Impingement pressure in the anatomical and nonanatomical anterior cruciate ligament reconstruction: a cadaver study

Size Comparison of the Cadaveric Anterior Cruciate Ligament Midsubstance Cross-Sectional Area and the Cross-Sectional Area of Semitendinosus Double-Bundle Anterior Cruciate Ligament Reconstruction Autografts in Surgery

The purpose of this study was to compare the cadaveric midsubstance cross-sectional anterior cruciate ligament (ACL) area and the cross-sectional semitendinosus (ST) double-bundle ACL autograft area in surgery. Thirty-nine nonpaired formalin-fixed cadaveric knees and 39 subjects undergoing ST double-bundle ACL reconstruction were included in this study. After soft tissue resection, cadaveric knees were flexed at 90 degrees, and the tangential line of the femoral posterior condyles was marked and sliced on the ACL midsubstance. The cross-sectional ACL area was measured using Image J software. In the patients undergoing ACL surgery, the harvested ST was cut and divided into anteromedial (AM) bundle and posterolateral (PL) bundle. Each graft edge diameter was measured by a sizing tube, and the cross-sectional graft area was calculated: (AM diameter/2)2 × 3.14 + (PL diameter/2)2 × 3.14. Statistical analysis was performed for the comparison of the cross-sectional area between the cadaveric ACL midsubstance and the ST double-bundle ACL autografts. The cadaveric midsubstance cross-sectional ACL area was 49.0 ± 16.3 mm2. The cross-sectional ST double-bundle autografts area was 52.8 ± 7.6 mm2. The ST double-bundle autograft area showed no significant difference when compared with the midsubstance cross-sectional ACL area. ST double-bundle autografts were shown to be capable of reproducing the midsubstance cross-sectional ACL area.

Rebranding the 'anatomic' ACL reconstruction: Current concepts

The anterior cruciate ligament (ACL) is a complex ribbon-like structure, which is approximately 3.5 times larger at the tibial and femoral insertions than at the midpoint. Accordingly, it is impossible to recreate with a single cylindrical graft. However, this has not stopped surgeons from using the term "anatomic" to describe multiple ACL reconstruction techniques inserting at a number of different locations within the original ACL footprint, causing confusion. The term "anatomic" should be discarded and replaced by an anatomic description of the tunnel placements on the tibia and femur. Current ACL reconstruction techniques cite anatomical studies that identified "direct and indirect fibres" of the ACL. The "direct fibres" bear 85-95% of the load and provide the main resistance to both anterior tibial translation and internal rotation/pivot shift. On the femur, these fibres insert in a line just posterior to the intercondylar ridge and comprise the portion of the ACL that surgeons should strive to restore. Placement of the graft just posterior to the intercondylar ridge creates a line of placement options from the anteromedial bundle to the "central" position and finally to the posterolateral bundle position. The authors prefer placing the femoral tunnel in the isometric anteromedial position and addressing a high-grade pivot shift at the IT-band with a lateral extra-articular tenodesis. As with the femoral tunnel, the native ACL footprint on the tibia is much larger than the ACL graft and thus can be placed in multiple "anatomic" locations. The authors prefer placement of the tibial tunnel in the anterior most position of the native footprint that does not cause impingement in the femoral notch. Additional research is needed to determine the ideal tunnel positions on the femur and tibia and validating the technique with patient outcomes. However, this cannot be accomplished without describing tunnel placement with specific anatomical locations so other surgeons can replicate the technique.

A wear model to predict damage of reconstructed ACL

Impingement with surrounding tissues is a major cause of failure of anterior cruciate ligament reconstruction. However, the complexity of the knee kinematics and anatomical variations make it difficult to predict the occurrence of contact and the extent of the resulting damage. Here we hypothesise that a description of wear between the reconstructed ligament and adjacent structures captures the in vivo damage produced with physiological loadings. To test this, we performed an in vivo study on a sheep model and investigated the role of different sources of damage: overstretching, excessive twist, excessive compression, and wear. Seven sheep underwent cranial cruciate ligament reconstruction using a tendon autograft. Necropsy observations and pull-out force measurements performed postoperatively at three months showed high variability across specimens of the extent and location of graft damage. Using 3D digital models of each stifle based on X-ray imaging and kinematics measurements, we determined the relative displacements between the graft and the surrounding bones and computed a wear index describing the work of friction forces underwent by the graft during a full flexion-extension movement. While tensile strain, angle of twist and impingement volume showed no correlation with pull-out force (ρ = -0.321, p = 0.498), the wear index showed a strong negative correlation (r = -0.902, p = 0.006). Moreover, contour maps showing the distribution of wear on the graft were consistent with the observations of damage during the necropsy. These results demonstrate that wear is a good proxy of graft damage. The proposed wear index could be used in implant design and surgery planning to minimise the risk of implant failure. Its application to sheep can provide a way to increase preclinical testing efficiency.

Bone-patellar tendon-bone autograft and female sex are associated with the presence of cyclops lesions and syndrome after anterior cruciate ligament reconstruction

PURPOSE

Associated risk factors for the development of cyclops lesions have been little. Investigated, because most previous studies have limited their research to cases with symptomatic cyclops lesions (cyclops syndrome). The purpose of this study was to evaluate the presence of cyclops lesions using magnetic resonance image (MRI) at 6 and 12 months after anterior cruciate ligament reconstruction (ACL-R), and to investigate the associated risk factors of cyclops lesions and syndrome.

METHODS

A retrospective analysis of patients who underwent ACL-R using bone-patellar tendon-bone (BTPB) or hamstring tendon autograft from 2008 to 2017 was conducted. Predictor variables (age, sex, body mass index [BMI], time from injury to ACL-R, preinjury Tegner activity score, graft, meniscal and cartilage injury, and notch width index on MRI for the presence of cyclops lesions and syndrome were analyzed with multivariate logistic regression.

RESULTS

Four hundred and fifty-five patients (225 males and 230 females) were enrolled. One hundred and four patients (22.9%) had cyclops lesions, and all cyclops lesions were detected on MRI at 6 months post-operatively. In addition, 20 patients (4.4%) had cyclops syndrome which means that these were symptomatic cases. The risk factors for presence of cyclops lesions were BPTB autograft (OR = 2.85; 95% CI 1.75-4.63; P < 0.001) and female sex (OR = 2.03; 95% CI 1.27-3.25; P = 0.003). The presence of cyclops syndrome increased with graft (BPTB) (OR = 18.0; 95% CI 3.67-88.3; Powered by Editorial Manager^® and ProduXion Manager^® from Aries Systems Corporation P < 0.001), female sex (OR = 3.27; 95% CI 1.07-10.0; P = 0.038), and increased BMI (OR = 1.21; 95% CI 1.05-1.39; P = 0.008).

CONCLUSIONS

All cyclops lesions were detected 6 months after ACL-R, and the majority of them were asymptomatic. BPTB autograft and female sex were the significant risk factors for the presence of cyclops lesions and syndrome. In addition, increased BMI was associated with a higher risk of developing cyclops syndrome. When BPTB autograft is used for a female patient, full active knee extension should be encouraged in the early period after ACL-R to prevent cyclops lesion formation.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Minimizing the risk of graft failure after anterior cruciate ligament reconstruction in athletes. A narrative review of the current evidence

Anterior cruciate ligament (ACL) tear is one of the most common sport-related injuries and the request for ACL reconstructions is increasing nowadays. Unfortunately, ACL graft failures are reported in up to 34.2% in athletes, representing a traumatic and career-threatening event. It can be convenient to understand the various risk factors for ACL failure, in order to properly inform the patients about the expected outcomes and to minimize the chance of poor results. In literature, a multitude of studies have been performed on the failure risks after ACL reconstruction, but the huge amount of data may generate much confusion.The aim of this review is to resume the data collected from literature on the risk of graft failure after ACL reconstruction in athletes, focusing on the following three key points: individuate the predisposing factors to ACL reconstruction failure, analyze surgical aspects which may have significant impact on outcomes, highlight the current criteria regarding safe return to sport after ACL reconstruction.

Quantifying graft impingement in anterior cruciate ligament reconstruction

BACKGROUND

Anterior cruciate ligament reconstructions (ACLR) fail at a rate of 10-15%, with graft impingement often a cause. In this study we investigate the prevalence and causes of impingement seen during ACLR surgery.

METHODS

We reviewed consecutive primary ACLR from 2012-2018. Graft impingement was estimated intraoperatively by placing the arthroscope through the tibial tunnel and passively extending the knee, observing how much was obscured by the lateral femoral condyle from an anterior and lateral direction. Preoperative MRI scans were used to measure the intercondylar notch; Notch Width Index (NWI) and Notch Depth Index (NDI). Positioning of the tunnels was determined on postoperative radiographs.

RESULTS

There were 283 ACLRs performed with 33 failures diagnosed on MRI (11.7%). 257 patients had complete imaging and follow up (91%). The mean age was 28 (±9) years and mean follow-up 5.3 (±1.8) years. The mean NWI was 0.26(±0.03), and NDI was 0.49(±0.06). The tibial tunnel aperture was located 42(±6) % of the way from anterior-posterior and 39(±6) % from medial-lateral. Impingement requiring a notchplasty was observed in 80% of cases, with lateral impingement more prominent.

CONCLUSIONS

The amount of impingement did not correlate with tunnel position, which was located within the recommended area. There was a weak negative correlation between NWI and lateral impingement (r_s = -0.16, p = 0.01), and NDI and anterior impingement (r_s = -0.12, p = 0.04), therefore a smaller notch is associated with greater impingement. Despite optimal tunnel positioning, impingement still occurs in a significant number of cases therefore notchplasty should always be considered to keep revision rates low.

Sensitivity analysis of the knee ligament forces to the surgical design variation during anterior cruciate ligament reconstruction: a finite element analysis

The purpose of this study is to understand the effect of essential surgical design parameters on collateral and cruciate ligaments behavior for a Bone-Patellar-Tendon-Bone (BPTB) anterior cruciate ligament reconstruction (ACL-R) surgery. A parametric finite element model of biomechanical experiments depicting the ACL-R surgery associated with a global sensitivity analysis was adopted in this work. The model parameters were six intraoperative variables, two-quadrant coordinates of femoral tunnel placement, femoral tunnel sagittal and coronal angles, graft pretension, and the joint angle at which the BPTB graft is tensioned (fixation angle). Our results indicated that cruciate ligaments (posterior cruciate ligament (PCL) and graft) were mainly sensitive to graft pretension (23%), femoral tunnel sites (56%), and the angle at which the surgeon decided to fix the graft (14%). The collateral ligaments (medial and lateral) were also affected by the same set of surgical parameters as the cruciate ligaments except for graft pretension. The output data of this study may help to identify a better role for the ACL-R intraoperative variables in optimizing the knee joint ligaments' postsurgical functionality.

The risk of graft impingement still exists in modern ACL surgery and correlates with degenerative MRI signal changes

PURPOSE

Anatomic tunnel placement in ACL reconstruction is crucial to restore knee function. The aims of this study were to (i) evaluate the accuracy of tunnel placement for primary state-of-the-art ACL reconstruction, and (ii) examine the correlation between incorrect tunnel placement, graft appearance, and notch impingement.

METHODS

In this retrospective study, all patients underwent primary single-bundle ACL reconstruction with independent drilling of the femoral and tibial tunnels according to anatomical landmarks. The accuracy of tunnel placement and the rate of notch impingement were analysed with MRI. The study cohort was subdivided according to the morphology of the graft: intact, degeneration, and re-rupture. The objective outcome was evaluated with the IKDC objective score, and the subjective outcomes were evaluated with the IKDC subjective score, the Lysholm knee score, the KOOS, and the Tegner activity scale score.

RESULTS

Eighty-seven consecutive patients with a mean follow-up of 3.8 ± 1.4 years were evaluated. There was no significant difference among the groups concerning the baseline characteristics. The re-rupture rate was 9.2%. The position of the femoral tunnel was correct in 92% of the patients, and the position of the tibial tunnel was correct in 93% of the patients. In the intact group, impingement was not found in any of the cases, whereas the rate of impingement in the degeneration (65%) and re-rupture (80%) groups was significantly higher than that in the intact group (p < 0.001). The risk of impingement was more likely with femoral (71% vs. 13%, p < 0.001) or tibial (100% vs. 11%, p < 0.001) malpositioning. The objective IKDC score was A in 52 patients (60%), B in 26 patients (30%), and C in 9 patients (10%). The average subjective IKDC score, Lysholm score, and KOOS were comparable in the intact and degeneration groups but significantly lower in the patient group with newly diagnosed re-ruptures (p = 0.05). The Tegner activity scale score was comparable in all three groups.

CONCLUSION

Even though the accuracy of femoral tunnel placement in modern single-bundle ACL reconstruction is greater, the risk of malpositioning and graft impingement remains. In our patient cohort, there was a clear correlation between ACL graft impingement, degenerative changes in MRI, and incorrect tunnel positioning. The surgeon must focus on accurate tunnel placement specific to individual patient anatomy.

LEVEL OF EVIDENCE

Level III.

Femoral Tunnel Widening After Double-Bundle Anterior Cruciate Ligament Reconstruction With Hamstring Autograft Produces a Small Shift of the Tunnel Position in the Anterior and Distal Direction: Computed Tomography-Based Retrospective Cohort Analysis

PURPOSE

To determine whether the femoral tunnel position remains in an anatomical footprint after tunnel widening and shifting.

METHODS

Patients who underwent unilateral double-bundle anterior cruciate ligament reconstruction with hamstring autograft and performed computed tomography scan evaluation at the time of 5 days and 1 year postoperatively were included in this retrospective cohort study. Three-dimensional models of the femur and femoral tunnels were reconstructed from computed tomography scan data. The location of the tunnel center and tunnel margins in the anatomical coordinate system, and the mean shifting distance of tunnel center and margin were measured with image analysis software during the period. The change of tunnel center location in Bernard quadrant was confirmed if the tunnel center remained within the boundaries of anatomical position after tunnel widening.

RESULTS

A total of 56 patients satisfied the inclusion criteria. The mean shifting distance of AM and PL tunnel centers were 1.7 ± 0.9 mm and 1.6 ± 0.6 mm. The Tunnel margin of the anteromedial (AM) and posteromedial (PL) tunnels were shifted to 2.5 ± 1.3 mm and 2.6 ± 1.4 mm in the anterior direction, and 1.4 ± 0.9 mm and 1.0 ± 0.7 mm in the distal direction, respectively. Among the anatomical located tunnel, 97% (32/33) and 87.1% (27/31) of AM and PL tunnel centers remained in a range of anatomical footprint. The tunnel center was shifted from the anatomical position into a nonanatomical position in 3% (1/33) of the AM tunnel and 12.9% (4/31) of PL tunnel after tunnel widening. The tunnel location which shifted nonanatomically were relatively anterior and distal position.

CONCLUSIONS

Tunnel widening shifts the tunnel position to the anterior and distal direction, which could change the initial tunnel position. Nevertheless, the majority of tunnel positions remained in the anatomical position after tunnel widening and shifting.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Combination of anterior tibial and femoral tunnels makes the signal intensity of antero-medial graft higher in double-bundle anterior cruciate ligament reconstruction

PURPOSE

To elucidate whether sagittal graft tunnel affects the signal intensity in anatomical ACL reconstruction (ACLR) and to clarify the prevalence of intercondylar roof impingement. It was hypothesized that if the tunnel apertures are located within the anatomical footprint of ACL, tunnel position would not affect the signal intensity.

METHODS

A total of 132 patients who underwent anatomical double-bundle ACLR (DB-ACLR) using hamstring autograft were recruited. Tunnel position was determined by the quadrant method on three-dimensional computed tomography; the femoral tunnel position was defined as "high and low" or "deep and shallow", while that of the tibial side was defined as "anterior and posterior" or "medial and lateral". Subjects were divided into three groups according to the tertile of % deep-shallow. The signal intensity was evaluated by the region of interest value of the antero-medial bundle (AMB) and postero-lateral bundle on magnetic resonance imaging at 12 months after reconstruction. Linear regression analysis was conducted to elucidate the relationship between the percentage position of each tunnel and the graft signal intensity.

RESULTS

In the shallow tertile group, AMB signal intensity increased in the anterior position of the tibial tunnel (β = - 0.34; P = 0.025). In the intermediate and deep tertile groups, the tunnel position did not correlate with the signal intensity.

CONCLUSIONS

A more anterior tibial tunnel position increases AMB signal intensity in shallower femoral tunnel. Conversely, this correlation is attenuated for deeper femoral tunnels. Surgeons should pay attention to sagittal femoral tunnel position to create a more anterior tibial tunnel position.

LEVEL OF EVIDENCE

Level III.

Interbundle Impingement Pressure in Individualized and Nonindividualized Double-Bundle Anterior Cruciate Ligament Reconstruction: A Cadaveric Study

Background:

Graft impingement is one of the main concerns in double-bundle anterior cruciate ligament reconstruction (DB-ACLR). Impingement between the anteromedial (AM) and posterolateral (PL) bundles has been postulated to cause graft deterioration or rerupture, but this has not been thoroughly investigated, and the interbundle impingement pressure (IIP) has not been well researched.

Purpose:

To determine the IIP between the AM and PL bundles in the native anterior cruciate ligament (ACL) and in DB-ACLR with individualized and nonindividualized double-tunnel placement.

Study Design:

Controlled laboratory study.

Methods:

A total of 30 fresh-frozen, nonpaired, human cadaveric knees were randomly divided into 3 groups of 10 knees: native intact ACL (NI group), DB-ACLR tunnel placement using the preserved remnant procedure (individualized reconstruction) (PR group), and DB-ACLR tunnel placement using the bony landmark procedure (nonindividualized reconstruction) (BL group). Pressure sensors were inserted between the AM and PL bundles. The knee was moved passively from full extension to full flexion, and the IIP between the 2 ACL bundles was measured every 15°. Similarly, the impingement pressure was measured between the ACL and intercondylar roof and between the ACL and posterior cruciate ligament (PCL).

Results:

No significant differences were found in the maximum, mean, or minimum ACL-roof and ACL-PCL impingement pressures among the 3 groups. The IIP significantly increased when the knee joint was flexed >120° in all 3 groups (P < .001). Compared with the other 2 groups, the BL group had significantly higher maximum and mean IIP throughout the range of knee movement (P < .001) and from maximum extension to 120° of flexion (P < .001). The BL group also had significantly higher minimum IIP than the other 2 groups when knee flexion was >120° (P < .001). No significant differences were seen in maximum, minimum, or mean IIP between the NI and PR groups.

Conclusion:

The PR procedure (individualized DB-ACLR) was more consistent with the interbundle biomechanical conditions of the native ACL, whereas the BL procedure (nonindividualized DB-ACLR) had higher maximum and mean IIP. The IIP was higher than the ACL–intercondylar roof or ACL-PCL pressures, and it increased significantly when knee flexion was >120°.

Clinical Relevance:

These data suggest that surgeons can perform individualized DB-ACLR using preserved remnants for tunnel placement as impingement-free DB-ACLR.

The location of the femoral ACL footprint center is different depending on the Blumensaat's line morphology

PURPOSE

The purpose of this study was to evaluate the difference in the center point of the femoral ACL footprint according to the morphological variations of the Blumensaat's line.

METHODS

Fifty-nine non-paired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. Digital images were evaluated using the Image J software. The periphery of the femoral ACL footprint was outlined and the center point was measured automatically. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). The center of the femoral ACL footprint and hilltop placement were evaluated using the quadrant method. A quadrant grid was placed uniformly, irregardless of hill existence, and not including the articular cartilage. A correlation analysis was performed between the center point of the femoral ACL footprint and hilltop placement.

RESULTS

The straight type consisted of 19 knees, and the hill type 40 knees (small hill type 13 knees and large hill type 27 knees). The center of the femoral ACL footprint (shallow-deep/high-low) in the straight and hill type knees was 33.7/47.6%, and 37.2/50.3%, respectively. In the hill type, the ACL footprint center was significantly more shallow when compared to the straight type. Significant correlation was observed between the center point of the femoral ACL footprint and hilltop placement of the Blumensaat's line.

CONCLUSION

The center point of the femoral ACL footprint was significantly more shallow in the hill type knees when compared to the straight type. For clinical relevance, considering that the location of the femoral ACL footprint center is different depending on the Blumensaat's line morphology, to perform accurate ACL reconstruction, femoral ACL tunnel placement should be made based on Blumensaat's line morphological variations.

Modified tibial tunnel placement for single-bundle posterior cruciate ligament reconstruction reduces the "Killer Turn" in a biomechanical model

BACKGROUND

Our previous three-dimensional finite element analysis found that posterior cruciate ligament (PCL) reconstruction in the modified tibial tunneling placement (MTT, 10 mm inferior and 5 mm lateral to the PCL anatomical insertion) could reduce the peak stress of the graft and may reduce the killer turn. The purpose of the current study was to compare the biomechanical results between MTT and traditional tibial tunneling technique (TTT, PCL anatomical insertion) during transtibial PCL reconstruction.

METHODS

Fifty-six 3D-printed tibia models and fresh mature porcine flexor digitorum tendons were studied. The PCL reconstruction specimens were randomly divided into TTT group and MTT group based on tibial tunnel placement. A 50 to 300 N cyclic loading was applied using a material testing system. Each specimen completed 2000 cycles at a rate of 200 mm/min and a loading frequency of 80 cycles/min. Load-displacement curves, failure mode, and graft displacement were recorded. Mean maximum contact pressure was measured using a pressure-sensitive film. After cyclic loading test, the surviving grafts were randomly assigned to load-to-failure group or Scanning Electron Microscopy (SEM) group. Ultimate failure load and the appearance of graft abrasion were recorded and analyzed.

RESULT

During the cyclic loading test, 3 samples in the TTT group, and 2 in the MTT group were excluded because of the graft pullout during the test. Mean maximum contact pressure of killer turn was 9.30 ± 0.29 MPa in the TTT group and 7.27 ± 0.25 MPa in MTT group (P < .05). Mean graft displacement was 4.54 ± 0.23 mm in the TTT group and 3.37 ± 3.56 mm in the MTT group (P < .05). Maximum failure load was 1886.0 ± 41.83 N in the TTT group and 2019.30 ± 20.10 N in the MTT group (P < .05). The SEM analysis showed heavy abrasion and fiber discontinuity in graft in the TTT group, while it showed slight abrasion and fiber arrangement disorders in the MTT group.

CONCLUSIONS

The MTT PCL reconstruction significantly reduced stress concentration and graft abrasion as compared with the TTT PCL reconstruction, and it may be a better choice for the reduction of "killer Turn" effect during transtibial PCL construction.

Functional double-bundle anterior cruciate ligament reconstruction using hamstring tendon autografts with preserved insertions is an effective treatment for tibiofemoral instability

PURPOSE

The aim of this study was to introduce a modified anatomical anterior cruciate ligament reconstruction using functional double bundles (F-DBACLR), which achieved sequential tensioning at all flexion angles postoperatively, and compare its clinical outcomes with the anatomical single-bundle technique (A-SBACLR).

METHODS

A total of 156 patients with an ACL injury underwent ACLR (A-SB group, n = 78; F-DB group, n = 78). All operations were performed by anatomically identifying the ACL footprints and fixing the graft at a pre-determined degree of knee flexion. Two observers blinded to the patient identities examined the patients preoperatively and during follow-up (median 28.2 months; range 26-31 months). Multiple subjective and objective clinical evaluation tests and assessment of clinical outcomes concerning the translational and rotational stability of the knee including the International Knee Documentation Committee (IKDC) questionnaire, Lysholm Knee Scoring Scale, Knee Injury and Osteoarthritis Outcome Score (KOOS), Tegner Activity Scale, KT-1000 laxity measurements, Lachman test and pivot-shift test were performed preoperatively and postoperatively.

RESULTS

Preoperatively, no differences were found between the two groups. During the 2-year observation period, patients in the F-DB group revealed better clinical outcomes in terms of the Tegner Activity Scale Score, IKDC, KOOS and Lysholm Knee Scoring Scale. Similar results were shown in regard to the translational stability in both groups, while the F-DB group had more rotational stability at 2 years of follow-up.

CONCLUSIONS

The clinical outcomes indicated that F-DBACLR is clinically practicable and advantageous in the treatment of the ACL-deficient knee.

LEVEL OF EVIDENCE

II.

The Blumensaat's line morphology influences to the femoral tunnel position in anatomical ACL reconstruction

PURPOSE

The purpose of this study was to reveal the influence of the morphological variations of the Blumensaat's line on femoral tunnel position in anatomical anterior cruciate ligament (ACL) reconstruction.

METHODS

Thirty-eight subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (22 female, 16 male: median age 45: 15-63). Using a trans-portal technique, the femoral tunnel was targeted to reproduce the center of antero-medial bundle. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). Femoral ACL tunnel position was evaluated using the quadrant method. When the quadrant method grid was applied, the baseline of the grid was matched to the anterior part of the Blumensaat's line, without considering the existence of a hill. Using pre-operative 3D-CT data, the axial and sagittal morphology of the knee was also compared, establlishing straight and hill types.

RESULTS

There were 12 straight type knees and 26 hill type knees (7 small hill type knees and 19 large hill type knees). The femoral tunnel position in straight type knees was 23.6 ± 3.7% in the shallow-deep direction, and 41.3 ± 8.2% in the high-low direction. In hill type knees, the tunnel position was 27 ± 4.7% in the shallow-deep direction, and 51 ± 10.1% in the high-low direction. The femoral tunnel was placed significantly more shallow and lower in hill type knees when compared with straight type knees.

CONCLUSION

Femoral ACL tunnel placement was significantly influenced by the morphological variations of the Blumensaat's line. As detecting morphological variation in arthroscopic surgery is difficult, surgeons should confirm such variations pre-operatively using radiograph or CT so as to avoid making extremely shallow and low tunnels in hill type knees.

LEVEL OF EVIDENCE

Case-controlled study, III.

Correlation between the mid-substance cross-sectional anterior cruciate ligament size and the knee osseous morphology

INTRODUCTION

One of the final goals of anatomical anterior cruciate ligament (ACL) reconstruction is the restoration of native anatomy. It is essential to obtain more accurate predictors of mid-substance ACL size before surgery. However, to the best of our knowledge, no study has reported correlation between the mid-substance cross-sectional ACL size and the knee osseous morphology. The purpose of this study was to reveal correlation between the mid-substance cross-sectional ACL size and the knee osseous morphology.

MATERIALS AND METHODS

We used 39 non-paired formalin fixed Japanese cadaveric knees. All surrounding muscles, ligaments and soft tissues in the knee were resected. After soft tissue resection, the knee was flexed at 90°, and a tangential plane of the femoral posterior condyles was marked and cut the ACL. Femoral ACL footprint size, Blumensaat's line length, lateral wall of the femoral intercondylar notch size, lateral wall of the femoral intercondylar notch height, tibial ACL footprint size, tibia plateau size, the whole anterior-posterior (AP) length, the medial and the lateral AP length of the tibia plateau, and the medial-lateral (ML) length of the tibia plateau were measured. The Pearson's product movement correlation was calculated to reveal correlation between the mid-substance cross-sectional ACL size and the measured parameters of the knee osseous morphology.

RESULTS

The measured mid-substance cross-sectional ACL size was 49.9 ± 16.3 mm². The tibial ACL footprint size, the tibia plateau size, the whole AP length of the tibia plateau, the lateral AP length of the tibia plateau and the ML length of the tibia plateau were significantly correlated with the mid-substance cross-sectional ACL size.

CONCLUSIONS

For clinical relevance, some tibial sides of the knee osseous morphology were significantly correlated with the mid-substance cross-sectional ACL size. It might be possible to predict the mid-substance ACL size measuring these parameters.

Anatomical Variability of Intercondylar Fossa Geometry in Patients Diagnosed with Primary Anterior Cruciate Ligament Rupture

The aims of this study were to (1) describe the three-dimensional characteristics and sources of anatomical variability in the geometry of the intercondylar fossa ("notch") in an anterior cruciate ligament (ACL)-injured sample and (2) assess the relationship between patient factors and anatomical variability of the fossa in the context of impingement risk. A retrospective analysis of preoperative magnetic resonance imaging (MRI) for 49 patients with ACL rupture was performed. Scans were examined in the axial plane using an online picture archiving and communication system (PACS) viewer and fossa width and angle assessed at multiple slices, as well as anteroposterior depth, fossa height, and calculated total volume. Principal component analysis was performed to prioritize the sources of variability. A multivariate linear regression was performed to assess relationships between different patient factors, controlling for imaging parameters and principal component loadings. Geometric properties were normally distributed for all but fossa volume, height, and distal angle. Three principal components (PCs) were identified explaining 80% of total variance, shape (PC1), size in the coronal plane (PC2), and size in the sagittal plane (PC3). Patient factors were significantly (P < 0.05) related to PC loadings; however, a substantial amount of variance in each model remained unexplained. Intercondylar fossa characteristics vary considerably within ACL-injury patients with shape and size in coronal and axial planes, explaining most of the variance. Although patient factors are associated with anatomical characteristics, further work is required to identify the correct combination of factors accurately predicting geometry of the fossa for planning ACL reconstruction. Clin. Anat. 33:610-618, 2020. © 2019 Wiley Periodicals, Inc.

Intercondylar Notch Impingement of the Anterior Cruciate Ligament: A Cadaveric In Vitro Study Using Robots

Background

Research has indicated that a smaller intercondylar notch could cause contact between the anterior cruciate ligament and the femoral notch, which may predispose individuals to an increased rate of anterior cruciate ligament injury.

Hypothesis

Contact between the lateral notch wall and the anterior cruciate ligament does increase the strain past the structural integrity of the ligament.

Study Design

A descriptive laboratory study.

Methods

A biomechanical study using robotic manipulators was conducted to investigate the occurrence of impingement in human cadaver specimens. Six cadaveric knees from six donors (three male and three female) were instrumented with a thin force sensor, placed on the lateral wall of the femoral condyle, and a differential variable reluctance transducer (DVRT) was attached to the middle section of the anterior medial bundle of the ACL. The knees were then moved through a series of flexion (5° to 90°), valgus (0 to 7.5°), and external rotation (0 to 7.5°) movements using two interacting robots.

Results

The results revealed that impingement occurred in both male and female specimens with a maximum impingement force of 28 N. Impingement occurred more prominently in female knees and in the combination loading of valgus and external rotation for both genders. The corresponding strain due to impingement was small or compressive, with the male knee maximum strain less than 1.28% and the female knee strain less than 7.1% in the worse case conditions.

Conclusion

The lack of increased force or strain when impingement occurred indicates that impingement may not affect the healthy function of the knee with a nonstenotic notch. Additionally, the analysis shows that impingement may not be a major contributing factor to anterior cruciate ligament injury, but rather a common occurrence in healthy knees.

Clinical Relevance

Impingement within the femoral notch does not appear to be a major contributory factor to ACL injury. Other more severe injuries to the knee would occur before ACL impingement with the femoral notch becoming a contributing factor to ACL injury. The small sample size limits the conclusivity of the results presented in this research; thus, additional large sample size studies are warranted.

Y-reconstruction could be better for ACL reconstruction in knee hyperextension versus double-bundle double-tunnel technique: a retrospective comparative study of 56 patients

PURPOSE

To compare the clinical outcomes of double-bundle (DB) single-tibial tunnel technique and double-tunnel technique for ACL reconstruction in patients with knee hyperextension.

METHODS

Defined as having constitutional hyperextension of greater than 10°, 56 patients with knee hyperextension who underwent ACL reconstruction were included in this study. To exclude concomitant lesions, preoperative magnetic resonance imaging (MRI) was performed in all knees. 24 patients (Group A) were treated with the anatomic DB/single-tibial tunnel ACL reconstruction and 32 patients (Group B) were treated with DB/double-tibial tunnel ACL reconstruction, all the included patients had knee hyperextension. Clinical results were evaluated by the extension angle, ROM, IKDC 2000 subjective score, rotational stability, pivot-shift test and anterior-posterior translation test before the operation and at the end of follow-up. MRI scan of the knee positioned in full extension was performed after 6 months post-operation. Location of tibial tunnels and graft signal intensity were assessed according to the MRI.

RESULTS

Postoperative extension deficit was detected in Group B, ROM of the injured knee in Group A was from extension angle 8.91 ± 3.16° to flexion angle 115.58 ± 10.53°. ROM of the injured knee in Group B was from extension angle - 2.13 ± 5.88° to flexion angle 119.25 ± 12.63°. Flexion angles of two groups did not show any significant difference (p = 0.24), while extension angles were quite different (p < 0.0001). Group A was slightly higher than Group B in IKDC subjective scores, but without significant difference (Group A 45.1 ± 6.5, Group B 42.4 ± 4.8, p = 0.09). There was no significant difference between two groups in pivot-shift test. Post-operational MRI showed more anterior located tibial tunnel and higher graft signal intensity in Group B when compared with Group A. One patient in the Group B had ligament retear, and required revision surgery.

CONCLUSION

DB/single-tibial tunnel technique restored the knee stability and overcame the shortcomings (such as knee extension deficit and graft impingement) of DB/double tibial tunnel, which might be more suitable for ACL reconstruction in knees with hyperextension.

LEVEL OF EVIDENCE

Level II to III.

Evaluation of Posterior Cruciate Ligament and Intercondylar Notch in Subjects With Anterior Cruciate Ligament Tear: A Comparative Flexed-Knee 3D Magnetic Resonance Imaging Study

PURPOSE

To determine if posterior cruciate ligament (PCL) and intercondylar notch (IN) morphometries and volumetrics act as risk factors for anterior cruciate ligament (ACL) tears.

METHODS

A prospective case-controlled magnetic resonance imaging (MRI) study was conducted with subjects presenting noncontact knee injuries. Exclusion criteria were previous surgery, PCL tear, osteoarthritis, tumors, or infectious and inflammatory conditions. All participants underwent a flexed-knee 3-dimensional (3D) magnetic resonance imaging (MRI) to uniformly straighten PCL. MR images were independently reviewed by 2 radiologists and assessed for 2D and 3D measurements (bicondylar width; IN angle, depth, width, and cross-sectional area; PCL width, thickness, and cross-sectional area; and IN and PCL volumes). Clinical profiles were tabulated and subjects were divided into cases (ACL tear) and controls (without ACL tear).

RESULTS

The study was composed of 50 cases versus 52 controls (N = 102), with a mean age of 36.8 years. There was no difference between groups (P > .05) regarding age, gender, body mass index, time from injury, Tegner score, flexion angle, limb side, intensity of injury, or familial or opposite limb history of tear. Agreement between readers ranged from substantial to almost perfect. Subjects with ACL tear presented with lower IN width, lower IN minus PCL widths, lower Notch Width Index, higher PCL/IN width proportion, higher PCL thickness, lower IN depth minus PCL thickness, and higher PCL thickness/IN depth proportion (P < .05). Moreover, higher PCL/IN cross-sectional area proportion, higher PCL volumes (OR = 9.01), and higher PCL/IN volume proportion were also found in cases.

CONCLUSIONS

Our study shows that subjects with ACL tears present not only reduced IN but also larger PCL dimensions. These findings, isolated and combined, and especially PCL volume, might be suggestive as risk factors for ACL tears owing to the reduction of its space inside the IN.

LEVEL OF EVIDENCE

Level III, comparative group.

The importance of Blumensaat's line morphology for accurate femoral ACL footprint evaluation using the quadrant method

PURPOSE

The purpose of this study was to evaluate the difference in the center position of the ACL footprint based on grid placement using the quadrant method according to the morphological variations of the Blumensaat's line.

METHODS

Fifty-nine non-paired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch, and the digital images were evaluated using Image J software. The femoral ACL footprint was periphery outlined and the center position was automatically measured. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight, small hill, and large hill types. From the images, grid quadrants were placed as: Grid (1) without consideration of hill existence and not including the chondral lesion. Grid (2) without consideration of hill existence and including the chondral lesion. Grid (3) with consideration of hill existence and not including the chondral lesion. Grid (4) with consideration of hill existence and including the chondral lesion.

RESULTS

The straight type consisted of 19 knees, the small hill type 13 knees, and the large hill type 27 knees. Depending on the quadrant grid placement, significant center position difference was observed both in the shallow-deep, and high-low direction. When hill existence was considered, the center position of the ACL was significantly changed to a high position.

CONCLUSION

The center position of the ACL footprint exhibited significant differences according to Blumensaat's line morphology. For clinical relevance, when ACL surgery is performed in knees with small or large hill type variations, surgeons should pay close attention to femoral tunnel evaluation and placement, especially when using the quadrant method.

Morphological size evaluation of the mid-substance insertion areas and the fan-like extension fibers in the femoral ACL footprint

PURPOSE

The purpose of this study was to evaluate the detailed anatomy of the femoral anterior cruciate ligament (ACL) insertion site, with special attention given to the morphology of the mid-substance insertion areas and the fan-like extension fibers.

METHODS

Twenty-three non-paired human cadaver knees were used (7 Males, 16 Females, median age 83, range 69-96). All soft tissues around the knee were resected except the ligaments. The ACL was divided into antero-medial (AM) and postero-lateral (PL) bundles according to the difference in macroscopic tension patterns. The ACL was carefully dissected and two outlines were made of the periphery of each bundle insertion site: those which included and those which excluded the fan-like extension fibers. An accurate lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The area of each bundle, including and excluding the fan-like extension fibers, was measured with Image J software (National Institution of Health). The width and length of the mid-substance insertion sites were also evaluated using same image.

RESULTS

The femoral ACL footprint was divided into four regions (mid-substance insertion sites of the AM and PL bundles, and fan-like extensions of the AM and PL bundles). The measured areas of the mid-substance insertion sites of the AM and PL bundles were 35.5 ± 12.5, and 32.4 ± 13.8 mm², respectively. Whole width and length of the mid-substance insertion sites were 5.3 ± 1.4, and 15.5 ± 2.9 mm, respectively. The measured areas of the fan-like extensions of the AM and PL bundles were 27 ± 11.5, and 29.5 ± 12.4 mm², respectively.

CONCLUSION

The femoral ACL footprint was divided into quarters of approximately equal size (mid-substance insertion sites of the AM and PL bundles, and fan-like extensions of the AM and PL bundles). For clinical relevance, to perform highly reproducible anatomical ACL reconstruction, the presence of the fan-like extension fibers should be taken into consideration.

The Graft Bending Angle Can Affect Early Graft Healing After Anterior Cruciate Ligament Reconstruction: In Vivo Analysis With 2 Years' Follow-up

BACKGROUND

A high graft bending angle (GBA) after anterior cruciate ligament (ACL) reconstruction has been suggested to cause stress on the graft. Nevertheless, evidence about its effect on graft healing in vivo is limited.

HYPOTHESIS

The signal intensity on magnetic resonance imaging (MRI) would be higher in the proximal region of the ACL graft, and higher signals would be correlated to a higher GBA.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Anatomic single-bundle ACL reconstruction was performed on 24 patients (mean age, 20 ± 4 years) using the transportal technique. A quadriceps tendon autograft with a bone plug was harvested. To evaluate graft healing, the signal/noise quotient (SNQ) was measured in 3 regions of interest (ROIs) of the proximal, midsubstance, and distal ACL graft using high-resolution MRI (0.45 × 0.45 × 0.70 mm), with decreased signals suggesting improved healing. Dynamic knee motion was examined during treadmill walking and running to assess the in vivo GBA. The GBA was calculated from the 3-dimensional angle between the graft and femoral tunnel vectors at each motion frame, based on tibiofemoral kinematics determined from dynamic stereo X-ray analysis. Graft healing and GBAs were assessed at 6 and 24 months postoperatively. Repeated-measures analysis of variance was used to compare the SNQ in the 3 ROIs at 2 time points. Pearson correlations were used to analyze the relationship between the SNQ and mean GBA during 0% to 15% of the gait cycle.

RESULTS

The SNQ of the ACL graft in the proximal region was significantly higher than in the midsubstance ( P = .022) and distal regions ( P < .001) at 6 months. The SNQ in the proximal region was highly correlated with the GBA during standing ( R = 0.64, P < .001), walking ( R = 0.65, P = .002), and running ( R = 0.54, P = .015) but not in the other regions. At 24 months, signals in the proximal and midsubstance regions decreased significantly compared with 6 months ( P < .001 and P = .008, respectively), with no difference across the graft area.

CONCLUSION

The signal intensity was highest in the proximal region and lowest in the distal region of the reconstructed graft at 6 months postoperatively. A steep GBA was significantly correlated with high signal intensities of the proximal graft in this early period. A steep GBA may negatively affect proximal graft healing after ACL reconstruction.

In Vivo Analysis of Dynamic Graft Bending Angle in Anterior Cruciate Ligament-Reconstructed Knees During Downward Running and Level Walking: Comparison of Flexible and Rigid Drills for Transportal Technique

PURPOSE

To determine the in vivo dynamic graft bending angle (GBA) in anterior cruciate ligament (ACL)-reconstructed knees, correlate the angle to tunnel positions and tunnel widening, and evaluate the effects of 2 femoral tunnel drilling techniques on GBA.

METHODS

Patients with an isolated ACL injury undergoing reconstruction from 2011 to 2012 were included. Transportal techniques were used to create femoral tunnels. Tunnel locations were determined by 3-dimensional computed tomography. Tibiofemoral kinematics during treadmill walking and running were assessed by dynamic stereo x-ray analysis 6 months and 2 years postoperatively. The GBA was calculated from the 3-dimensional angle between the graft and femoral tunnel vectors on each motion frame. The cross-sectional areas of femoral tunnels were measured at 6 months and compared with the initial size to assess tunnel widening.

RESULTS

A total of 54 patients were included. Use of flexible drills resulted in significantly higher GBAs during walking (80.6° ± 7.8°, P < .001) and running (80.5° ± 9.0°, P = .025) than rigid drills (walking, 67.5° ± 9.3°; running, 74.1° ± 9.6°). Their use led to greater tunnel widening of 113.9% ± 17.6%, as compared with 97.7% ± 17.5% for rigid drills (P = .003). The femoral and tibial apertures were located in similar anatomic positions in both groups, but the femoral tunnel exits were located more anteriorly (P < .001) in the flexible drill group. A higher GBA was highly correlated with anterior location of femoral exits (r = 0.63, P < .001) and moderately correlated with greater tunnel widening (r = 0.48, P < .001).

CONCLUSIONS

High GBAs were identified during dynamic activities after anatomic ACL reconstruction with a transportal femoral tunnel drilling technique. The GBA was greater when flexible drills were used. The high bending angle resulted from the more anterior location of the femoral tunnel exits, and it correlated with early bone tunnel widening at 6 months. These results suggest that a high GBA may increase stress at the bone-graft interface and contribute to greater tunnel widening after anatomic ACL reconstruction, although the clinical impact should be further investigated.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Impingement following anterior cruciate ligament reconstruction: comparing the direct versus indirect femoral tunnel position

PURPOSE

During anterior cruciate ligament (ACL) reconstruction, authors have suggested inserting the femoral tunnel at the biomechanically relevant direct fibres, but this higher position can cause more impingement. Therefore, we aimed to assess ACL graft impingement at the femoral notch for ACL reconstruction at both the direct and indirect tunnel positions.

METHODS

A virtual model was created for twelve cadaveric knees with computed tomography scanning in which a virtual graft was placed at direct and indirect tunnel positions of the anteromedial bundle (AM), posterolateral bundle (PL) or centre of the both bundles (C). In these six tunnel positions, the volume (mm³) and mid-point location of impingement (°) were measured at different flexion angles.

RESULTS

Generally, more impingement was seen with the indirect position compared with the direct position although this was only significant at 90° of flexion for the AM position (97 ± 28 vs. 76 ± 20 mm³, respectively; p = 0.046). The direct tunnel position impinged higher at the notch, whereas the indirect position impinged more towards the lateral wall, but this was only significant at 90° of flexion for the AM (24 ± 5° vs. 34 ± 4°, respectively; p < 0.001) and C position (34 ± 5° vs. 42 ± 5°, respectively; p = 0.003).

CONCLUSION

In this cadaveric study, the direct tunnel position did not cause more impingement than the indirect tunnel position. Based on these results, graft impingement is not a limitation to reconstruct the femoral tunnel at the insertion of the biomechanically more relevant direct fibres.

The correlation of femoral tunnel length with the height and area of the lateral wall of the femoral intercondylar notch in anatomical single-bundle ACL reconstruction

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length and the height and area of the lateral wall of the femoral intercondylar notch in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction .

METHODS

Twenty-four subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (19 females and 5 males; average age 45.5 ± 16.7). In the anatomical single-bundle ACL reconstruction, the femoral and tibial tunnels were created close to the anteromedial bundle insertion site. Using post-operative three-dimensional computed tomography (3D-CT), an accurate lateral view of the femoral condyle was evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analysed. Tunnel placement was also evaluated using 3D-CT (Quadrant method).

RESULTS

The average femoral tunnel length was 35.3 ± 4.9 mm. The length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were 33.6 ± 3.4, 22.8 ± 2.4, and 734.6 ± 136 mm², respectively. Both the height and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 24.1 ± 3.9 % in a shallow-deep direction, and 33.5 ± 7.7 % in a high-low direction.

CONCLUSION

The height and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single-bundle ACL reconstruction. For clinical relevance, surgeons should be careful not to make the femoral tunnel too short in knees in which the femoral intercondylar notch is low in height or small in size.

LEVEL OF EVIDENCE

Case-controlled study, Level III.

Comparison of graft bending angle during knee motion after outside-in, trans-portal and trans-tibial anterior cruciate ligament reconstruction

PURPOSE

To determine graft bending angle (GBA) during knee motion after anatomic anterior cruciate ligament (ACL) reconstruction and to clarify whether surgical techniques affect GBA. Our hypotheses were that the graft bending angle would be highest at knee extension and the difference of surgical techniques would affect the bending steepness.

METHODS

Eight healthy volunteers with a mean age of 29.3 ± 3.0 years were recruited and 3D MRI knee models were created at three flexion angles (0°, 90° and 130°). Surgical simulation of the tunnel drilling was performed with anatomic tunnel position using each outside-in (OI), trans-portal (TP) and trans-tibial (TT) techniques on the identical cases. The models were matched to other knee positions and the GBA in 3D was measured using computational software. Double-bundle ACL reconstruction was analysed first, and single-bundle reconstruction was also analysed to evaluate its effect to reduce GBA. A repeated-measures ANOVA was used to compare GBA difference at three flexion angles, by three techniques or of three bundles.

RESULTS

GBA changed substantially with knee motion, and it was highest at full extension (p < 0.001) in each surgical technique. OI technique exhibited highest GBA for anteromedial bundle (94.3° ± 5.2°) at extension, followed by TP (83.1° ± 6.5°) and TT (70.0° ± 5.2°) techniques (p < 0.01). GBA for posterolateral bundle at extension were also high in OI (84.6° ± 7.4°), TP (83.0° ± 6.3°) and TT (77.2° ± 7.0°) techniques (n.s.). Single-bundle grafts did not decrease GBA compared with double-bundle grafts. In OI technique, a more proximal location of the femoral exit reduced GBA of each bundle at extension and 90° flexion.

CONCLUSION

A significant GBA change with knee motion and considerably steep bending at full extension, especially with OI and TP techniques, were simulated. Although single-bundle technique did not reduce GBA as seen in double-bundle technique, proximal location of femoral exits by OI technique, with tunnels kept in anatomic position, was effective in decreasing GBA at knee extension and flexion. For clinical relevance, high stress on graft and bone interface has been suggested by steep GBA at full extension after anatomic ACL reconstruction.

LEVEL OF EVIDENCE

Therapeutic study (prospective comparative study), Level II.

Blumensaat's line is not always straight: morphological variations of the lateral wall of the femoral intercondylar notch

PURPOSE

The purpose of this study was to evaluate the morphological variations of the lateral wall of the femoral intercondylar notch.

METHODS

Fifty-two non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ACL. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch parallel to the plane of the femoral bone shaft. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on the femoral side. An accurate lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The morphological variations of Blumensaat's line, the height and area of the lateral wall of the femoral intercondylar notch and the size of the femoral ACL footprints were measured with Image J software.

RESULTS

Blumensaat's line exhibited three types of morphological variations. A straight line was observed in 19 knees (37 %) (straight type). A protrusion spanning less than half of the line was observed at the proximal part of Blumensaat's line in 10 knees (19 %) (small hill type). A protrusion spanning more than half of the line was observed at the proximal part of the line in 23 knees (44 %) (large hill type). In some knees with this large hill type variation, the appearance was similar to that of anterior spur. No significant differences between these three types were observed in either the height and area of the lateral wall of the femoral intercondylar notch or the area of the femoral ACL footprint.

CONCLUSION

In conclusion, Blumensaat's line has three types of morphological variations (straight, small hill and large hill types). For the clinical relevance, when ACL surgery is performed in knees with small or large hill type variations, surgeons should pay close attention to femoral tunnel evaluation and placement, especially for the use of Quadrant method. The grid placement of Quadrant method would be changed in the knees of these type variations.

The ACL Graft Has Different Cross-sectional Dimensions Compared With the Native ACL: Implications for Graft Impingement

BACKGROUND

Impingement of anterior cruciate ligament (ACL) grafts against the femoral notch and the posterior cruciate ligament (PCL) is thought to be influenced primarily by tunnel position and graft orientation. Recent data have implied that the native ACL is ribbon-shaped.

PURPOSE

To evaluate the 3-dimensional shape and cross-sectional area of the native ACL versus the ACL graft and to compare the degree of impingement against the femoral notch and PCL.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Bilateral knee magnetic resonance images were analyzed for 27 patients with unilateral bone-patellar tendon-bone (BPTB) ACL reconstruction performed via transtibial or anteromedial portal femoral tunneling techniques. Three-dimensional models of the ACL, PCL, femur, and tibia were digitally rendered. The cross-sectional area and dimensions of the native ACL and the reconstructed graft were determined at 3 equally spaced locations and compared via Wilcoxon-Mann-Whitney and Kruskal-Wallis tests. In addition, impingement of the ACL on the PCL and femoral notch was graded in 3 groups. Chi-square or Fisher exact tests were used to compare the proportional differences of impingement of the native and reconstructed ACL on the PCL and femoral notch, respectively. All analyses were performed using 2-sided hypothesis testing, with statistical significance at P < .05.

RESULTS

Cross-sectional areas at all 3 points on the ACL graft were significantly greater than those of the native ACL (P < .001). The long- to short-axis ratio for the native ACL was significantly greater at each location compared with the corresponding locations along the ACL graft (P < .001), implying that the native ACL is "flatter" than is an ACL graft. There were 19 operated knees (70%) with contact or impingement between the ACL graft and the femoral notch compared with zero knees with a native ACL (P < .001). In addition, 22 operated knees (81%) showed contact or impingement between the ACL graft and the PCL, compared with 7 knees (26%) with a native ACL (P < .001). No significant differences in impingement frequency were noted between the transtibial and anteromedial tunneling techniques for ACL graft specimens (P > .05).

CONCLUSION

Native ACLs have a smaller cross-sectional area, are "flatter," and experience less incidence of impingement compared with anatomically placed BPTB ACL grafts.

The difference in centre position in the ACL femoral footprint inclusive and exclusive of the fan-like extension fibres

PURPOSE

The purpose of this study was to compare the centre position of each anterior cruciate ligament bundle in its femoral footprint in measurements including and excluding the fan-like extension fibres.

METHODS

Fourteen non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ligaments. The ACL was divided into antero-medial (AM) and postero-lateral (PL) bundles according to the difference in tension patterns. The ACL was carefully dissected, and two outlines were made of the periphery of each bundle insertion site: those which included and those which excluded the fan-like extension fibres. An accurate lateral view of the femoral condyle was photographed with a digital camera, and the images were downloaded to a personal computer. The centre position of each bundle, including and excluding the fan-like extension fibres, was measured with ImageJ software (National Institution of Health). Evaluation of the centre position was performed using the modified quadrant method.

RESULTS

The centre of the femoral AM bundle including the fan-like extension was located at 28.8% in a shallow-deep direction and 37.2% in a high-low direction. When the AM bundle was evaluated without the fan-like extension, the centre was significantly different at 34.6% in a shallow-deep direction (p = 0.000) and 36% in a high-low direction. The centre of the PL bundle including the fan-like extension was found at 37.1% in a shallow-deep direction and 73.4% in a high-low direction. When the PL bundle was evaluated without the fan-like extension, the centre was significantly different at 42.7% in a shallow-deep direction (p = 0.000) and 69.3% in a high-low direction (p = 0.000).

CONCLUSION

The centre position of the AM and PL bundles in the femoral ACL footprint was significantly different depending on the inclusion or exclusion of the fan-like extension fibres. For the clinical relevance, to reproduce the direct femoral insertion in the anatomical ACL reconstruction, tunnels should be placed relatively shallow and high in the femoral ACL footprint.

Clinical Outcomes After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction: Comparison of Extreme Knee Hyperextension and Normal to Mild Knee Hyperextension

PURPOSE

The aim of this study was to compare postoperative outcomes after anatomic double-bundle anterior cruciate ligament reconstruction (ACLR) in extreme knee hyperextension versus normal to mild knee hyperextension.

METHODS

For 100 patients who underwent anatomic double-bundle ACLR using semitendinosus tendon, we evaluated the side-to-side difference (SSD) in anterior tibial translation (measured on stress radiographs) and rotational stability (assessed by the pivot-shift test) 2 years after surgery. Loss of extension (LOE) was evaluated on lateral radiographs of both knees in full extension, and graft integrity was assessed during second-look arthroscopy 1 to 2 years after surgery. In accordance with the Beighton and Honan criteria, patients with an extension angle less than or equal to 10° in the contralateral uninjured knee composed the group with 10° or less hyperextension (N group), and those with an extension angle of greater than 10° composed the group with more than 10° hyperextension (H group). Postoperative results were compared between these groups.

RESULTS

Mean extension angles in the N and H groups were 5.8° ± 2.9° and 14.7° ± 3.0°, respectively. The mean SSD in anterior translation was 2.2 ± 2.9 mm for the N group and 2.8 ± 2.9 mm for the H group, with no significant difference. The positive ratios on the pivot-shift test were not significantly different between the groups. Mean LOE in the N and H groups was -0.7° ± 3.7° and 1.3° ± 3.3°, respectively, with a significant difference (P = .007). During second-look arthroscopy, 6 of 58 knees in the N group and 13 of 42 knees in the H group had superficial graft laceration of the anteromedial bundle graft, with a significant difference (P = .01) seen between groups.

CONCLUSIONS

Anatomic double-bundle ACLR for extreme knee hyperextension may attain the same postoperative anterior and rotational stability as seen in knees with normal to mild hyperextension. However, it increased superficial graft laceration.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Eccentric graft positioning within the femoral tunnel aperture in anatomic double-bundle anterior cruciate ligament reconstruction using the transportal and outside-in techniques

BACKGROUND

Ellipticity of the femoral tunnel aperture, which is considered to better restore the native anterior cruciate ligament (ACL) footprint after ACL reconstruction, is different according to the femoral tunneling technique used. How much of the femoral tunnel aperture is filled with graft in different tunneling techniques has yet to be evaluated.

PURPOSE

The aim of this study was to evaluate and compare the graft filling area and graft position within the femoral tunnel aperture in ACL reconstruction using the transportal (TP) and outside-in (OI) techniques.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 70 patients were randomized to undergo double-bundle ACL reconstruction using either the TP (n=35) or OI (n=35) technique. The aperture filling was evaluated by calculating the ratio of the cross-sectional area of the graft to that of the femoral tunnel, and the graft center position within the tunnel was assessed using immediate postoperative magnetic resonance imaging.

RESULTS

The cross-sectional area of the femoral anteromedial (AM) tunnel aperture in the TP group (605.5±112.7 mm2) was larger than that in the OI group (537.9±126.8 mm2). The cross-sectional area of the femoral posterolateral (PL) tunnel aperture in the TP group (369.9±88.3 mm2) did not differ significantly from that of the OI group (387.9±87.0 mm2). The grafts filled only 52.0% of the AM tunnel and 55.3% of the PL tunnel in the TP group, compared with 54.9% of the AM tunnel and 54.4% of the PL tunnel in the OI group, but there was no statistically significant difference (P>.05). The AM graft center was positioned 1.7±0.6 mm from the center of the tunnel aperture in the TP group and 1.6±0.5 mm in the OI group, and the PL graft center was positioned 1.4±0.4 mm from the center in the TP group and 1.3±0.4 mm in the OI group, with no significant intergroup differences (P=.406 and P=.629, respectively). In the OI group, the PL graft center was positioned more perpendicular to the Blumensaat line in relation to the tunnel aperture center (-10.8°±7.6°) compared with the TP group (-4.0°±11.8°) (P=.04).

CONCLUSION

The grafts did not fill the tunnel aperture area in either group, and the centers of the grafts differed slightly from the centers of the tunnel apertures. The finding of eccentric graft positioning in the tunnel with condensation in a particular direction in each technique might suggest the necessity of an underreamed femoral tunnel for graft. In addition, it may be useful to standardize the starting position of the femoral tunnel according to anatomic landmarks.

Size correlation between the tibial anterior cruciate ligament footprint and the tibia plateau

PURPOSE

The purpose of this study was to reveal the correlation between the size of the native anterior cruciate ligament (ACL) footprint and the size of the tibia plateau.

METHODS

Twenty-four non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ACL. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on both the femoral and tibial sides. An accurate lateral view of the femoral condyle and the tibial plateau was photographed with a digital camera, and the images were downloaded to a personal computer. The size of the femoral and tibial ACL footprints, and anterior-posterior (AP) and medial-lateral (ML), lengths of the tibia plateau and area of tibia plateau were measured with Image J software (National Institution of Health).

RESULTS

The sizes of the native femoral and tibial ACL footprints were 72.3 ± 24.4 and 134.1 ± 32.4 mm(2), respectively. The AP lengths of the whole, medial and lateral facet of the tibia plateau were as follows: 44.5 ± 4.1, 40.8 ± 4.1 and 36.8 ± 4 mm, respectively. The ML length of the tibia plateau was 68.3 ± 5.5 mm. Total area of tibia plateau was 2,282.9 ± 378.7 mm(2). The AP length of the lateral facet of the tibia plateau (Pearson's correlation coefficient = 0.508, p = 0.011) and the total area of tibia plateau (Pearson's correlation coefficient = 0.442, p = 0.031) were significantly correlated with the size of the tibial ACL footprint.

CONCLUSION

For clinical relevance, the AP length of lateral facet of the tibia plateau and total area of tibia plateau are significantly correlated with the size of the tibial ACL footprint. It might be possible to predict the size of the ACL measuring these parameters.

Prospective randomized comparison of knee stability and joint degeneration for double- and single-bundle ACL reconstruction

PURPOSE

This study aims to determine the outcome of double-bundle anterior cruciate ligament (ACL) reconstruction using an allograft in comparison with ACL reconstruction using a double-bundle autograft or a single-bundle allograft.

METHODS

A total of 424 patients who accepted primary ACL reconstructions were divided randomly into three groups: double-bundle technique with autograft (DB-AU group, n = 154), double-bundle technique with allograft (DB-AL group, n = 128), and single-bundle technique with allograft (SB group, n = 142). The KT-1000 arthrometer and pivot-shift tests were performed at 3, 12, and 36 months after surgery, and clinical outcome measurements include the Lysholm score and the IKDC rating scales. Radiological assessments evaluated arthritic changes and tunnel expansion at 36 months postoperatively.

RESULTS

The KT-1000 test scores in the DB-AU and DB-AL groups were significantly better than those in the SB group at 12 and 36 months postoperatively (P < 0.05). The pivot-shift tests scores in the DB-AU and DB-AL groups were significantly better than those in the SB group at the 3, 12, and 36 month follow-ups (P < 0.05). Based on the IKDC score and Lysholm score, there were no significant difference between the three groups during follow-up (P > 0.05). At 36 months postoperatively, 42.3 % of patients in the SB group showed a progression in arthritic changes, which was greater than in the DB-AU (29.2 %) and DB-AL (27.3 %) groups (P < 0.05). At 36 months, the rates of tunnel expansion in the DB-AU group and the DB-AL group were lower than in the SB group (P < 0.05).

CONCLUSIONS

Double-bundle ACL reconstruction can be used to achieve better anterior and rotational stability and has a lower rate of arthritic progression and tunnel expansion than the single-bundle procedure.

LEVEL OF EVIDENCE

I.

Anatomic anterior cruciate ligament reconstruction: a changing paradigm

Injury to the anterior cruciate ligament (ACL) of the knee is potentially devastating for the patient and can result in both acute and long-term clinical problems. Consequently, the ACL has always been and continues to be of great interest to orthopaedic scientists and clinicians worldwide. Major advancements in ACL surgery have been made in the past few years. ACL reconstruction has shifted from an open to arthroscopic procedure, in which a two- and later one-incision technique was applied. Studies have found that traditional, transtibial arthroscopic single-bundle reconstruction does not fully restore rotational stability of the knee joint, and as such, a more anatomic approach to ACL reconstruction has emerged. The goal of anatomic ACL reconstruction is to replicate the knee's normal anatomy and restore its normal kinematics, all while protecting long-term knee health. This manuscript describes the research that has changed the paradigm of ACL reconstruction from traditional techniques to present day anatomic and individualized concepts.

Intercondylar notch dimensions and graft failure after single- and double-bundle anterior cruciate ligament reconstruction

PURPOSE

The objective of this study was to evaluate the dimensions of the femoral intercondylar notch intraoperatively and to determine whether a small intercondylar notch increases the risk of graft failure after individualized anatomic single- or double-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

A retrospective review of prospectively collected data was performed. One hundred and thirty-seven primary single- or double-bundle ACL reconstructions with at least 2-year follow-up were included in this study. Of these, 116 subjects had intraoperative notch measurements recorded. All operations were performed anatomically using a three-portal technique by the senior author. Intraoperative notch measurements (width at the base, middle, and top and height) were taken using a standard, commercially available arthroscopic ruler. Graft failure was defined as patient report of instability, pathologic laxity on clinical exam, or an MRI or arthroscopic diagnosis of rupture or absence of the ACL graft.

RESULTS

Graft failure at 2-year follow-up in the overall population was 13.9 % (19/137). Graft failure was reported to occur from contact or non-contact trauma, failure of the graft to incorporate, or hardware failure. The dimensions of the intercondylar notch and the graft type used did not influence the risk of graft failure.

CONCLUSIONS

Smaller intercondylar notch dimensions do not appear to be a risk factor for higher rates of graft failure after anatomic and individualized ACL reconstruction. Based on these data, the use of notchplasty is not supported in conjunction with individualized anatomic single- or double-bundle ACL reconstruction.

Comparison of double-bundle anterior cruciate ligament (ACL) reconstruction and single-bundle reconstruction with remnant pull-out suture

PURPOSE

The purpose of this study was to evaluate the stability and functional outcomes of anterior cruciate ligament (ACL) reconstruction by tensioning of the ACL remnant using pull-out sutures compared with ACL double-bundle reconstruction.

METHODS

Forty-four patients were included in single-bundle reconstruction with remnant tensioning group (Group 1), and 56 patients were included in the double-bundle reconstruction group (Group 2). The remnant tissue was tensioned to the direction of posterolateral bundle, which unrelated to the type of remnant bundle. Objective knee stability was evaluated by anterior stress radiography, KT-1000 and lateral pivot shift tests. The Tegner activity scale, International Knee Documentation Committee and OrthopädischeArbeitsgruppeKnie scoring systems were used for clinical evaluation.

RESULTS

No statistically significant intergroup differences were observed in mechanical stability and clinical results (n.s). However, surgical time of remnant tensioning group is shorter than double-bundle reconstruction group (P = 0.005).

CONCLUSION

Remnant tensioning suture with single-bundle reconstruction could be used with positive results as good as double-bundle technique if a good ACL remnant was found bridging the femur and tibia, rather than debride or damage to the remnant tissue during operation.

LEVEL OF EVIDENCE

Retrospective, comparative cohort study, Level IV.

Factors influencing graft impingement on the wall of the intercondylar notch after anatomic double-bundle anterior cruciate ligament reconstruction

BACKGROUND

Anatomic placement of the bone tunnel reportedly reduces impingement of the graft with the intercondylar roof, but as a trade-off, the risk of impingement with the lateral wall of the intercondylar notch would increase instead in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

PURPOSE

The 2 grafts for the anteromedial bundle (AMB) and posterolateral bundle (PLB) were separately analyzed for the frequency of and risk factors for graft impingement on the wall of the intercondylar notch.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

A total of 51 patients (53 knees) who underwent primary anatomic double-bundle ACL reconstruction were enrolled. Based on the graft orientation plane reconstructed with 3-dimensional imaging software, graft-wall impingement was defined as overlap between the lateral wall of the notch and the line connecting each center of the intra-articular apertures of the femoral and tibial bone tunnels. The rate of wall impingement was assessed for each bundle. Parameters for bone tunnel positioning in the femur and tibia, notch width index, and knee joint rotation angle were compared between patients with and without wall impingement. The most important risk factors for wall impingement were assessed by logistic regression analysis.

RESULTS

Wall impingement for the AMB was observed in 22 knees (42%), whereas no patients exhibited wall impingement for the PLB. Regarding femoral bone tunnel positioning according to the quadrant method, the AMB bone tunnel was placed significantly higher in impingement-positive patients than in impingement-negative patients (P = .03). Regarding tibial tunnel positioning, the tunnel was placed significantly more anteriorly (P = .02) and laterally (P = .02) in the impingement-positive group than in the impingement-negative group. Bone tunnels positioned 48% to 50% from the medial border of the tibia demonstrated a 100% incidence of wall impingement. Based on logistic regression analysis, lateral deviation of the AMB tibial bone tunnel was significantly associated with wall impingement (odds ratio, 1.403; P = .048).

CONCLUSION

The tibial bone tunnel position in the coronal orientation was most likely associated with wall impingement. Considering that tibial bone tunnels are generally created with the knee in 90° of flexion and move laterally as the knee extends because of screw-home movement, the AMB bone tunnel for the tibia should be positioned as medially as possible within its footprint to minimize the risk of wall impingement after anatomic double-bundle ACL reconstruction.

Effect of Notchplasty in Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

BACKGROUND

The effects of notchplasty on the clinical outcome after anatomic double-bundle anterior cruciate ligament (ACL) reconstruction remain unclear.

HYPOTHESIS

Anatomic ACL reconstruction with notchplasty would result in less risk of loss of extension and would provide adequate space for better graft healing, leading to better knee stability compared with anatomic ACL reconstruction without notchplasty.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 137 patients who underwent anatomic double-bundle ACL reconstruction were included. Seventy-three patients without notchplasty were classified as the control group, and 64 patients with 2-mm notchplasty were classified as the notchplasty group. The following evaluation methods were used: loss of extension, patient's subjective feeling of limited extension and pain at passive full extension, muscle strength, manual laxity tests, KT-1000 arthrometer measurement, patellofemoral joint findings, Tegner score, Lysholm score, subjective scores, and time to return to sports. Tearing of the reconstructed ACL and additional synovectomy were recorded. Both tibial and femoral tunnel positions were measured using 2-view radiographs: a Rosenberg and a lateral view.

RESULTS

Loss of extension was larger in the notchplasty group compared with controls (at 6 months: 0.8° vs 1.4°, P = .012; at 2 years: 0.4° vs 0.9°, P = .0053). The number of patients with a feeling of limited extension was also larger in the notchplasty group (at 6 months: 13 patients graded 1+ [somewhat limited] and 2 patients graded 2+ [very limited] vs 18 graded 1+ and 6 graded 2+, P = .015; at 2 years: 2 graded 1+ and 0 graded 2+ vs 4 graded 1+ and 5 graded 2+, P = .011). Six patients in the notchplasty group required additional synovectomy because of the prolonged loss of extension, whereas no patient in the control group required additional synovectomy. There were no differences between groups regarding muscle strength, patellofemoral findings, Lysholm score, Tegner score, subjective scores, or time to return to sports. The KT-1000 arthrometer measurement was better in the notchplasty group (1.2 vs 0.4 mm, P = .0017). However, 6 patients in the notchplasty group showed an overconstrained knee (KT-1000 measurement ≤-2 mm), compared with only 1 patient in the control group. There were no differences between groups in the other manual laxity tests or the tunnel positions.

CONCLUSION

In anatomic double-bundle ACL reconstruction, anterior stability was improved and there were no harmful effects on patellofemoral joint findings by 2-mm notchplasty; however, notchplasty likely caused overconstrained knee, leading to a need for additional synovectomy in some patients. In contrast, anatomic double-bundle ACL reconstruction without notchplasty did not increase the incidence of loss of extension or of graft failure.

Anatomic anterior cruciate ligament (ACL) reconstruction: a global perspective. Part 1

PURPOSE

In August 2011, orthopaedic surgeons from more than 20 countries attended a summit on anatomic anterior cruciate ligament (ACL) reconstruction. The summit offered a unique opportunity to discuss current concepts, approaches, and techniques in the field of ACL reconstruction among leading surgeons in the field.

METHODS

Five panels (with 36 panellists) were conducted on key issues in ACL surgery: anatomic ACL reconstruction, rehabilitation and return to activity following anatomic ACL reconstruction, failure after ACL reconstruction, revision anatomic ACL reconstruction, and partial ACL injuries and ACL augmentation. Panellists' responses were secondarily collected using an online survey.

RESULTS

Thirty-six panellists (35 surgeons and 1 physical therapist) sat on at least one panel. Of the 35 surgeons surveyed, 22 reported performing "anatomic" ACL reconstructions. The preferred graft choice was hamstring tendon autograft (53.1 %) followed by bone-patellar tendon-bone autograft (22.8 %), allograft (13.5 %), and quadriceps tendon autograft (10.6 %). Patients generally returned to play after an average of 6 months, with return to full competition after an average of 8 months. ACL reconstruction "failure" was defined by 12 surgeons as instability and pathological laxity on examination, a need for revision, and/or evidence of tear on magnetic resonance imaging. The average percentage of patients meeting the criteria for "failure" was 8.2 %.

CONCLUSIONS

These data summarize the results of five panels on anatomic ACL reconstruction. The most popular graft choice among surgeons for primary ACL reconstructions is hamstring tendon autograft, with allograft being used most frequently employed in revision cases. Nearly half of the surgeons surveyed performed both single- and double-bundle ACL reconstructions depending on certain criteria. Regardless of the technique regularly employed, there was unanimous support among surgeons for the use of "anatomic" reconstructions using bony and soft tissue remnant landmarks.

Commonly used ACL autograft areas do not correlate with the size of the ACL footprint or the femoral condyle

PURPOSE

The purpose of this study was to reveal the correlation between the size of the native anterior cruciate ligament (ACL) footprint and the area of commonly used autografts using cadaveric knees.

METHODS

Twenty-Four non-paired human cadaver knees were used. The size of the femoral and tibial ACL footprints, length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were photographed and measured with Image J software (National Institution of Health). Simulating an semitendinosus tendon (ST) graft, the ST was cut in half. The bigger half was regarded as the antero-medial (AM) bundle, and the remaining half was regarded as the postero-lateral (PL) bundle. Simulating an semitendinosus and gracilis (ST-G) graft, the bigger half of the ST and G was regarded as the AM bundle, and the smaller half of the ST was regarded as the PL bundle. Each graft diameter was measured, and the graft area was calculated. Simulating a bone-patella tendon-bone (BPTB) graft, a 10-mm wide BPTB graft was harvested and the area calculated.

RESULTS

The sizes of the native femoral and tibial ACL footprints were 72.3 ± 24.4 and 134.1 ± 32.4 mm(2), respectively. The length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were 29.5 ± 2.5 mm, 17.7 ± 2.3 mm, and 400.9 ± 62.6 mm(2), respectively. The average areas of the ST, ST-G, and BPTB graft were 52.7 ± 6.3, 64.7 ± 7.6, and 37.1 ± 7.5 mm(2). Both the height and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with the femoral size of the ACL footprint (p = 0.007 and 0.008, respectively). However, no significant correlation was observed between ACL footprint size and autograft size. No significant correlation was observed between autograft size and the size of the lateral wall of the femoral intercondylar notch.

CONCLUSION

In ACL reconstruction, if the reconstructed ACL size is determined by the harvested autograft size alone, native ACL size and anatomy are unlikely to be reproduced.

Arthrometric stability of horizontal versus vertical single-bundle arthroscopic anterior cruciate ligament reconstruction

The anteroposterior (AP) stability of standard anterior cruciate ligament (ACL) reconstruction, referred to as "vertical," was compared with that of a modified femoral position, referred to as "horizontal," which is lower than and anterior to an operative knee at 90° flexion. Two consecutive series of 50 patients underwent vertical and horizontal arthroscopic single-bundle ACL reconstruction, respectively. For vertical reconstruction, the clock position was chosen, placing the graft at 10:30 in right knees and 1:30 in left knees, 1 to 2 mm anterior to the posterior femoral cortical cortex and at the back of the resident ridge. In the horizontal reconstruction, the transplant replaced the original ligament insertion at approximately the 9:30 o'clock position in right knees and the 2:30 o'clock position in left knees, approximately 2 mm in front of the posterior femoral cortical cortex. One year after surgery, the results of stabilometric evaluation revealed good performance after horizontal transplant. The mean clinical results changed from 1.0 (±1.3) mm for vertical to 0.7 (±1.3) mm for horizontal reconstruction.

Sagittal view of the tibial attachment of the anterior cruciate ligament on magnetic resonance imaging and the relationship between anterior cruciate ligament size and the physical characteristics of patients

BACKGROUND

It is necessary to create bone tunnels within the native footprint during anatomic anterior cruciate ligament (ACL) reconstruction. Predicting the size of the ACL preoperatively may be useful in order to determine the diameter of the bone tunnels preoperatively or during surgery. The tibial insertion site of the ACL includes a depressed area, the ACL fovea, which is generally observed in the sagittal view on magnetic resonance imaging (MRI). The purposes of this study were to measure the anteroposterior diameter of the ACL fovea in the sagittal view on MRI and to investigate its associations with the physical characteristics of patients.

METHODS

One hundred patients (100 knees; 50 males and 50 females; mean age, 33 years) were included in this study. The anteroposterior diameter of the ACL fovea was measured in the sagittal view on MRI. The relationships between the diameter of the ACL fovea and physical characteristics including height, weight, and body mass index (BMI) were analyzed.

RESULTS

The mean diameter of the ACL fovea was 16.1 mm in male patients and 14.3 mm in female patients, which were comparable to the previously reported values. There were significant positive correlations between the diameter of the ACL fovea and height and weight, but not BMI. The number of knees in which the diameter of the ACL fovea was <13 mm was 14 (14 %), and females were more likely to have ACL fovea diameter <13 mm.

CONCLUSIONS

The study indicated that it is possible to predict the size of the ACL before surgery by measuring the diameter of the ACL fovea on MRI. Physical characteristics of patients correlated with the diameter of the ACL fovea. Especially in female patients, it is important to consider the size of the ACL preoperatively.

Evaluation of ACL mid-substance cross-sectional area for reconstructed autograft selection

PURPOSE

The purpose of this study was to compare the size of the native ACL mid-substance cross-sectional area and the size of commonly used autografts. Hypothesis of this study was that the reconstructed graft size with autografts would be smaller than the native ACL size.

METHODS

Twelve non-paired human cadaver knees were used. The ACL was carefully dissected, and the mid-substance of the ACL was cross-sectioned parallel to the articular surface of the femoral posterior condyles at 90 degrees of knee flexion. The size of the cross-sectional area of the ACL, and the femoral and tibial footprints were measured using Image J software (National Institute of Health). The semitendinosus tendon (ST) and the gracilis (G) tendon were harvested and prepared for ACL grafts. Simulating an ST graft, the ST was cut in half. The bigger half was regarded as the antero-medial (AM) bundle, and the remaining half was regarded as the postero-lateral (PL) bundle. Simulating an ST-G graft, the bigger half of the ST and G were regarded as the AM bundle, and the smaller half of the ST was regarded as the PL bundle. Each graft diameter was measured, and the graft area was calculated. Simulating a rectangular bone-patella tendon-bone (BPTB) graft, a 10-mm-wide BPTB graft was harvested and the area calculated.

RESULTS

The sizes of the ACL mid-substance cross-sectional area, femoral and tibial ACL footprint were 46.9 ± 18.3, 60.1 ± 16.9 and 123.5 ± 12.5 mm(2), respectively. The average areas of the ST, ST-G, and BPTB grafts were 52.0 ± 3.8, 64.4 ± 6.2, and 40.8 ± 6.7 mm(2), respectively. The ST and BPTB grafts showed no significant difference in graft size when compared with the ACL cross-sectional area.

CONCLUSION

ST and BPTB autografts were able to reproduce the native size of the ACL mid-substance cross-sectional area. The ST-G graft was significantly larger than the ACL cross-sectional area. For clinical relevance, ST and BPTB grafts are recommended in order to reproduce the native size of the ACL in anatomical ACL reconstruction with autograft.

Intercondylar roof impingement after anatomic double-bundle anterior cruciate ligament reconstruction in patients with knee hyperextension

BACKGROUND

Although an anatomically placed graft in anterior cruciate ligament (ACL) reconstruction is reported to have a low risk of roof impingement, which may cause deterioration of the graft or an extension deficit, the incidence of roof impingement by these grafts has not been evaluated in hyperextensible knees.

PURPOSE

To evaluate the incidence of roof impingement by the native ACL in hyperextensible knees and to examine the risk of roof impingement by anatomic placement of the ACL graft in hyperextensible knees.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve patients were selected for a hyperextensible knee group (group A), defined as having hyperextension of the knee of greater than 10°. Twelve patients were recruited to a normal extension knee group (group B) with normal extension of the knee of less than 5° of hyperextension. Magnetic resonance imaging (MRI) scans of the knee positioned in 30° of flexion and full extension were acquired from all patients. The shape of the native ACL at full extension was compared between the groups. A 3-dimensional (3D) bone model was created from the acquired 2D MRI scans. A virtual anatomic double-bundle ACL reconstruction in each patient and a virtual anatomic single-bundle reconstruction in the patients in group A were performed using the 3D MRI bone models. The volume of the overlap between the graft and roof was calculated to evaluate graft impingement in each instance.

RESULTS

The MRI scans showed posterior bowing of the native ACL in the group A knees. The simulated double-bundle ACL reconstruction showed that the overlapped volume was significantly greater in patients in group A than in patients in group B (P < .05). However, the overlap of the simulated single-bundle ACL reconstruction was significantly less than for the double-bundle ACL reconstruction (P < .05).

CONCLUSION

To reduce the risk of roof impingement by the graft, single-bundle ACL reconstruction with the graft placed at the center of the footprint might be the better method for patients with a hyperextensible knee than an anatomic double-bundle ACL reconstruction.

CLINICAL RELEVANCE

It is recommended that surgeons cautiously consider roof impingement after anatomic double-bundle ACL reconstruction in patients with a hyperextensible knee.

Femoral graft-tunnel angles in posterior cruciate ligament reconstruction: analysis with 3-dimensional models and cadaveric experiments

PURPOSE

The purpose of this study was to compare four graft-tunnel angles (GTA), the femoral GTA formed by three different femoral tunneling techniques (the outside-in, a modified inside-out technique in the posterior sag position with knee hyperflexion, and the conventional inside-out technique) and the tibia GTA in 3-dimensional (3D) knee flexion models, as well as to examine the influence of femoral tunneling techniques on the contact pressure between the intra-articular aperture of the femoral tunnel and the graft.

MATERIALS AND METHODS

Twelve cadaveric knees were tested. Computed tomography scans were performed at different knee flexion angles (0°, 45°, 90°, and 120°). Femoral and tibial GTAs were measured at different knee flexion angles on the 3D knee models. Using pressure sensitive films, stress on the graft of the angulation of the femoral tunnel aperture was measured in posterior cruciate ligament reconstructed cadaveric knees.

RESULTS

Between 45° and 120° of knee flexion, there were no significant differences between the outside-in and modified inside-out techniques. However, the femoral GTA for the conventional inside-out technique was significantly less than that for the other two techniques (p<0.001). In cadaveric experiments using pressure-sensitive film, the maximum contact pressure for the modified inside-out and outside-in technique was significantly lower than that for the conventional inside-out technique (p=0.024 and p=0.017).

CONCLUSION

The conventional inside-out technique results in a significantly lesser GTA and higher stress at the intra-articular aperture of the femoral tunnel than the outside-in technique. However, the results for the modified inside-out technique are similar to those for the outside-in technique.

The importance of tibial tunnel placement in anatomic double-bundle anterior cruciate ligament reconstruction

PURPOSE

The purposes of this study were to measure the anterior edge of the tibial tunnel after anatomic anterior cruciate ligament (ACL) reconstruction on lateral radiographs and to determine whether the difference in tibial tunnel placement affects postoperative outcomes.

METHODS

For 60 patients who underwent anatomic double-bundle ACL reconstruction with semitendinosus tendon, we evaluated the side-to-side difference in anterior tibial translation on stress radiographs, as well as rotational stability by the pivot-shift test, 2 years after surgery. Loss of extension (LOE) was evaluated on lateral radiographs of both knees in full extension, and graft integrity was assessed during second-look arthroscopy 1 to 2 years after surgery. On true lateral radiographs, we measured the anterior placement percentage of the tibial tunnel using the method described by Amis and Jakob. The cutoff value was set at 25% of the mean value of the anterior edge of the ACL that Amis and Jakob reported, and patients were divided into 2 groups (27 in the anterior group and 33 in the posterior group). Postoperative clinical results were compared between the groups.

RESULTS

The mean anterior placement percentage was 26.0% ± 4.1%. The postoperative mean side-to-side difference was 1.4 ± 2.7 mm for the anterior group and 3.0 ± 2.7 mm for the posterior group, a significant difference (P < .05). The positive ratio of the pivot-shift test was not significantly different between groups (P > .05). Mean LOE in the anterior and posterior groups was 0.9° ± 3.0° and -0.8° ± 4.0°, respectively; the difference was not significant (P > .05). Five of 27 knees in the anterior group and 5 of 33 knees in the posterior group had superficial graft laceration or elongation, which was not significantly different (P > .05).

CONCLUSIONS

Anterior placement of the tibial tunnel in anatomic double-bundle ACL reconstruction leads to better anterior knee stability than posterior placement does. Anterior tibial tunnel placement inside the footprint did not increase the incidence of LOE and graft failure.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Characterization of cruciate ligament impingement: the influence of femoral or tibial tunnel positioning at different degrees of knee flexion

PURPOSE

We aimed to analyze how different positions of the tibial and femoral tunnels when used for anterior cruciate ligament (ACL) reconstruction affect relations with the posterior cruciate ligament (PCL) at different degrees of knee flexion. Information gained from this study may be helpful in determining optimal placement of the graft in ACL reconstructive surgery.

METHODS

We divided 10 cadaveric knees into 2 groups of 5 and had either their femoral or tibial ACL insertion detached. For each specimen, 16 different positions were reproduced during ACL reconstruction based on a combination of 4 different tunnels in the tibia for group A (anterior-medial, anterior-lateral, posterior-medial, and posterior-lateral) and 4 in the femur for group B (anterior-proximal, anterior-distal, posterior-proximal, and posterior-distal) with 4° of knee flexion for each (0°, 45°, 90°, and 135°). We performed a magnetic resonance imaging (MRI) study for each configuration and analyzed the cruciate ligament positioning.

RESULTS

We identified 3 different situations: no contact between cruciate ligaments, contact without deformity, and contact with deformity. In group A, the degree of flexion (P = .003) and ligament insertion positioned in the posterior quadrants (P < .05) were statistically significant for the presence of ACL impingement. Ligament contact with deformity was identified in 18 (22.5%) configurations, mostly when the knee was flexed 45° and 90° and the ACL was in the posterior quadrants. For group B, "contact with deformity" was identified in 23 MR images, mostly (12 cases) with the graft position being in the anterior-distal configuration, but it was not significant for the occurrence of cruciate impingement.

CONCLUSIONS

Impingement with ligament deformity is greater when the graft is fixed at the posterior quadrants of the tibial footprint, regardless of the degree of knee flexion. Although quite common, the ligament position in the femoral footprint was not a primary cause of ACL impingement with deformity.

CLINICAL RELEVANCE

This study helps identify positions of the tibial or femoral tunnels during ACL reconstruction to avoid impingement between cruciate ligaments.

Size comparison of ACL footprint and reconstructed auto graft

PURPOSE

The purpose of this study was to compare the size of native anterior cruciate ligament (ACL) footprints and the size of commonly used auto grafts. The hypothesis was that the reconstructed graft size with auto grafts might be smaller than the native ACL footprint.

METHODS

Fourteen non-paired human cadaver knees were used. The semitendinosus tendon (ST) and the gracilis (G) tendon were harvested and prepared for ACL grafts. Simulating an ST graft, the ST was cut in half. The bigger half was regarded as the antero-medial (AM) bundle, and the remaining half was regarded as the postero-lateral (PL) bundle. Simulating an ST-G graft, the bigger half of the ST and G were regarded as the AM bundle, and the smaller half of the ST was regarded as the PL bundle. Each graft diameter was measured, and the graft area was calculated. Simulating a rectangular bone-patella tendon-bone (BPTB) graft, a 10-mm wide BPTB graft was harvested and the area calculated. The ACL was carefully dissected, and the size of the femoral and tibial footprints was measured using Image J software (National Institution of Health).

RESULTS

The average areas of the ST, ST-G, and BPTB graft were 52.3 ± 7.3, 64.4 ± 9.2, and 32.7 ± 6.5 mm(2), respectively. The sizes of the native femoral and tibial ACL footprints were 85.4 ± 26.3 and 145.4 ± 39.8 mm(2), respectively. Only the ST-G graft showed no significant difference in graft size when compared with the femoral ACL footprint.

CONCLUSION

Only the ST-G auto graft was able to reproduce the native size of the ACL footprint on the femoral side. None of the auto grafts could reproduce the size of the tibial ACL footprint. For clinical relevance, ST-G graft is recommended in order to reproduce the native size of the ACL in anatomical ACL reconstruction with auto graft.

ACL footprint size is correlated with the height and area of the lateral wall of femoral intercondylar notch

PURPOSE

The purpose of this study was to reveal the correlation between the size of the native anterior cruciate ligament (ACL) footprint and the size of the lateral wall of femoral intercondylar notch.

METHODS

Eighteen non-paired human cadaver knees were used. All soft tissues around the knee were resected except the ACL. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. The ACL was carefully dissected, and the periphery of the ACL insertion site was outlined on both the femoral and tibial sides. An accurate lateral view of the femoral condyle and the tibial plateau was photographed with a digital camera, and the images were downloaded to a personal computer. The size of the femoral and tibial ACL footprints, length of Blumensaat's line, and the height and area of the lateral wall of femoral intercondylar notch were measured with Image J software (National Institution of Health).

RESULTS

The sizes of the native femoral and tibial ACL footprints were 84 ± 25.3 and 144.7 ± 35.9 mm(2), respectively. The length of Blumensaat's line and the height and area of the lateral wall of femoral intercondylar notch were 29.4 ± 2.8 mm, 17.1 ± 2.7 mm, and 392.4 ± 86 mm(2), respectively. Both the height and the area of the lateral wall of femoral intercondylar notch were significantly correlated with the size of the ACL footprint on both the femoral and tibial sides.

CONCLUSION

For clinical relevance, the height and area of the lateral wall of femoral intercondylar notch can be a predictor of native ACL size prior to surgery. However, the length of Blumensaat's line showed no significant correlation with native ACL size.