Increase Joint Stability Research Articles

Effect of laser power during laser powder bed fusion on microstructure of joining interface between Tungsten and AISI 316L steel

This study investigates the deposition of tungsten (W) onto a 316L steel substrate by laser powder bed fusion (L-PBF), to optimize process parameters and analyze the interface between W and 316L. To obtain high-density W structure (98.89%), the optimal laser power was 350 W, and scan speed was 500 mm/s, but these parameters cause significant dilution of W in the W-316L interface; as a result, Fe7W6 intermetallics form, despite L-PBF being a non-equilibrium solidification process. These intermetallics which are brittle could degrade joint strength. By reducing laser power below 250 W, the dilution of W can be mitigated, and potentially minimize formation of intermetallics and increase joint stability for advanced manufacturing applications.

Arthroscopic anterior deltoid plication with bone anchor is an effective procedure to control residual talar anterior translation after lateral ligament repair.

Residual symptoms can be observed after ankle lateral ligament repairs commonly due to hyperlaxity, severe ankle instability or a failed stabilization. In order to increase joint stability, ligament or capsular-ligament plication has been used in other joints. Given that the anterior portion of the deltoid is a stabilizer against anterior talar translation, it could be used as an augmentation to restrict anterior talar translation. The aim of this study was to describe an arthroscopic anterior deltoid plication with a bony anchor as an augmentation to the lateral stabilization. The results in a series of eight patients were presented. Eight patients (seven males, median age 31 [range, 22-43] years) presented residual instability after arthroscopic all inside lateral collateral ligament repair. Arthroscopic anterior deltoid ligament plication was performed in these patients. Median follow-up was 22 (range, 15-27) months. Using an automatic suture passer and a knotless anchor, the anterior deltoid was arthroscopically plicated to the anterior aspect of the medial malleolus. During the arthroscopic procedure, only an isolated detachment of the anterior talofibular ligament was observed without any deltoid open-book injury in any case. All patients reported subjective improvement in their ankle instability after the arthroscopic all-inside ligament repair and the anterior deltoid plication with a bony anchor. On clinical examination, the anterior drawer test was negative in all patients. The median American Orthopedic Foot and Ankle Society score increased from 68 (range, 64-70) preoperatively to 100 (range, 90-100) at final follow-up. The arthroscopic anterior deltoid plication is a feasible procedure to augment stability and control anterior talar translation when treating chronic ankle instability in cases of residual excessive talar translation. Level IV.

High-Demand Spinal Deformity With Multi-Rod Constructs and Porous Fusion/Fixation Implants: A Finite Element Study.

Basic science (finite element analysis). Pedicle subtraction osteotomy (PSO) at L5 is an effective treatment for sagittal imbalance, especially in select cases of patients showing kyphosis with the apex at L4-L5 but has been scarcely investigated. The aim of this study was to simulate various "high-demand" instrumentation approaches, including varying numbers of rods and sacropelvic implants, for the stabilization of a PSO at L5. A finite element model of T10-pelvis was modified to simulate posterior fixation with pedicle screws and rods from T10 to S1, alone or in combination with an L5 PSO. Five additional configurations were then created by employing rods and novel porous fusion/fixation implants across the sacroiliac joints, in varying numbers. All models were loaded using pure moments of 7.5Nm in flexion-extension, lateral bending, and axial rotation. The osteotomy resulted in a general increase in motion and stresses in posterior rods and S1 pedicle screws. When the number of rods was varied, three- and four-rod configurations were effective in limiting the maximal rod stresses; values approached those of posterior fixation with no osteotomy. Maximum stresses in the accessory rods were similar to or less than those observed in the primary rods. Multiple sacropelvic implants were effective in reducing range of motion, particularly of the SIJ. Multi-rod constructs and sacropelvic fixation generally reduced maximal implant stresses and motion in comparison with standard posterior fixation, suggesting a reduced risk of rod breakage and increased joint stability, respectively, when a high-demand construct is utilized for the correction of sagittal imbalance.

Exploration of the minimum necessary FVIII level at different physical activity levels in pediatric patients with hemophilia A.

Physical activity can increase joint stability and reduce the risk of injury in hemophilia patients. There is limited clinical data on target trough FVIII levels during physical activity in hemophilia A patients. Hence, this study aimed to explore the target trough FVIII level required to avoid bleeding during different physical activities in hemophilia A patients. Patients with severe or moderate hemophilia A, who underwent pharmacokinetics (PK) tests at our center were enrolled in this study. Physical activities and clinical information such as bleeding were recorded. The FVIII level during physical activity was calculated by the WAPPS-Hemo. A total of 105 patients were enrolled in this study. A total of 373 physical activities were recorded, of which 57.6% (215/373) was low-risk activities and the remaining 42.4% (158/373) was medium-risk activities. Most common physical activities were bicycling (59.0%), swimming (43.8%), running (48.6%), and jumping rope (41.0%). The FVIII trough level of low-risk physical activity was 3.8 IU/dl (AUC = 0.781, p = 0.002) and moderate-risk physical activity was 7.7 IU/dl (AUC = 0.809, p < 0.001). FVIII trough levels [low-risk activities: 6.1 (3.1, 13.2) IU/dl vs. 7.7 (2.3, 10.5) IU/dl, moderate-risk activities: 9.6 (5.8, 16.9) IU/dl vs. 10.2 (5.5, 11.0) IU/dl] were not statistically different between the mild arthropathy group and the moderate-severe arthropathy group. Multiple bleeding risk tended to increase with physical activities classified as moderate-risk (OR [95% CI]: 3.815 [1.766-8.238], p = 0.001). The minimum necessary FVIII level increased with higher risk physical activity, irrespective of arthropathy.

MUSCULOSKELETAL SYMPTOMS IN PATIENTS WITH POST COVID-19 SYNDROME AND OPPORTUNITIES FOR INCREASED FUNCTIONAL ACTIVITY

There is an increasing number of patients surviving SARS-CoV-2 infection who have no evidence of acute infection but who continue to have symptoms that persist and shape the post COVID-19 symptoms (PCS). Musculoskeletal symptoms (MSK), as part of the PCS, lead to reduced functional activity and cause prolonged suffering. The purpose of this review is to identify the main MSK symptoms in PCS and to review physical interventions that may have a beneficial effect in reducing MSK complaints and increasing functional activity in PCS. Materials and methods: A review of the literature was performed, including articles about MSK symptoms in patients with PCS and the possible physical interventions used in rehabilitation of these patients, with impact on symptoms, functional capacity, and functional activity. The scientific articles research took place in the bibliographic database of PubMed. The search results were found for: post-COVID-19 (PCS) syndrome, long COVID, post-acute sequelae of SARS-CoV-2 infection (PASC), chronic COVID syndrome (CCS), Musculoskeletal symptom, Pain post-COVID, physical function, Rehabilitation post-COVID, exercise, physical activity, functional capacity, traditional Chinese medicine. Results: The review found evidence of prolonged persistence of MSK symptoms as part of PCS syndrome. Fatigue, myalgia, back, waist and neck pain and arthralgia (pain in the peripheral joints) are the most reported symptoms. Data showing the need for rehabilitation and the positive effect of physical therapy and therapeutic exercises in patients with PCS to reduce pain and increase functional activity was found. Conclusion: Increasing physical activity in patients with PCS is likely to have a beneficial effect on general conditioning, physical function, and functional recovery, helping to overcome the effects of infection, reducing pain, and reducing emotional stress. Individually targeted physical interventions are recommended, including multimodal programs, exercises for overall muscle strengthening, increasing joint stability, cycling training, Individually targeted physical interventions are recommended, including multimodal programs, exercises for overall muscle strengthening, increasing joint stability, cycling training, electrical modalities -Transcutaneous electrical nerve stimulation (TENS) for pain symptoms. Rehabilitation should be applied after detailed functional assessment and shaped be carried out with the participation of a multidisciplinary rehabilitation team. The development of appropriate rehabilitation strategies will allow the achievement of optimal functional recovery and increased functional activity, satisfactory to the patient and will reduce the economic burden of prolonged reduced work capacity.

Promoting physical activity in people with haemophilia: the MEMO (Movement for persons with haEMOphilia) expert consensus project.

Regular physical activity can increase joint stability and function, reduce the risk of injury, and improve quality of life of people with haemophilia (PwH). However, a recent review of the literature shows that appropriate physical activity and sport are not always promoted enough in the overall management of PwH. A group of Italian experts in haemophilia care undertook a consensus procedure to provide practical guidance on when and how to recommend physical exercise programmes to PwH in clinical practice. Three main topics were identified -haemophilia and its impact on movement, physical activity recommendations for PwH, and choice and management of sports activity in PwH- and ten statements were formulated. A modified Delphi approach was used to reach a consensus. The group also created practical tools proposing different physical activities and frequencies for different age groups, the Movement Pyramids, to be shared and discussed with patients and caregivers. In conclusion, in the opinion of the working group, physical activity can be considered as a low-price intervention that can prevent/reduce the occurrence of chronic diseases and should be further encouraged in PwH to obtain multiple physical and psychological benefits. Future research should include prospective studies focusing on participation in sports, specific risk exposure and clinical outcomes.

Muscle Synergies in People With Chronic Ankle Instability During Anticipated and Unanticipated Landing-Cutting Tasks.

Although neuromuscular deficits in people with chronic ankle instability (CAI) have been identified, previous researchers have mostly investigated the activation of multiple muscles in isolation. Investigating muscle synergies in people with CAI would provide information about the coordination and control of neuromuscular activation strategies and could supply important information for understanding and rehabilitating neuromuscular deficits in this population. To assess and compare muscle synergies using nonnegative matrix factorization in people with CAI and healthy control individuals as they performed different landing-cutting tasks. Cross-sectional study. Laboratory. A total of 11 people with CAI (5 men, 6 women; age = 22 ± 3 years, height = 1.68 ± 0.11 m, mass = 69.0 ± 19.1 kg) and 11 people without CAI serving as a healthy control group (5 men, 6 women; age = 23 ± 4 years, height = 1.74 ± 0.11 m, mass = 66.8 ± 15.5 kg) participated. Muscle synergies were extracted from electromyography of the lateral gastrocnemius, medial gastrocnemius, fibularis longus, soleus, and tibialis anterior (TA) muscles during anticipated and unanticipated landing-cutting tasks. The number of synergies, activation coefficients, and muscle-specific weighting coefficients were compared between groups and across tasks. The number of muscle synergies was the same for each group and task. The CAI group exhibited greater TA weighting coefficients in synergy 1 than the control group (P = .02). In addition, both groups demonstrated greater fibularis longus (P = .03) weighting coefficients in synergy 2 during the unanticipated landing-cutting task than the anticipated landing-cutting task. These results suggest that, although both groups used neuromuscular control strategies of similar complexity or dimensionality to perform the landing-cutting tasks, the CAI group displayed different muscle-specific weightings characterized by greater emphasis on TA function in synergy 1, which may reflect an effort to increase joint stability to compensate for ankle instability.

Promoting physical activity in people with haemophilia: the MEMO (Movement for persons with haEMOphilia) expert consensus project.

Regular physical activity can increase joint stability and function, reduce the risk of injury, and improve quality of life of people with haemophilia (PwH). However, a recent review of the literature shows that appropriate physical activity and sport are not always promoted enough in the overall management of PwH. A group of Italian experts in haemophilia care undertook a consensus procedure to provide practical guidance on when and how to recommend physical exercise programmes to PwH in clinical practice. Three main topics were identified-haemophilia and its impact on movement, physical activity recommendations for PwH, and choice and management of sports activity in PwH- and ten statements were formulated. A modified Delphi approach was used to reach a consensus. The group also created practical tools proposing different physical activities and frequencies for different age groups, the Movement Pyramids, to be shared and discussed with patients and caregivers. In conclusion, in the opinion of the working group, physical activity can be considered as a low-price intervention that can prevent/reduce the occurrence of chronic diseases and should be further encouraged in PwH to obtain multiple physical and psychological benefits. Future research should include prospective studies focusing on participation in sports, specific risk exposure and clinical outcomes.

Ultrasound evaluation shows increase in laxity after partial common extensor origin detachment but not after additional lesion of the radial band of the lateral collateral ligament

PurposeThe lateral elbow musculature conveys a dynamic valgus moment to the elbow, increasing joint stability. Muscular or tendinous lesions to the anterior half of the common extensor origin (CEO) may provoke a deficiency in the elbow dynamic stabilizers, regardless of their traumatic, degenerative, or iatrogenic aetiology. Furthermore, a role for the radial band of the lateral collateral ligament (R-LCL) has been postulated in the aetiology of lateral elbow pain. This study aimed to evaluate the effects of sequential lateral releases with dynamic ultrasound, evaluating its capability to detect lesions of the CEO and of the R-LCL.MethodsUltrasound investigation of the lateral compartment of the elbow was performed on nine cadaveric specimens with a 10 MHz linear probe in basal conditions, after the release of the anterior half of the CEO and after complete R-LCL release. The lateral joint line widening (λ) was the primary outcome parameter, measured as the linear distance between the humeral and radial articular surfaces.ResultsThe release of the anterior half of the CEO significantly increased λ by 200% compared to the starting position (p = 0.0008) and the previously loaded position (p = 0.0015). Conversely, further release of the R-LCL caused only a marginal, non-significant increase in λ.ConclusionsUltrasound evaluation can detect changes related to tendon tears or muscular avulsions of the CEO and can depict lateral elbow compartmental patholaxity by assessing articular space widening while scanning under dynamic stress. However, it cannot reliably define if the R-LCL is injured. Iatrogenic damage to the CEO should be carefully avoided, since it causes a massive increase in compartmental laxity.

Quantifying Muscle Forces and Joint Loading During Hip Exercises Performed With and Without an Elastic Resistance Band.

An increase in hip joint contact forces (HJCFs) is one of the main contributing mechanical causes of hip joint pathologies, such as hip osteoarthritis, and its progression. The strengthening of the surrounding muscles of the joint is a way to increase joint stability, which results in the reduction of HJCF. Most of the exercise recommendations are based on expert opinions instead of evidence-based facts. This study aimed to quantify muscle forces and joint loading during rehabilitative exercises using an elastic resistance band (ERB). Hip exercise movements of 16 healthy volunteers were recorded using a three-dimensional motion capture system and two force plates. All exercises were performed without and with an ERB and two execution velocities. Hip joint kinematics, kinetics, muscle forces, and HJCF were calculated based on the musculoskeletal simulations in OpenSim. Time-normalized waveforms of the different exercise modalities were compared with each other and with reference values found during walking. The results showed that training with an ERB increases both target muscle forces and HJCF. Furthermore, the ERB reduced the hip joint range of motion during the exercises. The type of ERB used (soft vs. stiff ERB) and the execution velocity of the exercise had a minor impact on the peak muscle forces and HJCF. The velocity of exercise execution, however, had an influence on the total required muscle force. Performing hip exercises without an ERB resulted in similar or lower peak HJCF and lower muscle forces than those found during walking. Adding an ERB during hip exercises increased the peak muscle and HJCF but the values remained below those found during walking. Our workflow and findings can be used in conjunction with future studies to support exercise design.

Effects of neuromuscular exercises on q-angle, knee joint stability and ankle mobility of handball athletes.

Background: The sport, when it comes to matters related to high performance, can lead the athlete to the development of risk factors for injuries. To minimize the effects of high load training, neuromuscular exercises may offer increased joint stability, thereby reducing risk factors, number of injuries, and minimizing the extent and severity of those that may arise. Objective: To evaluate the effects of neuromuscular exercises on Q-angle, knee joint stability and ankle mobility of high performance handball athletes. Methods: This is a controlled clinical trial conducted with 23 athletes (aged 18 to 37 years), randomly divided into intervention (n = 12) and control (n = 11) groups. Athletes were evaluated with clinical tests for knee joint instability. The risk factors evaluated were ankle range of motion (ROM) in the dorsal flexion movement (tibia over the tarsus) and the Q-angle, which are factors related to ankle sprains and anterior cruciate ligament injury, respectively. A protocol of three neuromuscular exercises for lower limb was applied three times a week, lasting approximately six minutes for 12 sessions. Results: All athletes presented Q-angle higher than expected and in the group that underwent neuromuscular exercises there was a significant reduction in right Q-angle (pre: 23.7 ± 2.9º; post: 20.2 ± 2.5º, p = 0.016) and left (pre: 22.5 ± 2.5º; post: 20.1 ± 1.8º, p = 0.021). The range of motion of both ankles did not increase significantly, but there was an average increase of 2.1º in the right ankle and 2.4º in the left of the athletes who participated in the intervention group. Clinical tests indicated improvement in joint stability. Conclusion: A significant reduction in the right and left Q-angle was observed, as well as reducing the frequency of excessive anterior tibial translocation, which may be positively reflected in the knee joint stability.

The effect of resistance exercise on strength and safety outcome for people with haemophilia: A systematic review.

IntroductionHaemophilia is a congenital bleeding disorder with severe musculoskeletal complications. Resistance exercise is important to increase joint stability and to improve physical performance.AimThis review aimed to investigate the safety and efficacy of resistance exercise interventions on people with haemophilia (PwH) and evaluate whether the American College of Sports Medicine resistance exercise criteria for healthy adults are valid for this population.MethodsA systematic search in literature was conducted, using the databases PubMed, MEDLiNE, CINAHL, SCOPUS, PEDro and Cochrane Library. Out of 2.440 studies published between 1960 and November 2019, 14 studies (9 randomized controlled trials, 1 controlled trial, 4 single‐group prospective studies) applying resistance exercise in juvenile and adult PwH corresponded to the inclusion criteria.ResultsStudies performed dynamic, isokinetic or a combination of isometric and dynamic resistance training. Most interventions were carried out in the context of a multimodal training. Resistance was provided using fixed and free weights, body weight, resistance bands and water resistance. Study protocols included clinical and home‐based settings. Several studies suggest that training intensities lower than those known to increase the strength of healthy people are effective in increasing the strength of PwH. Resistance exercise seems to be a safe intervention if it is adequately monitored, individually adapted and applied with sufficient factor therapy. Due to the heterogeneity of study designs, training interventions and outcome measures a meta‐analysis could not be performed.ConclusionsFurther studies of higher methodological quality are needed to determine the optimal types of exercise, optimal dosage and timing.

Predictors of Patient Function, Pain, and Satisfaction after Reimplantation for Infected Hip and Knee Arthroplasty

Background/Hypothesis: Prevalence of periprosthetic joint infection (PJI) is expected to rise as hip and knee arthroplasty procedures increase. This study purpose was to evaluate factors affecting patient-reported outcomes after resection and reimplantation procedures. &#x0D; Project Methods: 38 hips and 35 knees consecutively treated by a single surgeon were retrospectively reviewed. Prospectively collected preoperative and minimum one and two-year postoperative Knee Injury and Osteoarthritis Outcome Score/KOOS Jr., Hip Disability and Osteoarthritis Outcome Score/HOOS Jr., UCLA Activity Level, and satisfaction were compiled. Fifteen demographic variables and covariates of outcomes (sex, age, etc.) were accounted for in analysis. &#x0D; Results: 47% of hip and 71% of knee patients were chronically infected poor hosts (McPherson stage III-B/C). In hips, worse McPherson stage was associated with lower activity levels at latest follow-up (p=0.007). Activity was higher in hip patients with constrained liners compared to dual mobility implants at one (p=0.009) and two-year (p=0.001) follow-up. The same result was observed in knees with varus-valgus constrained liners vs. hinged implants (p=0.005, p=0.029). However, varus-valgus constrained articulations were associated with more stair pain at one (p=0.003) and two (p=0.012) years. 83% of hip and knee patients were satisfied or very satisfied with their outcome at latest follow-up. &#x0D; Conclusion/Potential Impact: Positive outcomes observed following reimplantation procedures will help establish patient expectations. It appears the increased joint stability imparted by hinged TKA and constrained liners in THA may offer advantage in stair pain and clinical function, respectively, in reimplantation arthroplasty after PJI.

Neuromuscular efficiency of the multifidus muscle in pilates practitioners and non-practitioners

BackgroundPilates exercises help stabilize the vertebral segments by recruiting the abdominal and spinal muscles. Pilates training may increase joint stability and improve neuromuscular efficiency (NME). ObjectiveThis study aimed to evaluate NME of the multifidus (MU) muscle through electromyography (EMG) analysis and torque test, applied to practitioners and non-practitioners of Pilates. MethodsParticipants included thirty women: Pilates practitioners (n = 15) and non-practitioners (n = 15). They were tested for trunk extension. Their right and left MU muscles were submitted to EMG to estimate NME. Results concerning torque, EMG, and NME from all participants were compared. ResultsStatistical analysis concerning isometric torque peak (p = 0.0275) and NME (p = 0.0062) showed significant difference (Student t test; p < 0.05) between practitioners and control. No significant difference (p = 0.3387) in EMG was observed. ConclusionOur results suggest Pilates exercises is effective in training spinal muscles to improve NME in women.

Preservation of the articular capsule and short lateral rotator in direct anterior approach to total hip arthroplasty

IntroductionIn total hip arthroplasty via a direct anterior approach, the femur must be elevated at the time of femoral implant placement. For adequate elevation, division of the posterior soft tissues is necessary. However, if we damage and separate the posterior muscle tissue, we lose the benefits of the intermuscular approach. Furthermore, damage to the posterior soft tissue can result in posterior dislocation. We investigate that protecting the posterior soft tissue increases the joint stability in the early postoperative period and results in a lower dislocation rate.MethodsWe evaluated muscle strength recovery by measuring the maximum width of the internal obturator muscle on CT images (GE-Healthcare Discovery CT 750HD). We compared the maximum width of the muscle belly preoperatively versus 10 days and 6 months postoperatively. As clinical evaluations, we also investigated the range of motion of the hip joint, hip joint function based on the Japanese Orthopaedic Association hip score (JOA score), and the dislocation rate 6 months after surgery.ResultsThe width of the internal obturator muscle increased significantly from 15.1 ± 3.1 mm before surgery to 16.4 ± 2.8 mm 6 months after surgery. The JOA score improved significantly from 50.8 ± 15.1 points to 95.6 ± 7.6 points. No dislocations occurred in this study.ConclusionsWe cut only the posterosuperior articular capsule and protected the internal obturator muscle to preserve muscle strength. We repaired the entire posterosuperior and anterior articular capsule. These treatments increase joint stability in the early postoperative period, thus reducing the dislocation rate.Level of evidenceTherapeutic, Level IV.

Computational evaluation of TKR stability using feedback-controlled compressive loading.

Pre-clinical assessment of stability in total knee replacement is crucial for developing preferred implant performance. Current total knee replacement patients often experience joint instability that the human body addresses with compensatory strategies. Specifically, an increased quadriceps-hamstrings co-contraction serves to increase joint stability through an increased compressive force across the tibiofemoral joint. The aim of this study is to introduce a novel method to evaluate total knee replacement by determining the compressive loading required to achieve natural knee stability. Four current total knee replacement geometries in both their cruciate-retaining and posterior-stabilized forms are modeled in a finite-element framework. The finite-element model is initially validated experimentally using traditional knee laxity testing with a constant compressive load and anterior-posterior displacement or internal-external rotation. Model predictions of constraint are in reasonable agreement with experimental results (average root mean square errors: 0.46 Nm, 62.5 N). The finite-element model is subsequently interfaced with a feedback controller to vary the compressive force that the implant requires in order to match experimental natural knee internal-external and anterior-posterior stability at different flexion angles. Results show that the lower constraint total knee replacement designs require on average 66.7% more compressive load than the higher constraint designs to achieve natural knee constraint. As expected, total knee replacement stability and compressive load requirements to replicate natural kinematics vary with inclusion of tibiofemoral ligaments. The current study represents a novel approach to evaluate stability in existing total knee replacement geometries and to design implants that better restore natural knee mechanics. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1901-1909, 2018.

Biomechanical evaluation of two extracapsular techniques for cranial cruciate ligament reconstruction in cadaver dogs

Cranial cruciate ligament rupture (CCLR) is one of the most important orthopedic conditions in dogs, leading to joint instability, pain, osteoarthritis and eventually to meniscal injuries. Several surgical techniques have been described to reestablish joint stability following CCLR, including extracapsular procedures. This study compared the biomechanical effects of two extracapsular stabilization techniques (lateral fabello-tibial suture – LFTS, and modified retinacular imbrication technique – MRIT) using nylon leader line following experimental CCLR in cadaver dogs. Twenty canine cadaveric stifles were used. Joint stiffness, cranial and caudal tibial displacement were evaluated in 4 different experimental scenarios: intact stifle, stifle with CCLR, CCLR treated with lateral fabello-tibial suture (LFTS), and CCLR treated with modified retinacular imbrication technique (MRIT). Results: Mean cranial tibial displacement increased progressively from intact to MRIT, LFTS and CCRL stifles. MRIT resulted in less caudal drawer motion than LFTS. Joint stiffness did not differ significantly between LFTS and MRIT treated stifles. Conclusion: LFTS and MRIT increase joint stability but MRIT is more effective; however none of the techniques studied was able to restore original intact stifle stiffness. Clinical implications of the results presented remain to be determined but kinetic gait analysis studies are warranted to determine whether this biomechanical advantage translates into improved hind limb function in dogs.

Abdominal hollowing and bracing strategies increase joint stability in the trunk region during sudden support surface translation but not in the lower extremities.

Application of hollowing and bracing, abdominal activation strategies (AAS), has focused on improving trunk stability. This study aimed to clarify the AAS effect on body sway during support surface translation while standing. Twenty healthy subjects (10 male, 10 female; aged 25.45 ± 3.22 years) performed hollowing, bracing, and natural strategies while standing, and exerted to maintain their balance during forward and backward translation. Ultrasonography evaluations confirmed the appropriate application of the 3 strategies by measuring abdominal muscle thickness. Additionally, a motion analysis system was used to capture the whole body sway along the sagittal plane. During backward translation, angular displacements of the trunk were significantly different among the 3 strategies (upper thoracic: F = 13.758, p < 0.001; lower thoracic: F = 8.477, p = 0.001; and lumbopelvis: F = 8.651, p = 0.001). AAS significantly decreased the sway by 25-36% in all inter-spinal segments compared with the natural strategy (p < 0.05). During forward translation, only angular displacement of the lower thoracic was significantly different among the 3 strategies (F = 7.640, p = 0.002), and bracing decreased the sway by 33.48% compared with the natural strategy (p = 0.003). No significant differences were seen between hollowing and bracing during forward and backward translation. AAS increased joint stability only in the trunk where joints are adjacent to abdominal muscles, but not in the lower extremities. The low impact of AAS on the lower extremities might have important implications on the paradigm of standing balance.

Neural Control Adaptation to Motor Noise Manipulation.

Antagonistic muscular co-activation can compensate for movement variability induced by motor noise at the expense of increased energetic costs. Greater antagonistic co-activation is commonly observed in older adults, which could be an adaptation to increased motor noise. The present study tested this hypothesis by manipulating motor noise in 12 young subjects while they practiced a goal-directed task using a myoelectric virtual arm, which was controlled by their biceps and triceps muscle activity. Motor noise was increased by increasing the coefficient of variation (CV) of the myoelectric signals. As hypothesized, subjects adapted by increasing antagonistic co-activation, and this was associated with reduced noise-induced performance decrements. A second hypothesis was that a virtual decrease in motor noise, achieved by smoothing the myoelectric signals, would have the opposite effect: co-activation would decrease and motor performance would improve. However, the results showed that a decrease in noise made performance worse instead of better, with no change in co-activation. Overall, these findings suggest that the nervous system adapts to virtual increases in motor noise by increasing antagonistic co-activation, and this preserves motor performance. Reducing noise may have failed to benefit performance due to characteristics of the filtering process itself, e.g., delays are introduced and muscle activity bursts are attenuated. The observed adaptations to increased noise may explain in part why older adults and many patient populations have greater antagonistic co-activation, which could represent an adaptation to increased motor noise, along with a desire for increased joint stability.

Muscle activity amplitudes and co-contraction during stair ambulation following anterior cruciate ligament reconstruction

The purpose of this study was to compare muscle activity amplitudes and co-contraction in those with anterior cruciate ligament (ACL) reconstruction to healthy controls during stair negotiation. Eighteen participants with unilateral ACL reconstruction and 17 healthy controls performed stair ascent and descent while surface electromyography was recorded from knee and hip musculature. During stair ascent, the ACL group displayed higher gluteus maximus activity (1–50% stance, p=0.02), higher vastus lateralis:biceps femoris co-contraction (51–100% stance, p=0.01), and higher vastus lateralis:vastus medialis co-contraction (51–100% stance, p=0.05). During stair descent, the ACL group demonstrated higher gluteus maximus activity (1–50% stance, p=0.01; 51–100% stance, p<0.01), lower rectus femoris activity (1–50% stance, p=0.04), higher semimembranosus activity (1–50% stance, p=0.01), higher gluteus medius activity (51–100% stance, p=0.01), and higher vastus medialis:semimembranosus co-contraction (1–50% stance, p=0.02). While the altered muscle activity strategies observed in the ACL group may act to increase joint stability, these strategies may alter joint loading and contribute to post-traumatic knee osteoarthritis often observed in this population. Our results warrant further investigation to determine the longterm effects of altered muscle activity on the knee joint following ACL reconstruction.