Rotational knee laxity: reliability of a simple measurement device in vivo

Internal Rotation Measurement of the Knee with Polymer-Based Capacitive Strain Gauges versus Mechanical Rotation Measurement Taking Gender Differences into Account: A Comparative Analysis

With the conventional mechanical rotation measurement of joints, only static measurements are possible with the patient at rest. In the future, it would be interesting to carry out dynamic rotation measurements, for example, when walking or participating in sports. Therefore, a measurement method with an elastic polymer-based capacitive measuring system was developed and validated. In our system, the measurement setup was comprised of a capacitive strain gauge made from a polymer, which was connected to a flexible printed circuit board. The electronics integrated into the printed circuit board allowed data acquisition and transmission. As the sensor strip was elongated, it caused a change in the spacing between the strain gauge's electrodes, leading to a modification in capacitance. Consequently, this alteration in capacitance enabled the measurement of strain. The measurement system was affixed to the knee by adhering the sensor to the skin in alignment with the anterolateral ligament (ALL), allowing the lower part of the sensor (made of silicone) and the circuit board to be in direct contact with the knee's surface. It is important to note that the sensor should be attached without any prior stretching. To validate the system, an in vivo test was conducted on 10 healthy volunteers. The dorsiflexion of the ankle was set at 2 Nm using a torque meter to eliminate any rotational laxity in the ankle. A strain gauge sensor was affixed to the Gerdii's tubercle along the course of the anterolateral ligament, just beneath the lateral epicondyle of the thigh. In three successive measurements, the internal rotation of the foot and, consequently, the lower leg was quantified with a 2 Nm torque. The alteration in the stretch mark's length was then compared to the measured internal rotation angle using the static measuring device. A statistically significant difference between genders emerged in the internal rotation range of the knee (p = 0.003), with female participants displaying a greater range of rotation compared to their male counterparts. The polymer-based capacitive strain gauge exhibited consistent linearity across all measurements, remaining within the sensor's initial 20% strain range. The comparison between length change and the knee's internal rotation angle revealed a positive correlation (r = 1, p < 0.01). The current study shows that elastic polymer-based capacitive strain gauges are a reliable instrument for the internal rotation measurement of the knee. This will allow dynamic measurements in the future under many different settings. In addition, significant gender differences in the internal rotation angle were seen.

Digital measurement of anterolateral knee laxity using strain sensors

PURPOSE

The ambition of the research group was to develop a sensor-based system that allowed the transfer of results with strain sensors applied to the knee joint. This system was to be validated in comparison to the current static mechanical measurement system. For this purpose, the internal rotation laxity of the knee joint was measured, as it is relevant for anterolateral knee laxity and anterior cruciate ligament (ACL) injury.

METHODS

This is a noninvasive measurement method using strain sensors which are applied to the skin in the course of the anterolateral ligament. The subjects were placed in supine position. First the left and then the right leg were clinically examined sequentially and documented by means of an examination form. 11 subjects aged 21 to 45 years, 5 women and 6 men were examined. Internal rotation of the lower leg was performed with a torque of 2 Nm at a knee flexion angle of 30°.

RESULTS

Comparison of correlation between length change and internal knee rotation angle showed a strong positive correlation (r = 1, p < 0.01). Whereas females showed a significant higher laxity vs. males (p = 0.003).

CONCLUSIONS

The present study showed that the capacitive strain sensors can be used for reproducible measurement of anterolateral knee laxity. In contrast to the previous static systems, a dynamic measurement will be possible by this method in the future.

The Anterior Fibers of the Superficial MCL and the ACL Restrain Anteromedial Rotatory Instability

BACKGROUND

There is limited knowledge about how the anterior cruciate ligament (ACL) and capsuloligamentous structures on the medial side of the knee act to control anteromedial rotatory knee instability.

PURPOSE

To investigate the contribution of the medial retinaculum, capsular structures (anteromedial capsule, deep medial collateral ligament [MCL], and posterior oblique ligament), and different fiber regions of the superficial MCL to restraining knee laxity, including anteromedial rotatory instability.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen human cadaveric knees were tested using a 6 degrees of freedom robotic testing system in a position-controlled mode. Loads of 10 N·m valgus rotation, 5 N·m tibial external rotation, 5 N·m tibial internal rotation, and 134 N anterior tibial translation in 5 N·m external rotation were applied at different flexion angles. The motion of the intact knee at 0° to 120° of flexion was replicated after sequential excision of the sartorial fascia; anteromedial retinaculum; anteromedial capsule; anterior, middle, and posterior fibers of the superficial MCL; the deep MCL; the posterior oblique ligament; and the ACL. The reduction in force/torque indicated the contribution of each resected structure to resisting laxity. A repeated-measures analysis of variance with a post hoc Bonferroni test was used to analyze the relative force and torque changes from the intact state.

RESULTS

The superficial MCL was the most important restraint to valgus rotation from 0° to 120° and provided the largest contribution to resisting external rotation between 30° and 120° of knee flexion, gradually increasing from 25.2% ± 7.4% at 30° to 36.9% ± 15.4% at 90°. The posterior oblique ligament contributed significantly to resisting valgus rotation only in extension (17.2% ± 12.1%) but was the major restraint to internal rotation at 0° (46.7% ± 13.1%) and 30° (30.4% ± 17.7%) of flexion. The sartorial fascia and anteromedial retinaculum resisted ER at all knee flexion angles (P < .05) and was the single most important restraint in the extended knee (19.5% ± 11%). The capsular structures (anteromedial capsule and deep MCL) had a combined contribution of 20% ± 11.5% at 0° and 23.4% ± 10.5% at 120° of knee flexion but were less important from 30° to 90°. The ACL was the primary restraint to anterior tibial translation in external rotation between 0° and 60° of flexion (50.2% ± 16.9% at 30°), but the superficial MCL was more important at 90° to 120° of knee flexion (36.8% ± 16.4% at 90°). The anterior, middle, and posterior regions of the superficial MCL contributed differently to the simulated laxity tests. The anterior fibers were the most important part of the superficial MCL in resisting external rotation and combined anterior tibial translation in external rotation.

CONCLUSION

The superficial MCL not only was the primary restraint to valgus rotation throughout the range of knee flexion but also importantly contributed to resisting anterior tibial translation in external rotation, particularly in deeper flexion in the cadaveric model. The anterior fibers of the superficial MCL are the most important superficial MCL fibers in resisting anterior tibial translation in external rotation. This study suggests that a medial reconstruction that reproduces the function of the posterior MCL fibers and posterior oblique ligament may not best control anteromedial rotatory instability.

CLINICAL RELEVANCE

Based on these data, there is a need for an individualized medial reconstruction to address different types of medial injury patterns and instabilities.

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

PURPOSE

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

STUDY DESIGN

Cross-sectional study, Level of evidence III.

METHODS

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

RESULTS

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

CONCLUSION

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

Reliability of a Robotic Knee Testing Tool to Assess Rotational Stability of the Knee Joint in Healthy Female and Male Volunteers

BACKGROUND

Several clinical tests exist to assess knee laxity. Although these assessments are the predominant tools of diagnosis, they are subjective and rely on the experience of the clinician. The robotic knee testing (RKT) device has been developed to quantitatively and objectively measure rotational knee laxity. The purpose of this study was primarily to determine the intra-tester reliability of rotational knee laxity and slack, the amount of rotation occurring between the two turning points of the load deformation curve, measured by the RKT device and investigate the differences between female and male measurements.

METHODS

Ninety-one healthy and moderately active volunteers took part in the study, of which twenty-five participated in the reliability study. Tibial rotation was performed using a servomotor to a torque of 6 N m, while measurements of motion in all 6° of freedom were collected. Reliability measurements were collected over 5 days at similar times of the day. Intra-class correlation coefficient (ICC) values and standard error of measurement (SEM) were determined across the load deformation curves. Linear mixed effects modelling was used to further assess the reliability of the measurement of external and internal tibial rotation using features of the curve (internal/external rotational laxity and slack). Measurements of internal/external rotational laxity and slack were compared between the sexes using the Student t test.

RESULTS

Pointwise axial rotation measurements of the tibia had good reliability [ICC (2,1) 0.83-0.89], while reliability of the secondary motions ranged between poor and good [ICC (2,1) 0.31-0.89]. All SEMs were less than 0.3°. Most of the variation of the curve features were accounted for by inter-subject differences (56.2-77.8%) and showed moderate to good reliability. Comparison of the right legs of the sexes revealed that females had significantly larger amounts of internal rotation laxity (females 6.1 ± 1.3° vs males 5.6 ± 0.9°, p = 0.037), external rotation laxity (females 6.0 ± 1.6° vs males 5.0 ± 1.2°, p = 0.002) and slack (females 19.2 ± 4.2° vs males 16.6 ± 2.9°, p = 0.003). Similar results were seen within the left legs.

CONCLUSIONS

Overall, the RKT is a reliable and precise tool to assess the rotational laxity of the knee joint in healthy individuals. Finally, greater amounts of laxity and slack were also reported for females.

A non-invasive biomechanical device to quantify knee rotational laxity: Verification of the device in human cadaveric specimens

BACKGROUND

Biomechanical measurement tools have been developed and widely used to precisely quantify knee anterior-posterior laxity after anterior cruciate ligament (ACL) injury. However, validated objective device to document knee rotational laxity, though being developed by different researchers, are not yet widely used in the daily clinical practice. A new biomechanical device was developed to quantify knee internal and external rotations.

METHODS

The reliability of the new biomechanical device which measures knee rotations were tested. Different torques (1-10Nm) were applied by the device to internally and externally rotate human cadaveric knees, which were held in a flexion angle of 30°. The rotations were measured by the device in degrees. There were two independent testers, and each tester carried out three trials. Intra-rater and inter-rater reliability were quantified in terms of intraclass correlation (ICC) coefficient among trials and between testers. The device was verified by the comparison with a computer assisted navigation system. ICC was measured. Mean, standard deviation and 95% confident interval of the difference as well as the root mean square difference were calculated. The correlations were deemed to be reliable if the ICC was above 0.75.

RESULTS

The intra-rater and inter-rater reliability achieved high correlation for both internal and external rotation, ranged from 0.959 to 0.992. ICC between the proposed meter and the navigation system for both internal and external rotation was 0.78. The mean differences were 2.3° and 2.5° for internal and external rotation respectively.

CONCLUSIONS

A new knee rotational laxity meter was proposed in this study. Its reliability was verified by showing high correlation among trials. It also showed good correlation to a gold standard of measurement. It might be used to document knee rotational laxity for various purposes, especially after ACL injury, after further validation of the device in human subjects.

A novel test for assessment of anterolateral rotatory instability of the knee: the tibial internal rotation test (TIR test)

Background

Rotational instability of the knee may persist after anterior cruciate ligament (ACL) reconstruction, which may be due to insufficiency of anterolateral stabilizing structures. However, no reliable diagnostic tool or physical examination test is available for identifying patients with anterolateral rotatory instability (ALRI). As shown in cadaveric studies, static internal rotation of the knee is increased in higher flexion angles of the knee after severing the anterolateral structures. This might also be the case in patients with an ACL-deficient knee and concomitant damage to the anterolateral structures. The objective of this study is to assess anterolateral rotatory instability of the knee during physical examination with a tibial internal rotation test.

Methods

ACL-injured knees of 52 patients were examined by two examiners and side-to-side differences were compared. Both lower legs were internally rotated by applying manual internal rotation torque to both feet in prone position with the knees in 30°, 60° and 90° of flexion. For quantification of the amount of rotation in degrees, a torque adapter on a booth was used. Intra-rater, inter-rater and rater-device agreement were determined by calculating kappa (κ) for the tibial internal rotation test.

Results

Tibial internal rotation is increased in 19.2% of the patients with ACL injury according to the tibial internal rotation test. Good intra-rater agreement was found for the tibial internal rotation test, κ_C = 0.63 (95%CI -0.02-1.28), p = 0.015. Fair inter-rater agreement was found, κ_F = 0.29 (95%CI 0.02–0.57), p = 0.038. Good rater-device agreement was found, κ_C = 0.62 (95%CI 0.15–1.10), p = 0.001.

Conclusion

The tibial internal rotation test shows increased tibial internal rotation in a small amount of patients with ACL injury. Even though no gold standard for assessment of increased tibial internal rotation of the knee is available yet, the test can be of additional value. It can be used for assessment of internal rotatory laxity of the knee as part of ALRI in addition to the pivot shift test. No clinical implications should yet be based on this test alone.

Electronic supplementary material

The online version of this article (10.1186/s40634-018-0141-9) contains supplementary material, which is available to authorized users.

Comparison of a simplified skin pointer device compared with a skeletal marker for knee rotation laxity: A cadaveric study using a rotation-meter

AIM

To compare the measurements of knee rotation laxity by non-invasive skin pointer with a knee rotation jig in cadaveric knees against a skeletally mounted marker.

METHODS

Six pairs of cadaveric legs were mounted on a knee rotation jig. One Kirscher wire was driven into the tibial tubercle as a bone marker and a skin pointer was attached. Rotational forces of 3, 6 and 9 nm applied at 0°, 30°, 45°, 60° and 90° of knee flexion were analysed using the Pearson correlation coefficient and paired t-test.

RESULTS

Total rotation recorded with the skin pointer significantly correlated with the bone marker at 3 nm at 0° (skin pointer 23.9 ± 26.0° vs bone marker 16.3 ± 17.3°, r = 0.92; P = 0.0), 30° (41.7 ± 15.5° vs 33.1 ± 14.7°, r = 0.63; P = 0.037), 45° (49.0 ± 17.0° vs 40.3 ± 11.2°, r = 0.81; P = 0.002), 60° (45.7 ± 17.5° vs 34.7 ± 9.5°, r = 0.86; P = 0.001) and 90° (29.2 ± 10.9° vs 21.2 ± 6.8°, r = 0.69; P = 0.019) of knee flexion and 6 nm at 0° (51.1 ± 37.7° vs 38.6 ± 30.1°, r = 0.90; P = 0.0), 30° (64.6 ± 21.6° vs 54.3 ± 15.1°, r = 0.73; P = 0.011), 45° (67.7 ± 20.6° vs 55.5 ± 9.5°, r = 0.65; P = 0.029), 60° (62.9 ± 22.4° vs 45.8 ± 13.1°, r = 0.65; P = 0.031) and 90° (43.6 ± 17.6° vs 31.0 ± 6.3°, r = 0.62; P = 0.043) of knee flexion and at 9 nm at 0° (69.7 ± 40.0° vs 55.6 ± 30.6°, r = 0.86; P = 0.001) and 60° (74.5 ± 27.6° vs 57.1 ± 11.5°, r = 0.77; P = 0.006). No statistically significant correlation with 9 nm at 30° (79.2 ± 25.1° vs 66.9 ± 15.4°, r = 0.59; P = 0.055), 45° (80.7 ± 24.7° vs 65.5 ± 11.2°, r = 0.51; P = 0.11) and 90° (54.7 ± 21.1° vs 39.4 ± 8.2°, r = 0.55; P = 0.079). We recognize that 9 nm of torque may be not tolerated in vivo due to pain. Knee rotation was at its maximum at 45° of knee flexion and increased with increasing torque.

CONCLUSION

The skin pointer and knee rotation jig can be a reliable and simple means of quantifying knee rotational laxity with future clinical application.

Rater agreement reliability of the dial test in the ACL-deficient knee

Background

Posterolateral rotatory instability (PLRI) of the knee can easily be missed, because attention is paid to injury of the cruciate ligaments. If left untreated this clinical instability may persist after reconstruction of the cruciate ligaments and may put the graft at risk of failure. Even though the dial test is widely used to diagnose PLRI, no validity and reliability studies of the manual dial test are yet performed in patients. This study focuses on the reliability of the manual dial test by determining the rater agreement.

Methods

Two independent examiners performed the dial test in knees of 52 patients after knee distorsion with a suspicion on ACL rupture. The dial test was performed in prone position in 30°, 60° and 90° of flexion of the knees. ≥10° side-to-side difference was considered a positive dial test. For quantification of the amount of rotation in degrees, a measuring device was used with a standardized 6 Nm force, using a digital torque adapter on a booth. The intra-rater, inter-rater and rater-device agreement were determined by calculating kappa (κ) for the dial test.

Results

A positive dial test was found in 21.2% and 18.0% of the patients as assessed by a blinded examiner and orthopaedic surgeon respectively. Fair inter-rater agreement was found in 30° of flexion, κ_F = 0.29 (95% CI: 0.01 to 0.56), p = 0.044 and 90° of flexion, κ_F = 0.38 (95% CI: 0.10 to 0.66), p = 0.007. Almost perfect rater-device agreement was found in 30° of flexion, κ_C = 0.84 (95% CI: 0.52 to 1.15), p < 0.001. Moderate rater-device agreement was found in 30° and 90° combined, κ_C = 0.50 (95% CI: 0.13 to 0.86), p = 0.008. No significant intra-rater agreement was found.

Conclusions

Rater agreement reliability of the manual dial test is questionable. It has a fair inter-rater agreement in 30° and 90° of flexion.

Assessment of knee laxity using a robotic testing device: a comparison to the manual clinical knee examination

PURPOSE

The purpose of this study was to collect knee laxity data using a robotic testing device. The data collected were then compared to the results obtained from manual clinical examination.

METHODS

Two human cadavers were studied. A medial collateral ligament (MCL) tear was simulated in the left knee of cadaver 1, and a posterolateral corner (PLC) injury was simulated in the right knee of cadaver 2. Contralateral knees were left intact. Five blinded examiners carried out manual clinical examination on the knees. Laxity grades and a diagnosis were recorded. Using a robotic knee device which can measure knee laxity in three planes of motion: anterior-posterior, internal-external tibia rotation, and varus-valgus, quantitative data were obtained to document tibial motion relative to the femur.

RESULTS

One of the five examiners correctly diagnosed the MCL injury. Robotic testing showed a 1.7° larger valgus angle, 3° greater tibial internal rotation, and lower endpoint stiffness (11.1 vs. 24.6 Nm/°) in the MCL-injured knee during varus-valgus testing when compared to the intact knee and 4.9 mm greater medial tibial translation during rotational testing. Two of the five examiners correctly diagnosed the PLC injury, while the other examiners diagnosed an MCL tear. The PLC-injured knee demonstrated 4.1 mm more lateral tibial translation and 2.2 mm more posterior tibial translation during varus-valgus testing when compared to the intact knee.

CONCLUSIONS

The robotic testing device was able to provide objective numerical data that reflected differences between the injured knees and the uninjured knees in both cadavers. The examiners that performed the manual clinical examination on the cadaver knees proved to be poor at diagnosing the injuries. Robotic testing could act as an adjunct to the manual clinical examination by supplying numbers that could improve diagnosis of knee injury.

LEVEL OF EVIDENCE

Level II.

The Restoration of Passive Rotational Tibio-Femoral Laxity after Anterior Cruciate Ligament Reconstruction

While the anterior cruciate ligament (ACL) is considered one of the most important ligaments for providing knee joint stability, its influence on rotational laxity is not fully understood and its role in resisting rotation at different flexion angles in vivo remains unknown. In this prospective study, we investigated the relationship between in vivo passive axial rotational laxity and knee flexion angle, as well as how they were altered with ACL injury and reconstruction. A rotometer device was developed to assess knee joint rotational laxity under controlled passive testing. An axial torque of ±2.5Nm was applied to the knee while synchronised fluoroscopic images of the tibia and femur allowed axial rotation of the bones to be accurately determined. Passive rotational laxity tests were completed in 9 patients with an untreated ACL injury and compared to measurements at 3 and 12 months after anatomical single bundle ACL reconstruction, as well as to the contralateral controls. Significant differences in rotational laxity were found between the injured and the healthy contralateral knees with internal rotation values of 8.7°±4.0° and 3.7°±1.4° (p = 0.003) at 30° of flexion and 9.3°±2.6° and 4.0°±2.0° (p = 0.001) at 90° respectively. After 3 months, the rotational laxity remained similar to the injured condition, and significantly different to the healthy knees. However, after 12 months, a considerable reduction of rotational laxity was observed towards the levels of the contralateral controls. The significantly greater laxity observed at both knee flexion angles after 3 months (but not at 12 months), suggests an initial lack of post-operative rotational stability, possibly due to reduced mechanical properties or fixation stability of the graft tissue. After 12 months, reduced levels of rotational laxity compared with the injured and 3 month conditions, both internally and externally, suggests progressive rotational stability of the reconstruction with time.

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.

The use of a robotic tibial rotation device and an electromagnetic tracking system to accurately reproduce the clinical dial test

PURPOSE

The purpose of this study was to: (1) determine whether a robotic tibial rotation device and an electromagnetic tracking system could accurately reproduce the clinical dial test at 30° of knee flexion; (2) compare rotation data captured at the footplates of the robotic device to tibial rotation data measured using an electromagnetic sensor on the proximal tibia.

METHODS

Thirty-two unilateral ACL-reconstructed patients were examined using a robotic tibial rotation device that mimicked the dial test. The data reported in this study is only from the healthy legs of these patients. Torque was applied through footplates and was measured using servomotors. Lower leg motion was measured at the foot using the motors. Tibial motion was also measured through an electromagnetic tracking system and a sensor on the proximal tibia. Load-deformation curves representing rotational motion of the foot and tibia were compared using Pearson's correlation coefficients. Off-axis motions including medial-lateral translation and anterior-posterior translation were also measured using the electromagnetic system.

RESULTS

The robotic device and electromagnetic system were able to provide axial rotation data and translational data for the tibia during the dial test. Motion measured at the foot was not correlated to motion of the tibial tubercle in internal rotation or in external rotation. The position of the tibial tubercle was 26.9° ± 11.6° more internally rotated than the foot at torque 0 Nm. Medial-lateral translation and anterior-posterior translation were combined to show the path of the tubercle in the coronal plane during tibial rotation.

CONCLUSIONS

The information captured during a manual dial test includes both rotation of the tibia and proximal tibia translation. All of this information can be captured using a robotic tibial axial rotation device with an electromagnetic tracking system. The pathway of the tibial tubercle during tibial axial rotation can provide additional information about knee instability without relying on side-to-side comparison between knees. The translation of the proximal tibia is important information that must be considered in addition to axial rotation of the tibia when performing a dial test whether done manually or with a robotic device. Instrumented foot position cannot provide the same information.

LEVEL OF EVIDENCE

IV.

Practicability for robot-aided measurement of knee stability in-vivo

Background

For the analysis of different treatments concerning anterior cruciate ligament (ACL) rupture, objective methods for the quantification of knee stability are needed. Therefore, a new method for in-vivo stability measurement using a robotic testing system should be developed and evaluated.

Methods

A new experimental setting was developed using a KUKA robot and a custom-made chair for the positioning and fixation of the participants. The tibia was connected to the robot via a Vacoped shoe and magnetic buttons, providing adequate safety. Anterior tibial translation and internal tibial rotation were measured on both legs of 40 healthy human subjects at 30°, 60° and 90° of flexion, applying anterior forces of 80 N and internal torques of 4 Nm, respectively.

Results

While the mean differences between the right and left leg measured for anterior tibial translation were within an acceptable range (<1.5 mm), the absolute values were substantially large (38–40.5 mm). For mean internal tibial rotation, between 17.5 and 20° were measured at the different sides and flexion angles, with a maximal difference of 0.75°. High reproducibility of the measurements could be demonstrated for both, anterior tibial translation (ICC(3,1) = 0.97) and internal tibial rotation (ICC(3,1) = 0.94).

Conclusions

Excellent results were achieved for internal tibial rotation, almost reproducing current in-vitro studies, but too large anterior tibial translation was measured due to soft-tissue compression. Therefore, high potential for the analysis of ACL related treatments concerning rotational stability is seen for the proposed method, but further optimization is necessary to enhance this method for the reliable measurement of anterior tibial translation.

The reliability and diagnostic accuracy of assessing the translation endpoint during the lachman test

BACKGROUND

Interpretation of Lachman testing when evaluating the status of the anterior cruciate ligament (ACL) typically includes a numerical expression classifying the amount of translation (Grade I, II, III) in addition to a categorical modifier (Grade A [firm] or B [absent]) to describe the quality of the passive anterior tibial translation's endpoint. Most clinicians rely heavily on this tactile sensation and place value in this judgment in order to render their diagnostic decision; however, the reliability and accuracy of this endpoint assessment has not been well established in the literature.

PURPOSE

The purpose of this study was to determine the intertester reliability of endpoint classification during the passive anterior tibial translation of a standard Lachman test and evaluate the classification's ability to accurately predict the presence or absence of an ACL tear.

STUDY DESIGN

Prospective, blinded, diagnostic reliability and accuracy study.

METHODS

Forty-five consecutive patients with a complaint of knee pain were independently evaluated for the endpoint classification during a Lachman test by two physical therapists before any other diagnostic assessment. The 21 men and 24 women ranged in age from 20 to 64 years (mean +/- SD age, 40.7 +/- 14) and in acuity of knee injury from 30 to 365 days (mean +/- SD, 238 +/-157).

RESULTS

17 of the 45 patients had a torn ACL. The agreement between examiners on A versus B endpoint classification was 91% with a kappa coefficient of 0.72. In contrast, classification agreement based on the translational amount had an agreement of 65% with a weighted kappa coefficient of 0.52. The sensitivity of the endpoint grade alone was 0.81 with perfect specificity resulting in a positive likelihood ratio of 6.2 and a negative likelihood ratio of 0.19. The overall accuracy of the Lachman test using the endpoint assessment grade alone was 93% with a number needed to diagnose of 1.2.

CONCLUSIONS

Nominal endpoint classification (A or B) from a Lachman test is a reliable and accurate reflection of the status of the ACL. The true dichotomous nature of the test's interpretation (positive vs. negative) is well-served by the quality of the endpoint during passive anterior tibial translation.

LEVEL OF EVIDENCE

2.

Robotic axial lower leg testing: repeatability and reproducibility

PURPOSE

The purpose of this study was to determine the test-retest reliability and the repeatability over multiple days of a robotic testing device when used to measure laxity of the lower leg during a simulated dial test.

METHODS

Ten healthy subjects were evaluated using an instrumented robotic lower leg testing system over 4 days. Three testing cycles were performed each day. Each leg was rotated into external and then internal rotation by servomotors until a torque threshold of 5.65 N m was reached. Load-deformation curves were generated from torque and rotation data. Both average-measure and single-measure intraclass correlation coefficients (ICC) were compared across the curves. ICC scores were also compared for features of the curves including: maximum external rotation at -5.65 N m of torque, maximum internal rotation at 5.65 N m of torque, rotation at torque 0, compliance (slope of load-deformation curve) at torque 0, endpoint compliance in external rotation, endpoint compliance in internal rotation, and play at torque 0. Play at torque 0 was defined as the width of the hysteresis curve at torque 0.

RESULTS

Average-measure ICC scores and test-retest scores were >0.95 along the entire load-deformation curve except around zero torque. ICC scores at maximum internal and external rotation ranged from 0.87 to 0.99 across the left and right knees. ICC scores for the other features of the curves ranged from 0.61 to 0.98. The standard error of the mean ranged from 0.0497 to 1.1712.

CONCLUSIONS

The robotic testing device in this study proved to be reliable for testing a subject multiple times both within the same day and over multiple days. These findings suggest that the device can provide a level of reliability in rotational testing that allows for clinical use of test results. Objective laxity data can improve consistency and accuracy in diagnosing knee injuries and may enable more effective treatment.

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.

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.

Can magnetic resonance imaging findings predict the degree of knee joint laxity in patients undergoing anterior cruciate ligament reconstruction?

Background

The present study was performed to determine whether MRI findings can predict the degree of knee joint laxity in patients undergoing ACL reconstruction and whether the accuracy of the prediction is affected by the MRI acquisition time.

Methods

We assessed prospectively collected data of 154 knees with ACL tears. The presence or absence of four primary findings of ACL tears, i.e., nonvisualization, discontinuity, abnormal signal intensity, and abnormal shape of the ACL, and five secondary findings, i.e., anterior translation of the tibia relative to the femur (≥7 mm), posterior cruciate ligament angle (<105°), bone contusion, Segond fracture, and the deep sulcus sign, were determined. Knee joint laxity was assessed using the Lachman and pivot shift tests. The associations between MRI findings and clinically assessed knee joint laxity were analyzed and compared between subgroups (≤3 months from injury to MRI, 89 knees; >3 months, 65 knees).

Results

Nonvisualization was related to the results of the Lachman test [Odds ratio (OR), 2.6; 95% confidence interval (CI), 1.2–5.5]. Anterior translation of the tibia relative to the femur was related to the results of the pivot shift test (OR, 3.8; 95% CI, 1.6–9.4). In subgroup comparisons of the early and late MRI groups, anterior translation of the tibia relative to the femur was related to the results of the pivot shift test in the early MRI group (OR, 4.5; 95% CI, 1.4–14.4). In contrast, no MRI findings had statistically significant relationships with physical findings in the late MRI group.

Conclusions

Our study indicates that MRI findings may have some usefulness for predicting the grade of knee laxity in patients with symptomatic ACL injury, but its value is limited, especially in patients with a longer time interval between injury and the performance of MRI.

Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of instrumented knee laxity tests

PURPOSE

The aims of this meta-analysis were to determine the sensitivity and specificity of the KT 1000 Arthrometer, Stryker Knee Laxity Tester and Genucom Knee Analysis System for ACL rupture. It was hypothesized that the KT 1000 test is the most sensitive and specific. Secondly, it was hypothesized that the sensitivity and specificity of the KT 1000 arthrometer increase when the amount of Newton force is increased.

METHODS

An electronic database search was performed using MEDLINE and EMBASE. All cross-sectional and cohort studies comparing one or more instrumented examination tests for diagnosing acute complete ACL rupture in living human subjects to an accepted reference standard such as arthroscopy, arthrotomy and MRI were included.

RESULTS

The sensitivity of the KT 1000 Arthrometer with 69 N was 0.54. With 89 N, the sensitivity was 0.78 and the specificity 0.92, and with maximum manual force, the sensitivity was 0.93 and the specificity 0.93. For the Stryker Knee Laxity Tester, the sensitivity was 0.82 and the specificity 0.90. And for the Genucom Knee Analysis System, the sensitivity was 0.74 and the specificity 0.82.

CONCLUSION

The KT Arthrometer performed with maximum manual force has the highest sensitivity, specificity, accuracy and positive predictive value for diagnosing ACL rupture.

LEVEL OF EVIDENCE

Meta-analysis, level I.

Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of physical examinations with and without anaesthesia

PURPOSE

The aims of this meta-analysis were to determine the sensitivity and specificity of the Lachman, pivot shift and anterior drawer test for acute complete ACL rupture in the office setting and under anaesthesia. It was hypothesized that the Lachman test is the most sensitive and the pivot shift test the most specific. Secondly, it was hypothesized that the sensitivity and specificity of all three exams increases when the examination is performed under anaesthesia.

METHODS

An electronic database search was performed using MEDLINE and EMBASE. All cross-sectional and cohort studies comparing one or more physical examination tests for diagnosing acute complete ACL rupture to an accepted reference standard such as arthroscopy, arthrotomy and MRI were included.

RESULTS

Twenty studies were identified and included. The overall sensitivity of the Lachman test was 0.81 and the specificity 0.81; with anaesthesia, the sensitivity was 0.91 and the specificity 0.78. For the anterior drawer test, the sensitivity was 0.38 and the specificity 0.81; with anaesthesia, the sensitivity was 0.63 and the specificity 0.91. The sensitivity of the pivot shift test was 0.28 and the specificity 0.81; with anaesthesia, the sensitivity was 0.73 and the specificity 0.98.

CONCLUSION

In the office setting, the Lachman test has the highest sensitivity for diagnosing an acute, complete ACL rupture, while all three tests had comparable specificity. When the examination was performed under anaesthesia, the Lachman test still obtained the highest sensitivity, but the pivot shift test was the most specific.

LEVEL OF EVIDENCE

Meta-analysis of diagnostic test accuracy, Level II.

Reliability of the dial test using a handheld inclinometer

PURPOSE

The primary purpose of this study was to investigate the intra-tester and inter-tester reliability of the dial test using a handheld digital inclinometer. Additionally, we examined the responsiveness of the test, and side-to-side differences for meaningful comparison.

MATERIALS/METHODS

Twenty-four healthy subjects (22.5 ± 2.8 years) participated in the study. The dial test was performed on both knees at 30° and 90° of knee flexion with the subject supine. While maintaining a neutral position of the ankle, an inclinometer was positioned parallel to the medial border of the foot to quantify external rotation of the tibia. Two examiners performed the dial test in a blinded manner. The minimal detectable change across repeated measures and side-to-side difference was calculated.

RESULTS

Intra-tester reliability for examiner 1 (E1) was 0.83 at 30° knee flexion and 0.89 at 90° knee flexion. Reliability values for examiner 2 (E2) were 0.86 at 30° and 0.87 at 90° knee flexion. Inter-tester reliability was 0.74 at 30° and 0.83 at 90°. The minimal detectable change (MDC) for E1 at 30° was ±9.4° and ±7.4° at 90°. For E2, the MDC value was ±9.1° at 30° and ±8.3° at 90°. Ninety-five percent limits of agreement for side-to-side difference was 16.1° and 11.3° ° for E1 at 30° and 90° and for E2 13.9° at 30° and 14.1° at 90°.

CONCLUSIONS

This instrumented dial test using a handheld digital inclinometer to measure external rotation can be performed with acceptable reliability in the clinical setting. A difference of 10° between two measurements on the same knee suggests that a meaningful change has occurred. For right to left comparison, differences greater than 15° suggest clinical significance.

LEVEL OF EVIDENCE

III.

Knee rotation in healthy individuals related to age and gender

An external device ("the Rottometer") was especially designed to measure passive knee rotation in vivo. The device had earlier been evaluated with respect to it's validity and reliability. In the present study, we evaluated knee rotation in knee-healthy individuals and studied possible age and gender related differences. Measurements of total internal-external rotation were made at 90°, 60°, and 30° of flexion using 6 and 9 N m torques, as well as the examiner's apprehension of end-feel as displacing forces. The study group constituted of 120 healthy subjects (60 females and 60 males) with no prior or present knee disorders. The sample was divided into four age groups (15-30, 31-45, 46-60, and >60 years). The results showed no differences in knee rotation between the right and left knees or between the different flexion angles. The females showed 10-20% (p < 0.01) larger knee rotation than the males at all the three flexion angles and at all the three applied torques in all age-matched groups. In all age groups in both genders, the internal rotation accounted for 40-44% and the external for 56-60% of the total internal-external knee rotation.

A clinical device for measuring internal-external rotational laxity of the knee

BACKGROUND

The dial test can be improved by providing reproducible, accurate measurements to improve diagnosis and treatment comparisons.

PURPOSE

Validation of a rotational measurement device (RMD) for measuring knee internal-external rotational laxity.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

The RMD consisted of 3 components: a femoral clamp and a tibial splint using paired inclinometers to measure rotations, and a boot to apply tibial internal-external rotation torque. A separate boot inclinometer allowed for foot rotations to be measured independently. The measurements were simultaneously compared with electromagnetic "nest of birds" (NOB) sensors. Sequential paired knee measurements were taken at 4, 6, and 8 N·m of torque at 30° and 90° of flexion in 46 volunteers.

RESULTS

The correlation coefficient was 0.92 (95% CI, 0.89 to 0.94) and 0.63 (95% CI, 0.54 to 0.70) between the NOB and RMD and between the NOB and boot inclinometer, respectively. Bland-Altman analysis revealed that the RMD was on average within 2° (95% CI, 1° to -4°) of NOB readings, whereas the boot overestimated by 34° (95% CI, -9° to -58°). Maximum side-to-side differences measured by the NOB, RMD, and boot were 1°, 3°, and 21°, respectively. The mean +2× standard deviation data gave a range of side-to-side differences of less than 5° for the RMD. The intraobserver intraclass correlation was 0.9 (95% CI, 0.78 to 0.97) at both 30° and 90° of flexion, and the 95% CI of the differences between readings taken on 2 occasions, the interobserver repeatability, was 1° or less.

CONCLUSION

The novel clinical RMD for measuring rotational laxity of the knee was portable, easy, and comfortable to use in the clinical setting. The RMD showed significant correlation and accuracy compared with sensors of known high accuracy. Side-to-side differences of less than 5° were found in 95% of normal knees, compared with differences of 13° or more for clinical diagnosis of pathological rotational laxity. Measuring knee rotation at the foot showed poor correlation and accuracy.

Evaluating rotational kinematics of the knee in ACL reconstructed patients using 3.0 Tesla magnetic resonance imaging

INTRODUCTION

Injury to the anterior cruciate ligament (ACL) is common. While prior studies have shown that surgical reconstruction of the ACL can restore anterior-posterior kinematics, ACL-injured and reconstructed knees have been shown to have significant differences in tibial rotation when compared to uninjured knees. Our laboratory has developed an MR compatible rotational loading device to objectively quantify rotational stability of the knee following ACL injuries and reconstructions. Previous work from our group demonstrated a significant increase in total tibial rotation following ACL injuries. The current study is a prospective study on the same cohort of patients who have now undergone ACL reconstruction. We hypothesize that ACL reconstructed knees will have less tibial rotation relative to the pre-operative ACL deficient condition. We also hypothesize that ACL reconstructed knees will have greater rotational laxity when compared to healthy contralateral knees.

METHODS

Patients. Six of the ACL injured patients from our initial study who had subsequently undergone ACL reconstruction were evaluated 8.1 ± 2.9 months after surgery. All patients underwent single-bundle ACL reconstruction using anteromedial portal drilling of the femoral tunnel with identical post-operative regimens. Magnetic Resonance (MR) Imaging. Patients were placed in a supine position in the MR scanner on a custom-built loading device. Once secured in the scanner bore, an internal/external torque was applied to the foot. The tibiae were semi-automatically segmented with in-house software. Tibial rotation comparisons were made within subjects (i.e. side-to-side comparison between reconstructed and contralateral knees) and differences were explored using paired sample t-tests with significance set at p=0.05.

RESULTS

Regarding tibial rotation, in the ACL deficient state, these patients experienced an average of 5.9 ± 4.1° difference in tibial rotation between their ACL deficient and contralateral knees. However, there was a -0.2 ± 6.1° difference in tibial rotation of the ACL reconstructed knee when compared to the contralateral uninjured knee. Regarding tibial translation, ACL deficient patients showed a difference of 0.75 ± 1.4mm of anterior tibial translation between injured and healthy knees. After ACL reconstruction, there was a 0.2 ± 1.1mm difference in coupled anterior tibial translation of the ACL reconstructed knee compared to the contralateral knee. No significant differences in contact area between the two time points could be discerned.

DISCUSSION

The objective of our study was to assess the rotational laxity present in ACL reconstructed knees using a previously validated MRI-compatible rotational loading device. Our study demonstrated that ACL reconstruction can restore rotational laxity under load. This may speak to the benefit of an anteromedial drilling technique, which allows for a more horizontal and anatomically appropriate graft position.

Biomechanical techniques to evaluate tibial rotation. A systematic review

PURPOSE

This article systematically reviewed the biomechanical techniques to quantify tibial rotation, for an overview of how to choose a suitable technique for specific clinical application.

METHODS

A systematic search was conducted and finally 110 articles were included in this study. The articles were categorized by the conditions of how the knee was examined: external load application, physical examination and dynamic task.

RESULTS

The results showed that two-thirds of the included studies measured tibial rotation under external load application, of which over 80% of the experiments employed a cadaveric model. The common techniques used included direct displacement measurement, motion sensor, optical tracking system and universal force moment sensor. Intra-operative navigation system was used to document tibial rotation when the knee was examined by clinical tests. For dynamic assessment of knee rotational stability, motion analysis with skin reflective markers was frequently used although this technique is less accurate due to the skin movement when compared with radiographic measurement.

CONCLUSION

This study reports various biomechanical measurement techniques to quantify tibial rotation in the literatures. To choose a suitable measurement technique for a specific clinical application, it is suggested to quantify the effectiveness of a new designed surgical technique by using a cadaveric model before applying to living human subjects for intra-operative evaluation or long-time functional stability assessment. Attention should also be paid on the study's purpose, whether to employ a cadaveric model and the way of stress applied to the knee.

LEVEL OF EVIDENCE

IV.

Optimal measurement of clinical rotational test for evaluating anterior cruciate ligament insufficiency

PURPOSE

Rotational instability in ACL insufficient knee addresses the symptom or the abnormal motion which can be reproduced and subjectively evaluated in the clinical exam. Clinically available quantitative measurement for this instability has not been established due to mixed testing maneuvers and complex kinematics. The purpose was to measure knee kinematics during three manually performed rotational tests and to determine the optimal method to detect the abnormality in ACL deficient knees.

METHOD

Thirteen unilateral ACL deficient patients were tested by internal and external pure rotational stress tests and pivot shift test under anesthesia before scheduled ACL reconstructions. Rotation and coupled motion, i.e., tibial anteroposterior translation, were measured using an electromagnetic measurement system. Additionally, the acceleration of the tibial posterior translation during pivot shift test was calculated. The differences of these parameters between ACL intact and deficient knees were tested.

RESULTS

Knee rotation is not different between ACL intact and deficient during both pure rotational stress test and pivot shift test. The coupled anterior tibial translation during pivot shift test was significantly different between ACL intact, 13.5 ± 4.1 mm, and deficient knees, 23.1 ± 4.4 mm, (P < 0.01) as well as the acceleration of the tibial posterior translation (1.1 ± 0.4 m/sec(2) in intact knees, 3.2 ± 1.5 m/sec(2) in deficient knees; P < 0.01). The coupled motion during pure rotational stress tests was similar regardless of ACL condition.

CONCLUSION

The rotational instability of the ACL deficiency was reproduced only by the pivot shift test and detected only by measuring the tibial anteroposterior translation and acceleration of the tibial posterior reduction. Level of evidence Diagnostic study, Level III.

Knee rotational laxity: an investigation of bilateral asymmetry for comparison with the contralateral uninjured knee

BACKGROUND

Instability associated with anterior cruciate ligament injury is commonly evaluated against the patient's contralateral knee. The objectives of this study were, therefore, to assess symmetry of rotational knee laxity in vivo under passive torsional loading in uninjured subjects, and to compare mean rotation of this control group with the contralateral, intact knees of anterior cruciate ligament deficient patients.

METHODS

Axial knee rotation was measured in 29 patients with unilateral anterior cruciate ligament injury and 15 uninjured age and gender-matched control subjects using an imaging-compatible torsional loading device. Side-to-side differences in internal, external, and range of knee rotation were assessed in the control group and mean bilateral knee rotation was compared to the patients' contralateral knee data at both full extension and 30° of flexion.

FINDINGS

Statistically significant differences in symmetry were found in three of the six measures of transverse plane rotation in the uninjured knees; a mean side-to-side difference of 2.2° in range of rotation was detected in the flexed position. No significant differences were observed between the mean values of the healthy control group and the contralateral knees of the anterior cruciate ligament deficient patients.

INTERPRETATION

Bilateral asymmetry of rotational laxity occurs in healthy individuals. Nevertheless, comparability of rotational knee laxity between the contralateral limbs of patients and the uninjured population was evidence that rotational laxity was not inherent or developed in the contralateral knees of the anterior cruciate ligament deficient participants.

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

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

Assessment of rotatory laxity in anterior cruciate ligament-deficient knees using magnetic resonance imaging with Porto-knee testing device

PURPOSE

Objective evaluation of both antero-posterior translation and rotatory laxity of the knee remains a target to be accomplished. This is true for both preoperative planning and postoperative assessment of different ACL reconstruction emerging techniques. The ideal measurement tool should be simple, accurate and reproducible, while enabling to assess both ‘‘anatomy’’ and ‘‘function’’ during the same examination. The purpose of this study is to evaluate the clinical effectiveness of a new in-house developed testing device, the so-called Porto-knee testing device (PKTD). The PKTD is aimed to be used on the evaluation of both antero-posterior and rotatory laxity of the knee during MRI exams.

METHODS

Between 2008 and 2010, 33 patients with ACLdeficient knees were enrolled for the purpose of this study. All patients were evaluated in the office and under anesthesia with Lachman test, lateral pivot-shift test and anterior drawer test. All cases were studied preoperatively with KT-1000 and MRI with PKTD, and examinations performed by independent observers blinded for clinical evaluation. During MRI, we have used a PKTD that applies antero-posterior translation and permits free tibial rotation through a standardized pressure (46.7 kPa) in the proximal posterior region of the leg. Measurements were taken for both knees and comparing side-to-side. Five patients with partial ruptures were excluded from the group of 33.

RESULTS

For the 28 remaining patients, 3 women and 25 men, with mean age of 33.4 ± 9.4 years, 13 left and 15 right knees were tested. No significant correlation was noticed for Lachman test and PKTD results (n.s.). Pivot-shift had a strong positive correlation with the difference in anterior translation registered in lateral and medial tibia plateaus of injured knees (cor. coefficient = 0.80; p\0.05), and with the difference in this parameter as compared to side-to-side (cor. coefficient = 0.83; p\0.05). Considering the KT-1000 difference between injured and healthy knees, a very strong positive correlation was found for side-to-side difference in medial (cor. coefficient = 0.73; p\0.05) and lateral (cor. coefficient = 0.5; p\0.05) tibial plateau displacement using PKTD.

CONCLUSION

The PKTD proved to be a reliable tool in assessment of antero-posterior translation (comparing with KT-1000) and rotatory laxity (compared with lateral pivotshift under anesthesia) of the ACL-deficient knee during MRI examination.

LEVEL OF EVIDENCE

Therapeutic studies, Level IV.

Reproducibility of an optical measurement system for the clinical evaluation of active knee rotation in weight-bearing, healthy subjects

INTRODUCTION

A knee is typically evaluated passively by a clinician during an office visit, without using dedicated measurement tools. When the knee is evaluated with the patient standing and actively participating in the movement, the results will differ than when the knee is passively moved through its range-of-motion by the surgeon. If a precise measurement system was available, it could provide additional information to the clinician during this evaluation.

HYPOTHESIS

The goal of this study was to verify the reproducibility of a fast, flexible optical measurement system to measure rotational knee laxity during weight-bearing.

MATERIAL AND METHODS

Two passive reflective targets were placed on the legs of 11 subjects to monitor femur and tibia displacements in three dimensions. Subjects performed internal and external rotation movements with the knee extended or flexed 30°. During each movement, seven variables were measured: internal rotation, external rotation and overall laxity in extension and 30° flexion, along with neutral rotation value in 30° flexion. Measurement accuracy was also assessed and the right and left knees were compared. Reproducibility was assessed over two measurements sessions.

RESULTS

The calculated intra-class correlation coefficient (ICC) for reproducibility was above 0.9 for five of the seven variables measured. The calculated ICC for the right/left comparison was above 0.75 for five of the seven variables measured.

DISCUSSION

These results confirmed that the proposed system provides reproducible measurements. Our right/left comparison results were consistent with the published literature. This system is fast, reproducible and flexible, which makes it suitable for assessing various weight-bearing movements during clinical evaluations.

LEVEL OF EVIDENCE

Level III, experimental study.

Influence of individual characteristics on static rotational knee laxity using the Rotameter

PURPOSE

The purpose of this study was to evaluate the influence of individual characteristics on rotational knee laxity in healthy participants. Our second aim was to verify whether the contralateral knee of patients with a non-contact ACL injury presents greater rotational knee laxity than a healthy control group.

METHODS

Sixty healthy participants and 23 patients having sustained a non-contact ACL injury were tested with a new Rotameter prototype applying torques up to 10 Nm. Multiple linear regressions were performed to investigate the influence of gender, age, height and body mass on rotational knee laxity and to establish normative references for a set of variables related to rotational knee laxity. Multiple analyses of covariance were performed to compare the contralateral knee of ACL-injured patients and healthy participants.

RESULTS

Being a women was associated with a significantly (P < 0.05) higher rotational knee laxity, and increased body mass was related to lower laxity results. In the multiple analyses of covariance, gender and body mass were also frequently associated with rotational knee laxity. When controlling for these variables, there were no differences in measurements between the contralateral leg of patients and healthy participants.

CONCLUSION

In the present setting, gender and body mass significantly influenced rotational knee laxity. Furthermore, based on these preliminary results, patients with non-contact ACL injuries do not seem to have excessive rotational knee laxity.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Evaluating rotational kinematics of the knee in ACL-ruptured and healthy patients using 3.0 Tesla magnetic resonance imaging

PURPOSE

Rotational knee laxity is an important measure in restoring knee stability following anterior cruciate ligament (ACL) injury, but is difficult to quantify with current clinical tools. The hypothesis of the study is that there is greater tibial rotation (TR) in women than men, and also in ACL-deficient than healthy knees.

METHODS

Sixteen healthy (8 men, 26.8 ± 6.4 years; 8 women, 26.9 ± 3.8 years) and ten ACL-deficient (5 men, 33.6 ± 10.5 years; 5 women, 36.3 ± 10.7 years) subjects received bilateral knee MRI in 15° of flexion using a custom device to apply a constant axial compressive load (44 N). A rotational torque (3.35 Nm) was sequentially applied to obtain images at internal and external rotation positions. T (2)-weighted images were acquired in internal and external rotation. Images were segmented and TR was calculated. To assess reproducibility, six knees were scanned twice on separate days. Group comparisons were made with unpaired t tests, while intrasubject comparisons were made using paired t tests.

RESULTS

Healthy women demonstrated greater TR than men (13.6° ± 4.7° vs. 8.3° ± 3.6°; P = 0.001). Male ACL-deficient knees showed greater TR than the contralateral knee (15.7° ± 6.9° vs. 7.7° ± 5.6°; P = 0.003), and compared to male controls (P = 0.002). ACL-deficient women showed greater TR compared to their contralateral leg (15.1° ± 2.3° vs. 10.0° ± 4.3°; P = 0.01). The intraclass correlation coefficient of the TR measurement was 0.913, and the SEM = 1.1°.

CONCLUSIONS

Kinematic MRI is a reproducible method to quantify total knee rotation. Women have more rotational laxity than men, particularly in the external rotation position. ACL rupture leads to increased rotational laxity of the knee.

LEVEL OF EVIDENCE

Retrospective case-control series, Level III.

Static rotational knee laxity in anterior cruciate ligament injuries

PURPOSE

The purpose was to provide an overview of the non-invasive devices measuring static rotational knee laxity in order to formulate recommendations for the future.

RESULTS

Early cadaver studies provided evidence that sectioning the anterior cruciate ligament (ACL) led to an increase of static rotational knee laxity of approximately 10-20% between full extension and 30° of knee flexion. Sections of the menisci or of the peripheral structures induced a much higher increase in rotation. This supported the hypothesis that static rotation measurements might be useful for the diagnosis of ACL or associated injuries. In vivo evaluations with measurement devices are relatively new. Several articles were published during the last decade with many different devices and important differences were seen in absolute rotational knee laxity between them. This was due to the varying precision of the devices, the variability in patient positioning, the different methods of measurement, examination protocols and data analysis. As a consequence, comparison of the available results should be performed with caution. Nevertheless, it has been established that rotational knee laxity was greater in females as compared to males and that the inter-subject variability was high. For this reason, it will probably be difficult to categorise injured patients preoperatively, and the interpretation of the results should probably be limited to side-to-side differences.

CONCLUSION

Future studies will show whether rotational laxity measurements alone will be sufficient to provide clinically relevant data or if they should be combined to static sagittal laxity measurements.

The quality of bone surfaces may govern the use of model based fluoroscopy in the determination of joint laxity

The assessment of knee joint laxity is clinically important but its quantification remains elusive. Calibrated, low dosage fluoroscopy, combined with registered surfaces and controlled external loading may offer possible solutions for quantifying relative tibio-femoral motion without soft tissue artefact, even in native joints. The aim of this study was to determine the accuracy of registration using CT and MRI derived 3D bone models, as well as metallic implants, to 2D single-plane fluoroscopic datasets, to assess their suitability for examining knee joint laxity. Four cadaveric knees and one knee implant were positioned using a micromanipulator. After fluoroscopy, the accuracy of registering each surface to the 2D fluoroscopic images was determined by comparison against known translations from the micromanipulator measurements. Dynamic measurements were also performed to assess the relative tibio-femoral error. For CT and MRI derived 3D femur and tibia models during static testing, the in-plane error was 0.4 mm and 0.9 mm, and out-of-plane error 2.6 mm and 9.3 mm respectively. For metallic implants, the in-plane error was 0.2 mm and out-of-plane error 1.5 mm. The relative tibio-femoral error during dynamic measurements was 0.9 mm, 1.2 mm and 0.7 mm in-plane, and 3.9 mm, 10.4 mm and 2.5 mm out-of-plane for CT and MRI based models and metallic implants respectively. The rotational errors ranged from 0.5° to 1.9° for CT, 0.5-4.3° for MRI and 0.1-0.8° for metallic implants. The results of this study indicate that single-plane fluoroscopic analysis can provide accurate information in the investigation of knee joint laxity, but should be limited to static or quasi-static evaluations when assessing native bones, where possible. With this knowledge of registration accuracy, targeted approaches for the determination of tibio-femoral laxity could now determine objective in vivo measures for the identification of ligament reconstruction candidates as well as improve our understanding of the consequences of knee joint instability in TKA.

Measurements of knee rotation-reliability of an external device in vivo

BACKGROUND

Knee rotation plays an important part in knee kinematics during weight-bearing activities. An external device for measuring knee rotation (the Rottometer) has previously been evaluated for validity by simultaneous measurements of skeletal movements with Roentgen Stereometric Analysis (RSA). The aim of this study was to investigate the reliability of the device.

METHOD

The within-day and test-retest reliability as well as intertester reliability of the device in vivo was calculated. Torques of 3, 6 and 9 Nm and the examiner's apprehension of end-feel were used at 90°, 60° and 30° of knee flexion. Intraclass Correlation Coefficient 2,1 (ICC 2,1), 95% confidence interval (CI) of ICC and 95% CI between test trials and examiners were used as statistical tests.

RESULT

ICC2,1 ranged from 0.50 to 0.94 at all three flexion angles at 6 and 9 Nm as well as end-feel, and from 0.22 to 0.75 at 3 Nm applied torque.

CONCLUSION

The Rottometer was a reliable measurement instrument concerning knee rotation at the three different flexion angles (90°, 60° and 30°) with 6 and 9 Nm applied torques as well as the examiner's apprehension of end-feel. Three Nm was not a reliable torque. The most reliable measurements were made at 9 Nm applied torque.

Effect of physiotherapy on the strength of tibial internal rotator muscles in males after anterior cruciate ligament reconstruction (ACLR)

BACKGROUND

The goal of this study was to evaluate the effect of physiotherapy on the strength of muscles responsible for tibial internal rotation (IR) in male patients after anterior cruciate ligament reconstruction (ACLR) using autografts of the semitendinosus and gracilis muscles (STGR).

MATERIAL/METHODS

Fifty-nine males were examined. The first group consisted of 19 patients subjected to 4-stage physiotherapy following ACLR. The second group consisted of 20 males without knee injuries. The third group consisted of 20 males who had not undergone systematic physiotherapy within the last 12 months following lower limb injuries. Moments of maximal strength (MMS), isometric torque (IT), and peak torque (PT) were measured under static and isokinetic conditions using the Humac Norm System. In the first group, IT measurements were performed during the 13th and 21st week of physiotherapy, while PT measurements were performed during the 16th and 21st weeks of physiotherapy following ACLR. In the control groups (II and III) the measurements were performed once.

RESULTS

In the first group, the IT (13 weeks) and PT (16 weeks) values of internal tibial rotator muscles, obtained from the operated extremities were significantly lower than the values obtained from the uninvolved knees and the control group results. During the 21st week of physiotherapy, the results obtained for IT and PT in patients after ACLR were similar to the values obtained from the uninvolved knees and the results of the second group subjects.

CONCLUSIONS

The 21-week physiotherapy in ACLR patients favorably affected the PT values of tibial rotator muscles of the operated knees. In the third group, the IT values did not indicate a complete improvement after 12 months without systematic physiotherapy.

Measurement of rotational laxity of the knee: in vitro comparison of accuracy between the tibia, overlying skin, and foot

BACKGROUND

Posterolateral corner (PLC) injuries are difficult to diagnose and cause significant morbidity. The ideal method for the dial test and its accuracy remain unclear.

PURPOSE

This study compares the accuracy of measuring tibial external rotation at the skeletal level to measuring the patella-tubercle angle (PTA) and the thigh-foot angle (TFA) in the supine position to assess the most accurate method to measure rotation during the dial test.

STUDY DESIGN

Controlled laboratory study.

METHODS

Measurements were compared simultaneously using rotational goniometers at a cutaneous splint over the tibia, at a foot splint, and directly from the tibial skeleton. Six lower limbs were used. The femur was held rigidly and the knee tested at 90° and 30° of flexion. External rotation torque up to 8 N·m was applied through the foot splint, and the rotations were measured by 2 testers.

RESULTS

Measurements at the tibial splint and directly on the tibia showed significant correlation at both knee flexion angles. The mean tibial external rotation was 24° at 90° of flexion and 26° at 30° of flexion (P < .05). The soft tissue effect caused the tibial splint to overestimate rotations by a mean of 6° and 9° at 90° and 30° of flexion, respectively. Foot splint measurements did not correlate significantly with tibial rotation, overestimating rotations by a mean of 103%. Intratester and intertester intraclass correlations were significant for the skin-mounted tibial splint measurements at both flexion angles but not for foot splint measurements at either flexion angles.

CONCLUSION

Rotation of the foot did not accurately represent the tibial external rotation at the knee, which could be measured more accurately by an instrument resting on the skin via a molded tibial splint. These results suggest that the PTA, and not the TFA, should be used in the dial test. This would support the use of the supine position during the dial test.

CLINICAL RELEVANCE

The dial test is a commonly used method for diagnosing PLC injuries. This study helps to identify the ideal position and measuring points to use for this test; measurements based on the tibia were more accurate than those that used rotation of the foot.

Association of internal rotation of the knee joint with recurrent subluxation of the lateral meniscus

PURPOSE

To compare the arc of rotation of the knee joint at 90° of flexion in control knee joints and those affected by recurrent subluxation of the lateral meniscus (RSLM), in determining whether rotatory instability of the knee joint is a risk factor for RSLM.

METHODS

Knee joints were diagnosed with RSLM when there was a history of mechanical locking episodes and when subluxation of the lateral meniscus with the peripheral margin of the posterior segment moving anteriorly beyond the lateral femoral condyle was recognized on arthroscopy. In this study 288 knee joints in 270 subjects were evaluated. The joints were classified into a control group (252 joints), an RSLM group (24 joints), and a contralateral RSLM group (12 joints). The arcs of external and internal rotation at 90° of flexion of the knee joint induced by 7 Nm of torque under non-weight-bearing conditions were measured with a Biodex System 3 (Biodex Medical Systems, Shirley, NY).

RESULTS

There were no significant differences in mean values of external rotation among the 3 groups. The mean values of internal rotation of both the RSLM and contralateral RSLM groups were significantly larger than that of the control group, by about 15° (P < .0001). The mean value of internal rotation was slightly higher than that of external rotation in the RSLM and contralateral RSLM groups, although the mean value of internal rotation was smaller than that of external rotation by 10.1° in the control group.

CONCLUSIONS

RSLM was found to be strongly related to bilateral increase in the arc of internal rotation at 90° of flexion of the knee joint, suggesting that internal rotatory instability of the flexed knee joint can be considered one of the risk factors for and diagnostic parameters of RSLM.

LEVEL OF EVIDENCE

Level III, diagnostic study of nonconsecutive patients.

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

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSION

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

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

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

A novel tool for objective assessment of femorotibial rotation: a cadaver study

Traumatic rupture of the anterior cruciate ligament (ACL) of the knee is one of the most frequent orthopaedic sports' injuries. However, the best operative reconstruction technique is still the focus of current discussions among experts. While single-bundle reconstruction primarily addresses anterior-posterior instability, the anatomical double-bundle reconstruction aims to stabilise anterior-posterior as well as rotational instability. So far no definite evidence to favour the one or the other technique exists due to the lack of an objective method for quantifying rotational knee stability. In this context several authors have recently reported on devices for the analysis of femorotibial rotation. However, most of these tools are still in the developmental stage. Therefore, the aim of this study was (1) to develop a new instrument for assessing rotational knee stability independent from the surrounding soft tissue with an adequate method of analysis and (2) to establish the possible field of application of this device in a human cadaver study. The so-called torsiometer evaluated was designed to assess internal and external knee joint rotation objectively in different flexion angles. Measurements were performed implying internal and external rotation at 90°, 30° and 0° knee flexion with and without intact ACL, respectively. Each measurement revealed valid and reproducible values. The restraint in ACL-absent knees was clearly lower and the course of rotation explicitly higher than in knee joints with intact ACL.

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.

Reliability testing of a new device to measure tibial rotation

The purpose of this study was to evaluate the reliability of a new developed device to measure tibial rotation, the Rotameter. Thirty healthy subjects (15 males, 15 females, 24 years) were examined with the Rotameter measurement device. External and internal rotation was performed at an applied torque of 5, 10 and 15 Nm by two independent examiners in order to test the inter-observer reliability. The patients were measured again after a mean of 31 +/- 43 days by the same examiners to test the intra-observer reliability. Statistical analysis was performed using the intra-class correlation coefficient. The Pearson Correlation coefficient was used to compare the measurements of the left with the right side of the participants. In the measurements, a high inter- and intra-observer reliability was found at 5, 10 and 15 Nm of applied torque for the external rotation, internal rotation and the rotational range (internal + external rotation). Comparison of the left and the right knee of the same participant also revealed high correlations in the Pearson correlation coefficient at all applied torques. In conclusion, the Rotameter testing device for the measurement of tibial rotation showed a high inter-observer and intra-observer reliability. It is easy to perform and might be used in a wide field as a non-invasive instrument to objectively determine rotational stability and to investigate the restoration of the rotational stability after surgical procedures.