Trends and advancements in shoulder biomechanics research.

The 12th International Shoulder Group (ISG) Conference was held at Mayo Clinic in Rochester, Minnesota, USA, from August 12-13, 2018, and was hosted by Dr. Melissa (Missy) Morrow of Mayo Clinic and Dr. Meghan Vidt of Pennsylvania State University. This conference was held as a satellite conference to the annual 2018 American Society of Biomechanics Conference. This Editorial accompanies the Special Issue of the Journal of Electromyography and Kinesiology, and contains a selection of the work presented during the 12th Meeting of the ISG. Fourteen full-length articles describe advancements in shoulder research relevant to both basic science and clinical outlets. The work presented herein spans the research areas of methodology, mechanistic understanding, and clinical management. These areas are synergistic and equally important to propel the field forward and enhance impact. These manuscripts reinforce the dedication of the ISG and its members and showcase the ongoing drive toward translational application of these concepts across the common themes of rotator cuff, muscle, wheelchair & ergonomics, and methods & modeling. Highlights of each of the special issue publications are described within the context of the current trends in shoulder research and areas for further advancement.

A kinematic and electromyographic comparison of a Grammont-style reverse arthroplasty combined with a l'Episcopo transfer compared to a lateralized humeral component reverse for restoration of active external rotation.

PURPOSE: To assess kinematic and electromyographic findings of two designs of reverse total shoulder arthroplasty (RTSA). We tested two hypotheses: (H1) Grammont-style (RTSA) with l'Episcopo tendon transfer gains similar postoperative kinematic findings of a lateralized humeral component RTSA without a tendon transfer; (H2) RTSA with lateralized humeral component induces earlier shoulder muscle activation during shoulder motion compared with standard Grammont prosthesis with l'Episcopo transfer. METHODS: Twenty-five patients with a cuff tear arthropathy, pseudoparalysis, and a positive dropping sign were sequentially included. A Grammont-style RTSA with a l'Episcopo tendon transfer was implanted in 13 patients (medialized humerus and transfer group) and an on-lay curved-stem RTSA in 12 (lateralized humerus group). Constant score; the disabilities of the arm, shoulder, and hand (DASH) score; and active shoulder range of motion (flexion, abduction, external rotation, and internal rotation) were measured pre- and postoperatively. Upper limb kinematic and surface electromyography (EMG) (anterior and posterior deltoid; upper, middle, and lower trapezius; and the upper and lower latissimus dorsi muscles) were recorded during active range of motion. RESULTS: At > 24 months of follow-up, the Constant and DASH scores and active shoulder range of motion improved in both groups (p < 0.0001). Internal rotation was significantly higher in the lateralized humerus group than in the medialized humerus and transfer group (p = 0.004). The dropping sign was found in 0/12 patients in the lateralized humerus group and in 5/13 patients in the medialized humerus and transfer group (p < 0.001). Kinematic findings were similar between groups (p = 0.286). A pattern of earlier muscle activation in the lateralized humerus group was found as compared to the transfer group as follows: (i) posterior deltoid during external rotation (p = 0.004); (ii) upper latissimus dorsi and middle and lower trapezius during flexion (p = 0.004, p = 0.005, and p = 0.042, respectively); (iii) lower latissimus dorsi during abduction (p = 0.016). CONCLUSION: RTSA with a lateralized humeral component provided similar active external rotation restoration to a Grammont-style RTSA with a l'Episcopo procedure in patients with a dropping sign. The posterior deltoid muscle underwent earlier activation during active external rotation in the lateralized humerus RTSA group as compared to the tendon transfer group. Our findings demonstrated the H1 and only partially demonstrated the H2 of the study.

Innovative alignment of sprinting prostheses for persons with transfemoral amputation: Exploratory study on a gold medal Paralympic athlete.

BACKGROUND: Recommendations for the alignment of the socket and foot in the sprinting prosthesis of athletes with transfemoral amputation are either based on walking biomechanics or lack public scientific evidence. OBJECTIVES: To explore the biomechanical changes and the sensations of a gold medal Paralympic sprinter, while running with three bench alignments: a conventional reference (A0), an innovative alignment based on the biomechanics of elite able-bodied sprinters (A2), and an intermediate alignment (A1). STUDY DESIGN: Single subject with repeated measures. METHODS: A1 and A2 feature a progressively greater socket tilt and a plantar-flexed foot compared to A0. The 30-year-old female athlete trained with three prostheses, one per alignment, for at least 2 months. We administered a questionnaire to collect her impressions. Then, she ran on a treadmill at full speed (5.5 m/s). We measured the kinematics and moments of the prosthetic side, and the ground reaction forces of both sides. RESULTS: A2 reduced the prosthetic side hip extension at foot-off while preserving hip range of motion, decreased the impulse of the hip moment, and increased the horizontal propulsion, leaving sufficient margin to prevent knee buckling without increasing sound side braking forces. Biomechanical outcomes matched well with subjective impressions. CONCLUSIONS: A2 appears promising to improve the performance and comfort of sprinters with transfemoral amputation, without compromising safety. CLINICAL RELEVANCE: Observation of elite able-bodied sprinters led to the definition of a new specific alignment for the sprinting prosthesis of athletes with transfemoral amputation, which appears promising to improve performance and comfort, without compromising safety. This may constitute a major improvement compared to alignments based on walking biomechanics.

Targeted Muscle Reinnervation and Osseointegration for Pain Relief and Prosthetic Arm Control in a Woman with Bilateral Proximal Upper Limb Amputation.

BACKGROUND: Bilateral proximal upper limb loss is a dramatic life-changing event. Replacement of the lost function with prosthetic arms, including multiple mechatronic joints, has remained a challenge from the control, comfort, and pain management perspectives. Targeted muscle reinnervation (TMR) is a peripheral nerve surgical procedure proposed to improve the intuitive control of the prosthetic arm and for neuroma and phantom pain management. Moreover, osseointegrated percutaneous implants (OPIs) allow for direct skeletal attachment of the prosthetic arm, ensuring freedom of movement to the patient's residual articulations. CASE DESCRIPTION: We have reported the first combined application of TMR and an OPI to treat a 24-year-old woman with a bilateral amputation at the shoulder level on the right side and at the very proximal transhumeral level on the left side. TMR was performed bilaterally in a single day, accounting for the peculiar patient's anatomy, as preparatory stage to placement of the OPI, and considering the future availability of implantable electromyographic sensors. The 2 OPI surgeries on the left side were completed after 8.5 months, and prosthetic treatment was completed 17 months after TMR. CONCLUSIONS: The use of TMR resolved the phantom pain bilaterally and the right-side neuroma pain. It had also substantially reduced the left side neuroma pain. The actual prosthetic control result was intuitive, although partially different from expectations. At 2 years after TMR, the patient reported improvement in essential activities of daily living, with a remarkable preference for the OPI prosthesis. Only 1 suspected case of superficial infection was noted, which had resolved. Overall, this combined treatment required a highly competent multidisciplinary team and exceptional commitment by the patient and her family.

Gaitography on lower-limb amputees: Repeatability and between-methods agreement.

BACKGROUND:: Gaitography is gait parametrization from center-of-pressure trajectories of walking on an instrumented treadmill. Gaitograms may be useful for prosthetic gait analyses, as they can be rapidly and unobtrusively collected over multiple gait cycles without constraining foot placement. However, its reliability must still be established for prosthetic gait. OBJECTIVES:: To evaluate (a) within-method test-retest repeatability and (b) between-methods agreement for temporal gait events (foot contact, foot off) and gait characteristics (e.g. step times, single-support duration). STUDY DESIGN:: Cohort study with repeated measurements. METHODS:: Ten male proficient prosthetic walkers with a unilateral trans-femoral or trans-tibial amputation were equipped with a pressure-insole system and were invited to walk on separate days on an instrumented treadmill. RESULTS:: We found better between-methods reproducibility than within-method repeatability in temporal gait characteristics. Step times, stride times, and foot-contact events matched well between the two methods. In contrast, insole-based foot-off events were detected one-to-two samples earlier. Likewise, a similar bias was observed for temporal gait characteristics that incorporated foot-off events. CONCLUSION:: Notwithstanding small systematic biases, the good between-methods agreement indicates that temporal gait characteristics may be determined interchangeably with gaitograms and insoles in persons with a prosthesis. However, the relatively poorer test-retest repeatability hinders longitudinal assessments with either method. CLINICAL RELEVANCE:: Clinical practice could potentially benefit from gaitography as an efficient, unobtrusive, easy to use, automatized, and patient-friendly means to objectively parametrize prosthetic gait, with immediate availability of test results allowing for prompt clinical decision-making. Temporal gait parameters demonstrate good between-methods agreement, but poorer within-method repeatability hinders detecting prosthetic gait changes.

Motion analysis of the shoulder in adults: kinematics and electromyography for the clinical practice.

In this paper, the principal aspects of kinematic and electromyographic (EMG) analysis of the shoulder and their potential for the every-day clinical practice are described. The text reports a brief description of standard recommendations for movement assessment, an overview of the main quantitative motion analysis protocols and a description of the most commonly investigated scapulothoracic muscles. To assess the possibility of using these protocols for clinical applications, reliability and repeatability of kinematic and EMG measures were investigated and reference data for scapulohumeral joint kinematics were provided. The last part of the manuscript reports the integration of the quantitative analysis of scapula dyskinesis within the widely accepted Constant-Murley clinical score. In addition, examples of assessment of muscles activity and recruitment patterns are discussed since they are crucial for the clinical evaluation of common shoulder pathologies.

Intermanual Transfer Effects in Below-Elbow Myoelectric Prosthesis Users.

OBJECTIVES: To determine intermanual transfer effects in patients with a below-elbow amputation using a myoelectric prosthesis and to establish whether laterality affects these effects. DESIGN: Case-control. SETTING: A standardized setting in a rehabilitation clinic. PARTICIPANTS: A convenience sample (N=44) of experienced myoelectric prosthesis users (n=22) and matched controls (n=22). Controls were matched on sex, age (±5y), and hand dominance. INTERVENTIONS: Both the experienced group and the control group performed several tasks using a prosthesis simulator attached to their nonaffected arm. MAIN OUTCOME MEASURES: Movement time, force control, Box and Block test (BBT) scores, and duration of hand opening. RESULTS: Movement times of myoelectric prosthesis users were shorter, and these users had significantly higher BBT scores and shorter hand opening durations than those of controls. No intermanual transfer effects on force control and no laterality effects were found. CONCLUSIONS: Intermanual transfer effects were present in experienced myoelectric prosthesis users with a below-elbow amputation, independent of laterality. These findings support the clinical relevance of intermanual transfer training, which may facilitate persons with an upper limb amputation to start training directly after the amputation.

Impact of Michelangelo prosthetic hand: Findings from a crossover longitudinal study.

This work explores the functional and psychosocial impact of the multigrip Michelangelo (M) prosthetic hand. Transradial myoelectric prosthesis users (6 men, median age: 47 y) participated in a crossover longitudinal study. A multifactorial assessment protocol was applied before the application of M and after 3 mo (functional assessment) and 6 mo (psychosocial assessment) of home use. Functional assessment included both practical tests (i.e., Southampton Hand Assessment Procedure [SHAP], Box and Blocks Test [BBT], and Minnesota Manual Dexterity Test [MMDT]) and self-report functional scales. Psychosocial assessment consisted of a clinical interview and a battery of self-report questionnaires concerning current anxious-depressive symptoms and health-related quality of life, body image concerns, adjustment and satisfaction with prosthesis, social support, coping style, and personality. Increased manual dexterity was observed after 3 mo based on improvements in the SHAP, BBT, and MMDT. Two important themes emerged from the clinical interviews at the 6 mo follow-up: (1) the enhanced functionality and (2) the "like a real hand" aspect of the M, which further increased prosthesis integration to the Self. A few patients expressed concerns about M dimension, noise, and weight. The M appeared to restore hand function and natural appearance. The present findings provide preliminary evidence, and additional studies are needed.

Gaitography applied to prosthetic walking.

During walking on an instrumented treadmill with an embedded force platform or grid of pressure sensors, center-of-pressure (COP) trajectories exhibit a characteristic butterfly-like shape, reflecting the medio-lateral and anterior-posterior weight shifts associated with alternating steps. We define "gaitography" as the analysis of such COP trajectories during walking (the "gaitograms"). It is currently unknown, however, if gaitography can be employed to characterize pathological gait, such as lateralized gait impairments. We therefore registered gaitograms for a heterogeneous sample of persons with a trans-femoral and trans-tibial amputation during treadmill walking at a self-selected comfortable speed. We found that gaitograms directly visualize between-person differences in prosthetic gait in terms of step width and the relative duration of prosthetic and non-prosthetic single-support stance phases. We further demonstrated that one should not only focus on the gaitogram's shape but also on the time evolution along that shape, given that the COP evolves much slower in the single-support phase than in the double-support phase. Finally, commonly used temporal and spatial prosthetic gait characteristics were derived, revealing both individual and systematic differences in prosthetic and non-prosthetic step lengths, step times, swing times, and double-support durations. Because gaitograms can be rapidly collected in an unobtrusive and markerless manner over multiple gait cycles without constraining foot placement, clinical application of gaitography seems both expedient and appealing. Studies examining the repeatability of gaitograms and evaluating gaitography-based gait characteristics against a gold standard with known validity and reliability are required before gaitography can be clinically applied.

Autobiographical memory and psychological distress in a sample of upper-limb amputees.

Amputation is a traumatic and life-changing event that can take years to adjust to. The present study (a) examines psychological adjustment in a specific trauma-exposed sample, (b) compares the phenomenology (e.g., vividness) of amputation-related memories to more recent memories, and (c) tests whether memory phenomenology is associated with psychological distress. A total of 24 upper-limb amputees recalled two autobiographical memories--an amputation-related memory and a recent memory--and rated the phenomenological qualities of each memory, including Vividness, Coherence, Emotional Intensity, Visual Perspective, and Distancing. Participants also completed self-rated measures of psychological distress and personality. The sample was generally well adjusted; participants showed no relevant symptoms of anxiety and depression, and personality scores were similar to the general population. There were no significant differences in phenomenology between the two types of memories recalled. Even though amputation-related memories were, on average, almost 20 years older than the recent memories, they retained their intense phenomenology. Despite the intensity of the memory, none of the phenomenological dimensions were associated with psychological distress. It is worth to further define which dimensions of phenomenology characterize memories of traumatic events, and their association with individuals' psychological reactions.

Differentiation between solid-ankle cushioned heel and energy storage and return prosthetic foot based on step-to-step transition cost.

Decreased push-off power by the prosthetic foot and inadequate roll-over shape of the foot have been shown to increase the energy dissipated during the step-to-step transition in human walking. The aim of this study was to determine whether energy storage and return (ESAR) feet are able to reduce the mechanical energy dissipated during the step-to-step transition. Fifteen males with a unilateral lower-limb amputation walked with their prescribed ESAR foot (Vari-Flex, Ossur; Reykjavik, Iceland) and with a solid-ankle cushioned heel foot (SACH) (1D10, Ottobock; Duderstadt, Germany), while ground reaction forces and kinematics were recorded. The positive mechanical work on the center of mass performed by the trailing prosthetic limb was larger (33%, p = 0.01) and the negative work performed by the leading intact limb was lower (13%, p = 0.04) when walking with the ESAR foot compared with the SACH foot. The reduced step-to-step transition cost coincided with a higher mechanical push-off power generated by the ESAR foot and an extended forward progression of the center of pressure under the prosthetic ESAR foot. Results can explain the proposed improvement in walking economy with this kind of energy storing and return prosthetic foot.

Gait analysis in children with cerebral palsy via inertial and magnetic sensors.

3D kinematic measurements in children with cerebral palsy (CP) to assess gait deviations can only be performed in gait laboratories using optoelectronic systems. Alternatively, an inertial and magnetic measurement system (IMMS) can be applied for ambulatory motion-tracking. A protocol named Outwalk has recently been developed to measure the 3D kinematics during gait with IMMS. This study preliminary validated the application of IMMS, based on the Outwalk protocol, in gait analysis of six children with CP and one typically developing child. Reference joint kinematics were simultaneously obtained from a laboratory-based system and protocol. On average, the root mean square error (RMSE) of Outwalk/IMMS, compared to the reference, was less than 17° in the transversal plane, and less than 10° in the sagittal and frontal planes. The greatest differences were found in offsets in the knee and ankle rotation, and in the hip flexion. These offset differences were mainly caused by a different anatomical calibration in the protocols. When removing the offsets, RMSE was always less than 4°. Therefore, IMMS is suitable for gait analysis of major joint angles in a laboratory-free setting. Further studies should focus on improvement of anatomical calibrations of IMMS that can be performed in children with CP.

Recommended number of strides for automatic assessment of gait symmetry and regularity in above-knee amputees by means of accelerometry and autocorrelation analysis.

BACKGROUND: Symmetry and regularity of gait are essential outcomes of gait retraining programs, especially in lower-limb amputees. This study aims presenting an algorithm to automatically compute symmetry and regularity indices, and assessing the minimum number of strides for appropriate evaluation of gait symmetry and regularity through autocorrelation of acceleration signals. METHODS: Ten transfemoral amputees (AMP) and ten control subjects (CTRL) were studied. Subjects wore an accelerometer and were asked to walk for 70 m at their natural speed (twice). Reference values of step and stride regularity indices (Ad1 and Ad2) were obtained by autocorrelation analysis of the vertical and antero-posterior acceleration signals, excluding initial and final strides. The Ad1 and Ad2 coefficients were then computed at different stages by analyzing increasing portions of the signals (considering both the signals cleaned by initial and final strides, and the whole signals). At each stage, the difference between Ad1 and Ad2 values and the corresponding reference values were compared with the minimum detectable difference, MDD, of the index. If that difference was less than MDD, it was assumed that the portion of signal used in the analysis was of sufficient length to allow reliable estimation of the autocorrelation coefficient. RESULTS: All Ad1 and Ad2 indices were lower in AMP than in CTRL (P < 0.0001). Excluding initial and final strides from the analysis, the minimum number of strides needed for reliable computation of step symmetry and stride regularity was about 2.2 and 3.5, respectively. Analyzing the whole signals, the minimum number of strides increased to about 15 and 20, respectively. CONCLUSIONS: Without the need to identify and eliminate the phases of gait initiation and termination, twenty strides can provide a reasonable amount of information to reliably estimate gait regularity in transfemoral amputees.

Gait symmetry and regularity in transfemoral amputees assessed by trunk accelerations.

BACKGROUND: The aim of this study was to evaluate a method based on a single accelerometer for the assessment of gait symmetry and regularity in subjects wearing lower limb prostheses. METHODS: Ten transfemoral amputees and ten healthy control subjects were studied. For the purpose of this study, subjects wore a triaxial accelerometer on their thorax, and foot insoles. Subjects were asked to walk straight ahead for 70 m at their natural speed, and at a lower and faster speed. Indices of step and stride regularity (Ad1 and Ad2, respectively) were obtained by the autocorrelation coefficients computed from the three acceleration components. Step and stride durations were calculated from the plantar pressure data and were used to compute two reference indices (SI1 and SI2) for step and stride regularity. RESULTS: Regression analysis showed that both Ad1 well correlates with SI1 (R2 up to 0.74), and Ad2 well correlates with SI2 (R2 up to 0.52). A ROC analysis showed that Ad1 and Ad2 has generally a good sensitivity and specificity in classifying amputee's walking trial, as having a normal or a pathologic step or stride regularity as defined by means of the reference indices SI1 and SI2. In particular, the antero-posterior component of Ad1 and the vertical component of Ad2 had a sensitivity of 90.6% and 87.2%, and a specificity of 92.3% and 81.8%, respectively. CONCLUSIONS: The use of a simple accelerometer, whose components can be analyzed by the autocorrelation function method, is adequate for the assessment of gait symmetry and regularity in transfemoral amputees.