A Tribological assessment of the porous coated anatomic total hip replacement

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

Complications after the Introduction of Well-Documented Components in Primary Total Hip Arthroplasty

Lonkan tekonivelleikkaus on yleensä menestyksekäs toimenpide joka vähentää kipua ja parantaa potilaan liikuntakykyä. Lonkan tekonivelleikkauksen tulokset ovat jatkuvasti parantuneet vuosikymmeniä jatkuneen komponenttien ja leikkaustekniikoiden kehittymisen ansiosta. Kuitenkin uusien komponenttien käyttöönoton seurauksena saattaa ilmetä odotettua enemmän komplikaatioita. Yleisimmät vakavat komplikaatiot lonkan tekonivelleikkauksen jälkeen ovat lonkkaproteesin sijoiltaanmeno eli luksaatio, tekonivelinfektio ja periproteettinen murtuma. Luksaatioalttiit potilaat saattavat hyötyä komponenteista, jotka on suunniteltu ehkäisemään sijoiltaanmenoja, kuten dual-mobility -kupista tai lukkomekanismin sisältävästä lineristä. Näitä aiemmin lähinnä uusintaleikkauksissa hyödynnettyjä komponentteja käytetään nykyään enenevästi jo ensitekonivel- leikkauksissa. Korkean murtumariskin potilailla on jo pidempää suosittu sementillistä varsikomponenttejaa, johon liittyy pienempi periproteettisen murtuman riski. Euroopan Unionin alueella sairaaloilla on velvollisuus kilpailuttaa säännöllisesti käyttämänsä tekonivelkomponentit julkisten varojen käytön tehostamiseksi ja eurooppalaisten yritysten kilpailukyvyn parantamiseksi. Todennäköisesti uusia komponentteja otetaan siis käyttöön säännöllisesti eurooppalaisissa sairaaloissa. Tekonivelsairaala Coxassa uudet tekonivelkomponentit otettiin käyttöön kilpailutusprosessin jälkeen huhtikuussa 2016. Kyseiset komponentit olivat tunnettuja ja niiden tulokset aiemmissa tutkimuksissa olivat olleet hyviä. Tämän väitöskirjan tavoite oli tutkia komplikaatiota, joita ilmeni näiden tunnettujen implanttien käyttöönoton jälkeen, sekä keinoja luksaatioiden ehkäisyksi. Ensimmäisessä osatyössä verrattiin aiemmin käytössä olleen Pinnacle-kupin ja uutena käyttöön otetun Continuum-kupin välistä luksaation riskiä. Toisessa osatyössä verrattiin periproteettisen murtuman esiintyvyyttä ja yleistä revision riskiä aiemmin käytetyn sementillisen Exeter-varren ja uutena käyttöönotetun sementillisen CPT-varren välillä, jotka molemmat ovat nk. taper-slip -varsia. Kolmannessa osatyössä rakennettiin varhaiselle luksaation vuoksi tehdylle revisiolle kaksi ennustemallia kahden erilaisen tilastollisen menetelmän pohjalta (perinteinen logistinen regressio ja koneoppimista hyödyntävä elastic net -menetelmä). Kolmen ensimmäisen osatyön aineistot pohjautuivat Coxan omaan tietokantaan. Neljännessä osatyössä selvitettiin lonkan ensitekonivelleikkauksessa käytettyihin dual-mobility - kuppeihin ja lukollisiin linereihin liittyvää uusintaleikkauksen kumulatiivista ilmaantuvuutta, ja selvitettiin tekonivelnupin koon vaikutusta lukollisten linerien tuloksiin Suomen Tekonivelrekisterin datassa. Verrokkiryhmänä tässä tutkimuksessa toimi iso kohortti perinteiset tekonivelkomponentit saaneita potilaita. Ensimmäisessä osatyössä havaittiin, että jopa 5.1% potilaista, joille oli asennettu uutena käyttöönotettu Continuum-merkkinen kuppi neutraalin linerin kanssa sai varhaisen luksaation. Monimuuttuja-analyysissä luksaatioriski oli korkeampi potilailla, jotka olivat saaneet Continuum-kupin ja neutraalin linerin verrattuna potilaisiin jotka saivat aiemmin käytössä olleen Pinnacle-kupin (odds ratio 4.8, 95% luottamusväli [LV95] 1.4-17). Sen sijaan kun Continuum-kuppia käytettiin reunakorotuksellisen elevated rim -linerin kanssa, luksaatioriski oli samaa tasoa Pinnacleen verrattuna (odds ratio 1.2, LV95 0.2-7.8). Toisessa osatyössä todettiin, että periproteettinen murtuma oli yleisin syy uusintaleikkaukselle potilailla, joilla käytettiin taper-slip -varsia. Periproteettinen murtuma kattoi 35% uusinta- leikkauksista jotka tehtiin 2 vuoden sisällä ensileikkauksesta. Periproteettisen murtuman esiintyvyys 2 vuoden kohdalla ensileikkauksesta oli 1.6% (LV95 1.0-2.4) CPT-varrella ja 1.0% (LV95 0.6-1.6) Exeter-varrella. CPT-varren käyttö lisäsi yleistä uusintaleikkauksen riskiä Exeter-varteen verrattuna (hazard ratio 1.8, LV95 1.2-2.7). Kolmannessa osatyössä molempien ennustemallien ennustekyky oli heikko ja erottelukyky kohtalainen. Mallien välillä ei ollut merkittävää eroa. Logistista regressiota hyödyntävässä mallissa varsikomponentin kiinnitystapa, epilepsialääkkeiden käyttö ja ensileikkauksen indikaatio olivat tärkeimmät ennustetekijät varhaiselle luksaation vuoksi tehdylle uusintaleikkaukselle. Neljännessä osatyössä ensileikkauksessa dual-mobility -kupin tai 36 mm:n nuppikoon lukollisen linerin saaneiden potilaiden uusintaleikkausriskin todettiin olevan samaa luokkaa kuin perinteiset tekonivelkomponentit saaneilla potilailla. Näiden ryhmien potilaista hyvin harva uusintaleikattiin luksaation vuoksi, vaikka erikoiskomponentin saaneet potilaat olivat keskimäärin monisairaampia ja alttiimpia komplikaatioille. Sen sijaan potilaista, jotka olivat saaneet pienempään (22-32 mm) nuppiin kombinoidun lukollisen linerin, huomattavasti suurempi osa uusintaleikattiin seuranta-aikana, ja tässä ryhmässä luksaatio oli yleisin uusintaleikkauksen syy. Uusien komponenttien käyttöönotto johti kohonneeseen luksaatioriskin ja suurempaan yleiseen uusintaleikkauksen riskiin suuren leikkausvolyymin tekonivelkirurgian yksikössämme. Kohonnut luksaatioriski selittyi Continuum-kupin neutraalin linerin heikolla kattavuudella, joka altisti sijoiltaanmenoille. Siksi elevated rim -mallista lineria tulisi käyttää rutiinisti Continuum-kupin kanssa. Taper slip - tyyppisiä varsia, erityisesti CPT:tä, tulisi välttää potilailla joilla on kohonnut periproteettisen murtuman riski. Kun uusia implantteja otetaan käyttöön, leikkaustuloksia tulisi tarkkailla erityisen huolellisesti, sillä yllättävän paljon komplikaatioita saattaa ilmetä, vaikka käyttöönotetut komponentit olisivat hyvin dokumentoituja ja olisivat saaneet hyviä tuloksia aiemmissa tutkimuksissa. Koska luksaatio on harvinainen ja monitekijäinen komplikaatio, luksaation vuoksi tehdyn uusintaleikkauksen ennustaminen on vaikeaa, vaikka ennustemalli rakennettaisiin ison potilasjoukon ja yksityiskohtaisten potilastietojen pohjalta, eikä monimutkaisten tilastollisten menetelmien hyödyntäminen tuo tällöin välttämättä merkittävää etua. Dual-mobility -kuppien käyttö korkean luksaatioriskin potilailla lonkan ensitekonivelleikkauksessa voidaan katsoa perustelluksi sekä tämän tutkimuksen tulosten että myös aiempien julkaisujen pohjalta, mutta pitkän aikavälin seurantatuloksia on julkaistu vasta niukasti. Suuremman tekonivelnupin käyttö lukollisen linerin kanssa saattaa pienentää uusintaleikkauksen riskiä, mahdollisesti pienemmän luksaatioriskin vuoksi. Siksi 36 mm:n nuppeja tulisi suosia potilailla, jotka tarvitsevat lukollisen linerin.Total hip arthroplasty (THA) is usually a very successful procedure that reduces pain and improves patients’ physical abilities. The results after THA have improved thanks to decades of development in implant designs and surgical techniques. However, there is always a risk for unexpectedly high complication rates when new components are introduced in a new institution. Currently, the most common major complication types in THA are prosthesis dislocation, periprosthetic infection, and periprosthetic femoral fracture (PFF). For dislocation-prone patients, unconventional implants that offer extra stability, such as dual-mobility cups and constrained liners, are increasingly being used in primary THA. In patients at high risk for PFF, cemented stems are preferred. Hospitals in the European Union are legally obligated to go through tendering processes frequently to increase the efficiency of the use of public funds and to improve the competitiveness of European companies. Thus, the introduction of new THA components is likely a frequent event in European hospitals. At Coxa Hospital for Joint Replacement, new THA implants were introduced after completion of a tendering process in April 2016. These were all well-documented implants with good scientific track records. The aim of this dissertation was to investigate complications after the introduction of well-documented components at our institution and to study the prevention of dislocation after primary THA. In Study I, the risk for dislocation was assessed between the previously used Pinnacle and the recently introduced Continuum cup systems. In Study II, the prevalence of revision for PFF and the risk for all-cause revision were compared between the previously used cemented Exeter stem and the recently introduced cemented CPT stem, which are both classified as ‘taper-slip stems’. In Study III, two prediction models employing different statistical approaches (traditional logistic regression and elastic net method that utilizes machine learning) were built with early revision for dislocation as the outcome. Studies I-III were based on Coxa’s own database. In Study IV, the survivorship of the dual-mobility cups and constrained liners used in primary THA and the effect of femoral head size on the survivorship of constrained liners were investigated from Finnish Arthroplasty Register data, with a large cohort of conventional primary THA patients as a reference group. In Study I, a high prevalence of early dislocation (5.1%) was found with the newly introduced Continuum cup when it was used with a neutral liner. Compared with the previously used Pinnacle cup system, the risk for dislocation was higher in the Continuum cup used with a neutral liner (odds ratio 4.8, 95% confidence interval [CI] 1.4-17), but similar in the Continuum cup used with an elevated rim liner (odds ratio 1.2, CI 0.2-7.8). In Study II, PFF was the most common reason for revision, covering 35% of all revisions during the first two postoperative years. The 2-year prevalence of PFF revision was 1.6% (CI 1.0-2.4) for the CPT stem and 1.0% (CI 0.6-1.6) for the Exeter stem. The use of the CPT stem increased the overall risk for revision compared with the use of the Exeter stem (hazard ratio 1.8, CI 1.2-2.7). In Study III, the predictive capability of both prediction models was low, and the discrimination of both models was moderate. In the logistic regression model, femoral fixation method, use of antiepileptic drugs, and the primary reason for operation were the most important predictors of revision for dislocation. In Study IV, the survivorship of the dual-mobility cups and constrained liners used with a large (36 mm) diameter femoral head was comparable with or only slightly lower than conventional THA implants even though the patients who received these unconventional implants were on average severely more morbid, and therefore more vulnerable to complications. In these study groups, only a few revisions for dislocation occurred. However, the constrained liners used with smaller (22-32 mm) femoral heads had a clearly higher revision rate, mostly due to a high rate of revisions for dislocation. The introduction of new primary THA components led to an increased risk for dislocation and a higher risk for revision in our high-volume academic joint replacement hospital. The higher risk for dislocation was explained by the weaker coverage of the recently introduced Continuum’s neutral liner compared with the previously used Pinnacle neutral liner. Therefore, the routine use of an elevated rim liner with the Continuum cup is recommended. Because the risk for PFF seems to be a concern with taper-slip stems, especially the CPT, the consideration of other stem designs for high-risk patients in primary THA is encouraged. Moreover, when new implants are introduced, the results should be carefully monitored because unexpectedly high complication rates may occur even though the implants are well- documented and have a good scientific track-record. Because dislocation is a quite rare and multifactorial event, the prediction of an early dislocation revision after primary THA is very difficult, even with a large cohort of patients and specific data available. Moreover, the use of sophisticated methods that utilize machine learning may not necessarily offer significant advantage. Our results, along with the recent literature, support the increased use of DMCs for dislocation-prone patients in primary THA. Still, more long-term results are needed before the use of these implants becomes more widespread. Also, it seems that enlarging the femoral head with CLs enhances the survival of the implant, potentially because of the decreased risk for dislocations. Therefore, it is recommended that a 36 mm femoral head is preferred when a CL is used

Bibliography of Lewis Research Center technical publications announced in 1980

This compilation of abstracts describes and indexes over 780 research reports, journal articles, conference presentations, patents and patent applications, and theses resulting from the scientific and engineering work performed and managed by the Lewis Research Center in 1980. All the publications were announced in Scientific and Technical Aerospace Reports and/or International Aerospace Abstracts

Bibliography of Lewis Research Center technical publications announced in 1986

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1986. All the publications were announced in the 1986 issues of Scientific and Technical Aerospace Reports (STAR) and/or International Aerospace Abstracts (IAA). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Aeronautical engineering: A continuing bibliography with indexes (supplement 286)

This bibliography lists 845 reports, articles, and other documents introduced into the NASA scientific and technical information system in Dec. 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical Engineering: A continuing bibliography with indexes

This bibliography lists 725 reports, articles and other documents introduced into the NASA scientific and technical information system in April 1985

Bibliography of Lewis Research Center technical publications announced in 1993

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1993. All the publications were announced in the 1993 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Space programs summary no. 37-26, volume IV FOR the period February 1, 1964 to March 31, 1964. Supporting research and advanced development

Research project summaries in propulsion, guidance and control, trajectory optimization, physics and chemistry, communications, and related space science

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Wings in Orbit: Scientific and Engineering Legacies of the Space Shuttle, 1971-2010

The Space Shuttle is an engineering marvel perhaps only exceeded by the station itself. The shuttle was based on the technology of the 1960s and early 1970s. It had to overcome significant challenges to make it reusable. Perhaps the greatest challenges were the main engines and the Thermal Protection System. The program has seen terrible tragedy in its 3 decades of operation, yet it has also seen marvelous success. One of the most notable successes is the Hubble Space Telescope, a program that would have been a failure without the shuttle's capability to rendezvous, capture, repair, as well as upgrade. Now Hubble is a shining example of success admired by people around the world. As the program comes to a close, it is important to capture the legacy of the shuttle for future generations. That is what "Wings In Orbit" does for space fans, students, engineers, and scientists. This book, written by the men and women who made the program possible, will serve as an excellent reference for building future space vehicles. We are proud to have played a small part in making it happen. Our journey to document the scientific and engineering accomplishments of this magnificent winged vehicle began with an audacious proposal: to capture the passion of those who devoted their energies to its success while answering the question "What are the most significant accomplishments?" of the longestoperating human spaceflight program in our nation s history. This is intended to be an honest, accurate, and easily understandable account of the research and innovation accomplished during the era