Bone-Patellar Tendon-Bone Autograft Thickness Is a Risk Factor for Graft Failure. A Case-Control Analysis.

Background: Graft failure following anterior cruciate ligament reconstruction (ACLR) is a devastating complication. Risk factors such as patient characteristics and tunnel positions are well described. The relationship between graft dimension and failure rates has been investigated mainly in soft tissue grafts. Less studied are the effects of patella tendon (PT) dimensions on the risk of graft failure following patella tendon autograft (PTA) reconstructions.
Purpose: The purpose of the current study was to investigate if patellar tendon thickness measured on preoperative magnetic resonance imaging (MRI) predicts failure after ACLR using PTA.
Methods: This was an institutional review board approved, single-center, retrospective case-control study comparing patients' preoperative patellar tendon thickness between July 2005 and January 2017. Sixteen patients (mean age 21.2 ± 5.0 years) with PTA failure requiring revision surgery were identified and compared to 34 control patients who had undergone primary ACLR with PTA without failure with a minimum of 2-years follow-up. Patients with failure were matched at approximately 1:2 based on age, sex, height, weight, associated meniscus injury, and associated meniscal surgery. Patellar tendon dimensions were measured at the inferior pole of the patella (IPP), tibial tubercle insertion (TT), and longitudinal midpoint (MP) on preoperative axial and sagittal cut MRIs. Interclass correlation coefficeint (ICC) and Bland-Altman analyses were evaluated to determine inter-observer reliability. The two cohorts were compared using independent samples t-tests and analysis of variance.
Results: All ACLR failures occurred after a non-contact, pivot type injury. There were no significant differences in age, sex, height, weight, meniscal injury, or meniscal surgery between the two groups. Mean time between primary ACLR and revision was 2.6 ± 2.6 years and mean follow-up time was 3.1 ± 1.0 years in the control group. Patellar tendon length and width were not significantly different between the two groups. The average thickness at both the inferior pole and longitudinal midpoint was significantly higher in the failure group compared to controls (IPP: 5.04 ± 1.1 mm versus 4.33 ± 0.7 mm, p = 0.01; MP: 4.60 ± 0.7 mm versus 4.22 ± 0.5 mm, p = 0.03). Additionally, ICC was high across all measurements, with all values > 0.978. Similarly, all values demonstrated bias of less than ± 0.05.
Conclusion: Patella tendon autograft anterior cruciate ligament reconstruction failures had significantly thicker patellar tendons at the inferior pole and longitudinal midpoint of the patella tendon.