The radiographic classification of the bone-screw interface in paediatric tibial lengthening.

Bone-screw loosening in monolateral external fixators is a significant problem. This study classifies the radiographic appearance of the bone-screw interface and predicts which screws will become loose and those that will remain solidly fixed to bone. Five radiographic features were identified at the bone-screw interface. The classification of these features was validated using interobserver and intraobserver studies. The reliability of the classification was improved by image enhancement with simple filters. Some radiographic features predicted which screws would eventually become loose, allowing the clinician to make earlier management decisions regarding the adjustment of screws.