KT-1000 records smaller side-to-side differences than radiostereometric analysis before and after an ACL reconstruction

Medial meniscal lesions increase antero-posterior laxity in knees with anterior cruciate ligament injury

PURPOSE

The aim of this study was to quantify the impact of concomitant meniscal lesions on knee laxity using a triaxial accelerometer in a large population of patients affected by anterior cruciate ligament (ACL) injury.

METHODS

A total of 326 consecutive patients (261 men and 65 women, mean age 31.3 ± 11.3) undergoing primary ACL reconstruction, were preoperatively evaluated through Lachman and pivot shift tests using a triaxial accelerometer to quantify knee laxity. An analysis based on the presence of meniscal tears assessed during surgery was performed to evaluate the impact of meniscal lesions on knee laxity.

RESULTS

The anterior tibial translation (Lachman test) presented significantly higher values in patients with medial meniscal lesions (7.3 ± 1.7 mm, p = 0.049) and both medial and lateral meniscal lesions (7.7 ± 1.6 mm, p = 0.001) compared to patients without concomitant meniscal lesions (6.7 ± 1.3 mm). Moreover, patients with both medial and lateral meniscal lesions presented significantly higher values of anterior tibial translation compared to patients with lateral meniscal lesions (p = 0.049). No statistically significant differences were found between the groups in terms of tibial acceleration (pivot shift test).

CONCLUSION

This study demonstrated that the contribution of concomitant meniscal lesions to knee laxity can be objectively quantified using a triaxial accelerometer in ACL-injured knees. In particular, medial meniscus lesions, alone or in association with lateral meniscus lesions, determine a significant increase of the anterior tibial translation compared to knees without meniscus tears.

LEVEL OF EVIDENCE

Level IV.

Retrospective analysis and risk of progression of partial anterior cruciate ligament injuries in a young population

BACKGROUND

The anterior cruciate ligament (ACL) is a common knee ligament injury. Partial ACL tears are common, and at least 10-27% of isolated ACL tears are diagnosed as partial tears. Patients with partial tears have high risk of progression of tears to complete tears, which may require surgical reconstruction. The risk factors associated with the progression to a complete tear are poorly understood.

METHODS

The present case-control study assessed the incidence and risk factors for the progression of conservatively treated partial ACL tears to complete tears in 351 patients younger than 45 years. The diagnosis of partial ACL tears was based on clinical evaluation, side-to-side difference on Rolimeter, and magnetic resonance imaging. These patients were managed conservatively and followed up for a mean of 17.5 months or until the progression of the tear into a complete tear, requiring surgery. The patients in whom the tear progressed to complete tear (group P) were compared with those in whom the tear remained stable for a minimum of 18-month follow-up period (group S).

RESULTS

Of the 351 partial ACL tear patients, 166 (47.3%) patients progressed to a complete tear at a mean duration of 17.5 months, whereas the tear in 185 (52.7%) patients remained stable and did not progress to a complete tear. Group P had mean international knee documentation committee (IKDC) scores and Tegner scores of 95.7 ± 3.7 and 7.6 ± 1.6, respectively, before the injury, and scores decreased to 52.4 ± 4.1 and 5.7 ± 2.2, respectively, at the 24-month follow-up.

CONCLUSION

Partial ACL tear progressed to a complete tear in 47.3% of evaluated patients. The associated risk factors were age less than 35 years, rigorous physical activities, high ACL-Return to Sport after Injury score during early rehabilitation days, early return to activity, and pivoting contact sports.

A new knee arthrometer demonstrated to be reliable and accurate to assess anterior tibial translation in comparison with stress radiographs

INTRODUCTION

For several years, many arthrometers have been developed to assess anterior knee laxity. The aim of our study was to evaluate the validity of a new practical and handy testing device with the hypothesis that the new arthrometer had good validity in terms of reliability and accuracy.

METHODS

Lachman test was performed on five fresh frozen cadaveric knees by five examiners. Anterior tibial translation (ATT) was measured with a new arthrometer (BLU-DAT) and on lateral stress radiographs. Data on ATT were obtained under 7 kg (69 N), 9 kg (88 N), and maximum manual traction (MMT). Tests were performed on the same specimens before and after arthroscopic ACL excision. Inter-rater reliability of the BLU-DAT measures was assessed with the intraclass correlation coefficient (ICC) for single and average measurements. The Bland-Altman method was used to estimate agreement between the BLU-DAT and stress radiographs.

RESULTS

ICC values for single measurements were 0.62, 0.54 and 0.58 for 7-kg, 9-kg and MMT assessment, respectively. Overall reliability was good (ICC = 0.63). ICC values for average measurements were 0.89, 0.85 and 0.88 for 7-kg, 9-kg and MMT assessment, respectively. Overall reliability was very good (ICC = 0.90) SEM ranged from 1.4 mm to 1.6 mm for single measurements and was below 1 mm at each testing condition for average measurements. Analysis of agreement between BLU-DAT and radiographic measurements showed a mean difference equal to 0.83 mm ± 2.1 mm (95% CI: 0.55-1.11). Upper LOA was equal to 4.9 mm (95% CI: 5.39-4.41). Lower LOA was equal to - 3.2 mm (95% CI: - 2.71 to - 3.69).

CONCLUSION

Measurement of anterior knee laxity with the BLU-DAT testing device has a good to very good inter-rater reliability and good agreement with a gold standard such as stress radiographs. Cadaveric Diagnostic Study, Level of Evidence IV.

Laxity measurement of internal knee rotation after primary anterior cruciate ligament rupture versus rerupture

PURPOSE

The aim of the current study was to objectify the rotational laxity after primary anterior cruciate ligament (ACL) rupture and rerupture after ACL reconstruction by instrumented measurement. It was hypothesized that knees with recurrent instability feature a higher internal rotation laxity as compared to knees with a primary rupture of the native ACL.

STUDY DESIGN

Cross-sectional study, Level of evidence III.

METHODS

In a clinical cross-sectional study successive patients with primary ACL rupture and rerupture after ACL reconstruction were evaluated clinically and by instrumented measurement of the rotational and antero-posterior laxity with a validated instrument and the KT1000^®, respectively. Clinical examination comprised IKDC 2000 forms, Lysholm Score, and Tegner Activity Scale. Power calculation and statistical analysis were performed (p value < 0.05).

RESULTS

24 patients with primary ACL rupture and 23 patients with ACL rerupture were included. There was no significant side-to-side difference in anterior translation. A side-to side difference of internal rotational laxity ≥ 10° was found significantly more frequent in reruptures (53.6%) compared to primary ruptures (19.4%; p < 0.001). A highly significant relationship between the extent of the pivot-shift phenomenon and side-to-side difference of internal rotation laxity could be demonstrated (p < 0.001). IKDC 2000 subjective revealed significantly better scores in patients with primary ACL tear compared to patients with ACL rerupture (56.4 ± 7.8 vs. 50.8 ± 6.2; p = 0.01). Patients with primary ACL tears scored significantly better on the Tegner Activity Scale (p = 0.02). No significant differences were seen in the Lysholm Score (p = 0.78).

CONCLUSION

Patients with ACL rerupture feature significantly higher internal rotation laxity of the knee compared to primary ACL rupture. The extend of rotational laxity can be quantified by instrumented measurements. This can be valuable data for the indication of an anterolateral ligament reconstruction in ACL revision surgery.

The Natural History of Medial Meniscal Tears in the ACL Deficient and ACL Reconstructed Rat Knee

OBJECTIVE

The process of anterior cruciate ligament (ACL) injury-induced meniscal tear formation is not fully understood. Clinical studies have shown that ACL reconstruction (ACLR) reduces the development of secondary meniscal tears, but it is difficult to gain insight into the protective effects of ACLR from clinical studies alone. Using rat ACL transection (ACLT) and ACLR models, we aimed to reveal (1) the formation process of meniscal tears secondary to ACLT and (2) the protective effects of ACLR on secondary meniscal tears.

DESIGN

ACLT surgery alone or with ACLR was performed on the knees of rats. Histomorphological and histopathological changes were examined in the posteromedial region of the meniscus in intact rats and in rats that received ACLT or ACLR up to 12 weeks postsurgery. In addition, anterior-posterior joint laxity was measured using the universal testing machine to evaluate the effects of ACLT and ACLR on joint laxity.

RESULTS

AAnterior-posterior laxity was significantly increased by ACLT compared to the intact knee. This ACLT-induced joint laxity was partially but significantly reduced by ACLR. Meniscal proliferation and hyaline cartilage-like tissue formation were detected in the medial meniscus at 4 weeks post-ACLT. At 12 weeks post-ACLT, hyaline cartilage-like tissue was replaced by ossicles and meniscal tears were observed. These ACLT-induced abnormalities were attenuated by ACLR.

CONCLUSIONS

Our results suggest that ACLT-induced joint laxity induces secondary medial meniscal tears through meniscal proliferation and ossicle formation via endochondral ossification. Joint re-stabilization by ACLR suppresses meniscal proliferation and ossicle formation and consequently prevents secondary meniscal tears.

Management of Partial Tears of the Anterior Cruciate Ligament: A Review of the Anatomy, Diagnosis, and Treatment

Partial anterior cruciate ligament (ACL) tears comprise an estimated 10% to 27% of isolated ACL injuries. Partial ACL tears may be challenging to clinically diagnose. We reviewed relevant studies focusing on the anatomy, diagnosis, imaging, and treatment of a partial injury with the goal of providing guidance to clinicians. Although a comprehensive patient history, thorough clinical examination, and imaging studies are helpful in arriving at a diagnosis, the benchmark for diagnosis remains visualization and examination of the ACL at the time of knee arthroscopy. Currently, limited data exist about the long-term outcomes of nonsurgical treatment. Some studies demonstrate that younger, active patients have the risk of progressing to a complete ACL rupture with conservative treatment. The decision to proceed with surgery is based on careful history and physical examination findings that suggest either a "functional" or "nonfunctional" ACL. Surgical treatment consists of augmenting the intact bundle with a selective bundle reconstruction versus a traditional ACL reconstruction. Selective bundle reconstruction has limited data available but is an option. The best evidence supports traditional ACL reconstruction for the surgical management of patients with documented nonfunctional partial tears of the ACL.

Incidence and Risk Factors for a Partial Anterior Cruciate Ligament Tear Progressing to a Complete Tear After Nonoperative Treatment in Patients Younger Than 30 Years

Background:

Partial anterior cruciate ligament (ACL) tears are observed in 10% to 27% of isolated ACL tears. There is currently no consensus on diagnosis and treatment protocols, and the outcomes of nonoperative treatment remain undefined.

Purpose:

To assess the incidence and risk factors for the progression of partial ACL tears to complete ruptures after nonoperative treatment in active patients younger than 30 years.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 41 patients, all younger than 30 years and active in sports, were diagnosed with a partial ACL tear, with no associated meniscal or chondral lesions on magnetic resonance imaging (MRI). All were assigned to a nonoperative treatment program. The Lachman test, ≤4-mm side-to-side difference in laxity by Rolimeter, and MRI were utilized for the diagnosis. Tegner and International Knee Documentation Committee (IKDC) scores were assessed before and after the first lesion, and the Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) score was assessed at last follow-up. Postinjury Tegner and IKDC scores were assessed before the second injury for patients progressing to a complete ACL tear and at last follow-up for patients without progression.

Results:

At a mean of 43 months (range, 24-96 months), the partial ACL injury progressed to a complete ACL tear in 16 (39%) patients. In the remaining 25 patients without progression, the mean Tegner and IKDC scores were 7.0 and 96.0 before the injury and 5.9 and 85.7, respectively, at last follow-up. The mean ACL-RSI score was 69.3. The Tegner and IKDC scores were significantly lower at final follow-up (P = .0002 and P < .0001, respectively). Only 18 (44%) patients returned to their preinjury level of sports activities. A significantly increased risk of progression to a complete ACL tear was seen in patients ≤20 years (odds ratio, 5.19; P = .037) or patients practicing pivoting contact sports (odds ratio, 6.29; P = .026). Meniscal lesions were found in 50% of patients with a partial tear that progressed to a complete ACL tear.

Conclusion:

A partial ACL injury progressed to a complete ACL tear in 39% of young active patients treated conservatively, with half of the complete tears presenting with a concomitant meniscal lesion at the time of reconstruction. Age ≤20 years and participation in pivoting contact sports were identified as significant risk factors for progression to a complete tear.

The Laxity of the Native Knee: A Meta-Analysis of in Vitro Studies

BACKGROUND

Although soft-tissue balancing plays an important role in knee arthroplasty, we are aware of no objective target parameters describing the soft-tissue tension of the native knee. In the present study, we aimed to meta-analyze data from studies investigating native knee laxity to create a guide for creating a naturally balanced knee joint.

METHODS

PubMed and Web of Science were searched for studies with laxity data published from 1996 through 2016. Graphs were digitally segmented in cases in which numerical data were not available in text or table form. Three-level random-effects meta-analyses were conducted.

RESULTS

Seventy-six studies evaluating knee laxity at various flexion angles (0° to 90°) were included. Knee laxity was significantly different between 0° and 90° of flexion (p < 0.001) in all 6 testing directions, with mean differences of 0.94 mm and -0.35 mm for anterior and posterior translation, 1.61° and 4.25° for varus and valgus rotation, and 1.62° and 6.42° for internal and external rotation, respectively.

CONCLUSIONS

Knee laxity was dependent on the flexion angle of the knee joint in all degrees of freedom investigated. Furthermore, asymmetry between anterior-posterior, varus-valgus, and internal-external rotation was substantial and depended on the joint flexion angle.

CLINICAL RELEVANCE

If the goal of knee arthroplasty is to restore the kinematics of the knee as well as possible, pooled laxity data of the intact soft tissue envelope could be useful as a general guide for soft-tissue balancing in total knee arthroplasty.

Passive anterior tibia translation in anterior cruciate ligament-injured, anterior cruciate ligament-reconstructed and healthy knees: a systematic review

Abstract

Anterior tibia translation (ATT) is mainly prevented by the anterior cruciate ligament. Passive ATT tests are commonly used to diagnose an anterior cruciate ligament (ACL) injury, to select patients for an ACL reconstruction (ACLR), and as an outcome measure after an ACLR. The aim of this review was to present an overview of possible factors determining ATT. A second purpose was to give a summary of the ATT measured in the literature in healthy, ACL-injured and ACLR knees and a comparison between those groups. A literature search was conducted with PubMed. Inclusion criteria were full-text primary studies published in English between January 2006 and October 2016. Studies included reported ATT in explicit data in healthy as well as ACL-injured or ACLR knees or in ACL-injured as well as ACLR knees. Sixty-one articles met inclusion criteria. Two articles measured the ATT in healthy as well as ACL-injured knees, 51 in ACL-injured as well as in ACLR knees, three in ACLR as well as in healthy knees and three in healthy, ACL-injured and ACLR knees. A difference in ATT is found between healthy, contralateral, ACLR and ACL-injured knees and between chronic and acute ACL injury. Graft choices and intra-articular injuries are factors which could affect the ATT. The mean ATT was lowest to highest in ACLR knees using a bone–patella tendon–bone autograft, ACLR knees using a hamstring autograft, contralateral healthy knees, healthy knees, ACLR knees with an allograft and ACL-injured knees. Factors which could affect the ATT are graft choice, ACL injury or reconstruction, intra-articular injuries and whether an ACL injury is chronic or acute. Comparison of ATT between studies should be taken with caution as a high number of different measurement methods are used. To be able to compare studies, more consistency in measuring devices used should be introduced to measuring ATT. The clinical relevance is that an autograft ACLR might give better results than an allograft ACLR as knee laxity is greater when using an allograft tendon.

Level of evidence

III.

Anterior tibial laxity using the GNRB® device in healthy knees

BACKGROUND

GRNB® is a non-radiating power tool that allows the evaluation of the anterior tibial translation.

HYPOTHESIS

The pressure exerted by the system against the patella and the body mass index (BMI) could affect the anterior tibial translation when we repeat the measurements in healthy knees.

MATERIALS AND METHODS

We retrospectively evaluated the measurements of anterior knee laxity in healthy knees carried out by the GNRB® in 69 consecutive patients who underwent anterior cruciate ligament (ACL) repair in the contralateral knee. Two measurements were carried out, the initial measurements (M1), and then repeated at a mean of seven months (M2) (4.9 to 13months).

RESULTS

There were 38 women and 31 men with an average age of 31years. In healthy knees, the Mean average anterior translation was 5.4±4mm with an average patellar force of 35.8 at time M1. The average anterior translation was 4.9±4mm with an average patellar force of 47 at time M2. There was a significant difference between the measurements M1 and M2 (P<0.03). The tightening force was significantly different between the two sets of measurements (P<10-7). There was a negative correlation between the pressure applied on the patella and anterior knee laxity (P<0.01).

CONCLUSION

The pressure force exerted on the patella during GNRB® affects the measurement of anterior laxity in healthy knees. This raises the problem of the reproducibility of the measurements during repeated examinations at different times.

Validity of rotational laxity coupled with anterior translation of the knee: A cadaveric study comparing radiostereometry and the Rotab®

BACKGROUND

In current practice, anterior cruciate ligament (ACL) tears can be diagnosed using several devices to measure anterior tibial translation and rotational knee laxity, but these measures are never collected together. The Rotab®, which yields simultaneous measurements of anterior tibial translation and passive lower limb rotation under stress, would therefore be advantageous in current practice, but its reliability has never been tested.

AIM OF STUDY

To evaluate the accuracy and reliability of the Rotab® compared to the reference system, radiostereometric analysis (RSA).

METHODS

This anatomical study was conducted on 14 lower limbs collected from fresh cadavers. Simultaneous measurements of anterior tibial translation and rotation were obtained with both systems, with antero-posterior (AP) forces of 134N and 250N using the Rotab®. Measurements were made on intact ACL and then repeated after ACL section. Variables were analyzed in univariate analysis by ANOVA, and the intraclass correlation coefficient (ICC) between the systems was determined by the Bland and Altman method.

RESULTS

The difference between the two methods for evaluating anterior tibial translation was 0.05±0.98mm at 134N and 0.29±1.04mm at 250N. The correlation between the tests was high (r₁₃₄=r₂₅₀=0.97, p=0.8). The difference between the two methods for rotational laxity was 0.69±2.7° at 134N and 0.5±0.6° at 250N. The Rotab® showed a significant difference only at 250N for rotational laxity after the ACL tear.

CONCLUSION

The Rotab® is a reliable device to measure rotational laxity coupled with anterior translation of the knee.

Application of a Novel Measure of In Vivo Knee Joint Laxity

Current measures of knee joint laxity, such as those found clinically using the KT-2000 arthrometer, are not highly repeatable or reliable by Huber et al. (1997, "Intratester and Intertester Reliability of the KT-1000 Arthrometer in the Assessment of Posterior Laxity of the Knee," Am. J. Sports Med., 25(4), pp. 479-485). In this study, a noninvasive in vivo magnetic resonance (MR) imaging-based measure of laxity, the knee loading apparatus (KLA) with anterior positioning frame, was evaluated with five normal subjects (repeatability study, n = 3). Effects of hormones and muscle guarding were considered. When compared to the KT-2000, the KLA was found to be more precise (±0.33 mm versus ±1.17 mm) but less reliable (Cronbach's alpha > 0.70 in 0/8 versus 5/8 load levels). Improved control of the initial subject position is recommended for future design iterations. The KLA shows promise as an accurate and reliable tool for measuring in vivo joint and ligament laxity.

Partial tears of the anterior cruciate ligament

Partial anterior cruciate ligament (ACL) tears were first described nearly fifty years ago but the optimal treatment for these injuries continues to be a subject of considerable debate. A question remains whether it is advantageous to preserve the ACL remnant and augment it with a graft, or to debride it and proceed with a standard ACL reconstruction unhindered by remnant fibers in the notch. Clinical outcomes of bundle preserving surgery are promising. An increasingly large body of scientific evidence suggests that augmenting the intact bundle is beneficial in terms of vascularity, proprioception and kinematics. With this knowledge, a number of surgeons have developed techniques to augment the intact bundle of the ACL in partial tears and to biologically enhance standard reconstruction techniques by preserving the ACL remnant. Correct tunnel placement is critical for achieving successful short and long-term outcomes after ACL reconstruction. However, published studies have several limitations including a limited number of patients and lack of control groups for direct comparison of outcomes. Concerns continue to exist with respect to an increased risk of impingement following augmentation, responsible of cyclops syndrome. The objective of this article was to outline the diagnostic approach, describe a reproducible and simple surgical procedure that allows correct femoral tunnel placement without the need for aggressive notch debridement and report the clinical outcome of partial ACL reconstruction.

Ultrasonographic test for complete anterior cruciate ligament injury

BACKGROUND

Although ultrasound (US) has a wide range of applications in orthopedic diagnostics, sonographic evaluation of traumatic anterior cruciate ligament (ACL) insufficiency is still inadequate. There is a growing need for diagnostic tests that allow for simple and reliable assessment of ACL instability. This investigation aims to evaluate feasibility of sonographic technique for diagnosing complete ACL insufficiency.

MATERIALS AND METHODS

Eighty three consecutive patients suspected of ACL injury were examined with sonographic, dynamic test of anterior instability. The translation of the intercondylar eminence against the patellar tendon was measured in the injured and opposite (injured) knee. Subsequent magnetic resonance imaging was performed on all patients. Forty-seven of them underwent a further arthroscopy. Five patients have been examined for the 2(nd) time to evaluate interclass and intraclass agreement and bias.

RESULTS

Complete ACL insufficiency has been confirmed in 37 patients. In those individuals, the total anterior knee translation and the difference between two joints (side-to-side difference) were significantly increased (8.67 mm standard deviation [SD] 2.65 mm in the affected knee versus 2.88 mm SD 1.26 mm in uninjured joint; P < 0.001). Based on a threshold of 2.0 mm for the side-to-side difference and 5.0 mm for the absolute translation, the sonographic test was found to have a sensitivity and specificity of 91.9% and 95.6%, respectively.

CONCLUSIONS

The present technique supports the clinician with additional fast and noninvasive diagnostic procedure that can facilitate the evaluation of anterior knee instability.

Non-invasive, non-radiological quantificationof anteroposterior knee joint ligamentous laxity: A study in cadavers

OBJECTIVES

We performed in vitro validation of a non-invasive skin-mounted system that could allow quantification of anteroposterior (AP) laxity in the outpatient setting.

METHODS

A total of 12 cadaveric lower limbs were tested with a commercial image-free navigation system using trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° of knee flexion and 100 N of force was applied perpendicular to the tibia. Acceptable coefficient of repeatability (CR) and limits of agreement (LOA) of 3 mm were set based on diagnostic criteria for anterior cruciate ligament (ACL) insufficiency.

RESULTS

Reliability and precision within the individual invasive and non-invasive systems was acceptable throughout the range of flexion tested (intra-class correlation coefficient 0.88, CR 1.6 mm). Agreement between the two systems was acceptable measuring AP laxity between full extension and 40° knee flexion (LOA 2.9 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (LOA > 3 mm).

CONCLUSIONS

These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard validated commercial system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative evaluation of ACL pathology. Cite this article: Bone Joint Res 2013;2:233-7.

Relationship between static anterior laxity using the KT-1000 and dynamic tibial rotation during motion in patients with anatomical anterior cruciate ligament reconstruction

The anterior cruciate ligament (ACL) plays an important role in controlling knee joint stability, not only by limiting tibial anterior translation but also by controlling knee axial rotation. The aim of ACL reconstruction is to reduce excessive anterior joint laxity, hoping to restore normal tibiofemoral kinematics including knee axial rotation. The purpose of this study was to investigate the relationship between static anterior instability and tibial rotation during several activities in an anterior cruciate ligament reconstructed knee. Seven patients with unilateral ACL injury performed plain walking, running, landing and side step cutting tasks after ACL reconstruction with a mean follow-up of 14 months. The kinematic data for the 4 motions was measured using a motion analysis system and the point cluster technique. The evaluation period was defined to be from the first contact to removal of the tested leg from the ground. Maximum tibial internal rotation during tasks was calculated using the point cluster technique (PCT). Passive anterior tibial translation was measured using a KT-1000 arthrometer. Regression analysis was used to determine the correlation of the maximum internal rotation with the side-to-side difference of static anterior tibial translation measured using a KT-1000 arthrometer. During side step cutting maneuvers, maximum tibial internal rotation significantly showed negative correlation with static anterior tibial translation (p<0.05, r=0.83). The anterior laxity contributed to the normal knee rotation kinematics. The normal anterior tibial translation obtained by ACL reconstruction is thought to be the key factor in successful restoration of normal knee kinematics.

Bench testing of a knee joint arthrometer

The KT1000 and KT2000 knee joint arthrometers (MEDmetric Corp, San Diego, California) have been shown to overestimate the measurement of knee joint sagittal laxity. The purpose of this study was to investigate the accuracy of the KT arthrometers as measures of anterior and posterior linear displacement. The anterior and posterior linear displacements of 3 KT arthrometers (2 KT1000 arthrometers and 1 KT2000 arthrometer) were compared with the simultaneous displacement measured by a precision linear Vernier Dial Test Indicator (Davenport Ltd, London, United Kingdom). The displacement calculated using the analog output of the KT2000 was also compared with the values on the KT2000 displacement dial. Compared with the Vernier Dial Test Indicator, the KT arthrometers overestimated anterior linear displacement by between 22% and 24%. True anterior displacement for all 3 arthrometers, as recorded by the Vernier Dial Test Indicator, was found by multiplying the KT value by 0.79. When compared with the Vernier Dial Test Indicator, the KT arthrometers underestimated posterior linear displacement by between 18% and 19%. True posterior displacement, as recorded by the Vernier Dial Test Indicator, was found by multiplying the KT1000 value by 1.17 and the KT2000 value by 1.16. The internal apparatus of the KT2000 and KT1000 knee joint arthrometers overestimates anterior displacement and underestimates posterior displacement with a predictable relative systematic error. Future validation studies should use these correction equations to assess the accuracy of the KT arthrometers. Sagittal plane knee laxity measured with the KT devices requires systematic correction for optimal accuracy.

Objective evaluation of anterior knee laxity; comparison of the KT-1000 and GNRB® arthrometers

PURPOSE

Accurate measurement of laxity after anterior cruciate ligament (ACL) rupture is usually performed with the KT-1000 arthrometer, and reproducibility and reliability are discussed. A new arthrometer, the GNRB(®), has been recently developed in an attempt to improve intra- and inter-examiner reproducibility. The aim of this diagnostic study was to evaluate the intra- and inter-examiner reproducibility of the GNRB(®) and the KT-1000.

METHODS

Three protocols were designed to evaluate and compare the two arthrometers. Fifteen physiotherapists conducted tests on 15 subjects with healthy knees. The intra- and inter-reproducibility of the two tests were compared by analysis of variance and the F-test.

RESULTS

Measure reproducibility was significantly worst with the KT-1000 than with the GNRB(®) (machine effect, P < 0.001) regardless of operator experience. There was no significant difference between experienced and inexperienced examiners with the GNRB(®) (no 'examiners effect'). Regardless of the machine, there was a 'side effect' with healthy knees.

CONCLUSION

This clinical study demonstrates the superior intra- and inter-examiner reproducibility of the GNRB(®) over the KT-1000. There appears to be some technological advantages to using the GNRB(®) including pressure control of the patella, accuracy of the displacement transducer, control of the load on the calf, and control of hamstring activity.

LEVEL OF EVIDENCE

Diagnostic study, Level I.

ACCURACY CHARACTERIZATION OF AN INTEGRATED OPTICAL-BASED METHOD FOR LOADS MEASUREMENT IN COMPUTER AIDED SURGERY

Generally in the anterior cruciate ligament (ACL) injury assessment specific laxity tests (i.e., Lachman, drawer tests) are clinically performed to evaluate the presence of ligamentous lesion. At present these tests are qualitatively evaluated by the surgeon and some quantitative measurements can be performed only for Lachman/drawer tests by means of dedicated devices. This study aimed to characterize the accuracy of a novel integrated optical-based method that can be used both in intra-operative and in office assessment of ACL injuries; in particular this technology was addressed to measure the loads/torques applied during clinical laxity tests, extending the current possible quantitative evaluations. The system, based on a commercial optical localizer and common springs, was spatially characterized in order to verify displacement/rotation and corresponding applied load/torque measurements. Evaluated limits of agreement between measured and applied loads were from –0.541 to 1.781 N, with a bias of 0.621 N (P = 0.05) in a dedicated clinical-like setup. This approach reported an excellent accuracy in load measurements, showing its possible integration in computer-aided surgery (CAS).

The combination of radiostereometric analysis and the telos stress device results in poor precision for knee laxity measurements after anterior cruciate ligament reconstruction

PURPOSE

Several devices for measuring knee laxity following anterior cruciate ligament ACL reconstruction exist, but the precision of the methods has never been optimal. Therefore, a new standardized protocol (NSP) was made, aiming at ensuring a reliable positioning of the Telos Stress Device (TSD) which theoretically could result in precise knee laxity measurements when using radiostereometric analysis (RSA) in combination with TSD.

METHOD

The TSD was applied to the knee of 30 healthy persons, using both the NSP and the official company instructions. The position of the stress arms of the TSD was marked following each measurement. The reliability of each protocol was calculated as the difference in length between the first and second markings. The NSP for the TSD was then used in a clinical study. Thirty-five patients underwent ACL reconstruction. Double measurements of knee laxity by RSA were performed at a 3-month follow-up.

RESULTS

Using the NSP for TSD positioning, the prediction interval at the marking sites ranged from ±0.4 to ±1.1 mm. Following the company instructions, the prediction interval ranged from ±0.8 to ±3.9 mm depending on marking site. Thus, the precision of positioning the stress arms of the TSD was improved at all marking sites using the NSP compared with the original company protocol. The double measurements of the knee laxity in the clinical study resulted in a mean difference of 0.0 mm and a prediction interval of ±5.2 mm.

CONCLUSION

Even though the NSP improved the positioning of the TSD on patients' extremities, the combination of NSP-TSD and RSA was not able to provide acceptable knee laxity measurements in a clinical setting compared with published precision data for other devices on the market. Therefore, the Telos Stress Device is not recommendable for use in knee laxity measurements following ACL reconstruction.

In vivo laxity of stable versus anterior cruciate ligament-injured knees using a navigation system: a comparative study

We compared antero-posterior translation and internal-external rotation of the tibia in stable knees without anterior cruciate ligament (ACL) injury with those of ACL injured knees using a navigation system and suggest an objective data. Forty-four patients treated for a meniscal tear without ACL injury were allocated to stable group, and 41 patients were allocated to ACL injury group. Antero-posterior displacement and rotation of knees were measured in 0, 30, 60 and 90 degrees of flexion using navigation. Mean anterior displacements were 3.6 +/- 2.0, 6.7 +/- 2.7, 6.0 +/- 2.4 and 4.7 +/- 1.8 mm at 0, 30, 60 and 90 degrees of flexion, respectively, in stable group, and 6.8 +/- 3.6, 14.7 +/- 3.5, 11.9 +/- 4.6 and 8.5 +/- 4.0 mm in ACL injury group. Mean total rotation values were 18.8 +/- 4.5 degrees, 31.4 +/- 4.2 degrees, 30.1 +/- 5.1 degrees and 29.2 +/- 5.9 degrees in stable group and 22.7 +/- 6.9 degrees , 37.6 +/- 5.8 degrees, 34.0 +/- 9.4 degrees and 31.8 +/- 8.8 degrees in ACL injury group. Quantitative values of antero-posterior translations and rotations of stable and ACL injured knees were obtained using a navigation system. The laxity data may be useful to establish the diagnosis of an ACL injury and evaluation of post-operative results.

A new knee arthrometer, the GNRB: experience in ACL complete and partial tears

INTRODUCTION

Clinical diagnosis of anterior cruciate ligament (ACL) tears (Lachman test and Pivot shift test in valgus and internal rotation) is reliable in case of complete ACL tear but reveals elusive in case of partial tears. Quantitative assessment of anterior tibial translation proves to be imprecise, subjective and poorly reproducible especially with the KT-1000 arthrometer. We developed the GNRB, an alternative original anterior knee laxity measurement device. The lower limb is placed in a rigid support with the knee at 0 degrees of rotation, the restraining power being recorded. A 0-250 N thrust force is transmitted by a jack to the upper segment of the calf. This force is only applied in the absence of hamstring muscles contraction. Displacement of the anterior tibial tubercle is recorded using a sensor with a 0.1mm precision.

HYPOTHESIS

We hypothesize that this knee laxity measurement device is more reliable and reproducible than other currently available arthrometers.

MATERIAL AND METHODS

During a first validation study, the GNRB was compared to the KT-1000 arthrometer, in 20 pairs of healthy knees, measurements being performed by two investigators. Variance analyses were carried out at 134 N. In a second clinical study, 21 complete ACL tears (the notch is devoid of ACL) and 24 partial ACL tears (anterior or posterior bundle tear and cicatricial ACL remnant in continuity) were tested with these arthrometers to exact a differential laxity threshold value between both knees at 250 N. Statistical analysis was subsequently performed using variance and ROC curves analysis.

RESULTS

The GNRB arthrometer reveals to be significantly more reproducible than the KT-1000, irrespectively of the tester's experience level. Moreover, unlike the KT-1000, the achieved measurement is independent from the uninvolved side. Reproducibility of laximetry proves to be significantly better with the GNRB than with the KT-1000, wherever the examiner's experience stands and whatever the evaluated side condition could be. When differential laxity threshold value was 3mm in complete ACL tears, sensitivity was 70% and specificity 99% at 134 N. Using a 1.5mm threshold value in ACL partial tears, the arthrometer sensitivity was 80% and specificity was 87% at 134 N.

DISCUSSION

Reproducibility of laximetry was significantly better with the GNRB than the KT-1000 device, wherever the examiner's experience stands and whatever the evaluated side-condition could be. The GNRB reports various supplementary advantages compared with other available laximeters. Good control of the investigated limb position in rotation, recording of translation in the absence of hamstring muscles contraction and in direct comparison with the KT-1000: reproducibility, constant pressure, arthrometry improved accuracy and automated measurements recording. The GNRB might be used for diagnosis of partial and complete ACL tears and during follow-up of reconstructed or not ACL tears.

LEVEL OF EVIDENCE

type II. Prospective comparative study.

Current concepts in instrumented knee-laxity testing

BACKGROUND

Instrumented knee laxity testing devices have been used in both the clinical and research setting to evaluate persons with injuries about the knee. The ability to accurately and reproducibly quantify knee motion has the potential to greatly benefit both clinical practice and research by improving the validity of the research involving treatment of knee-ligament injuries.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A thorough literature review was performed, and a systematic overview is provided evaluating the methods of use and the evidence for the use of instrumented knee laxity testing devices.

RESULTS

Devices that provide measurements of knee laxity have evolved during the past 30 years. The authors describe in detail their proper use and the best estimates of their validity based on clinical studies.

CONCLUSION

The review suggests that the KT-1000 knee arthrometer and the Rolimeter provide best results when testing anterior laxity at the knee, whereas the Telos device is superior for the assessment of posterior laxity.