Several studies have identified clinical, psychosocial, patient characteristic, and perioperative variables that are associated with persistent postsurgical pain; however, the relative effect of these variables has yet to be quantified. The aim of the study was to provide a systematic review and meta-analysis of predictor variables associated with persistent pain after total knee arthroplasty (TKA). Included studies were required to measure predictor variables prior to or at the time of surgery, include a pain outcome measure at least 3 months post-TKA, and include a statistical analysis of the effect of the predictor variable(s) on the outcome measure. Counts were undertaken of the number of times each predictor was analysed and the number of times it was found to have a significant relationship with persistent pain. Separate meta-analyses were performed to determine the effect size of each predictor on persistent pain. Outcomes from studies implementing uni- and multivariable statistical models were analysed separately. Thirty-two studies involving almost 30 000 patients were included in the review. Preoperative pain was the predictor that most commonly demonstrated a significant relationship with persistent pain across uni- and multivariable analyses. In the meta-analyses of data from univariate models, the largest effect sizes were found for: other pain sites, catastrophizing, and depression. For data from multivariate models, significant effects were evident for: catastrophizing, preoperative pain, mental health, and comorbidities. Catastrophizing, mental health, preoperative knee pain, and pain at other sites are the strongest independent predictors of persistent pain after TKA.

BACKGROUND: Conditioned pain modulation paradigms are often used to assess the diffuse noxious inhibitory control (DNIC) system. DNICs provide one of the main supraspinal pain inhibitory pathways and are impaired in several chronic pain populations. Only one previous study has examined the psychometric properties of the conditioned pain modulation technique and this study did not evaluate intersession reliability.OBJECTIVES: To evaluate and compare the intra‐ and intersession reliability of two conditioned pain modulation paradigms using different conditioning stimuli, and to determine the time course of conditioned pain inhibition following stimulus removal.METHODS: An electronic pressure transducer was used to determine the pressure‐pain threshold at the knee during painful conditioning of the opposite hand using the ischemic arm test and the cold pressor test. Assessments were completed twice on one day and repeated once approximately three days later.RESULTS: The two conditioning stimuli resulted in a similar increase in the pressure‐pain threshold at the knee, reflecting presumed activation of the DNIC system. Intrasession intraclass correlation coefficients for the cold pressor (0.85) and ischemic arm tests (0.75) were excellent. The intersession intraclass correlation coefficient for the cold pressor test was good (0.66) but was poor for the ischemic arm test (−0.4). Inhibition of the pressure‐pain threshold remained significant at 10 min following conditioning, but returned to baseline by 15 min.CONCLUSIONS: Within‐session reliability of DNIC assessment using conditioned pain modulation paradigms was excellent, but the applicability of assessing pain modulation over multiple sessions was influenced by the conditioning stimulus. The cold pressor test was the superior technique.

Purpose: To review quantitative and qualitative studies that have examined the users’ response to virtual reality game-based interventions in people with movement disorders associated with chronic neurological conditions. We aimed to determine key themes that influenced users’ enjoyment and engagement in the games and develop suggestions as to how future systems could best address their needs and expectations. Key message and implications: There were a limited number of studies that evaluated user opinions. From those found, seven common themes emerged: technology limitations, user control and therapist assistance, the novel physical and cognitive challenge, feedback, social interaction, game purpose and expectations, and the virtual environments. Our key recommendations derived from the review were to avoid technology failure, maintain overt therapeutic principles within the games, encompass progression to promote continuing physical and cognitive challenge, and to provide feedback that is easily and readily associated with success. Conclusions: While there have been few studies that have evaluated the users’ perspective of virtual rehabilitation games, our findings indicate that canvassing these experiences provides valuable information on the needs of the intended users. Incorporating our recommendations may enhance the efficacy of future systems to optimize the rehabilitation benefits of virtual reality games.

Introduction: A consequence of knee joint osteoarthritis (OA) is an inability to fully activate the quadriceps muscles, a problem termed arthrogenic muscle inhibition (AMI). AMI leads to marked quadriceps weakness that impairs physical function and may hasten disease progression. The purpose of the present study was to determine whether γ-loop dysfunction contributes to AMI in people with knee joint OA. Methods: Fifteen subjects with knee joint OA and 15 controls with no history of knee joint pathology participated in this study. Quadriceps and hamstrings peak isometric torque (Nm) and electromyography (EMG) amplitude were collected before and after 20 minutes of 50 Hz vibration applied to the infrapatellar tendon. Between-group differences in pre-vibration torque were analysed using a one-way analysis of covariance, with age, gender and body mass (kg) as the covariates. If the γ-loop is intact, vibration should decrease torque and EMG levels in the target muscle; if dysfunctional, then torque and EMG levels should not change following vibration. One-sample t tests were thus undertaken to analyse whether percentage changes in torque and EMG differed from zero after vibration in each group. In addition, analyses of covariance were utilised to analyse between-group differences in the percentage changes in torque and EMG following vibration. Results: Pre-vibration quadriceps torque was significantly lower in the OA group compared with the control group (P = 0.005). Following tendon vibration, quadriceps torque (P < 0.001) and EMG amplitude (P ≤0.001) decreased significantly in the control group but did not change in the OA group (all P > 0.299). Hamstrings torque and EMG amplitude were unchanged in both groups (all P > 0.204). The vibration-induced changes in quadriceps torque and EMG were significantly different between the OA and control groups (all P < 0.011). No between-group differences were observed for the change in hamstrings torque or EMG (all P > 0.554). Conclusions: γ-loop dysfunction may contribute to AMI in individuals with knee joint OA, partially explaining the marked quadriceps weakness and atrophy that is often observed in this population.

Purpose. The purpose of this study is to evaluate the feasibility and users' perspectives of a novel virtual reality (VR) game-based rehabilitation intervention for people with stroke.Method. Six people with upper limb hemiplegia participated in a 6-week intervention that involved VR games. A series of eight progressively complex games was developed that required participants to navigate a submarine in a virtual ocean environment. Movement of the submarine was directed by forces applied to an arm interface by the affected limb. Outcome measures included assessments of arm function, questionnaires evaluating the intervention and a semi-structured interview concerning the participants' opinion of the intervention. Results. All participants improved their performance on the games, although there were limited changes in clinical measures of arm function. All participants reported that they enjoyed the intervention with a wide range of overall perceptions of the experience of using VR. Three themes emerging from the interview data were: stretching myself, purpose and expectations of the intervention and future improvements. Conclusions. Participants found that taking part in this pilot study was enjoyable and challenging. Participants' feedback suggested that the games may be motivating and engaging for future users and have provided a basis for further development of the intervention.