Pearlene P. Lee BA, Presenter: Nothing to Disclose

Majid Chalian MD, Abstract Co-Author: Nothing to Disclose

Gaurav K. Thawait MD, Abstract Co-Author: Nothing to Disclose

Neda Faridian-Aragh MD, Abstract Co-Author: Nothing to Disclose

John Eng MD, Abstract Co-Author: Nothing to Disclose

Avneesh Chhabra MD, Abstract Co-Author: Research grant, Siemens AG Research Consultant, Siemens AG Research grant, Integra LifeSciences Holdings Corporation Research grant, General Electric Company

Anterior knee pain and evaluation of patellar misalignment are one of the most common reasons for radiographic and cross-sectional imaging. Although a variety of measurement ratios are used on X-rays, there is no uniform consensus on acceptable reference range for normal patellar height on CT and MRI. We tested the differences of 3 commonly used ratios on these imaging modalities to assess whether universally accepted range of normal patellar height ratios derived from X-ray could be similarly applied to MRI and CT.

A retrospective search of our database over a period of four years yielded 43 bimodality cases of knee X-ray and MRI and 18 trimodality cases of knee X-ray, MRI and CT in same subjects [age- 40.6 +/-22.9 years (range 11 to 75)]. In each patient, the patellar height was assessed quantatively by two independent readers using the Insall-Salvati (IS), Blackburne-Peel (BP) and deCarvalho (DC) methods on sagittal MRI and CT, and lateral X-ray of the knee. Average mean values and mean difference between X-ray and MRI and between X-ray and CT were computed. Readers were also compared regarding their interpretations on all modalities. Bland-Altman plot was generated to better depict the possible differences.

IS, BP, and DC values were statistically different (p= 0.0031, 0.049 and 0.02, respectively) on X-ray and MRI. On X-ray, mean values for IS, BP, and DC were 1.17+/-0.16, 0.92+/-0.15, and 1.00+/-0.1 respectively while on MRI these values were 1.25+/-0.20 (mean difference= 0.09), 0.96+/-0.16 (mean difference, 0.04), and 1.06+/-0.17 (mean difference =0.05) respectively. Between X-ray and CT, there was no statistical difference in terms of IS and BP values, but DC was statistically different (p=0.07) with a mean CT value of 1.11+/-0.05 (mean difference = 0.13). There was no difference between readers in their assessment of various parameters in 18 knee CT, 43 knee MRI and 43 knee X-rays.

Although there are statistical differences in patellar height ratios derived from the IS, BP and DC methods on X-ray, CT and MRI; the differences are less than 0.1 units. This minor difference should be incorporated in cross-sectional imaging measurement for the evaluation of patella alta and baja.

Similar patellar height ratio indices can be used on X-ray, CT and MRI with minor (0.1) adjustment.

Lee, P, Chalian, M, Thawait, G, Faridian-Aragh, N, Eng, J, Chhabra, A, Multimodality Measurements of Patellar Height on X-ray, CT, and MRI.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034552.html