Finite element analysis of the treatment of infant developmental dysplasia of the hip by traditional Chinese medical physical manipulation

This study used finite element analysis to biomechanically evaluate a traditional Chinese medicine physical manipulation for the reduction of developmental dysplasia of the hip (DDH) in infants. An infant-specific 3-dimensional finite element model of the hip, incorporating the pelvic bones and Y-cartilage, was developed. As direct segmentation of infant hip cartilage from clinical magnetic resonance imaging was unreliable, a validated scaling method based on an adult model was employed. A dynamic analysis compared the stress distribution and contact area in the acetabulum and femoral head during a simulated reduction maneuver across different abduction angles (40°, 60°, and 80°), chosen to represent the clinically applied range. A safe acetabular contact pressure limit was defined as ≤2.1 MPa based on published data from healthy infant hips. The results indicated that stress and contact area varied significantly with the abduction angle. The 60° abduction angle demonstrated the most favorable biomechanical profile, yielding the largest acetabular contact area of 216.8 mm2 and a peak acetabular contact pressure of 0.727 MPa, which was well within the safe limit. In contrast, an 80° abduction angle led to hazardous stress concentrations, with the peak acetabular contact pressure reaching 3.84 MPa, exceeding the safe limit, and a doubling of the peak femoral head pressure compared to the 60° position. The biomechanical analysis suggests that an abduction angle of 60° during the manipulation provides a safer and more effective profile for the initial reduction of DDH compared to higher angles, promoting a uniform stress distribution conducive to acetabular development while minimizing risks of cartilage injury and vascular compromise. The finite element analysis indicates that this traditional Chinese medicine physical manipulation is a feasible treatment approach for infant DDH, and the identified optimal 60° abduction may offer a biomechanical advantage over the often higher, sustained abduction angles used in the Pavlik harness.