Use of virtual reality for the management of phantom limb pain: a systematic review.

PURPOSE: To summarize the research on the effectiveness of virtual reality (VR) therapy for the management of phantom limb pain (PLP). METHODS: Three databases (SCOPUS, Ovid Embase, and Ovid MEDLINE) were searched for studies investigating the use of VR therapy for the treatment of PLP. Original research articles fulfilling the following criteria were included: (i) patients 18 years and older; (ii) all etiologies of amputation; (iii) any level of amputation; (iv) use of immersive VR as a treatment modality for PLP; (v) self-reported objective measures of PLP before and after at least one VR session; (vi) written in English. RESULTS: A total of 15 studies were included for analysis. Fourteen studies reported decreases in objective pain scores following a single VR session or a VR intervention consisting of multiple sessions. Moreover, combining VR with tactile stimulation had a larger beneficial effect on PLP compared with VR alone. CONCLUSIONS: Based on the current literature, VR therapy has the potential to be an effective treatment modality for the management of PLP. However, the low quality of studies, heterogeneity in subject population and intervention type, and lack of data on long-term relief make it difficult to draw definitive conclusions.IMPLICATION FOR REHABILITATIONVirtual reality (VR) therapy has emerged as a new potential treatment option for phantom limb pain (PLP) that circumvents some limitations of mirror therapy.VR therapy was shown to decrease PLP following a single VR session as well as after an intervention consisting of multiple sessions.The addition of vibrotactile stimuli to VR therapy may lead to larger decreases in PLP scores compared with VR therapy alone.

Complications and early recovery following hip hemiarthroplasty through the direct anterior approach: a systematic review and meta-analysis.

PURPOSE: Minimizing complications is an important focus in hip hemiarthroplasty (HHA) for femoral neck fracture (FNF) patients given the associated high morbidity and mortality rates. This systematic review and meta-analysis aimed to compare the clinical and functional outcomes associated with the direct anterior approach (DAA) compared to other surgical approaches used for HHA. METHODS: Studies evaluating HHA-treated FNFs using the DAA were compared through meta-analysis to all other surgical approaches combined and as distinct subgroups. Outcomes included overall complication rate, mortality rate, dislocation rate, reoperation rate, periprosthetic fracture rate, infection rate, length of stay (LOS), mobility, perioperative blood loss, operative time, and postoperative pain. RESULTS: Nineteen studies met the inclusion criteria, totaling 2,018 HHAs. DAA significantly reduced the overall complication rate (odds ratio (OR) = 0.73, 95% confidence interval (CI) 0.57 to 0.94, p = 0.01), dislocation rate (OR = 0.34, 95% CI 0.15 to 0.77, p = 0.01), and LOS (mean difference (MD) = -1.31 days, 95% CI - 2.12 to - 0.50, p = 0.002). Findings from studies that were not appropriate for meta-analysis were qualitatively summarized and suggested improved mobility and reduced postoperative pain with the DAA. Significant differences were not detected in any of the remaining outcomes. CONCLUSION: The DAA HHA appears to be safer, reduces hospital stay, and may improve early functional recovery. This article supports the DAA HHA as a safe option for the management of displaced intracapsular FNFs.

The induced membrane technique in animal models: a systematic review.

Objectives: The induced membrane technique (IMT) is a 2-stage surgical approach that has become increasingly popular to manage bone defects. Preclinical investigations have been conducted to better understand and define several aspects of this technique. This review summarizes the literature regarding the IMT performed in animal models and identifies potential future directions. Data Sources: Biosis Citation Index, Ovid Embase, and Ovid MEDLINE databases were searched from inception up to June 23, 2021 for articles related to the IMT. Study Selection: Animal studies involving the use of the IMT for segmental defects in long bones were selected. Only full-length original research articles published in English or French were included. Data Extraction: Two authors extracted the data from the selected studies and a third author verified the accuracy of the information. Data Synthesis: Information concerning the animal model, the surgical procedures, and the outcome measures were recorded for each study and compiled. Conclusions: Forty-seven studies were included in this review. Twenty-nine studies (62%) performed both stages of the technique, but only 8 (17%) reported on radiographic union rates explicitly and 5 (11%) included biomechanical testing. A large proportion of the preclinical literature on the IMT has failed to report on radiographic union as an outcome. While studies reporting membrane properties are valuable, they may not provide information that translates into clinical practice or further clinical research if the ultimate outcome of bony healing is not considered. Future animal studies of the IMT should consider this in their study design.

Firing rate trajectories of human motor units during isometric ramp contractions to 10, 25 and 50% of maximal voluntary contraction.

During low torque graded isometric contractions, motor units (MU) exhibit initial firing rate acceleration followed by saturation demonstrating a non-linear response attributed to persistent inward currents (PICs) which contribute to the net excitatory input. Firing rate saturation studies have been done exclusively at recruitment thresholds of low firing threshold MUs below 10% of isometric maximal voluntary contraction(MVC). It remains unclear whether later recruited (i.e. higher-threshold) MUs follow a similar firing rate trajectory as low-threshold units. Thus, MU firing rate trajectories were explored in relation to MU recruitment threshold (RT) at contraction levels between 10 and 50% of MVC. During graded isometric contractions to 10, 25 and 50% of MVC, single MU potentials were recorded from the tibialis anterior from 5 participants using tungsten microelectrodes. To characterize the firing rate trajectory, each MU train was fit by competing functions of torque as an exponential (i.e. saturated) and simple linear regression, using previous analysis methods (Fuglevand et al. 2015). Throughout a RT range of 0.02-41% of MVC, 261 MUs were compared. In 87% of MUs the better fit was by a linear function, whereas the remaining MUs (13%) were fit better with an exponential (saturated) firing rate trajectory. There was no statistical difference in the number of MUs better fit by the exponential function between low (<10% MVC) and relatively higher threshold MUs (>10% MVC; both p < 0.05). Increasing RT and rate of torque development (RTD) of the ramps were correlated with increased firing rate variability (larger error) in both fits (r = 0.3 and r = 0.4, both p < 0.01). Additionally, there was a 4-fold increase in peak antagonist surface electromyography (EMG) from 10 to 50% MVC contraction ramps. When all MUs were plotted with a normalized firing onset (i.e. 0% MVC) the data visually displayed an initial firing rate acceleration followed by a linear response (biphasic trajectory). Increased synaptic drive and greater antagonist surface EMG during moderate torque outputs may dampen PIC activity as compared with MUs during lower torque (<10% MVC) recruitment levels.

Effect of ankle joint position on triceps surae contractile properties and motor unit discharge rates.

The triceps surae (TS) length-tension relationship can be altered by changing the knee joint position, ankle joint position or both. However, studies exploring the effect of muscle length on neuromuscular properties have focused only on knee joint position changes affecting two of the three muscle components of the TS. Thus, the purpose of this study is to compare the neuromuscular properties of the three TS muscles during plantar flexion contractions at two ankle joint positions, 20° dorsiflexed (DF) and 20° plantar flexed (PF). Maximal isometric voluntary strength (MVC), voluntary activation, and evoked contractile properties of the ankle plantar flexors were compared between both ankle joint positions. Additionally, soleus, medial (MG), and lateral (LG) gastrocnemii motor unit discharge rates (MUDRs) were sampled during plantar flexion contractions at 25%, 50%, 75%, and 100% MVC using indwelling tungsten electrodes. MVC and peak twitch torque were lower by ~61% and 70%, respectively, whereas the maximal rate of torque relaxation was 39% faster in the PF compared with the DF position. Voluntary activation (~95%) was unaffected by changes in ankle joint position. LG MUDRs showed no differences between ankle joint positions, regardless of contraction intensity. Submaximal MG and soleus MUDRs showed no differences between the two ankle joint positions, however both muscles had 9% and 20% higher MUDRs in the DF position, respectively. These results provide further evidence for the differential activation among the three components of the TS with the greatest increases in soleus MUDRs compared with the gastrocnemii when the muscles are lengthened.

The effect of blood flow on tibialis anterior motor unit firing rates during sustained low-intensity isometric contractions.

Low-intensity contractions with blood flow occlusion (BFO) result in neuromuscular adaptations comparable with high-intensity (>70% maximal voluntary contraction, MVC) exercise. Because BFO exercise can only be applied to limb muscles, it is of interest to explore whether muscles proximal to the occlusion site are affected. Therefore, the purpose of this study was to assess neural activation of the tibialis anterior (TA) when flow is occluded proximal and distal to the active muscle. Five males completed three protocols to observe the effect of BFO on motor unit firing rates (MUFR) of the TA at a fatiguing contraction intensity of ∼15% MVC. Two occlusion protocols, one proximal (BFOprox) to and one distal (BFOdis) to the TA, were compared with a control (free-flow) protocol time-matched to BFOdis. MVC was significantly reduced following the BFOprox (∼41%; P < 0.001) and BFOdis (∼27%, P < 0.001), but not following the control protocol (∼15%; P = 0.13). Surface electromyography (EMG) during BFOdis and BFOprox increased ∼14% and ∼28%, respectively, but was not different among protocols. MUFRs for BFOdis and BFOprox were significantly reduced (by ∼33% and ∼23%, respectively; P < 0.01) at task failure. Results indicate that although BFOprox results in the largest reductions of MUFRs, BFOdis shows greater impairments compared with the free-flow control condition. Novelty Effects on motor unit firing rates of proximal versus distal blood flow occlusion were compared during low-intensity fatiguing task. Proximal occlusion results in greatest fatigue and reduction in motor unit rates, but distal occlusion elicits more fatigue and rate reduction than a control task.

Differential Modulation of Motor Unit Properties from the Separate Components of the Triceps Surae in Humans.

The triceps surae is comprised of the soleus, and medial (MG) and lateral (LG) gastrocnemii. Modulation of triceps surae motor units (MUs) is context- and muscle-dependent, yet it is unknown how the disparate components of the triceps surae work together to achieve the common goal of high-intensity voluntary isometric plantar flexion torque gradation. Thus, the purpose was to assess the interrelationships between MU recruitment thresholds (MURTs) and MU discharge rates (MUDRs) among these three muscles during contractions from low to high intensities. We sampled 157 MU action potential trains from the MG (68), LG (38) and soleus (51) using fine-wire intramuscular electromyography (EMG) during voluntary ramp isometric contractions up to 100% maximal voluntary contraction (MVC). The soleus exhibited 41% and 54% lower MURTs compared to the MG (p < 0.0001) and LG (p < 0.0001), respectively, whereas MG MURTs were 22% lower than the LG (p < 0.0001). Initial MUDRs were 35% and 26% greater for the LG compared with the MG (p < 0.0001) and soleus (p < 0.0001), but no difference was detected between the MG and soleus (p = 0.28). Finally, initial MUDRs displayed a positive relationship with MURTs for each independent triceps surae component (p ≤ 0.002). The relative differences in MU properties of each muscle in this synergistic group illustrate that MU control strategies are likely optimized with respect to the relative contribution of each muscle to plantar flexion torque or functional roles.

Effect of knee joint position on triceps surae motor unit recruitment and firing rates.

Gastrocnemii muscle fibers shorten when the knee joint is in a flexed compared to an extended position. This leads to inhibition of medial gastrocnemius (MG) motor units, however, it is unclear whether this affects motor unit properties of the lateral gastrocnemius (LG) or soleus (SOL). We recorded 171 motor units from the MG (61), LG (39) and SOL (71) at an extended (160°) and flexed (100°) knee joint position with the ankle and hip joints at 90°. Subjects performed isometric ramp plantar flexion contractions at 25, 50 and 100% of the maximal voluntary contraction. MG (p = 0.0002) and LG (p = 0.02) motor unit recruitment thresholds (RT) were higher, whereas only MG motor unit firing rates (FR) were lower (p = 0.008) in the flexed compared to the extended knee joint position. SOL motor unit RT (p = 0.66) and FR (p = 0.08) were not statistically different between positions. When comparing properties of the same motor unit followed during contractions at both knee joint positions, RT of ten gastrocnemii motor units were higher (p = 0.0008) and FR were lower (p = 0.01) when the knee was flexed. Additionally, in six SOL motor units, RT (p = 0.42) and FR (p = 0.96) were not different between the two positions. Thus, MG and LG activation is similarly inhibited during plantar flexion contractions in a flexed compared to an extended knee joint position. Furthermore, our findings indicate that knee joint position changes have no effect on SOL excitability.