Randomized Placebo-Controlled Trial of 60-Day Percutaneous Peripheral Nerve Stimulation Treatment Indicates Relief of Persistent Postoperative Pain, and Improved Function After Knee Replacement

OBJECTIVES

Total knee arthroplasty (TKA) is an effective surgery for end-stage knee osteoarthritis, but chronic postoperative pain and reduced function affect up to 20% of patients who undergo such surgery. There are limited treatment options, but percutaneous peripheral nerve stimulation (PNS) is a promising nonopioid treatment option for chronic, persistent postoperative pain. The objective of the present study was to evaluate the effect of a 60-day percutaneous PNS treatment in a multicenter, randomized, double-blind, placebo-controlled trial for treating persistent postoperative pain after TKA.

MATERIALS AND METHODS

Patients with postoperative pain after knee replacement were screened for this postmarket, institutional review board-approved, prospectively registered (NCT04341948) trial. Subjects were randomized to receive either active PNS or placebo (sham) stimulation. Subjects and a designated evaluator were blinded to group assignments. Subjects in both groups underwent ultrasound-guided placement of percutaneous fine-wire coiled leads targeting the femoral and sciatic nerves on the leg with postoperative pain. Leads were indwelling for eight weeks, and the primary efficacy outcome compared the proportion of subjects in each group reporting ≥50% reduction in average pain relative to baseline during weeks five to eight. Functional outcomes (6-minute walk test; 6MWT and Western Ontario and McMaster Universities Osteoarthritis Index) and quality of life (Patient Global Impression of Change) also were evaluated at end of treatment (EOT).

RESULTS

A greater proportion of subjects in the PNS groups (60%; 12/20) than in the placebo (sham) group (24%; 5/21) responded with ≥50% pain relief relative to baseline (p = 0.028) during the primary endpoint (weeks 5-8). Subjects in the PNS group also walked a significantly greater distance at EOT than did those in the placebo (sham) group (6MWT; +47% vs -9% change from baseline; p = 0.048, n = 18 vs n = 20 completed the test, respectively). Prospective follow-up to 12 months is ongoing.

CONCLUSIONS

This study provides evidence that percutaneous PNS decreases persistent pain, which leads to improved functional outcomes after TKA at EOT.

Network model of nociceptive processing in the superficial spinal dorsal horn reveals mechanisms of hyperalgesia, allodynia, and spinal cord stimulation

The spinal dorsal horn (DH) processes sensory information and plays a key role in transmitting nociception to supraspinal centers. Loss of DH inhibition during neuropathic pain unmasks a pathway from nonnociceptive Aβ-afferent inputs to superficial dorsal horn (SDH) nociceptive-specific (NS) projection neurons, and this change may contribute to hyperalgesia and allodynia. We developed and validated a computational model of SDH neuronal circuitry that links nonnociceptive Aβ-afferent inputs in lamina II/III to a NS projection neuron in lamina I via a network of excitatory interneurons. The excitatory pathway and the NS projection neuron were in turn gated by inhibitory interneurons with connections based on prior patch-clamp recordings. Changing synaptic weights in the computational model to replicate neuropathic pain states unmasked a low-threshold excitatory pathway to NS neurons similar to experimental recordings. Spinal cord stimulation (SCS) is an effective therapy for neuropathic pain, and accumulating experimental evidence indicates that NS neurons in the SDH also respond to SCS. Accounting for these responses may inform therapeutic improvements, and we quantified responses to SCS in the SDH network model and examined the role of different modes of inhibitory control in modulating NS neuron responses to SCS. We combined the SDH network model with a previously published model of the deep dorsal horn (DDH) and identified optimal stimulation frequencies across different neuropathic pain conditions. Finally, we found that SCS-generated inhibition did not completely suppress model NS activity during simulated pinch inputs, providing an explanation of why SCS does not eliminate acute pain.NEW & NOTEWORTHY Chronic pain is a severe public health problem that reduces the quality of life for those affected and exacts an enormous socio-economic burden worldwide. Spinal cord stimulation (SCS) is an effective treatment for chronic pain, but SCS efficacy has not significantly improved over time, in part because the mechanisms of action remain unclear. Most preclinical studies investigating pain and SCS mechanisms have focused on the responses of deep dorsal horn (DDH) neurons, but neural networks in the superficial dorsal horn (SDH) are also important for processing nociceptive information. This work synthesizes heterogeneous experimental recordings from the SDH into a computational model that replicates experimental responses and that can be used to quantify neuronal responses to SCS under neuropathic pain conditions.

Nurses as patient navigators in cancer diagnosis: review, consultation and model design

The diagnostic phase of cancer care is an anxious time for patients. Patient navigation is a way of assisting and supporting individuals during this time. The aim of this review is to explore patient navigation and its role in the diagnostic phase of cancer care. We reviewed the literature for definitions and models of navigation, preparation for the role and impact on patient outcomes, specifically addressing the role of the nurse in patient navigation. Interviews and focus groups with healthcare providers and managers provided further insight from these stakeholder groups. Common to most definitions of navigation is the navigator's multifaceted role in facilitating processes of care, assisting patients to overcome barriers and providing information and support. Navigation may be provided by laypersons, clerical staff and/or healthcare professionals. In the diagnostic phase it has the potential to affect efficiency of diagnostic testing, patients' experience during this time and preparation for decision-making around treatment options. Patient care during the diagnostic phase requires various levels of navigation, according to individual informational, physical and psychosocial needs. Identifying those individuals who require more support--whether physical or psychosocial--during the diagnostic phase is of critical importance.

The nature of increased hospital use in poor neighbourhoods: findings from a Canadian inner city

The relationship between socioeconomic factors and hospital use is not well understood in the Canadian context. We used the 1991 Canada census and 1990-92 Ontario hospital discharge abstracts for residents of southeast Toronto to calculate crude and age-sex adjusted rates of hospital admission, bed days, and costs by quintile of low-income households. Population-based rates of admission to hospital, bed days and costs were all significantly related to census tract income (p < 0.01 for males and females). The number of admissions per person admitted was significantly associated with census tract income (p < 0.01 for males and females), but length of stay and resource intensity weight were not. Hospital costs were 50.0% higher for the poorest quintile of neighbourhoods than for the wealthiest and 35.8% higher than for the middle-income quintile. Poor urban neighbourhoods may require more resources than previously anticipated, related to higher hospital admission and readmission rates.

The nature of increased hospital use in poor neighbourhoods: findings from a Canadian inner city

The relationship between socioeconomic factors and hospital use is not well understood in the Canadian context. We used the 1991 Canada census and 1990-92 Ontario hospital discharge abstracts for residents of southeast Toronto to calculate crude and age-sex adjusted rates of hospital admission, bed days, and costs by quintile of low-income households. Population-based rates of admission to hospital, bed days and costs were all significantly related to census tract income (p < 0.01 for males and females). The number of admissions per person admitted was significantly associated with census tract income (p < 0.01 for males and females), but length of stay and resource intensity weight were not. Hospital costs were 50.0% higher for the poorest quintile of neighbourhoods than for the wealthiest and 35.8% higher than for the middle-income quintile. Poor urban neighbourhoods may require more resources than previously anticipated, related to higher hospital admission and readmission rates.

Current treatment options for the restoration of articular cartilage

Over the past several decades, much has been learned about articular cartilage and its physiological capacity to restore itself. While articular cartilage does appear to have some regenerative capabilities, it appears to lose this capacity over a period of time, making restoration of articular surfaces more and more difficult. To date, no technique has been completely successful in achieving exactly normal regenerative articular cartilage. Arthroscopic lavage and debridement provides temporary relief of symptoms. This probably works by removing degradative enzymes that contribute to synovitis and also to the further breakdown of articular cartilage. Bone marrow stimulation techniques such as abrasion arthroplasty, drilling, and microfracture produce only fibrocartilage and therefore do not offer a long-term cure. Perichondral and periosteal interposition grafts produce repair tissue that is similar to hyaline cartilage but also lack the mechanical durability. Like bone marrow stimulation techniques, interposition grafts introduce precursor cells, which have a tendency to differentiate along lines other than cartilage. This leads to an inferior quality of repair tissue. Currently, chondrogenic-stimulating factors and artificial matrices are currently being researched and developed. Much has been learned about the various growth factors that stimulate chondrocyte differentiation and extracellular matrix production, but to date, there has not been a clinical technique that has shown any long-term promise. Ultimately, the goal will be to take precursor cells from an easily accessible source such as the iliac crest, mix them with growth factors that have been derived genetically in the lab, and provide an artificial matrix that in combination can produce restoration of articular cartilage at minimal cost and patient morbidity. Autologous osteochondral transplant systems have shown encouraging results but there are still problems. Graft matching and contouring to the recipient articular surface is difficult. Donor sites can be a limiting factor. Furthermore, the fibrocartilaginous interface between the donor and recipient site may contribute to breakdown in the long run. Autologous chondrocyte implantation is a biological repair process that also has shown encouraging results. It must be remembered that this is not normal articular cartilage--it is only hyaline-like cartilage. The technique is expensive and is technically difficult to perform. There are no randomized prospective studies that compare the natural history of the repair tissue to that of other forms of repair tissue. Long-term functional outcome is still a significant question mark. In addition, it has not been shown that autologous chondrocyte implantation can prevent degenerative changes. In the future, we probably will see delivery systems using stimulating growth factors, chondrocytes, and synthetically derived matrices. When placed in combination and with the right mechanical stimuli, we may ultimately achieve true restoration of articular cartilage.

Pulmonary stenosis with ventricular septal defect, common aorticopulmonary trunk, and dextroposition of the aorta: morphologic and qualitative physiologic effects in caffeine-treated chick embryos

Effects of caffeine administration to Hamburger-Hamilton stage 19 chick embryos (3 days of incubation) were investigated. A morphologic study of the effect of caffeine on cardiogenesis showed that caffeine produced total cardiac malformations in the chick in a dose-related fashion. A maximum frequency of 70.6% was observed with 4.7 mg caffeine. Major malformations included common aorticopulmonary trunk and dextroposition of the aorta accompanied by ventricular septal defect with/without pulmonary stenosis. Qualitative analysis of cinegraphs following exposure of embryos to a single teratogenic dose of caffeine (3.5 mg/egg) produced marked alterations in cardiac function when compared with chick Ringer's controls. Within 3 minutes after exposure to caffeine, dilation of the common ventricle and weak ventricular contractility were observed and persisted for 1 hour. Dose-response data and microcinematographic observations suggest that caffeine induced cardiac anomalies by a direct toxic effect on the embryo rather than by altering cardiac cell function. Our data also suggest that pathophysiologic changes in cardiac function may play an important role in the pathogenesis of caffeine-induced cardiac anomalies in the chick embryo.

Effect of fasting on liveweight and subcutaneous fat depth of cattle

Two groups of British bred steers, mean liveweight 384 kg, were held off feed for 5 days with or without water and their liveweights and subcutaneous fat depth at two points determined daily. Fat depths were determined using a Scanogram. The aim was to determine the possible effect of management during marketing on some of the carcase characteristics likely to be used for market specification in Australia. The curvilinear decrease in liveweight was less in the group with water available although their mean daily consumption of water was low (61 head-1). No difference in the rate of change of fat depth between the group with water and the group without it was detected. There was no detectable change in fat depth measured at a point 2.5 cm from the edge of the eye muscle (FD2) whereas fat depth over the eye muscle (FDI) appeared to increase in the 5 day period (0.043 mm day-1). Rates of change of fat depth at the two sites were not correlated. The rate of change of FD2 was negatively correlated (r = 0.45) with initial FD2 fat depth; in animals with an initial FD2 of < 5 mm, FD2 appeared to increase with fasting ; in animals with an initial FD2 of > 5 mm, FD2 decreased with fasting.