Rachel Umans BA, Presenter: Nothing to Disclose

Benjamin Umans BA, MSc, Abstract Co-Author: Nothing to Disclose

Hilary Ruth Umans MD, Abstract Co-Author: Nothing to Disclose

Elisabeth Elsinger, Abstract Co-Author: Nothing to Disclose

To identify qualitative and quantitative MRI findings correlated with lesser MPJ PP tear.

Non-contrast MRI (10/2012-01/2014, 1.5 or 3.0 T) of 50 PP tear cases (35 female, 15 male, av 52 yrs) and 50 controls (41 female, 9 male, av 35 yrs) were randomized and reviewed. All cases of PP tear demonstrated accepted MRI criterion of a bright T2 signal defect at the insertion of the PP. An MSK radiologist, blinded to diagnosis, reviewed potential qualitative correlates of PP tear including: metatarsal (MT) axis rotation, toe deviation, intermediate signal pericapsular soft tissue thickening (STT), toe enthesitis and flexor tendon subluxation or tenosynovitis. A trained, similarly-blinded non-physician, unfamiliar with MRI diagnosis of PP tear, measured MT axis rotation, 2nd MT protrusion, submetatarsal fat pad thickness and toe rotation. Each blindly double-read 20 MRI (11 cases, 9 controls) to evaluate intra-observer agreement for the qualitative findings and quantitative measures, respectively. Kappa statistic, t-test, Wilcoxon rank sum test were used as appropriate; p<0.05 was considered significant. Classification trees were created to identify combinations of findings correlated with PP tear. 

There were significant, reproducible differences in measured MT axis rotation and 2nd MT protrusion between PP tear and control groups. Lesser MT supination >36° or 2nd MT protrusion >4mm trend toward a correlation with PP tear. Lesser MT supination <24° is a strong negative predictor of PP tear. Lesser MT protrusion > 4.5mm is a strong positive predictor of PP tear. Among qualitative correlates, pericapsular STT correctly classified 95% of cases and controls, though there may be an element of diagnostic heterogeneity in assessment of this finding. Excluding pericapsular STT, 94% correct classification was achieved by a combination of 2nd toe enthesitis, 2nd flexor tendon subluxation and splaying of the 2nd and 3rd toes. Both quantitative measures (concordance=0.88-0.99) and qualitative assessments (kappa=0.71-1.0) were highly reproducible.

PP tear can be determined with high accuracy using a combination of correlated qualitative findings and quantitative measurements.

Correlative signs of PP tear are clinically important since primary MRI signs for diagnosis of PP tear may be subtle or occult, resulting in common misdiagnosis and mistreatment.

Umans, R, Umans, B, Umans, H, Elsinger, E, Predictive MRI Correlates of Lesser Metatarsophalangeal Joint (MPJ) Plantar Plate (PP) Tear.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005367.html