One-Year Serial Follow-up Magnetic Resonance Imaging Study of RigidFix for Femoral Fixation in Anterior Cruciate Ligament Reconstruction

Outcomes of RigidFix Cross Pin Fixation in Femoral and Tibial Tunnel for Anterior Cruciate Ligament Reconstruction

OBJECTIVES

There is no clear consensus so far on which fixation method is most favorable for the tibial tunnel in anterior cruciate ligament reconstruction (ACLR). The purpose of this paper is to investigate the outcome of RigidFix cross pins fixation in the tibial tunnel and to explore the advantages of RigidFix applied both in the femoral and tibial tunnel with hamstring tendon graft in anterior cruciate ligament reconstruction.

METHODS

This retrospective study included 53 patients (male/female, 45/8) who underwent anterior cruciate ligament reconstruction using autologous hamstring tendons between January 2013 and December 2017 at our institute. The participants in group A (n = 36) received anterior cruciate ligament reconstruction with RigidFix cross pins fixation in both femoral and tibial tunnels, while those in group B (n = 17) with RigidFix cross pins fixation in the femoral tunnel and Interference screw fixation in the tibial tunnel. The visual analogue scale (VAS) score, International Knee Documentation Committee subjective knee form 2000 (IKDC2000) score, Lysholm knee scoring scale, Tegner activity score and the side-to-side difference were compared at 2 and 5 years postoperatively. The graft diameter, number of strands in graft and the average diameter of each strand were also compared between the two groups. The categorical parameters were analyzed by chi-square test and the continuous variables conforming to a normal distribution were analyzed by Student's t-test.

RESULTS

At 2 years postoperation, the VAS score (1.61 ± 0.55), side-to-side difference (1.50 ± 0.58) in group A were significantly lower than that in group B, and the IKDC2000 score (88.81 ± 3.88), Tegner activity score (6.14 ± 0.60) in group A were significantly higher than that in group B. At 5 years postoperation, the VAS score (1.64 ± 0.68), side-to-side difference (1.73 ± 0.63) in group A were significantly lower than that in group B, and the IKDC2000 score (89.09 ± 3.85), Tegner activity score (6.58 ± 0.94) in group A were slso significantly higher than that in group B. There was statistical difference in the change of the side-to-side difference between the two groups (group A vs. B, 0.22 ± 0.08 vs. 0.34 ± 0.11, p < 0.001). There were also statistical differences in the graft diameter (group A vs. B, 7.83 ± 0.74 vs. 7.41 ± 0.51, p = 0,038), number of strands in graft (5.67 ± 0.72 vs. 4.00 ± 0.00, p < 0.001) and the average diameter of each strand (1.41 ± 0.22 vs. 1.85 ± 0.13, p < 0.001) between the two groups.

CONCLUSION

RigidFix cross pins fixation in the tibial tunnel for anterior cruciate ligament reconstruction can achieve better 5-year results when compared with the interference screw, and the hamstring tendon can be folded into a thicker graft when RigidFix cross pins were applied in both femoral and tibial tunnels.

Biomechanical effects of cross-pin's diameter in reconstruction of anterior cruciate ligament - A specific case study via finite element analysis

For anterior cruciate ligament reconstruction (ACL-R), one of the crucial aspects of treatment is the fixator selection that could provide initial graft fixation post-operatively. Literature on biomechanical stabilities of different sizes of fixators as femoral graft fixation is limited. Therefore, this study aims to analyse the influence of different diameters of cross-pins on the stability of graft fixations after ACL-R via finite element analysis (FEA). In the methodology, three-dimensional (3D) models of three different diameters of cross-pins were developed, of which anterior tibial loads (ATL) were applied onto the tibia. From the findings, the cross-pin with a smaller diameter (4 mm) provided optimum stability than larger diameter cross-pins, whereby it demonstrated acceptable stresses at the fixators (both cross-pin and interference screw) with a different percentage of 28%, while the stresses at the corresponding bones were favourable for osseointegration to occur. Besides, the strains of the knee joint with 4 mm diameter cross-pin were also superior in providing a good biomechanical environment for bone healing, while the recorded strain values at fixators were comparable with a larger diameter of cross-pins without being inferior in terms of deformation. To conclude, the cross-pin with 4 mm diameter depicted the best biomechanical aspects in graft fixation for ACL-R since it allows better assistance for the osseointegration process and can minimise the possibility of the breakage and migration of fixators. This study is not only useful for medical surgeons to justify their choices of pin diameter to treat patients, but also for researchers to conduct future studies.

Relationship between altered knee kinematics and subchondral bone remodeling in a clinically translational model of ACL injury

Abnormal joint kinematics are commonly reported in the acute and chronic stages of recovery after anterior cruciate ligament (ACL) injury and have long been mechanistically implicated as a primary driver in the development of posttraumatic osteoarthritis (PTOA). Though strongly theorized, it is unclear to what extent biomechanical adaptations after ACL injury culminate in the development of PTOA, as data that directly connects these factors does not exist. Using a preclinical, noninvasive ACL injury rodent model, our objective was to explore the direct effect of an isolated ACL injury on joint kinematics and the pathogenetic mechanisms involved in the development of PTOA. A total of 32, 16-week-old Long-Evans rats were exposed to a noninvasive ACL injury. Marker-less deep learning software (DeepLabCut) was used to track animal movement for sagittal-plane kinematic analyses and micro computed tomography was used to evaluate subchondral bone architecture at days 7, 14, 28, and 56 following injury. There was a significant decrease in peak knee flexion during walking (p < .05), which had a moderate-to-strong negative correlation (r = -.59 to -.71; p < .001) with subchondral bone plate porosity in all load bearing regions of the femur and tibia. Additional comprehensive analyses of knee flexion profiles revealed dramatic alterations throughout the step cycle. This occurred alongside considerable loss of epiphyseal trabecular bone and substantial changes in anatomical orientation. Knee flexion angle and subchondral bone microarchitecture are severely impacted after ACL injury. Reductions in peak knee flexion angle after ACL injury are directly associated with subchondral bone plate remodeling.

Biomechanical analysis of three different types of fixators for anterior cruciate ligament reconstruction via finite element method: a patient-specific study

Complication rates of anterior cruciate ligament reconstruction (ACL-R) were reported to be around 15% although it is a common arthroscopic procedure with good outcomes. Breakage and migration of fixators are still possible even months after surgery. A fixator with optimum stability can minimise those two complications. Factors that affect the stability of a fixator are its configuration, material, and design. Thus, this paper aims to analyse the biomechanical effects of different types of fixators (cross-pin, interference screw, and cortical button) towards the stability of the knee joint after ACL-R. In this study, finite element modelling and analyses of a knee joint attached with double semitendinosus graft and fixators were carried out. Mimics and 3-Matic softwares were used in the development of the knee joint models. Meanwhile, the graft and fixators were designed by using SolidWorks software. Once the meshes of all models were finished in 3-Matic, simulation of the configurations was done using MSC Marc Mentat software. A 100-N anterior tibial load was applied onto the tibia to simulate the anterior drawer test. Based on the findings, cross-pin was found to have optimum stability in terms of stress and strain at the femoral fixation site for better treatment of ACL-R.