Objectives Frailty, reflecting reduced physiological reserve and increased vulnerability to stressors, is common among patients with idiopathic normal pressure hydrocephalus (iNPH). The extent to which frailty influences gait outcomes following ventriculoperitoneal shunting (VPS) remains unclear. This study evaluated the association between frailty and objective gait changes after VPS in patients with iNPH. Methods A single-center database was reviewed for patients who underwent VPS for iNPH with preoperative gait analysis between October 2018 and May 2024. Gait parameters included cadence, velocity, stability ratio, step width, stride length, single and total support. Patients were stratified by the modified 5-item frailty index (mFI) into non-frail (mFI-0), pre-frail (mFI-1), and frail (mFI-2+). Generalized additive mixed-effects models evaluated time, mFI, and their interaction with patient-specific random effects. Results Of the 242 patients that were included, 60 (24.8%) were classified preoperatively as non-frail, 109 (45%) were pre-frail, and 73 (30.2%) were frail, with no difference in age distributions across groups. A total of 844 gait analyses were performed with a median of three per patient and a median latest follow-up time of 12.2 months. Preoperative gait parameters varied significantly across mFI groups. However, the degree of change in gait parameters between preoperative and first postoperative gait assessments did not differ across mFI groups, with most patients exhibiting improvement. Conclusion Frailty correlated with worse baseline gait performance but did not diminish the likelihood or durability of gait improvement following VPS. These findings suggest that VPS yields meaningful gait benefits in patients with iNPH regardless of frailty status.

OBJECTIVES:This study evaluated the impact of a powered myoelectric elbow orthosis (PMEO) on fatigue resistance and maximum endurance time (MET) of the gracilis muscle used in free functioning muscle transfer (FFMT) for elbow reconstruction. The PMEO was developed to support elbow flexion by mechanically locking the joint in place, reducing muscular demand during sustained tasks. DESIGN:Experimental clinical study. SETTING:Academic medical center. PARTICIPANTS:Seven participants (N=7) with brachial plexus injury and FFMT were enrolled and divided into more and less impaired groups based on manual muscle test scores. INTERVENTIONS:Participants performed repeated isometric elbow flexion trials with and without the PMEO while surface electromyography (EMG) and kinematic data were recorded. MAIN OUTCOME MEASURES:Spectro-temporal EMG metrics-median power frequency and integrated EMG-were analyzed, and endurance was estimated using a muscle-specific MET model. RESULTS:Four of the 7 participants, primarily in the more impaired group, demonstrated a 4-minute improvement in MET and more favorable fatigue metrics with the PMEO. Median power frequency increased, and integrated EMG decreased in these individuals, indicating delayed fatigue onset. The PMEO also enabled task completion in 3 participants who were otherwise unable to flex their elbow unaided. CONCLUSIONS:These results suggest that the PMEO can enhance functional endurance in individuals with brachial plexus injury and FFMT. Notably, this study provided one of the first applications of spectro-temporal metrics and MET to evaluate fatigue resistance in an FFMT, filling a gap in existing literature.

INTRODUCTION:Although powered orthotic devices are becoming more available and increasingly recognized by the medical community, several factors still prevent them from being widely adopted. These orthoses typically use a simple controller, often termed a "bang-bang" controller, which actuates a motor if the muscle's electromyography (EMG) signal is above a set threshold. A proportional controller that could actuate the elbow mechanism based on the EMG signal magnitude would enable a better human-machine connection. The real challenge for designing a proportional controller lies in the heterogeneity of the types of injury and surgeries used in this patient population, as well as the extent of recovery post-surgery. Neural networks effectively model nonlinear relationships in control system design. Recently, a novel powered myoelectric elbow orthosis (PMEO) was developed and tested on patients with a brachial plexus injury (BPI) that used a bang-bang controller. The report evaluated the possibility of using a proportional controller using a neural network-powered regression (NNR) for this exoskeleton. MATERIALS AND METHODS:Data from 31 participants with a BPI were collected after receiving IRB approval. A custom apparatus was designed to measure elbow flexion torque and EMG, while participants were instructed to match their torque to a predefined target (10%-40% of MVC). A 2-layered NNR (2 hidden nodes) with a Tanh activation and 5 cross-validation folds was used to find a relationship between the properties of the EMG (moving average, root mean square, variance, standard deviation, and slope) and the elbow torque for individual participants. The collected data were divided into a training set (70%) and a test set (30%). The root mean squared error (RMSE) for the test set was calculated for each NNR model, along with the training time and prediction speed. RESULTS:A standard computer (Intel Core i5-10500 with 16 GB RAM) was used to train the models. The trained models required 82 seconds (range: 3-332 seconds) to train on 8.2e4 (range: 7.7e4-8.9e4) samples. The test dataset consisted of 3.5e4 (range: 3.3e4-3.8e4) samples. The median test RMSE was 0.39 Nm (range: 0.1-3.09 Nm). The NNR took 7 milliseconds (range: 6-10 milliseconds) to predict the test dataset; 35% and 16% of the models had an R2 > 0.5 and >0.7, respectively. CONCLUSIONS:A low-powered office computer was sufficient to train an NNR with training time short enough to be completed in an orthotist's office within a typical appointment time. These data verify that the process can be field deployable.

Wearable inertial measurement units (IMUs) offer an accessible alternative to optical motion capture (MoCap) gait analysis, but their performance in Progressive Supranuclear Palsy (PSP) requires validation. We assessed the concurrent validity of IMU-derived versus MoCap-derived gait metrics and static postural sway in 30 patients with PSP using Bland–Altman analysis, Intraclass Correlation Coefficients (ICC), and Spearman rank correlations. Finally, we assessed equivalence using the Two one-sided tests (TOST) procedure. Multivariable linear regression was used to determine whether clinical severity, as measured by the PSP Rating Scale (PSPRS), independently predicted absolute IMU measurement error while controlling for patient age and gait velocity. IMUs demonstrated excellent between-system agreement for parameters such as cadence (100.76 ± 11.42 vs. 100.52 ± 11.59) and cycle time (1.21 ± 0.15 vs. 1.22 ± 0.15; ICC > 0.98), despite a systematic underestimation of gait velocity (p < 0.05). Agreement significantly diminished for micro-phases (e.g., single/double support times) and spatial asymmetry. Interestingly, the TOST procedure revealed that only sagittal and transverse trunk kinematics were equivalent between systems, with all other measures failing to find equivalency. For static sway, the IMU demonstrated strong rank-order correspondence for tracking relative postural instability (ρ = 0.82, p < 0.05). Multivariable analysis revealed that higher PSPRS scores are independently associated with greater between-system discrepancies in support phases and pelvic and trunk kinematics (p < 0.05), irrespective of reduced gait speed. These findings highlight the need to develop disease-specific algorithms, rather than relying on normative commercial models, to establish reliable digital biomarkers for monitoring progressive motor decline.

Objective To evaluate the feasibility and potential efficacy of percutaneous spinal stimulation (epidural stimulation, ES) combined with task-specific training to reduce spasticity and improve gait and balance in individuals with progressive multiple sclerosis (MS). Methods Two men with progressive MS (EDSS 6.5) underwent ES lead implantation targeting the lower spinal cord, followed by one month of rehabilitation involving 12 ES-assisted training sessions. Assessments included instrumented gait analysis, Modified Ashworth Scale (MAS), pendulum test, and static balance testing performed at baseline, and at end of the study with ES-Off and ES-On conditions. Results Participant 1, with spastic hemiparetic gait, demonstrated improved lower extremity joint kinematics and muscle activation during gait, reduced knee extensor spasticity, and enhanced functional movement patterns with ES-On. Participant 2, with significant paraparesis and minimal spasticity, showed limited gait changes but experienced marked improvements in static balance, particularly under eyes-closed conditions. No adverse events were reported. Conclusion This pilot study demonstrates the feasibility and tolerability of ES paired with task-specific training in progressive MS. Participant-specific responses were observed, including improvements in gait kinematics, neuromuscular activation, spasticity, or balance; however, spatiotemporal gait parameters did not improve. These preliminary findings highlight response heterogeneity and the need for individualized ES parameter tuning. Trial registry name and URL: https://clinicaltrials.gov/study/NCT06019611

Background Longevity is increasing worldwide due to improvements in healthcare and living standards. Aging is often associated with disability and multiple health concerns. To address these challenges, effective interventions are essential. This study investigated potential age-related declines in gait, balance, and strength. We also sought to assess any relationships between these three parameters and explore potential differences between women and men. Methods Healthy individuals over 50 years of age were recruited for this cross-sectional study. Upper extremity (grip) strength and lower extremity (knee) strength of the dominant side were measured. Static balance was performed on the force plate in different situations each for 30 seconds: bilateral stance with eyes open, bilateral stance with eyes closed, as well as dominant leg and non-dominant leg unilateral stance with eyes open. Gait was measured during level walking using an optical motion capture system. Additionally, the dynamic stability margin (DSM) was calculated for the level walking trials. Results The study results indicated that gait parameters were not significantly affected by age (p≥0.12), while knee and grip strength, along with several balance parameters, showed a significant decline with age. All individuals were able to maintain their bipedal balance, but their center of pressure movement increased significantly by age (p≤0.028). Z-scores were calculated to compare significant age parameters. Unipedal stance time was found to be the most affected by age compared to other contributing factors (p≤0.001). The duration of unipedal balance showed the most significant change per decade (non-dominant: -0.62 SDs; dominant: -0.53 SDs), while strength measures exhibited the lowest amount of change per decade (grip strength: -0.34 SDs; knee strength: -0.26 SDs). Sex differences were observed exclusively in strength parameters, with no discernible impact on the decline in balance parameters. Conclusions These findings suggest that the duration of unipedal stance can serve as a reliable and gender-independent measure of neuromuscular aging for both elderly male and female subjects.

Canada lacks a national data source on individuals with limb loss and limb difference (LLD), which limits understanding of incidence, prevalence, risk factors, etiology, and healthcare outcomes. In the absence of standardized data collection, the provision of LLD healthcare services in Canada remains inconsistent. The objective of this study was to gather key interest groups’ perspectives on the development of a Canadian LLD registry. Invitees were identified through professional networks and snowball recruitment techniques. A two-round modified Delphi approach was utilized to identify key LLD registry domains via a pre-meeting survey followed by a virtual workshop on February 14, 2024. Of 96 invitees, 53 completed the survey, and 64 attended the workshop (63 from Canada and 1 from the United States). Five key LLD registry domains were identified: representation, standardization, practice-based evidence, research and innovation, and policy and funding. Inclusivity of diverse populations, national outcome measures adoption, and integration of psychosocial and clinical data was emphasized. Foreseen challenges included privacy concerns, necessary infrastructure, and resources to ensure long-term sustainability. Despite these challenges, a Canadian LLD registry could support advocacy, strengthen practice-based evidence, enhance research collaboration, improve clinical care, and inform population-level policies. Efforts to develop the registry are ongoing. Layman's Abstract Canada currently lacks a national registry of individuals with limb loss and limb difference (LLD), which limits our understanding of how many Canadians have limb loss or limb difference, and the effectiveness of healthcare services. Without consistent national data collection, it is impossible to understand regional differences in care, including prosthetic interventions and rehabilitation. This initiative gathered insights from representatives of the LLD community on establishing a Canadian LLD registry to improve research, healthcare delivery, and advocacy. Ninety-six LLD experts and professionals were identified to participate in a two-stage process that included a survey and virtual workshop. Fifty-three individuals (55%) completed the survey. On February 14, 2024, 64 (67%) individuals (63 Canadian and 1 American) attended the virtual workshop. The workshop included presentations on the development of the American Limb Loss and Preservation registry and the Canadian Rick Hansen Spinal Cord Injury registry, and measuring Canadian LLD outcomes. The meeting explored the feasibility, vision, and strategies for creating a Canadian LLD registry. Findings from the survey and workshop showed strong support for the registry, and workshop attendees discussed a number of critical areas for its development and sustainability. While some challenges regarding privacy, infrastructure, and sustainability still need to be addressed, there was agreement among meeting attendees on a strategy to start planning a registry. A Canadian registry would support advocacy efforts, enhance clinical care, encourage collaborative research, and provide essential data about care nationwide to ensure that the health and social care needs of the LLD community are met. Work is continuing to create and fund a Canadian LLD registry. Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/46909/34865 How To Cite: Mayo A.L, Hitzig S.L, Zidarov D, MacKay C, Kaufman K.R, Noonan V.K, et al. A national strategy for a Canadian limb loss and limb difference registry. Canadian Prosthetics & Orthotics Journal. 2026; Volume 9, Issue 1, No. 3. https://doi.org/10.33137/cpoj.v9i1.46909 Corresponding Author: Dr. Amanda L. Mayo, MD, MHSc, FRCPC, Affiliations: 1) St. John’s Rehab, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 2) St. John’s Rehab Research Program, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 3) Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada. E-Mail: amanda.mayo@sunnybrook.ca ORCID ID: https://orcid.org/0000-0001-7061-2529

Objectives: To examine the effects of anterior load carriage on dynamic sagittal spinal alignment during the gait cycle in younger (<65 y) and older (≥65 y) adults. Design: Cross-sectional study of 47 participants aged 20–80 years categorized as young and older adults. Participants walked at self-selected speeds with and without a 4.5 kg anterior chest load. Whole-body kinematics were recorded using a 19-camera infrared motion capture system. Outcome measures included lumbar lordosis (LL), thoracic kyphosis (TK), trunk inclination (TI), sagittal trunk shift (STS), and pelvic tilt (PT). Gait-cycle–dependent differences were analyzed using statistical parametric mapping. Results: The mean age was 41 years in young adults (n=28) and 70 years in older adults (n=19). Anterior load carriage increased LL during portions of the gait cycle and reduced TI throughout the entire gait cycle. Younger adults demonstrated greater LL and lower TI than older adults. A significant age-by-load interaction for TI was observed during portions of the gait cycle. Conclusions: Anterior load carriage alters spinal alignment by increasing LL and reducing TI during walking, with distinct age-related patterns. These results provide valuable reference data and a foundation for future studies on load management and ergonomic interventions across the adult lifespan.

OBJECTIVES:To examine the effects of anterior load carriage on dynamic sagittal spinal alignment during the gait cycle in younger (<65 y) and older (≥65 y) adults. DESIGN:Cross-sectional study of 47 participants aged 20-80 years categorized as young and older adults. Participants walked at self-selected speeds with and without a 4.5 kg anterior chest load. Whole-body kinematics were recorded using a 19-camera infrared motion capture system. Outcome measures included lumbar lordosis (LL), thoracic kyphosis (TK), trunk inclination (TI), sagittal trunk shift (STS), and pelvic tilt (PT). Gait-cycle-dependent differences were analyzed using statistical parametric mapping. RESULTS:The mean age was 41 years in young adults (n=28) and 70 years in older adults (n=19). Anterior load carriage increased LL during portions of the gait cycle and reduced TI throughout the entire gait cycle. Younger adults demonstrated greater LL and lower TI than older adults. A significant age-by-load interaction for TI was observed during portions of the gait cycle. CONCLUSIONS:Anterior load carriage alters spinal alignment by increasing LL and reducing TI during walking, with distinct age-related patterns. These results provide valuable reference data and a foundation for future studies on load management and ergonomic interventions across the adult lifespan.

Spasticity results from upper motor neuron lesions and can create a deforming force and pain, and is often accompanied by contracture. Although the origin of spasticity is neural, there is ample evidence of secondary muscle changes. Here, we use direct measurement of the force-frequency relationship (FFR) to characterize human muscle's physiological properties. This study directly quantified the FFR of both healthy and spastic human skeletal muscles. Muscle force was measured intraoperatively in healthy gracilis (n = 13; aged 39.4 ± 10.6 yr; surgery due to brachial plexus injury) and spastic biceps brachii muscle (n = 8; aged 53.3 ± 10.3 yr; surgery due to stroke or traumatic brain injury). Nerve stimulation was applied at frequencies ranging from 1 to 70 Hz. Twitch contraction parameters, including time to peak tension (TPT) and half-relaxation time (HRT), were also compared. The FFR of the two muscles was modeled with sigmoid functions, and differences between muscles were assessed with an extra sum-of-squares F test. TPT did not significantly differ between groups (P = 0.12), whereas HRT was prolonged in the spastic biceps (P < 0.05). Despite small differences in twitch kinetics, both muscles exhibited nearly identical FFR profiles. This study represents the first direct in vivo report of spastic human muscle kinetic properties and shows that these contractile kinetics are similar in healthy and spastic muscles. This may suggest that there are no dramatic calcium handling or myosin heavy chain changes in the biceps muscle secondary to spasticity.NEW & NOTEWORTHY This study presents the first in vivo intraoperative measurement of the kinetic properties of spastic human muscle. Despite slower relaxation in spastic biceps, the force-frequency relationship was similar to that of the healthy gracilis muscle. This suggests that spasticity does not substantially alter frequency-dependent force summation, possibly due to similar fiber-type compositions and limited changes in calcium handling or myosin isoforms in human spastic muscle.

Six patients treated by hyperselective neurectomy were assessed using preoperative dynamic electromyography and intraoperative force measurements. Patients with lower preoperative biceps dynamic electromyography activation had significantly reduced force production at operation, suggesting that these findings could guide and improve procedure selection.Level of evidence: IV.

Traumatic brachial plexus injury (BPI) results in significant disability, often hindering functionality in the patient's daily life. Post- surgery, muscle strength recovery can take up to two years, with 40% of patients requiring even longer. A powered elbow orthosis can enhance functionality during activities of daily living (ADLs). This study tested a novel powered myoelectric elbow orthosis (PMEO) during ADLs. Subjects with BPI were fitted with the PMEO and divided into two groups: more impaired (Manual Muscle Test (MMT) < 3, N = 5) and less impaired (MMT≤ 3, N = 4). They performed four ADLs involving full elbow motion, including an activity requiring the subjects to lift a basket with weights. Upper extremity kinematics, electromyographic activity, weight lifted, and subject feedback on the device's form and fit were collected and analyzed. Results showed that the PMEO significantly improved elbow range of motion in the more impaired group (14 ± 23 degrees, p = 0.019) without any additional compensatory motions in the shoulder or trunk. More impaired subjects lifted an average of 1.1 ± 0.6 kg with the PMEO, whereas they could not do so without it (p = 0.011). Subjects appreciated the PMEO's weight, fit, and form. All could don and doff the device with minimal assistance. These findings demonstrate that the PMEO is a viable option to enhance ADL function for patients with BPI.

Wearable sensors are increasingly used to monitor physical activity, yet low-power devices often rely on data aggregation to conserve battery life, potentially impacting measurement accuracy. This study evaluates the performance of a new low-power wearable (LPW), designed for monitoring steps across multiple months in a free-living environment, compared to a research-grade sensor (RGS) that collects raw acceleration data, with a focus on how different aggregation intervals impact step count accuracy. Thirty-two participants wore both sensors over two days, with LPW data collected in 10 min, 1 min, or 10 s aggregation periods (APs). Sensitivity and specificity of wear time detection were high across all APs (0.96 and 0.98, respectively). While total daily step count error did not differ significantly between APs, the 10 min AP exhibited greater undercounting and wider limits of agreement, especially in APs containing more than 40 steps. These findings suggest that although AP does not affect total daily step count, it influences the accuracy and variability of more granular data windows. Aggregating step counts over longer intervals may obscure short, fragmented bouts common in daily activity, leading to underestimation of steps. Optimizing APs and sensor settings is critical for improving accuracy in low-power wearables used outside laboratory settings.

PURPOSE:This study analyzed the contributions of pronator teres (PT) and pronator quadratus (PQ) during different forearm pronation tasks using dynamic EMG to assess whether the function of these two muscles can be distinguished by elbow positioning during muscle activation testing. METHODS:Twelve healthy subjects were studied. Each subject underwent intramuscular dynamic EMG of the PT and PQ to evaluate muscle activation during forearm pronation at varying elbow flexion angles (elbow fully extended, elbow flexed 90°, and elbow maximally flexed). EMG data were collected under three conditions: maximal voluntary isometric contraction, no resistance, and high resistance. The primary outcome was the proportion of participants who exceeded the muscle activation threshold at each testing position. RESULTS:All participants demonstrated muscular activation of the PQ and PT, with all motions assessed when resistance was applied. However, the muscular activity varied when participants completed movements without resistance. Seven participants (58.3%, [32%-81%]) demonstrated simultaneous activation (≥10% maximal voluntary isometric contraction) of the PQ and PT with the elbow fully extended and elbow flexed 90°, whereas nine (75%, [43%-95%]) demonstrated simultaneous activation with the elbow maximally flexed. Six of twelve participants (50%, [21%-79%]) demonstrated simultaneous activation during all movements assessed with and without resistance. CONCLUSIONS:The findings suggest that the function of the PT and PQ cannot be isolated by elbow flexion positioning. CLINICAL RELEVANCE:When a precise functional assessment of the pronator group is needed for preoperative planning, a dynamic EMG assessment should be performed.

Background/Objectives: Traditional fusion leads to a loss of spine mobility across the fused vertebrae. Vertebral body tethering (VBT) was developed with the goal of increasing flexibility and maintaining some spinal mobility. However, it is not known if the additional mobility leads to significant functional improvement. This prospective motion analysis study evaluates functional outcomes, specifically gait stability, in pre-operative, post-fusion, and post-VBT patients by using postural perturbations on a treadmill. Methods: Overall, 79 subjects underwent a computer-controlled treadmill study with postural perturbations, which simulated trips and slips. The subjects were harnessed for safety. Overall, 21 subjects were healthy controls, 18 patients were at least one-year post-VBT, 15 patients were at least one-year post-fusion, and 25 were pre-operative scoliosis patients. Subject weight, height, and treadmill acceleration were recorded and used to determine anteroposterior single (ASSTs, PSSTs) and multiple (AMSTs, PMSTs) stepping thresholds to describe the maximum torque a patient could withstand before failing to recover from the simulated trip. Independent t-tests were run to compare groups under the advice of a master statistician with expertise in orthopedic surgery. Results: Pre-operative scoliosis patients had lower PSSTs than healthy controls (uncorrected p = 0.036). No significant differences were observed between pre-operative and post-operative groups for both fusion and VBT. There was no significant difference in ASST, AMST, or PMST between any of the groups. Conclusions: The lower PSST in pre-operative scoliosis patients compared to healthy controls may reflect impaired reactive balance and potentially increased fall risk. Interestingly, there was no significant difference in reactive balance measures between pre-operative and post-operative scoliosis patients or between post-fusion and post-VBT patients.

Gait and balance disorders are a leading cause of morbidity, mortality, and disability in central and peripheral neurologic disorders. Neurologic gait disorders are classically evaluated with a clinical examination and visual pattern recognition. Gait patterns such as a parkinsonian or ataxic gait may have distinct etiologies and are assessed using the neurologic physical examination and validated clinical scales. Technological advances have made gait analysis more accessible, allowing precise objective measurement of gait and balance deficits. Gait analysis may be more sensitive at detecting change compared with a physical examination alone. It has the potential to augment clinical diagnosis, track disease progression, and evaluate response to therapies in clinical trials. Additional applications of gait analysis include early disease screening, discriminating between conditions that have similar gait profiles, and use of quantified gait parameters to predict future outcomes. Numerous devices are now available to conduct gait performance measurements in the laboratory, clinic, or real-world settings. With the rapid growth of gait analysis technology and application of artificial intelligence to these data, there are clinical and research implications that should be carefully considered when evaluating patients with neurologic disorders. Important factors include the clinical or research question, reliability and validity of the method used, and the effect of environmental and patient factors. Knowledge of gait analysis technology is essential for clinicians to implement this tool in clinical practice or research and critically analyze literature on the topic in neurologic diseases. In this narrative review, we provide an overview of normal gait function, an appraisal of available gait analysis technologies (merits and applications), implications for clinicians and researchers, recent advances in gait analysis for neurologic disorders, and future considerations.

Progressive supranuclear palsy (PSP) is a neurodegenerative disease with severe gait and balance deficits. There are no effective ways to assess dynamic balance during walking in PSP. The Lyapunov Floquet (LF) theory has been utilized to study dynamic balance in healthy and pathologic gait but has not been applied to PSP affected gait. In the current study, the medio-lateral motion of the center of mass during gait for 40 patients with PSP (PSP group) and 33 healthy older adults (Control group) were studied. Metrics from LF theory, such as the maximal Floquet multiplier (FM), maximal long-term Lyapunov Exponent (LE ${}_{\text {L}}\text {)}$ , and maximal short-term Lyapunov Exponent (LE ${}_{\text {S}}\text {)}$ were used to study walking stability. Although all the gait dynamics for all the participants were stable and non-chaotic, the PSP group was observed to be closer to an unstable system and more susceptible to perturbations ( $\vert $ FM $\vert $ closer to 1 and LEL closer to 0) than the Control group (p < 0.001). The control group's stability deteriorated, and the gait system became more susceptible to perturbations with age. Such a trend was not observed in the PSP group. The risk of falls increased with increase in cadence in the PSP group (p < 0.001). These findings demonstrate the potential of LF theory measures to evaluate dynamic stability in patients with PSP and the need for future research using quantitative measures.

PURPOSE:Traumatic brachial plexus injury may cause either partial or complete loss of arm function. Surgical reconstruction of elbow flexion using a gracilis free-functioning muscle transfer (FFMT) may be necessary. The donor nerve, which could be the spinal accessory nerve (SAN) or intercostal nerves (ICN), can affect the final muscle strength, but little is known about how they affect voluntary neuromuscular control. This study aimed to examine the differences in voluntary neuromuscular control of the FFMT gracilis reinnervated by either SAN or ICN using biomechanical measures. METHODS:Patients with a gracilis FFMT for elbow flexion innervated with SAN or ICN (2-3 motor nerves) were studied. The voluntary control of their gracilis-produced elbow flexion was evaluated on a previously validated apparatus. Subjects were instructed to produce a predefined torque relative to their maximum elbow flexion torque. Objective measures of neuromuscular control, including elbow flexor contraction latency, relaxation latency, and duration of successfully achieved demanded torque, were studied. RESULTS:Twenty-two subjects were identified, 12 with SAN and 10 with ICN as the donor nerve to reinnervate the FFMT gracilis muscle for elbow flexion. The SAN group displayed a similar ability to contract and a better ability to relax elbow flexion produced by the gracilis muscle compared with the ICN group. The SAN group also demonstrated better modulation in their hold times with an increase in torque demand compared with the ICN group. CONCLUSIONS:This study demonstrated the superior neuromuscular control of SAN over ICN for control. TYPE OF STUDY/LEVEL OF EVIDENCE:Therapeutic IV.