Anterior cruciate ligament reconstruction and physiological joint laxity: earliest changes in joint stability and stiffness after reconstruction

Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing system

Background

Robot-based joint-testing systems (RJTS) can be used to perform unconstrained laxity tests, measuring the stiffness of a degree of freedom (DOF) of the joint at a fixed flexion angle while allowing the other DOFs unconstrained movement. Previous studies using the force-position hybrid (FPH) control method proposed by Fujie et al. (J Biomech Eng 115(3):211–7, 1993) focused on anterior/posterior tests. Its convergence and applicability on other clinically relevant DOFs such as valgus/varus have not been demonstrated. The current s1tudy aimed to develop a 6-DOF RJTS using an industrial robot, to propose two new force-position hybrid control methods, and to evaluate the performance of the methods and FPH in controlling the RJTS for anterior/posterior and valgus/varus laxity tests of the knee joint.

Methods

An RJTS was developed using an industrial 6-DOF robot with a 6-component load-cell attached at the effector. The performances of FPH and two new control methods, namely force-position alternate control (FPA) and force-position hybrid control with force-moment control (FPHFM), for unconstrained anterior/posterior and valgus/varus laxity tests were evaluated and compared with traditional constrained tests (CT) in terms of the number of control iterations, total time and the constraining forces and moments.

Results

As opposed to CT, the other three control methods successfully reduced the constraining forces and moments for both anterior/posterior and valgus/varus tests, FPHFM being the best followed in order by FPA and FPH. FPHFM had root-mean-squared constraining forces and moments of less than 2.2 N and 0.09 Nm, respectively at 0° flexion, and 2.3 N and 0.14 Nm at 30° flexion. The corresponding values for FPH were 8.5 N and 0.33 Nm, and 11.5 N and 0.45 Nm, respectively. Given the same control parameters including the compliance matrix, FPHFM and FPA reduced the constraining loads of FPH at the expense of additional control iterations, and thus increased total time, FPA taking about 10 % longer than FPHFM.

Conclusions

The FPHFM would be the best choice among the methods considered when longer total time is acceptable in the intended clinical applications. The current results will be useful for selecting a force-position hybrid control method for unconstrained laxity tests using an RJTS.

Synthetic devices for reconstructive surgery of the cruciate ligaments: a systematic review

PURPOSE

The role of synthetic devices in the management of the cruciate ligament-injured knee remains controversial. The aim of this systematic review was to assess the safety and efficacy of synthetic devices in cruciate ligament surgery.

METHODS

A systematic review of the electronic databases Medline, Embase, and The Cochrane Library (issue 1, 2014) on January 13, 2014, was performed to identify controlled and uncontrolled trials. Trials that assessed the safety and efficacy of synthetic devices for cruciate ligament surgery were included. The main variables assessed included rates of failure, revision, and noninfective effusion and synovitis. Patient-reported outcome assessments and complications were also assessed where reported.

RESULTS

From 511 records screened, we included 85 articles published between 1985 and 2013 reporting on 6 synthetic devices (ligament augmentation and reconstruction system [Ligament Augmentation and Reconstruction System (LARS; Surgical Implants and Devices, Arc-sur-Tille, France)]; Leeds-Keio [Xiros (formerly Neoligaments), Leeds, England]; Kennedy ligament augmentation device [3M, St Paul, MN]; Dacron [Stryker, Kalamazoo, MI]; Gore-Tex [W.L. Gore and Associates, Flagstaff, AZ]; and Trevira [Telos (limited liability company), Marburg, Germany]). The heterogeneity of the included studies precluded meta-analysis. The results were analyzed by device and then type of reconstruction (anterior cruciate ligament [ACL]/posterior cruciate ligament [PCL]/combined ACL and PCL). The lowest cumulative rates of failure were seen with the LARS device (2.6% for ACL and 1% for PCL surgery). The highest failure rate was seen in the Dacron ACL group (cumulative rate, 33.6%). Rates of noninfective synovitis and effusion ranged from 0.2% in the LARS ACL group to 27.6% in the Gore-Tex ACL group. Revision rates ranged from 2.6% (LARS) to 11.8% (Trevira-Hochfest; Telos). Recent designs, specifically the LARS, showed good improvement in the outcome scores. The mean preoperative and postoperative Lysholm knee scores were 54 and 88, respectively; the mean preoperative and postoperative Tegner activity scale scores were 3.3 and 6, respectively.

CONCLUSIONS

Preliminary results for newer-generation devices, specifically the LARS, show lower reported rates of failure, revision, and sterile effusion/synovitis when compared with older devices.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II through IV studies.

Status and headway of the clinical application of artificial ligaments

The authors first reviewed the history of clinical application of artificial ligaments. Then, the status of clinical application of artificial ligaments was detailed. Some artificial ligaments possessed comparable efficacy to, and fewer postoperative complications than, allografts and autografts in ligament reconstruction, especially for the anterior cruciate ligament. At the end, the authors focused on the development of two types of artificial ligaments: polyethylene glycol terephthalate artificial ligaments and tissue-engineered ligaments. In conclusion, owing to the advancements in surgical techniques, materials processing, and weaving methods, clinical application of some artificial ligaments so far has demonstrated good outcomes and will become a trend in the future.

Anterior knee stiffness changes in laxity "responders" versus "nonresponders" across the menstrual cycle

CONTEXT

Although changes in anterior knee laxity (AKL) across the menstrual cycle have been reported, the effects of cyclic knee laxity changes on the underlying characteristics of the load-displacement (stiffness) curve generated during anterior loading of the tibia relative to the femur are relatively unknown.

OBJECTIVE

To describe the anterior load-displacement curve during anterior loading of the tibia relative to the femur using incremental stiffnesses and to compare underlying stiffness measures between days of the cycle when AKL is at its minimum and maximum.

DESIGN

Descriptive laboratory study.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Fifty-seven recreationally active women.

MAIN OUTCOME MEASURE(S)

Anterior knee laxity and 6 incremental stiffness measures (N/mm) were obtained with an instrumented knee arthrometer on days 1-6 of menses and days 0-8 postovulation during 2 consecutive menstrual cycles. Participants were then classified in tertiles based on the maximum change (difference between maximum and minimum) in AKL, and incremental stiffness was compared on days of minimum versus maximum laxity between the lowest (<1.24 mm cyclic laxity change = laxity "nonresponders" [n = 19]) and highest (>1.75 mm cyclic laxity change = laxity "responders" [n = 19]) tertiles.

RESULTS

All participants displayed decreasing stiffness initially (0-20 N > 20-40 N and 40-60 N), followed by incrementally increasing stiffness (40-60 N < 60-80 N < 80-100 N < 100-130 N) (P ≤ .05). Responders demonstrated decreased stiffness between the days of minimum and maximum AKL at the 10-130-N increment versus the 0-20-N and 20-40-N increments (P ≤ .05); nonresponders had no change in stiffness.

CONCLUSIONS

Participants who experienced larger magnitudes of cyclic changes in AKL also experienced decreases in terminal (100-130 N) stiffness during anterior knee joint loading. Decreases in incremental stiffness at higher anterior directed loads may adversely affect passive restraint systems, resulting in altered arthrokinematics during functional activity.

A new diagnostic approach using regional analysis of anterior knee laxity in patients with anterior cruciate ligament deficiency

PURPOSE

The first purpose of this study was to analyze the characteristics of the anterior knee laxity in the three regions of different stiffness in the force-displacement curve, which was obtained from a frequently used arthrometer for quantifying knee joint stability in the patients with anterior cruciate ligament (ACL) rupture and the healthy controls. The second purpose was to compare the characteristics from the regional analysis of the anterior knee laxity between the two subject groups in order to explore proper diagnosis criteria.

METHODS

Seventy-one patients with unilateral ACL tear and eighty healthy controls were enrolled and their anterior knee laxities were tested using the KT-2000 arthrometer. The displacements and stiffness of the three regions were extracted separately and compared between groups to further develop the diagnostic criteria.

RESULTS

The results indicated that the laxity behavior was mostly affected in Region 2 and Region 3 after ACL tear. Two good indicators for ACL tear were found in the receiver operating characteristic (ROC) curve analysis: Region 2 with the displacement larger than 3.7 mm and Region 3 with the stiffness smaller than 22 N/mm. These two criteria provided a better diagnostic accuracy with increased sensitivity.

CONCLUSIONS

The regional analysis method developed in this study could provide more information for understanding the characteristics of the anterior knee laxity and help increase the diagnostic accuracy for ACL rupture.

LEVEL OF EVIDENCE

II.

Physiological anterior laxity in healthy young females: the effect of knee hyperextension and dominance

Female athletes are more likely to sustain an anterior cruciate ligament (ACL) injury. Knee laxity, hyperextension and limb dominance have been suggested as possible factors contributing to the knee injury. The aims of this study were to investigate the physiological anterior knee laxity between the dominant and non-dominant limb and in healthy young females with and without hyperextension knees. Forty-two healthy young females, 21 with hyperextension knees, were recruited voluntarily for this study. The subjects were tested with KT-2000 knee ligament arthrometer at both knees with flexion 30 degrees to obtain the anterior tibial displacements at loadings of 45, 67, 89 and 134 N. The initial and terminal stiffnesses were further calculated and analyzed to demonstrate the differences in the characteristics of knee laxity between limbs and groups. The results showed that there was no significant displacement difference between hyperextension and non-hyperextension groups. However, different physiological anterior laxities were illustrated for the different limbs and groups. The non-dominant side of the hyperextension group had significantly smaller terminal stiffness than that of the non-hyperextension group. The dominant side of the hyperextension group had larger laxity than the non-dominant side in the higher loading conditions. These findings may explain hyperextension knees are at greater risk of sustaining an ACL injury.

Influence of functional bracing on the kinetics of anterior cruciate ligament-injured knees during level walking

BACKGROUND

Use of functional knee braces has been suggested to provide protection and to improve kinetic performance of the knee in anterior cruciate ligament-injured patients. However, the efficacy of knee bracing in achieving these goals is still controversial. The purpose of this study was to examine the immediate effects of functional bracing on the three-dimensional kinetics of the knee in individuals with anterior cruciate ligament injuries during level walking.

METHODS

Fifteen anterior cruciate ligament-deficient and 15 anterior cruciate ligament-reconstructed subjects were each fitted with a DonJoy Goldpoint brace and walked at a self-selected pace, first without and then with the brace. Kinematic and kinetic data were measured and three-dimensional joint moments and angular impulses at the knee were calculated and compared between bracing conditions and between limbs.

FINDINGS

Functional knee bracing did not significantly affect the kinetics of the unaffected knees for either group. Bracing significantly increased the peak abductor moments in anterior cruciate ligament-deficient knees and reduced the bilateral kinetic asymmetry in the coronal plane. For the anterior cruciate ligament-reconstructed group, bracing increased peak moments and impulses of the abductors and extensors. It also reduced bilateral kinetic asymmetry in the sagittal and coronal planes.

INTERPRETATION

Effects of the knee brace were apparent in the coronal plane for both anterior cruciate ligament-deficient and anterior cruciate ligament-reconstructed patients, and in the sagittal plane for anterior cruciate ligament-reconstructed patients. Functional bracing can be recommended for anterior cruciate ligament-reconstructed patients to assist in achieving better bilateral kinetic symmetry during gait. For anterior cruciate ligament-deficient patients, apart from bracing, additional emphasis on the rehabilitative training for better kinetic knee performance in the sagittal plane is needed.

Differences in torsional joint stiffness of the knee between genders: a human cadaveric study

BACKGROUND

In many sports, female athletes have a higher incidence of anterior cruciate ligament injury than do male athletes. Among many risk factors, the lower rotatory joint stiffness of female knees has been suggested for the increased rate of anterior cruciate ligament injuries.

HYPOTHESIS

In response to combined rotatory loads, female knees have significantly lower torsional joint stiffness and higher rotatory joint laxity than do male knees at low flexion angles, despite the fact that no such gender differences would be found in response to an anterior tibial load.

STUDY DESIGN

Comparative laboratory study.

METHODS

Joint kinematics of 82 human cadaveric knees (38 female, 44 male) in response to (1) combined rotatory loads of 10 N x m valgus and +/- 5 N x m internal tibial torques and (2) a 134-N anterior-posterior tibial load were measured using a robotic/universal force-moment sensor testing system.

RESULTS

In response to combined rotatory loads, female knees had as much as 25% lower torsional joint stiffness (female: 0.79 N x m/deg; 95% confidence interval, 0.67-0.91; male: 1.06 N x m/deg; 95% confidence interval, 0.95-1.17) and up to 35% higher rotatory joint laxity (female: 26.2 degrees; 95% confidence interval, 24.5 degrees-27.9 degrees; male: 20.5 degrees; 95% confidence interval, 18.8 degrees-22.2 degrees) than did male knees (P < .05), whereas there were no gender differences in response to the anterior tibial load (P > .05).

CONCLUSION

Female knees had lower torsional joint stiffness and higher rotatory joint laxity than did male knees in response to combined rotatory loads.

CLINICAL RELEVANCE

Larger axial rotations of female knees in response to rotatory loads may affect the distribution of forces in soft tissues and the function of muscles that provide knee stability. Control algorithms used during the biomechanical testing of cadaveric knees and computational knee models might need to be gender specific.

Comparison of functional outcome after anterior cruciate ligament reconstruction resulting in low, normal and increased laxity

The aim of the study was to analyse and compare the results after arthroscopic anterior cruciate ligament (ACL) reconstruction using patellar tendon autografts in three groups of patients. The groups were determined by knee laxity as measured with the KT-1000 arthrometer at the follow-up two to five years after the reconstruction. Group A (n=15) had an anterior side-to-side laxity difference of <-3 mm (i.e. the reconstructed knee was less lax than the contralateral non-injured knee), Group B (n=376) had a difference of > or = -1, but < or = +2 mm and Group C (n=38) had a difference of > or g=6 mm. All the patients had a normal contralateral knee. In Group A, 7/15 (47%) patients and, in Group B, 82/375 (22%) patients had an extension deficit of > or =5 degrees (P=0.052). The corresponding values in terms of flexion deficit were 8/15 (53%) and 99/375 (26%) respectively (P=0.04) (one missing value in Group B). In Group C, 14/38 (37%) had an extension deficit (P=0.04; Group B vs Group C). Group C displayed worse results than Group B in terms of the Lysholm score and the one-leg-hop test (P=0.001 and P=0.011 respectively). The corresponding comparison between Group A and Group B revealed no significant differences. We conclude that a considerable number of patients showed persisting deficits in range of motion (ROM) after an ACL reconstruction. No major differences were found if they were analysed in subgroups with decreased, near normal or with increased knee laxity. The worst residual functional impairment, as measured with the Lysholm score and one-leg-hop test, was found in the group with increased knee laxity and most ROM deficits in the knees with decreased laxity.