Immediate ACL reconstruction prevents microvascular pathophysiology in the Uninjured MCL that is not fully reversed by delayed ACL reconstruction

Anterior cruciate ligament (ACL) injury induces maladaptive vascular responses that degrade medial collateral ligament (MCL) function. The purpose of this study was to determine if early or delayed ACL reconstruction can prevent or reverse the abnormal changes in vascular function that occur in the uninjured MCL after ACL injury. Twenty‐four rabbits were divided into four groups (n = 6); control, ACL‐deficient (ACL‐X), immediate ACL reconstructed (ACL‐IR) and delayed ACL reconstructed (ACL‐DR). After 8 weeks, MCLs were assessed for blood flow, responses to acetylcholine (ACh) and phenylephrine (Phe) and autoregulatory responses, using laser speckle perfusion imaging. In ACL‐X knees, blood flow in the MCL increased by 2.5‐fold compared to control. MCL hyperemia was diminished in ACL‐DR knees and was unaltered in ACL‐IR knees. MCL vasculature was unresponsive to ACh and Phe in ACL‐X. These responses were partially restored by ACL reconstruction. Autoregulatory responses were not significantly different between groups. ACL‐DR decreased hyperemia in the MCL and partially attenuated abnormal MCL vascular responses. ACL‐IR was more effective at preventing MCL hyperemia and preserving vascular responsiveness to ACh and Phe. This suggests that the vascular alterations in the uninjured rabbit MCL are largely caused by abnormal mechanical loading resulting from ACL deficiency and can be prevented through early reconstruction. Early ACL reconstruction could limit the progression of microvascular dysfunction of the MCL, and preserve physiological joint homeostasis. This might prevent joint degeneration and delay the progression of osteoarthritis. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1390–1396, 2011     

The Complex Relationship Between In Vivo ACL Elongation and Knee Kinematics During Walking and Running

In vivo anterior cruciate ligament (ACL) bundle (anteromedial bundle [AMB] and posterolateral bundle [PLB]) relative elongation during walking and running remain unknown. In this study, we aimed to investigate in vivo ACL relative elongation over the full gait cycle during walking and running. Ten healthy volunteers walked and ran at a self‐selected pace on an instrumented treadmill while biplane radiographs of the knee were acquired at 100 Hz (walking) and 150 Hz (running). Tibiofemoral kinematics were determined using a validated model‐based tracking process. The boundaries of ACL insertions were identified using high‐resolution magnetic resonance imaging (MRI). The AMB and PLB centroid‐to‐centroid distances were calculated from the tracked bone motions, and these bundle lengths were normalized to their respective lengths on MRI to calculate relative elongation. Maximum AMB relative elongation during running (6.7 ± 2.1%) was significantly greater than walking (5.0 ± 1.7%, p = 0.043), whereas the maximum PLB relative elongation during running (1.1 ± 2.1%) was significantly smaller than walking (3.4 ± 2.3%, p = 0.014). During running, the maximum AMB relative elongation was significantly greater than the maximum PLB relative elongation (p < 0.001). ACL relative elongations were correlated with tibiofemoral six degree‐of‐freedom kinematics. The AMB and PLB demonstrate similar elongation patterns but different amounts of relative elongation during walking and running. The complex relationship observed between ACL relative elongation and knee kinematics indicates that ACL relative elongation is impacted by tibiofemoral kinematic parameters in addition to flexion/extension. These findings suggest that ACL strain is region‐specific during walking and running. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1920–1928, 2019     

Multiple injections of leukoreduced platelet rich plasma reduce pain and functional impairment in a canine model of ACL and meniscal deficiency

Platelet rich plasma (PRP) is used to treat many musculoskeletal disorders. We used a canine model to determine the effects of multiple intra‐articular injections of leukoreduced PRP (ACP) on anterior cruciate ligament healing, meniscal healing, and progression of osteoarthritis (OA). With Animal Care and Use Committee (ACUC) approval, 12 dogs underwent partial ACL transection and meniscal release in one knee. At weeks 1, 2, 3, 6, and 8 after insult, dogs were treated with intra‐articular injections (2 ml) of either ACP (n = 6) or saline (n = 6). Dogs were assessed over 6 months to determine comfortable range of motion (CROM), lameness, pain, effusion, kinetics, and radiographic and arthroscopic assessments. At 6‐month endpoint, dogs were assessed for ACL material properties and histopathology. Saline‐treated dogs had significantly (p < 0.04) more CROM loss, significantly (p < 0.01) more pain, significantly (p < 0.05) more severe lameness, significantly (p < 0.05) lower function, and significantly (p < 0.05) lower %Total Pressure Index in affected hindlimbs compared to ACP‐treated dogs. Radiographic OA increased significantly (p < 0.01) over time within each group. Arthroscopically, saline‐treated knees showed moderate to severe synovitis, further ACL disruption, and medial compartment cartilage loss, and ACP‐treated knees showed evidence of ACL repair and less severe synovitis. ACL material properties in ACP‐treated knees were closer to normal than in saline‐treated knees, however, the differences were not statistically significant. ACL histopathology was significantly (p< 0.05) less severe in ACP‐treated knees compared to saline‐treated knees. Five intra‐articular injections of leukoreduced PRP had beneficial effects for ACL healing, improved range of motion, decreased pain, and improved limb function for up to 6 months in this model. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:607–615, 2016.     

Complete ACL/MCL deficiency induces variable degrees of instability in sheep with specific kinematic abnormalities correlating with degrees of early osteoarthritis

People are not equally disabled by combined anterior cruciate ligament (ACL)/medial collateral ligament (MCL) injuries, nor do they all develop osteoarthritis (OA). Although biological/biomechanical causes are not clear, some association presumably exists between joint instability and OA development. We hypothesized that degree of OA development following standardized complete ACL/MCL injuries will vary directly with the degree of biomechanical abnormality between individuals. Three groups of sheep were used to test the hypothesis: 17 normal, 9 ACL/MCL transected, and 7 sham animals. Normal joints were assessed morphologically while sham and experimental animals had gait assessment pre‐ and at 4 and 20 weeks post‐surgery, with cartilage and bone changes being mapped and graded at sacrifice at 20 weeks. Sham joints were morphologically normal and had only one minor kinematic change at 20 weeks. Although variable, ACL/MCL deficient animals showed significant kinematic abnormalities in 4/6 degrees of freedom (DOFs), as well as cartilage/bone damage by 20 weeks (p < 0.05). Linear regression analysis revealed that changes in medial–lateral (ML) translation were related to the current level of joint degradation as represented by total gross OA score (p = 0.0044, R² = 0.71) in the ACL/MCL transected group. Even identical ACL/MCL injuries result in inter‐animal variations in instability and OA, however significant kinematic abnormalities in ML translation do relate to early OA in sheep. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:384–392, 2012     

Vascular structure and function in the medial collateral ligament of anterior cruciate ligament transected rabbit knees

To determine if decreased vascular responsiveness in the medial collateral ligament (MCL) of anterior cruciate ligament transected (ACL‐t) rabbit knees is due to pericyte deficiency associated with angiogenesis. Vascular responses to potassium chloride (KCl), phenylephrine, acetylcholine, and sodium nitroprusside (SNP) were evaluated in ACL‐t rabbit knees (n = 6) and control knees (n = 5) using laser speckle perfusion imaging. Ligament degeneration was determined by ultrasound imaging. Vascular and pericyte volume were measured using quantitative immunohistochemical volumetric analysis using CD31 and α‐smooth muscle actin antibodies with co‐localization analysis. Perfusion was increased in the ACL‐t rabbits 2.5‐fold. Responsiveness to phenylephrine, SNP, and acetylcholine was significantly decreased in the ACL knee while no change in KCl responses was seen. MCL ultrasound imaging revealed decreased collagen organization, increased ligament thickness, and increased water content in the ACL‐t MCL. Vascular Volume was increased fourfold in ACL deficient knees, while pericyte volume to endothelial volume was not changed. No difference in CD31 and α‐SMA co‐localization was found. Blood vessels in the MCL of ACL‐t knees do not lack smooth muscle. The MCL vasculature can undergo constrictive response to KCl, but have impaired receptor mediated responses and impaired nitric oxide signaling. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1104–1110, 2014.     

Anatomical analysis of the anterior cruciate ligament femoral and tibial footprints

Background The current trend in anterior cruciate ligament (ACL) reconstruction has shifted to anatomical double-bundle (DB) reconstruction, which reproduces both the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of the ACL. Navigation systems have also been recently introduced to orthopedic surgical procedures, including ACL reconstruction. In DB-ACL reconstruction, the femoral and tibial tunnel positions are very important, but a representation of the ACL footprint under an arthroscopic view has not been established even though navigation systems have been introduced. The purpose of this study was to evaluate the anatomical footprints of both the AMB and the PLB using the representation method for application to arthroscopic DB-ACL reconstruction using a navigation system, and to evaluate the validity of the currently determined footprint position compared with other representation methods. Methods Thirty-six cadaveric knees were used for an anatomical evaluation of footprints of the AMB and PLB. On the tibial side, the ACL footprints were evaluated using an original method. On the femoral side, the ACL footprints were evaluated using Watanabe’s method and three other methods: (1) the quadrant method, (2) Mochizuki’s method, and (3) Takahashi’s method. Results The central points of the ACL footprints were represented almost constantly. The present data is in accordance with previous measurement data. Conclusion This study showed that the anatomical data of the ACL femoral and tibial footprints determined with Watanabe’s method at the femoral side and our original method at the tibial side were both applicable to arthroscopic surgery with a navigation system.     

Neural stimulation does not mediate attenuated vascular response in ACL‐deficient knees: Potential role of local inflammatory mediators

Chronic inflammation associated with osteoarthritis (OA) alters normal responses and modifies the functionality of the articular vasculature. Altered responsiveness of the vasculature may be due to excessive neural activity associated with chronic pain and inflammation, or from the production of inflammatory mediators which induce vasodilation. Using laser speckle perfusion imaging (LSPI), blood flow to the medial collateral ligament (MCL) of adult rabbits was measured in denervated ACL transected knees (n = 6) and compared to unoperated control (n = 6) and 6‐week anterial cruciate ligament (ACL)‐transected knees (n = 6). Phenylephrine and neuropeptide Y were applied to the MCL vasculature in topical boluses of 100 µL (dose range 10^?14 to 10^?8 mol and 10^?14 to 10^?9 mol, respectively). Denervation diminished vasoconstrictive responsiveness to phenylephrine compared to both control and ACL‐transected knees. Denervation minimally enhanced vascular responses to neuropeptide Y (NPY) compared to ACL deficiency alone, which nevertheless remained significantly diminished from control responses. To evaluate the potential role of inflammatory dilators in the diminished contractile responses, phenylephrine was coadministered with histamine, substance P, and prostaglandin E₂. High‐dose histamine, and low‐dose substance P and PGE₂ were able to inhibit contractile responses in the MCL of control knees. Excessive neural input does not mediate diminished vasoconstrictive responses in the ACL transected knee; inflammatory mediators may play a role in the deficient vascular responsiveness of the ACL transected knee. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:83–88, 2010     

双源CT三维重建评价前交叉韧带骨道位置的临床研究

目的 探讨双源CT三维重建前交叉韧带（ACL）股骨止点自然印迹与骨道中心点相对位置关系.方法 分别对55例志愿者110个膝关节和30例双束重建患者30个患膝关节进行双源CT扫描.使用CT图像后处理工作站行三维重建膝关节股骨外髁内侧壁三维模型,再现股骨外髁内侧壁ACL自然印迹及术后双束骨道,标记、测量自然印迹及骨道中心点相对位置,比较两者的位置关系,显著性差异设定P值0.05.结果 ACL自然印迹中心点相对位置与术后双束骨道中心点相对位置比较：前内束,h对=（26.2±2.2）%,h实=（23.6±8.5）%,中心点相对位置比较有统计学差异（t=4.906,P〈0.01）;t对=（25.0±2.1）%,t实=（25.2±3.9）%,中心点相对位置比较无统计学差异（t=0.480,P〉0.05）.后外束,h对=（46.5±3.2）%,h实=（45.0±4.6）%,中心点相对位置比较无统计学差异（t=0.608,P〉0.05）;t对=（34.2±2.5）%,t实=（37.9±4.2）%,中心点相对位置比较无统计学差异（t=0.530,P〉0.05）.结论 （1） DSCT三维重建可清晰重建出ACL股骨止点自然印迹和双束重建术后骨道位置;（2） DSCT 三维重建可用于ACL解剖双束重建术后骨道位置评估,对改进关节镜下ACL解剖双束重建有指导意义.     

Use of patellar tendon autograft for anterior cruciate ligament reconstruction in the rabbit: a long-term histologic and biomechanical study

To assess the degree of success of anterior cruciate ligament (ACL) replacement using the patellar tendon (PT) autograft, 29 New Zealand white rabbits underwent ACL reconstruction using a medial one-third PT autograft. The femur-ligament-tibia complexes were evaluated at 0, 6, 30, and 52 weeks postoperatively for gross and histologic appearances and tensile load to failure properties. Grossly, the autografts did not resemble the control ACLs. Histologically, the autografts progressed from being hypercellular with a random collagen fiber bundle organization to having a near normal cellularity with a more parallel collagen fiber bundle pattern. Anteroposterior knee laxity was more than two times that of the control knees 52 weeks after reconstruction. Biomechanically, the PT autografts plateaued at 30 weeks postoperatively. The ultimate load and stiffness were 15 +/- 5% and 24 +/- 6% of the control ACLs, respectively. At 52 weeks, the appearance of the PT autograft had some general histologic similarities as compared with the native ACL. However, these similarities did not extend to the functional properties of the autograft.     

Extracellular matrix‐blood composite injection reduces post‐traumatic osteoarthritis after anterior cruciate ligament injury in the rat

The objective of this study was to determine if an injection of a novel extracellular matrix scaffold and blood composite (EMBC) after anterior cruciate ligament (ACL) injury would have a mitigating effect on post‐traumatic osteoarthritis (PTOA) development in rat knees. Lewis rats underwent unilateral ACL transection and were divided into three groups as follows: (1) no further treatment (ACLT; n = 10); (2) an intra‐articular injection of EMBC on day 0 (INJ0; n = 11); and (3) an intra‐articular injection of EMBC on day 14 (INJ14; n = 11). Ten additional animals received capsulotomy only (n = 10, SHAM group). The OARSI histology scoring of the tibial cartilage and micro‐CT of the tibial epiphysis were performed after 35 days. The ratio of intact/treated hind limb forces during gait was determined using a variable resistor walkway. The OARSI cartilage degradation sum score and total degeneration width were significantly greater in the ACLT group when compared to the INJ0 (p = 0.031, and p = 0.005) and INJ14 (p = 0.022 and p = 0.04) group. Weight bearing on the operated limb only decreased significantly in the ACLT group (p = 0.048). In the rat ACL transection model, early or delayed injection of EMBC ameliorated the significant decrease in weight bearing and cartilage degradation seen in knees subjected to ACL transection without injection. The results indicate that the injection of EMBC may slow the process of PTOA following ACL injury and may provide a promising treatment for PTOA. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:995–1003, 2016.     

双源CT三维重建前交叉韧带股骨止点及隧道面积的临床研究

目的通过双源CT（DSCT）三维重建前交叉韧带（ACL）股骨止点印迹及骨隧道面积,为临床实现解剖重建提供依据。方法分别对55例志愿者110膝,30例双束重建60膝及30例单束重建患者60膝进行DSCT扫描。64排工作站（GE,Volume Share 2-AW4．4软件）三维重建膝关节股骨外髁三维模型,再现股骨外髁内侧壁ACL印迹,圈画、测量印迹及骨隧道面积,计算单、双束骨道面积覆盖率。结果ACL股骨自然印迹面积双膝之间：左（146．35±29．0）mm2,右（144．51±33．71）mm^2,两者间无统计学差异（t=0．52,P〉0．05）。性别间自然印迹面积比较：AMB：男（87．08±19．29）mm。,女（77．09±15．17）mm^2,两者间有统计学差异（t=2．04,P〈0．05）;PLB：男（62．82±15．19）mm^2,女（61．64±16．55）mm^2,两者间无统计学差异（t=0．27,P〉0．05）。术后隧道面积覆盖率比较：单束（53±18）％,双束（70±16）％,两者间有统计学差异（t=2．44,P〈0．05）。结论ACL股骨止点自然印迹面积存在性别间及个体化差异,双束重建止点面积覆盖率显著大于单束重建,要实现ACL解剖重建需采用个体化重建技术。     

The patella ligament insertion angle influences quadriceps usage during walking of anterior cruciate ligament deficient patients

Following ACL injury a reduction in the peak knee flexion moment during walking (thought to be created by a decrease of quadriceps contraction) has been described as an adaptation to reduce anterior tibial translation (ATT) relative to the femur. However, the amount of ATT caused by quadriceps contraction is influenced by the patellar ligament insertion angle (PLIA). The purpose of this study was to test the hypothesis that quadriceps usage during walking correlates to individual anatomical variations in the extensor mechanism as defined by PLIA. PLIA and gait were measured for ACL‐deficient knees, using subjects' contralateral knees as controls. In ACL‐deficient knees, PLIA was negatively correlated (R² = 0.59) to peak knee flexion moment (balanced by net quadriceps moment), while no correlation was found in contralateral knees. Reduction in peak flexion moment in ACL‐deficient knees compared to their contralateral knees was distinctive in subjects with large PLIA, possibly to avoid excessive ATT. These results suggest that subject‐specific anatomic variability of knee extensor mechanism may account for the individual variability previously observed in adaptation to a quadriceps reduction strategy following ACL injury. The average (±1 SD) PLIA of ACL‐deficient knees (21.1 ± 3.4°) was less than the average PLIA of contralateral knees (23.9 ± 3.1°). This altered equilibrium position of the tibiofemoral joint associated with reduced PLIA and adaptations of gait patterns following ACL injury may be associated with degenerative changes in the articular cartilage. In the future, individually tailored treatment and rehabilitation considering individuals' specific extensor anatomy may improve clinical outcomes. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1643–1650, 2007     

Abnormal tibial position is correlated to early degenerative changes one year following ACL reconstruction

Altered knee kinematics following ACL reconstruction may predispose patients to the development of early onset post‐traumatic osteoarthritis. The goal of our study was to examine the longitudinal interrelationship between altered tibial position relative to the femur and cartilage health measured by quantitative T_1ρ MRI. Twenty‐five patients with isolated unilateral ACL injury underwent kinematic and cartilage T_1ρ MRI at baseline prior to ACL reconstruction and then at 1‐year post‐reconstruction. Tibial position relative to the femur in the anterior–posterior plane was calculated as well as cartilage T_1ρ relaxation values in the injured and uninjured knee. At baseline prior to ACL reconstruction, the tibia was in a significantly more anterior position relative to the femur in the ACL deficient knee compared to the healthy contralateral knee. This difference was no longer present at 1‐year follow‐up. Additionally, the side–side difference in tibial position correlated to increased cartilage T_1ρ relaxation values in the medial compartment of the knee 1‐year post‐reconstruction. Altered tibial position following ACL reconstruction is correlated with detectable cartilage degeneration as soon as 1 year following ACL reconstruction. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1079–1086, 2015.     

Tension patterns of the anteromedial and posterolateral grafts in a double‐bundle anterior cruciate ligament reconstruction

The two functional bundles of the anterior cruciate ligament (ACL), namely, the anteromedial (AM) and posterolateral (PL) bundles, must work in concert to control displacement of the tibia relative to the femur for complex motions. Thus, the replacement graft(s) for a torn ACL should possess similar tension patterns. The objective of the study was to examine whether a double‐bundle ACL reconstruction with the semitendinosus‐gracilis autografts could replicate the tension patterns of those for the intact ACL under controlled in vitro loading conditions. By means of a robotic/universal force moment sensor (UFS) testing system, the in situ force vectors (both magnitude and direction) for the AM and PL bundles of the ACL, as well as their respective replacement grafts, were determined and compared on nine human cadaveric knees. It was found that double‐bundle ACL reconstruction could closely replicate the in situ force vectors. Under a 134‐N anterior tibial load, the resultant force vectors for the intact ACL and the reconstructed ACL had a difference of 5 to 11 N (p > 0.05) in magnitude and 1 to 13° (p > 0.05) in direction. Whereas, under combined rotatory loads of 10‐N‐m valgus and 5‐N‐m internal tibial torques, the corresponding differences were 10 to 16 N and 4° to 11°, respectively. Again, there were no statistically significant differences except at 30° of flexion where the force vector for the AM graft had a 15° (p < 0.05) lower elevation angle than did the AM bundle. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 879–884, 2009     

膝关节前交叉韧带前内束和后外束股骨止点位置的解剖研究

目的探讨膝关节前交叉韧带（ACL）前内束及后外束股骨止点的解剖位置,找到确定ACL前内束和后外束股骨止点的简单可行的方法,为双束重建ACL手术中的股骨骨道定位提供理论支持。方法解剖18个新鲜膝关节标本（25～45岁）的股骨端前内束和后外束的足迹,以标定前内束和后外束股骨止点中心点的位置。在屈膝90°位,测量ACL前内束及后外束股骨止点中心点距股骨髁间窝外侧壁前方、后方和下方软骨缘的距离。再对测量数据进行评估和对比。结果 ACL后外束股骨止点中心点距离股骨前方软骨缘（8.55±1.33）mm,距离股骨后方软骨缘（8.65±1.54）mm,二者间无统计学差异（t=-0.191,P〉0.05）;而ACL后外束股骨止点中心点距离股骨下方软骨缘（5.11±0.79）mm。ACL前内束股骨止点中心点距离股骨前方软骨缘（14.95±2.06）mm,距离股骨后方软骨缘（6.08±0.88）mm,二者间有统计学差异（t=16.633,P〈0.01）;而ACL前内束股骨止点中心点距离股骨下方软骨缘（9.10±1.55）mm。结论膝关节屈膝90°时,ACL后外束的股骨止点中心点位于股骨髁间窝外侧壁距离下方软骨缘5mm的高度,并处在与前方和后方软骨缘几乎等距的位置。而ACL前内束的股骨止点中心点位于股骨髁间窝外侧壁距离下方软骨缘9mm的高度,并处在前后连线大约后1/3的位置。在ACL双束重建的手术中,应用本研究的结果能够简单、快捷地确定ACL前内束和后外束股骨骨道位置。     

Biological and Biomechanical Evaluation of Autologous Tendon Combined with Ligament Advanced Reinforcement System Artificial Ligament in a Rabbit Model of Anterior Cruciate Ligament Reconstruction

Objective

To compare the biomechanical and histological changes in a rabbit model after reconstructing the anterior cruciate ligament (ACL) with solely autologous tendon and with autologous tendon combined with the ligament advanced reinforcement system (LARS) artificial ligament.

Methods

Anterior cruciate ligament reconstruction was performed in 72 knees from 36 healthy New Zealand white rabbits (bodyweight, 2500–3000 g). The Achilles tendons were harvested bilaterally. The left ACL were reconstructed solely with autografts (autologous tendon group), while the right ACL were reconstructed with autografts combined with LARS ligaments (combined ligaments group). The gross observation, histological determination, and the tension failure loads in both groups were evaluated at 12 weeks (n = 18) and 24 weeks (n = 18) postoperatively.

Results

Gross examination of the knee joints showed that all combined ligaments were obviously covered by a connective tissue layer at 12 weeks, and were completely covered at 24 weeks. Fibrous tissue ingrowth was observed between fascicles and individual fibers in the bone–artificial ligament interface at both time points; this fibrovascular tissue layer localized at the bone–artificial ligament interface tended to be denser in specimens obtained at 24 weeks compared with those obtained at 12 weeks. The tension failure loads of the knees were similar in the autologous tendon group and the combined ligaments group at 12 weeks (144.15 ± 3.92 N vs. 140.88 ± 2.75 N; P > 0.05), and at 24 weeks (184.15 ± 1.96 N vs. 180.88 ± 3.21 N; P > 0.05).

Conclusion

Reconstructing the ACL in rabbits using autologous tendon combined with the LARS artificial ligament results in satisfactory biointegration, with no obvious immunological rejection between the autologous tendon and the artificial ligament, and is, therefore, a promising ACL reconstruction method.

     

Anatomical versus Non-Anatomical Single Bundle Anterior Cruciate Ligament Reconstruction: A Cadaveric Study of Comparison of Knee Stability

Background

The purpose of this study was to compare the initial stability of anatomical and non-anatomical single bundle anterior cruciate ligament (ACL) reconstruction and to determine which would better restore intact knee kinematics. Our hypothesis was that the initial stability of anatomical single bundle ACL reconstruction would be superior to that of non-anatomical single bundle ACL reconstruction.

Methods

Anterior tibial translation (ATT) and internal rotation of the tibia were measured with a computer navigation system in seven pairs of fresh-frozen cadaveric knees under two testing conditions (manual maximum anterior force, and a manual maximum anterior force combined with an internal rotational force). Tests were performed at 0, 30, 60, and 90 degrees of flexion with the ACL intact, the ACL transected, and after reconstruction of one side of a pair with either anatomical or non-anatomical single bundle ACL reconstruction.

Results

Under manual maximal anterior force, both reconstruction techniques showed no significant difference of ATT when compared to ACL intact knee state at 30° of knee flexion (p > 0.05). Under the combined anterior and internal rotatory force, non-anatomical single-bundle ACL reconstruction showed significant difference of ATT compared to those in ACL intact group (p < 0.05). In contrast, central anatomical single bundle ACL reconstruction showed no significant difference of ATT compared to those in ACL intact group (p > 0.05). Internal rotation of the tibia showed no significant difference in the ACL intact, the ACL transected, non-anatomical reconstructed and anatomical reconstructed knees.

Conclusions

Anatomical single bundle ACL reconstruction restored the initial stability closer to the native ACL under combined anterior and internal rotational forces when compared to non-anatomical ACL single bundle reconstruction.     

Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing

ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the tensile stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps tensile stiffness would reduce peak anteromedial bundle (AM‐)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two‐times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased stiffness female quadriceps (i.e., 33% greater stiffness). Peak AM‐ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS? dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated‐measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM‐ACL relative strain and 21% reduction in change in flexion when quadriceps tensile stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p = 0.003). We conclude that increased quadriceps tensile stiffness reduces peak ACL strain during a controlled study simulating a pivot landing. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:423–430, 2014.

     

Tibiofemoral cartilage contact biomechanics in patients after reconstruction of a ruptured anterior cruciate ligament

We investigated the in vivo cartilage contact biomechanics of the tibiofemoral joint in patients after reconstruction of a ruptured anterior cruciate ligament (ACL). A dual fluoroscopic and MR imaging technique was used to investigate the cartilage contact biomechanics of the tibiofemoral joint during in vivo weight‐bearing flexion of the knee in eight patients 6 months following clinically successful reconstruction of an acute isolated ACL rupture. The location of tibiofemoral cartilage contact, size of the contact area, cartilage thickness at the contact area, and magnitude of the cartilage contact deformation of the ACL‐reconstructed knees were compared with those previously measured in intact (contralateral) knees and ACL‐deficient knees of the same subjects. Contact biomechanics of the tibiofemoral cartilage after ACL reconstruction were similar to those measured in intact knees. However, at lower flexion, the abnormal posterior and lateral shift of cartilage contact location to smaller regions of thinner tibial cartilage that has been described in ACL‐deficient knees persisted in ACL‐reconstructed knees, resulting in an increase of the magnitude of cartilage contact deformation at those flexion angles. Reconstruction of the ACL restored some of the in vivo cartilage contact biomechanics of the tibiofemoral joint to normal. Clinically, recovering anterior knee stability might be insufficient to prevent post‐operative cartilage degeneration due to lack of restoration of in vivo cartilage contact biomechanics. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1781–1788, 2012