Quadriceps Tendon Autograft in Pediatric Anterior Cruciate Ligament Reconstruction: Graft Dimensions and Prediction of Size on Preoperative MRI

Background: There has been a growth of interest in quadriceps autograft anterior cruciate ligament (ACL) reconstruction, both in pediatric and adult populations. However, there is limited evidence regarding the quadriceps graft dimensions and adequacy in children, and whether they could be predicted pre-operatively. The goal of this study was to evaluate children and adolescents who underwent ACL reconstruction using a quadriceps autograft to determine the properties of the harvested graft and to assess the value of demographic, anthropometric, and MRI measurements in predicting the graft size preoperatively.

Methods: A retrospective IRB-approved database search was performed from January 2018 through October 2020 for patients undergoing ACL reconstruction. Patients <18 years old at the time of surgery in whom a quadriceps tendon autograft was used were selected. Demographic data and anthropometric measurements were recorded, and graft measurements were abstracted from the operative note. Knee magnetic resonance images (MRI) were reviewed to measure the quadriceps tendon thickness on sagittal cuts (Figure 1). Graft length and diameter were then correlated with anthropometric and radiographic data.

Results: A total of 169 patients (98 male) were included in the final analysis, with a median age of 15 years (range, 9-17). A tendon length of 65mm or more was harvested in 159 (94%) patients. The mean final graft diameter was 8.4 ± 0.7mm (range, 7 – 11mm). All patients had a graft diameter of 7mm or more, and 139 (82%) had a diameter of 8mm or larger. Preconditioning decreased the graft diameter by a mean of 0.68 ± 0.23mm. Age (P=0.04) and quadriceps thickness on MRI (P <0.001) were significant predictors of the final graft diameter. An MRI sagittal thickness of >6.7mm was 97.4% sensitive for obtaining a graft of ≥8mm in diameter.

Conclusion: Our findings suggest that tendon-only quadriceps autograft is a reliable graft source in pediatric ACL reconstruction, yielding a graft of ≥8mm in diameter in 82% of pediatric patients. Furthermore, preoperative MRI measurements can be reliably used to predict a graft of adequate diameter in children and adolescents undergoing ACL reconstruction, with a sagittal thickness of >6.7mm being highly predictive of a final graft size ≥8mm.