Background Trapdoor fracture is a special type of orbital blowout fracture. Although early surgery is recommended, there still remain some patients delayed by various reasons. In this study, we analysed the clinical characteristics of delayed paediatric patients, especially those with different levels of ocular motility restriction before surgery.

Methods Thirty patients (3 to 14 years old) who underwent delayed surgery for trapdoor fractures between January 2008 and September 2016 were enrolled. Their demographics, causes of injury and delay, clinical features, imaging data and follow-up information were collected.

Results Muscular entrapment was found in 17 patients (group A) and soft-tissue entrapment in 13 patients (group B). 12 (7 in group A) presented with severe motility restriction and 18 (10 in group A) with mild restriction before surgery. 41.7% with severe restriction recovered after surgery, compared with 83.3% with mild restriction. Four (23.7%) in group A (all with severe restriction) and six (46.2%) in group B (half with severe restriction) presented with persistent diplopia.

Conclusions Long recovery time and a high percentage of persistent diplopia are the main problems of delayed trapdoor fracture in children. A prompt surgery within 48 hours is strongly recommended in patients with muscular entrapment even if an urgent treatment is hard to achieve. So are patients with soft-tissue entrapment and significant motility restriction. In the other patients without such indications, even though some recovery might be possible in the long term, a prompt surgery right after diagnosis is still preferable regardless of the entrapped contents.