Forefoot-rearfoot kinematics as risk factors for tibial stress injuries.

Overuse injuries represent a significant problem for runners with tibial stress injuries common. Identifying risk factors is a crucial step in the development of effective preventative measures and treatments for specific injuries. The foot has been suggested to be an intrinsic risk factor for tibial stress injury, however, literature is contradictory. Few studies have investigated dynamic foot function as a potential risk factor. A recent area of biomechanics research has focussed on the development of multisegment foot models for use in research and clinical settings. However to date, few studies have used such models to try and answer questions relating to overuse injuries. The overall purpose of this thesis was to answer the question, are forefoot-rearfoot kinematics risk factors for tibial stress injuries in runners? Chapter II conducted a systematic review of the literature to determine any relationship between tibial stress injuries and foot type. Results proved conflicting with limited evidence implicating any one foot type as a potential risk factor. Importantly, dynamic measures of foot function were suggested to be more useful in predicting injury risk. Chapter III examined methodological considerations with the measurement of forefoot-rearfoot kinematics. A new multisegment foot model (forefoot, rearfoot and shank) for use with gait sandals was developed and presented. Data was also presented to support the use of gait sandals as an effective means of measuring the kinematic motions seen when wearing running shoes. The Chapter also addressed the reliability of selected kinematic measures and tibial shock. Selected kinematic variables focused on peak joint angles, excursions and velocities which define the motions of the foot during loading. Chapter IV presents an application of the developed model. The study investigated foot function in relation to foot type and sought to compare forefoot-rearfoot kinematics in high and low-arched populations. Differences between high and low-arched feet were observed for some dynamic forefoot-rearfoot variables. Specifically, greater forefoot abduction excursion, forefoot dorsiflexion excursion and forefoot abduction velocity were found in high-arched compared to low-arched individuals. Further, differences between groups were also noted in the coupling between the forefoot and rearfoot, but these differences did not appear to be transferred proximally to the shank. Chapter V studied dynamic foot function in relation to tibial stress injury risk. The study sought to compare forefoot-rearfoot kinematics in those with a history of tibial stress injury and a matched control group. Key differences were found in kinematic variables between injury and control groups. Specifically, peak rearfoot eversion, peak forefoot dorsiflexion velocity and peak forefoot abduction velocity were found to be greater in those with a history of tibial stress injury compared to a control group. Differences were also noted between the coupling of the forefoot, rearfoot and shank, these may characterise the unique loading pattern seen in those with tibial stress injuries. Although only initial findings, this thesis has enhanced understanding of important dynamic risk factors for tibial stress injuries associated with the foot. Furthermore, findings serve to highlight the importance of forefoot motions as risk factors. It is hoped the findings of this thesis will be a useful basis for future research and represent an important step in the development of effective preventative measures and treatments for these injuries.