Independent Femoral Tunnel Research Articles

Anatomic Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament reconstruction (ACLR) techniques have substantially evolved over the past several decades, driven by evidence that nonanatomic techniques increase the risk for instability, loss of motion, surgical failure, and posttraumatic osteoarthritis. Early techniques used transtibial femoral tunnel drilling, although improved understanding of the anatomy and biomechanics has led to independent femoral tunnel. Anatomic ACLR requires careful consideration of the native ACL dimensions and orientation. Although there is significant variation between patients, understanding of anatomic patterns allows for reliable identification of the ACL footprints and appropriate tunnel positioning, particularly in chronic injuries where the remanent ACL stump is degraded or absent. The femoral tunnel should be placed low and posterior on the lateral femoral condyle using the lateral intercondylar and bifurcate ridges as landmarks. The center of the tibial footprint can be determined by referencing the medial tibial spine and posterior border of anterior horn of lateral meniscus. Measurement of the dimensions of the native ACL and intercondylar notch is also critical for determining graft size and minimizing the risk of impingement, with a goal of reconstructing 50% to 80% of the tibial footprint area. Clinical outcome studies have demonstrated superior anteroposterior and rotatory knee stability with low surgical revision rates (reported between 3% and 5%). By adhering to the principles of anatomic ACLR, surgeons can produce an appropriately sized and located graft for the individual patient, thereby best restoring native knee kinematics and maximizing function. The aim of this infographic is to highlight essential features of anatomic ACLR techniques, which a focus on the native anatomy and surgical planning to achieve an anatomic ACLR.

The "N+10 Rule" to Avoid Graft-Tunnel Mismatch in Bone-Patellar Tendon-Bone ACL Reconstruction Using Independent Femoral Tunnel Drilling.

Graft-tunnel mismatch (GTM) is a common problem in anterior cruciate ligament (ACL) reconstruction (ACLR) using bone-patellar tendon-bone (BPTB) grafts. Application of the "N+10 rule" in endoscopic ACLR with BPTB grafts will result in acceptable tibial tunnel length (TTL), minimizing GTM. Controlled laboratory study. Endoscopic BPTB ACLR was conducted on the paired knees of 10 cadaveric specimens using 2 independent femoral tunnel drilling techniques-accessory anteromedial portal and flexible reamer. The graft bone blocks were trimmed to 10 × 20 mm, and the intertendinous distance (represented by "N") between the bone blocks was measured. The N+10 rule was used to set the angle of the ACL tibial tunnel guide to the appropriate number of degrees for drilling. The amount of excursion or recession of the tibial bone plug in relation to the anterior tibial cortical aperture was measured in both flexion and extension. A GTM threshold of ±7.5 mm was set based on prior studies. The mean BPTB ACL intertendinous distance was 47.5 ± 5.5 mm. The mean measured intra-articular distance was 27.2 ± 3 mm. Using the N+10 rule, the mean total (flexion plus extension) GTM was 4.3 ± 3.2 mm (GTM in flexion, 4.9 ± 3.6 mm; GTM in extension, 3.8 ± 3.5 mm). In 18 of 20 (90%) cadaveric knees, the mean total GTM fell within the ±7.5-mm threshold. When comparing the actual measured TTL to the calculated TTL, there was a mean difference of 5.4 ± 3.9 mm. When comparing femoral tunnel drilling techniques, the total GTM for the accessory anteromedial portal technique was 2.1 ± 3.7 mm, while the total GTM for the flexible reamer technique was 3.6 ± 5.4 mm (P = .5). The N+10 rule resulted in an acceptable mean GTM in both flexion and extension. The mean difference between the measured versus calculated TTL using the N+10 rule was also acceptable. The N+10 rule is a simple and effective intraoperative strategy for achieving desired TTL regardless of patient-specific factors to avoid excessive GTM in endoscopic BPTB ACLR using independent femoral tunnel drilling.

Five-Stranded Hamstring Tendon Autograft for Anterior Cruciate Ligament Reconstruction

Background: Hamstring tendon (HT) autograft for anterior cruciate ligament (ACL) reconstruction has shown equivalent graft failure rates to bone-patellar-tendon-bone (BTB) with decreased prevalence of anterior knee pain. It should be noted that young athletes, particularly females athletes, may have increased graft failure rates with HT versus BTB. Additionally, HT graft diameters <8 mm have shown worse patient-reported outcomes and higher graft failure rates. Five-strand HT autograft offers a method to increase graft size without utilization of allograft tissue or synthetic material. Indications: This presentation describes the technique for 5-strand HT autograft reconstruction of the ACL. Tips and tricks on graft prep, tunnel placement, tunnel depth, and avoiding pitfalls in surgery are provided. Technique Description: Gracilis and semitendinosus tendon harvest is performed through an L-shaped flap of sartorial fascia. If the 4-strand configuration is <8 mm, the semitendinosus is tripled for a 5-strand configuration. Graft is attached to a 15-mm fixed-length button construct for femoral fixation. The tibial tunnel is typically drilled with the guide through the accessory anteromedial portal. Independent femoral tunnel drilling is then performed via the accessory anteromedial tunnel with the knee in hyperflexion, using an offset guide to aid in tunnel placement. Femoral tunnel is initially reamed to depth of 25 mm and then drilled through the far cortex with a 4.5-mm drill to allow for suspensory fixation. Total length to the lateral cortex is measured and reaming of the tunnel is performed to achieve a 5- to 7-mm difference between total tunnel length to the lateral cortex and reamed tunnel length, assuring room for the button to flip on the femoral cortex. Tibial fixation is achieved by interference fixation versus tying the free suture limbs over a post with a washer. Results: Recent studies show the HT autograft to have similar re-rupture rates for ACL reconstruction compared with other autograft options. Additionally, this option has low donor-site morbidity and has demonstrated significant less anterior knee pain and kneeling pain postoperatively. Discussion/Conclusion: ACL reconstruction with 5-strand HT autograft has shown to be an effective method to increase the graft diameter with low rates of donor-site morbidity.

Poster 256: The "N+10 Rule" to Avoid Graft Tunnel Mismatch in Bone-Patellar Tendon-Bone Anterior Cruciate Ligament Reconstruction Using Independent Femoral Tunnel Drilling

Objectives: To determine the amount of tibial graft tunnel mismatch during application of the “N+10” rule in arthroscopic assisted anterior cruciate ligament (ACL) reconstruction with bone-patellar tendon-bone (BTB) graft using independent femoral tunnel drilling.To compare actual (measured) tibial tunnel length and desired (calculated) tibial tunnel length when using the “N+10” rule for independent femoral tunnel drilling. Methods:Twenty paired knees from 10 fresh frozen cadaveric specimens (5 female and 5 male specimens) underwent arthroscopic assisted bone-patellar tendon-bone ACL reconstruction using independent femoral tunnel drilling with either a hyperflexion accessory anteromedial portal (n=10) or flexible reamer technique (n=10). The prepared patellar tendon graft bone blocks were trimmed to 10 x 20mm for all specimens and the intertendinous distance (N) between the bone blocks was measured. The “N+10 Rule” was used to set the angle of the ACL tibial tunnel guide to the appropriate degree setting for drilling. The amount of excursion or recession of the tibial bone plug in relation to the anterior tibial cortical aperture was measured in both flexion and extension. A +/-6mm threshold was used to assess this strategy based on prior biomechanical aperture fixation studies. As a secondary outcome, the intraarticular distance (IAD) and the actual tibial tunnel length (TTL) were measured and compared to the planned TTL based on the equation: IAD + TTL = N + 20 (size of bone plug in millimeters)Results:The average BTB ACL intertendinous distance (N) was 47.5mm (SD =5.5mm). The average measured IAD was 27.2mm (SD=3.0mm). Using the “N+10 Rule”, the average mismatch of the tibial tunnel was 4.9mm (SD=3.6mm) and 3.8mm (SD=3.5mm) in flexion and extension, respectively. Both values fall within the +/- 6mm threshold. When comparing the actual measured tibial tunnel length (TTL) to the desired TTL, there was an average difference of 5.4mm (SD=3.9mm)Conclusions:The “N+10” rule resulted in an acceptable average mismatch in both flexion and extension using the threshold of +/- 6mm for 20 cadaveric knees. Measured actual TTL compared to the desired calculated TTL were acceptable 61% of the time using the same threshold. The “N+10” is a simple and effective intraoperative strategy for achieving desired tibial tunnel length to avoid excessive graft tunnel mismatch.Figure 1:Derived formula for calculating ideal tibial tunnel length (TTL) using intraarticular distance (IAD), and the known values of the intertendinous distance (N) and lengths of the bone blocks (20mm).Figure 2:Intraoperative photo of BTB ACL graft measuring intertendinous distance between the bone plugs (N=55mm). Following the "N+10" ruleFigure 3:Intraoperative photo of tibial ACL guide measurement of tibial tunnel length at 50mm with guide set to 65 degrees.Figure 4:Intraoperative photo of the ACL tibial tunnel guide positioned on the anatomic tibial footprint set to 65 degrees (N=55mm). Using this setting for the guide, the tibial tunnel measured 50mm as seen in the zoomed in photo, as per the formula.

Flexible Versus Rigid Reaming Systems for Independent Femoral Tunnel Reaming During ACL Reconstruction: Minimum 2-Year Clinical Outcomes.

Background:Radiographic and cadaveric studies have suggested that anatomic anterior cruciate ligament reconstruction (ACLR) femoral tunnel drilling with the use of a flexible reaming system through an anteromedial portal (AM-FR) may result in a different graft and femoral tunnel position compared with using a rigid reamer through an accessory anteromedial portal with hyperflexion (AAM-RR). No prior studies have directly compared clinical outcomes between the use of these 2 techniques for femoral tunnel creation during ACLR.Purpose:To compare revision rates at a minimum of 2 years postoperatively for patients who underwent ACLR with AM-FR versus AAM-RR. The secondary objectives were to compare functional testing and patient-reported outcomes between the cohorts.Study Design:Cohort study; Level of evidence, 3.Methods:Included were consecutive patients at a single academic institution between 2013 and 2018 who underwent primary ACLR without additional ligamentous reconstruction. Patients were separated into 2 groups based on the type of anatomic femoral tunnel drilling: AM-FR or AAM-RR. Graft failure, determined by revision ACLR, was assessed with a minimum 2 years of postoperative follow-up. The authors also compared patient-reported outcome scores (International Knee Documentation Committee [IKDC] and Knee injury and Osteoarthritis Outcome Score [KOOS]) and functional performance testing performed at 6 months postoperatively.Results:A total of 284 (AAM-RR, 232; AM-FR, 52) patients were included. The mean follow-up time was 3.7 ± 1.5 years, with a minimum 2-year follow-up rate of 90%. There was no significant difference in the rate of revision ACLR between the AAM-RR and AM-FR groups (10.8% vs 9.6%, respectively; P = .806). At 6 months postoperatively, there were no significant between-group differences in peak knee extension strength, peak knee flexion strength, limb symmetry indices, or hop testing, as well as no significant differences in IKDC (AAM-RR, 81.1; AM-FR, 78.9; P = .269) or KOOS (AAM-RR, 89.0; AM-FR, 86.7; P = .104).Conclusion:In this limited study, independent femoral tunnel drilling for ACLR using rigid or flexible reaming systems resulted in comparable rates of revision ACLR at a minimum of 2 years postoperatively, with no significant differences in strength assessments or patient-reported outcomes at 6 months postoperatively.

Comparing the Use of Flexible and Rigid Reaming Systems Through an Anteromedial Portal for Femoral Tunnel Creation During Anterior Cruciate Ligament Reconstruction: A Systematic Review.

Background:Recent studies have suggested that femoral tunnel drilling during anterior cruciate ligament (ACL) reconstruction (ACLR) with the use of a flexible reaming system through a standard anteromedial portal (AM-FR) may result in a different tunnel geometry compared with a rigid reamer through an accessory anteromedial portal with hyperflexion (AM-RR).Purpose:To summarize radiologic, anatomic, and clinical outcomes from available studies that directly compared the use of AM-FR versus AM-RR for independent femoral tunnel creation during ACLR.Study Design:Systematic review; Level of evidence, 4.Methods:A literature search was performed using the MEDLINE (PubMed) and Web of Science databases to identify all studies that directly compared radiologic, anatomic, and clinical outcomes between the use of AM-FR and AM-RR. The literature search, data recording, and methodological quality assessment was performed by 2 independent reviewers. The outcomes analyzed included resultant ACL graft positioning and graft bending angle; femoral tunnel positioning, aperture morphology, length, and widening; posterior wall breakage; and distance from various posterolateral knee structures.Results:A total of 13 studies met the eligibility criteria for inclusion. There was no difference in femoral tunnel aperture location between techniques. There were conflicting findings among studies regarding which technique resulted in a more acute graft bending angle. One study reported greater femoral tunnel widening upon follow-up with the use of AM-FR. AM-FR produced longer and more anteverted femoral tunnels than did AM-RR. The difference in tunnel length was significant and more prominent in lesser degrees of knee flexion. With AM-FR, femoral tunnels were farther from the lateral collateral ligament and peroneal nerve, and 1 of 5 studies had fewer reports of posterior wall breakage. There has been no literature comparing the clinical or functional outcomes of these techniques.Conclusion:Although no clinical studies exist comparing AM-FR and AM-RR for femoral tunnel creation during ACLR, both systems allow for reproducible positioning of an anatomic femoral tunnel aperture. The use of AM-FR results in longer and more anteverted femoral tunnels than using AM-RR, with exit points on the lateral femur that are different but safe. Surgeons should be aware of the technical differences with each method; however, further study is needed to identify any clinically important difference that results.

Independent Versus Transtibial Drilling in Anterior Cruciate Ligament Reconstruction: A Meta-analysis With Meta-regression.

Background:Anterior cruciate ligament (ACL) reconstruction can be performed with different techniques for independent and transtibial (TT) drilling of femoral tunnels, but there is still no consensus on which approach leads to the best outcome.Purpose:To assess whether the independent or TT drilling approach for ACL reconstruction leads to the best functional outcomes.Study Design:Systematic review; Level of evidence, 2.Methods:A systematic literature search was conducted on July 1, 2020, using the PubMed, Web of Science, Cochrane Library, and Scopus databases. The influence of different femoral drilling techniques was analyzed through a meta-analysis in terms of patient-reported outcome measure scores, risk of complications, range of motion limitations, graft failure, and differential laxity. Subanalyses were performed to compare the different independent drilling techniques considered. Linear metaregression was performed to evaluate if the year of study publication influenced the results. The risk of bias and quality of evidence were assessed following the Cochrane guidelines.Results:A total of 22 randomized controlled trials including 1658 patients were included in the meta-analysis. Both International Knee Documentation Committee (IKDC) subjective score and Lysholm score were higher with the independent drilling approach (mean difference [MD], 1.24 [P = .02] and 0.55 [P = .005], respectively). No difference was documented in terms of the risk of reinjury, but independent drilling led to reduced KT-1000 arthrometer–assessed anterior tibial translation (MD, 0.23; P = .01) and a higher probability of a negative postoperative pivot-shift test finding (risk ratio, 1.13; P = .04). There were no significant differences in IKDC objective or Tegner scores. A P value of .07 was found for the association between the year of the study and IKDC objective scores.Conclusion:Independent femoral tunnel drilling provided better results than the TT approach, although the difference was not clinically significant. No difference was observed in the risk of reinjury. Increasingly better results were seen among surgical procedures performed in more recent years. Among the independent drilling options, the anteromedial portal technique seemed to provide the most favorable outcomes. The lack of clinically significant differences and the promising outcomes reported with new modified TT techniques suggest the importance of correct placement, rather than the tunnel drilling approach, to optimize the results of ACL reconstruction.

Arthroscopically Assisted Anterior Cruciate Ligament Reconstruction Using Bone–Patellar Tendon–Bone Autograft: Challenges and Solutions of Medial Independent Femoral Tunnel Drilling

Background: As the main translational and rotatory stabilizer of the knee, the anterior cruciate ligament (ACL) plays a critical role in knee biomechanics. Anterior cruciate ligament ruptures generally require surgical attention for not only restoration of knee stability but also prevention of meniscal and chondral injuries. There are countless options for both the surgeon and the patient when contemplating graft choice and surgical technique for ACL reconstruction. However, the literature assessing the outcomes following various autografts has varied with some studies citing no significant difference in clinical and patient-reported outcomes, while others showing notable advantage when using bone–patellar tendon–bone (BPTB) autograft. In addition, there have been challenges associated with femoral tunnel placement using an anteromedial portal technique. Indications: In this study, we present a young female patient with a history of remote mid-substance ACL tear now presenting with worsening knee instability and a bucket-handle medial meniscus tear as a sequela of the incompetent ACL. After extensive discussion regarding the treatment options, patient had decided to proceed with surgical intervention with a BPTB autograft using the anteromedial portal technique for femoral tunnel placement and compression technique with bio-absorbable interference screw fixation. Results: Bone–patellar tendon–bone autograft has been noted to have lower risk of revision when compared with other graft options. Discussion: In this surgical technique study, we underline the importance of peritenon handling. We highlight the use of a 70-degree arthroscope to improve posterolateral wall visualization during femoral tunnel placement as well as for inspection of the reamed tibial tunnel. We also provide technique commentary and solutions for management of the medial femoral condyle (MFC) articular surface and femoral tunnel placement using an anteromedial portal technique. Last, we review graft-related outcomes, postoperative management, and rehabilitation protocol.

Femoral Tunnel Techniques in ACL Reconstruction with Hamstrings Autograft: Transtibial versus Two Tunnels Technique

AbstractBackground: In spite of the considerable research focused on ACL reconstruction, the increased risk of early knee osteoarthritis and the presence of rotational instability post-surgery have not been fully investigated yet. As a result, controversy remains regarding the best technique for recon-struction; thus, it is still the subject of extensive research.Aim of the Work: To assess the radiological and clinical outcomes of arthroscopic single bundle ACL reconstruction using the transtibial or the anteromedial portal (two tunnels) technique for drilling the femoral tunnel in nonprofessional athletes.Patients and Methods: It is a prospective comparative study including forty patients with a torn ACL underwent arthroscopic reconstruction of the ACL, twenty patients had ACL reconstruction by transtibial (TT) technique and twenty patients had ACL reconstruction by Anteromedial Portal (AMP) technique using hamstring tendons as autograft for all the patients.Results: All the patients were followed-up clinically with IKDC scores, Lysholm score, Tegner activity score and Radi-ologically for assessment of tunnel widening and femoral tunnel position using plain X-ray and CT at 3, 6 and 12 months post-operatively.Conclusion: The AMP independent femoral tunnel drilling technique achieved a more horizontal and anatomic femoral tunnel, but the AMP technique has no clinical superiority compared to the TT technique in ACL reconstruction in nonprofessional athletes as reported by these short-term follow-up results.

Is Preoperative Anthropometric Data Assessment Reliable Indicator for Estimating Femoral Tunnel Length in Anterior Cruciate Ligament Reconstruction?

Introduction: Correct length of the femoral tunnel is required for adequate length of graft inside the femoral canal. Length of femoral tunnel depends on mass, height, dimensions of lateral femoral condyle and amount of flexion of knee intraoperatively. Increasing weight and BMI affects the length of femoral canal since they affect positioning of limb in maximal knee flexion.Aim: To measure tunnel length in independent femoral tunnel drilling using the medial portal and to correlate the tunnel length with anthropometric data (height, weight, BMI of patient) and with width and depth of Lateral Femoral Condyle (LFC) based on MRI.Materials and Methods: The present prospective study including 40 patients were conducted. Participants were selected by a non-random convenience sampling methodology. Complete details of patients were collected by verbal communication with the patients and their attendees, clinical examination, baseline investigations, radiological investigations and surgical findings. Radiological investigations included preoperative assessment of LFC in MRI. Surgical findings were determined by measuring the femoral tunnel length after initial drilling through the medial portal using a depth gauge placed through the medial portal. SPSS version 17.0 was used for data analysis. Results: A total of 40 patients, 30 males and 10 females were included. Mean BMI was 24.22 kg/m2 with the range of 18 to 30. Mean width of LFC was 32.9 mm with range of 26.2 mm to 37.3 mm and depth of LFC was 58.79 with range of 50.7 mm to 66.2 mm. Mean femoral tunnel length was 38.4 mm with range from 32 mm to 44 mm. Conclusion: Average femoral tunnel length in Anterior Cruciate Ligament (ACL) reconstruction was 38.4 mm for assessed 40 patients. This correlated positively with height and weight of the patient. It also correlated positively with the width (p=0.027) and depth (p=0.029) of lateral femoral condyle.

ACL Roof Impingement Revisited: Does the Independent Femoral Drilling Technique Avoid Roof Impingement With Anteriorly Placed Tibial Tunnels?

Background:Anatomic femoral tunnel placement for single-bundle anterior cruciate ligament (ACL) reconstruction is now well accepted. The ideal location for the tibial tunnel has not been studied extensively, although some biomechanical and clinical studies suggest that placement of the tibial tunnel in the anterior part of the ACL tibial attachment site may be desirable. However, the concern for intercondylar roof impingement has tempered enthusiasm for anterior tibial tunnel placement.Purpose:To compare the potential for intercondylar roof impingement of ACL grafts with anteriorly positioned tibial tunnels after either transtibial (TT) or independent femoral (IF) tunnel drilling.Study Design:Controlled laboratory study.Methods:Twelve fresh-frozen cadaver knees were randomized to either a TT or IF drilling technique. Tibial guide pins were drilled in the anterior third of the native ACL tibial attachment site after debridement. All efforts were made to drill the femoral tunnel anatomically in the center of the attachment site, and the surrogate ACL graft was visualized using 3-dimensional computed tomography. Reformatting was used to evaluate for roof impingement. Tunnel dimensions, knee flexion angles, and intra-articular sagittal graft angles were also measured. The Impingement Review Index (IRI) was used to evaluate for graft impingement.Results:Two grafts (2/6, 33.3%) in the TT group impinged upon the intercondylar roof and demonstrated angular deformity (IRI type 1). No grafts in the IF group impinged, although 2 of 6 (66.7%) IF grafts touched the roof without deformation (IRI type 2). The presence or absence of impingement was not statistically significant. The mean sagittal tibial tunnel guide pin position prior to drilling was 27.6% of the sagittal diameter of the tibia (range, 22%-33.9%). However, computed tomography performed postdrilling detected substantial posterior enlargement in 2 TT specimens. A significant difference in the sagittal graft angle was noted between the 2 groups. TT grafts were more vertical, leading to angular convergence with the roof, whereas IF grafts were more horizontal and universally diverged from the roof.Conclusion:The IF technique had no specimens with roof impingement despite an anterior tibial tunnel position, likely due to a more horizontal graft trajectory and anatomic placement of the ACL femoral tunnel. Roof impingement remains a concern after TT ACL reconstruction in the setting of anterior tibial tunnel placement, although statistical significance was not found. Future clinical studies are planned to develop better recommendations for ACL tibial tunnel placement.Clinical Relevance:Graft impingement due to excessively anterior tibial tunnel placement using a TT drilling technique has been previously demonstrated; however, this may not be a concern when using an IF tunnel drilling technique. There may also be biomechanical advantages to a more anterior tibial tunnel in IF tunnel ACL reconstruction.

Physeal Disruption During ACL Reconstruction in Skeletally Immature Patients

Objectives:The purpose of this study was to radiographically assess differences in distal femoral physeal disruption between transtibial and independent femoral tunnel drilling techniques following ACL reconstruction in skeletally immature patients.Methods:A retrospective, matched comparative cohort study was performed of skeletally immature patients who underwent transphyseal ACL reconstruction between January 1, 2008 and March 31, 2011. All skeletally immature patients between ten and fifteen years old who underwent independent femoral tunnel drilling and had adequate baseline and post-operative radiographs were analyzed. These patients were matched with a transtibial technique cohort based on age and sex. Demographic characteristics and peri-operative metrics were collected. Radiographic measurements were recorded from pre-operative MRI and post-operative plain radiographs.Results:Twenty patients were analyzed. Between groups, there were significant differences between independent tunnel drilling and transtibial tunnel drilling in the estimated area of physeal disruption (1.64 cm2 vs. 0.74 cm2, P<0.001), femoral (32.1º vs. 72.8º, P<0.001) and tibial (50.1º vs. 60.5º, P=0.003) tunnel angles, medial/lateral location of the femoral tunnel (24.2 mm vs. 36.1 mm from lateral cortex, P=0.001), and distance from the lateral aspect of the distal femoral physis and the femoral tunnel exit (4.7 mm vs. 26.7 mm from the perichondrial ring, P<0.001), respectively. All patients who underwent femoral tunnel drilling at an angle of less than 25º from the transverse axis experienced a greater than 6% disruption of physeal area. There was a significant inverse correlation between femoral tunnel angle and estimated area of femoral physeal involvement (r=-0.8255, P=0.003).Conclusion:With femoral tunnel drilling techniques that create more oblique tunnels, the area of distal femoral physeal damage is larger, more eccentric and closer to the perichondrial ring. Since most studies noting the safety of transphyseal ACL reconstruction have utilized a vertical femoral tunnel, surgeons should be aware that if an independent femoral tunnel drilling technique is utilized during transphyseal ACL reconstruction, the physis is at greater risk when drilling at more horizontal angles. Angles greater than 25º from the transverse axis may safely create <6% physeal area damage.

Transphyseal ACL Reconstruction in Skeletally Immature Patients: Does Independent Femoral Tunnel Drilling Place the Physis at Greater Risk Compared With Transtibial Drilling?

Background:Most studies examining the safety and efficacy of transphyseal anterior cruciate ligament (ACL) reconstruction for skeletally immature patients utilize transtibial drilling. Independent femoral tunnel drilling may impart a different pattern of distal femoral physeal involvement.Purpose:To radiographically assess differences in distal femoral physeal disruption between transtibial and independent femoral tunnel drilling. We hypothesized that more oblique tunnels associated with independent drilling involve a significantly larger area of physeal disruption compared with vertically oriented tunnels.Study Design:Cross-sectional study; Level of evidence, 3.Methods:We analyzed skeletally immature patients aged between 10 and 15 years who underwent transphyseal ACL reconstruction utilizing an independent femoral tunnel drilling technique between January 1, 2008, and March 31, 2011. These patients were matched with a transtibial technique cohort based on age and sex. Radiographic measurements were recorded from preoperative magnetic resonance imaging and postoperative radiographs.Results:Ten patients in each group were analyzed. There were significant differences between independent drilling and transtibial drilling cohorts in the estimated area of physeal disruption (1.64 vs 0.74 cm2; P < .001), femoral tunnel angles (32.1° vs 72.8°; P < .001), and medial/lateral location of the femoral tunnel (24.2 vs 36.1 mm from lateral cortex; P = .001), respectively. There was a significant inverse correlation between femoral tunnel angle and estimated area of distal femoral physeal disruption (r = –0.8255, P = .003).Conclusion:Femoral tunnels created with an independent tunnel drilling technique disrupt a larger area of the distal femoral physis and create more eccentric tunnels compared with a transtibial technique.Clinical Relevance:As most studies noting the safety of transphyseal ACL reconstruction have utilized a central, vertical femoral tunnel, surgeons should be aware that if an independent femoral tunnel technique is utilized during transphyseal ACL reconstruction, more physeal tissue is at risk and tunnels are more eccentrically placed across the physis when drilling at more horizontal angles. Prior studies have shown that greater physeal involvement and eccentric tunnels may increase the risk of growth disturbance.

Transphyseal ACL Reconstruction in Skeletally Immature Patients: Does Independent Femoral Tunnel Drilling Place the Physis at Greater Risk Compared to Transtibial Drilling?

The purpose of this study was to radiographically assess differences in physeal disruption between transtibial and independent tunnel drilling techniques following ACL reconstruction in skeletally immature patients. A retrospective, matched comparative cohort study was performed of skeletally immature patients who underwent transphyseal ACL reconstruction between January 1, 2008 and March 31, 2011. All skeletally immature patients between 10 and 15 years old who underwent independent femoral tunnel drilling and had adequate baseline and post-operative radiographs were analyzed. These patients were matched with a transtibial technique cohort based on age and sex. Demographic characteristics and peri-operative metrics were collected. Radiographic measurements were recorded from pre-operative MRI and post-operative plain radiographs. Twenty patients were analyzed. Between groups, there were significant differences in the estimated area of physeal disruption (1.64 cm2 vs. 0.74 cm2, P<0.001), femoral (32.1° vs. 72.8°, P<0.001) and tibial (50.1° vs. 60.5°, P=0.003) tunnel drill angles, medial/lateral location of the femoral tunnel (24.2 mm vs. 36.1 mm from lateral cortex, P=0.001), and distance from the lateral aspect of the distal femoral physis and the femoral tunnel exit (4.7mm vs. 26.7mm from the perichondrial ring, P<0.001). All patients who underwent femoral tunnel drilling at an angle of greater than 25° from the transverse axis experienced a <6% disruption of physeal area. With femoral tunnel drilling techniques that create more oblique tunnels, the area of physeal damage is larger, more eccentric and closer to the perichondrial ring. Since most studies noting the safety of transphyseal ACL reconstruction have utilized a vertical femoral tunnel, surgeons should be aware that if an independent femoral tunnel drilling technique is utilized during transphyseal ACL reconstruction, the physis is at greater risk when drilling at more horizontal angles. Angles greater than 25° from the transverse axis may safely create <6% physeal area damage.

Femoral Condyle Fracture during Anterior Cruciate Ligament Reconstruction.

Dear Editor,We have greatly enjoyed reading the case report entitled “‘Femoral Condyle Fracture during Revision of Anterior Cruciate Ligament Reconstruction: Case Report and a Review of Literature in the issue of Arch Bone Jt Surg. 2015;3(2) with great interest. We would like to commend the authors for their detailed and valuable work. Although various case reports have described postoperative distal femur fracture at a range of time intervals (1,2) intraoperative intra-articular distal femur fracture is a unique entity.However, we believe that some important additional observations seem necessary to be contributed through this study. In this article, the authors stated that, to the best of their knowledge, there is no other case report in the literature introducing a femoral condyle fracture during arthroscopic ACL reconstruction or revision reconstruction. Nevertheless, we would like to call the attention of the readers to the fact that that the literature contains one additional case report re‌porting on intraoperative distal femoral coronal plane (Hoffa) fracture during primary ACL reconstruction (2). Werner BC and Miller MD presented of case report of an intraoperative distal femoral coronal plane (Hoffa) fracture that occurred during independent femoral tunnel drilling and dilation in a primary ACL reconstruction. As in the their case, this type of fracture can occur with appropriately placed femoral tunnels, but the risk can increase with larger graft diameters in patients with smaller lateral femoral condyles The patient was treated with open reduction and internal fixation, without compromise of graft stability and with good recovery of function. We believe that tailoring graft size to the size of the patient is important to prevent similar adverse events.

ACL Roof Impingement Revisited

Objectives:Anatomic femoral tunnel placement for single-bundle ACL reconstruction is now well accepted. The ideal location for the tibial tunnel, however, has not been studied extensively. A wide range of anterior to posterior (A-P) tibial tunnel locations are considered acceptable. Biomechanical data suggests that the anterior fibers of the native ACL are more functional. Similarly, ACL grafts placed more anteriorly in the footprint have resulted in improved clinical results in at least one study. However, the concern for intercondylar roof impingement has tempered enthusiasm for a more anterior tibial tunnel placement. Investigations by Howell and others on roof impingement have focused only on the transtibial technique. Our study seeks to characterize intercondylar roof impingement in a 3-D cadaveric model with both transtibial and independent femoral tunnel drilling techniques in the setting of an anteriorly positioned tibial tunnel.Methods:Twelve fresh frozen cadaver knees (six matched pairs) were randomized to either a transtibial or an independent femoral (IF) drilling technique. Tibial guide pins were placed in the anterior half of the ACL tibial footprint following arthroscopic debridement of the native ACL. A fluoroscopic calculation of the tibial guide pin location using the technique described by Staubli was used to ensure a relatively anterior position of the tibial tunnel (Staubli < 35). All efforts were made to place the femoral tunnel anatomically in the center of the footprint. An 8 mm Gore-Tex smoother was passed into the knee to function as a radiopaque surrogate graft, and the knees then underwent computed tomography in maximal extension. Graft-visualized 3D-CT reformatting was used to evaluate for roof impingement by analyzing the Impingement Review Index (IRI) as described by Iriuchishima. Tunnel morphology, knee flexion, and intra-articular graft angles were also recorded.Results:Two grafts (2/6, 33.3 %) in the TT group impinged upon the intercondylar roof and sustained an angular deformity (IRI Type 1) Figure 1. No grafts in the IF group impinged; 4/6 (66.7%) grafts in the IF group touched the roof but did not deflect (IRI Type 2). The average tibial tunnel fluoroscopic Staubli ratio was 31.9 (range 22 - 39). The impinging TT grafts had an average Staubli ratio of 29.4 while the non-impinging TT grafts had more posterior tibial tunnels (Staubli 38). This did not reach statistical significance. All other grafts avoided contact with the roof (IRI Type 3). Two tibial tunnels in the TT group migrated posteriorly more than 6 mm after femoral tunnel drilling, and this may have prevented graft impingement. No significant differences were found between the tibial tunnel locations in the IF group.Conclusion:The independent femoral drilling technique appears to have a low risk for roof impingement in the setting of anterior tibial tunnel positioning, likely because of more favorable graft trajectory afforded by an anatomic femoral tunnel that lies below Blumensaat's line. Roof impingement remains a concern after transtibial ACL reconstruction with a more anterior tibial tunnel. An unintended protective effect may occur during transtibial drilling that expands the tibial tunnel posteriorly. Future clinical studies are planned to develop better recommendations for ACL tibial tunnel placement.

Tibial Tunnel Placement Accuracy During Anterior Cruciate Ligament Reconstruction: Independent Femoral Versus Transtibial Femoral Tunnel Drilling Techniques

This study aimed to compare the accuracy of tibial tunnel placement using independent femoral (IF) versus transtibial (TT) techniques. Ten matched pairs of cadaveric knees were randomized so that one knee in the pair underwent arthroscopic TT drilling of the femoral tunnel and the other underwent IF drilling through an accessory medial portal. For both techniques, an attempt was made to place the femoral and tibial tunnels as close to the center of the respective anterior cruciate ligament (ACL) footprints as possible. Preoperative and postoperative computed tomography using a technique optimized for ligament evaluation allowed comparison of the anatomic ACL tibial footprint to the tibial tunnel aperture. The percentage of tunnel aperture contained within the native footprint, as well as the distance from the center of the tunnel aperture to the center of the footprint, was measured. Additionally, graft obliquity relative to the tibial plateau was evaluated in the sagittal plane. The percentage of tibial tunnel aperture contained within the native footprint averaged 71.6% ± 17.2% versus 52.1% ± 23.4% (P = .04) in the IF and TT groups, respectively. The distance from the center of the footprint to the center of the tibial tunnel aperture was 3.50 ± 1.6 mm and 4.40 ± 1.7 mm (P = .27) in the IF and TT groups, respectively. TT drilling placed 6 of 10 tunnels posterior to the center of the footprint versus 3 of 10 tunnels in IF drilling. The graft obliquity angles were 54.8° in TT specimens and 47.5° in IF specimens (P = .09). This study adds to the literature suggesting that TT drilling with an 8-mm reamer has deleterious effects on tibial tunnel aperture and position. IF drilling, which does not involve repeated reaming of the tibial tunnel, is associated with the placement of a higher percentage of the tunnel aperture within the native tibial footprint. There was not a significant difference between the IF and TT techniques in their ability to place the center of the tibial aperture near the center of the footprint or in graft obliquity. ACL reconstruction has continued to evolve in an attempt to restore the functional anatomy and biomechanical behavior of the knee. Tibial tunnel characteristics-such as location, aperture topography, and tunnel obliquity-are important factors to consider in ACL reconstruction. This study compares tibial tunnels after IF and TT techniques.

Femoral Tunnel Length in Primary Anterior Cruciate Ligament Reconstruction Using an Accessory Medial Portal

The purpose of this study was to evaluate tunnel length during independent femoral tunnel drilling using an accessory medial portal with the knee in maximal hyperflexion, and correlate the tunnel length and flexion angle with anthropometric data. During a 1-year period, 106 consecutive patients undergoing primary anterior cruciate ligament (ACL) reconstruction were included in the study. All patients underwent independent femoral tunnel drilling using an accessory medial portal with maximal knee hyperflexion. Tunnel length and maximal intraoperative knee flexion angles were measured. Additionally, height, weight, and body mass index (BMI), plus the width and depth ofthe lateral femoral condyle (LFC), were recorded to correlate with tunnel length and knee flexion angles. Average tunnel length was 37.0 ± 3.3 mm (range, 26 to 45), with all but one tunnel greater than 30 mm. Average knee flexion angle was 134.4 ± 5.0° (range, 122° to 147°). Height (r= 0.5, P < .001) and weight (r= 0.33, P= .001), but not BMI (r= 0.14, P= .17), correlated positively with tunnel length. Width (r= 0.46, P < .001) and depth (r=0.38, P < .001) of the LFC also correlated positively with tunnel length. Knee flexion angle was not correlated with tunnel length (r=-0.09, P= .39) or width (r=-0.04, P= .7) and depth (r=-0.01, P= .91) of the LFC. Knee flexion angle was negatively correlated with weight (r=-0.44, P < .001) and BMI (r=-0.46, P < .001). Using an accessory medial portal for independent femoral tunnel drilling, with maximal knee hyperflexion, in ACL reconstruction consistently produced tunnel lengths greater than 30 mm with no posterior wall fractures. Tunnel lengths tend to be longer with increasing patient height, mass, and larger LFC dimensions. Maximum knee flexion angle achieved intraoperatively tends to be less for patients with increasing weight and BMI. Level IV, therapeutic case series.

Femoral Tunnel Length in Anterior Cruciate Ligament Reconstruction Using an Accessory Medial Portal (SS-66)

Independent femoral tunnel drilling has been described in anterior cruciate ligament (ACL) reconstruction, however there is concern that tunnels will be too short. To counterbalance that and also provide better exposure to the notch, hyperflexion of the knee and the use of an accessory medial portal have been described. (Figure 1) The purpose of this study was to evaluate tunnel length during independent femoral tunnel drilling using an accessory medial portal with the knee in maximal hyperflexion, and then correlate the tunnel length and flexion angle with anthropometric data. During a 9 month period, 83 consecutive patients undergoing primary ACL reconstruction by the three senior authors were included in the study. All patients underwent independent femoral tunnel drilling using an accessory medial portal with maximal knee hyperflexion. Tunnel length and maximal intra-operative knee flexion angles were measured. In addition, height, weight, and body mass index (BMI) were recorded in order to correlate with tunnel length and knee flexion angles. The size of the lateral femoral condyle (LFC), as measured on magnetic resonance imaging (MRI) or plain radiograph, was also correlated with tunnel length and knee flexion angles (available in 67 patients). The average tunnel length was 36.8 +/− 3.3 mm (range 26-45) with all but one tunnel greater than 30 mm. The average knee flexion angle was 134.3 +/− 5.0 degrees (range 122-147). The average BMI was 27.7 +/− 7.9 kg/m2 (range 17.7-63.3), calculated from average height 173.3 +/− 9.1 cm (range 150-195.6) and weight 83.3 +/− 24.8 kg (range 49.7-172.2). Average LFC width was 32.6 +/− 4.8 cm (range 26.1-60.3), and depth was 60.6 +/− 5.0 cm (range 48.1-73.3). Height (r=0.52, P<0.001) and weight (r=0.34, P=0.002), but not BMI, correlated positively with tunnel length. Width (r=0.33, P=0.006) and depth (r=0.34, P=0.005) of the LFC also correlated positively with tunnel length. Knee flexion angle was not correlated with tunnel length (r=-0.08, P=0.45), or width (r=−0.06, P=0.62) and depth (r=−0.14, P=0.28) of the LFC. Knee flexion angle was negatively correlated with weight (r=−0.55, P<0.001) and BMI (r=−0.55, P<0.001). Using an accessory medial portal for independent femoral tunnel drilling with maximal knee hyperflexion in ACL reconstruction produced only one tunnel less than 30mm. This technique, therefore, consistently produces tunnels of adequate length. Tunnel lengths tend to be longer with increasing patient height, mass, and larger LFC dimensions. Maximum knee flexion angle achieved intraoperatively tends to be less for patients with increasing weight and BMI.

Anatomic Femoral Tunnel Drilling in Anterior Cruciate Ligament Reconstruction

Background: During anatomic anterior cruciate ligament (ACL) reconstruction, we have found that the femoral footprint can best be visualized from the anteromedial portal. Independent femoral tunnel drilling can then be performed through an accessory medial portal, medial and inferior to the standard anteromedial portal. Purpose: To compare the accuracy of independent femoral tunnel placement relative to the ACL footprint using an accessory medial portal versus tunnel placement with a traditional transtibial technique. Study Design: Controlled laboratory study. Methods: Ten matched pairs of cadaveric knees were randomized such that within each pair, one knee underwent arthroscopic transtibial (TT) drilling, and the other underwent drilling through an accessory medial portal (AM). All knees underwent computed tomography (CT) both preoperatively and postoperatively with a technique optimized for ligament evaluation (80 keV with maximum mAs). Computed tomography was performed with a dual-energy scanner. Commercially available third-party software was used to fuse the preoperative and postoperative CT scans, allowing anatomic comparison of the ACL footprint to the drilled tunnel. The ACL footprint was marked in consensus by an orthopaedic surgeon and a musculoskeletal radiologist and then compared with the tunnel aperture after drilling. The percentage of tunnel aperture contained within the native footprint as well as the distance from the center of the tunnel aperture to the center of the footprint was measured. Results: The AM technique placed 97.7% ± 5% of the tunnel within the native femoral footprint, significantly more than 61.2% ± 24% for the TT technique (P = .001). The AM technique placed the center of the femoral tunnel 3.6 ± 1.2 mm from the center of the native footprint, significantly closer than 6.0 ± 1.9 mm for the TT technique (P = .003). Conclusion: This study demonstrates that use of an accessory medial portal will facilitate more accurate placement of the femoral tunnel in the native ACL femoral footprint. Clinical Relevance: More accurate placement of the femoral tunnel in the native ACL femoral footprint should improve the ability to achieve more anatomic positioning of the ACL graft.