LAUSR

Objectives: Partial patellar tendon tears (PPTTs) can be a frustrating injury for athletes and physicians. Determining the location and size of the PPTT are fundamental in understanding prognosis and selecting the most effective treatment. With recent enhancements in MRI quality, the size and dimensions of the tear can be more easily and accurately estimated. While some PPTTs respond to therapy, medication, bracing, biologic injections, and/or ultrasound procedures, other PPTTs in do not respond and require surgical intervention. The goal of this study is to correlate PPTT size and location to clinical outcomes, in order to create a classification system to help guide treatment decisions for athletes with PPTT. Methods: 112 athletic patients (range: 15-45 y/o, mean 23.9+7.2 y/o) who underwent knee MRI were included in this study. 85 of those patients (mean 24.9+8.1 y/o) presented with history and physical examination concerning for recalcitrant patellar tendonitis or suspicion of a partial patellar tendon tear. The other 27 athletic patients (mean 25.6+6.3 y/o) underwent MRI for other pathology and were included as age-matched controls. MR scans were evaluated for patellar tendon tear size, thickness, and location with respect to the entire patellar tendon. Descriptive statistics were used to evaluate tendon size and tear distributions. Pearson correlation, univariate regressions, and logistic regression were performed to correlate tendon geometry and tear sizes. Tear geometry variables were compared to patient outcome measures (return to previous activity level, surgical treatment) using t-tests. Results: 56 out of 85 symptomatic patients had partial patellar tendon tears. 91% of PPTTs involved the posterior and posteromedial region of the proximal patellar tendon (Figure 1). On axial MRI imaging, patients with PPTT had mean tendon thickness of 10 mm compared to 5.9 mm for athletes with no PPTT, including healthy controls (p<.0001). There was a significant correlation between patellar tendon thickness and PPTT size (R=0.85, p<0.0001). Logistic regression analysis showed that athletes with patellar tendon thickness above 7.45 mm are likely to have PPTTs (100% sensitivity). Tear distributions according to MRI grading are shown in Table 1. 11 out of 56 patients underwent surgery for PPTT. All 11 of these patients had tear sizes on axial images > 50% of tendon thickness (mean thickness of tear 6.3 mm). Logistic regression showed that patellar tendon thickness > 8.8 mm, and/or tear size > 55% correlated with surgical intervention. Five of the surgical patients did not make a return to sport at the same level. No patient in this series had surgery for tear thickness less than 4.5 mm. Basketball, track and field and soccer were the most common sports involved in the study. Conclusion: PPTTs are located posterior/posteromedially in the proximal patellar tendon. The most sensitive metric for PPTTs are patellar tendon thickness (anterior to posterior), where thickness more than 8.8 mm is strongly predictive of having a partial tear in the tendon. Athletes with greater than a 55% tear thickness on axial MRI imaging or with a tear measuring more than 4.5 mm on axial cuts are less likely to respond to non-operative treatment. Tracking thickness changes on axial views, specifically in the posterior/posteromedial region, may predict effectiveness of non-operative therapy. Distribution of PPTTs according to MRI based grading - Criteria [tear % in thickness] Thickness [mm] (A->P) Tear Thickness[mm] (A->P) Repair Surgeries [patients] Did NOT return to previous activity [patients] Grade 1 No tears 6.15 +/- 1.86 0 0 2 Grade 2 Tears <25% 8.71 +/- 1.65 1.8 +/- 0.6 0 1 Grade 3 25% < 50% 10.03 +/- 2.37 3.8 +/- 1.4 0 3 Grade 4 above 50% > 10.27 +/- 2.22 6.3 +/- 1.5 11 5 Total - - - 11 11 Figure 1. Frequency heat map for partial patellar tendon tears in axial view (anterior to posterior)