Feasibility of additive manufacturing for patient-specific knee replacements.
| dc.contributor.advisor | Van der Merwe, J. H. | en_ZA |
| dc.contributor.advisor | Becker, Thorsten Hermann | en_ZA |
| dc.contributor.author | Nortje, B. D. | en_ZA |
| dc.date.accessioned | 2021-06-23T15:06:38Z | |
| dc.date.accessioned | 2021-12-22T14:12:02Z | |
| dc.date.available | 2021-06-23T15:06:38Z | |
| dc.date.available | 2021-12-22T14:12:02Z | |
| dc.date.issued | 2021-12 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Osteoarthritis causes the degradation of the articular cartilage of the knee. This results in a loss of function of the joint. With a total knee replacement surgery, these articular surfaces are removed and replaced with artificial components. The ability to integrate patient-specific implant components can improve the results of a total knee replacement. The focus of this research is to investigate the feasibility of manufacturing methods required for a femoral knee replacement component for patient-specific implants. Through understanding what has been accomplished in literature, a multi-directional pin-on-flat wear tester is developed. This machine is based on the motion that is observed by the knee articulation in specific. A cross-shear ratio is designed to achieve similar wear characteristics to that seen in a knee replacement. This development is validated through the use of Co-Cr-Mo samples. The developed and implemented machine is utilised to perform an assessment of laser powder bed fusion, a powder bed based additive manufacturing technique, for use in patient-specific femoral knee replacements. Focus is placed on the use of Ti-6Al-4V and Co-Cr-Mo; where the latter is used for a benchmark to indicate the relative wear properties of the former. The average wear rates that resulted after 3 x 106 cycles were 2.58 mg/MC and 2.63 mg/MC for Co-Cr-Mo and Ti-6Al-4V, respectively. Additive manufacturing provides the ability to manufacture a near net shape component that is suited for the patient’s geometry. Orthopaedic surgeons consider the full and natural functioning of the replaced joint to be an indication of the operation’s success. The unsatisfactory performance of an implant can be attributed to the incorrect tension of the ligaments surround- ing the joint; this is often found to be a result of geometric intolerances of the standard implant sizes in relation to the patient’s natural joint. This can be rectified through the use of additive manufacturing which provides the ability to manufacture components of high geometric tolerances. A feasibility analysis is done with regards to cost and suitability of man- ufacturing processes for patient-specific femoral knee replacements. Additive manufacturing is compared to CNC machining to assess the feasibility of pur- suing a patient-specific femoral knee replacement that is manufactured from Ti-6Al-4V. The device that was developed illustrated satisfactory performance in ac- cordance to what is expected from literature. Through these tests, Ti-6Al-4V displayed suitable wear properties for use in articulating joints. The study places focus on the knee joint, but can be adapted for many other articulating joints with lower loading. It can then be shown that additive manufacturing may not be a feasible option for manufacturing based on cost, but may prove beneficial for reasons such as geometry complexities, surface finish, accuracy and extent to which the surfaces can be altered. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Artrose veroorsaak die agteruitgang van die artikulêre kraakbeen van die knie. Dit lei tot ’n verlies aan funksie van die gewrig. Met ’n totale knievervan- gingsoperasie word hierdie artikulêre oppervlaktes verwyder en vervang met kunsmatige komponente. Die vermoë om pasiëntspesifieke inplantaatkompo- nente te integreer, kan die resultate van ’n totale knievervanging verbeter. Die fokus van hierdie navorsing is om die haalbaarheid van vervaardigingsme- todes wat benodig word vir ’n vervangingsonderdeel vir ’n femorale knie vir pasiëntspesifieke inplantings te ondersoek. Deur te verstaan wat in die literatuur gedoen is, word ’n multi-rigting-pen- op-flat-dra-toetser ontwikkel. Hierdie masjien is gebaseer op die beweging wat spesifiek deur die knieartikulasie waargeneem word. ’n Kruis-skuifverhouding is ontwerp om soortgelyke slytasie-eienskappe te bereik as wat gesien word in ’n knievervanging. Hierdie ontwikkeling word gevalideer deur die gebruik van Co-Cr-Mo-monsters. Die ontwikkelde en geïmplementeerde masjien word gebruik om ’n beoorde- ling van die samesmelting van laserpoeierbed, ’n poeierbed-gebaseerde toevoe- gingvervaardigingstegniek, uit te voer vir gebruik in pasiënt-spesifieke femorale knievervangings. Daar word gefokus op die gebruik van Ti-6Al-4V en Co-Cr- Mo; waar die laasgenoemde gebruik word as ’n maatstaf om die relatiewe slytasie-eienskappe van eersgenoemde aan te dui. Die gemiddelde slytas wat na 3 x 106 siklusse gelei het, was onderskeidelik 2.58 mg/MC en 2.63 mg/MC vir Co-Cr-Mo en Ti-6Al-4V. Addisionele vervaardiging bied die vermoë om ’n byna netto vormkompo- nent te vervaardig wat geskik is vir die pasiënt se meetkunde. Ortopediese chirurge beskou die volledige en natuurlike werking van die vervangde gewrig as ’n aanduiding van die sukses van die operasie. Die onbevredigende werking van ’n inplantaat kan toegeskryf word aan die verkeerde spanning van die liga- mente rondom die gewrig; dit word dikwels gevind as gevolg van meetkundige onverdraagsaamhede van die standaardinplantingsgroottes in verhouding tot die natuurlike gewrig van die pasiënt. Dit kan reggestel word deur die gebruik van toevoegingsvervaardiging, wat die vermoë bied om komponente met hoë meetkundige toleransies te vervaardig. ’n Uitvoerbaarheidsanalise word gedoen met betrekking tot die koste en geskiktheid van vervaardigingsprosesse vir pasiëntspesifieke femorale kniever- vangings. Toevoegingsvervaardiging word vergelyk met CNC-bewerking om die haalbaarheid van die voortsetting van ’n pasiëntspesifieke femorale knie- vervanging wat van Ti-6Al-4V vervaardig is, te bepaal Die apparaat wat ontwikkel is, illustreer bevredigende werkverrigting in ooreenstemming met wat uit literatuur verwag word. Na hierdie toetse het Ti-6Al-4V geskikte slytasie-eienskappe vertoon vir gebruik in artikulasiever- bindings. Die studieplekke fokus op die kniegewrig, maar kan aangepas word vir baie ander artikulerende gewrigte met laer lading. Daar kan dan aan- getoon word dat toevoegingsvervaardiging nie ’n haalbare opsie vir vervaar- diging is nie, gebaseer op koste, maar dit kan voordelig wees vir redes soos meetkunde-kompleksiteit, oppervlakafwerking, akkuraatheid en mate waarin die oppervlaktes verander kan word. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/123609 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.subject | Additive manufacturing | en_ZA |
| dc.subject | Ti-6Al-4V | en_ZA |
| dc.subject | Knee replacement | en_ZA |
| dc.subject | Wear testing | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | Artificial knee | en_ZA |
| dc.subject | Osteoarthritis | en_ZA |
| dc.title | Feasibility of additive manufacturing for patient-specific knee replacements. | en_ZA |
| dc.type | Thesis | en_ZA |