Assessment of the normal and pathological alignment of the elbow in children using the trochleocapitellar index

BACKGROUND The current research is a retrospective study that involves the description of a new trochleocapitellar index (TCI), on basis of anteroposterior (AP) radiographs of normal and fractured paediatric elbows. This index may be useful in assessing the alignment of the elbow with a supracondylar fracture. METHODS The index was evaluated to define its normal and pathological range in children between the ages of 1-13 years. A total of 212 elbows in 141 children were radiographically evaluated. 70 children without fracture elbows were evaluated by radiographs taken at the time of trauma. 35 children with unilateral fractures that healed in a normal alignment were compared to 33 patients that had a mal-union and three patients with bilateral elbow fractures. The patients were radiographically assessed at the time of fracture as well as after fracture healing as part of a routine clinical assessment. Treatment included observation, cast or internal fixation as needed. RESULTS The current study establishes that the normal range of the TCI was 0.25-0.8. The average TCI is 0.45. The lower range correlates with a valgus alignment of the elbow while the higher range indicates a neutral alignment. The TCI in fractured elbows that have healed in a clinically normal alignment is different than the contra-lateral elbow's TCI. This might indicate a sub-clinical remaining deformity. CONCLUSIONS In current practice, paediatric patients with elbow trauma, often undergo bilateral radiographs during emergency room visits. The TCI has high negative and positive predictive values and might be superior to direct angle measurement that is currently in use. The use of the TCI measurement is expected to reduce exposure to irradiation in elbow trauma patients as bilateral comparative films appear to be superfluous when this measurement is used.