Proximal ulna morphology in various pediatric population age groups: proximal ulna dorsal angulation (PUDA) and olecranon tip-to-apex (TTA) distance

PURPOSE: To measure proximal ulna dorsal angulation (PUDA) and olecranon tip-to-apex distance (TTA) in pediatric population to aid surgeons with data for proximal ulna fractures fixation. METHODS: Retrospective review of the hospital radiographic database. All elbow radiographs were identified and after implementing exclusion criteria, included were 95 patients aged 0–10; 53 patients aged 11–14; and 53 patients aged 15–18. PUDA was defined as the angle between lines placed on the “flat spot” of the olecranon and the dorsal edge of the ulnar shaft and TTA as the distance between the tip of the olecranon to the apex of angulation. Two evaluators performed measurements independently. RESULTS: In age group 0–10, mean PUDA was 7.53°, range 3.8–13.7, 95% CI 7.16–7.91, while mean TTA was 22.04 mm, range 8.8–50.5, 95% CI 19.92–24.17. In age group 11–14, mean PUDA was 4.99°, range 2.5–9.3, 95% CI (4.61–5.37), while mean TTA was 37.41 mm, range 16.5–66.6, 95% CI (34.91–39.90). In age group 15–18, mean PUDA was 5.18°, range 2.9–8.1, 95% CI (4.75–5.61), while mean TTA was 43.79 mm, range 24.5–79.4, 95% CI (41.38–46.19). PUDA was negatively correlated with age (r = − 0.56, p < 0.001), while TTA was positively correlated with age (r = 0.77, p < 0.001). Reliability levels of 0.81–1 or 0.61–0.80 were achieved for most of intra- and inter-rater reliabilities besides two levels of 0.41–60 and one of 0.21–0.40. CONCLUSION: The main study finding is that in most cases mean age-group values may serve as a template for proximal ulna fixation. There are some cases in which X-ray of contralateral elbow may provide surgeon with a better template. LEVEL OF EVIDENCE: II.