Optimal Timing for Resumption of Anticoagulation After Intracranial Hemorrhage in Patients With Mechanical Heart Valves.

BACKGROUND: Anticoagulation in patients with intracranial hemorrhage (ICH) and mechanical heart valves is often held for risk of ICH expansion; however, there exists a competing risk of acute ischemic stroke (AIS). Optimal timing to resume anticoagulation remains uncertain. METHODS AND RESULTS: We retrospectively studied patients with ICH and mechanical heart valves from 2000 to 2018. The primary outcome was a composite end point of symptomatic hematoma expansion or new ICH, AIS, and intracardiac thrombus up to 30 days post-ICH. The exposure was timing of reinitiation of anticoagulation classified as early (resumed up to 7 days after ICH), late (≥7 and up to 30 days after ICH), and never if not resumed or resumed after 30 days post-ICH. We included 184 patients with ICH and mechanical heart valves (65 anticoagulated early, 100 late, 19 not resumed by day 30 post-ICH). Twelve patients had AIS, 16 new ICH, and 6 intracardiac thromboses. The mean time from ICH to anticoagulation was 12.7 days. Composite outcomes occurred in 12 patients resumed early (18.5%), 14 resumed late (14.0%), and 4 never resumed (21.1%). There was no increased hazard of the composite outcome (hazard ratio [HR], 1.1 [95% CI, 0.2-6.0]), AIS, or worsening or new ICH among patients resumed early versus late. There was no difference in the composite among patients never resumed versus resumed. Patients who never resumed anticoagulation had significantly more severe ICH (median Glasgow Coma Scale: 10.6, 13.9, and 13.9 among those who resumed never, early, and late, respectively; P=0.0001), higher in-hospital mortality (56.5%, 0%, and 0%, respectively; P<0.0001), and an elevated 30-day AIS risk (HR, 15.9 [95% CI, 1.9-129.7], P=0.0098). CONCLUSIONS: In this study of patients with ICH and mechanical heart valves, there was no difference in 30-day thrombotic and hemorrhagic brain-related outcomes when anticoagulation was resumed within 7 versus 7 to 30 days after ICH. Withholding anticoagulation >30 days was associated with severe baseline ICH, higher in-hospital case fatality, and elevated AIS risk.

Secondary Prevention in Patients With Stroke Versus Myocardial Infarction: Analysis of 2 National Cohorts.

BACKGROUND: The implementation of preventive therapies among patients with stroke remains inadequately explored, especially when compared with patients with myocardial infarction (MI), despite sharing similar vascular risk profiles. We tested the hypothesis that participants with a history of stroke have a worse cardiovascular prevention profile in comparison to participants with MI. METHODS AND RESULTS: In cross-sectional analyses within the UK Biobank and All of Us Research Program, involving 14 760 (9193 strokes, 5567 MIs) and 7315 (2948 strokes, 4367 MIs) participants, respectively, we evaluated cardiovascular prevention profiles assessing low-density lipoprotein (<100 mg/dL), blood pressure (systolic, <140 mm Hg; and diastolic, <90 mm Hg), statin and antiplatelet use, and a cardiovascular prevention score that required meeting at least 3 of these criteria. The results revealed that, within the UK Biobank, patients with stroke had significantly lower odds of meeting all the preventive criteria compared with patients with MI: low-density lipoprotein control (odds ratio [OR], 0.73 [95% CI, 0.68-0.78]; P<0.001), blood pressure control (OR, 0.63 [95% CI, 0.59-0.68]; P<0.001), statin use (OR, 0.45 [95% CI, 0.42-0.48]; P<0.001), antiplatelet therapy use (OR, 0.30 [95% CI, 0.27-0.32]; P<0.001), and cardiovascular prevention score (OR, 0.42 [95% CI, 0.39-0.45]; P<0.001). Similar patterns were observed in the All of Us Research Program, with significant differences across all comparisons (P<0.05), and further analysis suggested that the odds of having a good cardiovascular prevention score were influenced by race and ethnicity as well as neighborhood deprivation levels (interaction P<0.05 in both cases). CONCLUSIONS: In 2 independent national cohorts, patients with stroke showed poorer cardiovascular prevention profiles and lower adherence to guideline-directed therapies compared with patients with MI. These findings underscore the need to explore the reasons behind the underuse of secondary prevention in vulnerable stroke survivors.

Impaired mobility and MRI markers of vascular brain injury: Atherosclerosis Risk in Communities and UK Biobank studies.

Background: Vascular brain injury (VBI) may be an under-recognised contributor to mobility impairment. We examined associations between MRI VBI biomarkers and impaired mobility. Methods: We separately analysed Atherosclerosis Risk in Communities (ARIC) and UK Biobank (UKB) study cohorts. Inclusion criteria were no prevalent clinical stroke, and available brain MRI and balance and gait data. MRI VBI biomarkers were (ARIC: ventricular and white matter hyperintensity (WMH) volumes, non-lacunar and lacunar infarctions, microhaemorrhage; UKB: ventricular, brain and WMH volumes, fractional anisotropy (FA), mean diffusivity (MD), intracellular and isotropic free water volume fractions). Quantitative biomarkers were categorised into tertiles. Mobility impairment outcomes were imbalance and slow walk in ARIC and recent fall and slow walk in UKB. Adjusted multivariable logistic regression analyses were performed. Results: We included 1626 ARIC (mean age 76.2 years; 23.4% imbalance, 25.0% slow walk) and 40 098 UKB (mean age 55 years; 15.8% falls, 2.8% slow walk) participants. In ARIC, imbalance associated with four of five VBI measures (all p values<0.05), most strongly with WMH (adjusted OR, aOR 1.64; 95% CI 1.18 to 2.29). Slow walk associated with four of five VBI measures, most strongly with WMH (aOR 2.32; 95% CI 1.66 to 3.24). In UKB, falls associated with all VBI measures except WMH, most strongly with FA (aOR 1.16; 95% CI 1.08 to 1.24). Slow walking associated with WMH, FA and MD, most strongly with FA (aOR 1.57; 95% CI 1.32 to 1.87). Conclusions: VBI is associated with mobility impairment in community-dwelling, clinically stroke-free cohorts. Consequences of VBI may extend beyond clinically apparent stroke to include mobility.

Association of Neighborhood-Level Socioeconomic Factors With Delay to Hospital Arrival in Patients With Acute Stroke.

BACKGROUND AND OBJECTIVES: Delivery of acute ischemic stroke (AIS) therapies is contingent on the duration from last known well (LKW) to emergency department arrival time (EDAT). One reason for treatment ineligibility is delay in presentation to the hospital. We evaluate patient and neighborhood characteristics associated with time from LKW to EDAT. METHODS: This was a retrospective observational study of patients presenting to the Yale New Haven Hospital in the AIS code pathway from 2010 to 2020. Patients presenting within 4.5 hours from LKW who were recorded in the institutional Get With the Guidelines Stroke registry were classified as early while those presenting beyond 4.5 hours were designated as late. Temporal trends in late presentation were explored by univariate logistic regression. Using variables significant in univariate analysis at p < 0.05, we developed a mixed-effect logistic regression model to estimate the probability of late presentation as a function of patient-level and neighborhood (ZIP)-level characteristics (area deprivation index [ADI] derived from the Health Resources and Services Administration), adjusted for calendar year and geographic distance from the centroid of the ZIP code to the hospital. RESULTS: A total of 2,643 patients with AIS from 2010 to 2020 were included (63.4% presented late and 36.6% presented early). The frequency of late presentation increased significantly from 68% in 2010 to 71% in 2020 (p = 0.002) and only among non-White patients. Patients presenting late were more likely to be non-White (37.1% vs 26.9%, p < 0.0001), arrive by means other than emergency medical services (EMS) (32.7% vs 16.1%, p < 0.0001), have an NIHSS <6 (68.7% vs 55.2%, p < 0.0001), and present from a neighborhood with a higher ADI category (p = 0.0001) that was nearer to the hospital (median 5.8 vs 7.7 miles, p = 0.0032). In the mixed model, the ADI by units of 10 (odds ratio [OR] 1.022, 95% confidence interval [CI] 1.020-1.024), non-White race (OR 1.083, 95% CI 1.039-1.127), arrival by means other than EMS (OR 1.193, 95% CI 1.145-1.124), and an NIHSS <6 (OR 1.085, 95% CI 1.041-1.129) were associated with late presentation. DISCUSSION: In addition to patient-level factors, socioeconomic deprivation of neighborhood of residence contributes to delays in hospital presentation for AIS. These findings may provide opportunities for targeted interventions to improve presentation times in at-risk communities.

Addressing disparities in the global epidemiology of stroke.

Stroke is the second leading cause of death and the third leading cause of disability worldwide. Though the burden of stroke worldwide seems to have declined in the past three decades, much of this effect reflects decreases in high-income countries (HICs). By contrast, the burden of stroke has grown rapidly in low-income and middle-income countries (LMICs), where epidemiological, socioeconomic and demographic shifts have increased the incidence of stroke and other non-communicable diseases. Furthermore, even in HICs, disparities in stroke epidemiology exist along racial, ethnic, socioeconomic and geographical lines. In this Review, we highlight the under-acknowledged disparities in the burden of stroke. We emphasize the shifting global landscape of stroke risk factors, critical gaps in stroke service delivery, and the need for a more granular analysis of the burden of stroke within and between LMICs and HICs to guide context-appropriate capacity-building. Finally, we review strategies for addressing key inequalities in stroke epidemiology, including improvements in epidemiological surveillance and context-specific research efforts in under-resourced regions, development of the global workforce of stroke care providers, expansion of access to preventive and treatment services through mobile and telehealth platforms, and scaling up of evidence-based strategies and policies that target local, national, regional and global stroke disparities.

Caring for Patients With Diabetes in Stroke Neurology.

Diabetes is a heterogeneous disease that affects 9% of the world's population (11% in the United States). The consequences of diabetes for the brain are severe; it nearly doubles a person's risk of stroke and is a major contributor to risk for cerebral small vessel disease and dementia. These effects on the brain are in addition to peripheral neuropathy, retinopathy, nephropathy, and coronary heart disease. In this article, we explain the treatments that can prevent or mitigate its harmful effects and propose a role for neurologists and other neurology clinicians in managing patients during routine care.

Technical Dissonance in Home Blood Pressure Monitoring After Stroke: Having the Machine, but Not Using Correctly.

BACKGROUND: In individuals with hypertension (HTN), lowering blood pressure (BP) after a stroke can lower the risk of stroke recurrence, but many patients do not reach the goal. Home blood pressure monitoring (HBPM) can help patients get to the goal, but rates of use and quality of technique have not been evaluated. METHODS: We conducted a cross-sectional study of patients with stroke. Patients were eligible if they had a stroke within 2 years, had HTN, and lived at home. We classified patients as correctly performing HBPM if they used an arm cuff, sat ≥ 1 min before measurement, took ≥ 2 measurements, and use within 6 months. The primary outcome was the proportion of patients who had an HBPM and used it correctly, which we calculated according to race and ethnicity. We also asked patients what they would do if they found results outside the goal. RESULTS: Among 150 participants, 120 (81%) possessed an HBPM and 29 (21%) used it correctly. We observed no significant disparity in rates of possession or correct use between non-Hispanic White participants and participants from underrepresented groups. Seventy percent of non-Hispanic White patients said they would contact their provider if their BP was above goal vs. 52% of underrepresented patients (P = 0.21). CONCLUSIONS: Most patients after stroke have an HBPM, but only about 1 in 5 use it correctly. Approximately half of the patients from underrepresented racial or ethnic groups do not have a plan for responding to the values above goal. Our results indicate opportunities to improve the dissemination and correct use of HBPM.

Central vs site outcome adjudication in the IRIS trial.

BACKGROUND: Central adjudication of outcome events is the standard in clinical trial research. We examine the benefit of central adjudication in the Insulin Resistance Intervention after Stroke (IRIS) trial and show how the benefit is influenced by outcome definition and features of the adjudicated events. METHODS: IRIS tested pioglitazone for prevention of stroke and myocardial infarction in patients with a recent transient ischemic attack or ischemic stroke. We compared the hazard ratios for study outcomes classified by site and central adjudication. We repeated the analysis for an updated stroke definition. RESULTS: The hazard ratios for the primary outcome were identical (0.76) and statistically significant regardless of adjudicator. The hazard ratios for stroke alone were nearly identical with site and central adjudication, but only reached significance with site adjudication (HR, 0.80; p = 0.049 vs. HR, 0.82; p = 0.09). Using the updated stroke definition, all hazard ratios were lower than with the original IRIS definition and statistically significant regardless of adjudication method. Agreement was higher when stroke type was certain, subtype was large vessel or cardioembolic, signs or symptoms lasted > 24 h, imaging showed a stroke, and when NIHSS was ≥3. DISCUSSION: Central stroke adjudication caused the hazard ratio for a main secondary outcome in IRIS (stroke alone) to be higher and lose statistical significant compared with site review. The estimate of treatment effects were larger with the updated stroke definition. There may be benefit of central adjudication for events with specific features, such as shorter symptom duration or normal brain imaging.

Protecting the Brain, From the Heart: Safely Mitigating the Consequences of Thrombosis in Intracerebral Hemorrhage Survivors With Atrial Fibrillation.

Optimal antithrombotic management after intracerebral hemorrhage remains one of the central unresolved issues for patients who survive, especially for those patients with atrial fibrillation. Given the observational nature of the studies regarding anticoagulation resumption after intracerebral hemorrhage, there is uncertainty regarding resumption of oral anticoagulation therapy and its timing. There is limited high-quality evidence to guide clinical practice, leading to significant practice variation and uncertainty for patients and providers. Here, we aim to provide the key elements to guide clinicians in their individual decision: whether or not to start or resume anticoagulation in patients with a history of intracerebral hemorrhage.

The risk for developing a secondary cancer after breast radiation therapy: Comparison of photon and proton techniques.

BACKGROUND AND PURPOSE: To compare secondary malignancy risks of modern proton and photon therapy techniques for locally advanced breast cancer. METHODS AND MATERIALS: We utilized dosimetric data from 34 [10 photon-VMAT, 10 photon-3DCRT, 14 pencil beam scanning proton (PBS)] breast cancer patients who received comprehensive nodal irradiation. Employing a model based on organ equivalent dose to account for both inhomogeneous organ dose distributions and non-linear functional dose relationships, we estimated excess absolute risk, excess relative risk, and lifetime attributable risk (LAR) for secondary malignancies. The model uses dose distribution, number of fractions, age at exposure, attained age, the linear-quadratic dose response relationship for cell survival, repopulation factor, as well as gender specific age dependencies, and initial slopes of dose response curves. RESULTS: The LAR for carcinoma at age 70 was estimated to be up to 3.64% for esophagus with an advantage of 3DCRT over PBS and VMAT. For the ipsilateral lung, risks were lowest for PBS (up to 5.56%), followed by 3DCRT (up to 6.54%) and VMAT (up to 7.7%). For the contralateral lung, there is a clear advantage of 3DCRT and PBS techniques (risk <0.86%) over VMAT (up to 4.4%). The risk for the contralateral breast is negligible for 3DCRT and PBS but was estimated as up to 1.2% for VMAT. Risks for the thyroid are overall negligible. Independently performed comparative treatment plans on 10 patients revealed that the risk for the contralateral lung and breast using VMAT can be more than an order of magnitude higher compared to PBS. Sarcoma risks were estimated as well showing similar trends but were overall lower compared to carcinoma. CONCLUSION: Conventional (3DCRT) techniques led to the lowest estimated risks of, thyroid and esophageal secondary cancers while PBS demonstrated a benefit for secondary lung and contralateral breast cancer risks, with the highest risks overall associated with VMAT techniques.

Intracerebral Hemorrhage Outcomes in the Very Elderly.

BACKGROUND: There is a paucity of outcomes data in patients over 80 years presenting with intracerebral hemorrhage (ICH). The primary aim of our study is to describe outcomes in this patient population. METHOD: Retrospective study of patients admitted with primary ICH from January 2012 to July 2018. Data were obtained from the Rush University Get With The Guidelines database; only patients 80 or above were included. RESULTS: A total of 1713 patients were screened and 220 patients met inclusion criteria. About 68.2% were female and mean age was 85.6 years old. Median ICH score on admission was 2 (IQR 1-3). Location of ICH included: deep (48.2%), lobar (40%), and cerebellum (9.5%). ICH etiologies included hypertensive (51.8%), cerebral amyloid angiopathy (26.8%), coagulopathy (5.9%), and the remaining were undetermined. CT angiograms were performed in 34.5% (n = 76) of patients; of these patients one arteriovenous malformation was identified. Patients underwent the following procedures: external ventricular drains (8.6%), decompression (3.6%), and ventriculoperitoneal shunts (1.8%). Tracheostomy and percutaneous gastrostomy placement were performed in 8.2%. About 4.5% had seizures and 1.5% were treated for status epilepticus. Disposition at hospital discharge included: subacute nursing facility ([SNF] 24.1%), acute rehabilitation (23.2%), hospice (18.2%), death (18.2%), home (11.8%), long-term acute care facility ([LTAC] 3.6%), and unknown (1%). Patients with an ICH score ≥2 on admission had a roughly 6 times higher chance of experiencing an unfavorable outcome (LTAC, SNF, or death), when compared to patients with lower ICH score. CONCLUSIONS: This study shows that a significant proportion (35%) of ICH patients ≥80 years old have a good outcome, with discharge to home or to rehabilitation. Our data suggest that older patients with ICH presenting with supratentorial hemorrhages (volume < 30 cc) without intraventricular extension can have good outcomes despite their age.

The Impact of an Introductory Radiation Oncology Curriculum (IROC) for Radiation Oncology Trainees Across the United States and Canada.

PURPOSE: Despite interest from both radiation oncology residents and program directors, many residency training programs lack a formalized introductory curriculum to orient incoming radiation oncology residents to the specialty. METHODS AND MATERIALS: Using the 6-step model for medical education curriculum development, a structured introductory radiation oncology curriculum (IROC) was created for incoming post-graduate year 2 (PGY-2) radiation oncology residents to address foundational concepts including patient simulation, contouring, and plan evaluation. The curriculum was distributed to 55 training programs across the United States and Canada at the start of the 2018 to 2019 and 2019 to 2020 academic years. Feasibility of curriculum dissemination was assessed via a survey of participating program directors. Curriculum effectiveness was assessed using an anonymous survey of participating residents administered pre- and postcurriculum and consisting of both subjective and objective knowledge-based questions. RESULTS: A total of 236 residents participated in IROC at the start of the 2018 to 2019 and 2019 to 2020 academic years. Of those, 228 of 236 (97%) completed both the pre- and postcurriculum surveys. Of participating residents, the median residency program size was 10 (range, 2-28), and the median number of residents in each program per year was 3 (range, 1-7). At baseline, most PGY-2s (142 of 228, 62%) reported being "not at all" or "slightly" prepared to function in the radiation oncology clinic, and after IROC most (188 of 228, 82%) felt "moderately," "quite," or "extremely" prepared. Objective knowledge improved pre- to postcurriculum on a multiple-choice test from 70% to 81% (P < .0001) correct, with improvements observed across all question items. Program directors also reported that the curriculum was easier to use and more effective than prior orientation materials. CONCLUSIONS: The implementation of an international introductory curriculum for PGY-2 radiation oncology residents is both feasible and effective. Similar strategies should be employed to enhance and standardize radiation oncology educational initiatives across training programs.

The Spectrum of Nontraumatic Convexity Subarachnoid Hemorrhage.

BACKGROUND: Nontraumatic convexity subarachnoid hemorrhage (cSAH) is a nonaneurysmal variant that is associated with diverse etiologies. METHODS: With IRB approval, we retrospectively reviewed consecutive nontraumatic cSAH from July 1, 2006 to July 1, 2016. Data were abstracted on demographics, medical history, neuroimaging, etiology, and clinical presentation. RESULTS: We identified 94 cases of cSAH. The cases were classified according to the following etiologies: reversible cerebral vasoconstriction syndrome (RCVS) 17 (18%), cerebral amyloid angiopathy (CAA) 15 (16%), posterior reversible encephalopathy syndrome 16 (17%), cerebral venous thrombosis 10 (11%), large artery occlusion 7 (7%), endocarditis 6 (6%), and cryptogenic 25 (27%). Early rebleeding occurred in 9 (10%) patients. Time from initial imaging to CT rebleeding was 40 hours (range, 5-74). CAA was associated with the highest mean age at 75.8 and RCVS the lowest at 47.6 years (P< .0001). Among patients with RCVS, initial vascular imaging was negative in 6 (35%), and repeat imaging documented vasoconstriction at a mean delay of 5 days (range, 3-16). CONCLUSION: There were significant differences among the subgroups in cSAH, with CAA presenting as older men with transient neurological deficits, and RCVS presenting as younger women with thunderclap headache. Rebleeding was seen in 10% of cSAH patients. One-third of RCVS patients with cSAH required repeat vascular imaging to diagnose vasoconstriction.

In Vitro Studies on Degradation of Gamma-L-Glutamyl-L-Cysteine and Gamma-L-Glutamyl-D-Cysteine in Blood: Implications for Treatment of Stroke.

Treatment for ischemic stroke involves a thrombolytic agent to re-establish blood flow in the brain. However, delayed reperfusion may cause injury to brain capillaries. Previous studies indicate that the antioxidant gamma-L-glutamyl-L-cysteine (γ-Glu-Cys) contributes to reducing reperfusion injury to the cerebral vasculature in rats, when administered intravascularly. To determine the stability of γ-Glu-Cys in blood, the peptide was incubated in rat serum in vitro, and its degradation was quantified by high-pressure liquid chromatography. The half-time (t1/2) for degradation of γ-Glu-Cys was 11 ± 1 minute (mean ± SD, n = 3). A similar pattern of degradation was observed when γ-Glu-Cys was incubated in the presence of human plasma (t1/2 = 17 ± 8 minutes, n = 3). In a second series of experiments, degradation of an analog (γ-Glu-D-Cys) was tested in rat serum and found to be more stable than the native molecule. The initial velocity for degradation of γ-Glu-D-Cys (0.12 ± 0.02 mM/min; mean ± SD, n = 3) was significantly (P = 0.006) less than that of γ-Glu-Cys (0.22 ± 0.03 mM/min; mean ± SD, n = 3). Furthermore, an in vitro assay indicated that the analog has as an oxidative capacity that equals that of the original peptide in the presence of rat serum and human plasma. Finally, both peptides were found to be similarly effective in preventing lysis of intact cells using in vitro assays. These studies show that γ-Glu-Cys remains intact in blood for several minutes, and the analog γ-Glu-D-Cys may be a more stable, but similarly effective antioxidant.

Anterior-posterior stability of the knee by an MR image subtraction method.

The purpose of our study was to test the hypothesis that when a shear force was applied posteriorly to the loaded knee in vivo, there would be no relative motion between the tibia and the medial femoral condyle. Siemens 7 Tesla high-resolution MRI machine was used to scan eight healthy male volunteers with the knee at 15° of flexion. Two scans were obtained: the first with a compressive force of 660 N along the tibial long axis and a second with the compressive force and a posterior shear force of 36 N applied to the tibia. Solid models were created of the femur, tibia, and menisci for both loading conditions. The tibial models were superimposed enabling the displacements of the femur and menisci to be determined, relative to a fixed tibia. On average, the lateral femoral condyle displaced anteriorly by 0.66 mm but the medial femoral condyle displaced posteriorly by 0.36 mm. This indicated an axial rotation with a center between the lateral and medial condyles, but closer to the medial. The menisci displaced with the femoral condyles, but there was no indication that the medial meniscus was contributing to the pivoting action. This study supported the concept of medial anterior-posterior stability under weight-bearing conditions, but with structures other than the medial meniscus providing the stability. This study has application to the treatment of knee injuries and to knee arthroplasty design.

Analysis of reverse total shoulder joint forces and glenoid fixation.

Reverse total shoulder arthroplasty (rTSA) implants are intended to restore stability and function to shoulders with rotator cuff deficiency. The implant consists of a glenosphere projecting from a glenoid baseplate and articulating in a socket at the proximal end of a humeral component. Despite the demonstrated clinical efficacy, little information is available regarding the joint forces about this construct and the stability of the glenoid component against these forces. Our hypotheses were that the joint forces about the rTSA were comparable to that about a normal shoulder joint, and that the micromotion between the baseplate and the scapula against these loads would be sufficiently low to induce bone ingrowth. To investigate this, a custom testing rig was constructed to simulate active shoulder elevation in fresh-frozen shoulder specimens. The forces about the rTSA were calculated and found to include compressive and shear forces up to 0.7 and 0.4 BW, respectively. In contrast to a normal shoulder, where the joint forces peak at 90° of abduction, forces about the rTSA were highest at about 60° of abduction. These forces were then applied in cyclic loading conditions to the glenoid baseplate, and the micromotion of the implant relative to the bone was measured in the four quadrants of the component. For two different rTSA designs (DePuy Delta III® and Encore RSP®) and in the entire range of the fixation testing, the cyclical micromotions were always less than 62 µm. Thus, under loading conditions similar to physiological shoulder elevation, micromotion of the glenoid component was sufficiently low and within previously published limits to induce bone ingrowth.

Differential strain of the axially loaded scapholunate interosseus ligament.

PURPOSE: To directly measure strain changes in the scapholunate ligament via magnetic resonance imaging (MRI) when axially loading the wrist in the neutral and extended positions. METHODS: Six asymptomatic male volunteers without known history of previous wrist injury were enrolled in this MRI-based study. Each subject underwent 3 MRI scans in a 3T scanner: in resting neutral position, in neutral with axial load applied, and in extension with axial load applied. Axial load was applied via extension of an elastic band with known force/elongation curve. We analyzed images and converted them to 3-dimensional stereolithographs. Attachment points of the palmar, proximal, and dorsal sections of the scapholunate interosseus ligament (SLIL) were identified. The lengths of the resulting vectors were recorded for each position. Strain, defined as change in length divided by original length, was calculated for the axially loaded neutral and extended wrists. We used the Bonferroni adjusted multiple comparisons from an analysis of variance model, with statistical significance defined as p < .05. RESULTS: Strains were significantly greater in the palmar (p = .02) and proximal (p = .01) subregions of the SLIL in loaded extension versus loaded neutral positions. In contrast, the strain on the dorsal component in extension was not statistically greater than in the neutral position (p = .45). Axial load in neutral resulted in minimal strain of all 3 components of the SLIL complex, and these were not significantly different from each other (p > .99). With extension, the strains of the palmar (p = .03) and proximal (p = .006) regions were statistically greater than that of the dorsal component. CONCLUSIONS: In extension, strain is greatest in the palmar and proximal portions of the intact SLIL. Axial load in neutral applies minimal strain to the SLIL complex. Avoiding axial loading in extension and encouraging loading in neutral position may allow for decreased injury and more effective healing of the scapholunate ligament.

Development and evaluation of an instrumented linkage system for total knee surgery.

The principles and application of total knee surgery using optical tracking have been well demonstrated, but electromagnetic tracking may offer further advantages. We asked whether an instrumented linkage that attaches directly to the bone can maintain the accuracy of the optical and electromagnetic systems but be quicker, more convenient, and less expensive to use. Initial testing using a table-mounted digitizer to navigate a drill guide for placing pins to mount a cutting guide demonstrated the feasibility in terms of access and availability. A first version (called the Mark 1) instrumented linkage designed to fix directly to the bone was constructed and software was written to carry out a complete total knee replacement procedure. The results showed the system largely fulfilled these goals, but some surgeons found that using a visual display for pin placement was difficult and time consuming. As a result, a second version of a linkage system (called the K-Link) was designed to further develop the concept. User-friendly flexible software was developed for facilitating each step quickly and accurately while the placement of cutting guides was facilitated. We concluded that an instrumented linkage system could be a useful and potentially lower-cost option to the current systems for total knee replacement and could possibly have application to other surgical procedures.