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Patients with multiligament knee injuries require a thorough examination (Lachman, posterior-drawer, varus, valgus, and rotational testing). Diagnoses are confirmed with magnetic resonance imaging as well as stress radiographs (posterior, varus, and valgus) when indicated. Multiple systematic reviews have reported that early (<3 weeks after injury) single-stage surgery and early knee motion improves patient-reported outcomes. Anatomic-based reconstructions of the torn primary static stabilizers and repair of the capsular structures and any tendinous avulsions are performed in a single-stage. Open anteromedial or posterolateral incisions are preferentially performed first to identify the torn structures and to prepare the posterolateral corner (PLC) and medial knee reconstruction tunnels. Next, arthroscopy allows preparation of the anterior cruciate ligament (ACL) and double-bundle (DB) posterior cruciate ligament (PCL) tunnels. Careful attention to tunnel trajectory minimizes the risk for convergence. Meniscal tears are preferentially repaired (root and ramp tears are commonly seen in this patient group). Graft passage is performed after all tunnels are reamed. The graft tensioning and fixation sequence is as follows: anterolateral bundle of the PCL to restore the central pivot, posteromedial bundle of the PCL, ACL, PLC (including fibular [lateral] collateral ligament), and posteromedial corner (including medial collateral ligament). Graft integrity and full knee range of motion should be verified before closure. Physical therapy commences on postoperative day 1 with immediate knee motion (flexion from 0°-90°; prone for DB-PCL reconstruction) and quadriceps activation. Patients are nonweightbearing for 6 weeks. Patients with ACL-based reconstructions wear an immobilizer for 6 weeks then transition to a hinged ACL brace. Patients with PCL-based reconstructions transition into a dynamic PCL brace once swelling subsides and wear it routinely for 6 months. Functional testing and stress radiography are performed to validate return to sports., (Copyright © 2021 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To perform an updated systematic review of the anatomy, biomechanics, function of the anterolateral ligament (ALL), and the clinical outcomes of anterolateral ligament reconstruction (ALLR) when performed in conjunction with anterior cruciate ligament reconstruction (ACLR)., Methods: A systematic search of the literature was performed by searching PubMed, the Cochrane Library, and Embase with the search phrase anterolateral ligament for articles published from February 2017 to May 2020. Inclusion criteria included studies that evaluated the anatomy, function, or biomechanics of the ALL; surgical technique articles on ALLR; clinical articles reporting outcomes of ALLR; studies published in English; and full-text articles. Exclusion criteria included studies published before February 2017. A subjective synthesis was performed, in which ranges were reported, and individual study data were presented in forest plots., Results: Overall, 40 articles were included in this systematic review, with 11 articles describing ALL anatomy, 14 articles analyzing ALL function and biomechanics, 7 articles discussing the surgical technique of combined ACLR and ALLR (ACLR/ALLR), and 8 articles describing the clinical outcomes of ACLR/ALLR. The addition of ALLR in combination with ACLR (ACLR+) results in lower graft failure rates for ACLR/ALLR (0.0%-15.7%) when compared with isolated ACLR (I-ACLR) patients (7.4%-21.7%). Three of 5 studies using the Subjective International Knee Documentation Committee score, 2 of 5 studies using the Lysholm score, and 1 of 2 studies using the Tegner score reported significantly better scores at latest follow-up among ACLR+ patients compared with I-ACLR (P < .05)., Conclusions: The ALL acts as a secondary stabilizer to the anterior cruciate ligament and helps resist internal knee rotation and anterior tibial translation. Based on the current literature, combined ACLR with ALLR may result in lower graft failure rates and improved patient-reported outcomes when compared with I-ACLR in patients with specific indications, although several studies have shown equivalent outcomes between these 2 cohorts., Clinical Relevance: The contents of this review provide great insight for orthopaedic surgeons who are performing ACLR and considering additional procedures to increase overall knee stability and decrease likeliness for re-rupture. The postoperative functional and clinical outcomes shown in patients undergoing ACLR+ compared with I-ACLR should be given proper consideration when evaluating available treatment courses., (Copyright © 2020 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To determine the statistical and predictive correlation between instrumented Lachman and pivot-shift tests with progressive loss of anterior cruciate ligament (ACL) function., Methods: The kinematic correlations between pivot-shift and Lachman anterior tibial translations (ATTs) in ACL-deficient and ACL-reconstructed states and in partially lax ACL grafts were determined with precise robotic testing in cadaveric knees. The Lachman test (100-N anteroposterior) and 2 pivot-shift loadings were conducted: anterior tibial loading (100 N), valgus rotation (7 Nm), and internal rotation (5 Nm and 1 Nm). The tibia was digitized to study the resulting medial, central, and lateral tibiofemoral compartment translations. In group 1 knees, 15 bone-patellar tendon-bone reconstructions were first tested, followed by ACL graft loosening with 3- and 5-mm increases in Lachman ATT. In group 2, 43 knees underwent robotic testing before and after ACL sectioning and underwent analysis of the effect of 3- and 5-mm increases in Lachman ATT and complete ACL sectioning on pivot-shift compartment translations., Results: In group 1 knees, ACL graft loosening allowing a 3-mm increase in Lachman ATT resulted in increases in pivot-shift lateral compartment translation (lateral compartment ATT) of only 1.6 ± 0.3 mm and 2.2 ± 1.0 mm (internal rotation of 5 Nm and 1 Nm, respectively) that were one-half of those required for a positive pivot-shift test finding. In group 2, for a 3-mm increased Lachman test, there were no positive pivot-shift values. In both groups, a Lachman test with an increase in ATT of 3 mm or less (100 N) had a 100% predictive value for a negative pivot-shift test finding. With ACL graft loosening and a 5-mm increase in the Lachman ATT, group 1 still had no positive pivot-shift values, and in group 2, a positive pivot-shift test finding occurred in 3 of 43 knees (7%, pivot shift 1-Nm internal rotation). After ACL sectioning, a highly predictive correlation was found between abnormal increases in Lachman and pivot-shift translations (P < .001)., Conclusions: ACL graft slackening and an instrumented Lachman test with an increase in ATT of 3 mm or less were 100% predictive of a negative pivot-shift subluxation finding and retained ACL stability. Further graft slackening and a 5-mm increase in the Lachman ATT produced pivot-shift lateral compartment ATT increases still less than the values in the ACL-deficient state; however, 7% of the knees (3 of 43) were converted to a positive pivot-shift test finding indicative of ACL graft failure., Clinical Relevance: Instrumented Lachman tests provide objective data on ACL function and graft failure to supplement subjective pivot-shift tests and are highly recommended for single-center and multicenter ACL studies. In the past decade, a near majority of published ACL studies no longer reported on instrumented Lachman tests, relying solely on highly subjective pivot-shift grading by multiple examiners., (Copyright © 2020 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

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 investigate the changes in landing biomechanics over a 3-year period and their correlation with cartilage degenerative changes in the medial tibiofemoral joint of the knee after anterior cruciate ligament reconstruction (ACLR) using magnetic resonance T1ρ mapping., Methods: Thirty-one anterior cruciate ligament-injured patients underwent magnetic resonance imaging of the injured knee before ACLR and 3 years after ACLR, as well as biomechanical analysis of a drop-landing task at 6 months and 3 years after ACLR. Sixteen healthy individuals were recruited and underwent knee magnetic resonance imaging and biomechanical assessment during a drop-landing task. T1ρ cartilage relaxation times were calculated for the medial femur and tibia., Results: ACLR patients exhibited increased peak vertical ground reaction force (VGRF), VGRF impulse, peak knee flexion moment (KFM), and KFM impulse from 6 months to 3 years (P < .001 for each). Although the ACLR knees showed significantly lower peak VGRF and KFM at 6 months (P < .001 for both) when compared with the controls, there were no significant differences at 3 years. At 3 years, ACLR patients showed higher T1ρ values over the medial femur (P < .001) and tibia (P = .012) when compared with their preoperative values and with healthy control values. Within the ACLR group, side-to-side differences in peak VGRF and sagittal knee biomechanics at 6 months were associated with increased T1ρ values from baseline to 3 years., Conclusions: The results of this longitudinal study show that landing biomechanics are altered after ACLR but biomechanical abnormalities tend to recover at 3 years after ACLR. Differences in lower-extremity mechanics during a landing task at 6 months may be associated with cartilage degeneration at 3 years after anterior cruciate ligament injury and reconstruction., Level of Evidence: Level II, prospective trial., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the effect of progressive lesions of the anterior cruciate ligament (ACL) and anterolateral ligament (ALL) on anterior tibial translation (ATT) as evaluated through the Lachman test and internal tibial rotation (ITR) during a dynamic pivot-shift test in a cadaveric model., Methods: A total of 7 specimens were tested using a navigation system (2.2 OrthoPilot ACL navigation system). The anterior stability of the knee was measured through the Lachman test and dynamic rotational stability was measured through the pivot-shift test in 3 different conditions: intact knee; ACL-deficient knee; and finally, ACL- and ALL-deficient knee. The resulting measurements from the navigation system recorded the real-time changes in both translation and internal rotation during the Lachman and pivot-shift maneuvers., Results: Mean ATT was 7.57 ± 0.53 mm in the intact knee, 14 ± 2.44 mm in the ACL-deficient knee, and 14 ± 2.44 mm in the ACL- and ALL-deficient knee. Mean ITR during the pivot-shift test was 10.14° ± 2.26° in the intact knee, 12.14° ± 2.19° in the ACL-deficient knee, and 18.86° ± 2.73° in the ACL- and ALL-deficient knee. There was a statistically significant difference in static ATT between the intact and ACL-deficient knees (P = .039) but no difference through the addition of an ALL lesion (P = .068). For dynamic rotational control testing, there was no significant difference in ATT between groups but a significant difference in ITR was found (F = 25.17, P = .00034)., Conclusions: During the pivot-shift test, a combined lesion of the ACL and ALL has a significant effect on ITR whereas an isolated lesion of the ACL has no effect on either ATT or ITR. During the Lachman test, an isolated lesion of the ACL has a significant effect on ATT but an additional lesion of the ALL does not affect ATT., Clinical Relevance: Dynamic rotational control as tested by the pivot-shift test is greatly influenced by a combined lesion of the ACL and ALL. In clinical cases of a pivot shift, addressing the anterolateral structures may be considered., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

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: The purpose of this systematic review and meta-analysis was to evaluate the effect of the timing of anterior cruciate ligament (ACL) reconstruction on clinical and stability outcomes by analyzing high-quality studies that assessed timing as a primary objective., Methods: The MEDLINE, EMBASE, and Cochrane database were systematically searched. The inclusion criteria were as follows: (1) English articles, (2) noncomparative study or relevant study reporting clinical and/or stability results, and (3) timing of the ACL reconstruction as a primary objective. Study type, level of evidence, randomization method, exclusion criteria, number of cases, age, sex, timing of ACL reconstruction, follow-up, clinical outcomes, stability outcomes, and other relevant findings were recorded. Statistical analysis of the Lysholm scores and KT-1000 arthrometer measurements after early and delayed ACL reconstruction was performed using R version 3.3.1., Results: Seven articles were included in the final analysis. There were 6 randomized controlled trials and 1 Level II study. Pooled analysis was performed using only Level I studies. All studies assessed the timing of ACL reconstruction as a primary objective. The definition of early ranged broadly from 9 days to 5 months and delayed ranged from 10 weeks to >24 months, and there was an overlap of the time intervals between some studies. The standard timing of the delayed reconstruction was around 10 weeks from injury in the pooled analysis. After pooling of data, clinical result was not statistically different between groups (I 2 : 47%, moderate level of heterogeneity). No statistically significant difference was observed in the KT-1000 arthrometer measurements between groups (I 2 : 76.2%, high level of heterogeneity) either., Conclusion: This systematic review and meta-analysis performed using currently available high-quality literature provides relatively strong evidence that early ACL reconstruction results in good clinical and stability outcomes. Early ACL reconstruction results in comparable clinical and stability outcomes compared with delayed ACL reconstruction., Level of Evidence: Level II, a systematic review and meta-analysis of Level I and II studies., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the effect of the anterior cruciate ligament (ACL) torsion in 90° knee flexion on the morphological appearance of the ACL., Methods: Sixty knees from fresh frozen anatomical specimens were dissected. Eighteen knees were excluded according to selection criteria (torn ACL, mucoid degeneration of the ACL, arthritic lesions of the notch, or knees harboring synovial inflammatory pathologies). After the removal of the synovial membrane, the morphology of the ligamentous fibers of the ACL and the twist were analyzed. Twisting of the ACL was measured using a goniometer in 90° knee flexion and defined by the angle of external rotation of the femur on the axis of the tibia required to visualize a flat ACL. The orientation of tibial and femoral footprint was described in a coronal plane for the tibia and a sagittal plane for the femur., Results: In the 42 knees that were finally included, the ACL was always displayed as a single ribbon-like structure. The torsion of the fibers was on average 83.6° (± 9.4°) in 90° knee flexion. The twisting could be explained by the different orientations of the femoral (vertical in a sagittal plane) and tibial (horizontal in a coronal plane) footprints. An intraligamentous proximal cleavage area was encountered in 11 cases (i.e., 26%)., Conclusions: The ACL is a twisted structure with 83.6° of external torsion of fibers in 90° knee flexion. It is the torsion in the fibers, due to the relative position of bone insertions, which gives the ACL the appearance of being double bundle., Clinical Relevance: The concept of the torsional flat structure of the native ACL may be of importance during ACL reconstruction, both in terms of graft choice (flat rather than cylindrical) and of technical positioning (torsion)., (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 quantitatively the biomechanical function of anterior cruciate ligament (ACL) remnants in patients with ACL injuries. Anterior tibial translation (ATT) with KT-1000 and during the Lachman test with an electromagnetic measurement system (EMS) and tibial acceleration during the pivot shift test with EMS were measured., Methods: A total of 121 unilateral ACL injuries were examined. ACL remnants were morphologically classified as being attached to the posterior cruciate ligament (PCL group), to the roof of the intercondylar notch (RIN group), to the lateral wall of the intercondylar notch (LWIN group), or as having no substantial remnants (NONE group). Partial ACL tears were excluded. ATT was measured using KT-1000. ATT during the Lachman test and tibial acceleration during the pivot shift test were measured using EMS., Results: ACL remnant patterns were as follows: PCL group, 27 knees; RIN group, 34 knees; LWIN group, 27 knees; and NONE group, 33 knees. The ATT side-to-side difference in LWIN group (3.4 ± 0.7 mm) by KT-1000 was significantly smaller than the RIN (5.7 ± 1.0 mm) and NONE groups (5.9 ± 1.0 mm) (P < .05). The ATT side-to-side difference during the Lachman test was significantly smaller in the LWIN group (5.3 ± 1.2 mm) than the PCL (8.6 ± 1.4 mm), RIN (8.5 ± 1.2 mm), and NONE groups (7.6 ± 1.0 mm) (P < .05). Tibial accelerations were 2.0 ± 0.4, 1.7 ± 0.2, 1.9 ± 0.2, and 1.8 ± 0.3 m/s(2) in the PCL, RIN, LWIN, and NONE groups, respectively. There were no significant differences among groups., Conclusions: ACL remnants attached to the lateral wall of the intercondylar notch partially contributed to anterior-posterior stability but did not contribute to dynamic knee stability. These findings suggest that ACL remnants attached to nonanatomic insertion sites do not contribute significantly to knee stabilization., Level of Evidence: Level III, diagnostic study of nonconsecutive patients., (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: To conduct a systematic review to identify and summarize the various techniques that have been used to simulate the pivot-shift test in vitro., Methods: Medline, Embase, and the Cochrane Library were screened for studies involving the simulated pivot-shift test in human cadaveric knees published between 1946 and May 2014. Study parameters including sample size, study location, simulated pivot-shift technique, loads applied, knee flexion angles at which simulated pivot shift was tested, and kinematic evaluation tools were extracted and analyzed., Results: Forty-eight studies reporting simulated pivot-shift testing on 627 cadaveric knees fulfilled the criteria. Reviewer inter-rater agreement for study selection showed a κ score of 0.960 (full-text review). Twenty-seven studies described the use of internal rotation torque, with a mean of 5.3 Nm (range, 1 to 18 Nm). Forty-seven studies described the use of valgus torque, with a mean of 8.8 Nm (range, 1 to 25 Nm). Four studies described the use of iliotibial tract tension, ranging from 10 to 88 N. Regarding static simulated pivot-shift test techniques, 100% of the studies performed testing at 30° of knee flexion, and the most tested range of motion in the continuous tests was 0° to 90°. Anterior tibial translation was the most analyzed parameter during the simulated pivot-shift test, being used in 45 studies. In 22% of the studies, a robotic system was used to simulate the pivot-shift test. Robotic systems were shown to have better control of the loading system and higher tracking system accuracy., Conclusions: This study provides a reference for investigators who desire to apply simulated pivot shift in their in vitro studies. It is recommended to simulate the pivot-shift test using a 10-Nm valgus torque and 5-Nm internal rotation torque. Knee flexion of 30° is mandatory for testing., Level of Evidence: Level IV, systematic review of basic science studies., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To determine the initial minimal tension for restoring knee stability during double-bundle anterior cruciate ligament (ACL) reconstruction in vivo., Methods: Patients who underwent primary double-bundle ACL reconstruction with an autologous semitendinosus tendon during 2012 were included. The bundles were fixed to a graft-tensioning system during surgery. Initial graft tensions were set to the following tensions per 6 mm in graft diameter: (1) 30 N, (2) 25 N, and (3) 20 N. Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. In addition, anterior knee laxity was measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA), and the pivot-shift test was evaluated., Results: Sixty patients were evaluated. The tension curves of both bundles among different initial tension settings were significantly different (P < .0001), with the tension in the 30-N setting being highest and that in the 20-N setting being lowest. The tension in both bundles showed reciprocal pattern during flexion-extension (P = .019). The tension of the posterolateral bundle graft was significantly lower than that of the anteromedial bundle graft in response to the anterior load at all settings (P = .0017, P = .0019, and P = .0021 at 30° in the 30-N, 25-N, and 20-N settings, respectively, and P < .0001 at 90° at all settings), whereas the tensions in both bundles in response to rotatory loads were equivalent. Two cases showed a grade 1 pivot shift in the 20-N setting, whereas no case showed a positive pivot shift in the other settings. KT measurements in the 30-N and 25-N settings showed no difference., Conclusions: In double-bundle ACL reconstruction, initial tension could be set as low as 25 N; however, initial tension of 20 N is not recommended because it might result in residual pivot shift in some cases, although the pivot-shift difference was not significant., Level of Evidence: Level IV, therapeutic case series., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the effect of high axial loading (AL) on anterior tibial translation (ATT) according to the increase in knee flexion and the effect of valgus stress (VS) and internal rotation (IR) combined with high AL in intact and anterior cruciate ligament (ACL)-deficient knees according to the increase in knee flexion., Methods: We used 10 fresh-frozen, human cadaveric knees. Different loading conditions (134-N anterior drawer, 1,000-N AL, 10-Nm VS, and 5-Nm IR) were sequentially combined, and ATT was measured at 0°, 15°, 30°, 45°, and 60° of flexion in the intact and ACL-deficient knees., Results: ATT increased significantly by adding high AL in intact knees (P = .001) and ACL-deficient knees (P < .0001) according to the change in flexion angle (P < .0001). Under high AL, ATT in the ACL-deficient knees was significantly larger than that in the intact knees for all loading conditions, and it also increased gradually according to the increase in knee flexion (P = .0001). ATT increased significantly after adding IR or VS with high AL in intact knees (VS, P = .002; VS/IR, P = .03) and ACL-deficient knees (VS, P = .0004) at some of the flexion angles., Conclusions: The added high AL increased ATT in intact and ACL-deficient knees from 0° to 60° of flexion. The effect of high AL on ATT became greater in ACL-deficient knees than in intact knees, and ATT also gradually increased according to the increase in knee flexion from 0° to 60°. In both the intact and ACL-deficient knees, ATT increased significantly after valgus stress or IR from 0° to 60°., Clinical Relevance: ATT during weight bearing increases stress to the ACL, which worsens with valgus stress and/or IR forces. This finding should be considered when one is studying ACL injury mechanisms, as well as prescribing rehabilitation after ACL surgery., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: This study analyzed the interaction of the anteromedial and posterolateral portions of the anterior cruciate ligament (ACL) in resisting medial and lateral tibiofemoral compartment subluxations under multiple loading conditions., Methods: By use of a 6-df robotic simulator, 10 human cadaveric knees were tested in 3 states: intact ACL, partial ACL (loss of either the anteromedial bundle [AMB] or posterolateral bundle [PLB]), and deficient ACL. The testing profile involved anterior-posterior translation and internal-external rotation, as well as 3 pivot-shift loading conditions with varying internal rotation torque (1- or 5-Nm) and coupled anterior force (35- or 100-N). Digitization of anatomic landmarks provided tibiofemoral compartment translations and centers of tibial rotation., Results: During pivot-shift testing (100-N anterior force, 1-Nm internal rotation torque, and 7-Nm valgus), the lateral and medial compartment anterior translation increased by a mean of 2.5 ± 0.8 mm (P = .016) and 3.4 ± 2.0 mm (P = .001), respectively, on AMB sectioning and 1.3 ± 0.9 mm (P = .329) and 0.6 ± 0.7 mm (P = .544), respectively, on PLB sectioning. Higher internal rotation torque (5 Nm v 1 Nm) on pivot-shift testing reduced central and medial anterior translation after ACL sectioning. There was no change in internal rotation on AMB or PLB sectioning. During the Lachman test (100-N), AMB and PLB sectioning increased central translation by 3.6 ± 1.6 mm (P = .001) and 0.7 ± 0.6 mm (P = .498), respectively., Conclusions: Both ACL bundles function synergistically in resisting medial and lateral compartment subluxations on the Lachman and pivot-shift tests. The AMB provided more restraint to anterior tibial translation during both tests as compared with the PLB. PLB sectioning produced no statistically significant change in anterior translation on the Lachman or pivot-shift test. Neither bundle contributed to resisting internal rotation., Clinical Relevance: An ACL graft designed to duplicate the AMB would theoretically resist medial and lateral compartment anterior subluxations under multiple loading conditions. The PLB provides a secondary restraint at low flexion angles. Neither ACL bundle resists internal tibial rotation or allows a positive pivot-shift subluxation., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to evaluate the effectiveness of 2 anterior cruciate ligament (ACL) reconstruction techniques using a bone-patellar tendon-bone (BPTB) graft with femoral tunnel, either a rectangular tunnel (RET) or a round tunnel (ROT)., Methods: For experiment 1, nine fresh-frozen human cadaveric knees were tested with a robotic/universal force-moment sensor system to determine the initial optimal tension: the amount of graft tension at 15° of flexion most closely resembling the anterior laxity of a normal knee. The value was estimated by repeatedly measuring anterior laxity when 100 N of anteroposterior drawer load was applied to the knees at 30° of flexion after RET ACL or ROT ACL reconstruction. For experiment 2, six fresh-frozen human cadaveric knees were selected. On the basis of the initial tension determined in experiment 1, RET ACL reconstruction was conducted with the graft tensioned to 10 N, followed by ROT ACL reconstruction on the same knee at 40 N of initial tension, and the biomechanical efficacy of the 2 methods was compared., Results: For experiment 1, the mean laxity match tension at 15° of flexion was 8.6 ± 4.8 N and 34.8 ± 9.2 N for RET- and ROT-reconstructed knees, respectively. For experiment 2, both RET and ROT ACL reconstructions were successful in controlling anterior tibial translation under anterior tibial loads, with the graft initially tensioned to 10 N in the former and to 40 N in the latter. However, the greater tensioning in ROT reconstruction led to proximal, posterior, and lateral displacement of the tibia along with its external and valgus rotation., Conclusions: The RET ACL-reconstructed knee more closely resembled the normal knee in biomechanical behavior. Although ROT reconstruction successfully controlled anterior translation with greater initial tensioning to the graft, the normal positional relation between the tibia and femur was impaired., Clinical Relevance: Rectangular femoral ACL fixation constructs and grafts may prove more efficacious at restoring in vivo ACL kinematics than round femoral tunnels., (Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to clarify the changes in the kinematics of the knee that result from isolated deficiency of the anteromedial (AM) or posterolateral (PL) bundle., Methods: Fourteen cadaveric knees were mounted in a 6-df rig and tested using the following 5 loading conditions: 90-N anterior and posterior tibial loads, 5-Nm internal and external tibial torques, and a simulated pivot-shift test. Tibiofemoral kinematics during flexion-extension was recorded with an optical tracking system for (1) intact knees, (2) knees in which the isolated AM bundle was cut, (3) knees in which the isolated PL bundle was cut, and (4) anterior cruciate ligament (ACL)-deficient knees. The distances between the femoral and tibial attachments of the AM and PL bundles of the ACL were also calculated., Results: Anterior translation laxity under an anterior tibial load, rotational laxity under an internal tibial torque, and anterior translation laxity under pivot-shift loading were significantly different between the knees with AM and PL bundle deficiencies (P < .024), but the changes were small: less than 3 mm or 1.5°. The AM bundle distance increased significantly more after an AM bundle tear (P = .004) than after a PL bundle tear in flexion. Cutting the PL bundle did not have a significant effect on the lengths between the bundle attachments., Conclusions: An isolated AM or PL bundle tear caused a small increase in laxity (<3 mm or <1.5°)., Clinical Relevance: If there is a clinically identifiable increase in laxity, then--in addition to the isolated tear of the AM or PL bundle--there must also be a tear of the other bundle of the ACL, or at least a partial tear., (Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The objective of this study was to validate a new technique to safely obtain core biopsy specimens of the anterior cruciate ligament (ACL) without jeopardizing the ACL's biomechanical properties., Methods: Eleven pairs of fresh porcine femur-ACL-tibia complexes were tested in a loading frame. The ACL of one knee was biopsied using a spring-loaded core biopsy device, whereas the contralateral ACL was tested as the control. Biomechanical properties of the biopsied and control ACLs were compared., Results: The ultimate load to failure was 1,202 N ± 171.1 N and 1,193 N ± 228.7 N (P = .8984) for biopsied and non-biopsied ACLs, respectively. No significant differences were noted for maximal elongation at failure, maximal strain, absorbed energy, and stiffness between biopsied and non-biopsied ACLs., Conclusions: The results of this study indicate that a new ACL core biopsy technique can be performed while preserving the ligament's structural integrity., Clinical Relevance: The presented core biopsy technique could be regarded as a dedicated tool to elucidate the poorly understood (patho)biological processes occurring in both the native and reconstructed ACLs., (Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to compare the functional outcome, ligament laxity, and tibial tunnel enlargement between 3-tunnel double-bundle (DB) anterior cruciate ligament (ACL) and single-bundle (SB) ACL reconstruction., Methods: This retrospective study identified primary arthroscopic ACL reconstruction from July 2006 to July 2008. The cohort consisted of 50 knees in 49 patients, comprising 26 knees with SB ACL reconstruction and 24 with DB ACL reconstruction. Semitendinosus autograft was used in SB ACL reconstruction, and semitendinosus and gracilis grafts were used in DB ACL reconstruction. Both groups received the same rehabilitation protocol postoperatively. The evaluations included functional assessment, ligament laxity, and radiographs of the knee. Functional assessments included a pain score, the Lysholm functional score, the Tegner activity score, and the grade on the International Knee Documentation Committee knee examination form. Ligament laxity was measured by the anterior drawer test, Lachman test, pivot-shift test, and KT-1000 arthrometer (MEDmetric, San Diego, CA) testing. It was graded as 0 for no laxity, 0 to 5 mm for mild laxity, 5 to 10 mm for moderate laxity, and 10 to 15 mm for severe laxity. Radiographs of the knee were used for the evaluation of bony appearance, alignment of the knee, joint space narrowing, and measurement of the tibial tunnel., Results: Significant improvements in knee function and ligament laxity were noted after surgery in both groups. However, no statistical differences in functional scores and ligament laxity were noted between the 2 groups (P = .275 and P = .413, respectively). A mild increase in laxity was noted in 3 cases (14%) in the DB ACL reconstruction group and 3 cases (13%) in the SB ACL reconstruction group. A moderate increase in laxity was noted in 2 cases (9%) in the SB ACL reconstruction group and none in the DB ACL reconstruction group. Radiographic evaluations showed no statistical difference between the 2 groups (P = .114)., Conclusions: Both 3-tunnel Y-graft DB ACL reconstruction and SB ACL reconstruction significantly improved the function and stability of the knee after surgery., Level of Evidence: Level IV, therapeutic case series., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To determine the effect of remnant preservation on the healing of anterior cruciate ligament (ACL) tendon graft after reconstruction in an animal model., Methods: Fifty-two New Zealand rabbits were divided into 6 groups. Revascularization and graft healing were studied in groups 1 through 4 (n = 8 each). The biomechanical properties of the graft complex were evaluated in group 5 (n = 12). The blood flow and biomechanical characteristics of the intact ACL were evaluated in group 6 (n = 8). Both knees of each rabbit were subjected to ACL reconstruction with 2-mm grafts of Achilles tendon splits. The right knees were reconstructed with remnant preservation, whereas the remnants in the left knees were debrided. The revascularization and remodeling of grafts were evaluated at 6, 12, 18, and 24 weeks after reconstruction. Tendon-to-bone integration was investigated histomorphologically. The tensile load strengths of graft complexes were also tested., Results: The blood flow in the graft was significantly higher in the remnant-preserved group than in the remnant-debrided group (P < .01). Specifically, the blood flow of the graft with remnant preservation was markedly enhanced at 6 weeks and 12 weeks after reconstruction (P < .05). The number of CD34-positive vessels in the graft was higher in the remnant-preservation group (P < .05). The ligamentization and remodeling of the graft were improved and the collagen type III content in the graft was higher in the remnant-preserved group (P < .05). Tendon-to-bone integration was improved by remnant preservation. At 24 weeks after reconstruction, the failure load of the graft complex was significantly higher in the remnant-preserved group (23.46 ± 7.40 N) than in the remnant-debrided group (18.63 ± 4.26 N) (P < .05)., Conclusions: The preservation of the remnant attachment in ACL reconstruction improved the revascularization and remodeling of the graft and enhanced the biomechanical properties of the integrated graft., Clinical Relevance: Preservation of the remnant attachment may benefit healing of the tendon graft in ACL reconstruction., (Copyright © 2013 Arthroscopy Association of North America. All rights reserved.)

Purpose: This study aimed to undertake a retrospective analysis of prospectively collected data comparing, at a minimum follow-up of 5 years (78.1 ± 5.3 months v 75.6 ± 4.8 months), the clinical, functional, and radiographic outcomes of 2 homogeneous groups of athletes who had undergone arthroscopic single-bundle autologous hamstring reconstruction of the anterior cruciate ligament (ACL) using a transtibial (TT) or an anteromedial portal (AMP) approach to drill the femoral tunnel., Methods: Ninety-four patients were operated on in 2005 and 2006, and 88 (93.6%) (73 men, 15 women) were evaluated subjectively and objectively, using the Lysholm and International Knee Documentation Committee (IKDC) scores, manual maximum displacement test with a KT-1000 arthrometer (MEDmetric, San Diego, CA) and the Lachman test, and rotational instability with the pivot shift test. Degenerative changes were assessed on radiographs according to the Fairbank classification., Results: The median age at operation was 29 years (20 to 43 years; SD, 5.4) in the TT group 1 and 28 years (19 to 45 years; SD, 6.1) in the AMP group 2. At the last appointment, the 2 groups had similar results for the Lysholm and IKDC scores (primary outcome). Patients who underwent the AMP approach had less glide pivot shift (P = .42) and Lachman (P = .47) phenomena, with no statistically significant intergroup difference. Radiography showed fewer, but not significantly different, degenerative changes in the AMP ACL reconstruction group at final follow-up (P = .47)., Conclusions: In our series, ACL reconstruction using a femoral tunnel drilled through an AMP provided better rotational stability and anterior translation than drilling the femoral tunnel using the TT technique. This difference likely is not relevant from a clinical and functional viewpoint. The 2 groups of patients were not significantly different in terms of development of degenerative changes seen radiographically at a minimum follow-up of 5 years., Level of Evidence: Level III, retrospective comparative study., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: We compared functional outcomes after primary hamstring-graft anterior cruciate ligament (ACL) reconstruction in patients with different body mass index (BMI) classes., Methods: Functional outcomes after ACL reconstruction were measured using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Lysholm score. The procedures were carried out by a single surgeon between 2001 and 2009 in 2 groups of patients with different BMI classes: a normal-BMI group (BMI 18.5 to 24.9) and a high-BMI group (BMI ≥ 25), with a minimum of 2 years' follow-up. Rolimeter readings for ligament laxity as well as complications between the 2 groups were also analyzed., Results: A total of 92 patients were reviewed, with the normal-BMI group consisting of 49 patients, whereas there were 43 patients in the high-BMI group. There were no significant differences between the groups in any of the preoperative and postoperative scores or ligament laxity. Both groups showed comparable clinically significant improvement in their postoperative scores compared with their preoperative scores. Patients in the high-BMI group had a slightly increased postoperative complication rate when compared with the normal-BMI group., Conclusions: Primary hamstring ACL reconstruction is an effective treatment option in patients irrespective of preoperative BMI. High BMI does not adversely affect functional outcomes as measured by the KOOS and Lysholm scores up to and at 2 years postoperatively, and these patients benefit in a manner comparable to that of patients with normal BMI., Level of Evidence: Level III, retrospective comparative study., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purposes of this study were to assess tissue ingrowth within the Ligament Advanced Reinforcement System (LARS) artificial ligament (LARS AC; LARS, Arc sur Tille, France) and to study the biomechanical characteristics of the reconstructed knees in a sheep model of anterior cruciate ligament (ACL) replacement., Methods: Twenty-five female sheep underwent excision of the proximal third of the left ACL and intra-articular joint stabilization with a 44-strand polyethylene terephthalate ligament (mean ultimate tensile failure load, 2,500 N). Animals were killed either 3 or 12 months after surgery. Explanted knees were processed for histology (n = 10) or mechanical tests including tests of laxity and loading to failure in tension (n = 15)., Results: Well-vascularized tissue ingrowth within the artificial ligament was only observed in the portions of the ligament in contact with the host's tissues (native ligament and bone tunnels). Ligament wear was observed in 40% of explanted knees. The ultimate tensile failure loads of the operated knees at both time points were inferior to those of the contralateral, intact knees (144 ± 69 N at 3 months and 260 ± 126 N at 12 months versus 1,241 ± 270 N and 1,218 ± 189 N, respectively) (P < .01). In specimens with intact artificial ligaments, failure occurred by slippage from the bone tunnels in all specimens explanted 3 months postoperatively and in half of the specimens explanted 12 months postoperatively., Conclusions: This study provides evidence that the LARS AC has a satisfactory biointegration but that it is not suitable for ACL replacement if uniform tissue ingrowth is contemplated. Despite good clinical performance up to 1 year after implantation, none of the reconstructions approached the mechanical performance of the normal ACL in the ovine model. Partial tearing of the artificial ligament, which led to a significant decrease in ultimate tensile strength, was observed in 40% of cases in the ovine model., Clinical Relevance: The LARS is not a suitable scaffold for ACL replacement. Further animal studies are needed to evaluate its potential for augmentation of ligament repair., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the biomechanical function of anterior cruciate ligament (ACL) remnants in ACL-deficient knees with both partial and complete tears., Methods: Twenty partial ACL-deficient (group P), 20 complete ACL-deficient (group C), and 40 contralateral ACL-intact knees were examined. The end point during the Lachman test, side-to-side differences of KT-1000 measurements, and the pivot shift test were evaluated. Additionally, the side-to-side difference of anterior tibial translation during the Lachman test and the acceleration during the pivot shift test were calculated using an electromagnetic measurement system (EMS)., Results: The end point was found in 9 patients in group P, whereas it was not detected in group C. In KT-1000 measurements, the mean side-to-side differences were 3.8 ± 2.4 mm in group P and 5.4 ± 2.3 mm in group C. There was a significant difference between these 2 groups (P < .05). In the pivot shift test evaluation in group P, one patient was evaluated as grade 0, 17 patients as grade 1+, and 2 patients as grade 2+. In group C, 10 patients were evaluated as grade 1+, 9 patients as grade 2+, and one patient as grade 3+. Using the EMS, mean side-to-side differences during the Lachman test were 3.1 ± 2.1 mm in group P and 7.2 ± 3.2 mm in group C. The anterior-posterior displacement in group P was significantly less than that in group C (P < .05). In the quantitative pivot shift test, the mean acceleration in the contralateral ACL-intact knees was -632.7 ± 254.5 mm/s(2), whereas it was -1107.5 ± 398.9 mm/s(2) in group P and -1652.2 ± 754.9 mm/s(2) in group C. Significant differences were detected between the 3 knee conditions (P < .05)., Conclusions: The quantitative assessments of knees with partial ACL ruptures during the Lachman test and the pivot shift test using the EMS showed less laxity than did knees with complete ACL tears, whereas their laxity was greater than the contralateral knees with intact ACLs., Level of Evidence: Level III, diagnostic study of nonconsecutive patients., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the effect of posterolateral bundle (PLB) graft fixation angles on graft tension curves and load sharing between the anteromedial bundle (AMB) and the PLB in double-bundle anterior cruciate ligament (ACL) reconstruction., Methods: Twenty-four patients who underwent double-bundle ACL reconstruction were included in this study. AMB and PLB were provisionally fixed to a graft tensioning system during surgery. The graft fixation settings were as follows: (1) AMB at 20° and PLB at 0° (A20P0), (2) AMB at 20° and PLB at 20° (A20P20), and (3) AMB at 20° and PLB at 45° (A20P45). Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. A pivot-shift test, as well as factors affecting the residual pivot-shift, was also evaluated., Results: A20P45 created reciprocal tension curves and load sharing, in which the tension in both bundles was equivalent during flexion-extension and during each loading test at 30°. In A20P0, the tension of the AMB was constantly higher than that of the PLB. Seven patients showed grade 1 pivot-shift phenomenon in A20P0, whereas no patient showed a positive pivot-shift at other settings. Larger tension reduction of the PLB between 0° and 30° and smaller load sharing of the PLB were significant factors affecting residual pivot-shift., Conclusions: In double-bundle ACL reconstruction, fixation of the AMB at 20° and the PLB at 45° created reciprocal tension curves and load sharing between the bundles. Fixation of the AMB at 20° and the PLB at 0° led to insufficient tension in the PLB, resulting in a residual pivot-shift phenomenon in 7 of 24 patients., Level of Evidence: Level IV, therapeutic case series., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The aim of this study was to determine the end-to-end distance changes in anterior cruciate ligament (ACL) fibers during flexion/extension and internal/external rotation of the knee., Methods: The positional relation between the femur and tibia of 10 knees was digitized on a robotic system during flexion/extension and with an internal/external rotational torque (5 Nm). The ACL insertion site data, acquired by 3-dimensional scanning, were superimposed on the positional data. The end-to-end distances of 5 representative points on the femoral and tibial insertion sites of the ACL were calculated., Results: The end-to-end distances of all representative points except the most anterior points were longest at full extension and shortest at 90°. The distances of the anteromedial (AM) and posterolateral (PL) bundles were 37.2 ± 2.1 mm and 27.5 ± 2.8 mm, respectively, at full extension and 34.7 ± 2.4 mm and 20.7 ± 2.3 mm, respectively, at 90°. Only 4 knees had an isometric point, which was 1 of the 3 anterior points. Under an internal torque, both bundles became longer with statistical meaning at all flexion angles (P = .005). The end-to-end distances of all points became longest with internal torque at full extension and shortest with an external torque at 90°., Conclusions: Only 4 of 10 specimens had an isometric point at a variable anterior point. The end-to-end distances of the AM and PL bundles were longer in extension and shorter in flexion., Clinical Relevance: The nonisometric tendency of the ACL and the end-to-end distance change during knee flexion/extension and internal/external rotation should be considered during ACL reconstruction to avoid overconstraint of the graft., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose was to analyze the association between posterior tibial slope (PTS) and mucoid degeneration of the anterior cruciate ligament (ACL)., Methods: From October 1999 to May 2010, 84 arthroscopies were performed in 82 patients (18 men and 64 women) with mucoid degeneration of the ACL. The mean patient age was 53 years (range, 25 to 75 years). In addition to this patient group (group I), the study included a control group without mucoid degeneration of the ACL that was randomly matched for age, sex, body mass index, left or right side, and associated lesions (group II). For each group, the diagnosis was made by use of magnetic resonance imaging and arthroscopy, and a plain lateral radiograph was used to measure the PTS., Results: The mean PTS was 13.5° ± 2.6° (range, 8.2° to 19.5°) in group I and 9.4° ± 2.5° (range, 4.8° to 15.5°) in group II. The mean PTS in group I was significantly greater than that in group II (P < .001). For group I, the mean PTS of the involved knee was significantly greater than that of the uninvolved contralateral knee (P = .044). There were no differences according to age, sex, left or right side, body weight, and body mass index (P > .05)., Conclusions: Mucoid degeneration of the ACL was found to be associated with an increased PTS. The patients with mucoid degeneration of the ACL had a greater mean PTS than matched control patients (13.5° v. 9.4°, P < .001)., Level of Evidence: Level III, diagnostic study of nonconsecutive patients without consistently applied gold standard., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the effect of coronal- and sagittal-plane anterior cruciate ligament (ACL) graft obliquity on tibial rotation (TR) range of motion (ROM) during dynamic pivoting activities after ACL reconstruction with bone-patellar tendon-bone (BPTB) autograft., Methods: We evaluated 19 ACL-reconstructed patients (mean age, 29 years; age range, 18 to 38 years; mean time interval postoperatively, 19.9 months) and 19 matched control subjects (mean age, 30.6 years; age range, 24 to 37 years) using motion analysis during (1) descending a stairway and pivoting and (2) landing from a jump and pivoting. Magnetic resonance imaging was used to measure the coronal and sagittal ACL graft angle. The dependent variables were TR ROM during pivoting and the side-to-side difference (SSD) in TR ROM between the reconstructed knee and the contralateral intact knee., Results: TR ROM of the ACL-reconstructed knee was significantly increased compared with both the contralateral intact knee and the healthy control knee (P < .05). A significant positive correlation was observed between TR ROM and coronal ACL graft angle (r = 0.727, P = .0006 for descending and pivoting; r = 0.795, P = .0001 for landing and pivoting) as well as between SSD of TR ROM and coronal ACL graft angle (r = 0.789, P < .0001 for descending and pivoting; r = 0.799, P < .0001 for landing and pivoting). No correlation was found with the sagittal ACL graft angle., Conclusions: After ACL reconstruction with a BPTB graft, patients' knees showed higher TR values than their uninjured knees and the knees of uninjured control volunteers during dynamic pivoting activities. The findings of this study show that TR was better restored in ACL-reconstructed patients with a more oblique graft in the coronal plane. A similar relation was not observed for graft orientation in the sagittal plane. Although these data do not imply a cause-and-effect relation between the 2 variables, they may indicate that a more oblique placement of a single BPTB ACL graft in the coronal plane is correlated with better control of TR., Level of Evidence: Level IV, case series., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: Anterior cruciate ligament (ACL) reconstruction is commonly performed in athletes, with the goal of return to sports activities. Unfortunately, this operation may fail, and the rates of either reinjuring an ACL-reconstructed knee or sustaining an ACL rupture to the contralateral knee range from 3% to 49%. One problem that exists is a lack of information and consensus regarding the appropriate criteria for releasing patients to unrestricted sports activities postoperatively. The purpose of this study was to determine the published criteria used to allow athletes to return to unrestricted sports activities after ACL reconstruction., Methods: A systematic search was performed to identify the factors investigators used to determine when return to athletics was allowed after primary ACL reconstruction. Inclusion criteria were English language, publication within the last 10 years, clinical trial, all adult patients, primary ACL reconstruction, original research investigation, and minimum 12 months' follow-up., Results: Of 716 studies identified, 264 met the inclusion criteria. Of these, 105 (40%) failed to provide any criteria for return to sports after ACL reconstruction. In 84 studies (32%) the amount of time postoperatively was the only criterion provided. In 40 studies (15%) the amount of time along with subjective criteria were given. Only 35 studies (13%) noted objective criteria required for return to athletics. These criteria included muscle strength or thigh circumference (28 studies), general knee examination (15 studies), single-leg hop tests (10 studies), Lachman rating (1 study), and validated questionnaires (1 study)., Conclusions: The results of this systematic review show noteworthy problems and a lack of objective assessment before release to unrestricted sports activities. General recommendations are made for quantification of muscle strength, stability, neuromuscular control, and function in patients who desire to return to athletics after ACL reconstruction, with acknowledgment of the need for continued research in this area., Level of Evidence: Level IV, systematic review of Level I to IV studies., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to use magnetic resonance (MR) imaging to evaluate the translational and rotational kinematics of anterior cruciate ligament (ACL) reconstructed knees with transtibial (TT) and anteromedial (AM) femoral tunnel drilling., Methods: ACL reconstruction was performed in 21 subjects: 12 with AM drilling (5 men and 7 women; mean age, 33 ± 9 years; imaged 18 ± 5 months after surgery) and 9 with TT drilling (5 men and 4 women; mean age, 32 ± 9 years; imaged 12 ± 8 months after surgery). Three-tesla MR imaging was obtained bilaterally at extension and 30° to 40° of flexion under simulated loading (125 N). MR images were segmented and kinematic calculations done with in-house MATLAB software (The MathWorks, Natick, MA). Translation and rotation of the tibia and the tibiofemoral contact area were measured. Statistical analysis treated reconstructed and contralateral knees as independent groups. Reconstructed groups were compared with analysis of covariance using contralateral knees as baseline. P < .05 indicated significance., Results: All kinematic measures in the AM group were similar to contralateral knees. The TT group showed significantly more total tibial rotation than contralateral knees (TT, 8.4° ± 3.9°; contralateral, 2.9° ± 6.8°) (P = .03), whereas the AM group did not (AM, 3.1° ± 5.6°; contralateral, 2.3° ± 5.4°) (P = .36). At knee extension, the tibia was more externally rotated in the TT group than in controls. Medial tibial translation was greater in the TT group than in controls. The AM group showed increased contact area in the lateral compartment compared with controls; no differences were seen in the TT group., Conclusions: Using an MR-based approach, we found that knee kinematics were better restored with the AM femoral tunnel drilling ACL reconstruction than with the TT femoral tunnel drilling approach, which resulted in increased knee laxity. Our in vivo results support previous cadaveric and clinical studies that have found AM ACL reconstruction to restore anatomy and stability better than the TT approach. However, the clinical significance of increased contact area in the AM group remains unclear., Level of Evidence: Level III, retrospective comparative study., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: This study aimed to assess knee laxity before and after resection of the anterior cruciate ligament (ACL) remnants, using a computer navigation system., Methods: This prospective study included 83 knees undergoing primary navigated ACL reconstruction. ACL remnants were classified into 4 morphologic types based on the arthroscopic findings: type 1, bridging between the posterior cruciate ligament and tibia; type 2, bridging between the roof of the intercondylar notch and tibia; type 3, bridging between the lateral wall of the intercondylar notch and tibia; and type 4, no substantial ACL remnants. Anterior tibial translation (ATT) and range of internal-external rotation of tibia (total rotation) at 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion were measured before and after resection of the ACL remnants by use of the additional functions of the navigation system., Results: The different morphologic types of the ACL remnants were as follows: type 1, 12 knees; type 2, 16 knees; type 3, 51 knees; and type 4, 4 knees. There were no significant differences in the mean ATT before and after resection at any knee flexion angle in type 1, 2, or 4 knees. In type 3 knees the mean ATT at 15° of knee flexion before resection significantly increased after resection. There were no significant differences in the mean total rotation before and after resection at any knee flexion angle for each type. After resection of the ACL remnants, 12 knees (14.5%) in the type 3 showed an increased ATT by 3 mm or more., Conclusions: This study suggests that the ACL remnant does not play a major role in stabilization of the knee. Although type 3 ACL remnants significantly decreased anterior knee laxity in the knee extension position, the knee stability provided by the ACL remnants was not adequate., Level of Evidence: Level II, prognostic study., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. 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: A test setup for clinical use in the awake and non-anesthetized patient measuring anteroposterior translation and rotation of the knee joint is the subject of validation., Methods: A measuring device featuring fixation of the foot at 30° of knee flexion with varus/valgus stress posts for the knee was developed. Tibial rotation (external/internal) was imposed with a torque of 2 Nm on the footrest with the ankle locked in dorsiflexion. Anterior translation of the tibia in relation to the femur was measured with a commercially available arthrometer. Measurements were performed in a neutral position, internal rotation, and external rotation. Intrarater and inter-rater reliability was validated in 10 healthy volunteers (Cronbach α). We examined 10 patients with isolated anterior cruciate ligament (ACL) rupture, as well as 10 patients with ACL rupture plus medial instability and 10 patients with additional lateral instability. Side-to-side differences were used for calculation., Results: Comparison of healthy volunteers and subjects with isolated ACL rupture showed significant differences: internal rotation, 0.79 mm and 2.46 mm, respectively (P = .001); neutral position, 0.4 mm and 3.35 mm, respectively (P < .0001); and external rotation, 0.29 mm and 2.5 mm, respectively (P = .003). Significant differences (P = .008) were found between isolated ACL rupture and ACL rupture plus medial instability by use of the ratio of anterior translation in external rotation versus the neutral position. Inter-rater reliability was 0.948 in 10 healthy volunteers and 0.981 in 10 subjects with unilateral ACL rupture. Intrarater reliability in the volunteers was 0.829., Conclusions: By use of the developed measurement device, the "Laxitester" (ORTEMA Sport Protection, Markgroeningen, Germany), objective differentiation between isolated ACL rupture and ACL rupture plus additional medial instability is possible. Values for anterior translation are reliable and reproducible by different examiners and by the same examiner at different times., Clinical Relevance: The Laxitester allows objectification of medial instability in combination with ACL injuries and provides a reference regarding the need for additional medial stabilization. Compared with the isolated measurement of anteroposterior translation, knee instability can be assessed in a more differentiated manner., (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.)

Purpose: The purpose of this study was to assess quantitative anterior/posterior values during the Lachman test by an electromagnetic measurement system and to compare data with KT-1000 arthrometric measurements (MEDmetric, San Diego, CA), as well as the measurement of radiologic laxity by dynamic radiographs., Methods: We used an electromagnetic device to quantitatively evaluate anterior knee displacements. We tested 82 knees in 41 patients (30 isolated anterior cruciate ligament [ACL]-deficient, 11 ACL-reconstructed, and 41 contralateral ACL-intact knees). Anterior displacements during the Lachman test were calculated by the electromagnetic measurement system and fluoroscopic measurement, and anterior displacements were also measured by the KT-1000 arthrometer. Anterior/posterior displacements measured by these methods were compared, and correlations were assessed., Results: In ACL-deficient knees, mean anterior/posterior displacement (±SE) was 22.4 ± 0.8 mm in electromagnetic measurements, 22.0 ± 0.7 mm in fluoroscopic measurements, and 15.0 ± 0.6 mm in KT-1000 measurements. In contralateral ACL-intact knees, it was 15.7 ± 0.6 mm, 15.6 ± 0.5 mm, and 9.9 ± 0.4 mm, respectively. In ACL-reconstructed knees, it was 15.7 ± 0.7 mm, 16.2 ± 0.8 mm, and 11.2 ± 0.6 mm, respectively. In all knee conditions, significant differences between fluoroscopic measurements and KT-1000 measurements were detected (P < .01). Significant differences were also detected between electromagnetic measurements and KT-1000 measurements (P < .01). No significant differences were detected between fluoroscopic measurements and electromagnetic measurements. A strong correlation was obtained between KT-1000 measurements and fluoroscopic measurements (r = 0.62, P < .01) and between electromagnetic measurements and KT-1000 measurements (r = 0.64, P < .01). However, the strongest correlation was observed between electromagnetic measurements and fluoroscopic measurements (r = 0.96, P < .01)., Conclusions: An electromagnetic measurement system to test anterior/posterior tibial translation determined that quantification of the Lachman test could be performed as accurately as fluoroscopic measurements., Level of Evidence: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied reference gold standard., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: This study aimed to evaluate the biomechanical function of anterior cruciate ligament (ACL) remnants in anteroposterior and rotational knee stability in patients with a complete ACL injury., Methods: ACL remnants were classified into 5 morphologic patterns: group 1, bridging between the posterior cruciate ligament and tibia; group 2, bridging between the intercondylar notch and tibia; group 3, partial rupture of the posterolateral bundle; group 4, partial rupture of the anteromedial bundle; and group 5, no substantial ACL remnants. The decision of whether the remaining bundle represented partial or complete rupture of the ACL was made based on physical, magnetic resonance imaging, and arthroscopic findings in a comprehensive manner. Patients in groups 1 (n = 18) and 2 (n = 12) underwent intraoperative arthrometry with a navigation system before and immediately after resection of the ACL remnant. The effects of chronicity (duration between injury and surgery) and ACL remnant pattern on changes in knee laxity after debridement of the ACL remnant were investigated., Results: Chronicity had a significant effect on changes in anteroposterior knee laxity evaluated at 30° of knee flexion after resection of the ACL remnant (change in laxity of 2.22 mm for chronicity ≤1 year and 0.17 mm for chronicity >1 year). Chronicity did not influence changes in rotational knee stability after resection of the remnant. There were no significant differences between groups 1 and 2 with regard to any of the evaluated changes in knee stability., Conclusions: In groups 1 and 2 ACL remnants contributed to anteroposterior knee stability evaluated at 30° of knee flexion for up to 1 year after injury, beyond which this biomechanical function was lost. Chronicity and remnant pattern did not influence changes in rotational knee stability after resection of the remnant., Level of Evidence: Level III, diagnostic study of nonconsecutive patients., (Copyright © 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate whether anatomic restoration of the anterior cruciate ligament (ACL) functional bundles results in significant reduction in transverse-plane instability compared with the conventional single-bundle technique during a dynamic 60 degrees pivoting maneuver with the supporting knee in extension., Methods: Using an 8-camera optoelectronic system and a force plate, we examined 10 patients with double-bundle ACL reconstruction, 12 patients with single-bundle reconstruction, 10 ACL-deficient subjects, and 10 healthy control individuals. The 4 groups did not differ in terms of age, body mass index, duration of follow-up, and number of meniscectomies performed. Kinematic and kinetic data were collected from these subjects while performing a pivoting maneuver on each side with the supporting knee in extension. Maximum range of motion for internal-external knee rotation and maximum knee rotational moment were examined., Results: There was no significant difference in tibial rotation either between the 4 groups or between sides. The mean knee rotation for the single- and double-bundle groups was lower than the control group. Rotational moment values were substantially reduced on the affected side of the reconstructed and the ACL-deficient groups. However, rotational moment was not found to affect the degree of angular displacement significantly., Conclusions: Double-bundle ACL reconstruction does not reduce knee rotation further compared with the single-bundle reconstruction technique. The affected side of ACL-deficient or -reconstructed individuals is subjected to reduced knee rotational moments compared with the intact side during stressful functional maneuvers., Level of Evidence: Level III, retrospective comparative study., (Copyright (c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: Because tibial fixation of soft-tissue grafts in anterior cruciate ligament (ACL) reconstruction is problematic, this study aimed to develop a means of delivering bone graft evenly around tendon autograft and define any mechanical, radiologic, or histologic benefit using an ovine model., Methods: A device to deliver bone graft evenly throughout the tibial tunnel was developed. Forty mature sheep underwent simulated quadruple hamstring tendon-ACL reconstruction by use of a bioresorbable interference screw, either with or without bone graft augmentation of the tibial tunnel. Endpoint data were derived at time 0 and after 6 weeks in vivo. Radiostereometric analysis provided quantitation of the translational characteristics; computed tomography evaluated tunnel volume, and measures of yield strength and stiffness were obtained. Sequential fluorochrome administration assessed bone formation, and light microscopy surveyed the biological response., Results: Radiostereometric analysis highlighted differences in the translational characteristics of ACL-deficient knees when compared with intact knees. Reconstructed knees (with or without autograft) showed significantly greater translation when compared with unoperated knees at 6 weeks; autograft bone augmentation provided no benefit. Neither tunnel volume nor yield strength nor stiffness was improved with the addition of autograft bone. No untoward histologic responses were observed. Bone apposition rates were similar between treatment groups. An even distribution of bone graft throughout the tunnels was observed., Conclusions: This model has confirmed the ability of the bone graft-delivery system to evenly distribute bone graft throughout the tunnels. However, the study has failed to show improvement in stability or fixation strength after augmentation with autograft bone., Clinical Relevance: The autograft bone-delivery system may provide a means of establishing an osteoconductive/inductive environment. At this early juncture (6 weeks), no benefit could be defined. Its use in combination with bone morphogenetic proteins or stem cells may provide more rapid fixation, rehabilitation, and reconstitution of bone volume within the tunnel., (Copyright (c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of our study was to clarify the events that take place during anterior cruciate ligament (ACL) failure, focusing on the behavior of the ACL as a composition of multiple fibers, during uniaxial tension along the ligament., Methods: Ten fresh-frozen human cadaveric knee specimens were fixed in an Instron machine (Instron, Norwood, MA), and load was applied parallel to the ACL axis. Two cameras were used to detect the failure mode of the ACL and its different groups of fibers. The distinct bundles of fibers were marked in each specimen before testing. The macroscopic findings during the experiment were used for comparison with the biomechanical results., Results: The ACL showed a non-monotonic response during testing. The load-elongation curve showed a plateau or a second peak after the initial drop in load. Macroscopically, some fibers were failing initially, whereas the intact fibers had a remaining load potential. In our setting, 3 different failure patterns were recognized, specifically, a midsubstance tear of the anteromedial or the posterolateral bundle with a subsequent failure of the intact bundle or an initial avulsion of the anteromedial attachment. Analysis of the video frames showed a direct connection between the failure patterns in the load-elongation curves and the macroscopic sequence of events during ACL failure., Conclusions: The ACL ligament acts as a multifiber construction. In our setting, rupture follows 3 specific patterns where a complete or partial tear of the fiber bundles occurs first and the remaining intact fiber bundles have a potential load resistance., Clinical Relevance: Our study allows a better understanding of the mechanical properties of the ACL. An update on the biomechanics of ACL failure during uniaxial tension after the "double-bundle revolution" could provide data helpful for ACL reconstruction., (Copyright (c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The aim of this study was to evaluate and compare the clinical and inflammatory parameters with the addition of platelet-derived growth factor (PDGF) in primary anterior cruciate ligament (ACL) reconstruction with bone-patellar tendon-bone allograft., Methods: We prospectively randomized 100 patients undergoing arthroscopic patellar tendon allograft ACL reconstruction to a group in whom platelet-enriched gel was used (n = 50) and a non-gel group (n = 50). The platelet concentration was 837 x 10(3)/mm(3), and the gel was introduced inside the graft and the tibial tunnel. Demographic data were comparable between groups. The mean follow-up was 24 months for both groups and included a history, clinical evaluation with the International Knee Documentation Committee score, radiographs, and magnetic resonance imaging., Results: There were no differences in the number of associated injuries. The results did not show any statistically significant differences between the groups for inflammatory parameters (perimeters of the knee and C-reactive protein level), magnetic resonance imaging appearance of the graft, and clinical evaluation scores (visual analog scale, International Knee Documentation Committee, and KT-1000 arthrometer [MEDmetric, San Diego, CA])., Conclusions: At this time, the therapeutic role of PDGF in ACL reconstruction remains unclear. The use of PDGF, on the graft and inside the tibial tunnel, in patients treated with bone-patellar tendon-bone allografts has no discernable clinical or biomechanical effect at 2 years' follow-up. More clinical studies will be needed to show the efficacy and use of these factors in daily practice in ACL reconstruction., Level of Evidence: Level I, prospective, randomized, double-blind study.

Purpose: Our purpose was to evaluate the biomechanical difference between 2 new soft-tissue anterior cruciate ligament (ACL) fixation devices (RetroButton [Arthrex, Naples, FL] and ToggleLoc [Biomet, Warsaw, IN]) and a clinically established implant (EndoButton CL; Smith & Nephew, Andover, MA)., Methods: In test session 1 biomechanical testing was performed by use of 48 porcine femora fixed to a material testing machine. In session 2 the implants were tested alone. Cyclic loading was carried out for 1,000 cycles, followed by a load-to-failure test. The tested devices were as follows: EndoButton CL, 20-mm and 40-mm loops; RetroButton, 12/20-mm and 12/40-mm loops; and ToggleLoc, 20-mm and 40-mm loops., Results: In test session 1 the EndoButton CL showed higher motion per cycle (0.30 +/- 0.09 mm for 20-mm loop and 0.43 +/- 0.03 mm for 40-mm loop) but lower plastic displacement values (0.66 +/- 0.19 mm for 20-mm loop and 0.50 +/- 0.13 mm for 40-mm loop) than the objects of comparison. The RetroButton devices were the stiffest (331.47 +/- 133.92 N/mm for 12/20-mm loop and 265.66 +/- 103.97 N/mm for 12/40-mm loop). The highest ultimate failure load, however, was shown by the EndoButton CL devices. In test session 2 the EndoButton CL oscillated the most. The ToggleLoc devices elongated more than the objects of comparison (0.66 +/- 0.12 mm for 20-mm loop and 0.76 +/- 0.06 mm for 40-mm loop). The RetroButton devices were both the stiffest among the respective implants (542.7 +/- 148.0 N/mm for 12/20-mm loop and 379.0 +/- 40.1 N/mm for 12/40-mm loop). The EndoButton CL showed the highest values for displacement to failure (3.6 +/- 0.4 mm for 20-mm loop and 6.4 +/- 0.4 mm for 40-mm loop). The ToggleLoc devices failed the latest on load-to-failure testing., Conclusions: All tested implants could provide adequate fixation strength. Despite advantages in the design of the EndoButton CL regarding its handling, the 2 newly released products showed superior material properties., Clinical Relevance: Suspensory fixation of hamstring grafts in ACL reconstruction is frequently associated with bone tunnel enlargement. Material properties and implant design may limit graft-tunnel motion and result in enlargement of the femoral bone tunnel. With improved implant design, suspensory graft fixation may still be an attractive fixation technique in primary and revision ACL reconstruction.

Purpose: The purpose of this study was to assess the pivot-shift phenomenon during double-bundle anterior cruciate ligament (ACL) reconstruction using a navigation system., Methods: Ninety patients who received navigated double-bundle ACL reconstruction were included in this study. The mean age of the patients was 21.9 years. During reconstruction, pivot-shift tests were performed 4 times: before reconstruction, after the posterolateral bundle fixation, after the anteromedial bundle fixation, and after the double-bundle reconstruction. Both tibial internal rotation and anterior translation under the pivot-shift test were measured at each phase by the additional functions of the navigation. The navigation system used in this study was the image-free, which does not require preoperative or intraoperative images, OrthoPilot ACL (version 2.0; B. Braun Aesculap, Tuttlingen, Germany)., Results: Before ACL reconstruction, average (+/- standard deviation) tibial internal rotation and anterior translation under the pivot-shift test were 23.7 degrees +/- 6.1 degrees and 5.2 +/- 2.4 mm. They were significantly decreased to 20.9 degrees +/- 6.4 degrees and 2.3 +/- 1.1 mm after the posterolateral bundle fixation, and also decreased to 22.2 degrees +/- 5.7 degrees and 2.4 +/- 1.1 mm after the anteromedial bundle fixation. There was no significant difference between the groups. After double-bundle reconstruction, they improved to 20.3 degrees +/- 6.3 degrees and 2.0 +/- 1.0 mm., Conclusions: Our results indicate that both the posterolateral and the anteromedial bundle similarly control both anterior translation and internal rotation during pivot-shift testing. Double-bundle reconstruction may further improve knee stability., Level of Evidence: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied reference gold standard.

Purpose: This study presents the clinical results of a procedure for treating tibial eminence fractures of the anterior cruciate ligament (ACL) using arthroscopic reduction and No. 5 Ethibond sutures (Ethicon, Somerville, NJ)., Methods: This prospective study analyzed 36 patients who underwent arthroscopic reduction and suture fixation for image-proven ACL avulsion fractures of the tibial eminence. The classification of Meyers and McKeever identified 6 type II, 16 type III, and 14 type IV fractures. The mean follow-up period was 34.4 months (range, 24 to 91 months). Follow-up assessment included Lysholm knee score, Tegner activity score, International Knee Documentation Committee (IKDC) score, and KT-1000 arthrometer (MEDmetric, San Diego, CA) and radiographic evaluation., Results: The mean preoperative Lysholm score in the 36 knees was 38 (range, 28 to 54); the mean postoperative Lysholm score was 98 (range, 83 to 100). The mean preinjury and preoperative Tegner scores in the 36 knees were 7.5 +/- 1.5 (range, 5 to 9) and 3 +/- 1.7 (range, 2 to 5), respectively. The mean postoperative Tegner score was 7.3 +/- 1.7 (range, 5 to 9). At final follow-up, 34 patients (94.5%) were classified by IKDC score as normal or nearly normal (grade A or B). The IKDC classification was abnormal (grade C) in 2 patients (5.5%). All 36 fractures achieved union within 3 months. No significant complications, such as arthrofibrosis, loss of initial fixation, or wound infection, were noted., Conclusions: Treating ACL avulsion fracture by arthroscopic suture fixation by use of 4 No. 5 Ethibond sutures can restore ACL length, stabilize fragments, promote early motion, and minimize morbidity., Level of Evidence: Level IV, therapeutic case series.

Purpose: Our purpose was to document the tibiofemoral (TF) compression forces produced during clinical initial graft tension protocols., Methods: An image analysis system was used to track the position of the tibia relative to the femur in 11 cadaveric knees. TF compression forces were quantified by use of thin-film pressure sensors. Before anterior cruciate ligament (ACL) reconstructions were performed with patellar tendon grafts, measurements of TF compression force were obtained from the ACL-intact knee with knee flexion. ACL reconstructions were then performed by use of "force-based" and "laxity-based" graft tension approaches. Within each approach, high- and low-tension conditions were compared with the ACL-intact condition over the range of knee flexion angles., Results: The TF compression forces for all initial graft tension conditions were significantly greater than those of the normal knee when the knee was in full extension (0 degrees ). The TF compression forces produced with the laxity-based approach were greater than those produced with the force-based approach. However, the laxity-based approach was necessary to restore normal laxity at the time of surgery., Conclusions: The results of this study show that initial graft tension conditions influence TF compressive forces at the time of surgery and that clinically relevant initial graft tension conditions produce different TF compressive forces., Clinical Relevance: This study showed that the TF compression forces were greater in the ACL-reconstructed knee for all of the initial graft tension conditions when compared with the ACL-intact knee and that clinically relevant initial graft tension conditions produce different TF compressive forces.