Surgical Intervention Following a First Traumatic Anterior Shoulder Dislocation Is Worthy of Consideration.

Up to 60% of patients experience recurrence after a first traumatic anterior shoulder dislocation (FTASD), which is often defined as having experienced either dislocation or subluxation. Thus surgical intervention after FTASD is worthy of consideration and is guided by the number of patients who need to receive surgical intervention to prevent 1 redislocation (i.e., number needed to treat), (subjective) health benefit, complication risk, and costs. Operative intervention through arthroscopic stabilization can be successful in reducing recurrence risk in FTASD, as has been shown in multiple randomized controlled trials. Nevertheless, there is a large "gray area" for the indication of arthroscopic stabilization, and it is therefore heavily debated which patients should receive operative treatment. Previous trials showed widely varying redislocation rates in both the intervention and control group, meta-analysis shows 2% to 19% after operative and 20% to 75% after nonoperative treatment, and redislocation rates may not correlate with patient-reported outcomes. The literature is quite heterogeneous, and a major confounder is time to follow-up. Furthermore, there is insufficient standardization of reporting of outcomes and no consensus on definition of risk factors. As a result, surgery is a reasonable intervention for FTASD patients, but in which patients it best prevents redislocation requires additional refinement.

Classification of Wheelchair Related Shoulder Loading Activities from Wearable Sensor Data: A Machine Learning Approach.

Shoulder problems (pain and pathology) are highly prevalent in manual wheelchair users with spinal cord injury. These problems lead to limitations in activities of daily life (ADL), labor- and leisure participation, and increase the health care costs. Shoulder problems are often associated with the long-term reliance on the upper limbs, and the accompanying "shoulder load". To make an estimation of daily shoulder load, it is crucial to know which ADL are performed and how these are executed in the free-living environment (in terms of magnitude, frequency, and duration). The aim of this study was to develop and validate methodology for the classification of wheelchair related shoulder loading ADL (SL-ADL) from wearable sensor data. Ten able bodied participants equipped with five Shimmer sensors on a wheelchair and upper extremity performed eight relevant SL-ADL. Deep learning networks using bidirectional long short-term memory networks were trained on sensor data (acceleration, gyroscope signals and EMG), using video annotated activities as the target. Overall, the trained algorithm performed well, with an accuracy of 98% and specificity of 99%. When reducing the input for training the network to data from only one sensor, the overall performance decreased to around 80% for all performance measures. The use of only forearm sensor data led to a better performance than the use of the upper arm sensor data. It can be concluded that a generalizable algorithm could be trained by a deep learning network to classify wheelchair related SL-ADL from the wearable sensor data.

Increased enslaving in elderly is associated with changes in neural control of the extrinsic finger muscles.

Aging has consequences for hand motor control, among others affecting finger force enslaving during static pressing tasks. The aim of this study was to assess whether the extent of finger force enslaving changes with aging during a task that involves both static and dynamic phases. Ten right-handed young (22-30 years) and ten elderly subjects (67-79 years) were instructed to first exert a constant force (static phase) and then flex their index finger while counteracting constant resistance forces orthogonal to their fingertips (dynamic phase). The other fingers (non-instructed) were held in extension. EMG activities of the flexor digitorum superficialis (FDS) and extensor digitorum (ED) muscles in the regions corresponding to the index, middle and ring fingers together with their forces and position of index finger were measured. In both elderly and young, forces exerted by the non-instructed fingers increased (around 0.6 N for both young and elderly) during isotonic flexion of the index finger, but with a different delay of on average 100 ± 72 ms in elderly and 334 ± 101 ms in young subjects. Results also suggest different responses in activity of FDS and ED muscle regions of the non-instructed fingers to index finger flexion between elderly and young subjects. The enslaving effect was significantly higher in elderly than in young subjects both in the static (12% more) and dynamic (14% more) phases. These differences in enslaving can at least partly be explained by changes in neuromuscular control.

Are pushing and pulling work-related risk factors for upper extremity symptoms? A systematic review of observational studies.

Systematically review observational studies concerning the question whether workers that perform pushing/pulling activities have an increased risk for upper extremity symptoms as compared to workers that perform no pushing/pulling activities. A search in MEDLINE via PubMed and EMBASE was performed with work-related search terms combined with push/pushing/pull/pulling. Studies had to examine exposure to pushing/pulling in relation to upper extremity symptoms. Two authors performed the literature selection and assessment of the risk of bias in the studies independently. A best evidence synthesis was used to draw conclusions in terms of strong, moderate or conflicting/insufficient evidence. The search resulted in 4764 studies. Seven studies were included, with three of them of low risk of bias, in total including 8279 participants. A positive significant relationship with upper extremity symptoms was observed in all four prospective cohort studies with effect sizes varying between 1.5 and 4.9. Two out of the three remaining studies also reported a positive association with upper extremity symptoms. In addition, significant positive associations with neck/shoulder symptoms were found in two prospective cohort studies with effect sizes of 1.5 and 1.6, and with shoulder symptoms in one of two cross-sectional studies with an effect size of 2.1. There is strong evidence that pushing/pulling is related to upper extremity symptoms, specifically for shoulder symptoms. There is insufficient or conflicting evidence that pushing/pulling is related to (combinations of) upper arm, elbow, forearm, wrist or hand symptoms.

The effect of crank position and backrest inclination on shoulder load and mechanical efficiency during handcycling.

Handbikes come in different models and setups, but only limited knowledge is available on the handbike-user interface. The aim of this study was to identify optimal handbike setups, assuming that in such a setup mechanical efficiency is high, while shoulder load is low. Thirteen subjects with a spinal cord injury (paraplegia) performed handcycling with different handbike setups at constant power output: four crank positions (two distances, two heights) and four backrest inclinations. The O2-consumption, kinetics, and kinematics were measured to calculate mechanical efficiency and shoulder load (glenohumeral contact force, net shoulder moments, and rotator cuff force). The analysis showed that more upright backrest positions resulted in lower shoulder load compared with the most reclined position [glenohumeral contact force (260 vs 335 N), supraspinatus (14.4% vs 18.2%), and infraspinatus force (5.4% vs 9.8%)], while there was no difference in efficiency. Except for a reduction in subscapularis force at the distant position, no differences in shoulder load or efficiency were found between crank positions. Recreational handbike users, who want to improve their physical capacity in a shoulder-friendly way, should set up their handbike with a more upright backrest position and a distant crank placement.

Impact of combined skin sparing mastectomy and immediate subpectoral prosthetic reconstruction on the pectoralis major muscle function: a preoperative and postoperative comparative study.

BACKGROUND: We assessed the subjective and objective functional loss induced by detachment of the pectoralis major muscle and whether synergistic function of adjacent muscles compensates for such loss. METHODS: A preoperative to postoperative comparison of the Disability of the Arm, Shoulder and Hand score, 3-dimensional video-analysis of the range of motion, and dynamometric force assessment with electromyography registration were prospectively conducted in 22 women who underwent bilateral preventive breast surgery. RESULTS: Although the statistically significant postoperative increase of the Disability of the Arm, Shoulder and Hand score (P = < 0.01) was indicative of more subjective disability, this difference is irrelevant for activities of daily life. This is in line with the observed postoperative lack of restrictions of range of motion of the shoulder. The mean postoperative maximum force measured in 4 directions reflective of the pectoralis major muscle function was 7.13 N, or 3.8%, lower than the preoperative force (P = 0.079). The mean postoperative maximum force in the 2 contramovement directions was 15.5 N, or 14%, higher than the preoperative force (P = 0.04). Electromyographically, both parts of the deltoid muscle preoperatively and postoperatively showed the same peaks in the 6 directions. Contrastingly, the clavicular part of the pectoralis major muscle postoperatively showed a statistically significant increase of peak of muscle activity in 3 of 4 directions reflective of pectoralis major function and in both contramovement directions, indicating compensatory activity. CONCLUSIONS: Daily life consequences of partial detachment of the pectoralis major muscle were acceptable in our patients.

From theory to practice: Monitoring mechanical power output during wheelchair field and court sports using inertial measurement units.

An important performance determinant in wheelchair sports is the power exchanged between the athlete-wheelchair combination and the environment, in short, mechanical power. Inertial measurement units (IMUs) might be used to estimate the exchanged mechanical power during wheelchair sports practice. However, to validly apply IMUs for mechanical power assessment in wheelchair sports, a well-founded and unambiguous theoretical framework is required that follows the dynamics of manual wheelchair propulsion. Therefore, this research has two goals. First, to present a theoretical framework that supports the use of IMUs to estimate power output via power balance equations. Second, to demonstrate the use of the IMU-based power estimates during wheelchair propulsion based on experimental data. Mechanical power during straight-line wheelchair propulsion on a treadmill was estimated using a wheel mounted IMU and was subsequently compared to optical motion capture data serving as a reference. IMU-based power was calculated from rolling resistance (estimated from drag tests) and change in kinetic energy (estimated using wheelchair velocity and wheelchair acceleration). The results reveal no significant difference between reference power values and the proposed IMU-based power (1.8% mean difference, N.S.). As the estimated rolling resistance shows a 0.9-1.7% underestimation, over time, IMU-based power will be slightly underestimated as well. To conclude, the theoretical framework and the resulting IMU model seems to provide acceptable estimates of mechanical power during straight-line wheelchair propulsion in wheelchair (sports) practice, and it is an important first step towards feasible power estimations in all wheelchair sports situations.

Shoulder and elbow symptoms in talented Dutch baseball pitchers: results of a two-season prospective study.

CONTEXT: Baseball pitching requires fast and coordinated motions of the whole body to reach high ball speeds, putting considerable strain on the musculoskeletal system, particularly the shoulder and elbow. DESIGN: Descriptive epidemiology study. OBJECTIVE: To describe musculoskeletal symptoms and the functional status of the shoulder and elbow in male high school baseball pitchers. SETTING: Dutch baseball talent academies. PATIENTS OR OTHER PARTICIPANTS: 125 male high school baseball pitchers aged 12 to 18 years, who participated in one of the six Dutch baseball talent academies and the Dutch National U-18 team were recruited and enrolled. MAIN OUTCOME MEASURE(S): Musculoskeletal symptoms, functional status of the shoulder and elbow were registered for each player every six months over two consecutive baseball seasons through self-assessment questionnaires, including the Kerlan-Jobe Orthopaedic Clinic (KJOC) and the Western Ontario Shoulder Instability Index (WOSI) questionnaires. RESULTS: 570 musculoskeletal (MSS) symptoms in 93 of the 125 players were reported. The average six-month prevalence for symptoms of the throwing shoulder was 37% (95% CI: 33% - 41%), and for the elbow 37% (95% CI: 31% - 42%), followed by the lower back with 36% (95% CI: 26% - 45%). The baseball pitchers who experienced only shoulder symptoms had an average KJOC score of 80.0 (95% CI: 75.3-84.7) points, while those with only elbow symptoms reported a score of 90.2 (95% CI: 89.2-95.3). On the WOSI questionnaire, baseball pitchers scored an average of 421.2 (95% CI: 200.1 - 642.4) points. CONCLUSION: In a cohort of Dutch high school baseball pitchers, one-third reported shoulder and elbow symptoms on the throwing side, with reduced functional status and lower back symptoms. Future efforts should focus on developing preventive strategies through early symptom detection, aiming to prevent symptom progression and, ultimately, the development of severe injuries.

Effects of bench press technique variations on musculoskeletal shoulder loads and potential injury risk.

While shoulder injuries resulting from the bench press exercise are commonly reported, no biomechanical evidence for lowering injury risk is currently available. Therefore, the aim of the present study was to compare musculoskeletal shoulder loads and potential injury risk during several bench press variations. Ten experienced strength athletes performed 21 technical variations of the barbell bench press, including variations in grip width of 1,1.5 and 2 bi-acromial widths (BAW), shoulder abduction angles of 45°, 70° and 90°, and scapula poses including neutral, retracted, and released conditions. Motions and forces were recorded by an opto-electronic measurement system and an instrumented barbell. An OpenSim musculoskeletal shoulder model was employed to estimate joint reaction forces in the glenohumeral and acromioclavicular joints. Time-series of joint reaction forces were compared between techniques by statistical non-parametric mapping. Results showed that narrower grip widths of < 1.5 BAW decreased acromioclavicular compression (p < 0.05), which may decrease the risk for distal clavicular osteolysis. Moreover, scapula retraction, as well as a grip width of < 1.5 BAW (p < 0.05), decreased glenohumeral posterior shear force components and rotator cuff activity and may decrease the risk for glenohumeral instability and rotator cuff injuries. Furthermore, results showed that mediolaterally exerted barbell force components varied considerably between athletes and largely affected shoulder reaction forces. It can be concluded that the grip width, scapula pose and mediolateral exerted barbell forces during the bench press influence musculoskeletal shoulder loads and the potential injury risk. Results of this study can contribute to safer bench press training guidelines.

Less Pain, but no changes in maximal inclination angles during an overhead reach task following local anesthetic in patients with ongoing shoulder pain.

This multicenter observational study aimed to assess how pain reduction, induced by local anesthesia, affects the relative angular contributions of the shoulder girdle and trunk to the maximal angular performance during a semi-constrained overhead reach task in patients with ongoing shoulder pain. Twenty-nine individuals (age 59.0 SD 12.8 years;16-male) with symptomatic shoulders were administered corticosteroid and lidocaine injections by their attending orthopedic surgeon. Immediately before and after the injections, participants reached for a target on the ceiling ten times as high as possible while their pain levels, shoulder, and trunk movements were recorded. The analysis revealed that there was a significant reduction in pain following the injections. However, there were no significant differences in maximum shoulder and trunk inclination angles between the pre- and post-injection conditions. Notably, there were slight but statistically significant alterations in humeroscapular kinematics during the initial phase of arm elevation following the injections. In conclusion, acute pain relief following local anesthetics is not associated with immediate alterations in maximum shoulder girdle and trunk inclination angles during a semi-constrained overhead reach task in patients with ongoing shoulder pain. However, there are signs of small alterations in humeroscapular kinematics during the initial phase of arm elevation.

Motor control retraining exercises for shoulder impingement: effects on function, muscle activation, and biomechanics in young adults.

OBJECTIVE: Evidence for effective management of shoulder impingement is limited. The present study aimed to quantify the clinical, neurophysiological, and biomechanical effects of a scapular motor control retraining for young individuals with shoulder impingement signs. METHOD: Sixteen adults with shoulder impingement signs (mean age 22 ± 1.6 years) underwent the intervention and 16 healthy participants (24.8 ± 3.1years) provided reference data. Shoulder function and pain were assessed using the Shoulder Pain and Disability Index (SPADI) and other questionnaires. Electromyography (EMG) and 3-dimensional motion analysis was used to record muscle activation and kinematic data during arm elevation to 90° and lowering in 3 planes. Patients were assessed pre and post a 10-week motor control based intervention, utilizing scapular orientation retraining. RESULTS: Pre-intervention, patients reported pain and reduced function compared to the healthy participants (SPADI in patients 20 ± 9.2; healthy 0 ± 0). Post-intervention, the SPADI scores reduced significantly (P < .001) by a mean of 10 points (±4). EMG showed delayed onset and early termination of serratus anterior and lower trapezius muscle activity pre-intervention, which improved significantly post-intervention (P < .05). Pre-intervention, patients exhibited on average 4.6-7.4° less posterior tilt, which was significantly lower in 2 arm elevation planes (P < .05) than healthy participants. Post-intervention, upward rotation and posterior tilt increased significantly (P < .05) during 2 arm movements, approaching the healthy values. CONCLUSION: A 10-week motor control intervention for shoulder impingement increased function and reduced pain. Recovery mechanisms were indicated by changes in muscle recruitment and scapular kinematics. The efficacy of the intervention requires further examined in a randomized control trial.

Changes in Scapular Function, Shoulder Strength, and Range of Motion Occur After Latarjet Procedure.

Purpose: To evaluate the current literature on the effects of anatomic changes caused by the Latarjet procedure and to identify areas for future research. Methods: English-language studies that addressed the consequences of anatomic alterations after the open Latarjet procedure were included. Articles written in languages other than English, reviews, and case reports were excluded. Titles and abstracts were screened by 2 authors. Studies that met the inclusion criteria were screened by the same authors. The following data were extracted from the included studies: authors, year of publication, journal, country of origin, aims or purpose, study population and sample size, methods, procedure, intervention type, and key findings that relate to the scoping review questions. Results: Twenty-two studies were included for analysis, yielding the following findings: First, the Latarjet procedure may change the position of the scapula owing to pectoralis minor tenotomy and/or transfer of the conjoint tendon. Second, dissection of the coracoacromial ligament may result in increased superior translation of the humeral head. The impact of this increased translation on patients' function remains unclear. Third, the subscapularis split shows, overall, better internal rotation strength compared with subscapularis tenotomy. Fourth, passive external rotation may be limited after capsular repair. Fifth, despite the movement of the conjoint tendon, elbow function seems unchanged. Finally, the musculocutaneous nerve is lengthened with a changed penetration angle into the coracobrachialis muscle, but the clinical impact seems limited. Conclusions: The Latarjet procedure leads to anatomic and biomechanical changes in the shoulder. Areas of future research may include better documentation of scapular movement (bilateral, as well as preoperative and postoperative) and elbow function, the effect of (degenerative) rotator cuff ruptures after the Latarjet procedure on shoulder function, and the impact of capsular closure and its contribution to the development of glenohumeral osteoarthritis. Clinical Relevance: This comprehensive overview of anatomic changes after the Latarjet procedure, with its effects on shoulder and elbow function, showed gaps in the current literature. Orthopaedic shoulder surgeons and physical therapists could use our findings when providing patient information and performing future clinical research.

Are shoulders with a reverse shoulder prosthesis strong enough? A pilot study.

BACKGROUND: It has been suggested that limited active ROM of reverse shoulder prostheses relates to lack of strength. However, the postoperative strength has not been quantified. QUESTIONS/PURPOSES: We therefore measured joint torques in patients with reverse shoulder prostheses and correlated torques with functional scores. METHODS: We recruited 33 patients (age, 72 ± 8 years) with a reverse prosthesis (37 shoulders, 21 primary and 16 revisions). We obtained Constant-Murley, DASH, and Simple Shoulder Test ([D]SST) scores, and performed two isokinetic protocols (abduction/adduction and external/internal rotation) at 60° per second. Minimum followup was 4 months (average, 23 months; range, 4-63 months). RESULTS: Twenty-three patients (24 shoulders; 13 primaries, 11 revisions) were able to perform at least one of the defined tasks. Mean abduction and adduction torques were 15 Nm ± 7 Nm and 16 Nm ± 10 Nm (19%-78% of normal shoulders). External and internal rotation tasks could be performed by only 13 patients (14 shoulders; nine primary, five revisions) generating 9 Nm ± 4 Nm and 8 Nm ± 3 Nm, respectively (13%-71% of normal shoulders). We found moderate correlations between Constant-Murley, DASH and (D)SST (D = Dutch translation) scores and abduction and external rotation. CONCLUSIONS: Patients with a reverse prosthesis had reduced strength when compared with normal values reported in the literature (only 65% of patients could perform the protocol). This effect was greatest for external rotation and might explain clinical outcomes with which a moderately strong relationship was observed. Our observations suggest limited strength is a major factor in reduced ROM.

Feasibility and validity of a single camera CNN driven musculoskeletal model for muscle force estimation during upper extremity strength exercises: Proof-of-concept.

Muscle force analysis can be essential for injury risk estimation and performance enhancement in sports like strength training. However, current methods to record muscle forces including electromyography or marker-based measurements combined with a musculoskeletal model are time-consuming and restrict the athlete's natural movement due to equipment attachment. Therefore, the feasibility and validity of a more applicable method, requiring only a single standard camera for the recordings, combined with a deep-learning model and musculoskeletal model is evaluated in the present study during upper-body strength exercises performed by five athletes. Comparison of muscle forces obtained by the single camera driven model against those obtained from a state-of-the art marker-based driven musculoskeletal model revealed strong to excellent correlations and reasonable RMSD's of 0.4-2.1% of the maximum force (Fmax) for prime movers, and weak to strong correlations with RMSD's of 0.4-0.7% Fmax for stabilizing and secondary muscles. In conclusion, a single camera deep-learning driven model is a feasible method for muscle force analysis in a strength training environment, and first validity results show reasonable accuracies, especially for prime mover muscle forces. However, it is evident that future research should investigate this method for a larger sample size and for multiple exercises.

Fastball pitching performance only slightly decreases after mobility impediment of the pelvis and trunk-Do (catch-up) compensation strategies come into play?

Background: Baseball pitching performance can be mechanically explained by the summation of speed principle and the principle of optimal coordination of partial momenta. Impeding optimal energy generation or transfer by or between the pelvis and trunk segments could provide valuable insight into possible compensation or catch-up mechanisms that may manifest themselves based on these principles. Aim: The aim of the present study was to explore the effects of experimentally impeding the mobility of and between the pelvis and trunk segments (1) on ball speed and mechanical peak joint power, and (2) on mechanical peak load of the elbow and shoulder joints at maximal external rotation (MER) during fastball pitching. Methods: Eleven elite baseball pitchers (mean age 17.4, SD 2.2 years; mean pitching experience 8.9, SD 3.0 years) were instructed to throw at least 15 fastballs as fast and accurately as possible under two conditions. One condition involved impeding the mobility of the pelvis and trunk segments to hamper their ability to rotate independently, which consequently should affect the separation time, defined as the time interval between the pelvis and trunk peak angular velocities. In the other condition, pitchers threw unimpeded. Ball speed, mechanical peak joint power and peak net moment of the elbow and shoulder at MER were compared between conditions using Generalized Estimating Equations (GEE). Results: In the impeded pitching condition, the mean difference of the separation time was 12.4 milliseconds [95% CI (4.0, 20.7)] and for ball speed 0.6 mph [95% CI (0.2, 0.9)] lower compared to the unimpeded condition. Only the peak pelvic angular velocity, in addition to the trunk, upper arm and forearm, was 45 deg/s [95% CI (24, 66)] higher impeded condition. The mean differences of the joint power and net moments at the shoulder and elbow did not reach statistical significance. Conclusion: In elite adolescent baseball, the observed pitching performance after experimentally impeding pelvic and trunk mobility undermines a potential distal catch-up strategy based on the summation of speed principle. The increased peak pelvic angular velocity may indicate a compensation strategy following the optimal coordination of partial momenta principle to practically maintain pitching performance.

Cross-Cultural Adaption and Validation of the Dutch Version of the Kerlan-Jobe Orthopaedic Clinic Questionnaire in Juvenile Baseball Pitchers.

Monitoring the performance and functional status of baseball pitchers' upper extremity is important in maintaining the athlete's health and performance. This study validated a Dutch translation of the original English Kerlan-Jobe Orthopaedic Clinic (KJOC) against the previously validated Disabilities of the Arm, Shoulder and Hand (DASH) and Western Ontario Shoulder Instability Index (WOSI) questionnaires in a group of talented juvenile Dutch baseball pitchers. Three times, from 2014-2016, 107 pitchers completed the Dutch KJOC, DASH and WOSI questionnaires. Participants' questionnaire scores were analysed for the whole group and the symptomatic player subgroup separately. Internal consistency, construct validity and ceiling and floor effects were examined. Cronbach's alpha was consistently above 0.8 for the three time periods for the whole group, and ranged between 0.62 and 0.86 for the symptomatic subgroup. Spearman's rank correlation coefficients ranged from 0.47 to 0.67 for the whole group and 0.32 to 0.99 for the symptomatic subgroup. No floor effects were observed in the scores of the KJOC and only a ceiling effect for the whole group (15.2%) at one time period. The Dutch version of the KJOC has shown acceptable internal consistency and construct validity and can be used to assess overhead athletes' shoulder and elbow functionality.

Technical Note: A Novel Servo-Driven Dual-Roller Handrim Wheelchair Ergometer.

The measurement of handrim wheelchair propulsion characteristics and performance in the field is complicated due to the non-stationary nature of wheelchair driving. In contrast, the laboratory provides a constrained and standardisable environment to conduct measurements and experiments. Apart from wheelchair treadmills, dynamometers or ergometers for handrim wheelchairs are often custom-made, one-of-a-kind, expensive, and sparsely documented in the research literature. To facilitate standardised and comparable lab-based measurements in research, as well as in clinical settings and adapted sports, a new wheelchair ergometer was developed. The ergometer with instrumented dual rollers allows for the performance analysis of individuals in their personal handrim wheelchair and facilitates capacity assessment, training and skill acquisition in rehabilitation or adapted sports. The ergometer contains two servomotors, one for each rear wheel roller, that allow for the simulation of translational inertia and resistive forces as encountered during wheelchair propulsion based on force input and a simple mechanical model of wheelchair propulsion. A load cell configuration for left and right roller enables the measurement of effective user-generated torque and force on the handrim and the concomitant timing patterns. Preliminary results are discussed.

Joint stiffness of the ankle during walking after successful mobile-bearing total ankle replacement.

INTRODUCTION: It has been shown that walking kinematics remain near to normal after mobile bearing total ankle replacement (TAR). However, no information is available on mechanical joint loading. The purpose of this study was to determine whether mechanical load and 'quasi-stiffness' of the ankle joint after TAR differs from the normal load and stiffness of a healthy ankle joint during walking. METHODS: Ten TAR patients and 10 age-matched healthy control subjects (CO) participated in this study. Participants walked barefooted on an indoor track at self-selected walking speed. 3D ankle kinematics and ground reaction force were measured and used for the calculation of 3D net joint moments, joint quasi-stiffness coefficients and internal net joint ankle work. RESULTS: Between patients and control subjects no differences were observed in peak moments and stiffness coefficient at the ankle. Internal work at the ankle during the step differed however, significantly (-0.078 (0.088) J kg(-1) versus 0.005 (0.048) J kg(-1) for TAR versus CO, p=0.02), although it could be argued that this difference was due to a minor difference in walking speed between both groups (1.02 (0.07) versus 1.09 (0.07) for TAR versus CO, p=0.02). CONCLUSION: Despite the small difference in internal work at the ankle, there was no significant difference in mechanical loading of the ankle after TAR compared to normal.

Getting in shape: Reconstructing three-dimensional long-track speed skating kinematics by comparing several body pose reconstruction techniques.

In gait studies body pose reconstruction (BPR) techniques have been widely explored, but no previous protocols have been developed for speed skating, while the peculiarities of the skating posture and technique do not automatically allow for the transfer of the results of those explorations to kinematic skating data. The aim of this paper is to determine the best procedure for body pose reconstruction and inverse dynamics of speed skating, and to what extend this choice influences the estimation of joint power. The results show that an eight body segment model together with a global optimization method with revolute joint in the knee and in the lumbosacral joint, while keeping the other joints spherical, would be the most realistic model to use for the inverse kinematics in speed skating. To determine joint power, this method should be combined with a least-square error method for the inverse dynamics. Reporting on the BPR technique and the inverse dynamic method is crucial to enable comparison between studies. Our data showed an underestimation of up to 74% in mean joint power when no optimization procedure was applied for BPR and an underestimation of up to 31% in mean joint power when a bottom-up inverse dynamics method was chosen instead of a least square error approach. Although these results are aimed at speed skating, reporting on the BPR procedure and the inverse dynamics method, together with setting a golden standard should be common practice in all human movement research to allow comparison between studies.

Power in sports: A literature review on the application, assumptions, and terminology of mechanical power in sport research.

The quantification of mechanical power can provide valuable insight into athlete performance because it is the mechanical principle of the rate at which the athlete does work or transfers energy to complete a movement task. Estimates of power are usually limited by the capabilities of measurement systems, resulting in the use of simplified power models. This review provides a systematic overview of the studies on mechanical power in sports, discussing the application and estimation of mechanical power, the consequences of simplifications, and the terminology. The mechanical power balance consists of five parts, where joint power is equal to the sum of kinetic power, gravitational power, environmental power, and frictional power. Structuring literature based on these power components shows that simplifications in models are done on four levels, single vs multibody models, instantaneous power (IN) versus change in energy (EN), the dimensions of a model (1D, 2D, 3D), and neglecting parts of the mechanical power balance. Quantifying the consequences of simplification of power models has only been done for running, and shows differences ranging from 10% up to 250% compared to joint power models. Furthermore, inconsistency and imprecision were found in the determination of joint power, resulting from inverse dynamics methods, incorporation of translational joint powers, partitioning in negative and positive work, and power flow between segments. Most inconsistency in terminology was found in the definition and application of 'external' and 'internal' work and power. Sport research would benefit from structuring the research on mechanical power in sports and quantifying the result of simplifications in mechanical power estimations.