Hallux valgus (HV) is a common foot deformity that presents with lateral deviation of the first toe (hallux) and progressive subluxation of the first metatarsophalangeal joint. A precise prevalence estimate for HV has been unclear from a wide range of reports, and there is disagreement surrounding associated clinical and radiographic findings, with no synthesis of best available evidence to date. Although a number of studies have linked HV to an increased risk of falls in older adults, the mechanisms underlying potential functional disability in HV are not well understood. There is also debate surrounding the association between HV and foot pain and disability. The primary aim of this thesis was to explore the impact of HV on otherwise healthy adults in terms of population prevalence, associated factors, foot pain, functional disability, concerns about appearance, and footwear.
Systematic literature reviews were conducted to provide a synthesis and quality appraisal of studies investigating HV prevalence and associated factors. Meta-analysis revealed a high prevalence of HV in the overall population, with increased prevalence in females and older adults. Several radiographic measures of foot structure were found to differ in HV participants compared to controls, such as an increased first intermetatarsal angle, a greater first metatarsal protrusion distance, a more round-shaped first metatarsal head, lateral sesamoid displacement and first metatarsophalangeal joint subluxation. Specific gait parameters were also found to be altered in individuals with HV compared to controls. These systematic reviews identified a lack of studies with rigorous methodology investigating clinical factors such as foot posture, joint mobility and footwear. Furthermore, critical appraisal revealed limitations in existing literature surrounding definitions of HV, and reliability and validity of measurement methods.
To investigate foot pain and disability associated with HV, a cross-sectional study was conducted with volunteers recruited from the community (60 HV, 30 controls; aged 20 to 76 years). HV was assessed by measuring the HV angle on weight bearing radiographs and photographs. Photographic HV angle measurements were found to be reliable and valid compared to standard radiographic measurements. Foot pain and function, footwear and concerns about appearance were investigated via a range of self-report and physical measures. Comparison of 30 HV participants with 30 age and gender matched controls identified that HV participants reported significantly more foot pain, functional limitation, difficulty with footwear and cosmetic concerns. Assessment of physical function revealed hallux plantarflexion and abduction weakness and increased mediolateral postural sway in participants with HV, although walking performance and global participation in physical activities were not adversely affected. Further investigation of foot pain in 60 HV participants revealed that 16 out of 60 participants reported disabling foot pain. Multiple regression modelling showed that variation in foot pain intensity could be partly attributed to individual patient factors such as general health status, occupational physical activity levels and educational attainment, while hallux plantarflexion weakness and reduced force-time integral under the second metatarsal head were also associated with increasing foot pain. Static foot posture, severity of HV angle, first metatarsophalangeal joint osteoarthritis and footwear characteristics were not found to be significant predictors of foot pain in HV. Finally, hallux muscle strength, plantar pressures, postural sway, walking performance and foot posture were investigated in participants with mild (n = 21), moderate (n = 25) and severe (n = 14) HV compared to controls (n = 30). Those with moderate to severe HV were found to have reduced hallux muscle strength, reduced hallux plantar pressures during gait and a more pronated foot posture compared to controls. Individuals with severe HV also displayed significantly increased mediolateral postural sway in single leg stance. There were no significant differences in these parameters between those with mild HV and controls.
HV is highly prevalent and is associated with significant self-reported foot pain and disability in otherwise healthy adults. It is important for clinicians managing HV assess the patient’s specific presenting complaint, which may include difficulty with footwear and cosmetic concerns. The level of foot pain experienced by individuals with HV varies to a large extent, and global patient factors may account for more of this variability than local structural factors. This thesis has highlighted the importance of a valid definition of HV that considers severity of deformity, since moderate to severe HV has more impact than mild HV on functional parameters such as hallux muscle strength, plantar pressures and postural sway. Digital photographs provide clinicians and researchers with a valid and reliable means of determining the severity of HV deformity and monitoring its progression. Future research efforts should be directed towards investigating conservative interventions that could potentially target hallux muscle weakness, biomechanical foot function and impaired balance. Appropriate and early intervention is important for maintaining optimum levels of physical function in adults with HV.