Use of Triggers to Detect Adverse Events After Outpatient Orthopedic Surgery at a Single Ambulatory Surgery Center.

Literature on adverse events (AEs) after outpatient orthopedic surgery is relatively sparse, and efforts to detect, measure, and track AEs after outpatient surgery lag behind those for the inpatient setting. Detection of AEs has traditionally relied on patient safety indicators (from billing data) and self-reporting, but these methods have been shown to have low sensitivity, missing up to 90% of AEs. There is growing recognition that the trigger method, which uses "triggers" as red flags to initiate more detailed chart audits, can serve as a more sensitive alternative to detect AEs. Moreover, the recent widespread adoption of electronic health records (EHRs) can provide faster automated methods for identifying triggers and estimating AE rates. This study evaluates the ability of 6 separate EHR-based triggers to predict AEs after outpatient orthopedic surgery and compares this trigger method with AE self-reporting. Triggers have the potential to decrease postoperative morbidity after outpatient orthopedic surgery and may lead to quality improvement. Further research is needed to qualify triggers as screening tools in the outpatient setting. [Orthopedics. 2022;45(2):116-121.].

Predictors of Success in an Orthopaedic Residency.

¼: Orthopaedic surgery is one of the most competitive residencies to match into. Meanwhile, the average applicant's United States Medical Licensing Examination (USMLE) test scores, research involvement, and number of clinical honors increase every year. ¼: Measures such as USMLE scores, productivity in research, Alpha Omega Alpha (AΩA) honor society status, number of clinical honors, and performance on away rotations have all been cited as factors contributing to program directors choosing applicants for interviews and ranking them for their program. However, questions remain as to whether these measures translate to success on board examinations, high faculty evaluations, and designation as chief resident during orthopaedic residency. ¼: USMLE scores have been shown to correlate with Orthopaedic In-Training Examination (OITE) and American Board of Orthopaedic Surgery (ABOS) scores, while clinical grades and AΩA status correlate with faculty evaluations. Participating in research as a medical student was predictive of research productivity in residency but did not correlate with standardized testing scores or faculty evaluations. ¼: The literature has suggested ways in which measures such as personality and grit may be used in the application process and how these factors may contribute to predictors of success. However, additional research is needed to measure and define personality and grit during the application evaluation process.

Radiologic Measurements in the Assessment of Patellar Instability: A Systematic Review and Meta-analysis.

BACKGROUND: Numerous diagnostic imaging measurements related to patellar instability have been evaluated in the literature; however, little has been done to compare these findings across multiple studies. PURPOSE: To review the different imaging measurements used to evaluate patellar instability and to assess the prevalence of each measure and its utility in predicting instability. We focused on reliability across imaging modalities and between patients with and without patellar instability. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: We performed a systematic review of the literature using the PubMed, SCOPUS, and Cochrane databases. Each database was searched for variations of the terms "patellar instability," "patellar dislocation," "trochlear dysplasia," "radiographic measures," "computed tomography," and "magnetic resonance imaging." Studies were included if they were published after May 1, 2009, and before May 1, 2019. A meta-analysis using a random effects model was performed on several measurements, comparing instability and control groups to generate pooled values. RESULTS: A total of 813 articles were identified, and 96 articles comprising 7912 patients and 106 unique metrics were included in the analysis. The mean patient age was 23.1 years (95% CI, 21.1-24.5), and 41% were male. The tibial tubercle-trochlear groove (TT-TG) distance was the most frequently included metric (59 studies), followed by the Insall-Salvati ratio and Caton-Deschamps index (both 26 studies). The interobserver intraclass correlation coefficients were excellent or good for the TT-TG distance and Insall-Salvati ratio in 100% of studies reporting them; however, for the Caton-Deschamps index and Blackburne-Peel ratio, they were excellent or good in only 43% and 40% of studies. Pooled magnetic resonance imaging values for TT-TG distance (P < .01), Insall-Salvati ratio (P = .01), and femoral sulcus angle (P = .02) were significantly different between the instability and control groups. Values for tibial tubercle-posterior cruciate ligament distance (P = .36) and Caton-Deschamps index (P = .09) were not significantly different between groups. CONCLUSION: The most commonly reported measurements for evaluating patellar instability assessed patellar tracking and trochlear morphology. The TT-TG distance was the most common measurement and was greater in the patellar instability group as compared with the control group. In addition, the TT-TG, tibial tubercle-posterior cruciate ligament, and patellar tendon-trochlear groove distances were highly reproducible measurements for patellar tracking, and the Insall-Salvati ratio had superior reproducibility for assessing patellar height.

The Financial Implications of Telehealth Visits Within a Hand and Wrist Surgery Clinical Practice During the COVID-19 Pandemic.

PURPOSE: Telehealth use is likely to increase as a result of practice changes during the COVID-19 pandemic, although the overall picture surrounding the billing, coding, and continued insurance coverage of these visits remains uncertain. The purpose of this study was to identify potential financial implications of continued telehealth use in hand and wrist surgery clinical practice. METHODS: Two hundred telehealth visits were randomly selected and matched 1:1 based on primary diagnosis code to in-person visits. Medical and billing records were reviewed to compare visit complexities, total visit charges, work relative value units (wRVUs), and approved insurance reimbursement. Postoperative visits and visits with radiographic evaluation were excluded. RESULTS: Level 4 visits were more common with in-person encounters compared to telehealth (11% vs 2%, respectively), and level 1 and 2 visits were more common with telehealth compared to in-person encounters (14% vs 6%, respectively). Twenty-seven in-person visits (13%) had at least 1 additional procedure code billed. The mean total visit charge was 26% less in telehealth compared to in-person. Based on the primary procedure code alone, the sum of wRVUs was 15.1 points less in the telehealth cohort compared to in-person (per visit average, 1.1 [telehealth] vs 1.2 [in-person]). The 28 additional services provided during in-person visits accounted for an added 20.7 wRVUs. Unpaid claims were more common among telehealth encounters (8% [telehealth] vs 3% [in-person]). CONCLUSIONS: Higher complexity visits and visits with additional procedural codes billed were more common with in-person visits. This led to a lower number of total wRVUs and lower total visit charges among the included telehealth visits compared to the matched in-person controls. CLINICAL RELEVANCE: It is important to understand and consider the long-term financial impact of telehealth implementation. Practices must develop strategies to incorporate radiographic evaluation into telehealth visits and effectively stratify those patients that may require procedural interventions for in-person visits. Understanding the economic implications of this changing care delivery paradigm, providers can continue to provide telehealth services while protecting the financial sustainability of hand surgery practices.

Characteristics and outcomes of gastrointestinal bleeding in patients with continuous-flow left ventricular assist devices: A systematic review.

Gastrointestinal bleeding (GIB) is a common adverse event after continuous-flow left ventricular assist device (CF-LVAD) implantation. We sought to evaluate patterns of GIB development and related outcomes in CF-LVAD recipients. An electronic search was performed to identify all articles related to GIB in the setting of CF-LVAD implantation. A total of 34 studies involving 1087 patients were pooled for analysis. Mean patient age was 60 years (95% CI 57-64) and 24% (95% CI 21-28%) were female. The mean time from CF-LVAD implantation to the first GIB was 54 days (95% CI 24-84) with 40% (95% CI 34-45%) of patients having multiple episodes of GIB. Anemia was present in 75% (95% CI 41-93%) and the most common etiology of bleeding was arteriovenous malformations (36% [95% CI 24-50%]). The mean duration of follow-up was 14.6 months (95% CI 6.9-22.3) during which the all-cause mortality rate was 21% (95% CI 12-36%) and the mortality rate from GIB was 4% (95% CI 2-9%). Thromboembolic events occurred in 32% (95% CI 22-44%) of patients with an ischemic stroke rate of 16% (95% CI 3-51%) and a pump thrombosis rate of 8% (95%CI 3-22%). Heart transplantation was performed in 31% (95% CI 18-47%) of patients, after which 0% (95% CI 0-10%) experienced recurrent GIB. GIB is a major source of morbidity among CF-LVAD recipients. While death due to GIB is rare, cessation of anticoagulation during treatment increases the risk of subsequent thrombotic events. Heart transplant in these patients appears to reliably resolve the risk of future GIB.

Repair of ischemic ventricular septal defect with and without coronary artery bypass grafting.

BACKGROUND AND AIM OF THE STUDY: Ventricular septal defect (VSD) following myocardial infarction (MI) is a relatively infrequent complication with high mortality. We sought to investigate the effect of concomitant coronary artery bypass graft (CABG) on outcomes following post-MI VSD repair. METHODS: Electronic search was performed to identify all relevant studies published from 2000 to 2018. Sixty-seven studies were selected for the analysis comprising 2174 patients with post-MI VSD. Demographic information, perioperative variables, and outcomes including survival data were extracted and pooled for systematic review and meta-analysis. RESULTS: Single-vessel disease was most common (47%, 95% confidence interval [CI], 42-52), left anterior descending coronary artery was the most commonly involved vessel (55%, 95% CI, 46-63), and anterior wall was the most commonly affected territory (57%, 95% CI, 51-63). Concomitant CABG was performed in 52% (95% CI, 46-57) of patients. Of these, infarcted territory was re-vascularized in 54% (95% CI, 23-82). A residual/recurrent shunt was present in 29% (95% CI, 24-34) of patients. Of these, surgical repair was performed in 35% (95% CI, 28-41) and transcatheter repair in 11% (95% CI, 6-21). Thirty-day mortality was 30% (95% CI, 26-35) in patients who had preoperative coronary angiogram, and 58% (95% CI, 43-71) in those who did not (P < .01). No significant survival difference observed between those who had concomitant CABG vs those without CABG. CONCLUSIONS: Concomitant CABG did not have a significant effect on survival following VSD repair. Revascularization should be weighed against the risks associated with prolonged cardiopulmonary bypass.

Comparison of SynCardia total artificial heart and HeartWare HVAD biventricular support for management of biventricular heart failure: a systematic review and meta-analysis.

BACKGROUND: The aim of this study was to compare the outcomes of patients undergoing SynCardia total artificial heart (TAH) and biventricular HeartWare ventricular assist device (Bi-HVAD) support for biventricular heart failure (HF). METHODS: Electronic search was performed to identify all relevant studies detailing patients who underwent biventricular assist device implantation using Bi-HVAD devices and those who underwent TAH placement for biventricular HF. Twelve studies including 512 patients in the TAH group versus 38 patients in the Bi-HVAD group were pooled for meta-analysis. RESULTS: Ischemic cardiac etiology was present in 32% (95% CI, 24-47) of TAH vs. 15% (95% CI, 4-44) of Bi-HVAD patients (P=0.21). There was a comparable incidence of stroke [TAH 11% (95% CI, 7-16) vs. Bi-HVAD 13% (95% CI, 2-51), P=0.86] and acute kidney injury [TAH 28% (95% CI, 2-89) vs. Bi-HVAD 27% (95% CI, 9-59), P=0.98]. Overall infection rate was 67% (95% CI, 47-82) in TAH and 36% (95% CI, 10-74) in Bi-HVAD (P=0.16). Driveline infections were comparable between the two groups [TAH 11% (95% CI, 6-19) vs. Bi-HVAD 8% (95% CI, 1-39), P=0.73] and although a higher incidence of mediastinitis was found in the Bi-HVAD group [TAH 4% (95% CI, 2-7) vs. Bi-HVAD 15% (95% CI, 4-45), P=0.07] there was no statistically significant difference between the groups. Postoperative bleeding was present in 42% (95% CI, 28-58) of TAH vs. 23% (95% CI, 8-52) of Bi-HVAD (P=0.22). Patients in the TAH group had shorter duration of support [TAH 71 days (95% CI, 15-127) vs. Bi-HVAD 167 days (95% CI, 116-217), P=0.01]. At the mean follow-up time of 120 days, (95% CI, 83-157) patients in both groups had similar overall mortality [TAH 36% (95% CI, 22-49) vs. Bi-HVAD 26% (95% CI, 6-46), P=0.44] including mortality on device support [TAH 26% (95% CI, 17-36) vs. Bi-HVAD 21% (95% CI, 4-37), P=0.55]. Discharge home on support was achieved in 6% (95% CI, 4-17%) of TAH patients vs. 73% (95% CI, 48-89%) of Bi-HVAD (P<0.01), and 68% (95% CI, 52-84) of TAH patients were transplanted vs. 61% (95% CI, 47-75) in the Bi-HVAD group (P=0.14). CONCLUSIONS: Patients on Bi-HVAD support were more likely to be able to be discharged home on support and had similar overall mortality to TAH, albeit with much longer duration of support.

Validation of 9-Grid Scheme for Localizing Osteochondral Lesions of the Talus.

BACKGROUND: A 9-grid scheme has been integrated into the foot and ankle literature to help clinicians and researchers localize osteochondral lesions of the talus (OLTs). We hypothesized that fellowship-trained orthopedic foot and ankle surgeons would have a high rate of intra/inter-observer reliability when localizing OLTs, therefore validating the scheme. METHODS: We queried our institution's foot and ankle radiographic database for magnetic resonance images with OLTs. Each MRI was reviewed by the senior author, and 2 key images (widest OLT diameter) from each tangential view were copied and combined onto one slide. Fifty consecutive deidentified images of ankles were then sent to 4 practicing fellowship-trained foot and ankle surgeons. Each was asked to identify which zone the OLT was localized within. A radiologist's report served as the control. Statistical analyses were performed using Cohen and Fleiss kappa tests. RESULTS: The reviewers demonstrated majority consensus on 45/50 images with substantial agreement for zones 4 and 6. The interobserver reliability was moderate with a κ = 0.55. The mean intraobserver reliability was substantial, with a κ = 0.79. A musculoskeletal radiologist determined there were 3 lesions in zone 7, 18 lesions in zone 4, and 29 lesions in zone 6. CONCLUSION: This study is the first to critically evaluate the 9-grid scheme and its reliability among orthopedic foot and ankle surgeons. Our study found that the 9-grid scheme is an accurate method of localization for OLTs with high intra- and moderate interobserver reliability between surgeons. LEVEL OF EVIDENCE: Level IV, retrospective diagnostic study.

Left Ventricular Assist Device Decommissioning Compared with Explantation for Ventricular Recovery: A Systematic Review.

Left ventricular assist device (LVAD) withdrawal with ventricular recovery represents the optimal outcome for patients previously implanted with an LVAD. The aim of this systematic review was to examine the patient outcomes of device withdrawal via minimally invasive pump decommissioning as compared with reoperation for pump explantation. An electronic search was performed to identify all studies in the English literature assessing LVAD withdrawal. All identified articles were systematically assessed for inclusion and exclusion criteria. Overall, 44 studies (85 patients) were included in the analysis, of whom 20% underwent decommissioning and 80% underwent explantation. The most commonly used LVAD types included the HeartMate II (decommissioning 23.5% vs. explantation 60.3%; p = 0.01) and HeartWare HVAD (decommissioning 76.5% vs. explantation 17.6%; p < 0.001). At median follow-up of 389 days, there were no significant differences in the incidence of cerebrovascular accidents (p = 0.88), infection (p = 0.75), and survival (p = 0.20). However, there was a trend toward a higher recurrence of heart failure in patients who underwent decommissioning as compared with explantation (decommissioning 15.4% vs. explantation 8.2%, cumulative hazard; p = 0.06). Decommissioning appears to be a feasible alternative to LVAD explantation in terms of overall patient outcomes.

Role of muscle coactivation in adaptation of standing posture during arm reaching.

The ability to maintain stable, upright standing in the face of perturbations is a critical component of daily life. A common strategy for resisting perturbations and maintaining stability is muscle coactivation. Although arm muscle coactivation is often used during adaptation of seated reaching movements, little is known about postural muscle activation during concurrent adaptation of arm and standing posture to novel perturbations. In this study we investigate whether coactivation strategies are employed during adaptation of standing postural control, and how these strategies are prioritized for adaptation of standing posture and arm reaching, in two different postural stability conditions. Healthy adults practiced planar reaching movements while grasping the handle of a robotic arm and standing on a force plate; the robotic arm generated a velocity-dependent force field that created novel perturbations in the forward (more stable) or backward (less stable) direction. Surprisingly, the degree of arm and postural adaptation was not influenced by stability, with similar adaptation observed between conditions in the control of both arm movement and standing posture. We found that an early coactivation strategy can be used in postural adaptation, similar to what is observed in adaptation of arm reaching movements. However, the emergence of a coactivation strategy was dependent on perturbation direction. Despite similar adaptation in both directions, postural coactivation was largely specific to forward perturbations. Backward perturbations led to less coactivation and less modulation of postural muscle activity. These findings provide insight into how postural stability can affect prioritization of postural control objectives and movement adaptation strategies.NEW & NOTEWORTHY Muscle coactivation is a key strategy for modulating movement stability; this is centrally important in the control of standing posture. Our study investigates the little-known role of coactivation in adaptation of whole body standing postural control. We demonstrate that an early coactivation strategy can be used in postural adaptation, but muscle activation strategies may differ depending on postural stability conditions.

Management and outcomes of left ventricular assist device-associated endocarditis: a systematic review.

BACKGROUND: Left ventricular assist device (LVAD)-associated endocarditis remains poorly studied, especially in newer continuous-flow LVADs (CF-LVADs). The aim of this review was to assess outcomes of patients with LVAD-associated endocarditis, as stratified by CF-LVAD and pulsatile LVAD (P-LVAD) use as well as by different interventions and pathogen types. METHODS: An electronic search was performed to identify studies in the English literature on LVAD-associated endocarditis. RESULTS: Overall, 16 articles with 26 patients were included; seven had CF-LVADs and 19 had P-LVADs; time to development of endocarditis was 91 days (152 vs. 65 days, respectively, P=0.05). Eleven of 25 patients were treated with antibiotics only. Remaining 14 patients received antibiotics, however, they also underwent additional surgical intervention. One patient was treated with embolization alone for mycotic aneurysm and was therefore excluded. At a median follow-up time of 344 days post implant, there was no difference in overall mortality between CF-LVAD and P-LVAD-associated endocarditis patients (57.9% vs. 42.9%, P=0.81). Patients who underwent additional surgical intervention had higher overall survival compared to those treated with antibiotics alone (71.4% vs. 27.3%, P=0.07); with no difference in outcomes amongst those who underwent surgical device exchange as compared to heart transplantation (80.0% vs. 66.7%; P=0.23). CONCLUSIONS: Compared to patients with P-LVADs, CF-LVAD patients appeared to be resistant to early development of LVAD-associated endocarditis. There was a trend towards high survival observed amongst patients who underwent additional surgical intervention as compared to those treated with antibiotics alone, with no difference amongst surgical device exchange as compared to heart transplantation. Advantages of additional surgical intervention vs. medical therapy alone deserves further exploration to determine its applicability in CF-LVADs.

Valvectomy versus replacement for the surgical treatment of infective tricuspid valve endocarditis: a systematic review and meta-analysis.

BACKGROUND: Optimal surgical treatment of infective tricuspid valve endocarditis in patients with intravenous drug use (IVDU) remains controversial. Tricuspid valvectomy has been proposed for infective tricuspid valve endocarditis in this patient population given the inherent social concerns. The aim of this systematic review and meta-analysis was to compare outcomes of valvectomy versus replacement for the surgical treatment of isolated infective tricuspid valve endocarditis. METHODS: An electronic search was performed to identify all relevant studies published. After assessment for inclusion and exclusion criteria, 16 original studies were pooled for systematic review and meta-analysis. RESULTS: There were a total of 752 patients with infective tricuspid valve endocarditis, of which 14% underwent valvectomy and 86% underwent replacement (mean follow-up 4.2 years, 95% CI, 1.9-6.4 years). The most common indications for surgical intervention were septic pulmonary embolism in the valvectomy group (74%, 95% CI, 28-95%) and persistent sepsis in the replacement group (62%, 95% CI, 31-86%). There were no differences in rates of stroke [valvectomy 4% (95% CI, 1-11%) vs. replacement 3% (95% CI, 1-16%), P=0.85] but there was increased likelihood of prolonged ventilation in those who underwent valvectomy [valvectomy 40% (95% CI, 30-51%) vs. replacement 26% (95% CI, 23-30%), P<0.01]. There were no differences in 30-day post-operative mortality [valvectomy 13% (95% CI, 5-30%) vs. replacement 7% (95% CI, 5-10%), P=0.21], post-operative right heart failure [valvectomy 27% (95% CI, 10-53%) vs. replacement 11% (95% CI, 5-25%), P=0.17] and recurrent endocarditis [valvectomy 7% (95% CI, 2-23%) vs. replacement 19% (95% CI, 12-28%), P=0.81]. Valvectomy had a higher rate of tricuspid valve reoperation [valvectomy 56% (95% CI, 15-90%) vs. initial replacement 14% (95% CI, 7-27%), P=0.06]. CONCLUSIONS: Tricuspid valvectomy is an acceptable initial therapy for infective tricuspid valve endocarditis in patients with IVDU, providing a bridge to identify those who will self-select as candidates for staged valve replacement.

Concomitant vs staged orthotopic liver transplant after cardiac surgical procedures.

BACKGROUND: In patients who require orthotopic liver transplant (OLT), cardiac surgery may be needed to optimize preoperative cardiac status for OLT. The aim of this systematic review was to evaluate patient characteristics and outcomes of those undergoing staged versus concomitant cardiac procedures with OLT. METHODS: An electronic search was performed to identify all case reports and series, from which patient-level data was extracted regarding cardiac procedures associated with OLT. After assessment for inclusion and exclusion criteria, 26 articles were pooled for systematic review. RESULTS: Overall, 49 patients were included in the analysis, of whom 12 (24%) underwent staged procedures and 37 (76%) underwent concomitant procedures. The median age was lower in the staged group [staged: 51 (IQR, 43.8-59.2) years vs. concomitant: 60 (IQR, 55.0-64.0) years, p = .02]. Other baseline characteristics were comparable between the two groups. For staged procedures, the median time between heart procedures and OLT was 2 (IQR, 1.0-3.5) months. The most commonly reported cardiac procedures were coronary artery bypass graft (CABG) [staged: 4/12 (33.3%) vs. concomitant: 21/37 (56.8%), p = .28], aortic valve replacement (AVR) [staged: 3/12 (25.0%) vs. concomitant: 19/37 (51.2%), p = .21], and transcatheter aortic valve replacement (TAVR) [staged: 4/12 (33.3%) vs. concomitant: 0/37 (0%), p = .002]. Regarding outcomes, there was a significantly shorter post-OLT hospital stay for those who had staged procedures versus those who had concomitant procedures [staged: 8 (IQR, 5-13) days vs. concomitant: 17 (IQR, 14-24) days, p = .007]. However, both groups had similar in-hospital mortality rates [staged: 1/12 (8.3%) vs. concomitant: 4/37 (10.8%), p = 1.0]. Overall survival stratified between the two groups was comparable. CONCLUSIONS: Patients who underwent the staged approach had a shorter post-transplant hospital stay, but comparable survival with respect to those who underwent concomitant cardiac procedures and OLT.

Graft patency after open versus endoscopic saphenous vein harvest in coronary artery bypass grafting surgery: a systematic review and meta-analysis.

BACKGROUND: Saphenous vein grafts (SVG) are a commonly used conduit for coronary artery bypass graft (CABG) surgery and can be harvested by either an open or endoscopic technique. Our goal was to evaluate long-term angiographic and clinical outcomes of open compared to endoscopic SVG harvest for CABG. METHODS: Electronic search was performed to identify all studies in the English literature that compared open and endoscopic SVG harvesting for CABG with at least one year of follow-up. The primary outcome was graft patency. Secondary outcomes included perioperative morbidity and mortality. RESULTS: Of 3,255 articles identified, a total of 11 studies were included for analysis. Of 18,131 patients, 10,873 (60%) patients underwent open SVG harvest and 7,258 (40%) patients underwent endoscopic SVG harvest. The mean age of patients was 65 years and 87% were male. The overall mean follow-up period was 2.6 years. During follow-up, patients who underwent open SVG harvest had superior graft patency per graft [open 82.3% vs. endoscopic 75.1%; OR: 0.61 (95% CI, 0.43-0.87); P=0.01], but higher rates of overall wound complications in the immediate post-operative period [open 3.3% vs. endoscopic 1.1%; OR: 0.02 (95% CI, 0.01-0.06); P<0.001]. Patients who underwent open SVG harvest had higher postoperative 30-day mortality [open 3.4% vs. endoscopic 2.1%; OR: 0.59 (95% CI, 0.37-0.94); P=0.03], but no significant difference in overall mortality [open 4.9% vs. endoscopic 4.9%; OR: 0.34 (95% CI, 0.50-1.27); P=0.34]. CONCLUSIONS: Patients who underwent an open SVG harvest technique had improved graft patency and comparable overall mortality to endoscopic SVG harvest at average follow-up time of 2.6 years. Patients with open SVG harvest had higher rates of early wound complications and postoperative 30-day mortality, however, there was no difference in overall mortality.

Trial-to-trial adaptation in control of arm reaching and standing posture.

Classical theories of motor learning hypothesize that adaptation is driven by sensorimotor error; this is supported by studies of arm and eye movements that have shown that trial-to-trial adaptation increases with error. Studies of postural control have shown that anticipatory postural adjustments increase with the magnitude of a perturbation. However, differences in adaptation have been observed between the two modalities, possibly due to either the inherent instability or sensory uncertainty in standing posture. Therefore, we hypothesized that trial-to-trial adaptation in posture should be driven by error, similar to what is observed in arm reaching, but the nature of the relationship between error and adaptation may differ. Here we investigated trial-to-trial adaptation of arm reaching and postural control concurrently; subjects made reaching movements in a novel dynamic environment of varying strengths, while standing and holding the handle of a force-generating robotic arm. We found that error and adaptation increased with perturbation strength in both arm and posture. Furthermore, in both modalities, adaptation showed a significant correlation with error magnitude. Our results indicate that adaptation scales proportionally with error in the arm and near proportionally in posture. In posture only, adaptation was not sensitive to small error sizes, which were similar in size to errors experienced in unperturbed baseline movements due to inherent variability. This finding may be explained as an effect of uncertainty about the source of small errors. Our findings suggest that in rehabilitation, postural error size should be considered relative to the magnitude of inherent movement variability.