Introduction: PP, also called plantar ligament, is a fibrocartilaginous structure found in the metatarsophalangeal (MP) and interphalangeal (IP) joints. The aim of our study is to evaluate the role of MRI, both in standard position and with joint hyperextension, “stress test” (ST), in the study of the plantar plate (PP) disease that involves metatarsophalangeal joints.
Material and methods: 25 patients were recruited into our study over a two-year period, 15 positive for metatarsal pain and 10 controls. All symptomatic patients were evaluated before treatment (surgery). Hence, the imaging features were reflective of the natural and true state of the lesions.
Results:25 patients were recruited into our study over a two-year period, 15 positive for metatarsal pain and 10 controls.
In symptomatic patients: 11/15 demonstrated plantar plate tear/dysfunction on both standard position and stress test, 2/15 had plantar plate tear on stress test (tear not showed on standard position), and 2/12 had no plantar plate tear on both standard position and stress test. The latter two patients showed dorsal subluxation on stress test due to micro-instability for plantar plate failure.
In asymptomatic patients, 9/10 were negative for plantar plate dysfunction, and 1/10 was positive for plantar plate dysfunction (dorsal subluxation demonstrated only on stress test), without plantar plate tear.
Conclusion:Standard MRI reported, in asymptomatic patients, a specificity of 100% and high NPV (90%), incremented by the ST (NPV and specificity 100%).
In symptomatic patients, PP evaluation on standard MRI reported sensitivity of 80%, while stress test increased sensitivity to 100%; in the evaluation of dorsal subluxation of the metatarsophalangeal joint, the sensitivity was 60% (standard MRI) but reached 100% with ST.
"Stress test" is an easy task to perform and even affordable in terms of time-consuming (requiring only one additional T2-weighted MRI sequence) for both patients and operators.