Effect of elbow position on radiographic measurements of radio-capitellar alignment

摘要

AIM:To evaluate the effect of different elbow and forearm positions on radiocapitellar alignment.METHODS:Fifty-one healthy volunteers were recruited and bilateral elbow radiographs were taken to form a radiologic database.Lateral elbow radiographs were taken with the elbow in five different positions:Maximal extension and forearm in neutral,maximal flexion and forearm in neutral,elbow at 90° and forearm in neutral,elbow at 90° and forearm in supination and elbow at 90° and forearm in pronation.A goniometer was used to verify the accuracy of the elbow's position for the radiographs at a 90° angle.The radiocapitellar ratio(RCR)measurements were then taken on the collected radiographs using the Slice Omatic software.An orthopedic resident performed the radiographic measurements on the 102 elbows,for a total of 510 lateral elbow radiographic measures.ANOVA paired t-tests and Pearson coefficients were used to assess the differences and correlations between the RCR in each position.RESULTS:Mean RCR values were-2% ± 7%(maximal extension),-5% ± 9%(maximal flexion),and for elbow at 90° and forearm in neutral-2% ± 5%,supination 1% ± 6% and pronation 1% ± 5%.ANOVA analyses demonstrated significant differences between the RCRin different elbow and forearm positions.Paired t-tests confirmed significant differences between the RCR at maximal flexion and flexion at 90°,and maximal extension and flexion.The Pearson coefficient showed significant correlations between the RCR with the elbow at 90°-maximal flexion;the forearm in neutralsupination;the forearm in neutral-pronation.CONCLUSION:Overall,95% of the RCR values are included in the normal range(obtained at 90° of flexion)and a value outside this range,in any position,should raise suspicion for instability.