Progressive submaximal effort hamstring muscle endurance is reduced after reconstruction of the anterior cruciate ligament.

BACKGROUND: Endurance capability in the muscles controlling the knee is poorly understood post anterior cruciate ligament (ACL) reconstruction, despite many sporting activities requiring notable muscle endurance. The hamstring muscles, when active, provide important anatomical support to protect the reconstructed graft. In the absence of good hamstring endurance, fatigue may predispose individuals to re-injury. OBJECTIVE: To assess whether ACL reconstruction (ACLR) with a hamstring graft leads to reduced hamstring endurance 9-13 months post-surgery. STUDY DESIGN: A cross-sectional inter-limb comparison study was undertaken with participants 9-13 months after an ACLR with a hamstring graft, and a group of age, sex, and activity-matched controls. There were 22 participants in each group. METHOD: Submaximal hamstring endurance was measured using a progressive fatigue test on an isokinetic dynamometer at a joint angular velocity of 120°/second. The dependant variable was the maximum number of repetitions performed. Statistical comparisons were made across injured, uninjured and control group limbs. RESULTS: There was a significant (p < 0.05) deficit in hamstring endurance observed between the injured leg (mean: 111 repetitions, SD 49) and uninjured leg (mean: 136 repetitions, SD 67) of the ACL group, but not between the uninjured and control group legs (mean: 124 repetitions, SD 50). CONCLUSION: The 18% deficit in submaximal hamstring endurance across the ACL-reconstructed individual's limbs is indicative of a notable loss in muscle performance at 9-13 months post-surgery. These results provide initial evidence for supporting further research examining the inclusion of hamstring endurance training in ACL rehabilitation programmes post-surgery.

Validity and Reliability of 3-D Ultrasound Imaging to Measure Hamstring Muscle and Tendon Volumes.

OBJECTIVE: The validity and reliability of 3-D ultrasound (US) in estimation of muscle and tendon volume was assessed in a very limited number of muscles that can be easily immersed. The objective of the present study was to assess the validity and reliability of muscle volume measurements for all hamstring muscle heads and gracilis (GR), as well as tendon volume for the semitendinosus (ST) and GR using freehand 3-D US. METHODS: Three-dimensional US acquisitions were performed for 13 participants in two distinct sessions on separate days, in addition to one session dedicated to magnetic resonance imaging (MRI). Volumes of ST, semimembranosus (SM), biceps femoris short (BFsh) and long (BFlh) heads, and GR muscles and from the tendon from semitendinosus (STtd) and gracilis (GRtd) were collected. RESULTS: The bias and the 95% confidence intervals of 3-D US compared with MRI ranged from -1.9 mL (-0.8%) to 1.2 mL (1.0%) for muscle volume and from 0.01 mL (0.2%) to -0.03 mL (-2.6%) for tendon volume. For muscle volume assessed using 3-D US, intraclass correlation coefficients (ICCs) ranged from 0.98 (GR) to 1.00, and coefficients of variation (CV) from 1.1% (SM) to 3.4% (BFsh). For tendon volume, ICCs were 0.99, and CVs between 3.2% (STtd) and 3.4% (GRtd). CONCLUSION: Three-dimensional US can provide a valid and reliable inter-day measurement of hamstrings and GR for both muscle and tendon volumes. In the future, this technique could be used as an outcome for strengthening interventions and potentially in clinical environments.

Trajectories of Pain and Function Outcomes up to 5 to 8 Years Following Total Knee Arthroplasty.

BACKGROUND: There appears to be substantial variability in outcomes > 2 years following total knee arthroplasty (TKA) that is masked by whole group analyses. The goal of the study was to identify trajectories of pain and function outcomes up to 5 to 8 years post-TKA and to identify baseline factors that are associated with different trajectories of recovery. METHODS: Baseline, 6-month, and 12-month pain and function data were collected in a previous study investigating predictors of outcome following primary TKA (n = 286), along with a variety of baseline predictor variables. The present study obtained pain and function data at 5 to 8 years following TKA in the same cohort (n = 201). Latent class linear mixed models were used to identify different classes of pain and functional trajectories over time. The extent to which differences across latent classes were explained by baseline predictor variables was determined. RESULTS: Three classes of pain and two classes of function trajectory were identified. While most patients (84% to 93%) followed a trajectory that showed an initial rapid gain following surgery that was sustained through 5 to 8 years, both pain and function included at least one trajectory class that showed a meaningful change after 12 months. No predictor variables were significantly associated with either the pain or function classes. CONCLUSIONS: Most patients follow a traditional trajectory of recovery in knee pain and function over 5 to 8 years. However, alternative trajectories are observed in an important minority of patients such that knee pain and function at 12 months after surgery does not always reflect outcomes at 5 to 8 years.

The effect of Tubigrip and a rigid belt on rectus abdominus diastasis immediately postpartum: A randomised clinical trial.

BACKGROUND: Rectus abdominis (RA) diastasis is a risk factor for abdominal muscle dysfunction and reduced quality of life postpartum. It is thought that supplementary abdominal supports might reduce the diastasis. However, there is limited research assessing the efficacy of abdominal supports/binding. OBJECTIVE: To determine the effects of Tubigrip and a rigid abdominal belt in reducing RA diastasis in the first eight weeks postpartum. DESIGN: Randomised clinical trial. METHODS: 62 women undertook ultrasound imaging to measure their RA diastasis prior to and after an eight week intervention wearing either Tubigrip or a rigid abdominal belt. Data analyses involved repeated measures ANOVA and correlational methods. RESULTS: The RA diastasis reduced by 46% from a mean 4.6 cm-2.5 cm over the eight week intervention period with no significant difference (p > 0.05) across groups. Women wore the Tubigrip for a significantly (p < 0.05) longer number of hours (Median: 278) compared to those in the belt group (Median: 81 h). The length of time that women wore Tubigrip or the belt was not associated with the percentage reduction in the RA diastasis (p > 0.05). There was no significant difference in the diastasis across vaginal and Caesarean section deliveries at baseline. There was a significant difference (p < 0.05) in the percent reduction of the RA diastasis across deliveries post-intervention (vaginal delivery mean: 48% vs C-section: 40%). CONCLUSION: There was no difference across groups post-intervention in the RA diastasis, and it is questionable whether either support improves upon that associated with natural healing alone.

A combination of high preoperative pain and low radiological grade of arthritis is associated with a greater intensity of persistent pain 12 months after total knee arthroplasty.

AIMS: Despite new technologies for total knee arthroplasty (TKA), approximately 20% of patients are dissatisfied. A major reason for dissatisfaction and revision surgery after TKA is persistent pain. The radiological grade of osteoarthritis (OA) preoperatively has been investigated as a predictor of the outcome after TKA, with conflicting results. The aim of this study was to determine if there is a difference in the intensity of pain 12 months after TKA in relation to the preoperative radiological grade of OA alone, and the combination of the intensity of preoperative pain and radiological grade of OA. METHODS: The preoperative data of 300 patients who underwent primary TKA were collected, including clinical information (age, sex, preoperative pain), psychological variables (depression, anxiety, pain catastrophizing, anticipated pain), and quantitative sensory testing (temporal summation, pressure pain thresholds, conditioned pain modulation). The preoperative radiological severity of OA was graded according to the Kellgren-Lawrence (KL) classification. Persistent pain in the knee was recorded 12 months postoperatively. Generalized linear models explored differences in postoperative pain according to the KL grade, and combined preoperative pain and KL grade. Relative risk models explored which preoperative variables were associated with the high preoperative pain/low KL grade group. RESULTS: Pain 12 months after TKA was not associated with the preoperative KL grade alone. Significantly increased pain 12 months after TKA was found in patients with a combination of high preoperative pain and a low KL grade (p = 0.012). Patients in this group were significantly more likely to be male, younger, and have higher preoperative pain catastrophizing, higher depression, and lower anxiety (all p ≤ 0.05). CONCLUSION: Combined high preoperative pain and low radiological grade of OA, but not the radiological grade alone, was associated with a higher intensity of pain 12 months after primary TKA. This group may have a more complex cause of pain that requires additional psychological interventions in order to optimize the outcome of TKA.Cite this article: Bone Joint J 2022;104-B(11):1202-1208.

Mobilisation or immobilisation-based treatments for first carpometacarpal joint osteoarthritis: A systematic review and meta-analysis with subgroup analyses.

Introduction: Both joint mobilisation and immobilisation are thought to be effective in the treatment of first carpometacarpal joint (CMCJ) osteoarthritis (OA). The objective of this review was to establish whether either intervention reduced pain and improved pinch strength in people with first CMCJ OA in the short term and assess whether one intervention is superior to the other. Method: This was a systematic review and meta-analysis. Seven databases were searched until May 2021. Only RCTs were included. The Cochrane Risk of Bias Tool and the Grade of Recommendations Assessment, Development and Evaluation system were utilised to rate the evidence. Random-effects meta-analysis with subgroup analyses were used. Results: Eight studies were included with a total of 417 participants. Mobilisation treatments included manual therapy with or without exercise while immobilisation interventions utilised thumb splinting with several different designs. Very low-quality and low-quality evidence showed that mobilisation led to statistically but not clinically significant improvements in pain (standardised mean difference (SMD) = 0.53; 95% confidence interval (CI) = 0.03 to 1; I2 = 60%; p = 0.06) and pinch strength (SMD = 0.35; 95% CI = 0.03 to 0.7; I2 = 12%; p = 0.3) compared to placebo. Very low-quality and low-quality evidence showed no effect on pain and pinch strength compared to a control or no intervention. Subgroup analyses revealed no difference between interventions. Discussion: Neither mobilisation nor immobilisation alone led to clinically important improvements in pain or pinch strength in the short term in people with symptomatic first CMCJ OA. Neither therapeutic strategy appeared to be superior.

Neuropathic Pain in Hand Osteoarthritis: A Cross-Sectional Study.

Symptomatic hand osteoarthritis (OA) is a severely debilitating condition. Neuropathic pain (NP) has been shown to be a factor affecting pain severity, hand function, psychological wellbeing, body schema, and the number of pain medications in people with OA of other joints. The aim of this study was to assess the prevalence of NP in symptomatic hand OA and assess its association with pain, hand function, measures of psychological wellbeing, sleep, body schema disturbances, and number of pain medications. Participants with symptomatic hand OA diagnosed through the American College of Rheumatology criteria, were recruited and completed a series of online questionnaires. These included the Douleur Neuropathique 4 interview (DN4-interview), Short Form Brief Pain Inventory (SF-BPI), Neglect-like Symptoms questionnaire, Functional Index of Hand Osteoarthritis (FIHOA), Centre for Epidemiologic Studies Depression Scale (CES-D), Pain Catastrophising Scale (PCS), and the Pittsburgh Sleep Quality Index (PSQI). Logistic regression with age, body mass index, and sex as covariates were utilised to assess differences between participants with and without NP as identified through the DN4-interview. Correlation analysis assessed the relationship between pain intensity, body schema alterations, and number of pain medications. A total of 121 participants were included in the present study. Forty-two percent of participants presented with NP. Participants with NP reported higher levels of worst pain (OR: 10.2 95% CI: 2.2 to 48.5; p = 0.007). Worst pain intensity correlated with the number of pain medications (rho = 0.2; p = 0.04), and neglect-like symptoms (rho = 0.4; p < 0.0001). No difference between phenotypes was shown for catastrophising, function, depression, neglect-like symptoms, pain interference, or sleep. A large proportion of people with symptomatic hand OA present with NP. This phenotype is characterised by greater levels of pain intensity. Pain intensity is associated with number of pain relief medications and body schema alteration. Psychological factors, hand function, and sleep do not appear to be affected by the presence of NP.

Robotic devices for paediatric rehabilitation: a review of design features.

Children with physical disabilities often have limited performance in daily activities, hindering their physical development, social development and mental health. Therefore, rehabilitation is essential to mitigate the adverse effects of the different causes of physical disabilities and improve independence and quality of life. In the last decade, robotic rehabilitation has shown the potential to augment traditional physical rehabilitation. However, to date, most robotic rehabilitation devices are designed for adult patients who differ in their needs compared to paediatric patients, limiting the devices' potential because the paediatric patients' needs are not adequately considered. With this in mind, the current work reviews the existing literature on robotic rehabilitation for children with physical disabilities, intending to summarise how the rehabilitation robots could fulfil children's needs and inspire researchers to develop new devices. A literature search was conducted utilising the Web of Science, PubMed and Scopus databases. Based on the inclusion-exclusion criteria, 206 publications were included, and 58 robotic devices used by children with a physical disability were identified. Different design factors and the treated conditions using robotic technology were compared. Through the analyses, it was identified that weight, safety, operability and motivation were crucial factors to the successful design of devices for children. The majority of the current devices were used for lower limb rehabilitation. Neurological disorders, in particular cerebral palsy, were the most common conditions for which devices were designed. By far, the most common actuator was the electric motor. Usually, the devices present more than one training strategy being the assistive strategy the most used. The admittance/impedance method is the most popular to interface the robot with the children. Currently, there is a trend on developing exoskeletons, as they can assist children with daily life activities outside of the rehabilitation setting, propitiating a wider adoption of the technology. With this shift in focus, it appears likely that new technologies to actuate the system (e.g. serial elastic actuators) and to detect the intention (e.g. physiological signals) of children as they go about their daily activities will be required.

A Prospective, Median 15-Year Comparison of Ponseti Casting and Surgical Treatment of Clubfoot.

BACKGROUND: In 2010, 2 authors of this current study reported the results of Ponseti treatment compared with primary posteromedial release (PMR) for congenital talipes equinovarus in a cohort of 51 prospective patients. This current study shows outcomes recorded at a median of 15 years after the original treatment. METHODS: Patient health records were available for all 51 patients at a median of 15 years (range, 13 to 17 years) following treatment of congenital talipes equinovarus with either the Ponseti method (25 patients [38 feet]) or PMR (26 patients [42 feet]). Thirty-eight of 51 patients could be contacted, and 33 patients (65%) participated in the clinical review, comprising patient-reported outcomes, clinical examination, 3-dimensional gait analysis, and plantar pressures. RESULTS: Sixteen (42%) of 38 Ponseti-treated feet and 20 (48%) of 42 PMR-treated feet had undergone a further surgical procedure. The PMR-treated feet were more likely to undergo osteotomies and intra-articular surgical procedures (15 feet) than the Ponseti-treated feet (5 feet) (p < 0.05). Of the 33 patients reviewed with multimodal assessment, the Ponseti group, compared with the PMR group, demonstrated better Dimeglio scores (5.8 compared with 7.0 points; p < 0.05), Disease Specific Instrument (80.7 compared with 65.6 points; p < 0.05), Functional Disability Inventory (1.1 compared with 5.1; p < 0.05), and American Academy of Orthopaedic Surgeons (AAOS) Foot and Ankle Outcomes Questionnaire scores (52.2 compared with 46.6 points; p < 0.05), as well as improved total sagittal ankle range of motion in gait and ankle plantar flexion range at toe-off. The PMR group with clinical hindfoot varus displayed higher pressures in the lateral midfoot and the forefoot. CONCLUSIONS: Although the numbers of repeat surgical interventions following Ponseti treatment and primary PMR were similar, the PMR-treated feet had greater numbers of osteotomies and intra-articular surgical procedures. Functional outcomes were improved at a median of 15 years for feet treated with the Ponseti method compared with feet treated with PMR, with advantages seen in the Ponseti group over several domains. This study provides the most comprehensive evaluation of outcomes close to skeletal maturity in prospective cohorts, reinforcing the Ponseti method as the initial treatment of choice for idiopathic clubfeet. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Impairments in grip and pinch force accuracy and steadiness in people with osteoarthritis of the hand: A case-control comparison.

BACKGROUND: Symptomatic hand osteoarthritis (OA) is severely disabling condition. Limited evidence has focused on force control measures in this population. OBJECTIVES: It was the aim of the present study to determine whether force matching accuracy and steadiness are impaired in people with hand OA. In addition, the relationship between force control measures (accuracy and steadiness) and measures of hand function and pain in people with symptomatic hand OA was explored. DESIGN: Case-control study. METHOD: Sixty-two participants with symptomatic hand OA and 26 healthy pain-free controls undertook an isometric grip and pinch force matching task at 50 % of their maximum voluntary contraction. Average pain hand pain was recorded. In addition, the Disability of the Arm Shoulder and Hand Questionnaire (DASH), and the Functional Index of Hand Osteoarthritis were collected. RESULTS: Grip force-matching accuracy and steadiness were significantly impaired in the hand OA group compared to controls (P < 0.05). Pinch force-matching error was greater in people with hand OA (P < 0.05), however, pinch force steadiness was not different between groups. There was a learning effect in people with hand OA, with resolution of force matching impairments with task repetition. A small positive correlation was identified between grip force control and the DASH. No association was found between other measures of force control and self-reported measures of function or pain. CONCLUSIONS: People with hand OA presented with greater impairments in measures of submaximal force control. These were correlated with self-reported hand function but not pain. Future studies may wish to examine whether objective measures of functional performance are related to force-matching error and steadiness.

Effects of worn and new footwear on plantar pressure in people with gout.

BACKGROUND: In clinical trials, good quality athletic shoes offer short-term improvements (two-months) in foot pain and disability in people with gout, but these improvements are not sustained over time. This may be due to wear and subsequent changes to the structural integrity of the shoe. The aim of this study was to examine the effects of wear on plantar pressures and footwear characteristics in shoes over six-months in people with gout. METHODS: Forty people with gout participated in a cross-sectional repeated measures study. Participants wore a pair of commercially available athletic footwear for six-months. Participants then attended a study visit where the worn footwear was compared with a new pair of the same model and size of footwear. Wear characteristics (upper, midsole, outsole) and plantar pressure were measured in the two footwear conditions. Wear characteristics were analysed using paired t-tests and Fisher's exact tests. Plantar pressure data were analysed using linear mixed models. RESULTS: Increases in medial midsole (P < 0.001), lateral midsole (P < 0.001) and heel midsole (P < 0.001) hardness were observed in the worn shoes. Normal upper wear patterns (P < 0.001) and outsole wear patterns (P < 0.001) were observed in most of the worn shoes. No differences in peak plantar pressures (P < 0.007) were observed between the two footwear conditions. Reduced pressure time integrals at the first metatarsophalangeal joint (P < 0.001), second metatarsophalangeal joint (P < 0.001) and hallux (P = 0.003) were seen in the worn shoes. CONCLUSIONS: The study found signs of wear were observed at the upper, midsole and outsole in the worn footwear after six-months. These changes to the structural properties of the footwear may affect forefoot loading patterns in people with gout.

Exercises, Tubigrip and taping: can they reduce rectus abdominis diastasis measured three weeks post-partum?

BACKGROUND: Rectus abdominis diastasis is regarded as a risk factor for abdominal muscle dysfunction and reduced quality of life postpartum. It is thought that specific exercises and additional physical support might reduce the diastasis, with a need to establish efficacy in doing so. OBJECTIVES: Determine the effect of four abdominal exercises as well as Tubigrip or taping in reducing rectus abdominis diastases three weeks postpartum. DESIGN: Cross-sectional repeated measures comparison. METHODS: 32 women undertook a single session of ultrasound imaging. Ultrasound measurements of inter-rectus distance were taken at rest and during: 1) crook lying abdominal "drawing in" exercise; 2) crook lying trunk curl-up; 3) early Sahrmann level leg raise; 4) McGill side lying plank. The curl-up and abdominal "drawing in" exercises were assessed under two further conditions: a) wearing Tubigrip, b) taping across the diastasis. Data analyses involved repeated measures ANOVA. RESULTS: At rest the mean inter-rectus distance above and below the umbilicus was 3.5 cm (SD:1.1) and 2.6 cm (SD:1.2) respectively. A significant decrease (19%, p < 0.05) was observed at both measurement points during the curl-up exercise. No other exercises elicited a significant difference compared to resting. At rest, wearing Tubigrip reduced the inter-rectus distance (7%, p < 0.05). During exercise, there was no additional change in the inter-rectus distance (p > 0.05) with supports. CONCLUSION: The curl-up exercise was most effective in reducing inter-rectus distance. As no exercises invoked an increase in the rectus diastasis, they could not be regarded as potentially detrimental. Tubigrip and taping did not add to the effects of these exercises.

Experimental Hand and Knee Pain Cause Differential Effects on Corticomotor Excitability.

Acute pain elicits a well-known inhibitory effect on upper limb corticomotor excitability, whereas the temporal effects of lower-limb experimental pain and pain in a remote limb are less clear. The aim of this study was to compare the temporal corticomotor excitability changes in the upper and lower limbs in response to acute upper and lower limb pain. In a cross-over design, 13 participants (age 29 ± 9 years; 12 male) attended 2 sessions where experimental pain was induced by injecting hypertonic saline into either the first dorsal interosseous (FDI) muscle or infrapatellar fat pad at the knee, inducing a short-lasting pain experience scored on a numerical rating scale (NRS). Motor evoked potentials (MEPs) in response to transcranial magnetic stimulation were recorded in the FDI and vastus lateralis (VL) muscles before, during, and following pain. Hand and knee pain NRS scores were not significantly different. Hand pain elicited a short duration inhibition of the FDI MEPs (P < .0001) together with a facilitation of VL MEPs (P = .001) that outlasted the duration of pain. Knee pain elicited a short-duration facilitation of VL MEPs (P = .003) with no significant effect in the FDI MEPs (P = .46). The findings indicate a limb-specific corticomotor response to experimental pain that may be related to limb function. PERSPECTIVE: These data demonstrate the impact of acute, experimental pain on corticomotor excitability in the upper and lower limbs. This facilitates our understanding of the effect of pain on motor control of both local and distant muscles.

A Gel Pad Designed to Measure Muscle Volume Using Freehand 3-Dimensional Ultrasonography.

We developed an innovative gel pad that covers the entire lower leg to remove artifacts due to the pressure of the transducer in freehand 3-dimensional ultrasonography. In comparison to the reference method in water, this study showed that this new method was valid (bias, 3.4 mL; limit of agreement, 7.7 mL for a volume of ≈220 mL) and reliable (coefficient of variation, <1.1%) for the measurement of gastrocnemius medialis muscle volume. Considering that it is easier to use than the water tank technique, it has much promise for volumetric measurement of many muscles.

Impaired Regulation of Submaximal Force after ACL Reconstruction: Role of Muscle Spindles.

Ongoing motor deficits are routinely present following anterior cruciate ligament (ACL) reconstruction, including the ability to regulate muscle force. While such deficits are known, it is unclear why this occurs. The goal of the current study was to investigate the potential influence of muscle spindle input on submaximal force regulation and muscle activity at the knee in people following ACL reconstruction. Fourteen participants (8 female) who were 6-24 months post-ACL reconstruction and 15 control participants (8 female) undertook submaximal force matching and force modulation tasks before and after 20 min of vibration applied to the patella tendon. Across all tasks, the ACL reconstruction participants were poorer at force matching (P=0.007). The effect of vibration was not significant in either group for the force matching tasks (P=0.06), although there was a reduction in maximum voluntary contraction post-vibration in the control group (P<0.001). The ACL reconstruction group also showed evidence of greater activation of the medial hamstring muscles in comparison to controls (P=0.04). Individuals who have undergone ACL reconstruction have a diminished ability to accurately match and regulate submaximal muscle force, but this does not appear to be related to impaired muscle spindle input. Neuromuscular retraining programs that involve force regulation tasks may be necessary to optimize rehabilitation after ACL reconstruction.

Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production.

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

A Higher Grey Matter Density in the Amygdala and Midbrain Is Associated with Persistent Pain Following Total Knee Arthroplasty.

OBJECTIVE: The development of persistent pain following total knee arthroplasty (TKA) is common, but its underlying mechanisms are unknown. The goal of the study was to assess brain grey matter structure and its correlation with function of the nociceptive system in people with good and poor outcomes following TKA. SUBJECTS: Thirty-one people with LOW_PAIN (<3/10 on the numerical ratings scale [NRS]) at six months following TKA and 15 people with HIGH_PAIN (≥3/10 on the NRS) were recruited into the study. METHODS: Grey matter in key brain areas related to nociception was analyzed using voxel-based morphometry (VBM). Nociceptive facilitatory and inhibitory processes were evaluated using quantitative sensory testing (QST). QST scores and grey matter density in prespecified brain regions were compared between the LOW_PAIN and HIGH_PAIN groups. Regression analyses were used to analyze the associations between the grey matter and QST scores. RESULTS: There were no between-group differences in QST measures. In the VBM analysis, the HIGH_PAIN group had a higher grey matter density in the right amygdala, right nucleus accumbens, and in the periaqueductal grey (PAG), but lower grey matter density in the dorsal part of the left caudate nucleus. Grey matter density in the right amygdala and PAG correlated positively with temporal summation of pain. CONCLUSIONS: Persistent pain at six months after TKA is associated with a higher grey matter density in the regions involved in central sensitization and pain-related fear, which may contribute to the development of persistent pain after surgery.

Chronic effects of muscle and nerve-directed stretching on tissue mechanics.

Tissue-directed stretching interventions can preferentially load muscular or nonmuscular structures such as peripheral nerves. How these tissues adapt mechanically to long-term stretching is poorly understood. This randomized, single-blind, controlled study used ultrasonography and dynamometry to compare the effects of 12-wk nerve-directed and muscle-directed stretching programs versus control on maximal ankle dorsiflexion range of motion (ROM) and passive torque, shear wave velocity (SWV; an index of stiffness), and architecture of triceps surae and sciatic nerve. Sixty healthy adults were randomized to receive nerve-directed stretching, muscle-directed stretching, or no intervention (control). The muscle-directed protocol was designed to primarily stretch the plantar flexor muscle group, whereas the nerve-directed intervention targeted the sciatic nerve tract. Compared with the control group [mean; 95% confidence interval (CI)], muscle-directed intervention showed increased ROM (+7.3°; 95% CI: 4.1-10.5), decreased SWV of triceps surae (varied from -0.8 to -2.3 m/s across muscles), decreased passive torque (-6.8 N·m; 95% CI: -11.9 to -1.7), and greater gastrocnemius medialis fascicle length (+0.4 cm; 95% CI: 0.1-0.8). Muscle-directed intervention did not affect the SWV and size of sciatic nerve. Participants in the nerve-directed group showed a significant increase in ROM (+9.9°; 95% CI: 6.2-13.6) and a significant decrease in sciatic nerve SWV (> -1.8 m/s across nerve regions) compared with the control group. Nerve-directed intervention had no effect on the main outcomes at muscle and joint levels. These findings provide new insights into the long-term mechanical effects of stretching interventions and have relevance to clinical conditions where change in mechanical properties has occurred.NEW & NOTEWORTHY This study demonstrates that the mechanical properties of plantar flexor muscles and sciatic nerve can adapt mechanically to long-term stretching programs. Although interventions targeting muscular or nonmuscular structures are both effective at increasing maximal range of motion, the changes in tissue mechanical properties (stiffness) are specific to the structure being preferentially stretched by each program. We provide the first in vivo evidence that stiffness of peripheral nerves adapts to long-term loading stimuli using appropriate nerve-directed stretching.