Description
【Purpose】This study aimed to investigate whether any difference existed between the cortical suspensory button (CSB) and the interference screw (IS) fixation in graft maturation and bone-tendon healing within the tibial tunnel after ACLR.
【Methods】One-hundred eighteen patients who underwent single-bundle ACLR with a minimum one-year follow-up were included in this study. The tibial end of the graft was fixed using IS in 82 knees and CSB in 36 knees. The MR studies were performed six months after surgery. The graft maturation was assessed using the signal-to-noise quotient (SNQ) measured by selecting a region of interest centered around the graft at the level of the tibial articular surface on oblique sagittal proton density-weighted MRI. The bone-tendon healing within the tibial tunnel was examined by evaluating the intensity of the fibrous interzone (FIZ) on axial fat-suppressed proton density-weighted images at the articular surface level (ASL), 5mm and 10mm below the ASL. The intensity of FIZ was evaluated according to the classification of Silva and Sampaio, in which FIZ signal intensity was classified as grade 0 if similar to the patellar tendon, grade 1 if similar to skeletal muscle, grade 2 if greater than muscle but less than fluid, and grade 3 if similar to joint fluid (Fig.1). The percentage of the FIZ with each grade and screw in each image was calculated as the virtual circle (Fig.2). Tibial tunnel expansion was calculated from the MRI scans. Knee stability was measured Kneelax 3 side-to-side difference at one year after surgery. Statistical analyses were performed using the Mann-Whitney U test and the chi-square test.
【Results】The mean SNQ was 1.77±3.6 in the IS group and 0.86±4.5 in the CSB group (p=0.184). Most of the FIZ showed intermediate intensity (grade 1 or 2) in both groups. Still, the ratio of FIZ with grade 1+2 was significantly lower in the IS group than in the CSB group (p<0.001) due to the screw-occupied portion. The grade 0 or 3 was not significantly different between the two groups (Table 1). The tunnel enlargement was not significantly different between the IS (2.3±1.4mm) and CSB (1.9±1.0 mm) groups (p=0.08). The side-to-side difference of Kneelax 3 was not significantly different between the IS (0.99±2.1mm) and CSB (0.94±2.1 mm) groups (p=0.908).
【Conclusion】Graft maturation, tunnel expansion, and anterior knee stability were not significantly different between the two groups. The pattern of graft incorporation in the tibial tunnel was similar in both groups. However, the tendon-bone contact area of the IF group was significantly smaller than the CSB group due to the interference screws.
