Grading the pivot shift. Objective tests with implications for treatment

Assessment of the pivot shift using inertial sensors

The pivot shift test is an important clinical tool used to assess the stability of the knee following an injury to the anterior cruciate ligament (ACL). Previous studies have shown that significant variability exists in the performance and interpretation of this manoeuvre. Accordingly, a variety of techniques aimed at standardizing and quantifying the pivot shift test have been developed. In recent years, inertial sensors have been used to measure the kinematics of the pivot shift. The goal of this study is to present a review of the literature and discuss the principles of inertial sensors and their use in quantifying the pivot shift test.

Knee instability scores for ACL reconstruction

Despite abundant biological, biomechanical, and clinical research, return to sport after anterior cruciate ligament (ACL) injury remains a significant challenge. Residual rotatory knee laxity has been identified as one of the factors responsible for poor functional outcome. To improve and standardize the assessment of knee instability, a variety of instability scoring systems is available. Recently, devices to objectively quantify static and dynamic clinical exams have been developed to complement traditional subjective grading systems. These devices enable an improved evaluation of knee instability and possible associated injuries. This additional information may promote the development of new treatment algorithms and allow for individualized treatment. In this review, the different subjective laxity scores as well as complementary objective measuring systems are discussed, along with an introduction of injury to an individualized treatment algorithm.

Experimental Execution of the Simulated Pivot-Shift Test: A Systematic Review of Techniques

PURPOSE

To conduct a systematic review to identify and summarize the various techniques that have been used to simulate the pivot-shift test in vitro.

METHODS

Medline, Embase, and the Cochrane Library were screened for studies involving the simulated pivot-shift test in human cadaveric knees published between 1946 and May 2014. Study parameters including sample size, study location, simulated pivot-shift technique, loads applied, knee flexion angles at which simulated pivot shift was tested, and kinematic evaluation tools were extracted and analyzed.

RESULTS

Forty-eight studies reporting simulated pivot-shift testing on 627 cadaveric knees fulfilled the criteria. Reviewer inter-rater agreement for study selection showed a κ score of 0.960 (full-text review). Twenty-seven studies described the use of internal rotation torque, with a mean of 5.3 Nm (range, 1 to 18 Nm). Forty-seven studies described the use of valgus torque, with a mean of 8.8 Nm (range, 1 to 25 Nm). Four studies described the use of iliotibial tract tension, ranging from 10 to 88 N. Regarding static simulated pivot-shift test techniques, 100% of the studies performed testing at 30° of knee flexion, and the most tested range of motion in the continuous tests was 0° to 90°. Anterior tibial translation was the most analyzed parameter during the simulated pivot-shift test, being used in 45 studies. In 22% of the studies, a robotic system was used to simulate the pivot-shift test. Robotic systems were shown to have better control of the loading system and higher tracking system accuracy.

CONCLUSIONS

This study provides a reference for investigators who desire to apply simulated pivot shift in their in vitro studies. It is recommended to simulate the pivot-shift test using a 10-Nm valgus torque and 5-Nm internal rotation torque. Knee flexion of 30° is mandatory for testing.

LEVEL OF EVIDENCE

Level IV, systematic review of basic science studies.

A mechanical pivot-shift device for continuously applying defined loads to cadaveric knees

PURPOSE

Current techniques to study the biomechanics of the pivot-shift utilize either static or poorly defined loading conditions. Here, a novel mechanical pivot-shift device that continuously applies well-defined loads to cadaveric knees is characterized and validated against the manual pivot-shift.

METHODS

Six fresh-frozen human lower limb specimens were potted at the femur, mounted on a hinged testing base, and fitted with the mechanical device. Five mechanical and manual pivot-shift tests were performed on each knee by two examiners before and after transecting the ACL. Three-dimensional kinematics (anterior and internal-rotary displacements, and posterior and external-rotary velocities) and kinetics (forces and moments applied to the tibia by the device) were recorded using an optical navigation system and 6-axis load cell. Analysis of variance and Bland-Altman statistics were used to gauge repeatability within knees, reproducibility between knees, agreement between the mechanical and manual test methods, and agreement between examiners.

RESULTS

The forces and moments applied by the device were continuous and repeatable/reproducible to within 4/10 % of maximum recorded values. Kinematic variables (excluding external-rotary velocity) were qualitatively and quantitatively similar to manual pivot-shift kinematics, and were more repeatable and reproducible.

CONCLUSION

The presented device induces pivot-shift-like kinematics by applying highly repeatable three-dimensional loads to cadaver knees. It is based on a simple mechanical principle and designed using easily obtainable components. Consequently, the device enables orthopaedic biomechanists to easily and reliably quantify the effect of ACL injury and reconstruction on pivot-shift kinematics.

Lateral Extra-articular Tenodesis Reduces Rotational Laxity When Combined With Anterior Cruciate Ligament Reconstruction: A Systematic Review of the Literature

PURPOSE

To determine whether the addition of lateral extra-articular tenodesis (LET) to anterior cruciate ligament (ACL) reconstruction would provide greater control of rotational laxity and improved clinical outcomes compared with ACL reconstruction alone.

METHODS

Two independent reviewers searched 9 databases for randomized and nonrandomized clinical studies comparing ACL reconstruction plus LET versus ACL reconstruction alone in a human adult population. All years and 5 languages were included. Animal and cadaveric studies, revision or repair surgical techniques, and studies focused on biomechanical outcomes were excluded. Quality assessment of the included studies was performed with the Cochrane Collaboration tool. Outcomes of interest included the pivot-shift test, KT-1000/-2000 measurements (MEDmetric, San Diego, CA), and International Knee Documentation Committee scores.

RESULTS

The literature search yielded 3,612 articles. After titles and abstracts were reviewed, 106 articles were selected for full-text review, of which 29 studies met the inclusion criteria (8 randomized and 21 nonrandomized studies). Of the 8 randomized studies, 3 concluded that the results were nonsignificant between treatment groups, 4 were in favor of the extra-articular tenodesis, and 1 was in favor of the ACL reconstruction alone. The Cochrane Collaboration tool showed an unclear to high risk of bias for most articles. A meta-analysis showed a statistically significant difference for the pivot-shift test (P = .002, I2 = 34%) in favor of ACL reconstruction with LET. No difference was found between the groups for International Knee Documentation Committee scores (P = .75, I2 = 19%) and KT-1000/-2000 measurements (P = .84, I2 = 34%).

CONCLUSIONS

Meta-analysis showed a statistically significant reduction in pivot shift in favor of the combined procedure. Studies lacked sufficient internal validity, sample size, methodologic consistency, and standardization of protocols and outcomes.

LEVEL OF EVIDENCE

Level III, systematic review of Level I, II, and III studies.

An analysis of normative data on the knee rotatory profile and the usefulness of the Rotatometer, a new instrument for measuring tibiofemoral rotation: the reliability of the knee Rotatometer

PURPOSE

This study proposes a simple and noninvasive instrument called the "Rotatometer" to measure tibiofemoral rotation and investigates its clinical applicability to the assessment of static rotational knee laxity.

METHODS

The degree of tibiofemoral rotation was measured for a sample of 94 healthy volunteers with 188 knees by using the Rotatometer. The measurement was made by two independent and blinded examiners in three sessions at one-month intervals. The normative rotational profile and its relationship with gender and age were evaluated, and inter-observer reliability and intra-observer reliability were calculated.

RESULTS

Males showed 62° ± 5° of external rotation, whereas females, 64° ± 5°. Males showed 44° ± 5° of internal rotation, whereas females, 49° ± 4°. Females showed significantly higher degrees of rotation than males. Tibiofemoral rotation was not correlated with age, and external rotation and internal rotation had a moderate positive relationship. Inter-observer reliability ranged from 0.84 to 0.91 for external rotation and 0.90 to 0.95 for internal rotation, and intra-observer reliability ranged from 0.69 to 0.89 for external rotation and 0.87 to 0.95 for internal rotation.

CONCLUSIONS

The results suggest the Rotatometer to be a simple and noninvasive device with high inter- and intra-observer reliability. The device can provide a normative rotational profile for reference purposes and thus can be used to determine the preoperative and postoperative rotational status of knees with anterior cruciate ligament injuries and compare results from different reconstruction techniques.

Quantitative pivot shift assessment using combined inertial and magnetic sensing

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

After revision anterior cruciate ligament reconstruction, who returns to sport? A systematic review and meta-analysis

BACKGROUND

Return to sport and to pre-injury level represents an important outcome after both primary and revision anterior cruciate ligament (ACL) reconstructions.

PURPOSE

The aim of the present meta-analysis was to determine the return to sport rate after revision ACL reconstruction.

MATERIAL AND METHODS

A systematic search was performed of the MEDLINE, Embase and the Cochrane Central Register of Controlled Trials Databases. All the studies that reported return to sport, return to pre-injury sport level and return to high level/competitive sport was considered for the meta-analysis. The overall pooled mean of post-operative knee laxity and pooled rate of positive pivot-shift and objective International Knee Documentation Committee (IKDC) categories was calculated as well.

RESULTS

Overall, 472 abstracts were identified and screened for inclusion and only 16 studies reported the rate of return to any level of sport activity at the final follow-up of 4.7 years (range 1.0-13.2 years), showing a pooled rate of 85.3% (CI 79.7 to 90.2). The return to pre-injury sport level was achieved in 53.4% (CI 37.8 to 68.7) of cases. Normal or quasi-normal objective IKDC, less than 5 mm of side-to-side difference at arthrometric evaluations and grade I-II pivot-shift test were reported in 84%, 88% and 93% patients, respectively.

CONCLUSIONS

In spite of almost 8 patients out of 10 returning to sport after revision ACL reconstruction and showing good stability, only half of the patients returned to the same pre-injury sport level.

Effect of lateral meniscal root tear on the stability of the anterior cruciate ligament-deficient knee

BACKGROUND

Meniscal root tears are an increasingly recognized subset of meniscal injury. The menisci are critical secondary stabilizers of the anterior cruciate ligament (ACL). The kinematic effect of lateral meniscus posterior root tear in the setting of ACL injury is not known.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine the effect of tear of the lateral meniscal root on stability of the ACL-deficient knee. The hypothesis was that disruption of the lateral meniscal root will further destabilize the ACL-deficient knee during a simulated pivot shift.

STUDY DESIGN

Controlled laboratory study.

METHODS

Pivot-shift testing of 8 fresh-frozen cadaveric knees was performed after attachment of photoreflective flags and preparation of CT scans. Each knee was mounted in a custom activity simulator and dynamically loaded from 15° to 90° of flexion with all the permutations of the following: iliotibial band force (50, 75, 100, 125, 150, and 175 N), internal rotation moments (1, 2, and 3 N·m), and valgus moments (5 and 7 N·m). In addition, anterior stability tests were performed by applying a 90-N anterior force to the tibia at flexion angles of 15°, 30°, 45°, 60°, and 90°. During each test, the anterior tibial translation and rotation of the tibia were measured with a high-resolution multiple infrared camera motion analysis system for the following 3 conditions: ACL-intact (ACL-I), ACL-deficient (ACL-D), and ACL-deficient/lateral meniscal posterior root avulsion (ACL-D/LMR-A).

RESULTS

A pivot-shift phenomenon was observed in the ACL-D and ACL-D/LMR-A conditions. The mean tibial translation of the lateral tibial condyle during the pivot-shift maneuver was 2.62 ± 0.53 mm for the ACL-I knees, 6.01 ± 0.51 mm for the ACL-D knees (P value vs. intact: .0005), and 8.13 ± 0.75 mm for the ACL-D/LMR-A knees (P value vs intact: <.0001). During the pivot-shift maneuver, translation was significantly increased in the ACL-D/LMR-A condition compared with the ACL-D condition (P = .0146). Compared with the intact group, anterior tibial translation during the Lachman maneuver also increased at 30° and 90° of flexion in the ACL-D group (P < .0001) and the ACL-D/LM group (P < .0001). No statistically significant difference was found between the ACL-D and ACL-D/LMR-A groups during the Lachman maneuver at 30° and 90° (P = .16 and .72, respectively).

CONCLUSION

A tear of the lateral meniscal posterior root further reduces the stability of the ACL-deficient knee during rotational loading.

CLINICAL RELEVANCE

This study shows that lateral meniscal root injury further destabilizes the ACL-deficient knee and thus advances the concept that the lateral meniscus is a secondary stabilizer of the knee under pivot-shift loading. In the absence of stronger evidence, the study data suggest a rationale for surgical repair of lateral meniscal root tears encountered in the setting of ACL tears.

Individualized ACL reconstruction

The pivot shift test is the only physical examination test capable of predicting knee function and osteoarthritis development after an ACL injury. However, because interpretation and performance of the pivot shift are subjective in nature, the validity of the pivot shift is criticized for not providing objective information for a complete surgical planning for the treatment of rotatory knee laxity. The aim of ACL reconstruction was eliminating the pivot shift sign. Many structures and anatomical characteristics can influence the grading of the pivot shift test and are involved in the genesis and magnitude of rotatory instability after an ACL injury. The objective quantification of the pivot shift may be able to categorize knee laxity and provide adequate information on which structures are affected besides the ACL. A new algorithm for rotational instability treatment is presented, accounting for patients' unique anatomical characteristics and objective measurement of the pivot shift sign allowing for an individualized surgical treatment.

LEVEL OF EVIDENCE

V.

Extra-articular ACL Reconstruction and Pivot Shift: In Vivo Dynamic Evaluation With Navigation

BACKGROUND

The pivot-shift test is considered a reliable examination to evaluate the results of anterior cruciate ligament (ACL) reconstruction, as it strongly correlates with patient satisfaction, giving-way episodes, and activity level. The addition of lateral tenodesis (LT) to current techniques of intra-articular reconstruction with a hamstring graft could potentially improve knee laxity in cases of severe rotational instability.

PURPOSE

To biomechanically investigate the effect of intra- and extra-articular ACL reconstructions on knee laxity and the pivot-shift phenomenon.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty patients underwent anatomic single-bundle ACL reconstruction with doubled semitendinosus and gracilis tendons with the addition of extra-articular reconstruction. In patients in group A, intra-articular reconstruction was performed first and LT thereafter; in patients in group B, LT was performed first and intra-articular reconstruction thereafter. A navigator equipped with software designed for both static and dynamic evaluations was used to measure maximum anterior tibial translation (ATT) and axial tibial rotation (ATR) at 30° of flexion (static evaluation) and during the pivot-shift test (dynamic evaluation). Measurements were performed before reconstruction, after the first procedure, and after the second procedure.

RESULTS

For the static evaluation, in group A, the mean ATT significantly decreased from 14.1 ± 3.7 mm in the preoperative (ACL-deficient) condition to 6.0 ± 1.9 mm after ACL reconstruction and to 5.3 ± 1.6 mm after LT. The mean ATR at 30° of knee flexion significantly decreased from 35.7° ± 4.8° to 28.9° ± 4.1° and to 20.9° ± 4.8°, respectively. In group B, the mean ATT significantly decreased from 13.5 ± 6.5 mm in the preoperative (ACL-deficient) condition to 10.2 ± 3.2 mm after LT and to 4.0 ± 1.6 mm after ACL reconstruction. The mean ATR at 30° of knee flexion significantly decreased from 36.7° ± 4.8° to 26.2° ± 6.2° and to 23.5° ± 4.9°, respectively. For the dynamic evaluation (pivot-shift test), in group A, the mean ATT significantly decreased from 15.0 ± 6.8 mm in the preoperative (ACL-deficient) condition to 9.4 ± 6.4 mm after ACL reconstruction and to 8.5 ± 5.4 mm after LT. The mean ATR significantly decreased from 16.9° ± 4.7° to 11.6° ± 4.1° and to 6.1° ± 2.2°, respectively. In group B, the mean ATT significantly decreased from 12.5 ± 3.3 mm in the preoperative (ACL-deficient) condition to 9.1 ± 5.9 mm after LT and to 8.1 ± 5.4 mm after ACL reconstruction. The mean ATR significantly decreased from 16.0° ± 4.5° to 9.2° ± 4.3° and to 7.5° ± 4.0°, respectively.

CONCLUSION/CLINICAL RELEVANCE

Extra-articular reconstruction had little effect in reducing the anterior displacement of the tibia at 30° of flexion, but it was more effective than intra-articular reconstruction in reducing ATR. Anatomic ACL reconstruction and LT were synergic in controlling the pivot-shift phenomenon.

A Preliminary In Vivo Assessment of Anterior Cruciate Ligament-Deficient Knee Kinematics With the KneeM Device: A New Method to Assess Rotatory Laxity Using Open MRI

BACKGROUND

Methods of objectively measuring rotational knee laxity are either experimental or difficult to use in daily practice. A new method has been developed to quantitatively assess rotatory laxity using an open MRI system and new tool, the KneeM device.

PURPOSE/HYPOTHESIS

To perform a preliminary evaluation of a novel knee rotation measurement device to assess knee kinematics during flexion in an MRI field, in both anterior cruciate ligament (ACL)-deficient and healthy contralateral knees. The hypothesis was that the KneeM device would allow in vivo reproduction and analysis of knee kinematics during flexion in healthy and ACL-deficient knees.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten subjects (7 men and 3 women; mean age ± standard deviation, 32.3 ± 9.4 years) with ACL-deficient knees and contralateral uninjured knees participated in the study. An open MRI was performed with the KneeM device at a mean 4.9 months (range, 3.0-7 months) after ACL injury. The device exerted on the knee an anterior drawer force of 100 N, with an internal rotation of 20°, through the range of flexion (0°, 20°, 40°, and 60°). Both ACL-deficient and healthy contralateral knees were analyzed using the Iwaki method.

RESULTS

There was no statistical difference of anterior translation in the medial compartment between intact and ACL-deficient knees at all degrees of flexion. However, significant differences in the anterior translation of the lateral compartment were observed between ACL-deficient and intact contralateral knees at 0° and 20° of flexion (P = .005 and P = .002, respectively). Between 20° and 40°, the lateral plateau of ACL-deficient knees translated 7.7 mm posteriorly, whereas the medial compartment remained stable, reflecting a sudden external rotation of the lateral plateau under the femoral condyle.

CONCLUSION

This preliminary study suggests that measurement of tibiofemoral movements in both compartments during flexion using the KneeM device was useful for quantifying rotatory laxity in ACL-deficient knees. Moreover, this device seemed to allow a "mechanized pivot shift" and allowed reproduction of the "pivot" phase in the MRI field between 20° and 40° of flexion.

CLINICAL RELEVANCE

This device could be used for diagnostic purposes or to investigate the outcomes of ACL reconstructions.

Anatomic and nonanatomic double-bundle anterior cruciate ligament reconstruction: an in vivo kinematic analysis

BACKGROUND

There have been no direct in vivo biomechanical comparisons performed between an anatomic double-bundle (ADB) and a nonanatomic double-bundle (NADB) anterior cruciate ligament (ACL) reconstruction.

HYPOTHESIS

There are differences in kinematic outcomes between ADB and NADB ACL reconstruction techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-six consecutive patients (mean age, 30 years; range, 18-32 years; 23 men, 3 women; 17 right knees, 9 left knees) with an isolated ACL injury were included in the study. The first 13 consecutive patients underwent NADB reconstruction (combination of a single-bundle and an over-the-top reconstruction), and the following 13 consecutive patients were treated with an ADB approach (using 2 tibial tunnels and 2 femoral tunnels placed in the center of the native femoral and tibial insertion sites). Grafts were pretensioned at 80 N and secured with cortical fixation systems under manual maximum force tension. Standard clinical laxity and pivot-shift tests were quantified at time zero before and after ACL reconstruction by means of a surgical navigation system dedicated to kinematic assessment; displacement of the medial and lateral compartments during the tests was also analyzed.

RESULTS

The ADB-reconstructed knees showed a larger preoperative-to-postoperative difference in anterior-posterior tibial plateau displacement of the medial and lateral compartments when compared with the NADB-reconstructed knees during the internal-external rotation test at 30° of flexion (P < .050). No other significant differences in laxity or pivot-shift values were noted. The mean surgical time for ADB reconstruction was significantly higher than that for NABD reconstruction (62 ± 13 and 43 ± 10 minutes, respectively; P < .0001).

CONCLUSION

Results showed a greater anterior-posterior translation of both compartments during the rotational passive laxity test in the ADB reconstruction group or overconstraint caused by the NADB technique. The 2 analyzed double-bundle ACL reconstructions did not show any significant quantitative difference in isolated anterior-posterior laxity and pivot-shift phenomenon at time zero.

CLINICAL RELEVANCE

Nonanatomic double-bundle ACL reconstruction can control anterior-posterior laxity and the pivot-shift phenomenon as well as ABD ACL reconstruction.

Biomechanical characteristics of 3 pivot-shift maneuvers for the anterior cruciate ligament-deficient knee: in vivo evaluation with an electromagnetic sensor system

BACKGROUND

A disadvantage of pivot-shift maneuvers is that the examiner has to subjectively evaluate the degree of pivot shift observed. It is unknown whether the various maneuvers are biomechanically identical.

PURPOSE

To compare biomechanical features of 3 clinical maneuvers for the anterior cruciate ligament (ACL)-deficient knee: the pivot-shift test, the jerk test, and the N-test.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 28 patients with an isolated ACL injury were examined by use of 3 pivot-shift maneuvers (pivot-shift test, jerk test, and N-test). An electromagnetic sensor system was used to evaluate the 3-dimensional knee kinematics of each patient's injured and uninjured knees during each maneuver. Peak coupled anterior tibial translation (pCAT) and maximal acceleration of posterior translation (APT) were measured relative to results during a flexion-extension motion in each test.

RESULTS

The pCAT of the pivot-shift test was significantly greater than that of both the jerk test and the N-test (P = .0020 and P < .0001, respectively); there was no statistical difference in pCAT between the jerk test and the N-test. The APT of the N-test was significantly greater than that of both the pivot-shift test and the jerk test (P < .0001), while there was no statistical difference between the pivot-shift and the jerk tests. There was no correlation between pCAT and APT in each test.

CONCLUSION

The pivot-shift test, jerk test, and N-test have different biomechanical characteristics to induce the pivot-shift phenomenon in the ACL-deficient knee. The pivot-shift test produced the largest side-to-side difference in pCAT, whereas the N-test provoked the largest side-to-side difference in APT.

CLINICAL RELEVANCE

The biomechanical differences in pivot-shift maneuvers are caused by technical differences, and clinicians should understand these biomechanical differences while practicing the maneuvers. The electromagnetic sensor system is clinically useful for quantifying the pivot-shift phenomenon.

Anterior cruciate ligament reconstruction with 4-strand hamstring autograft and accelerated rehabilitation: a 10-year prospective study on clinical results, knee osteoarthritis and its predictors

PURPOSE

Analysis of long-term clinical and radiological outcomes after anterior cruciate ligament (ACL) reconstruction with special attention to knee osteoarthritis and its predictors.

METHODS

A prospective, consecutive case series of 100 patients. Arthroscopic transtibial ACL reconstruction was performed using 4-strand hamstring tendon autografts with a standardized accelerated rehabilitation protocol. Analysis was performed preoperatively and 10 years postoperatively. Clinical examination included Lysholm and Tegner scores, IKDC, KT-1000 testing (MEDmetric Co., San Diego, CA, USA) and leg circumference measurements. Radiological evaluation included AP weight bearing, lateral knee, Rosenberg and sky view X-rays. Radiological classifications were according to Ahlbäck and Kellgren & Lawrence. Statistical analysis included univariate and multivariate logistic regressions. RESULTS CLINICAL OUTCOME: A significant improvement (p < 0.001) between preoperative and postoperative measurements could be demonstrated for the Lysholm and Tegner scores, IKDC patient subjective assessment, KT-1000 measurements, pivot shift test, IKDC score and one-leg hop test. A pivot shift phenomenon (glide) was still present in 43 (50%) patients and correlated with lower levels of activity (p < 0.022). Radiological outcome: At follow-up, 46 (53.5%) patients had signs of osteoarthritis (OA). In this group, 33 patients (72%) had chondral lesions (≥grade 2) at the time of ACL reconstruction. A history of medial meniscectomy before or at the time of ACL reconstruction increased the risk of knee OA 4 times (95% CI 1.41-11.5). An ICRS grade 3 at the time of ACL reconstruction increased the risk of knee OA by 5.2 times (95% CI 1.09-24.8). There was no correlation between OA and activity level (Tegner score ≥6) nor between OA and a positive pivot shift test.

CONCLUSION

Transtibial ACL reconstruction with 4-strand hamstring autograft and accelerated rehabilitation restored anteroposterior knee stability. Clinical parameters and patient satisfaction improved significantly. At 10-year follow-up, radiological signs of OA were present in 53.5 % of the subjects. Risk factors for OA were meniscectomy prior to or at the time of ACL reconstruction and chondral lesions at the time of ACL reconstruction.

LEVEL OF EVIDENCE

II.

The loss of extension test (LOE test): a new clinical sign for the anterior cruciate ligament insufficient knee

Background

This prospective study was created to evaluate the reliability of a new clinical test, which we termed the “loss of extension test” (LOE test). The LOE test investigates the loss of normal maximum passive extension (MPE) of the knee due to an anterior cruciate ligament tear in comparison to the normal MPE of the healthy knee.

Materials and methods

The study was divided into two consecutive parts. Part 1 was designed to assess the side-to-side difference in normal MPE in a healthy population. In part 1, 100 healthy adults were enrolled. Part 2 was designed to evaluate the LOE test reliability in injured knees. In part 2, we included 196 selected patients.

Results

In part 1, the average side-to-side difference in MPE in the healthy population was not statistically significant. In part 2, the overall average side-to-side difference in MPE of the injured group was 10.1 mm ± 14.1 (min −20; max 60), which was not statistically significant (p = 0.52). An anterior cruciate ligament (ACL) tear was found in 121 knees among 196 patients. The average side-to-side difference in MPE in the ACL-insufficient group was 16.9 mm ± 13.4 (min −20; max 60), which was statistically significant (p < 0.0001). The accuracy of the loss of extension test was 83.7 %, its specificity was 93.3 %, its sensitivity was 77.7 %, its positive predictive value was 95 %, and its negative predictive value was 72.2 %.

Conclusions

The reliability of the LOE test is comparable to those reported in the literature for the Lachman test and dynamic tests, so the LOE test could represent a useful tool for the diagnosis of the anterior cruciate ligament insufficient knee.

Quantitative evaluation of the pivot shift by image analysis using the iPad

PURPOSE

To enable comparison of test results, a widely available measurement system for the pivot shift test is needed. Simple image analysis of lateral knee joint translation is one such system that can be installed on a prevalent computer tablet (e.g. iPad). The purpose of this study was to test a novel iPad application to detect the pivot shift. It was hypothesized that the abnormal lateral translation in ACL deficient knees would be detected by the iPad application.

METHODS

Thirty-four consecutive ACL deficient patients were tested. Three skin markers were attached on the following bony landmarks: (1) Gerdy's tubercle, (2) fibular head and (3) lateral epicondyle. A standardized pivot shift test was performed under anaesthesia, while the lateral side of the knee joint was monitored. The recorded movie was processed by the iPad application to measure the lateral translation of the knee joint. Lateral translation was compared between knees with different pivot shift grades.

RESULTS

Valid data sets were obtained in 20 (59 %) ACL deficient knees. The remaining 14 data sets were invalid because of failure to detect translation or detection of excessive translation. ACL deficient knees had larger lateral translation than the contra-lateral knees (p < 0.01). In the 20 valid data sets, which were graded as either grade 1 (n = 10) or grade 2 (n = 10), lateral translation was significantly larger in the grade 2 pivot shift (3.6 ± 1.2 mm) than the grade 1 pivot shift (2.7 ± 0.6 mm, p < 0.05).

CONCLUSION

Although some technical corrections, such as testing manoeuvre and recording procedure, are needed to improve the image data sampling using the iPad application, the potential of the iPad application to classify the pivot shift was demonstrated.

Variability in knee laxity in anterior cruciate ligament deficiency using a mechanized model

PURPOSE

To establish normative values for the magnitude of anterior tibial translation (ATT) in the Lachman and pivot shift tests in the intact and anterior cruciate ligament (ACL)-deficient states, and to explore whether a correlation in ATT magnitude exists between the Lachman and pivot shift tests.

METHODS

Twenty-six fresh frozen cadaveric hip-to-toe specimens were used. Mechanized testing was performed to simulate both a Lachman and pivot shift test with the ACL intact. Tests were repeated after sectioning the ACL. ATT was recorded using a computer navigation system. Difference in ATT after sectioning was calculated for each specimen.

RESULTS

For the Lachman, mean lateral compartment ATT in the intact knee was 5.3 mm (SD = 2.8 mm). After sectioning the ACL, translation increased to 11.4 mm (SD = 3.9 mm; P < 0.05). For the mechanized pivot shift, mean lateral compartment ATT in the intact knee was -0.2 mm (SD = 2.6 mm). After sectioning the ACL, translation increased to 8.2 mm (SD = 3.1 mm; P < 0.05). No correlation in the magnitude of ATT was found between the intact and ACL-deficient knees for either the Lachman or pivot shift tests, or between both tests (Cronbach's α < 0.7).

CONCLUSIONS

No correlation was found between the Lachman and pivot shift test in both the intact and ACL-deficient knee. This suggests that the Lachman cannot be used as a surrogate for the pivot shift as the magnitude of the Lachman did not predict the magnitude of the pivot shift.

Quantifying the pivot shift test: a systematic review

PURPOSE

This study aims to identify and summarize the evidence on the biomechanical parameters and the corresponding technologies which have been used to quantify the pivot shift test during the clinical and functional assessment of anterior cruciate ligament (ACL) injury and surgical reconstruction.

METHODS

Search strategy Internet search of indexed scientific articles on the PubMed database, Web of Science and references on published manuscripts. No year restriction was used. Selection criteria Articles included were written only in English and related to search terms: "pivot shift" AND (OR "ACL"). The reviewers independently selected only those studies that included at least one quantitative parameter for the analysis of the pivot shift test, including both in vitro and in vivo analyses performed on human joint. Those studies that analysed only clinical grading were excluded from the analysis. Analysis After evaluating the methodological quality of the articles, the parameters found were summarized.

RESULTS

Six hundred and eight studies met the inclusion criteria, and finally, 68 unique studies were available for the systematic review. Quantitative results were heterogeneous. The pivot shift test has been quantified by means of 25 parameters, but most of the studies focused on anterior-posterior translations, internal-external rotation and acceleration in anterior-posterior direction.

CONCLUSION

Several methodologies have been identified and developed to quantify pivot shift test. However, clinical professionals are still lacking a 'gold standard' method for the quantification of knee joint dynamic laxity. A widespread adoption of a standardized pivot shift manoeuvre and measurement method to allow objective comparison of the results of ACL reconstructions is therefore desirable. Further development of measurement methods is indeed required to achieve this goal in a routine clinical scenario.

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.

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

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

Effect of tibial slope on the stability of the anterior cruciate ligament-deficient knee

PURPOSE

We aimed to quantify the effect of changes in tibial slope on the magnitude of anterior tibial translation (ATT) in the anterior cruciate ligament (ACL)-deficient knee during the Lachman and mechanized pivot shift tests. We hypothesized that increased posterior tibial slope would increase the amount of ATT of an ACL-deficient knee, while leveling the slope of the tibial plateau would decrease the amount of ATT.

METHODS

Lachman and mechanized pivot shift tests were performed on hip-to-toe cadaveric specimens, and ATT of the lateral and the medial compartments was measured using navigation (n = 11). The ACL was then sectioned. Stability testing was repeated, and ATT was recorded. A proximal tibial osteotomy in the sagittal plane was then performed achieving either +5 or -5° of tibial slope variation after which stability testing was repeated (n = 10).

RESULTS

Sectioning the ACL resulted in a significant increase in ATT in both the Lachman and mechanized pivot shift tests (P < 0.05). Increasing or decreasing the slope of the tibial plateau had no effect on ATT during the Lachman test (n.s.). During the mechanized pivot shift tests, a 5° increase in posterior slope resulted in a significant increase in ATT compared to the native knee (P < 0.05), while a 5° decrease in slope reduced ATT to a level similar to that of the intact knee.

CONCLUSIONS

Tibial slope changes did not affect the magnitude of translation during a Lachman test. However, large changes in tibial slope variation affected the magnitude of the pivot shift.

Femoral press-fit fixation in ACL reconstruction using bone-patellar tendon-bone autograft: results at 15 years follow-up

Background

If anterior cruciate ligament (ACL) reconstruction is to be performed, decision regarding graft choice and its fixation remains one of the most controversial. Multiple techniques for ACL reconstruction are available. To avoid disadvantages related to fixation devices, a hardware-free, press-fit ACL reconstruction technique was developed.

The aim of this study was to evaluate clinical outcome and osteoarthritis progression in long term after ACL reconstruction with central third patellar-tendon autograft fixed to femur by press-fit technique.

Methods

Fifty two patients met inclusion/excusion criteria for this study. The patients were assessed preoperatively and at 15 years after surgery with International Knee Documentation Committee Knee Ligament Evaluation Form, Lysholm knee score, Tegner activity scale and radiographs.

Results

Good overall clinical outcomes and self-reported assessments were documented, and remained good at 15 years. The mean Lysholm and Tegner scores improved from 59.7 ± 18.5 and 4.2 ± 1.0 preoperatively to 86.4 ± 5.6 (p = 0.004) and 6.9 ± 1.4 (p = 0.005) respectively at follow-up. The IKDC subjective score improved from 60.1 ± 9.2 to 80.2 ± 8.1 (p = 0.003).

According to IKDC objective score, 75% of patients had normal or nearly normal knee joints at follow-up. Grade 0 or 1 results were seen in 85% of patients on laxity testing. Degenerative changes were found in 67% of patients. There was no correlation between arthritic changes and stability of knee and subjective evaluation (p > 0.05).

Conclusions

ACL reconstruction with patellar tendon autograft fixed to femur with press-fit technique allows to achieve good self-reported assessments and clinical ligament evaluation up to 15 years. Advantages of the bone-patellar-tendon-bone (BPTB) press-fit fixation include unlimited bone-to-bone healing, cost effectiveness, avoidance of disadvantages associated with hardware, and ease for revision surgery. BPTB femoral press-fit fixation technique can be safely applied in clinical practice and enables patients to return to preinjury activities including high-risk sports.

Clinical grading of the pivot shift test correlates best with tibial acceleration

PURPOSE

Recently, different measurement systems have been developed to quantitatively measure the pivot shift in vivo. These systems lack validation and a large inter-examiner variability for the manually performed pivot shift test exists. The purpose of this study was to perform objective measurements of the pivot shift using three different measurement devices and to examine the correlation of the measurements with clinical grading of the pivot shift.

METHODS

A cadaver knee on a whole lower body specimen was prepared to display a high-grade pivot shift. The pivot shift tests were performed three times by 12 blinded expert surgeons using their preferred technique. Simultaneous data samplings were recorded using three different measurement devices: (1) electromagnetic tracking system using bone-attached and skin-fixed sensors, respectively, (2) triaxial accelerometer system, and (3) simple image analysis. The surgeons graded the knee clinically using pivot shift grades I-III. Correlations were calculated using the Spearman's rank correlation coefficient.

RESULTS

The expert surgeons average clinical grading was 2.3 (SD ± 0.5). Clinical grading displayed best correlation with the acceleration of reduction as measured by electromagnetic tracking system with bone-attached sensors (r = 0.67, P < 0.05). Similar correlation coefficient was found for the acceleration of reduction (r = 0.58, P = 0.05) and the "jerk" component of acceleration (r = 0.61, P < 0.05) measured by means of the triaxial accelerometer system.

CONCLUSION

The pivot shift can be quantified by several in vivo measurement devices. Best correlation with clinical grading was found with tibial acceleration parameters. Future studies will have to analyze how quantitative parameters can be utilized to standardize clinical grading of the pivot shift.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

Quantitative assessment of pivot-shift using inertial sensors

PURPOSE

The pivot-shift phenomenon has been identified to be one of the essential signs of functional anterior cruciate ligament (ACL) insufficiency. However, the pivot-shift test remains a surgeon-subjective examination, lacking a general recognized quantitative measurement. The goal of the present study was to validate the use of an inertial sensor for quantifying the pivot-shift test, using a commercial navigation system.

METHODS

An expert surgeon intra-operatively performed the pivot-shift test on 15 consecutive patients before ACL reconstruction. A single accelerometer and a commercial navigation system simultaneously acquired limb kinematics. An additional optical tracker mounted on the accelerometer allowed following sensor movements. Anteroposterior (a-p) tibial acceleration obtained with the navigation system was compared with three-dimensional (3D) acceleration acquired by the accelerometer. The effect of skin artifacts and test-retest positioning were estimated. Repeatability of the acceleration parameter and waveform was analyzed. Correlation between the two measurements was also assessed.

RESULTS

Average root mean square (RMS) error in test-retest positioning reported a good value of 5.5 ± 2.9 mm. Mean RMS displacement due to soft tissue artifacts was 4.9 ± 2.6 mm. The analysis of acceleration range repetitions reported a good intra-tester repeatability (Cronbach's alpha = 0.86). Inter-patients similarity analysis showed a mean acceleration waveform correlation of 0.88 ± 0.14. The acceleration ranges demonstrated a good positive correlation between the two measurements (rs = 0.72, P < 0.05).

CONCLUSION

This study showed good reliability of the new device and good correlation with the navigation system results. Therefore, the accelerometer is a valid method to assess dynamic joint laxity.

LEVEL OF EVIDENCE

II.

Can the pivot-shift be eliminated by anatomic double-bundle anterior cruciate ligament reconstruction?

PURPOSE

To assess the ability of anatomic double-bundle anterior cruciate ligament reconstruction in eliminating the pivot-shift phenomenon when identified by a quantitative measuring system (computer navigation or magnetic resonance imaging).

METHODS

Literature review. Medline, Google Scholar and Cochrane Reviews computerized databases research using the keywords "pivot-shift," "anterior cruciate ligament reconstruction" and "double bundle." Twelve (7 in vitro and 5 in vivo) studies met the inclusion criteria.

RESULTS

There was a wide variation in the absolute value of translation and rotation measured after anatomic double-bundle anterior cruciate ligament reconstruction. There were also differences in fixation methods, pivot-shift execution conditions, applied stresses during the pivot-shift, calculation methods and reference systems utilized by measurement systems.

CONCLUSIONS

The double-bundle reconstruction was shown to over-constrain the knee with respect to the intact value, especially closer to knee extension. This review demonstrated that anatomic double-bundle anterior cruciate ligament reconstruction is able to eliminate pathological translations and rotations during the pivot-shift phenomenon, as identified by quantitative measurement systems.

LEVEL OF EVIDENCE

Review of Level III studies, Level III.

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.

What does it take to have a high-grade pivot shift?

The pivot shift is the most specific clinical test to assess pathological knee joint rotatory laxity following ACL injury. This article attempts to describe the anatomic structures responsible for creating a high-grade pivot shift and their potential role in customizing ACL reconstruction. A review of the literature demonstrates that disruption of the secondary stabilizers of anterior translation of the lateral compartment including the lateral meniscus, anterolateral capsule, and IT band contributes to a high-grade pivot shift in the ACL-deficient knee. The morphology of the lateral tibial plateau, including increased posteroinferior tibial slope and small size, can also contribute to high-grade pivot shift. Factors that may decrease the grade of the pivot shift include medial compartment injury, MCL injury, patient guarding, and osteoarthritis. In conclusion, a high-grade pivot shift in the ACL-deficient knee is often associated with incompetence of the lateral soft tissue envelope. Rotatory laxity as assessed by the pivot shift may also be falsely underestimated by concomitant injuries.

LEVEL OF EVIDENCE

IV.

Quantitative measurement of the pivot shift, reliability, and clinical applications

Static load-displacement measurement is unrelated to the dynamic knee function of anterior cruciate ligament (ACL) insufficiency. Performing an accurate, dynamic functional evaluation is necessary not only for the primary ACL injury, but also as an outcome measurement in ACL reconstruction. The pivot shift test is commonly used for assessing dynamic rotatory knee laxity in ACL-insufficient knees and is related to subjective knee function. Residual pivot shift after ACL reconstruction is a crucial factor related to poor clinical outcome. However, the pivot shift test is subjectively determined by the examiners' hands. Not only 3-dimensional (3D) position displacement but also its 3D acceleration should be measured for quantitative evaluation of the pivot shift test and is currently feasible by using recent advanced technology, i.e., electromagnetic devices. We summarize the basic knowledge and current concepts of quantitative exploration of the dynamic knee movement during the pivot shift test.

Anatomic double-bundle and over-the-top single-bundle with additional extra-articular tenodesis: an in vivo quantitative assessment of knee laxity in two different ACL reconstructions

PURPOSE

Combinations of intra- and extra-articular procedures have been proposed for anterior cruciate ligament reconstruction with the aim of achieving an optimal control of translational and rotational knee laxities. Recently, the need for better reproducing the structural and functional behavior of the native anterior cruciate ligament led to the definition of anatomic double-bundle surgical approach. This study aimed to quantitatively verify whether the in vivo static and dynamic behavior obtained using over-the-top single-bundle with extra-articular tenodesis reconstruction was comparable to the results achieved by anatomic double-bundle approach.

METHODS

Thirty-five consecutive patients, with an isolated anterior cruciate ligament injury, were included in the study. Standard clinical laxities and pivot-shift test were quantified before and after anterior cruciate ligament reconstruction by means of a surgical navigation system dedicated to kinematic assessment; displacements of medial and lateral compartment during stress tests were also analyzed.

RESULTS

Single-bundle with extra-articular tenodesis approach presented statistically better laxity reduction in varus/valgus stress test at full extension and in internal/external rotation at 90° of flexion; lateral plasty controlled better the lateral compartment during drawer test and varus/valgus stress test both at 0° and 30° of flexion and both the compartments during internal/external rotation at 90° of flexion. On the other hand, pivot-shift phenomenon was better controlled by anatomic double-bundle reconstruction.

CONCLUSIONS

Both the reconstructions worked similarly for static knee laxity. The extra-articular procedure played an important role in better constraining the displacement of lateral tibial compartment, whereas the anatomic double-bundle reconstruction better restored the dynamic behavior of knee joint highlighted under pivot-shift stress test.

STUDY DESIGN

Case series.

Similarities and differences of diagnostic manual tests for anterior cruciate ligament insufficiency: a global survey and kinematics assessment

BACKGROUND

The Lachman and pivot-shift tests are 2 standard manual tests to diagnose anterior cruciate ligament (ACL) insufficiency. However, the global variation of these testing procedures is not known.

PURPOSE

To survey currently used testing techniques and to measure the knee movement during manual tests among various expert surgeons from across the globe.

STUDY DESIGN

Controlled laboratory study.

METHODS

Part 1: descriptive survey. A questionnaire asking about testing procedures of Lachman and pivot-shift tests was conducted among 33 ACL surgeons. Part 2: knee kinematics comparison. Lachman and pivot-shift tests were performed on a unilateral ACL-injured patient by 5 surgeons, while knee kinematics was recorded by an electromagnetic system. Tibial translation was measured during the Lachman test, while tibial translation, rotation, and pivot-shift acceleration were calculated during the pivot-shift test.

RESULTS

Part 1: Tibial anterior drawer by a medially placed hand was widely advocated for the Lachman test. Flexion type of the pivot-shift test maneuver was supported by two thirds, while extension type was supported by one third. However, the "feeling" of subluxation or reduction during the pivot shift was the primary evaluation method used by the vast majority of surgeons. Part 2: Increased tibial translation during the Lachman test was observed in the ACL-injured knee with significant variation between examiners (P < .01). Tibial translation and pivot-shift acceleration during the pivot-shift test increased in the ACL-injured side (P < .01), but tibial rotation was too diverse to find any trend (P = .31). Tibial translation and acceleration of the pivot shift in the ACL-injured knee showed no significant difference between examiners (P > .05).

CONCLUSION

The Lachman test can display a wide variation of actual movement despite maneuver similarity, while the pivot-shift test could possibly be measurable by tibial translation and/or acceleration beyond their procedural variation.

CLINICAL RELEVANCE

We should recognize the limitations of these manual tests and the possibilities of their objective measurement.

An original clinical methodology for non-invasive assessment of pivot-shift test

Even if pivot-shift (PS) test has been clinically used to specifically detect anterior cruciate ligament (ACL) injury, the main problem in using this combined test has been yet associated with the difficulty of clearly quantifying its outcome. The goal of this study was to describe an original non-invasive methodology used to quantify PS test, highlighting its possible clinical reliability. The method was validated on 66 consecutive unilateral ACL-injured patients. A commercial triaxial accelerometer was non-invasively mounted on patient's tibia, the corresponding 3D acceleration was acquired during PS test execution and a set of specific parameters were automatically identified on the signal to quantify the test. PS test was repeated three times on both injured and controlateral limbs. Reliability of the method was found to be good (mean intra-rater intraclass correlation coefficient was 0.79); moreover, we found that ACL-deficient knees presented statistically higher values for the identified parameters--than the controlateral healthy limbs, averagely reporting also large effect size.

In vitro and intraoperative laxities after single-bundle and double-bundle anterior cruciate ligament reconstructions

PURPOSE

The purpose of this study was to objectively evaluate whether double-bundle anterior cruciate ligament (ACL) reconstruction can better restore the normal translational and rotational laxities than the conventional single-bundle ACL reconstruction among the reported biomechanical studies.

METHODS

A systematic literature search was conducted to identify in vitro and in vivo (intraoperative) biomechanical studies that compared the laxities (anterior or anteroposterior or rotational) between single- and double-bundle ACL reconstructions. Because of large variability among the loading conditions and testing methods used to determine the rotational laxities among the studies, a meta-analysis of rotational laxities was not feasible.

RESULTS

Seven in vitro and three in vivo studies were included in this analysis based on the predefined inclusion criteria. The overall mean differences calculated by the random effects model in anteroposterior laxity between the single-bundle and double-bundle ACL reconstruction techniques at 0°, 30°, 60°, and 90° of flexion were 0.99 mm, 0.38 mm, 0.34 mm, and 0.07 mm, respectively. No statistically significant difference was noted between the 2 treatments at all flexion angles. Among the 9 studies that compared the rotational laxity of single-bundle and double-bundle ACL reconstructions, 4 reported that double-bundle reconstruction can provide better rotational control than single-bundle reconstruction. The other 5 studies could not identify any significant difference between the 2 reconstructions in terms of rotational laxity.

CONCLUSIONS

Both single- and double-bundle treatment options for ACL injury result in similar anteroposterior knee joint laxity at time 0. No conclusive evidence on the superiority of 1 reconstruction technique over the other in terms of rotation laxity can be obtained because of several variations in the experimental protocol and the kinematics used to measure the rotational laxity among the studies.

LEVEL OF EVIDENCE

Level III, meta-analysis.

A mechanized and standardized pivot shifter: technical description and first evaluation

PURPOSE

The pivot shift test (PST) is a complex, multiplanar maneuver used to assess rotatory instability of the knee. The grading is subjective due to the broad range of examination techniques and lack of tibiofemoral motion quantification. The goal of this study was to develop and evaluate a mechanized device for quantitative assessment of the PST.

METHODS

We constructed a mechanized pivot shifter (MPS). In five cadaveric hip-to-toes specimens, the anterior cruciate ligament was resected. We used a surgical navigation system for acquisition of the tibiofemoral motion path during the PST. Two sets of measurements were obtained for the MPS and for two examiners performing the manual technique.

RESULTS

Mean lateral compartment translation magnitudes for each MPS measurement were 13.5 mm (σ = 6.7) and 13.6 mm (σ = 6.7). For examiner 1, 14.9 mm (σ = 6.5) and 15.7 mm (σ = 6.3). For examiner 2, 16.9 mm (σ = 6.3) and 16.1 mm (σ = 5.2). Differences were not significant (n.s.). The MPS had narrower limits of agreement than both examiner 1 and examiner 2.

CONCLUSION

The MPS demonstrated no significant differences in the tibiofemoral translation magnitudes compared to the manual technique. It resulted in better test-retest reliability and more consistent measurements of tibiofemoral translation when compared to manual PST. The high repeatability factor conferred by the MPS is a clinical advantage.

Accounting for velocity of the pivot shift test manoeuvre decreases kinematic variability

The pivot shift test is the only clinical test which correlates with knee function following rupture of the ACL. A grade is given to the pivot shift in a subjective manner, leading to efforts to quantify the bone movements and correlate them to the grade. However, the dynamic and unconstrained nature of the manoeuvre introduces important kinematic variability. Our main objective was to develop a method to lessen the variability attributable to clinician technique, therefore increasing inter-grade differences. Three different orthopaedic surgeons each performed the pivot shift test on 12 subjects. Knee joint kinematics were recorded using electromagnetic motion capture devices. Inter-clinician variability was quantified and a method was developed to diminish it, using the angular velocity of flexion. This method was then applied to a larger population composed of 127 knees with various degrees of instability, evaluated by one of eight different orthopaedic surgeons. The clinical grades given by the clinicians were in almost perfect agreement (kappa=0.83). Normalization of kinematic parameters using the angular velocity of knee joint flexion produced by the clinicians reduced the intra-clinician variability by 20%, resulting in an intra-class correlation coefficient (ICC) of 0.52, up from 0.41 before normalization. This allowed for more significant differences between the grades of pivot shift. Simple normalisation of pivot shift kinematics using the angular velocity of flexion reduces clinician-related variability and allows for significant differences between the different grades. These results are an important step towards developing an objective measurement tool for the pivot shift phenomenon.

Reconstructive versus non-reconstructive treatment of anterior cruciate ligament insufficiency. A retrospective matched-pair long-term follow-up

In this retrospective case series 80 patients divided in 40 matched pair groups with an arthroscopically proven ACL insufficiency were followed up for 15 years. One half was reconstructed using an autologous BTB patella graft, the other half was treated by a conservative physiotherapeutic based rehabilitation program. At follow-up the clinical scores (Lysholm, IKDC) showed no significant differences between subjects who had undergone ACL reconstruction and those who had not. Furthermore there was no detectable difference in the incidence of osteoarthritis between the cohorts. Patients having a negative pivot shift test showed significantly less signs of radiographic osteoarthritis and better functional assessment scores whether reconstructed or not. Based on these results and a review of the literature there is no clear evidence that ACL reconstruction reduces the rate of OA development or improves the long-term symptomatic outcome. Probably review of reconstruction by an anatomical approach will be more successful than operative techniques decades ago.

Comparison between clinical grading and navigation data of knee laxity in ACL-deficient knees

Background

The latest version of the navigation system for anterior cruciate ligament (ACL) reconstruction has the supplementary ability to assess knee stability before and after ACL reconstruction. In this study, we compared navigation data between clinical grades in ACL-deficient knees and also analyzed correlation between clinical grading and navigation data.

Methods

150 ACL deficient knees that received primary ACL reconstruction using an image-free navigation system were included. For clinical evaluation, the Lachman, anterior drawer, and pivot shift tests were performed under general anesthesia and were graded by an examiner. For the assessment of knee stability using the navigation system, manual tests were performed again before ACL reconstruction. Navigation data were recorded as anteroposterior (AP) displacement of the tibia for the Lachman and anterior drawer tests, and both AP displacement and tibial rotation for the pivot shift test.

Results

Navigation data of each clinical grade were as follows; Lachman test grade 1+: 10.0 mm, grade 2+: 13.2 ± 3.1 mm, grade 3+: 14.5 ± 3.3 mm, anterior drawer test grade 1+: 6.8 ± 1.4 mm, grade 2+: 7.4 ± 1.8 mm, grade 3+: 9.1 ± 2.3 mm, pivot shift test grade 1+: 3.9 ± 1.8 mm/21.5° ± 7.8°, grade 2+: 4.8 ± 2.1 mm/21.8° ± 7.1°, and grade 3+: 6.0 ± 3.2 mm/21.1° ± 7.1°. There were positive correlations between clinical grading and AP displacement in the Lachman, and anterior drawer tests. Although positive correlations between clinical grading and AP displacement in pivot shift test were found, there were no correlations between clinical grading and tibial rotation in pivot shift test.

Conclusions

In response to AP force, the navigation system can provide the surgeon with correct objective data for knee laxity in ACL deficient knees. During the pivot shift test, physicians may grade according to the displacement of the tibia, rather than rotation.

Pivot-shift test: analysis and quantification of knee laxity parameters using a navigation system

Lachman, drawer, and pivot-shift (PS) tests are important in the assessment of ACL reconstruction. The goal of this work was to analyze the reliability of the PS test using a navigation system, identifying a set of new quantitative parameters and evaluating their clinical relevance. Eighteen patients that underwent anatomic double-bundle ACL reconstruction were included. The new dynamic parameters were: anteroposterior translation of the medial and lateral compartments and the joint center and internal/external and varus/valgus rotations of the joint. For each parameter we measured the peaks and the areas obtained during the test. Intratester repeatability, comparisons of pre- and postoperative laxities, and correlations between the PS peaks and the corresponding peaks obtained with standard static tests were evaluated. Areas, peaks, and static laxity outcomes were compared, grouping patients according to the preoperative International Knee Documentation Committee (IKDC) score. The PS test was reliable in identifying the surgical reconstruction. Correlation analysis showed good coefficients both for pre- and postoperative values. Patients with IKDC grade "D" had larger areas during the PS compared to patients with grade "C". Our analysis is helpful for characterizing patient-specific laxity and surgical performance, thus highlighting the clinical relevance of the PS test.

Assessment of the antero-posterior and rotational stability of the anterior cruciate ligament analogue in a guided motion bi-cruciate stabilized total knee arthroplasty

Abnormal knee kinematics and sagittal instability after most knee replacements are due in part to deficient anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) function. The guided motion bi-cruciate stabilized knee replacement aspires to stabilize the knee posteriorly and anteriorly by means of a cam-post mechanism. This investigation studies the ACL-stabilizing function of that mechanism in early flexion, and 25 knees that had undergone replacement with this implant were studied. Antero-posterior laxity at 15 degrees flexion was adequately restored for 76% (16/21) of the knees (side-to-side difference <3 mm on KT assessment), and 72% (18/25) knees exhibited a positive pivot shift test. The findings of this study suggest excellent early clinical outcomes for this implant, but the goal of replicating ACL function has only been partially achieved.

Unlocking the 'pivot shift' in ACL surgery: medial meniscus evaluation and treatment

Meniscal injury commonly occurs in conjunction with anterior cruciate ligament (ACL) disruption. Failure to recognize and treat these injuries may lead to less than ideal outcomes in ACL reconstruction. With their unique anatomical location, often at the peripheral rim of the posterior horn of the medial meniscus, the instability pattern of ACL deficiency may contribute to failure of injury recognition. Standard anterior viewing portals do not allow adequate visualization of a large portion of the posterior horn of the medial meniscus. Alternative viewing techniques, such as an accessory posteromedial arthroscopy portal or the Gillquist maneuver, may improve visualization of the posteromedial compartment, but require additional surgery and/or equipment. The pattern of instability inherent to ACL deficiency, or the "pivot shift," occurs when the surgeon attempts to visualize the posteromedial compartment with full extension of the knee and a valgus load. The knee "pivots" as the lateral tibial plateau anteriorly subluxes and rotates around the tibial spines. This rotation and subluxation closes down the posteromedial compartment and blocks visualization. A simple maneuver helps to eliminate this pathologic motion, or "unlock the pivot." During attempted visualization of the medial meniscus, the leg is held in mild flexion (207) with a valgus moment on the knee. While this position is held, the surgical assistant externally rotates the lower leg about the knee axis as the knee is extended and valgus is applied. This maneuver increases the surgeon's viewing area of the posteromedial compartment, which may decrease the need for accessory portals and additional equipment in the ACL deficient knee.

The pivot shift

The Lachman and the pivot shift are the two clinical tests most commonly used to assess instability in the anterior cruciate ligament (ACL)-deficient knee. Because it is quantifiable, the Lachman test has become the benchmark for assessing the success of ACL reconstruction. As a result, surgical techniques have been developed that effectively eliminate anterior laxity of the knee. Recent studies have shown, however, that rotational stability is not always restored after ACL reconstruction. Furthermore, there is mounting evidence that the pivot shift examination correlates with functional instability and patient outcomes better than does any other physical examination test. This test attempts to reproduce the functional combined rotary and translational instability in the ACL-deficient knee. Although the pathologic kinematics of the pivot shift are difficult to measure, recent technological advances have allowed more accurate and objective descriptions of the pivot shift, which have furthered our understanding of the complex motions involved. These advances may lead to a method of quantifying the pivot shift for research purposes and, ultimately, to ACL reconstruction that is tailored specifically to each patient's objectively measured rotational instability.

Contributory factors to the results of gravity-assisted pivot-shift test for anterior cruciate ligament injury: the significance of muscle torque around the knee

Gravity-assisted pivot-shift (GAPS) test is a newly advocated test for anterior cruciate ligament (ACL) injury. It induces anterolateral rotatory instability with valgus stress to the knee applied by gravitational force during patient's active knee motion. We investigated prospectively the relationships between the results of the GAPS test and the possible contributory factors and sought to clarify the determinant factors of the GAPS test. A total of 54 knee joints of 54 patients with unilateral ACL injury (29 males, 25 females, average 23.4 +/- 9.0 years old) were enrolled in this study and were divided into two groups, i.e., positive GAPS test group and negative GAPS test group. Muscle torque around the knee joints measured before surgery, configuration of the femoral condyle and tibial posterior slope angle measured on lateral radiograph, and other clinical factors were compared between the two groups using Mann-Whitney U test or chi-square test. According to the results of these analyses, factors having a statistically significant difference were additionally evaluated using multiple logistic regression analysis to reveal items with strong relevance to a positive GAPS test. The results of the multiple logistic regression analysis showed that the flexor/extensor peak torque ratio of contralateral uninjured knees and sex had a significant correlation with the results of the GAPS test. The relatively less flexor muscle torque compared with extensor muscle torque, and being a female patient were considered to be the determinant factors of a positive GAPS test.