Flexion withdrawal reflex as recorded from single human biceps femoris motor neurones (2023)

Citation Excerpt :

The physiology of individual anterior horn cells can be studied by selective SFEMG recordings of F responses (Fig. 13) (Trontelj, 1973a) and H reflexes (Trontelj, 1973b). Polyneuronal reflexes such as the blink reflex, sacral reflexes and flexion reflex can be studied by measuring jitter in the SFAP responses after reflex activation (Trontelj and Trontelj, 1978; Vodušek et al., 1982; Janko and Trontelj, 1983). The SFE jitter in responses to transcortical electrical stimulation has been studied to assess the physiology of the entire motor pathway (Rossini et al., 1988).

The present study examines the inhibitory effect of segmentally applied TENS on the nociceptive component of the flexion reflex elicited in various lower limb muscles, in an attempt to gain some insight into the underlying mechanism.

The flexion reflex from 11 normal subjects was recorded electromyographically from the biceps femoris (BF), the tibialis anterior (TA), and in 2 subjects, the hip flexor (HF), in the manner described in a previous paper [9]. Amplitude and area values of the flexion reflex of each muscle were computerized prior to, during, and 50 min after the application of placebo or low intensity TENS at 100 Hz, for 30 min to the low back, at levels of segmentai innervation (L4-S1) similar to those of the muscles under study.

In the majority of subjects, we found that:

• 1.

  (1) Low intensity TENS caused a significant inhibition of the flexion reflex in proximal limb flexors. Thus, the BF measured 64% and 52%, and the HF 45% and 51%, of their respective mean control amplitude and area values at the time of maximum inhibition during TENS.

• 2.

  (2) Moreover, less reduction of the mean values of the flexion reflex was observed in the TA, a distal limb (ankle) flexor.

• 3.

  (3) It is noteworthy that in both the BF and HF, the time to peak maximum inhibitory effect took 30 and 20 min respectively after the onset of TENS, and the flexion reflex often did not return to control values even at 40–50 min after TENS.

  (Video) REFLEXES IN UMN LESIONS 4TH YR

• 4.

  (4) In contrast, placebo TENS application resulted in no significant change of the flexion reflex in all the muscles examined.

These findings showed that prolonged stimulation of large diameter fibers by conventional TENS application to the lumbosacral level, exerts a progressive and long latency inhibitory influence on a number of lower limb flexor motoneurons. In keeping with functional demand, this effect was found to be more prominent on the proximal than distal limb muscles. Furthermore, a gradual onset and offset of this inhibitory action is consistent with the results of some investigators demonstrating the possible involvement of endogenous opioids.

Interventional strategies for massive and submassive pulmonary embolism (smPE) have historically included either systematic intravenous thrombolytic alteplase or surgical embolectomy, both of which are associated with significant morbidity and mortality. However, with the advent of endovascular techniques, recent studies have suggested that an endovascular approach to the treatment of acute smPE may be both safe and effective with excellent outcomes. The purpose of this study was to evaluate the outcomes of patients who have undergone catheter-directed thrombolysis (CDT) for smPE at our institution in an effort to determine the safety of the procedure.

A retrospective review was conducted from December 2012 to June 2015 to identify patients whom underwent CDT in the treatment of a smPE at our institution. Primary measure was safety of the procedure. Outcome variables were classified as serious or minor adverse events. Serious events included death, stroke, myocardial infarction, and bleeding complications requiring surgical intervention or transfusion. Minor events included groin hematoma, development of arteriovenous fistula, and bleeding requiring interruption or cessation of CDT. In addition, a secondary measure included effectiveness of CDT based on preinterventional and postinterventional clinical examination and radiographic findings.

A total of 27 patients undergoing CDT for smPE at our institution were evaluated. The standard procedure included access via bilateral femoral veins and placement of bilateral EKOS catheters for ultrasound-assisted thrombolysis (USAT), with Activase (alteplase) at 1mg per hour in each catheter for a total of 12hr. There were no serious adverse events and only 4 patients (14.8%) had minor events, of which only 1 patient required premature termination of therapy due to bleeding resulting in a 3.7% clinically relevant bleeding rate. In addition, a reduction in a right-to-left ventricular end-diastolic diameter ratio (RV/LV ratio) on follow-up imaging was observed in each of the 18 patients where preinterventional and postinterventional imaging was available. Likewise, via chart review, all patients reported significant cessation of shortness-of-breath and resolution of chest pain with associated decrease in supplemental oxygen requirement.

Current evidence, the majority of which has been industry funded, suggests that CDT should be considered as the first-line therapy for smPE. Our experience, in this single-institution retrospective review, demonstrates that CDT with USAT in the treatment of smPE is safe, while providing immediate resolution of both RV strain and clinical symptoms such as shortness-of-breath and chest pain. We hope that these data will allow other institutions to consider CDT as a plausible option in the treatment of smPE.

The increasing demand for rotator cuff (RC) repair patients to return to work as soon as they are physically able has led to exploration of when this is feasible. Current guidelines from our orthopedic surgery clinic recommend a return to work at 9 weeks postoperation. To more fully define capacity to return to work, the current study was conducted using a unique series of quantitative tools. To date, no study has combined 3-dimensional (3D) motion analysis with electromyography (EMG) assessment during activities of daily living (ADLs), including desk tasks, and commonly prescribed rehabilitation exercise.

To apply a quantitative, validated upper extremity model to assess the kinematics and muscle activity of the shoulder following repair of the supraspinatus RC tendon compared to that in healthy shoulders.

A prospective, cross-sectional comparison study.

All participants were evaluated during a single session at the Medical College of Wisconsin Department of Orthopaedic Surgery's Motion Analysis Laboratory.

Ten participants who were 9-12 weeks post–operative repair of a supraspinatus RC tendon tear and 10 participants with healthy shoulders (HS) were evaluated.

All participants were evaluated with 3D motion analysis using a validated upper extremity model and synchronized EMG. Data from the 2 groups were compared using multivariate Hotelling T² tests with post hoc analyses based on Welch t-tests.

Participants' thoracic and thoracohumeral joint kinematics, temporal-spatial parameters, and RC muscle activity were measured by applying a quantitative upper extremity model during 10 ADLs and 3 rehabilitation exercises. These included tasks of hair combing, drinking, writing, computer mouse use, typing, calling, reaching to back pocket, pushing a door open, pulling a door closed, external rotation, internal rotation, and rowing.

There were significant differences of the thoracohumeral joint motion in only a few of the tested tasks: comb maximal flexion angle (P = .004), pull door internal/external rotation range of motion (P = .020), reach abduction/adduction range of motion (P = .001), reach flexion/extension range of motion (P = .001), reach extension minimal angle (P = .025), active external rotation maximal angle (P = .012), and active external rotation minimal angle (P = .004). The thorax showed significantly different kinematics of maximal flexion angle during the call (P = .011), mouse (P = .007), and drink tasks (P = .005) between the 2 groups. The EMG data analysis showed significantly increased subscapularis activity in the RC repair group during active external rotation.

Although limited abduction was expected due to repair of the supraspinatus tendon, only a single ADL (reaching to back pocket) had a significantly reduced abduction range of motion. Thoracic motion was shown to be used as a compensatory strategy during seated ADLs. Less flexion of the thorax may create passive shoulder flexion at the thoracohumeral joint in efforts to avoid active flexion. The RC repair group participants were able to accomplish the ADLs within the same time frame and through thoracohumeral joint kinematics similar to those in the healthy shoulder group participants. In summary, this study presents a quantification of the effects of RC repair and rehabilitation on the ability to perform ADLs. It may also point to a need for increased rehabilitation focus on either regaining external rotation strength or range of motion following RC repair to enhance recovery and return to the workforce.

III

Patients with serious mental illness (i.e., SMI; bipolar disorder, major depressive disorder, and schizophrenia) are at increased risk of readmission, yet little is known about the extent to which readmission rates among these patients vary across hospitals. The purpose of this study was to examine the variation across hospitals in readmissions for patients with SMI and differences in the characteristics of hospitals with the highest and lowest adjusted readmission rates.

We conducted a cross-sectional analysis of pooled inpatient claims from 2013-2016. Mixed logit models with hospital random effects were used to estimate the hospital-level variance. The sample included patients with SMI from a 5% sample of fee-for-service Medicare beneficiaries.

We identified 2066 hospitals with at least 30 index admissions for Medicare beneficiaries with SMI. In multivariate analyses, factors most strongly associated with increased risk of readmission included substance use disorder (OR 2.311; p<0.001) and end stage renal disease (OR 2.024; p<0.001). Unadjusted readmission for hospitals at the 5th and 95th percentiles of performance were 7.05% and 15.24%, respectively, constituting an 8.2% difference. Adjusting for patient and community characteristics reduced the spread in readmission rates between the 5th and 95th percentiles of hospitals by 1.0% (i.e. to 7.2%). Hospitals in the lowest vs. highest quintiles of adjusted readmission rates were more likely to be teaching hospitals (11.1% vs. 16.7%; p<0.05) and located in the South (37.7% vs. 40.4%) or Midwest (19.8% vs. 30.0%; p<0.001 for region differences).Conclusions: There is substantial hospital-level variation in readmission rates among patients with serious mental illness, even after adjusting for patient and community characteristics. This has implications for policy guiding investment in hospital-based services and community resources, to improve transitions of care for patients with SMI.

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4h.

Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively.

In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.

To compare the kinematics and muscle activity of subjects with facioscapulohumeral dystrophy (FSHD) and healthy control subjects during the performance of standardized upper extremity tasks.

Exploratory case-control study.

A movement laboratory.

Subjects (N=19) with FSHD (n=11) and healthy control subjects (n=8) were measured.

Not applicable.

Kinematic data were recorded using a 3-dimensional motion capturing system. Muscle activities, recorded using electromyography, were obtained from 6 superficial muscles around the glenohumeral joint. Shoulder elevation and elbow flexion angles, and maximum electromyographic activity during the movements as a percentage of maximum voluntary contraction (MVC) were calculated.

Kinematic differences between the FSHD group and the healthy control group were found in the shoulder elevation angle during single shoulder movements and both reaching tasks. In general, subjects with FSHD had higher percentages of muscle activation. The median activity of the trapezius was close to the MVC activity during the single shoulder movements. Moreover, deltoid and pectoralis muscles were also highly active.

Higher activation of the trapezius in subjects with FSHD indicates a mechanism that could help relieve impaired shoulder muscles during arm elevation around shoulder height. Compared with healthy subjects, persons with FSHD activated their shoulder muscles to a greater extent during movements that required arm elevation.