Association Between T2* Relaxation Times Derived From Ultrashort Echo Time MRI and Symptoms During Exercise Therapy for Patellar Tendinopathy: A Large Prospective Study.

Abstract

BackgroundExercise therapy is considered preferential treatment for patellar tendinopathy (PT). However, there is conflicting evidence for structural patellar tendon adaptation in response to exercise therapy and its association with symptoms is weak.PurposeTo assess the association between 1) T2 * relaxation times and symptom severity; 2) baseline T2 * and clinical outcome; and 3) longitudinal T2 * changes and clinical outcome in athletes with PT performing exercise therapy.Study TypeRandomized controlled clinical trial.SubjectsSeventy‐six athletes (18–35 years) with clinically diagnosed and ultrasound‐confirmed PT.Field strength/Sequence3D gradient echo sequence (3.0 T).AssessmentPatients were enrolled in a randomized trial of progressive tendon‐loading exercises (PTLE) versus eccentric exercise therapy (EET). Symptoms were assessed using the Victorian Institute of Sports Assessment (VISA‐P) questionnaire. 3D‐Ultrashort echo time (UTE)‐MRI was acquired at baseline, 12 and 24 weeks. Voxel‐wise T2 * relaxation times were quantified using mono‐exponential and bi‐exponential models. T2 * analysis was performed in three patellar tendon tissue compartments representing: aligned collagen, degenerative tissue, and interface.Statistical TestsAdjusted general linear, mixed‐linear models, and generalized estimating equations.ResultsWe included 76 patients with PT (58 men, mean age 24 ± 4 years); 38 in the PTLE‐group and 38 in the EET‐group, of which 57 subjects remained eligible for analysis. T2 * relaxation times were significantly associated with VISA‐P in degenerative and interface tissues of the patellar tendon. No association was found between baseline T2 * and VISA‐P after 24 weeks (P > 0.29). The estimated mean T2 * in degenerative tissue decreased from 14 msec (95%CI: 12–16) at baseline to 13 msec (95%CI: 11–15) at 12 weeks and to 13 msec (95%CI: 10–15) at 24 weeks. The significant decrease in T2 * from baseline to 24 weeks was associated with improved clinical outcome.Data ConclusionTissue‐specific T2 * relaxation times, identified with 3D‐UTE‐MRI, decreased significantly in athletes with patellar tendinopathy performing exercise therapy and this decrease was associated with improved clinical outcome.Evidence Level1Technical EfficacyStage 4