Hip Joint Muscle Activation Patterns During Gait in Patients With Hip Dysplasia Versus Healthy Controls Using Musculoskeletal System Modeling

Background and Aims Hip dysplasia is a pathological condition of the hip joint characterized by abnormal acetabular geometry, resulting in insufficient femoral head coverage. This inadequate coverage, along with the relative lateral displacement of the femoral head, reduces the articular contact surface, alters intra-articular loading, and increases mechanical stress throughout the hip joint. Such stress accelerates cartilage wear, making patients more susceptible to early-onset hip osteoarthritis. Muscle forces and joint reaction forces are the primary mechanical factors in hip joint loading, and these forces are altered in patients with hip dysplasia. Examining the relationship between muscle activity, gait patterns, and joint contact forces can enhance the understanding of the pathophysiological mechanisms underlying hip dysplasia and aid in developing more effective treatment strategies. This study aims to analyze these interactions and identify factors influencing the improvement of hip joint function in individuals with hip dysplasia. The findings and insights derived from this research can be applied in clinical settings to aid muscle-strengthening exercises, thereby enhancing rehabilitation and clinical management of such patients. The primary objective of this study is to investigate and compare the activity of pelvic girdle muscles in individuals with hip dysplasia and healthy controls using musculoskeletal modeling. Methods In this study, 10 healthy individuals (mean age: 23±1.68 years) and 10 patients with left-side hip dysplasia (mean age: 25±2.54 years) were recruited and voluntarily participated. The study aimed to analyze and compare the activity of the gluteus medius, gluteus maximus, rectus femoris, and tensor fascia lata (TFL) muscles in the two groups. The OpenSim software, version 4.4 utilized gait data from healthy and dysplastic participants to calculate and analyze muscle activity for further investigation. Results No significant differences were observed in the demographic characteristics of participants between the healthy and dysplasia groups (P>0.05). However, the significance level of muscle activity in the gluteus medius, TFL, and rectus femoris muscles was <0.05. The gluteus medius and TFL muscles exhibited significantly higher activity in individuals with hip dysplasia compared to the control group. Additionally, the gluteus maximus muscle activity increased relative to the control group. Conversely, the rectus femoris muscle demonstrated a decrease in activity. Conclusion This study demonstrated that individuals with hip dysplasia exhibit elevated muscle activation levels during the gait cycle compared to healthy controls. Furthermore, the GRFs and center of pressure dynamics showed distinct patterns in the dysplasia group. The altered biomechanics of hip dysplasia shorten the muscle moment arm, necessitating greater muscle forces to achieve the required joint torques. These findings highlight that increased muscle activity in hip dysplasia impairs movement efficiency and elevates intra-articular forces. Therefore, developing targeted therapeutic interventions aimed at optimizing biomechanical function and mitigating excessive muscle activation is crucial for effectively managing hip dysplasia.