Abstract
Objectives:
The quadriceps tendon (QT) autograft has garnered popularity for anterior cruciate ligament (ACL) reconstruction (ACLR) in the last decade. However, as with other autograft choices, re-ruptures of QT autografts can occur especially in high-level athletes, with reported rates ranging from 2%-22%. ACL revision surgery is an option for these athletes, but it can be difficult for surgeons to decide what type of graft to select. Numerous studies have examined postoperative morphologic changes in the PT, and suggest the postoperative PT was thicker than the contralateral tendon at least 2 years postoperatively. However, there is a paucity of literature on postoperative morphologic changes in the QT, and the possibility of re-harvesting the QT remains unknown. Therefore, the purpose of this study was to reveal the postoperative morphologic changes in the QT harvest site at a minimum of 2 years following ACLR. The hypothesis was that the postoperative QT would remain the same in width but increase in thickness.
Methods:
Patients who underwent primary ACLR using QT autograft in our institution between January 2014 and March 2021 were retrospectively reviewed. Patients under 14 years of age and patients undergoing concomitant osteotomy, multi-ligament surgery, or ACL revision were excluded. Out of 493 patients meeting inclusion criteria, 30 patients who underwent magnetic resonance imaging (MRI) at a minimum of 2 years following ACLR were studied. The anterior-posterior (A-P) thickness, medial-lateral (M-L) width, and cross-sectional area (CSA) were measured at 5 mm, 15 mm, and 30 mm proximal to the superior pole of the patella (Figure 1). Since the axial plane was not perpendicular to the long axis of the QT, the CSA was adjusted by the angle between the QT and the plane of the axial cut based on a cosine function (adjusted CSA). Moreover, to obtain the signal/noise quotient (SNQ) of regions of interest (ROI) of the QT, the signal intensity of ROI with 10 mm2 was measured on the QT at 5 mm, 15 mm, and 30 mm proximal to the superior pole of the patella, the center of the PT, and the background on the same sagittal plane. SNQ of the QT was calculated using the following equation: SNQ = (mean signal value of the QT – mean signal value of the PT) / mean signal value of the background. In addition, the existence of defect or scar tissue formation at the harvest site was investigated by reviewing postoperative MRI. A defect was defined as a depression deformity at the harvest site, while a scar tissue formation was defined as a change in iso- to high-intensity signal at the harvested site on a fat suppression T2-weighted images compared to the preoperative tendon. To compare the A-P thickness, M-L width, adjusted CSA, and SNQ values between pre- and post-operative states, a Wilcoxon signed-rank test or paired t-test were used for non-normally and normally distributed data, respectively. Statistical significance was set at P < 0.05.
Results:
Following all exclusion criteria, a total of 30 patients (mean age, 20.7 ± 5.5 years, 66.7% male) were included. The mean duration between primary ACLR and postoperative MRI was 2.8 ± 1.1 years. The axial plane of QTs at 30 mm proximal to the patella was included on both pre- and postoperative MRI in 8 patients. Compared with pre-surgery, the A-P thickness of the postoperative QT donor site was increased by 10.3% at 5 mm (8.7 ± 1.4 mm vs. 9.6 ± 1.6 mm, P < 0.01), and 11.9% at 15 mm proximal to the patella (8.4 ± 1.1 mm vs. 9.4 ± 1.8 mm, P < 0.05). Meanwhile, the M-L width was decreased by 7.3% at 5 mm (52.2 ± 6.9 mm vs. 48.4 ± 7.5 mm, P < 0.01), and 6.5% at 15 mm proximal to the patella (43.0 ± 8.4 mm vs. 40.2 ± 8.0 mm, P < 0.01). No difference in the CSA of the QT at each assessment location was observed between pre- and post-operative states. The SNQ of the QT was not significantly changed postoperatively at each assessment location (Figure 2). Defect and scar formation at the harvest site was observed in 4 (13.3%) cases, and 5 (16.6%) cases, respectively.
Conclusions:
At a minimum of 2 years following ACLR, the QT became slightly thicker and narrower, and defects or scar tissue formation were observed in only 30% of cases at the harvest site. Harvest thickness did not affect the postoperative morphologic change of the QT. Given the nearly normalized tendon morphology and post-surgical SNQ of the QT similar to pre-surgical state, re-harvesting the QT may be possible.
