 was used during in vitro reservoir release testing. Three dosage injections were made into each of six samples during a cumulative incubation period of 100 h. A biocompatible 5,000 Da molecular weight cut off polyethersulfone nanoporous membrane was employed as release rate-controlling device. Released vancomycin was quantified with reversed phase high performance liquid chromatography. The resulting release profile was characterised by means of the Korsmeyer-and-Peppas model for diffusion based drug delivery. Constraint diffusion was identified as the mechanism controlling release, implying interplay between Fickian diffusion and polymer relaxation for effecting vancomycin release from within the reservoir. The concept created in this study provides a basis towards the development of full scale intelligent implants with multiple dose in situ drug delivery capabilities. Implants incorporating this concept could aid in the perpetual struggle against infection by providing a new strategy for delivery of high level antibiotics directly to the site of infection. / AFRIKAANSE OPSOMMING: Kolonisering van bakterieë en die vorming van biofilms op totale heupvervanging femorale stamme bly ʼn ernstige komplikasie tot die sukses van ʼn totale heupvervanging. Huidige behandelingsprosedures gaan gepaard met ʼn swaar finansiële las en infeksies vir die pasiënt sonder versekering van ʼn suksesvolle uitkoms. Die voorkoms van infeksie is tipies hoër vir revisie prosedures as vir primêre heupvervangings. Hierdie studie ondersoek konseptuele dwelmvoorsieningskanale wat in sementvrye femorale stamme geïnkorporeer kan word deur middel van toevoegingsvervaardiging as bemagtigingstegnologie. Dwelmtoediening deur hierdie strukture is gemik op beide voorkoming en behandeling van infeksie met ʼn klem op die konsep van ʼn herlaaibare antimikrobiese depot in die implantaat. Die nuwigheid lê in die fasilitasie van toediening van veelvuldige dwelm dosisse vanaf binne die implantaat in plaas van die huidige eenmalige implantaatgebaseerde toedieningstrategieë. Die ontwerp van monsters wat interne kanale bevat is baseer op vergelykings met literatuur op kommersiële beensement, Palacos R+G, wat met gentamisien belaai is. Hierdie monsters is vervaardig met LaserCUSING® van Ti-6Al-4V ELI poeier. Kanale is gevul met Palacos R+G en uitgedaag met twee kliniese isolate van Staphylococcus aureus in ʼn bakteriële groei inhibisie studie. Gentamisien-sensitiewe S.aureus Xen 36 is verhoed tot kolonisasie vir ʼn minimum van 72 uur, terwyl gentamisien-weerstandige S.aureus Xen 31 die materiaal binne 24 uur bereik het. Vervolgens was ‘n oplossing van vankomisien in fosfaatbuffer soutoplossing pH 7.4 gebruik tydens in vitro vrystellingstoetse. Drie dosisse inspuitings is in elk van ses monsters oor ʼn inkubasietydperk van 100 uur toegedien. ʼn Biokompatibiele 5,000 Da molekulêre massa afsnypunt polietersulfoon nanoporeuse membraan is as vrystellingskoers regulerende apparaat gebruik. Vrygestelde vankomisien is gekwantifiseer met omgekeerde fase hoë verrigting vloeistof-chromatografie. Die vrystellingsprofiel is gekarakteriseer met die Korsmeyer-en-Peppas model vir diffusie gebaseerde dwelmtoediening. Beperkte diffusie is geïdentifiseer as die meganisme wat vrystelling beheer. Dit impliseer ʼn tussenspel in Fickiaanse diffusie en polimeer verslapping vir die tot stand bring van vankomisien vrystelling vanaf binne die reservoir. Hierdie konsep van die studie verskaf ʼn basis vir die ontwikkeling van volskaalse intelligente implantate met ʼn veelvuldige in situ dwelmtoedienings vermoë. Implantate met hierdie konseptuele strukture kan steun gee aan die voortdurende stryd teen infeksie deur ʼn nuwe strategie daar te stel vir die toediening van hoë vlak antibiotika direk by die infeksie area.

Unicompartmental knee replacement (UKR) is the principal alternative to total knee replacement (TKR) in the treatment of end-stage knee osteoarthritis. It involves less tissue resection, resulting in lower rates of morbidity and faster recoveries compared to TKR. However, UKR has a significantly higher revision rate compared to TKR. As a result, whilst over a third of patients are eligible for UKR, only around 8% receive it. A comprehensive comparison of matched patients undergoing TKR and UKR was undertaken using a large dataset from the National Joint Registry for England and Wales (NJR). Failure rates (revision, reoperation, complications and mortality), length of stay and patient-reported outcomes (PROMs) were studied. Whilst patients undergoing TKR had lower reoperation and revision rates, they had higher rates of morbidity and mortality, longer hospital stays, and inferior PROMs compared to UKR. The main reason for revision in UKR was loosening. In view of the high revision rate in UKR, NJR data was studied to identify modifiable risk factors for failure in UKR. Important patient factors were identified including age, gender and pre-operative function. Surgeons with a higher UKR caseload had significantly lower revision rates and superior patient-reported outcomes. Increasing usage (offering UKR to a greater proportion of knee replacement patients) appears to be a viable method of increasing caseload and therefore of improving results. Surgeons with optimal usage (around 50% of patients, using appropriate implants) achieved revision/reoperation rates similar to matched patients undergoing TKR. Two clinical studies were conducted to establish whether the use of cementless fixation would improve fixation and reduce the revision rate of UKR. Cementless UKR was demonstrated to be safe and reliable, with PROMs similar or superior to those demonstrated in cemented UKR. Patients with suboptimal cementless fixation were examined and pre-disposing technical factors were identified. Finally, using NJR data, the effect of the introduction of cementless UKR on overall outcomes was examined. The number of cementless cases was small, and no significant effect on implant survival was demonstrated. However, patients undergoing cementless UKR demonstrated superior PROMs. These studies demonstrate that UKR has numerous advantages over TKR in terms of morbidity, mortality and PROMs. If surgeons perform high volumes of UKR (achievable by increasing their UKR usage), these advantages can be attained without the large difference in revision rates previously demonstrated. Cementless UKR is safe and provides superior fixation and outcomes in the hands of high-volume surgeons. Further work is needed to quantify the revision rate of cementless UKR, and to assess its results in the hands of less experienced surgeons.

Le but du travail réalisé dans cette thèse était d’approfondir les connaissances en matière d’utilisation du couple de frottement céramique-céramique dans l’implantologie moderne de hanche sans ciment. L’étude clinique de 100 prothèses totales de hanche sans ciment avec un recul de 9 ans a permis de montrer la fiabilité du couple de frottement céramique en terme d’usure, de biocompatibilité et d’ostéointégration. Par la suite, la comparaison de la méthode d’implantation de ces implants (impaction du métal-back avec ou sans adjonction de vis supplémentaires) a montré que la rigidité de la céramique n’était pas incompatible avec une impaction simple du métal-back, pour des patients qui ne présentent pas de fragilité osseuse. Nous avons ensuite étudié plus particulièrement une complication de la céramique, le grincement ou squeaking. Une étude in vitro du phénomène, a permis de reproduire ce phénomène dans des conditions de lubrification optimale, avec la présence d’un troisième corps métallique entre les surfaces de frottement, suggérant l’importance des problèmes de lubrification dans la genèse du phénomène. L’analyse d’explant a conforté notre hypothèse, mettant en évidence l’importance du dessin des implants afin d’éviter les conflits prothétiques pouvant générer des particules métalliques. Enfin, l’analyse sur le long terme du phénomène de squeaking a montré son faible impact sur la survie des implants et sur la qualité de vie des patients. Ce travail, qui a associé des analyses cliniques et biomécaniques nous conforte dans l’utilisation de la céramique comme couple de frottement dans les prothèses totales de hanche sans ciment, insiste sur l’importance du dessin et du positionnement des implants pour éviter les complications qui peuvent survenir et permet de mieux connaître le problème du squeaking et ses conséquences / The aim of the study done in this thesis was to enhance the knowledge in the use of ceramic on ceramic bearing for cementless total hip arthroplasty. A clinical study of 100 cementless total hip arthroplasty at 9 years of follow-up showed the reliability of ceramic in terms of wear, biocompatibility and osseointegration. Subsequently, the comparison of the method for implantation of the implants (press-fit with or without additional screws fixations) showed that the stiffness of ceramic was not inconsistent with a simple impaction, for patients who do not present bone fragility. We then studied a particular complication of ceramic bearing, the squeaking noise. An in vitro study of this phenomenon, allowed us to reproduce squeaking in lubricated conditions, with the presence of a third metal body between the frictions surfaces, suggesting the importance on lubrication damages in the genesis of this phenomenon. Analysis of explants has confirmed our hypothesis, highlighting the importance of implant design, to avoid impingement, potentially generating metal particles. Finally, the long-term analysis of squeaking phenomenon showed its low impact on implant survival and patient’s quality of life. This work, which involved clinical and biomechanical analysis, confirms the interest for the use of ceramics bearings in total hip arthroplasty, emphasizes the importance of implant design and implant positioning, to avoid complications, and helps for a better understanding with the problem of squeaking and its consequences

Klubo sąnario endoprotezavimo operacija efektyviai sumažina arba visiškai panaikina skausmus, daugeliu atveju atstato funkcinį kojos stabilumą ir atraminę funkciją, iš dalies, bet ne visiškai atstato sąnario mobilumą (Drobniewski et al., 2012). Susidėvėjęs klubo sąnarys keičiamas cementiniu, becemenčiu arba mišriu endoprotezu (Laupacis et al., 2002). Darbo objektas: tiriamųjų emocinė būklė bei klubo sąnario funkcija po klubo endoprotezavimo operacijos. Darbo tikslas: įvertinti kineziterapijos poveikį cementinio ir becemenčio endoprotezų grupių ligoniams po klubo sąnario endoprotezavimo operacijos dėl koksartrozės, ankstyvajame reabilitacijos etape. Hipotezė: manome, kad kineziterapijos taikymas ankstyvajame reabilitacijos etape po klubo endoprotezavimo operacijos turėtų labiau pagerinti klubo sąnario funkciją becemenčio nei cementinio endoprotezo grupėje. Darbo uždaviniai: 1) Įvertinti cementinio endoprotezo grupės tiriamųjų operuoto klubo sąnario funkciją bei emocinę būklę prieš ir po kineziterapijos; 2) Įvertinti becemenčio endoprotezo grupės tiriamųjų operuoto klubo sąnario funkciją bei emocinę būklę prieš ir po kineziterapijos; 3) Palyginti operuoto klubo sąnario funkciją bei emocinę būklę tarp grupių prieš ir po kineziterapijos. Tyrimas atliktas AB „Ortopedijos technika“, kuriame dalyvavo 14 pacientų po klubo sąnario endoprotezavimo operacijos dėl koksartrozės. Jie buvo suskirstyti į dvi grupes: cementinio ir becemenčio endoprotezo grupes. Testavimai atlikti dukart –... [toliau žr. visą tekstą] / Endoprosthesis operation of the hip joint relieves or removes pain, restores functional leg stability and function of the supporting foot (Drobniewski et al., 2012). The obsolete hip joint is changed to cemented, cementless or hybrid hip prosthesis (Laupacis et al., 2002). Object: patients emotional condition and hip joint function after hip joint endoprosthesis operation. The purpose of the study was to evaluate influence of physical therapy between cemented and cementless hip prosthesis groups after hip joint endoprosthesis operation due to coxarthritis at early rehabilitation process. Hypothesis: applying physical therapy after hip joint endoprosthesis operation at early rehabilitation process should more improve hip joint function in cementless than in cemented hip prosthesis group. The tasks: 1) To evaluate operated hip joint function and emotional condition of the cemented hip prosthesis group before and after physical therapy. 2) To evaluate operated hip joint function and emotional condition of the cementless hip prosthesis group before and after physical therapy. 3) To compare hip joint function and emotional condition after operation between groups before and after physical therapy. The research has been done at AB „Ortopedijos technika“. All 14 patients were after hip joint endoprosthesis operations due to coxarthritis. They were divided into two groups: cemented and cementless hip prosthesis groups. Subjects were tested before and after psysical therapy use. It... [to full text]

L' arthroplastie de la hanche par prothèse non cimentée est une solution couramment employée pour les patients rencontrant des problèmes du système locomoteur. Une telle solution présente toutefois un inconvénient majeur, souligné par tous les utilisateurs : le manque de stabilité primaire de la prothèse. Or, cette faiblesse peut provoquer des complications graves, voire l'échec de l'opération chirurgicale. Par conséquent, parvenir à une bonne fixation primaire est un point crucial de ce type d'opération chirurgicale pour assurer cliniquement une satisfaction à court et long terme.Dans le but de mieux appréhender cette problématique centrale, une piste préopératoire a été adoptée. Un modèle éléments finis permettant de décrire le comportement mécanique du système couplé « os-prothèse non cimentée : DePuy Corail® » a été développé et validé par des expérimentations in vitro. Puis, pour tenir compte de la forte variabilité des paramètres du modèle, inhérente à la nature même du problème, une modélisation stochastique de ces derniers a été introduite et une stratégie mécano-probabiliste proposée, destinée d'une part à quantifier en termes probabilistes l'effet sur la réponse des incertitudes affectant les paramètres du modèle, et d'autre part à évaluer la stabilité primaire du système os-prothèse en contexte fiabiliste. La mise en oeuvre pratique de cette approche a été réalisée à l'aide d'outils numériques basés sur la méthode de Monte-Carlo standard et une procédure de collocation stochastique.L'originalité du travail présenté réside avant tout dans la proposition d'une méthodologie probabiliste capable de prendre en compte les incertitudes dans la problématique de la stabilité primaire des prothèses de hanche non cimentées. Elle tient également dans la potentialité de cette méthodologie à être facilement transplantable en contexte industriel. / The hip arthroplasty with cementless hip prosthesis is a solution usually used for the patients suffering the problems of the musculoskeletal system. However, such a solution has a major disadvantage, pointed by all users : the lack of primary stability of the prosthesis. This weakness can cause serious complications or failure of the surgery. Therefore, to achieve a good primary fixation is a crucial point of this type of surgery to ensure a short and a long term clinical satisfaction. In order to better understand this central issue, a preoperative track is adopted. A finite element model to describe the mechanical behavior of the coupled system " femur-cementless prosthesis : DePuy Corail® "has been created and validated by the experiments in vitro. Then, in order to take into account the high variability of model parameters, inherent to the nature of the problem, the stochastic modeling of random input parameters has been introduced and a mechanical-probabilistic strategy has been proposed, on the one hand to quantify, in probabilistic terms, the effect, on the response, of the uncertainties affecting the input parameters of the model, and on the other hand to evaluate the primary stability of the bone-prosthesis system in reliability context. The practical implementation of this approach is realized by using the numerical tools based on the standard Monte Carlo method and the stochastic collocation procedure. The originality of the work presented is primarily in the proposition of a probabilistic methodology capable of taking into account the uncertainties in the problem of primary stability of cementless hip prostheses. It also lies in the potentiality of this methodology to be transplantable easily in industrial context.