Spatial Sensors for Quantitative Assessment of Retrieved Arthroplasty Bearings

Evaluation of retrieved joint arthroplasty bearings provides unique evidence related to the physiological environment in which bearing materials are expected to perform. This dissertation describes the development of novel spatial sensors and measurement strategies for standardized, quantitative assessments of arthroplasty bearings, including total knee replacements, unicompartmental knee replacements, and total hip replacements. The approach is to assess bearings that endured a finite duration of function in patients, with particular emphasis on expanding our understanding of the biomechanical conditions specific to bearing function and wear in the physiological environment. Several quantifiable parameters are identified that prove comparable to pre-clinical in vitro tibological evaluations, including knee wear simulation and analytical modeling. These comparisons provide clinical relevance to the existing methodologies, helping to verify that the biomechanical simulations accurately represent the in vivo conditions they are meant to simulate. The broad objective of this dissertation is to improve the longevity and function of arthroplasty bearing materials and designs. Assessments from the retrieved prostheses are discussed within the context of developing comprehensive approaches for the prospective evaluation of new materials and designs in joint replacements

Objective clinical performance outcome of total knee prostheses. A study of mobile bearing knees using fluoroscopy, electromyography and roentgenstereophotogrammetry

The aim of the thesis was to to assess with accurate and objective methods the function and fixation of total knee prostheses with special emphasis on mobile bearing total knee designs. The mobile bearing of a rotating platform design showed limited motion or no motion during a step-up task thereby nullifying the theoretical advantages of a mobile bearing prosthesis. Apatite coated implants show excellent mid-term Roentgen Stereophotogrammetric Analysis (RSA) results and offer some clinical advantages above cemented total knee arthroplasty. A prospective RSA study also revealed that the studied mobile bearing design is more predictable and forgiving with respect to micromotion of the tibial component than a posterior stabilised prosthesis. However, mobile bearing prostheses showed to be more demanding for the soft tissue structures surrounding the knee joint. The techniques used in gait analysis and fluoroscopy are sensitive for measurement errors. This restricts the applicability and interpretation of the results acquired when using these methods. In general one needs to be aware of the limitations of measurement tools since one needs accurate and objective methods to assess evidence about the clinical performance of (new) total knee prostheses.Biomet Nederland B.V., DePuy Nederland B.V., Mathys Orthopaedics B.V., Medis medical imaging systems B.V., Medis specials B.V., Smith & Nephew B.V, Stryker Nederland B.V., Wright Medical Nederland B.V., Zimmer Nederland B.V.UBL - phd migration 201

Radiostereometric analysis in total hip arthroplasty and hip fracture patients

Complications related to primary total hip arthroplasty (THA) are relatively rare but still impose a significant burden on the recovery of individual patients and incur significant costs to the healthcare system. Research aimed at improving the results of THA is challenging as complications can take up to decades to manifest clinically. However, radiostereometric analysis (RSA) can, in some cases, be used to predict the long-term revision rates of THA with only a two-year follow-up. The purpose of this doctoral thesis was to examine the causes of RSA-measured micromotion and to further develop the methodology for the research of THA and hip fracture patients. The first study examined whether preoperative systemic bone mineral density (BMD) had an effect on the early RSA-measured micromotion of a cementless acetabular cup in female patients with osteoarthritis. The second study considered tha suitability of model-based RSA (MBRSA) for the analysis of a cementless femoral stem using both a phantom model and a clinical cohort. The third study validated differentially-loaded RSA (DLRSA) for the study of internally-fixated femoral neck fractures in a clinical cohort of 16 patients. The final study examined if RSA data analysis would benefit from the use of a multivariate three-dimensional analytical method. Low systemic BMD was associated with increased proximal migration of the cementless acetabular cups. The MBRSA proved to have comparable accuracy and precision compared to conventional RSA thereby validating the method for future clinical studies using the examined femoral stem. The deployed DLRSA methodology could be used to detect inducibile micromotion of femoral neck fractures. A multivariate linear mixed-effects model could provide a more robust and sensitive method for the analysis of three-dimensional RSA data.   Radiostereometrinen analyysi lonkan kokotekonivelen ja lonkkamurtumien tutkimuksessa Lonkan kokotekonivelleikkauksen komplikaatiot ovat harvinaisia mutta aiheuttavat merkittävää haittaa yksittäisille potilaille sekä merkittäviä taloudellisia kustannuksia terveydenhuollolle. Tutkimustyö lonkan kokotekonivelleikkauksien tuloksien parantamiseksi on haastavaa, koska komplikaatioiden ilmenemiseen voi kulua jopa vuosikymmeniä ja silloinkin harvinaisten komplikaatioiden todentamiseksi tarvittaisiin suuria potilasjoukkoja. Radiostereometrisellä analyysillä (RSA) voidaan tietyissä tapauksissa kuitenkin ennakoida uusintaleikkauksen riskiä jo kahden vuoden seuranta-ajalla. Tämän väitöskirjan tavoitteena oli laajentaa nykyistä tietoa RSA:lla mitattavan mikroliikkeen syistä ja merkityksestä sekä kehittää RSAmenetelmää lonkan kokotekonivel- ja lonkkamurtumapotilailla. Ensimmäisessä osatyössä tutkittiin, onko luuntiheydellä merkitystä sementittömän lonkan kokotekonivelen kuppiosan RSA:lla mitattuun mikroliikkeeseen nivelrikkoa sairastaneilla naispotilailla. Toisessa osatyössä tutkittiin kolmiulotteiseen mallinnukseen perustuvan RSA-menetelmän (MBRSA) soveltuvuutta sementittömän lonkan tekonivelen varren tutkimukseen. MBRSA menetelmää tutkittiin ensin fantomia käyttäen ja myöhemmin tulokset varmistettiin lonkan kokotekoniveltutkimukseen osallistuneilla potilailla. Kolmannessa osatyössä selvitettiin kuormituksen aiheuttaman RSA-mikroliikkeen (DLRSA) käyttöä reisiluun kaulan murtumien tutkimuksessa. Neljännessä osatyössä selvitettiin, hyötyisivätkö RSA-tutkimukset moniulotteisesta tilastollisesta menetelmästä. Sementittömän lonkan kokotekonivelen kuppiosan varhainen mikroliike olisuurentunutta potilailla, joiden luuntiheys oli alentunut. MBRSA menetelmä soveltuu tutkitun tekonivelen varren seurantaan ja käyttöön tulevissa tutkimuksissa. Kehitettyä DLRSA-menetelmää voidaan käyttää reisiluun kaulan murtumien tutkimuksessa. Kolmiulotteisella tilastollisella mallintamisella voidaan havaita yksiulotteisia menetelmiä herkemmin ja spesifisemmin eroja RSA-mikroliikkeessä

Factores biomecânicos e estrutura do gluteus medius na artrose da anca: indicadores clínicos e radiográficos

Doutoramento em Ciências BiomédicasO presente trabalho teve como objectivo o estudo da relação entre a função, os factores biomecânicos e o grau das alterações radiográficas em doentes com diferentes graus de osteoartrose (OA) da anca. Foi efectuado protocolo de avaliação clínica e radiográfica a ambas as ancas de 65 doentes a aguardar cirurgia para colocação de prótese total da anca (PTA). Durante a cirurgia foram efectuadas, em todos os doentes, biópsias do músculo glúteo médio (GM) ipsilateral. A reavaliação 6 meses após cirurgia foi efectuada em 18 destes doentes. Utilizando a soma das medidas da entrelinha articular (EA) efectuadas em ambas as ancas e em 3 pontos da região de suporte de carga (lateral, superior e axial), obteve-se uma correlação mais forte com a função das ancas medida pelo índice de Lequesne (r=0.67, p<0.05), relativamente a qualquer valor individual incluindo a EA mínima; esta correlação foi também mais marcada com todas as amplitudes articulares com destaque para a abdução (r=0.60, p<0.05) e a rotação externa (r=0.57, p<0.05). O comprimento dos osteófitos acetabulares superiores (OAS) teve uma correlação positiva significativa com o score de dor do índice de Lequesne (r=0.38, p<0.05) e negativa com a abdução máxima (r=-0.50, p<0.05); a abdução teve a correlação mais forte com o ângulo de abdução livre radiográfico (r=0.60, p<0.05), situado entre o colo do fémur e a extremidade dos OAS e com vértice no centro da cabeça do fémur. Após mais de 6 meses da cirurgia, a anca operada apresentou correlação significativa dos parâmetros radiográficos (braço de alavanca dos músculos abdutores e índice disfuncional) com o tempo de permanência na abdução activa máxima (respectivamente r=0.61 e r=0.63; p<0.05). A soma das 3 medidas da EA teve correlação significativa com a área média das fibras do GM, sendo esta mais marcada com a EA da anca oposta (r=0.49, p<0.05) do que da anca a aguardar cirurgia (r=0.32, p<0.05). Este trabalho sugere que, nos doentes submetidos a PTA, o braço de alavanca abdutor é determinante nos resultados funcionais pós-cirurgia. A soma dos valores da EA em 3 pontos estandardizados da área de suporte de carga tem a maior correlação com o grau de evolução da OA da anca. Os OAS limitam a amplitude da abdução da anca. A atrofia do GM correlaciona-se com a medida da EA de ambas as ancas. O défice de força dos abdutores pode condicionar o desgaste articular da anca contralateral. Estes resultados apontam para a importância do reforço dos músculos abdutores e da adopção de estratégias que diminuam a sobrecarga mecânica articular de forma a prevenir e limitar a evolução da OA da anca.This study investigated the possible relationship between function, biomechanical factors and radiographic degenerative changes in patients with several degrees of hip osteoarthritis (OA). A clinical and radiographic evaluation protocol was performed on both hips of 65 patients awaiting surgery for total hip replacement (THR). During surgery a biopsy of the ipsilateral gluteus medius (GM) muscle was done in all patients. Post-surgery follow up was performed in 18 patients. The sum of radiographic joint space width (JSW) made in three points of the load bearing region (lateral, superior and axial) in both hips, evidenced a stronger correlation with hip function measured by the Lequesne Index (r=0.67, p<0.05), when compared to any individual value, including minimum JSW. This correlation was also stronger with all joint ranges, particularly abduction (r=0.60, p<0.05) and external rotation (r=0.57, p<0.05). Cranial acetabular osteophytes (CAO) length correlated positively and significantly with pain score of Lequesne Index (r=0.38, p<0.05) and negatively with maximal abduction (r=-0.50, p<0.05); abduction had the strongest correlation with the radiographic abduction free angle (r=0.60, p<0.05), located between the femoral neck and CAO lateral extremity, and with the apex at the centre of the femoral head. Follow up conducted over 6 months showed a significant correlation between post-surgery radiographic parameters (abductor muscle lever arm and hip dysfunction index) and time of maximal active abduction (r=0.61, r=0.63 and p<0.05, respectively). The sum of the three measures of hip JSW was correlated significantly with the mean GM fibre area. This correlation was stronger with the JSW of contralateral hip (r=0.49, p<0.05) than in hip awaiting surgery (r=0.32, p<0.05). This study suggests that in THR the abductor lever arm length is critical to post-surgery functional results. The sum of three standard measurements of JSW in hip weight-bearing area has the strongest correlation with the clinical development of hip OA; the hip abduction range of motion is limited by CAO; the GM atrophy correlates with JSW of both hips. The abductor weakness leads to the increase of mechanical impact during load shift, which may determine the wearing-off of the contralateral hip. Therefore, the present results point to the importance of reinforcing the abductor muscles, together with strategies to decrease the joint mechanical overload, in order to prevent and limit the evolution of hip OA.Universidade de Aveiro - Projectos I&DT em Ciências e Tecnologias da Saúde – 200

Radiostereometric analysis of initial femoral stem migration in cementless total hip arthroplasty of postmenopausal women : Exploring contributing factors in initial femoral stem migration

In cementless total hip arthroplasty (THA), femoral stems rely on the initial press‐fit fixation against the cortical bone to achieve osseointegration. In aging women, structural changes of the proximal femur may jeopardize the stem stability. Preoperative screening of bone quality and exploring the factors that cause stem migration may help in the selection process of patients for the use of cementless fixation techniques. Antiresorptive denosumab therapy might be efficient in preventing periprosthetic bone loss and reducing femoral stem migration in postmenopausal women. Sixty-five postmenopausal women with primary hip osteoarthritis (60 to 85 years old and Dorr A-type or B-type femur morphology) underwent cementless THA with implantation of a parallel-sided femoral component in a randomized double-blind placebo-controlled trial. The patients randomly received denosumab or a placebo 1 month before and 5 months after the surgery. The three-dimensional stem migration was measured using model-based radiostereometric analysis (RSA). Patient’s baseline characteristics, local and systemic bone mineral density (BMD) values measured by dual-energy X-ray absorptiometry (DXA), cortical-bone thicknes measured by pulse-echo ultrasonometry, surgery-related factors, and postoperative walking activity were examined for the association with stem migration. The accuracy and clinical precision of model-based RSA were comparable to those of marker-based RSA. Denosumab significantly decreased periprosthetic bone loss but did not reduce stem migration which occurred predominately during the first 3 months. DXA and pulse-echo ultrasonometry of the distal radius helped to identify patients at high risk of stem subsidence of more than 2 mm. Walking activity and local BMD dictated the direction and magnitude of stem rotation around y-axis. Femoral stem stability is sensitive to adequate bone stock. In postmenopausal women, stem migration is predominantly due to impaired bone quality. Inhibition of periprosthetic bone resorption did not prevent stem migration. Preoperative evaluation of the skeletal status is recommended for all postmenopausal women with hip osteoarthritis before scheduling cementless THA.Lonkan tekonivelen biologinen kiinnittyminen ikääntyvillä naisilla: varsiosan liikkeen radiostereometrinen analyysi Sementitön lonkan tekonivelleikkaus perustuu implantin biologiseen kiinnittymiseen. Kantavan varsiosan luutuminen edellyttää, että implantti saadaan leikkauksessa tukevasti paikoilleen kuoriluuta vasten. Tämän saavuttaminen voi olla vaikeaa naisilla, joille on kehittynyt vaihdevuosien jälkeen reisiluun kuoriluun ohentumista ja huokoistumista. Tästä johtuen on tärkeää selvittää ennen leikkausta potilaan luuston kunto. On myös arvioitava muita tekijöitä, jotka voivat lisätä varsiosan liikettä. Ennen leikkausta aloitettu luukatoa estävä lääkitys voi vahvistaa kuoriluuta ja näin parantaa varsiosan tukevuutta. Satunnaistettuun kliiniseen potilastutkimukseen osallistui 65 lonkan nivelrikkoa sairastavaa naispotilasta (keski-ikä 69 vuotta). Potilaille tehtiin sementitön lonkan tekonivelleikkaus. Ennen leikkausta aloitettiin luulääkitys (denosumabi), jonka tiedetään vahvistavan reisiluun kuoriluuta osteoporoosia sairastavilla naisilla. Potilaiden subjektiivista toipumista seurattiin kuvaavilla kyselykaavakkeilla ja myös objektiivisilla mittauksilla (kävelynopeus, kävelyaktiviteetti, luuntiheysmittaus, kuoriluun ultraäänimittaus ja luuaineenvaihdunnan merkkiaineet). Varsiosan kolmiulotteista liikettä seurattiin 3D-mallinnukseen perustuvalla radiostereometrisellä analyysillä. Menetelmän tarkkuus ja toistettavuus varmistettiin prekliinisessä kokeessa muoviluumalleilla. Lääkehoito esti reisiluun yläosan paikallisen luukadon varsiosan ympärillä, mutta se ei vähentänyt varsiosan painumista ja kiertymistä. Liikettä tapahtui ensimmäisten kuukausien aikana leikkauksesta. Varsiosat luutuivat ja hoitoryhmien välillä ei ollut eroa kliinisessä toipumisessa. Ennen leikkausta tehty ranteen kuoriluun paksuuden ultraäänimittaus (Bindex®) ja luuntiheysmittaus auttoivat tunnistamaan kohtalaisen hyvin ne potilaat, joille kehittyi varsiosan yli 2 mm painuminen leikkauksen jälkeen. Varsiosan kiertymisen suunta ja määrä heijastivat kävelyaktiivisuutta leikkauksen jälkeen. Tulokset vahvistivat aiempia tuloksia, että biologisesti kiinnittyvä lonkan tekonivelen varsiosa vaatii hyvää luuainesta. Luulääkkeellä (denosumabi) voidaan estää paikallista luukatoa, mutta luuresorption esto ei vähennä varsiosan alkuvaiheen liikettä. Luuston kunnon seulontaa suositellaan kaikille vaihevuosi-iän ohittaneille naisille, joille suunnitellaan sementitöntä lonkan tekonivelleikkausta

Development of assessment in hip arthroplasty review

AbstractThis thesis describes the development of criteria in hip arthroplasty review. The insertion of a hip replacement brings relief from pain and improved function but the artificial joint does not last indefinitely. Periodic review provides the opportunity to assess the state of the joint in order to identify a failing hip arthroplasty.A literature search was conducted on the subject of failing hip arthroplasty and the findings are summarised. There was a lack of standardisation of methodology but an emphasis on the need for review because of the commonly asymptomatic nature of a failing hip arthroplasty.The review process has traditionally been completed by medical members of the orthopaedic team but there has been a recent change to include non-medical health professionals in this work. A lack of formalised educational programmes has led to innovative ways of achieving the required competency, and one such method is described for the development of a skill in interpretation of x-ray images of hip replacements.Radiographic assessment is an important component of hip arthroplasty review and includes the measurement of osteolytic lesions, a phenomenon caused by the wear particles produced from the articulating surfaces of the artificial joint. A simple, clinical tool was developed to measure these irregularly shaped lesions and the testing of the tool is described.Finally, a clinical study was conducted to explore the association between changes on a patient reported outcome measure and x-ray changes over the same period of time. The patients had all received a hip replacement approximately seven years earlier (mid-term) and so were at a stage when signs of deterioration of the hip joint were likely to appear. This thesis makes a contribution to the scientific base of arthroplasty review. It demonstrates a training model for non-medical health professions to acquire the skills needed to conduct the review. It employs basic research to develop a simple and reliable tool for use in the clinical situation. It shows that, for patients reviewed at mid-term, it is essential to include an x-ray as well as a joint-specific patient reported outcome measure. This information is important for future service planning and development of practitioners, and is of benefit to patients through adding to the evidence about the criteria for arthroplasty review