Developmental dysplasia of the hip (DDH) is considered to be one of the most common orthopaedic disorders, referring to a range of conditions from mild to severe
dislocation of the hip joint. Knowledge of ankle-foot orthosis (AFO) use in patients with severe developmental dysplasia of the hip bone is crucial and may help improve the gait cycle during walking. The plantar pressure sensing mat and insole plantar sensor pad are ideal low cost alternatives to the force plate for capturing plantar centre pressure excursion during gait. Acquired centre of pressure (COP) traces are favoured by many medical clinicians and allied health professionals evaluating foot loading and body balance with respect to foot biomechanics, foot injury, foot deformation and foot ulceration. Researchers have recommended the use of COP traces for the study of the deformed foot and deformed lower limb to improve orthosis assessment and orthosis performance testing. Knowledge of the COP and plantar pressure characteristics such as peak pressure, contact pressure and pressure time integral during walking can help identify possible foot pathology, help determine the most effective foot orthosis, and allow for the appropriate calculation of balance control and joint kinetics and kinematics during gait.
However, there are unclear gait alterations in individuals with DDH which have clinical implications such as the investigation of AFOs and their effect on lower limb kinematics and kinetics, and their impact on the plantar pressure characteristics of the joints during walking and running. This research aimed to provide a better understanding of the gait characteristics of patients with severe DDH. The first set of objectives was to study and evaluate the kinematics and kinetics of the
ankle, knee and hip joints during walking in the sagittal plane for a patient aged 27 years (the author of this research) with severe dysplasia of the left hip, using two different types of ankle-foot orthosis (custom-made, and leaf-AFO). The data were collected using ten cameras and one force plate under four conditions: barefoot,
custom-made AFO, leaf AFO, and shoes only. The angles between every two segments were calculated using the Euler rotation sequence. An inverse dynamic approach was used to calculate sagittal joint moments and power. The results showed that the planter flexion angle reached its maximum during the time between the toes-off, the ground
phase and the initial swing phase with a mean difference of 21.1° and 14°, respectively.
Moreover, the results indicated that the fabricated orthosis decreased both the right and left extensor moments significantly during the load-bearing phase in comparison to barefoot by a mean difference of 0.29, and 0.43 Nm/kg respectively for both limbs. Results showed that the custom-orthosis had a higher moment during the late stance of the gait cycle compared to barefoot, with the data showing significant change by a mean difference of 0.1604 Nm/kg. However, the Leaf Spring AFO had little impact on the flexion moment during the late stance phase.
The second set of objectives of this study was to evaluate the effect of wearing the two ankle-foot orthosis on the plantar pressure distribution of specific foot regions for the patient with DDH. These objectives were achieved by developing a correlation technique between the COP trajectory and the lower limb trajectory during the three main phases of gait (heel strike, midstance and push off). The lower limb trajectory data were collected using a new close-range photogrammetry system that employed six HD video cameras to capture the lower limb trajectory. The COP trace and pressure data were collected using 3000E F-scan in-shoe sensors sampling at 100 Hz inserted inside the patient’s shoes. Six walking trials (ten steps per trial) were recorded
for each condition (barefoot, custom-made orthosis, and Leaf-AFO). The average of the three middle steps was taken out of the ten steps for each trial under each condition. The corresponding results showed that the highest values of the pressure time integral for the left foot barefoot condition were registered under the lateral heel (LH) 115.92±2.91 kPa.sec, medial heel (MH) 101.66±2.55 kPa.sec, first toe (T1) 73.79±1.85 kPa.sec, fourth and fifth toes (T45) 49.90±1.25 kPa.sec and second toe (T2) 42.94±1.08 kPa.sec.
The research concluded that the kinematics and kinetics of the ankle and hip joint were improved by the custom-made orthosis more than that of the Leaf AFO-Spring
Orthoses. The current work also concluded that both AFOs did not much change the kinematics of the knee joint however, there were some improvements in the moments and power generated. Finally, the researcher concluded that both orthoses enhanced body stability, minimized foot pain, and minimizing the risk of injury beneath specific foot regions. More investigations are required in the future, such as the investigation of the customized Knee-Ankle-Foot Orthosis (KAFOs) and increasing the number of samples.