Are all the ways to measure the Reimer`s migration percentage equal?

Reimers` migration percentage (MP) is the accepted method for determining hip displacement in children with neuromuscular hip dysplasia (NMHD). Measurement by clinicians have showed low reliability, and applications were developed for improved measurement accuracy. The aim of this study was to determine reliability and clinical use of two of the applications for MP measurement, compared to the traditional measurement method.

Radiographs of the pelvis from 50 children with NMHD between the age of 2 to 14 years were selected. Five evaluators (3 experienced pediatric orthopedics, 2 orthopedic residents) measured 100 hip joints using the hospital PACS system. All 5 evaluators measured the MP manually using the PACS graphic tools, 3 of them measured the MP using the Hipscreen application and one used the Traumacad add on to the PACS. The differences within the methods between the examiners and the differences between the different methods were calculated. The manual measurements were compared to the most experienced surgeon. The minimum clinically significant difference (MCSD)was defined as 4 degrees.

No statistically significant differences were found between four of the manual examiners, but the 5^th showed a significant difference above the MCSD. The Hipscreen measurements were all between 0.52% to 3.89% lower than the mean manual measurement, below the MCSD. The Traumacad measurement was 5.53% higher the mean manual measurement and 4.68% higher than the most experienced evaluator.

The differences seen between manual examiners can be attributed to the level of involvement in CP care. The Hipscreen application showed no clinically significant difference from the manual examinations. The Traumacad application showed a clinically significant difference from the manual measurements and should not be used alone. This is a preliminary study and further work with more examiners is still needed.