Keywords:
Performed at one institution, Observational, Retrospective, Athletic injuries, Comparative studies, MR, Musculoskeletal joint, Extremities, Musculoskeletal
Authors:
W. C. W. Tsui, K. K. Cheng; Hong Kong/HK
DOI:
10.26044/ecr2020/C-08610
Methods and materials
Patient Data:
MRI scans of the knee were retrospectively analyzed at our institution during the period from May 2017 to November 2018. The study inclusion criteria included cases of MRI detected complete ACL tears with arthroscopic confirmation. Cases that were excluded were due to concomitant PCL injury, systemic/rheumatologic diseases, and prior operation to the involved knee.
MRI Technique:
All MRI scans were performed using a 1.5 Tesla MR imaging system (Achieva, Philips Medical Systems, Netherlands) with the knee in extension. Support was given to the knee to reduce motion. Images were acquired in axial, coronal, and sagittal planes. Proton density-weighted spin-echo and T2-weighted fat-saturated sequences were acquired. A 12 to 13cm field of view with a 512 x 512 matrix was used. A 3.5mm section thickness was used with no gaps.
Imaging Analysis:
All images were analyzed retrospectively by a musculoskeletal radiologist using the institutional PACS (Picture Archiving and Communication Systems) (Carestream Health, Rochester, NY). The presence of the wavy patellar tendon sign and the magnitude of anterior tibial translation was evaluated. The wavy patellar tendon sign was considered positive if the patellar tendon deviated completely away from a straight line drawn from the inferior patellar pole to the tibial tuberosity in the sagittal plane. The magnitude of anterior tibial translation was assessed by drawing two parallel lines perpendicular to the tibial plateau and the lateral tibial plateau posterior margin with the distance measured.
Fig. 1: Sagittal PD-weighted image of a normal patellar tendon.
Fig. 2: Sagittal PD-weighted image showing wavy patellar tendon with deviation of the patellar tendon away from a line drawn from the inferior patellar pole to the tibial tuberosity.
The cases were further classified into two groups: 1) positive for wavy patellar tendon sign 2) negative for wavy patellar tendon sign. The degree of anterior tibial translation was evaluated in the sagittal plane. Comparison of the two groups for differences in severity of anterior tibial translation was assessed.
Statistical analysis:
Data was analyzed using SPSS statistical software. Descriptive statistics including the mean and standard deviation were analyzed. The student t-test was used to compare the two groups for statistically significant difference in the magnitude of anterior tibial translation. A p-value of less than 0.05 was considered significant.
Fig. 3: Examples of wavy patellar tendon sign in four different patients.