Rotational Knee Laxity Research Articles

Aggravated Rotational Laxity Due To The Concomitant Meniscus Tear In The Anterior Cruciate Ligament-Injured Knees Detected By The Quantitative Measurement Of The Pivot-Shift Test

The impact of meniscus injury on the rotational laxity in the ACL injured knees has not been fully examined in clinical cases due to lack of quantitative evaluation. Electromagnetic system was then used to quantify the rotational laxity in ACL-injured cases with and without meniscus tear. As a result, concomitant lateral meniscus tear deteriorated the rotational laxity in the ACL-injured knees. Meniscus injury is quite frequently accompanied with the anterior cruciate ligament (ACL) injury and assumed to have significant impact on the rotational laxity based on previous in-vitro studies. However, it is still unknown how the concomitant meniscus injury affects the rotational laxity of the ACL-deficient knees in vivo because of the roughness and variability of the clinical pivot-shift test. Recently, a meticulous assessment of the pivot-shift test has become possible in clinical cases with the development of the quantitative measurement technology. The purpose of this study was to determine the effect of the meniscus tear on the rotational laxity in the ACL-deficient knees. Fifty-seven unilateral ACL-injured patients (26 males and 31 females, 24 ± 10 y.o.) were included. Just prior to the ACL reconstruction, the pivot-shift test was performed under general anesthesia while conducting the quantitative evaluation using electromagnetic measurement system (EMS) to provide the tibial acceleration (m/sec2) concurrently with clinical IKDC grading (none, glide, clunk, and gross). Meniscus injuries were arthroscopically diagnosed during the ACL reconstruction. Chi-square test and independent t-test was used to assess the difference between the knees with and without meniscus tear. Subgroup analysis was then performed in the same manner for each medial and lateral meniscus tear separately. Statistical significance was defined as p-value of <0.05. Concomitant meniscus tear was observed in 32 knees. There was a significant difference of clinical grading between the ACL injured knees with and without meniscus tear (p<0.05). Tendency of increased pivot-shift measurements in the meniscus torn knees was demonstrated by the quantitative evaluation, but statistical significance was not achieved (meniscus-injured knees 1.6 ± 1.1 m/sec2 vs meniscus-intact knees 1.3 ± 0.8 m/sec2, p=0.09). Subgroup analysis showed that the ACL-deficient knees with lateral meniscus tear had larger tibial acceleration (1.8 ± 1.1 m/sec2, n=19) than the meniscus intact knees (p<0.05), whereas the medial meniscus torn knees (1.4 ± 1.0 m/sec2, n=20) did not show aggravated rotational laxity (p=0.33). There are several potential anatomic structures which were suggested to affect the knee rotational laxity in the ACL injured knees, including other ligaments, meniscus, cartilage and anterolateral capsular ligament. Although the meniscus injury is the most common in addition to the ACL injury, the impact of the meniscus injury on the knee rotational laxity has not been fully examined. This study demonstrated the significant impact of the meniscus injury, especially lateral meniscus injury, on the rotational laxity in the ACL-deficient knees, which was successfully detected by using the quantitative measurement device. The meniscus injury should not be overlooked when considering the secondary restraint for the rotational laxity in the ACL injury, though the anterolateral capsular ligament has been recently focused on. The clinical demand to repair the lateral meniscus, if any, can be reaffirmed, and a careful inspection of the lateral meniscus tear should be required in the ACL-deficient knees with a substantial pivot-shift. The concomitant meniscus tear, especially lateral meniscus tear, has a significant impact on the knee rotational laxity in the ACL-injured knees.

The Influence of the Section of the Antero-Lateral Knee Ligament on Rotational Laxity of the Knee. An Experimental Study

Anterolateral knee ligament may have little impact on rotational laxity when ilio-tibial band is preserved. The anatomy of the antero-lateral ligament (ALL) of the knee has been described on anatomic preparation, suggesting that this ligament might be a restraint of knee internal rotation. However, experimental results showed conflicting results about the impact of the ALL on knee stability. The goal of the study was to measure the changes in the rotational knee laxity according to the status of the antero-lateral ligament (ALL) and of the anterior cruciate ligament (ACL). We hypothesized that section of the ALL will significantly increase the rotational laxity of the knee. 5 pairs of fresh frozen gross specimens were analyzed. The knee was positioned at 20° of flexion on a special splint. An increasing calibrated internal/external torque was applied; the knee internal/external rotation was measured by a navigation system for each applied torque. Three settings were used for each knee: intact ACL and ALL, section of the ACL or ALL (randomly assigned to each knee of a pair), section of both ACL and ALL. The reference for each knee was the measurement by intact knee. The primary criterion was the rotational laxity at 8 Nm. The paired increase of rotational laxity was calculated for each situation. The results were compared between all couples of situations with a Mann-Whitney test at a 0.05 level of significance. Similar process was performed for stiffness. The mean rotational laxity for intact knees was 27.1 ± 3.7 degrees. There was no significant difference between right (26.6 ± 4.0 degrees) and left (27.6 ± 3.8 degrees) knees. The mean paired increase was 0.8 degrees after isolated ALL section, 1.2 degrees after isolated ACL section, and 0.8 degrees after combined ALL and ACL section. There was no significant increase of rotational laxity after isolated ALL section. There was no significant increase after isolated ACL section. There was no significant difference after additional ALL section by ACL deficient knees. The mean knee stiffness in rotation for intact knees was 3.18 ± 0.7 Nm/degree. There was no significant difference between right (3.2 ± 0.6 Nm/degree) and left (3.2 ± 0.9 Nm/degree) knees. The mean paired increase was 0.16 Nm/degree after isolated ALL section, 0.16 Nm/degree after isolated ACL section, and 0.24 Nm/degree after combined ALL and ACL section. There was no significant increase after isolated ALL section. There was no significant increase after isolated ACL section. There was no significant difference after additional ALL section by ACL deficient knees. The main result of this study is that section of the ALL did not significantly impact rotational knee laxity and rotational stiffness of the knee in comparison to normal knee, neither isolated or by ACL deficient knee. The expected role of ALL in controlling rotational knee laxity could not be confirmed. We suggest that preservation of the iliotibial band may be a major explanation for these unexpected results. We suggest that the potential influence of the ALL on knee stability should be further investigated before performing routine ALL reconstruction. Anterolateral knee ligament may have little impact on rotational laxity when iliotibial band is preserved.

Satisfactory knee function after single-stage posterolateral corner reconstruction in the multi-ligament injured/dislocated knee using the anatomic single-graft technique.

Increasing importance has been placed on the posterolateral corner (PLC) in maintaining varus and rotational stability of the knee. The goal of this study was to evaluate knee function and clinical stability following a single-graft PLC reconstruction technique and identify factors associated with poor knee function. This study identified patients with a multi-ligament knee injury between 2006 and 2013. Patients who received a single-graft fibular collateral ligament and PLC reconstruction with a single-stage surgery during the study period and had a minimum follow-up of 2years after surgery were included. Functional outcomes were assessed using Lysholm and IKDC scores. Varus and rotational knee laxity and range of motion were assessed using physical examination. The final study cohort included 61 patients who underwent PLC reconstruction using a single-graft technique. The mean IKDC score was 74.1 (±22.3) and the mean Lysholm score was 80.3 (±21.8) at mean follow-up of 3.8years (range 2-9years). Mean range of motion at final follow-up measured from 0° to 126° [range flexion: 95-145, range extension: 0-5]. Fifty-eight patients (95%) had grade 0 varus laxity in full knee extension, and 54 patients (88.5%) had grade 0 varus laxity at 30° of knee flexion. Female gender was associated with a lower postoperative IKDC score (p=0.04). Surgical treatment of the PLC using a single-graft technique can result in satisfactory knee function and stable physical examination findings at minimum 2years after surgery. Female gender was predictive of poor knee function after PLC reconstruction. Surgical treatment of PLC injuries should be individualized based on the timing of surgery, specific injured knee structures, and physical examination findings. This study helps validate the use of a single-graft technique for PLC reconstruction and can be used to help counsel patients about expected knee function after surgical treatment of PLC injuries. Level of evidence IV.

Concomitant Lateral Meniscus Injury Aggravates Rotational Laxity of the Anterior Cruciate Ligament Injured Knees

Objectives:Residual rotational laxity in the anterior cruciate ligament (ACL) reconstructed knees is a remaining problem after the ACL reconstruction. Improper detection and treatment of the secondary restraint for the knee rotational laxity after the ACL were considered as the major reason for the problem. Although anterolateral ligamentous structure of the knee has increasingly been focused on, meniscus injury is frequently accompanied with the ACL injury and assumed to have significant impact on the rotational laxity based on previous studies. The purpose of this study was to determine the effect of the meniscus tear on the rotational laxity in the ACL-deficient knees.Methods:Fifty-seven unilateral ACL-injured patients (26 males and 31 females, 24 ± 10 y.o.) were tested. The protocol of this study was approved by the IRB in Kobe University, and the informed consent was obtained from all the patients. The pivot-shift test was performed under general anesthesia during their ACL reconstruction. (Fig.1) Clinical grading according to the IKDC (none, glide, clunk, and gross) was determined, whereas the quantitative assessment of the pivot-shift was conducted using electromagnetic measurement system to provide the tibial acceleration (m/sec2). Meniscus injuries were finally confirmed under arthroscopy during the ACL reconstruction. The difference of clinical grading and tibial acceleration between the ACL-injured knees with and without additional meniscus tear was assessed, followed by subgroup analysis for each medial and lateral meniscus tear separately. Statistical significance was set at p-value of 0.05.Results:Concomitant meniscus tear was confirmed in 32 knees. Clinical grading was different between the ACL-injured knees with and without meniscus tear (p<0.05), while the quantitative evaluation did not find a statistical significance (meniscus-injured knees 1.6 ± 1.1 m/sec2 vs meniscus-intact knees 1.3 ± 0.8 m/sec2, p=0.09). Subgroup analysis demonstrated increased tibial acceleration in the ACL-deficient knees with lateral meniscus tear (1.8 ± 1.1 m/sec2, n=19) compared to the meniscus-intact knees (p<0.05), whereas the rotational laxity did not rise in the medial meniscus torn knees (1.4 ± 1.0 m/sec2, n=20, p=0.33).Conclusion:Although the meniscus injury is the most common in addition to the ACL injury, the impact of the meniscus injury on the knee rotational laxity has not been fully examined. This study demonstrated the significant impact of the meniscus injury, especially lateral meniscus injury, on the rotational laxity in the ACL-deficient knees, which was successfully detected by using the quantitative measurement device. A careful inspection of the lateral meniscus tear should be required in the ACL-deficient knees with a substantial pivot-shift and, if there is any, it should be repaired as much as possible to avoid additional rotational laxity.

Anterolateral Capsule Injury Did Not Aggravate Rotational Laxity of the Anterior Cruciate Ligament Injured Knees Measured by Quantitative Pivot-shift Evaluation

Objectives:The anterolateral capsule (ALC) injury concomitant with the anterior cruciate ligament (ACL) injured knees has been recently focused with potential effect on the knee rotational laxity. Although some basic in-vitro studies explored the effect of the additional ALC injury, most of such studies utilized their original rotational stress test rather than the clinically-used pivot-shift test. The knee rotational instability should be examined by the clinical pivot-shift test. Some quantitative measurement devices for the pivot-shift test have been clinically available lately. The purpose of this study were to evaluate the pivot-shift test using a quantitative measurement in clinical cases and to compare them between ACL injured knees with and without the ALC injury determined by magnetic resonance imaging (MRI).Methods:Eighty-five unilateral ACL injury patients (40 male and 45 female, age 25.3±11.7 y.o.) who were scheduled to have primary ACL reconstruction were included. Just prior to the ACL reconstruction, the pivot-shift test was performed under anesthesia while making the quantitative evaluation using electromagnetic measurement system (Fig.1). The tibial acceleration (m/sec2) during the pivot-shift was calculated, and the four levels of clinical grading was also determined according to the IKDC (none, glide, clunk, and gross). The concomitant ALC injury in the ACL injured knees was diagnosed on the MRI and divided into two groups ALC injured group (ALC+) and ALC intact group (ALC-). The differences of clinical grading and quantitative measurements were tested between ALC+ and ALC- groups. P-value of <0.05 was considered as statistically significant.Results:Forty-two patients had concomitant ALC injury. 21 knees of ALC+ group were graded as glide in clinical grading, 18 knees as clunk, and 3 knees as gross in ALC+ group, meanwhile 22 knees were assessed as glide, 17 knees as clunk, and 3 knees as gross in ALC- group. There was no difference in clinical grading between ALC+ and ALC- groups (p=0.97). The tibial acceleration measurement during the pivot-shift test demonstrated no significant difference between ALC+ group (1.4±1.2 m/sec2) and ALC- group (1.6±1.3 m/sec2) (p=0.21).Conclusion:This study demonstrated that the ALC injury accompanied with the ACL injury did not have significant effect on the rotational laxity based on either clinical grading or quantitative evaluation. There was a limitation of this study that statistical power was not so strong around 0.6, but, interestingly, the rotational laxity measurements was slightly larger in the ALC intact group. The ALC injury has been advocated as a major factor to aggravate the knee rotational laxity. In this study, however, the impact of the ALC injury on the rotational laxity was not confirmed. Therefore, we should pay more attention to other common and identifiable injures such as meniscus and cartilage tear.

The Complimentary Contributions of the Anterolateral Ligament and the Lateral Meniscus to the Control of Rotational Knee Laxity

Objectives:Anatomical studies consistently describe an anatomical connection between the anterolateral ligament (ALL) and the lateral meniscus. The aim of this study was to investigate the role of the ALL and lateral meniscal posterior root (LMPR) in internal rotational (IR) control in the ACL deficient knee.Methods:Sixteen cadaveric knees were potted into a hip simulator proximally and a six degree of freedom load cell distally. Positional data for femur and tibia were collected using a navigation system. Testing was performed in 15° increments from extension to 90° of flexion under a 5 Nm internal rotational torque. Specimens were tested in the intact state and after division of the ACL (ACL-), before randomization to division of the ALL (ALL-/M+) or LMPR (ALL+/M-), and finally after division of the remaining structure (ALL-/LMPR-). A one-way ANOVA was performed for each sectioning condition at each knee flexion angle (α = 0.05).Results:In extension, there was no significant increase in IR after division of the ACL. After division of the LMPR, there was a significant increase in IR compared to the intact state of 2.93° (p<0.05). Division of the ALL caused only a small increase in IR compared to the intact state (0.87°, NS). Division of the ALL after the LMPR caused no additional increase in IR. At 30° flexion, division of the ALL caused a greater magnitude increase in IR when compared to the intact state than division of the LMPR (4.04° vs 1.32°), although neither reached statistical significance. At 45° flexion, division of the ALL increased IR compared to the intact state by 10.92° (p<0.05), whilst IR caused by division of the PRLM did not reach significance. This pattern of ALL dominance was maintained at 60° and 75° of knee flexion, where the increase in IR was significant compared to both the intact and ACL deficient states.Discussion:The ALL and LMPR demonstrate complimentary roles in the control of internal rotation, with the meniscal root more important near extension and the ALL beyond 30° of flexion. These results do not support anatomical ALL reconstruction for control of the pivot shift. LMPR repair may improve stability and have benefits for chondroprotection.

Reconstructing the anterolateral ligament does not decrease rotational knee laxity in ACL-reconstructed knees

Little is known about the anterolateral ligament's (ALL) influence on knee laxity. The purpose of this study was to investigate rotational knee laxity against a pure axial rotational stress using radiostereometric analysis (RSA) after cutting and reconstructing both the anterior cruciate ligament (ACL) and the ALL. Eight human donor legs were positioned and stereoradiographically recorded at 0°, 30° and 60° of knee flexion using a motorised fixture, while an internally rotating force of 4Nm was applied to the foot. Anterior-posterior and rotational laxity were investigated for knees with intact ligaments and compared with those observed after successive ACL and ALL resection and reconstruction. After cutting the ALL in ACL-deficient knees, the internal rotation was increased in all three knee flexion angles, 0° (p = 0.04), 30° (p = 0.03) and 60° (p < 0.01) by 1.0°, 1.6° and 2.5°, respectively. However, no decrease in laxity was found after reconstructing the ALL in ACL-reconstructed knees. The ALL was confirmed as a stabiliser of internal rotation in ACL-deficient knees. However, reconstructing the ALL using a gracilis autograft tendon did not decrease the internal rotation laxity in the ACL-reconstructed knee. Based on the results of this study, we do not recommend reconstructing the ALL in ACL-reconstructed knees to decrease internal knee laxity.

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

BackgroundIn 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 studyTo evaluate the accuracy and reliability of the Rotab® compared to the reference system, radiostereometric analysis (RSA). MethodsThis 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. ResultsThe 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. ConclusionThe Rotab® is a reliable device to measure rotational laxity coupled with anterior translation of the knee.

Clinical assessment of antero-medial rotational knee laxity: a systematic review.

To inventory the examination methods available to assess antero-medial rotational laxity (AMRL) of the knee following medial collateral ligament injury. Searches were conducted in accordance with the PRISMA guidelines and using four online databases: WEB OF SCIENCE, MEDLINE, EMBASE, and AMED. The Critical Appraisal Skills Programme guidelines for Diagnostic Test Studies were used for the quality assessment of the articles. A total of 2241 articles were identified from the database searches. From this, four articles were included in the final review. All were case-control studies, considered a combined ACL/MCL injury and had small study populations. Specialised equipment was required in all studies, and one needed additional imaging support before measurements could be taken. Two employed commercially available measuring equipment as part of the assessment process. Clinical assessment of AMRL in relation to a MCL injury remains challenging. Although methods have been developed to support clinical examination, they are limited by a number of factors, including the need for additional time in the clinical environment when setting up equipment, the need for specific equipment to produce and measure rotational movement and imaging support. In addition, there are patient safety concerns from the repeated imaging. A reliable and valid clinical examination remains to be found to truly assess antero-medial rotational laxity of the knee. IV.

The anterior cruciate ligament clinical pathway: Towards a systematic evaluation of ACL injured patients

Summary Purpose To systematically record pre-and post-operative clinical data after ACL reconstruction in an institutional clinical pathway. Material and methods From 2011 to 2014, 285 patients had an ACL reconstruction with a bone patellar tendon bone (BPTB) ( n =123) or a hamstring (HS) ( n =162) auto-graft. Isokinetic quadriceps and hamstrings force, anterior and rotational knee laxity, hop tests and subjective knee function were evaluated. Results All outcomes improved significantly throughout the follow-up. Anterior knee laxity was significantly improved by ACL reconstruction ( p p p Discussion and conclusion The present study highlighted the progression of ACL-reconstructed patients throughout their rehabilitation. The results of this institutional clinical pathway may serve as an internal and external benchmark, as well as a potential baseline to individualize patient care including return-to-sports.

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.

Rotational Knee Laxity in Anterior Cruciate Ligament Deficiency: An Additional Secondary Sign on MRI.

The objective of this study was to evaluate the accuracy of tibial rotation measurement as a secondary sign for diagnosing anterior cruciate ligament (ACL) tears with the use of MRI. A total of 893 MRI studies were retrospectively reviewed, and 239 patients were identified as having either an intact ACL (group 1; n = 182), an arthroscopically confirmed acutely torn ACL (group 2; n = 22), or a chronically torn ACL (group 3; n = 35). Tibial rotation was estimated by measuring the femorotibial angle (FTA). The mean (± SD) FTA was significantly higher in group 2 (10.7° ± 4.8°) and group 3 (11° ± 5.5°) than in group 1 (3.2° ± 3.3°) (p < 0.001, for all cases). An FTA of 4.9° was the optimal threshold (sensitivity, 93%; specificity, 80%) for separating completely torn ACLs from intact ACLs. An FTA ranging from 4.9° to 5.5° (sensitivity, 95%; specificity, 80%) indicated a complete acute ACL tear, whereas an FTA of 5.6° or greater (sensitivity, 91.4%; specificity, 83.5%) suggested a complete chronic ACL tear. An increased FTA indicates alteration in the femorotibial anatomic relationship and could be of value in assessing ACL tears in patients with equivocal signs on MRI.

Use of a Computed Tomography Based Approach to Validate Noninvasive Devices to Measure Rotational Knee Laxity.

The purpose of this study is to validate a noninvasive rotational knee laxity measuring device called “Rotameter P2” with an approach based on Computed Tomography (CT). This CT-approach using X-rays is hence invasive and can be regarded as a precise reference method that may also be applied to similar devices. An error due to imperfect femur fixation was observed but can be neglected for small torques. The most significant estimation error is due to the unavoidable soft tissues rotation and hence flexibility in the measurement chain. The error increases with the applied torque. The assessment showed that the rotational knee angle measured with the Rotameter is still overestimated because of thigh and femur displacement, soft tissues deformation, and measurement artefacts adding up to a maximum of 285% error at +15 Nm for the Internal Rotation of female volunteers. This may be questioned if such noninvasive devices for measuring the Tibia-Femoral Rotation (TFR) can help diagnosing knee pathologies and investigate ligament reconstructive surgery.

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

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. 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 200N (ATD200), primary compliance from 30 to 50N (PCA) and secondary compliance from 100 to 200N (SCA). Furthermore, four variables in rotational laxity were considered: internal and external rotation at 5Nm (IR5/ER5) and compliance from 2 to 5Nm (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. Sensitivity and specificity reached, respectively, 75 and 95% for ATD200 (threshold: 1.2mm) 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 >3.7mm, PCA>48μm/N or SCA>17.5µm/N had ACL remnants that were either totally resorbed or healed on the posterior cruciate ligament. Combined instrumented anterior and rotational knee laxity measurements have excellent diagnostic value for ACL injury, provided that several measurements be considered concomitantly. Diagnostic study, Level III.

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

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

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

Background: Excessive physiological anterior and rotational knee laxity is thought to be a risk factor for noncontact anterior cruciate ligament (ACL) injuries and inferior reconstruction outcomes, but no thresholds have been established to identify patients with increased laxity. Purpose: (1) To determine if the healthy contralateral knees of ACL-injured patients have greater anterior and rotational knee laxity, leading to different laxity profiles (combination of laxities), compared with healthy control knees and (2) to set a threshold to help discriminate anterior and rotational knee laxity between these groups. Study Design: Case-sectional study; Level of evidence, 3. Methods: A total of 171 healthy contralateral knees of noncontact ACL-injured patients (ACL-H group) and 104 healthy knees of control participants (CTL group) were tested for anterior and rotational laxity. Laxity scores (measurements corrected for sex and body mass) were used to classify knees as hypolax (score <–1), normolax (between −1 and 1), or hyperlax (>1). Proportions of patients in each group were compared using χ2 tests. Receiver operating characteristic curves were computed to discriminate laxity between the groups. Odds ratios were calculated to determine the probability of being in the ACL-H group. Results: The ACL-H group displayed greater laxity scores for anterior displacement and internal rotation in their uninjured knee compared with the CTL group (P < .05). Laxity profiles were different between the groups for the following associations: normolax in anterior displacement/hypolax in internal rotation (6% [ACL-H] vs 15% [CTL]; P = .02) and hyperlax in anterior displacement/normolax in internal rotation (27% [ACL-H] vs 10% [CTL]; P < .01). The laxity score thresholds were 0.75 for anterior laxity and −0.55 for internal rotation. With both scores above these thresholds, a patient was 3.18-fold more likely to be in the ACL-H group (95% CI, 1.74-5.83). Conclusion: The healthy contralateral knees of patients with noncontact ACL injuries display different laxity values both for internal rotation and anterior displacement compared with healthy control knees. The identification of knee laxity profiles may be of relevance for primary and secondary prevention programs of noncontact ACL injuries.

Combined anterior and rotational laxity measurements allow characterizing personal knee laxity profiles in healthy individuals.

PurposeThe aim of this study was to quantify sagittal and rotational knee laxity profiles taking into account individual influencing factors.MethodsLinear regression models were used to determine which individual characteristics (age, height, body mass and sex) influenced the outcome in a group of 104 healthy subjects. The standardized residuals were used as individualized (corrected) laxity scores and were combined to determine knee laxity profiles. ResultsAnterior knee laxity was not influenced by individual characteristics. Rotational knee laxity was higher in females and inversely related to body mass. The correlation between anterior laxity and internal rotation scores was weak (r = 0.24, p = 0.02). The proportion of knees concerned by increased laxity scores (scores >1) was similar for anterior displacement, internal and external rotation (15 %). Only 32 % of the tested subjects showed a normal profile (score >−1 and <1) for all three directions, 33 % were concerned by hyperlaxity, 40 % by hypolaxity and 5 % by both. ConclusionsThe diversity of laxity profiles found here highlights that the interpretation of multidirectional knee laxity is complex and suggests the necessity for individualized care of knee diseases and injuries. These results contribute to the understanding of knee laxity and throw the basis for prevention strategies and improvement of treatment outcomes in injuries and diseases.Level of evidenceCase series with no comparison groups, Level IV.

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

This study proposes a simple and noninvasive instrument called the "Rotatometer" to measure tibiofemoral rotation and investigates its clinical applicability to the assessment of static rotational knee laxity. The degree of tibiofemoral rotation was measured for a sample of 94 healthy volunteers with 188 knees by using the Rotatometer. The measurement was made by two independent and blinded examiners in three sessions at one-month intervals. The normative rotational profile and its relationship with gender and age were evaluated, and inter-observer reliability and intra-observer reliability were calculated. Males showed 62° ± 5° of external rotation, whereas females, 64° ± 5°. Males showed 44° ± 5° of internal rotation, whereas females, 49° ± 4°. Females showed significantly higher degrees of rotation than males. Tibiofemoral rotation was not correlated with age, and external rotation and internal rotation had a moderate positive relationship. Inter-observer reliability ranged from 0.84 to 0.91 for external rotation and 0.90 to 0.95 for internal rotation, and intra-observer reliability ranged from 0.69 to 0.89 for external rotation and 0.87 to 0.95 for internal rotation. The results suggest the Rotatometer to be a simple and noninvasive device with high inter- and intra-observer reliability. The device can provide a normative rotational profile for reference purposes and thus can be used to determine the preoperative and postoperative rotational status of knees with anterior cruciate ligament injuries and compare results from different reconstruction techniques.

Rotational laxity and collateral ligament laxity following total knee arthroplasty with rotating platform

The aim of this study was to evaluate laxity in knees with pre-operative (preop) valgus alignment compared to knees with pre-operative varus alignment after total knee arthroplasty (TKA). This was a retrospective study including 81 patients, with six years follow-up, for pre-operative valgus- or varus alignment of the leg. All patients had been supplied with the same cruciate retaining (CR) TKA with rotating platform. Clinical findings were assessed by KSS, OKS and IKDC 2000 score. Rotational knee laxity was evaluated by a validated instrument (Laxitester®) with 2 Nm torque in 30° flexion. Collateral ligament laxity was tested manually in 30° flexion with a bending moment of approximately 5 Nm. Biomechanical results were compared to the contralateral side. Thirty-one patients had a preop valgus alignment of 8.96° and 50 patients a varus leg axis of 4.99° in the mean. In the preop valgus knees rotational analysis showed an increased laxity of 10.7° compared to preop varus knees (p = 0.001). There was no significant difference in medial (valgus 2.6 mm, varus 2.5 mm) and lateral (valgus 2.8 mm, varus 2.7 mm) laxity. KSS and OKS showed no significant differences in the follow-up results. In the IKDC 2000 objective score 50 % of the preop varus knees and 25.8 % of the preop valgus knees were classified as nearly normal. The difference in the IKDC objective was highly significant (p < 0.001). Preop valgus knees show a significantly increased rotational laxity but no increased collateral ligament laxity compared to pre-operative varus knees six years after TKA with rotating platform. There is a significant difference in IKDC objective.

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

Background:Methods of objectively measuring rotational knee laxity are either experimental or difficult to use in daily practice. A new method has been developed to quantitatively assess rotatory laxity using an open MRI system and new tool, the KneeM device.Purpose/Hypothesis:To perform a preliminary evaluation of a novel knee rotation measurement device to assess knee kinematics during flexion in an MRI field, in both anterior cruciate ligament (ACL)–deficient and healthy contralateral knees. The hypothesis was that the KneeM device would allow in vivo reproduction and analysis of knee kinematics during flexion in healthy and ACL-deficient knees.Study Design:Controlled laboratory study.Methods:Ten subjects (7 men and 3 women; mean age ± standard deviation, 32.3 ± 9.4 years) with ACL-deficient knees and contralateral uninjured knees participated in the study. An open MRI was performed with the KneeM device at a mean 4.9 months (range, 3.0-7 months) after ACL injury. The device exerted on the knee an anterior drawer force of 100 N, with an internal rotation of 20°, through the range of flexion (0°, 20°, 40°, and 60°). Both ACL-deficient and healthy contralateral knees were analyzed using the Iwaki method.Results:There was no statistical difference of anterior translation in the medial compartment between intact and ACL-deficient knees at all degrees of flexion. However, significant differences in the anterior translation of the lateral compartment were observed between ACL-deficient and intact contralateral knees at 0° and 20° of flexion (P = .005 and P = .002, respectively). Between 20° and 40°, the lateral plateau of ACL-deficient knees translated 7.7 mm posteriorly, whereas the medial compartment remained stable, reflecting a sudden external rotation of the lateral plateau under the femoral condyle.Conclusion:This preliminary study suggests that measurement of tibiofemoral movements in both compartments during flexion using the KneeM device was useful for quantifying rotatory laxity in ACL-deficient knees. Moreover, this device seemed to allow a “mechanized pivot shift” and allowed reproduction of the “pivot” phase in the MRI field between 20° and 40° of flexion.Clinical Relevance:This device could be used for diagnostic purposes or to investigate the outcomes of ACL reconstructions.