Knee biomechanics during a jump-cut maneuver: effects of sex and ACL surgery

Can Wearable Sensors Provide Accurate and Reliable 3D Tibiofemoral Angle Estimates during Dynamic Actions?

The ability to accurately measure tibiofemoral angles during various dynamic activities is of clinical interest. The purpose of this study was to determine if inertial measurement units (IMUs) can provide accurate and reliable angle estimates during dynamic actions. A tuned quaternion conversion (TQC) method tuned to dynamics actions was used to calculate Euler angles based on IMU data, and these calculated angles were compared to a motion capture system (our "gold" standard) and a commercially available sensor fusion algorithm. Nine healthy athletes were instrumented with APDM Opal IMUs and asked to perform nine dynamic actions; five participants were used in training the parameters of the TQC method, with the remaining four being used to test validity. Accuracy was based on the root mean square error (RMSE) and reliability was based on the Bland-Altman limits of agreement (LoA). Improvement across all three orthogonal angles was observed as the TQC method was able to more accurately (lower RMSE) and more reliably (smaller LoA) estimate an angle than the commercially available algorithm. No significant difference was observed between the TQC method and the motion capture system in any of the three angles (p < 0.05). It may be feasible to use this method to track tibiofemoral angles with higher accuracy and reliability than the commercially available sensor fusion algorithm.

Long-Term Bilateral Neuromuscular Function and Knee Osteoarthritis after Anterior Cruciate Ligament Reconstruction

Neuromuscular function is thought to contribute to posttraumatic osteoarthritis (PTOA) risk in anterior cruciate ligament (ACL)-reconstructed (ACLR) patients, but sensitive and easy-to-use tools are needed to discern whether complex muscle activation strategies are beneficial or maladaptive. Using an electromyography (EMG) signal analysis technique coupled with a machine learning approach, we sought to: (1) identify whether ACLR muscle activity patterns differed from those of healthy controls, and (2) explore which combination of patient outcome measures (thigh muscle girth, knee laxity, hop distance, and activity level) predicted the extent of osteoarthritic changes via magnetic resonance imaging (MRI) in ACLR patients. Eleven ACLR patients 10-15 years post-surgery and 12 healthy controls performed a hop activity while lower limb muscle EMG was recorded bilaterally. Osteoarthritis was evaluated based on MRI. ACLR muscle activity patterns were bilaterally symmetrical and differed from those of healthy controls, suggesting the presence of a global adaptation strategy. Smaller ipsilateral thigh muscle girth was the strongest predictor of inferior MRI scores. The ability of our EMG analysis approach to detect meaningful neuromuscular differences that could ultimately be related to thigh muscle girth provides the foundation to further investigate a direct link between muscle activation patterns and PTOA risk.

Lower Patellofemoral Joint Contact Force During Side-Step Cutting After Return-to-Sports Clearance Anterior Cruciate Ligament Reconstruction

BACKGROUND

Low patellofemoral joint (PFJ) contact force has been associated with PFJ osteoarthritis. Quadriceps force and knee flexion angles, which are typically altered after an anterior cruciate ligament reconstruction (ACLR), primarily influence PFJ contact forces. It is still inconclusive whether differences in PFJ contact forces are present during high knee flexion tasks such as side-step cutting after clearance to return to sports (RTS) after ACLR.

PURPOSE

To explore PFJ contact forces in the ACLR limb and compare them with those of the contralateral and control limbs during side-step cutting tasks after clearance to RTS.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 26 male athletes with ACLR who were previously cleared to RTS were matched with 23 healthy men serving as the control group. Three-dimensional motion capture and force plate data were collected while both groups performed anticipated side-step cutting tasks. Joint kinematics, kinetics, muscle forces, and PFJ contact forces were calculated using musculoskeletal modeling.

RESULTS

Peak PFJ force was lower in the ACLR limbs compared with the contralateral limbs (mean difference [MD], 5.89 body weight [BW]; 95% CI, 4.7-7.1 BW; P < .001) and the control limbs (MD, 4.44 BW; 95% CI, 2.1-6.8 BW; P < .001). During peak PFJ force, knee flexion angle was lower in ACLR limbs compared with the contralateral (MD, 4.88°; 95% CI, 3.0°-6.7°; P < .001) and control (MD, 6.01°; 95% CI, 2.0°-10.0°; P < .002) limbs. A lower quadriceps force compared with the contralateral (MD, 4.14 BW; 95% CI, 3.4-4.9 BW; P < .001) and control (MD, 2.83 BW; 95% CI, 1.4-4.3 BW; P < .001) limbs was also found.

CONCLUSION

Lower PFJ contact forces and a combination of quadriceps force deficits and smaller knee flexion angle were found in the ACLR compared with the contralateral and control limbs even after clearance to RTS.

CLINICAL RELEVANCE

Despite rehabilitation and subsequent clearance to RTS, differences in PFJ contact forces are present after ACLR. Current rehabilitation and RTS battery may not be effective and sensitive enough to identify and address these differences.

Effects of soft tissue artifacts on the calculated kinematics of the knee during walking and running

Kinematics of the knee during gait has mostly been studied using optical motion capture systems (MCS). The presence of soft tissue artifacts (STA) between the skin markers and the underlying bone presents a major impediment to obtaining a reliable joint kinematics assessment. In this study, we determined the effects of STA on the calculation of knee joint kinematics during walking and running, through the combination of high-speed dual fluoroscopic imaging system (DFIS) and magnetic resonance imaging technique. Ten adults walked and ran while data was collected simultaneously from MCS and high-speed DFIS. The study showed that measured STA underestimated knee flexion angle, but overestimated knee external and varus rotation. The absolute error values of the skin markers derived from knee flexion-extension angle, internal-external rotation, and varus-valgus rotation during walking were -3.2 ± 4.3 deg, 4.6 ± 3.1 deg, and 4.5 ± 3.2 deg respectively, and during running were -5.8 ± 5.4 deg, 6.6 ± 3.7 deg, and 4.8 ± 2.5 deg respectively. Average errors relative to the DFIS for flexion-extension angle, internal-external rotation, and varus-valgus rotation were 78 %, 271 %, 265 % during walking respectively, and were 43 %, 106 %, 200 % during running respectively. This study offers reference for the kinematic differences between MCS and high-speed DFIS, and will contribute to optimizing methods for analyzing knee kinematics during walking and running.

Personalised pose estimation from single-plane moving fluoroscope images using deep convolutional neural networks

Measuring joint kinematics is a key requirement for a plethora of biomechanical research and applications. While x-ray based systems avoid the soft-tissue artefacts arising in skin-based measurement systems, extracting the object’s pose (translation and rotation) from the x-ray images is a time-consuming and expensive task. Based on about 106’000 annotated images of knee implants, collected over the last decade with our moving fluoroscope during activities of daily living, we trained a deep-learning model to automatically estimate the 6D poses for the femoral and tibial implant components. By pretraining a single stage of our architecture using renderings of the implant geometries, our approach offers personalised predictions of the implant poses, even for unseen subjects. Our approach predicted the pose of both implant components better than about 0.75 mm (in-plane translation), 25 mm (out-of-plane translation), and 2° (all Euler-angle rotations) over 50% of the test samples. When evaluating over 90% of test samples, which included heavy occlusions and low contrast images, translation performance was better than 1.5 mm (in-plane) and 30 mm (out-of-plane), while rotations were predicted better than 3−4°. Importantly, this approach now allows for pose estimation in a fully automated manner.

Wavelet analysis reveals differential lower limb muscle activity patterns long after anterior cruciate ligament reconstruction

The purpose of this study was to test whether differences in muscle activity patterns between anterior cruciate ligament-reconstructed patients (ACLR) and healthy controls could be detected 10 to 15 years post-surgery using a machine learning classification approach. Eleven ACLR subjects and 12 healthy controls were recruited from an ongoing prospective randomized clinical trial. Surface electromyography (EMG) signals were recorded from gastrocnemius medialis and lateralis, tibialis anterior, vastus medialis, rectus femoris, biceps femoris, and semitendinosus muscles. Muscle activity was analyzed using wavelet analysis and examined within four sub-phases of the hop test, as well as an average of the task as a whole. K-nearest neighbor machine learning combined with a leave-one-out validation was used to classify the muscle activity patterns as either ACLR or Control. When muscle activity was averaged across the whole hop task, activity patterns for all muscles except the tibialis anterior were identified as being different between the study cohorts. ACLR patients demonstrated continuous muscle activities that spanned take-off, airborne, and landing hop phases versus healthy controls who displayed timed and regulated islets of muscle activities specific to each hop phase. The most striking features were 25-50% greater relative quadriceps intensity and approximately 66% diminished biceps femoris intensity in ACLR patients. The current findings are in contrast to previous work using conventional co-contraction and muscle activation onset EMG measures of the same dataset, underscoring the sensitivity and potential of the wavelet approach coupled with machine learning to reveal meaningful adaptation strategies in this at-risk population.

The effect of lateral extra-articular tenodesis on in vivo cartilage contact in combined anterior cruciate ligament reconstruction

PURPOSE

Lateral extra-articular tenodesis (LET) may confer improved rotational stability after anterior cruciate ligament reconstruction (ACLR). Little is known about how LET affects in vivo cartilage contact after ACLR. The aim of this study was to investigate the effect of LET in combination with ACLR (ACLR + LET) on in vivo cartilage contact kinematics compared to isolated ACLR (ACLR) during downhill running. It was hypothesised that cartilage contact area in the lateral compartment would be larger in ACLR + LET compared with ACLR, and that the anterior-posterior (A-P) position of the contact center on the lateral tibia would be more anterior after ACLR + LET than after ACLR.

METHODS

Twenty patients were randomly assigned into ACLR + LET or ACLR during surgery (ClinicalTrials.gov:NCT02913404). At 6 months and 12 months after surgery, participants were imaged during downhill running using biplane radiography. Tibiofemoral motion was tracked using a validated registration process. Patient-specific cartilage models, obtained from 3 T MRI, were registered to track bone models and used to calculate the dynamic cartilage contact area and center of cartilage contact in both the medial and lateral tibiofemoral compartments, respectively. The side-to-side differences (SSD) were compared between groups using a Mann-Whitney U test.

RESULTS

At 6 months after surgery, the SSD in A-P cartilage contact center in ACLR + LET (3.9 ± 2.6 mm, 4.4 ± 3.1 mm) was larger than in ACLR (1.2 ± 1.6 mm, 1.5 ± 2.0 mm) at 10% and 20% of the gait cycle, respectively (p < 0.01, p < 0.05). There was no difference in the SSD in cartilage contact center at 12 months after surgery. There was no difference in SSD of cartilage contact area in the medial and lateral compartments at both 6 and 12 months after surgery. There were no adverse events during the trial.

CONCLUSION

LET in combination with ACLR may affect the cartilage contact center during downhill running in the early post-operation phase, but this effect is lost in the longer term. This suggests that healing and neuromuscular adaptation occur over time and may also indicate a dampening of the effect of LET over time. (337 /350 words) LEVEL OF EVIDENCE: Level II.

Symmetry and sex differences in knee kinematics and ACL elongation in healthy collegiate athletes during high-impact activities revealed through dynamic biplane radiography

The objectives of this study were to determine symmetry and sex differences in knee kinematics and anterior cruciate ligament (ACL) elongation waveforms in healthy athletes without a history of a knee injury during fast running, drop jump, and 180° internal/external rotation hops. It was hypothesized that knee abduction angle and ACL relative elongation would be greater in women than in men during all activities. Bilateral knee kinematics and ACL relative elongation were determined in 19 collegiate athletes using dynamic biplane radiography. Sex differences in kinematics and ACL relative elongation waveforms were identified using statistical parametric mapping. Average absolute side-to-side differences (SSD_A ) in kinematics and ACL relative elongation waveforms were determined for each activity. Women had up to 2.3° (all p < 0.05) less knee adduction angle and had greater ACL relative elongation (max. 4.8%-9.2%; all p < 0.01) than men during all activities, in support of the hypotheses. SSD_A in kinematics were 1.4 mm and 5.5° or less in all components of translation and rotation, respectively, while SSD_A in ACL relative elongation was 3.6% or less across all activities. Greater ACL relative elongation across a variety of activities may make women more susceptible to ACL injury than men. This study provides valuable reference data for identifying abnormal asymmetry in knee kinematics and ACL elongation in athletes after the ACL injury. These novel results improve our understanding of ACL elongation during demanding athletic activities and may help guide the development of sex-specific risk screening metrics, return to play assessments, and rehabilitation protocols after the ACL injury.

Acute effects of a neuromuscular warm-up on potential re-injury risk factors associated with unanticipated jump landings after anterior cruciate ligament reconstruction: A crossover trial

OBJECTIVE

To investigate acute effects of a single bout of football specific neuromuscular injury preventive warm-up on potential anterior cruciate ligament (ACL) re-injury risk factors during anticipated and unanticipated jump-landings.

DESIGN

Crossover.

METHODS

Fourteen participants (mean ± SD age, 23.4 ± 4.1 years) 6-24 months after ACL reconstruction performed the Prevent Injury and Enhance Performance (PEP) and bicycle ergometer warm-up in a randomised sequence. Washout phase was one week. Countermovement jumps with anticipated and unanticipated single-leg-landings were assessed. Decision-making quality was measured using landing error count.

RESULTS

No carry-over effects occurred (p > 0.05). The unanticipated task produced significantly higher peak ground reaction forces (Δ+4%, F₍₁₁₎ = 3.46, p < 0.001, eta² = 0.21) after PEP warm-up compared to ergometer warm-up. A lower number of decision (Δ+12%, F ₍₅₎ = 17.1, p < 0.001, eta² = 0.57) and cumulated (Δ+15%, F ₍₃₎ = 17.2, p < 0.001, eta² = 0.57) errors were recorded during the unanticipated condition following PEP compared to ergometer warm-up.

CONCLUSIONS

Evaluating unanticipated jump-landing ability prior to return to sports clearance may provide information on potential re-injury risk factors. PEP warm-up may be superior to bicycle ergometer warm-up at improving unanticipated decision-making quality among athletes cleared to return to sports.

A Prediction Model for Primary Anterior Cruciate Ligament Injury Using Artificial Intelligence

Background

Supervised machine learning models in artificial intelligence (AI) have been increasingly used to predict different types of events. However, their use in orthopaedic surgery has been limited.

Hypothesis

It was hypothesized that supervised learning techniques could be used to build a mathematical model to predict primary anterior cruciate ligament (ACL) injuries using a set of morphological features of the knee.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were 50 adults who had undergone primary ACL reconstruction between 2008 and 2015. All patients were between 18 and 40 years of age at the time of surgery. Patients with a previous ACL injury, multiligament knee injury, previous ACL reconstruction, history of ACL revision surgery, complete meniscectomy, infection, missing data, and associated fracture were excluded. We also identified 50 sex-matched controls who had not sustained an ACL injury. For all participants, we used the preoperative magnetic resonance images to measure the anteroposterior lengths of the medial and lateral tibial plateaus as well as the lateral and medial bone slope (LBS and MBS), lateral and medial meniscal height (LMH and MMH), and lateral and medial meniscal slope (LMS and MMS). The AI predictor was created using Matlab R2019b. A Gaussian naïve Bayes model was selected to create the predictor.

Results

Patients in the ACL injury group had a significantly increased posterior LBS (7.0° ± 4.7° vs 3.9° ± 5.4°; P = .008) and LMS (-1.7° ± 4.8° vs -4.0° ± 4.2°; P = .002) and a lower MMH (5.5 ± 0.1 vs 6.1 ± 0.1 mm; P = .006) and LMH (6.9 ± 0.1 vs 7.6 ± 0.1 mm; P = .001). The AI model selected LBS and MBS as the best possible predictive combination, achieving 70% validation accuracy and 92% testing accuracy.

Conclusion

A prediction model for primary ACL injury, created using machine learning techniques, achieved a >90% testing accuracy. Compared with patients who did not sustain an ACL injury, patients with torn ACLs had an increased posterior LBS and LMS and a lower MMH and LMH.

Kinetic measurement system use in individuals following anterior cruciate ligament reconstruction: a scoping review of methodological approaches

Purpose

Our primary objectives were to (1) describe current approaches for kinetic measurements in individuals following anterior cruciate ligament reconstruction (ACLR) and (2) suggest considerations for methodological reporting. Secondarily, we explored the relationship between kinetic measurement system findings and patient-reported outcome measures (PROMs).

Methods

We followed the PRISMA extension for scoping reviews and Arksey and O’Malley’s 6-stage framework. Seven electronic databases were systematically searched from inception to June 2020. Original research papers reporting parameters measured by kinetic measurement systems in individuals at least 6-months post primary ACLR were included.

Results

In 158 included studies, 7 kinetic measurement systems (force plates, balance platforms, pressure mats, force-measuring treadmills, Wii balance boards, contact mats connected to jump systems, and single-sensor insoles) were identified 4 main movement categories (landing/jumping, standing balance, gait, and other functional tasks). Substantial heterogeneity was noted in the methods used and outcomes assessed; this review highlighted common methodological reporting gaps for essential items related to movement tasks, kinetic system features, justification and operationalization of selected outcome parameters, participant preparation, and testing protocol details. Accordingly, we suggest considerations for methodological reporting in future research. Only 6 studies included PROMs with inconsistency in the reported parameters and/or PROMs.

Conclusion

Clear and accurate reporting is vital to facilitate cross-study comparisons and improve the clinical application of kinetic measurement systems after ACLR. Based on the current evidence, we suggest methodological considerations to guide reporting in future research. Future studies are needed to examine potential correlations between kinetic parameters and PROMs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-021-00397-0.

High-speed fluoroscopic imaging for investigation of three-dimensional knee kinematics before and after marathon running

BACKGROUND

Knee injuries often occur during or shortly after marathon running, and are linked to altered knee kinematics.

RESEARCH QUESTION

The kinematics of healthy knees during pre- and post-marathon running have not been examined with high-speed fluoroscopy. This study aimed to evaluate the effects of marathon running on knee kinematics during walking and running by using a combined high-speed fluoroscopy and MRI technique.

METHODS

Ten healthy runners underwent knee MRI within 24 h before marathon running to construct three-dimensional (3D) knee models. Knee kinematics during treadmill walking and running were evaluated using high-speed fluoroscopy (200hz) within 24 h before and as soon as possible (within 5 h) after marathon running. All pre- and post-marathon measurements were compared.

RESULTS

(1) For post-marathon walking, posterior femoral translation increased 1.4 mm at initial contact (p = 0.015); proximal-distal distance of tibia and femur decreased 0.7 mm and 0.8 mm at initial contact and after contact, respectively (p = 0.039, p = 0.046); and valgus femur rotation increased 1.2° after contact (p = 0.027). (2) For post-marathon running, proximal-distal distance decreased 0.7 mm and 1.0 mm at initial contact and after contact (p = 0.011, p = 0.003) respectively; knee flexion decreased 4.3° before contact (p = 0.007); knee flexion increased 1.8° and 2.6° at initial contact and after contact, respectively (p = 0.038, p = 0.011); external femoral rotation increased 1.2° and 1.8° at initial contact and after contact, respectively (p = 0.012, p = 0.037). Valgus femoral rotation after contact increased 2.3° (p = 0.001).

SIGNIFICANCE

Post-marathon changes in valgus and external femoral rotation, knee flexion, posterior femoral translation, and proximal-distal distance may increase the risk of knee injury. This study provides information to better understand the response of the knee to marathon running.

Lateral Extra-articular Tenodesis Contributes Little to Change In Vivo Kinematics After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

BACKGROUND

Lateral extra-articular tenodesis (LET) in combination with anterior cruciate ligament (ACL) reconstruction (ACLR) has been proposed to improve residual rotatory knee instability in patients having ACL deficiency.

PURPOSE/HYPOTHESIS

The purpose was to compare the effects of isolated ACLR (iACLR) versus LET in combination with ACLR (ACLR+LET) on in vivo kinematics during downhill running. It was hypothesized that ACLR+LET would reduce the internal rotation of the reconstructed knee in comparison with iACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 18 patients with ACL deficiency were included. All participants were randomly assigned to receive ACLR+ LET or iACLR during surgery. Six months and 12 months after surgery, knee joint motion during downhill running was measured using dynamic biplane radiography and a validated registration process that matched patient-specific 3-dimensional bone models to synchronized biplane radiographs. Anterior tibial translation (ATT; positive value means "anterior translation") and tibial rotation (TR) relative to the femur were calculated for both knees. The side-to-side differences (SSDs) in kinematics were also calculated (operated knee-contralateral healthy knee). The SSD value was compared between ACLR+LET and iACLR groups using a Mann-Whitney U test.

RESULTS

At 6 months after surgery, the SSD of ATT in patients who had undergone ACLR+LET (-1.9 ± 2.0 mm) was significantly greater than that in patients who had undergone iACLR (0.9 ± 2.3 mm) at 0% of the gait cycle (foot strike) (P = .031). There was no difference in ATT 12 months after surgery. Regarding TR, there were no differences between ACLR+LET and iACLR at either 6 months (P value range, .161-.605) or 12 months (P value range, .083-.279) after surgery.

CONCLUSION

LET in combination with ACLR significantly reduced ATT at the instant of foot strike during downhill running at 6 months after surgery. However, this effect was not significant at 12 months after surgery. The addition of LET to ACLR had no effect on TR at both 6 and 12 months after surgery.

CLINICAL RELEVANCE

LET in combination with ACLR may stabilize sagittal knee motion during downhill running in the early postoperation phase, but according to this study, it has no effect on 12-month in vivo kinematics.

REGISTRATION

NCT02913404 (ClinicalTrials.gov identifier).

Long-term outcomes of anterior cruciate ligament reconstruction surgery: 2020 OREF clinical research award paper

ACL injuries place the knee at risk for post-traumatic osteoarthritis (PTOA) despite surgical anterior cruciate ligament (ACL) reconstruction. One parameter thought to affect PTOA risk is the initial graft tension. This randomized controlled trial (RCT) was designed to compare outcomes between two graft tensioning protocols that bracket the range commonly used. At 7 years postsurgery, we determined that most outcomes between the two tension groups were not significantly different, that they were inferior to an uninjured matched control group, and that PTOA was progressing in both groups relative to controls. The trial database was also leveraged to gain insight into mechanisms of PTOA following ACL injury. We determined that the inflammatory response at the time of injury undermines one of the joint's lubricating mechanisms. We learned that patients continue to protect their surgical knee 5 years postinjury compared to controls during a jump-pivot activity. We also established that presurgical knee function and mental health were correlated with symptomatic PTOA at 7 years, that there were specific anatomical factors associated with poor outcomes, and that there were no changes in outcomes due to tunnel widening in patients receiving hamstring tendon autografts. We also validated a magnetic resonance imaging technique to noninvasively assess graft strength. In conclusion, the RCT determined that initial graft tensioning does not have a major influence on 7-year outcomes. Therefore, surgeons can reconstruct the ACL using a graft tensioning protocol that is within the window of the two graft tensioning techniques evaluated in this RCT.

Quantifying Coordination and Variability in the Lower Extremities after Anterior Cruciate Ligament Reconstruction

Patients experience various biomechanical changes following reconstruction for anterior cruciate ligament (ACL) injury. However, previous studies have focused on lower extremity joints as a single joint rather than simultaneous lower extremity movements. Therefore, this study aimed to determine the movement changes in the lower limb coordination patterns according to movement type following ACL reconstruction. Twenty-one post ACL reconstruction patients (AG) and an equal number of healthy adults (CG) participated in this study. They were asked to perform walking, running, and cutting maneuvers. The continuous relative phase and variability were calculated to examine the coordination pattern. During running and cutting at 30 and 60°, the AG demonstrated a lower in-phase hip–knee coordination pattern in the sagittal plane. The AG demonstrated low hip–knee variability in the sagittal plane during cutting at 60°. The low in-phase coordination pattern can burden the knee by generating unnatural movements following muscle contraction in the opposite direction. Based on the results, it would be useful to identify the problem and provide the fundamental evidence for the optimal timing of return-to-sport after ACL reconstruction (ACLR) rehabilitation, if the coordination variable is measured with various sensors promptly in the sports field to evaluate the coordination of human movement.

EFFECTS OF SURFACE ON TRIPLE HOP DISTANCE AND KINEMATICS

Background

The single leg triple hop (SLTH) test is often utilized by rehabilitation practitioners as a functional performance measure in a variety of patient groups. Accuracy and consistency are important when measuring the patient progress and recovery. Administering the SLTH test on different surfaces, consistent with the patient's sport, may affect the hop distances and movement biomechanics.

Purpose

The purpose of this study was to examine the effects of court and turf surfaces on the hop distance, limb symmetry index (LSI), and lower extremity kinematics of a SLTH test.

Methods

Recreationally active female participants (n=11, height 163.8 ± 7.1cm, mass 63.1 ± 7.1kg, age 18.9 ± 0.9yrs), without injury, volunteered to participate in the study. Three maximal effort SLTH test trials on two different surfaces (court, synthetic turf) were collected and analyzed using 3D motion analysis techniques. Outcome variables included SLTH test distances and LSI values and sagittal plane kinematics including trunk, hip, knee and ankle range of motion (ROM) during the last two landings of each SLTH test trial. The second landing involves an absorption phase and propulsion phase in contrast to the final landing which involves absorption and final balance on the single leg. Paired t-tests were used to determine differences between surfaces in hop distance and LSI values. Two-way repeated measures ANOVA were used to determine differences between surfaces in kinematic variables.

Results

The total SLTH test distance was not statistically different between the court (4.11 ± 0.47m) and turf (4.03 ± 0.42m, p=0.47) surfaces. LSI for the court surface was 100.8 ± 3.0% compared to 99.7 ± 3.0% for turf surface, which was not statistically different (p=0.30). Knee flexion ROM was significantly less (p=0.04) on the turf compared to the court surface during the second landing. Ankle flexion range of motion was also significantly less (p=0.03) during the second landing on turf compared to court.

Conclusions

Type of surface influenced landing kinematics but not total SLTH test distance. When evaluating the quality of landings during a SLTH test, it may be warranted to observe each type of landing and the type of surface used during single leg tests.

Level of Evidence

2.

A Practical Guide to Measuring Ex vivo Joint Mobility Using XROMM

X-Ray Reconstruction of Moving Morphology (XROMM), though traditionally used for studies of in vivo skeletal kinematics, can also be used to precisely and accurately measure ex vivo range of motion from cadaveric manipulations. The workflow for these studies is holistically similar to the in vivo XROMM workflow but presents several unique challenges. This paper aims to serve as a practical guide by walking through each step of the ex vivo XROMM process: how to acquire and prepare cadaveric specimens, how to manipulate specimens to collect X-ray data, and how to use these data to compute joint rotational mobility. Along the way, it offers recommendations for best practices and for avoiding common pitfalls to ensure a successful study.

Greater knee flexion excursion/moment in hopping is associated with better knee function following anterior cruciate ligament reconstruction

PURPOSE

Individuals with impaired knee function after anterior cruciate ligament reconstruction (ACLR) may be at greater risk of developing knee osteoarthritis related to abnormal knee joint movement and loading. The aim of this study was to assess the association between knee biomechanics and knee laxity during hopping and clinically assessed knee function (i.e., patient-reported knee function and hop tests) following ACLR.

METHODS

Sixty-six participants (23 women, mean age 28 ± 6 years, mean 18 ± 3 months following ACLR) completed a standardized single-leg hopping task. Three-dimensional movement analysis was used to assess knee flexion excursion and body weight/height normalized knee flexion moments during landing for the involved limb. Anterior-posterior knee laxity was assessed with a KT-1000 knee arthrometer. Participants then completed a patient-reported knee function questionnaire and three separate hop tests (% of uninvolved limb) and were divided into poor and satisfactory knee function groups (satisfactory: ≥85% patient-reported knee function and ≥ 85% hop test symmetry). Associations between knee function and hop biomechanics/knee laxity were assessed using logistic regression and interquartile range scaled odds ratios (OR^IQR).

RESULTS

Greater knee flexion excursion (OR^IQR 2.9, 95%CI 1.1-7.8), greater knee flexion moment (OR^IQR 4.9, 95%CI 1.6-14.3) and lesser knee laxity (OR^IQR 4.7, 95%CI 1.5-14.9) were significantly associated with greater odds of having satisfactory knee function (≥ 85% patient-reported knee function and ≥ 85% hop test symmetry).

CONCLUSION

Greater knee flexion excursion/moment during hop-landing and lesser knee laxity is associated with better patient-reported knee function and single-leg hop test performance following ACLR. Patients with lower levels of knee function following ACLR demonstrated hop-landing biomechanics previously associated with early patellofemoral osteoarthritis. Therefore, interventions aimed at improving hop landing biomechanics in people with poor knee function are likely required.

LEVEL OF EVIDENCE

III, Cross-sectional study.

Anterior cruciate ligament reconstruction improves subjective ability but not neuromuscular biomechanics during dynamic tasks

PURPOSE

The purpose of this study was to identify high-functioning anterior cruciate ligament-deficient patients and assess the effects of reconstruction on their self-reported functionality, muscle activations and biomechanical properties.

METHODS

Twenty young and active patients participated pre- (11.5 ± 14.3 months post-injury) and again 10.5 ± 1.7 months post-reconstruction and were individually matched to 20 healthy controls. Participants completed hop and side cut movements while patient-related outcome measures, lower limb electromyography, kinetic, and whole body kinematic data were collected. One-dimensional statistical parametric mapping was used to test for group differences (healthy vs deficient; deficient vs reconstructed; reconstructed vs healthy).

RESULTS

When comparing healthy to anterior cruciate ligament-deficient participants, all questionnaires indicated significant lower subjective function while the only substantial biomechanical difference between these participants was a decreased knee extensor moment in both the hop (peak difference: 0.63 Nm/kg, p < 0.001) and side cut (peak difference: 0.76 Nm/kg, p < 0.001). When comparing patients' pre- and post-reconstruction, no biomechanical differences were observed whereas only half of the questionnaires (Tegner, Lysholm, KNEES-ADL, KNEES-Slackness, KNEES-Looseness, KNEES-Sport Behaviour, IKDC, and KOOS-QoL) indicated higher function in the reconstructed state. When comparing the reconstructed patients to the healthy participants, all questionnaires were still significantly higher in the healthy controls. The reconstructed group also had a smaller flexion angle (peak difference: 14.5°, p = 0.007) and knee extensor moment (peak difference: 0.62 Nm/kg, p < 0.001) during the hop and a smaller knee extensor moment (peak difference: 0.90 Nm/kg, p < 0.001) during the side-cut task.

CONCLUSION

At 10-months post-reconstruction, the current results indicate that in high-functioning anterior cruciate ligament-deficient patients, reconstruction had little impact on objective measures of functional ability during dynamic tasks although self-reported function was improved.

LEVEL OF EVIDENCE

Therapeutic prospective cohort study, Level II.

Sex Differences on the Landing Error Scoring System Among Individuals With Anterior Cruciate Ligament Reconstruction

CONTEXT: 

After anterior cruciate ligament reconstruction (ACLR), women have a greater risk of incurring a second anterior cruciate ligament injury and they display different landing movement patterns than men. It remains unclear if clinical movement-assessment tools, such as the Landing Error Scoring System (LESS), can detect sex differences in movement patterns after ACLR.

OBJECTIVE: 

To compare total LESS scores and individual LESS errors between men and women with a history of ACLR.

DESIGN: 

Cross-sectional study.

SETTING: 

Laboratory.

PATIENTS OR OTHER PARTICIPANTS: 

A total of 168 individuals (41 men and 127 women; mean age: men = 20 years [range, 19-25 years], women = 19 years [range, 18-20 years]; mean time since surgery: men = 21 months [range, 12-36 months], women = 27.5 months [range, 17-39 months]) with a history of primary, unilateral ACLR.

MAIN OUTCOME MEASURE(S): 

Participants completed a minimum of 3 trials of a drop vertical-jump task scored using the LESS. The between-sexes difference in LESS score was assessed using analysis of covariance, whereas the associations between participant sex and errors on each LESS item were assessed using logistic or multinomial regression.

RESULTS: 

Women displayed a greater number of total landing errors (men = 4.6 ± 2.3, women = 6.1 ± 2.3; P < .001) and were more likely to commit errors in trunk flexion at initial contact (men = 4.9%, women = 23.6%; odds ratio [OR] = 4.94), medial knee position at initial contact (men = 17.1%, women = 42.5%; OR = 6.01), medial knee displacement (men = 24.4%, women = 73.2%; OR = 7.88), total joint displacement (1 error: men = 58.5%, women = 71.7%, OR = 2.10; 2 errors: men = 7.3%, women = 14.2%, OR = 3.71), and overall impression (1 error: men = 75.6%, women = 84.3%, OR = 3.24; 2 errors: men = 2.4%, women = 10.2%, OR = 12.89) compared with men.

CONCLUSIONS: 

Women with ACLR displayed worse LESS scores and were more likely to commit errors related to medial knee displacement and overall landing quality than men with ACLR.

INFLUENCE OF ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION ON DYNAMIC POSTURAL CONTROL

BACKGROUND

Athletes that have had anterior cruciate ligament (ACL) reconstruction are at a greater risk for reinjury. The relationship between ACL reconstruction and the dynamic postural sway index (DPSI) has not yet been examined.

HYPOTHESIS/PURPOSE

The purpose of this study was to examine the DPSI in a surgically reconstructed ACL limb compared to the uninjured leg in athletes that had been cleared for sport. It was hypothesized that in a bilateral limb comparison, the leg that underwent ACL reconstruction would demonstrate poorer postural stability measures (greater DPSI) during a single leg landing activity as compared to the non-surgical limb.

DESIGN

Case-control study.

METHODS

14 subjects (7 male, 7 female; age range 16-23 years) with a history of unilateral ACL reconstruction and clearance for return to sport (mean 14 months post-operatively, range 8 to 24 months) performed five single leg hops over a 12 inch hurdle in the anterior direction from a distance corresponding with 40% of their height, onto a force platform. DPSI for the medial-lateral, anterior-posterior, vertical directions and a composite score were calculated for each trial on the surgical and non-surgical legs. A multivariate analysis with repeated measures was used to compare surgical and non-surgical legs for the total DPSI measure as well as for each component.

RESULTS

Significant differences (p < .05) in dynamic postural stability were observed in the medial-lateral, anterior-posterior, vertical indices and DPSI total between the surgical and non-surgical limb.

CONCLUSION

Deficits in dynamic postural control persist in ACL-reconstructed limbs compared to the non-surgical limb after the clearance for full activity. Clinicians should consider assessing single limb dynamic stability prior to releasing the athlete back to full activity.

LEVEL OF EVIDENCE

Level 3.

Hip and Knee Kinematics and Kinetics During Landing Tasks After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis

OBJECTIVE

  To evaluate the current evidence concerning kinematic and kinetic strategies adopted during dynamic landing tasks by patients with anterior cruciate ligament reconstruction (ACLR).

DATA SOURCES

  PubMed, Web of Science.

STUDY SELECTION

  Original research articles that evaluated kinematics or kinetics (or both) during a landing task in those with a history of ACLR were included.

DATA EXTRACTION

  Methodologic quality was assessed using the modified Downs and Black checklist. Means and standard deviations for knee or hip (or both) kinematics and kinetics were used to calculate Cohen d effect sizes and corresponding 95% confidence intervals between the injured limb of ACLR participants and contralateral or healthy matched limbs. Data were further stratified by landing tasks, either double- or single-limb landing. A random-effects-model meta-analysis was used to calculate pooled effect sizes and 95% confidence intervals.

DATA SYNTHESIS

  The involved limbs of ACLR patients demonstrated clinically and significantly lower knee-extension moments during double-legged landing compared with healthy contralateral limbs and healthy control limbs (Cohen d range = -0.81 to -1.23) and decreased vertical ground reaction forces when compared with healthy controls, regardless of task (Cohen d range = -0.39 to -1.75).

CONCLUSIONS

  During single- and double-legged landing tasks, individuals with ACLR demonstrated meaningful reductions in injured-limb knee-extension moments and vertical ground reaction forces. These findings indicate potential unloading of the injured limb after ACLR, which may have significant implications for secondary ACL injury and long-term joint health.

ACL Injury Prevention Training Results in Modification of Hip and Knee Mechanics During a Drop-Landing Task

Background:

Injury prevention training has been shown to be effective in reducing the incidence of noncontact anterior cruciate ligament (ACL) injury; however, the underlying reason for the success of these training programs is unclear.

Purpose:

To investigate whether an ACL injury prevention program that has been shown to reduce the incidence of ACL injury alters sagittal plane hip and knee biomechanics during a drop-landing task.

Study Design:

Descriptive laboratory study.

Methods:

Thirty female club soccer players (age range, 11-17 years) with no history of knee injury participated in this study. Kinematics and ground-reaction forces were collected while each participant performed a drop-landing task prior to and immediately after participation in a 12-week ACL injury prevention training program.

Results:

After ACL injury prevention training, participants demonstrated decreased knee extensor moments (P = .03), increased energy absorption at the hip (P = .04), decreased knee-to-hip extensor moment ratios (P = .05), and decreased knee-to-hip energy absorption ratios (P = .03).

Conclusion:

Participation in an ACL injury prevention training program decreased reliance on the knee extensor muscles and improved use of the hip extensor muscles, which may explain the protective effect of this type of training program on ACL injury.

Clinical Relevance:

Based on these findings, clinicians can better understand how ACL injury prevention training, such as the Prevent Injury and Enhance Performance (PEP) Program, may change movement behavior at both the hip and knee. Furthermore, the study findings may support the implementation of the PEP Program, or a similar program, for clinicians aiming to improve use of the hip in an effort to reduce knee loading and consequent injuries.

Impaired voluntary quadriceps force control following anterior cruciate ligament reconstruction: relationship with knee function

PURPOSE

Impairments in quadriceps force control and altered quadriceps and hamstring muscle activation strategies have been observed following anterior cruciate ligament reconstruction; however, the functional implications of these impairments are unclear. This study examined the cross-sectional associations between quadriceps force control, quadriceps activation, hamstring coactivation and clinically assessed knee function following anterior cruciate ligament reconstruction with a hamstring graft.

METHODS

Sixty-six patients (18 ± 3 months following surgery) and 41 uninjured individuals participated. Quadriceps force control was assessed using an isometric knee extension task. Participants cyclically increased and decreased quadriceps force at slow speeds between 5 and 30 % maximum voluntary isometric contraction matching a moving target displayed on a screen. Quadriceps activation and hamstring coactivation were assessed concurrently using surface electromyography. Knee function was assessed with the Cincinnati Knee Rating Scale and three single-leg hop tests.

RESULTS

The reconstructed group completed the task with 48 % greater root-mean-square error (RMSE), indicating significantly worse quadriceps force control (p < 0.001). In a multivariable model adjusted for sex, greater RMSE and greater lateral hamstring coactivation were significantly associated with worse knee function that is greater odds of scoring <85 % on one or more knee functional assessment.

CONCLUSIONS

Less-accurate quadriceps force output and greater hamstring coactivation are associated with worse knee joint function following anterior cruciate ligament reconstruction and may contribute to irregular knee joint loading and the onset or progression of knee osteoarthritis. Impairments in quadriceps force control and altered muscle activation strategies may be modifiable through neuromuscular training, and this is an area for future research.

LEVEL OF EVIDENCE

Case-control study, Level III.

Exploring the High Reinjury Rate in Younger Patients Undergoing Anterior Cruciate Ligament Reconstruction

BACKGROUND

Younger age is being increasingly recognized as a risk factor for anterior cruciate ligament (ACL) graft rupture and contralateral ACL injury after ACL reconstruction. Recent reports estimate second ACL injury rates to be in the range of 20% to 40%, which is a significant concern and requires further exploration.

PURPOSE

The primary purpose was to determine the rates of graft rupture and injury to the contralateral native ACL in younger athletes. We also sought to explore the influence of sex and age groupings (<18 years vs 18-19 years at the time of surgery) on the risk of subsequent ACL injury.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The study cohort consisted of 354 consecutive patients who were younger than 20 years when they underwent their first primary hamstring tendon autograft ACL reconstruction. The number of subsequent ACL injuries (graft rupture or a contralateral injury to the native ACL) was determined at a mean follow-up of 5 years (range, 3-10 years). Subgroup analysis included sex and age (<18 years vs 18-19 years at the time of surgery) comparisons. Descriptive statistics were calculated for the timing of ACL graft rupture and contralateral ACL injury.

RESULTS

The overall follow-up rate was 89% (316/354). Graft ruptures occurred in 57 patients (18%) at an average time of 1.8 years after surgery. Almost half (47%) occurred within the first postoperative year, and 74% occurred within the first 2 years. The highest graft rupture rate of 28.3% was in the youngest males (<18 years), and this was significantly higher than in females of the same age (12.9%), as well as in male patients older than 18 years (13.8%). Contralateral ACL injuries occurred in 56 patients (17.7%) at an average time of 3.7 years after surgery. There were no significant age- or sex-based differences for contralateral ACL injuries. The total number of patients who had at least 1 further ACL injury subsequent to the primary surgery was 110 (35%).

CONCLUSION

The high rate of subsequent ACL injury in younger patients was confirmed. Early graft ruptures were more prevalent in patients who underwent surgery when they were younger than 18 years versus those in the 18- to 19-year age group. Males had higher rates of graft rupture than did females, with the youngest males (<18 years) at the highest risk in the investigated cohort.

Evaluation of RSA set-up from a clinical biplane fluoroscopy system for 3D joint kinematic analysis

PURPOSE

dinamic roentgen stereophotogrammetric analysis (RSA), a technique currently based only on customized radiographic equipment, has been shown to be a very accurate method for detecting three-dimensional (3D) joint motion. The aim of the present work was to evaluate the applicability of an innovative RSA set-up for in vivo knee kinematic analysis, using a biplane fluoroscopic image system. To this end, the Authors describe the set-up as well as a possible protocol for clinical knee joint evaluation. The accuracy of the kinematic measurements is assessed.

METHODS

the Authors evaluated the accuracy of 3D kinematic analysis of the knee in a new RSA set-up, based on a commercial biplane fluoroscopy system integrated into the clinical environment. The study was organized in three main phases: an in vitro test under static conditions, an in vitro test under dynamic conditions reproducing a flexion-extension range of motion (ROM), and an in vivo analysis of the flexion-extension ROM. For each test, the following were calculated, as an indication of the tracking accuracy: mean, minimum, maximum values and standard deviation of the error of rigid body fitting.

RESULTS

in terms of rigid body fitting, in vivo test errors were found to be 0.10±0.05 mm. Phantom tests in static and kinematic conditions showed precision levels, for translations and rotations, of below 0.1 mm/0.2° and below 0.5 mm/0.3° respectively for all directions.

CONCLUSIONS

the results of this study suggest that kinematic RSA can be successfully performed using a standard clinical biplane fluoroscopy system for the acquisition of slow movements of the lower limb.

CLINICAL RELEVANCE

a kinematic RSA set-up using a clinical biplane fluoroscopy system is potentially applicable and provides a useful method for obtaining better characterization of joint biomechanics.

Anterior cruciate ligament (ACL) loading in a collegiate athlete during sidestep cutting after ACL reconstruction: A case study

BACKGROUND

Athletes with anterior cruciate ligament (ACL) injuries usually undergo ACL-reconstruction (ACLR) in order to restore joint stability, so that dynamic maneuvers such as the sidestep cut can be performed. Despite restoration of joint stability after ACLR, many athletes do not return to pre-injury levels and may be at a high risk of a second ACL injury. The purpose of this study was to determine whether or not ACL loading, would increase after ACLR.

METHODS

One female Division I collegiate athlete performed bilateral unanticipated sidestep cuts both before ACL injury and 27months after ACLR. Musculoskeletal simulations were used to calculate ACL loading during the deceleration phase of the sidestep cuts.

RESULTS

Twenty-seven months after ACLR, the athlete demonstrated higher total ACL loading in the ipsilateral limb as well as altered joint kinematics, moments, and quadriceps muscle force production. In the contralateral limb, there were no increases in total ACL loading or muscle force production yet altered lower extremity joint kinematics and moments were present after ACLR.

CONCLUSIONS

Higher total ACL loading in the ipsilateral limb of this athlete may suggest an increased risk of second ACL injury. The results of this study provide an initial step in understanding the effects of ACLR on the risk of second ACL injury in an elite athlete and suggest that it is important to develop a better understanding of this surgical intervention on knee joint loading, in order to reduce the risk of second ACL injury while performing dynamic maneuvers.

Mapping current research trends on anterior cruciate ligament injury risk against the existing evidence: In vivo biomechanical risk factors

BACKGROUND

Whilst many studies measure large numbers of biomechanical parameters and associate these to anterior cruciate ligament injury risk, they cannot be considered as anterior cruciate ligament injury risk factors without evidence from prospective studies. A review was conducted to systematically assess the in vivo biomechanical literature to identify biomechanical risk factors for non-contact anterior cruciate ligament injury during dynamic sports tasks; and to critically evaluate the research trends from retrospective and associative studies investigating non-contact anterior cruciate ligament injury risk.

METHODS

An electronic literature search was undertaken on studies examining in vivo biomechanical risk factors associated with non-contact anterior cruciate ligament injury. The relevant studies were assessed by classification; level 1 - a prospective cohort study, level 2 - a retrospective study or level 3 - an associative study.

FINDINGS

An initial search revealed 812 studies but this was reduced to 1 level 1 evidence study, 20 level 2 evidence studies and 175 level 3 evidence studies that met all inclusion criteria. Level 1 evidence showed that the knee abduction angle, knee abduction moment and ground reaction force were biomechanical risk factors. Nine level 2 studies and eighty-three level 3 studies used these to assess risk factors in their study. Inconsistencies in results and methods were observed in level 2 and 3 studies.

INTERPRETATION

There is a lack of high quality, prospective level 1 evidence related to biomechanical risk factors for non-contact anterior cruciate ligament injury. More prospective cohort studies are required to determine risk factors and provide improved prognostic capability.

Motion Task Selection for Kinematic Evaluation After Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To examine the different motion tasks and the protocols used to objectively quantify dynamic stability in terms of knee kinematics at different stages of anterior cruciate ligament reconstruction (ACLR) recovery.

METHODS

A systematic search was done using OVID in Embase, Cochrane Central Register of Controlled Trials, Medline, PsychINFO, and AMED. A combination of the following keywords and their variations were used: anterior cruciate ligament, motion tasks (e.g., jump, hop, gait), and stability. The inclusion criteria were as follows: (1) ACLR subjects were recruited, (2) at least 1 motion task was performed and kinematics data were recorded, and (3) uninjured subjects or the contralateral uninjured limbs were included as a control group. Exclusion criteria were as follows: (1) non-English language publications, (2) retrospective studies and review articles, (3) animal studies, and (4) cadaveric studies.

RESULTS

The search returned 2,195 studies, and 56 were included in this review according to the criteria. A total of 1,086 ACLR subjects were included. Pivoting, landing, walking, running, stair negotiation, and squats were assessed using optoelectronic motion capture, electrogoniometry, or video-radiography.

CONCLUSIONS

The appropriate selection of motion tasks is an integral factor in dynamic stability testing as it evokes different kinematic outcomes in relation to the different stages of ACLR recovery. Stair negotiation and landing tasks are best performed during the early stages of recovery, and landing and pivoting are recommended 6 months after ACLR surgery.

LEVEL OF EVIDENCE

Level II, systematic review of Level I and II studies.

Validation of XMALab software for marker-based XROMM

Marker-based XROMM requires software tools for: 1) correcting fluoroscope distortion; 2) calibrating X-ray cameras; 3) tracking radio-opaque markers; and 4) calculating rigid body motion. In this paper we describe and validate XMALab, a new open-source software package for marker-based XROMM (C++ source and compiled versions on Bitbucket). Most marker-based XROMM studies to date have used XrayProject in MATLAB. XrayProject can produce results with excellent accuracy and precision, but it is somewhat cumbersome to use and requires a MATLAB license. We have designed XMALab to accelerate the XROMM process and to make it more accessible to new users. Features include the four XROMM steps (listed above) in one cohesive user interface, real-time plot windows for detecting errors, and integration with an online data management system, XMAPortal. Accuracy and precision of XMALab when tracking markers in a machined object are ±0.010 and ±0.043 mm, respectively. Mean precision for nine users tracking markers in a tutorial dataset of minipig feeding was ±0.062 mm in XMALab and ±0.14 mm in XrayProject. Reproducibility of 3D point locations across nine users was tenfold greater in XMALab than in XrayProject, and six degree-of-freedom bone motions calculated with a joint coordinate system were three- to sixfold more reproducible in XMALab. XMALab is also suitable for tracking white or black markers in standard light videos with optional checkerboard calibration. We expect XMALab to increase both the quality and quantity of animal motion data available for comparative biomechanics research.

Validation of a method for combining biplanar radiography and magnetic resonance imaging to estimate knee cartilage contact

Combining accurate bone kinematics data from biplane radiography with cartilage models from magnetic resonance imaging, it is possible to estimate tibiofemoral cartilage contact area and centroid location. Proper validation of such estimates, however, has not been performed under loading conditions approximating functional tasks, such as gait, squatting, and stair descent. The goal of this study was to perform an in vitro validation to resolve the accuracy of cartilage contact estimations in comparison to a laser scanning gold standard. Results demonstrated acceptable reliability and accuracy for both contact area and centroid location estimates. Root mean square errors in contact area averaged 8.4% and 4.4% of the medial and lateral compartmental areas, respectively. Modified Sorensen-Dice agreement scores of contact regions averaged 0.81 ± 0.07 for medial and 0.83 ± 0.07 for lateral compartments. These validated methods have applications for in vivo assessment of a variety of patient populations and physical activities, and may lead to greater understanding of the relationships between knee cartilage function, effects of joint injury and treatment, and the development of osteoarthritis.

A Reconfigurable High-Speed Stereo-Radiography System for Sub-Millimeter Measurement of In Vivo Joint Kinematics

Relative motions within normal and pathological joints of the human body can occur on the sub-millimeter and sub-degree scale. Dynamic radiography can be used to create a rapid sequence of images from which measurements of bone motion can be extracted, but available systems have limited speed and accuracy, limit normal subject movement, and do not easily integrate into existing traditional motion capture laboratories. A high-speed stereo radiography (HSSR) system is described that addresses these limitations. The custom radiography system was placed on a standalone reconfigurable gantry structure designed to allow freedom of subject movement while integrating into an existing motion capture laboratory. Validation of the system and measurement of knee kinematics of subjects during gait confirmed the ability to record joint motion with high accuracy and high-speed.

What is normal? Female lower limb kinematic profiles during athletic tasks used to examine anterior cruciate ligament injury risk: a systematic review

BACKGROUND

It has been proposed that the performance of athletic tasks where normal motion is exceeded has the potential to damage the anterior cruciate ligament (ACL). Determining the expected or 'normal' kinematic profile of athletic tasks commonly used to assess ACL injury risk can provide an evidence base for the identification of abnormal or anomalous task performances in a laboratory setting.

OBJECTIVE

The objective was to conduct a systematic review of studies examining lower limb kinematics of females during drop landing, drop vertical jump, and side-step cutting tasks, to determine 'normal' ranges for hip and knee joint kinematic variables.

DATA SOURCES

An electronic database search was conducted on the SPORTDiscus(TM), MEDLINE, AMED and CINAHL (January 1980-August 2013) databases using a combination of relevant keywords.

STUDY SELECTION

Studies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined three-dimensional hip and knee kinematics of female subjects during the athletic tasks of interest were included for review. Articles were excluded if subjects had a history of lower back or lower limb joint injury or isolated data from the female cohort could not be extracted.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently assessed the quality of included studies. Data on subject characteristics, the athletic task performed, and kinematic data were extracted from included studies. Studies were categorised according to the athletic task being examined and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate the weighted means and standard deviations for hip and knee kinematics (initial contact and peak values). 'Normal' motion was classified as the weighted mean plus/minus one standard deviation.

RESULTS

Of 2,920 citations, a total of 159 articles were identified as potentially relevant, with 29 meeting all inclusion/exclusion criteria. Due to the limited number of studies available examining double-leg drop landings and single-leg drop vertical jumps, insufficient data was available to include these tasks in the review. Therefore, a total of 25 articles were included. From the included studies, 'normal' ranges were calculated for the kinematic variables of interest across the athletic tasks examined.

LIMITATIONS

Joint forces and other additional elements play a role in ACL injuries, therefore, focusing solely on lower limb kinematics in classifying injury risk may not encapsulate all relevant factors. Insufficient data resulted in no normal ranges being calculated for double-leg drop land and single-leg drop vertical jump tasks. No included study examined hip internal/external rotation during single-leg drop landings, therefore ranges for this kinematic variable could not be determined. Variation in data between studies resulted in wide normal ranges being observed across certain kinematic variables.

CONCLUSIONS

The ranges calculated in this review provide evidence-based values that can be used to identify abnormal or anomalous athletic task performances on a multi-planar scale. This may be useful in identifying neuromuscular factors or specific muscular recruitment strategies that contribute to ACL injury risk.

Altered tibiofemoral kinematics in the affected knee and compensatory changes in the contralateral knee after anterior cruciate ligament reconstruction

BACKGROUND

Previous studies of knee kinematics after anterior cruciate ligament (ACL) reconstruction have generally employed low-effort tasks and typically not assessed changes in kinematics over time.

HYPOTHESES

(1) During single-legged hop landing, ACL-reconstructed limbs will have altered kinematics compared with contralateral (ACL-intact) limbs 5 months after surgery. (2) Kinematic differences between limbs will decrease over time because of changes in both ACL-reconstructed and ACL-intact limbs.

STUDY DESIGN

Controlled laboratory study.

METHODS

In vivo kinematics of ACL-reconstructed and contralateral ACL-intact knees were evaluated for 14 subjects during single-legged forward-hop landings at 5 and 12 months after surgery on the basis of dynamic stereo x-ray imaging. Differences between limbs and changes over time were assessed via repeated-measures analysis of variance.

RESULTS

Five months after surgery, ACL-reconstructed knees landed significantly less flexed compared with contralateral ACL-intact knees (20.9° vs 28.4°, respectively; P < .05). The ACL-reconstructed knees were significantly more externally rotated (12.2° vs 6.5°; P < .05) and medially translated (3.8 vs 2.3 mm; P < .009) compared with ACL-intact knees. Anterior-posterior translation was similar between limbs. From 5 to 12 months, knee flexion at landing increased in ACL-reconstructed knees (mean change, +3.4°; P < .05) and decreased in contralateral knees (mean change, -3.3°; P < .05). External tibial rotation also significantly decreased in ACL-reconstructed knees (-2.2°; P < .05) and increased in contralateral knees (+1.1°; P = .117) over time. Medial tibial translation decreased slightly over time only in ACL-reconstructed knees (-0.3 mm).

CONCLUSION

Five months after ACL reconstruction, landing kinematics differed between ACL-reconstructed and contralateral ACL-intact knees during a dynamic high-loading activity. These differences decreased over time, owing to changes in both the ACL-reconstructed and contralateral ACL-intact limbs.

CLINICAL RELEVANCE

This study identified kinematic changes over time in both the ACL-injured and contralateral ACL-intact knees after ACL reconstruction. These kinematic adaptations could have important implications for postoperative care, including evaluating the optimal timing of return to sports and the development of bilateral neuromuscular rehabilitation programs that may improve patient outcomes and reduce reinjuries in both the short and long terms.

Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction

BACKGROUND

Graft rupture of the same knee or injury to the anterior cruciate ligament (ACL) in the contralateral knee is a devastating outcome after ACL reconstruction surgery. While a number of factors have been identified as potentially increasing the risk of subsequent ACL injury, the literature is far from definitive.

PURPOSE

To determine the rates of graft rupture and contralateral ACL injury in a large cohort and to investigate patient characteristics that may be associated with these.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A consecutive cohort of 750 patients who had undergone primary ACL reconstruction surgery with a minimum 3-year follow-up were questioned about the incidence of ACL graft rupture, contralateral ACL injury, family history of ACL injury, and current activity level. Patient databases provided details for age, sex, original injury mechanism, meniscus or articular surface injury, and graft diameter.

RESULTS

Responses were received from 561 patients (75%) at a mean ± SD follow-up time of 4.8 ± 1.1 years. Anterior cruciate ligament graft ruptures occurred in 25 patients (4.5%), and contralateral ACL injuries occurred in 42 patients (7.5%). The highest incidence of further ACL injury occurred in patients younger than 20 years at the time of surgery. In this group, 29% sustained a subsequent ACL injury to either knee. The odds for sustaining an ACL graft rupture or contralateral injury increased 6- and 3-fold, respectively, for patients younger than 20 years. Returning to cutting/pivoting sports increased the odds of graft rupture by a factor of 3.9 and contralateral rupture by a factor of 5. A positive family history doubled the odds for both graft rupture and contralateral ACL injury.

CONCLUSION

Patients younger than 20 years who undergo ACL reconstruction are at significantly increased risk for both graft rupture and contralateral ACL injury. Whether age per se is a risk factor or age represents a proxy for other factors remains to be determined.

Effects of ACL reconstruction surgery on muscle activity of the lower limb during a jump-cut maneuver in males and females

We compared muscle activity of the quadriceps, hamstring, and gastrocnemius muscles when ACL-intact (ACL(INT)) and ACL-reconstructed (ACL(REC)) male and female subjects performed a jump-cut task. Surface electromyography sensors were used to evaluate time to peak muscle activity and muscle activity ratios. Rectus femoris (RF) and vastus medialis (VM) peak timing was 71 and 78 ms earlier in ACL(INT) than in ACL(REC) subjects, respectively. Biceps femoris (BF) peak timing was 90 ms earlier in ACL(INT) than in ACL(REC) subjects and 75 ms earlier in females than in males. Medial gastrocnemius (MG) muscle peak timing was 77 ms earlier in ACL(INT) than in ACL(REC) subjects. Lateral gastrocnemius (LG) and MG muscle peak times were 106 ms and 87 ms earlier in females than in males, respectively. The RF, VM, BF, and MG peaked later in ACL(REC) than in ACL(INT) subjects. There was evidence suggesting that the loading phase quadriceps:hamstring (quad:ham) muscle activity ratio was greater in ACL(REC) than in ACL(INT) subjects. Finally, the injury risk phase quad:ham muscle activity ratio was 4.8 times greater in females than in males. In conclusion, differences exist in muscle activity related to ACL status and sex that could potentially help explain graft failure risk and the sex bias.