Soft-tissue Anterior Cruciate Ligament Reconstruction Research Articles

Effects of Platelet-Rich Osteoconductive-Osteoinductive Allograft Compound on Tunnel Widening of ACL Reconstruction: A Randomized Blind Analysis Study.

The anterior cruciate ligament (ACL) is a commonly injured ligament in the knee. Bone tunnel widening is a known phenomenon after soft-tissue ACL reconstruction and etiology and the clinical relevance has not been fully elucidated. Osteoconductive compounds are biomaterials providing an appropriate scaffold for bone formation such as a demineralized bone matrix. Osteoinductive materials contain growth factors stimulating bone lineage cells and bone growth. A possible application of osteoinductive/osteoconductive (OIC) material is in ACL surgery. We hypothesized that OIC placed in ACL bone tunnels: (1) reduces tunnel widening, (2) improves graft maturation, and (3) reduces tunnel ganglion cyst formation. To test this hypothesis, this study evaluated the osteogenic effects of demineralized bone matrix (DBM) and platelet-rich plasma (PRP) on tunnel widening, graft maturation, and ganglion cyst formation. This was a randomized controlled clinical trial pilot study. A total of 26 patients that elected to have ACL reconstruction surgery were randomized between the OIC and control group. Measurements of tunnel expansion and graft-tunnel incorporation were conducted via the quantitative image analysis of MRI scans performed at six months after surgery for both groups. No patients had adverse post-operative reactions or infections. The use of OIC significantly reduced tunnel widening (p < 0.05) and improved graft maturation (p < 0.05). Patients treated with OIC had a significantly lower prevalence of ganglion cyst compared to the control group (p < 0.05). The use of OIC has measurable effects on the reduction of tunnel widening, improved graft maturation, and decreased size of ganglion cyst after ACL reconstruction. This study explored the utilization of biologics to minimize bone tunnel widening in ACL reconstruction surgery.

Biomechanical Evaluation of Suture Tape Internal Brace Reinforcement of Soft Tissue Allografts for ACL Reconstruction Using a Porcine Model.

Background:Internal bracing of anterior cruciate ligament (ACL) surgery is a newer concept gaining popularity.Purpose/Hypothesis:To assess the biomechanical performance of soft tissue ACL reconstruction allografts reinforced with suture tape. It was hypothesized that load to failure would increase and cyclic displacement would decrease at time zero in the constructs reinforced with internal brace suture tape compared with those without suture tape augmentation.Study Design:Controlled laboratory study.Methods:We performed ACL reconstruction on porcine knees using bovine extensor tendon soft tissue allografts: 10 knees without (control) and 10 knees with (reinforced) suture tape reinforcement. An all-inside reconstruction technique was utilized with retrograde tunnel creation. An adjustable-loop device was used for femoral and tibial fixation of all grafts. The suture tape was placed through the tension loop in the femoral fixation construct and independently fixed in the tibia with an interference screw anchor. For each specimen, the authors recorded ultimate load, yield load, stiffness, cyclic displacement, and mode of failure. Outcomes between groups were compared using the Student t test.Results:There was a 33% decrease in mean cyclic displacement in the specimens with reinforced grafts (reinforced vs control: 3.9 ± 0.7 vs 5.8 ± 1.5 mm; P = .001). The reinforced grafts also had a 22% higher mean ultimate load (921 ± 180 vs 717 ± 122 N; P = .008) and a 25% higher mean yield load (808 ± 201 vs 602 ± 155 N; P = .020). There was no significant difference in stiffness between the reinforced versus nonreinforced grafts (136 ± 16 vs 132 ± 18 N/mm; P = .617). Three of the 10 control specimens failed at the graft, compared with 1 of 10 reinforced grafts. All other constructs in both groups failed at the tibial fixation site.Conclusion:Suture tape reinforcement of soft tissue grafts significantly decreased cyclic displacement while significantly increasing ultimate and yield loads without increasing graft construct stiffness during biomechanical testing at time zero in a porcine animal model.Clinical Relevance:The improved biomechanical performance of suture tape–reinforced graft constructs could allow patients to participate in earlier advancement of aggressive rehabilitation and potentially reduce failure rates as graft remodeling progresses.

A Comparative Biomechanical Study of Femoral Cortical Suspension Devices for Soft-Tissue Anterior Cruciate Ligament Reconstruction: Adjustable-Length Loop Versus Fixed-Length Loop

To determine whether there are differences between adjustable-length loop and fixed-length loop devices in terms of the amount of displacement, temporal pattern of displacement, and ultimate failure load when tested using 4,500 cycles of sinusoidal loading with high loads (100-400N). Two cortical suspension devices with a fixed- or adjustable-length loop were tested. For our comparisons, a 20-mm fixed-length loop device and a fixed-length loop device with the same loop length were used. Comparisons between the devices used both a device-only model (DOM) and a device-bone-soft-tissue graft construct model (CM). In the DOM, the adjustable-length loop device showed weaker mechanical properties. Mean cumulative peak displacement was 1.91mm for the adjustable-length loop device and 0.74mm for the fixed-length loop device (P= .001). The displacement of the adjustable-length loop device increased between 1,000 and 4,500 cycles; in contrast, that of the fixed-length loop device reached a plateau. However, there was never displacement greater than 3mm. In addition, the adjustable-length loop device showed a weaker ultimate failure load (925N vs 1,410N, P= .001). In the CM, the difference in cumulative peak displacement between the 2 groups decreased and did not reach statistical significance. The displacement of both devices showed a similar pattern. In addition, there was no difference in ultimate failure load between the 2 groups. There was no significant difference in terms of total displacement, temporal pattern of displacement, and ultimate failure load between the 2 devices in the CM, which is the more clinically relevant model. Furthermore, even in the DOM, the difference in total displacement was small and did not reach a clinically meaningful level. Therefore, both devices can be used effectively during anterior cruciate ligament reconstruction with soft-tissue graft. Both femoral cortical suspension devices with adjustable- and fixed-length loops can be used with similar mechanical properties during anterior cruciate ligament reconstruction.

Résistance à l’arrachement d’une fixation hybride (Tape Locking Screw™) dans la reconstruction du ligament croisé antérieur. Une étude biomécanique sur os humain et porcin

IntroductionA novel hybrid anterior cruciate ligament (ACL) reconstruction technique known as Tape Locking Screw™ (TLS) is gaining popularity. Utilizing a suspension-type construct in conjunction with an interference screw, this technique has demonstrated successful initial clinical results with the use of quadruple hamstring graft. However, there is currently limited data available on the biomechanical strength of this fixation. This study investigates the pullout strength of the constructing human distal femora as well as in a porcine model. The construct is tested in isolation, without the use of any graft. We hypothesized that the pullout strength of this construct would be similar to or better than current fixation systems available. Materials and methodsThe Tape Locking Screw hybrid fixation system was implanted into 22 fresh frozen human distal femora (50–89 years old) randomized to 10×20mm titanium or polyether ether ketone (PEEK) screws by a single sports fellowship trained orthopedic surgeon. Given that the graft is secured to polyethylene terephthalate tape within the construct, the construct was implanted without any graft in order to isolate the device for biomechanical testing. After implantation, a tensile force was applied directly to the loop of tape at a loading rate of 5mm/min using an electromechanical testing system. The failure load was calculated from the resultant load-displacement curve. Specimens were then visually examined for mode of failure. Similar biomechanical tests were performed on 16 porcine femora. ResultsIn the human model, the mean pullout strength was 523±269N with the PEEK screw and 578±245N with the titanium screw. In the porcine femur model, mean strength was 616±177 N with PEEK, 584±245N with titanium. There was no statistically significant difference in failure loads between these four groups. Tape slippage at the screw bone interface was the primary mode of failure in all the groups tested. DiscussionOur results demonstrate that the hybrid technique provides excellent pullout strength in comparison to other soft-tissue ACL fixation methods, with tape slippage being the mode of failure in all specimens tested. This data, in addition to the advantages of the TLS system, support its consideration in the armamentarium of constructs available for soft-tissue ACL reconstruction. Type of studyLaboratory controlled study level 2.

Pullout strength of a novel hybrid fixation technique (Tape Locking Screw™) in soft-tissue ACL reconstruction: A biomechanical study in human and porcine bone

IntroductionA novel hybrid anterior cruciate ligament (ACL) reconstruction technique known as Tape Locking Screw™ (TLS) is gaining popularity. Utilizing a suspension-type construct in conjunction with an interference screw, this technique has demonstrated successful initial clinical results with the use of quadruple hamstring graft. However, there is currently limited data available on the biomechanical strength of this fixation. This study investigates the pullout strength of the construct in human distal femora as well as in a porcine model. The construct is tested in isolation, without the use of any graft. We hypothesized that the pullout strength of this construct would be similar to or better than current fixation systems available. Materials and methodsThe Tape Locking Screw hybrid fixation system was implanted into twenty-two fresh frozen human distal femora (50–89 years old) randomized to 10×20mm titanium or polyether ether ketone (PEEK) screws by a single sports fellowship trained orthopedic surgeon. Given that the graft is secured to polyethylene terephthalate tape within the construct, the construct was implanted without any graft in order to isolate the device for biomechanical testing. After implantation, a tensile force was applied directly to the loop of tape at a loading rate of 5mm/min using an electromechanical testing system. The failure load was calculated from the resultant load–displacement curve. Specimens were then visually examined for mode of failure. Similar biomechanical tests were performed on sixteen porcine femora. ResultsIn the human model, the mean pullout strength was 523±269N with the PEEK screw and 578±245N with the titanium screw. In the porcine femur model, mean strength was 616±177N with PEEK, 584±245N with titanium. There was no statistically significant difference in failure loads between these four groups. Tape slippage at the screw bone interface was the primary mode of failure in all the groups tested. DiscussionOur results demonstrate that the hybrid technique provides excellent pullout strength in comparison to other soft-tissue ACL fixation methods, with tape slippage being the mode of failure in all specimens tested. This data, in addition to the advantages of the TLS system, support its consideration in the armamentarium of constructs available for soft-tissue ACL reconstruction. Level of evidenceLaboratory controlled study level 2.

Femoral Aperture Fixation Improves Anterior Cruciate Ligament Graft Function When Added to Cortical Suspensory Fixation: An In Vivo Computer Navigation Study.

Background:Recommendations for bone tunnel placement during anterior cruciate ligament (ACL) reconstruction have become more precise. However, these recommendations differ neither with the choice of graft nor with the method of fixation used. The influence of the method of femoral fixation used on the biomechanical function of a soft tissue ACL graft remains unknown.Hypothesis:Our null hypothesis was that adding femoral aperture fixation to femoral cortical fixation, using the same bone tunnels, will not alter the control of anterior translation (AT) and internal rotation (IR) during ACL reconstruction using a hamstring graft.Study Design:Controlled laboratory study.Methods:A total of 22 patients with an acute isolated ACL rupture underwent reconstruction using a single-bundle autologous hamstring graft. Computer navigation was used intraoperatively to plot the AT and IR during the pivot-shift test before reconstruction, after ACL reconstruction using cortical suspensory fixation, and after the addition of femoral aperture fixation. Statistical analysis (analysis of variance) was used to compare the AT and IR during the pivot shift at each stage in the procedure.Results:Before ACL reconstruction, the mean (±SD) AT was 14.2 ± 7.3 mm and mean IR was 17.2° ± 5.5°. After reconstruction using femoral cortical suspension, these figures were significantly reduced to 6.2 ± 3.5 mm and 12.5° ± 3.20°, respectively (P < .001). The addition of the aperture fixation was associated with a further significant reduction to 4.6 ± 3.2 mm and 10.4° ± 2.7°, respectively (P < .001).Conclusion:The addition of femoral aperture fixation to suspensory fixation results in a significant reduction in both the AT and IR that occurs during the pivot-shift assessment immediately after ACL reconstruction using autologous hamstring graft.Clinical Relevance:The most precise positioning of bone tunnels during soft tissue ACL reconstruction needs to take into consideration the type of fixation being used.

Self-flip Technique of the TightRope RT Button for Soft-Tissue Anterior Cruciate Ligament Reconstruction

The TightRope RT (Arthrex, Naples, FL) is a suspensory device for anterior cruciate ligament reconstruction. However, there is a potential risk of the button being pulled too far off the lateral femoral cortex into the soft tissue because the adjustable loop is long. The purpose of this article is to present an easy and safe technique for self-flip. As to the preparation of the graft, we draw the first line in the loop of the TightRope RT at the same length as the femoral tunnel, and we draw the second line 7 mm longer than the length of the femoral tunnel as a self-flip line. Concerning passing of the graft, the side sutures are pulled from the lateral side. We stop pulling the sutures just at the self-flip line by holding the graft at the tibial end. The side suture is inclined to the medial side with strong pulling of the suture at full extension of the knee. Then the surgeon pulls the tibial end of the graft to feel a secure positioning of the button on the lateral femoral cortex. Although it has limitations, the present technique is easy and certainly helps surgeons achieve appropriate positioning of the button.

Lack of consensus regarding pretensioning and preconditioning protocols for soft tissue graft reconstruction of the anterior cruciate ligament.

Pretensioning and preconditioning of soft tissue grafts are often performed to obviate graft stress relaxation and elongation due to viscoelastic graft properties following anterior cruciate ligament (ACL) reconstruction. It was hypothesized that a consensus could be identified in the current literature regarding the biomechanical effects and clinical benefits of an optimal protocol. A systematic electronic literature search was performed by two independent reviewers to identify relevant publications. Only studies describing and/or comparing pretensioning or preconditioning protocols of soft tissue grafts or equivalent animal research models were eligible for inclusion. Study design, graft type, and protocol, including method, magnitude, mode (cyclic and/or static loading), and duration of load application, were compared. Research results and clinical conclusions were also evaluated for each study. Five studies, including four in vitro biomechanical investigations and one histological analysis of patient tissue, met the predefined criteria for inclusion. Studies described numerous pretensioning and/or preconditioning protocols with varying force, time, and application modalities for multiple soft tissue graft types and animal models. The majority of studies (80%) utilized at least one pretensioning or preconditioning protocol between 80 and 89N, while only one study investigated substantially higher loads (500N). Despite common trends demonstrating the effects of pretensioning and preconditioning, no clear consensus regarding an optimal protocol, magnitude, or modality could be identified within the currently available relevant literature. Further multidisciplinary research is required before an optimal or consensus protocol can be established for soft tissue ACL reconstruction. Regardless, the current biomechanical literature demonstrates the potential clinically beneficial effects of pretensioning and preconditioning, including reduced graft elongation and greater preservation of graft tension and stiffness following fixation. Systematic review, Level II.

Transtibial Versus Anteromedial Portal Anterior Cruciate Ligament Reconstruction Using Soft-Tissue Graft and Expandable Fixation

To compare clinical outcomes between transtibial drilling and anteromedial portal techniques for anterior cruciate ligament (ACL) reconstruction using soft-tissue grafts secured with expandable fixation. Patients undergoing soft-tissue ACL reconstruction using expandable fixation between 2007 and 2011 were reviewed for inclusion in this study. Revision ACL cases were excluded. All surgeries were performed by 1 of 2 sports medicine fellowship-trained surgeons (T.S.D., K.D.M.). A total of 128 patients (67 comprising transtibial cohort and 61 comprising anteromedial portal cohort) had a minimum of 24 months' follow-up (mean, 27 months) and met the inclusion criteria. The patients were divided into 2 groups based on the method used for creation of the femoral tunnel. At final follow-up, outcomes were assessed with KT-1000 (MEDmetric, San Diego, CA) measurements, as well as International Knee Documentation Committee, Lysholm, and Tegner scores. Data were screened for normality and skew before use of parametric statistics and were transformed if necessary. Data were analyzed by 1-way analysis of variance with post hoc paired comparisons using the Bonferroni approximation. No differences in demographic characteristics were observed between the 2 groups. There was no significant difference in postoperative KT-1000 measurements between the 2 cohorts (1.571 ± 0.2275 mm in transtibial cohort [n = 35] and 1.246 ± 0.09249 mm in anteromedial cohort [n = 61], P = .1259). A significant improvement in International Knee Documentation Committee scores was observed in the anteromedial cohort, increasing from 41 ± 16 to 89 ± 7.4 (mean ± SD) (P < .0001). Similar changes were observed for the Lysholm score. There was no significant difference between cohorts for any postoperative scores measured (P > .2). Our data show comparable KT-1000 measurements for both anteromedial and transtibial femoral drilling techniques when using a soft-tissue graft with expandable fixation. Level IV, therapeutic case series.

Effect of Interference Screw Fixation on ACL Graft Tensile Strength

Tibial-sided fixation of soft tissue grafts in anterior cruciate ligament (ACL) reconstruction has often been identified as the weak link in the fixation construct, with interference screws being a commonly used technique. A significant concern surrounding the use of interference screws for soft tissue fixation is graft laceration and the possibility of loss of pull-out strength and slippage. The act of interference screw insertion for soft tissue graft fixation in ACL reconstruction alters the biomechanical properties of the graft. Two groups of 12 porcine knees (24 total) were utilized for the tibial-sided fixation of porcine flexor digitorum tendons using single-insertion interference screws, in a model of soft tissue ACL reconstruction. Two different screw types were used for comparison. Following screw insertion, the grafts were dissected free and underwent biomechanical testing in tension to failure. Control flexor digitorum tendons underwent the same biomechanical testing for comparison. Control soft tissue grafts exhibited significantly higher yield load, ultimate load, and stiffness (p < 0.001) in comparison to both groups of treated grafts, without evidence of significant macroscopic damage. Single insertion of interference screws for soft tissue graft fixation in ACL reconstruction weakens the biomechanical properties of the graft itself.

A biomechanical comparison of the Delta screw and RetroScrew tibial fixation on initial intra-articular graft tension

The purpose of this study is to determine the effect of bioabsorbable interference screw (BIS) tibial fixation with the Delta screw (antegrade) and RetroScrew (retrograde) on initial (time zero) intra-articular graft tension in soft tissue anterior cruciate ligament (ACL) reconstruction in a cadaveric model. Ten matched pairs of cadaveric tibias received one of two tibial fixation constructs using quadrupled hamstring grafts, Delta screw (antegrade) or the RetroScrew (retrograde). Each specimen was mounted to the materials testing device with the displacement force vector in line with the tibial tunnel. The construct was pre-tensioned (10-30N, 0.1Hz, 10 cycles), a baseline tension of 25N was introduced, and the change in intra-articular graft tension before and after screw insertion was recorded. Segmental (proximal, middle, distal) BMD was utilized to assess BMD using quantitative computed tomography (qCT). The Delta screw had a higher maximum insertion torque (P=0.03) and exhibited a larger increase in intra-articular graft tension as compared to the RetroScrew (38.3±17.9N, 7.6N±14.4, P=0.004), respectively. There were no significant correlations between intra-articular graft tension increase to maximum insertion torque (P=NS) or corresponding segmental BMD (P=NS). Delta screw tibial fixation (antegrade) in soft tissue ACL reconstruction significantly increases the initial intra-articular graft tension as compared to RetroScrew screw fixation (retrograde) in this cadaveric model. Delta screw (antegrade) tibial fixation may increase initial quadrupled hamstring graft intra-articular tension with currently accepted insertion techniques.

Effect of Tunnel-Graft Length on the Biomechanics of Anterior Cruciate Ligament-Reconstructed Knees

Background In anterior cruciate ligament (ACL) reconstruction using hamstring grafts, the graft can be looped, resulting in an increased graft diameter but reducing graft length within the tunnels. Hypothesis After 6 and 12 weeks, structural properties and knee kinematics after soft tissue ACL reconstruction with 15 mm within the femoral tunnel will be significantly inferior when compared with the properties of ACL reconstruction with 25 mm in the tunnel. Study Design Controlled laboratory study. Methods In an intra-articular goat model, 36 ACL reconstructions using an Achilles tendon split graft were performed with 15-mm (18 knees) and 25-mm (18 knees) graft length in the femoral tunnel. Animals were sacrificed 6 weeks and 12 weeks after surgery and knee kinematics was tested. In situ forces as well as the structural properties were determined and compared with those in an intact control group. Histologic analyses were performed in 2 animals in each group 6 and 12 weeks postoperatively. Statistical analysis was performed using a 2-factor analysis of variance test. Results Anterior cruciate ligament reconstructions with 15 mm resulted in significantly less anterior tibial translation after 6 weeks (P < .05) but not after 12 weeks. Kinematics after 12 weeks and in situ forces of the replacement grafts at both time points showed no statistically significant differences. Stiffness, ultimate failure load, and ultimate stress revealed no statistically significant differences between the 15-mm group and the 25-mm group. Conclusion The results suggest that there is no negative correlation between short graft length (15 mm) in the femoral tunnel and the resulting knee kinematics and structural properties. Clinical Relevance Various clinical scenarios exist in which the length of available graft that could be pulled into the bone tunnel (femoral or tibial) could be in question. To address this concern, this study showed that reducing the tendon graft length in the femoral bone tunnel from 25 mm to 15 mm did not have adverse affects in a goat model.

Controversies in Soft-tissue Anterior Cruciate Ligament Reconstruction: Grafts, Bundles, Tunnels, Fixation, and Harvest

Increased stability has been reported with both autografts and allografts for anterior cruciate ligament (ACL) reconstruction. However, meta-analysis has shown significantly lower overall knee stability rates and more than double the abnormal stability rate with allografts. Some issues surrounding allograft sterilization (ie, risk of disease transmission) are unresolved, and cost is also a concern. Single-bundle ACL reconstruction can produce high stability rates when tunnels are properly placed, but there is evidence that double-bundle repair may offer greater rotatory stability. Cortical fixation has been associated with increased stability owing to the high stiffness of cortical bone. Anterior and posterior approaches are both recommended. The controversy related to single-bundle versus double-bundle ACL reconstruction remains unresolved.

Graft Laceration and Pullout Strength of Soft-Tissue Anterior Cruciate Ligament Reconstruction: In Vitro Study Comparing Titanium, Poly-D,L-Lactide, and Poly-D,L-Lactide–Tricalcium Phosphate Screws

The aim of part 1 of this study was to compare the structural properties of tibia-graft-interference screw constructs of soft-tissue graft fixation via the anterior cruciate ligament (ACL) by use of different interference screws. In part 2 the influence of graft laceration as a result of 1 single interference screw insertion on the mechanical properties of the graft was evaluated. In part 1 of the study, in a bovine knee model, soft-tissue graft fixation with titanium, biodegradable poly-D,L-lactide (PLDLA), and PLDLA-tricalcium phosphate (TCP) interference screws was performed, and the structural properties were determined by use of a materials testing machine at a rate of 12.5 mm/s. In part 2 the bone was cut after 1 single insertion of titanium, PLDLA, or PLDLA-TCP interference screws, and the mechanical properties of the graft were determined. Soft-tissue graft fixation with a biodegradable PLDLA interference screw showed a statistically significantly higher maximum load when compared with PLDLA-TCP and titanium interference screws. PLDLA-TCP screw fixation revealed a significantly higher ultimate load than titanium screw fixation. The mechanical properties of the grafts after 1 single insertion of PLDLA-TCP interference screws showed a statistically significantly higher stiffness, yield load, and maximum load when compared with the PLDLA and titanium interference screw groups. The results of this study suggest that the use of a titanium screw to fix a soft-tissue graft in cruciate ligament reconstruction surgery may cause damage to the graft. Soft-tissue ACL reconstruction fixed with a PLDLA interference screw resulted in a significantly higher pullout strength than ACL reconstructions fixed with a PLDLA-TCP or titanium interference screw. In contrast to fixation with a biodegradable interference screw, fixation with a titanium interference screw may damage the integrity of a soft-tissue graft in cruciate ligament reconstruction and should therefore be avoided.

Central Versus Peripheral Tibial Screw Placement in Hamstring Anterior Cruciate Ligament Reconstruction: In Vitro Biomechanics

To determine whether a cone-shaped interference screw positioned centrally during tibial fixation in hamstring anterior cruciate ligament (ACL) reconstruction was equal to or better than a peripheral position in terms of stiffness, yield load, ultimate load, and mode of failure. Randomized matched-pair biomechanical pullout study. One of each of 7 matched pairs of human cadaveric tendon in porcine tibia with titanium cone-shaped screws were randomly allocated to either the peripheral or central group. Bone tunnels were drilled 45 degrees to the long axis of the tibia, akin to standard ACL reconstruction. Tunnel diameter was matched to tendon diameter and a screw 1 mm larger than tunnel diameter was inserted. A Universal Materials Testing Machine (Hounsfield Testing Equipment, Horsham, PA) was used to pull in the line of the tendon. Tendons were inspected after construct disassembly. The central screw configuration showed significantly higher stiffness (P = .0085), yield load (P = .0135), and ultimate load (P = .0075). The mode of failure in the peripheral screw position was slippage at the screw-tendon interface in all cases. In the central group, 87.5% of cases had a breakage in the tendon and 12.5% had slippage at the tendon-bone interface. Central interference screw fixation of soft-tissue ACL reconstruction offers superior fixation strength and stiffness in single pullout mode when compared with peripheral interference screw fixation. Failure in the central group was mostly by tendon breakage, suggesting that a larger difference may be exhibited by the central over the peripheral fixation than demonstrated in this study. Central interference screw fixation compared with peripheral fixation may allow greater confidence in early rehabilitation and reduced clinical failure rates in the long term.