Biomechanical assessment of passive ankle joint complex dorsiflexion

• Main Author: Gatt, Alfred
• Published: Staffordshire University 2012
• Subjects: 617.585; B800 Medical Technology
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556584

The measurement of ankle joint dorsiflexion is an important component of the clinical examination of the foot and is also an outcome measure often employed in research. Diagnosis of ankle equinus or limited ankle dorsiflexion is based solely on this measurement. Although a great majority of research papers in this field utilise normal clinical goniometers for obtaining the maximum ankle dorsiflexion angle (MADA) and important clinical decisions are based on these findings, there is overwhelming evidence that this method is highly unreliable. Thus this thesis aimed to investigate alternative methods of measuring ankle dorsiflexion and various issues that affect the MADA in order to obtain a clear picture of foot segment movement from which an Ankle Goniometer could be consequently designed and validated. Ten different techniques were identified that included various apparatuses designed specifically for measuring ankle dorsiflexion. However, during validation, their methodological quality would have benefitted from the use of an actual patient population and comparison with a reference standard, which caused papers to score poorly on methodological quality assessment. It was concluded that issues affecting this measurement and that needed to be researched further include: foot posture, the amount of moment applied and the stretching characteristics of the calf muscle tendon unit. Experiments within this study indicated that in adults, the mean maximum pronated angles were always higher than in other postures, with 8.27o difference between the pronated and supinated postures (p=0.032) and 5.78o between pronated and neutral (p=0.000). However, the reported difference between neutral and supinated (mean angle of 2.49o) is of little clinical significance. It was observed that the forefoot always travels through a greater angle than the hindfoot in all 3 foot postures, while the hindfoot to forefoot angle increases during the application of a moment, indicating that the ‘midtarsal joint locking mechanism’ cannot be applied to passive dorsiflexion of the foot. In adolescents, there are no significant differences in the mean MADA between the 3 postures, implying that this measurement technique may be performed in any of these postures. It was also concluded that there is no need to control moment applied during this measurement procedure to produce consistent results between raters and that the calf muscle tendon unit does not stretch significantly following brief repetitive passive stretching. ii An ankle goniometer that measured purely hindfoot movement by eliminating forefoot influence and that increased reliability by holding the foot in the chosen posture, was consequently designed. This was validated by synchronizing with an electrogoniometer and an optoelectronic motion capture system. Reliability testing, with the foot held in a supinated posture as opposed to the traditional Rootian method of placing the foot at subtalar joint neutral position, spanned a number of different trials, including intra-tester and inter-tester reliability studies utilising both controlled and uncontrolled conditions, in convenience samples of healthy participants and a random sample of patients. Reliability testing between 4 raters with little experience on the utilization of this device was finally conducted. It has been shown that the Ankle Goniometer is a valid and reliable device for measuring ankle joint complex dorsiflexion both in healthy adults and in a patient population.