Quadriceps tendon autograft has lower mri signal than hamstring tendon autograft in anterior cruciate ligament reconstructions in adolescent athletes

Objectives: Hamstring tendon autograft (HTA) is a common graft choice for anterior cruciate ligament (ACL) reconstructions in skeletally immature patients. However, quadriceps tendon autografts (QTA) have recently shown superior preliminary outcomes in this population. The objective of this study was to evaluate graft maturity by comparing MRI signal intensity of HTA and QTA used in primary ACL reconstruction. Given the promising preliminary results of QTA reconstructions in our center, we hypothesized that QTA would have lower signal than HTA at both 6 and 12 months. Methods: Patients under the age of 18 who underwent a primary ACL reconstruction between 2011 and 2018 by the senior authors using either a HTA or QTA with available MRIs at 6 and 12 months post-operatively were included. Signal intensity ratio (SIR) was measured on sagittal MRI by averaging the signal at three regions of interest (ROIs) along the ACL graft (Figure 1) and dividing each by the signal of the tibial footprint of the PCL. Statistical analysis was performed to determine interrater reliability and differences between time points and groups. Results: 71 patients (38 in the HTA group and 33 in the QTA group) were reviewed retrospectively. Age, sex, and type of surgery were not different between groups (Table 1). There was no significant difference in SIR between groups on the 6-month MRI. At 12 months, SIR of the QTA group was significantly less that in the HTA group ( p=.029). Within the HTA group, there was no significant difference in SIR between time points. In the QTA group, there was a significant decrease in SIR between the 6 month and 12-month post-operative MRI ( p=.045) (Figure 2). Conclusions: The decrease in signal between 6 and 12 months post-operatively suggests quicker graft maturation and improved structural integrity of QTA as compared to HTA (Figure 3). This provides evidence that one year postoperatively, QTA may have a superior rate of incorporation and synovialization as compared to the HTA. [Table: see text]