Purpose: To determine, the foot pressure pattern in ankle osteoarthritis before and after ankle fusion. To compare the results with those of normal individuals.

Method: The distribution of plantar pressures of the foot has been measured by different means ranging from crude methods to modern techniques using transducers in the form of mats and insole devices. A less cumbersome in-sole transducer called FSCAN sensor has become commercially available. This device has been used to measure dynamic pressures at the Shoe-Foot interface in normal people and in pathological conditions in the foot. However the pressure distribution in the soles of patients with ankle osteoarthritis has not been studied. We present a prospective case control study of 18 participants (9 with ankle osteoarthritis and 9 controls). Ethical approval was obtained for this study. The controls were matched to cases by foot shape, gender and weight. The pressure measurement device, technique of ankle fusion and post operative protocol (for the arthritis patients) were standardised for all the participants. The Ankle-Hindfoot Scale and SF-36 Health Survey scores were obtained pre-operatively and at six months post-operatively and compared.

Results: There were four females and 14 males. The average age was 67 years. The forefoot in patients with arthritis bore more weight compared to controls and this was statistically significant (P< 0.05). The forefoot pressure was also higher than the hind foot pressure in the patients, both preoperatively and post operatively. This was also statistically significant, (P< 0.05). The Ankle-Hindfoot Scale improved significantly postoperative, (P< 0.05). There was no statistically significant difference in the SF-36 Health Survey scores.

Conclusion: The study shows that ankle osteoarthritis changes the pressure distribution in the foot, with preponderance in the forefoot. It also shows that after ankle fusion there is a change in the pressure. However, the forefoot still bears more pressure compared to the hind foot. The result may help in predicting areas of the foot at risk in developing problems due to high pressure load post ankle fusion. It may also help in designing foot orthosis in the peri-operative management of the foot in ankle osteoarthritis.