Ph.D Thesis

Ph.D StudentAvnon Deborah
SubjectShort-Term and Long-Term Biomechanical Effects of Foot
Center of Pressure Manipulation on the Hip Joint
in Healthy Subjects and in Patients with
Degenerative Changes of the...
DepartmentDepartment of Mechanical Engineering
Supervisors PROF. Alon Wolf


Degenerative pathologies of the lower limb joints are exceptionally detrimental to quality of life because they affect ambulation and cause pain and deteriorated physical function.  Osteoarthritis (OA), the most common of the degenerative pathologies, is a disease causing degeneration of articular cartilage and other secondary pathological findings of joint deformity.  It is characterized by pain, stiffness, limited range of motion, dysfunctional muscle activation, and overall joint deformity, and causes tremendous personal and economic burden.  It affects approximately 9.2 % of people over the age of 45 in the United States, with prevalence progressing with age.  Left untreated, hip OA progresses, often rapidly, ultimately leaving joint replacement as the sole treatment.  Current nonsurgical treatment recommendations include medication, exercise, diet, use of walking aids, appropriate footwear, and in general, unloading of the diseased joint.  To date, however, footwear recommendations are based solely on clinician opinion, and no biomechanical mechanism by which to unload the hip joint has been described or investigated.  The current study was a two-stage clinical trial study investigating the use of a foot-worn biomechanical device capable of manipulating foot center of pressure, and consequently biomechanics of all the lower limb joints, during gait.  In the first stage we investigated immediate effects of frontal-plane foot center of pressure manipulation on hip biomechanics in healthy subjects and bilateral hip OA patients, as well as effects on neuromuscular pattern in the patients.   In the second stage, we investigated the efficacy of a one-year long gait treatment program implementing foot center of pressure manipulation, by analysis of subjective quality of life measures and objective gait parameters in bilateral and unilateral hip OA patients.  In the first stage of the study, we found a specific foot center of pressure location which significantly reduced peak hip joint reaction force by an average of 8 % and 2 % in healthy subjects and hip OA patients, respectively.  In hip OA patients, the 2 % reduction was observed in both the more and less symptomatic legs.  Additionally, we showed that this center of pressure location had a significant bilateral impact on neuromuscular activity of hip-spanning and back muscles in hip OA patients that caused an increase in average neuromuscular activity during each step.  We described in detail the possible biomechanical mechanism by which hip loads are reduced.  Given the results of the first stage of the study, we speculated that, with a specific foot center of pressure location, maximum hip joint load is reduced, while joint stability is increased by means of increased neuromuscular activity during the duration of each step.  In the second stage of the study, we showed evidence for efficacy of the gait treatment program, as seen by improvement in subjective quality of life measures and objective gait outcome measures.  Additionally, we showed that the improved objective gait parameters were significant predictors of improvement in subjective quality of life measures.  The results from both stages of the study have substantial biomechanical, and potential clinical, significance in the field of non-invasive hip OA treatment interventions.