Purpose or Case Report: To date, a standard for CRD has not been established. Plain radiographs are a cost-effective, low-risk option for studying osseous structures in great detail. It is well known that bone age is superior to chronological age for determining biological and structural maturity; for decades, pediatricians have relied on plain films of the wrist and hand for assessing bone age in children (e.g. Greulich & Pyle Atlas, Tanner Whitehouse Method). However, some have proposed new approaches with greater accuracy and reliability across all ages and ethnic groups. Here, we present a new standardized radiographic dimension, CRD, as a tool to assess developmental maturity, which can be readily obtained from standard medical imaging platforms.
Methods & Materials: X-rays of the elbow were systematically searched in the electronic medical record at a single institution from a 15-month period (June 1, 2017 – Sept 30, 2018). Inclusion criteria included patients <18 years of age with plain films in anteroposterior (AP) and lateral views. Patients with radial head dislocation, displaced supracondylar fractures, or a history of dysplasia were excluded. Follow up images were also excluded. CRD values, measured as closest linear distance from the humeral capitellum to the radial head, were measured by a staff radiologist. P-values <0.5 using a two-tailed Student’s t-test were deemed to be statisticallysignificant.
Results: 75 patients ages 3 months to 18 years were included in the study. 45 were male (mean age=10 yrs, range=24 mo-18 yrs) and 29 were female (mean age=9 yrs, range=3 mo-17 yrs).CRD decreased with age, with the most significant drop off observed after age 5, when most patients developed a radial head ossification center. Mean AP CRD for ages 5 and below was 7.25 mm [SD ±1.54 mm], while mean AP CRD for ages 6 and above was 3.41 mm [SD ±0.81 mm] (P <0.0001).
Conclusions: The standard for determining developing skeletal maturity has historically involved X-rays of the hand and wrist. However, these methods have shown inconsistency across certain age groups and ethnic groups. Here, we present another radiographic measurement to aid in the determination of skeletal maturity. CRD proves to have a strong negative curvilinear relationship with increasing age, particularly from ages 3 months to 5 years, before many healthy patients have developed a radial head ossification center and thus demonstrate largest CRD values. Knowledge of this measurement will aid diagnosis of radial head subluxation.