Intermittent Hypoxia-Induced Enhancements in Corticospinal Excitability Predict Gains in Motor Learning and Metabolic Efficiency.

Acute intermittent hypoxia (AIH) enhances human motor function after incomplete spinal cord injury. Although the underlying mechanisms in humans are unknown, emerging evidence indicates that AIH facilitates corticospinal excitability to the upper limb. However, the functional relevance of this plasticity remains unexplored, and it is unclear whether similar plasticity can be induced for lower limb motor areas. We recently demonstrated that AIH improves motor learning and metabolic efficiency during split-belt walking. Thus, we hypothesized that AIH increases lower limb excitability and that these enhancements would predict the magnitude of motor learning and the corresponding reductions in net metabolic power. We assessed tibialis anterior (TA) excitability using transcranial magnetic stimulation and quantified changes in spatiotemporal asymmetries and net metabolic power in response to split-belt speed perturbations. We show that AIH enhances TA excitability, and that the magnitude of this facilitation positively correlates with greater spatiotemporal adaptation. Notably, we demonstrate a novel association between increased excitability and reduced net metabolic power during motor learning and savings. Together, our results suggest that AIH-induced gains in excitability predict both the magnitude of motor learning and the associated metabolic efficiency. Determining indices of AIH-induced improvements in motor performance is critical for optimizing its therapeutic reach.

Cannabis Use Does Not Affect Outcomes After Total Hip Arthroplasty.

BACKGROUND: Cannabis use in patients undergoing arthroplasty has increased with ongoing legalization throughout the United States. The purpose of this study was to report total hip arthroplasty (THA) outcomes in patients self-reporting cannabis use. METHODS: There were 74 patients who underwent primary THA from January 2014 to December 2019 at a single institution with minimum 1-year follow-up who had their self-reported cannabis use retrospectively reviewed. Patients who had a history of alcohol or illicit drug abuse were excluded. A match control was conducted based on age; body mass index; sex; Charlson Comorbidity Index; insurance status; and use of nicotine, narcotics, antidepressants, or benzodiazepines to patients undergoing THA who did not self-report cannabis use. Outcomes included Harris Hip Score (HHS), Hip Disability and Osteoarthritis Outcome Score for Joint Reconstruction (HOOS JR), in hospital morphine milligram equivalents (MMEs) consumed, outpatient MMEs prescribed, in hospital lengths of stay (LOS), postoperative complications, and readmissions. RESULTS: There was no difference in the preoperative, postoperative, or change in Harris Hip Score or HOOS JR between cohorts. There was also no difference in hospital MMEs consumed (102.4 versus 101, P = .92), outpatient MMEs prescribed (119 versus 156, P = .11) or lengths of stay (1.4 versus 1.5 days, P = .32). Also, readmissions (4 versus 4, P = 1.0) and reoperations (2 versus 1, P = .56) were not different between groups. CONCLUSION: Self-reported cannabis use does not influence 1-year outcomes after THA. Further studies are warranted to determine the efficacy and safety of perioperative cannabis use after THA to help guide orthopaedic surgeons in counseling patients.

Effectiveness of Manual Terminal Cleaning Varies on High-Touch Surfaces Near the Operative Field.

Background: Periprosthetic joint infection may result from pathogen to patient transmission within the environment. The purpose of this study is to evaluate the contamination level of selected high-touch surfaces in the operating room (OR) using a blacklight fluorescent marking system after a manual terminal clean. Methods: Prior to the manual terminal clean, 16 high-touch surfaces were marked using a blacklight fluorescent gel. The marked areas were assessed the next morning for thoroughness of cleaning. Surfaces were categorized based on the average percent of the marks removed as "clean" (>75%), "partially clean" (26%-74%), or poorly cleaned (<25%). This process was repeated randomly 12 times. Terminal cleaning was done in the standard fashion, and the perioperative team was unaware of the initiation of this study. Results: A total of 936 marks were analyzed. There was a significant difference in the number of marks completely clean (29.1%, 272/936) vs marks that were not touched (40.8%, 382/936), P < .001. Only the OR back table (75%) had a rating of clean. Partially clean areas included Mayfield table (72%), overhead lights (70.1%), infusion pump (61.1%), clock reset button (58.3%), table remote control (50%), tourniquet machine (50%), and the OR table (33.3%). Poorly cleaned surfaces included anesthesia medication cart (21.8%), door handles (20.8%), phone (16.7%), electrocautery unit (16.7%), foot pedal (16.7%), anesthesia cart (16.2%), nurses' station (14.1%), and supply cabinet doors (6%). Conclusions: Effectiveness of manual terminal cleaning varied greatly across surfaces. In general, surfaces further from the operative field were less likely to have markings removed.

Does the contribution of the paretic hand to bimanual tasks change with grip strength capacity following stroke?

INTRODUCTION: The majority of tasks we perform every day require coordinated use of both hands. Following a stroke, the paretic hand contribution to bimanual tasks is often impaired, leading to asymmetric hand use. Grip strength is a commonly used clinical indicator of progress towards stroke motor recovery. The extent to which the paretic hand's contribution to bimanual tasks improves with increasing grip strength is not known. The purpose of this study is to determine how grip strength capacity of the paretic hand influences its contribution to bimanual tasks. METHODS: Twenty-one chronic stroke participants and ten older control participants volunteered to take part in this study. The individuals with stroke were recruited in two distinct groups based on the grip strength capacity of paretic hand, i.e., paretic hand strength/non-paretic hand strength, expressed as a percentage. The low strength-capacity group was identified as individuals with grip strength capacity less than 60% and the high strength-capacity group was individuals with grip strength capacity greater than or equal to 60%. All groups performed isometric, grip force contractions in two bimanual tasks - a maximum force production (MVC) task and a submaximal force control task. We quantified the magnitude of force contributed by the paretic and non-paretic hands during both tasks. Additionally, in the force control task we quantified the amount and structure of force variability using coefficient of variation (CV) and approximate entropy (ApEn) for both hands. RESULTS: The amount of force contributed by the paretic hand increased in bimanual tasks with an increase in its grip strength capacity, (maximal force production: r = 0.85, p < 0.01; submaximal force control: r = 0.62, p < 0.01). In the bimanual MVC task and bimanual force control task, both hands contributed equal magnitudes of force in the high strength-capacity group but unequal forces in low strength-capacity group. Surprisingly, the amount and structure of force variability in bimanual force control tasks did not change with the increase in grip strength capacity, (CV of force: r = - 0.07, p = 0.77; ApEn: r = - 0.23, p = 0.31). Both low and high strength-capacity stroke groups showed significantly higher CV of force and heightened ApEn compared with the control group. CONCLUSION: With the increase in grip strength capacity, the paretic hand contributes greater magnitude of force but continues to show persistent deficits in force modulation in bimanual tasks. Therefore, stroke rehabilitation should emphasize retraining of the paretic hand for force modulation to maximize its use in bimanual tasks.

A back table ultraviolet light decreases environmental contamination during operative cases.

BACKGROUND: The purpose of this study is to assess the impact of a germicidal ultraviolet light-emitting diode (LED) on the contamination level of a back table in the operating room (OR) during total joint arthroplasty procedures. METHODS: Eight Tryptic Soy Agar petri plates were placed on a table located near the operative field and exposed to air. One plate was removed on the hour over an 8-hour time span. The back table had either an UV-LED for disinfection or a sham UV-LED. This process was repeated in 12 different ORs (6 with UV light, 6 with sham device). The plates were then incubated for 48 hours at 36°C ± 1°C . Colony forming units (CFU) were recorded 24 and 48 hours after incubation. RESULTS: There was a statistically significant difference in total CFUs between the intervention vs sham at 24-hours (27 vs 95, P = .0001) and 48-hours (38 vs 122, P < .0001). The multivariate analysis revealed that the 24-hour and 48-hour count, the predictors UV light (P = .002) and hour of plate removal (P = .050) were statistically significantly associated with CFU counts. Together, the predictor variables explained 15.8% and 23.0% of the variance in CFU counts at 24- and 48-hours, respectively. CONCLUSIONS: A back table UV-LED may decrease environmental contamination near the operative field. This has potential to lead to a decrease in joint infection.

Incidence and Predictive Risk Factors of Postoperative Urinary Retention After Primary Total Knee Arthroplasty.

BACKGROUND: Postoperative urinary retention (POUR) after total knee arthroplasty (TKA) may cause urologic injury and delay patient discharge. This study measures the incidence of POUR and identifies predictive risk factors. METHODS: Two-hundred seventy-one consecutive patients undergoing primary unilateral TKA were prospectively enrolled. Bladder scans were performed in the postanesthesia care unit (PACU) and every four hours thereafter. POUR was defined as >400cc with inability to void and was treated with catheterization. Patient demographics, urologic history, operative data, perioperative medications, and bladder scanner volumes were investigated with the univariate and multivariate logistic regression analysis. RESULTS: Fifty-five patients (20%) developed POUR. Compared with non-POUR patients, PACU bladder scan volumes were greater in patients who developed POUR (344cc vs 120cc, P < .001). POUR patients had lower BMI (27.8 vs 29.4, P = .03), longer operative duration (83.9 vs 76.0 minutes, P = .002), and lower ASA scores (2.2 vs 2.4, P = .02). Total intravenous fluid was equivalent between groups (1134cc vs 1185cc, P = .41). POUR patients received less narcotics measured by morphine milligram equivalents (16.1 vs 23.9, P < .001). Fifteen variables including spinal type (bupivacaine and ropivacaine) and paralytic use were not predictive of POUR. Potentially predictive variables included anesthetic types administered (spinal, general, regional, and combination) and perioperative administration of nonsteroidal anti-inflammatory drugs (NSAIDs), glycopyrrolate, and muscle relaxants. The multivariate analysis showed that NSAIDs (P = .05) and glycopyrrolate (P = .04) were significant predictors. CONCLUSION: A significant percentage of patients develop POUR after TKA. Select patient demographics and PACU bladder scanning may identify those at risk. Appropriate pain control and judicious use of perioperative NSAIDs and glycopyrrolate may help minimize the risk of POUR.

Alpha-Defensin Is Not Superior to Traditional Diagnostic Methods for Detection of Periprosthetic Joint Infection in Total Hip Arthroplasty and Total Knee Arthroplasty Patients.

BACKGROUND: Synovial fluid alpha-defensin (AD) may improve diagnostic accuracy of periprosthetic joint infection (PJI) following total knee (TKA) and hip (THA) arthroplasty but is only available as send-out test. This study evaluated laboratory result accuracy between send-out test vs hospital labs and if AD made a difference in treatment plan. METHODS: A retrospective review was performed of 152 consecutive patients with a TKA or THA joint aspiration for painful or clinically concerning joint. Synovial fluid was sent to our institution (hospital-based labs, HBL) and send-out immunoassay laboratory (Synovasure). Patients were scored with specific criteria from validated scoring system for PJI using HBL and Synovasure results. The score with and without AD test was compared to determine if AD impacted patient management. RESULTS: Overall, there was strong agreement between institutions for PJI diagnosis (Cohen's kappa score 0.96). Twenty-nine patients had PJI diagnosis (score ≥6), of which 28 (97%) had positive AD with 1 false-negative result. Sixty-three patients had inconclusive score (between 2 and 5) and 60 patients had negative PJI diagnosis (score ≤1). Of these patients, 5 underwent surgery for infection. Two patients had surgery for positive AD, 2 for positive culture, and 1 because of elevated HBL results. The AD test changed the PJI diagnosis and influenced decision for surgery in only 1.3% (2/152) of patients. CONCLUSION: Minimal differences were found in laboratory values between institutions. The addition of AD may be useful in cases of equivocal laboratory results but does not appear to be necessary for routine diagnosis of PJI after TKA/THA. LEVEL EVIDENCE: Level III.

Alpha-Defensin Offers Limited Utility in Routine Workup of Periprosthetic Joint Infection.

BACKGROUND: Alpha-defensin (AD) is a synovial biomarker included as a minor criterion in the scoring system for diagnosing periprosthetic joint infection (PJI). The purpose of this study is to study the impact of AD on diagnosis and management of PJI. METHODS: Synovial fluid from 522 patients after total knee and hip arthroplasty was retrospective reviewed. Synovial white blood cell count, percentage of neutrophils, and culture from the AD immunoassay laboratory were reviewed with serum erythrocyte sedimentation rate and C-reactive protein values from our institution. A modified version of the 2018 scoring system for diagnosis of PJI was used, only scoring white blood cell count, percentage of neutrophils, erythrocyte sedimentation rate, and C-reactive protein. AD was then analyzed with these scores to determine if AD changed diagnostic findings or clinical management. RESULTS: Eight-two patients were categorized as "infected" (score ≥6), of which 76 patients had positive AD. Of the 6 "infected" patients with negative AD, 2 had positive cultures (Staphylococcus epidermidis). Two-hundred thirteen patients were diagnosed as "possibly infected" (score 2-5). Fourteen of these patients had positive AD, of which 5 had positive cultures assisting with the diagnosis. The AD test changed the diagnosis from "possibly infected" to "infected" in 8 patients (1.5%) but only altered treatment plan in 6 patients (1.1%). A score <2 (not infected) was calculated in 227 patients with no patients having positive AD. CONCLUSION: AD may be beneficial in some cases where laboratory values are otherwise equivocal; however, its routine use for the diagnosis of PJI may not be warranted.