The effect of tunnel placement on rotational stability after ACL reconstruction: evaluation with use of triaxial accelerometry in a porcine model

The 45° and 60° of sagittal femoral tunnel placement in anterior cruciate ligament reconstruction provide similar knee stability

PURPOSE

The aim of the present study was to compare 45° and 60° of sagittal femoral tunnel angles in terms of anterior tibial translation (ATT), valgus angle and graft in situ force following anterior cruciate ligament reconstruction (ACLR).

METHODS

Ten porcine knees were subjected to the following loading conditions: (1) 89 N anterior tibial load at 35° (full extension), 60° and 90° of knee flexion and (2) 5 N m valgus tibial moment at 35° and 45° of knee flexion. ATT and graft in situ force of the intact anterior cruciate ligament (ACL) and ACLR were collected using a robotic universal force/moment sensor (UFS) testing system for (1) ACL intact, (2) ACL-deficient (ACLD) and (3) two different ACLR using different sagittal femoral tunnel angles (coronal 45°/sagittal 45° and coronal 45°/sagittal 60°).

RESULTS

During the anterior tibial load, the femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° and 60° had significantly higher ATT than that of the ACL-intact knees at 60° of knee flexion (p < 0.05). The femoral tunnel angle of ACLR knees at coronal 45°/sagittal 60° had significantly lower graft in situ force than that of the ACL-intact knees at 60° and 90° of knee flexion (p < 0.05). During the valgus tibial moment, the femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° and 60° had significantly lower graft in situ force than that of the ACL-intact knees at all knee flexions (p < 0.05).

CONCLUSIONS

The femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° provided similar ATT, valgus angle and graft in situ force to that of ACLR knees at coronal 45°/sagittal 60°. Therefore, both femoral tunnel angles could be used in ACLR, as the sagittal femoral tunnel angle does not appear to be relevant in post-operative knee stability.

LEVEL OF EVIDENCE

Not applicable.

Graft Reorientation and Lateral Extra-articular Tenodesis in Revision Surgery for Persistent Rotational Instability of a Verticalized Anterior Cruciate Ligament Graft

Persistent rotational instability after anterior cruciate ligament reconstruction is a relatively common postoperative complication, typically associated with graft verticalization due to improper femoral tunnel placement, especially with classic transtibial femoral tunnel techniques. This article describes a technique designed to reorient a verticalized anterior cruciate ligament graft at its femoral insertion to a more anatomic position in the coronal and sagittal planes, aiming to restore knee stability without the need for a complete revision operation. Additionally, a lateral extra-articular tenodesis with fascia lata is added to reinforce rotational stability.

Graft isometry during anatomical ACL reconstruction has little effect on surgical outcomes

PURPOSE

To investigate the surgical outcomes of anatomical anterior cruciate ligament (ACL) reconstruction according to the graft isometry measured during surgery.

METHODS

Electrical medical records of patients who underwent an arthroscopic ACL reconstruction through the transportal technique using hamstring tendon autograft between 2012 and 2016 were retrospectively reviewed. The patients were classified into two groups based on the graft length change throughout the knee range of motion measured just before graft fixation (Group 1, graft length change ≤ 2 mm; Group 2, graft length change > 2 mm). Comparative analyses, including a non-inferiority trial, were performed regarding the clinical scores, knee laxity, and radiographic parameters between the groups.

RESULTS

A total of 67 patients were included in the study. The total change in the length of ACL graft throughout the knee range of motion was 1.4 ± 0.4 mm in Group 1 (range, 0.2-2.0 mm), and 3.0 ± 0.7 mm in Group 2 (range, 2.2-5.0 mm). Group 1 showed a relatively high (proximal) femoral tunnel and shallow (anterior) tibial tunnel compared to Group 2 (P < 0.001 and P = 0.028, respectively), but there were no apparent differences in the macroscopic view. There were no statistically significant differences in the clinical outcomes between groups at 2 years after surgery, which satisfied the non-inferiority criterion of Group 1 in terms of clinical scores and knee laxity compared to Group 2.

CONCLUSION

The surgical outcomes of anatomical ACL reconstruction in patients with non-isometric ACL graft were not inferior in terms of clinical scores and knee laxity, compared to those with nearly-isometric ACL graft. The graft tunnel placement in the isometric position during anatomical ACL reconstruction, which is technically challenging in the clinical setting, is not a crucial factor in terms of clinical outcomes.

LEVEL OF EVIDENCE

Level IV.

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.

ACL Reconstruction Graft Angle and Outcomes: Transtibial vs Anteromedial Reconstruction

BACKGROUND

The importance of creating an anatomic anterior cruciate ligament (ACL) reconstruction has been receiving significant attention. The best technique by which to achieve this anatomic reconstruction continues to be debated. The two most common methods are the transtibial (TT) and anteromedial (AM) techniques. Each has its advantages and disadvantages, and the literature comparing the two remains uncertain.

QUESTIONS/PURPOSES

In this prospective comparative study, we aimed to compare the ACL graft and tunnel angles achieved using the anatomic transtibial (TT) and anteromedial (AM) techniques; compare the ACL graft and tunnel angles in knees that have undergone ACL reconstruction and knees with intact ACLs; and determine whether differences in the graft or tunnel angle produce differences in clinical outcomes, as measured using both physical exam and patient-reported outcomes, after ACL reconstruction.

METHODS

Patients who underwent primary ACL reconstruction with bone-tendon-bone grafts using a TT or AM technique were included. Femoral graft angle (FGA), tibial graft angle (TGA), and sagittal orientation of the reconstructed ACL and contralateral native ACL were measured on post-operative magnetic resonance imaging. Post-operatively, patients underwent measurement of knee stability and completed the Knee Injury and Osteoarthritis Outcome Score (KOOS) survey.

RESULTS

Twenty-nine patients were enrolled (AM group, 14; TT group, 15); at follow-up, KOOS data were available for 26 patients (13 in each group). There were no differences in sagittal ACL graft angle between groups or in comparison with the normal knee. The FGA was more vertical after TT reconstructions; the TGA was comparable between groups. There were no significant differences in 2-year post-operative physical exam measurements or in KOOS scores.

CONCLUSION

Anatomic ACL angle was restored after reconstruction with both the TT and AM techniques, despite different FGAs. No significant differences in clinical outcome were noted between groups on physical exam or KOOS at 2 years after surgery. These results suggest that TT reconstruction results in a graft position similar to that seen in AM reconstruction and that the location of the intra-articular tunnel aperture matters more than the orientation of the tunnel.

Accuracy of the femoral tunnel position in robot-assisted anterior cruciate ligament reconstruction using a magnetic resonance imaging-based navigation system: A preliminary report

BACKGROUND

Tunnel misplacement is a common cause of failed anterior cruciate ligament (ACL) reconstruction. In this study, the accuracy of the femoral tunnel position was evaluated in robot-assisted ACL reconstruction using a magnetic resonance imaging (MRI)-based navigation system. We hypothesized that a difference of less than 2 mm between the planned femoral tunnel position and the created one was achievable.

METHODS

Four cadaveric knees underwent robot-assisted ACL reconstruction. A 3-dimensional model using pre-operative MRI images was used for preoperative planning, and a computed tomography (CT) scan was performed postoperatively. The planned and the created femoral tunnels were compared to assess the accuracy of the femoral tunnel position.

RESULTS

The distance between the intra-articular points of the planned and the created tunnels was 7.78 mm in the first experiment and 1.47 mm in the last one. The difference in tunnel length was 4.62 mm in the first experiment and 0.99 mm in the last one.

CONCLUSIONS

Accuracy of the femoral tunnel position improved with each robot-assisted ACL reconstruction using an MRI-based navigation system. In the last experiment, the accuracy of the femoral tunnel position was satisfactory.

The iliotibial band and anterolateral capsule have a combined attachment to the Segond fracture

The purpose of this report was to describe the injury mechanism, surgical findings, and outcomes in a 21-year-old professional female football player who presented with a complete anterior cruciate ligament (ACL) rupture and Segond fracture. Interview and video analysis were performed to elicit the injury mechanism. Clinical examination and imaging revealed a complete ACL tear, Segond fracture, lateral meniscus tear, MCL sprain, and posterolateral corner sprain. Examination under anaesthesia revealed Grade 2 pivot shift and varus/valgus instability. Surgical examination revealed attachment of the posterior fibres of the iliotibial band and the lateral capsule to the Segond fragment. The fracture was reduced with suture fixation, and an anatomic ACL reconstruction was performed. Follow-up demonstrated rotatory and anterior tibial translation stability, and imaging at 7 months post-operatively revealed no movement and continued osseous integration of the Segond fragment. Level of evidence V.

Anterolateral Ligament Reconstruction or Extra-Articular Tenodesis: Why and When?

Residual rotational laxity following anterior cruciate ligament (ACL) reconstruction has been identified as significant concern in many patients, despite evolution of techniques. The expanding body of knowledge on the anatomy and biomechanics of the anterolateral soft tissue restraints in rotational control of the knee has reignited an interest in extra-articular reconstruction techniques for augmenting ACL reconstruction. Reconstruction techniques currently used can be broadly categorized as either lateral extra-articular tenodesis or reconstruction of the anterolateral ligament. In this article, we outline the relevant anatomy, biomechanics, and rationale behind the indications and technique of our current extra-articular augmentation procedure.

Evaluation of pivot shift phenomenon while awake and under anaesthesia by different manoeuvres using triaxial accelerometer

PURPOSE

Evaluating pivot shift phenomenon is difficult due to its subjectivity, wide variation of testing manoeuvres, and difficulty in evaluating patients while awake. The purpose of this study was to evaluate the pivot shift phenomenon using a triaxial accelerometer by two different manoeuvres, the pivot shift test as representative of flexion manoeuvre and N test as a representative of extension manoeuvre, and in two different conditions, awake and under anaesthesia.

METHODS

Twenty-nine patients with unilateral anterior cruciate ligament (ACL)-injured knee were included. Pivot shift test and N test were performed for both injured and uninjured legs while awake and under anaesthesia, with the acceleration measurements using a triaxial accelerometer (KiRA). The tests were also subjectively graded on a scale of 0-6 based on the modification of IKDC criteria.

RESULTS

Under anaesthesia, acceleration of ACL-injured knees was greater than that of uninjured knees in both pivot shift test (P < 0.001) and N test (P < 0.001) , whereas the acceleration value was greater in the N test. Furthermore, there were significant positive correlations between the acceleration and subjective grading in both tests, whereas the N test was more significant than the pivot shift test. On the other hand, there was no statistical significance in acceleration between ACL-injured and uninjured knees in either test while the patient was awake.

CONCLUSION

The triaxial accelerometer was useful to objectively detect and quantitatively evaluate the pivot shift phenomenon by both the pivot shift test and N test under anaesthesia. The acceleration of ACL-injured knees was greater than that of uninjured knees, and the acceleration was correlated with the subjective manual grading, especially in the N test. On the other hand, its use while the patient was awake was likely limited.

LEVELS OF EVIDENCE

Diagnostic study of non-consecutive patients without a universally applied gold standard, Level III.

Influence of change of tunnel axis angle on tunnel length during double-bundle ACL reconstruction via the transportal technique

BACKGROUND

Commercially available flexible reamer and curved guide systems allow a certain degree of control over intra-articular tunnel orientation, therefore allows a wide range of intra-osseous femoral tunnel orientations, contrary to the femoral tunneling technique using a straight guide pin, which are determined by knee flexion angle. We sought to find the clinical relevance of intra-osseous femoral tunnel orientations in the respect of tunnel length. To evaluate the relationship between the tunnel axis angle in three orthogonal planes and tunnel length in the anteromedial (AM) and posterolateral (PL) femoral tunnels in patients who underwent anatomic double-bundle anterior cruciate ligament reconstruction (DB-ACLR) using the transportal (TP) technique with a 42^o curved guide.

METHODS

A total of 40 patients who underwent primary DB-ACLR with the TP technique using a curved guide were evaluated retrospectively. The tunnel axis angle in three orthogonal planes were evaluated on a three-dimensional surface model constructed using an axial computed tomography scan obtained after reconstruction. Then, correlations with tunnel length were analyzed.

RESULTS

In the AM tunnel, tunnel axis angles in the coronal (β = 0.0252, p = 0.022) and sagittal (β = 0.0168, p = 0.029) plane showed significant correlations with tunnel length, while the axial plane did not (p = 0.493) (adjusted R² = 0.801). In the PL tunnel, only tunnel axis angles in the axial plane (β = 0.0262, p = 0.008) showed a significant relationship with tunnel length (adjusted R² = 0.700).

CONCLUSION

Drilling at a higher angle in the coronal and sagittal planes in AM tunnels and at a higher angle in the axial plane in PL tunnels decreases the incidence of short femoral tunnels.

The evolution of primary double-bundle ACL reconstruction and recovery of early post-operative range of motion

PURPOSE

The aim of this study was to analyse early post-operative range of motion (ROM) as our anatomic double-bundle (DB) anterior cruciate (ACL) reconstruction technique with respect to tunnel placement evolved. It is the hypothesis of this study that more anatomic placement of the femoral insertion site of the anteromedial (AM) bundle of the ACL results in better restoration of early post-operative knee range of motion.

METHODS

Two methods of DB ACL reconstruction regarding more accurate placement of the femoral AM tunnel in relation to its anatomic origin were compared. Patients presenting for 1- and 3-month post-operative clinical visits were examined for passive extension and active flexion by members of the clinical staff. Only patients undergoing primary DB reconstruction with allograft were included in the analyses. To determine the effects of the modified AM bundle placement on recovery of post-operative ROM, patients undergoing surgery in the 6 months before July 2006 (Group A, n = 50) were compared to patients undergoing surgery in the 6 months after July 2006 (Group B, n = 49).

RESULTS

A total of 99 patients met the inclusion criteria. More accurate placement of the AM bundle of the ACL was associated with a smaller side-to-side difference in flexion at 1 month (n.s.) and at 3 months (3° reduction, p < 0.03) after surgery. There was no effect on extension (n.s.) CONCLUSION: More anatomic placement of the femoral insertion of the AM bundle was associated with improved knee flexion. The study translates the findings of previous anatomic basic science research to demonstrate improved restoration of normal joint motion. This ideally leads to improved long-term clinical outcomes and maintenance of joint and cartilage health.

LEVEL OF EVIDENCE

III.

Dynamic Evaluation of Pivot-Shift Phenomenon in Double-Bundle Anterior Cruciate Ligament Reconstruction Using Triaxial Accelerometer

PURPOSE

To evaluate the effect of initial graft tension on rotational stability and to determine the minimum required tension (MRT) based on the pivot-shift phenomenon in isolated anteromedial bundle (AMB), isolated posteromedial bundle (PLB), and double-bundle anterior cruciate ligament (ACL) reconstructions using a triaxial accelerometer during surgery.

METHODS

Primary double-bundle ACL reconstructions were included. The pivot-shift test and N-test were performed before and during surgery with the acceleration measurements using a triaxial accelerometer. The pivot-shift test was also manually graded. The AMB and PLB were fixed to a graft tensioning system during surgery with the following settings: (1) AMB only (AMB), (2) PLB only (PLB), and (3) AMB and PLB (A+P). The total graft tension was first set at 20 N and then was increased in increments of 10 N until the pivot-shift test became negative, which was defined as the MRT in each setting.

RESULTS

Twenty-five patients were evaluated. The MRT in the AMB setting averaged 26 N (range, 20 to 40 N); in the PLB setting, 28 N (range, 20 to 40 N); and in the A+P setting, 24 N (range, 20 to 40 N). The MRT in the A+P setting was significantly smaller than that in the PLB setting (P = .008). The acceleration in the A+P setting was significantly smaller than that in the AMB and PLB settings both in the pivot-shift test (vs AMB: P = .007, vs PLB: P = .011) and in the N-test (vs AMB: P < .001, vs PLB: P < .001).

CONCLUSIONS

Double-bundle ACL reconstruction better controlled rotational stability with smaller MRT than isolated PLB reconstruction at the time of surgery. In double-bundle reconstruction, the MRT based on the pivot-shift phenomenon could be larger than previously reported MRT based on anteroposterior laxity.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

The Influence of Knee Flexion Angle for Graft Fixation on Rotational Knee Stability During Anterior Cruciate Ligament Reconstruction: A Biomechanical Study

PURPOSE

To evaluate the effect of knee flexion angle for hamstring graft fixation, full extension (FE), or 30°, on acceleration of the knee motion during pivot-shift testing after either anatomic or nonanatomic anterior cruciate ligament (ACL) reconstruction using triaxial accelerometry.

METHODS

Two types of ACL reconstructions (anatomic and nonanatomic) using 2 different angles of knee flexion during graft fixation (FE and 30°) were performed on 12 fresh-frozen human knees making 4 groups: anatomic-FE, anatomic-30°, nonanatomic-FE, and nonanatomic-30°. Manual pivot-shift testing was performed at ACL-intact, ACL-deficient, and ACL-reconstructed conditions. Three-dimensional acceleration of knee motion was recorded using a triaxial accelerometer.

RESULTS

The anatomic-30° group showed the smallest overall magnitude of acceleration among the ACL-reconstructed groups (P = .0039). There were no significant differences among the anatomic-FE group, the nonanatomic-FE group, and the nonantomic-30° group (anatomic-FE vs nonanatomic-FE, P = .1093; anatomic-FE vs nonanatomic-30°, P = .8728; and nonanatomic-FE vs nonanatomic-30°, P = .1093). After ACL transection, acceleration was reduced by ACL reconstruction with the exception of the nonanatomic-FE group that did not show a significant difference when compared with the ACL-deficient (P = .4537).

CONCLUSIONS

The anatomic ACL reconstruction with the graft fixed at 30° of knee flexion better restored rotational knee stability compared with FE. An ACL graft fixed with the knee at FE in anatomic position did not show a significant difference compared with the nonanatomic ACL reconstructions.

CLINICAL RELEVANCE

Knee flexion angle at the time of graft fixation for ACL reconstruction can be considered to maximize the rotational knee stability.

Clinical advantages of image-free navigation system using surface-based registration in anatomical anterior cruciate ligament reconstruction

PURPOSE

To evaluate the clinical advantages of a navigation system developed with an emphasis on attaining an appropriate femoral tunnel length and posterior wall margin with no posterior wall blowout, as well as having accurate tunnel positioning, in anatomical anterior cruciate ligament reconstruction (ACLR).

METHODS

Ten freshly frozen human knees were transected at mid-femur and mid-tibia. Each knee specimen underwent arthroscopic single-bundle anterior cruciate ligament reconstruction using the outside-in technique, with two knees by manual ACLR (control group) and another eight knees by only the navigational ACLR without arthroscopic assistance (experimental group). The position/orientation information of tunnel entry point, tunnel length, and posterior wall distance of pre-, intra-, and postoperative tunnel were recorded, and the reliability and errors among them were evaluated.

RESULTS

From comparison of the 3D models for preoperative planning and postoperative reconstruction, the mean differences for navigational femoral tunnelling and arthroscopic-assisted femoral tunnelling were recorded, respectively: (1) tunnel entry position, 1.4 mm (SD 0.3) versus 4.9 mm; (2) tunnel length, 0.7 mm (SD 0.2), similar to 0.6 mm in arthroscopic-assisted femoral tunnelling, and (3) posterior wall distance, 0.5 mm (SD 0.2), much smaller than 4.7 mm for arthroscopic-assisted femoral tunnelling. The intraclass correlation coefficients, calculated to determine the accuracy and reliability of navigational femoral tunnelling, showed excellent internal consistency that ranged from 0.965 to 0.989 for tunnel length and from 0.810 to 0.953 for posterior wall distance.

CONCLUSION

Navigation systems with enhancement of the registration accuracy by the developed system are feasible in anatomical ACLR, in reducing surgical failures such as short tunnel length or posterior wall breakage of distal femur. The present study revealed that computer navigation could aid in avoiding major mistakes in exact positioning and posterior wall blowout and help in attaining appropriate length for femoral tunnelling in anatomical ACLR.

Rotational laxity after anatomical ACL reconstruction measured by 3-D motion analysis: a prospective randomized clinical trial comparing anatomic and nonanatomic ACL reconstruction techniques

PURPOSE

To compare the ability of three different anterior cruciate ligament (ACL) reconstruction techniques to normalize rotational knee stability 1 year after ACL reconstruction. Two of these techniques are so-called anatomic techniques.

METHODS

Three different ACL reconstruction techniques were tested for their ability to normalize rotational knee stability in a prospective randomized study. Forty-seven ACL-deficient (ACLD) patients were randomized to transtibial single-bundle (SB), anatomic SB, and double-bundle ACL reconstruction. Three-dimensional motion analysis was performed preoperatively and at 1-year follow-up to evaluate tibial rotation and rotational stiffness. Motion data were captured using an eight-camera motion analysis system. Tibial rotation was determined during walking, running, and a pivoting task. Other outcome parameters were KT-1000 knee laxity measurements and the subjective outcome scores KOOS and IKDC.

RESULTS

Three-dimensional motion analysis demonstrated that the tibial internal rotation and the rotational stiffness did not differ between the ACL reconstruction techniques during walking, running, and pivoting at 1-year follow-up. Objective knee stability and subjective outcome scores did not differ between the reconstruction groups.

CONCLUSION

No significant difference in rotational stability walking, running, and pivoting was seen between anatomic and nonanatomic ACL reconstruction techniques at 1-year follow-up.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Is the native ACL insertion site "completely restored" using an individualized approach to single-bundle ACL-R?

PURPOSE

The goal of individualized anatomic anterior cruciate ligament reconstruction (ACL-R) is to reproduce each patient's native insertion site as closely as possible. The amount of the native insertion site that is recreated by the tunnel aperture area is currently unknown, as are the implications of the degree of coverage. As such, the goals of this study are to determine whether individualized anatomic ACL-R techniques can maximally fill the native insertion site and to attempt to establish a crude measure to evaluate the percentage of reconstructed area as a first step towards elucidating the implications of complete footprint restoration.

METHODS

This is a prospective pilot study of 45 patients who underwent primary single-bundle anatomic ACL-R from May 2011 to April 2012. Length and width of the native insertion site were measured intraoperatively. Using published guidelines, reconstruction technique and graft choice were determined to maximize the percentage of reconstructed area. Native femoral and tibial insertion site area and femoral tunnel aperture area were calculated using the formula for area of an ellipse. On the tibial side, tunnel aperture area was calculated with respect to drill diameter and drill guide angle. Percentage of reconstructed area was calculated by dividing total tunnel aperture area by the native insertion site area.

RESULTS

The mean areas for the native femoral and tibial insertion sites were 83 ± 20 and 125 ± 20 mm(2), respectively. The mean tunnel aperture area for the femoral side was 65 ± 17, and 86 ± 17 mm(2) for the tibial tunnel aperture area. On average, percentage of reconstructed area was 79 ± 13 % for the femoral side, and 70 ± 12 % for the tibial side.

CONCLUSION

Anatomic ACL-R does not restore the native insertion site in its entirety. Percentage of reconstructed area serves as a rudimentary tool for evaluating the degree of native insertion site coverage using current individualized anatomic techniques and provides a starting point from which to evaluate the clinical significance of complete footprint restoration.

LEVEL OF EVIDENCE

IV.

Quantitative pivot shift assessment using combined inertial and magnetic sensing

PURPOSE

The purpose of the study was to demonstrate the feasibility of a new measurement system using micro-electromechanical systems (MEMS)-based sensors for quantifying the pivot shift phenomenon.

METHODS

The pivot shift test was performed on 13 consecutive anterior cruciate ligament-deficient subjects by an experienced examiner while femur and tibia kinematics were recorded using two inertial sensors each composed of an accelerometer, gyroscope and magnetometer. The gravitational component of the acquired data was removed using a novel method for estimating sensor orientations. Correlation between the clinical pivot shift grade and acceleration and velocity parameters was measured using Spearman's rank correlation coefficients.

RESULTS

The pivot shift phenomenon was best characterized as a drop in femoral acceleration observed at the time of reduction. The correlation between the femoral acceleration drop and the clinical grade was shown to be very strong (r = 0.84, p < 0.0001).

CONCLUSIONS

The present study demonstrates the feasibility of quantifying the pivot shift using MEMS-based sensors and removing the gravitational component of acceleration using an estimation of sensor orientation for improved correlation to the clinical grade.

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.

Updates in biological therapies for knee injuries: anterior cruciate ligament

There have been many advances in anterior cruciate ligament reconstruction (ACLR) techniques incorporating biological treatment. The aim of this review is to discuss the recent contributions that may enlighten our understanding of biological therapies for anterior cruciate ligament (ACL) injuries and improve management decisions involving these enhancement options. Three main biological procedures will be analyzed: bio-enhanced ACL repair, bio-enhanced ACLR scrutinized under the four basic principles of tissue engineering (scaffolds, cell sources, growth factors/cytokines including platelet-rich plasma, and mechanical stimuli), and remnant-preserving ACLR. There is controversial information regarding remnant-preserving ACLR, since different procedures are grouped under the same designation. A new definition for remnant-preserving ACLR surgery is proposed, dividing it into its three major procedures (selective bundle augmentation, augmentation, and nonfunctional remnant preservation); also, an ACL lesion pattern classification and a treatment algorithm, which will hopefully standardize these terms and procedures for future studies, are presented.

A comparison of dynamic rotational knee instability between anatomic single-bundle and over-the-top anterior cruciate ligament reconstruction using triaxial accelerometry

PURPOSE

Recently, single-bundle (SB) anterior cruciate ligament (ACL) reconstruction has been advanced by the anatomic concept, but the biomechanical outcome of the anatomic method has not been fully investigated, especially for rotational instability. Anatomic SB and the single over-the-top procedures are the treatment of choice for primary cases and revision or skeletally immature cases, respectively. The purpose of this study was to investigate the dynamic rotational instability of anatomic SB and over-the-top reconstruction during a pivot shift test using triaxial accelerometry.

METHODS

Eight fresh frozen human cadaveric knees were used in this study. Rotational instability measurement was conducted during a pivot shift test by the use of a triaxial accelerometer attached to the tibia. The tests were performed in the ACL-intact, ACL-deficient and ACL-reconstructed knees with two different procedures (anatomic SB and over-the-top). The acceleration in three directions and the magnitude of acceleration were measured to evaluate rotational instability and compare between four different knee states.

RESULTS

The overall magnitude of acceleration was significantly different (P < 0.01) between the ACL-intact knees and the ACL-deficient knees. Both anatomic SB and over-the-top ACL reconstruction significantly reduced the overall magnitude of acceleration compared to the ACL-deficient knees, but still had larger accelerations compared to the ACL-intact knees. There was no significant difference for the overall magnitude of acceleration between anatomic SB and over-the-top reconstruction procedure.

CONCLUSION

Over-the-top reconstruction provides comparable result to anatomic SB reconstruction in terms of controlling the dynamic rotational stability. Over-the-top reconstruction might be one of the options for revision cases and in skeletally immature patients.

Innovative technology for knee laxity evaluation: clinical applicability and reliability of inertial sensors for quantitative analysis of the pivot-shift test

There has been an increased interest in the quantification of the knee laxity secondary to anterior cruciate ligament (ACL) injury. In clinical practice, the diagnosis is performed by clinical examination and magnetic resonance imaging analysis and confirmed arthroscopically. The pivot shift phenomenon has been identified as one of the essential signs of functional ACL insufficiency. A reliable system to adequately assess patients with ACL injury, quantifying the pivot shift test outcome, is needed. Several studies have been conducted in this regard but the proposed methods remain confined to a research area. The goal of this article is to summarize the actual knowledge and current concepts.