Preliminary Evaluation of a New Orthotic for Patellofemoral and Multicompartment Knee Osteoarthritis.

PURPOSE: Traditional knee osteoarthritis (OA) braces are usually indicated for a minority of patients with knee OA, as they are only suitable for those with unicompartmental disease affecting the tibiofemoral joint. A new assistive brace design is intended for use in a wider range of knee OA patients with heterogeneous symptoms characteristic of patellofemoral, tibiofemoral, or multicompartmental knee OA. The purpose of this case series was to explore whether the use of this novel "tricompartment offloader" (TCO) brace was associated with clinically relevant improvements in pain and function. MATERIALS AND METHODS: A retrospective analysis of individuals with knee OA (n = 40) was conducted to assess pain, function, physical activity, and use of medication and other treatments before and after brace use. Validated outcome measures including the Visual Analog Scale (VAS) and Lower Extremity Functional Scale (LEFS) were used to assess pain and physical function (primary outcome measures). Exploratory measures were used to quantify physical activity levels and use of medication and other treatments (secondary outcome measures). RESULTS: Average total pain (VAS) scores decreased by 36.6 mm and physical function (LEFS) scores increased by 16.0 points following the use of the TCO brace. Overall, 70% of the participants indicated increased weekly physical activity and 60% reported a decrease in their use of at least one other treatment. CONCLUSIONS: Results from this case series suggest that the TCO brace shows strong potential to fill a conservative treatment gap for patients with heterogeneous symptoms of knee OA that are characteristic of patellofemoral or multicompartment disease. Further investigation is warranted.

Design Evaluation of a Novel Multicompartment Unloader Knee Brace.

Knee osteoarthritis (OA) is a significant problem in the aging population, causing pain, impaired mobility, and decreased quality of life. Conservative treatment methods are necessary to reduce rapidly increasing rates of knee joint surgery. Recommended strategies include weight loss and knee bracing to unload knee joint forces. Although weight loss can be beneficial for joint unloading, knee OA patients often find it difficult to lose weight or begin exercise due to knee pain, and not all patients are overweight. Unicompartment offloader knee braces can redistribute joint forces away from one tibiofemoral (TF) compartment; however, <5% of patients have unicompartmental tibiofemoral osteoarthritis (TFOA), while patients with isolated patellofemoral or multicompartmental OA are much more common. By absorbing body weight (BW) and assisting the knee extension moment using a spring-loaded hinge, sufficiently powerful knee-extension-assist (KEA) braces could be useful for unloading the whole knee. This paper (1) describes the design of a spring-loaded tricompartment unloader (TCU) knee brace intended to provide unloading in all three compartments of the knee while weight-bearing, (2) measures and compares the force output of the TCU against the only published and commercially available KEA brace, and (3) calculates the static unloading capacity of each device. The TCU and KEA braces delivered maximum assistive moments equivalent to reducing BW by approximately 45 and 6 lbs, respectively. The paper concludes that sufficiently powerful spring-loaded knee braces show promise in a new class of multicompartment unloader knee orthoses, capable of providing a clinically meaningful unloading effect across all three knee compartments.

Spatial interactions between consecutive manual responses.

We have shown that the latency to initiate a reaching movement is increased if its direction is the same as a previous movement compared to movements that differ by 90° or 180° (Cowper-Smith and Westwood in Atten Percept Psychophys 75:1914-1922, 2013). An influential study (Taylor and Klein in J Exp Psychol Hum Percept Perform 26:1639-1656, 2000), however, reported the opposite spatial pattern for manual keypress responses: repeated responses on the same side had reduced reaction time compared to responses on opposite sides. In order to determine whether there are fundamental differences in the patterns of spatial interactions between button-pressing responses and reaching movements, we compared both types of manual responses using common methods. Reaching movements and manual keypress responses were performed in separate blocks of trials using consecutive central arrow stimuli that directed participants to respond to left or right targets. Reaction times were greater for manual responses made to the same target as a previous response (M = 390 ms) as compared to the opposite target (M = 365 ms; similarity main effect: p < 0.001) regardless of whether the response was a reaching movement or a keypress response. This finding is broadly consistent with an inhibitory mechanism operating at the level of motor output that discourages movements that achieve the same spatial goal as a recent action.

Further evidence against a momentum explanation for IOR.

Reaction times to targets presented in the same location as a preceding cue are greater than those to targets presented opposite the cued location. This observation can be explained as a result of inhibition at the attended location (IOR), or as facilitation at the location opposite the cue (opposite facilitation effect or OFE). Past research has demonstrated that IOR is observed reliably, whereas OFE is observed only occasionally. The present series of four experiments allows us to determine whether or not OFE can be explained by eye movements as suggested by previous authors. Participants' eye movements were monitored as they were presented with an array of four placeholders aligned with the four cardinal axes. Exogenous cues and targets were presented successively. Participants (N=37) completed either: i.) cue-manual and cue-saccade experiments, ignoring the cue and then responding with a keypress or saccade, respectively, or ii.) manual-manual and saccade-saccade experiments, responding to both the cue and the target with a keypress or saccade respectively. Results demonstrated a reliable IOR effect in each of the four experiments (reaction time greater for same versus adjacent and opposite cue-target trials). None of the four experiments demonstrated evidence of an OFE (reaction times were not significantly lower for opposite versus adjacent cue-target trials). These results are inconsistent with a momentum-based account of cue-target task performance, and furthermore suggest that the OFE cannot be attributed to occasional eye movements to the cue and/or target in previous studies.

Directional interactions between current and prior saccades.

One way to explore how prior sensory and motor events impact eye movements is to ask someone to look to targets located about a central point, returning gaze to the central point after each eye movement. Concerned about the contribution of this return to center movement, Anderson et al. (2008) used a sequential saccade paradigm in which participants made a continuous series of saccades to peripheral targets that appeared to the left or right of the currently fixated location in a random sequence (the next eye movement began from the last target location). Examining the effects of previous saccades (n-x) on current saccade latency (n), they found that saccadic reaction times (RT) were reduced when the direction of the current saccade matched that of a preceding saccade (e.g., two left saccades), even when the two saccades in question were separated by multiple saccades in any direction. We examined if this pattern extends to conditions in which targets appear inside continuously marked locations that provide stable visual features (i.e., target "placeholders") and when saccades are prompted by central arrows. Participants completed 3 conditions: peripheral targets (PT; continuous, sequential saccades to peripherally presented targets) without placeholders; PT with placeholders; and centrally presented arrows (CA; left or right pointing arrows at the currently fixated location instructing participants to saccade to the left or right). We found reduced saccadic RT when the immediately preceding saccade (n-1) was in the same (vs. opposite) direction in the PT without placeholders and CA conditions. This effect varied when considering the effect of the previous 2-5 (n-x) saccades on current saccade latency (n). The effects of previous eye movements on current saccade latency may be determined by multiple, time-varying mechanisms related to sensory (i.e., retinotopic location), motor (i.e., saccade direction), and environmental (i.e., persistent visual objects) factors.

Changes in trunk orientation do not induce asymmetries in covert orienting.

We explored the effect of trunk orientation on responses to visual targets in five experiments, following work suggesting a disengage deficit in covert orienting related to changes in the trunk orientation of healthy participants. In two experiments, participants responded to the color of a target appearing in the left or right visual field following a peripheral visual cue that was informative about target location. In three additional experiments, participants responded to the location (left/right) of a target using a spatially compatible motor response. In none of the experiments did trunk orientation interact with spatial-cuing effects, suggesting that orienting behavior is not affected by the rotation of the body relative to the head. Theoretical implications are discussed.

Spatial interactions between successive eye and arm movements: signal type matters.

Spatial interactions between consecutive movements are often attributed to inhibition of return (IOR), a phenomenon in which responses to previously signalled locations are slower than responses to unsignalled locations. In two experiments using peripheral target signals offset by 0°, 90°, or 180°, we show that consecutive saccadic (Experiment 1) and reaching (Experiment 3) responses exhibit a monotonic pattern of reaction times consistent with the currently established spatial distribution of IOR. In contrast, in two experiments with central target signals (i.e., arrowheads pointing at target locations), we find a non-monotonic pattern of reaction times for saccades (Experiment 2) and reaching movements (Experiment 4). The difference in the patterns of results observed demonstrates different behavioral effects that depend on signal type. The pattern of results observed for central stimuli are consistent with a model in which neural adaptation is occurring within motor networks encoding movement direction in a distributed manner.

Refractory effects of the N1 event-related potential in experienced cochlear implant patients.

OBJECTIVE: To determine if cochlear implant (CI) patients exhibit a temporal processing deficit for auditory stimuli, by examining refractory effects of the N1 event-related potential (ERP) component. DESIGN: CI patients and normally-hearing controls were tested in an auditory refractory period paradigm while ERP recordings were collected across the scalp. Participants were presented with brief 500-Hz tones that were separated by inter-stimulus intervals (ISIs) of 500, 1000, or 3000 ms. The amplitude of the N1 was examined as a function of ISI within each group. STUDY SAMPLE: Ten adult CI patients and 13 age-matched normally-hearing controls were tested. Patients had long-lasting severe or profound sensorineural hearing loss prior to implantation, and a minimum of two years experience with CI activation. RESULTS: Unlike normally-hearing controls, CI users showed no refractory effect for tones at 500 ms ISIs compared to 1000 ms. However, similar to controls, recovery from refractoriness was observed in anterior locations at 3000 ms. CONCLUSION: The refractory period threshold, defined as the minimum ISI where different N1 amplitudes are elicited, is greater than 1000 ms in CI patients; at least double that of normally-hearing controls.

Neural coding of movement direction in the healthy human brain.

Neurophysiological studies in monkeys show that activity of neurons in primary cortex (M1), pre-motor cortex (PMC), and cerebellum varies systematically with the direction of reaching movements. These neurons exhibit preferred direction tuning, where the level of neural activity is highest when movements are made in the preferred direction (PD), and gets progressively lower as movements are made at increasing degrees of offset from the PD. Using a functional magnetic resonance imaging adaptation (fMRI-A) paradigm, we show that PD coding does exist in regions of the human motor system that are homologous to those observed in non-human primates. Consistent with predictions of the PD model, we show adaptation (i.e., a lower level) of the blood oxygen level dependent (BOLD) time-course signal in M1, PMC, SMA, and cerebellum when consecutive wrist movements were made in the same direction (0° offset) relative to movements offset by 90° or 180°. The BOLD signal in dorsolateral prefrontal cortex adapted equally in all movement offset conditions, mitigating against the possibility that the present results are the consequence of differential task complexity or attention to action in each movement offset condition.