Three-dimensional kinematics of the scapula and trunk, and associated scapular muscle timing in individuals with stroke.

Poor scapulothoracic control is a risk for developing shoulder pathology, but has received little attention so far in individuals with stroke (IwS). Trunk and scapular kinematics and surface muscle activity were measured in 15 healthy controls and 18 IwS during a low and high forward flexion (FF). Group-differences in trunk and scapular kinematics were assessed during low and high FF using a t-test (independent samples). Differences in muscle onset and offset time relative to movement start (both FF tasks) were determined using a mixed model taking into account the different groups and muscles. Recruitment patterns per group and task were described based on significant differences between muscles. In IwS, earlier lower trapezius and late infraspinatus offset were found during low FF, as well as a later onset and earlier offset of serratus anterior. For low FF, significantly more trunk axial rotation was found in IwS during both elevation and lowering. During high FF, IwS showed significantly less scapular posterior tilt during elevation and more scapular lateral rotation during lowering. IwS demonstrated adaptive muscle timing with earlier initiation and late inactivation of lower trapezius and infraspinatus, possibly to compensate for a late activation and early deactivation of the serratus anterior and to establish as such the correct pattern of scapulothoracic movement.

Scapulohumeral control after stroke: A preliminary study of the test-retest reliability and discriminative validity of a clinical scapular protocol (ClinScaP).

BACKGROUND: Clinical scapulohumeral tests are lacking post-stroke. OBJECTIVE: To test reliability and discriminant validity of clinical scapulohumeral assessments post-stroke. METHODS: Following tests were assessed in 57 individuals with stroke (IwS) (subdivided in a low, moderate, high proximal arm function (PAF) group) and 15 healthy controls: (1) Observation of tilting/winging; (2) shoulder girdle position tests (pectoralis minor index, acromial index, scapular distance test); (3) scapular lateral rotation measurement; (4) maximal humeral elevation and (5) medial rotation test were executed. 15 IwS were measured twice by the same assessor to determine test-retest reliability. Differences between controls and IwS and between IwS with different levels of PAF were assessed. RESULTS: ICCs were very high for all tests (>0.80), except the pectoralis minor index (0.66). Weighted Kappas were high for observation and the medial rotation test (>0.70). Group differences were found for observation, lateral rotation and humeral elevation. IwS compared to controls, and IwS with lower compared to higher PAF generally showed increased lateral rotation (p < .01); decreased maximal active humeral elevation (p < .001); and more often tilting and winging (p < .05). CONCLUSIONS: The use of these tests in clinical settings will allow for identification of altered scapular characteristics, which will enhance treatment planning for PAF post-stroke.

Characteristics of neuromuscular control of the scapula after stroke: a first exploration.

This study aimed to characterize scapular muscle timing in stroke patients with and without shoulder pain. Muscle activity of upper trapezius, lower trapezius, serratus anterior, infraspinatus, and anterior deltoid (AD) was measured (Delsys Trigno surface EMG system, USA) in 14 healthy controls (dominant side) and 30 stroke patients (hemiplegic side) of whom 10 had impingement-like shoulder pain. Participants performed 45° and full range anteflexion, in two load conditions. The impact of group, anteflexion height, load condition, and muscle was assessed for onset and offset of the different muscles relative to the onset and offset of AD, using a 3 (group) × 2 (height) × 2 (load) × 4 (muscle) mixed model design. Recruitment patterns were additionally described. Across all load conditions and groups, serratus anterior had a significantly earlier onset and, together with lower trapezius, a significantly later offset in 45° compared to full range anteflexion tasks (p < 0.001). In stroke patients without pain, lower trapezius had furthermore a significantly earlier onset in comparison to stroke patients with shoulder pain (all tasks, p = 0.04). Serratus anterior also showed a significantly earlier offset in stroke patients with shoulder pain in comparison to controls (p = 0.01) and stroke patients without pain (p < 0.001). Analysis of muscle recruitment patterns indicated that for full range tasks, stroke patients without pain used early and prolonged activity of infraspinatus. In stroke patients with shoulder pain, recruitment patterns were characterized by delayed activation and early inactivity of serratus anterior. These timing results can serve as a reference frame for scapular muscle timing post-stroke, and when designing upper limb treatment protocols and clinical guidelines for shoulder pain after stroke.

Dynamic scapular movement analysis: is it feasible and reliable in stroke patients during arm elevation?

Knowledge of three-dimensional scapular movements is essential to understand post-stroke shoulder pain. The goal of the present work is to determine the feasibility and the within and between session reliability of a movement protocol for three-dimensional scapular movement analysis in stroke patients with mild to moderate impairment, using an optoelectronic measurement system. Scapular kinematics of 10 stroke patients and 10 healthy controls was recorded on two occasions during active anteflexion and abduction from 0° to 60° and from 0° to 120°. All tasks were executed unilaterally and bilaterally. The protocol's feasibility was first assessed, followed by within and between session reliability of scapular total range of motion (ROM), joint angles at start position and of angular waveforms. Additionally, measurement errors were calculated for all parameters. Results indicated that the protocol was generally feasible for this group of patients and assessors. Within session reliability was very good for all tasks. Between sessions, scapular angles at start position were measured reliably for most tasks, while scapular ROM was more reliable during the 120° tasks. In general, scapular angles showed higher reliability during anteflexion compared to abduction, especially for protraction. Scapular lateral rotations resulted in smallest measurement errors. This study indicates that scapular kinematics can be measured reliably and with precision within one measurement session. In case of multiple test sessions, further methodological optimization is required for this protocol to be suitable for clinical decision-making and evaluation of treatment efficacy.

A systematic review of 3D scapular kinematics and muscle activity during elevation in stroke subjects and controls.

Through the onset of post-stroke motor disorders, the normal scapular function is compromised. As a result, shoulder pain and associated upper limb dysfunctions frequently arise after stroke. This review aimed to provide a systematic overview of available literature on scapular function, i.e. scapular three-dimensional (3D) kinematics and muscle activity during elevation, in healthy persons, persons with primary shoulder disorders and post-stroke patients. 3D scapular kinematics have been widely reported in healthy persons and persons with primary shoulder disorders, whereby a general pattern of upward rotation and posterior tilt during elevation has been agreed upon. Results on scapular internal/external rotation are inconsistent. In a post-stroke population, 3D scapular kinematics are less frequently reported. Scapular muscle activity has thus far been studied to very limited extend and firm conclusions could not be drawn. Although 3D scapular kinematics and muscle activity registrations are being increasingly used, some general methodological aspects should be considered. While the International Society of Biomechanics already proposed recommendations on the definition of upper limb joint coordinate systems and rotation sequences, proper result comparison necessitates further guidelines on other methodological aspects, i.e. data collection, processing, analyzing, and reporting.

Sway activity and muscle recruitment order during transition from double to single-leg stance in subjects with chronic ankle instability.

Subjects with CAI (chronic ankle instability) are slower in activating their leg muscles when shifting weight (from double to single leg stance; DLS and SLS). We examined if these delays are associated with longer transition/stabilization times. This was tested by analyzing the center of pressure (COP) trajectory data (1) in the DLS phase before onset of transition, (2) in the quasi-stable phase of the SLS, immediately after the transition phase but before time to stabilization (TTS) and (3) in the SLS phase after TTS. Data were recorded from 20 subjects with CAI and 20 controls. The TTS was longer for the CAIs than for controls (3.25 vs. 2.28 s in EO and 3.41 vs. 2.51 s in EC; p<0.001). Similarly, the time of transition (TTR) was prolonged in CAIs (1.48 vs. 1.14 s in EO and 1.53 vs. 1.20 s in EC; p<0.05). These prolonged periods came in parallel with an increase in the ML sway in the quasi-stable phase (mean displacement 2.20 vs. 1.75 cm in EO; 3.37 vs. 2.62 cm in EC; significant for EC p<0.05). The TTR in CAIs was positively correlated with time onsets of the adductor longus muscle during transitions with EC (R=0.51, p=0.03). The findings support the use of a weight-shifting paradigm for the evaluation of balance control in CAI. Specifically, we underscore the transition phase and quasi-stable phase of the SLS as promising time windows for documenting balance control deficits in CAI.

Stability of measurement outcomes for voluntary task performance in participants with chronic ankle instability and healthy participants.

CONTEXT: Acceptable measurement stability during data collection is critically important to research. To interpret differences in measurement outcomes among participants or changes within participants after an intervention program, we need to know whether the measurement is stable and consistent. OBJECTIVE: To determine the within-session stability of muscle activation patterns for a voluntary postural-control task in a group of noninjured participants and a group of participants with chronic ankle instability (CAI). DESIGN: Descriptive laboratory study. SETTING: Musculoskeletal laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty control participants (8 men, 12 women; age = 21.8 ± 2.4 years, height = 164.3 ± 13.4 cm, mass = 68.4 ± 17.9 kg) and 20 participants with CAI (12 men, 8 women; age = 21.2 ± 2.1 years, height = 176 ± 10.2 cm, mass = 71.7 ± 11.3 kg). INTERVENTION(S): Participants performed 4 barefoot standing trials, each of which included a 30-second double-legged stance followed by a 30-second single-legged stance in 3 conditions: with vision, without vision, and with vision on a balance pad. MAIN OUTCOME MEASURE(S): The activity of 7 muscles of the lower limb was measured for the stance task in the 3 different conditions for each trial. The onset of muscle activity and muscle recruitment order were determined and compared between the first and the fourth trials for both groups and for each condition. RESULTS: We found no differences in the onset of muscle activity among trials for both groups or for each condition. The measurement error was 0.9 seconds at maximum for the control group and 0.12 seconds for the CAI group. In the control group, 70% to 80% of the participants used the same muscle recruitment order in both trials. In the CAI group, 75% to 90% used the same recruitment order. CONCLUSIONS: Within 1 session, measurement stability for this task was acceptable for use in further research. Furthermore, no differences were found in measurement stability across conditions in the control or CAI groups.

Relationship of chronic ankle instability to muscle activation patterns during the transition from double-leg to single-leg stance.

BACKGROUND: Impaired muscle activation may predispose subjects to develop chronic ankle instability. It has been suggested that impairments are found not only in structures around the injured ankle but also around the more proximal joint complexes. HYPOTHESIS: Subjects with chronic ankle instability were expected to show later onset times for lower limb and trunk muscle activation when compared with control subjects. They were expected to show less variability in muscle activation patterns compared with the control group. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty control subjects and 10 subjects with chronic ankle instability participated in the study. The onset of muscle activity of 14 muscles of the lower limb and trunk was measured during the transition from a double-leg stance position to a single-leg stance position in eyes-open and eyes-closed test conditions. RESULTS: Subjects with chronic ankle instability showed significantly later onset times for the ankle, hip, and hamstring muscles compared with control subjects. They used a similar muscle activation pattern in both test conditions, whereas control subjects adjusted their activation pattern according to the condition. CONCLUSIONS: Differences in muscle activation patterns between subjects with chronic ankle instability and control subjects occur not only around the ankle but also around other joints. Subjects with chronic ankle instability show less variability in muscle activation patterns between test conditions. CLINICAL RELEVANCE: Knowledge of muscle activation patterns in the whole lower limb and trunk in noninjured subjects and the differences found in chronic ankle instability subjects broadens the physical therapy approach to the treatment of chronic ankle instability.