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The choice of grafts for anterior cruciate ligament (ACL) reconstruction is a critical issue in sports medicine. Previous studies have revealed that scaffolds prepared from a single material could not achieve complete integration between the graft and autogenous bone tunnel. To solve this problem, we hypothesize that combining degradable scaffolds with nondegradable scaffolds can produce a novel hybrid ligament with the advantages of both types of scaffolds. In this study, a bone morphogenetic protein 7 (BMP-7)-loaded polycaprolactone (PCL) nanofibrous membrane was first manufactured as the degradable part of the hybrid ligament by using layer-by-layer (LbL) self-assembly. Then, we fabricated a multifunctional novel hybrid ligament by rolling up this nanofibrous membrane and polyethylene terephthalate (PET) mesh fabric (nondegradable part) into a "swiss roll" structure. The in vitro experimental results showed that this hybrid ligament could significantly improve the biocompatibility of pure PET ligament and further promote cell mineralization. The in vivo experimental results showed that this unique structure significantly promoted the integration of hybrid ligaments and bone tunnels, thereby achieving real "ligamentization" after ACL reconstruction surgery. These results suggest that this novel hybrid biomimetic artificial ligament scaffold provides a new direction for graft selection for ACL reconstruction.

Purpose: To compare the effect of independent suture tape reinforcement on the dynamic elongation and stiffness behavior as well as ultimate strength of tripled smaller-diameter and quadrupled soft-tissue grafts for anterior cruciate ligament reconstruction (ACLR) with tibial screw fixation in a biomechanical in vitro study., Methods: Tripled smaller-diameter (8 mm) and quadrupled (9 mm) bovine tendon grafts with and without suture tape reinforcement (n = 8 in each group) were tested using femoral suspensory and tibial interference screw fixation. The suture tape was femoral sided and fixed independent from the graft by passing it through the suspensory button and securing the 2 open tibial strands with a secondary interference screw. Dynamic testing was performed in position and force control at 250 N and 400 N, followed by pull to failure with the mode of failure noted. Dynamic elongation, stiffness, and ultimate strength were analyzed., Results: Tripled constructs showed a significantly worse structural performance than quadrupled constructs at higher loads. Reinforcement of tripled and quadrupled grafts substantially decreased total elongation by 56% (4.54 ± 0.75 mm vs 2.01 ± 0.50 mm, P < .001) and 39% (3.25 ± 0.49 mm vs 1.98 ± 0.51 mm, P < .001), respectively, by significantly increasing dynamic stiffness. No statistical significance was found between the reinforced groups. Failure loads of reinforced tripled (1,074 ± 148 N vs 829 ± 100 N, P = .003) and quadrupled (1,125 ± 157 N vs 939 ± 76 N, P = .023) grafts were also significantly improved., Conclusions: Independent reinforcement of soft-tissue grafts with suture tape strengthened the performance especially of tripled smaller-diameter grafts for ACLR with tibial screw fixation by significantly improving dynamic elongation at increased stiffness and ultimate strength. Quadrupled reinforced grafts showed no over-constraining and structurally behaved similarly to tripled grafts with reinforcement., Clinical Relevance: Independent reinforcement for ACLR may provide an option for protecting autografts or allografts against irreversible lengthening during the maturation and remodeling phases of healing., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the effects of different stitching methods and suture diameters on the graft fixation of soft tissue human quadriceps tendon grafts for anterior cruciate ligament (ACL) reconstruction., Methods: The Krackow locking stitch (K), whipstitch (W), and baseball stitch (B) were combined with either a 2× no. 2 (#2) or a 1× no. 5 (#5) braided composite suture for graft fixation of 36 human quadriceps tendons in 6 groups. Biomechanical testing was performed using a cyclic protocol with loads between 0 and 100 N. The maximum load until failure, cyclic elongation, and failure mode were recorded., Results: The highest mean maximum load to failure was observed in the 2 Krackow stitch groups. The K#2 group had significantly higher load to failure values compared with those of the W#2 and B#2 groups (K#2, 553 ± 82 N vs W#2, 392 ± 107 N, P = .0349; K#2 vs B#2 366 ± 118 N, P = .0129). The mean cyclic elongation was lowest in the Krackow groups (K#2, 10.59 ± 2.63 mm; K#5, 13.66 ± 2.3 mm). The regular failure mode was the rupture of the suture for the Krackow stitch (8 of 12) and suture pullout for the whipstitch (11 of 12) and baseball stitch groups (12 of 12)., Conclusions: The double Krackow stitch with no. 2 braided composite suture exhibits a high maximum load to failure combined with a low amount of elongation in a biomechanical study for human quadriceps tendon soft tissue graft fixation. Unlike the whipstitch and the baseball stitch, it can solidly prevent suture pullout., Clinical Relevance: A safe soft tissue graft fixation technique is especially important for quadriceps tendon grafts with their laminar anatomical structure and physiologically varying diameter. Unlike other grafts for ACL replacement, it fully relies on the soft tissue suture fixation to resist the pullout force., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To reveal the effects of the positional and length relationships between the interference screws (ISs) and the tendon graft in the bone tunnel on the fixation strength in ligament reconstruction., Methods: We compared three IS positions on the anterior (the Anterior group) or posterior (the Posterior group) or side (the Side group) of the tendon graft in relation to the pullout direction. The tendon graft was pulled at 0°, 30°, 60°, and 90° to the bone tunnel, and the maximum pullout load at each angle was compared among the groups. We also investigated the relationship between the length of the tendon graft and the length of the IS in the bone tunnel. The direction of the pullout force was the same as that of the Anterior group, and the maximum load was compared between groups in which the tendon graft was longer or shorter than the IS., Results: The maximum loads of the Anterior group were significantly greater than those of the Posterior and Side groups at the traction angles of 30° and 60°, respectively. An IS shorter than the tendon graft was found to provide significantly superior fixation strength compared to an IS longer than the tendon graft., Conclusions: Better fixation strength was achieved when the IS was placed on the side of the anchorage tunnel on which the tendon graft was loaded and the IS was shorter than the tendon graft.

The sensorimotor system helps to maintain functional joint stability during movement. After anterior cruciate ligament (ACL) injury and reconstruction, several sensorimotor deficits may arise, including altered proprioception and changes in neuromuscular control. It is still unknown whether the type of autograft used in the reconstruction may influence knee sensorimotor impairments. The aim of this study was to comparatively assess the effects of the hamstring tendon (HT) and bone-patellar tendon-bone (BPTB) ACL reconstruction techniques on knee sensorimotor control 6-12 months post-operation. A total of 83 male subjects participated in this study: 27 healthy participants, 30 BPTB-operated patients and 26 HT-operated patients. Active joint position sense in 3 ranges of motion (90-60°, 60-30°, and 30-0° of knee flexion), isometric steadiness, and onset of muscle activation were used to compare sensorimotor system function between groups. Both operated groups had a small (< 5°) but significant joint position sense error in the 30-0° range when compared to the healthy group. No significant differences were found between the operated and the control groups for isometric steadiness or onset of muscle activation. The results of this study suggest that operated patients present knee proprioceptive deficits independently of surgical technique. Nevertheless, the clinical implications of this impairment are still unknown. It seems that selected surgical approach for ACL reconstruction do not affect functioning of the sensorimotor system to a large degree., Competing Interests: The authors have the following interests. Cristóbal San Martín-Mohr, Iver Cristi-Sánchez and Claudio Oyarzo are employed by Clínica MEDS. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Purpose: To evaluate and compare the effect of preconditioning according to intraoperative workflow on the elongation behavior of single-side and fully knotted all-inside anterior cruciate ligament (ACL) reconstruction configurations in a biomechanical in vitro study., Methods: Four full construct all-inside ACL reconstruction groups (n = 8 per group) were tested using porcine tibias and bovine tendons. Groups included both an all-inside configuration with one- (group 1) and both-side knotted adjustable loop-length devices (group 2), without and with performing intraoperative preconditioning (group 1-intraoperative preconditioned [IPC], group 2-IPC). Adjustable loop-length devices for control groups were knotted according to test configurations. Intraoperative preconditioning specimens were further precycled for 10 times at 0.5 Hz and manually retensioned before knotting. All groups underwent dynamic cycling in position and force control mode each for 1,000 cycles at 0.75 Hz according to in vitro loading parameters replicating the in vivo ACL environment. Finally, a load-to-failure test at 50 mm/min was performed., Results: Intraoperative preconditioning increases initial graft tension for single- (242 ± 22 N vs 174 ± 13 N; P < .0001) and both-side knotted configurations (225 ± 15 N vs 159 ± 10 N; P < .0001) compared with controls and allows maintained graft tension at higher levels until reaching the end of position-controlled cyclic loading. Furthermore, dynamic elongation is reduced for one- (1.93 ± 0.28 vs 0.76 ± 0.12; P < .0001) and both-side knotted (1.84 ± 0.20 vs 0.96 ± 0.32; P < .0001) configurations by 61% and 47%, respectively. No intergroup (group 1 vs group 2 and group 1-IPC vs group 2-IPC) statistically significant differences could be found between one- and both-side knotted configurations., Conclusions: All-inside ACL reconstruction with preconditioning according to intraoperative workflow leads to a statistically significant improved mechanical behavior and may allow for optimizing initial graft tension and elongation for all-inside ACL reconstruction to reduce knee laxity. A single-side knotted configuration achieves similar stabilization strength to fully knotted constructs., Clinical Relevance: Graft insertion until tunnel docking increases the intratunnel graft portion that may optimize graft incorporation. Eliminating a suture knot stack may improve intraoperative workflow and reduce postoperative knot irritation., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: 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 (100-400 N)., Methods: 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)., Results: In the DOM, the adjustable-length loop device showed weaker mechanical properties. Mean cumulative peak displacement was 1.91 mm for the adjustable-length loop device and 0.74 mm 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 3 mm. In addition, the adjustable-length loop device showed a weaker ultimate failure load (925 N vs 1,410 N, 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., Conclusions: 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., Clinical Relevance: Both femoral cortical suspension devices with adjustable- and fixed-length loops can be used with similar mechanical properties during anterior cruciate ligament reconstruction., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To determine when patients recover the ability to safely operate the brakes of an automobile after a right-knee anterior cruciate ligament reconstruction (ACLR)., Methods: A computerized driving simulator was used to determine braking ability after an isolated right-knee ACLR. Thirty healthy volunteers were tested at 1 visit to determine normal mean values, and 27 treatment subjects were tested at 1 week, 3 weeks, and 6 weeks after ACLR. Nine study subjects were treated with a patella tendon (BPTB) autograft, 9 were treated with a hamstring (HS) autograft, and 9 were treated with a tibialis anterior (TA) allograft. The driving simulator collected data on brake reaction time (BRT), brake travel time (BTT), and total brake time (TBT) at each visit., Results: The control group generated a BRT of 725 milliseconds, BTT of 2.87 seconds, and TBT of 3.59 seconds. At week 1, all treatment patients had significant differences compared with controls for BRT, BTT, and TBT, except the BTT of the HS group. At week 3, all measures for the allograft group and the BRT for both autograft groups were no longer significantly different compared with controls, but significant differences were found for TBT in the HS and BPTB groups (P = .03, P = .01). At week 6, BRT, BTT, and TBT were no longer significantly different for either the HS group or BPTB group., Conclusions: Patients who underwent a right-knee ACLR with a TA allograft regained normal braking times by week 3 postoperatively. In contrast, those treated with a BPTB or HS autograft demonstrated significantly delayed braking times at 3 weeks but returned to normal braking ability by week 6. Those treated with an autograft had an earlier return of normalized BRT than BTT., Level of Evidence: Level III, case-control series., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: This mechanical study using an in vitro porcine model compared composite interference screw fixation of soft tissue ACL grafts in tibial tunnels., Methods: Forty-eight porcine profundus tendons and tibiae were divided into four groups of 12 closely matched specimens. Equivalent diameter grafts were assigned to each group. Tibial bone tunnels were drilled to 0.5mm greater than graft diameter. Grafts were fixed in tunnels using one 10 × 35 mm composite interference screw designed by four different manufacturers. Maximal insertion torque and perceived within group mechanical testing outcome predictions were recorded. Constructs were potted and loaded into a six degrees of freedom clamp that placed the servohydraulic device tensile loading vector in direct tunnel alignment. Constructs were pre-loaded to 25 N, pre-conditioned between 0 and 50 N for 10 cycles (0.5 Hz), submaximally tested between 50 and 250 N for 500 cycles (one hertz) and load to failure tested at 20mm/min., Results: Statistically significant differences were not observed between groups for displacement during submaximal cyclic loading, yield load, displacement at yield load, stiffness, ultimate load at failure and displacement at ultimate load. One composite screw group displayed a slightly greater proportion of specimens that required use of more than one screw during insertion., Conclusions: Under highly controlled conditions groups displayed comparable fixation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Introduction: Two types of transplant are commonly used in the surgical management of anterior cruciate ligament lesions: the central part of the patellar ligament and quadruple tendons of the gracilis muscle and semitendinosus muscle., Aims: The aim of this study was to determine the biomechanical characteristics of patellar ligament transplants and transplants of the quadruple tendons of the hamstring muscles under tensile force in the laboratory, and to compare the results in each group of samples., Materials and Methods: The study comprised 160 specimens: 40 specimens of gracilis muscle tendons, 40 of semitendinosus muscle tendons, 40 of quadruple tendons and 40 of the patellar ligament, approximately equally distributed according to sex, age (50-70 years) and the side of the body from which the specimen had been taken., Results: The working curve analysis of the specimens under tensile load of a maximum force of 30N showed the least elongation (0.31%) in the quadruple tendon, followed by the gracilis muscle tendon (1.48%) and patellar ligament tendon (3.91%)., Conclusions: The quadruple tendon specimen showed greater strength and higher elasticity compared with the patellar ligament specimen, which proved the starting hypothesis., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Purpose: The presented biomechanical study focused on the in vitro analysis of tractile forces working on the anterior cruciate ligament (ACL) and the ACL transplants, respectively, using a semitendinosus and/or patellar tendon during a passive flexion-extension movement (150-0°)., Material and Methods: Overall, 15 fresh frozen human knee joint pairs were examined. At first during arthroscopy, the tibial insertion of the ACL was drilled using a special hollow drill. Thereby, a bone cylinder was exposed at which a dynamometer was attached to enable for direct registration of tractile forces on the ACL via the connection between ACL-dynamometer and computer. The ACL transplant was fixed at the femur using a so-called endo-button, whereas the dynamometer was attached to the tibial end of the ACL transplant. The dynamic part of the examination was performed using the knee kinemator device developed by Plitz and Wirth et al. using different preload., Results: The curves of the tractile forces of the ACL were qualitatively homogeneous with only low force values in the middle flexion position, whereas during maximum flexion and extension the forces increased reaching a maximum in the 0° position. Also, in testing the ACL transplants a force decrease between 0 and 50° flexion was recognized with even greater forces resulting at the 150° position depending on the anterior position of the femoral drill channel for implanting the ACL transplant. The amount of pre-loading showed no influence on the form of the tractile force curve. However, by enhancing the preload to 70 N, the maximal force in the ACL transplant increased significantly., Conclusion: The tractile forces assessed within the ACL during passive flexion movements between 10 and 90° were not greater than the forces measured in the ACL transplants. Thus, the clinical consequence is that in the early postoperative phase passive mobilization might be performed in this motion range without putting the ACL transplant at risk for damage.

Quadriceps tendon with a patellar bone block may be a viable alternative to Achilles tendon for anterior cruciate ligament reconstruction (ACL-R) if it is, at a minimum, a biomechanically equivalent graft. The objective of this study was to directly compare the biomechanical properties of quadriceps tendon and Achilles tendon allografts. Quadriceps and Achilles tendon pairs from nine research-consented donors were tested. All specimens were processed to reduce bioburden and terminally sterilized by gamma irradiation. Specimens were subjected to a three phase uniaxial tension test performed in a custom environmental chamber to maintain the specimens at a physiologic temperature (37 ± 2 °C) and misted with a 0.9 % NaCl solution. There were no statistical differences in seven of eight structural and mechanical between the two tendon types. Quadriceps tendons exhibited a significantly higher displacement at maximum load and significantly lower stiffness than Achilles tendons. The results of this study indicated a biomechanical equivalence of aseptically processed, terminally sterilized quadriceps tendon grafts with bone block to Achilles tendon grafts with bone block. The significantly higher displacement at maximum load, and lower stiffness observed for quadriceps tendons may be related to the failure mode. Achilles tendons had a higher bone avulsion rate than quadriceps tendons (86 % compared to 12 %, respectively). This was likely due to observed differences in bone block density between the two tendon types. This research supports the use of quadriceps tendon allografts in lieu of Achilles tendon allografts for ACL-R.

Background: Anterior cruciate ligament (ACL) reconstruction using a single-bundle transtibial technique can achieve good or excellent results in more than 90% of patients, but anatomical and biomechanical studies have questioned its ability to restore knee function. The purpose of this study was to evaluate clinical and tomographic results (patient satisfaction, knee function, and tunnel location) of patients who underwent transportal or transtibial single-bundle ACL reconstruction., Methods: Seventy-one patients with ACL tears were included. Forty-one patients were treated by the single-bundle transportal technique and 30 patients were treated by the single-bundle transtibial technique. Clinical and tomographic data were analyzed in both groups., Results: After a minimum of 2-year period, the transportal group showed more patients with normal clinical tests than the transtibial group (Lachman [p=0.037], pivot shift [0.00], anterior drawer [0.002]; and arthrometer [0.002] tests). Regarding CT evaluation, transportal and transtibial groups obtained the following femoral central tunnel location (mean [SD]), as percentage: 30 (6.5) and 4.2 (6.4) in high-low axis; and 30.9 (5.9) and 33.2 (4.6) in the deep-shallow axis. Values in the tibial side were, respectively: 38 (6.5) and 46.0 (6.8) in the anterior-posterior axis; and 47.2 (2.5) and 46.9 (2.1) in the medial-lateral axis., Conclusion: CT findings showed that the transportal single-bundle technique positions the ACL tunnel closer to the native ACL footprint in both femur and tibia compared with the transtibial single-bundle technique. Moreover, mild asymptomatic instability and extension deficit were observed more often in the transtibial group., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Semitendinosus and gracilis muscles whose tendons are used in surgical reconstruction of the anterior cruciate ligament maintain their contractile ability, and a limited decrease of hamstring muscles force is observed postoperatively despite important changes. The goal was to quantify the influence of the myofascial structures on excursions and moment arms of knee muscles to attempt explaining the above-mentioned post-surgical observations., Methods: Hamstring harvesting procedures were performed by a senior orthopaedic surgeon on seven lower limbs from fresh-frozen specimens. Femoro-tibial kinematics and tendons excursion were simultaneously recorded at each steps of the surgery., Findings: No significant difference was demonstrated for excursions and moment arms after tenotomies and gracilis tendon harvesting (P≥0.05). The first significant semitendinosus excursion (P<1.17×10(-4)) and moment arm (P<6.88×10(-5)) decrease was observed after semitendinosus tendon harvesting (46% of the initial excursion)., Interpretation: Gracilis and semitendinosus myofascial pathway is crucial for force transmission towards the knee joint., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: The purpose of this study was to determine the tibial fixation strength provided by different intraosseous soft tissue graft lengths within the tibial tunnel., Methods: Porcine tibial bones and digital flexor tendons were used for testing. Bone mineral densities of proximal tibial medial condyles were measured, and two-strand tendon bundles of 8 mm diameter were used. An intraosseous graft length of 2 cm was used in group 1 (n = 10), and a graft length of 4 cm was used in group 2 (n = 10). Tunnels were 4 cm in length and 8 mm in diameter. Tibial fixation was performed using a suture tied around a screw post with a washer and an additionally inserted 7 × 20 mm bioabsorbable screw. After applying preconditioning loading of 10 cycles, 1,000 cycles between 70-220 N were applied at a frequency of 1 Hz. Graft slippage and total graft movement were recorded. Ultimate tensile strength was measured by pull-out testing at an Instron crosshead speed of 1,000 mm/min., Results: No significant intergroup difference was found for total graft movement after cyclic loading (slippage in group 1, 1.2 mm and group 2, 1.2 mm, respectively, p = 0.917; and total graft movement in group 1, 3.3 mm and group 2, 2.7 mm, respectively, p = 0.199). However, mean ultimate tensile strength in group 2 was significantly higher than that in group 1 (group 1, 649.9 N; group 2, 938 N; p = 0.008)., Conclusions: In a porcine model, ultimate tensile strength was greater for a 4 cm long intraosseous flexor tendon in the tibial tunnel. However, no intergroup difference in graft slippage or total graft movement was observed. The results show that a 2 cm intraosseous graft length in the tibial tunnel is safe and has sufficient strength (> 450 N) for adequate rehabilitation after anterior cruciate ligament reconstruction.

As a new strategy for enhancing recovery after anterior cruciate ligament (ACL) reconstruction, we developed a cell sheet wrapped graft using ACL-derived CD34+ cells. Our results from an ex vivo cell migration assay demonstrated gradual cell migration into the graft from the cell sheet, and an enzyme-linked immunosorbent assay indicated that the cell sheet cultures secreted a significantly greater amount of VEGF than typical monolayer cultures. In the in vivo study, the rats received one of three possible ACL reconstruction treatments; 1) a tendon graft wrapped in an ACL-derived CD34+ cell sheet, 2) a tendon graft and ACL-derived CD34+ cell injection, or 3) the control group that received just the tendon graft. The in vivo studies revealed that the ACL-derived CD34+ cell sheet wrapped grafts demonstrated a greater number of the cells derived from the cell sheets incorporated within the bone tunnel site and grafted tendon. We believe the incorporated CD34+ cells enhanced the healing of both the bone-tendon junction and the grafted tendon in the reconstructed rat ACLs by increasing proprioceptive recovery, graft maturation, and biomechanical strength. ACL-derived CD34+ cell sheet wrapped grafts could become a promising strategy to revitalize tendon autografts and recovery after ACL reconstruction resulting in superior and quicker recovery in patients requiring ACL reconstruction., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The anterior cruciate ligament (ACL) is a major ligament that helps maintain the stability of the knee joint. Injury to the ACL can be treated by replacing the torn ligament. This study determined the optimal flexor tendon length in the bone tunnel in ACL reconstruction.Autologous ACL reconstruction was performed using a flexor tendon in 54 male beagles, with the graft length in the bone tunnel at 5, 9, 13, 17, 21, and 25 mm (9 dogs per graft length). The maximum tensile strength and stiffness of the reconstructed joint (tibia-ACL-femur triad) were recorded at 45, 90, and 180 days after ACL reconstruction (6 joints per time point). The experiment also included an intact control group (3 dogs) and a control group tested immediately after the reconstruction (3 dogs). For the intact control group, the normal ACL (unreconstructed) and flexor tendon mechanical testing was performed. For the other control group, the normal ACL (unreconstructed) mechanical testing was performed first and then mechanical testing of the specimens was performed immediately after reconstruction. The maximum tensile strength and stiffness of the reconstructed tibia-ACL-femur triad increased with time after reconstruction, regardless of the graft length in the bone tunnel. Maximum tensile strength and stiffness of the grafts increased with graft length but reached a plateau at 17 mm. Optimal strength and stiffness of the reconstructed ACL are achieved with 17-mm grafts., (Copyright 2013, SLACK Incorporated.)

Anterior cruciate ligament (ACL) rupture is a common knee injury and an understanding of current medical knowledge regarding its management is essential. Accurate and prompt diagnosis requires an awareness of injury mechanisms and risk factors, common symptoms and physical/radiologic findings. Early mobilization and physical therapy improves outcomes regardless of treatment modality. Many older patients regain sufficient stability and function after non-operative rehabilitation. Early ACL reconstruction is appropriate for younger patients and those who engage in activities requiring frequent pivoting and rapid direction changes. ACL surgery involves reconstruction of the torn ligament tissue with various replacement graft options, each with advantages and disadvantages. The guidance of a knowledgeable and experienced therapist is required throughout an intensive and prolonged rehabilitation course. Generally excellent outcomes and low complication rates are expected, but treatment does not prevent late osteoarthritis.

Background: As a result of recent studies describing the double-bundle anterior cruciate ligament (ACL), selected ACL augmentation procedures, either anteromedial (AM) or posterolateral (PL), have been introduced as the treatment of choice for partial ACL ruptures. The preserved mechanoreceptor and vascularity of the remnant ACL are considered to provide additional biological benefits. Although enhanced knee joint proprioception in ACL augmented patients has been previously reported, there is no study assessing biological healing advantages of the graft after the ACL augmentation procedure., Hypothesis: Selected ACL augmentation for partial tears can accelerate the healing process of the grafted tendon, which promotes better biomechanical recovery of the tendon, compared with conventional ACL reconstruction of complete tears., Study Design: Controlled laboratory study., Methods: Two rat models were established in this study: an ACL augmentation partial tear model and conventional ACL reconstruction for a complete tear. Biological assessments of cellularity and angiogenesis were measured by hematoxylin and eosin staining and immunostaining, respectively. Additionally, rat-specific type III collagen and α-smooth muscle actin were evaluated by immunohistochemical staining to analyze the healing process, whereas anti-rat neurofilament antigen was assessed to examine proprioceptive recovery. Biological assessments of the augmented and reconstructed grafts were conducted postoperatively at week 2, whereas biomechanical testing was performed postoperatively at week 8., Results: An increase in cellularity and angiogenesis was observed in the augmented grafts compared with the conventionally reconstructed grafts. Also, increased amounts of rat-specific type III collagen, α-smooth muscle actin, and anti-rat neurofilament antigen were expressed in the augmented grafts. Biomechanical testing showed that failure to load was significantly higher in the augmentation group compared with the conventional reconstruction group (augmentation, 15.9 ± 1.0; reconstruction, 7.0 ± 1.3; P < .01)., Clinical Relevance: Selected ACL augmentation could be a good choice for the repair of partial ACL injury by preserving the uninjured portion of the ACL, which in turn could maintain the anatomic position of the ligament and its biomechanical function.

Peri-tunnel bone loss after anterior cruciate ligament (ACL) reconstruction is commonly observed, both clinically and experimentally. We aimed to study the effect and mechanisms of different doses of alendronate in the reduction of peri-tunnel bone loss and promotion of graft-bone tunnel healing in ACL reconstruction. Eighty-four ACL-reconstructed rats were divided into 4 groups. Alendronate at different dosages, or saline, were injected subcutaneously weekly, for 2 or 6 weeks post-reconstruction, for vivaCT (computed tomography) imaging, biomechanical tests, histology and immunohistochemistry. Alendronate significantly increased bone mass and density of tissue inside bone tunnels except at the epiphyseal region of tibial tunnel. The femoral tunnel diameter decreased significantly in the mid-dose and high-dose alendronate groups compared to that in the saline group at week 6. Alendronate significantly increased the peri-tunnel bone mass and density along all tunnel regions at week 6. Better graft-bone tunnel integration and intra-tunnel graft integrity were observed in the alendronate groups. The ultimate load was significantly higher in the mid-dose and high-dose alendronate groups at week 2, but not at week 6. There was a reduction in matrix metalloprotein (MMP)1, MMP13 and CD68-positive cells at the peri-tunnel region and graft-bone interface in the alendronate-treated group compared to the saline group. Alendronate reduced peri-tunnel bone resorption, increased mineralised tissue inside bone tunnel as well as histologically and biomechanically promoted graft-bone tunnel healing, probably by reducing the expression of MMP1, MMP13 and CD68-positive cells. Alendronate might be used for reducing peri-tunnel bone loss and promoting graft-bone tunnel healing at early stage post-ACL reconstruction.

Background: Allografts offer potential advantages over autografts in anterior cruciate ligament reconstruction (ACLR), including the absence of donor site morbidity, shorter operative times, improved cosmesis, and easier rehabilitation. There is limited and conflicting outcome data for ACLR with tibialis anterior allograft. The purpose of this study was to evaluate the functional outcomes of ACLR with tibialis anterior allograft., Methods: We retrospectively evaluated primary ACL reconstructions using tibialis anterior allograft between January 2004 and December 2006. Clinical outcomes were measured by KT-1000 arthrometry, and International Knee Documentation Committee (IKDC), Lysholm, and Tegner scores., Results: 19 patients were available for follow-up at a mean of 2.7 years (range: 2.0 to 3.2). One patient experienced a traumatic re-rupture that required revision and another patient was advised to undergo revision reconstruction for a failed graft. Based on IKDC and Lysholm scoring, 12 patients (63%) had good or excellent results, 4 (21%) patients had fair results, and 3 (16%) patients had poor results. The mean side-to-side difference was 2.7 mm (0 to 8.2) and the mean decrease in Tegner activity level was 1.4 (0 to 6)., Conclusion: An alarming number of patients demonstrated residual laxity after ACL reconstruction with tibialis anterior allograft. We recommend against using tibialis anterior allograft as a first choice graft for high demand patients.

Introduction: Interference screws used in fixation of anterior cruciate ligament (ACL) hamstring grafts create mechanical hold by forcing the graft into frictional contact with the bone tunnel. We analyzed the resultant graft-tunnel contact pressure using an in vitro model of human cadaver 8mm hamstring grafts., Methods: Contact characteristics were assessed using both pressure sensitive films and a force sensor. Two screw sizes were investigated (8 and 9 mm in an 8mm Sawbone tunnel), both with and without a bone wedge between graft and screw. Separately, time dependent relaxation of contact force was recorded over a one hour epoch and associated tendon water loss was measured. Pullout testing of 8mm tendon grafts from 8mm holes in Sawbone and porcine femora were performed after 1 min and 1h., Results: During screw insertion, measured peak pressures (>40 MPa) exceeded the compressive failure stress of metaphyseal bone by more than an order of magnitude. Using a bone wedge between tendon and screw reduced local peak pressure by 85% but produced also inferior average contact pressure. In all approaches, initially achieved graft contact pressure rapidly decreased to approximately 25% within 30 min. Pullout strength was significantly reduced after 1h in comparison to 1 min in porcine bone as well as Sawbone., Conclusion: Viscoelastic adaptation of the tendon is severe and critically reduces effective graft-bone contact pressure. Consideration of this newly recognized effect may open new and improved approaches for tendon graft fixation., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: Press-fit fixation of hamstring tendon autografts for anterior cruciate ligament reconstruction is an interesting technique because no hardware is necessary. This study compares the biomechanical properties of press-fit fixations to an interference screw fixation., Methods: Twenty-eight human cadaveric knees were used for hamstring tendon explantation. An additional bone block was harvested from the tibia. We used 28 porcine femora for graft fixation. Constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclic loading were investigated., Results: The maximum load to failure was 970±83 N for the press-fit tape fixation (T), 572±151 N for the bone bridge fixation (TS), 544±109 N for the interference screw fixation (I), 402±77 N for the press-fit suture fixation (S) and 290±74 N for the bone block fixation technique (F). The T fixation had a significantly better maximum load to failure compared to all other techniques (p<0.001)., Conclusion: This study demonstrates that a tibial press-fit technique which uses an additional bone block has better maximum load to failure results compared to a simple interference screw fixation.

Background: This article describes an arthroscopic anterior cruciate ligament (ACL) reconstruction technique with a quadriceps tendon autograft using an anteromedial portal technique., Methods: A 5 cm quadriceps tendon graft is harvested with an adjacent 2 cm bone block. The femoral tunnel is created through a low anteromedial portal in its anatomical position. The tibial tunnel is created with a hollow burr, thus acquiring a free cylindrical bone block. The graft is then passed through the tibial tunnel and the bone block, customized at its tip, is tapped into the femoral tunnel through the anteromedial portal to provide press-fit fixation. The graft is tensioned distally and sutures are tied over a bone bridge at the distal end of the tibial tunnel. From the cylindrical bone block harvested from the tibia the proximal end is customized and gently tapped next to the graft tissue into the tibial tunnel to assure press fitting of the graft in the tibial tunnel. The distal part of the tibial tunnel is filled up with the remaining bone.All patients were observed in a prospective fashion with subjective and objective evaluation after 6 weeks, 6 and 12 months., Results: Thirty patients have been evaluated at a 12 months follow-up. The technique achieved in 96.7% normal or nearly normal results for the objective IKDC. The mean subjective IKDC score was 86.1 ± 15.8. In 96.7% the Tegner score was the same as before injury or decreased one category. A negative or 1+ Lachman test was achieved in all cases. Pivot-shift test was negative or (+) glide in 86.7%. The mean side-to-side difference elevated by instrumental laxity measurement was 1.6 ± 1.1 mm. Full ROM has been achieved in 92.3%. The mean single one-leg-hop index was 91.9 ± 8.0 at the follow-up., Conclusions: Potential advantages include minimum bone loss specifically on the femoral side and graft fixation without implants.

The aim of this study is to evaluate the midterm results of using Ligament Advanced Reinforcement System (LARS) artificial ligament for augmentation of the short (<15 cm length) and small-sized (3-4 mm) diameter for the gracilis and (4-5 mm) for the semitendinosus harvested hamstring tendons in anterior cruciate ligament (ACL) reconstruction, and to assess the knee stability, patient satisfaction and early- and midterm complications following surgery. A total of 112 patients were included in this study and were operated with arthroscopic ACL reconstruction using (augmented hamstring tendon graft with LARS) between January 2004 and December 2006. Assessment before and after the surgery include the history, clinical examination, modified international knee documentation committee score (IKDC), KT1000 measurements for clinical knee stability and osteoarthritis outcome score (KOOS) for patient satisfaction. Clinical results measured by IKDC evaluation, KT1000 and Lysholm scores showed significant postoperative values compared with the preoperative ones. Our findings suggest that at the end of a 5-year follow-up, augmented hamstring tendon graft with LARS artificial ligament is a useful, safe and satisfactory treatment option for ACL reconstruction in deficient knees with short- and small-sized harvested hamstring tendons, especially when an early return to high levels of sport activity is needed., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Purpose: Previous studies have reported that Anterior Cruciate Ligament (ACL) reconstruction does not restore normal tibial rotation in patients with chronic instability and repeated episodes of giving way. We hypothesised that early ACL reconstruction, using quadruple hamstring autografts, before the pivoting episodes had occurred, would protect the knee joint from developing abnormal kinematics with increased external tibial rotation during flexion., Methods: Fourteen consecutive patients (8 men, 6 women) with a median age of 24 years (18-43), with a complete, isolated unilateral ACL rupture and an intact contralateral knee, were studied. The operations were performed by one experienced surgeon, using quadruple hamstring autografts. We used dynamic radiostereometry (RSA) with tantalum markers inserted in both the injured and the intact contralateral knee to study the pattern of knee motion during active and weight-bearing knee extension. The patients were evaluated pre-operatively and followed for 2 years after the ACL reconstruction. The anterior-posterior laxity was measured using the KT-1000., Results: Before surgical repair of the ACL, the internal/external tibial rotation or abduction/adduction did not differ significantly between the injured and intact knees (P = 0.27-0.91). Separate studies of the anterior-posterior translation of the medial and lateral femoral flexion facet centres (MFC and LFC) relative to a fixed tibia did not reveal any significant differences between the injured and intact knees (P = 0.21-0.59). Pre-operatively, the KT-1000 laxity measurements showed a side-to-side difference of 2.5 (1.0-5.5) mm. At 2 years, the laxity side-to-side difference was 0.5 (0-3.0) mm (P = 0.001), and there were still no significant differences between the injured and intact knees in terms of internal/external tibial rotation and abduction/adduction (P = 0.13-0.60). Nor did the anterior-posterior translation of the flexion facet centres differs (P = 0.27-0.97)., Conclusion: During the first 6-8 weeks after the ACL injury, before pivoting episodes had occurred, the kinematics of the injured knee were normal and did not differ from those of the intact contralateral knee. Reconstruction of the ACL within 10 weeks after injury using quadruple hamstring autografts resulted in unchanged knee kinematics for 2 years and no difference compared with the intact contralateral knee. Surgical repair during the early phase after the injury appears to protect the knee from developing abnormal knee motion after an ACL rupture., Level of Evidence: III.

The objective of this study was to evaluate the effectiveness of hamstring (HT) autografts versus bone-patellar tendon-bone (BPTB) autografts for reconstruction of the anterior cruciate ligament (ACL). We searched the Cochrane Library, MEDLINE, EMBASE and the Chinese Biomedicine Database (CBM) for published randomised clinical trials (RCTs) relevant to ACL reconstruction comparing HT and BPTB autografts. Data analyses were performed with Cochrane Collaboration's RevMan 5.0. A total of 23 reports of 19 randomised controlled trials (RCTs) (1643 patients) met the inclusion criteria. Outcomes favouring BPTB autografts were found in terms of KT-1000 arithmometer values, negative rates of Lachman tests and negative rates of Pivot tests. Outcome measures that favoured HT autografts included anterior knee pain, kneeling pain and extension loss. There was no statistical difference of postoperative graft failure. Overall, postoperative complications of the knee joint were lower for HT autografts than for BPTB autografts, and BPTB autografts were superior to HT autografts in resuming stability of the knee joint, but four-strand HT combined with application of the modern endobutton HT graft-fixation technique could increase knee-joint stability., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Purpose: To compare the clinical outcomes of arthroscopic anterior cruciate ligament (ACL) reconstruction with hamstring tendon autograft versus irradiated allograft., Methods: All irradiated hamstring tendon allografts (gracilis and semitendinosus), which were sterilized with 2.5 Mrad of irradiation before distribution, were obtained from a single certified tissue bank. A total of 78 patients undergoing arthroscopic ACL reconstruction were prospectively randomized consecutively into 1 of 2 groups: autograft and irradiated allograft. The same surgical technique was used in all operations, which were performed by the same senior surgeon. Before surgery and at a mean of 42.2 months of follow-up, patients were evaluated by the same observer according to objective and subjective clinical evaluations., Results: Of the patients, 67 (36 in autograft group and 31 in irradiated allograft group) were available for full evaluation. When the irradiated allograft group was compared with the autograft group at the final follow-up by the Lachman test, anterior drawer test, pivot-shift test, and KT-2000 arthrometer (MEDmetric, San Diego, CA) assessment, statistically significant differences were found (P = .00011, P = .00016, P = .008, and P = .00021, respectively). Most importantly, 86.1% of patients in the autograft group and only 32.3% in the irradiated allograft group had a side-to-side difference of less than 3 mm according to KT-2000 assessment. The rate of laxity (side-to-side difference >5 mm) with irradiated allograft (32.3%) was higher than that with autograft (8.3%). The anterior and rotational stabilities decreased significantly in the irradiated allograft group. According to the overall International Knee Documentation Committee rating, functional and subjective evaluations, and activity level testing, no statistically significant differences were found between the 2 groups. However, patients in the irradiated allograft group had a shorter operative time and a longer duration of postoperative fever. When the patients had a fever, the laboratory examination findings of all patients were almost normal (white blood cell count, normal; erythrocyte sedimentation rate, 8 to 20 mm/h; and C-reactive protein level, 4 to 11 mg/L)., Conclusions: The clinical outcome of ACL reconstruction with hamstring tendon autograft was satisfactory, whereas the difference in instrumented laxity between the 2 groups was significant and the difference in functional test results was not significant., Level of Evidence: Level II, prospective comparative study., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the effect of graft length within the bone tunnel on tendon-bone healing at an early stage after anterior cruciate ligament (ACL) reconstruction using Achilles tendon autograft in a canine model., Methods: We divided 40 adult dogs into 4 groups (n = 10 per group). Each dog underwent ACL reconstruction with Achilles tendon autograft in both knees. In groups I, II, III, and IV, the graft length within the tibia tunnel was 5 mm, 10 mm, 15 mm, and 20 mm, respectively. Five dogs in each group were killed 6 and 12 weeks postoperatively, with 3 knees used for histologic observation and 7 knees for mechanical testing., Results: Six weeks after surgery, the histologic scores in group I were lower than those in the other groups (P < .01) and those in group II were lower than those in group III and group IV (P < .01). However, there was no difference between group III and group IV (P > .05). At 12 weeks, there were no significant differences in histologic scores between groups (P > .05). The biomechanical test at 6 weeks showed that the mean graft pullout strength improved from group I to group IV. Except between groups III and IV (P = .142), there was a significant difference in the pullout strength among other groups. At week 12, the failure points were in the midsubstance of most specimens and more tibial-side graft pullout was found in group I than in the other groups (P < .001)., Conclusions: The histologic maturity and biomechanical strength of the tendon-bone junction after ACL reconstruction in dogs will be delayed at an early stage if the graft length in the bone tunnel is less than 15 mm., Clinical Relevance: There is a minimal acceptable amount of intratunnel tendon graft to allow satisfactory early tendon-bone healing, and attempts to save tendon graft length that lower the amount of intratunnel graft below a minimum of 15 mm should be avoided., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: Deep fresh freezing is the most commonly used preservation method for allografts, which is followed by a routine procedure before application-the thawing of the grafts. This work was to explore the biomechanics effects of repetitive freezing-thawing on human tendons., Methods: Thirty tendons (flexor digitorum superficialis and flexor pollicis longus tendons) were taken from three fresh cadavers. We assigned these tendons into six groups randomly. After the preparation and measurement of cross-sectional area, Fresh Group was tested immediately. The remaining five groups, before biomechanical testing, underwent multiple cycles (1, 2, 3, 5 or 10 cycles) of freezing (-80°C for 4 days) and thawing (room temperature for 6h). Using a material-testing machine, we performed a stress-relaxation test, a creep test and a load to failure test to estimate structural and mechanical properties as well as viscoelastic changes of each group., Findings: The results of fewer cycles (<3) of freezing-thawing groups were similar to Fresh Group. The tendons that underwent more than five freezing-thawing cycles demonstrated a significantly smaller ultimate load, stiffness, ultimate stress and Young's modulus. Moreover, the 5 and 10 Cycle Groups showed a significant increase of elongation in creep test and a decrease of load in stress-relaxation test compared with other groups., Interpretation: Repetitive freezing-thawing (>5 cycles) declines the structural, mechanical and viscoelastic properties of human tendons. From our results, it is recommended that for deep-frozen preservation of tendon allografts the cycles of freezing-thawing should be less than five times with caution., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

We conducted a prospective randomised study of anatomical single-bundle (A-SB group) versus double-bundle (A-DB group) anterior cruciate ligament (ACL) reconstruction using the hamstrings tendons. Twenty patients with unilateral ACL deficiency were randomised into two groups. We created the bone tunnels at the position of the original insertion of the anteromedial bundle footprint and posterolateral bundle footprint in the A-DB group and at the central position between these two bundles in the A-SB group. All of the patients were tested before ACL reconstruction and one year after surgery. The KT-1000 measurements, isokinetic muscle peak torque and heel-height difference were evaluated and the general knee condition was assessed by Lysholm score. For pre- and postoperative stability assessment, we used the six-degrees-of-freedom of knee kinematic measurement system using an electromagnetic device (the EMS) for quantitative assessment during the Lachman test and the pivot shift test. There were no significant differences in the KT-1000 measurements, isokinetic muscle peak torque, heel-height difference, and Lysholm score at one-year follow-up between these two groups. The EMS data showed there were significant differences in the acceleration of the pivot shift test between the operated knee and the contralateral normal knees in the A-SB group. In conclusion, clinical outcomes were equally good in both groups. However, the EMS data showed the anatomical double-bundle ACL reconstruction tended to be biomechanically superior to the single-bundle reconstruction.

Background: Successful anterior cruciate ligament reconstruction with use of soft-tissue grafts requires healing between tendon and bone. Little is known about the effect of mechanical load on the cellular and molecular cascade of tendon-to-bone healing. Understanding these mechanical influences has critical implications for postoperative rehabilitation following anterior cruciate ligament reconstruction. The purpose of this study was to test the hypothesis that, compared with perioperative immobilization, short-duration low-magnitude cyclic axial loading would result in impaired tendon-to-bone healing after anterior cruciate ligament reconstruction in a rat model., Methods: Fifty-two male Sprague-Dawley rats underwent anterior cruciate ligament reconstruction with use of a flexor digitorum longus autograft. The patellar tendon, capsule, and ligamentous structures were circumferentially released, and an external fixator parallel to the anterior cruciate ligament graft was placed across the knee. Mechanical loading, consisting of cyclic displacement of the femur and tibia constrained to axial translation parallel to the graft, was applied daily. The rats were randomly assigned to immobilization or daily loading, for fourteen or twenty-eight days. Biomechanical, micro-computed tomographic, and histomorphometric analysis was performed on the bone-tendon-bone complexes., Results: The load measured across the knees during cyclic displacement increased over time (p < 0.05). Load-to-failure testing of the isolated femur-anterior cruciate ligament graft-tibia specimens revealed no significant differences between groups at two or four weeks. By two weeks postoperatively, a greater number of ED1+ inflammatory macrophages (phagocytic cells involved in the initial injury response) were seen at the tendon-bone interface after loading in the cyclically loaded group than in the immobilized group (p = 0.01). Compared with the baseline values, the number of trabeculae was significantly lower after loading for four weeks (p = 0.02)., Conclusions: Short-duration low-magnitude cyclic axial loading of the anterior cruciate ligament graft in the postoperative period is not detrimental to the strength of the healing tendon-bone interface but appears to be associated with greater inflammation and less bone formation in the tunnel in this rat model.

Press-fit fixation of anterior cruciate ligament autografts is an interesting technique because no hardware is necessary. A total of 168 cadaveric human patellar, quadriceps and hamstring tendons (average age 49.2 +/- 18.5 years) were used and 15 different fixation methods were tested. Constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclical loading were compared. Some techniques showed comparable biomechanical qualities to interference screw fixation. All investigated double bundle fixation techniques were equal in terms of maximum load to failure, stiffness and elongation. All techniques exhibited greater elongation during initial cyclical loading. Some of the press-fit fixation techniques investigated exhibited comparable biomechanical properties and preconditioning of the constructs is critical. Press-fit fixation enhances tendon to bone contact at the entry of the bone tunnel to the joint.

This retrospective study compared the results after anterior cruciate ligament (ACL) reconstruction using a four-strand hamstring tendon graft (4SHG) versus Ligament Advanced Reinforcement System (LARS) artificial ligament in 60 patients between January 2003 and July 2004 with a minimum four-year follow-up. The KT-1000 examination, the International Knee Documentation Committee (IKDC) scoring systems and Lysholm knee scoring scale were used to evaluate the clinical results. The mean side-to-side difference was 2.4 +/- 0.5 mm and 1.2 +/- 0.3 mm in the 4SHG group and LARS group, respectively (P = 0.013). Although other results of ACL reconstruction, measured by IKDC evaluation, Lysholm scores and Tegner scores, showed using a LARS graft clinically tended to be superior to using a 4SHG, there were no significant differences calculated. Our results suggest that four years after ACL reconstruction using a LARS ligament or 4SHG dramatically improves the function outcome, while the patients in the LARS group displayed a higher knee stability than those in the 4SHG group.

Anterior cruciate ligament (ACL) reconstruction is one of the most important aspects of knee surgery. For this purpose, several fixation devices have been developed, although the interference screw is the most frequently used. The most typical biomechanical test of these devices consists of placing them in a testing machine and subjecting them to a pull-out test. However, insufficient attention has been paid to the influence of the displacement test rate on the mechanical properties of the fixation system. The aim of this study is to compare the influence of the crosshead rate in the biomechanical test of two different devices for the fixation of ACL tendon grafts. One hundred in vitro tests were performed using porcine tibiae and bovine tendons. The fixation devices used were (1) an interference screw and (2) a new expansion device. All ACL reconstructions were subjected to pull-out test to failure. Five crosshead rates were employed in a range from 30 mm/min to 4000 mm/min. Statistical analyses of the results show that, for the two devices, the rate has a significant effect on both maximum force and stiffness. Moreover, the new expansion device showed lesser dependency on the crosshead rate than the interference screw.

Twenty-six patients with anteroposterior (AP) laxity of the knee, associated with torn anterior cruciate ligament (ACL), were prospectively randomized for arthroscopic lower femoral tunnel placed single- or double-bundle reconstruction using hamstring tendons. We evaluated AP and rotational stabilities under regular loads (a 100-N anterior load and a 1.5-N m external-internal load) before and after ACL reconstruction, comparing single- and double-bundle reconstruction with our original device for applying quantitative tibial rotation and the navigation system intraoperatively. No significant differences were found between the two groups in AP displacement and total range of tibial rotation at 30 degrees and 60 degrees of knee flexion. We found that a lower femoral tunnel placed single-bundle reconstruction reproduced AP and rotational stability as well as double-bundle reconstruction after reconstruction intraoperatively.

The purpose of this study was to compare two different strategies of management for ACL rupture in skeletally immature patient. In group 1, patients were treated in a children hospital by ACL reconstruction with open physis. In group 2, patients were treated in an adult hospital by delayed reconstruction at skeletal maturity assessed radiologically. Fifty-six consecutive patients were included in this retrospective study. Mean time from injury to surgery in group 1 and 2 was, respectively, 13.5 and 30 months. Patients from group 2 exhibited a higher rate of medial meniscal tears (41%) compare to group 1 (16%) and higher rate of meniscectomy. Both groups had the same rate of lateral meniscal tears. A temporary tibial valgus deformity was reported which was subsequently spontaneously resolved. No definitive growth disturbance was noticed. At 27 months mean follow-up, a best subjective IKDC score was found in group 1. Objective IKDC and radiological results were similar in both groups. Early ACL reconstruction is therefore a recommended option.

Objectives: We investigated the effects of anatomic and non-anatomic tunnel fixations on femoral tunnel widening and clinical results in anterior cruciate ligament (ACL) reconstructions., Methods: We retrospectively evaluated 35 patients who underwent arthroscopic ACL reconstruction with quadrupled hamstring tendon graft. Fixation was performed in the tunnel using the transcondylar RigidFix pin (group 1) in 18 patients (mean age 32 years), and from outside the tunnel using the EndoButton-CL device (group 2) in 17 patients (mean age 30 years). The patients were assessed using the IKDC (International Knee Documentation Committee) and Lysholm knee scores and tunnel widening was assessed by computed tomography. Ligament laxity was measured bilaterally using the Rolimeter knee tester. The mean follow-up was 24 months (range 21 to 38 months) in group 1, and 24.6 months (range 12 to 36 months) in group 2., Results: The two groups were similar with respect to age and sex distribution, operated side, the size of the tunnel created, and follow-up period (p>0.05). Postoperative knee scores did not show a significant difference (p>0.05). There was marked and excessive tunnel enlargement in 14 patients (77.8%) in group 1, and in 15 patients (88.2%) in group 2, with no significant difference between the two groups (p>0.05). Ligament laxity exceeded 3 mm in eight patients (44.4%) in group 1, and in three patients (17.7%) in group 2 (p<0.001). There was no relationship between tunnel widening and ligament laxity (p>0.05; r=0.175 and r=-0.01 for group 1 and group 2, respectively)., Conclusion: Our results suggest that differences in the localization of the tunnel fixation have no effect on tunnel enlargement and that joint laxity may be affected by biomechanical properties of fixation materials.

After reconstruction of the cruciate ligaments, replacement grafts have to undergo several phases of healing in the intra-articular graft region and at the site of graft-to-bone incorporation. The changes in the biological and mechanical properties of the healing graft in its intra-articular region are described as the ligamentization process. Significant knowledge has been added in the understanding of the several processes during the course of graft healing and is summarized in this article. The understanding of the spatial and time-dependent changes as well as the differences between the different models of graft healing are of significant importance to develop strategies of improved treatment options in cruciate ligament surgery, so that full restoration of function and mechanical strength of the intact cruciate ligaments will be achieved.

Background: Macrophages accumulate following tendon-to-bone repair and may contribute to the formation of a scar-tissue interface rather than to the reformation of a normal insertion site. We hypothesized that macrophage depletion may lead to improved insertion site regeneration, in a form of "scar-less" healing rather than reactive scar-tissue formation., Methods: One hundred and ninety-two Sprague-Dawley rats underwent anterior cruciate ligament reconstruction with use of a flexor tendon autograft and were divided into a control group (ninety-six rats) and a liposomal clodronate-injected group (ninety-six rats). Clodronate is a bisphosphonate that selectively induces macrophage apoptosis. Animals in the liposomal clodronate group received weekly intraperitoneal injections of liposomal clodronate (1.33 mL/100 g of body weight). Rats were killed at serial time points from three to forty-two days. Immunostaining identified macrophages and transforming growth factor-beta (TGF-beta) at the tendon-bone interface. Fibrous interface width, osteoid formation, and collagen fiber continuity were evaluated with use of histomorphometry. Serial fluorochrome labeling was used to measure mineral apposition rate. Additional rats were killed for biomechanical testing at seven, fourteen, twenty-eight, and forty-two days., Results: Liposomal clodronate significantly decreased macrophages and TGF-beta accumulation at the tendon-bone interface (p < 0.05). Specimens from rats that received liposomal clodronate exhibited a significantly narrower fibrous tissue interface between tendon and bone at all time points compared with specimens from controls (p < 0.05). In specimens from the liposomal clodronate group, healing proceeded at an accelerated rate, characterized by enhanced collagen fiber continuity and a greater degree of interface remodeling between tendon and bone. There were significant increases in osteoid formation (p < 0.05) and mineral apposition rates (p < 0.05) among experimental specimens. At forty-two days, the specimens from the liposomal clodronate group had significantly greater increases than the control specimens with respect to load to failure (mean and standard deviation, 13.5 +/- 4.2 N and 9.7 +/- 3.9 N, respectively; p < 0.05) and stiffness (mean, 11.5 +/- 5.0 N/mm and 7.5 +/- 3.2 N/mm; p < 0.05)., Conclusions: Macrophage depletion following anterior cruciate ligament reconstruction resulted in significantly improved morphologic and biomechanical properties at the healing tendon-bone interface, which we hypothesize are due to diminished macrophage-induced TGF-beta production.

Purpose: The purposes of this study were to determine the relation between the graft tension and the knee flexion angle in the anteromedial (AM) and posterolateral (PL) bundles of a clinically simulated anatomic double-bundle anterior cruciate ligament (ACL) reconstruction procedure and to clarify the effect of initial tension on the tension-versus-flexion curve of each graft, as well as the effect of internal rotation of the tibia on the tension of the 2 grafts., Methods: During ACL reconstruction in 30 patients, 2 suture anchors with a No. 1 polyester suture were firmly screwed into the center of the anatomic attachment of the AM and PL bundles on the femur, respectively, and each graft tension was measured with a strain gauge-type tensiometer attached at the end of the suture under 2 conditions of initial tension., Results: The averaged tension-versus-flexion curves were significantly different between the AM and PL grafts under each initial tension condition (P < .0001). The initial tension applied at 30 degrees of knee flexion significantly affected the absolute values of each graft tension at each knee flexion angle (P < .0001) but did not significantly affect the tension-versus-flexion curve pattern of each graft. The maximal internal rotation of the tibia significantly increased the tension on both the AM and PL grafts at knee flexion angles of less than 60 degrees under each initial tension condition (P < .0001)., Conclusions: The tension-versus-flexion curves of the 2 sutures, which mimicked the AM and PL grafts reconstructed clinically with the anatomic double-bundle ACL reconstruction procedure, were significantly different in the tension values. Differences in initial tension applied to the 2 grafts significantly affected the absolute values of each graft tension at each knee flexion angle but did not significantly affect the tension-versus-flexion curve pattern. The maximal internal rotation of the tibia significantly increased the tension on both the AM and PL suture grafts at knee flexion angles of less than 60 degrees ., Level of Evidence: Level I, testing of previously developed diagnostic criteria in series of consecutive patients with universally applied gold standard.

Purpose: The purpose of this study was to compare the clinical results of a double-bundle anterior cruciate ligament (ACL) reconstruction with 4 strands versus 8 strands of hamstring tendon graft., Methods: Seventy-six patients with chronic ACL rupture were randomly separated into two groups for double-bundle ACL reconstruction. In the 4-strand hamstring graft (4SHG) group, the semitendinosus tendon was used to make two 2-stranded hamstring tendon grafts, whereas in the 8-strand hamstring graft (8SHG) group, the semitendinosus tendon was used to make one 4SHG and the gracilis tendon was used to make the other 4SHG. The 4SHG group comprised 33 patients and the 8SHG group comprised 35 patients, with a minimum follow-up of 2 years. International Knee Documentation Committee (IKDC) and Lysholm scales were used to evaluate the clinical results., Results: In the 4SHG group the side-to-side difference was less than 3 mm in 26 patients (78.8%), 3 to 5 mm in 4 patients (12.1%), and 6 to 10 mm in 3 patients (9.0%), with a mean value of 2.8 +/- 0.5 mm; the pivot-shift test was negative in 29 patients (89.9%) and positive in 4 (12.1%). In the 8SHG group the side-to-side difference was less than 3 mm in 32 patients (91.4%), 3 to 5 mm in 2 patients (5.7%), and 6 mm in 1 patient (2.9%) (P = .004), with a mean value of 1.3 +/- 0.4 mm (P = .0003); the pivot-shift test was negative in 34 patients (97.1%) and positive in 1 (2.9%). According to the IKDC scale, 29 patients (87.9%) in the 4SHG group and 33 patients (94.3%) in the 8SHG group had a grade of normal or nearly normal. In the 4SHG and 8SHG groups the mean IKDC subjective knee evaluation results were 86.4 +/- 4.2 and 96.3 +/- 2.8 (P = .0007), respectively, and the mean Lysholm scores were 89.6 +/- 3.7 and 96.5 +/- 2.9 (P = .0006), respectively., Conclusions: On the basis of KT-1000 examination (MEDmetric, San Diego, CA) and clinical measures, double-bundle ACL reconstruction with 8SHG yields significantly better results than double-bundle ACL reconstruction with 4SHG, with a mean side-to-side difference in anterior knee laxity of 1.3 +/- 0.4 mm versus 2.8 +/- 0.5 mm (P = .0003), IKDC subjective result of 96.3 +/- 2.8 versus 86.4 +/- 4.2 (P = .0007), and Lysholm score of 96.5 +/- 2.9 versus 89.6 +/- 3.7 (P = .0006)., Level of Evidence: Level II, lesser-quality randomized controlled trial.

Background: The purpose of this study was to determine whether current post-operative rehabilitation protocols return the strength of the contralateral uninjured limb knee flexors and extensors after an anterior cruciate ligament (ACL) reconstruction to those of an uninjured control group., Methods: Subjects with a hamstring tendon ACL reconstruction (n=12) were compared to an active control group (n=30). Comprehensive bilateral knee flexor and extensor isovelocity strength testing was performed (five speeds, 5-95 degrees , concentric and eccentric contractions)., Findings: After hamstring tendon ACL reconstruction and rehabilitation, bilateral strength normalization (within 10% of the contralateral limb) is achieved by the knee extensors but not the knee flexors. When compared to the uninjured control group, large and statistically significant strength deficits were demonstrated in the knee extensors and knee flexors of both the anterior cruciate ligament reconstructed (extensors 24.8%; flexors 26.8%) and the contralateral uninjured (extensors 21%; flexors 13.5%) limbs., Interpretation: These findings suggest that improvement can be made in knee flexor rehabilitation after ACL reconstruction and limit the validity of the use of a contralateral leg as a rehabilitation endpoint or as a control in the ACL reconstructed population.

Background: This research was undertaken to determine whether there is a need for a second tibial tunnel in anatomic anterior cruciate ligament reconstruction., Hypothesis: Anatomic two-bundle reconstruction with two tibial tunnels restores knee anterior tibial translation in response to 134 N and to 5-N.m internal tibial torque combined with 10-N.m valgus torque more closely to normal than does double-bundle reconstruction with one tibial tunnel., Study Design: Controlled laboratory study., Methods: Ten cadaveric knees were subjected to a 134-N anterior tibial load at 0 degrees, 30 degrees, 60 degrees, and 90 degrees and to 5-N.m internal tibial torque and 10-N.m valgus torque at 15 degrees and 30 degrees. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for (1) intact, (2) anterior cruciate ligament-deficient, (3) double-bundle/one tibial tunnel, and (4) double-bundle/two tibial tunnels., Results: Anterior tibial translation for the reconstruction with two tibial tunnels was significantly closer to that of the intact knee than was the reconstruction with one tibial tunnel at 0 degrees and 30 degrees of flexion (0 degrees = 3.82 vs 6.0 mm, P < .05; 30 degrees = 7.99 vs 11 mm, P < .05). The in situ force normalized to the intact anterior cruciate ligament for the reconstruction with two tibial tunnels was significantly higher than the in situ force of the reconstruction with one tibial tunnel (30 degrees = 89 vs 82 N, P < .05). With a combined rotatory load, the anterior tibial translation of specimens with a tibial two-tunnel technique was significantly lower than that of specimens with one tunnel (0 degrees = 5.7 vs 8.4 mm, P < .05; 30 degrees = 7.5 vs 9.5 mm, P < .05)., Conclusions: Anatomic reconstruction with two tibial tunnels may produce a better biomechanical outcome, especially close to extension., Clinical Relevance: At the time of initial fixation, there appears to be a small biomechanical advantage to the second tibial tunnel in the setting of two-bundle anterior cruciate ligament reconstruction.

Background: The 2 most frequently used autografts for anterior cruciate ligament reconstruction are the bone-patellar tendon-bone and the quadrupled hamstrings tendon., Hypothesis: Hamstring tendon graft is superior to patellar tendon graft in restoring tibial rotation during highly demanding activities because of its superiority in strength and linear stiffness and because it is closer morphologically to the anatomy of the natural anterior cruciate ligament., Study Design: Case control study; Level of evidence, 3., Methods: Eleven patients with patellar tendon graft anterior cruciate ligament reconstruction, 11 patients with hamstring tendon graft anterior cruciate ligament reconstruction, and 11 controls were assessed. Kinematic data were collected (50 Hz) with a 6-camera optoelectronic system while the subjects descended stairs and, immediately after, pivoted on their landing leg. The dependent variable examined was the tibial internal-external rotation during pivoting. All patients in both groups were also assessed clinically and with the use of a KT-1000 arthrometer to evaluate anterior tibial translation., Results: The results demonstrated that reconstructions with either graft successfully restored anterior tibial translation. However, both anterior cruciate ligament reconstruction groups had significantly increased tibial rotation when compared with the controls, whereas no differences were found between the 2 reconstructed groups., Conclusion: The 2 most frequently used autografts for anterior cruciate ligament reconstruction cannot restore tibial rotation to normal levels., Clinical Relevance: New surgical techniques are needed that can better approximate the actual anatomy and function of the anterior cruciate ligament.

In this paper the design and experimental analysis is presented of a new fixation device of anterior cruciate ligament (ACL) grafts of the knee. This device is inserted into the bone tunnel, after the graft, in the same way as an interference screw. However, the fixation device described in this paper has been designed in such a way that, after the insertion of a threaded element in its interior, some of its components expand in a radial direction, pressing against the walls of the bone tunnel and thereby increasing the fixation of the graft. This expansion device can be used in both the femur and the tibia. The device proposed in this paper was compared with an interference screw for load failure and fixation stiffness in experiments performed using porcine bones. The failure load was significantly higher in the new expansion device group (633+/-202 N) than in the interference screw group (471+/-179 N). The stiffness obtained when the new device was used (59+/-20 N/mm) was also significantly higher than that obtained using the interference screw (37+/-19 N/mm) (t-test, P<0.05). According to these results, this new device could be considered a good alternative to improve fixation of anterior cruciate ligament grafts.

Recent research suggests ACL reconstruction does not restore tibial rotation to normal levels during high demand activities when a bone-patellar tendon-bone graft is used. We asked if an alternative graft, the semitendinosus-gracilis (ST/G) tendon graft, could restore tibial rotation during a high demand activity. Owing to its anatomic similarity with the normal ACL we hypothesized the ST/G graft could restore excessive tibial rotation to normal healthy levels along with a successful reinstatement of the clinical stability of the knee. We assessed tibial rotation in vivo, using gait analysis. We compared the knees of ACL reconstructed patients with an ST/G graft to their intact contralateral and healthy controls during a pivoting task that followed a stair descent. We also evaluated knee stability after ACL reconstruction with standard clinical tests. ACL reconstruction with the ST/G graft and with current techniques did not restore tibial rotation to previous physiological levels during an activity with increased rotational loading at the knee, although abnormal anteroposterior (AP) tibial translation was restored.

Most of the techniques described in the literature for the repair of chronic partial ACL tears, don't spare the intact portion of the ligament. The aim of this study was to perform a prospective analysis of the results of augmentation surgery using gracilis and semitendinosus tendons to treat partial sub-acute lesions of the ACL. This technique involves an "over the top" femoral passage, which enables salvage and strengthening of the intact portion of the ACL. The study included 47 patients treated consecutively at our institute from 1993 to 1998, with a mean injury-surgery interval of 18 weeks (range 12-36). The patients were followed up by clinical and instrumental assessment criteria at 3 months, 1 and 5 years after surgery. Clinical assessment was performed using the IKDC form. Subjective and functional parameters were assessed by the Tegner activity scale. Instrumental evaluation was done using the KT-2000 instrument: the 30-pound passive test and the manual maximum displacement test were performed. We obtained good or excellent results in 95.7% of cases. No recurrences in ligamentous laxity were observed. We believe that the described technique has the advantage of being compatible with ACL anatomy, and enables very rapid functional recovery.