Selection of experimental animals and modeling methods in developmental dysplasia of the hip research.

Developmental dysplasia of the hip (DDH) is a common neonatal musculoskeletal condition characterized by hip instability and inadequate acetabular coverage. If untreated, it can lead to osteoarthritis, chronic pain, and eventual hip replacement. Animal models, including dogs, pigs, sheep, rabbits, rodents, and chickens, are essential tools for studying DDH pathogenesis and testing therapeutic strategies. Larger species closely resemble human anatomy, while smaller species facilitate cost-effective, high-throughput studies and advanced genetic manipulation. Key modeling strategies include surgical interventions (e.g. joint dislocation, femoral or pelvic osteotomy), external fixation, and genetic modifications (e.g. gene knockout or lentiviral transduction) to simulate various aspects of DDH and reflect its multifactorial etiology. Evaluation techniques such as radiography, microcomputed tomography, MRI, and ultrasound are employed to image bony and cartilaginous structures. Histological and immunohistochemical analyses provide insights into cellular and extracellular matrix changes, while gait assessments evaluate functional deficits and pain-related behaviors. Selecting an appropriate animal model requires careful consideration of research objectives, ethical standards, and translational potential. Advances in gene editing technologies (e.g. CRISPR), three-dimensional-printed implants, and in vivo imaging are enhancing model fidelity and accelerating the discovery of novel therapies. Ongoing innovations in DDH research are expected to bridge gaps in understanding the disease's etiology and improve long-term outcomes for affected patients through optimized therapeutic interventions.