Hip abduction orthosis devices (HAOD) are used to reduce the hip joint of infants affected by developmental dysplasia of the hip (DDH). HAOD have been successful for mild cases of DDH and ineffective for severe cases. Efforts in understanding the biomechanics of lower limbs have been made to improve the success rate of current treatment methods, especially for Grade IV dislocations (G4). The aim of this dissertation is twofold: first, it proposes the use of a varying fulcrum point (FP) located below the leg to improve DDH treatment; and secondly, it defines the optimal FP (OP) location for a broad spectrum of hip joint configurations. An iterative 3D computational model of a 10-week-old infant was developed using parameters of the femur, pelvis, and lower limb muscles along with their anatomical location. The computational model provides a variety of scenarios of closed reduction and the location of the OP, which is believed to be a key parameter for a successful reduction in severe cases of DDH. The problem is posed as a maximization of an objective function whose independent parameter is the location of the FP constrained to vary over an anatomically feasible range along the femur. For each location of the FP, the model computes resultant forces and evaluates a potential energy function. The OP maximizes the projection of the resultant vector force of the femur over the least energy path to assist in achieving G4 reduction. The results of this study suggest that for the range of the parameters used in the model, G4 reduction can be achieved as the FP reaches the femoral head with the aid of additional external traction forces. Results from this study may be used to customize current orthosis design by using patient-specific parameters, which can be obtained from imaging.


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Graduation Date





Kassab, Alain


Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science


Mechanical and Aerospace Engineering

Degree Program

Mechanical Engineering




CFE0008378; DP0023815





Release Date

December 2020

Length of Campus-only Access


Access Status

Doctoral Dissertation (Open Access)

Restricted to the UCF community until December 2020; it will then be open access.