Plantar fasciitis is a chronic pain condition caused by the inflammation of the connective tissue along the sole of the foot (the plantar fascia). The condition affects up to 10% of the total population during the course of their lives. While non-invasive treatment methods are effective in most cases, surgical procedure is considered if the pain persists for several months. Shock wave therapy has been used as a last resort to avoid surgical intervention after other conservative treatment methods have proved to be ineffective. Radial shock wave therapy uses a ballistic method to generate high-amplitude pressure in the tissue; a metal object of 6-15 mm in diameter (an applicator) is applied superficially to the location that has to be treated. The applicator is impacted by a small cylindrical metal object (projectile) which is driven by compressed air. The understanding of the mechanical effects of shock wave therapy is not complete, and the insight into the mechanisms through which these effects may promote the healing process is at the level of speculation. The objectives of this research are to gain a better understanding of: the physical mechanisms through which the ballistic shock wave source operates; the mechanical stimuli that this method produces in the context of plantar fasciitis treatment; and the potential biological effects of these stimuli on the tissues of the foot. A finite element model of the pressure wave source was constructed based on the geometry of an actual device. The model consisted of the applicator, the projectile, parts of the casing, and the o-rings on which the applicator is suspended in the casing. A finite element model of the foot was also constructed. The model was based on the geometry reconstructed from MRI images of a volunteer and it comprised of bon~s, cartilage, soft tissue, plantar fascia, and Achilles tendon. The material properties for the model components were taken from the literature. Simulations were conducted both to characterise the behaviour of the shock wave source and to simulate the effect of shock wave therapy on the foot. When . the shock wave device is "fired in the air", the bulk movement of the applicator is in the fmm of highly damped oscillations with a maximum displacement of 0.2 mm and a period of about 0.5 ms. The collision between the projectile and the applicator lasts for about 10 f1S which is the time needed for the stress wave to traverse the ii applicator in both directions. After the collision, there is a standing stress wave in the applicator with amplitude of the order of 10 MPa. When the device is applied to the soft tissue of the foot, pressure waves are generated that propagate in all directions. The waves consist of positive and negative pressure phases with the wave length of approximately 10 mm. The magnitude of the pressure generated in the soft tissue is of the order of several MPa, which is consistent with data reported for'· experiments conducted in water. The pressure amplitude at the surface of the soft tissue can be related in a simple way to the speed of the projectile and acoustic impedance of the soft tissue. The pressure magnitude and energy density decrease rapidly with the distance from the source, so that the effect of the treatment is localised to the region where the device is applied. The negative pressure at the plantar fascia origin reaches values of up to 3 MPa which should be sufficient to generate cavitation in the tissue. This result supports the hypothesis that cavitation-induced micro-trauma may be one of the mechanisms that enhance the healing process. Simulations of multiple pulses delivered at 20 Hz show that energy transferred to the foot with a pulse is not dissipated before the subsequent pulse. This result suggests that multiple pulses may lead to accumulation of energy in the foot.

Therapeutic footwear is provided to patients with the primary aims of reducing foot pain and improving foot health. Therefore, it is of concern that patients choose not to wear it. This choice has been attributed to its poor appearance. However, there may be other reasons for this choice and the reasons may be more complex than previously acknowledged. Therefore, the aim of this study was to investigate the users’ experiences of this footwear. In the context of this study the ‘users’ are women with rheumatoid arthritis. This study was based on an interpretive phenomenological approach (IPA) that employed conversational style interviews to gather data. Ten women with RA and experience of wearing the footwear were recruited and following ethical approval the interviews were carried out, transcribed, organised and analysed. Five organising themes emerged as findings. These were the participants: • feelings about themselves, • feelings about the footwear, • unmet needs and expectations, • behaviour with the footwear and • feelings about the consultation with the practitioner. The final, global theme was that the patient/practitioner consultation has a powerful influence on the women’s feelings about themselves, the footwear, their expectations of it and their behaviour with it. This study has provided insight into their experiences of this footwear in that, unlike any other intervention, it replaces something that is normally worn and is part of an individual’s perception of self and their perception of how others see them. The footwear impacts more on women’s emotions than previously acknowledged and in addition, it has been found that the consultation influences their emotions and behaviour with the footwear. As well as improvements in footwear design and the service that delivers it, the training of the practitioners in a more patient focussed consultation style could improve the women’s experience and engagement in the footwear as a health intervention, as well as something that is ‘worn’.