Wrist Motion Assessment in Tennis Players using Three-Dimensional Motion Capture and Dynamic Electromyography.

Background Tennis players often present with ulnar-sided wrist pain, which may reflect repetitive stress and/or faulty mechanics. There is a role for investigating the biomechanics of tennis strokes and how they may relate to wrist pathology. The purpose of this study was to investigate whether three-dimensional motion capture technology and dynamic electromyography (EMG), when used to study groundstrokes in elite junior tennis players, reveals patterns of upper extremity motion that may correlate with the development of clinically relevant pathology. Case Description Three-dimensional kinematic and EMG data were collected from two United States Tennis Association-ranked adolescent tennis players during groundstrokes. There were several observed differences in the two players' degree and timing of pronation/supination, ulnar/radial deviation, and flexion/extension during their strokes. Clinical Significance Advanced motion capture technology facilitates a nuanced understanding of complex movements involved in groundstroke production. This methodology may be useful for identifying athletes who are at risk for injury and guiding rehabilitation for players experiencing pain. Level of Evidence IV.

Are 4D Motion Sensors Valid and Reliable for Studying Baseball Pitching?

BACKGROUND: Baseball pitching injuries are on the rise. Inertial measurement units (IMUs) provide immediate feedback to players and coaches, allowing for collection outside of the traditional laboratory setting with real-world application. The 4D Motion system provides kinematics throughout the pitching motion and may be beneficial for individualized programs in the throwing athlete. A systematic analysis of these sensors has not been completed. PURPOSE: To evaluate the validity of the 4D Motion IMU system for analyzing the baseball pitching motion compared with marker-based motion capture, and evaluate the internal reliability and consistency of the device. STUDY DESIGN: Controlled laboratory study. METHODS: Ten high school pitchers participated in this study (10 male; 9 right-hand dominant; mean age, 16.6 ± 1.3 years; mean body mass index, 24.1 ± 3.9). Participants were simultaneously outfitted with six 4D Motion IMU sensors and retroreflective markers. The pitchers threw fastballs at maximum effort off a mound at the standard height and distance. A comparison was made between the IMUs and corresponding motion capture values for shoulder external rotation, elbow flexion, chest extension, pelvis and chest rotation velocity, and rotation acceleration. RESULTS: Significant differences were found for 5 of 7 metrics analyzed. The IMU overreported most metrics, except for elbow flexion and pelvis rotation angular acceleration, where both positive and negative errors were observed. The root mean square error and percentage errors indicated smaller discrepancies for chest extension (4°± 5°) and pelvis (38 ± 19 deg/s) and chest (96 ± 42 deg/s) rotation velocity, with elbow flexion having the largest variance (21°± 9°). CONCLUSION: The values of the 4D Motion IMU system should not be considered equivalent when compared with marker-based motion capture studies. The system lacked internal consistency and reliability, with angular velocities being the most consistent. Caution should be used when using the metrics provided by an IMU-based system for individualized monitoring. CLINICAL RELEVANCE: If found valid and reliable, IMUs could be used for longitudinal workload monitoring, individualized throwing and rehabilitation programs, and ultimately injury prevention. This study demonstrates that the data obtained from a 4D Motion system using Gen 3 sensors are not equivalent to the data obtained from a marker-based motion capture system.

Changes in Elbow Stress and Ball Velocity During Reduced Effort Pitching: A Marker-Based Motion Capture Analysis.

BACKGROUND: Baseball pitchers often participate in throwing programs that involve throwing at reduced effort levels to gradually increase the amount of stress experienced across the elbow. It is currently unknown how reduced effort pitching compares with maximum effort with respect to elbow stress and ball velocity. PURPOSE/HYPOTHESIS: The purpose was to determine the correlation between elbow stress and ball velocity with reduced effort pitching. We hypothesized that decreased perceived effort would disproportionately correlate with elbow stress and ball velocity. STUDY DESIGN: Descriptive laboratory study. METHODS: Ten healthy male high school baseball pitchers threw 5 pitches from a regulation pitching mound at 3 effort levels: maximum effort, 75% effort, and 50% effort. Elbow stress, specifically elbow varus torque, was calculated for all pitches using a validated marker-based 3-dimensional motion capture system. Ball velocity was measured using a Doppler radar gun. Intrathrower variability was calculated for each effort level. RESULTS: Elbow stress and ball velocity decreased with reduced effort throws (P < .001 and P = .003, respectively). However, the reductions in elbow stress and ball velocity were not proportional. At 75% effort throws, elbow stress measured 81% (intraclass correlation coefficient [ICC], 0.95), and ball velocity measured 90% (ICC, 0.80) of maximum, respectively. At 50% effort throws, elbow stress measured 75% (ICC, 0.93), and ball velocity measured 85% (ICC, 0.87) of maximum. Intrathrower reliability was excellent for elbow stress and ball velocity, with all ICCs ≥0.80. CONCLUSION: Pitching at a reduced effort level resulted in decreased elbow stress and ball velocity. However, for every 25% reduction in perceived effort, elbow stress decreased by a mean 13%, and ball velocity decreased 7.5%. When baseball pitchers attempt to throw at a reduced effort of maximum, throwing metrics do not decrease proportionately. CLINICAL RELEVANCE: While pitching at a reduced effort of maximum decreases elbow stress and ball velocity, the decrease is not proportional, subjecting the elbow to more stress than intended. This has significant clinical importance to pitchers, coaches, and medical professionals in the setting of injury prevention and return to sports.

Human Exposure to Hand-Arm Vibration from a Surgical Drill During Simulated Spine Surgery.

OBJECTIVE: During spine surgery, surgeons are exposed to vibrations from surgical drills. Increased exposure to vibration can result in neurologic, vascular, and musculoskeletal impairments. To reduce these risks, occupational health standards have been implemented to limit exposure levels. The purpose of this study was to quantify human exposure to hand-arm vibration from a surgical drill during a simulation of a common spine procedure. METHODS: Vibration measurements were collected during three 30-second surgical trials on a fresh frozen cadaver torso specimen using a standard surgical drill. The daily vibration exposure A(8) was evaluated on the basis of International Organization for Standardization 5349-1, and the occupational health standards, exposure action value, and exposure limit value were calculated. RESULTS: On the basis of vibration exposure, surgeons in this study reached their exposure limits in 8 minutes to monitor tool usage and 32 minutes to terminate equipment usage. CONCLUSIONS: The results demonstrate that a common surgical drill transmits hand-arm vibration levels approaching the exposure action value and exposure limit value over short periods of use. Further investigation is needed to determine the total vibration exposure over an entire workday, specifically in surgeons who perform multiple surgeries within a single day.

Ulnar Wrist Pain in a Tennis Player: Case Review and Discussion: A Team-Based Approach.

¼: Ulnar-sided wrist pain is a common cause of debilitating wrist pain in stick-handling athletes. Due to the complexity of surrounding anatomy, the evaluation and diagnosis can be challenging. ¼: Injury of the triangular fibrocartilage complex (TFCC) is the most common cause of ulnar-sided wrist pain. Repetitive, unrestricted pronosupination, wrist deviation, and axial-loading activity, such as in tennis, place substantial stress on the TFCC. ¼: The ulnotriquetral (UT) ligament is a palmar thickening of the ulnar capsule arising from the palmar radioulnar (PRU) ligament of the TFCC. When injured, the UT ligament can be a source of acute or chronic ulnar-sided wrist pain. The ligament can avulse off bone, can rupture completely, or can split longitudinally. ¼: Arthroscopic-assisted repair is a safe, reliable, and effective treatment for UT ligament split tears and peripheral TFCC tears. ¼: Although the benefit of a team-based approach may be realized by most patients, high-performing, stick-handling athletes are part of a unique population who execute repetitive, extraordinary wrist movements. The high demand and functional requirement expected of the wrists require a uniquely tailored approach to return them to the same level of competitive play.

Neuroimaging correlates of gait abnormalities in progressive supranuclear palsy.

Progressive supranuclear palsy is a neurodegenerative disorder characterized primarily by tau inclusions and neurodegeneration in the midbrain, basal ganglia, thalamus, premotor and frontal cortex. Neurodegenerative change in progressive supranuclear palsy has been assessed using MRI. Degeneration of white matter tracts is evident with diffusion tensor imaging and PET methods have been used to assess brain metabolism or presence of tau protein deposits. Patients with progressive supranuclear palsy present with a variety of clinical syndromes; however early onset of gait impairments and postural instability are common features. In this study we assessed the relationship between multimodal imaging biomarkers (i.e., MRI atrophy, white matter tracts degeneration, flortaucipir-PET uptake) and laboratory-based measures of gait and balance abnormalities in a cohort of nineteen patients with progressive supranuclear palsy, using univariate and multivariate statistical analyses. The PSP rating scale and its gait midline sub-score were strongly correlated to gait abnormalities but not to postural imbalance. Principal component analysis on gait variables identified velocity, stride length, gait stability ratio, length of gait phases and dynamic stability as the main contributors to the first component, which was associated with diffusion tensor imaging measures in the posterior thalamic radiation, external capsule, superior cerebellar peduncle, superior fronto-occipital fasciculus, body and splenium of the corpus callosum and sagittal stratum, with MRI volumes in frontal and precentral regions and with flortaucipir-PET uptake in the precentral gyrus. The main contributor to the second principal component was cadence, which was higher in patients presenting more abnormalities on mean diffusivity: this unexpected finding might be related to compensatory gait strategies adopted in progressive supranuclear palsy. Postural imbalance was the main contributor to the third principal component, which was related to flortaucipir-PET uptake in the left paracentral lobule and supplementary motor area and white matter disruption in the superior cerebellar peduncle, putamen, pontine crossing tract and corticospinal tract. A partial least square model identified flortaucipir-PET uptake in midbrain, basal ganglia and thalamus as the main correlate of speed and dynamic component of gait in progressive supranuclear palsy. Although causality cannot be established in this analysis, our study sheds light on neurodegeneration of brain regions and white matter tracts that underlies gait and balance impairment in progressive supranuclear palsy.

Laboratory based assessment of gait and balance impairment in patients with progressive supranuclear palsy.

BACKGROUND: Gait and balance abnormalities are a significant source of morbidity and mortality in progressive supranuclear palsy (PSP). Gait impairment in PSP is primarily assessed clinically on exam or with the use of rating scales. Three dimensional video based gait and balance analysis performed in a laboratory setting is a highly accurate method of motion analysis (Wren et al., 2020), however limited data is available in patients with PSP. RESEARCH QUESTION: In this study we assess the objective features of postural control, kinematics, kinetic and temporal-spatial gait metrics in PSP, using three-dimensional video motion analysis in a laboratory setting compared to normal controls. METHODS: Three-dimensional motion was captured using a 10-camera motion capture system, 41 body markers and ground embedded force plates in 16 patients with PSP patients and compared to motorically normal controls. RESULTS: Spatiotemporal, kinematic, and kinetic gait measures effectively differentiated patients with PSP from controls. Patients had slower gait velocity, lower cadence, increased double support time and abnormal antero-posterior sway. Joint kinematics and kinetics were reduced and showed less variation among patients with PSP compared to controls which is suggestive of bradykinesia. Objective gait measures of abnormality correlated with clinical disease severity. Postural sway metrics distinguished PSP from controls and captured gait imbalance. SIGNIFICANCE: Objective measures of gait and balance abnormalities in patients with PSP provide an outcome measure that can be potentially used for early disease detection, in clinical trials and to validate portable motion capture devices in the future.

Are Wearable Sensors Valid and Reliable for Studying the Baseball Pitching Motion? An Independent Comparison With Marker-Based Motion Capture.

BACKGROUND: In recent years, the prevalence of medial ulnar collateral ligament injuries has increased in throwers of all ages and skill levels. The motusBASEBALL sensor possesses an inertial measurement unit (IMU) that has been developed and applied to the throwing arm to allow for measurements of several objective parameters, which may prove beneficial for monitoring, rehabilitation, and injury prevention in the throwing athlete. However, the reliability, consistency, and validity of the IMU have not been independently assessed. PURPOSE: To evaluate the reliability, consistency, and validity of the motusBASEBALL sensor compared with the historic gold standard of marker-based motion capture. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 10 healthy male baseball athletes with varsity-level high school experience volunteered to participate in this study. Participants were fitted with 37 retroreflective markers for motion capture and the motusBASEBALL IMU sensor. Participants threw 5 fastballs at maximum effort, with measurements recorded simultaneously by motion capture and the IMU. Arm slot, arm speed, arm stress, and shoulder rotation were measured and compared. RESULTS: Of the 4 metrics generated by the IMU, significant differences were found for 3 of the throwing metrics compared with motion capture including arm slot (5.0°± 6.1°; P = .037), elbow varus torque (9.4 ± 12.0 N·m; P = .037), and shoulder rotation (6.3°± 6.1°; P = .014). Arm speed did not demonstrate a statistically significant difference (29.2 ± 96.8 rpm; P = .375). The IMU consistently underreported pitching performance values. Shoulder rotation exhibited excellent reliability with <5° of error, and arm slot demonstrated good reliability with <10° of error. Arm stress and arm speed were less reliable. CONCLUSION: The IMU was not accurate or valid for arm slot, arm stress, and shoulder rotation compared with marker-based motion capture. It was relatively accurate for arm speed. Despite its lack of validity, it was consistent and reliable for arm speed and shoulder rotation and relatively reliable for arm slot and arm stress. Caution should be used when comparing values provided by this IMU to the gold standard of marker-based motion capture. CLINICAL RELEVANCE: IMU technology has potential to be used in monitoring, rehabilitation, and injury prevention in throwing athletes if valid. This study demonstrates that the values provided by the IMU should not be considered equivalent to those generated by the gold standard of marker-based motion capture; however, there may still be a role for this technology when relying on its internal consistency for intrathrower comparisons and tracking.

Method for characterization of dynamic ankle stiffness in patients with spasticity.

BACKGROUND: Dynamic ankle stiffness has been quantified as the slope of the ankle joint moment-angle curve over the gait interval of the second rocker, defined explicitly as the period of the gait cycle from the first relative maximum plantar flexion in early stance to maximum dorsiflexion in midstance. However, gastrocnemius spasticity may interfere with the second ankle rocker in patients with spasticity. This gait disruption results in stiffness calculations which are misleading. Current dynamic stiffness metrics need to be modified. RESEARCH QUESTION: The main goal of this study was to develop and test a new method to better evaluate dynamic ankle stiffness in individuals with pathologic gait who lack a second rocker interval. METHODS: Twenty unimpaired ambulators (10/20 female, 26.7 ± 5.0 years, BMI: 23.2 ± 2.2) and 9 individuals with cerebral palsy (5/9 female, 5.7 ± 1.7 years, BMI: 14.6 ± 2.1, GMFCS Levels: I - 2, II - 5, III - 2) participated in this study. Dynamic ankle stiffness was evaluated using the previous kinematic method, defined by the interval of maximum plantar flexion to maximum dorsiflexion angle in midstance, and the proposed kinetic method, defined by the interval from the maximum dorsiflexion moment to first peak plantar flexion moment. Stiffness was quantified as the linear slope between the sagittal plane ankle angle and moment. Method differences were explored using an equivalence test (α = 0.05). RESULTS AND SIGNIFICANCE: There was equivalence between the methods for unimpaired ambulators (p = 0.000) and a lack of equivalence for patients with spasticity (p = 0.958). The new method was successfully applied to all 9 pediatric ambulators with CP and demonstrated increased stiffness in patients with spasticity as compared to the previous method. The ability to objectively calculate ankle stiffness in pathologic gait is critical for determining change associated with clinical intervention.