The decision whether to diagnose an infant with DDH is rooted in the orthopaedic surgeon’s judgment about the value and meaning of different criteria suggestive of this diagnosis. These judgments are pivotal as they will determine further management plan (observe, treat, discharge) and ultimately affect clinical outcomes. The lack of uniform diagnostic criteria has the potential for incorrect or delayed diagnoses. Using a consensus technique, we aimed to identify the most relevant diagnostic criteria for DDH in early infancy by an international survey of expert pediatric orthopaedic surgeons.
Our study has potential limitations. First, as clinical knowledge evolves, the opinions of experts change. However, most of the criteria identified in this study have been in use for decades, and those regarded as most relevant are unlikely to change in the near future. The research is aimed at discerning any consensus (rather than the validity) of diagnostic criteria. The criteria need to be validated in additional research. Second, the Delphi technique has been criticized, as opinions can centralize around the most commonly expressed ideas. This can be addressed by a high degree of methodologic precision in data collation and analysis, which we adhered to. Particular attention was paid to the process of item reduction, which was performed by a panel of four international experts with different training and practice backgrounds. Third, inherent to the methodology of this research was that the importance of each criterion was established in isolation, when in clinical practice two or more criteria could occur simultaneously in a patient. However, this does not limit our study because its aim was first to define the nature and working definition of criteria important for the diagnosis of DDH, and second, to define the importance of each of these criteria. Examining combinations of criteria will be subject to future research.
The panelists reached consensus regarding the importance of the 37 criteria after two iterations [2
]. Cronbach α was adequate with 0.9, the highest ranked items were identical in both iterations, and the standard deviations notably decreased for each item in iteration 2. Response rates were high for all surveys suggesting that the data are based on a representative sample of international specialist surgeons. The high response rate suggests there is considerable interest in the specialty in a consensus of this type. The high Cronbach α suggests that the pattern of data seen in this study is stable and similar results would be obtained if a second panel selected from the same population of content experts was studied [6
]. While our observations are generalizable to pediatric orthopaedic surgeons internationally who treat patients with DDH, we did not include pediatricians, general practitioners, and other healthcare professionals and are unable to quantify if and to what degree their opinions differ from those of pediatric orthopaedic surgeons. However, as pediatric orthopaedic surgeons are considered to provide the final opinions in the diagnosis of DDH, we took a pragmatic approach and focused on clinical experts for this study of diagnostic criteria. Incorporating the opinions of clinicians other than surgeons probably is more likely to establish referral criteria as opposed to definite diagnostic criteria. We did not attempt to reach a standardized case definition of DDH defined by long-term consequences such as osteoarthritis. Such an approach, based on a prognostic definition of disease [15
], would require longitudinal research in which different characteristics of DDH are examined in relation to outcomes of interest.
Specialist surgeons identified 37 potentially important criteria in the diagnosis of DDH during the first 8 weeks of an infant’s life. As expected, these criteria predominantly concerned clinical examination, ultrasound, and patient characteristics and history. Consensus regarding the relative importance of these criteria was established. Delphi was a key factor in avoiding a consensus that might be skewed by one or more persuasive panelists. The movement in the opinions between iterations 1 and 2 (Table ) appeared to result from the feedback of information describing the group opinion. Half of the top-ranked items related to criteria obtained from clinical examination and a third related to criteria obtained from ultrasound underlining the value of clinical and ultrasound tests. All listed items seem clinically reasonable and are among the most commonly cited diagnostic criteria for DDH [1
]. Classic clinical tests such as Ortolani, Barlow, Galeazzi, and asymmetry in abduction were among the highest-ranking criteria (Table ). This confirms the wide agreement regarding the relevance of these criteria among surgeons internationally. Questionable but commonly cited criteria such as ‘hip click’ or ‘asymmetric groin creases’ were among the lowest ranking items confirming that these criteria are of limited to no value in making a diagnosis [9
]. However, they might be of value for initiating referrals from primary care professionals to specialist surgeons.
Several criteria relating to patient characteristics and history, commonly referred to as risk factors for DDH, were examined. The highest-ranking criteria included breech presentation and a positive first-degree family history of DDH. This is in agreement with current clinical guidelines [1
]. Consistent with current guidelines [1
], other commonly cited factors such as female gender or oligohydramnios were rated less important by the panelists. However, the panelists rated each criterion in isolation when the importance of one criterion actually might increase if it occurs together with another factor. For example, the absolute risk for DDH is between 70 to 120 of 1000 when the factors ‘female gender’ and ‘breech presentation’ occur together in one patient [12
]. Understanding the meaning of such combinations will be part of our next research to validate the criteria. The majority of the ultrasound criteria generated in the first survey related to the commonly cited alpha angle and femoral head coverage [14
], for which several thresholds were explored in the Delphi process. The panelist-specified thresholds for femoral head coverage of 45% and 50% are similar to the criteria outlined by Terjesen et al. [18
]. As for the alpha angle, the panelists specified three important thresholds –45°, 50°, and 55°. These are in agreement with Graf’s classification, which recommends immediate treatment for hips with an alpha angle less than 45° and surveillance or treatment for hips with an alpha angle less than 55° in infants 8 weeks old or younger [13
]. The threshold of 60° was given the lowest rating suggesting that the panelists’ group opinion regarded an alpha angle of 56° as sufficient in this age group. Three radiographic criteria were listed in the item generation survey but their importance was rated as low in the consensus process with a low Cronbach α, confirming that ultrasound is the preferred imaging test in the age group in interest [15
], with no value for radiography.
We have established an international consensus of diagnostic criteria for DDH in early infancy by well-experienced surgeons. Clinicians can now distinguish and choose between criteria internationally regarded as the best for a definite diagnosis and those regarded as unimportant. This consensus will pave the way for additional research to produce a novel diagnostic index. Although these criteria remain to be validated, our findings are useful for clinicians in that we provide them with a reference of their peers’ opinions. Clinicians can determine how their personal preferences for diagnostic criteria differ from others’ preferences. Such a comparison will reassure clinicians either that their practice is mirrored by their peers, or, if not, it will provide a basis for reconsidering their practice. Although we did not establish criteria for DDH defined by long-term consequences such as osteoarthritis, our study provides the groundwork for such research in that it determined what these different characteristics could be.