Mechanical and biological aspects of impaction bone grafting in revision hip surgery and the use of a new synthetic bone graft

AIMS: This thesis aims to examine the biological and mechanical factors which influence the strength of impacted morsellised bone graft. The use of synthetic materials as bone graft enhancers was also analysed (Controlled Release Glass - Corglaes®, Giltech Ltd, Ayr, Scotland and Tricalcium Phosphate Hydroxyapatite - TCP/HA, Stryker Howmedica Osteonics, Berkshire, UK). METHODS: Phase I - the mechanical strength of different fresh frozen human bone graft preparations were analysed in the laboratory, looking specifically at the effect of particle size, washing the graft and using synthetic additives. Phase II - mixtures of bone graft and bone graft/Corglaes®, which had been identified as being mechanically stronger than standard bone graft, were analysed for their biological response in an in-vivo ovine defect model, compared to controls. Bone densitometry and histological analysis was performed. Phase III - a mixture of bone graft and Corglaes® was compared to the current 'gold standard' of allograft bone alone, in a simulated revision in-vivo ovine femoral hip replacement model. Outcome measures of subsidence, micromotion on cyclical loading and histomorphometry were performed. RESULTS: Phase 1 - Fresh frozen human bone-graft behaves in a similar fashion to theoretical predictions based on Engineering principles. These principles follow Soil Mechanics theory and are commonly used by engineers when designing stable foundations for roads or buildings. In general, when the spread of different particle sizes is uniform over a given range, the material is stronger (more resistant to shear) than if the particles are all the same size. This allowed determination of which bone mills produce the strongest graft. These results were dependent on the degree of fluid release on graft milling, with more fluid release when the average particle size is reduced. Shear strength was improved for all mills after washing the morsellised graft or by the addition of synthetic additives (Corglaes® and TCP/HA). Phase 2 - The defect model allowed analysis of remodelling of the impacted pellets, highlighting rapid dissolution of the Corglaes®, without a significant inflammatory response. The model may be closer to a fracture model when the histological results of phase III are considered. Phase 3 - No statistically significant difference in subsidence over the implantation period (12 weeks) or micromotion of the retrieved implant / femur composites could be elicited between the two groups. Histological analysis revealed the distal impacted graft to be in an isolated environment, both from biological ingress and solution exchange. Bone graft and Corglaes® that was remodelled or resorbed after time in the Phase II defect experiments, was little changed with time in the distal femur. The proximal femur histologically behaved in a similar fashion to the defect experiments. This suggests that a defect model alone is not ideal to analyse materials for impaction grafting. CONCLUSIONS: • Graft strength is variable depending on the bone mill that produces it - washing bone graft improves the strength from all bone mills tested. • Tight compaction with smaller particles does not inhibit neovascularisation. • Novel biomaterials by themselves were inferior mechanically and biologically. • 50/50 mixes of allograft and Corglaes® are stronger mechanically and do not appear to have an adverse effect on biological incorporation. • In this sheep hemiarthroplasty model, subsidence, micromotion and histomorphometry results better replicate the equivalent reported human results than previous models, especially unloaded defect models in lower vertebrates

Bone and metal - an orthopaedic perspective on osseointegration of metals

The area of implant osseointegration is of major importance, given the predicted significant rise in the number of orthopaedic procedures and an increasingly ageing population. Osseointegration is a complex process involving a number of distinct mechanisms affected by the implant bulk properties and surface characteristics. Our understanding and ability to modify these mechanisms through alterations in implant design is continuously expanding. The following review considers the main aspects of material and surface alterations in metal implants, and the extent of their subsequent influence on osseointegration. Clinically, osseointegration results in asymptomatic stable durable fixation of orthopaedic implants. The complexity of achieving this outcome through incorporation and balance of contributory factors is highlighted through a clinical case report

Wave propagation in a quasi-periodic waveguide network

We investigate the transport properties of a classical wave propagating through a quasi-periodic Fibonacci array of waveguide segments in the form of loops. The formulation is general, and applicable for electromagnetic or acoustic waves through such structures. We examine the conditions for resonant transmission in a Fibonacci waveguide structure. The local positional correlation between the loops are found to be responsible for the resonance. We also show that, depending on the number of segments attached to a particular loop, the intensity at the nodes displays a perfectly periodic or a self-similar pattern. The former pattern corresponds to a perfectly extended mode of propagation, which is to be contrasted to the electron or phonon characteristics of a pure one dimensional Fibonacci quasi-crystal.Comment: 15 pages, 5 figure

Philosophical predecessors and contemporaries of Ibn Bajjah

MakaleÇıkış noktamız arkadaşı İbn el-İmam’ın (tam adı Ebul Hasan Ali b. Abd el-Aziz b. El-İmam el-Ensâri, bkz.) İbn Bâcce’nin eserlerinden oluşan bir koleksiyonun önsözünde (onun hakkında) yazmış olduğu ve İbn El Useybia tarafından da tekrar edilen, İbn Bâcce’nin (felsefî görüşlerinin) ortaya konulmasıdır. İbn el-İmam arkadaşı hakkında şöyle diyor: Zekâsının ve derin araştırmasının, bu saygın, asil ve derin fikirlere nüfuz etmesinde (yani felsefede) o çağının harikası idi ve zamanında adını göklere yazdırmıştı. Bunun için (gerekli) felsefî kitaplar, (bahsedilen kitapları) ve doğuda yazılan nadir eserleri, eskilerin ve diğer (filozofların) kitaplarını getiren, El-Hakem (yani el-Hakem II. 350/961-366/976), -Allah ondan razı olsun- zamanından beri İspanya’da mevcuttu. Onlar tekrar tekrar incelendi, ondan (İbn Bâcce’den) önce araştırmacıların hiçbiri tarafından bu eserler herhangi birşekilde açılmadı, İşbiliye’li İbn Hazm’ın durumunda olduğu gibi onlar hakkında hatalar ve değişiklikler haricinde yazılmış bir şey bırakan olmadı. O (İbn Bâcce) zamanının en büyük araştırmacıları arasındaydı, onların çoğu fikirlerinin hiç birini kaydetmeye çabalamadı, o araştırmacıların en üstünü idi ve doğal olarak analiz yapmada (onlardan) daha keskin bir zekâya sahipti. Bu ilimlerdeki araştırma yolları yalnızca bu bilge kişi ve İşbiliyeli Malik b. Vuheyb tarafından açıldı. Onlar birbirinin çağdaşı idi,fakat Malik mantık ilkeleri üzerine yazılmış sadece küçük hacimli bir eser (Es-Sına’ah ed-Diniyyeh) bıraktı. Sonra ikincisi, hayatına yapılan teşebbüsleri kendi hesabına dikkate aldığı için ve bilimsel konulardaki toplantılarının tamamında zafer hedeflediğinden bu bilimleri açıkça araştırmaktan ve onlar hakkında konuşmaktan vazgeçti. Dini ilimlere döndü ve neredeyse onların en önde geleni oldu, fakat ne bu tür bir felsefî bilginin ışığı sözleri üzerinde parladı, ne de ölümünden sonra bulunacak özel bir felsefî yazı bıraktı

Evidence of a Lombard response in migrating humpback whales (Megaptera novaeangliae)

The Lombard reflex is an increase in the subject's vocal levels in response to increased noise levels. This functions to maintain an adequate signal-to-noise ratio at the position of the receiver when noise levels vary. While it has been demonstrated in a small number of mammals and birds including some whales, it has not yet been shown to occur in one of the most vocal species of baleen whale, the humpback whale (Megaptera novaeangliae). Humpback whales were simultaneously visually and acoustically tracked (using an array of calibrated hydrophone buoys) as they migrated southward. Source levels of social vocalizations were estimated from measured received levels and a site-specific empirical sound propagation model developed. In total, 226 social vocalizations from 16 passing groups of whales were selected for final analysis. Noise levels were predominantly wind-dependent (from sea surface motion) and ranged from 81 to 108 dB re 1 mu Pa in the 36Hz-2.8 kHz band. Vocalization source levels increased by 0.9 dB for every 1 dB increase in wind-dependent background noise levels, with source levels (at 1 m) being maintained similar to 60 dB above the noise level. (C) 2014 Acoustical Society of America

Submillimetre Constraints on Hyper-Extremely Red Objects in the Subaru Deep Field

We have mapped the submillimetre wavelength continuum emission from the Subaru Deep Field (SDF) at 450 and 850 microns with the Submillimetre Common-User Bolometer Array (SCUBA) detector on the James Clerk Maxwell Telescope (JCMT). The near-IR image of the SDF is one of the deepest near-IR images available and contains four `hyper extremely red objects' (HEROs). These data allow us to test the connection between `extremely red objects' (EROs) found in IR surveys and the population of bright submillimetre sources found with SCUBA. We present a weak measurement of the average flux of the four K-band selected HEROs of 1.15 (+/-0.46) mJy, which fails to support the hypothesis that HEROs should be bright SCUBA sources. Our data are consistent with the HEROs being objects with SEDs like that of Arp220 out to z~1.7, however, the extinction in the HEROs must be about 1 magnitude greater in the J-band than is the case for Arp220 and they would need to be 1.7 times as luminous as Arp220. On the other hand, an evolutionary model of elliptical galaxies at z~2-3 in a dusty starburst phase is also in agreement with the submillimetre data, as was originally proposed for the HEROs.Comment: 7 pages, 5 figures, accepted for publication in MNRAS July 5th, 200