Mechanical properties of morcellised bone graft with the addition of hydroxyapatite.

Mixtures of morcellised bone graft (MBG) and hydroxyapatite (HA) are frequently used in revision arthroplasty surgery. However, the changes in the mechanical properties from adding HA to MBG are unknown. This study used a uniaxial compression test to replicate impaction bone grafting and subsequent early postoperative weightbearing to investigate the effect of adding different proportion of HA to MBG. To achieve this aim, human MBG was subjected to increasing impaction forces and the apparent stiffness and creep for each stress level determined. Subsequently, increasing proportions porous and non porous HA were added to the MBG. The major findings were that the apparent stiffness for MBG increased and the associated creep decreased both with the application of increasing stress and with the addition of increasing proportions of HA. In conclusion, greater proportions of HA in the graft mixture improved the mechanical response compared with MBG impacted under the same force. This improvement replicated the properties of pure MBG under high axial stress. This study indicates that graft mixtures of MBG and HA can be tailormade for patients. The need for less impaction force in MBG:HA mixtures to obtain the same properties as pure MBG may decrease the risk of intraoperative fracture.

The effect of the addition of hydroxyapatite graft substitutes upon the hoop strain and subsequent subsidence of a femoral model during impaction bone grafting.

Impaction bone grafting using morcellised allograft can successfully restore bone stock in revision surgery. However, concerns exist regarding supply of bone and transmission of infection. Bone-graft extenders, such as tricalcium phosphate (TCP) and hydroxyapatite (HA), are used to minimise the use of donor bone. However, concerns exist around a reported increased risk of femoral fracture during impaction bone grafting with a 1:1 mixture of TCP/HA and morcellised bone graft (MBG) during impaction grafting in human cadaveric femora. Using a sawbones model, it was evaluated whether there was increased femoral cortical strain with a HA:MBG mixture during impaction grafting compared to MBG impacted at the same and a greater force. Subsequently the subsidence behaviour of the different graft mixes was compared by using a loaded femoral stem in an endurance test. It was demonstrated that the femora with the MBG:HA graft had greater cortical hoop stresses but improved subsidence behaviour compared to a graft composed of pure MBG impacted at the same force.

Hearing impairments in middle age: the acceptability, benefit and cost of detection (ABCD).

The major epidemiological investigations of hearing impairment, disability and handicap show that the elderly are the group most disabled by their hearing impairment. There is considerable debate concerning the most efficient way of reducing this inevitable burden of age-related hearing impairments in the next generation. Early fitting of 'targeted' individuals with hearing aids may help but there are a large number of methodological problems associated with conducting and evaluating such a programme of research (especially retrospectively). The logical prerequisite to early fitting as a means of reducing later disability is to ascertain the acceptability of and benefit given by intervention at this early stage. This study therefore set out to investigate the age/sex register provided by the primary physician (GP) as an appropriate base to identify candidates for early aid fitting among a sample of middle-aged patients (50-65 years) living in Roath, Cardiff. Of the 662 who replied to an initial contact letter (1050 were on the age/sex register), 21 already possessed hearing aids. After screening and examination 66 people were offered some form of management which was accepted by 43 during the course of the study. Aid use thereby increased from about 3% to over 9% in this middle-aged group. A 2 year follow-up indicated continued use of the aids, and benefit on a speech reception task was measured. The cost of detecting those who might benefit was calculated using a two-question 'paper and pencil' screen as the first step. A national programme for Wales would cost at least 188,000 pounds per annum at 1990 prices over an initial 5 year span if a criterion which aimed to find at least 45 dB HTL impairments over mid-frequencies was implemented. For a criterion of 35 dB the cost would be 378,000 pounds pa.

Acceptability of binaural hearing aids: a cross-over study.

Using screening questionnaires we were able to detect individuals aged 50-65 years with hearing disability in a general practice population. Those who had better ear hearing levels of 30 dB or worse were invited to take place in a cross-over study comparing the acceptability of a monaural or binaural hearing-aid fitting. Fifty-five per cent ultimately opted for a binaural fitting and had greater hearing disability and worse mean hearing levels than those who opted for a monaural fitting. They made their choice for acoustical reasons, particularly on the basis of improved localization ability.

Hearing disability in people aged 50-65: effectiveness and acceptability of rehabilitative intervention.

OBJECTIVE: To determine the best means of detecting hearing disability in subjects aged 50-65 and whether rehabilitative intervention is acceptable in this age group. DESIGN: Questionnaire survey of patients on general practice age-sex registers. Two types of questionnaire were used, one being based on the closed set approach of the Institute of Hearing Research questionnaire, which had been used in a pilot study, and the other being a simplified version of this questionnaire developed by the Welsh Hearing Institute and based on open set questions. Questionnaires were sent up to three times, and any patients who had not responded two months after the last posting were personally contacted. SETTING: Two general practices in Glyncorrwg and Blaengwynfi in the Afan valley, West Glamorgan. PATIENTS: 271 Patients in Glyncorrwg (136 men, 135 women) and 333 patients in Blaengwynfi (173 men, 160 women) aged 50-65. INTERVENTIONS: All patients indicating hearing disability in answering the questionnaires were invited to attend for a evaluative session in their village. After audiometric testing advice and arrangements for fitting a hearing aid were offered as appropriate. MAIN OUTCOME MEASURES: Response rates and prevalence of hearing disability before intervention and of possession of hearing aids before and after intervention. RESULTS: After three postings and personal contact the response rate was 98% (266/271) in Glyncorrwg, where the complex questionnaire was used, and 97% (322/333) in Blaengwynfi. The prevalence of hearing disability was respectively 53% (141/266) and 46% (148/322) and the prevalence of owning a hearing aid 7% (19/266) and 8% (24/322). After intervention the possession of hearing aids rose to 24% (64/266) in Glyncorrwg and 22% (71/322) in Blaengwynfi; six months later the aids were being used regularly. A direct comparison of the two questionnaires in 69 subjects from Blaengwynfi showed no significant differences in the amount of disability detected by each one. The first posting of questionnaires detected 65% (189/289) of the hearing disability in the two villages or 78% (72/92) of those prepared to accept hearing aids for the first time; 96% (88/92) of those who accepted hearing aids were detected by two postings. CONCLUSIONS: Simple questionnaires are effective in detecting hearing disabilities in people aged 50-65, and intervention was acceptable in many of those who reported having difficulties in hearing. The response rates from successive postings suggest that two postings are sufficient in terms of the return in detecting those who will accept intervention.

Early intervention and rehabilitation: factors influencing outcome.

Detection of hearing disability in a pre-retirement working class population of people aged 50-65 years has been achieved using simple questionnaires. Patients who reported disability were offered rehabilitation, including hearing aids, and the hearing aids use increased from 7% to 23% of the population. Those who accepted or refused hearing aids differed only minimally in mean worse or better ear hearing levels, but markedly in terms of hearing handicap. Similarly, those who indicated that they would like help with their hearing had increased disability and handicap levels but hearing levels no different from those who did not want help. Tinnitus in addition to hearing disability increased the individual's acceptance of a hearing aid. Sex, social class and exposure to occupational noise had no significant effect.

A comparison of three types of earmoulds in elderly users of post-aural hearing aids.

The objective of this study was to assess the ease of handling, comfort, and general effectiveness of three types of earmould in patients who, due to their age, could be expected to experience handling difficulties. The three mould types were, meatal tip, skeleton and skeleton with the 'top prong' removed. The results indicated that the skeleton with the top prong removed was the best in all contexts but one. It was easiest and quickest to fit and least likely to be badly fitted. Only in feedback control did it perform less well. It was concluded that it should be routinely used for elderly patients fitted with low gain hearing aids.