Biomechanical Comparison of Cross-Pin and Endobutton-CL Femoral Fixation of a Flexor Tendon Graft for Anterior Cruciate Ligament Reconstruction—A Porcine Femur-Graft-Tibia Complex Study

Comparison of Cross-Pin Versus Cortical Button Femoral Fixation in Anterior Cruciate Ligament Reconstruction With Hamstrings Autograft: A Long-Term Clinical Study and Review of the Literature

Background Anterior cruciate ligament reconstruction (ACLR) is a common operative procedure and many options regarding the type of the selected graft and fixation technique have been described to date. Although many studies have addressed the issue of the optimal femoral fixation device during ACLR with a hamstring tendon (HT) autograft, no clear evidence to indicate one technique over another has been found. Objective The purpose of this study was to compare the long-term postoperative outcomes and complication rates between transfemoral Cross-pin (CP) and Endobutton-Cortical Button (CB) fixation techniques in patients undergoing ACLR with an HT autograft. Methods One hundred and seven consecutive patients underwent ACLR by using a quadruple HT autograft that was stabilized with either a CP (CP Group: 52 patients) or a CB (CB Group: 55 patients) fixation technique. The Lachman test (LT), the Pivot-shift test (PST), the side-to-side difference in anterior translation of the tibia, the International Knee Documentation Committee (IKDC), and the Lysholm knee scoring systems were evaluated before surgery and during long-term follow up. The femoral and tibial tunnel diameter was measured in the anteroposterior (AP) and lateral radiographs after surgery and at the final follow-up. A review of the literature was also carried out to identify any differences between both techniques. Results Study groups were comparable in terms of patient demographics. The mean follow-up was 10.4 ± 1.3 and 10.6 ± 1.3 years in the CP and CB Groups, respectively (p = 0.47). In the CP Group, improvements after surgery in LT and PST from grade 2 (n=34) or 3 (n=18) to grade 0 (n = 41) or 1 (n = 11) and from grade 2 (n=36) or 3 (n = 16) to grade 0 (n = 44) or 1 (n = 8), respectively, were observed. In the CB Group, similar improvements in LT and PST scores from grade 2 (n = 40) or 3 (n = 15) to grade 0 (n = 46) or 1 (n = 9) and from grade 2 (n = 41) or 3 (n = 14) to grade 0 (n = 47) or 1 (n = 8), respectively, were observed. However, no differences between the groups (p = 0.53 for LT and p = 0.90 for PST) were noted. The mean Lysholm scores were 89.7 ± 6.8 and 90.2 ± 7.2 in the CP and CB groups, respectively (p = 0.59). Side-to-side difference improved from 9.1 ± 2.8 to 1.7 ± 1.5 mm and from 8.6 ± 2.5 to 1.6 ± 1.4 mm in the CP and CB groups, respectively (p = 0.89 between groups). According to IKDC grades, 92.1% and 91.4% of knees in the CP and CB groups, respectively were reported to be Grade A (Normal) or B (Nearly Normal) with a p = 0.7. Femoral and tibial tunnel widening was found in the last follow-up in both groups. However, there was no difference in the degree of tunnel widening among the two techniques. With respect to LT, PST, anterior drawer test, and IKDC score, none of the 15 published comparative studies demonstrated any significant differences between the two techniques and only one study detected a difference regarding the Lysholm score in favor of CP fixation. Conclusion In the long term, both CB and CP femoral stabilization techniques were shown to be associated with similar functional outcomes and low complication rates. Further large multicenter random clinical trials are still required to identify the most effective method of femoral fixation for HT autograft during ACLR surgery.

Hamstring autograft utilization in reconstructing anterior cruciate ligament: Review of harvesting techniques, graft preparation, and different fixation methods

Rupture of the anterior cruciate ligament (ACL) is a common orthopedic injury. Various graft options are available for the reconstruction of ruptured ACL. Using the hamstring muscle as an autograft was first described in 1934, and it remains a commonly harvested graft for ACL reconstruction. Hamstring autografts can be harvested using the traditional anteromedial approach or the newer posteromedial technique. An isolated semitendinosus tendon can be used or combined with the gracilis tendon. There are numerous methods for graft fixation, such as intra-tunnel or extra-tunnel fixation. This comprehensive review discusses the different hamstring muscle harvesting techniques and graft preparation options and fixation methods. It provides a comprehensive overview for choosing the optimal surgical technique when treating patients.

BIOMECHANICAL EVALUATION OF AN INVERTED FIXATION FOR ACL RECONSTRUCTION WITH NONMETALLIC HARDWARE AND TIBIAL SUBCORTICAL SUPPORT TO INCREASE STRENGTH AT THE TIBIAL SITE

In this paper, we evaluate the initial biomechanical properties of an anterior cruciate ligament (ACL) reconstruction technique that inverts the anatomical location of the commonly used hardware and relies the tibial fixation on the subcortical bone to increase tibial site strength. Four 7-specimen groups were tested in a porcine model: for the control ACL reconstruction technique, the femur with a cross-pin fixation supported in the trabecular bone and the tibia with a biodegradable interference screw (BIS); for the new proposed technique, the femur with a BIS and the tibia with a cross-pin fixation leaned on the tibial subcortical bone. The specimens were subjected to cyclic and load-to-failure tests to compute their biomechanical performance. At the tibia, the cross-pin fixation revealed higher resistance than the BIS ([Formula: see text] for ultimate load and [Formula: see text] = 0.006 for yield load), additionally cyclic and total displacement at representative loads showed extremely high values with BIS fixation (in two specimens greater than 9[Formula: see text]mm for 250 N and greater than 10[Formula: see text]mm for 450[Formula: see text]N). At the femur, no differences between fixations were observed. The inverted ACL reconstruction improves resistance at the tibial site with respect to the control technique, with similar resistance at the femoral site and no differences in total displacement at representative loads. It offers a useful and robust solution when greater tibial resistance is required.

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.

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.

Femoral Tunnel Widening Via Transcondylar Cross-Pin Fixation Versus Extracortical Suspensory Fixation After Single-Bundle ACLR: A Systematic Review and Meta-analysis

Background:

Compared with extracortical suspensory fixation, the close-to-joint transcondylar cross-pin fixation method in anterior cruciate ligament reconstruction (ACLR) is believed to entail less intratunnel graft motion and subsequently lead to less tunnel widening.

Purpose:

To assess femoral tunnel widening via the transcondylar cross-pin method or the suspensory femoral fixation method in patients who had undergone ACLR.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

This review focused on studies on femoral-tunnel widening after single-bundle ACLR with cross-pin (Rigidfix or Transfix) and/or Endobutton closed loop (CL). Two reviewers independently recorded data from each study, including the sample size and magnitude of tunnel widening after ACLR.

Results:

Overall, 19 studies were included in this meta-analysis. There was no significant difference between cross-pin and Endobutton CL fixations in the pooled absolute change in tunnel widening from the immediate postoperative period to the final follow-up; this was true at both the tunnel aperture (2.48 mm [95% CI, 1.76-3.2 mm] vs 2.93 mm [95% CI, 1.73-4.13 mm], respectively; P = .527) and the midpoint of the femoral tunnel (2.43 mm [95% CI, 1.77-3.1 mm] vs 2.54 mm [95% CI, –0.33 to 5.42 mm], respectively; P = .937). No significant difference was found in the relative percentage of femoral-tunnel widening between the 2 fixation methods (cross-pin, 43.3% [95% CI, 25.8%-60.8%] vs Endobutton CL, 42.0% [95% CI, 34.1%-49.9%]; P = .965).

Conclusion:

No significant difference in femoral tunnel widening was found to be associated with the use of either cross-pin or extracortical suspensory fixation in patients who underwent single-bundle ACLR.

Estudo biomecânico de diferentes dispositivos de fixação femoral na reconstrução do ligamento patelofemoral medial em joelhos de suínos

Objetivo Avaliar diferentes dispositivos de fixação femoral na reconstrução do ligamento patelofemoral medial para comparar sua eficácia quanto à força de fixação até a falha em joelhos suínos.

Métodos Foram ensaiados 30 joelhos de suínos subdivididos em 3 grupos de 10 joelhos. Os enxertos retirados foram dissecados de tendões extensores das patas dos suínos. Cada grupo teve o enxerto fixado ao fêmur com parafuso de interferência, âncora, ou tenodese no tendão adutor. Os 3 métodos foram submetidos à testes biomecânicos utilizando uma máquina universal de ensaio de tração com uma velocidade de 20 mm/min.

Resultados Verificamos que a média mais elevada da resistência linear sob tração lateral (185,45 ± 41,22 N) ocorreu no grupo 1: “fixação por parafuso,” seguido do grupo 2: “fixação por âncora” (152,97 ± 49,43 N), e a média foi menor no grupo 3: “fixação por tenodese” (76,69 ± 18,90 N). Para a margem de erro fixada (5%), comprovou-se a diferença significativa entre os grupos (p < 0,001) e também através dos testes de comparações múltiplas (entre os pares de grupos) verificou-se a ocorrência de diferenças significativas. A variabilidade expressada por meio do coeficiente de variação mostrou-se reduzida, já que a referida medida foi inferior a 33,3%.

Conclusão O uso de parafusos de interferência no túnel ósseo de joelhos porcinos é suficientemente forte para fixação femoral na reconstrução do ligamento patelofemoral medial, assim como a fixação com âncoras montáveis com fio de alta resistência. Entretanto, a tenodese no tendão adutor mostrou-se frágil para essa finalidade.

The interposition of soft tissue between the cortical button and femoral lateral cortex significantly increases button migration but does not negatively affect knee stability and clinical outcome

BACKGROUND

In clinical practice, soft tissue interposition may occur during femoral graft fixation. Soft tissue interposition between the lateral femoral cortex and the cortical button may affect graft tension and related longitudinal graft motion in the tunnel. We aimed to investigate the effect of soft tissue interposition on button migration and clinical outcomes in anatomical single-bundle anterior cruciate ligament reconstruction.

METHODS

Eighty-four patients aged 18-40 years, who underwent anatomical single-bundle anterior cruciate ligament reconstruction with quadruple hamstring autograft were included. Patients were divided into two groups as Group 1 (n = 32) with soft tissue interposition between the cortical button and cortex, and Group 2 (n = 52) without soft tissue interposition. At the one-year follow-up visit, the anteroposterior knee stability of the patients was evaluated using the Lachman test and KT-2000 arthrometer, and rotational stability was assessed with the pivot shift test. The Lysholm knee score was used to evaluate the functional outcome of the patients. Relationship between tissue interposition and clinical outcome, and button migration was examined.

RESULTS

Button migration was observed in 12 patients in Group 1 (37.5%) and two patients (3.84%) in Group 2 (p < 0.001). However, no significant difference was observed between patients with and without tissue interposition or those with and without button migration regarding knee stability parameters and clinical outcome (p < 0.05).

CONCLUSIONS

Postoperative tissue interposition is found to be associated with cortical button migration during the follow-up. However, it does not affect the clinical outcome.

Stratifying the mechanical performance of a decellularized xenogeneic tendon graft for anterior cruciate ligament reconstruction as a function of graft diameter: An animal study

Objectives

This study investigated the biomechanical performance of decellularized porcine superflexor tendon (pSFT) grafts of varying diameters when utilized in conjunction with contemporary ACL graft fixation systems. This aimed to produce a range of ‘off-the-shelf’ products with predictable mechanical performance, depending on the individual requirements of the patient.

Methods

Decellularized pSFTs were prepared to create double-bundle grafts of 7 mm, 8 mm, and 9 mm diameter. Femoral and tibial fixation systems were simulated utilizing Arthrex suspension devices and interference screws in bovine bone, respectively. Dynamic stiffness and creep were measured, followed by ramp to failure from which linear stiffness and load at failure were measured. The mechanisms of failure were also recorded.

Results

Dynamic stiffness was found to increase with greater graft diameter, with significant differences between all groups. Conversely, dynamic creep reduced with increasing graft diameter with significant differences between the 7 mm and 9 mm groups and the 8 mm and 9 mm groups. Significant differences were also found between the 7 mm, 8 mm, and 9 mm groups for linear stiffness, but no significant differences were found between groups for load at failure. The distribution of failure mechanisms was found to change with graft diameter.

Conclusion

This study showed that decellularized pSFTs demonstrate comparable biomechanical properties to other ACL graft options and are a potentially viable option for ACL reconstruction. Although grafts can be stratified by their diameter to provide varying biomechanical properties, it may be more appropriate to alter the fixation technique to stratify for a greater diversity of biomechanical requirements.

Cite this article: Bone Joint Res 2019;8:518–525.

Cortical Button Versus Cross-pin Femoral Fixation for Hamstring Anterior Cruciate Ligament Reconstruction: A Meta-analysis of Randomized Controlled Trials

BACKGROUND

Incidences of graft rupture are associated with postoperative knee laxity after anterior cruciate ligament (ACL) reconstruction. Reports of postoperative knee laxity after ACL reconstruction using different femoral fixation techniques in several studies are controversial.

PURPOSE

To compare, via meta-analysis of randomized controlled trials (RCTs), the clinical outcomes and postoperative knee laxity of autogenous hamstring ACL reconstruction using cortical button versus cross-pin femoral fixation.

STUDY DESIGN

Meta-analysis.

METHODS

This study followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The online PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases were searched from inception to April 1, 2017. The study included only level 1 or 2 RCTs that compared cortical button and cross-pin femoral fixation for ACL reconstruction with hamstring autografts and that reported clinical outcomes or postoperative knee laxity. The Cochrane Collaboration's risk of bias tool was used to assess the risk of bias for all included studies. For the meta-analysis, the investigators extracted data on clinical outcomes measured by postoperative International Knee Documentation Committee (IKDC) score or Lysholm score and postoperative knee laxity defined as >5 mm side-to-side difference by the arthrometric measurement, Lachman test ≥2+, and pivot-shift test ≥2+. The risk ratio (RR) and its corresponding 95% confidence interval (CI) were computed for dichotomous data. Heterogeneity was assessed by I² tests.

RESULTS

A total of 6 RCTs with 445 patients were included. Statistical analysis of pooled data showed no significant difference between the cortical button and cross-pin groups on postoperative IKDC score (RR, 0.94; 95% CI, 0.88-1.02; P = .13; I² = 4%) and Lysholm score (RR, 0.97; 95% CI, 0.91-1.04; P = .45; I² = 0%). Postoperative knee laxity was reported in 5 studies, and no significant difference was found between the 2 groups (RR, 1.49; 95% CI, 0.83-2.68; P = .18; I² = 37%).

CONCLUSION

Cortical button femoral fixation for autogenous hamstring ACL reconstruction had no significant difference in terms of clinical outcomes and postoperative knee laxity compared with cross-pin femoral fixation.

Are porcine flexor digitorum profundus tendons suitable graft substitutes for human hamstring tendons in biomechanical in vitro-studies?

INTRODUCTION

Although a plenty of studies exist assessing the strength of ligamentous fixation techniques using porcine flexor digitorum profundus tendons as graft substitutes for human hamstring tendons, there is no biomechanical study comparing these two tendons. To interpret the results obtained with porcine flexor digitorum profundus tendons, knowledge of their biomechanical properties is essential. The purpose of this study was to compare the biomechanical properties of human hamstring tendons and porcine flexor digitorum profundus tendons.

MATERIALS AND METHODS

A total of six human hamstring tendons and six porcine flexor digitorum profundus tendons were analysed in this study. Quadruple-bundle human hamstring tendons and double-bundle porcine flexor digitorum profundus tendons with a diameter of 9 mm were used. Specimens were placed into a tensile loading fixation of a servohydraulic testing machine. Biomechanical analysis included pretensioning of the constructs at 50 N for 10 min following cyclic loading of 1500 cycles between 50 and 200 N at 0.5 Hz for measurement of elongation. Subsequently, ultimate failure load and failure mode analysis were performed with a ramp speed of 20 mm/min.

RESULTS

Human hamstring tendons showed significantly higher maximum load to failure values compared to porcine flexor digitorum profundus tendons (1597 ± 179.6 N vs. 1109 ± 101.9 N; p = 0.035). Human hamstring tendons yielded significantly lower initial elongation during preload, but not during cyclical loading.

CONCLUSIONS

When porcine flexor digitorum profundus tendons are used as graft substitutes for human hamstring tendons in biomechanical studies, maximum load to failure is underestimated while elongation is comparable to that of human hamstring tendons. Transferring results of biomechanical studies into clinical practice, the lower maximum load to failure of porcine flexor digitorum profundus tendons needs to be taken into consideration.

Biomechanical and Computed Tomography Analysis of Adjustable Femoral Cortical Fixation Devices for Anterior Cruciate Ligament Reconstruction in a Cadaveric Human Knee Model

PURPOSE

To evaluate and compare two adjustable femoral cortical suspensory fixation devices used for anterior cruciate ligament reconstruction through a novel, direct computed tomography (CT) analysis metric and biomechanical laxity testing in a matched cadaveric human knee study.

METHODS

Anterior cruciate ligament reconstructions with bovine tendon grafts were performed using two adjustable femoral cortical suspensory fixation devices (RigidLoop Adjustable [DePuy Synthes Mitek, Raynham, MA] and TightRope [Arthrex, Naples, FL]) in 12 knees (6 matched pairs). A mechanical testing series was used to determine each knee's laxity in the intact condition. After reconstruction, each specimen was again tested for laxity and also imaged with CT. The laxity testing and CT imaging were then repeated after 1,000 cycles of anteroposterior loading on each knee to compare changes in laxity for the two fixation devices and to visualize changes in button-to-graft distance migration through a three-dimensional CT imaging method.

RESULTS

No significant differences were found between the two fixation groups' laxity measures after reconstruction (all P values ≥ .620) or after cycling (all P values ≥ .211) at any flexion angle. In addition, no significant differences were found between the two groups regarding button-to-graft distance migration (P = .773; mean, 0.61 ± 0.6 mm [95% confidence interval, -0.1 to 1.3 mm] in RigidLoop Adjustable group and 0.53 ± 0.6 mm [95% confidence interval, -0.1 to 1.2 mm] in TightRope group).

CONCLUSIONS

There were no significant differences between the two femoral cortical suspensory adjustable-loop devices regarding laxity outcomes or loop displacement as measured by button-to-graft distance migration.

CLINICAL RELEVANCE

Use of either of the adjustable-loop cortical suspensory devices in our analysis would appear to produce similar, acceptable laxity outcomes and minimal effects in terms of device-related loop displacement.

In vitro comparison between cortical and cortico-cancellous femoral suspension devices for anterior cruciate ligament reconstruction: implications for mobilization

PURPOSE

To analyse the capability of cortical and cortical-cancellous suspension devices to provide a strong fixation in order to follow an aggressive early mobilization protocol.

METHODS

Anterior cruciate ligament (ACL) reconstruction was performed in vitro on 40 porcine femurs employing a high-strength braided cord as a graft. Four femoral suspension devices were analysed: the cortical suspension devices Endobutton and XO Button and the cortical-cancellous suspension devices Biosteon Cross-pin and Cross-pin ACL. Two kinds of biomechanical testing were carried out: static and post-fatigue failure strength tests. Stiffness, failure load, elongation at failure load, elongation after 20 cycles and elongation after 1,000 cycles were assessed. The bones were cut after testing to analyse the failure pattern.

RESULTS

All of the devices exceed 50 % of total elongation in the first 20 cycles of fatigue. In the static failure tests, there were significant differences (p < 0.05) in elongation to failure between the cortical-cancellous suspension devices Biosteon Cross-pin and Cross-pin ACL and the cortical suspension device Endobutton. No significant differences were found in the failure tests after 1,000 cycles of loading. The failure mode of the cortical devices comprised breakage of the cortical bone, accompanied by introduction of the device into the tunnel. The failure mode of the cortical-cancellous devices was pin breakage accompanied by tunnel enlargement.

CONCLUSION

The first cycles of mobilization are critical for elongation. This mobilization process does not significantly diminish the mechanical characteristics of the reconstructions. All the fixations support an intensive early mobilization protocol, with loads of over 500 N.

Comparison of tendon-bone healing between autografts and allografts after anterior cruciate ligament reconstruction using magnetic resonance imaging

PURPOSE

The purpose of the study is to compare tendon-bone healing between autograft tendons and allograft tendons after anterior cruciate ligament (ACL) reconstruction using 3.0T magnetic resonance imaging.

METHODS

A total of 36 participants (18 with autograft and 18 with allograft reconstruction) underwent MRI scans at least 2 years after the ACL reconstruction operation. Oblique axial images were obtained on three-dimensional dual-echo steady-state images and imported into solid modelling software for three-dimensional model reconstruction of the bone tunnel. The graft signal intensity in the tunnel, tendon-bone interface, tunnel morphology, and tunnel area was analysed using the Siemens software packages to determine the tendon-bone healing between the groups.

RESULTS

For the tunnel morphology, both groups exhibited bone tunnel enlargement either at the femoral or tibial tunnel aperture. For the tendon-bone interface, one patient in the autograft group and two patients in the allograft group exhibited a significant fibrous scar tissue bands at the tendon-bone interface. The graft signal/noise quotient values of the allograft group were higher than the autograft group. However, there was no significant difference in the tunnel area between the allograft group and the autograft group.

CONCLUSIONS

Although the autograft tendons exhibited a better remodelling effect than did the allograft tendons in the bone tunnel, there was no significant difference in the tendon-bone healing between the autograft tendons and the allograft tendons postoperatively. These findings indicate that the biomechanical effect of graft motion may play a significant role in the tunnel aperture.

LEVEL OF EVIDENCE

III.

Anterior cruciate ligament reconstruction: a new cortical suspension device for femoral fixation with transtibial and transportal techniques

Background

In the field of anterior cruciate ligament (ACL) reconstruction, there is still no consensus regarding the proper fixation method and position of the tunnels. The primary objective of this paper was to describe a new fixation device, the Endo Tunnel Device (ETD®), for both techniques (transtibial and transportal), as well as the associated difficulties and the intraoperative and postoperative intercurrences. The secondary objective was to describe a preliminary clinical evaluation (6 months of follow-up) comparing these techniques.

Methods

This was a prospective, randomized study involving 80 patients with ACL reconstructions using the ETD® for femoral fixation. Forty patients underwent the transtibial technique, and 40 patients underwent the transportal technique. Patients were evaluated by radiography, physical examination, the KT1000 arthrometer, and Lysholm and the International Knee Documentation Committee (IKDC) scores.

Results

There were more intraoperative intercurrences in the transportal group (soft tissue device fixation, short femoral tunnel, and short graft inside the tunnel). The IKDC scores were significantly better in the transportal group.

Conclusions

The ETD® was demonstrated to be a safe femoral fixation device in this trial; its use in both the transtibial and transportal techniques is technically simple and is associated with few intra- or postoperative complications.

Clinical and functional outcomes after anterior cruciate ligament reconstruction using cortical button fixation versus transfemoral suspensory fixation: a systematic review of randomized controlled trials

PURPOSE

To compare clinical and functional outcomes after anterior cruciate ligament (ACL) reconstruction using cortical button versus transfemoral suspensory fixation.

METHODS

This systematic review was conducted following the Cochrane handbook guidelines and PROSPERO registration. Only Level I and II randomized controlled trials comparing cortical button and transfemoral suspensory fixation in hamstring ACL reconstruction were included. A literature search was performed using electronic databases. The methodologic quality of included studies was assessed using The Cochrane Collaboration's risk-of-bias tool. All outcomes reported by each study were evaluated. Primary outcome measures were postoperative International Knee Documentation Committee (IKDC) and Lysholm knee scores. Statistical analysis was performed using RevMan software (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen). Dichotomous data were reported as risk ratio and 95% confidence intervals. Heterogeneity was assessed using I(2).

RESULTS

Five studies involving 317 patients were included. The mean follow-up period was 21.7 ± 7.0 months (range, 12 to 38 months). The mean age of participants was 26.7 ± 1.89 years (range, 16 to 48 years). The Lysholm score, Tegner activity score, and IKDC score were compiled. Clinical assessment was performed by Lachman testing, assessment of side-to-side differences on KT-1000 (MEDmetric, San Diego, CA) testing, and measurements of thigh atrophy, as well as imaging (radiography and computed tomography) to assess for femoral tunnel widening. Pooled statistical analysis was possible only for postoperative IKDC and Lysholm scores. No significant differences were found between the cortical button and transfemoral fixation groups. Included studies did not report differences in clinical outcomes between the 2 groups. Radiographic results suggest increased femoral tunnel widening in the cortical button group. However, tunnel widening was not found to affect clinical results.

CONCLUSIONS

The present evidence suggests that there are no short- to medium-term differences in knee-specific outcome measures between patients treated with cortical button femoral graft fixation and those treated with suspensory transfemoral fixation when undergoing ACL reconstruction. In addition, radiologic evidence of tunnel widening does not seem to affect short- to medium-term clinical outcomes.

LEVEL OF EVIDENCE

Level II, systematic review of Level I and II studies.

Biomedical coatings on polyethylene terephthalate artificial ligaments

This review comprehensively covers research conducted to enhance polyethylene terephthalate (PET) artificial ligament osseointegration in the bone tunnel. These strategies, using biocompatible or bioactive coatings, had a positive effect in promoting PET ligament osseointegration by increasing bone formation and decreasing fibrous scar tissue at the ligament-to-bone interface. The improved osseointegration can be translated into a significant increase in the biomechanical pull-out loads. However, the load-to-failure of coated ligament is far lower than that of native ACL. Coatings to promote intra-articular ligamentization are also discussed in this study. Collectively, our investigations may arouse further study of the biological coating of PET artificial ligaments in order to effectively enhance ligament osseointegration and promote artificial ligament ligamentization.

Improvement of primary stability in ACL reconstruction by mesh augmentation of an established method of free tendon graft fixation. A biomechanical study on a porcine model

PURPOSE

The aim of the present study was to compare primary stability in ACL reconstruction and ultimate load to failure of a mesh augmented hamstring tendon graft fixed with two cross pins to established hamstrings and bone-patellar-tendon-bone (BTB) graft fixation methods.

METHODS

Forty fresh porcine femora were divided into four groups: (A): BTB graft fixed with two RigidFix® pins, (B): hamstring tendon graft fixed with a Milagro® interference screw, (C): hamstring tendon graft fixed with two RigidFix® pins, and (D): hamstring tendon graft augmented with Ultrapro® mesh fixed with two RigidFix® pins. Each graft underwent cyclic loading in tension and load to failure. Elastic and plastic displacements were measured by 3-dimensional digital image correlation. Groups were compared by one-way ANOVA and Tukey-Kramer post-hoc tests.

RESULTS

After 1000 cycles, the mean plastic displacement was lowest in the BTB graft (p < 0.001). Plastic displacement was significantly lower in the mesh augmented group compared to the plain hamstring graft and the Milagro screw group (p < 0.05). Load to failure was highest in the mesh-augmented group; significant to the hamstring tendon (p = 0.023).

CONCLUSION

Although the BTB-graft represented the most stable construct against plastic displacement in our study, mesh augmentation of free tendon grafts significantly increased primary stability and reduced plastic displacement of femoral cross pin fixation. This new augmentation device may better protect the hamstrings graft from secondary elongation during postoperative rehabilitation.

CLINICAL RELEVANCE

Mesh augmentation seems to be an effective technique to stabilise free hamstring tendon autografts during postoperative rehabilitation with significant reduction of graft slippage.

Design Considerations for a Prosthetic Anterior Cruciate Ligament

Anterior cruciate ligament (ACL) tearing is a common knee injury often requiring reconstruction with an autograft or an allograft. A prosthetic ligament replacement with off-the-shelf availability could potentially provide significant advantages over the current options for both patients and surgeons. Limitations of previous prosthetics include lack of biocompatibility and susceptibility to fatigue, creep, and failure of bony incorporation. This paper describes design considerations and possible improvements for the next generation prosthetic ACL. Design controls, as mandated by the FDA, are a systematic set of practices within the design and development process used to ensure that a new medical device meets the needs of the intended users. The specified requirements, called the design inputs, for a prosthetic ACL are discussed pertaining to material and structural properties, resistance to creep and fatigue, ability to support secure initial fixation, biocompatibility, and long-term osseointegration. Design innovations to satisfy the design inputs are discussed with regards to material selection, textile pattern, bone tunnel features, and short term fixation. A risk analysis is presented along with descriptions of proposed testing. Design control methodology and tissue engineering may be used to develop a next generation prosthetic ligament, solving multiple problems, simultaneously, on a holistic level, providing major improvements over earlier devices and current treatment options.

The fixation strength of a novel ACL soft-tissue graft fixation device compared with conventional interference screws: a biomechanical study in vitro

Anterior cruciate ligament reconstruction using autologous hamstring tendons is an established surgical procedure but some grafts fail due to poor fixation. This study compared the fixation of a new ACL graft fixation device (the EZ KneeSpan) to conventional soft-tissue threaded titanium interference screws (IS). The EZ device was designed to provide secure fixation while avoiding soft-tissue graft damage associated with use of an IS. Eight paired fresh-frozen cadaveric human knees and bovine digital extensor tendons were used. Two tunnels were placed in each tibia and femur, and grafts were fixed using the EZ device and the IS in each bone. Cyclic tensile loading and pull-out testing measured graft slippage (mm) and ultimate strength (N) of the fixation. The results were compared using the non-parametric Wilcoxon signed-rank test. Graft slippage after cyclic loading was significantly lower in the EZ group at 2.4 ± 0.1 mm versus 9.5 ± 6.2 mm for the IS group in the femur and 3.3 ± 1.4 mm versus 17.7 ± 13.6 mm in the tibia. The mean ultimate load for the femoral EZ group was significantly higher than the IS group (769 ± 223 N versus 468 ± 60 N), but they did not differ significantly in the tibia (518 ± 48 N versus 546 ± 139 N). Our results indicate that with the EZ device the initial fixation of cyclically loaded hamstring grafts could be superior to that with an IS. The EZ KneeSpan device also had similar tibial and higher femoral ultimate fixation strength than an IS.

Femoral cross-pin safety in anterior cruciate ligament reconstruction as a function of femoral tunnel position and insertion angle

PURPOSE

To compare femoral cross-pin guidewire insertion at differing angles to identify "safe zones" relative to saphenous nerve, popliteus tendon, fibular collateral ligament, peroneal nerve, and femoral artery/vein locations between transtibial and medial-portal femoral tunnel drilling methods.

METHODS

Five paired cadaveric knees were randomly assigned to a transtibial or medial-portal femoral (anatomic) tunnel drilling group. Guidewires were inserted at differing frontal plane angles (+10°, 0°, -10°, and -20°). Distances between the guidewire and the anatomic structure of interest were measured with an electronic caliper.

RESULTS

Two-way analysis of variance showed that guidewire angle, not tunnel drilling method, created significant differences between guidewire-saphenous nerve (P < .001) and guidewire-femoral artery/vein (P < .001) distances. The +10° angle showed a shorter guidewire-saphenous nerve distance than the 0°, -10°, and -20° angles. The +10° angle also showed a shorter guidewire-femoral artery/vein distance than the -10° and -20° angles, and the 0° insertion angle created a shorter guidewire-femoral artery/vein distance than the -10° and -20° angles. Fisher exact tests showed that guidewires inserted at a +10° angle showed a greater incidence of safe-zone violations for the saphenous nerve (P = .04) and femoral artery/vein (P < .0001).

CONCLUSIONS

Insertion angle, not tunnel drilling method, influenced saphenous nerve and femoral artery/vein injury risk. At the +10° angle, the saphenous nerve and femoral artery/vein are at greater risk for surgically induced injury. Guidewire insertion at -10° or -20° angles should increase concerns about potential popliteus tendon and fibular collateral ligament injury.

CLINICAL RELEVANCE

Insertion angle, not tunnel drilling method, influenced saphenous nerve and femoral artery/vein injury risk.

Mechanical evaluation of cross pins used for femoral fixation of hamstring grafts in ACL reconstructions

The goal of this study was to test the mechanical strength of 4 different cross pins currently available for femoral fixation by loading each cross pin to failure as received and determine the effect of 1 million cycles of fatigue loading. Additionally, the strength of resorbable pins was tested after prolonged exposure to biologic conditions. Six implants each of the Arthrotek LactoSorb (Biomet, Warsaw, Indiana), Mitek RigidFix (DePuy Mitek Inc, Raynham, Massachusetts), Arthrotek Bone Mulch Screw (Biomet), cortical allograft, and control were tested for 3-point failure without prior loading and after cyclic loading between 50 to 200 N at 10 Hz for 1 million cycles. The bioabsorbable pins were placed in sterile water at 37°C and tested after 2, 4, and 6 months for 3-point failure strength. All implants tested without antecedent loading demonstrated adequate strength for initial fixation for hamstring grafts. During fatigue testing, RigidFix implants (n=6) failed at 18,893±8365 cycles (with a central deformation of 0.48±0.11 mm prior to fracture). All of the other implants tested endured 1 million cycles of loading (50-200 N) without fracture or 1.5 mm central deformation. Neither of the bioabsorbable pins demonstrated a significant change in yield strength after prolonged exposure to water. All implants tested demonstrated adequate strength for initial fixation of hamstring grafts. The metal and bone implants far exceed the strength required to sustain mechanical fixation until biological fixation occurs; both polymeric implants demonstrated that they maintained enough mechanical strength to achieve this goal.