Bone Staples Provide Favorable Primary Stability in Cortical Fixation of Tendon Grafts for Medial Collateral Ligament Reconstruction: A Biomechanical Study

Abstract

Background: The use of the interference screw (IFS) for the cortical fixation of tendon grafts in knee ligament reconstruction may lead to converging tunnels in the multiligament reconstruction setting. It is unknown whether alternative techniques using modern suture anchor (SA) or bone staple (BS) fixation provide sufficient primary stability. Purpose: To assess the primary stability of cortical fixation of tendon grafts for medial collateral ligament (MCL) reconstruction using modern SA and BS methods in comparison with IFS fixation. Study Design: Controlled laboratory study. Methods: Cortical tendon graft fixation was performed in a porcine knee model at the tibial insertion area of the MCL using 3 different techniques: IFS (n = 10), SA (n = 10), and BS (n = 10). Specimens were mounted in a materials testing machine, and cyclic loading for 1000 cycles at up to 100 N was applied to the tendon graft, followed by load-to-failure testing. Statistical analysis was performed using 1-way analysis of variance. Results: There were no statistical differences in elongation during cyclic loading or peak failure load during load-to-failure testing between BS (mean ± standard deviation: 3.4 ± 1.0 mm and 376 ± 120 N, respectively) and IFS fixation (3.9 ± 1.2 mm and 313 ± 99.5 N, respectively). SA fixation was found to have significantly more elongation during cyclic loading (6.4 ± 0.9 mm; P < .0001) compared with BS and IFS fixation and lower peak failure load during ultimate failure testing (228 ± 49.0 N; P < .01) compared with BS fixation. Conclusion: BS and IFS fixation provided comparable primary stability in the cortical fixation of tendon grafts in MCL reconstruction, whereas a single SA fixation led to increased elongation with physiologic loads. However, load to failure of all 3 fixation techniques exceeded the loads expected to occur in the native MCL. Clinical Relevance: The use of BS as a reliable alternative to IFS fixation for peripheral ligament reconstruction in knee surgery can help to avoid the conflict of converging tunnels.

Comparison of Time-Zero Primary Stability Between a Biodegradable Magnesium Bone Staple and Metal Bone Staples for Knee Ligament Fixation: A Biomechanical Study in a Porcine Model

“…The anatomy of porcine knees was shown to be sufficiently similar to that of human knees, 46 and porcine flexor tendons possess biomechanical properties similar to those of human hamstring tendons, 17 making it a frequently used model to assess the biomechanical primary stability of orthopaedic implants. 19,23,24,43 Nevertheless, bone density in the porcine model is significantly higher in comparison with humans, 1 which could have affected the findings of the present study. 8,42 A recent study showed that, in a test setup like that used in this study, the displacement of the machine actuator used to calculate the elongation was significantly higher than the actual graft slippage, as measured by optical tracking at the tunnel aperture, although both values were highly correlated.…”

The Biomechanical Stability of Bone Staples in Cortical Fixation of Tendon Grafts for Medial Collateral Ligament Reconstruction Depends on the Implant Design

“…Our previous investigation 9 revealed the promising biomechanical stability of BSs for cortical fixation of MCL grafts in comparison with interference screw fixation and suture anchor fixation in the same porcine knee model: no statistical differences in elongation during cyclic loading or peak failure load were found between narrow BSs with spikes (3.4 ± 1.0 mm and 376 ± 120 N, respectively) and interference screw fixation (3.9 ± 1.2 mm and 313.0 ± 99.5 N, respectively), whereas graft fixation with a single suture anchor was found to have significantly more elongation during cyclic loading (6.4 ± 0.9 mm) and a lower peak failure load (228 ± 49 N). 9 Omar et al 25 compared the biomechanical stability of 4.0-mm cancellous screws with different washers as well as single or double titanium suture anchors in a porcine knee model of MCL reconstruction. Spiked polyetheretherketone washers with polyester sutures resulted in the most favorable biomechanical properties for both elongation during cyclic loading (2.9 ± 0.7 mm) and ultimate failure load (470 ± 64 N).…”

“…An a priori power analysis showed that a sample size of 10 per group would yield 90% power to detect a difference of 50 N between group means of peak failure load at the f ≥ 0.8 level based on the standard deviations of MCL graft fixation methods in porcine knee models in previous studies. 9 , 25 The normal distribution was evaluated using the Shapiro-Wilk test. The Kruskal-Wallis test was used to compare groups, and the post hoc Dunn test was performed for multiple comparisons.…”

“…5 A previous investigation revealed the promising biomechanical stability of BSs for cortical fixation of MCL grafts in a porcine knee model without inferiority in comparison with interference screw fixation. 9 However, currently available BS designs vary regarding the length of their branches, a smooth or spiked surface toward the bone, the width of the implant, and 2-or 4-prong designs. 8,10,18,21,30 It is currently unknown if the biomechanical stability of cortical fixation of tendon grafts with BSs varies depending on the design of the implant.…”

Comparison of Onlay Anchor Fixation Versus Transosseous Fixation for Lateral Extra-articular Tenodesis During Revision ACL Reconstruction

“…4 Recent studies have investigated the concept of onlay fixation using different metal or soft tissue anchors. 8,19,21 Clinical studies comparing onlay and intraosseus screw fixation are missing, but a recent animal study examined the biological properties of an onlay MCL fixation, which demonstrated nonsignificant differences when compared with the native MCL. 35 These results are in line with clinical data showing good to excellent results of ligament fixation using the anchor technique.…”