Knee-laxity measurements examined by a left-hand- and a right-hand-dominant physiotherapist, in patients with anterior cruciate ligament injuries and healthy controls

Anterior Cruciate Ligament Stability in Soft-Embalmed Cadaver vs In vivo Knee: Alternative Approaches to Medical Education

Introduction

Soft-embalmed cadavers have been used in medical education with a variety of success in different curriculum objectives. In the United States, the ACL is the most commonly injured ligament. Yet, there has been little focus on the stability of the knee in the sagittal plane provided by the anterior cruciate ligament within the soft-embalmed cadaver model. If the soft-embalmed cadaver ligaments contain similar elastic properties as an in-vivo knees, this will offer yet another means for further advancements in medical education to detect and assess musculoskeletal injuries.

Purpose

Evaluate how similarly the anterior tibial translation of soft-embalmed cadaver anterior cruciate ligaments compares to in-vivo tissue.

Methods

The KT-1000 arthrometer was used to assess the laxity of the anterior cruciate ligament of thirteen soft-embalmed cadavers consisting of five females and eight males with a mean age of 79.3 years and duration of time since embalming ranging from 250 to 1156 days. Anterior displacement of the tibia in relation to the femur was registered at 67N and 89N. The soft-embalmed cadaver measurements were compared against twenty-one healthy uninjured individuals whose anterior tibial translation was measured using the same process. Data sets were analyzed using a welch two-sample t-test to determine the similarity between the means of the data sets.

Results

The t-tests proved a significant difference between live and soft-embalmed cadaver knees. The anterior tibial translation in the set of healthy live knees directly compared to the soft-embalmed cadaver group for 67N depicts an average difference of 1.76mm. The same comparison at 89N depicts an average difference of 2.12mm.

Conclusion

While soft-embalmed cadavers may not directly replicate ATT to an exact number to that of in vivo tissue, they still allow the perception of the tibial translation against a stationary femur. The difference is less than 2.5 mm in both data sets when compared to an in-vivo knee, equivalent to one-tenth of an inch. Suggesting the viability of soft-embalmed cadavers ATT and should not exclude their use in medical education.

BLU-DAT: a new reliable and accurate arthrometer for measuring anterior knee laxity

PURPOSE

Although many arthrometers have been developed to assess anterior knee laxity, reliability and diagnostic accuracy of these devices are still debated. The aim of the present study was to evaluate the validity of a new arthrometer in the outpatient setting, with the hypothesis that it had good validity in terms of reliability and diagnostic accuracy.

METHODS

Seventy-eight subjects (39 with ACL injury and 39 with normal ACL) were tested. ATT was assessed by means of the Lachman test at 30° of flexion with a new testing device (BLU-DAT) under three different loading conditions: 7 kg (69 N), 9 kg (88 N) and maximum (MMT). The tests were performed on both knees to obtain SSD. In the ACL injury group, the tests were performed by two examiners and one of them repeated a second test series. Inter- and intra-observer reliability were assessed with the intraclass correlation coefficients (ICCs) for the average SSD measures. In the normal-ACL group, the analysis was performed with the same testing setup. Side-to-side difference measures of the two groups at every loading condition were compared by Student's t test. Data of test series were dichotomized based on the threshold value of 3-mm SSD as pathological ATT and 2 × 2 contingency tables were used to assess diagnostic accuracy.

RESULTS

The ICCs for intra-observer reliability at 7-kg (69 N), 9-kg (88 N) and MMT measurements were 0.781, 0.855 and 0.913, respectively. The ICC for inter-observer reliability at 7-kg (69 N), 9-kg (88 N) and MMT measurements were 0.701, 0.845 and 0.834, respectively. Comparison between the two groups showed a significant mean difference ranging from 3.4 mm for 7-kg (69 N) load to 4.6 mm for MMT. Overall accuracy ranged from 84.6% for 7-kg load to 98.7% for MMT.

CONCLUSION

The BLU-DAT has proven to be an instrument with good intra- and inter-observer reliability and very good accuracy in the diagnosis of ACL injuries in the outpatient setting. So, the BLU-DAT can be a new useful tool in everyday clinical practice to assist in the diagnosis of ACL injury.

LEVEL OF EVIDENCE

II.

A novel digital arthrometer to measure anterior tibial translation

BACKGROUND

Measurement of knee laxity after anterior cruciate ligament (ACL) injury is crucial for appropriate treatment and rehabilitation decision-making. This study examined the potential of a new digital arthrometer (Ligs, Innomotion, Shanghai, China) to quantify anterior tibial translation (ATT) in patients with ACL injuries and in healthy subjects.

METHODS

A total of 60 participants included 30 subjects with single-leg ACL injuries and 30 healthy subjects included as controls. The lower leg was immobilized. The thruster is positioned posterior to the lower leg and parallel to the tibial tuberosity in the sagittal plane. The load is applied vertically to the tibia under a dynamic load of 0-150 N, with continuous displacement recorded. The intrarater and interrater reliability will be examined. ATT and side-to-side differences (SSD) between the control and ACL injury groups were compared. Receiver operating characteristic (ROC) curves were analyzed, and the area under the curve (AUC) was calculated to determine the diagnostic accuracy of the Ligs.

RESULTS

The interrater ICC was 0.909 and the intrarater ICC was 0.943. Significant differences in the SSD were observed between the control and ACL injury groups (for all P < 0.05), with the largest effect size (ES = 1.12) at 80 N. When comparing ATT at different loads between injured and healthy sides in the ACL injury group, displacement was statistically significant at different loads. At a load of 150 N, the AUC was the maximum (0.857) and the sensitivity and specificity were 0.87 and 0.73, respectively.

CONCLUSIONS

A digital arthrometer can be used as a quantitative instrument to quantify knee laxity. Quantitative measurement of ATT and SSD under controlled loading can be an objective and effective tool for clinical practice.

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.

Clinical Outcomes After Anterior Cruciate Ligament Injury: Panther Symposium ACL Injury Clinical Outcomes Consensus Group

A stringent outcome assessment is a key aspect of establishing evidence-based clinical guidelines for anterior cruciate ligament (ACL) injury treatment. To establish a standardized assessment of clinical outcome after ACL treatment, a consensus meeting including a multidisciplinary group of ACL experts was held at the ACL Consensus Meeting Panther Symposium, Pittsburgh, Pennsylvania, USA, in June 2019. The aim was to establish a consensus on what data should be reported when conducting an ACL outcome study, what specific outcome measurements should be used, and at what follow-up time those outcomes should be assessed. The group reached consensus on 9 statements by using a modified Delphi method. In general, outcomes after ACL treatment can be divided into 4 robust categories: early adverse events, patient-reported outcomes (PROs), ACL graft failure/recurrent ligament disruption, and clinical measures of knee function and structure. A comprehensive assessment after ACL treatment should aim to provide a complete overview of the treatment result, optimally including the various aspects of outcome categories. For most research questions, a minimum follow-up of 2 years with an optimal follow-up rate of 80% is necessary to achieve a comprehensive assessment. This should include clinical examination, any sustained reinjuries, validated knee-specific PROs, and health-related quality of life questionnaires. In the midterm to long-term follow-up, the presence of osteoarthritis should be evaluated. This consensus paper provides practical guidelines for how the aforementioned entities of outcomes should be reported and suggests the preferred tools for a reliable and valid assessment of outcome after ACL treatment.

Healthy knee KT1000 measurements of anterior tibial translation have significant variation

PURPOSE

The most commonly used arthrometer for measuring and reporting anterior tibial translation after anterior cruciate ligament reconstruction is the KT1000. Reports on its consistency and reproducibility vary in the literature, but it remains the "gold standard". The purpose of this study was to assess agreement of KT1000 measurements in a daily clinical setting.

METHODS

A retrospective analysis of anterior knee translation in the healthy knee of 770 patients over a 17-year time period was performed. In this cohort, a total of 24 investigators performed 1890 measurement sets at 89 Newtons (N), 134N and at maximum manual force (MMax) level. To assess the inter- and intra-observer agreement, the intraclass-correlation coefficient (ICC) was calculated. The "investigator effect" was a difference between two examiners in the same patient and the "device effect'' a difference within one examiner in the same patient. Minimally important difference (MID) was calculated as 0.5 of the standard deviation.

RESULTS

Thirteen investigators were female, performing 1099 measurements and 11 were male, performing 791 measurements. ICC ranged between 0.558 and 0.644. At the MMax level, male investigators had a higher mm reading than female investigators (p < 0.001). Increased experience did not correlate with a higher ICC. MID ranged between 0.85 and 1.65 mm.

CONCLUSION

This study investigated the KT1000 arthrometer in a clinical setting with a large number of investigators. This device delivers moderate agreement of results. Both the device and investigator effect are present. The MMax level has shown the lowest agreement and a dependency on the investigator gender.

LEVEL OF EVIDENCE

Level III diagnostic study.

Clinical outcomes after anterior cruciate ligament injury: panther symposium ACL injury clinical outcomes consensus group

PURPOSE

A stringent outcome assessment is a key aspect for establishing evidence-based clinical guidelines for anterior cruciate ligament (ACL) injury treatment. The aim of this consensus statement was to establish what data should be reported when conducting an ACL outcome study, what specific outcome measurements should be used and at what follow-up time those outcomes should be assessed.

METHODS

To establish a standardized approach to assessment of clinical outcome after ACL treatment, a consensus meeting including a multidisciplinary group of ACL experts was held at the ACL Consensus Meeting Panther Symposium, Pittsburgh, PA; USA, in June 2019. The group reached consensus on nine statements by using a modified Delphi method.

RESULTS

In general, outcomes after ACL treatment can be divided into four robust categories-early adverse events, patient-reported outcomes, ACL graft failure/recurrent ligament disruption and clinical measures of knee function and structure. A comprehensive assessment following ACL treatment should aim to provide a complete overview of the treatment result, optimally including the various aspects of outcome categories. For most research questions, a minimum follow-up of 2 years with an optimal follow-up rate of 80% is necessary to achieve a comprehensive assessment. This should include clinical examination, any sustained re-injuries, validated knee-specific PROs and Health-Related Quality of Life questionnaires. In the mid- to long-term follow-up, the presence of osteoarthritis should be evaluated.

CONCLUSION

This consensus paper provides practical guidelines for how the aforementioned entities of outcomes should be reported and suggests the preferred tools for a reliable and valid assessment of outcome after ACL treatment.

LEVEL OF EVIDENCE

V.

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.

Prospective comparative study of knee laxity with four different methods in anterior cruciate ligament tears

BACKGROUND AND PURPOSE

Anterior knee laxity can be evaluated using different devices, the most commonly used being the Telos®, KT1000®, Rolimeter®, and GNRB®. However, the laxity values obtained with these devices have never been compared to one another. As such, the outcomes of studies using these different knee laxity measurement devices may not be comparable. The primary purpose of this study was to determine the side-to-side laxity difference in patients with one ACL-injured knee, using each of these devices, and to compare the values obtained from each. We hypothesized that the measurements of laxity would vary depending on the device used.

METHODS

This was a prospective study. All patients with an ACL injury, in which surgical reconstruction was planned, underwent pre-operative knee laxity measurements using four different devices. The concordance correlation coefficient (CCC) of the results was compared between the four devices.

RESULTS

The study enrolled 52 patients. With regard to the values of the side-to-side differences, the KT1000® and the GNRB® obtained the most similar values (CCC = 0.51, 95% CI 0.37-0.63). The two devices with the lowest correlation were the Telos® and the Rolimeter® (CCC = 0.04, 95% CI - 0.14-0.23). The comparability was considered average for the KT1000® and GNRB® and poor for the other devices.

CONCLUSIONS

The knee laxity devices used in regular practice are not comparable to one another. As a result, caution must be taken when comparing results from studies using these different devices.

Changes in anteroposterior stability and proprioception after different types of knee arthroplasty

PURPOSE

To compare different types of knee arthroplasty, in selected patients with a knee score above 80 points, for their post-operative changes in anteroposterior (AP) laxity and proprioception.

METHODS

Four groups of each ten patients were tested for AP translation after different types of arthroplasty with a KT-1000 device at 30°, 60° and 90° of flexion. Proprioception of the joint was evaluated by joint position sense with three different tests. Clinical outcome of stability and proprioceptive testing was analysed by comparing the results of three (KSS, KOOS and FJS-12) patient-reported outcome measurement scores (PROMS) for each of the different implant types.

RESULTS

Anteroposterior laxity was observed at 30° and 90° of flexion for the two PS TKA designs included in this study, but not for the UKA or the medial pivot design. All knee designs, except UKA, had an increased laxity at 60° of flexion. Proprioceptive testing was inconclusive. PROMS were not able to identify differences in clinical outcome among different knee designs in these selected patients, despite observed differences in AP laxity.

CONCLUSION

Increased AP laxity is a result of the surgical procedure in knee arthroplasty. UKA is the only design mimicking native laxity of the knee. A medial pivot design can obtain the same result as UKA at 30° and 90° of flexion, but not at the importantly cited 60° of flexion as tested under non-load-bearing conditions. The clinical relevance of this study is that despite of an important range of AP translations among the different knee designs, good-to-excellent patient-reported outcome was observed within the findings of this study.

LEVEL OF EVIDENCE

II.

Anterior cruciate ligament assessment using arthrometry and stress imaging

Arthrometry and stress imaging are useful clinical tools for the objective assessment of anterior cruciate ligament (ACL) integrity. They are most frequently used for the diagnosis of a complete ACL tear when other workup is equivocal, in conjunction with history and clinical exam findings. Other applications include the diagnosis of partial ACL tears, injury prognosis, and post-operative monitoring. However, further studies are needed to validate these uses. Many different devices and techniques exist for objective examination, which have been compared in recent literature. Reliability and validity measures of these methods vary, and often depend upon examiner familiarity and skill. The KT series of devices is the current gold standard for arthrometry, although the newer robotic GNRB device shows promising early results. Newer methods of data interpretation have been developed for stress imaging, and portable technology may impact this field further.

Objective measurements of static anterior and rotational knee laxity

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Diagnostic study, Level III.

Comparative reproducibility of TELOS™ and GNRB® for instrumental measurement of anterior tibial translation in normal knees

BACKGROUND

TELOS™ is among the reference tools for the instrumental measurement of anterior tibial translation during the initial work-up and follow-up of patients with injuries to the anterior cruciate ligament (ACL). GRNB(®) is a non-irradiating but recently developed tool for which only limited data are available.

HYPOTHESIS

The GRNB(®) offers better reproducibility than TELOS™ for measuring anterior tibial translation without rotation in normal knees.

MATERIAL AND METHODS

We retrospectively evaluated instrumental laxity measurements in normal knees. Data were available for 60 TELOS™ measurements (9kg load) and 57 GNRB(®) measurements (89N and 134N loads). For each instrument, we compared the absolute variation in anterior tibial translation between two measurements performed 6 months apart. For each GNRB(®) measurement, patellar pressure was recorded.

RESULTS

No significant differences were found between mean (± SD) variations in translation between the two instruments. A greater than 2.5mm variation between the two measurements was significantly more common with TELOS™ than with GRNB(®) (P<0.05, Chi(2) test). GRNB(®) translation values did not correlate with patellar pressure.

DISCUSSION

The GNRB(®) device offers greater reproducibility than TELOS™ when used to quantitate anterior tibial translation. The limited sample size may have prevented the detection of a significant difference between mean values. In addition, disadvantages of the TELOS™ include radiation exposure of the patient, operator-dependency of measurements made on the radiographs, and absence of a biofeedback system to limit hamstring contraction. GNRB(®) does have hamstring contraction biofeedback control but uses another parameter, namely, patellar pressure, for which the optimal value is unknown. Quadriceps and hamstring co-contraction induced by excessive patellar pressure may influence anterior tibial translation. The optimal patellar pressure value needs to be determined.

Inter-rater reliability of the GNRB® knee arthrometer

BACKGROUND

In clinical settings, where arthrometers are mainly used by different clinicians, knowing the inter-rater reliability of the instrument is crucial in order for the results from different examiners to be accurately interpreted and limitations fully understood. The aim of this study was to evaluate the inter-rater reliability of the GNRB® knee arthrometer.

METHODS

Knee anterior laxity in both knees was tested in a group of young, uninjured subjects (N=27, 13 females) by two examiners. Knee anterior laxity was calculated at test forces of 134 N and 250 N with values presented for the unstandardised and standardised conditions (relative to patellar stabilisation force).

RESULTS

The ICCs ranged from 0.220 to 0.424.

CONCLUSIONS

The inter-rater reliability of the GNRB® knee arthrometer is low.

Robotic knee laxity testing: reliability and normative data

PURPOSE

To evaluate the reliability of the GeNouRoB knee arthrometer and present normative values of knee anterior laxity using this device on young females.

METHODS

Anterior laxity in both knees was tested in two groups of young, uninjured females using the hamstrings electromyography biofeedback feature of the device. There were 13 participants in the group tested for reliability and 23 for the normative study. Laxity (mm of movement of the proximal tibia in the anterior direction relative to the femur) was calculated at test forces of 134 N and 250 N with values presented for the unstandardised and standardised (relative to stabilisation force) conditions.

RESULTS

The relative reliability (95% limits of agreement) of the device for laxity at a test force of 134 N was 2 to 3mm. Left knee anterior laxity was almost 1mm greater than the right.

CONCLUSIONS

The relative reliability of the GeNouRoB arthrometer is comparable to the KT device. In agreement with previous work on the nonrobotic KT arthrometer, the knee anterior laxity values found with the GeNouRoB are greater in the left as compared to the right knee.

Dynamic knee laxity measurement devices

PURPOSE

Studies have reported that knee kinematics and rotational laxity are not restored to native levels following traditional anterior cruciate ligament (ACL) reconstruction. This has led to the development of anatomic ACL reconstruction, which aims to restore native knee kinematics and long-term knee health by replicating normal anatomy as much as possible. The purpose of this review is to give an overview of current dynamic knee laxity measurement devices with the purpose of investigating the significance of dynamic laxity measurement of the knee. Gait analysis is not included.

METHODS

The subject was discussed with experts in the field in order to perform a level V review. MEDLINE was searched according to the discussions for relevant articles using multiple different search terms. All found abstracts were read and scanned for relevance to the subject. The reference lists of the relevant articles were searched for additional articles related to the subject.

RESULTS

There are a variety of techniques reported to measure dynamic laxity of the knee. Technical development of methods is one important part toward better understanding of knee kinematics. Validation of devices has shown to be difficult due to the lack of gold standard. Different studies use various methods to examine different components of dynamic laxity, which makes comparisons between studies challenging.

CONCLUSION

Several devices can be used to evaluate dynamic laxity of the knee. At the present time, the devices are continuously under development. Future implementation should include primary basic research, including validation and reliability testing, as well as part of individualized surgery and clinical follow-up.

LEVEL OF EVIDENCE

Diagnostic study, Level V.

Instrumented examination of anterior cruciate ligament injuries: minimizing flaws of the manual clinical examination

The clinical examination is a basic language of orthopaedics; it is how orthopaedic surgeons communicate with one another. However, each surgeon speaks a different dialect that has been influenced by where and with whom that surgeon trained, as well as that person's own experiences. Because of the inherent variability in the magnitude, direction, and rate of force application during the clinical examination, manual arthrometers were developed in an attempt to more consistently quantify the clinical examination. Instrumented manual devices, such as the KT-1000 (MEDmetric, San Diego, CA), were the first to provide objective numbers to surgeons and researchers evaluating anteroposterior (AP) knee joint laxity. Although these devices provide surgeons with feedback related to the amount of force applied, the rate at which the force is applied is uncontrolled, resulting in a lack of reliability similar to that of the clinical examination itself. In addition to potential errors in measuring AP laxity, rotational laxity has proven to be very difficult to quantify. Robotic systems that make use of computer-driven motors to perform laxity testing have recently been developed to control the magnitude, direction, and rate of force application and thus improve the accuracy and reliability of both AP and rotational laxity evaluation. This review discusses the evolution of instrumented clinical knee examination over the past 3 decades and highlights the advantages and disadvantages of the various testing systems, as well as how current and future developments in this area may improve the field of orthopaedics by minimizing the flaws of the manual clinical examination.

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.