GNRB® laximeter with magnetic resonance imaging in clinical practice for complete and partial anterior cruciate ligament tears detection: A prospective diagnostic study with arthroscopic validation on 214 patients.

BACKGROUND: Accurate diagnosis of anterior cruciate ligament (ACL) injury is not always obtained with magnetic resonance imaging (MRI). Other tools, such as the GNRB® arthrometer, help to accurately identify the type of ACL tear. The aim of this study was to show that the GNRB® could be a relevant complementary solution to MRI in ACL injuries detection. METHODS: A prospective study performed between 2016 and 2020 included 214 patients who had undergone knee surgery. The study compared sensitivity/specificity pairs of MRI and the GNRB® at 134 N to detect healthy ACL, partial and complete ACL tears. Arthroscopies were the 'gold standard'. Forty-six patients had a healthy ACL with associated knee lesions, 168 patients had ACL tears where 107 were complete tears and 61 were partial tears. RESULTS: For healthy ACL, MRI scored 100% for sensitivity (SE) and 95% for specificity (SP), and the GNRB® scored SE 95.65% and SP 97.5% at 134 N. For complete ACL tears, MRI scored 80.81% for sensitivity (SE) and 64.49% for specificity (SP), and the GNRB® scored SE 77.78% and SP 85.98% at 134 N. For partial tears, MRI scored SE 29.51% and SP 88.97%, and the GNRB® scored SE 73.77% and SP 85.52% at 134 N. CONCLUSION: GNRB® sensitivity and specificity were equivalent to those of MRI for healthy ACL and complete ACL tear detection. However, MRI had some difficulty in detecting partial ACL tears compared with the GNRB® which showed better sensitivity.

Intra-rater reliability of the knee arthrometer GNRB® for measuring knee anterior laxity in healthy, active subjects.

Background: Arthrometers are used to assess knee anterior laxity and to evaluate the integrity of the anterior cruciate ligament. Assessment of knee anterior laxity is crucial part of the clinical examination. The aim of this study was to investigate the intra-rater reliability of the GNRB® in healthy subjects. Methods: In the study participated 97 subjects and two measurements using a GNRB® arthrometer were performed. Males were tested two times one week a part. Females were tested two times within 24 h. Measurements were performed at the following forces 134 N, 134 N, 150 N, 200 N, and 200 N. To evaluate the reliability of GNRB® measurements an intraclass correlation coefficient was calculated. Results: Intra-rater reliability of the GNRB® measurements is good for 134 N on the left knee (ICC = 0.848) and the right knee (ICC = 0.788) and for 200 N on the left knee (ICC = 0.805) and the right knee (ICC = 0.756). Conclusion: The GNRB® knee arthrometer has good intra-reliability for measurements at the 134 N and 200 N forces. Reliability can be increased with the standardize position of the subject, the stabilization of the patella and standardize measurement protocol.

Suture-tape augmentation of anterior cruciate ligament reconstruction: a prospective, randomised controlled trial (STACLR).

BACKGROUND: Anterior cruciate ligament (ACL) reconstruction aims to restore anteroposterior and rotatory stability to the knee following ACL injury. This requires the graft to withstand the forces applied during the process of ligamentisation and the rehabilitative period. We hypothesise that the use of suture tape augmentation of single bundle ACL reconstruction (ACLR) will reduce residual knee laxity and improve patient-reported outcomes at 2-year follow-up. We will conduct a 1:1 parallel arm single-centre randomised controlled trial comparing suture tape augmented ACLR to standard ACLR technique. METHODS: The study design will be a parallel arm 1:1 allocation ratio randomised controlled trial. Sixty-six patients aged 18 and over waitlisted for primary ACLR will be randomised. Patients requiring osteotomy and extra-articular tenodesis and who have had previous contralateral ACL rupture or repair of meniscal or cartilage pathology that modifies the post-operative rehabilitation will be excluded. The primary outcome measure will be the side-to-side difference in anterior tibial translation (measured on the GNRB arthrometer) at 24 months post-surgery. GNRB arthrometer measures will also be taken preoperatively, at 3 months and 12 months post-surgery. Secondary outcomes will include patient-reported outcome measures (PROMs) collected online, including quality of life, activity and readiness to return to sport, complication rates (return to theatre, graft failure and rates of sterile effusion), examination findings and return to sport outcomes. Participants will be seen preoperatively, at 6 weeks, 3 months, 12 months and 24 months post-surgery. Participants and those taking arthrometer measures will be blinded to allocation. DISCUSSION: This will be the first randomised trial to investigate the effect of suture-tape augmentation of ACLR on either objective or subjective outcome measures. The use of suture-tape augmentation in ACLR has been associated with promising biomechanical and animal-level studies, exhibiting equivalent complication profiles to the standard technique, with initial non-comparative clinical studies establishing possible areas of advantage for the technique. The successful completion of this trial will allow for an improved understanding of the in situ validity of tape augmentation whilst potentially providing a further platform for surgical stabilisation of the ACL graft. TRIAL REGISTRATION: Australia New Zealand Clinical Trial Registry ACTRN12621001162808. Universal Trial Number (UTN): U1111-1268-1487. Registered prospectively on 27 August 2021.

Outcomes of Combined Anterior Cruciate Ligament and Anterolateral Ligament Reconstruction According to GNRB Arthrometer Measurement.

Background and Objectives: To investigate the prognosis of combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstruction, we used a GNRB (Genourob, Laval, France) arthrometer to measure surgical outcomes. Materials and Methods: This retrospective study reviewed patients who underwent combined ACL and ALL reconstruction and had a minimum follow-up of 2 years. Subjective outcomes, namely the International Knee Documentation Committee (IKDC) evaluation form scale scores and Lysholm scores, were evaluated preoperatively and postoperatively. We used a GNRB arthrometer to test the side-to-side laxity under pressures of 134 and 200 N, and we calculated the differential of the slope of the curves. We also recorded complications. Results: Our study examined 18 patients (mean age: 30.56 ± 8.9 years, range: 19-53) with a mean follow-up of 27.37 ± 3.4 months (range: 24-36). Both Lysholm and IKDC scores were significantly improved following the operation. The GNRB arthrometer measured mean anteroposterior laxity side-to-side as 0.76 ± 0.78 mm and 0.82 ± 0.8 mm under pressures of 134 and 200 N, respectively. The mean side-to-side differential slope under 200 N was 3.52 ± 2.17 µm/N. These values indicated that patients displayed no graft tear or low functional knee instability. All patients had a grade 3 pivot shift preoperatively; only two patients had a grade 1 pivot shift postoperatively, with the rest having a negative pivot shift. Conclusions: Our study revealed that combined ACL and ALL reconstruction has an excellent prognosis. GNRB measurement demonstrated excellent stability, and most patients had no residual pivot shift.

The lateral femoral notch sign and coronal lateral collateral ligament sign in magnetic resonance imaging failed to predict dynamic anterior tibial laxity.

PURPOSE: To investigate the relationship between the lateral femoral notch sign as well as the coronal lateral collateral ligament (LCL) sign and anterior tibial translation using the GNRB arthrometer in patients with anterior cruciate ligament (ACL) injuries. METHODS: Forty-six patients with ACL injuries were retrospectively included from May 2020 to February 2022; four patients were excluded due to incomplete data. Magnetic resonance imaging (MRI) were reviewed for the lateral femoral notch sign and the coronal LCL sign. The GNRB arthrometer was used to evaluate the dynamic anterior tibial translation of the knee, and the side-to-side differences (SSDs) in tibial translation between the injured knee and healthy knee were calculated at different force levels. Two types of slopes for displacement-force curves were acquired. RESULTS: Six patients (14.3%) had the positive lateral femoral notch sign (notch depth > 2.0 mm), and 14 patients (33.3%) had the positive coronal LCL sign. The SSD of the anterior tibial translations under different loads as well as the slopes of displacement-force curves were the same in the positive and negative notch sign groups (p all > 0.05) and between the positive and negative coronal LCL sign groups (p all > 0.05). Meanwhile, the measured notch depth and notch length were also not significantly correlated with the anterior tibial translation SSD in the GNRB. CONCLUSION: The presence of the lateral femoral notch sign and the coronal LCL sign did not indicate greater dynamic tibial laxity as measured using the GNRB.

Influence of residual anterior laxity on functional outcomes after anterior cruciate ligament reconstruction.

INTRODUCTION: Residual laxity can persist after anterior cruciate ligament (ACL) reconstruction. This increased anterior translation can be measured with a knee arthrometer. Nevertheless, the measurement parameters and functional impact of this residual laxity are not well understood. The aims of this study were to (1) evaluate the effect of applying loads of 134N, 200N and 250N on the measured residual laxity after ACL reconstruction and (2) evaluate the prognostic ability of the various measurement parameters on the functional outcomes. HYPOTHESIS: After ACL reconstruction, the functional outcomes will be correlated to the postoperative residual laxity. METHODS: We did a prospective study of 61 recreational athletes who underwent surgical reconstruction of their ACL with the Kenneth-Jones technique between 2016 and 2019. The mean age of these patients was 27±7 years, and most were men (75%). The side-to-side difference in laxity was measured pre- and postoperatively using the GNRB® arthrometer at three load levels: 134N, 200N and 250N. The functional outcomes were determined based on the return to sports and the KOOS, IKDC and ARPEGE scores. The mean follow-up was 30±10 months. RESULTS: Half the patients had returned to sport at their pre-injury levels, while 25% had returned to a lower level and 25% had stopped doing any physical activity. At 134N, a 1-mm increase in side-to-side difference was associated with a 2-fold higher risk of not returning to sports (OR 2; 95% CI 1.22-3.23; p<0.01). At 200N, a 1-mm increase in side-to-side difference was associated with a 50% higher probability of having a poor/fair ARPEGE score (OR 1.5; 95% CI 1.05-2.02; p=0.02). At 200N, a 4-mm side-to-side difference was the prognostic threshold for failure to return to sports with a positive predictive value of 86% and specificity of 98%. CONCLUSIONS: This case series found a strong correlation between residual laxity and the functional outcomes after ACL reconstruction. A threshold of 4mm residual laxity evaluated on the GNRB® at 200N was predictive of adverse outcomes and failure to return to sports in our population of recreational athletes. LEVEL OF EVIDENCE: IV, retrospective study.

Anterior knee translation measurements after ACL reconstruction are influenced by the type of laximeter used.

PURPOSE: Laximeters were designed to diagnose an anterior cruciate ligament (ACL) deficient knee, but their use has now focused on providing an objective assessment of the anterior translation (AT) of an intact and ACL-reconstructed knee. In this study we report the introduction and direct comparison of an automated and computerized AT measurement device, GNRB, with the device previously established by the institute and as the current literature standard, the KT1000. METHODS: A prospective data collection was commenced upon introduction of the GNRB. The measurements of AT in each patient were performed by the same investigator with each device using 134 N applied to both knees, giving a side-to-side difference. The investigators were a sport scientist, a biomechanical engineer and a physiotherapist. Increased AT was defined as a difference > 3 mm. RESULTS: Three investigators performed the measurements in 122 patients, 9.8 (± 1.8) months after ACL reconstruction. Mean AT of the healthy knee was 5.7 mm with KT1000 and 4.4 mm with GNRB (p = 0.002). Mean AT of the ACL reconstructed knee was 7.0 mm with the KT1000 and 5.3 mm with the GNRB (p = 0.037). The KT1000 had a higher variance of results than the GNRB (p < 0.001). There were 25 patients with increased AT measured by KT1000 compared with 12 patients using the GNRB (p < 0.016), with only 5 on both devices. CONCLUSIONS: GNRB has better consistency of results when compared to the KT1000. Both devices lack comparability for detecting increased AT, with the KT1000 recording a side-to-side difference of more than 3 mm in twice as many patients as the GNRB. LEVEL OF EVIDENCE: II.

[Performance of magnetic resonance imaging ang genourob laximetry in anterior cruciate ligament rupture in 30 cases]. / Performance de l'imagerie par resonance magnetique et de la laximetrie a genourob dans les ruptures du ligament croise anterieur a propos de 30 cas.

INTRODUCTION: The aim of this work was to evaluate the diagnostic contribution of magnetic resonance imaging and genourob compared to intraoperative arthroscopy. The objective was to implement a protocol based on magnetic resonance imaging and / or genourob. MATERIALS AND METHODS: We did a cross-sectional study from July 18, 2016 to July 19, 2017 at the Maltese hospital comparing the results of MRI and GNRB from 30 patients compared to intraoperative arthroscopy data. RESULTS: Complete break.- In MRI, we obtained a sensitivity (Se) of 95.7%, a specificity (Sp) of 85.7%.- At the GNRB, we found a Se of 87%, a Sp of 42.9%.Partially broken.- In MRI we obtained a Se of 85.7%, a Sp of 95.7%.- At the GNRB, we found a Se of 42.9%, a Sp of 87%. CONCLUSION: MRI is better than GNRB. The GNRB does not improve the results of the MRI. It has no diagnostic contribution in the rupture of the ACL knee. It is a device used by the orthopedists to evaluate knee laxity that does not depend on the ACL alone.

INTRODUCTION: Le but de ce travail était d'évaluer l'apport diagnostique de l'imagerie par résonance magnétique (IRM) et du genourob (GNRB) par rapport à l'arthroscopie per opératoire. L'objectif était de mettre en place un protocole basé sur l'IRM et / ou le GNRB. MATÉRIELS ET MÉTHODES: Nous avons fait une étude transversale allant du 18 Juillet 2016 au 19 juillet 2017au centre hospitalier de l'ordre de malte en comparant les résultats d'IRM et du GNRB de 30 patients par rapport aux données de l'arthroscopie per opératoire. RÉSULTATS: ✓ Rupture complète.- En IRM, nous avons obtenu une sensibilité (Se) de 95,7 %, une spécificité(Sp) de 85,7%.- Au GNRB, nous avons trouvé une Se de 87 %, une Sp de 42,9%.✓ Rupture partielle.- En IRM, nous avons obtenu une Se de 85,7 %, une Spde 95,7%.- Au GNRB, nous avons trouvé uneSe de 42,9 %, une Sp de 87%. CONCLUSION: L'IRM est plus performante que le GNRB. Le GNRB ne permet pas d'améliorer les résultats de l'IRM. Il n'a pas d'apport diagnostique dans la rupture du LCA du genou. C'est un dispositif utilisé par les orthopédistes pour évaluer une laxité du genou qui ne dépend pas du LCA à lui seul.

Joint laxity and graft compliance increase during the first year following ACL reconstruction with short hamstring tendon grafts.

PURPOSE: Evaluating joint laxity and graft compliance after ACL surgery may be used to quantify biomechanical graft properties during the ligamentization process. This study aimed to analyse the evolvement of joint laxity and graft compliance of short hamstring tendon grafts after ACL reconstruction (ACLR). METHODS: Forty-seven patients that underwent ACLR were retrospectively enrolled. Joint laxity was quantified with a GNRB® arthrometer before surgery, then at 15 days, at 1/3/6/9 months (M1-M9), at 1 year postoperatively and then again at the last mean follow-up (FU) of 14.7 ± 3.0 months. The side-to-side laxity difference (ΔL in mm) was measured at 30 and 60 N at every FU, additionally at 90 N from M3 on and at 134 N from M6 on. The side-to-side compliance difference (ΔC in µm/N) was calculated for each graft. RESULTS: Mean ΔL and ΔC decreased significantly between preoperative and M1 for all applied forces (at 30 N, ΔL: 0.8 mm, p < 0.0001; ΔC: 25.9 µm/N, p < 0.001). Between M1 and M9, ΔL increased significantly at 30 N (p = 0.02) and 60 N (p < 0.001), while ΔC increased by 15.2 µm/N at 30 N (p = 0.003) and 14.9 µm/N at 60 N (p = 0.001). Between M9 and the last FU, there were no significant differences for ΔL and ΔC. CONCLUSION: Joint laxity and graft compliance evolve during the first postoperative year with a phase between the first and ninth postoperative month of relative weakness. According to the established evolvement profile, return to pivoting or contact sports should be considered only after stabilization of joint laxity and graft compliance. LEVEL OF EVIDENCE: Retrospective cohort study, Level III.

Evaluation of reproducibility of robotic knee testing device (GNRB) on 60 healthy knees.

INTRODUCTION: There is a main concern about the usefulness and the accuracy of the different laximeters. The GnrB device is becoming more popular, but according to the literature it's not clear whether it is fully reliable. OBJECTIVE: GNRB laxity measurements are not reproducible for measurement of anterior translation of the tibia. MATERIAL AND METHODS: We analyzed the reproducibility of GNRB measurements in healthy subjects by the Test-Retest method in 2 sessions. RESULTS: 30 pairs of healthy knees were assessed. Test-Retest agreement was poor for both absolute values and for differentials at 134 and 200 N with an intra-class correlation ranging from 0.210 to 0.486. There was a significant differance in anterior tibial translation, in side-to-side difference, according to the patellar pressure. CONCLUSION: The reproducibility is found to be poor under optimum conditions of comparability. The patellar pressure influences strongly thelaxity value.

Diagnostic Tools for Acute Anterior Cruciate Ligament Injury: GNRB, Lachman Test, and Telos.

PURPOSE: The purpose of this study is to compare the accuracy of the GNRB arthrometer (Genourob), Lachman test, and Telos device (GmbH) in acute anterior cruciate ligament (ACL) injuries and to evaluate the accuracy of each diagnostic tool according to the length of time from injury to examination. MATERIALS AND METHODS: From September 2015 to September 2016, 40 cases of complete ACL rupture were reviewed. We divided the time from injury to examination into three periods of 10 days each and analyzed the diagnostic tools according to the time frame. RESULTS: An analysis of the area under the curve (AUC) of a receiver operating characteristic curve showed that all diagnostic tools were fairly informative. The GNRB showed a higher AUC than other diagnostic tools. In 10 cases assessed within 10 days after injury, the GNRB showed statistically significant side-to-side difference in laxity (p＜0.001), whereas the Telos test and Lachman test did not show significantly different laxity (p=0.541 and p=0.413, respectively). CONCLUSIONS: All diagnostic values of the GNRB were better than other diagnostic tools in acute ACL injuries. The GNRB was more effective in acute ACL injuries examined within 10 days of injury. The GNRB arthrometer can be a useful diagnostic tool for acute ACL injuries.

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.

Diagnostic Tools for Acute Anterior Cruciate Ligament Injury: GNRB, Lachman Test, and Telos

PURPOSE: The purpose of this study is to compare the accuracy of the GNRB arthrometer (Genourob), Lachman test, and Telos device (GmbH) in acute anterior cruciate ligament (ACL) injuries and to evaluate the accuracy of each diagnostic tool according to the length of time from injury to examination. MATERIALS AND METHODS: From September 2015 to September 2016, 40 cases of complete ACL rupture were reviewed. We divided the time from injury to examination into three periods of 10 days each and analyzed the diagnostic tools according to the time frame. RESULTS: An analysis of the area under the curve (AUC) of a receiver operating characteristic curve showed that all diagnostic tools were fairly informative. The GNRB showed a higher AUC than other diagnostic tools. In 10 cases assessed within 10 days after injury, the GNRB showed statistically significant side-to-side difference in laxity (p<0.001), whereas the Telos test and Lachman test did not show significantly different laxity (p=0.541 and p=0.413, respectively). CONCLUSIONS: All diagnostic values of the GNRB were better than other diagnostic tools in acute ACL injuries. The GNRB was more effective in acute ACL injuries examined within 10 days of injury. The GNRB arthrometer can be a useful diagnostic tool for acute ACL injuries.

Experimental validation of the GNRB® for measuring anterior tibial translation.

INTRODUCTION: The objective of this study was to validate the technique used to measure anterior tibial translation in cadaver knees using the GNRB® device by comparing it with the gold standard, the OrthoPilot® navigation system. HYPOTHESIS: Simultaneous measurement of anterior tibial translation by the GNRB® and the OrthoPilot® in the chosen experimental conditions will result in significant differences between devices. MATERIAL AND METHODS: Five fresh frozen cadavers were used. The knee was placed in 20° flexion. Four calibrated posterior-anterior forces (134N to 250N) were applied. For each applied force, the anterior tibial translation was measured simultaneously by both devices. Two conditions were analyzed: anterior cruciate ligament (ACL) intact and ACL transected. The primary criterion was anterior tibial translation at 250N. The measurements were compared using a paired Student's t-test and the correlation coefficient was calculated. Agreement between the two methods was determined using Bland-Altman plots. Consistency of the measurements was determined by calculating the intraclass correlation coefficient. RESULTS: For all applied forces and ligament conditions, the mean difference between the GNRB® and the navigation system was 0.1±1.7mm (n.s). Out of the 80 measurements taken, the difference between devices was less than ±2mm in 66 cases (82%). There was a strong correlation, good agreement and high consistency between the two measurement methods. DISCUSSION: The differences between the measurements taken by the GNRB® and the navigation system were small and likely have no clinical impact. We recommend using the GNRB® to evaluate anterior knee laxity. LEVEL OF EVIDENCE: II controlled laboratory study.

ACL reconstruction in 11 children using the Clocheville surgical technique: Objective and subjective evaluation.

INTRODUCTION: The over-the-top position of the femoral metaphyseal tunnel during extraphyseal ligament reconstruction of the anterior cruciate ligament (ACL) according to Clocheville may be responsible for negative anisometry. Until now, the follow-up of children operated using this pediatric technique was limited to screening for iatrogenic epiphysiodesis and the search for postoperative clinical instability. The objective of this study was to measure residual laxity using objective tests, to quantify muscle recovery, and to evaluate the quality of life of these patients in terms of the sports activities. MATERIAL AND METHODS: Eleven patients with a mean age of 13.5years were seen at a mean 2.1years of follow-up. They underwent objective clinical tests (GNRB(®) arthrometer and CON-TREX(®) dynamometer) as well as subjective questionnaires (IKDC and KOOS). RESULTS: No significant difference was found between the healthy knee and the operated knee for either the GNRB(®) at 134N (P=0.79) or at 200N (P=0.98). The CON-TREX(®) system allowed us to measure a median percentage of quadriceps recovery of 80.7% (range, 52.2-114.5) in terms of muscle power (60°/s) and 81.2% (range, 51.6-109.6) for muscle response (180°/s). The median subjective IKDC score was 94.73/100 (range, 73.68-98.93); 72.7% of the patients resumed competitive sports. DISCUSSION: This study's lack of statistical power did not show a significant difference in terms of residual laxity at rest of GNRB(®) transplants, while a mean differential of +0.4mm was observed. Although pediatric transphyseal ligament reconstruction techniques are increasingly used, the Clocheville technique remains, in our opinion, an attractive surgical alternative in the youngest subjects, with no major risk of iatrogenic epiphysiodesis even though it is theoretically anisometric. LEVEL OF EVIDENCE: IV.

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.

Diagnostic value of the GNRB ® in relation to pressure load for complete ACL tears: A prospective case-control study of 118 subjects.

INTRODUCTION: The GNRB(®) is a reliable, validated arthrometer. A pressure pad exerts 0 to 250 Newtons of pressure on the upper calf. The goal of this study was to compare the diagnostic value of the different pressure loads that are usually applied for the diagnosis of complete anterior cruciate ligament (ACL) tears. Our hypothesis was that a load of 200N would be sufficient to diagnose these tears. PATIENTS AND METHODS: A prospective comparative case-control study was performed in 2012. One group included all the male athletes aged 15 to 21 who presented with a complete ACL tear confirmed by arthroscopy (the study group). The control group included male soccer players in a training center aged 15 to 19 with no history of knee injuries (the control group). Anterior laxity was measured in both knees by the same experienced operator using the GNRB(®) system. The main judgment criteria were the diagnostic values of each pressure load evaluated by the area under the curve (AUC), from "Null" (AUC < 0.5) to "Perfect" (AUC = 1). RESULTS: This study included 118 men: 64 in the study group, mean age 18.1 ± 2.3-years-old, who were mainly soccer players (39/64) or rugby men (16/64) and 54 control subjects, mean age 17.3 ± 1.5-years-old. Three hyperalgesic patients could not receive a pressure load of 250N. The mean differential laxity was significantly higher in the control group, whatever the pressure load (P < 10(-5)). The test was "highly informative" for all loads (0.9 ≤ AUC < 1). Analysis of the AUC revealed a diagnostic value in descending order of: 200N(0.97[0.94-1]) > 134N(0.97[0.93-0.99]) > 250N(0.96[0.93-0.99]) > 89N(0.95[0.90-0.99]). CONCLUSION: The GNRB(®) at 200N was shown to be sufficient to diagnose complete ACL tears. Applying a pressure load of 250N does not appear to be useful.

Anterior knee laxity measurement using stress radiographs and the GNRB(®) system versus intraoperative navigation.

BACKGROUND: Anterior knee laxity measurement serves both to diagnose and to evaluate the severity of anterior cruciate ligament (ACL) damage. HYPOTHESIS: We tested the hypothesis that anterior laxity measurements of ACL-deficient knees obtained using the GNRB(®) system and stress radiographs differed from each other and from intraoperative navigation measurement taken as the reference standard. MATERIAL AND METHODS: Twenty-one patients with chronic ACL deficiency underwent arthroscopic ACL reconstruction. Anterior knee laxity was measured preoperatively using the GNRB(®) system without anaesthesia and anterior-drawer stress radiographs under anaesthesia then intraoperatively using a non-image-based navigation system. RESULTS: The three measurements differed significantly (P=0.05). A systematic measurement error of -3.7 mm occurred for both preoperative measurements versus the reference standard. No significant difference was found between the two preoperative measurements. DISCUSSION: The GNRB(®) system should be preferred over stress radiographs, as reliability is similar but no radiation exposure is required. Both preoperative measurement methods underestimate anterior laxity as measured intraoperatively using the navigation system. This systematic bias may be relevant to treatment decision-making. LEVEL OF EVIDENCE: II, development of a diagnostic criterion in consecutive patients versus a validated reference standard.