Biomechanical Analysis of Forward Head Posture: Postural Control, Gait Adaptation, and Performance-Based Criteria

  • Guohao Lin

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Background: Forward head posture (FHP) is a common postural deviation in the sagittal plane. Due to the significant association between sagittal spinal alignment, postural control, and fall risks, people with FHP have been considered to exhibit reduced postural control and gait adaptation. However, standard assessment methods and diagnostic criteria for FHP have been unavailable to date. Current evidence for the relationship between FHP and postural control is inconclusive. Research on gait adaptation in people with FHP is also scarce.

Aim: The overall aim was to determine whether adults with FHP exhibit reduced postural control, and/or gait adaptations, and to propose performance-based criteria for FHP diagnosis.

Methods: This thesis comprises two major parts: a systematic review and a biomechanical experiment with three sub-studies. The systematic review was conducted to synthesise and summarise current evidence, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Eligible studies included observational studies addressing the relationship between FHP, postural control, and/or gait. Quality assessment was conducted using the Joanna Briggs Institute Critical Appraisal Checklist for Cross-Sectional Studies. The biomechanical experiment recruited 51 healthy adults without any condition impairing postural control or gait (mean age = 27.65 years, SD = 7.03). All participants attended three assessments in a single session with their natural head posture (NHP) and an induced FHP (a maximal anterior head translation). The three assessments included the single leg stance test (static postural control), limits of stability test (dynamic postural control), and walking gait analysis.

Results: The systematic review included nineteen studies from 7142 studies after screening. Consistent evidence supported that people with FHP had significant alterations in limits of stability (n = 3), performance-based balance (n = 3), and cervical proprioception (n = 4). Controversial evidence existed for a relationship of FHP with static postural control (n = 4) or postural stability control (n = 4). Limited evidence existed to support an alteration in gait and vestibular function in people with FHP. Three studies on induced FHP consistently identified no effect of induced FHP on postural control. Additionally, there appeared to be no standard method to assess FHP and set diagnostic criteria for FHP.

By postural control assessment in the biomechanical experiment, the performance-based criteria for FHP assessment were determined to be a CVA value of 48 degrees for males and 49 degrees for females. The results of the single leg stance test showed no significant difference between the FHP and control groups or induced FHP and NHP groups. The limits of stability test revealed that the FHP group had a significantly reduced leaning ability in the forward excursion of the centre of pressure (COP). A maximal anterior head translation (i.e., the induced FHP) resulted in a persistent reduction in dynamic postural control and further affected the COP location during static standing.

The findings of the three-dimensional gait analysis indicated a two-level gait adaptation strategy for FHP. The first level involved increases in trunk flexion, while the second level involved adaptations in the hip, knee and ankle joints. Through gait adaptations, participants with FHP or induced FHP maintained a comparable moment arm between the COM gravity line and weight-bearing joint axes. However, there were still significant differences in stride length, walking speed and vertical COM trajectories between the induced FHP and NHP groups. The gait performance-based criterion for FHP was a CVA value of 44 degrees.

Conclusion: This thesis clarified the relationship between FHP and postural control, and identified gait adaptations in adults with FHP. Additionally, this thesis established performance-based FHP criteria for future studies investigating postural control or gait performance in adults with FHP.
Date of Award2024
Original languageEnglish
SupervisorWeijie Wang (Supervisor), Tracey Wilkinson (Supervisor) & Craig Cunningham (Supervisor)

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