Influence of the anteromedial and posterolateral bundles of the anterior cruciate ligament on external and internal tibiofemoral rotation

Role of the Anterior Cruciate Ligament, Anterolateral Complex, and Lateral Meniscus Posterior Root in Anterolateral Rotatory Knee Instability: A Biomechanical Study

BACKGROUND

Injuries to the anterior cruciate ligament (ACL), Kaplan fibers (KFs), anterolateral capsule/ligament (C/ALL), and lateral meniscus posterior root (LMPR) have been separately linked to anterolateral instability.

PURPOSE

To investigate the contributions of the ACL, KFs, C/ALL, and LMPR to knee stability and to measure instabilities resulting from their injury.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen human knees were tested robotically to determine restraints of knee laxity at 0° to 90° of flexion. An 88-N anterior-posterior force (anterior and posterior tibial translation), 5-N·m internal-external rotation, and 8-N·m valgus-varus torque were imposed and intact kinematics recorded. The kinematics were replayed after sequentially cutting the structures (order varied) to calculate their contributions to stability. Another 10 knees were tested in a kinematics rig with optical tracking to measure instabilities after sequentially cutting the structures across 0° to 100° of flexion. One- and 2-way repeated-measures analyses of variance with Bonferroni correction were used to find significance (P < .05) for the robotic and kinematics tests.

RESULTS

The ACL was the primary restraint for anterior tibial translation; other structures were insignificant (<10% contribution). The KFs and C/ALL resisted internal rotation, reaching 44% ± 23% (mean ± SD; P < .01) and 14% ± 13% (P < .05) at 90°. The LMPR resisted valgus but not internal rotation. Anterior tibial translation increased after ACL transection (P < .001) and after cutting the lateral structures from 70° to 100° (P < .05). Pivot-shift loading increased anterolateral rotational instability after ACL transection from 0° to 40° (P < .05) and further after cutting the lateral structures from 0° to 100° (P < .01).

CONCLUSION

The anterolateral complex acts as a functional unit to provide rotatory stability. The ACL is the primary stabilizer for anterior tibial translation. The KFs are the most important internal rotation restraint >30° of flexion. Combined KFs + C/ALL injury substantially increased anterolateral rotational instability while isolated injury of either did not. LMPR deficiency did not cause significant instability with the ACL intact.

CLINICAL RELEVANCE

This study is a comprehensive biomechanical sectioning investigation of the knee stability contributions of the ACL, anterolateral complex, and LMPR and the instability after their transection. The ACL is significant in controlling internal rotation only in extension. In flexion, the KFs are dominant, synergistic with the C/ALL. LMPR tear has an insignificant effect with the ACL intact.

In vivo knee rotational stability 2 years after the ACL reconstruction using a quadriceps tendon graft with bone block and bone-patellar tendon-bone graft

INTRODUCTION

The aim of this prospective randomised study was to evaluate clinical results and rotational stability at least 2 years after single-bundle anatomic anterior cruciate ligament reconstruction using a quadriceps tendon graft with bone block (BT) and bone-patellar tendon-bone graft (BTB).

MATERIALS AND METHODS

In both groups (BT and BTB), 40 patients selected prospectively at random were evaluated. The mean follow-up after the surgery was 28 months (range 24-33 months). A navigation system was used to measure rotational stability of the knee joint. Cincinnati, Lysholm, and IKDC scores and visual analog score (VAS) were used to evaluate clinical results and the non-parametric Wilcoxon test was used for the statistical analysis.

RESULTS

After the BT reconstruction, the mean internal rotation of the tibia (IR) was 9.5°. In the contralateral healthy knee joint, IR was 8.6° at average. After the BTB reconstruction, the mean IR was 9.9°. In the contralateral healthy knee joint, IR was 8.7° at average. We did not find any statistically significant difference in IR stability between BT and BTB reconstruction. In terms of clinical results, regarding the VAS, patients perceive significantly more pain after the BTB reconstruction (p < 0.05). Kneeling was reported more difficult and painful after BTB reconstruction.

CONCLUSIONS

The BT reconstruction of the ACL provides similar clinical results, less pain, better flexion and the same rotational stability of the knee in comparison with the BTB reconstruction.

An Anterior Cruciate Ligament In Vitro Rupture Model Based on Clinical Imaging

BACKGROUND

Biomechanical studies on anterior cruciate ligament (ACL) injuries and reconstructions are based on ACL transection instead of realistic injury trauma.

PURPOSE

To replicate an ACL injury in vitro and compare the laxity that occurs with that after an isolated ACL transection injury before and after ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine paired knees were ACL injured or ACL transected. For ACL injury, knees were mounted in a rig that imposed tibial anterior translation at 1000 mm/min to rupture the ACL at 22.5° of flexion, 5° of internal rotation, and 710 N of joint compressive force, replicating data published on clinical bone bruise locations. In contralateral knees, the ACL was transected arthroscopically at midsubstance. Both groups had ACL reconstruction with bone-patellar tendon-bone graft. Native, ACL-deficient, and reconstructed knee laxities were measured in a kinematics rig from 0° to 100° of flexion with optical tracking: anterior tibial translation (ATT), internal rotation (IR), anterolateral (ATT + IR), and pivot shift (IR + valgus).

RESULTS

The ACL ruptured at 26 ± 5 mm of ATT and 1550 ± 620 N of force (mean ± SD) with an audible spring-back tibiofemoral impact with 5^o of valgus. ACL injury and transection increased ATT (P < .001). ACL injury caused greater ATT than ACL transection by 1.4 mm (range, 0.4-2.2 mm; P = .033). IR increased significantly in ACL-injured knees between 0° and 30° of flexion and in ACL transection knees from 0° to 20° of flexion. ATT during the ATT + IR maneuver was increased by ACL injury between 0° and 80° and after ACL transection between 0° and 60°. Residual laxity persisted after ACL reconstruction from 0° to 40° after ACL injury and from 0° to 20° in the ACL transection knees. ACL deficiency increased ATT and IR in the pivot-shift test (P < .001). The ATT in the pivot-shift increased significantly at 0° to 20° after ACL transection and 0° to 50° after ACL injury, and this persisted across 0° to 20° and 0° to 40° after ACL reconstruction.

CONCLUSION

This study developed an ACL injury model in vitro that replicated clinical ACL injury as evidenced by bone bruise patterns. ACL injury caused larger increases of laxity than ACL transection, likely because of damage to adjacent tissues; these differences often persisted after ACL reconstruction.

CLINICAL RELEVANCE

This in vitro model created more realistic ACL injuries than surgical transection, facilitating future evaluation of ACL reconstruction techniques.

Risk of overconstraining femorotibial rotation after anatomical ACL reconstruction using bone patella tendon bone autograft

INTRODUCTION

Numerous studies have focused on the anteroposterior stability after anterior cruciate ligament (ACL) reconstruction, with less emphasis on rotational stability. It has been hypothesized that bone patella tendon bone (BTB) autograft for ACL reconstruction restores knee rotation closely to normal due to its comparable fiber orientation to the native ACL.

MATERIALS AND METHODS

Twenty patients with unilateral ACL rupture and an uninjured contralateral knee were included in this study. The ACL was reconstructed using the medial third of the patellar tendon. Tunnel placement was controlled by fluoroscopy. Implant-free press-fit graft fixation was used on both femoral and tibial side. Bone blocks were carefully placed to restore fiber orientation of both the anteromedial and posterolateral bundle, similar to the native ACL. Rotatory laxity of both knees was measured at 0° and 25° of flexion pre- and post-surgery, using an active opto-electronical motion-analysis system (LUKOTRONIC AS 100^®). All measurements were performed under general anesthesia during surgery.

RESULTS

Knee rotation was reduced significantly in both 0°and 25° of flexion following ACL reconstruction (p < 0.001). The side to side difference (SSD) of the rotatory laxity in extension was greater in the ACL-deficient knee (14.9° ± 8.9°), but decreased significantly after ACL reconstruction (- 5.9° ± 7.7°, minus value means less than in the uninjured knee). There was a similar finding at 25° of knee flexion where greater rotation of the ACL-deficient knee (5.7° ± 10.3°) prior to surgery changed to lower degree of rotation after surgery (- 11.3° ± 8.4°) in comparison to the uninjured knee.

CONCLUSIONS

ACL reconstruction with a BTB graft in anatomical position using press-fit implant-free fixation is able to restore rotatory knee stability close to the intact contralateral knee. Despite the fact that the BTB graft offers fiber orientation close to the natural ACL, the surgeon should be aware of the potential risk of over-constraining the knee in terms of rotation.

LEVEL OF EVIDENCE

II.

Reliability of a Robotic Knee Testing Tool to Assess Rotational Stability of the Knee Joint in Healthy Female and Male Volunteers

BACKGROUND

Several clinical tests exist to assess knee laxity. Although these assessments are the predominant tools of diagnosis, they are subjective and rely on the experience of the clinician. The robotic knee testing (RKT) device has been developed to quantitatively and objectively measure rotational knee laxity. The purpose of this study was primarily to determine the intra-tester reliability of rotational knee laxity and slack, the amount of rotation occurring between the two turning points of the load deformation curve, measured by the RKT device and investigate the differences between female and male measurements.

METHODS

Ninety-one healthy and moderately active volunteers took part in the study, of which twenty-five participated in the reliability study. Tibial rotation was performed using a servomotor to a torque of 6 N m, while measurements of motion in all 6° of freedom were collected. Reliability measurements were collected over 5 days at similar times of the day. Intra-class correlation coefficient (ICC) values and standard error of measurement (SEM) were determined across the load deformation curves. Linear mixed effects modelling was used to further assess the reliability of the measurement of external and internal tibial rotation using features of the curve (internal/external rotational laxity and slack). Measurements of internal/external rotational laxity and slack were compared between the sexes using the Student t test.

RESULTS

Pointwise axial rotation measurements of the tibia had good reliability [ICC (2,1) 0.83-0.89], while reliability of the secondary motions ranged between poor and good [ICC (2,1) 0.31-0.89]. All SEMs were less than 0.3°. Most of the variation of the curve features were accounted for by inter-subject differences (56.2-77.8%) and showed moderate to good reliability. Comparison of the right legs of the sexes revealed that females had significantly larger amounts of internal rotation laxity (females 6.1 ± 1.3° vs males 5.6 ± 0.9°, p = 0.037), external rotation laxity (females 6.0 ± 1.6° vs males 5.0 ± 1.2°, p = 0.002) and slack (females 19.2 ± 4.2° vs males 16.6 ± 2.9°, p = 0.003). Similar results were seen within the left legs.

CONCLUSIONS

Overall, the RKT is a reliable and precise tool to assess the rotational laxity of the knee joint in healthy individuals. Finally, greater amounts of laxity and slack were also reported for females.

Evaluation of the intraoperative kinematics during double-bundle anterior cruciate ligament reconstruction using a navigation system

Background/objective

There is controversy regarding the biomechanical function of the anteromedial (AM) and posterolateral (PL) bundles in isolated tibiofemoral rotation during double-bundle anterior cruciate ligament (ACL) reconstruction. This study aimed to evaluate the biomechanical function of the AM and PL bundles of the ACL using a computer navigation system.

Methods

This study involved 15 patients who underwent double-bundle ACL reconstruction. Anteroposterior and isolated rotational knee laxity were measured with a navigation system. The measurements were performed four times, namely, before fixation, after temporary PL bundle fixation, after AM bundle fixation, and after double-bundle reconstruction. With knee flexion ranging from 20° to 60°, we continuously measured the anterior tibial displacement under an anterior drawer stress (100 N using a spring balance). The total range of tibial rotation was also measured under an external and internal rotational torque of 3 Nm.

Results

Fixation of either the AM or the PL bundle significantly reduced the anteroposterior displacement at all knee flexion angles. Although the anteroposterior displacement after AM bundle fixation was relatively similar throughout the range of motion (2.4–3.2 mm), the anteroposterior displacement after PL bundle fixation increased continuously with knee flexion (2.2–4.6 mm). With respect to the total range of tibial rotation under external and internal rotational torque, there was no significant difference between AM and PL bundle fixation throughout the range of motion. The total range of tibial rotation was significantly reduced only on double-bundle reconstruction at 20° and 25° knee flexion compared to the pre-reconstruction range (P = 0.015 and 0.036, respectively).

Conclusion

The AM and PL bundles function differently for controlling anterior knee laxity throughout the range of motion. The function of the AM and PL bundles was similar for controlling isolated tibiofemoral rotation. Isolated tibiofemoral rotation was significantly controlled only on double-bundle reconstruction at knee flexion angles of 20° and 25°.

The Contribution of Partial Meniscectomy to Preoperative Laxity and Laxity After Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction: In Vivo Kinematics With Navigation

BACKGROUND

Limited in vivo kinematic information exists on the effect of clinical-based partial medial and lateral meniscectomy in the context of anterior cruciate ligament (ACL) reconstruction.

HYPOTHESIS

In patients with ACL deficiency, partial medial meniscus removal increases the anteroposterior (AP) laxity with compared with those with intact menisci, while partial lateral meniscus removal increases dynamic laxity. In addition, greater postoperative laxity would be identified in patients with partial medial meniscectomy.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 164 patients with ACL tears were included in the present study and divided into 4 groups according to the meniscus treatment they underwent: patients with partial lateral meniscectomy (LM group), patients with partial medial meniscectomy (MM group), patients with partial medial and lateral meniscectomy (MLM group), and patients with intact menisci who did not undergo any meniscus treatment (IM group). A further division in 2 new homogeneous groups was made based on the surgical technique: 46 had an isolated single-bundle anatomic ACL reconstruction (ACL group), while 13 underwent a combined single-bundle anatomic ACL reconstruction and partial medial meniscectomy (MM-ACL group). Standard clinical laxities (AP translation at 30° of knee flexion, AP translation at 90° of knee flexion) and pivot-shift (PS) tests were quantified before and after surgery by means of a surgical navigation system dedicated to kinematic assessment. The PS test was quantified through 3 different parameters: the anterior displacement of the lateral tibial compartment (lateral AP); the posterior acceleration of the lateral AP during tibial reduction (posterior acceleration); and finally, the area included by the lateral AP translation with respect to the flexion/extension angle (area).

RESULTS

In the ACL-deficient status, the MM group showed a significantly greater tibial translation compared with the IM group (P < .0001 for AP displacement at 30° [AP30] and 90° [AP90] of flexion) and the LM group (P = .002 for AP30 and P < .0001 for AP90). In the PS test, the area of LM group was significantly larger (57%; P = .0175) than the one of the IM group. After ACL reconstruction, AP translation at 30° was restored, while the AP90 remained significantly greater at 1.3 mm (P = .0262) in the MM-ACL group compared with those with intact menisci.

CONCLUSION

Before ACL reconstruction, partial medial meniscectomy increased AP laxity at 30° and 90° and lateral meniscectomy increased dynamic PS laxity with respect to intact menisci. Anatomic single-bundle ACL reconstruction decreased laxities, but a residual anterior translation of 1.3 mm at 90° remained in patients with partial medial meniscectomy, with respect to those with intact menisci.

The Role of Fibers Within the Tibial Attachment of the Anterior Cruciate Ligament in Restraining Tibial Displacement

PURPOSE

To evaluate the load-bearing functions of the fibers of the anterior cruciate ligament (ACL) tibial attachment in restraining tibial anterior translation, internal rotation, and combined anterior and internal rotation laxities in a simulated pivot-shift test.

METHODS

Twelve knees were tested using a robot. Laxities tested were: anterior tibial translation (ATT), internal rotation (IR), and coupled translations and rotations during a simulated pivot-shift. The kinematics of the intact knee was replayed after sequentially transecting 9 segments of the ACL attachment and fibers entering the lateral gutter, measuring their contributions to restraining laxity. The center of effort (COE) of the ACL force transmitted to the tibia was calculated. A blinded anatomic analysis identified the densest fiber area in the attachment of the ACL and thus its centroid (center of area). This centroid was compared with the biomechanical COE.

RESULTS

The anteromedial tibial fibers were the primary restraint of ATT (84% across 0° to 90° flexion) and IR (61%) during isolated and coupled displacements, except for the pivot-shift and ATT in extension. The lateral gutter resisted 28% of IR at 90° flexion. The anteromedial fibers showed significantly greater restraint of simulated pivot-shift rotations than the central and posterior fibers (P < .05). No significant differences (all <2 mm) were found between the anatomic centroid of the C-shaped attachment and the COE under most loadings.

CONCLUSIONS

The peripheral anteromedial fibers were the most important area of the ACL tibial attachment in the restraint of tibial anterior translation and internal rotation during isolated and coupled displacements. These mechanical results matched the C-shaped anteromedial attachment of the dense collagen fibers of the ACL.

CLINICAL RELEVANCE

The most important fibers in restraining tibial displacements attach to the C-shaped anteromedial area of the native ACL tibial attachment. This finding provides an objective rationale for ACL graft position to enable it to reproduce the physiological path of load transmission for tibial restraint.

Current use of navigation system in ACL surgery: a historical review

PURPOSE

The present review aims to analyse the available literature regarding the use of navigation systems in ACL reconstructive surgery underling the evolution during the years.

METHODS

A research of indexed scientific papers was performed on PubMed and Cochrane Library database. The research was performed in December 2015 with no publication year restriction. Only English-written papers and related to the terms ACL, NAVIGATION, CAOS and CAS were considered. Two reviewers independently selected only those manuscripts that presented at least the application of navigation system for ACL reconstructive surgery.

RESULTS

One hundred and forty-six of 394 articles were finally selected. In this analysis, it was possible to review the main uses of navigation system in ACL surgery including tunnel positioning for primary and revision surgery and kinematic assessment of knee laxity before and after different surgical procedures. In the early years, until 2006, navigation system was mainly used to improve tunnel positioning, but since the last decade, this tool has been principally used for kinematics evaluation. Increased accuracy of tunnel placement was observed using navigation surgery, especially, regarding femoral, 42 of 146 articles used navigation to guide tunnel positioning. During the following years, 82 of 146 articles have used navigation system to evaluate intraoperative knee kinematic. In particular, the importance of controlling rotatory laxity to achieve better surgical outcomes has been underlined.

CONLUSIONS

Several applications have been described and despite the contribution of navigation systems, its potential uses and theoretical advantages, there are still controversies about its clinical benefit. The present papers summarize the most relevant studies that have used navigation system in ACL reconstruction. In particular, the analysis identified four main applications of the navigation systems during ACL reconstructive surgery have been identified: (1) technical assistance for tunnel placement; (2) improvement in knowledge of the kinematic behaviour of ACL and other structures; (3) comparison of effectiveness of different surgical techniques in controlling laxities; (4) navigation system performance to improve the outcomes of ACL reconstruction and cost-effectiveness.

LEVEL OF EVIDENCE

IV.

The Restoration of Passive Rotational Tibio-Femoral Laxity after Anterior Cruciate Ligament Reconstruction

While the anterior cruciate ligament (ACL) is considered one of the most important ligaments for providing knee joint stability, its influence on rotational laxity is not fully understood and its role in resisting rotation at different flexion angles in vivo remains unknown. In this prospective study, we investigated the relationship between in vivo passive axial rotational laxity and knee flexion angle, as well as how they were altered with ACL injury and reconstruction. A rotometer device was developed to assess knee joint rotational laxity under controlled passive testing. An axial torque of ±2.5Nm was applied to the knee while synchronised fluoroscopic images of the tibia and femur allowed axial rotation of the bones to be accurately determined. Passive rotational laxity tests were completed in 9 patients with an untreated ACL injury and compared to measurements at 3 and 12 months after anatomical single bundle ACL reconstruction, as well as to the contralateral controls. Significant differences in rotational laxity were found between the injured and the healthy contralateral knees with internal rotation values of 8.7°±4.0° and 3.7°±1.4° (p = 0.003) at 30° of flexion and 9.3°±2.6° and 4.0°±2.0° (p = 0.001) at 90° respectively. After 3 months, the rotational laxity remained similar to the injured condition, and significantly different to the healthy knees. However, after 12 months, a considerable reduction of rotational laxity was observed towards the levels of the contralateral controls. The significantly greater laxity observed at both knee flexion angles after 3 months (but not at 12 months), suggests an initial lack of post-operative rotational stability, possibly due to reduced mechanical properties or fixation stability of the graft tissue. After 12 months, reduced levels of rotational laxity compared with the injured and 3 month conditions, both internally and externally, suggests progressive rotational stability of the reconstruction with time.

Objective measurements of static anterior and rotational knee laxity

Several devices allow to measure anterior and rotational static knee laxity. To date, the use of rotational laxity measurements in the daily clinical practice however remains to be improved. These measurements may be systematically integrated to the follow-up of knee injuries. Physiologic laxity measurements may particularly be of interest for the identification of risk factors in athletes. Furthermore, knee laxity measurements help to improve the diagnosis of knee soft tissue injuries and to follow up reconstructions. Further prospective follow-ups of knee laxity in the injured/reconstructed knees are however required to conclude on the best treatment strategy for knee soft tissue injuries.

The Comparative Role of the Anterior Cruciate Ligament and Anterolateral Structures in Controlling Passive Internal Rotation of the Knee: A Biomechanical Study

PURPOSE

To determine the respective functions of the anterior cruciate ligament (ACL) and the anterolateral structures (ALSs) in controlling the tibia's passive internal rotation (IR) with respect to the femur, under uniaxial rotation.

METHODS

To test the function of the ACL and the anterolateral ligament (ALL) in IR, we designed a sequential transection study of the ACL and the anterolateral structures (including the ALL) in 24 cadaveric knees divided in 2 groups. Two sequences were conducted successively: group 1 (12 knees) in which the ACL was sectioned first followed by the ALS, and group 2 (12 knees) with reversed transections. Each knee, in neutral rotation position and at flexion angle of 30°, was subjected to a 5 Nm torsion torque of IR. IR was measured using a rotatory laximeter, the Rotam with a gyroscope's measurement accuracy of 0.1°. Laxities were compared using paired t test within each group and using t test between groups. Fisher exact test was used to compare proportions.

RESULTS

In group 1, IR increased from 22.1° ± 10.6° to 25.7° ± 10.9° after ACL transection then to 28.1° ± 10.5° after we sectioned the ALS. In group 2, IR increased from 22.5° ± 8.9° to 25.2° ± 8.4° after sectioning the ALS, then to 29.1° ± 8.8° after we sectioned the ACL. Total postsectioning increase in IR was 6.4° ± 2° in group 1, and 6.55° ± 0.9° in group 2. The IR increase after each stage of transection and final IR were statistically significant (P < .001).

CONCLUSIONS

In a pure rotational cadaveric test model, the ACL and the ALS contribute to resistance to passive IR of the knee.

CLINICAL RELEVANCE

In some specific clinical cases, peripheral lesions may be considered, and injuries to these structures may need to be addressed to improve results controlling postoperative IR.

Practicability for robot-aided measurement of knee stability in-vivo

Background

For the analysis of different treatments concerning anterior cruciate ligament (ACL) rupture, objective methods for the quantification of knee stability are needed. Therefore, a new method for in-vivo stability measurement using a robotic testing system should be developed and evaluated.

Methods

A new experimental setting was developed using a KUKA robot and a custom-made chair for the positioning and fixation of the participants. The tibia was connected to the robot via a Vacoped shoe and magnetic buttons, providing adequate safety. Anterior tibial translation and internal tibial rotation were measured on both legs of 40 healthy human subjects at 30°, 60° and 90° of flexion, applying anterior forces of 80 N and internal torques of 4 Nm, respectively.

Results

While the mean differences between the right and left leg measured for anterior tibial translation were within an acceptable range (<1.5 mm), the absolute values were substantially large (38–40.5 mm). For mean internal tibial rotation, between 17.5 and 20° were measured at the different sides and flexion angles, with a maximal difference of 0.75°. High reproducibility of the measurements could be demonstrated for both, anterior tibial translation (ICC(3,1) = 0.97) and internal tibial rotation (ICC(3,1) = 0.94).

Conclusions

Excellent results were achieved for internal tibial rotation, almost reproducing current in-vitro studies, but too large anterior tibial translation was measured due to soft-tissue compression. Therefore, high potential for the analysis of ACL related treatments concerning rotational stability is seen for the proposed method, but further optimization is necessary to enhance this method for the reliable measurement of anterior tibial translation.

Combined anterior and rotational knee laxity measurements improve the diagnosis of anterior cruciate ligament injuries

PURPOSE

This study analysed whether associating the side-to-side difference in displacement and the slope of the load-displacement curve of anterior and rotational knee laxity measurements would improve the instrumental diagnosis of anterior cruciate ligament (ACL) ruptures and help to detect different types of ACL tears.

METHODS

Anterior and rotational knee laxity was measured in 128 patients with an arthroscopically confirmed ACL injury and 104 healthy controls. Side-to-side differences were determined for three variables in anterior laxity: anterior displacement at 200 N (ATD200), primary compliance from 30 to 50 N (PCA) and secondary compliance from 100 to 200 N (SCA). Furthermore, four variables in rotational laxity were considered: internal and external rotation at 5 N m (IR5/ER5) and compliance from 2 to 5 N m (C IR/C ER). Receiver operating characteristic curves allowed to determine thresholds, specificities and sensitivities to detect ACL lesions, based on single variables considered and combinations thereof.

RESULTS

Sensitivity and specificity reached, respectively, 75 and 95 % for ATD200 (threshold: 1.2 mm) and 38 and 95 % for IR5 (threshold: 3.2°). If either two out of the three variables were positive for anterior laxity or both IR5 and C IR were positive, 81 % of patients were identified without a false positive. All patients for whom ATD200 was >3.7 mm, PCA > 48 μm/N or SCA > 17.5 µm/N had ACL remnants that were either totally resorbed or healed on the posterior cruciate ligament.

CONCLUSION

Combined instrumented anterior and rotational knee laxity measurements have excellent diagnostic value for ACL injury, provided that several measurements be considered concomitantly.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

Noninjured Knees of Patients With Noncontact ACL Injuries Display Higher Average Anterior and Internal Rotational Knee Laxity Compared With Healthy Knees of a Noninjured Population

BACKGROUND

Excessive physiological anterior and rotational knee laxity is thought to be a risk factor for noncontact anterior cruciate ligament (ACL) injuries and inferior reconstruction outcomes, but no thresholds have been established to identify patients with increased laxity.

PURPOSE

(1) To determine if the healthy contralateral knees of ACL-injured patients have greater anterior and rotational knee laxity, leading to different laxity profiles (combination of laxities), compared with healthy control knees and (2) to set a threshold to help discriminate anterior and rotational knee laxity between these groups.

STUDY DESIGN

Case-sectional study; Level of evidence, 3.

METHODS

A total of 171 healthy contralateral knees of noncontact ACL-injured patients (ACL-H group) and 104 healthy knees of control participants (CTL group) were tested for anterior and rotational laxity. Laxity scores (measurements corrected for sex and body mass) were used to classify knees as hypolax (score <-1), normolax (between -1 and 1), or hyperlax (>1). Proportions of patients in each group were compared using χ(2) tests. Receiver operating characteristic curves were computed to discriminate laxity between the groups. Odds ratios were calculated to determine the probability of being in the ACL-H group.

RESULTS

The ACL-H group displayed greater laxity scores for anterior displacement and internal rotation in their uninjured knee compared with the CTL group (P < .05). Laxity profiles were different between the groups for the following associations: normolax in anterior displacement/hypolax in internal rotation (6% [ACL-H] vs 15% [CTL]; P = .02) and hyperlax in anterior displacement/normolax in internal rotation (27% [ACL-H] vs 10% [CTL]; P < .01). The laxity score thresholds were 0.75 for anterior laxity and -0.55 for internal rotation. With both scores above these thresholds, a patient was 3.18-fold more likely to be in the ACL-H group (95% CI, 1.74-5.83).

CONCLUSION

The healthy contralateral knees of patients with noncontact ACL injuries display different laxity values both for internal rotation and anterior displacement compared with healthy control knees. The identification of knee laxity profiles may be of relevance for primary and secondary prevention programs of noncontact ACL injuries.

Design, Repeatability, and Comparison to Literature Data of a New Noninvasive Device Called "Rotameter" to Measure Rotational Knee Laxity

The present paper deals with the design, the repeatability, and the comparison to literature data of a new measuring device called “Rotameter” to characterize the rotational knee laxity or the tibia-femoral rotation (TFR). The initial prototype P1 of the Rotameter is shortly introduced and then modified according to trials carried out on a prosthetic leg and on five healthy volunteers, leading therefore to an improved prototype P2. A comparison of results obtained from P1 and P2 with the same male subject shows the enhancements of P2. Intertester and intratester repeatability of this new device were shown and it was observed that rotational laxities of left and right knees are the same for a healthy subject. Moreover, a literature review showed that measurements with P2 presented lower TFR values than other noninvasive devices. The measured TFR versus torque characteristic was quite similar to other invasive devices, which are more difficult to use and harmful to the patient. Hence, our prototype P2 proved to be an easy-to-use and suitable device for quantifying rotational knee laxity. A forthcoming study will validate the Rotameter thanks to an approach based on computed tomography in order to evaluate its precision.

Rotational profile alterations after anatomic posterolateral corner reconstructions in multiligament injured knees

PURPOSE

Injuries of the posterolateral corner (PLC) are rare and severe knee injuries, resulting in posterolateral rotatory instability and an increase in external rotation. Surgical reconstruction techniques reproducing the normal anatomy showed promising results. In vivo evaluations of static rotational knee laxity at 30° of knee flexion have not been reported so far. The purpose of this study was to evaluate static rotational knee laxity after anatomic PLC reconstructions.

METHODS

This is a retrospective clinical cohort study. Twenty patients with PLC reconstructions with an average follow-up time of 39 ± 22 months and no history of knee trauma or surgery of the contralateral knee were included in the study. They underwent a routine clinical examination and static rotational laxity measurements at 30° of knee flexion in the prone position. Side-to-side differences were recorded and compared to a group of matched controls.

RESULTS

The postoperative IKDC score was graded A for 8 patients, B for 16, C for 6 and D for one patient. The primary goal of the surgical procedure which consists in reducing excessive external tibiofemoral rotation could be reached in 18 of the 20 patients (90%). Anatomic PLC reconstructions yielded a comparable rotational profile in operated and healthy knees in 7 patients (35%). Thirteen patients (65%) presented a significantly altered rotational profile in comparison with a healthy control group. Unexpected increases in internal rotation were found in 8 patients (40%).

CONCLUSION

Anatomic PLC reconstructions reduced excessive external tibiofemoral rotation in a vast majority of patients. Static rotational laxity measurements allowed for a determination of the patients' individual rotational profile after PLC reconstructions. This profile was normalised in only one-third of the patients. The understanding of this finding needs further investigation as well as the clinical impact of rotational profile alterations on knee function.

LEVEL OF EVIDENCE

Diagnostic studies, Level III.

In vivo kinematic evaluation of anatomic double-bundle anterior cruciate ligament reconstruction

BACKGROUND

There is controversy regarding the functional role of the posterolateral (PL) bundle of the anterior cruciate ligament (ACL).

PURPOSE

To evaluate the in vivo function of the PL and anteromedial (AM) bundles of the ACL during anatomic double-bundle (DB) ACL reconstruction for acute, isolated ACL tears utilizing a computer navigation system to track intraoperative knee kinematics.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifteen patients with acute, isolated ACL tears who underwent anatomic DB ACL reconstruction formed the sample for this study. During surgery, knees were examined by a clinician preoperatively, after fixation of the PL bundle, and after fixation of both the PL and AM bundles. An image-free computer navigation system with custom-made software recorded the data during kinematic tests. The examination consisted of the Lachman and anterior drawer tests, internal-external rotation at 30° of knee flexion, and varus-valgus rotation at 30° of knee flexion. Paired Wilcoxon tests were performed to evaluate the effects of each bundle. The comparisons included ACL-deficient to PL bundle-reconstructed knees, ACL-deficient to DB ACL-reconstructed knees, and PL bundle-reconstructed to DB ACL-reconstructed knees. Significance was set at P < .017 to account for the multiple comparisons.

RESULTS

Fixation of the PL bundle significantly improved knee laxity during the Lachman and anterior drawer tests as well as internal-external rotation at 30° of knee flexion (P < .017 for all tests). The addition of the AM bundle further improved knee laxity during the Lachman and anterior drawer tests compared with PL bundle fixation as well as during varus-valgus rotation at 30° of knee flexion compared with ACL-deficient knees (P < .017 for all tests).

CONCLUSION

This in vivo study demonstrates that isolated PL bundle reconstruction improves laxity in an ACL-deficient knee and that the addition of the AM bundle improves laxity parameters further.

CLINICAL RELEVANCE

Abnormal knee kinematics is known to be linked to the earlier onset of osteoarthritis and lower rates of return to sport. This study suggests that both the AM and PL bundles are important to stabilize ACL-deficient knees.

AM bundle controls the anterior-posterior and rotational stability to a greater extent than the PL bundle - a cadaver study

BACKGROUND

The purpose of this study was to evaluate the influence of both bundles of the anterior cruciate ligament (ACL) on knee stability, anterior-posterior translation (APT) and internal (IR) and external (ER) rotation in cadaveric knees using a computer navigation system.

METHODS

The APT, IR, and ER of the knees were recorded in the intact condition, the anterolateral bundle (AM) or the posterolateral bundle (PL) deficit condition and in the ACL-deficient condition. The KT-1000 arthrometer was used for APT evaluation. The measurement of rotational movements was done using a rollimeter. All tests were performed at 30°, 60° and 90° of flexion.

RESULTS

At 30° of flexion: In the intact knee APT was 5.8mm, IR 12.1°, ER 10.1°. After the AM was cut, the APT increased to 9.1mm, IR to 13.9° and ER to 12.6°. After the PL was cut, the APT was 6.4mm, IR 13.1° and ER 10.6°. After the AM and PL were cut, the APT was 10.8mm, IR 15.7° and the ER was 12.9° on average.

CONCLUSIONS

The AM has a greater impact on the APT than the PL in all knee joint flexion angles. The PL does not resist the rotational stability more than the AM. The rotational stability is better controlled by both bundles of ACL as compared to one bundle of the ACL.

CLINICAL RELEVANCE

This study acknowledges the fact that the both bundles of the ACL are importants for AP and rotational stability of the knee joint.

Isokinetic Quadriceps and Hamstring Muscle Strength after Anterior Cruciate Ligament Reconstruction: Comparison between Single-bundle and Double-bundle Reconstruction

Introduction

Clinical studies have not yet proven whether single-bundle (SB) or double-bundle (DB) anterior cruciate ligament (ACL) reconstruction is superior. Nonetheless, quadriceps and hamstring muscle deficit is common after ACL reconstruction and it may affect the final outcome. The purpose of this study was to compare the isokinetic quadriceps and hamstring muscle strength after SB-ACL and DB-ACL reconstruction.

Materials and methods

We recruited 40 patients with ACL reconstruction (20 SB and 20 DB) by the same team of surgeons from 2006 to 2009. Demographic data of both groups were comparable. Lower extremity concentric isokinetic peak extension and flexion torques were assessed at angular velocities of 60°/second, 180°/second, and 300°/second preoperatively and at least 1 year postoperatively. Clinical evaluation was performed, including anterior stability with an arthrometer (model KT-1000), Lysholm score, Tegner activity score, single leg hop test, and International Knee Documentation Committee score. Data were analysed statistically.

Results

The isokinetic quadriceps and hamstring peak torque values in both the SB and DB groups did not show any significant difference. The maximum displacement upon KT-1000 arthrometer measurement appeared lower in the DB group but the difference was not significant. The side-to-side percentage deficits in quadriceps and hamstring peak torque at postoperative assessment were comparable in both groups.

Conclusion

Isokinetic quadriceps and hamstring muscle strength after SB-ACL or DB-ACL reconstruction was comparable.

Rotatory knee laxity

Evaluation of injured-knee laxity is essential for treatment selection, clinical follow-up, and research. Interest in rotatory knee laxity increased with implementation of anatomic anterior cruciate ligament reconstruction. The pivot shift test represents a link between static testing with 1° of freedom and dynamic testing during functional activity. Difficulties lie in standardizing the performance of the pivot shift test and extracting measurable and relevant kinematic data. Noninvasive methodologies based on electromagnetic or acceleration sensors can evaluate the pivot shift in a quantitative and reliable manner. Further validation and reliability testing of devices for examination of rotatory laxity is warranted.

Current concept in rotational laxity control and evaluation in ACL reconstruction

Rotation combined with translation; compose the three-dimensional motion of the knee subluxation in anterior cruciate ligament deficient knee. The worldwide scientists were focused initially on the translation part of this complex 3D motion, but since the beginning of the century there was a large interest on knee rotational laxity study. Lot of paper reported new devices and results with an explosion since the beginning of the decade. The purpose of this review is to provide an extensive critical analysis of the literature and clarify the knowledge on this topic. We will start with a dismemberment of different rotational laxities reported: the rotation coupled with translation in 2D tests such as Lachman test and anterior drawer test; the rotational envelope considering the maximum internal external rotation; and the "active rotation" occurring in 3D Pivot-shift (PS) test. Then we will analyze the knee kinematics and the role of different anterior cruciate ligament (ACL) bundle on rotation. A review of different mechanical and radiological devices used to assess the different rotations on ACL deficient knees will be presented. Two groups will be analyzed, dynamic and static conditions of tests. Navigation will be described precisely; it was the starter of this recent interest in rotation studies. Opto electronic and electromagnetic navigation systems will be presented and analyzed. We will conclude with the last generation of rotational laxity assessment devices, using accelerometers, which are very promising.

Double-bundle bone-patellar tendon-bone and gracilis in ACL reconstruction

An original technique for the reconstruction of the anterior cruciate ligament is explained. Two bundles are reconstructed using the central third of the patellar tendon and the gracilis tendon, passed through four tunnels but requiring only two interference screws for fixation. Level of evidence V.

Double-bundle anterior cruciate ligament reconstruction: a review of literature

PURPOSE

Anterior cruciate ligament (ACL) reconstruction has been under intensive discussion and debate, although the anatomy of this ligament was resolved thoroughly almost 200 years ago. The ACL consist of two bundles, anteromedial (AM) and posterolateral (PL). The conventional single-bundle method reconstructs the AM bundle only, while the modern double-bundle technique recreates both bundles for their anatomical sites.

METHODS

An English language literature search was undertaken over the years 2000-2012 for ACL reconstruction, double-bundle versus single bundle technique. The search found 14 RCTs and two meta-analyses published to date.

RESULTS

Two of the 14 studies (14 %) showed no difference between the two reconstruction methods while the remaining majority (12 trials, 86 %) concluded that the DB technique was better than the SB method. After the DB reconstruction, rotational stability of the knee was better in seven studies (50 %) and anteroposterior stability in six (43 %). No study spoke for the single-bundle technique. In addition, with the double-bundle technique knee scores were reported to be better in five (36 %) studies, and three trials (21 %) revealed less reoperations in the double-bundle group.

CONCLUSIONS

The double-bundle ACL reconstruction technique was reported to have better or at least the same results as the conventional single-bundle method-even at a five-year follow-up. However, the majority of these studies had a rather short follow-up, and thus, longer studies are needed to confirm the true long-term results of ACL surgery. Long follow-up periods are also needed to find out whether double-bundle ACL reconstruction can eventually prevent knee osteoarthritis.

Does the posterolateral bundle influence rotational movement more than the anteromedial bundle in anterior cruciate ligament reconstruction?

The biomechanical function of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) remains controversial. Some studies report that the AM bundle stabilises the knee joint in anteroposterior (AP) translation and rotational movement (both internal and external) to the same extent as the PL bundle. Others conclude that the PL bundle is more important than the AM in controlling rotational movement.

The objective of this randomised cohort study involving 60 patients (39 men and 21 women) with a mean age of 32.9 years (18 to 53) was to evaluate the function of the AM and the PL bundles of the ACL in both AP and rotational movements of the knee joint after single-bundle and double-bundle ACL reconstruction using a computer navigation system. In the double-bundle group the patients were also randomised to have the AM or the PL bundle tensioned first, with knee laxity measured after each stage of reconstruction. All patients had isolated complete ACL tears, and the presence of a meniscal injury was the only supplementary pathology permitted for inclusion in the trial. The KT-1000 arthrometer was used to apply a constant load to evaluate the AP translation and the rolimeter was used to apply a constant rotational force. For the single-bundle group deviation was measured before and after ACL reconstruction. In the double-bundle group deviation was measured for the ACL-deficient, AM- or PL-reconstructed first conditions and for the total reconstruction.

We found that the AM bundle in the double-bundle group controlled rotation as much as the single-bundle technique, and to a greater extent than the PL bundle in the double-bundle technique. The double-bundle technique increases AP translation and rotational stability in internal rotation more than the single-bundle technique.

Static rotational and sagittal knee laxity measurements after reconstruction of the anterior cruciate ligament

PURPOSE

The goal of the present study was to evaluate static anteroposterior and rotational knee laxity after ACL reconstructions with two noninvasive measurement devices by comparing the measured results of the operated with the contralateral healthy knees of the patients.

METHODS

Fifty-two consecutive patients were reviewed after isolated single-bundle transtibial ACL reconstruction using a BPTB graft. At a mean follow-up of 27 months, sagittal AP laxity was tested using a noninvasive knee measurement system (Genourob) with an applied pressure of 67 N, 89 N and 134 N. Rotational laxity was measured using a noninvasive rotational knee laxity device (Rotameter) with an applied torque of 5, 8 and 10 Nm. The results were compared with the measurements of the patients' healthy contralateral knees. Tegner, Lysholm and IKDC score were used in order to evaluate the clinical outcome.

RESULTS

Pivot shift was negative (33) or glide (16) in 49 patients with 12 of 16 (75%) patients having also a pivot glide on the healthy contralateral side; Lachman tests were negative in 50 cases. Subjective assessment of the IKDC score was classified according to category A in 44 patients, B in 5 patients and C in 3 patients. Mean Lysholm score was 94.5 ± 9.5, median Tegner score was 7 (3-9) preoperative and 6 (3-9) at follow-up (n.s.). Anteroposterior knee laxity measurements revealed mean side-to-side differences of 0.6-1.3 mm (P < 0.0001). Rotational laxity measurements revealed no statistical significant differences between the operated and the contralateral knee (n.s.). The measured differences in the entire rotational range varied from 0.2° to 1° depending on the applied torque. In those 3 patients with a positive pivot shift, differences in the entire rotational range of 4.5° at 5 N, 4.6° at 8 N and 4.1° at 10 N were found.

CONCLUSION

Static knee laxity was quantified after ACL surgery using the introduced noninvasive measurement systems by comparing the measured results of the operated with the contralateral healthy knees. Significant differences were found in AP laxity although they were defined as clinically successful according to the IKDC classification. No significant differences were found in rotational knee laxity measurements. Therefore, the used noninvasive masurement devices might offer a high potential for objective quality control in knee ligament injuries and their treatment.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

The role of static and dynamic rotatory laxity testing in evaluating ACL injury

In this article, we discuss current topics for rotatory knee laxity. All tests for knee laxity have a value. Static knee laxity tests reveal information for each individual patient's laxity status, especially compared to the contralateral side. Static knee laxity tests are simple to do, and some of them are instrumented, therefore quantifiable. Dynamic knee laxity tests are more complex. Dynamic stereo radiography (DSX) is considered the gold standard. Utilizing DSX, information can be gained on 3-D kinematics, functional joint space, and joint contact patterns. The disadvantage is that DSX is expensive and can only be performed in a laboratory environment. The pivot shift test is a unique test, because it is dynamic and easily performed in the office. However, it is subjective and only recently quantifiable. Future endeavors will attempt to improve the value of the pivot shift test by standardizing the test and improving measurement technologies, while keeping the pivot shift test simple and non-invasive.

Objective measurement devices to assess static rotational knee laxity: focus on the Rotameter

PURPOSE

The present article summarizes the development of a simple, objective, and non-invasive measurement device for tibiofemoral rotation to assess static rotational knee laxity.

METHODS AND RESULTS

The device is based on the dial test with the patient lying prone and the knee flexed to 30°. From measurements of 30 healthy participants, the device achieved high inter- and intra-observer reliability and showed a high correlation of the measured results with the contralateral knees of the participants. Measurements of the device were also performed in a human cadaver study and revealed highly correlated results when compared to the simultaneous measurements of a knee navigation system, which was used as an invasive standard method to assess tibial rotation. In human cadaver specimens, it was shown that a simulated tear of the posterolateral bundle as well as a complete ACL tear led to a significant increase in isolated tibiofemoral rotation compared to the intact ACL. A retrospective case series investigated the clinical results as well as knee laxity measurements after ACL surgery in vivo. Rotational, as well as anteroposterior (AP), knee laxity was objectively assessed in 52 patients at a mean postoperative follow-up of 27 months by comparing the measured results with the results of the contralateral unaffected knee in each patient. The clinical results were comparable to the results reported in the literature. Moreover, rotational laxity was successfully restored after ACL reconstruction, whereas AP laxity showed significant differences compared to the contralateral knees although they were defined as clinically successful according to the IKDC classification.

CONCLUSIONS

A non-invasive and objective knee rotational measurement device has been developed, which offers good potential for objective quality control in knee ligament injuries and their treatment.

LEVEL OF EVIDENCE

Review article, Level IV.

Static rotational knee laxity in anterior cruciate ligament injuries

PURPOSE

The purpose was to provide an overview of the non-invasive devices measuring static rotational knee laxity in order to formulate recommendations for the future.

RESULTS

Early cadaver studies provided evidence that sectioning the anterior cruciate ligament (ACL) led to an increase of static rotational knee laxity of approximately 10-20% between full extension and 30° of knee flexion. Sections of the menisci or of the peripheral structures induced a much higher increase in rotation. This supported the hypothesis that static rotation measurements might be useful for the diagnosis of ACL or associated injuries. In vivo evaluations with measurement devices are relatively new. Several articles were published during the last decade with many different devices and important differences were seen in absolute rotational knee laxity between them. This was due to the varying precision of the devices, the variability in patient positioning, the different methods of measurement, examination protocols and data analysis. As a consequence, comparison of the available results should be performed with caution. Nevertheless, it has been established that rotational knee laxity was greater in females as compared to males and that the inter-subject variability was high. For this reason, it will probably be difficult to categorise injured patients preoperatively, and the interpretation of the results should probably be limited to side-to-side differences.

CONCLUSION

Future studies will show whether rotational laxity measurements alone will be sufficient to provide clinically relevant data or if they should be combined to static sagittal laxity measurements.

The functions of the fibre bundles of the anterior cruciate ligament in anterior drawer, rotational laxity and the pivot shift

This paper reviews the functional anatomy of the anterior cruciate ligament (ACL), which has a parallel array of collagen fascicles that have usually been divided into two 'fibre bundles': anteromedial (AM) and posterolateral (PL), according to their tibial attachment sites. The PL bundle has shorter fibres, and so it is subjected to greater tensile strains than the AM bundle when the whole ACL is stretched; its oblique orientation in the coronal plane imbues it with greater ability to resist tibial rotation than the more vertical AM fibre bundle. Most studies have found that the AM bundle is close to isometric when the knee flexes, while the PL bundle slackens approximately 6 mm. There is little evidence of significant fibre bundle elongation in response to tibial rotation. Selective bundle cutting studies have been performed, allowing both the bundle tensions and their contributions to resisting tibial anterior translation and tibial rotation to be calculated. These show that the function of the PL bundle was dominant near knee extension in some studies, particularly when resisting anterior drawer and that its contribution reduced rapidly with knee flexion through 30 degrees. There has been little study of the contributions of the fibre bundles in control of tibial internal-external rotation or the pivot shift: one study found that the AM bundle had larger tensions than the PL bundle during a simulated pivot shift, but another study found that cutting the PL bundle allowed a larger increase in coupled tibial anterior translation than cutting the AM bundle. It was concluded that the AM bundle is most important for resisting tibial anterior drawer-the primary function of the ACL-while the PL bundle is tight near knee extension, when it has a role in control of tibial rotational laxity. There is a clear need for further study of dynamic knee instability, to gain better understanding of how best to reconstruct the ACL and associated tissues.

The influence of posterolateral rotatory instability on ACL reconstruction: comparison between isolated ACL reconstruction and ACL reconstruction combined with posterolateral corner reconstruction

BACKGROUND

The purpose of the present retrospective study was to evaluate the influence of posterolateral corner reconstruction on anterior cruciate ligament (ACL) reconstruction in terms of anterior laxity and clinical outcomes. We hypothesized that the effects of combined ACL and posterolateral corner reconstruction would be less satisfactory than those of isolated ACL reconstruction in terms of anterior laxity and clinical outcomes.

METHODS

We retrospectively studied sixty-nine patients who underwent ACL reconstruction from February 2001 to December 2005. Forty-six patients underwent isolated ACL reconstruction (Group I), and twenty-three patients underwent combined ACL and posterolateral corner reconstruction (Group II). Clinical outcomes were determined from data obtained before surgery and at the time of the twenty-four-month follow-up examination.

RESULTS

Postoperatively, the mean side-to-side difference (and standard deviation) in anterior tibial translation, measured with a KT2000 arthrometer, was greater for Group I (2.2 ± 1.0 mm) than for Group II (1.6 ± 0.8 mm) (p = 0.031). Seven knees (15.2%) in Group I and two knees (8.7%) in Group II had grade-1 anterior translation. The mean Lysholm score was 93.2 in Group I and 90.1 in Group II (p = 0.392). Thirty-eight knees (82.6%) in Group I and twenty knees (87.0%) in Group II were classified as normal or nearly normal according to the International Knee Documentation Committee scoring system (p = 0.882).

CONCLUSIONS

On the basis of the evaluation of ligamentous laxity with use of the KT2000 arthrometer, we observed that combined ACL and posterolateral corner reconstruction allows less anterior translation than isolated ACL reconstruction. However, we could not identify significant differences between the two groups in terms of functional outcomes.

Does physiologic posterolateral laxity influence clinical outcomes of anterior cruciate ligament reconstruction?

BACKGROUND

The purpose of this retrospective study was to evaluate the influence of physiologic posterolateral rotatory laxity on anterior cruciate ligament (ACL) reconstruction in terms of anterior knee stability and clinical outcomes.

METHODS

We retrospectively studied 113 patients who had undergone ACL reconstruction between June 2004 and August 2008. Patients were categorized into three groups according to the degree of tibial external rotation at 90° of knee flexion: Group 1 (<40°), Group 2 (40° to 50°), and Group 3 (≥50°). Ligament stability was determined with use of the Lachman test, the pivot-shift test, and KT-2000 arthrometer testing. Function was assessed with use of the Lysholm score and the International Knee Documentation Committee (IKDC) score. Clinical outcomes were determined from data obtained before surgery and at the twenty-four-month follow-up visit.

RESULTS

We observed differences in postoperative knee translation between the groups (p < 0.001). A post hoc test showed increased mean knee translation in Group 3 compared with Groups 1 and 2. The degree of external rotation at 90° was positively correlated with anterior knee translation (r = 0.428; p = 0.007). However, there was an inverse correlation with the Lysholm knee scores (r = -0.146; p = 0.015) and IKDC scores (r = -0.205; p = 0.003).

CONCLUSIONS

The stability and functional scores after ACL reconstruction had a negative correlation with the degree of external rotation of the tibia at 90° (physiologic posterolateral rotatory laxity). After ACL reconstruction, patients with ≥ 50° of tibial external rotation had increased anterior translation and worse functional outcomes in comparison with those who had < 50° of tibial external rotation.

[Evaluation of anterior knee laxity on MRI]

PURPOSE

Evaluation of the ACL and anterior knee laxity on MR during anterior tibial translation.

PATIENTS AND METHODS

Three groups were identified based on clinical and arthrometric (KT-1000) data: normal ACL (n=12), complete tear (n=10) and partial tear (n=20). MRI was performed without and with anterior tibial translation (pneumatic device) with morphological and laximetric analysis: drawer tests and dynamic evaluation of ligamentous tension.

RESULTS

Intra- and inter-observer reproducibility was excellent, correlated to arthrometric data and clinical tests (Lachman, pivot shift). The difference between the drawer signs of normal subjects and patients with ACL tear was significant for a threshold value of 1,1mm for the anterior drawer (sensitivity: 93.33%, specificity: 91.7%) and 2.8 mm for the posterior drawer (sensitivity: 86.7%, specificity: 100%). Dynamic evaluation of ligamentous tension was also reproducible, statistically correlated to the MR drawer tests and reliable for the diagnosis of ACL lesions. In this preliminary study, the distinction between complete and partial ACL tears could not be detected.

CONCLUSION

Anterior cruciate ligament function can be demonstrated on MR. The predictive value of this morphological and functional association should be determined in the management of patients with partial tears.