Biomechanical comparison of three anatomic ACL reconstructions 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.

Arthroscopic reconstruction of anterior cruciate ligaments with allograft: single-tunnel single-bundle versus single-tunnel double-bundle techniques

Purpose

To compare the clinical results of anterior cruciate ligament (ACL) reconstruction using the single-tunnel single-bundle (STSB) technique versus the single-tunnel double-bundle (STDB) technique.

Methods

This was a retrospective, single-center, single-surgeon study based on data collected from March 2012 to June 2013. According to our inclusion/exclusion criteria, a total of 78 patients (64 males, 14 females; mean age, 25.1 years) who underwent arthroscopic ACL reconstruction with anterior tibialis tendon allografts through either the STSB technique (36 cases) or the STDB technique (42 cases) in our department were recruited. The International Knee Documentation Committee (IKDC), Lysholm, and Tegner scores were used to evaluate the subjective function of the knee joint during the postoperative follow-up. The Lachman test and pivot shift test were used to objectively assess the stability of the knee.

Results

The average follow-up duration was 24.9 ± 1.8 months in the STSB group and 24.6 ± 1.7 months in the STDB group (P > 0.05). Patients in both groups recovered to the preoperative sports level with few complications. The postoperative Lysholm score (86.1 ± 7.5 vs. 47.7 ± 9.0 in the STSB group; 87.0 ± 7.1 vs. 48.2 ± 8.3 in the STDB group), IKDC score (87.8 ± 7.2 vs. 49.3 ± 6.1 in the STSB group; 88.7 ± 6.6 vs. 49.8 ± 6.3 in the STDB group), Tegner score (6.5 ± 1.3 vs. 2.5 ± 1.3 in the STSB group; 6.6 ± 1.2 vs. 2.6 ± 1.2 in the STDB group), Lachman test positive rate (8.3% vs. 89.9% in the STSB group; 7.1% vs. 85.7% in the STDB group), and pivot shift test positive rate (27.8% vs. 63.9% in the STSB group; 7.1% vs. 69.0% in the STDB group) were significantly improved compared to the preoperative status in both groups (P < 0.05). However, no statistically significant difference was observed between the two groups at the final follow-up (P > 0.05), except for the pivot shift test positive rate in the STDB group versus the STSB group (7.1% vs. 27.8%, P < 0.05).

Conclusions

The STDB technique achieved a satisfactory clinical outcome with better rotational stability compared to the traditional STSB technique and therefore provided an effective option for ACL reconstruction.

Level of evidence

Case series, Level IV.

Flat-Tunnel Technique With Independently Tensioned Bundles Better Restores Rotational Stability Than Round-Tunnel Technique in Anatomic Anterior Cruciate Ligament Reconstruction Using Hamstring Graft: A Cadaveric Biomechanical Study

PURPOSE

To investigate the kinematics differences between round-tunnel (ROT) and flat-tunnel (FLT) techniques in anterior cruciate ligament (ACL) reconstruction when using hamstring graft.

METHODS

Nine matched pairs of fresh-frozen cadaveric knees were evaluated for the kinematics of intact, ACL-sectioned, and either ROT or FLT reconstructed knees. The graft bundles for FLT technique were separately tensioned. A 6 degrees of freedom robotic system was used to assess knee laxity: (1) 134-N anterior tibial load at 0°, 15°, 30°, 60°, and 90°of knee flexion; (2) 10 Nm of valgus torque followed by 5 Nm of internal rotation torque simulates a pivot-shift test at 15° and 30°; (3) 5-Nm internal and external rotation torques at 0°, 15°, 30°, 60°, and 90°; (4) 10-Nm varus and valgus torques at 15° and 30°.

RESULTS

Significant differences were found for ROT versus FLT techniques in terms of the simulated pivot-shift test at 15° (2.5 mm vs 1.4 mm, respectively, difference from intact; P =.039) and the internal rotation test at 15° (2.5° vs 0.5°, respectively, difference from intact; P =.034) and 30° (2.0° vs 0.4°, respectively, difference from intact; P =.014). No significant differences were found between groups during 134-N anterior tibial load, external rotation and valgus/varus rotation. Neither technique was able to reproduce the intact state during an anterior tibial load and simulated pivot-shift test.

CONCLUSIONS

The FLT technique with independently tensioned bundles shows the same anterior control as the ROT technique but better restores rotational stability in terms of the simulated pivot-shift test and the internal rotation test in anatomic ACL reconstruction at time zero.

CLINICAL RELEVANCE

The FLT technique with independently tensioned bundles of ACL reconstruction appears to be a viable, more anatomic technique than the ROT technique in mimicking flat anatomy and rotational stability of native ACL.

Effect of the positional relationship between the interference screw and the tendon graft in the bone tunnel in ligament reconstruction

PURPOSE

To reveal the effects of the positional and length relationships between the interference screws (ISs) and the tendon graft in the bone tunnel on the fixation strength in ligament reconstruction.

METHODS

We compared three IS positions on the anterior (the Anterior group) or posterior (the Posterior group) or side (the Side group) of the tendon graft in relation to the pullout direction. The tendon graft was pulled at 0°, 30°, 60°, and 90° to the bone tunnel, and the maximum pullout load at each angle was compared among the groups. We also investigated the relationship between the length of the tendon graft and the length of the IS in the bone tunnel. The direction of the pullout force was the same as that of the Anterior group, and the maximum load was compared between groups in which the tendon graft was longer or shorter than the IS.

RESULTS

The maximum loads of the Anterior group were significantly greater than those of the Posterior and Side groups at the traction angles of 30° and 60°, respectively. An IS shorter than the tendon graft was found to provide significantly superior fixation strength compared to an IS longer than the tendon graft.

CONCLUSIONS

Better fixation strength was achieved when the IS was placed on the side of the anchorage tunnel on which the tendon graft was loaded and the IS was shorter than the tendon graft.

Transportal central femoral tunnel placement has a significantly higher revision rate than transtibial AM femoral tunnel placement in hamstring ACL reconstruction

PURPOSE

It is proposed that central femoral ACL graft placement better controls rotational stability. This study evaluates the consequence of changing the femoral tunnel position from the AM position drilled transtibially to the central position drilled transportally. The difference in ACL graft failure is reported.

METHODS

This prospective consecutive patient single surgeon study compares the revision rates of 1016 transtibial hamstring ACL reconstructions followed for 6-15 years with 464 transportal hamstring ACL reconstructions followed for 2-6 years. Sex, age, graft size, time to surgery, meniscal repair and meniscectomy data were evaluated as contributing factors for ACL graft failure to enable a multivariate analysis. To adjust for the variable follow-up a multivariate hazard ratio, failure per 100 graft years and Kaplan-Meier survivorship was determined.

RESULTS

With transtibial ACLR 52/1016 failed (5.1%). With transportal ACLR 32/464 failed (6.9%). Significant differences between transportal and transtibial ACLR were seen for graft diameter, time to surgery, medial meniscal repair rates and meniscal tissue remaining after meniscectomy. Adjusting for these the multivariate hazard ratio was 2.3 times higher in the transportal group (p = 0.001). Central tunnel placement resulted in a significantly 3.5 times higher revision rate compared to an anteromedial tunnel placement per 100 graft years (p = 0.001). Five year survival was 980/1016 (96.5%) for transtibial versus 119/131 (90.5%) for transportal. Transportal ACLR also showed a significantly higher earlier failure rate with 20/32 (61%) of the transportal failing in the first year compared with 14/52 (27%) for transtibial. (p = 0.001.) CONCLUSION: Transportal central femoral tunnel ACLR has a higher failure rate and earlier failure than transtibial AM femoral tunnel ACLR.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

A biomechanical comparison of all-inside cruciate ligament graft preparation techniques

Background

The all-inside cruciate ligament graft preparation technique has become popular due to its utility in sparing a growing physis, preserving a tendon in ACL surgery, and/or reduction of pain. However, few studies have compared graft preparation techniques to determine the ideal construct for cruciate ligament reconstruction. We sought to compare biomechanical properties of two quadrupled all-inside cruciate ligament graft preparation techniques and three alternative all-inside graft preparation techniques that may be used when the available tendon is too short to be quadrupled.

Methods

Fifty porcine extensor tendons were evenly divided into five groups (n = 10) representing all-inside graft preparation techniques, including two quadrupled (Quad-A, Quad-B) and three alternative methods (Tripled, Folded, Two-Doubled). Each graft construct underwent preconditioning (10 loading cycles from 20 to 50 N at 0.1 Hz), cyclic loading (500 loading cycles from 50 to 250 N at 1.0 Hz) and load-to-failure (tension applied at 20 mm/min).

Results

Quad-A and Quad-B demonstrated no significant differences in cyclic displacement (10.5 ± 0.3 vs 11.7 ± 0.4 mm; p = 0.915), cyclic stiffness (1086.2 ± 487.3 vs 460.4 ± 71.4 N/mm; p = 0.290), pullout stiffness (15.9 ± 4.3 vs 7.4 ± 4.4 N/mm; p = 0.443), ultimate failure load (641.2 ± 84.7 vs 405.9 ± 237.4 N; p = 0.672), or ultimate failure displacement (47.3 ± 6.7 vs 55.5 ± 0.7 mm; p = 0.778). The mean cyclic displacement of the Two-Doubled group was significantly greater than the Quad-A (29.7 ± 2.2 vs 10.5 ± 0.3 mm; p < 0.001), Quad-B (29.7 ± 2.2 vs 11.7 ± 0.4 mm; p < 0.001), Tripled (29.7 ± 2.2 vs 11.3 ± 0.2 mm; p < 0.001), and Folded group (29.7 ± 2.2 vs 13.3 ± 0.2 mm; p < 0.001). There were no other statistically significant differences between the three alternative all-inside graft preparation techniques.

Conclusion

The current study demonstrates the biomechanical properties of two quadrupled all-inside graft constructs, Quad-A and Quad-B, are not significantly different. When the available tendon is of insufficient length, the Two-Doubled group demonstrated more than twice the cyclic displacement of all other graft preparation techniques, and is therefore not recommended for use in all-inside cruciate ligament reconstruction.

Medial collateral ligament reconstruction is necessary to restore anterior stability with anterior cruciate and medial collateral ligament injury

PURPOSE

The purpose of this study was to compare knee kinematics and graft forces in anterior cruciate ligament (ACL) reconstruction combined with one of two superficial medial collateral ligament (sMCL) reconstruction techniques (parallel or triangular vector sMCL reconstruction).

METHODS

Twenty porcine knees were divided into two groups (n = 20), parallel or triangular vector sMCL reconstruction, with both groups having anatomic single-bundle ACL reconstruction. The knees were tested under (1) an 89-N anterior tibial load, (2) 4 Nm internal and external rotational tibial torques, and (3) a 7 Nm valgus torque.

RESULTS

With ACL/sMCL co-injuries, single-bundle ACL reconstruction alone does not restore anterior, valgus, and internal stability. Triangular vector sMCL reconstruction better restored anterior stability, and parallel sMCL reconstruction better restored valgus stability.

CONCLUSION

This study showed that single-bundle ACL reconstruction alone was not able to restore anterior tibial translation, valgus rotation, and external rotation of the intact knee with combined ACL and sMCL injuries and sMCL reconstruction was also required. The combined ACL and parallel sMCL reconstruction better restored valgus and external rotation stability, while the combined ACL and triangular vector method better restored anterior tibial translation. With combined ACL and severe sMCL injury, both ligaments should be reconstructed. The two sMCL reconstruction techniques exhibited slightly different kinematics and graft force; however, there was not enough difference to recommend one over the other.

ACL double-bundle reconstruction with one tibial tunnel provides equal stability compared to two tibial tunnels

PURPOSE

The purpose of this study was to investigate whether an anterior cruciate ligament (ACL) double-bundle reconstruction with one tibial tunnel displays the same in vitro stability as a conventional double-bundle reconstruction with two tibial tunnels when using the same tensioning protocol.

METHODS

In 11 fresh-frozen cadaveric knees, ACL double-bundle reconstruction with one and two tibial tunnels was performed. The two grafts were tightened using 80 N in different flexion angles (anteromedial-bundle at 60° and posterolateral-bundle at 15°). Anterior tibial translation (134 N) and translation with combined rotatory and valgus loads (10 Nm valgus stress and 4 Nm internal tibial torque) were determined at 0°, 30°, 60° and 90° flexion. Measurements were taken in intact ACL, resected ACL, three-tunnel reconstruction and four-tunnel reconstruction. Additionally, the tension on the grafts was determined. Student's t test was performed for statistical analysis of the related samples. Significance was set at p < 0.017 according to Bonferroni correction.

RESULTS

The two reconstructive techniques displayed no significant differences in comparison with the intact ACL in anterior tibial translation at 0°, 60° and 90° of flexion. The same results were obtained for the anterior tibial translation with a combined rotatory load at 60° and 90°. When directly comparing both reconstructive techniques, there were no significant differences for the anterior tibial translation and combined rotatory load at all flexion angles. The measured tension on grafts displayed similar load sharing between both bundles. Except at full extension, both grafts displayed a significantly different tension increase under anterior tibial translation for both techniques (p = 0.0086).

CONCLUSIONS

Tightening both bundles in ACL double-bundle reconstruction with one or two tibial tunnels in different flexion angles achieved comparable restoration of stability, although there was different load sharing on the bundles. With regard to individualized ACL reconstruction, the double-bundle technique with one tibial tunnel offers a possibility to address small tibial insertion sites without compromising the advantages of a double-bundle procedure.

Biomechanical evaluation of knee endpoint during anterior tibial loading: Implication for physical exams

BACKGROUND

Physical exams that apply anterior tibial loads are typically used to evaluate knees with anterior cruciate ligament (ACL) injuries. The amount of anterior tibial translation that occurs during these exams can be difficult to assess due to a "soft" endpoint. Therefore, the objective of this study is to determine the biomechanical characteristics of the endpoint for the intact and ACL deficient knee using quantitative criteria.

METHODS

Eight porcine knees were tested using a robotic testing system. An 89N anterior tibial load was applied to the intact and ACL deficient knee at 30°, 45°, 60° and 75° of flexion. The stiffness of the toe and linear regions was determined from the load-translation curve. The width of the transition region was defined by the distance between the points where the best-fit lines used to define the stiffness of the toe and linear regions diverged from the load-translation curve.

RESULTS

Stiffness of the toe and linear regions significantly decreased after transecting the ACL at all flexion angles (71-85% and 38-62%, respectively). Width of the transition region was significantly increased in the ACL deficient knee at all flexion angles (approximately four to five times and four to nine times, respectively).

CONCLUSIONS

The novel quantitative criteria developed in this study have the potential to be deployed in clinical practice by coupling them with data from knee arthrometers that are commonly used in clinical practice. Thus, additional information from the load-translation curve can be provided to improve the diagnosis of ACL injury.

The anatomy of the anterior cruciate ligament and its relevance to the technique of reconstruction

Anterior cruciate ligament (ACL) reconstruction is commonly performed and has been for many years. Despite this, the technical details related to ACL anatomy, such as tunnel placement, are still a topic for debate. In this paper, we introduce the flat ribbon concept of the anatomy of the ACL, and its relevance to clinical practice.

Cite this article: Bone Joint J 2016;98-B:1020–6.

Biomechanical Properties of Different Fixation Techniques for Posterior Cruciate Ligament Avulsion Fractures

PURPOSE

To analyze the ultimate failure load, yield load, stiffness, and cyclic elongation of 4 different fixation techniques for posterior cruciate ligament avulsion fractures under cyclic loading and load-to-failure conditions.

METHODS

In 40 porcine knees, a standardized bony avulsion of the posterior cruciate ligament was generated. The osseous avulsion was fixed by the following techniques through an open approach: (1) direct anterograde screw fixation (3.5 mm with washer), (2) retrograde screw fixation (3.5 mm with washer), (3) cortical suspension button fixation (with No. 2 braided suture), and (4) direct suture cerclage (with No. 2 braided suture). The constructs were cyclically loaded 500 times (10 to 100 N) to measure the maximum elongation. Subsequently, loading to failure was performed, and stiffness, yield load, and maximum load were measured. A 1-way analysis-of-variance test was performed with significance set at P < .05.

RESULTS

Button fixation resulted in lower elongation (1.25 ± 0.27 mm) than anterograde screw fixation (2.17 ± 0.74 mm, P = .0058) and the cerclage technique (2.02 ± 0.24 mm, P = .0290). The cerclage technique showed a lower yield load (493.55 ± 88.86 N) than anterograde screw fixation (720.39 ± 139.0 N, P = .0012) and retrograde screw fixation (668.58 ± 147.59 N, P = .0145); it also had lower stiffness and maximum load values (51.2 ± 6.11 N/mm and 631.22 ± 101.22 N, respectively) than the anterograde screw fixation technique (65.6 ± 12.74 N/mm, P = .041, for stiffness and 817.5 ± 145.9 N, P = .008, for maximum load). None of the other results were significantly different (P > .05).

CONCLUSIONS

The cortical suspension button and retrograde screw fixation techniques showed comparable structural properties to the direct screw fixation technique. The raw structural properties of suture cerclage still seem eligible enough to consider using this technique for fixation.

CLINICAL RELEVANCE

In this in vitro model, all techniques appear to constitute a biomechanically stable alternative to traditional anterograde screw fixation. In contrast to anterograde screw fixation, these techniques can be performed minimally invasively.

Basic biomechanic principles of knee instability

Motion at the knee joint is a complex mechanical phenomenon. Stability is provided by a combination of static and dynamic structures that work in concert to prevent excessive movement or instability that is inherent in various knee injuries. The anterior cruciate ligament (ACL) is a main stabilizer of the knee, providing both translational and rotatory constraint. Despite the high volume of research directed at native ACL function, pathogenesis and surgical reconstruction of this structure, a gold standard for objective quantification of injury and subsequent repair, has not been demonstrated. Furthermore, recent studies have suggested that novel anatomic structures may play a significant role in knee stability. The use of biomechanical principles and testing techniques provides essential objective/quantitative information on the function of bone, ligaments, joint capsule, and other contributing soft tissues in response to various loading conditions. This review discusses the principles of biomechanics in relation to knee stability, with a focus on the objective quantification of knee stability, the individual contributions of specific knee structures to stability, and the most recent technological advances in the biomechanical evaluation of the knee joint.

In situ forces and length patterns of the fibular collateral ligament under controlled loading: an in vitro biomechanical study using a robotic system

PURPOSE

The aim of this study was to determine the in situ forces and length patterns of the fibular collateral ligament (FCL) and kinematics of the knee under various loading conditions.

METHODS

Six fresh-frozen cadaveric knees were used (mean age 46 ± 14.4 years; range 20-58). In situ forces and length patterns of FCL and kinematics of the knee were determined under the following loading conditions using a robotic/universal force-moment sensor testing system: no rotation, varus (10 Nm), external rotation (5 Nm), and internal rotation (5 Nm) at 0°, 15°, 30°, 60º, 90°, and 120° of flexion, respectively.

RESULTS

Under no rotation loading, the distances between the centres of the FCL attachments decreased as the knee flexed. Under varus loading, the force in FCL peaked at 15° of flexion and decreased with further knee flexion, while distances remained nearly constant and the varus rotation increased with knee flexion. Using external rotation, the force in the FCL also peaked at 15° flexion and decreased with further knee flexion, the distances decreased with flexion, and external rotation increased with knee flexion. Using internal rotation load, the force in the FCL was relatively small across all knee flexion angles, and the distances decreased with flexion; the amount of internal rotation was fairly constant.

CONCLUSIONS

FCL has a primary role in preventing varus and external rotation at 15° of flexion. The FCL does not perform isometrically following knee flexion during neutral rotation, and tibia rotation has significant effects on the kinematics of the FCL. Varus and external rotation laxity increased following knee flexion. By providing more realistic data about the function and length patterns of the FCL and the kinematics of the intact knee, improved reconstruction and rehabilitation protocols can be developed.

The effect of medial meniscal horn injury on knee stability

PURPOSE

This study investigated the effect of damage of the posterior and anterior horns of the medial meniscus on knee stability.

METHODS

Twenty fresh-frozen porcine knees were divided into two groups (anterior horn and posterior horn injury). Each group was tested in three states: intact medial meniscus, posterior or anterior horn of medial meniscus resection and total medial meniscectomy. A robotic testing system was used to test anterior tibial translation (ATT) at 30° (full extension), 60° and 90° of knee flexion with an external anterior tibial load of 89 N, internal rotation (IR) and external rotation (ER) at 30° and 60° of knee flexion under a 4 N m tibial rotation torque.

RESULTS

In response to an IR torque, there was a significant difference between the state of intact medial meniscus and anterior and posterior horn damage, except for anterior horn resection at 60° of knee flexion. In response to an ER torque, there were no significant differences between the state of intact meniscus and horn damage except for anterior horn resection at 30° of knee flexion. Meniscal damage had no significant effect on ATT.

CONCLUSION

The results indicated that the posterior horn was more important in controlling the IR stability than the anterior horn with knee flexion, and the anterior horn was more important in controlling the ER stability than the posterior horn at full knee extension in the anterior cruciate ligament-intact knee. These findings further the understanding of the mechanisms, the prevention of injuries and rehabilitation of meniscal horn injury in clinical practice.

Anterior cruciate ligament biomechanics during robotic and mechanical simulations of physiologic and clinical motion tasks: a systematic review and meta-analysis

Investigators use in vitro joint simulations to invasively study the biomechanical behaviors of the anterior cruciate ligament. The aims of these simulations are to replicate physiologic conditions, but multiple mechanisms can be used to drive in vitro motions, which may influence biomechanical outcomes. The objective of this review was to examine, summarize, and compare biomechanical evidence related to anterior cruciate ligament function from in vitro simulations of knee motion. A systematic review was conducted (2004 to 2013) in Scopus, PubMed/Medline, and SPORTDiscus to identify peer-reviewed studies that reported kinematic and kinetic outcomes from in vitro simulations of physiologic or clinical tasks at the knee. Inclusion criteria for relevant studies were articles published in English that reported on whole-ligament anterior cruciate ligament mechanics during the in vitro simulation of physiologic or clinical motions on cadaveric knees that were unaltered outside of the anterior-cruciate-ligament-intact, -deficient, and -reconstructed conditions. A meta-analysis was performed to synthesize biomechanical differences between the anterior-cruciate-ligament-intact and reconstructed conditions. 77 studies met our inclusion/exclusion criteria and were reviewed. Combined joint rotations have the greatest impact on anterior cruciate ligament loads, but the magnitude by which individual kinematic degrees of freedom contribute to ligament loading during in vitro simulations is technique-dependent. Biomechanical data collected in prospective, longitudinal studies corresponds better with robotic-manipulator simulations than mechanical-impact simulations. Robotic simulation indicated that the ability to restore intact anterior cruciate ligament mechanics with anterior cruciate ligament reconstructions was dependent on loading condition and degree of freedom examined.

Effect of suturing the femoral portion of a four-strand graft during an ACL reconstruction

PURPOSE

A suture passed along the part of the graft that will be inserted into the femoral tunnel is widely used by surgeons, because it could prevent the graft sliding on the femoral fixation device during pulling from the tibial side. The aim of this study was to evaluate the biomechanical effects of suturing the intratunnel femoral part of the graft during an anterior cruciate ligament (ACL) reconstruction.

METHODS

Bovine digital extensor tendons and tibias were harvested from 20 fresh-frozen mature bovine knees ranging in age from 18 to 24 months. Quadruple-strand bovine tendons were passed through the tibial tunnel and secured distally with a bioabsorbable interference screw. In one half of all grafts (N = 10), the looped-over part of the graft was sutured in a whipstitch technique over a distance of 30 mm (Group 1). In one half of all grafts (N = 10), the looped-over part was left free from any suture (Group 2). The grafts were preconditioned at 50 N for 10 min, followed by cyclic loading at 1 Hz between 50 N and 250 N for 1,000 cycles. Load-to-failure test was then carried out at a rate of 1 mm/s.

RESULTS

There was no statistically significant difference between mean stiffness at pullout and yield load between the two groups. In all specimens on Group 1, failure occurred following to partial breaking and then slipping of the tendons between the screw and the tunnel. Concerning Group 2, in six cases failure occurred as described for Group 1 specimens. In the remaining four cases, failure occurred entirely through the ligament mid-substance.

CONCLUSIONS

Suturing in a whipstitch fashion the femoral portion of the graft doesn't affect the mechanical proprieties of the ACL graft. When suspension fixation device is used, suturing the looped-over part of the graft could be helpful in order to provide equal tension in all of the strands of the graft at time of tibial fixation.

Functional outcomes of Y-graft double-bundle and single-bundle anterior cruciate ligament reconstruction of the knee

PURPOSE

The purpose of this study was to compare the functional outcome, ligament laxity, and tibial tunnel enlargement between 3-tunnel double-bundle (DB) anterior cruciate ligament (ACL) and single-bundle (SB) ACL reconstruction.

METHODS

This retrospective study identified primary arthroscopic ACL reconstruction from July 2006 to July 2008. The cohort consisted of 50 knees in 49 patients, comprising 26 knees with SB ACL reconstruction and 24 with DB ACL reconstruction. Semitendinosus autograft was used in SB ACL reconstruction, and semitendinosus and gracilis grafts were used in DB ACL reconstruction. Both groups received the same rehabilitation protocol postoperatively. The evaluations included functional assessment, ligament laxity, and radiographs of the knee. Functional assessments included a pain score, the Lysholm functional score, the Tegner activity score, and the grade on the International Knee Documentation Committee knee examination form. Ligament laxity was measured by the anterior drawer test, Lachman test, pivot-shift test, and KT-1000 arthrometer (MEDmetric, San Diego, CA) testing. It was graded as 0 for no laxity, 0 to 5 mm for mild laxity, 5 to 10 mm for moderate laxity, and 10 to 15 mm for severe laxity. Radiographs of the knee were used for the evaluation of bony appearance, alignment of the knee, joint space narrowing, and measurement of the tibial tunnel.

RESULTS

Significant improvements in knee function and ligament laxity were noted after surgery in both groups. However, no statistical differences in functional scores and ligament laxity were noted between the 2 groups (P = .275 and P = .413, respectively). A mild increase in laxity was noted in 3 cases (14%) in the DB ACL reconstruction group and 3 cases (13%) in the SB ACL reconstruction group. A moderate increase in laxity was noted in 2 cases (9%) in the SB ACL reconstruction group and none in the DB ACL reconstruction group. Radiographic evaluations showed no statistical difference between the 2 groups (P = .114).

CONCLUSIONS

Both 3-tunnel Y-graft DB ACL reconstruction and SB ACL reconstruction significantly improved the function and stability of the knee after surgery.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

The effect of notchplasty in anterior cruciate ligament reconstruction: a biomechanical study in the porcine knee

INTRODUCTION

Notchplasty is frequently performed by many orthopaedic surgeons during anterior cruciate ligament (ACL) reconstruction. The effect of notchplasty on tunnel placement and knee biomechanics with ACL reconstruction is not known.

METHODS

Twelve (n = 12) porcine knees were tested using a robotic testing system. Four knee states were compared: (1) intact ACL, (2) ACL-deficient, (3) anatomic single bundle (SB) ACL reconstruction and (4) anatomic SB ACL reconstruction with a 5-mm notchplasty. The graft was fixed at 60° of flexion (full extension of porcine knee is 30°) with an 80-N tension. The knees were subjected to two loading conditions: an 89-N anterior tibial load (ATT) and 4 Nm internal (IR) and external tibial (ER) rotational torques. The kinematics and in situ force obtained from the different knee conditions were compared.

RESULTS

There were no significant differences between pre- and post-notchplasty in the ER at 30° and 60° of knee flexion (n.s.). However, a significant difference was found between pre- and post-notchplasty in ATT at 30° and 60° of flexion (p < 0.05). The in situ force in the anatomic SB reconstruction with notchplasty was significant lower than the intact and anatomic reconstructed ACL pre-notchplasty at 30°, 60° and 90° of knee flexion (p < 0.05). In response to the IR tibial torque, there were significant differences between pre- and post-notchplasty in IR at 60° (p < 0.05) of knee flexion.

CONCLUSION

Notchplasty had greater effect on anterior stability than rotational stability. This change in knee kinematics could be detrimental to a healing bone graft, ligamentization and could lead to failure of the reconstruction in early post-operative period.

Use of bovine carpal joints as a training model for cruciate ligament repair

BACKGROUND

Currently, there is a lack of cheap and effective training models to allow orthopaedic surgery trainees to learn the basics of anterior cruciate ligament reconstruction. The aim of this paper was to investigate the viability of using various animal joints as models for the training of anterior cruciate ligament reconstruction.

METHOD

Equine stifles, bovine stifles and carpal joints, sheep stifles and porcine stifles, were sourced from a local abattoir. Each joint was assessed for the following criteria: suitable tendons for harvesting, ease of arthroscopy access, adequacy of arthroscopy view and suitable joint surfaces. Tendon harvesting, preparation, joint arthroscopy and tendon tunnelling were performed on the most suitable joint.

RESULTS

Equine, bovine, sheep and porcine stifles were found to be unsuitable. The bovine carpal joint was similar to a human wrist joint with two rows of carpal bones and fused metacarpal bones, but with deeper flexion - similar to a human knee joint. The distal joint space was found to provide a greater range of flexion and space than the narrower proximal joint space. The joint capsule provided sufficient integrity during saline irrigation to allow adequate visualization of joint structures. Tendons surrounding the joint were found to be of similar diameter to human hamstring tendons and easily accessible. Tendon tunnelling was successfully performed in a manner similar to human anterior cruciate ligament repair.

CONCLUSION

The use of bovine carpal joints is a cost-effective, safe and easily reproducible model for education on basic anterior cruciate ligament repair skills and technique prior to patient contact.

Specific compartmental analysis of cartilage status in double-bundle ACL reconstruction patients: a comparative study using pre- and postoperative MR images

PURPOSE

The purpose of this study was to evaluate the changes in the site-specific cartilage status after a double-bundle ACL reconstruction using preoperative and follow-up MR images.

METHODS

Thirty-six knees that underwent a double-bundle ACL reconstruction from 2001 to 2009 with the available preoperative and follow-up magnetic resonance imaging were included. Patients with a meniscal injury were compared with those without a meniscal injury. The cartilage morphology was classified using a 6-grade scale [from 0 = normal thickness and signal, to 6 = diffuse full-thickness loss (>75 % of the region)]. The changes in cartilage status were evaluated at 14 sites.

RESULTS

Cartilage changes were observed in all sites and were classified according to the site and degree of change. The majority of changes were grade 0 and 1, which accounted for 68 and 16.8 % of changes, respectively. The patella medial facet and anterolateral and centromedial femoral regions showed significantly more cartilage loss than the posteromedial, centrolateral, anterolateral, and anteromedial tibial regions. No significance was observed between the knees with or without combined injuries (n.s.). On the other hand, knees with or without combined injuries showed a different pattern of cartilage change, as demonstrated by different levels of grade change at sites.

CONCLUSIONS

The change in cartilage status was minimal after a double-bundle ACL reconstruction. The patella medial facet, lateral femur anterior region, and medial femur central region showed significantly more cartilage loss than the medial tibia posterior, lateral tibia central, lateral tibia anterior, and medial tibia anterior regions. The presence of a combined injury did not affect the cartilage status changes, even though it was underpowered and too short term to assess the influence of the meniscal injury.

LEVEL OF EVIDENCE

Case series, Level IV.

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

PURPOSE

Conventional transtibial technique fails to restore the rotational knee stability in spite of successful anterior laxity, while anatomic anterior cruciate ligament reconstruction using the anteromedial portal technique has been developed expecting better rotational kinematics because of closer reproduction of the native anterior cruciate ligament anatomy. However, the rotational instability after those two procedures has not been fully examined especially in terms of dynamic component of the rotational stability. The purpose was to assess the effect of anatomic versus non-anatomic tunnel placement on rotational knee stability after anterior cruciate ligament reconstruction using triaxial accelerometry.

METHODS

Sixteen porcine knees underwent a manual pivot-shift test at four different conditions: (1) anterior cruciate ligament intact, (2) anterior cruciate ligament deficient, (3) non-anatomic transtibial reconstruction, and (4) anatomic anteromedial portal reconstruction. The three-dimensional acceleration of knee motion during the pivot-shift test was recorded using a triaxial accelerometer.

RESULTS

Both anterior cruciate ligament reconstructions decreased significantly the acceleration of the pivot-shift test from the increased level in the anterior cruciate ligament-deficient condition. However, the transtibial technique fails to reach the intact level of acceleration, while the anteromedial portal technique reduced the acceleration to even less than the intact level.

CONCLUSION

The transtibial anterior cruciate ligament reconstruction could not restore the dynamic rotational stability of the intact knee, whereas the anteromedial portal technique restored the dynamic rotational stability closer to the intact level.

LEVEL OF EVIDENCE

III.

Interference screws should be shorter than the hamstring tendon graft in the bone tunnel for best fixation

PURPOSE

Interference screw fixation of hamstring tendon grafts in bone has to overcome the challenges that tendons have a slippery surface and viscoelastically adapt under pressure. As the typical failure mode of the graft is to slip past the interference screw, it was hypothesized that the position and configuration of the graft end may be of influence on the fixation strength.

METHODS

Different configurations of the graft ending and its effect to primary fixation with interference screws after viscoelastic adaptation were tested in six groups: I: graft and the screw inserted at the same depth, II/III: the graft overlaps the tip of the screw (interference screw of 28 and 19 mm in length, respectively), IV: strengthening of the graft ending with additional suture knots, V: Endopearl, respectively, and VI: effect of partial retraction of the screw after excessive insertion. In vitro tests were performed with fresh calf tendon grafts and interference screws in bone tunnels (fresh porcine distal femur) all of 8 mm in diameter.

RESULTS

The relative position of the graft ending to the tip of the interference screw thereby was recognized as a significant factor on pullout forces. Further strengthening at the graft endings with additional suture knots or an Endopearl device could improve primary hold as well.

CONCLUSIONS

Better fixation strength is achieved if the tip of interference screw does not extend past the end of a tendon graft. Enforcement of the tendon end with sutures or an implant can further improve fixation.

Graft impingement in anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) graft impingement is one of the most troubling complications in ACL reconstruction. In the previous strategy of isometric "non-anatomical" ACL reconstruction, posterior tibial tunnel placement and notchplasty were recommended to avoid graft impingement. Recently, the strategy of ACL reconstruction is shifting towards "anatomical" reconstruction. In anatomical ACL reconstruction, the potential risk of graft impingement is higher than in non-anatomical reconstruction because the tibial tunnel is placed at a more anterior portion on the tibia. However, there have been few studies reporting on graft impingement in anatomical ACL reconstruction. This study will provide a review of graft impingement status in both non-anatomical and the more recent anatomical ACL reconstruction techniques. In conclusion, with the accurate creation of bone tunnels within ACL native footprint, the graft impingement might not happen in anatomical ACL reconstruction. For the clinical relevance, to prevent graft impingement, surgeons should pay attention of creating correct anatomical tunnels when they perform ACL reconstruction. Level of evidence IV.

Is femoral tunnel length correlated with the intercondylar notch and femoral condyle geometry after double-bundle anterior cruciate ligament reconstruction using the transportal technique? An in vivo computed tomography analysis

PURPOSE

To analyze femoral tunnel geometry using computed tomography (CT) imaging and evaluate the anatomic factors affecting femoral tunnel length after anterior cruciate ligament (ACL) reconstruction by the transportal technique.

METHODS

Twenty-nine patients underwent an anatomic double-bundle ACL reconstruction with a femoral tunnel drill by the transportal technique. CT imaging with OsiriX software (version 3.8; Pixmeo, Geneva, Switzerland) was used to measure femoral tunnel length (anteromedial [AM], posterolateral [PL], and central), femoral tunnel divergent angle, and femoral condyle size and intercondylar notch size parameters. Correlations between femoral tunnel length and femoral condyle size and intercondylar notch size parameters were analyzed.

RESULTS

The mean AM, PL, and central femoral tunnel lengths were 33.3 ± 3.9 mm, 33.6 ± 3.6 mm, and 34.3 ± 3.2 mm, respectively. A femoral tunnel length of less than 30 mm developed in 7 cases (24.1%) in the AM aspect and 4 cases (13.8%) in the PL aspect. The mean femoral tunnel divergent angle was 14.4° ± 4.1°. A positive correlation was found between AM, not PL or central, femoral tunnel length and medial femoral condyle anteroposterior (AP) distance (P = .01, r = 0.46), lateral femoral condyle AP distance (P = .01, r = 0.43), medial-to-lateral epicondylar distance (P = .03, r = 0.39), middle notch width (P = .009, r = 0.47), notch height (P = .001, r = 0.57), and notch area (P < .001, r = 0.58).

CONCLUSIONS

After double-bundle ACL reconstruction with the transportal technique through the accessory anteromedial portal, the AM and PL femoral tunnels showed mean tunnel length greater than 30 mm and a divergent angle. However, a femoral tunnel length of less than 30 mm developed in some cases. AM femoral tunnel length was correlated with femoral condyle size (medial femoral condyle AP distance, lateral femoral condyle AP distance, and medial-to-lateral epicondylar distance) and intercondylar notch size (notch width, notch height, and notch area).

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

PCL to graft impingement pressure after anatomical or non-anatomical single-bundle ACL reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) graft impingement against the posterior cruciate ligament (PCL) has been postulated, but not thoroughly investigated.

PURPOSE

To evaluate PCL impingement pressure and biomechanical stability with different tibial and femoral tunnel positions in ACL reconstruction.

METHODS

In 15 porcine knees, the impingement pressure between ACL and PCL was measured using pressure sensitive film before and after ACL single-bundle reconstruction. ACL reconstructions were performed in each knee with three different tibial and femoral tunnel position combinations: (1) tibial antero-medial (AM) tunnel to femoral AM tunnel (AM-AM), (2) tibial postero-lateral (PL) tunnel to femoral High-AM tunnel (PL-High-AM) and (3) tibial AM tunnel to femoral High-AM tunnel (AM-High-AM). Anterior tibial translation (ATT) was evaluated after each ACL reconstruction using robotic/universal force-moment sensor testing system.

RESULTS

There was no significant difference of the impingement pressure between AM and AM, PL-High-AM reconstructed groups and intact ACL. Only AM-High-AM ACL reconstruction group showed significantly higher impingement pressure compared with intact ACL. With regard to ATT, AM-AM group had significantly higher stiffness than PL-High-AM group.

CONCLUSION

Anatomical ACL reconstruction does not cause PCL impingement and it has biomechanical advantage in ATT when compared with non-anatomical ACL reconstructions in porcine knee. For the clinical relevance, in the anatomical ACL reconstruction, no ACL-PCL impingement is found.

Evaluation of a simulated pivot shift test: a biomechanical study

PURPOSE

Double-bundle anterior cruciate reconstructions have led to an increased interest in quantifying anterolateral rotatory stability. The application of combined internal rotation and valgus torques to the knee can more nearly recreate the anterolateral subluxation that occurs in the pivot shift test in vitro compared to coupled internal rotation torque and anterior tibial loads.

METHODS

Twelve non-paired cadaveric knees were biomechanically tested with the ACL intact and sectioned. For each test state, six-degree-of-freedom positional data were collected for two simulated pivot shift loads consisting of a 5-Nm internal rotation torque coupled with either a 10-Nm valgus torque or an 88 N anterior tibial load at 0°, 20°, 30°, 60°, and 90° of knee flexion.

RESULTS

The coupled internal rotation and valgus torques produced a significant increase in anterolateral subluxation between the ACL intact and sectioned states at all tested angles except 90º (5.9 ± 0.4 mm at 0°, 4.3 ± 0.6 mm at 20°, 3.5 ± 0.6 mm at 30°, 2.1 ± 0.6 mm at 60°). The coupled internal rotation and an anterior tibial load produced significant increases between the ACL intact and sectioned states at all tested angles except 30º (5.4 ± 0.5 mm at 0°, 3.7 ± 0.5 mm at 20°, 2.1 ± 0.8 mm at 60°, 1.4 ± 0.3 mm at 90°).

CONCLUSIONS

We found that the coupled internal rotation and valgus torques best recreated the anterolateral subluxation that occurs in the pivot shift in vitro. This study describes an anterolateral subluxation test for ACL integrity in the laboratory setting.

Effects of age and platelet-rich plasma on ACL cell viability and collagen gene expression

Platelet-rich plasma (PRP) has shown in vivo potential to stimulate anterior cruciate ligament (ACL) healing at early time points in large animal models. However, in animal models, the healing potential of the ACL is dependent on animal age. In this study, we hypothesized that there are age-dependent differences in ACL cell metabolism, collagen gene expression, and the ability of the cells to respond to growth factors in PRP. To test this hypothesis, ACL cells were obtained from skeletally immature, adolescent and adult pigs, and cultured in a collagen type I hydrogel with or without PRP for 14 days. When cultured in collagen-only hydrogel, ACL cells from adult pigs had a 19% lower apoptotic rate as compared to immature pigs (p = 0.001) and a 25% higher cellular metabolic activity as compared to adolescent pigs (p = 0.006). The addition of PRP to the collagen hydrogel resulted in a significantly increased cellular metabolic activity, reduced apoptotic rate, and stimulation of collagen production in the cells from the immature and adolescent animals (p < 0.05 for all comparisons) but had less effect on adult cells. These findings suggest that skeletal maturity may influence ACL cells' metabolic activity, apoptosis, collagen production, and response to PRP.