Sensorimotor control of functional joint stability: Scientific concepts, clinical considerations, and the articuloneuromuscular cascade paradigm in peripheral joint injury.

Human movement depends on sensorimotor control. Sensorimotor control refers to central nervous system (CNS) control of joint stability, posture, and movement, all of which are effected via the sensorimotor system. Given the nervous, muscular, and skeletal systems function as an integrated "neuromusculoskeletal system" for the purpose of executing movement, musculoskeletal conditions can result in a cascade of impairments that affect negatively all three systems. The purpose of this article is to revisit concepts in joint stability, sensorimotor control of functional joint stability (FJS), joint instability, and sensorimotor impairments contributing to functional joint instability. This article differs from historical work because it updates previous models of joint injury and joint instability by incorporating more recent research on CNS factors, skeletal muscle factors, and tendon factors. The new 'articuloneuromuscular cascade paradigm' presented here offers a framework for facilitating further investigation into physiological and biomechanical consequences of joint injury and, in turn, how these follow on to affect physical activity (functional) capability. Here, the term 'injury' represents traumatic joint injury with a focus is on peripheral joint injury. Understanding the configuration of the sensorimotor system and the cascade of post-injury sensorimotor impairments is particularly important for clinicians reasoning rational interventions for patients with mechanical instability and functional instability. Concurrently, neurocognitive processing and neurocognitive performance are also addressed relative to feedforward neuromuscular control of FJS. This article offers itself as an educational resource and scientific asset to contribute to the ongoing research and applied practice journey for developing optimal peripheral joint injury rehabilitation strategies.

Impact of whole-body vibration training on ankle joint proprioception and balance in stroke patients: a prospective cohort study.

BACKGROUND: Although whole-body vibration (WBV) training is acknowledged for its benefits in enhancing motor functions across several neurological disorders, its precise influence on ankle joint proprioception and balance in stroke patients is still not well understood. This research seeks to assess the impact of WBV training on ankle joint proprioception and balance in stroke patients, thereby filling this important research void. METHODS: In this prospective cohort study, thirty-five stroke patients were randomly assigned to either the WBV group (n = 17) or a control group (n = 18) using a random number table method. The control group received daily general rehabilitation for four weeks, while the WBV group received an additional 30 min of WBV training each day with the Trunsan S110 Vibration Training System. Blinded outcome assessments were conducted at baseline and post-treatment, utilizing the Berg balance scale (BBS), Functional reach test (FRT), Romberg test length (RTL) and area (RTA), and completion rates of ankle joint dorsiflexion-plantar flexion (DP) and inversion-eversion (IE) tests. Follow-up assessments were performed after four weeks of intervention, focusing on RTL, RTA, DP, and IE as primary outcomes. RESULTS: Analysis of intra-group changes from baseline to post-treatment revealed significant improvements across the BBS, FRT, RTL, RTA, and DP and IE assessments (p < 0.001). Notably, the WBV group showed significant enhancements compared to the control group in DP and IE (p < 0.001 and p < 0.05, respectively), with mean values increasing from 13.556 to 16.765 (23.7%) and from 5.944 to 8.118 (36.6%), respectively. However, WBV did not provide additional benefits over the control treatment for balance recovery parameters such as BBS, FRT, RTL, and RTA (p > 0.05). CONCLUSIONS: This study demonstrates that WBV therapy is equally effective as conventional methods in enhancing proprioception and balance in stroke patients, but it does not provide additional benefits for balance recovery. WBV significantly improves proprioceptive functions, particularly in DP and IE parameters. However, it does not surpass traditional rehabilitation methods in terms of balance recovery. These findings indicate that WBV should be incorporated into stroke rehabilitation primarily to enhance proprioception rather than to optimize balance recovery. TRIAL REGISTRATION: This study was retrospectively registered in the ISRCTN Registry on 29/07/2024 ( https://www.isrctn.com/ , ISRCTN64602845).

Balancing Function and Proprioception: A Case Report Featuring Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM)-Fabricated Marburg Denture System.

The ultimate purpose of a partial prosthetic denture is to protect the rest of the teeth as their discarded functionality is being put back together. A Marburg double crown is a form of retainer that works well by providing splinting action between many abutment teeth as well as retention and support. Compared to traditional clasp-retained removable partial dentures (RPDs), the Marburg double crown transfers load to the abutment teeth's long axis. The Marburg double crown system fabricated efficiently using the computer-aided design/computer-aided manufacturing (CAD/CAM) system for treating partially edentulous patients is highlighted in this case report.

Maintained volitional activation of the muscle alters the cortical processing of proprioceptive afference from the ankle joint.

Cortical proprioceptive processing of intermittent, passive movements can be assessed by extracting evoked and induced electroencephalographic (EEG) responses to somatosensory stimuli. Although the existent prior research on somatosensory stimulations, it remains unknown to what extent ongoing volitional muscle activation modulates the proprioceptive cortical processing of passive ankle-joint rotations. Twenty-five healthy volunteers (28.8 ± 7 yr, 14 males) underwent a total of 100 right ankle-joint passive rotations (4° dorsiflexions, 4 ± 0.25 s inter-stimulus interval, 30°/s peak angular velocity) evoked by a movement actuator during passive condition with relaxed ankle and active condition with a constant plantarflexion torque of 5 ± 2.5 Nm. Simultaneously, EEG, electromyographic (EMG) and kinematic signals were collected. Spatiotemporal features of evoked and induced EEG responses to the stimuli were extracted to estimate the modulation of the cortical proprioceptive processing between the active and passive conditions. Proprioceptive stimuli during the active condition elicited robustly ∼26 % larger evoked response and ∼38 % larger beta suppression amplitudes, but ∼42 % weaker beta rebound amplitude over the primary sensorimotor cortex than the passive condition, with no differences in terms of response latencies. These findings indicate that the active volitional motor task during naturalistic proprioceptive stimulation of the ankle joint enhances related cortical activation and reduces related cortical inhibition with respect to the passive condition. Possible factors explaining these results include mechanisms occurring at several levels of the proprioceptive processing from the peripheral muscle (i.e. mechanical, muscle spindle status, etc.) to the different central (i.e. spinal, sub-cortical and cortical) levels.

Toward mechanical proprioception in autonomously reconfigurable kirigami-inspired mechanical systems.

Mechanical metamaterials have recently been exploited as an interesting platform for information storing, retrieval and processing, analogous to electronic devices. In this work, we describe the design and fabrication a two-dimensional (2D) multistable metamaterial consisting of building blocks that can be switched between two distinct stable phases, and which are capable of storing binary information analogous to digital bits. By changing the spatial distribution of the phases, we can achieve a variety of different configurations and tunable mechanical properties (both static and dynamic). Moreover, we demonstrate the ability to determine the phase distribution via simple probing of the dynamic properties, to which we refer as mechanical proprioception. Finally, as a simple demonstration of feasibility, we illustrate a strategy for building autonomous kirigami systems that can receive inputs from their environment. This work could bring new insights for the design of mechanical metamaterials with information processing and computing functionalities. This article is part of the theme issue 'Origami/Kirigami-inspired structures: from fundamentals to applications'.

Agonist-antagonist myoneural interface surgery on the proprioceptive reconstruction of rat hind limb.

Currently, prosthesis users rely on visual cues to control their prosthesis. One reason for this is that prostheses cannot provide users with proprioceptive functional signals. For this reason, we propose an agonist-antagonist myoneural interface (AMI) surgery. We examined how this surgery affects the restoration of motor function and proprioceptive reconstruction in the hind limb of Sprague-Dawley rats. The procedure entails grafting the soleus muscle, suturing the two tendon ends of the soleus muscle, and anastomosing the tibial and common peroneal nerves to the soleus muscle. We found that, following surgery, AMI rats exhibited improved neurological repair, shorter walking swings, braking, propulsion, and stance times, and greater compound action potentials than control rats. This means that in rats with neurological impairment of the hind limb, the proposed AMI surgical method significantly improves postoperative walking stability and muscle synergy. AMI surgery may become an option for regaining proprioception in the lost limb.

Does proprioceptive reweighting contribute to reactive balance strategies during slip-like perturbations? a proof-of-concept in healthy adults.

Falls commonly occur during walking, particularly when struggling to respond to unexpected perturbations. Proprioception plays a significant role in detecting body destabilization even before reactions to perturbations are required. This study investigates the contribution of proprioceptive reweighting strategies to reactive balance during walking. This cross-sectional, proof-of-concept study included fifteen healthy adults (18-40 years). Ankle and back muscle vibrators disrupted proprioceptive input in stance, allowing calculation of the proprioceptive reweighting index. Walk-slip perturbations were then administered on an ActiveStep treadmill. A linear regression model assessed the significance of proprioceptive reweighting in predicting post-slip stability (margin of stability). Participants shifted from an ankle-steered to a central-steered proprioceptive strategy on a foam surface with closed eyes (Difference = 15.70 % (SD=37.87), 95 %CI [0.41, 30.99], p = 0.045). The regression model explained 22.7 % of the variance in pre-touchdown margin of stability, with proprioceptive reweighting on foam significantly contributing to post-perturbation postural control (p < 0.001). Proprioceptive reweighting provides a moderate explanation for the mechanisms of reactive balance, highlighting that the key to effective balance recovery strategies may lie in the person's ability to both detect and respond to imbalances. Further research should explore if these proprioceptive strategies are a matter of directional control and if responses differ in older adults.

Somatosensory cortex and body representation: Updating the motor system during a visuo-proprioceptive cue conflict.

The brain's representation of hand position is critical for voluntary movement. Representation is multisensory, relying on both visual and proprioceptive cues. When these cues conflict, the brain recalibrates its unimodal estimates, shifting them closer together to compensate. Converging lines of evidence from research in perception, behavior, and neurophysiology suggest that such updates to body representation must be communicated to the motor system to keep hand movements accurate. We hypothesized that primary somatosensory cortex (S1) plays a crucial role in conveying the proprioceptive aspects of the updated body representation to the motor system. We tested this hypothesis in two experiments. We predicted that proprioceptive, but not visual, recalibration would be associated with change in short latency afferent inhibition (SAI), a measure of sensorimotor integration (influence of sensory input on motor output) (Expt. 1). We further predicted that modulating S1 activity with repetitive transcranial magnetic stimulation (TMS) should affect variance and recalibration associated with the proprioceptive estimate of hand position, but have no effect on the visual estimate (Expt. 2). Our results are consistent with these predictions, supporting the idea that (1) S1 is indeed a key region in facilitating motor system updates based on changes in body representation, and (2) this function is mediated by unisensory (proprioceptive) processing, upstream of multisensory visuo-proprioceptive computations. Other aspects of the body representation (visual and multisensory) may be conveyed to the motor system via separate pathways, e.g. from posterior parietal regions to motor cortex.

Impairments in Proprioceptively-Referenced Limb and Eye Movements in Chronic Stroke.

BACKGROUND: Upper limb proprioceptive impairments are common after stroke and affect daily function. Recent work has shown that stroke survivors have difficulty using visual information to improve proprioception. It is unclear how eye movements are impacted to guide action of the arm after stroke. Here, we aimed to understand how upper limb proprioceptive impairments impact eye movements in individuals with stroke. METHODS: Control (N = 20) and stroke participants (N = 20) performed a proprioceptive matching task with upper limb and eye movements. A KINARM exoskeleton with eye tracking was used to assess limb and eye kinematics. The upper limb was passively moved by the robot and participants matched the location with either an arm or eye movement. Accuracy was measured as the difference between passive robot movement location and active limb matching (Hand-End Point Error) or active eye movement matching (Eye-End Point Error). RESULTS: We found that individuals with stroke had significantly larger Hand (2.1×) and Eye-End Point (1.5×) Errors compared to controls. Further, we found that proprioceptive errors of the hand and eye were highly correlated in stroke participants (r = .67, P = .001), a relationship not observed for controls. CONCLUSIONS: Eye movement accuracy declined as a function of proprioceptive impairment of the more-affected limb, which was used as a proprioceptive reference. The inability to use proprioceptive information of the arm to coordinate eye movements suggests that disordered proprioception impacts integration of sensory information across different modalities. These results have important implications for how vision is used to actively guide limb movement during rehabilitation.

Effects of postural and kinesthetic awareness on static standing balance and plantar pressure in chronic stroke: a randomized controlled trial.

OBJECTIVE: To determine effects of postural and kinesthetic awareness on plantar pressure and static standing stability in chronic stroke patients. METHODS: The cross-sectional single-blind study was conducted at the University of Lahore Teaching Hospital, Lahore, Pakistan, from January 19 to March 2, 2023, and comprised stroke patients of both genders. aged 45-60 years having visual spatial neglect. They were randomised into control group A and experimental group B. Group A received routine physical therapy, while group B additionally received postural and kinesthetic awareness sessions. Static component of the Berg balance scale was used to measure balance, and PoData Stabiliometeric plate ("Chinesport, Italy") to measure plantar pressure. Data was analysed using SPSS version 25. RESULTS: Of the 52 patients, 26(50%) were in group A with mean age 51.97±4.37 years and mean weight 79.48±5.7kg. The remaining 26(50%) patients were in group B with mean age 50.69±4.41 years and mean weight 78.27±4.55kg. The outcome measures were significantly better in group B compared to group A (p<0.05). CONCLUSIONS: Postural and kinesthetic awareness could possibly be a well-grounded rehabilitative strategy that may support and enhance the balance of individuals with chronic stroke. Clinical Trial Number: The study was registered at the United States National Institutes of Health (ClinicalTrials.gov) with registration number NCT05915195.

Cervical Spine Vibration Modifies Oculomotor Function in Young Adults with Traumatic Brain Injury.

OBJECTIVE: The purpose of this study was to investigate if vibrational interference of spinal proprioception affects oculomotor function, visual attention and processing, and selective attention in individuals with mild traumatic brain injury (mTBI) compared to healthy age-matched controls. METHODS: This study was a parallel design, single-session intervention with 20 young adults with mTBI and 20 age-matched controls. Each completed a battery of computerized eye-tracking assessments (CEAs), including egocentric localization, fixational stability, smooth pursuit, saccades, Stroop, and the vestibulo-ocular reflex (VOR), and then had their cervical spine function (flexion-relaxation ratio) recorded at baseline. Spinal vibration (100 Hz) was applied to the cervical spine and the CEA battery was repeated. CEA outcomes were compared to baseline and between mTBI and control groups. RESULTS: Following cervical vibration, significant pre to post-differences were seen in both the mTBI and control group for egocentric localization, fixation stability, pursuit, saccades, Stroop, and VOR. At baseline, there was a significant difference between the mTBI and control groups across many CEA measures, with the mTBI group performing more poorly in egocentric localization, pursuit, saccades, Stroop, and VOR. The mTBI group also had a poorer flexion-relaxation ratio than the control group. CONCLUSION: Cervical spine vibration improved cognitive and oculomotor performance in the mTBI group for VOR, Stroop, and pursuit, but had mixed effects on the control group. These findings suggest that some optometric mTBI symptoms may result from spinal or proprioceptive dysfunction, as altering proprioceptive input appears to positively impact visual outcomes.

Bayesian inference in arm posture perception.

To configure our limbs in space the brain must compute their position based on sensory information provided by mechanoreceptors in the skin, muscles, and joints. Because this information is corrupted by noise, the brain is thought to process it probabilistically, and integrate it with prior belief about arm posture, following Bayes' rule. Here, we combined computational modeling with behavioral experimentation to test this hypothesis. The model conceives the perception of arm posture as the combination of a probabilistic kinematic chain composed by the shoulder, elbow, and wrist angles, compromised with additive Gaussian noise, with a Gaussian prior about these joint angles. We tested whether the model explains errors in a VR-based posture matching task better than a model that assumes a uniform prior. Human participants were required to align their unseen right arm to a target posture, presented as a visual configuration of the arm in the horizontal plane. Results show idiosyncratic biases in how participants matched their unseen arm to the target posture. We used maximum likelihood estimation to fit the Bayesian model to these observations and estimate key parameters including the prior means and its variance-covariance structure. The Bayesian model including a Gaussian prior explained the response biases and variance much better than a model with a uniform prior. The prior varied across participants, consistent with the idiosyncrasies in arm posture perception, and in alignment with previous behavioral research. Our work clarifies the biases in arm posture perception within a new perspective on the nature of proprioceptive computations.

Microinstability of Major Joints in Movement Disorders: The Hidden Challenge.

Microinstability, characterized by subtle and often painful disturbances in joint stability, significantly impacts individuals engaged in activities requiring extensive ranges of motion, such as dancing or gymnastics, and is particularly prevalent in young female athletes. This condition, resulting from progressive microtrauma, architectural and functional abnormalities, or iatrogenic factors, is challenging to diagnose and often underreported. Understanding the biomechanical nuances of microinstability is essential for accurate diagnosis and effective management. Upper limb joints, including the shoulder, elbow, wrist, and hand, each exhibit unique anatomical and functional characteristics that contribute to their susceptibility to microinstability. Movement disorders, such as Parkinson's disease, essential tremor, dystonia, and cerebral palsy, exacerbate joint instability due to impaired proprioception, altered muscle tone, and uncoordinated muscle contractions. Effective diagnosis involves physical examination techniques and advanced imaging modalities. Therapeutic interventions encompass physical therapy, pharmacological treatments, surgical procedures, and assistive devices, tailored to enhance joint stability and improve the quality of life for affected individuals.

Proprioception and its relationship with range of motion in hypermobile and normal mobile children.

To investigate differences in proprioception using four proprioceptive tests in children with and without hypermobility. Additionally, it was tested if the results on one proprioceptive test predict the results on the other tests. Of the children (8-11years), 100 were classified as normal mobile (Beighton score 0-4) and 50 as hypermobile (Beighton score 5-9). To test proprioception, in the upper extremity the unilateral and bilateral joint position reproduction tasks were used and for the lower extremity the loaded and unloaded wedges task. No differences were found in any of the proprioception tests between the two groups. Estimating the height of the wedges was easier in the loaded position (mean penalty in standing and sitting position, 4.78 and 6.19, respectively). Recalling the elbow position in the same arm resulted in smaller errors compared to tasks reproducing the position with the contralateral arm. Of the four angles used (110°, 90°, 70°, 50°), the position recall in the 90° angle had the smallest position error (1.8°). Correlations between the proprioception tests were weak (Loaded and Unloaded (r 0. 28); Uni and Bilateral (r 0.39), Upper and Lower extremity not significant). No indication of poorer proprioception was found in children with hypermobile joints compared to their normal mobile peers. Loading gives extra information that leads to fewer errors in the wedges task performed while standing, but this effect is independent of joint mobility. Proprioception test outcomes are dependent on the test used; upper extremity results do not predict lower extremity outcomes or vice versa.

No difference in laxity, proprioception and neuromuscular control after suture-tape augmented ACL repair of acute proximal avulsions versus ACL reconstruction using hamstring autografts in young, active population.

Purpose: The purpose of this study is to compare results of suture-tape augmented anterior cruciate ligament (ACL) repair (internal bracing [IB]) and ACL reconstruction (ACLR) with hamstring autograft in terms of laxity, proprioception and neuromuscular control. The hypothesis was that with strict indications IB may provide better results in proprioception and neuromuscular control. Methods: Patients with unilateral ACL injury treated with IB or ACLR with hamstring autograft were enroled in this retrospective study. Anterior tibial translation (ATT) in 30° and 90° of flexion was measured with Rolimeter. The joint position sense (JPS) test was performed in 30° and 60° of flexion using Biodex System 4Pro. The time-synchronized motion capture system and surface electromyography set were used during dynamic tasks to assess knee valgus and semitendinosus (ST) and biceps femoris (BF) activities. Comparisons between both techniques and operated versus contralateral healthy knees were performed. Results: The study groups involved 28 patients after ACLR (21.8 ± 4.8 years) and 20 patients after IB (25.8 ± 10.5 years) with the average follow-up 30 ± 18 and 28 ± 15 months, respectively. The ATT did not differ significantly between operated groups. In 30° of flexion ATT for ACLR was significantly higher in operated than in contralateral knee (5.8 ± 2.4 mm vs. 4.3 ± 1.3 mm, p < 0.001). The JPS test and dynamic knee valgus presented no significant differences. The ACLR group presented significantly higher ST (p = 0.048) and BF (p = 0.012) activity comparing operated to contralateral knee in dynamic tasks. Conclusion: Suture-tape augmented ACL repair and ACLR with hamstring autograft yield similar results in terms of laxity, proprioception and neuromuscular control. Level of Evidence: Level III: Retrospective comparative study.

Eyes and hand are both reliable at localizing somatosensory targets.

Body representations (BR) for action are critical to perform accurate movements. Yet, behavioral measures suggest that BR are distorted even in healthy people. However, the upper limb has mostly been used as a probe so far, making difficult to decide whether BR are truly distorted or whether this depends on the effector used as a readout. Here, we aimed to assess in healthy humans the accuracy of the eye and hand effectors in localizing somatosensory targets, to determine whether they may probe BR similarly. Twenty-six participants completed two localization tasks in which they had to localize an unseen target (proprioceptive or tactile) with either their eyes or hand. Linear mixed model revealed in both tasks a larger horizontal (but not vertical) localization error for the ocular than for the manual localization performance. However, despite better hand mean accuracy, manual and ocular localization performance positively correlated to each other in both tasks. Moreover, target position also affected localization performance for both eye and hand responses: accuracy was higher for the more flexed position of the elbow in the proprioceptive task and for the thumb than for the index finger in the tactile task, thus confirming previous results of better performance for the thumb. These findings indicate that the hand seems to beat the eyes along the horizontal axis when localizing somatosensory targets, but the localization patterns revealed by the two effectors seemed to be related and characterized by the same target effect, opening the way to assess BR with the eyes when upper limb motor control is disturbed.

Using Electrical Muscle Stimulation to Enhance Electrophysiological Performance of Agonist-Antagonist Myoneural Interface.

The agonist-antagonist myoneural interface (AMI), a surgical method to reinnervate physiologically-relevant proprioceptive feedback for control of limb prostheses, has demonstrated the ability to provide natural afferent sensations for limb amputees when actuating their prostheses. Following AMI surgery, one potential challenge is atrophy of the disused muscles, which would weaken the reinnervation efficacy of AMI. It is well known that electrical muscle stimulus (EMS) can reduce muscle atrophy. In this study, we conducted an animal investigation to explore whether the EMS can significantly improve the electrophysiological performance of AMI. AMI surgery was performed in 14 rats, in which the distal tendons of bilateral solei donors were connected and positioned on the surface of the left biceps femoris. Subsequently, the left tibial nerve and the common peroneus nerve were sutured onto the ends of the connected donor solei. Two stimulation electrodes were affixed onto the ends of the donor solei for EMS delivery. The AMI rats were randomly divided into two groups. One group received the EMS treatment (designated as EMS_on) regularly for eight weeks and another received no EMS (designated as EMS_off). Two physiological parameters, nerve conduction velocity (NCV) and motor unit number, were derived from the electrically evoked compound action potential (CAP) signals to assess the electrophysiological performance of AMI. Our experimental results demonstrated that the reinnervated muscles of the EMS_on group generated higher CAP signals in comparison to the EMS_off group. Both NCV and motor unit number were significantly elevated in the EMS_on group. Moreover, the EMS_on group displayed statistically higher CAP signals on the indirectly activated proprioceptive afferents than the EMS_off group. These findings suggested that EMS treatment would be promising in enhancing the electrophysiological performance and facilitating the reinnervation process of AMI.

Knee joint position sense and kinematic control in relation to motor competency in 13 to 14-year-old adolescents.

BACKGROUND: Motor competence (MC) is a key component reflecting one's ability to execute motor tasks and is an important predictor of physical fitness. For adolescents, understanding the factors affecting MC is pertinent to their development of more sophisticated sporting skills. Previous studies considered the influence of poor proprioceptive ability on MC, however, the relationship between lower limb joint position sense, kinematic control, and MC is not well understood. Therefore, the aim of this study was to determine the relation between joint position sense and kinematic control with MC in adolescents during a lower limb movement reproduction task. METHODS: This study was a cross-sectional design. Young people (n = 427, 196 girls and 231 boys) aged 13 to 14 years were recruited. A movement reproduction task was used to assess joint position sense and kinematic control, while the Movement Assessment Battery for Children (mABC-2) was used to assess MC. In this study, participants were categorized into the Typically Developed (TD, n = 231) and Probable Developmental Coordination Disorder (DCD, n = 80) groups for further analysis of joint position sense, kinematic control, and MC between groups. RESULTS: Kinematic data, specifically normalized jerk, showed a significant correlation with MC. There was no correlation between knee joint position sense and MC, and no group differences between DCD and TD were found. CONCLUSIONS: Joint position sense should not be used as a measure to distinguish TD and DCD. Rather than joint position sense, control of kinematic movement has a greater influence on the coordination of the lower limbs in adolescents. Movement control training should be implemented in the clinical setting to target kinematic control, rather than focus on joint position sense practice, to improve motor competency. TRIAL REGISTRATION IDENTIFIER: NCT03150784. Registered 12 May 2017, https://clinicaltrials.gov/study/NCT03150784 .

Comparing postoperative proprioception of the glenohumeral joint between the open and the arthroscopic Latarjet procedure.

BACKGROUND: Shoulder proprioception, in which the anterior glenohumeral capsule plays a major role, is critical to the functioning of the shoulder. Consequently, most surgeons either do not resect or reinsert the anterior capsule in shoulder stabilization surgery. In the original open Latarjet procedure (OLP), the anterior capsule is preserved. However, in the all-arthroscopic Latarjet procedure (ALP), complete anterior capsule resection is recommended for better view and access to the coracoid. This raises the question if there is a postoperative difference in proprioception between these 2 procedures. Therefore, the aims of this study are (1) to assess the difference in postoperative proprioception between the operated and healthy sides after the OLP and ALP and (2) to compare the difference in postoperative proprioception on the operated side between the OLP and ALP. METHODS: We conducted a retrospective analysis including all patients who underwent a proprioception test after an OLP or ALP at our center. Collected baseline characteristics included sex, age at surgery, operated side, hand dominance, presence of a Hill-Sachs lesion, and time between surgery and the proprioception test. For the test, patients were positioned 1 meter from a wall. They were blindfolded and had to point at a target with a laser pointer taped to their index finger. The laser point was marked and the errors were measured horizontally and vertically and categorized as <4 cm, 4-8 cm, 8-16 cm, and >16 cm. RESULTS: Between April 2022 and April 2024, a total of 91 cases were identified, of which 24 underwent an OLP and 67 underwent an ALP. No significant difference was found in error distribution between the healthy and operated side after both the OLP (P = .30 horizontally, P = .67 vertically) and ALP (P = .20 horizontally, P = .34 vertically). Moreover, there was no significant difference in error distribution between the operated sides after the OLP vs. ALP (P = .52 horizontally; P = .61 vertically). CONCLUSION: Our data suggest that postoperative proprioception is not significantly different between the operated and healthy sides after both the OLP and ALP, nor between the operated sides after the OLP vs. after the ALP. This might imply that completely resecting the anterior glenohumeral capsule does not have a detrimental effect on shoulder proprioception. However, these results are multifactorial and prospective studies are needed to better understand the regeneration potential of glenohumeral capsule mechanoreceptors and the importance of the anterior capsule for shoulder proprioception.

Peripheral neuropathy, an independent risk factor for falls in the elderly, impairs stepping as a postural control mechanism: A case-cohort study.

BACKGROUND/AIMS: Peripheral neuropathies perturbate the sensorimotor system, causing difficulties in walking-related motor tasks and, eventually, falls. Falls result in functional dependency and reliance on healthcare, especially in older persons. We investigated if peripheral neuropathy is a genuine risk factor for falls in the elderly and if quantification of postural control via posturography is helpful in identifying subjects at risk of falls. METHODS: Seventeen older persons with a clinical polyneuropathic syndrome of the lower limbs and converging electrophysiology were compared with 14 older persons without polyneuropathy. All participants were characterized via quantitative motor and sensory testing, neuropsychological assessment, and self-questionnaires. Video-nystagmography and caloric test excluded vestibulocochlear dysfunction. For further analysis, all subjects were stratified into fallers and non-fallers. Overall, 28 patients underwent computerized dynamic posturography for individual fall risk assessment. Regression analyses were performed to identify risk factors and predictive posturography parameters. RESULTS: Neuropathy is an independent risk factor for falls in the elderly, while no differences were observed for age, gender, weight, frailty, DemTect test, timed "Up & Go" test, and dizziness-related handicap score. In computerized dynamic posturography, fallers stepped more often to regain postural control in challenging conditions, while the Rhythmic Weight Shift test showed a lack of anterior-posterior bidirectional voluntary control. INTERPRETATION: Our study confirms peripheral neuropathy as a risk factor for older persons' falls. Fallers frequently used stepping to regain postural control. The voluntary control of this coping movement was impaired. Further investigations into these parameters' value in predicting the risk of falls in the elderly are warranted.