Hip Joint Angles and Moments during Stair Ascent Using Neural Networks and Wearable Sensors.

End-stage hip joint osteoarthritis treatment, known as total hip arthroplasty (THA), improves satisfaction, life quality, and activities of daily living (ADL) function. Postoperatively, evaluating how patients move (i.e., their kinematics/kinetics) during ADL often requires visits to clinics or specialized biomechanics laboratories. Prior work in our lab and others have leveraged wearables and machine learning approaches such as artificial neural networks (ANNs) to quantify hip angles/moments during simple ADL such as walking. Although level-ground ambulation is necessary for patient satisfaction and post-THA function, other tasks such as stair ascent may be more critical for improvement. This study utilized wearable sensors/ANNs to quantify sagittal/frontal plane angles and moments of the hip joint during stair ascent from 17 healthy subjects. Shin/thigh-mounted inertial measurement units and force insole data were inputted to an ANN (2 hidden layers, 10 total nodes). These results were compared to gold-standard optical motion capture and force-measuring insoles. The wearable-ANN approach performed well, achieving rRMSE = 17.7% and R2 = 0.77 (sagittal angle/moment: rRMSE = 17.7 ± 1.2%/14.1 ± 0.80%, R2 = 0.80 ± 0.02/0.77 ± 0.02; frontal angle/moment: rRMSE = 26.4 ± 1.4%/12.7 ± 1.1%, R2 = 0.59 ± 0.02/0.93 ± 0.01). While we only evaluated healthy subjects herein, this approach is simple and human-centered and could provide portable technology for quantifying patient hip biomechanics in future investigations.

Developing a method for quantifying hip joint angles and moments during walking using neural networks and wearables.

Quantifying hip angles/moments during gait is critical for improving hip pathology diagnostic and treatment methods. Recent work has validated approaches combining wearables with artificial neural networks (ANNs) for cheaper, portable hip joint angle/moment computation. This study developed a Wearable-ANN approach for calculating hip joint angles/moments during walking in the sagittal/frontal planes with data from 17 healthy subjects, leveraging one shin-mounted inertial measurement unit (IMU) and a force-measuring insole for data capture. Compared to the benchmark approach, a two hidden layer ANN (n = 5 nodes per layer) achieved an average rRMSE = 15% and R2=0.85 across outputs, subjects and training rounds.

Mouse splenocyte enrichment strategies via negative selection for broadened single-cell transcriptomics.

Mammalian splenic tissue is rich in functional immune cells, primarily lymphocytes which can mask low-abundance populations in downstream analyses. This protocol enriches minority immune cell populations from mouse spleen via immunomagnetic negative depletion to generate an untouched enriched cell fraction. Enriched cells are then spiked with untouched splenocytes in a controlled repopulation, validated by flow cytometry and results in a single-cell transcriptomic clustering analysis with a broadened cellular landscape.

REVIEW OF DNA VACCINE APPROACHES AGAINST THE PARASITE TOXOPLASMA GONDII.

Toxoplasma gondii is an apicomplexan parasite that affects both humans and livestock. Transmitted to humans through ingestion, it is the second-leading cause of foodborne illness-related death. Currently, there exists no approved vaccine for humans or most livestock against the parasite. DNA vaccines, a type of subunit vaccine which uses segments of the pathogen's DNA to generate immunity, have shown varying degrees of experimental efficacy against infection caused by the parasite. This review compiles DNA vaccine efforts against Toxoplasma gondii, segmenting the analysis by parasite antigen, as well as a review of concomitant adjuvant usage. No single antigenic group was consistently more effective within in vivo trials relative to others.

Effect of head size and rotation on taper corrosion in a hip simulator.

AIMS: This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads. METHODS: In all, six 28 mm and six 36 mm titanium stem-cobalt chrome head pairs with polyethylene sockets were tested in a novel instrumented hip simulator. Samples were tested using simulated gait data with incremental increasing loads to determine corrosion onset load and electrochemical activity. Half of each head size group were then cycled with simulated gait and the other half with gait compression only. Damage was measured by area and maximum linear wear depth. RESULTS: Overall, 36 mm heads had lower corrosion onset load (p = 0.009) and change in open circuit potential (OCP) during simulated gait with (p = 0.006) and without joint movement (p = 0.004). Discontinuing gait's joint movement decreased corrosion currents (p = 0.042); however, wear testing showed no significant effect of joint movement on taper damage. In addition, 36 mm heads had greater corrosion area (p = 0.050), but no significant difference was found for maximum linear wear depth (p = 0.155). CONCLUSION: Larger heads are more susceptible to taper corrosion; however, not due to frictional torque as hypothesized. An alternative hypothesis of taper flexural rigidity differential is proposed. Further studies are necessary to investigate the clinical significance and underlying mechanism of this finding. Cite this article: Bone Jt Open 2021;2(11):1004-1016.

Measurement of the 160Gd(p,n)160Tb excitation function from 4-18 MeV using stacked-target activation.

The  160Gd(p,n)160Tb excitation function was measured between 4-18 MeV using stacked-target activation at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Nine copper and eight titanium foils served as proton fluence monitor foils, using the  natCu(p,x)65Zn,  natTi(p,x)48V, and  natTi(p,x)46Sc monitor standards, respectively. Variance minimization using an MCNP v.6.2 model reduced the systematic uncertainties in proton energy and fluence. A priori predictions of the  160Gd(p,n) reaction using ALICE, CoH, EMPIRE, and TALYS, as well as the TENDL database, are compared to the experimentally measured values.

Bilateral Femoral Component Fractures After Primary Total Knee Arthroplasty With Cruciate-Retaining Femoral Component.

A 69-year-old male presented with atraumatic bilateral femoral component fractures at different time intervals after simultaneous bilateral total knee arthroplasty using the cemented Biomet Ascent Knee System. The right and left knee implant fractures occurred 12 and 17 years after primary arthroplasty, respectively. This patient was notably tall (190.5 cm, 98th percentile) and maintained an active lifestyle before implant fractures. Sequential, bilateral knee implant fractures in a system with a previously acceptable track record suggest that biomechanics, patient characteristics, and surgical factors can significantly influence the risks for fracture of an implant.

In Vivo Corrosion of Modular Dual-Mobility Implants: A Retrieval Study.

BACKGROUND: Modular dual-mobility (MDM) total hip arthroplasty (THA) implants have an additional metal-metal interface between the metal liner and outer metal shell that poses a risk of corrosion. The purpose of this study is to evaluate retrieved MDM liners to evaluate qualitative and quantitative damage and corrosion patterns at this interface. METHODS: Twelve MDM implants of one design with a mean in situ duration of 26 months (range, 1-57 months) were evaluated. Six implants (50%) were from primary THAs and 6 (50%) from revision THAs. The taper region of the liner at risk of damage was qualitatively graded using modified Goldberg criteria while quantitative dimensional assessment was performed with a validated coordinate measurement machine. RESULTS: Among the retrieved implants, 2 (17%) demonstrated severe grade 4 corrosion, 5 (42%) moderate grade 3 corrosion, 4 (33%) mild grade 2 corrosion, and 1 (8%) grade 1 (no visible corrosion). Mean maximum linear corrosion depth at the taper interface measured 35.5 microns (range, 8.4-176.2 microns). All implants had a maximum linear corrosion depth >7 microns, a threshold suggestive of potentially clinically significant material loss. Three corrosion patterns were identified: generalized corrosion, a stripe of corrosion about the middle of the taper region, and focal areas of corrosion at the portion of the taper closest to the joint surface. CONCLUSION: Visual and dimensional analysis of all 12 retrieved MDM implants demonstrated identifiable corrosion/wear of the cobalt-chromium metal liner taper of varying severity. These implants should be used judiciously until larger series with clinical correlation can be completed.

Continuously monitoring shoulder motion after total shoulder arthroplasty: maximum elevation and time spent above 90° of elevation are critical metrics to monitor.

BACKGROUND: Traditional clinical shoulder range-of-motion (ROM) measurement methods (ie, goniometry) have limitations assessing ROM in total shoulder arthroplasty (TSA) patients. Inertial measurement units (IMUs) are superior; however, further work is needed using IMUs to longitudinally assess shoulder ROM before TSA and throughout post-TSA rehabilitation. Accordingly, the study aims were to prospectively capture shoulder elevation in TSA patients and to compare the results with healthy controls. We hypothesized that patients would have reduced maximum elevation before TSA compared with controls but would have improved ROM after TSA. METHODS: A validated IMU-based shoulder elevation quantification method was used to continuously monitor 10 healthy individuals (4 men and 6 women; mean age, 69 ± 20 years) without shoulder pathology and 10 TSA patients (6 men and 4 women; mean age, 70 ± 8 years). Controls wore IMUs for 1 week. Patients wore IMUs for 1 week before TSA, for 6 weeks at 3 months after TSA, and for 1 week at 1 year after TSA. Shoulder elevation was calculated continuously, broken into 5° angle "bins" (0°-5°, 5°-10°, and so on), and converted to percentages. The main outcome measures were binned movement percentage, maximum elevation, and average elevation. Patient-reported outcome measures and goniometric ROM were also captured. RESULTS: No demographic differences were noted between the cohorts. Average elevation was not different between the cohorts at any time. Control maximum elevation was greater than pre-TSA and post-TSA week 1 and week 2 values. Time under 30° and time above 90° were equal between the cohorts before TSA. After TSA, patients showed decreased time under 30° and increased time above 90°. DISCUSSION: This study demonstrates that acute and chronic recovery after TSA can be assessed via maximum elevation and time above 90°, respectively. These results inform how healthy individuals and patients use their shoulders before and after TSA.

Screening duplex ultrasonography in neurosurgery patients does not correlate with a reduction in pulmonary embolism rate or decreased mortality.

OBJECTIVE: Deep vein thrombosis (DVT) is a major focus of patient safety indicators and a common cause of morbidity and mortality. Many practices have employed lower-extremity screening ultrasonography in addition to chemoprophylaxis and the use of sequential compression devices in an effort to reduce poor outcomes. However, the role of screening in directly decreasing pulmonary emboli (PEs) and mortality is unclear. At the University of Mississippi Medical Center, a policy change provided the opportunity to compare independent groups: patients treated under a prior paradigm of weekly screening ultrasonography versus a post-policy change group in which weekly surveillance was no longer performed. METHODS: A total of 2532 consecutive cases were reviewed, with a 4-month washout period around the time of the policy change. Criteria for inclusion were admission to the neurosurgical service or consultation for ≥ 72 hours and hospitalization for ≥ 72 hours. Patients with a known diagnosis of DVT on admission or previous inferior vena cava (IVC) filter placement were excluded. The primary outcome examined was the rate of PE diagnosis, with secondary outcomes of all-cause mortality at discharge, DVT diagnosis rate, and IVC filter placement rate. A p value < 0.05 was considered significant. RESULTS: A total of 485 patients met the criteria for the pre-policy change group and 504 for the post-policy change group. Data are presented as screening (pre-policy change) versus no screening (post-policy change). There was no difference in the PE rate (2% in both groups, p = 0.72) or all-cause mortality at discharge (7% vs 6%, p = 0.49). There were significant differences in the lower-extremity DVT rate (10% vs 3%, p < 0.01) or IVC filter rate (6% vs 2%, p < 0.01). CONCLUSIONS: Based on these data, screening Doppler ultrasound examinations, in conjunction with standard-of-practice techniques to prevent thromboembolism, do not appear to confer a benefit to patients. While the screening group had significantly higher rates of DVT diagnosis and IVC filter placement, the screening, additional diagnoses, and subsequent interventions did not appear to improve patient outcomes. Ultimately, this makes DVT screening difficult to justify.

Assessing Shoulder Biomechanics of Healthy Elderly Individuals During Activities of Daily Living Using Inertial Measurement Units: High Maximum Elevation Is Achievable but Rarely Used.

Current shoulder clinical range of motion (ROM) assessments (e.g., goniometric ROM) may not adequately represent shoulder function beyond controlled clinical settings. Relative inertial measurement unit (IMU) motion quantifies ROM precisely and can be used outside of clinic settings capturing "real-world" shoulder function. A novel IMU-based shoulder elevation quantification method was developed via IMUs affixed to the sternum/humerus, respectively. This system was then compared to in-laboratory motion capture (MOCAP) during prescribed motions (flexion, abduction, scaption, and internal/external rotation). MOCAP/IMU elevation were equivalent during flexion (R2 = 0.96, µError = 1.7 deg), abduction (R2 = 0.96, µError = 2.9 deg), scaption (R2 = 0.98, µError = -0.3 deg), and internal/external rotation (R2 = 0.90, µError = 0.4 deg). When combined across movements, MOCAP/IMU elevation were equal (R2 = 0.98, µError = 1.4 deg). Following validation, the IMU-based system was deployed prospectively capturing continuous shoulder elevation in 10 healthy individuals (4 M, 69 ± 20 years) without shoulder pathology for seven consecutive days (13.5 ± 2.9 h/day). Elevation was calculated continuously daily and outcome metrics included percent spent in discrete ROM (e.g., 0-5 deg and 5-10 deg), repeated maximum elevation (i.e., >10 occurrences), and maximum/average elevation. Average elevation was 40 ± 6 deg. Maximum with >10 occurrences and maximum were on average 145-150 deg and 169 ± 8 deg, respectively. Subjects spent the vast majority of the day (97%) below 90 deg of elevation, with the most time spent in the 25-30 deg range (9.7%). This study demonstrates that individuals have the ability to achieve large ROMs but do not frequently do so. These results are consistent with the previously established lab-based measures. Moreover, they further inform how healthy individuals utilize their shoulders and may provide clinicians a reference for postsurgical ROM.

Stance and swing phase knee flexion recover at different rates following total knee arthroplasty: An inertial measurement unit study.

Total knee arthroplasty (TKA) is the most common joint replacement in the United States. Range of motion (ROM) monitoring includes idealized clinic measures (e.g. goniometry during passive ROM) that may not accurately represent knee function. Accordingly, a novel, portable, inertial measurement unit (IMU) based ROM measurement method was developed, validated, and implemented. Knee flexion was computed via relative motion between two IMUs and validated via optical motion capture (p > 0.05). Prospective analyses of 10 healthy individuals (5M, 50 ±â€¯19 years) and 20 patients undergoing TKA (3 lost to follow up, 10M, 65 ±â€¯6 years) were completed. Controls wore IMUs for 1-week. Patients wore IMUs for 1-week pre-TKA, 6-weeks immediately post-TKA, and 1-week at 1-year post-TKA. Flexion was computed continuously each day (8-12 h). Metrics included daily maximum flexion and flexion during stance/swing phases of gait. Maximum flexion was equal between cohorts at all time points. Contrastingly, patient stance and swing flexion were reduced pre-TKA, yet improved post-TKA. Specifically, patient stance and swing flexion were reduced below control/pre-TKA values during post-TKA week 1. Stance flexion exceeded pre-TKA and equaled control levels after week 2. However, swing flexion only exceeded pre-TKA and equaled control levels at 1-year post-TKA. This novel method improves upon the accuracy/portability of current methods (e.g. goniometry). Interestingly, surgery did not impact maximum ROM, yet improved the ability to flex during gait allowing more efficient and safe ambulation. This is the first study continuously monitoring long-term flexion before/after TKA. The results offer richer information than clinical measures about expected TKA rehabilitation.

Higher offset cross-linked polyethylene acetabular liners: is wear a significant clinical concern?

INTRODUCTION: Total hip arthroplasty (THA) is the 2nd most common total joint replacement surgery in the United States. However, not all THA devices perform well and need revised for several reasons including dislocation. Higher offset acetabular liners reduce this problem by creating a more anatomically/biomechanically natural hip joint, increasing soft-tissue tension, and accommodating larger femoral heads in smaller acetabular cups via increased polyethylene thickness. To our knowledge, however, in vivo wear (another failure mode) performance of offset acetabular liners remains unknown. METHODS: 2 cohorts of 40 individuals (0-mm, 4-mm offset acetabular liners, respectively) from a single surgeon's consecutive caseload were assessed. 6-week/5-year post-op radiographs were compared using a validated method using SolidWorks software to assess in vivo linear and volumetric wear rates. Resultant surgical offset was also quantified using this method. RESULTS: Linear wear rate for 0-mm and 4-mm offset cohorts were 0.01 ± 0.09 mm/year and 0.08 ± 0.12 mm/year, respectively. Volumetric wear rate for 0-mm and 4-mm offset cohorts were 30.4 ± 20.4 mm3/year and 61.6 ± 42.1 mm3/year, respectively. Both of these were statistically significant. Neither linear nor volumetric wear rate was correlated with resultant surgical offset. DISCUSSION: To our knowledge, this is the 1st study to compare in vivo wear performance of 0-mm and 4-mm offset acetabular liners. Although linear and volumetric wear rates were different between cohorts, neither reached previously established osteolysis thresholds. Moreover, wear rates were not correlated with resultant surgical offset. Finally, no patients in either cohort showed signs of osteolysis nor needed revision. As such, the clinical relevance of the wear rate differences is potentially less significant.

Usefulness of intra-procedural cone-beam computed tomography in modified balloon-occluded retrograde transvenous obliteration of gastric varices.

AIM: To evaluate whether intra-procedural cone-beam computed tomography (CBCT) performed during modified balloon-occluded retrograde transvenous obliteration (mBRTO) can accurately determine technical success of complete variceal obliteration. METHODS: From June 2012 to December 2014, 15 patients who received CBCT during mBRTO for treatment of portal hypertensive gastric variceal bleeding were retrospectively evaluated. Three-dimensional (3D) CBCT images were performed and evaluated prior to the end of the procedure, and these were further analyzed and compared to the pre-procedure contrast-enhanced computed tomography to determine the technical success of mBRTO including: Complete occlusion/obliteration of: (1) gastrorenal shunt (GRS); (2) gastric varices; and (3) afferent feeding veins. Post-mBRTO contrast-enhanced CT was used to confirm the accuracy and diagnostic value of CBCT within 2-3 d. RESULTS: Intra-procedural 3D-CBCT images were 100% accurate in determining the technical success of mBRTO in all 15 cases. CBCT demonstrated complete occlusion/obliteration of GRS, gastric varices, collaterals and afferent feeding veins during mBRTO, which was confirmed with post-mBRTO CT. Two patients showed incomplete obliteration of gastric varices and feeding veins on CBCT, which therefore required additional gelfoam injections to complete the procedure. No patient required additional procedures or other interventions during their follow-up period (684 ± 279 d). CONCLUSION: CBCT during mBRTO appears to accurately and immediately determine the technical success of mBRTO. This may improve the technical and clinical success/outcome of mBRTO and reduce additional procedure time in the future.

Differences in hip-knee joint coupling during gait after anterior cruciate ligament reconstruction.

BACKGROUND: After anterior cruciate ligament injury, patients have increased risk for developing degenerative osteoarthritis, potentially due to the kinematic changes that persist after surgical reconstruction. Current research only describes single joint kinematic differences rather than the way in which two joints behave concurrently, termed joint coupling. The purpose of this study was to compare knee motion relative to hip motion in anterior cruciate ligament reconstructed and healthy limbs during walking and jogging. METHODS: Thirty-seven recreationally active volunteers (22 reconstructed, 15 healthy) walked and jogged at 4.83 km/h and 9.66 km/h respectively. Vector coding methods were used to calculate stride-to-stride variability, magnitude, and vector angle of 6 joint couples during walking and jogging: hip frontal-knee frontal planes, hip frontal-knee sagittal, hip frontal-knee transverse, hip sagittal-knee frontal, hip sagittal-knee transverse, and hip transverse-knee frontal planes. FINDINGS: The hip sagittal-knee frontal and hip sagittal-knee transverse joint couples had decreased variability during mid-stance, and all other couples had increased variability during the stance phase in the reconstructed group. The reconstructed group had decreased magnitude of joint excursion in the hip frontal-knee sagittal couple during all phases of gait during walking. Vector angles of the hip frontal-knee transverse couple increased in the reconstructed group during the loading, middle, and terminal stance phases, and swing phase of gait during walking. INTERPRETATION: The increased variability and decreased magnitude of joint excursion indicate that movement patterns were less consistent during walking gait despite employing a more constrained system during movement in the reconstructed limb compared to healthy controls.