A BIOMECHANICAL COMPARISON OF SUTURE ANCHOR VS. INTERFERENCE SCREW TECHNIQUE FOR PATELLAR FIXATION FOR MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION

Abstract

Background: There are numerous techniques for MPFL reconstruction, however, one single technique has not been proven to be superior to another. Suture anchor reconstruction has been shown to provide stable fixation while decreasing the risk of patellar fracture. Purpose: The aim of the study was to compare the stiffness and clinical load to failure of two common MPFL reconstruction techniques. Our hypothesis was that there would be no significant difference in the stiffness and the clinical load to failure between the suture anchor and interference screw reconstructions. Methods: Eight pairs of fresh frozen cadaveric knees were randomized into two groups undergoing MPFL reconstruction using either a suture anchor technique (n = 8) or an interference screw technique (n = 8). Testing was performed at 0, 30, 60, and 90 degrees of flexion for the native knee, transected medial structures, and reconstructed MPFL. Next, the reconstructed MPFL specimens were tested until failure in 0 degrees of flexion. t-Test, One-Way ANOVA, and repeated measures of ANOVA were used for statistical analysis, p values less than 0.05 were considered significant. Results: The average stiffness for the suture anchor and interference screw reconstructions was 12.02 ± 3.96 N/mm and 14.21 ± 4.20 N/mm, respectively (t-test, p = 0.27), while average clinical load to failure was 256.57 ± 54.1 N and 237.81 ± 23.82 N, respectively (t-test, p = 0.38). There was no significant difference in stiffness between the suture anchor and interference screw techniques at 0, 30, and 60 degrees of flexion. Conclusions: The suture anchor and interference screw reconstruction techniques produce comparable stiffness for sub-failure testing at 0 and 30 degrees of flexion. For testing to failure, the initial stiffness for both reconstruction techniques have been shown to be concordant with previously published values for the native MPFL. Both reconstruction techniques provide greater ultimate failure loads than those reported for the native MPFL in previous studies. Suture anchor reconstruction described in our study provides another reliable option for the reconstruction of the medial patellofemoral ligament. Clinical relevance: Our study provides biomechanical data that the suture anchor technique described in this study provides comparable fixation compared to interference screw fixation and has the potential of reducing fracture to patella particularly in the pediatric population with small patellae.