DDH is the most common pediatric hip condition, with 1-3% of all newborns diagnosed at birth. However, the true incidence of DDH is difficult to quantify due to significant variations in diagnostic criteria, terminology, screening and monitoring procedures, as well as ethnic and cultural differences. The spectrum of DDH encompasses mild dysplasia or instability of a reduced hip, to a completely dislocated, irreducible hip. If left undetected or untreated, it can lead to debilitating complications later in life. Much of the evidence existing to date in the DDH literature is from retrospective and/or single-centre studies, and the spectral nature of the condition has resulted in inconsistent or ill-defined terminology to classify patients in regard to diagnosis and laterality. Consequently, the patient population is often not clearly defined or reported, making it difficult to compare or combine different study results in order to produce strong evidence to guide treatment and management. This issue was highlighted in the updated clinical practice guidelines released in partnership between the American Academy of Orthopaedic Surgery (AAOS) and the Pediatric Orthopaedic Society of North America (POSNA) in 2014. Of the nine recommendations made, only two were of moderate strength, while the other seven were of low strength.
Discrepancies begin with DDH screening practices. Clinical examination for hip instability is a universal standard practice; however, not all cases are detectable by this method, leading to potential missed diagnoses or late-presentations that are more difficult to treat. Beyond the clinical exam, screening, management and treatment practices are highly variable across surgeons, centres and countries. Some countries, particularly those in Europe, employ universal ultrasound screening, while others use selective ultrasound screening as a supplement to the clinical exam for infants with specific risk factors. Defined risk factors that have currently been deemed to warrant further screening and monitoring include breech presentation, family history of DDH or a clinical history of hip instability. Regardless of screening program, missed or late-presentations still occur, warranting further investigation. Further variability is introduced with primary treatment and management. Bracing is the most common first-line treatment, particularly in younger patients or patients with unstable or reducible hips. Surgical treatment (closed or open reduction) is more often used as first-line treatment in older patients, or patients with more severe dislocations. However, significant variation is seen in practice patterns, complication rates and treatment success with each of these methods, and identification and analysis of prognostic factors have been lacking methodological rigor. Development of a comprehensive, prospective registry will provide a unique and unprecedented platform for examining numerous aspects of the full DDH spectrum, including long-term treatment outcomes and risk factors.
