Editorial Commentary: Graft Orientation in Anterior Cruciate Ligament Reconstruction-Does It Really Matter?

The search for an isometric, anatomic, biomechanically optimal anterior cruciate ligament (ACL) reconstruction remains elusive. To better approximate the native ACL, surgeons have used a host of different graft options and repair techniques. Surgical techniques involving single-tunnel and double-tunnel (or even triple-tunnel!) fixation sites have been used in an attempt to re-create the "2 (or more) bundles" of the ACL. Transtibial and independent femoral drilling techniques are used in an effort to create a more "anatomic" femoral tunnel placement. Once the anatomic femoral attachment site is identified, there is then a debate on how best to "fill" the attachment site with the surgical graft. These are all important discussions and debates, but one question remains . . . Does any of it really matter?

Biomechanics Following Isolated Posterolateral Corner Reconstruction Comparing a Fibular-Based Docking Technique With a Tibia and Fibular-Based Anatomic Technique Show Either Technique is Acceptable.

PURPOSE: To analyze the biomechanical integrity of 2 posterolateral corner (PLC) reconstruction techniques using a sophisticated robotic biomechanical system that enables analysis of joint kinematics under dynamic external loads. METHODS: Eight cadaveric human knee specimens were tested. Five N·m external torque followed by 5 N·m varus torque was dynamically applied to each specimen. The 6 degrees of freedom kinematics of the joint were measured in 4 states (intact, PLC-deficient, fibular-based docking, and anatomic PLC reconstructed) at 30°, 60°, and 90° of flexion. Tibial external rotation (ER) and varus rotation (VR) were compared. RESULTS: Under external torque, ER significantly increased from the intact state to the PLC-deficient state across all flexion angles. At 30° of flexion, ER was not significantly different between the intact state (19.9°) and fibular-based (18.7°, P = .336) and anatomic reconstructions (14.9°, P = .0977). At 60°, ER was not significantly different between the intact state and fibular-based reconstruction (22.4°, compared with 19.8° in intact; P = .152) but showed overconstraint after anatomic reconstruction (15.7°; P = .0315). At 90°, ER was not significantly different between the intact state and anatomic reconstruction (15.4°, compared with 19.7° in intact; P = .386) but was with the fibular-based technique (23.5°; P = .0125). CONCLUSION: Both a fibular-based docking technique and an anatomic technique for isolated PLC reconstruction provided appropriate constraint through most tested knee range of motion, yet the fibular-based docking technique underconstrained the knee at 90°, and the anatomic reconstruction overconstrained the knee at 60°. Biomechanically, either technique may be considered for surgical treatment of high-grade isolated PLC injuries. CLINICAL RELEVANCE: This biomechanical study utilizing clinically-relevant dynamic forces on the knee shows that either a simplified fibular-based docking technique or a more complex anatomic technique may be considered for surgical treatment of high-grade isolated PLC injuries.

A Wide-Range, Wireless Wearable Inertial Motion Sensing System for Capturing Fast Athletic Biomechanics in Overhead Pitching.

The standard technology used to capture motion for biomechanical analysis in sports has employed marker-based optical systems. While these systems are excellent at providing positional information, they suffer from a limited ability to accurately provide fundamental quantities such as velocity and acceleration (hence forces and torques) during high-speed motion typical of many sports. Conventional optical systems require considerable setup time, can exhibit sensitivity to extraneous light, and generally sample too slowly to accurately capture extreme bursts of athletic activity. In recent years, wireless wearable sensors have begun to penetrate devices used in sports performance assessment, offering potential solutions to these limitations. This article, after determining pressing problems in sports that such sensors could solve and surveying the state-of-the-art in wearable motion capture for sports, presents a wearable dual-range inertial and magnetic sensor platform that we developed to enable an end-to-end investigation of high-level, very wide dynamic-range biomechanical parameters. We tested our system on collegiate and elite baseball pitchers, and have derived and measured metrics to glean insight into performance-relevant motion. As this was, we believe, the first ultra-wide-range wireless multipoint and multimodal inertial and magnetic sensor array to be used on elite baseball pitchers, we trace its development, present some of our results, and discuss limitations in accuracy from factors such as soft-tissue artifacts encountered with extreme motion. In addition, we discuss new metric opportunities brought by our systems that may be relevant for the assessment of micro-trauma in baseball.

A Prospective, Blinded, Multicenter Clinical Trial to Compare the Efficacy, Accuracy, and Safety of In-Office Diagnostic Arthroscopy With Magnetic Resonance Imaging and Surgical Diagnostic Arthroscopy.

PURPOSE: The purpose of this study was to compare the efficacy, accuracy, and safety of in-office diagnostic arthroscopy with magnetic resonance imaging (MRI) and surgical diagnostic arthroscopy. METHODS: A prospective, blinded, multicenter, clinical trial was performed on 110 patients, ages 18 to 75 years, who presented with knee pain. The study period was April 2012 to April 2013. Each patient underwent a physical examination, an MRI, in-office diagnostic imaging, and a diagnostic arthroscopic examination in the operating room. The attending physician completed clinical report forms comparing the in-office arthroscopic examination and surgical diagnostic arthroscopy findings on each patient. Two blinded experts, unaffiliated with the clinical care of the study's subjects, reviewed the in-office arthroscopic images and MRI images using the surgical diagnostic arthroscopy images as the "control" group comparison. Patients were consecutive, and no patients were excluded from the study. RESULTS: In this study, the accuracy, sensitivity, and specificity of in-office arthroscopy was equivalent to surgical diagnostic arthroscopy and more accurate than MRI. When comparing in-office arthroscopy with surgical diagnostic arthroscopy, all kappa statistics were between 0.766 and 0.902. For MRI compared with surgical diagnostic arthroscopy, kappa values ranged from a low of 0.130 (considered "slight" agreement) to a high of 0.535 (considered "moderate" agreement). The comparison of MRI to in-office arthroscopy showed very similar results as the comparison of MRI with surgical diagnostic arthroscopy, ranging from a low kappa of 0.112 (slight agreement) to a high of 0.546 (moderate agreement). There were no patient-related or device-related complications related to the use of in-office arthroscopy. CONCLUSIONS: Needle-based diagnostic imaging that can be used in the office setting is statistically equivalent to surgical diagnostic arthroscopy with regard to the diagnosis of intra-articular, nonligamentous knee joint pathology. In-office diagnostic imaging can provide a more detailed and accurate diagnostic assessment of intra-articular knee pathology than MRI. Based on the study results, in-office diagnostic imaging provides a safe, accurate, real-time, minimally invasive diagnostic modality to evaluate intra-articular pathology without the need for surgical diagnostic arthroscopy or high-cost imaging. LEVEL OF EVIDENCE: Level II, comparative prospective trial.

An In Vivo Prediction of Anisometry and Strain in Anterior Cruciate Ligament Reconstruction - A Combined Magnetic Resonance and Dual Fluoroscopic Imaging Analysis.

PURPOSE: To evaluate the in vivo anisometry and strain of theoretical anterior cruciate ligament (ACL) grafts in the healthy knee using various socket locations on both the femur and tibia. METHODS: Eighteen healthy knees were imaged using magnetic resonance imaging and dual fluoroscopic imaging techniques during a step-up and sit-to-stand motion. The anisometry of the medial aspect of the lateral femoral condyle was mapped using 144 theoretical socket positions connected to an anteromedial, central, and posterolateral attachment site on the tibia. The 3-dimensional wrapping paths of each theoretical graft were measured. Comparisons were made between the anatomic, over the top (OTT), and most-isometric (isometric) femoral socket locations, as well as between tibial insertions. RESULTS: The area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. The most isometric attachment site was found midway on the Blumensaat line with approximately 2% and 6% strain during the step-up and sit-to-stand motion, respectively. Posterior femoral attachments resulted in decreased graft lengths with increasing flexion angles, whereas anterodistal attachments yielded increased lengths with increasing flexion angles. The anisometry of the anatomic, OTT and isometric grafts varied between tibial insertions (P < .001). The anatomic graft was significantly more anisometric than the OTT and isometric graft at deeper flexion angles (P < .001). CONCLUSIONS: An area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. ACL reconstruction at the isometric and OTT location resulted in nonanatomic graft behavior, which could overconstrain the knee at deeper flexion angles. Tibial location significantly affected graft strains for the anatomic, OTT, and isometric socket location. CLINICAL RELEVANCE: This study improves the knowledge on ACL anisometry and strain and helps surgeons to better understand the consequences of socket positioning during intra-articular ACL reconstruction.

Articular cartilage generation applying PEG-LA-DM/PEGDM copolymer hydrogels.

BACKGROUND: Injuries to the human native cartilage tissue are particularly problematic because cartilage has little to no ability to heal or regenerate itself. Employing a tissue engineering strategy that combines suitable cell sources and biomimetic hydrogels could be a promising alternative to achieve cartilage regeneration. However, the weak mechanical properties may be the major drawback to use fully degradable hydrogels. Besides, most of the fully degradable hydrogels degrade too fast to permit enough extracellular matrix (ECM) production for neocartilage formation. In this study, we demonstrated the feasibility of neocartilage regeneration using swine articular chondrocytes photoencapsualted into poly (ethylene glycol) dimethacrylate (PEGDM) copolymer hydrogels composed of different degradation profiles: degradable (PEG-LA-DM) and nondegradable (PEGDM) macromers in molar ratios of 50/50, 60/40, 70/30, 80/20, and 90/10. METHODS: Articular chondrocytes were isolated enzymatically from juvenile Yorkshire swine cartilage. 6 × 10(7) cells cells were added to each milliliter of macromer/photoinitiator (I2959) solution. Nonpolymerized gel containing the cells (100 µL) was placed in cylindrical molds (4.5 mm diameter × 6.5 mm in height). The macromer/photoinitiator/chondrocyte solutions were polymerized using ultraviolet (365 nm) light at 10 mW/cm(2) for 10 mins. Also, an articular cartilaginous ring model was used to examine the capacity of the engineered cartilage to integrate with native cartilage. Samples in the pilot study were collected at 6 weeks. Samples in the long-term experimental groups (60/40 and 70/30) were implanted into nude mice subcutaneously and harvested at 6, 12 and 18 weeks. Additionally, cylindrical constructs that were not implanted used as time zero controls. All of the harvested specimens were examined grossly and analyzed histologically and biochemically. RESULTS: Histologically, the neocartilage formed in the photochemically crosslinked gels resembled native articular cartilage with chondrocytes in lacunae and surrounded by new ECM. Increases in total DNA, glycosaminoglycan, and hydroxyproline were observed over the time periods studied. The neocartilage integrated with existing native cartilage. CONCLUSIONS: Articular cartilage generation was achieved using swine articular chondrocytes photoencapsulated in copolymer PEGDM hydrogels, and the neocartilage tissue had the ability to integrate with existing adjacent native cartilage.

Posteromedial knee friction syndrome: an entity with medial knee pain and edema between the femoral condyle, sartorius and gracilis.

OBJECTIVE: To describe MRI features of an entity consisting of medial knee pain and edema between the posteromedial femoral condyle (PMFC), sartorius and/or gracilis tendons and determine whether reduced tendon-bone distances may account for these findings. METHODS: We retrospectively identified MRI cases of edema between the PMFC, sartorius and/or gracilis tendons (25 subjects, 26 knees). Two musculoskeletal radiologists independently graded edema and measured the sartorius- and gracilis-PMFC distances and knee flexion angle. Age- and gender-matched subjects with normal knee MRIs (27 subjects, 27 knees) served as controls for measurements. Statistical analyses compared abnormal to control subjects. RESULTS: Sartorius-PMFC and gracilis-PMFC spaces were narrower in abnormal compared to control subjects (1.6 ± 1.0 vs. 2.1 ± 1.2 mm, P = 0.04; 2.3 ± 2.0 vs. 4.6 ± 3.0 mm, P = 0.002, respectively). The knee flexion angle was similar between groups (P > 0.05). In subjects with clinical information, medial knee pain was the main complaint in 58 % (15/26) of abnormal subjects, with 42 % (11/26) having clinical suspicion of medial meniscal tear. Edema between the PMFC, sartorius and/or gracilis was mild in 54 % (14/26), moderate in 35 % (9/26) and severe in 12 % (3/26), and it was most frequent deep to both the sartorius and gracilis (50 %, 13/26). CONCLUSIONS: Edema between the PMFC, sartorius and/or gracilis tendons identified on knee MRI may be associated with medial knee pain and may represent a friction syndrome.

Articular cartilage of the knee 3 years after ACL reconstruction. A quantitative T2 relaxometry analysis of 10 knees.

BACKGROUND AND PURPOSE: T1ρ or T2 relaxation imaging has been increasingly used to evaluate the cartilage of the knee. We investigated the cartilage of ACL-reconstructed knees 3 years after surgery using T2 relaxation times. PATIENTS AND METHODS: 10 patients with a clinically successful unilateral ACL reconstruction were examined 3 years after surgery. Multiple-TE fast-spin echo sagittal images of both knees were acquired using a 3T MRI scanner for T2 mapping of the tibiofemoral cartilage. T2 values of the superficial and deep zones of the tibiofemoral cartilage were analyzed in sub-compartmental areas and compared between the ACL-reconstructed and uninjured contralateral knees. RESULTS: Higher T2 values were observed in 1 or more sub-compartmental areas of each ACL-reconstructed knee compared to the uninjured contralateral side. Most of the T2 increases were observed at the superficial zones of the cartilage, especially at the medial compartment. At the medial compartment of the ACL-reconstructed knee, the T2 values of the femoral and tibial cartilage were increased by 3-81% compared to the uninjured contralateral side, at the superficial zones of the weight-bearing areas. T2 values in the superficial zone of the central medial femoral condyle differed between the 2 groups (p = 0.002). INTERPRETATION: The articular cartilage of ACL-reconstructed knees, although clinically satisfactory, had higher T2 values in the superficial zone of the central medial femoral condyle than in the uninjured contralateral side 3 years after surgery. Further studies are warranted to determine whether these patients would undergo cartilage degeneration over time.

T2 relaxometry of the infrapatellar fat pad after arthroscopic surgery.

OBJECTIVE: To investigate the T2 relaxation values of the infrapatellar fat pad (IFP) after arthroscopic surgery. MATERIALS AND METHODS: This study was approved by the institutional review board; all individuals signed informed consent. We performed MRI in 16 knees from 8 subjects. Prior to imaging, each subject had unilateral arthroscopic knee surgery and an asymptomatic non-operated contralateral knee. We used a 10-echo multiple-TE fast-spin echo pulse sequence for creation of T2 relaxation time maps. Two musculoskeletal radiologists independently placed regions of interest in the IFP, suprapatellar subcutaneous and deep intermuscular adipose tissue. Qualitative assessments were performed to assess fibrotic changes affecting patellar retinaculum and IFP. Statistical analyses of T2 values determined differences between groups, correlation with time after surgery, and cut-off values to differentiate groups. RESULTS: The average time between arthroscopy and imaging was 3.5 ± 0.4 years. IFP of knees with prior surgery had significantly shorter mean T2 values (133 ± 14 ms) compared with control knees (147 ± 8 ms, P = 0.03). There was no significant difference between operated and control knees regarding T2 values of suprapatellar subcutaneous (P = 0.3) or deep intermuscular adipose tissue (P = 0.2). There was no correlation between IFP T2 values and time after surgery (P > 0.2). IFP T2 values ≤ 139 ms had 75 % sensitivity and 88 % specificity in identifying prior arthroscopy. CONCLUSION: Shortening of T2 relaxation values is present in IFP chronically after arthroscopic surgery and may be an indicator of adipose tissue fibrosis.

Core Muscle Injury: Evaluation and Treatment in the Athlete.

BACKGROUND: Pain in the groin region, where the abdominal musculature attaches to the pubis, is referred to as a "sports hernia,""athletic pubalgia," or "core muscle injury" and has become a topic of increased interest due to its challenging diagnosis. Identifying the cause of chronic groin pain is complicated because significant symptom overlap exists between disorders of the proximal thigh musculature, intra-articular hip pathology, and disorders of the abdominal musculature. PURPOSE: To present a comprehensive review of the pathoanatomic features, history and physical examination, and imaging modalities used to make the diagnosis of core muscle injury. STUDY DESIGN: Narrative and literature review; Level of evidence, 4. METHODS: A comprehensive literature search was performed. Studies involving the diagnosis, treatment, and rehabilitation of athletes with core muscle injury were identified. In addition, the senior author's extensive experience with the care of professional, collegiate, and elite athletes was analyzed and compared with established treatment algorithms. RESULTS: The differential diagnosis of groin pain in the athlete should include core muscle injury with or without adductor longus tendinopathy. Current scientific evidence is lacking in this field; however, consensus regarding terms and treatment algorithms was facilitated with the publication of the Doha agreement in 2015. Pain localized proximal to the inguinal ligament, especially in conjunction with tenderness at the rectus abdominis insertion, is highly suggestive of core muscle injury. Concomitant adductor longus tendinopathy is not uncommon in these athletes and should be investigated. The diagnosis of core muscle injury is a clinical one, although dynamic ultrasonography is becoming increasingly used as a diagnostic modality. Magnetic resonance imaging is not always diagnostic and may underestimate the true extent of a core muscle injury. Functional rehabilitation programs can often return athletes to the same level of play. If an athlete has been diagnosed with athletic pubalgia and has persistent symptoms despite 12 weeks of nonoperative treatment, a surgical repair using mesh and a relaxing myotomy of the conjoined tendon should be considered. The most common intraoperative finding is a deficient posterior wall of the inguinal canal with injury to the distal rectus abdominis. Return to play after surgery for an isolated sports hernia is typically allowed at 4 weeks; however, if an adductor release is performed as well, return to play occurs at 12 weeks. CONCLUSION: Core muscle injury is a diagnosis that requires a high level of clinical suspicion and should be considered in any athlete with pain in the inguinal region. Concurrent adductor pathology is not uncommon.

Adult Prg4+ progenitors repair long-term articular cartilage wounds in vivo.

The identity and origin of the stem/progenitor cells for adult joint cartilage repair remain unknown, impeding therapeutic development. Simulating the common therapeutic modality for cartilage repair in humans, i.e., full-thickness microfracture joint surgery, we combined the mouse full-thickness injury model with lineage tracing and identified a distinct skeletal progenitor cell type enabling long-term (beyond 7 days after injury) articular cartilage repair in vivo. Deriving from a population with active Prg4 expression in adulthood while lacking aggrecan expression, these progenitors proliferate, differentiate to express aggrecan and type II collagen, and predominate in long-term articular cartilage wounds, where they represent the principal repair progenitors in situ under native repair conditions without cellular transplantation. They originate outside the adult bone marrow or superficial zone articular cartilage. These findings have implications for skeletal biology and regenerative medicine for joint injury repair.

The effect of humeral torsion on rotational range of motion in the shoulder and throwing performance.

Several recent studies have found that throwing athletes typically have lower humeral torsion (retroversion) and a greater range of external rotation at the shoulder than non-athletes. How these two parameters are related is debated. This study uses data from a sample of both throwers and non-throwers to test a new model that predicts torsion values from a range of motion data. The model proposes a series of predicted regressions which can help provide new insight into the factors affecting rotational range of motion at the shoulder. Humeral torsion angles were measured from computed tomography scans collected from 25 male subjects. These values are compared to predicted torsion values for the same subjects calculated from both kinematic and goniometric range-of-motion data. Results show that humeral torsion is negatively correlated (goniometric: r = -0.409, P = 0.047; kinematic: r = -0.442, P = 0.035) with external rotational range of motion and positively correlated (goniometric: r = 0.741, P < 0.001; kinematic: r = 0.559, P = 0.006) with internal rotational range of motion. The predicted torsion values are highly correlated (goniometric: r = 0.815, P < 0.001; kinematic: r = 0.617, P = 0.006) with actual torsion values. Deviations in the data away from predicted equations highlight significant differences between high torsion and low torsion individuals that may have significant functional consequences. The method described here may be useful for non-invasively assessing the degree of torsion in studies of the evolution and biomechanics of the shoulder and arm, and for testing hypotheses about the etiology of repetitive stress injuries among athletes and others who throw frequently.

Surgical technique: aperture fixation in PCL reconstruction: applying biomechanics to surgery.

BACKGROUND: Biomechanical studies suggest reducing the effective graft length during transtibial posterior cruciate ligament (PCL) reconstruction by augmenting the distal tibial fixation with a proximal screw near the tibial tunnel aperture could increase graft stiffness and provide a more stable reconstruction. However, it remains unknown to what extent this mechanical theory influences in vivo graft performance over time. SURGICAL TECHNIQUE: We developed a technique to augment tibial distal fixation with a proximal screw near the tibial tunnel aperture to shorten the effective graft length and increase graft stiffness. PATIENTS AND METHODS: We retrospectively reviewed all 10 patients who had isolated PCL reconstructions with combined distal and proximal tibial fixation from 2003 to 2007. Mean age of the patients was 36.5 years. We measured ROM and obtained Tegner, International Knee Documentation Committee (IKDC), and Lysholm scores. Anteroposterior stability was evaluated with a KT-2000 arthrometer. Minimum followup was 1 year (mean, 2.5 years; range, 1-4.8 years). RESULTS: Mean Tegner scores before injury and at last followup were 7.3 and 6.5, respectively. Mean postoperative IKDC score was 87 versus a preoperative IKDC score of 43. Mean Lysholm score was 89 at last followup. All patients achieved full terminal extension. No patient had greater than a 5-mm difference in anterior or posterior displacement from the contralateral knee as measured by a KT-2000 arthrometer postoperatively (0.93 ± 0.79 mm). CONCLUSIONS: In this small series, augmentation of tibial distal fixation with a proximal screw near the tibial tunnel aperture during reconstruction of the isolated PCL rupture restored function, motion, and stability. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Quantitative magnetic resonance imaging (MRI) morphological analysis of knee cartilage in healthy and anterior cruciate ligament-injured knees.

PURPOSE: To analyze the morphological change in the cartilage of the knee after anterior cruciate ligament (ACL) injury by comparing with that of the intact contralateral knee. METHODS: A total of 22 participants (12 male and 10 female patients) who had unilateral ACL injury underwent MRI scan of both the injured and intact contralateral knees. Sagittal plane images were segmented using a modeling software to determine cartilage volume and cartilage thickness in each part of the knee cartilage that were compared between the ACL-injured and the intact contralateral knees. Furthermore, the male and female patients' data were analyzed in subgroups. RESULTS: The ACL-injured knees had statistically significant lower total knee cartilage volume than the intact contralateral knees (P = 0.0020), but had similar mean thickness of total knee cartilage (not significant: n.s.). In the male subgroup, there was no significant difference in cartilage volume and thickness between normal and ACL-injured knees. In the female subgroup, the ACL-injured knees demonstrated statistically significant difference in total knee cartilage volume (P = 0.0004) and thickness (P = 0.0024) compared with the normal knees. The percentage change in the cartilage thickness in women was significantly greater than that in men. CONCLUSION: Cartilage volume was significantly smaller in the ACL-injured knees than in the contralateral intact knees in this cohort. Women tended to display greater cartilage volume and thickness change after ACL injury than men. These findings indicated that women might be more susceptible to cartilage alteration after ACL injuries. LEVEL OF EVIDENCE: III.

Tunnel position and graft orientation in failed anterior cruciate ligament reconstruction: a clinical and imaging analysis.

PURPOSE: It has been reported that technical error in positioning the graft tunnel is the most common problem in anterior cruciate ligament (ACL) reconstruction. The objective of this study was to quantitatively evaluate femoral and tibial tunnel positions and intra-articular graft orientation of primary ACL reconstruction in patients who had undergone revision ACL reconstruction. We postulated that this patient cohort had a nonanatomically positioned tunnel and graft orientation. METHODS: Twenty-six patients who had undergone a revision ACL were investigated. Clinical magnetic resonance (MR) images prior to revision were analysed. Three-dimensional models of bones and tunnels on the femur and tibia were created. Intra-articular graft orientation was measured in axial, sagittal and coronal planes. Graft positions were measured on the tibial plateau as a percentage from anterior to posterior and medial to lateral; graft positions on the femur were measured using the quadrant method. RESULTS: Sagittal elevation angle for failed ACL reconstruction graft (69.6° ± 13.4°) was significantly greater (p < 0.05) than that of the native anteromedial (AM) and posterolateral (PL) bundles of the ACL (AM 56.2° ± 6.1°, PL 55.5° ± 8.1°). In the transverse plane, the deviation angle of the failed graft (37.3° ± 21.0°) was significantly greater than native ACL bundles. The tibial tunnel in this patient cohort was placed posteromedially and medially to the anatomical AM and PL bundles, respectively. The femoral tunnel was placed anteriorly to the anatomical AM and PL bundles. CONCLUSIONS: This study reveals that both the tibial and femoral tunnel positions and consequently the intra-articular graft orientation in this patient group with failed ACL reconstruction were nonanatomical when compared with native ACL values. The results can be used to improve tunnel placement in ACL reconstruction.